Author: "Tasse, C." / Topic: astrophysics::high energy astrophysical phenomena - Searchworks@Jio Institute Digital Library Search Results

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45 results on '"Tasse, C."'

1. Radio footprints of a minor merger in the Shapley Supercluster: from supercluster down to galactic scales

Author: Venturi, T, Giacintucci, S, Merluzzi, P, Bardelli, S, Busarello, G, Dallacasa, D, Sikhosana, SP, Marvil, J, Smirnov, O, Bourdin, H, Mazzotta, P, Rossetti, M, Rudnick, L, Bernardi, G, Bruggen, M, Carretti, E, Cassano, R, Di Gennaro, G, Gastaldello, F, Kale, R, Knowles, K, Koribalski, BS, Heywood, I, Hopkins, AM, Norris, RP, Reiprich, TH, Tasse, C, Vernstrom, T, Zucca, E, Bester, LH, Diego, JM, Kanapathippillai, J, Ministero degli Affari Esteri e della Cooperazione Internazionale, Department of Atomic Energy (India), South African Radio Astronomy Observatory, and National Research Foundation (South Africa)
Subjects: clusters: individual: A3558 [Galaxies], Galaxies - clusters - individual - A3558, Cosmology and Nongalactic Astrophysics (astro-ph.CO), Settore FIS/05, Astrophysics::High Energy Astrophysical Phenomena, Galaxies - clusters - individual - SC 1329-313, Astrophysics - cosmology and nongalactic astrophysics, Astrophysics - astrophysics of galaxies, Galaxies - clusters - individual - SC 1327-312, FOS: Physical sciences, Astronomy and Astrophysics, Galaxies - clusters - individual - A3562, Astrophysics::Cosmology and Extragalactic Astrophysics, clusters: general [Galaxies], Galaxies - clusters - general, Radio continuum - galaxies, clusters: individual: A3562 [Galaxies], Galaxies: clusters: individual: A3558, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Galaxies: clusters: individual: SC 1329–313, clusters: individual: SC 1329–313 [Galaxies], Galaxies: clusters: general, Galaxies: clusters: individual: A3562, Astrophysics::Galaxy Astrophysics
Abstract: et al., [Context] The Shapley Supercluster (⟨z⟩≈0.048) contains several tens of gravitationally bound clusters and groups, making it an ideal subject for radio studies of cluster mergers., [Aims] We used new high sensitivity radio observations to investigate the less energetic events of mass assembly in the Shapley Supercluster from supercluster down to galactic scales., [Methods] We created total intensity images of the full region between A3558 and A3562, from ∼230 to ∼1650 MHz, using ASKAP, MeerKAT and the GMRT, with sensitivities ranging from ∼6 to ∼100 μJy beam−1. We performed a detailed morphological and spectral study of the extended emission features, complemented with ESO-VST optical imaging and X-ray data from XMM-Newton., [Results] We report the first GHz frequency detection of extremely low brightness intercluster diffuse emission on a ∼1 Mpc scale connecting a cluster and a group, namely: A3562 and the group SC 1329–313. It is morphologically similar to the X-ray emission in the region. We also found (1) a radio tail generated by ram pressure stripping in the galaxy SOS 61086 in SC 1329–313; (2) a head-tail radio galaxy, whose tail is broken and culminates in a misaligned bar; (3) ultrasteep diffuse emission at the centre of A3558. Finally (4), we confirm the ultra-steep spectrum nature of the radio halo in A3562., [Conclusions] Our study strongly supports the scenario of a flyby of SC 1329–313 north of A3562 into the supercluster core. This event perturbed the centre of A3562, leaving traces of this interaction in the form of turbulence between A3562 and SC 1329–313, at the origin of the radio bridge and eventually affecting the evolution of individual supercluster galaxies by triggering ram pressure stripping. Our work shows that minor mergers can be spectacular and have the potential to generate diffuse radio emission that carries important information on the formation of large-scale structures in the Universe., T. Venturi and G. Bernardi acknowledge the support from the Ministero degli Affari Esteri e della Cooperazione Internazionale, Direzione Generale per la Promozione del Sistema Paese, Progetto di Grande Rilevanza ZA18GR02. R. Kale acknowledges the support of the Department of Atomic Energy, Government of India under project no. 12-R&D-TFR-5.02-0700. S. P. Sikhosana acknowledges funding support from the South African Radio Astronomy Observatory (SARAO) and the National Research Foundation (NRF). O. Smirnov’s research is supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation.
Published: 2022

2. Nearby galaxies in LoTSS-DR2: insights into the non-linearity of the radio-SFR relation

Author: Heesen, V., Staffehl, M., Basu, A., Beck, R., Stein, M., Tabatabaei, F. S., Hardcastle, M. J., Chyży, K. T., Shimwell, T. W., Adebahr, B., Beswick, R., Bomans, D. J., Botteon, A., Brinks, E., Brüggen, M., Dettmar, R. -J., Drabent, A., de Gasperin, F., Gürkan, G., Heald, G. H., Horellou, C., Nikiel-Wroczynski, B., Paladino, R., Piotrowska, J., Röttgering, H. J. A., Smith, D. J. B., and Tasse, C.
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics::Galaxy Astrophysics
Abstract: Context. Cosmic rays and magnetic fields are key ingredients in galaxy evolution, regulating both stellar feedback and star formation. Their properties can be studied with low-frequency radio continuum observations, free from thermal contamination. Aims. We define a sample of 76 nearby (< 30 Mpc) galaxies, with rich ancillary data in the radio continuum and infrared from the CHANG-ES and KINGFISH surveys, which will be observed with the LOFAR Two-metre Sky Survey (LoTSS) at 144 MHz. Methods. We present maps for 45 of them as part of the LoTSS data release 2 (LoTSS-DR2), where we measure integrated flux densities and study integrated and spatially resolved radio spectral indices. We investigate the radio-SFR relation, using star-formation rates (SFR) from total infrared and H $\alpha$ + 24-$\mu$m emission. Results. The radio-SFR relation at 144 MHz is clearly super-linear with $L_{144} \propto SFR^{1.4-1.5}$. The mean integrated radio spectral index between 144 and $\approx$1400 MHz is $\langle \alpha\rangle = -0.56 \pm 0.14$, in agreement with the injection spectral index for cosmic ray electrons (CRE). However, the radio spectral index maps show a variation of spectral indices with flatter spectra associated with star-forming regions and steeper spectra in galaxy outskirts and, in particular, in extra-planar regions. We found that galaxies with high star-formation rates (SFR) have steeper radio spectra; we find similar correlations with galaxy size, mass, and rotation speed. Conclusions. Galaxies that are larger and more massive are better electron calorimeters, meaning that the CRE lose a higher fraction of their energy within the galaxies. This explains the super-linear radio-SFR relation, with more massive, star-forming galaxies being radio bright. We propose a semi-calorimetric radio-SFR relation, which employs the galaxy mass as a proxy for the calorimetric efficiency., Comment: Accepted to Astronomy & Astrophysics. 16 pages, 8 figures, 3 tables + 45-page image atlas
Published: 2022
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3. The LOFAR view of giant, early-type galaxies: radio emission from active nuclei and star formation

Author: Capetti, A., Brienza, M., Balmaverde, B., Best, P. N., Baldi, R. D., Drabent, A., Gürkan, G., Rottgering, H. J. A., Tasse, C., and Webster, B.
Subjects: Galaxies: Jets, Astrophysics::High Energy Astrophysical Phenomena, jets [galaxies], FOS: Physical sciences, Astronomy and Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxies: Elliptical and Lenticular, Galaxies: Active, Astrophysics - Astrophysics of Galaxies, cD, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), active [galaxies], elliptical and lenticular, cD [galaxies], Astrophysics::Galaxy Astrophysics
Abstract: We study the properties and the origin of the radio emission in the most luminous early-type galaxies (ETGs) in the nearby Universe (MK, Comment: Pre-proofs version - Accepted for publication in A&A
Published: 2022
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4. III. Host-galaxy identifications and value added catalogues

Author: Kondapally, R., Best, P. N., Hardcastle, M. J., Nisbet, D., Bonato, M., Sabater, J., Duncan, K. J., McCheyne, I., Cochrane, R. K., Bowler, R. A. A., Williams, W. L., Shimwell, T. W., Tasse, C., Croston, J. H., Goyal, A., Jamrozy, M., Jarvis, M. J., Mahatma, V. H., Röttgering, H. J. A., Smith, D. J. B., Wołowska, A., Bondi, M., Brienza, M., Brown, M. J. I., Brüggen, M., Chambers, K., Garrett, M. A., Gürkan, G., Huber, M., Kunert-Bajraszewska, M., Magnier, E., Mingo, B., Mostert, R., Nikiel-Wroczyński, B., O’Sullivan, S. P., Paladino, R., Ploeckinger, T., Prandoni, I., Rosenthal, M. J., Schwarz, D. J., Shulevski, A., Wagenveld, J. D., and Wang, L.
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We present the source associations, cross-identifications, and multi-wavelength properties of the faint radio source population detected in the deep tier of the LOFAR Two Metre Sky Survey (LoTSS): the LoTSS Deep Fields. The first LoTSS Deep Fields data release consists of deep radio imaging at 150 MHz of the ELAIS-N1, Lockman Hole, and Boötes fields, down to RMS sensitives of around 20, 22, and 32 μJy beam−1, respectively. These fields are some of the best studied extra-galactic fields in the northern sky, with existing deep, wide-area panchromatic photometry from X-ray to infrared wavelengths, covering a total of ≈26 deg2. We first generated improved multi-wavelength catalogues in ELAIS-N1 and Lockman Hole; combined with the existing catalogue for Boötes, we present forced, matched aperture photometry for over 7.2 million sources across the three fields. We identified multi-wavelength counterparts to the radio detected sources, using a combination of the Likelihood Ratio method and visual classification, which greatly enhances the scientific potential of radio surveys and allows for the characterisation of the photometric redshifts and the physical properties of the host galaxies. The final radio-optical cross-matched catalogue consists of 81 951 radio-detected sources, with counterparts identified and multi-wavelength properties presented for 79 820 (>97%) sources. We also examine the properties of the host galaxies, and through stacking analysis find that the radio population with no identified counterpart is likely dominated by active galactic nuclei (AGN) at z ~ 3−4. This dataset contains one of the largest samples of radio-selected star-forming galaxies and AGN at these depths, making it ideal for studying the history of star-formation, and the evolution of galaxies and AGN across cosmic time.
Published: 2021

5. The LOFAR LBA Sky Survey: Deep Fields I. The Bo��tes Field

Author: Williams, W. L., de Gasperin, F., Hardcastle, M. J. H., van Weeren, R., Tasse, C., Shimwell, T. W., Best, P. N., Bonato, M., Bondi, M., Br��ggen, M., R��ttgering, H. J. A., and Smith, D. J. B.
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Astrophysics::Galaxy Astrophysics
Abstract: We present the first sub-mJy ($\approx0.7$ mJy beam$^{-1}$) survey to be completed below 100 MHz, which is over an order of magnitude deeper than previously achieved for widefield imaging of any field at these low frequencies. The high resolution ($15 \times 15$ arcsec) image of the Bo��tes field at 34-75 MHz is made from 56 hours of observation with the LOw Frequency ARray (LOFAR) Low Band Antenna (LBA) system. The observations and data reduction, including direction-dependent calibration, are described here. We present a radio source catalogue containing 1,948 sources detected over an area of $23.6$ deg$^2$, with a peak flux density threshold of $5��$. Using existing datasets, we characterise the astrometric and flux density uncertainties, finding a positional uncertainty of $\sim1.2$ arcsec and a flux density scale uncertainty of about 5 per cent. Using the available deep 144-MHz data, we identified 144-MHz counterparts to all the 54-MHz sources, and produced a matched catalogue within the deep optical coverage area containing 829 sources. We calculate the Euclidean-normalised differential source counts and investigate the low-frequency radio source spectral indices between 54 and 144 MHz, both of which show a general flattening in the radio spectral indices for lower flux density sources, from $\sim-0.75$ at 144-MHz flux densities between 100-1000 mJy to $\sim-0.5$ at 144-MHz flux densities between 5-10 mJy, due to a growing population of star forming galaxies and compact core-dominated AGN., 15 pages, 17 figures. Accepted for publication by A&A. Data available online at lofar-surveys.org
Published: 2021
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6. Extraction and self-calibration of individual LOFAR targets

Author: van Weeren, R. J., Shimwell, T. W., Botteon, A., Brunetti, G., Br��ggen, M., Boxelaar, J. M., Cassano, R., Di Gennaro, G., Andrade-Santos, F., Bonnassieux, E., Bonafede, A., Cuciti, V., Dallacasa, D., de Gasperin, F., Gastaldello, F., Hardcastle, M. J., Hoeft, M., Kraft, R . P., Mandal, S., Rossetti, M., R��ttgering, H. J. A., Tasse, C., and Wilber, A. G.
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Diffuse cluster radio sources, in the form of radio halos and relics, reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). These cosmic rays are thought to be (re-)accelerated through ICM turbulence and shock waves generated by cluster merger events. Here we characterize the presence of diffuse radio emission in known galaxy clusters in the HETDEX Spring Field, covering 424 deg$^2$. For this, we developed a method to extract individual targets from LOFAR observations processed with the LoTSS DDF-pipeline. This procedure enables improved calibration and joint imaging and deconvolution of multiple pointings of selected targets. The calibration strategy can also be used for LOFAR Low-Band Antenna (LBA) and international-baseline observations. The fraction of Planck PSZ2 clusters with any diffuse radio emission apparently associated with the ICM is $73\pm17\%$. We detect a total of 10 radio halos and 12 candidate halos in the HETDEX Spring Field. Five clusters host radio relics. The fraction of radio halos in Planck PSZ2 clusters is $31\pm11\%$, and $62\pm15\%$ when including the candidate radio halos. Based on these numbers, we expect that there will be at least $183 \pm 65$ radio halos found in the LoTSS survey in PSZ2 clusters, in agreement with predictions. The integrated flux densities for the radio halos were computed by fitting exponential models to the radio images. From these flux densities, we determine the cluster mass (M$_{500}$) and Compton Y parameter (Y$_{500}$) 150 MHz radio power (P$_{\rm{150 MHz}}$) scaling relations for Planck PSZ2-detected radio halos. We find that the slopes of these relations are steeper than those determined from the 1.4 GHz radio powers. However, considering the uncertainties this is not a statistically significant result., submitted, 35 pages and 45 figures
Published: 2020

7. NGC 326: X-shaped no more

Author: Hardcastle, M. J., Croston, J. H., Shimwell, T. W., Tasse, C., Gurkan, G., Morganti, R., Murgia, M., Rottgering, H. J. A., van Weeren, R. J., and Williams, W. L.
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We present new 144-MHz LOFAR observations of the prototypical `X-shaped' radio galaxy NGC 326, which show that the formerly known wings of the radio lobes extend smoothly into a large-scale, complex radio structure. We argue that this structure is most likely the result of hydrodynamical effects in an ongoing group or cluster merger, for which pre-existing X-ray and optical data provide independent evidence. The large-scale radio structure is hard to explain purely in terms of jet reorientation due to the merger of binary black holes, a previously proposed explanation for the inner structure of NGC 326. For this reason, we suggest that the simplest model is one in which the merger-related hydrodynamical processes account for all the source structure, though we do not rule out the possibility that a black hole merger has occurred. Inference of the black hole-black hole merger rate from observations of X-shaped sources should be carried out with caution in the absence of deep, sensitive low-frequency observations. Some X-shaped sources may be signposts of cluster merger activity, and it would be useful to investigate the environments of these objects more generally., 7 pages, 2 colour figures. Accepted by MNRAS
Published: 2019
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8. The LOFAR window on star-forming galaxies and AGNs – curved radio SEDs and IR–radio correlation at 0

Author: Calistro Rivera, G., Williams, W. L., Hardcastle, M. J., Duncan, K., Rottgering, H.J.A., Best, P. N., Chy?y, K. T., Conselice, Christopher J., de Gasperin, F., Engels, D., Intema, H. T., Jarvis, M. J., Mahony, E. K., Miley, G. K., Morabito, L. K., Prandoni, I., Sabater, J., Smith, D. J. B., Tasse, C., van der Werf, P. P., and White, G. J.
Subjects: Astrophysics::High Energy Astrophysical Phenomena, galaxies: evolution, galaxies: nuclei, galaxies: photometry, galaxies: starburst, infrared: galaxies, radio continuum: galaxies, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We present a study of the low-frequency radio properties of star-forming (SF) galaxies and active galactic nuclei (AGNs) up to redshift z = 2.5. The new spectral window probed by the Low Frequency Array (LOFAR) allows us to reconstruct the radio continuum emission from 150 MHz to 1.4 GHz to an unprecedented depth for a radio-selected sample of 1542 galaxies in ∼ 7 deg2 of the LOFAR Boötes field. Using the extensive multiwavelength data set available in Boötes and detailed modelling of the far-infrared to ultraviolet spectral energy distribution (SED), we are able to separate the star formation (N = 758) and the AGN (N = 784) dominated populations. We study the shape of the radio SEDs and their evolution across cosmic time and find significant differences in the spectral curvature between the SF galaxy and AGN populations. While the radio spectra of SF galaxies exhibit a weak but statistically significant flattening, AGN SEDs show a clear trend to become steeper towards lower frequencies. No evolution of the spectral curvature as a function of redshift is found for SF galaxies or AGNs. We investigate the redshift evolution of the infrared–radio correlation for SF galaxies and find that the ratio of total infrared to 1.4-GHz radio luminosities decreases with increasing redshift: q1.4 GHz = (2.45 ± 0.04) (1 + z)−0.15 ± 0.03. Similarly, q150 MHz shows a redshift evolution following q150 GHz = (1.72 ± 0.04) (1 + z)−0.22 ± 0.05. Calibration of the 150 MHz radio luminosity as a star formation rate tracer suggests that a single power-law extrapolation from q1.4 GHz is not an accurate approximation at all redshifts.
Published: 2017

9. The LOFAR window on star-forming galaxies and AGNs - curved radio SEDs and IR-radio correlation at 0

Author: Calistro Rivera, G., Hardcastle, M. J., Duncan, K., Röttgering, H. J. A., Best, P. N., Brüggen, M., Chyży, K. T., Conselice, C. J., de Gasperin, F., Engels, D., Gürkan, G., Intema, H. T., Jarvis, M. J., Mahony, E. K., Miley, G. K., Morabito, L. K., Prandoni, I., Sabater, J., Tasse, C., van der Werf, P. P., and White, G. J.
Subjects: starburst [galaxies], Astrophysics::High Energy Astrophysical Phenomena, nuclei [galaxies], photometry [galaxies], Astrophysics::Cosmology and Extragalactic Astrophysics, galaxies [infrared], Astrophysics::Galaxy Astrophysics, evolution [galaxies], galaxies [radio continuum]
Abstract: We present a study of the low-frequency radio properties of star-forming (SF) galaxies and active galactic nuclei (AGNs) up to redshift z = 2.5. The new spectral window probed by the Low Frequency Array (LOFAR) allows us to reconstruct the radio continuum emission from 150 MHz to 1.4 GHz to an unprecedented depth for a radio-selected sample of 1542 galaxies in ˜ 7 deg2 of the LOFAR Boötes field. Using the extensive multiwavelength data set available in Boötes and detailed modelling of the far-infrared to ultraviolet spectral energy distribution (SED), we are able to separate the star formation (N = 758) and the AGN (N = 784) dominated populations. We study the shape of the radio SEDs and their evolution across cosmic time and find significant differences in the spectral curvature between the SF galaxy and AGN populations. While the radio spectra of SF galaxies exhibit a weak but statistically significant flattening, AGN SEDs show a clear trend to become steeper towards lower frequencies. No evolution of the spectral curvature as a function of redshift is found for SF galaxies or AGNs. We investigate the redshift evolution of the infrared-radio correlation for SF galaxies and find that the ratio of total infrared to 1.4-GHz radio luminosities decreases with increasing redshift: q1.4 GHz = (2.45 ± 0.04) (1 + z)-0.15 ± 0.03. Similarly, q150 MHz shows a redshift evolution following q150 GHz = (1.72 ± 0.04) (1 + z)-0.22 ± 0.05. Calibration of the 150 MHz radio luminosity as a star formation rate tracer suggests that a single power-law extrapolation from q1.4 GHz is not an accurate approximation at all redshifts.
Published: 2017
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10. LOFAR-Bo��tes: Properties of high- and low-excitation radio galaxies at $0.5 < z < 2.0$

