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19 results on '"Hamaker, J.P."'

1. The shape of the radio wavefront of extensive air showers as measured with LOFAR

Author: 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., and Zarka, P.
Published: 2015
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2. A very brief description of LOFAR -- the Low Frequency Array

Author: Falcke, H.D.E., Haarlem, M.P. van, Bruyn, A.G. de, Braun, R., Röttgering, H.J.A., Stappers, B., Boland, W.H.W.M., Butcher, H.R., Geus, E.J. de, Koopmans, L.V., Fender, R.P., Kuijpers, H.J.M.E., Miley, G.K., Schilizzi, R.T., Vogt, C., Wijers, R.A.M.J., Wise, M.W., Brouw, W.N., Hamaker, J.P., Noordam, J.E., Oosterloo, T., Bähren, L., Brentjens, M.A., Wijnholds, S.J., Bregman, J.D., Cappellen, W.A. van, Gunst, A.W., Kant, G.W., Reitsma, J., Schaaf, K. van der, Vos, C.M. de, Falcke, H.D.E., Haarlem, M.P. van, Bruyn, A.G. de, Braun, R., Röttgering, H.J.A., Stappers, B., Boland, W.H.W.M., Butcher, H.R., Geus, E.J. de, Koopmans, L.V., Fender, R.P., Kuijpers, H.J.M.E., Miley, G.K., Schilizzi, R.T., Vogt, C., Wijers, R.A.M.J., Wise, M.W., Brouw, W.N., Hamaker, J.P., Noordam, J.E., Oosterloo, T., Bähren, L., Brentjens, M.A., Wijnholds, S.J., Bregman, J.D., Cappellen, W.A. van, Gunst, A.W., Kant, G.W., Reitsma, J., Schaaf, K. van der, and Vos, C.M. de
Abstract: Contains fulltext : 35235.pdf ( ) (Open Access), LOFAR (Low Frequency Array) is an innovative radio telescope optimized for the frequency range 30-240 MHz. The telescope is realized as a phased aperture array without any moving parts. Digital beam forming allows the telescope to point to any part of the sky within a second. Transient buffering makes retrospective imaging of explosive short-term events possible. The scientific focus of LOFAR will initially be on four key science projects (KSPs): 1) detection of the formation of the very first stars and galaxies in the universe during the so-called epoch of reionization by measuring the power spectrum of the neutral hydrogen 21-cm line (Shaver et al. 1999) on the ~5' scale; 2) low-frequency surveys of the sky with of order $10^8$ expected new sources; 3) all-sky monitoring and detection of transient radio sources such as gamma-ray bursts, x-ray binaries, and exo-planets (Farrell et al. 2004); and 4) radio detection of ultra-high energy cosmic rays and neutrinos (Falcke & Gorham 2003) allowing for the first time access to particles beyond 10^21 eV (Scholten et al. 2006). Apart from the KSPs open access for smaller projects is also planned. Here we give a brief description of the telescope.
Published: 2007

3. The synthesis radio telescope at Westerbork.

Author: Baars, J.W.M., van der Brugge, J.F., Jean L. Casse, Hamaker, J.P., Sondaar, L.H., Visser, J.J., and Wellington, K.J.
Published: 1973
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4. Understanding radio polarimetry

Author: Hamaker, J.P.
Abstract: Paper II of this series studied the calibration process in mostly qualitative terms. In developing the underlying mathematics this paper completes that analysis and extends it in several directions. It exploits the analogy between scalar and matrix algebras to reformulate the self-calibration method in terms of $2 \times 2\ $ Jones and coherency matrices. The basic condition that the solutions must satisfy in either case is developed and its consequences are investigated. The fourfold nature of the matrices and the non-commutativity of their multiplication are shown to lead to a number of new effects. In the same way that scalar selfcal leaves the brightness scale undefined, matrix selfcal gives rise to a more complicated indeterminacy. The calibration is far from complete: self-alignment describes more properly what is actually achieved. The true brightness is misrepresented in the image obtained by an unknown brightness-scale factor (as in scalar selfcal) and an undefined poldistortion of the Stokes brightness. The latter is the product of a polrotation of the polvector $(Q,U,V)$ and a polconversion between unpolarized and polarized brightness. The relation of these concepts to conventional "quasi-scalar" calibration methods is demonstrated. Like scalar selfcal, matrix self-alignment is shown to suppress spatial scattering of brightness in the image, which is a condition for attaining high dynamic range. Poldistortion of the brightness is an in-place transformation, but must be controlled in order to obtain polarimetric fidelity. The theory is applied to reinterpret the quasi-scalar methods of polarimetry including those of Paper II, and to prove two major new assertions: (a.) An instrument calibrated on an unpolarized calibrator measures the degree of polarization correctly regardless of poldistortion; (b.) Under the usual a priori assumptions, a heterogeneous instrument (i.e. one with unequal feeds) can be completely calibrated without requiring a phase-difference measurement.
Published: 2000