Author: Williams, W. L., Rivera, G. Calistro, Best, P. N., Hardcastle, M. J., R��ttgering, H. J. A., Duncan, K. J., de Gasperin, F., Jarvis, M. J., Miley, G. K., Mahony, E. K., Morabito, L. K., Nisbet, D. M., Prandoni, I., Smith, D. J. B., Tasse, C., and White, G. J.
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: This paper presents a study of the redshift evolution of radio-loud active galactic nuclei (AGN) as a function of the properties of their galaxy hosts in the Bo��tes field. To achieve this we match low-frequency radio sources from deep $150$-MHz LOFAR observations to an $I$-band-selected catalogue of galaxies, for which we have derived photometric redshifts, stellar masses and rest-frame colours. We present spectral energy distribution (SED) fitting to determine the mid-infrared AGN contribution for the radio sources and use this information to classify them as High- versus Low-Excitation Radio Galaxies (HERGs and LERGs) or Star-Forming galaxies. Based on these classifications we construct luminosity functions for the separate redshift ranges going out to $z = 2$. From the matched radio-optical catalogues, we select a sub-sample of $624$ high power ($P_{150\mathrm{\,MHz}}>10^{25}$ W Hz$^{-1}$) radio sources between $0.5 \leq z < 2$. For this sample, we study the fraction of galaxies hosting HERGs and LERGs as a function of stellar mass and host galaxy colour. The fraction of HERGs increases with redshift, as does the fraction of sources in galaxies with lower stellar masses. We find that the fraction of galaxies that host LERGs is a strong function of stellar mass as it is in the local Universe. This, combined with the strong negative evolution of the LERG luminosity functions over this redshift range, is consistent with LERGs being fuelled by hot gas in quiescent galaxies., 25 pages, 21 figures, accepted for publication in MNRAS
Published: 2017
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11. The LOFAR window on star-forming galaxies and AGN - curved radio SEDs and IR-radio correlation at $0 < z < 2.5$

Author: Rivera, G. Calistro, Williams, W. L., Hardcastle, M. J., Duncan, K., R��ttgering, H. J. A., Best, P. N., Br��ggen, M., Chyzy, K. T., Conselice, C. J., de Gasperin, F., Engels, D., G��rkan, G., Intema, H. T., Jarvis, M. J., Mahony, E. K., Miley, G. K., Morabito, L. K., Prandoni, I., Sabater, J., Smith, D. J. B., Tasse, C., van der Werf, P. P., and White, G. J.
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: We present a study of the low-frequency radio properties of star forming (SF) galaxies and active galactic nuclei (AGN) up to redshift $z=2.5$. The new spectral window probed by the Low Frequency Array (LOFAR) allows us to reconstruct the radio continuum emission from 150 MHz to 1.4 GHz to an unprecedented depth for a radio-selected sample of $1542$ galaxies in $\sim 7~ \rm{deg}^2$ of the LOFAR Bo��tes field. Using the extensive multi-wavelength dataset available in Bo��tes and detailed modelling of the FIR to UV spectral energy distribution (SED), we are able to separate the star-formation (N=758) and the AGN (N=784) dominated populations. We study the shape of the radio SEDs and their evolution across cosmic time and find significant differences in the spectral curvature between the SF galaxy and AGN populations. While the radio spectra of SF galaxies exhibit a weak but statistically significant flattening, AGN SEDs show a clear trend to become steeper towards lower frequencies. No evolution of the spectral curvature as a function of redshift is found for SF galaxies or AGN. We investigate the redshift evolution of the infrared-radio correlation (IRC) for SF galaxies and find that the ratio of total infrared to 1.4 GHz radio luminosities decreases with increasing redshift: $ q_{\rm 1.4GHz} = (2.45 \pm 0.04) \times (1+z)^{-0.15 \pm 0.03} $. Similarly, $q_{\rm 150MHz}$ shows a redshift evolution following $ q_{\rm 150GHz} = (1.72 \pm 0.04) \times (1+z)^{-0.22 \pm 0.05}$. Calibration of the 150 MHz radio luminosity as a star formation rate tracer suggests that a single power-law extrapolation from $q_{\rm 1.4GHz}$ is not an accurate approximation at all redshifts., Accepted for publication in MNRAS, 21 pages, 16 figures
Published: 2017
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12. Investigating the Unification of LOFAR-detected powerful AGN in the Bo��tes Field

Author: Morabito, Leah K., Williams, W. L., Duncan, Kenneth J., R��ttgering, H. J. A., Miley, George, Saxena, Aayush, Barthel, Peter, Best, P. N., Bruggen, M., Brunetti, G., Chy��y, K. T., Engels, D., Hardcastle, M. J., Harwood, J. J., Jarvis, Matt J., Mahony, E. K., Prandoni, I., Shimwell, T. W., Shulevski, A., and Tasse, C.
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, Astrophysics of Galaxies (astro-ph.GA), FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Low radio frequency surveys are important for testing unified models of radio-loud quasars and radio galaxies. Intrinsically similar sources that are randomly oriented on the sky will have different projected linear sizes. Measuring the projected linear sizes of these sources provides an indication of their orientation. Steep-spectrum isotropic radio emission allows for orientation-free sample selection at low radio frequencies. We use a new radio survey of the Bo��tes field at 150 MHz made with the Low Frequency Array (LOFAR) to select a sample of radio sources. We identify 44 radio galaxies and 16 quasars with powers $P>10^{25.5}$ W Hz$^{-1}$ at 150 MHz using cross-matched multi-wavelength information from the AGN and Galaxy Evolution Survey (AGES), which provides spectroscopic redshifts. We find that LOFAR-detected radio sources with steep spectra have projected linear sizes that are on average 4.4$\pm$1.4 larger than those with flat spectra. The projected linear sizes of radio galaxies are on average 3.1$\pm$1.0 larger than those of quasars (2.0$\pm$0.3 after correcting for redshift evolution). Combining these results with three previous surveys, we find that the projected linear sizes of radio galaxies and quasars depend on redshift but not on power. The projected linear size ratio does not correlate with either parameter. The LOFAR data is consistent within the uncertainties with theoretical predictions of the correlation between the quasar fraction and linear size ratio, based on an orientation-based unification scheme., 14 pages, accepted for publication in MNRAS
Published: 2017
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13. A large light-mass component of cosmic rays at 10^{17} - 10^{17.5} eV from radio observations

Author: Buitink, S., Corstanje, A., Falcke, H., H��randel, J. R., Huege, T., Nelles, A., Rachen, J. P., Rossetto, L., Schellart, P ., Scholten, O., ter Veen, S., Thoudam, S., Trinh, T. N. G., Anderson, J., Asgekar, A., Avruch, I. M., Bell, M. E., Bentum, M. J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J. W., Brouw, W. N., Br��ggen, M., Butcher, H. R., Carbone, D., Ciardi, B., Conway, J. E., de Gasperin, F., de Geus, E., Deller, A., Dettmar, R. -J., van Diepen, G., Duscha, S., Eisl��ffel, J., Engels, D., Enriquez, J. E., Fallows, R. A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M. A., Griessmeier, J. M., Gunst, A. W., van Haarlem, M. P., Hassall, T. E., Heald, G., Hessels, J. W. T., Hoeft, M., Horneffer, A., Iacobelli, M., Intema, H., Juette, E., Karastergiou, A., Kondratiev, V. I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Loose, G. M., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J. P., Mevius, M., Mulcahy, D. D., Munk, H., Norden, M. J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V. N., Pietka, M., Pizzo, R., Polatidis, A. G., Reich, W., R��ttgering, H. J. A., Scaife, A. M. M., Schwarz, D. J., Serylak, M., Sluman, J., Smirnov, O., Stappers, B. W., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Toribio, M. C., Vermeulen, R., Vocks, C., Vogt, C., van Weeren, R. J., Wijers, R. A. M. J., Wijnholds, S. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., and Zensus, J. A.
Subjects: High Energy Astrophysical Phenomena (astro-ph.HE), astro-ph.HE, High Energy Physics - Experiment (hep-ex), hep-ex, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Experiment
Abstract: Cosmic rays are the highest energy particles found in nature. Measurements of the mass composition of cosmic rays between 10^{17} eV and 10^{18} eV are essential to understand whether this energy range is dominated by Galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate cascades of secondary particles (air showers) in the atmosphere and their masses are inferred from measurements of the atmospheric depth of the shower maximum, Xmax, or the composition of shower particles reaching the ground. Current measurements suffer from either low precision, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique, suitable for determination of Xmax with a duty cycle of in principle nearly 100%. The radiation is generated by the separation of relativistic charged particles in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean precision of 16 g/cm^2 between 10^{17}-10^{17.5} eV. Because of the high resolution in $Xmax we can determine the mass spectrum and find a mixed composition, containing a light mass fraction of ~80%. Unless the extragalactic component becomes significant already below 10^{17.5} eV, our measurements indicate an additional Galactic component dominating at this energy range., 35 pages, 11 figures, updated version: Pierre Auger Observatory data ICRC 2015 added to Fig 2
Published: 2016
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14. LOFAR 150-MHz observations of the Bo��tes field: Catalogue and Source Counts

Author: Williams, W. L., van Weeren, R. J., R��ttgering, H. J. A., Best, P., Dijkema, T. J., de Gasperin, F., Hardcastle, M. J., Heald, G., Prandoni, I., Sabater, J., Shimwell, T. W., Tasse, C., van Bemmel, I. M., Br��ggen, M., Brunetti, G., Conway, J. E., En��lin, T., Engels, D., Falcke, H., Ferrari, C., Haverkorn, M., Jackson, N., Jarvis, M. J., Kapinska, A. D., Mahony, E. K., Miley, G. K., Morabito, L. K., Morganti, R., Orr��, E., Retana-Montenegro, E., Sridhar, S. S., Toribio, M. C., White, G. J., Wise, M. W., and Zwart, J. T. L.
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract: We present the first wide area (19 deg$^2$), deep ($\approx120-150$ ��Jy beam$^{-1}$), high resolution ($5.6 \times 7.4$ arcsec) LOFAR High Band Antenna image of the Bo��tes field made at 130-169 MHz. This image is at least an order of magnitude deeper and 3-5 times higher in angular resolution than previously achieved for this field at low frequencies. The observations and data reduction, which includes full direction-dependent calibration, are described here. We present a radio source catalogue containing 6276 sources detected over an area of $19$\,deg$^2$, with a peak flux density threshold of $5��$. As the first thorough test of the facet calibration strategy, introduced by van Weeren et al., we investigate the flux and positional accuracy of the catalogue. We present differential source counts that reach an order of magnitude deeper in flux density than previously achieved at these low frequencies, and show flattening at 150 MHz flux densities below 10 mJy associated with the rise of the low flux density star-forming galaxies and radio-quiet AGN., 29 pages, 27 figures, accepted for publication in MNRAS
Published: 2016
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15. A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations

Author: Buitink, S, Corstanje, A, Falcke, H, Hörandel, JR, Huege, T, Nelles, A, Rachen, JP, Rossetto, L, Schellart, P, Scholten, O, Ter Veen, S, Thoudam, S, Trinh, TNG, Anderson, J, Asgekar, A, Avruch, IM, Bell, ME, Bentum, MJ, Bernardi, G, Best, P, Bonafede, A, Breitling, F, Broderick, JW, Brouw, WN, Brüggen, M, Butcher, HR, Carbone, D, Ciardi, B, Conway, JE, De Gasperin, F, De Geus, E, Deller, A, Dettmar, RJ, Van Diepen, G, Duscha, S, Eislöffel, J, Engels, D, Enriquez, JE, Fallows, RA, Fender, R, Ferrari, C, Frieswijk, W, Garrett, MA, Grießmeier, JM, Gunst, AW, Van Haarlem, MP, Hassall, TE, Heald, G, Hessels, JWT, Hoeft, M, Horneffer, A, Iacobelli, M, Intema, H, Juette, E, Karastergiou, A, Kondratiev, VI, Kramer, M, Kuniyoshi, M, Kuper, G, Van Leeuwen, J, Loose, GM, Maat, P, Mann, G, Markoff, S, McFadden, R, McKay-Bukowski, D, McKean, JP, Mevius, M, Mulcahy, DD, Munk, H, Norden, MJ, Orru, E, Paas, H, Pandey-Pommier, M, Pandey, VN, Pietka, M, Pizzo, R, Polatidis, AG, Reich, W, Röttgering, HJA, Scaife, AMM, Schwarz, DJ, Serylak, M, Sluman, J, Smirnov, O, Stappers, BW, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, M, Tang, Y, Tasse, C, Toribio, MC, Vermeulen, R, Vocks, C, Vogt, C, Van Weeren, RJ, Wijers, RAMJ, Wijnholds, SJ, and Wise, MW
Subjects: General Science & Technology, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics
Abstract: © 2016 Macmillan Publishers Limited. All rights reserved. Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 1017-1018 electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers - cascades of secondary particles in the atmosphere - and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 1017-1017.5 electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 1017.5 electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 1017-1017.5 electronvolt range.
Published: 2015

16. The 'Sausage' and 'Toothbrush' clusters of galaxies and the prospects of LOFAR observations of clusters of galaxies

Author: Röttgering, H., van Weeren, R., Brüggen, M., Croston, J., Hoeft, M., Ogrean, G., Barthel, P., Best, P., Bonafede, A., Brunetti, G., Cassano, R., Chyży, K., Conway, J., De Gasperin, F., Ferrari, C., Heald, G., Jackson, N., Jarvis, M., Lehnert, M., Macario, G., Miley, G., Orrú, E., Pizzo, R., Rafferty, D., Stroe, A., Tasse, C., van der Tol, S., White, G., Wise, M., Röttgering, H., Van Weeren, R., Brüggen, M., Croston, J., Hoeft, M., Ogrean, G., Barthel, P., Best, P., Bonafede, A., Brunetti, G., Cassano, R., Chyzy, K., Conway, J., De Gasperin, F., Ferrari, C., Heald, G., Jackson, N., Jarvis, M., Lehnert, M., Macario, G., Miley, G., Orrú, E., Pizzo, R., Rafferty, D., Stroe, A., Tasse, C., Van der Tol, S., White, G., Wise, M., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: clusters: individual(CIZA J2242.8+5301 [galaxies], Space and Planetary Science, Astrophysics::High Energy Astrophysical Phenomena, 1RXS J0603.3+4214), clusters: general [galaxies], Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxies: clusters: general, Galaxies: clusters: individual(CIZA J2242.8+5301, 1RXS J0603.3+4214), Astronomy and Astrophysic, Telescope, Astrophysics::Galaxy Astrophysics, Telescopes
Abstract: LOFAR, the Low Frequency Radio Array, is a new pan-European radio telescope that is almost fully operational. One of its main drivers is to make deep images of the low frequency radio sky. To be able to do this a number of challenges need to be addressed. These include the high data rates, removal of radio frequency interference, calibration of the beams and correcting for the corrupting influence of the ionosphere. One of the key science goals is to study merger shocks, particle acceleration mechanisms and the structure of magnetic fields in nearby and distant merging clusters. Recent studies with the GMRT and WSRT radio telescopes of the "Sausage" and the "Toothbrush" clusters have given a very good demonstration of the power of radio observations to study merging clusters. Recently we discovered that both clusters contain relic and halo sources, large diffuse regions of radio emission not associated with individual galaxies. The 2 Mpc northern relic in the Sausage cluster displays highly aligned magnetic fields and and exhibits a strong spectral index gradient that is a consequence of cooling of the synchrotron emitting particles in the post-shock region. We have argued that these observations provide strong evidence that shocks in merging clusters are capable of accelerating particles. For the Toothbrush cluster we observe a puzzling linear relic that extends over 2 Mpc. The proposed scenario is that a triplemerger can lead to such a structure. With LOFAR's sensitivity it will not only be possible to trace much weaker shocks, but also to study those shocks due to merging clusters up to redshifts of at least one. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Published: 2013

17. Wide-field LOFAR imaging of the field around the double-double radio galaxy B1834+620

Author: Orrù, E, Van Velzen, S, Pizzo, R. F., Yatawatta, S, Paladino, R, Iacobelli, M, Murgia, M, Falcke, H, Morganti, R, De Bruyn, A. G., Ferrari, C, Anderson, J, Bonafede, A, Mulcahy, D, Asgekar, A, Avruch, I. M., Beck, R, Bell, M.E., Van Bemmel, I, Bentum, M. J., Bernardi, G, Best, P, Breitling, F, Brüggen, M, Broderick, J.W., Ciardi, B, Corstanje, A, Conway, J. E., De Geus, E, Butcher, H. R., Ciardi, B., Deller, A, Duscha, S, Eislöffel, J, Engels, D, Frieswijk, W, Grießmeier, Jean-Mathias, Heald, G, Hoeft, M, Intema, H, Juette, E, Kohler, J, Kuniyoshi, M, Kuper, G, Loose, M, Maat, P, Mann, G, Markoff, S, Mcfadden, R, Mckay-Bukowski, D, Miley, G, Moldon, J, Molenaar, G, Munk, H, Nelles, A, Paas, H, Pandey-Pommier, M, Pietka, G, Reich, W, Röttgering, H, Rowlinson, A, Scaife, A, Schoenmakers, A, Schwarz, D., Serylak, M, Shulevski, A, Smirnov, O, Steinmetz, M, Stewart, A, Swinbank, J, Tagger, Michel, Tasse, C., Thoudam, S, Toribio, M.C, Vermeulen, R, Vocks, C, Van Weeren, R.J., Wijers, R.A.M.J, Wise, M.W., Wucknitz, O, Netherlands Institute for Radio Astronomy (ASTRON), INAF - Osservatorio Astronomico di Bologna (OABO), Istituto Nazionale di Astrofisica (INAF), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Institute for Nanostructured Materials (CNR-ISMN), Consiglio Nazionale delle Ricerche (CNR), Radboud university [Nijmegen], Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Département de Géologie, Université de Montréal (UdeM), University of Hamburg, Jacobs University [Bremen], University of Southampton, SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Onsala Space Observatory, Dept. of Radio and Space Science, Chalmers University of Technology, Chalmers University of Technology [Göteborg], Medstar Research Institute, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Ruhr-Universität Bochum [Bochum], Karlsruhe Institute of Technology (KIT), Max-Planck-Institut für Radioastronomie (MPIFR), Queen's Medical Centre, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Anton Pannekoek Institute for Astronomy, Center for Information Technology CIT, Université de Groningen, Université de Montréal [Montréal], Deutsches GeoForschungsZentrum GFZ, Department Geodesy and Remote Sensing, Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden, National Research Council of Italy | Consiglio Nazionale delle Ricerche (CNR), Radboud University [Nijmegen], and Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Radiation mechanisms: non-thermal, techniques: interferometric, [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Galaxies: active, Astroparticle physics, Astrophysics::Galaxy Astrophysics, Radio continuum: galaxies, Instrumentation:interferometers
Abstract: International audience; Context. The existence of double-double radio galaxies (DDRGs) is evidence for recurrent jet activity in AGN, as expected from standard accretion models. A detailed study of these rare sources provides new perspectives for investigating the AGN duty cycle, AGN-galaxy feedback, and accretion mechanisms. Large catalogues of radio sources, on the other hand, provide statistical information about the evolution of the radio-loud AGN population out to high redshifts.Aims. Using wide-field imaging with the LOFAR telescope, we study both a well-known DDRG as well as a large number of radio sources in the field of view. Methods. We present a high resolution image of the DDRG B1834+620 obtained at 144 MHz using LOFAR commissioning data. Our image covers about 100 square degrees and contains over 1000 sources.Results. The four components of the DDRG B1834+620 have been resolved for the first time at 144 MHz. Inner lobes were found to point towards the direction of the outer lobes, unlike standard FR II sources. Polarized emission was detected at +60 rad m −2 in the northern outer lobe. The high spatial resolution allows the identification of a large number of small double-lobed radio sources; roughly 10% of all sources in the field are doubles with a separation smaller than 1.Conclusions. The spectral fit of the four components is consistent with a scenario in which the outer lobes are still active or the jets recently switched off, while emission of the inner lobes is the result of a mix-up of new and old jet activity. From the presence of the newly extended features in the inner lobes of the DDRG, we can infer that the mechanism responsible for their formation is the bow shock that is driven by the newly launched jet. We find that the density of the small doubles exceeds the density of FR II sources with similar properties at 1.4 GHz, but this difference becomes smaller for low flux densities. Finally, we show that the significant challenges of wide-field imaging (e.g., time and frequency variation of the beam, directional dependent calibration errors) can be solved using LOFAR commissioning data, thus demonstrating the potential of the full LOFAR telescope to discover millions of powerful AGN at redshift z ∼ 1.
Published: 2015
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18. The 'Sausage' and 'Toothbrush' clusters of galaxies and the prospects of LOFAR observations of clusters of galaxies

Author: Rottgering, H, van Weeren, R, Brueggen, M, Croston, J, Hoeft, M, Ogrean, G, Barthel, P, Best, P, Bonafede, A, Brunetti, G, Cassano, R, Chyzy, K, Conway, J, De Gasperin, F, Ferrari, C, Heald, G, Jackson, N, Jarvis, M, Lehnert, M, Macario, G, Miley, G, Orru, E, Pizzo, R, Rafferty, D, Stroe, A, Tasse, C, van der Tol, S, White, G, Wise, M, Collaboration, LOFAR, and Kapteyn Astronomical Institute
Subjects: CALIBRATION, galaxies: clusters: general, Astrophysics::High Energy Astrophysical Phenomena, MERGERS, CIZA J2242.8+5301, telescopes, Astrophysics::Cosmology and Extragalactic Astrophysics, galaxies: clusters: individual(CIZA J2242.8+5301, 1RXS J0603.3+4214), Astrophysics::Galaxy Astrophysics
Abstract: LOFAR, the Low Frequency Radio Array, is a new pan-European radio telescope that is almost fully operational. One of its main drivers is to make deep images of the low frequency radio sky. To be able to do this a number of challenges need to be addressed. These include the high data rates, removal of radio frequency interference, calibration of the beams and correcting for the corrupting influence of the ionosphere. One of the key science goals is to study merger shocks, particle acceleration mechanisms and the structure of magnetic fields in nearby and distant merging clusters. Recent studies with the GMRT and WSRT radio telescopes of the "Sausage" and the "Toothbrush" clusters have given a very good demonstration of the power of radio observations to study merging clusters. Recently we discovered that both clusters contain relic and halo sources, large diffuse regions of radio emission not associated with individual galaxies. The 2 Mpc northern relic in the Sausage cluster displays highly aligned magnetic fields and and exhibits a strong spectral index gradient that is a consequence of cooling of the synchrotron emitting particles in the post-shock region. We have argued that these observations provide strong evidence that shocks in merging clusters are capable of accelerating particles. For the Toothbrush cluster we observe a puzzling linear relic that extends over 2 Mpc. The proposed scenario is that a triplemerger can lead to such a structure. With LOFAR's sensitivity it will not only be possible to trace much weaker shocks, but also to study those shocks due to merging clusters up to redshifts of at least one. © 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.
Published: 2013

19. Studying Galactic interstellar turbulence through fluctuations in synchrotron emission

Author: Iacobelli, M., Haverkorn, M., Orrú, E., Pizzo, R. F., Anderson, J., Beck, R., Bell, M. R., Bonafede, A., Chyzy, K., Dettmar, R.-J., Enßlin, T. A., Heald, G., Horellou, C., Horneffer, A., Jurusik, W., Junklewitz, H., Kuniyoshi, M., Mulcahy, D. D., Paladino, R., Reich, W., Scaife, A., Sobey, C., Sotomayor-Beltran, C., Alexov, A., Asgekar, A., Avruch, I. M., Bell, M. E., van Bemmel, I., Bentum, M. J., Bernardi, G., Best, P., Bırzan, L., Breitling, F., Broderick, J., Brouw, W. N., Brüggen, M., Butcher, H. R., Ciardi, B., Conway, J. E., de Gasperin, F., de Geus, E., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R. A., Ferrari, C., Frieswijk, W., Garrett, M. A., Grießmeier, J., Gunst, A. W., Hamaker, J. P., Hassall, T. E., Hessels, J. W. T., Hoeft, M., Hörandel, J., Jelic, V., Karastergiou, A., Kondratiev, V. I., Koopmans, L. V. E., Kramer, M., Kuper, G., van Leeuwen, J., Macario, G., Mann, G., McKean, J. P., Munk, H., Pandey-Pommier, M., Polatidis, A. G., Röttgering, H., Schwarz, Dominik, Sluman, J., Smirnov, O., Stappers, B. W., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Vogt, C., van Weeren, R. J., Wise, M. W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., Leiden Observatory [Leiden], Universiteit Leiden, Netherlands Institute for Radio Astronomy (ASTRON), Radboud University [Nijmegen], Max-Planck-Institut für Radioastronomie (MPIFR), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Jacobs University [Bremen], Uniwersytet Jagielloński w Krakowie = Jagiellonian University (UJ), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Alma Mater Studiorum Università di Bologna [Bologna] (UNIBO), School of Physics and Astronomy [Southampton], University of Southampton, Sydney Institute for Astronomy (SIfA), The University of Sydney, SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leibniz-Institut für Astrophysik Potsdam (AIP), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Oxford Astrophysics, University of Oxford, Université de Nice Sophia-Antipolis (UNSA), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universität Bielefeld, Rhodes University, Grahamstown, SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), This work is part of the research programme 639.042.915, which is (partly) financed by the Netherlands Organisation for Scientific Research (NWO)., European Project: 239490,EC:FP7:PEOPLE,FP7-PEOPLE-IRG-2008,MAGNETIC_MILKYWAY(2009), Universiteit Leiden [Leiden], Radboud university [Nijmegen], Harvard University [Cambridge]-Smithsonian Institution, Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Oxford [Oxford], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), and Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)
Subjects: Galaxy, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], astronomical techniques, synchrotron radiation, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, interstellar matter, cosmic ray propagation, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], Astrophysics::Galaxy Astrophysics
Abstract: International audience; Aims: The characteristic outer scale of turbulence (i.e. the scale at which the dominant source of turbulence injects energy to the interstellar medium) and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters.Methods: We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l,b) ~ (137.0°, +7.0°) at 80' × 70' resolution in the range [146, 174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations.Results: We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum displays a power law behaviour for scales between 100 and 8 arcmin with a slope α = -1.84 ± 0.19. We find an upper limit of ~20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region, which is in agreement with previous estimates in literature. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes.Conclusions. We present the first LOFAR detection and imaging of the Galactic diffuse synchrotron emission around 160 MHz from the highly polarized Fan region. The power spectrum of the foreground synchrotron fluctuations is approximately a power law with a slope α ≈ -1.84 up to angular multipoles of ≤1300, corresponding to an angular scale of ~8 arcmin. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence (Lout) of the Galactic synchrotron foreground, finding a range of plausible values of 10-20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates.
Published: 2013
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20. First LOFAR results on galaxy clusters

Author: Ferrari, C., van Bemmel, I., Bonafede, A., Bîrzan, L., Brüggen, M., Brunetti, G., Cassano, R., Conway, J., De Gasperin, F., Heald, G., Jackson, N., Macario, G., McKean, J., Offringa, A. R., Orrù, E., Pizzo, R., Rafferty, D. A., Röttgering, H. J. A., Shulevski, A., Tasse, C., van der Tol, S., van Weeren, R. J., Wise, M., van Zwieten, J. E., Boissier, S., de Laverny, P., Nardetto, N., Samadi, R., Valls-Gabaud, D., Wozniak, H., and Kapteyn Astronomical Institute
Subjects: galaxies: clusters: general, Astrophysics::High Energy Astrophysical Phenomena, radio continuum: general, telescopes, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch (z ˜ 1). We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies.
Published: 2012

21. First LOFAR results on galaxy clusters

Author: Ferrari, C., Bemmel, I., Bonafede, A., Bîrzan, L., Brüggen, M., Brunetti, G., Cassano, R., Conway, J., Gasperin, F., Heald, G., Jackson, N., Macario, G., Mckean, J., Offringa, A. R., Orrù, E., Pizzo, R., Rafferty, D. A., Röttgering, H. J. A., Aleksandar Shulevski, Tasse, C., Tol, S., Weeren, R. J., Wise, M., and Zwieten, J. E.
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch. We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies., Comment: Proceedings of the 2012 week of the French Society of Astronomy and Astrophysics (SF2A) held in Nice, June 5th-8th
Published: 2012
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22. First LOFAR results on galaxy clusters

Author: Ferrari, C., van Bemmel, I., Bonafede, A., Bîrzan, L., Brüggen, M., Brunetti, G., Cassano, R., Conway, J., De Gasperin, F., Heald, G., Jackson, N., Macario, G., McKean, J., Offringa, A.R., Orrù, E., Pizzo, R., Rafferty, D.A., Röttgering, H.J.A., Shulevski, A., Tasse, C., van der Tol, S., van Weeren, R.J., Wise, M., van Zwieten, J.E., LOFAR Collaboration, [Unknown], Boissier, S., de Laverny, P., Nardetto, N., Samadi, R., Valls-Gabaud, D., Wozniak, H., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract: Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch (z ˜ 1). We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies.
Published: 2012

23. Host galaxies and environment of active galactic nuclei : a study of the XMM large scale structure survey

Author: Tasse, C., Miley, G., Röttgering, H., and Leiden University
Subjects: Active galactic nuclei, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics, Cosmology
Abstract: Active galactic nuclei (AGN) result from the infall of matter onto the super-massive black holes that are situated at the centres of galaxies. This process releases an enormous amount of energy into the inter-stellar and inter-galactic medium. Hence, the study of AGN becomes essential in the context of galaxy formation theories. With the advent of large astronomical surveys, it has become possible to study many of their properties in great detail. In this thesis, we study the host galaxies and environment of AGN populations in the XMM-LSS multi-wavelength survey. Our aim is to address the following questions: How are the different classes of AGN distributed within the large scale structure of the Universe? What are the mechanisms that trigger AGN activity? Are there connections between triggering processes and AGN properties such as the accretion mode? How have these relations evolved through cosmic time?
Published: 2008

24. The LOFAR Two-meter Sky Survey: Deep Fields Data Release 1

Author: K. C. Chambers, T. Ploeckinger, M. E. Huber, Rachel Cochrane, L. Wang, M. J. Rosenthal, Isabella Prandoni, A. Wo łowska, R. Kondapally, Rosita Paladino, B. Nikiel-Wroczy ński, Philip Best, H. J. A. R öttgering, Timothy W. Shimwell, Martin J. Hardcastle, E. A. Magnier, A. Shulevski, Kenneth Duncan, J. Sabater, V. H. Mahatma, Dominik J. Schwarz, J. H. Croston, Daniel J. Smith, Magdalena Kunert-Bajraszewska, I. McCheyne, D. Nisbet, R. I. J. Mostert, J. D. Wagenveld, Michael J. I. Brown, Matt J. Jarvis, Beatriz Mingo, Wendy L. Williams, S. P. OŚullivan, G. G ürkan, M. Brienza, Arti Goyal, Rebecca A. A. Bowler, M. A. Garrett, M. Br üggen, M. Bondi, M. Bonato, C. Tasse, Marek Jamrozy, Kondapally, R., Best, P. N., Hardcastle, M. J., Nisbet, D., Bonato, M., Sabater, J., Duncan, K. J., McCheyne, I., Cochrane, R. K., Bowler, R. A. A., Williams, W. L., Shimwell, T. W., Tasse, C., Croston, J. H., Goyal, A., Jamrozy, M., Jarvis, M. J., Mahatma, V. H., Röttgering, H. J. A., Smith, D. J. B., Wołowska, A., Bondi, M., Brienza, M., Brown, M. J. I., Brüggen, M., Chambers, K., Garrett, M. A., Gürkan, G., Huber, M., Kunert-Bajraszewska, M., Magnier, E., Mingo, B., Mostert, R., Nikiel-Wroczyński, B., O’Sullivan, S. P., Paladino, R., Ploeckinger, T., Prandoni, I., Rosenthal, M. J., Schwarz, D. J., Shulevski, A., Wagenveld, J. D., Wang, L., Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), and Astronomy
Subjects: catalog, Active galactic nucleus, Cosmology and Nongalactic Astrophysics (astro-ph.CO), media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Population, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Photometry (optics), surveys, Astrophysics - Astrophysics of Galaxie, 0103 physical sciences, survey, Astrophysics - Cosmology and Nongalactic Astrophysic, education, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, media_common, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), radio continuum: galaxies, education.field_of_study, 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, BOOTES, LOFAR, Astrophysics - Astrophysics of Galaxies, Galaxy, Redshift, galaxies [radio continuum], Space and Planetary Science, Sky, Astrophysics of Galaxies (astro-ph.GA), radio continuum: galaxie, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, catalogs, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present the source associations, cross-identifications, and multi-wavelength properties of the faint radio source population detected in the deep tier of the LOFAR Two Metre Sky Survey (LoTSS): the LoTSS Deep Fields. The first LoTSS Deep Fields data release consists of deep radio imaging at 150~MHz of the ELAIS-N1, Lockman Hole, and Bo\"{o}tes fields, down to RMS sensitives of around 20, 22, and 32$~\mu$Jy\,beam$^{-1}$, respectively. These fields are some of the best studied extra-galactic fields in the northern sky, with existing deep, wide-area panchromatic photometry from X-ray to infrared wavelengths, covering a total of $\approx$~26~\mbox{deg$^{2}$}. We first generated improved multi-wavelength catalogues in ELAIS-N1 and Lockman Hole; combined with the existing catalogue for Bo\"{o}tes, we present forced, matched aperture photometry for over 7.2 million sources across the three fields. We identified multi-wavelength counterparts to the radio detected sources, using a combination of the Likelihood Ratio method and visual classification, which greatly enhances the scientific potential of radio surveys and allows for the characterisation of the photometric redshifts and the physical properties of the host galaxies. The final radio-optical cross-matched catalogue consists of 81\,951 radio-detected sources, with counterparts identified and multi-wavelength properties presented for 79\,820 ($>$97\%) sources. We also examine the properties of the host galaxies, and through stacking analysis find that the radio population with no identified counterpart is likely dominated by AGN at $z\sim3-4$. This dataset contains one of the largest samples of radio-selected star-forming galaxies and active galactic nuclei (AGN) at these depths, making it ideal for studying the history of star-formation, and the evolution of galaxies and AGN across cosmic time., Comment: 34 pages, 14 figures and 14 tables. Accepted for publication in A&A special issue. This paper is part of the 1st data release of the LoTSS Deep Fields. Electronic data catalogues will be made available on journal publication
Published: 2021
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25. A snapshot of the oldest active galactic nuclei feedback phases

Author: Annalisa Bonafede, Gianfranco Brunetti, Timothy W. Shimwell, Fabio Gastaldello, Rashid Sunyaev, R. A. Burenin, S. J. D. Purser, Martin J. Hardcastle, F. de Gasperin, Subhash C. Mandal, I. F. Bikmaev, Cyril Tasse, R. J. van Weeren, Marisa Brienza, A. Botteon, Aurora Simionescu, Alessandro Capetti, Marcus Brüggen, I. Khabibullin, E. Churazov, N. Lyskova, H. J. A. Röttgering, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Brienza M., Shimwell T.W., de Gasperin F., Bikmaev I., Bonafede A., Botteon A., Bruggen M., Brunetti G., Burenin R., Capetti A., Churazov E., Hardcastle M.J., Khabibullin I., Lyskova N., Rottgering H.J.A., Sunyaev R., van Weeren R.J., Gastaldello F., Mandal S., Purser S.J.D., Simionescu A., and Tasse C.
Subjects: Buoyancy, Active galactic nucleus, 010504 meteorology & atmospheric sciences, Radiative cooling, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics - astrophysics of galaxies, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, engineering.material, 01 natural sciences, Astrophysics - high energy astrophysical phenomena, Physics::Fluid Dynamics, Galaxy group, 0103 physical sciences, Thermal, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, Physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Galaxy, Magnetic field, engineering, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract: Active galactic nuclei inject large amounts of energy into their host galaxies and surrounding environment, shaping their properties and evolution1,2. In particular, active-galactic-nuclei jets inflate cosmic-ray lobes, which can rise buoyantly as light ‘bubbles’ in the surrounding medium3, displacing and heating the encountered thermal gas and thus halting its spontaneous cooling. These bubbles have been identified in a wide range of systems4,5. However, due to the short synchrotron lifetime of electrons, the most advanced phases of their evolution have remained observationally unconstrained, preventing us from fully understand their coupling with the external medium, and thus active galactic nuclei feedback. Simple subsonic hydrodynamic models6,7 predict that the pressure gradients, naturally present around the buoyantly rising bubbles, transform them into toroidal structures, resembling mushroom clouds in a stratified atmosphere. The way and timescales on which these tori will eventually disrupt depend on various factors including magnetic fields and plasma viscosity8,9. Here we report observations below 200 MHz, sensitive to the oldest radio-emitting particles, showing the late evolution of multiple generations of cosmic-ray active-galactic-nuclei bubbles in a galaxy group with unprecedented level of detail. The bubbles’ buoyancy power can efficiently offset the radiative cooling of the intragroup medium. However, the bubbles still have not thoroughly mixed with the thermal gas, after hundreds of million years, probably under the action of magnetic fields.
Published: 2021
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26. The ultra-steep diffuse radio emission observed in the cool-core cluster RX J1720.1+2638 with LOFAR at 54 MHz

Author: Timothy W. Shimwell, G. Brunetti, A. Botteon, F. de Gasperin, Pasquale Mazzotta, H. J. A. Röttgering, H. Edler, F. Gastaldello, Simona Giacintucci, Cyril Tasse, C. J. Riseley, A. Drabent, Annalisa Bonafede, Rossella Cassano, M. Rossetti, Marcus Brüggen, R. J. van Weeren, Torsten A. Enßlin, Nadia Biava, A. C. Edge, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Biava N., De Gasperin F., Bonafede A., Edler H.W., Giacintucci S., Mazzotta P., Brunetti G., Botteon A., Bruggen M., Cassano R., Drabent A., Edge A.C., Ensslin T., Gastaldello F., Riseley C.J., Rossetti M., Rottgering H.J.A., Shimwell T.W., Tasse C., and Van Weeren R.J.
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Individual, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Secondary electrons, Clusters, 0103 physical sciences, Cluster (physics), Surface brightness, 010303 astronomy & astrophysics, Galaxy cluster, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Spectral index, galaxies: clusters: individual: RX J1720.1+2638, 010308 nuclear & particles physics, Settore FIS/05, Astronomy and Astrophysics, LOFAR, Galaxies, Astrophysics - Astrophysics of Galaxies, RX J1720.1+2638, Radio halo, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Halo, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Diffuse radio emission at the centre of galaxy clusters has been observed both in merging clusters on scales of Mpc, called giant radio haloes, and in relaxed systems with a cool-core on smaller scales, named mini haloes. Giant radio haloes and mini haloes are thought to be distinct classes of sources. However, recent observations have revealed the presence of diffuse radio emission on Mpc scales in clusters that do not show strong dynamical activity. RX J1720.1+2638 is a cool-core cluster, presenting both a bright central mini halo and a fainter diffuse, steep-spectrum emission extending beyond the cluster core that resembles giant radio halo emission. In this paper, we present new observations performed with the LOFAR Low Band Antennas (LBA) at 54 MHz. These observations, combined with data at higher frequencies, allow us to constrain the spectral properties of the radio emission. The large-scale emission presents an ultra-steep spectrum with $\alpha_{54}^{144}\sim3.2$. The radio emission inside and outside the cluster core have strictly different properties, as there is a net change in spectral index and they follow different radio-X-ray surface brightness correlations. We argue that the large-scale diffuse emission is generated by particles re-acceleration after a minor merger. While for the central mini halo we suggest that it could be generated by secondary electrons and positrons from hadronic interactions of relativistic nuclei with the dense cool-core gas, as an alternative to re-acceleration models., Comment: 13 pages, 10 figures; accepted for publication in MNRAS
Published: 2021
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27. LOFAR observations of galaxy clusters in HETDEX: Extraction and self-calibration of individual LOFAR targets