5. Measurement Errors in Rotational Synthesis and their Effects in the Map Plane

Author: Hamaker, J.P., primary
Published: 1979
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6. “Kneading”: The Adjustment of Instrumental Phase and Gain Parameters to Suppress Error Patterns in a Synthesis Map

Author: Hamaker, J.P., primary
Published: 1979
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7. A simple RC realization of the 90° phase-difference network including source and load resistances

Author: Hamaker, J.P., primary and Pezij, J., additional
Published: 1975
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8. 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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9. 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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10. The LOFAR Multifrequency Snapshot Sky Survey (MSSS): I. Survey description and first results

Author: G. H. Heald, R. F. Pizzo, E. Orrú, R. P. Breton, D. Carbone, C. Ferrari, M. J. Hardcastle, W. Jurusik, G. Macario, D. Mulcahy, D. Rafferty, A. Asgekar, M. Brentjens, R. A. Fallows, W. Frieswijk, M. C. Toribio, B. Adebahr, M. Arts, M. R. Bell, A. Bonafede, J. Bray, J. Broderick, T. Cantwell, P. Carroll, Y. Cendes, A. O. Clarke, J. Croston, S. Daiboo, F. de Gasperin, J. Gregson, J. Harwood, T. Hassall, V. Heesen, A. Horneffer, A. J. van der Horst, M. Iacobelli, V. Jelić, D. Jones, D. Kant, G. Kokotanekov, P. Martin, J. P. McKean, L. K. Morabito, B. Nikiel-Wroczyński, A. Offringa, V. N. Pandey, M. Pandey-Pommier, M. Pietka, L. Pratley, C. Riseley, A. Rowlinson, J. Sabater, A. M. M. Scaife, L. H. A. Scheers, K. Sendlinger, A. Shulevski, M. Sipior, C. Sobey, A. J. Stewart, A. Stroe, J. Swinbank, C. Tasse, J. Trüstedt, E. Varenius, S. van Velzen, N. Vilchez, R. J. van Weeren, S. Wijnholds, W. L. Williams, A. G. de Bruyn, R. Nijboer, M. Wise, A. Alexov, J. Anderson, I. M. Avruch, R. Beck, M. E. Bell, I. van Bemmel, M. J. Bentum, G. Bernardi, P. Best, F. Breitling, W. N. Brouw, M. Brüggen, H. R. Butcher, B. Ciardi, J. E. Conway, E. de Geus, A. de Jong, M. de Vos, A. Deller, R.-J. Dettmar, S. Duscha, J. Eislöffel, D. Engels, H. Falcke, R. Fender, M. A. Garrett, J. Grießmeier, A. W. Gunst, J. P. Hamaker, J. W. T. Hessels, M. Hoeft, J. Hörandel, H. A. Holties, H. Intema, N. J. Jackson, E. Jütte, A. Karastergiou, W. F. A. Klijn, V. I. Kondratiev, L. V. E. Koopmans, M. Kuniyoshi, G. Kuper, C. Law, J. van Leeuwen, M. Loose, P. Maat, S. Markoff, R. McFadden, D. McKay-Bukowski, M. Mevius, J. C. A. Miller-Jones, R. Morganti, H. Munk, A. Nelles, J. E. Noordam, M. J. Norden, H. Paas, A. G. Polatidis, W. Reich, A. Renting, H. Röttgering, A. Schoenmakers, D. Schwarz, J. Sluman, O. Smirnov, B. W. Stappers, M. Steinmetz, M. Tagger, Y. Tang, S. ter Veen, S. Thoudam, R. Vermeulen, C. Vocks, C. Vogt, R. A. M. J. Wijers, O. Wucknitz, S. Yatawatta, P. Zarka, Heald, G.H., Pizzo, R.F., Orrú, E., Breton, R.P., Carbone, D., Ferrari, C., Hardcastle, M.J., Jurusik, W., Macario, G., Mulcahy, D., Rafferty, D., Asgekar, A., Brentjens, M., Fallows, R.A., Frieswijk, W., Toribio, M.C., Adebahr, B., Arts, M., Bell, M.R., Bonafede, A., Bray, J., Broderick, J., Cantwell, T., Carroll, P., Cendes, Y., Clarke, A.O., Croston, J., Daiboo, S., De Gasperin, F., Gregson, J., Harwood, J., Hassall, T., Heesen, V., Horneffer, A., Van Der Horst, A.J., Iacobelli, M., Jelić, V., Jones, D., Kant, D., Kokotanekov, G., Martin, P., McKean, J.P., Morabito, L.K., Nikiel-Wroczyński, B., Offringa, A., Pandey, V.N., Pandey-Pommier, M., Pietka, M., Pratley, L., Riseley, C., Rowlinson, A., Sabater, J., Scaife, A.M.M., Scheers, L.H.A., Sendlinger, K., Shulevski, A., Sipior, M., Sobey, C., Stewart, A.J., Stroe, A., Swinbank, J., Tasse, C., Trüstedt, J., Varenius, E., Van Velzen, S., Vilchez, N., Van Weeren, R.J., Wijnholds, S., Williams, W.L., De Bruyn, A.G., Nijboer, R., Wise, M., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Breitling, F., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., De Geus, E., De Jong, A., De Vos, M., Deller, A., Dettmar, R.-J., Duscha, S., Eislöffel, J., Engels, D., Falcke, H., Fender, R., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hessels, J.W.T., Hoeft, M., Hörandel, J., Holties, H.A., Intema, H., Jackson, N.J., Jütte, E., Karastergiou, A., Klijn, W.F.A., Kondratiev, V.I., Koopmans, L.V.E., Kuniyoshi, M., Kuper, G., Law, C., Van Leeuwen, J., Loose, M., Maat, P., Markoff, S., McFadden, R., McKay-Bukowski, D., Mevius, M., Miller-Jones, J.C.A., Morganti, R., Munk, H., Nelles, A., Noordam, J.E., Norden, M.J., Paas, H., Polatidis, A.G., Reich, W., Renting, A., Röttgering, H., Schoenmakers, A., Schwarz, D., Sluman, J., Smirnov, O., Stappers, B.W., Steinmetz, M., Tagger, M., Tang, Y., Ter Veen, S., Thoudam, S., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R.A.M.J., Wucknitz, O., Yatawatta, S., Zarka, P., High