Author: F. Gastaldello, Martin J. Hardcastle, G. Brunetti, R. P. Kraft, F. de Gasperin, E. Bonnassieux, Annalisa Bonafede, Daniele Dallacasa, Matthias Hoeft, C. Tasse, A. Botteon, A. G. Wilber, H. J. A. Röttgering, Timothy W. Shimwell, G. Di Gennaro, M. Rossetti, Marcus Brüggen, V. Cuciti, R. J. van Weeren, F. Andrade-Santos, S. Mandal, J. M. Boxelaar, Rossella Cassano, Van Weeren R.J., Shimwell T.W., Botteon A., Brunetti G., Bruggen M., Boxelaar J.M., Cassano R., DI Gennaro G., Andrade-Santos F., Bonnassieux E., Bonafede A., Cuciti V., Dallacasa D., De Gasperin F., Gastaldello F., Hardcastle M.J., Hoeft M., Kraft R.P., Mandal S., Rossetti M., Rottgering H.J.A., Tasse C., Wilber A.G., Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)
Subjects: Large-scale structure of Universe, Radiation mechanisms: non-thermal, Radiation Mechanisms, Astrophysics::High Energy Astrophysical Phenomena, Cosmic ray, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Clusters, symbols.namesake, Radio relics, Intracluster medium, 0103 physical sciences, Cluster (physics), Planck, General, 010303 astronomy & astrophysics, Galaxy cluster, Astrophysics::Galaxy Astrophysics, Physics, 010308 nuclear & particles physics, X-Rays, Astronomy and Astrophysics, LOFAR, Galaxies, Non-Thermal, Space and Planetary Science, X-rays: galaxies: clusters, Intracluster Medium, symbols, Halo, Galaxies: clusters: general, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena, Galaxies: clusters: intracluster medium, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Diffuse cluster radio sources, in the form of radio halos and relics, reveal the presence of cosmic rays and magnetic fields in the intracluster medium (ICM). These cosmic rays are thought to be (re)accelerated through the ICM turbulence and shock waves generated by cluster merger events. Here we characterize the presence of diffuse radio emission in known galaxy clusters in the HETDEX Spring Field, covering 424 deg2. For this, we developed a method to extract individual targets from LOFAR observations processed with the LoTSS DDF-pipeline software. This procedure enables improved calibration as well as the joint imaging and deconvolution of multiple pointings of selected targets. The calibration strategy can also be used for LOFAR low-band antenna and international-baseline observations. The fraction of Planck PSZ2 catalog clusters with any diffuse radio emission apparently associated with the ICM is 73 ± 17%. We detect a total of ten radio halos and twelve candidate halos in the HETDEX Spring Field. Of these ten radio halos, four are new discoveries, two of which are located in PSZ2 clusters. Five clusters host radio relics, two of which are new discoveries. The fraction of radio halos in Planck PSZ2 clusters is 31 ± 11%, or 62 ± 15% when including the candidate radio halos. Based on these numbers, we expect that there will be at least 183 ± 65 radio halos found in the LoTSS survey in PSZ2 clusters, in agreement with past predictions. The integrated flux densities for the radio halos were computed by fitting exponential models to the radio images. From these flux densities, we determine the cluster mass (M500) and Compton Y parameter (Y500) 150 MHz radio power (P150 MHz) scaling relations for Planck PSZ2-detected radio halos. Using bivariate correlated errors and intrinsic scatter orthogonal regression, we find slopes of 6.13 ± 1.11 and 3.32 ± 0.65 for the M500–P150 MHz and M500–P150 MHz relations, respectively. These values are consistent with the results of previous works.
Published: 2021
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28. Diffuse radio emission from galaxy clusters in the LOFAR two-metre sky survey deep fields

Author: F. Gastaldello, C. Tasse, Subhash C. Mandal, Matteo Bonato, Timothy W. Shimwell, M. Rossetti, Rossella Cassano, R. J. van Weeren, G. Brunetti, Annalisa Bonafede, Martin J. Hardcastle, A. Botteon, G. Di Gennaro, J. Sabater, Philip Best, Huub Röttgering, E. Osinga, J. M. Boxelaar, Marcus Brüggen, Osinga, E., van Weeren, R. J., Boxelaar, J. M., Brunetti, G., Botteon, A., Brüggen, M., Shimwell, T. W., Bonafede, A., Best, P. N., Bonato, M., Cassano, R., Gastaldello, F., di Gennaro, G., Hardcastle, M. J., Mandal, S., Rossetti, M., Röttgering, H. J. A., Sabater, J., and Tasse, C.
Subjects: galaxies: clusters: intracluster medium, Radio Continuum, Astrophysics::High Energy Astrophysical Phenomena, Radiation Mechanisms, Population, radio continuum: general, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Luminosity, Clusters, Radio relics, 0103 physical sciences, education, General, 010303 astronomy & astrophysics, Galaxy cluster, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), education.field_of_study, 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, radiation mechanisms: non-thermal, Galaxies, Non-Thermal, Radio halo, Space and Planetary Science, galaxies: clusters: general, Intracluster Medium, Halo, Low Mass, Astrophysics - High Energy Astrophysical Phenomena
Abstract: Low-frequency radio observations are revealing an increasing number of diffuse synchrotron sources from galaxy clusters, dominantly in the form of radio halos or radio relics. The existence of this diffuse synchrotron emission indicates the presence of relativistic particles and magnetic fields. It is still an open question what mechanisms exactly are responsible for the population of relativistic electrons driving this synchrotron emission. The LOFAR Two-metre Sky Survey Deep Fields offer a unique view of this problem. Reaching noise levels below 30 $��$Jy/beam, these are the deepest images made at the low frequency of 144 MHz. This paper presents a search for diffuse emission in galaxy clusters in the first data release of the LOFAR Deep Fields. We detect a new high-redshift radio halo with a flux density of $8.9 \pm 1.0$ mJy and corresponding luminosity of $P_{144\mathrm{MHz}}=(3.6 \pm 0.6)\times10^{25}$ W Hz$^{-1}$ in an X-ray detected cluster at $z=0.77$ with a mass estimate of $M_{500} = 3.3_{-1.7}^{+1.1} \times 10^{14} M_\odot.$ Deep upper limits are placed on clusters with non-detections. We compare the results to the correlation between halo luminosity and cluster mass derived for radio halos found in the literature. This study is one of few to find diffuse emission in low mass ($M_{500} < 5\times10^{14} M_\odot$) systems and shows that deep low-frequency observations of galaxy clusters are fundamental for opening up a new part of parameter space in the study of non-thermal phenomena in galaxy clusters., This paper is part of the 1st data release of the LoTSS Deep Fields. Re-submitted paper (reply to referee)
Published: 2021

29. Pulsars with NenuFAR: backend and pipelines

Author: Cyril Tasse, A. Possenti, Serge Yerin, Siyuan Chen, L. Bondonneau, C. Viou, M. Serylak, G. Shaifullah, Richard Dallier, J. W. McKee, Z. Wu, Julien N. Girard, Baptiste Cecconi, J.-M. Grießmeier, V. I. Kondratiev, M. Tagger, L. Guillemot, M. Brionne, Maura Pilia, R. A. Main, A. Loh, Ismaël Cognard, P. Zarka, Joris P. W. Verbiest, Caterina Tiburzi, Lilian Martin, Carine Briand, Stephane Corbel, A. V. Bilous, G. Theureau, Olaf Wucknitz, Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Univers et Théories (LUTH (UMR_8102)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Laboratoire de physique subatomique et des technologies associées (SUBATECH), Université de Nantes - Faculté des Sciences et des Techniques, Université de Nantes (UN)-Université de Nantes (UN)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-IMT Atlantique Bretagne-Pays de la Loire (IMT Atlantique), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), INAF - Osservatorio Astronomico di Cagliari (OAC), Istituto Nazionale di Astrofisica (INAF), Universität Bielefeld = Bielefeld University, Institut de Recherches sur les lois Fondamentales de l'Univers (IRFU), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay, Université de Nantes - UFR des Sciences et des Techniques (UN UFR ST), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Laboratoire d'études spatiales et d'instrumentation en astrophysique = Laboratory of Space Studies and Instrumentation in Astrophysics (LESIA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Université de Nantes (UN)-Université de Nantes (UN)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-IMT Atlantique (IMT Atlantique), Bondonneau, L, Griessmeier, J, Theureau, G, Cognard, I, Brionne, M, Kondratiev, V, Bilous, A, Mckee, J, Zarka, P, Viou, C, Guillemot, L, Chen, S, Main, R, Pilia, M, Possenti, A, Serylak, M, Shaifullah, G, Tiburzi, C, Verbiest, J, Wu, Z, Wucknitz, O, Yerin, S, Briand, C, Cecconi, B, Corbel, S, Dallier, R, Girard, J, Loh, A, Martin, L, Tagger, M, Tasse, C, Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)
Subjects: Physics - Instrumentation and Detectors, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, 4/3, 01 natural sciences, frequency: high, Radio telescope, High Energy Physics - Phenomenology (hep-ph), Pulsar, Millisecond pulsar, Observatory, pulsars: general, 0103 physical sciences, site, Instrumentation (computer programming), structure, [PHYS.PHYS.PHYS-INS-DET]Physics [physics]/Physics [physics]/Instrumentation and Detectors [physics.ins-det], 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), pulsar, Physics, radio wave, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], 010308 nuclear & particles physics, Crab Pulsar, Astrophysics::Instrumentation and Methods for Astrophysics, resolution, Astronomy and Astrophysics, LOFAR, Instrumentation and Detectors (physics.ins-det), sensitivity, coherence, observatory, High Energy Physics - Phenomenology, frequency: low, Space and Planetary Science, [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph], dispersion, methods: observational, Astrophysics - Instrumentation and Methods for Astrophysics, performance, Radio wave
Abstract: NenuFAR (New extension in Nan\c{c}ay upgrading LoFAR) is a new radio telescope developed and built on the site of the Nan\c{c}ay Radio Observatory. It is designed to observe the largely unexplored frequency window from 10 to 85\,MHz, offering a high sensitivity across its full bandwidth. NenuFAR has started its "early science" operation in July 2019, with 58\% of its final collecting area being available. Pulsars are one of the major topics for the scientific exploitation of this frequency range and represent an important challenge in terms of instrumentation. Designing instrumentation at these frequencies is complicated by the need to compensate for the effects of both the interstellar medium and the ionosphere on the observed signal. Our real-time pipeline LUPPI (Low frequency Ultimate Pulsar Processing Instrumentation) is able to cope with a high data rate and to provide real-time coherent de-dispersion down to the lowest frequencies reached by NenuFAR (10\,MHz). The full backend functionality is described, as well as the main pulsar observing modes (folded, single-pulse, waveform, and dynamic spectrum). This instrumentation allowed us to detect 172 pulsars in our first targeted search below 85\,MHz, including 10 millisecond pulsars (6 of which detected for the first time below 100 MHz). We also present some of the "early science" results of NenuFAR on pulsars: a high frequency resolution mapping of PSR B1919$+$21's emission profile and a detailed observation of single-pulse sub-structures from PSR~B0809$+$74 down to 16\,MHz, the high rate of giant-pulse emission from the Crab pulsar detected at 68.7\,MHz (43 events/min), and the illustration of the very good timing performance of the instrumentation, allowing us to study dispersion measure variations in great detail., Comment: 13 pages, 14 figures, submitted to A&A
Published: 2020
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30. New constraints on the magnetization of the cosmic web using LOFAR Faraday rotation observations

Author: C. Stuardi, Huub Röttgering, Timothy W. Shimwell, Martin J. Hardcastle, Marcus Brüggen, Cathy Horellou, Nicola Locatelli, V. Vacca, Shane O'Sullivan, Franco Vazza, George Heald, C. Tasse, Ettore Carretti, Tessa Vernstrom, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), O’Sullivan, S P, Brüggen, M, Vazza, F, Carretti, E, Locatelli, N T, Stuardi, C, Vacca, V, Vernstrom, T, Heald, G, Horellou, C, Shimwell, T W, Hardcastle, M J, Tasse, C, Röttgering, H, and PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Astrophysics::High Energy Astrophysical Phenomena, galaxies: active, FOS: Physical sciences, magnetic field, Astrophysics::Cosmology and Extragalactic Astrophysics, magnetization, 01 natural sciences, rotation, techniques: polarimetric -galaxies:active, symbols.namesake, Magnetization, Cosmic web, 0103 physical sciences, Faraday effect, Astrophysics - Cosmology and Nongalactic Astrophysic, structure, AGN, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Physics, radio continuum: galaxies, 010308 nuclear & particles physics, galaxy: radio wave, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy, Astronomy and Astrophysics, LOFAR, Astrophysics - Astrophysics of Galaxies, Automatic Keywords, techniques: polarimetric, field strength, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), symbols, galaxy: cluster, galaxies: magnetic field, large-scale structure of Universe, radio continuum: galaxie, galaxies: magnetic fields, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Measuring the properties of extragalactic magnetic fields through the effect of Faraday rotation provides a means to understand the origin and evolution of cosmic magnetism. Here we use data from the LOFAR Two-Metre Sky Survey (LoTSS) to calculate the Faraday rotation measure (RM) of close pairs of extragalactic radio sources. By considering the RM difference ($\Delta$RM) between physical pairs (e.g. double-lobed radio galaxies) and non-physical pairs (i.e. close projected sources on the sky), we statistically isolate the contribution of extragalactic magnetic fields to $\Delta$RM along the line of sight between non-physical pairs. From our analysis, we find no significant difference between the $\Delta$RM distributions of the physical and non-physical pairs, limiting the excess Faraday rotation contribution to $< 1.9$ rad/m$^2$ ($\sim$$95\%$ confidence). We use this limit with a simple model of an inhomogeneous universe to place an upper limit of 4 nG on the cosmological co-moving magnetic field strength on Mpc scales. We also compare the RM data with a more realistic suite of cosmological MHD simulations, that explore different magnetogenesis scenarios. Both magnetization of the large scale structure by astrophysical processes such as galactic and AGN outflows, and simple primordial scenarios with seed magnetic field strengths $< 0.5$ nG cannot be rejected by the current data; while stronger primordial fields or models with dynamo amplification in filaments are disfavoured., Comment: 13 pages, 8 figures, 2 tables. Accepted to MNRAS. Full version of Table 2 available at https://www.dropbox.com/s/axqrl8sbmj1f2c1/RMpairs_Table_2.dat?dl=0
Published: 2020
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31. LOFAR discovery of a radio halo in the high-redshift galaxy cluster PSZ2 G099.86+58.45

Author: Martin J. Hardcastle, F. Gastaldello, R. J. van Weeren, C. Tasse, Rossella Cassano, Annalisa Bonafede, F. de Gasperin, Mauro Sereno, L. Bîrzan, G. Di Gennaro, Luca Izzo, A. P. Mechev, A. Botteon, Marcus Brüggen, Huub Röttgering, Gianfranco Brunetti, V. Cuciti, Timothy W. Shimwell, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Cassano R., Botteon A., Di Gennaro G., Brunetti G., Sereno M., Shimwell T.W., Van Weeren R.J., Bruggen M., Gastaldello F., Izzo L., Birzan L., Bonafede A., Cuciti V., De Gasperin F., Rottgering H.J.A., Hardcastle M., Mechev A.P., Tasse C., Netherlands Organization for Scientific Research, Ministerio de Ciencia e Innovación (España), Istituto Nazionale di Astrofisica, and European Research Council
Subjects: galaxies: clusters: intracluster medium, Cosmology and Nongalactic Astrophysics (astro-ph.CO), 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, clusters: intracluster medium [Galaxies], Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Largescale structure of universe, Luminosity, Jansky, Intracluster medium, 0103 physical sciences, 010303 astronomy & astrophysics, Galaxy cluster, Astrophysics::Galaxy Astrophysics, clusters: individual (PSZ2 G099.86+58.45) [Galaxies], 0105 earth and related environmental sciences, Physics, non-thermal [Radiation mechanisms], largescale structure of universe, Astronomy and Astrophysics, LOFAR, radiation mechanisms: non-thermal, Astrophysics - Astrophysics of Galaxies, Redshift, Radio halo, Space and Planetary Science, X-rays: galaxies: clusters, Astrophysics of Galaxies (astro-ph.GA), galaxies: clusters [X-rays], Halo, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], galaxies: clusters: individual (PSZ2 G099.86+58.45), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: In this Letter, we report the discovery of a radio halo in the high-redshift galaxy cluster PSZ2 G099.86+58.45 (z = 0.616) with the LOw Frequency ARray (LOFAR) at 120-168 MHz. This is one of the most distant radio halos discovered so far. The diffuse emission extends over ∼1 Mpc and has a morphology similar to that of the X-ray emission as revealed by XMM-Newton data. The halo is very faint at higher frequencies and is barely detected by follow-up 1-2 GHz Karl G. Jansky Very Large Array observations, which enable us to constrain the radio spectral index to be α ≲ 1.5-1.6, i.e., with properties between canonical and ultra-steep spectrum radio halos. Radio halos are currently explained as synchrotron radiation from relativistic electrons that are re-accelerated in the intracluster medium by turbulence driven by energetic mergers. We show that in such a framework radio halos are expected to be relatively common at ∼150 MHz (∼30%-60%) in clusters with mass and redshift similar to PSZ2 G099.86+58.45; however, at least two-thirds of these radio halos should have a steep spectrum and thus be very faint above ∼1 GHz frequencies. Furthermore, because the luminosity of radio halos at high redshift depends strongly on the magnetic field strength in the hosting clusters, future LOFAR observations will also provide vital information on the origin and amplification of magnetic fields in galaxy clusters.© 2019. The American Astronomical Society. All rights reserved., M.S. acknowledges financial contribution from ASI-INAF n.2017-14-H.0. The Leiden LOFAR team acknowledge support from the European Research Council under the FP/2007-2013/ERC Advanced Grant NEWCLUSTERS-321271. R.J.v.W. acknowledges support from the VIDI research program, project number 639.042.729, which is financed by the NWO. A.B. acknowledges financial support from the ERC-Stg DRANOEL, no 714245, and from the MIUR grant FARE SMS. L.I. acknowledges support from funding associated with Juan de la Cierva Incorporacion fellowship IJCI-2016-30940. A.P.M. acknowledge support from the NWO/DOME/IBM program >Big Bang Big Data: Innovating ICT as a Driver For Astronomy,> project #628.002.001. G.B. acknowledges partial support from ASI/INAF n.2017-14-H.O
Published: 2019
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32. LOFAR discovery of a quiet emission mode in PSR B0823+26

Author: F. Breitling, Gottfried Mann, R. Pizzo, John D. Anderson, Cees Bassa, Sera Markoff, Rene P. Breton, Ashish Asgekar, Charlotte Sobey, E. Jütte, George Heald, Heino Falcke, P. Maat, M. J. Norden, M. A. Garrett, Jean-Mathias Grießmeier, Ph. Zarka, Rebecca McFadden, H. Paas, Ben Stappers, E. de Geus, Sarod Yatawatta, V. I. Kondratiev, D. D. Mulcahy, J. van Leeuwen, S. ter Veen, M. Pilia, M. Pandey-Pommier, Ralph A. M. J. Wijers, A. W. Gunst, J. Sluman, Olaf Wucknitz, H. J. A. Röttgering, Philip Best, Christian Vocks, D. McKay-Bukowski, Michel Tagger, D. Carbone, A. Alexov, Andrew Lyne, Antonia Rowlinson, A. Noutsos, Adam Stewart, Chiara Ferrari, T. E. Hassall, Evan Keane, Patrick Weltevrede, Jason W. T. Hessels, Satyendra Thoudam, S. Duscha, M. Serylak, A. van Duin, G. Pietka, Laura Birzan, Jochen Eislöffel, J. P. Hamaker, Wilfred Frieswijk, C. Toribio, Michael Kramer, D. A. Rafferty, A. G. Polatidis, Arthur Corstanje, A. Nelles, John D. Swinbank, Y. Tang, Anna M. M. Scaife, Martin Bell, N. J. Young, V. N. Pandey, Gerard H. Kuper, Cyril Tasse, J. W. Broderick, H. Munk, John McKean, Marcus Brüggen, Matthias Steinmetz, Annalisa Bonafede, A. Renting, Richard Fallows, R. Vermeulen, Mark J. Bentum, Matthias Hoeft, M. de Vos, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, Jörg R. Hörandel, Rob Fender, Oleg Smirnov, Emanuela Orru, Dominik J. Schwarz, I. M. Avruch, Anna V. Bilous, R. J. van Weeren, Sobey, C., Young, N.J., Hessels, J.W.T., Weltevrede, P., Noutsos, A., Stappers, B.W., Kramer, M., Bassa, C., Lyne, A.G., Kondratiev V.I., null, Hassall, T.E., Keane, E.F., Bilous, A.V., Breton, R.P., Grießmeier, J.M., Karastergiou, A., Pilia, M., Serylak, M., Ter Veen, S., Van Leeuwen, J., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Best, P., Bĭrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Corstanje, A., Carbone, D., De Geus, E., De Vos, M., Van Duin, A., Duscha, S., Eislöffel, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Gunst, A.W., Hamaker, J.P., Heald, G., Hoeft, M., Hörandel, J., Jütte, E., Kuper, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orrù, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Rafferty, D., Renting, A., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Sluman, J., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Max-Planck-Institut für Radioastronomie (MPIFR), University of Minnesota [Twin Cities] (UMN), University of Minnesota System, University of Amsterdam [Amsterdam] (UvA), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Columbia Astrophysics Laboratory (CAL), Columbia University [New York], Cornell University [New York], Netherlands Institute for Radio Astronomy (ASTRON), Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Oxford Astrophysics, University of Oxford, Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), SRON Netherlands Institute for Space Research (SRON), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Département de Géologie, Université de Montréal (UdeM), University Bochum, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, School of Physics and Astronomy [Southampton], Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, We would like to thank R. Karuppusamy for his help with the Effelsberg observations. CF acknowledges financial support by the Agence Nationale de la Recherche through grant ANR-09-JCJC-0001-01., European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), ITA, GBR, FRA, DEU, NLD, Radboud university [Nijmegen], Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: stars, PSR B0823+26-radio telescopes, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Pulsar planet, FOS: Physical sciences, neutron- pulsars, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, neutron [stars], Pulsar, Millisecond pulsar, Pulsars: individual: PSR B0823+26, individual, Solar and Stellar Astrophysics (astro-ph.SR), Astrophysics::Galaxy Astrophysics, Astroparticle physics, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Stars: neutron, Stars, Neutron star, Astrophysics - Solar and Stellar Astrophysics, magnetosphere-pulsars, [SDU]Sciences of the Universe [physics], Space and Planetary Science, QUIET, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, individual: PSR B0823+26 [pulsars]
Abstract: PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over timescales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insight into the relationship between these various emission phenomena and what they might teach us about pulsar magnetospheres. Here we report on the LOFAR discovery that PSR B0823+26 has a weak and sporadically emitting 'quiet' (Q) emission mode that is over 100 times weaker (on average) and has a nulling fraction forty-times greater than that of the more regularly-emitting 'bright' (B) mode. Previously, the pulsar has been undetected in the Q-mode, and was assumed to be nulling continuously. PSR B0823+26 shows a further decrease in average flux just before the transition into the B-mode, and perhaps truly turns off completely at these times. Furthermore, simultaneous observations taken with the LOFAR, Westerbork, Lovell, and Effelsberg telescopes between 110 MHz and 2.7 GHz demonstrate that the transition between the Q-mode and B-mode occurs within one single rotation of the neutron star, and that it is concurrent across the range of frequencies observed., Comment: 15 pages, 8 figures, 2 tables, accepted for publication in MNRAS
Published: 2015
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33. Synchronous X-ray and Radio Mode Switches: A Rapid Global Transformation of the Pulsar Magnetosphere

Author: Y. Tang, Anna M. M. Scaife, Steve Rawlings, Aris Karastergiou, Michael W. Wise, Harvey Butcher, B. Ciardi, S. Duscha, V. N. Pandey, Gianni Bernardi, John McKean, Charlotte Sobey, Emanuela Orrú, Chiara Ferrari, M. Kuniyoshi, H. Munk, Marcus Brüggen, Michael Kramer, Cyril Tasse, J. W. Broderick, E. de Geus, Ashish Asgekar, Jason W. T. Hessels, F. de Gasperin, Matthias Hoeft, George Heald, L. Kuiper, A. P. Schoenmakers, P. Maat, R. H. van de Brink, Sera Markoff, Dipanjan Mitra, Philip Best, G. Wright, Ralph A. M. J. Wijers, J. de Plaa, Heino Falcke, V. I. Kondratiev, Rahul Basu, A. Noutsos, T. Coenen, Benjamin Stappers, Michel Tagger, Frank Breitling, Giulia Macario, Rob Fender, Rene C. Vermeulen, Michael R. Bell, F. Batejat, A. Alexov, Marco Iacobelli, H. Paas, Sarod Yatawatta, Patrick Weltevrede, Tim Hassall, R. J. van Weeren, W. Reich, M. Pilia, Laura Birzan, W. Hermsen, Evan Keane, Aleksandar Shulevski, Mark J. Bentum, M. Serylak, Martin Bell, Annalisa Bonafede, J. van Leeuwen, A. Horneffer, Jochen Eislöffel, Maaijke Mevius, H. J. A. Röttgering, A. G. Polatidis, R. Morganti, I. M. Avruch, S. ter Veen, A. W. Gunst, Olaf Wucknitz, Matthias Steinmetz, M. Pandey-Pommier, K. Zagkouris, J. Sluman, Roberto Pizzo, Jean-Mathias Grießmeier, G. Kuper, Philippe Zarka, Joanna M. Rankin, M. A. Garrett, James Miller-Jones, Wilfred Frieswijk, Hermsen, W., Hessels, J.W.T., Kuiper, L., Van Leeuwen, J., Mitra, D., De Plaa, J., Rankin, J.M., Stappers, B.W., Wright, G.A.E., Basu, R., Alexov, A., Coenen, T., Grießmeier, J.-M., Hassall, T.E., Karastergiou, A., Keane, E., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Noutsos, A., Serylak, M., Pilia, M., Sobey, C., Weltevrede, P., Zagkouris, K., Asgekar, A., Avruch, I.M., Batejat, F., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Duscha, S., Eislöffel, J., Falcke, H., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., De Gasperin, F., De Geus, E., Gunst, A.W., Heald, G., Hoeft, M., Horneffer, A., Iacobelli, M., Kuper, G., Maat, P., Macario, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Morganti, R., Munk, H., Orrú, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Rawlings, S., Reich, W., Röttgering, H., Scaife, A.M.M., Schoenmakers, A., Shulevski, A., Sluman, J., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Vermeulen, R., Van De Brink, R.H., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., SRON Netherlands Institute for Space Research (SRON), University of Amsterdam [Amsterdam] (UvA), National Centre for Radio Astrophysics [Pune] (NCRA), Tata Institute for Fundamental Research (TIFR), University of Vermont [Burlington], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Astronomy Centre, University of Sussex, Space Telescope Science Institute (STSci), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Oxford Astrophysics, University of Oxford, Centre for Astrophysics and Supercomputing, Swinburne University of Technology [Melbourne], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], University of Southampton, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Leiden Observatory [Leiden], Universiteit Leiden, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Medstar Research Institute, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], SKA South Africa, Ska South Africa, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Kapteyn Astronomical Institute, Astronomy, Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Electromagnetic field, POLARIZATION, Electromagnetic spectrum, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, FOS: Physical sciences, Magnetosphere, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, EMPIRICAL-THEORY, 01 natural sciences, Binary pulsar, Pulsar, Millisecond pulsar, 0103 physical sciences, 010306 general physics, XMM-NEWTON OBSERVATIONS, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, DRIFTING SUBPULSES, Multidisciplinary, B0943+10, Polarization (waves), GAMMA-RAY, [SDU]Sciences of the Universe [physics], 13. Climate action, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, RADIATION, EMISSION, Astrophysics - High Energy Astrophysical Phenomena, PHOTON IMAGING CAMERA, POWERED PULSARS, Radio wave
Abstract: Pulsars emit low-frequency radio waves through to high-energy gamma-rays that are generated anywhere from the surface out to the edges of the magnetosphere. Detecting correlated mode changes in the multi-wavelength emission is therefore key to understanding the physical relationship between these emission sites. Through simultaneous observations, we have detected synchronous switching in the radio and X-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio 'bright' mode, the X-rays show only an un-pulsed, non-thermal component. Conversely, when the pulsar is in a radio 'quiet' mode, the X-ray luminosity more than doubles and a 100%-pulsed thermal component is observed along with the non-thermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories., Paper published in Science including supplementary material
Published: 2013
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34. Wide-band, low-frequency pulse profiles of 100 radio pulsars with LOFAR

Author: J. van Leeuwen, Matthias Steinmetz, T. E. Hassall, A. Nelles, E. de Geus, M. Pilia, B. W. Stappers, Heino Falcke, H. J. A. Röttgering, Annalisa Bonafede, Oleg Smirnov, Anna V. Bilous, Satyendra Thoudam, Evan Keane, Peter G. Jonker, W. Frieswijk, Rudy Wijnands, A. Noutsos, M. Pietka, John D. Swinbank, Richard Fallows, R. J. van Weeren, M. Pandey-Pommier, Olaf Wucknitz, A. Alexov, Rebecca McFadden, E. Juette, F. Breitling, Stefan J. Wijnholds, Aris Karastergiou, Benedetta Ciardi, H. Paas, Antonia Rowlinson, Dominik J. Schwarz, Michael Kramer, A. I. F. Stewart, Y. Tang, Ashish Asgekar, K. Zagkouris, James A. Anderson, Chiara Ferrari, S. Duscha, James Miller-Jones, Andrew Lyne, Stefan Oslowski, Adam T. Deller, A. de Jong, R. C. Vermeulen, Gianni Bernardi, I. M. Avruch, M. A. Garrett, M. C. Toribio, Jochen Eislöffel, Charlotte Sobey, A. J. van der Horst, Rene P. Breton, Cyril Tasse, Marcus Brüggen, J. W. Broderick, Gerard H. Kuper, S. ter Veen, A. W. Gunst, Rob Fender, P. Zarka, D. McKay-Bukowski, Martin Bell, A. Horneffer, M. Kuniyoshi, Patrick Weltevrede, M. Serylak, A. G. Polatidis, Ralph A. M. J. Wijers, Mark J. Bentum, Christian Vocks, Jean-Mathias Grießmeier, Sera Markoff, Jason W. T. Hessels, Stephane Corbel, Laura Birzan, J. P. Hamaker, Wolfgang Reich, Michel Tagger, P. Maat, V. I. Kondratiev, George Heald, Gottfried Mann, R. Pizzo, Astronomy, Netherlands Institute for Radio Astronomy (ASTRON), Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Oxford Astrophysics, University of Oxford, School of Physics and Astronomy [Southampton], University of Southampton, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Centre for Astrophysics and Supercomputing [Swinburne] (CAS), Swinburne University of Technology [Melbourne], Department of Physics [Oxford], Max-Planck-Institut für Radioastronomie (MPIFR), Universität Bielefeld = Bielefeld University, University of Cape Town, Space Telescope Science Institute (STSci), Epidémiologie et Biostatistique [Bordeaux], Université Bordeaux Segalen - Bordeaux 2-Institut de Santé Publique, d'Épidémiologie et de Développement (ISPED)-Institut National de la Santé et de la Recherche Médicale (INSERM), SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], University of Hamburg, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), University of Edinburgh, Max-Planck-Institut für Astrophysik (MPA), Max-Planck-Gesellschaft, Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Structural Dynamics and Acoustics, University of Twente, Thüringer Landessternwarte Tautenburg (TLS), Institute of Mathematical and Physical Sciences, Department of Astrophysics [Oxford], Département de Géologie, Université de Montréal (UdeM), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Leibniz-Institut für Astrophysik Potsdam (AIP), Department of Physical Sciences, University of Oulu, University of Oulu, Curtin University [Perth], Planning and Transport Research Centre (PATREC), University of Groningen [Groningen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Australia Telescope National Facility (ATNF), Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Institute of Farm Animal Genetics (ING), Friedrich-Loeffler-Institut (FLI), SKA South Africa, Ska South Africa, Astrophysikalisches Institut Potsdam (AIP), Department of Physics [Dunedin], University of Otago [Dunedin, Nouvelle-Zélande], Princeton University, Edinburgh Research Station, Centre for Ecology and Hydrology, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Department of Astrophysics [Nijmegen], Radboud University [Nijmegen]-Radboud University [Nijmegen], Anton Pannekoek Institute for Astronomy, Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Alexander von Humboldt Foundation Agence Nationale de la Recherche ANR-09-JCJC-0001-01, ANR-09-JCJC-0001,OPALES(2009), European Project: 337062,EC:FP7:ERC,ERC-2013-StG,DRAGNET(2014), European Project: 617199,EC:FP7:ERC,ERC-2013-CoG,ALERT(2014), European Project: 224838,EC:FP7:PEOPLE,FP7-PEOPLE-2007-4-3-IRG,PULSARS WITH LOFAR(2008), ROUCHON, Nathalie, Jeunes chercheuses et jeunes chercheurs - - OPALES2009 - ANR-09-JCJC-0001 - JCJC - VALID, DRAGNET: A high-speed, wide-angle camera for catching extreme astrophysical events - DRAGNET - - EC:FP7:ERC2014-01-01 - 2018-12-31 - 337062 - VALID, ALERT - The Apertif-LOFAR Exploration of the Radio Transient Sky - ALERT - - EC:FP7:ERC2014-12-01 - 2019-11-30 - 617199 - VALID, Radio pulsars with LOFAR: a study of extreme physics laboratories. - PULSARS WITH LOFAR - - EC:FP7:PEOPLE2008-05-01 - 2012-04-30 - 224838 - VALID, High Energy Astrophys. & Astropart. Phys (API, FNWI), University of Oxford [Oxford], Radboud university [Nijmegen], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Fakultät für Physik, Universität Bielefeld, Universität Bielefeld, University of the Western Cape, Cape Town, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), University of Twente [Netherlands], Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Radboud university [Nijmegen]-Radboud university [Nijmegen], Harvard University-Smithsonian Institution, Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Pilia, M., Hessels, J.W.T., Stappers, B.W., Kondratiev, V.I., Kramer, M., Van Leeuwen, J., Weltevrede, P., Lyne, A.G., Zagkouris, K., Hassall, T.E., Bilous, A.V., Breton, R.P., Falcke, H., Grießmeier, J.-M., Keane, E., Karastergiou, A., Kuniyoshi, M., Noutsos, A., Osłowski, S., Serylak, M., Sobey, C., Ter Veen, S., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Bîrzan, L., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Ciardi, B., Corbel, S., De Geus, E., De Jong, A., Deller, A., Duscha, S., Eislöffel, J., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Gunst, A.W., Hamaker, J.P., Heald, G., Horneffer, A., Jonker, P., Juette, E., Kuper, G., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., Miller-Jones, J.C.A., Nelles, A., Paas, H., Pandey-Pommier, M., Pietka, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Rowlinson, A., Schwarz, D., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J.D., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, M.C., Van Der Horst, A.J., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wijnands, R., Wijnholds, S.J., Wucknitz, O., and Zarka, P.
Subjects: Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Astrophysics, METIS-321663, Astrophysics::Cosmology and Extragalactic Astrophysics, Low frequency, 01 natural sciences, Radio spectrum, law.invention, Telescope, Radio telescope, [SDU] Sciences of the Universe [physics], stars: neutron, Pulsar, law, pulsars: general, 0103 physical sciences, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), IR-103184, Solar and Stellar Astrophysics (astro-ph.SR), Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Interstellar medium, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Radio frequency, EWI-27451, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: LOFAR offers the unique capability of observing pulsars across the 10-240 MHz frequency range with a fractional bandwidth of roughly 50%. This spectral range is well-suited for studying the frequency evolution of pulse profile morphology caused by both intrinsic and extrinsic effects: such as changing emission altitude in the pulsar magnetosphere or scatter broadening by the interstellar medium, respectively. The magnitude of most of these effects increases rapidly towards low frequencies. LOFAR can thus address a number of open questions about the nature of radio pulsar emission and its propagation through the interstellar medium. We present the average pulse profiles of 100 pulsars observed in the two LOFAR frequency bands: High Band (120-167 MHz, 100 profiles) and Low Band (15-62 MHz, 26 profiles). We compare them with Westerbork Synthesis Radio Telescope (WSRT) and Lovell Telescope observations at higher frequencies (350 and1400 MHz) in order to study the profile evolution. The profiles are aligned in absolute phase by folding with a new set of timing solutions from the Lovell Telescope, which we present along with precise dispersion measures obtained with LOFAR. We find that the profile evolution with decreasing radio frequency does not follow a specific trend but, depending on the geometry of the pulsar, new components can enter into, or be hidden from, view. Nonetheless, in general our observations confirm the widening of pulsar profiles at low frequencies, as expected from radius-to-frequency mapping or birefringence theories. We offer this catalog of low-frequency pulsar profiles in a user friendly way via the EPN Database of Pulsar Profiles (http://www.epta.eu.org/epndb/)., Comment: 38 pages, 11 figures, 5 tables, A&A in press, updated with editorial corrections
Published: 2016
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35. Imaging Jupiter's radiation belts down to 127 MHz with LOFAR

Author: Gianni Bernardi, Jörg R. Hörandel, A. G. Polatidis, Ashish Asgekar, A. Nelles, Angélica Sicard, H. Munk, R. J. van Weeren, Jason W. T. Hessels, D. McKay-Bukowski, I. de Pater, Matthias Hoeft, Oleg Smirnov, A. W. Gunst, Frank Breitling, Arthur Corstanje, Sebastien Hess, Quentin Nénon, Mark J. Bentum, J. van Leeuwen, R. C. Vermeulen, M. Loose, P. Zarka, H. J. A. Röttgering, P. Maat, M. J. Norden, M. Tagger, J. Moldón, F. de Gasperin, S. Bourdarie, Rene P. Breton, Annalisa Bonafede, John D. Swinbank, I. van Bemmel, Stephane Corbel, Martin Bell, V. I. Kondratiev, M. Pandey-Pommier, M. Iacobelli, James M. Anderson, Roberto Pizzo, Marcus Brüggen, Satyendra Thoudam, M. C. Toribio, Gerard H. Kuper, Antonia Rowlinson, Jochen Eislöffel, S. Duscha, Rebecca McFadden, M. A. Garrett, Daniel Santos-Costa, Julien N. Girard, Matthias Steinmetz, B. Ciardi, O. Wucknitz, J.-M. Grießmeier, M. Kuniyoshi, Ralph A. M. J. Wijers, Wilfred Frieswijk, Heino Falcke, C. Tasse, W. N. Brouw, S. Markov, Emanuela Orrú, H. Paas, Adam Deller, W. Reich, Dominik J. Schwarz, J. W. Broderick, E. Juette, G. Mann, Philip Best, C. Vocks, E. de Geus, Girard, J.N., Zarka, P., Tasse, C., Hess, S., De Pater, I., Santos-Costa, D., Nenon, Q., Sicard, A., Bourdarie, S., Anderson, J., Asgekar, A., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Breton, R.P., Broderick, J.W., Brouw, W.N., Brüggen, M., Ciardi, B., Corbel, S., Corstanje, A., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Falcke, H., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hessels, J.W.T., Hoeft, M., Hörandel, J., Iacobelli, M., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Loose, M., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., Moldon, J., Munk, H., Nelles, A., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Rowlinson, A., Schwarz, D., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wucknitz, O., Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, ONERA - The French Aerospace Lab [Toulouse], ONERA, Netherlands Institute for Radio Astronomy (ASTRON), University of Southampton, Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Royal Observatory Edinburgh (ROE), University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Radboud University [Nijmegen], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Department of Pure Mathematics and Mathematical Statistics (DPMMS), Faculty of mathematics Centre for Mathematical Sciences [Cambridge] (CMS), University of Cambridge [UK] (CAM)-University of Cambridge [UK] (CAM), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), University of Oulu, University of Groningen [Groningen], Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), CSIRO Astronomy and Space Science, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Universität Bielefeld, Rhodes University, Grahamstown, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, ANR-11-IDEX-0005,USPC,Université Sorbonne Paris Cité(2011), European Project: 228261,EC:FP7:ERC,ERC-2008-AdG,SPARSEASTRO(2009), ITA, GBR, FRA, DEU, NLD, Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Radboud university [Nijmegen], Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Jodrell Bank Centre for Astrophysics, Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), DPMMS/CMS, University of Cambridge [UK] (CAM), ANR-11-IDEX-0005-02/10-LABX-0023,UnivEarthS,Earth - Planets - Universe: observation, modeling, transfer(2011), Astronomy, High Energy Astrophys. & Astropart. Phys (API, FNWI), and Faculty of Science
Subjects: radio continuum: planetary systems, Brightness, 010504 meteorology & atmospheric sciences, radio continuum: planetary, EWI-27447, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Magnetosphere, FOS: Physical sciences, Astrophysics, Electron, METIS-321662, 7. Clean energy, 01 natural sciences, Jupiter, symbols.namesake, 0103 physical sciences, Emission spectrum, IR-103183, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 0105 earth and related environmental sciences, Physics, Earth and Planetary Astrophysics (astro-ph.EP), [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Radio continuum: planetary system, Planets and satellites: magnetic field, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, planets and satellites: magnetic fields, Spectral flux density, 13. Climate action, Space and Planetary Science, Van Allen radiation belt, Techniques: interferometric, symbols, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, systems, Astrophysics::Earth and Planetary Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: Context. Observing Jupiter's synchrotron emission from the Earth remains today the sole method to scrutinize the distribution and dynamical behavior of the ultra energetic electrons magnetically trapped around the planet (because in-situ particle data are limited in the inner magnetosphere). Aims. We perform the first resolved and low-frequency imaging of the synchrotron emission with LOFAR at 127 MHz. The radiation comes from low energy electrons (~1-30 MeV) which map a broad region of Jupiter's inner magnetosphere. Methods (see article for complete abstract) Results. The first resolved images of Jupiter's radiation belts at 127-172 MHz are obtained along with total integrated flux densities. They are compared with previous observations at higher frequencies and show a larger extent of the synchrotron emission source (>=4 $R_J$). The asymmetry and the dynamic of east-west emission peaks are measured and the presence of a hot spot at lambda_III=230 {\deg} $\pm$ 25 {\deg}. Spectral flux density measurements are on the low side of previous (unresolved) ones, suggesting a low-frequency turnover and/or time variations of the emission spectrum. Conclusions. LOFAR is a powerful and flexible planetary imager. The observations at 127 MHz depict an extended emission up to ~4-5 planetary radii. The similarities with high frequency results reinforce the conclusion that: i) the magnetic field morphology primarily shapes the brightness distribution of the emission and ii) the radiating electrons are likely radially and latitudinally distributed inside about 2 $R_J$. Nonetheless, the larger extent of the brightness combined with the overall lower flux density, yields new information on Jupiter's electron distribution, that may shed light on the origin and mode of transport of these particles., Comment: 10 pages, 12 figures, accepted for publication in A&A (27/11/2015) - abstract edited because of limited characters
Published: 2015
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36. LOFAR tied-array imaging and spectroscopy of solar S bursts

Author: B. Ciardi, Helmut O. Rucker, Mario M. Bisi, J. van Leeuwen, J. Sluman, Roberto Pizzo, M. C. Toribio, Jochen Eislöffel, J. W. Broderick, Gerard H. Kuper, Pietro Zucca, Harvey Butcher, V. I. Kondratiev, Aidan M. O'Flannagain, Alain Kerdraon, Mark J. Bentum, Matthias Hoeft, Wilfred Frieswijk, W. N. Brouw, M. A. Garrett, E. de Geus, A. A. Konovalenko, Anna M. M. Scaife, G. Mann, H. Munk, Annalisa Bonafede, James M. Anderson, A. Karastergiou, Philippe Zarka, H. Paas, I. M. Avruch, Heino Falcke, Jean-Mathias Griessmeier, F. Breitling, R. Vermeulen, Jason W. T. Hessels, Bo Thidé, Peter T. Gallagher, John McKean, A. G. Polatidis, Emanuela Orrú, C. Tasse, Ashish Asgekar, D. McKay-Bukowski, Diana E. Morosan, C. Vocks, Jasmina Magdalenic, Richard Fallows, A. Alexov, A. W. Gunst, Gianni Bernardi, Hamish A. S. Reid, Alexander L. MacKinnon, Trinity College Dublin, Netherlands Institute for Radio Astronomy (ASTRON), University of Glasgow, Leibniz-Institut für Astrophysik Potsdam (AIP), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute of Radio Astronomy of NASU [Kharkiv] (IRA), National Academy of Sciences of Ukraine (NASU), Lawrence Livermore National Laboratory (LLNL), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Swedish Institute of Space Physics [Uppsala] (IRF), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Jacobs University [Bremen], University of Southampton, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), University of Amsterdam [Amsterdam] (UvA), University of Oxford, University of Oulu, School of Physics and Astronomy [Southampton], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Kapteyn Astronomical Institute, Astronomy, ITA, GBR, FRA, DEU, NLD, High Energy Astrophys. & Astropart. Phys (API, FNWI), Harvard University [Cambridge]-Smithsonian Institution, Radboud university [Nijmegen], Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Smithsonian Institution-Harvard University [Cambridge], Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Morosan, D.E., Gallagher, P.T., Zucca, P., O'Flannagain, A., Fallows, R., Reid, H., Magdalenic, J., Mann, G., Bisi, M.M., Kerdraon, A., Konovalenko, A.A., MacKinnon, A.L., Rucker, H.O., Thide, B., Vocks, C., Alexov, A., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Bonafede, A., Breitling, F., Broderick, J.W., Brouw, W.N., Butcher, H.R., Ciardi, B., De Geus, E., Eisloffel, J., Falcke, H., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hessels, J.W.T., Hoeft, M., Karastergiou, A., Kondratiev, V.I., Kuper, G., Van Leeuwen, J., McKay-Bukowski, D., McKean, J.P., Munk, H., Orru, E., Paas, H., Pizzo, R., Polatidis, A.G., Scaife, A.M.M., Sluman, J., Tasse, C., Toribio, M.C., Vermeulen, R., and Zarka, P.
Subjects: POLARIZATION, 010504 meteorology & atmospheric sciences, corona [Sun], Astronomy, METIS-315083, Astrophysics, particle emission [Sun], 01 natural sciences, CORONA, law.invention, law, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, Maser, 010303 astronomy & astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), Sun: magnetic fields, Physics, Sun: radio radiation, Nanoflares, Astrophysics - Solar and Stellar Astrophysics, magnetic fields [Sun], Physical Sciences, Radio frequency, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Context (language use), Low frequency, Astronomy & Astrophysics, FREQUENCY, Radio telescope, Sun: particle emission, 0103 physical sciences, Sun: magnetic field, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Science & Technology, III RADIO-BURSTS, Sun: corona, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], radio radiation [Sun], Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Sun: corona – Sun: radio radiation – Sun: particle emission – Sun: magnetic fields, 13. Climate action, Space and Planetary Science, DENSITY, SPIKES, IR-98664, RADIATION, EWI-26541, FINE-STRUCTURE
Abstract: Context. The Sun is an active source of radio emission that is often associated with energetic phenomena ranging from nanoflares to coronal mass ejections (CMEs). At low radio frequencies (, 6 pages, 4 figures
Published: 2015
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37. Lunar occultation of the diffuse radio sky: LOFAR measurements between 35 and 80 MHz

Author: Vibor Jelić, Martin Bell, Gottfried Mann, Michael W. Wise, Gianni Bernardi, Wilfred Frieswijk, Jörg R. Hörandel, Garrelt Mellema, J. W. Broderick, J. Anderson, E. de Geus, George Heald, Y. Tang, K. M. B. Asad, M. J. Norden, Heino Falcke, Michiel A. Brentjens, Luitje Koopmans, V. I. Kondratiev, Arthur Corstanje, de Antonius Bruyn, A. Renting, Michel Tagger, Ben Stappers, Elizabeth Fernandez, F. de Gasperin, S. Kazemi, Emanuela Orrú, O. Martinez-Rubi, Rob Fender, A. Nelles, Oleg Smirnov, Stefan J. Wijnholds, P. Lambropoulos, A. R. Offringa, Annalisa Bonafede, Emma Chapman, Hannes Jensen, E. Juette, D. Engels, Sera Markoff, C. Toribio, Abhik Ghosh, F. B. Abdalla, Rebecca McFadden, Roberto Pizzo, Marco Iacobelli, Sarod Yatawatta, S. Daiboo, Satyendra Thoudam, W. Reich, D. McKay-Bukowski, Dominik J. Schwarz, D. D. Mulcahy, A. H. Patil, Frank Breitling, Jochen Eislöffel, B. Ciardi, Maaijke Mevius, Mark J. Bentum, C. Tasse, V. Veligatla, A. G. Polatidis, Matthias Steinmetz, S. Bus, Vishambhar Pandey, M. Kuniyoshi, Philippe Zarka, S. ter Veen, Adam Deller, Chiara Ferrari, A. W. Gunst, Ashish Asgekar, Matthias Hoeft, Philip Best, A. Shulevski, John D. Swinbank, H. Munk, Marcus Brüggen, Geraint Harker, Jean-Mathias Grießmeier, Tim Hassall, Christian Vocks, Saleem Zaroubi, Rajat M. Thomas, John McKean, Harvey Butcher, M. Pandey-Pommier, S. Duscha, Harish Vedantham, Richard Fallows, M. A. Garrett, H. J. A. Röttgering, Olaf Wucknitz, G. Kuper, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), Netherlands Institute for Radio Astronomy (ASTRON), University College of London [London] (UCL), Laboratoire de Mécanique des Contacts et des Structures [Villeurbanne] (LaMCoS), Institut National des Sciences Appliquées de Lyon (INSA Lyon), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS), Mécanique multiphysique pour les matériaux et les procédés (MULTIMAP), Université de Lyon-Institut National des Sciences Appliquées (INSA)-Université de Lyon-Institut National des Sciences Appliquées (INSA)-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées de Lyon (INSA Lyon), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Howard Hugues Medical Institute, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Departamento de Geologıa, Universidad de Santiago de Chile [Santiago] (USACH), Advanced Computing and Microelectronics Unit [Kolkata] (ACMU), Indian Statistical Institute [Kolkata], Department of Physics and Astronomy [UCL London], Stockholm University, Department of process and energy, Delft University of Technology (TU Delft), Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Stockholm Observatory Department of Astronomy, Department of Physics and Astronomy [Ghent], Ghent University [Belgium] (UGENT), Spatial Ecology and Epidemiology Group, University of Oxford [Oxford], Plant Ind, Hort Unit, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Institute for Mathematics Applied to Geoscience, National Center for Atmospheric Research [Boulder] (NCAR), CSIRO Astronomy and Space Science, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), University of Southampton, Radboud university [Nijmegen], Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Metacohorts Consortium, Thüringer Landessternwarte Tautenburg (TLS), Département de Géologie, Université de Montréal [Montréal], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Unité Scientifique de la Station de Nançay (USN), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), University of Oulu, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Centre de Recherche Astrophysique de Lyon (CRAL), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-École normale supérieure - Lyon (ENS Lyon), Interactions Son Musique Mouvement, Sciences et Technologies de la Musique et du Son (STMS), Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC)-IRCAM-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen]-Radboud university [Nijmegen], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Observatoire de Paris - Site de Paris (OP), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), European Project: 258942,EC:FP7:ERC,ERC-2010-StG_20091028,FIRSTLIGHT(2010), Howard Hughes Medical Institute (HHMI), Universiteit Gent = Ghent University (UGENT), University of Oxford, Radboud University [Nijmegen], Université de Montréal (UdeM), Universiteit Leiden, Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche et Coordination Acoustique/Musique (IRCAM)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, Grahamstown, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen]-Radboud University [Nijmegen], Agence Nationale de la Recherche (ANR-09-JCJC-0001-01), Peuplements végétaux et bioagresseurs en milieu tropical (UMR PVBMT), Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Institut de Recherche pour le Développement (IRD)-Institut National de la Recherche Agronomique (INRA)-Université de La Réunion (UR), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Gent = Ghent University [Belgium] (UGENT), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Vedantham, H.K., Koopmans, L.V.E., de Bruyn, A.G., Wijnholds, S.J., Brentjens, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E.R., Ghosh, A., Harker, G., Jelic, V., Jensen, H., Kazemi, S., Lambropoulos, P., Martinez-Rubi, O., Mellema, G., Mevius, M., Offringa, A.R., Pandey, V.N., Patil, A.H., Thomas, R.M., Veligatla, V., Yatawatta, S., Zaroubi, S., Anderson, J., Asgekar, A., Bell, M.E., Bentum, M.J., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Corstanje, A., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hassall, T.E., Heald, G., Hoeft, M., Hörandel, J., Iacobelli, M., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., Markoff, S., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orru, E., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Renting, A., Röttgering, H., Schwarz, D., Shulevski, A., Smirnov, O., Stappers, B.W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Thoudam, S., Toribio, C., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Astronomy, Kapteyn Astronomical Institute, ITA, GBR, FRA, DEU, NLD, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), media_common.quotation_subject, Astrophysics::High Energy Astrophysical Phenomena, Astronomy, first stars, observational [methods], FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, methods: observational, techniques: interferometric, Moon, dark ages, reionization, methods: observational – techniques: interferometric – Moon – cosmology: dark ages, Occultation, IR-98655, Reionization, Instrumentation and Methods for Astrophysics (astro-ph.IM), media_common, EWI-26150, Astroparticle physics, Physics, Epoch (reference date), Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Universe, interferometric [techniques], Dark ages, reionization, first star, Sky, Space and Planetary Science, [SDU]Sciences of the Universe [physics], Physics::Space Physics, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Dark Ages, Astrophysics::Earth and Planetary Astrophysics, METIS-314921, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present radio observations of the Moon between $35$ and $80$ MHz to demonstrate a novel technique of interferometrically measuring large-scale diffuse emission extending far beyond the primary beam (global signal) for the first time. In particular, we show that (i) the Moon appears as a negative-flux source at frequencies $35z>12$) and the Epoch of Reionization ($12>z>5$)., Comment: 15 pages, 11 figures, 1 table
Published: 2015
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38. Probing Atmospheric Electric Fields in Thunderstorms through Radio Emission from Cosmic-Ray-Induced Air Showers

Author: A. Alexov, M. Serylak, M. A. Garrett, E. Juette, B. Ciardi, C. Tasse, C. Koehn, M. Kuniyoshi, Dominik J. Schwarz, M. C. Toribio, A. Nelles, F. Breitling, Jean-Mathias Grießmeier, John McKean, John D. Swinbank, Jochen Eislöffel, W. Reich, J. Moldon, Maaijke Mevius, Marcus Brüggen, Casper Rutjes, R. J. van Weeren, Emanuela Orrú, J. W. Broderick, A. G. Polatidis, Rebecca McFadden, D. McKay-Bukowski, E. de Geus, Heino Falcke, M. J. Norden, V. I. Kondratiev, Harvey Butcher, M. Pandey-Pommier, Philip Best, Pim Schellart, Jason W. T. Hessels, Philippe Zarka, S. Duscha, Richard Fallows, Arthur Corstanje, Matthias Steinmetz, H. Paas, Ute Ebert, G. Kuper, Olaf Scholten, H. J. A. Röttgering, Oleg Smirnov, R. Vermeulen, Annalisa Bonafede, Mark J. Bentum, Michel Tagger, Michael W. Wise, Jörg P. Rachen, Gianni Bernardi, Jörg R. Hörandel, H. A. Holties, Olaf Wucknitz, T. N. G. Trinh, J. E. Enriquez, S. ter Veen, A. W. Gunst, M. de Vos, I. M. Avruch, Laura Rossetto, James M. Anderson, Gottfried Mann, Stijn Buitink, Roberto Pizzo, Wilfred Frieswijk, Christian Vocks, Satyendra Thoudam, Anna M. M. Scaife, Matthias Hoeft, George Heald, Department of Astrophysics [Nijmegen], Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen]-Radboud University [Nijmegen], KVI Center for Advanced Radiation Technology, University of Groningen [Groningen], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), National Institute for Subatomic Physics [Amsterdam] (NIKHEF), Vrije Universiteit Brussel (VUB), Centrum Wiskunde & Informatica (CWI), Space Telescope Science Institute (STSci), GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ), SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Institute for Astronomy [Edinburgh] (IfA), University of Edinburgh, University of Hamburg, Leibniz-Institut für Astrophysik Potsdam (AIP), Oxford Astrophysics, University of Oxford, University of Southampton, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Thüringer Landessternwarte Tautenburg (TLS), Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], National Astronomical Observatory of Japan (NAOJ), University of Oulu, Center for Information Technology CIT, Université de Groningen, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Universität Bielefeld = Bielefeld University, SKA South Africa, Ska South Africa, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), NOVA, SNN and FOM as well as from NWO, VENI Grant No. 639-041-130, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Schellart, P., Trinh, T.N.G., Buitink, S., Corstanje, A., Enriquez, J.E., Falcke, H., Hörandel, J.R., Nelles, A., Rachen, J.P., Rossetto, L., Scholten, O., Ter Veen, S., Thoudam, S., Ebert, U., Koehn, C., Rutjes, C., Alexov, A., Anderson, J.M., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J.W., Brüggen, M., Butcher, H.R., Ciardi, B., De Geus, E., De Vos, M., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Heald, G., Hessels, J.W.T., Hoeft, M., Holties, H.A., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J.P., Mevius, M., Moldon, J., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D.J., Serylak, M., Smirnov, O., Steinmetz, M., Swinbank, J., Tagger, M., Tasse, C., Toribio, M.C., Van Weeren, R.J., Vermeulen, R., Vocks, C., Wise, M.W., Wucknitz, O., Zarka, P., Kapteyn Astronomical Institute, Elementary Processes in Gas Discharges, Center for Wireless Technology Eindhoven, Physics, Astronomy and Astrophysics Research Group, Elementary Particle Physics, Multiscale Dynamics, Radboud university [Nijmegen]-Radboud university [Nijmegen], Harvard University [Cambridge]-Smithsonian Institution, University of Oxford [Oxford], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National d’Études Spatiales [Paris] (CNES), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Universiteit Leiden [Leiden], Fakultät für Physik, Universität Bielefeld, Universität Bielefeld, ITA, GBR, FRA, DEU, and NLD
Subjects: Astronomy, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, General Physics and Astronomy, Cosmic ray, Astrophysics, Neutrino muon pion and other elementary particles, Physics and Astronomy (all), cosmic rays, IR-99169, Atmospheric electricity lightning, Electric field, Extensive air showers, Instrumentation and Methods for Astrophysics (astro-ph.IM), METIS-315601, Physics::Atmospheric and Oceanic Physics, High Energy Astrophysical Phenomena (astro-ph.HE), Earth and Planetary Astrophysics (astro-ph.EP), Astroparticle physics, Physics, [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph], [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, EWI-26542, LOFAR, Polarization (waves), SIMULATIONS, COREAS, 13. Climate action, Experimental High Energy Physics, Thunderstorm, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, ARRAY, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract: We present measurements of radio emission from cosmic ray air showers that took place during thunderstorms. The intensity and polarization patterns of these air showers are radically different from those measured during fair-weather conditions. With the use of a simple two-layer model for the atmospheric electric field, these patterns can be well reproduced by state-of-the-art simulation codes. This in turn provides a novel way to study atmospheric electric fields., 6 pages, 3 figures, accepted for publication in Physical Review Letters
Published: 2015
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39. The shape of the radio wavefront of extensive air showers as measured with LOFAR

Author: J. E. Enriquez, Wilfred Frieswijk, Y. Tang, Anna M. M. Scaife, Emanuela Orrú, Gottfried Mann, M. van den Akker, H. J. A. Röttgering, Stefan J. Wijnholds, W. Reich, Mark J. Bentum, Olaf Wucknitz, Sarod Yatawatta, Heino Falcke, Frank Breitling, Chiara Ferrari, D. Engels, Adam Stewart, Aris Karastergiou, Richard Fallows, Maria Krause, P. Maat, A. Horneffer, C. Toribio, Michel Tagger, M. A. Garrett, Jörg P. Rachen, Gianni Bernardi, Jörg R. Hörandel, M. J. Norden, Vishambhar Pandey, Matthias Hoeft, R. J. van Weeren, Jochen Eislöffel, V. I. Kondratiev, D. McKay-Bukowski, Marco Iacobelli, F. de Gasperin, A. Alexov, J.-M. Grießmeier, Maaijke Mevius, T. N. G. Trinh, G. Kuper, A. G. Polatidis, Arthur Corstanje, A. Nelles, E. Juette, I. M. Avruch, Roberto Pizzo, Olaf Scholten, Oleg Smirnov, J. Kohler, H. Paas, Satyendra Thoudam, M. de Vos, Dominik J. Schwarz, Rene C. Vermeulen, P. Zarka, Annalisa Bonafede, J. P. Hamaker, Martin Bell, J. Anderson, Matthias Steinmetz, S. ter Veen, Rebecca McFadden, A. W. Gunst, Stijn Buitink, Christian Vocks, J. W. Broderick, E. de Geus, John D. Swinbank, Harvey Butcher, M. Pandey-Pommier, S. Duscha, B. Ciardi, C. Tasse, M. Kuniyoshi, H. Munk, Marcus Brüggen, Philip Best, Pim Schellart, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Extraterrestrische Physik (MPE), Leibniz-Institut für Astrophysik Potsdam (AIP), SRON Netherlands Institute for Space Research (SRON), Delft University of Technology (TU Delft), University of Edinburgh, University of Southampton, Universität Hamburg (UHH), Thüringer Landessternwarte Tautenburg (TLS), Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Unité Scientifique de la Station de Nançay (USN), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Department of Astrophysical Sciences [Princeton], Princeton University, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Netherlands Research School for Astronomy (NOVA), the Samenwerkingsverband Noord-Nederland (SNN) and the Foundation for Fundamental Research on Matter (FOM) as well as support from the Netherlands Organization for Scientific Research (NWO), VENI grant 639-041-130, European Project: 227610,EC:FP7:ERC,ERC-2008-AdG,LOFAR-AUGER(2009), ITA, GBR, FRA, DEU, NLD, Corstanje, A., Schellart, P., Nelles, A., Buitink, S., Enriquez, J.E., Falcke, H., Frieswijk, W., Hörandel, J.R., Krause, M., Rachen, J.P., Scholten, O., Ter Veen, S., Thoudam, S., Trinh, T.N.G., Van Den Akker, M., Alexov, A., Anderson, J., Avruch, I.M., Bell, M.E., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., De Gasperin, F., De Geus, E., De Vos, M., Duscha, S., Eislöffel, J., Engels, D., Fallows, R.A., Ferrari, C., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hoeft, M., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Maat, P., Mann, G., McFadden, R., McKay-Bukowski, D., Mevius, M., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D., Smirnov, O., Stewart, A., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijnholds, S.J., Wucknitz, O., Yatawatta, S., Zarka, P., Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Universiteit Leiden [Leiden], École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Astronomy, Research unit Astroparticle Physics, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: Physics::Instrumentation and Detectors, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, Extensive air shower, FOS: Physical sciences, Cosmic ray, Astrophysics, 01 natural sciences, Radio telescope, Optics, 0103 physical sciences, Extensive air showers, Ultra-high-energy cosmic ray, Radio emission, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), Cosmic rays, Wavefront, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), 010308 nuclear & particles physics, business.industry, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], Astrophysics::Instrumentation and Methods for Astrophysics, Astronomy and Astrophysics, LOFAR, Air shower, Wavefront shape, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Hyperboloid, business, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics, Shape analysis (digital geometry)
Abstract: Extensive air showers, induced by high energy cosmic rays impinging on the Earth's atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or hyperbolic shape of the wavefront has been proposed, but measurements of individual air showers have been inconclusive so far. For a selected high-quality sample of 161 measured extensive air showers, we have reconstructed the wavefront by measuring pulse arrival times to sub-nanosecond precision in 200 to 350 individual antennas. For each measured air shower, we have fitted a conical, spherical, and hyperboloid shape to the arrival times. The fit quality and a likelihood analysis show that a hyperboloid is the best parametrization. Using a non-planar wavefront shape gives an improved angular resolution, when reconstructing the shower arrival direction. Furthermore, a dependence of the wavefront shape on the shower geometry can be seen. This suggests that it will be possible to use a wavefront shape analysis to get an additional handle on the atmospheric depth of the shower maximum, which is sensitive to the mass of the primary particle., Accepted for publication in Astroparticle Physics
Published: 2014
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40. Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field

Author: F. de Gasperin, A. Horneffer, Jochen Eislöffel, M. A. Garrett, Geraint Harker, Michael Kramer, A. Nelles, J. van Leeuwen, Maaijke Mevius, Wilfred Frieswijk, Y. Tang, Anna M. M. Scaife, S. ter Veen, J. P. Hamaker, V. Veligatla, Marijke Haverkorn, G. Mann, A. W. Gunst, Chiara Ferrari, Rob Fender, D. Engels, Philip Best, Harish Vedantham, A. R. Offringa, John Conway, M. Iacobelli, M. Serylak, E. Juette, Hannes Jensen, James M. Anderson, C. Vocks, Annalisa Bonafede, Heino Falcke, Vibor Jelić, R. J. Dettmar, John McKean, Matthias Hoeft, A. H. Patil, J. W. Broderick, Saleem Zaroubi, P. Maat, Tim Hassall, Harvey Butcher, Aris Karastergiou, H. J. A. Röttgering, Rajat M. Thomas, M. J. Norden, V. I. Kondratiev, Olaf Wucknitz, M. Pandey-Pommier, H. Paas, Gianni Bernardi, Jörg R. Hörandel, Mark J. Bentum, Antonia Rowlinson, Michel Tagger, Garrelt Mellema, H. Munk, C. Tasse, O. Martinez-Rubi, W. Reich, J. D. Bregman, S. Kazemi, Abhik Ghosh, George Heald, Oleg Smirnov, Elizabeth Fernandez, S. Duscha, Dominik J. Schwarz, A. G. Polatidis, I. M. Avruch, Michiel A. Brentjens, W. N. Brouw, Roberto Pizzo, P. Labropoulos, Marcus Brüggen, Ralph A. M. J. Wijers, G. Pietka, Gerard H. Kuper, K. M. B. Asad, Martin Bell, Satyendra Thoudam, Jean-Mathias Griessmeier, Richard Fallows, A. Alexov, Emma Chapman, Ron Beck, A. G. de Bruyn, Luitje Koopmans, Vishambhar Pandey, Adam Deller, C. Toribio, F. B. Abdalla, P. Zarka, Matthias Steinmetz, F. Breitling, B. Ciardi, Jason W. T. Hessels, S. Bus, M. Kuniyoshi, R. Vermeulen, Stefan J. Wijnholds, E. de Geus, Sarod Yatawatta, S. Daiboo, Adam Stewart, A. J. van der Horst, R. J. van Weeren, D. McKay-Bukowski, Netherlands Institute for Radio Astronomy (ASTRON), University College of London [London] (UCL), Laboratoire de Physique Nucléaire et de Hautes Énergies (LPNHE (UMR_7585)), Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, University of Pennsylvania [Philadelphia], SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, University of Edinburgh, Jacobs University [Bremen], Leibniz-Institut für Astrophysik Potsdam (AIP), Thüringer Landessternwarte Tautenburg (TLS), Radboud university [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], University of Amsterdam [Amsterdam] (UvA), Ruhr-Universität Bochum [Bochum], Vrije Universiteit Medical Centre (VUMC), Vrije Universiteit Amsterdam [Amsterdam] (VU), University of Oulu, Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), School of Physics and Astronomy [Southampton], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), ANR-09-JCJC-0001,OPALES(2009), Jelić, V., De Bruyn, A.G., Mevius, M., Abdalla, F.B., Asad, K.M.B., Bernardi, G., Brentjens, M.A., Bus, S., Chapman, E., Ciardi, B., Daiboo, S., Fernandez, E.R., Ghosh, A., Harker, G., Jensen, H., Kazemi, S., Koopmans, L.V.E., Labropoulos, P., Martinez-Rubi, O., Mellema, G., Offringa, A.R., Pandey, V.N., Patil, A.H., Thomas, R.M., Vedantham, H.K., Veligatla, V., Yatawatta, S., Zaroubi, S., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Bentum, M.J., Best, P., Bonafede, A., Bregman, J., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Conway, J.E., De Gasperin, F., De Geus, E., Deller, A., Dettmar, R.-J., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Haverkorn, M., Heald, G., Hessels, J.W.T., Hoeft, M., Hörandel, J., Horneffer, A., Van Der Horst, A., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Van Leeuwen, J., Maat, P., Mann, G., McKay-Bukowski, D., McKean, J.P., Munk, H., Nelles, A., Norden, M.J., Paas, H., Pandey-Pommier, M., Pietka, G., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Serylak, M., Smirnov, O., Steinmetz, M., Stewart, A., Tagger, M., Tang, Y., Tasse, C., Ter Veen, S., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wijnholds, S.J., Wucknitz, O., Zarka, P., Astronomy, Kapteyn Astronomical Institute, University of Pennsylvania, Radboud University [Nijmegen], Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Jodrell Bank Centre for Astrophysics, Observatoire de Paris - Site de Paris (OP), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), and ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009)
Subjects: Brightness, Astronomy, techniques, Astrophysics, Cosmology: observation, 01 natural sciences, EWI-25428, law.invention, law, polarimetric [techniques], dark ages, Faraday cage, 010303 astronomy & astrophysics, Physics, Line-of-sight, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astrophysics::Instrumentation and Methods for Astrophysics, Polarization (waves), observations [cosmology], interferometric [techniques], radio continuum: ISM, techniques: interferometric, Brightness temperature, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, IR-93232, reionization, Astrophysics - Instrumentation and Methods for Astrophysics, techniques: polarimetric, cosmology: observations, diffuse radiation, first stars, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, ISM [radio continuum], Astrophysics::Cosmology and Extragalactic Astrophysics, Radio telescope, 0103 physical sciences, Instrumentation and Methods for Astrophysics (astro-ph.IM), Reionization, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, Astronomy and Astrophysics, METIS-309730, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Dark ages, reionization, first star, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), polarimetric
Abstract: This study aims to characterise the polarized foreground emission in the ELAIS-N1 field and to address its possible implications for the extraction of the cosmological 21-cm signal from the Low-Frequency Array - Epoch of Reionization (LOFAR-EoR) data. We use the high band antennas of LOFAR to image this region and RM-synthesis to unravel structures of polarized emission at high Galactic latitudes. The brightness temperature of the detected Galactic emission is on average 4 K in polarized intensity and covers the range from -10 to +13rad m^-2 in Faraday depth. The total polarized intensity and polarization angle show a wide range of morphological features. We have also used the Westerbork Synthesis Radio Telescope (WSRT) at 350 MHz to image the same region. The LOFAR and WSRT images show a similar complex morphology, at comparable brightness levels, but their spatial correlation is very low. The fractional polarization at 150 MHz, expressed as a percentage of the total intensity, amounts to 1.5%. There is no indication of diffuse emission in total intensity in the interferometric data, in line with results at higher frequencies. The wide frequency range, good angular resolution and good sensitivity make LOFAR an exquisite instrument for studying Galactic polarized emission at a resolution of 1-2 rad m^-2 in Faraday depth. The different polarised patterns observed at 150 MHz and 350 MHz are consistent with different source distributions along the line of sight wring in a variety of Faraday thin regions of emission. The presence of polarised foregrounds is a serious complication for Epoch of Reionization experiments. To avoid the leakage of polarized emission into total intensity, which can depend on frequency, we need to calibrate the instrumental polarization across the field of view to a small fraction of 1%., 12 pages, 9 figures, accepted for publication in A&A
Published: 2014
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41. LOFAR tied-array imaging of Type III solar radio bursts

Author: Rene C. Vermeulen, John McKean, R. J. van Weeren, P. Maat, M. J. Norden, Gerard H. Kuper, Jean-Mathias Grießmeier, Sera Markoff, H. Paas, T. E. Hassall, V. I. Kondratiev, Jochen Eislöffel, Eoin P. Carley, A. G. Polatidis, A. A. Konovalenko, Hamish A. S. Reid, D. Engels, D. D. Mulcahy, Y. Tang, A. Nelles, Anna M. M. Scaife, A. Kerdraon, Oleg Smirnov, Olaf Wucknitz, Chiara Ferrari, Wolfgang Reich, Heino Falcke, Peter T. Gallagher, I. M. Avruch, Aris Karastergiou, Joel N. Bregman, H. Munk, Gianni Bernardi, Jörg R. Hörandel, Marcus Brüggen, Ashish Asgekar, F. de Gasperin, M. A. Garrett, W. Frieswijk, Marco Iacobelli, Pietro Zucca, E. de Geus, Sarod Yatawatta, Harvey Butcher, Diana E. Morosan, V. N. Pandey, Michel Tagger, Dominik J. Schwarz, Adam Stewart, M. Pandey-Pommier, E. Juette, Mark J. Bentum, Michael Kramer, A. W. Gunst, Emanuela Orru, S. Duscha, G. Pietka, H. O. Rucker, A. Horneffer, Philip Best, Matthias Hoeft, J. W. Broderick, C. Tasse, Gottfried Mann, R. Pizzo, James M. Anderson, M. Kuniyoshi, Ben Stappers, John Conway, Mario M. Bisi, Adam T. Deller, Christian Vocks, Alexander L. MacKinnon, Jasmina Magdalenic, Richard Fallows, Philippe Zarka, M. Serylak, Jason W. T. Hessels, Annalisa Bonafede, Benedetta Ciardi, C. Toribio, F. Breitling, Bo Thidé, H. J. A. Röttgering, Satyendra Thoudam, Morosan, D.E., Gallagher, P.T., Zucca, P., Fallows, R., Carley, E.P., Mann, G., Bisi, M.M., Kerdraon, A., Konovalenko, A.A., MacKinnon, A.L., Rucker, H.O., Thidé, B., Magdalenić, J., Vocks, C., Reid, H., Anderson, J., Asgekar, A., Avruch, I.M., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Bregman, J., Breitling, F., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., Deller, A., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Hörandel, J., Horneffer, A., Iacobelli, M., Juette, E., Karastergiou, A., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., Maat, P., Markoff, S., McKean, J.P., Mulcahy, D.D., Munk, H., Nelles, A., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Reich, W., Röttgering, H., Scaife, A.M.M., Schwarz, D., Serylak, M., Smirnov, O., Stappers, B.W., Stewart, A., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Van Weeren, R.J., Wucknitz, O., Yatawatta, S., Zarka, P., Trinity College Dublin, Leibniz-Institut für Astrophysik Potsdam (AIP), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institute of Radio Astronomy of NASU [Kharkiv] (IRA), National Academy of Sciences of Ukraine (NASU), Lawrence Livermore National Laboratory (LLNL), Space Research Institute of Austrian Academy of Sciences (IWF), Austrian Academy of Sciences (OeAW), Swedish Institute of Space Physics [Uppsala] (IRF), SRON Netherlands Institute for Space Research (SRON), Jacobs University [Bremen], University of Southampton, Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Netherlands Institute for Radio Astronomy (ASTRON), Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], Joseph Louis LAGRANGE (LAGRANGE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Unité Scientifique de la Station de Nançay (USN), Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Ruhr-Universität Bochum [Bochum], Max-Planck-Institut für Radioastronomie (MPIFR), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), National Radio Astronomy Observatory [Charlottesville] (NRAO), National Radio Astronomy Observatory (NRAO), School of Physics and Astronomy [Southampton], Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Université Paris-Sud - Paris 11 (UP11), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, ANR-09-JCJC-0001,OPALES(2009), Kapteyn Astronomical Institute, Radboud university [Nijmegen], Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Universiteit Leiden [Leiden], Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Harvard University [Cambridge]-Smithsonian Institution, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Nice Sophia Antipolis (... - 2019) (UNS), Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Centre National d’Études Spatiales [Paris] (CNES), Smithsonian Institution-Harvard University [Cambridge], ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: 010504 meteorology & atmospheric sciences, corona [Sun], Astronomy, WAVES, Astrophysics, particle emission [Sun], 01 natural sciences, CORONA, EWI-25429, Sun: coronal, Coronal mass ejection, Astrophysics::Solar and Stellar Astrophysics, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Physics, Solar flare, Sun: radio radiation, [SDU.ASTR.HE]Sciences of the Universe [physics]/Astrophysics [astro-ph]/High Energy Astrophysical Phenomena [astro-ph.HE], ELECTRONS, Astrophysics - Solar and Stellar Astrophysics, Physical Sciences, IR-93233, Physics::Space Physics, SHOCK, Radio frequency, Astrophysics::Earth and Planetary Astrophysics, Sun: coronal mass ejections (CMEs), Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Solar radius, Astronomy & Astrophysics, ACCELERATION, Radio telescope, PLASMA EMISSION, SPACECRAFT, Sun: particle emission, 0103 physical sciences, Solar and Stellar Astrophysics (astro-ph.SR), 0105 earth and related environmental sciences, Science & Technology, RADIOHELIOGRAPH, radio radiation [Sun], [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Sun: corona, Astronomy and Astrophysics, LOFAR, METIS-309731, Astronomy and Astrophysic, Corona, coronal mass ejections (CMEs) [Sun], Space and Planetary Science, DENSITY, Temporal resolution, mass ejections (CMEs)
Abstract: The Sun is an active source of radio emission which is often associated with energetic phenomena such as solar flares and coronal mass ejections (CMEs). At low radio frequencies (, 9 pages, 6 figures
Published: 2014
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42. Studying Galactic interstellar turbulence through fluctuations in synchrotron emission First LOFAR Galactic foreground detection

Author: Torsten A. Enßlin, I. van Bemmel, A. W. Gunst, H. Junklewitz, Wilfred Frieswijk, J. W. Broderick, Martin Bell, C. Vogt, Rainer Beck, M. Iacobelli, Cathy Horellou, E. de Geus, Vibor Jelić, Y. Tang, Sarod Yatawatta, Anna M. M. Scaife, Aris Karastergiou, R. J. van Weeren, Krzysztof T. Chyzy, J. Sluman, Michael W. Wise, Gianni Bernardi, Harvey Butcher, G. Mann, Jörg R. Hörandel, George Heald, J. van Leeuwen, D. D. Mulcahy, A. Horneffer, V. I. Kondratiev, M. Pandey-Pommier, Roberto Pizzo, Charlotte Sobey, Emanuela Orrú, Marcus Brüggen, W. Jurusik, Michel Tagger, C. Toribio, W. N. Brouw, R. Vermeulen, S. Duscha, F. de Gasperin, Jean-Mathias Griessmeier, I. M. Avruch, Heino Falcke, Gerard H. Kuper, John McKean, R. J. Dettmar, C. Tasse, Tim Hassall, Rosita Paladino, Ashish Asgekar, Anton Zensus, Michael R. Bell, Laura Birzan, J. P. Hamaker, H. J. A. Röttgering, Oleg Smirnov, Chiara Ferrari, Olaf Wucknitz, John Conway, W. Reich, Dominik J. Schwarz, Luitje Koopmans, P. Zarka, Matthias Hoeft, Carlos Sotomayor-Beltran, F. Breitling, D. Engels, H. Munk, Richard Fallows, A. Alexov, Philip Best, M. A. Garrett, C. Vocks, Jochen Eislöffel, Marijke Haverkorn, Annalisa Bonafede, B. Ciardi, M. Kuniyoshi, Matthias Steinmetz, Jason W. T. Hessels, Giulia Macario, Ben Stappers, A. G. Polatidis, Mark J. Bentum, Michael Kramer, James M. Anderson, Astronomy, Kapteyn Astronomical Institute, Iacobelli, M., Haverkorn, M., Orrú, E., Pizzo, R.F., Anderson, J., Beck, R., Bell, M.R., Bonafede, A., Chyzy, K., Dettmar, R.-J., Enßlin, T.A., Heald, G., Horellou, C., Horneffer, A., Jurusik, W., Junklewitz, H., Kuniyoshi, M., Mulcahy, D.D., Paladino, R., Reich, W., Scaife, A., Sobey, C., Sotomayor-Beltran, C., Alexov, A., Asgekar, A., Avruch, I.M., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Birzan, L., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Gasperin, F., De Geus, E., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fallows, R.A., Ferrari, C., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Hessels, J.W.T., Hoeft, M., Hörandel, J., Jelic, V., Karastergiou, A., Kondratiev, V.I., Koopmans, L.V.E., Kramer, M., Kuper, G., Van Leeuwen, J., MacArio, G., Mann, G., McKean, J.P., Munk, H., Pandey-Pommier, M., Polatidis, A.G., Röttgering, H., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B.W., Steinmetz, M., Tagger, M., Tang, Y., Tasse, C., Toribio, C., Vermeulen, R., Vocks, C., Vogt, C., Van Weeren, R.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: ISM: general, ISM: magnetic fields, ISM: structure, radio continuum: general, radio continuum: ISM, techniques: interferometric, POLARIZATION, Astronomy, Continuum (design consultancy), Astrophysics, 01 natural sciences, Power law, GHZ, EWI-24132, 010303 astronomy & astrophysics, Physics, general [ISM], MAGNETIC-FIELD, Magnetic field, interferometric [techniques], METIS-302576, WIDE-FIELD, interferometric, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Galactic coordinate system, general [radio continuum], ANGULAR POWER SPECTRUM, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, ISM [radio continuum], IR-89497, Astrophysics::Cosmology and Extragalactic Astrophysics, ISM: magnetic field, radio continuum: ISM techniques, 0103 physical sciences, Radio continuum: ISM, ALGORITHM, Astrophysics::Galaxy Astrophysics, 010308 nuclear & particles physics, magnetic fields [ISM], Spectral density, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, W-PROJECTION, Galaxy, radiation mechanisms: non-thermal / galaxies: active / galaxies: individual: M 87 / galaxies: clusters: individual: Virgo / galaxies: jets / radio continuum: galaxies, GALAXY, 350 MHZ, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), Techniques: interferometric, RADIO-EMISSION
Abstract: The characteristic outer scale of turbulence and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters. We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l,b) (137.0,+7.0) at 80"x70" resolution in the range [146,174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations . We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum of the foreground synchrotron fluctuations displays a power law behaviour for scales between 100 and 8 arcmin with a slope of (-1.84+/-0.19). We find an upper limit of about 20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of turbulence of the Galactic synchrotron foreground, finding a range of plausible values of 10-20 pc. Then, we use this information to deduce lower limits of the ratio of ordered to random magnetic field strength. These are found to be 0.3, 0.3, and 0.5 for the LOFAR, WSRT and GMRT fields considered respectively. Both these constraints are in agreement with previous estimates., Comment: 13 pages, 11 figures, accepted for publication in A&A
Published: 2013

43. Wide-band simultaneous observations of pulsars: disentangling dispersion measure and profile variations

Author: P. Maat, Benjamin Stappers, Heino Falcke, Charlotte Sobey, Emanuela Orrú, Jason W. T. Hessels, E. Rol, L. Bähren, H. Meulman, Joris P. W. Verbiest, C. Tasse, A. Alexov, Matthias Hoeft, M. A. Garrett, Sarod Yatawatta, James Miller-Jones, Evan Keane, Michael Kramer, S. ter Veen, J. Masters, A. W. Gunst, Casey J. Law, Jochen Eislöffel, B. Scheers, Maaijke Mevius, T. E. Hassall, J. W. Broderick, R. C. Vermeulen, B. Ciardi, Martin Bell, John McKean, Luitje Koopmans, J. E. Noordam, Gerard H. Kuper, Annalisa Bonafede, Harvey Butcher, Sera Markoff, M. P. van Haarlem, E. J. Daw, Rudy Wijnands, M. Kuniyoshi, V. I. Kondratiev, M. Pandey-Pommier, A. Noutsos, K. Zagkouris, Michael R. Bell, H. Paas, J. Sluman, Michiel A. Brentjens, Ashish Asgekar, Roberto Pizzo, Marcus Brüggen, C. G. M. Sterks, W. Reich, R. A. Osten, Albert-Jan Boonstra, Michel Tagger, Stephane Corbel, A. G. Polatidis, P.G. Jonker, M. Gerbers, Stefan J. Wijnholds, J. van Leeuwen, H. Spreeuw, A. de Jong, Matthias Steinmetz, R. J. van Weeren, P. Zarka, K. Lazaridis, George Heald, Mark J. Bentum, G. M. Loose, W. N. Brouw, Patrick Weltevrede, V. S. Dhillon, Aris Karastergiou, Michael W. Wise, Gianni Bernardi, M. Serylak, Rob Fender, Ralph A. M. J. Wijers, H. J. A. Röttgering, H. A. Holties, Y. Tang, Anna M. M. Scaife, Olaf Wucknitz, H. Munk, John D. Swinbank, Jean-Mathias Griessmeier, Vishambhar Pandey, Philip Best, Pim Schellart, T. Coenen, Kenneth C. Anderson, Kapteyn Astronomical Institute, Astronomy, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Netherlands Institute for Radio Astronomy (ASTRON), Max-Planck-Institut für Radioastronomie (MPIFR), Oxford Astrophysics, University of Oxford [Oxford], Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), University of Southampton, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), University of Sheffield [Sheffield], Thüringer Landessternwarte Tautenburg (TLS), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud university [Nijmegen], Space Telescope Science Institute (STSci), School of Physics and Astronomy [Southampton], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, University of Edinburgh, Jacobs University [Bremen], Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Leiden Observatory [Leiden], Universiteit Leiden [Leiden], National Radio Astronomy Observatory (NRAO), Applied Stochastics (IMAPP), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Center for Information Technology CIT, Université de Groningen, Netherlands Foundation for Scientific Research. Joeri van Leeuwen and ThijsCoenen are supported by the Netherlands Research School for Astronomy (GrantNOVA3-NW3-2.3.1), European Project: 224838,EC:FP7:PEOPLE,FP7-PEOPLE-2007-4-3-IRG,PULSARS WITH LOFAR(2008), European Project: 236394,EC:FP7:PEOPLE,FP7-PEOPLE-IEF-2008,PULSAR SURVEY(2010), Hassall, T.E., Stappers, B.W., Hessels, J.W.T., Kramer, M., Alexov, A., Anderson, K., Coenen, T., Karastergiou, A., Keane, E.F., Kondratiev, V.I., Lazaridis, K., Van Leeuwen, J., Noutsos, A., Serylak, M., Sobey, C., Verbiest, J.P.W., Weltevrede, P., Zagkouris, K., Fender, R., Wijers, R.A.M.J., Bähren, L., Bell, M.E., Broderick, J.W., Corbel, S., Daw, E.J., Dhillon, V.S., Eislöffel, J., Falcke, H., Grießmeier, J.-M., Jonker, P., Law, C., Markoff, S., Miller-Jones, J.C.A., Osten, R., Rol, E., Scaife, A.M.M., Scheers, B., Schellart, P., Spreeuw, H., Swinbank, J., Ter Veen, S., Wise, M.W., Wijnands, R., Wucknitz, O., Zarka, P., Asgekar, A., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Boonstra, A.J., Brentjens, M., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Garrett, M.A., Gerbers, M., Gunst, A.W., Van Haarlem, M.P., Heald, G., Hoeft, M., Holties, H., De Jong, A., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., Loose, G.M., Maat, P., Masters, J., McKean, J.P., Meulman, H., Mevius, M., Munk, H., Noordam, J.E., Orrú, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A., Reich, W., Röttgering, H., Sluman, J., Steinmetz, M., Sterks, C.G.M., Tagger, M., Tang, Y., Tasse, C., Vermeulen, R., Van Weeren, R.J., Wijnholds, S.J., Yatawatta, S., University of Oxford, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Radboud University [Nijmegen], Harvard University-Smithsonian Institution, Universiteit Leiden, École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), High Energy Astrophys. & Astropart. Phys (API, FNWI), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), PSL Research University (PSL)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Rhodes University, SKA South Africa, and Ska South Africa
Subjects: 010504 meteorology & atmospheric sciences, Astronomy, Magnetosphere, Astrophysics, magnetic fields, 01 natural sciences, law.invention, law, Dispersion (optics), 010303 astronomy & astrophysics, Telescope, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, [PHYS]Physics [physics], Astrophysics::Instrumentation and Methods for Astrophysics, SPECTRAL BEHAVIOR, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Astrophysics - High Energy Astrophysical Phenomena, ARRIVAL-TIME DELAY, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, SUPERDISPERSION DELAY, EMPIRICAL-THEORY, Pulsar, pulsars: general, 0103 physical sciences, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences, ISM: general, METIS-287956, Gravitational wave, Astronomy and Astrophysics, telescopes, LOFAR, Astronomy and Astrophysic, EWI-22107, Pulse (physics), PULSES, Interstellar medium, PSR 0809&74, FREQUENCY-DEPENDENCE, Magnetic field, Space and Planetary Science, [SDU]Sciences of the Universe [physics], RADIO-EMISSION, IR-80985, REFRACTION, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], INTERSTELLAR SCATTERING
Abstract: Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR (at 40-190 MHz), the 76-m Lovell Telescope (at 1400 MHz) and the Effelsberg 100-m Telescope (at 8000 MHz) to test the accuracy of the dispersion law over a broad frequency range. In this paper we present the results of these observations which show that the dispersion law is accurate to better than 1 part in 100000 across our observing band. We use this fact to constrain some of the properties of the ISM along the line-of-sight and use the lack of any aberration or retardation effects to determine upper limits on emission heights in the pulsar magnetosphere. We also discuss the effect of pulse profile evolution on our observations, and the implications that it could have for precision pulsar timing projects such as the detection of gravitational waves with pulsar timing arrays., 20 Pages, 14 Figures, Accepted for publication in Astronomy & Astrophysics
Published: 2012
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44. First LOFAR observations at very low frequencies of cluster-scale non-thermal emission: the case of Abell 2256

Author: R. J. van Weeren, H. J. A. Röttgering, D. A. Rafferty, R. Pizzo, A. Bonafede, M. Brüggen, G. Brunetti, C. Ferrari, E. Orrù, G. Heald, J. P. McKean, C. Tasse, F. de Gasperin, L. Bîrzan, J. E. van Zwieten, S. van der Tol, A. Shulevski, N. Jackson, A. R. Offringa, J. Conway, H. T. Intema, T. E. Clarke, I. van Bemmel, G. K. Miley, G. J. White, M. Hoeft, R. Cassano, G. Macario, R. Morganti, M. W. Wise, C. Horellou, E. A. Valentijn, O. Wucknitz, K. Kuijken, T. A. Enßlin, J. Anderson, A. Asgekar, I. M. Avruch, R. Beck, M. E. Bell, M. R. Bell, M. J. Bentum, G. Bernardi, P. Best, A.-J. Boonstra, M. Brentjens, R. H. van de Brink, J. Broderick, W. N. Brouw, H. R. Butcher, W. van Cappellen, B. Ciardi, J. Eislöffel, H. Falcke, R. Fender, M. A. Garrett, M. Gerbers, A. Gunst, M. P. van Haarlem, J. P. Hamaker, T. Hassall, J. W. T. Hessels, L. V. E. Koopmans, G. Kuper, J. van Leeuwen, P. Maat, R. Millenaar, H. Munk, R. Nijboer, J. E. Noordam, V. N. Pandey, M. Pandey-Pommier, A. Polatidis, W. Reich, A. M. M. Scaife, A. Schoenmakers, J. Sluman, B. W. Stappers, M. Steinmetz, J. Swinbank, M. Tagger, Y. Tang, R. Vermeulen, M. de Vos, Astronomy, Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Centre de Recherche Astrophysique de Lyon (CRAL), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de Physique et Chimie de l'Environnement et de l'Espace (LPC2E), Observatoire des Sciences de l'Univers en région Centre (OSUC), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), ANR-09-JCJC-0001,OPALES(2009), European Project: 224897,EC:FP7:PEOPLE,FP7-PEOPLE-2007-2-2-ERG,WIDEMAP(2008), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Université Côte d'Azur (UCA)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure de Lyon (ENS de Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Van Weeren, R.J., Röttgering, H.J.A., Rafferty, D.A., Pizzo, R., Bonafede, A., Brüggen, M., Brunetti, G., Ferrari, C., Orrù, E., Heald, G., McKean, J.P., Tasse, C., De Gasperin, F., Bîrzan, L., Van Zwieten, J.E., Van Der Tol, S., Shulevski, A., Jackson, N., Offringa, A.R., Conway, J., Intema, H.T., Clarke, T.E., Van Bemmel, I., Miley, G.K., White, G.J., Hoeft, M., Cassano, R., MacArio, G., Morganti, R., Wise, M.W., Horellou, C., Valentijn, E.A., Wucknitz, O., Kuijken, K., Enßlin, T.A., Anderson, J., Asgekar, A., Avruch, I.M., Beck, R., Bell, M.E., Bell, M.R., Bentum, M.J., Bernardi, G., Best, P., Boonstra, A.-J., Brentjens, M., Van De Brink, R.H., Broderick, J., Brouw, W.N., Butcher, H.R., Van Cappellen, W., Ciardi, B., Eislöffel, J., Falcke, H., Fender, R., Garrett, M.A., Gerbers, M., Gunst, A., Van Haarlem, M.P., Hamaker, J.P., Hassall, T., Hessels, J.W.T., Koopmans, L.V.E., Kuper, G., Van Leeuwen, J., Maat, P., Millenaar, R., Munk, H., Nijboer, R., Noordam, J.E., Pandey, V.N., Pandey-Pommier, M., Polatidis, A., Reich, W., Scaife, A.M.M., Schoenmakers, A., Sluman, J., Stappers, B.W., Steinmetz, M., Swinbank, J., Tagger, M., Tang, Y., Vermeulen, R., De Vos, M., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: galaxies: clusters: individual: Abell 2256, Cosmology and Nongalactic Astrophysics (astro-ph.CO), PARTICLE-ACCELERATION, COMA CLUSTER, Astronomy, Astrophysics::High Energy Astrophysical Phenomena, ASTROPHYSICAL SHOCKS, radio continuum: general, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Radio spectrum, MAGNETIC-FIELDS, Relativistic particle, X-RAY-EMISSION, METIS-293218, 0103 physical sciences, MERGING GALAXY CLUSTER, EXTENDED RADIO-EMISSION, Telescope, 010303 astronomy & astrophysics, Galaxy cluster, Astrophysics::Galaxy Astrophysics, Physics, [PHYS]Physics [physics], Spectral index, 010308 nuclear & particles physics, Astronomy and Astrophysics, telescopes, LOFAR, Astronomy and Astrophysic, EWI-22624, Galaxy, SHOCK ACCELERATION, DEEP 1.4 GHZ, Radio halo, Space and Planetary Science, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Halo, large-scale structure of Universe, IR-82401, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], SKY SURVEY, Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: Abell 2256 is one of the best known examples of a galaxy cluster hosting large-scale diffuse radio emission that is unrelated to individual galaxies. It contains both a giant radio halo and a relic, as well as a number of head-tail sources and smaller diffuse steep-spectrum radio sources. The origin of radio halos and relics is still being debated, but over the last years it has become clear that the presence of these radio sources is closely related to galaxy cluster merger events. Here we present the results from the first LOFAR Low band antenna (LBA) observations of Abell 2256 between 18 and 67 MHz. To our knowledge, the image presented in this paper at 63 MHz is the deepest ever obtained at frequencies below 100 MHz in general. Both the radio halo and the giant relic are detected in the image at 63 MHz, and the diffuse radio emission remains visible at frequencies as low as 20 MHz. The observations confirm the presence of a previously claimed ultra-steep spectrum source to the west of the cluster center with a spectral index of -2.3 \pm 0.4 between 63 and 153 MHz. The steep spectrum suggests that this source is an old part of a head-tail radio source in the cluster. For the radio relic we find an integrated spectral index of -0.81 \pm 0.03, after removing the flux contribution from the other sources. This is relatively flat which could indicate that the efficiency of particle acceleration at the shock substantially changed in the last \sim 0.1 Gyr due to an increase of the shock Mach number. In an alternative scenario, particles are re-accelerated by some mechanism in the downstream region of the shock, resulting in the relatively flat integrated radio spectrum. In the radio halo region we find indications of low-frequency spectral steepening which may suggest that relativistic particles are accelerated in a rather inhomogeneous turbulent region., Comment: 13 pages, 13 figures, accepted for publication in A\&A on April 12, 2012
Published: 2012
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45. Wide-field LOFAR imaging of the field around the double-double radio galaxy B1834+620

Author: E. Orrù, S. van Velzen, R. F. Pizzo, S. Yatawatta, R. Paladino, M. Iacobelli, M. Murgia, H. Falcke, R. Morganti, A. G. de Bruyn, C. Ferrari, J. Anderson, A. Bonafede, D. Mulcahy, A. Asgekar, I. M. Avruch, R. Beck, M. E. Bell, I. van Bemmel, M. J. Bentum, G. Bernardi, P. Best, F. Breitling, J. W. Broderick, M. Brüggen, H. R. Butcher, B. Ciardi, J. E. Conway, A. Corstanje, E. de Geus, A. Deller, S. Duscha, J. Eislöffel, D. Engels, W. Frieswijk, M. A. Garrett, J. Grießmeier, A. W. Gunst, J. P. Hamaker, G. Heald, M. Hoeft, A. J. van der Horst, H. Intema, E. Juette, J. Kohler, V. I. Kondratiev, M. Kuniyoshi, G. Kuper, M. Loose, P. Maat, G. Mann, S. Markoff, R. McFadden, D. McKay-Bukowski, G. Miley, J. Moldon, G. Molenaar, H. Munk, A. Nelles, H. Paas, M. Pandey-Pommier, V. N. Pandey, G. Pietka, A. G. Polatidis, W. Reich, H. Röttgering, A. Rowlinson, A. Scaife, A. Schoenmakers, D. Schwarz, M. Serylak, A. Shulevski, O. Smirnov, M. Steinmetz, A. Stewart, J. Swinbank, M. Tagger, C. Tasse, S. Thoudam, M. C. Toribio, R. Vermeulen, C. Vocks, R. J. van Weeren, R. A. M. J. Wijers, M. W. Wise, O. Wucknitz, High Energy Astrophys. & Astropart. Phys (API, FNWI), Kapteyn Astronomical Institute, Astronomy, Orru, E., Van Velzen, S., Pizzo, R.F., Yatawatta, S., Paladino, R., Iacobelli, M., Murgia, M., Falcke, H., Morganti, R., De Bruyn, A.G., Ferrari, C., Anderson, J., Bonafede, A., Mulcahy, D., Asgekar, A., Avruch, I.M., Beck, R., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Breitling, F., Broderick, J.W., Bruggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., De Geus, E., Deller, A., Duscha, S., Eisloffel, J., Engels, D., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Heald, G., Hoeft, M., Van Der Horst, A.J., Intema, H., Juette, E., Kohler, J., Kondratiev, V.I., Kuniyoshi, M., Kuper, G., Loose, M., Maat, P., Mann, G., Markoff, S., McFadden, R., McKay-BGBRowski, D., Miley, G., Moldon, J., Molenaar, G., Munk, H., Nelles, A., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pietka, G., Polatidis, A.G., Reich, W., Rottgering, H., Rowlinson, A., Scaife, A., Schoenmakers, A., Schwarz, D., Serylak, M., Shulevski, A., Smirnov, O., Steinmetz, M., Stewart, A., Swinbank, J., Tagger, M., Tasse, C., Thoudam, S., Toribio, M.C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wijers, R.A.M.J., Wise, M.W., and Wucknitz, O.
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), Radio galaxy, Astrophysics::High Energy Astrophysical Phenomena, interferometers [instrumentation], galaxies: active, Population, FOS: Physical sciences, Field of view, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Astroparticle physic, Radio continuum: galaxie, 01 natural sciences, Instrumentation: interferometer, law.invention, Telescope, law, 0103 physical sciences, Bow shock (aerodynamics), instrumentation: interferometers, education, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, radio continuum: galaxies, Physics, education.field_of_study, Accretion (meteorology), 010308 nuclear & particles physics, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, radiation mechanisms: non-thermal, non-thermal [radiation mechanisms], Astrophysics - Astrophysics of Galaxies, galaxies [radio continuum], Redshift, interferometric [techniques], techniques: interferometric, astroparticle physics, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), active [galaxies], Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: The existence of double-double radio galaxies (DDRGs) is evidence for recurrent jet activity in AGN, as expected from standard accretion models. A detailed study of these rare sources provides new perspectives for investigating the AGN duty cycle, AGN-galaxy feedback, and accretion mechanisms. Large catalogues of radio sources provide statistical information about the evolution of the radio-loud AGN population out to high redshifts. Using wide-field imaging with the LOFAR telescope, we study both a well-known DDRG as well as a large number of radio sources in the field of view. We present a high resolution image of the DDRG B1834+620 obtained at 144 MHz using LOFAR commissioning data. Our image covers about 100 square degrees and contains over 1000 sources. The four components of the DDRG B1834+620 have been resolved for the first time at 144 MHz. Inner lobes were found to point towards the direction of the outer lobes, unlike standard FR~II sources. Polarized emission was detected in the northern outer lobe. The high spatial resolution allows the identification of a large number of small double-lobed radio sources; roughly 10% of all sources in the field are doubles with a separation smaller than 1 arcmin. The spectral fit of the four components is consistent with a scenario in which the outer lobes are still active or the jets recently switched off, while emission of the inner lobes is the result of a mix-up of new and old jet activity. From the presence of the newly extended features in the inner lobes of the DDRG, we can infer that the mechanism responsible for their formation is the bow shock that is driven by the newly launched jet. We find that the density of the small doubles exceeds the density of FR-II sources with similar properties at 1.4 GHz, but this difference becomes smaller for low flux densities., Comment: 13 pages, 8 figures, Accepted for publication in Astronomy & Astrophysics
Published: 2015
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