Energy Astrophys. & Astropart. Phys (API, FNWI), Netherlands Institute for Radio Astronomy (ASTRON), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], University of Hertfordshire [Hatfield] (UH), Uniwersytet Jagielloński w Krakowie = Jagiellonian University (UJ), 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), University of Southampton, Jacobs University [Bremen], 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), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), School of Physics and Astronomy [Southampton], Leiden Observatory, Leiden University (Leiden Observatory), 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), Max-Planck-Institut für Radioastronomie (MPIFR), Laboratory for Atmospheric and Space Physics [Boulder] (LASP), University of Colorado [Boulder], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), 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)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden, SRON Netherlands Institute for Space Research (SRON), Leibniz-Institut für Astrophysik Potsdam (AIP), Research School of Astronomy and Astrophysics [Canberra] (RSAA), Australian National University (ANU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Los Alamos National Laboratory (LANL), Astronomisches Institut der Ruhr-Universität Bochum, Ruhr-Universität Bochum [Bochum], Thüringer Landessternwarte Tautenburg (TLS), Radboud University [Nijmegen], 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), Leibniz-Institut DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH / Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures (DSMZ), Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), ANR-09-JCJC-0001,OPALES(2009), European Project: 247295,EC:FP7:ERC,ERC-2009-AdG,AARTFAAC(2010), European Project: 267697,EC:FP7:ERC,ERC-2010-AdG_20100224,4PI-SKY(2011), ITA, GBR, FRA, DEU, NLD, 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 d'études européennes et de politique comparée (CEE), Sciences Po (Sciences Po)-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), Institut national des sciences de l'Univers (INSU - CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Harvard University [Cambridge]-Smithsonian Institution, Universiteit Leiden [Leiden], 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), 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), Astronomy, Kapteyn Astronomical Institute, Jodrell Bank Centre for Astrophysics, Jagiellonian University [Krakow] (UJ), 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), 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)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS), 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)-Centre National d’Études Spatiales [Paris] (CNES), ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), and Database Architectures
Subjects: 010504 meteorology & atmospheric sciences, Computer science, Astronomy, media_common.quotation_subject, FOS: Physical sciences, METIS-315082, 01 natural sciences, Radio spectrum, Radio continuum: general, surveys, 0103 physical sciences, radio continuum: general, Survey, GeneralLiterature_REFERENCE(e.g.,dictionaries,encyclopedias,glossaries), 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), 0105 earth and related environmental sciences, Remote sensing, media_common, Giant Metrewave Radio Telescope, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Square kilometre array, IR-98663, Sky, [SDU]Sciences of the Universe [physics], Space and Planetary Science, Experimental High Energy Physics, EWI-26540, Snapshot (computer storage), general [radio continuum], Astrophysics - Instrumentation and Methods for Astrophysics
Abstract: We present the Multifrequency Snapshot Sky Survey (MSSS), the first northern-sky LOFAR imaging survey. In this introductory paper, we first describe in detail the motivation and design of the survey. Compared to previous radio surveys, MSSS is exceptional due to its intrinsic multifrequency nature providing information about the spectral properties of the detected sources over more than two octaves (from 30 to 160 MHz). The broadband frequency coverage, together with the fast survey speed generated by LOFAR's multibeaming capabilities, make MSSS the first survey of the sort anticipated to be carried out with the forthcoming Square Kilometre Array (SKA). Two of the sixteen frequency bands included in the survey were chosen to exactly overlap the frequency coverage of large-area Very Large Array (VLA) and Giant Metrewave Radio Telescope (GMRT) surveys at 74 MHz and 151 MHz respectively. The survey performance is illustrated within the "MSSS Verification Field" (MVF), a region of 100 square degrees centered at J2000 (RA,Dec)=(15h,69deg). The MSSS results from the MVF are compared with previous radio survey catalogs. We assess the flux and astrometric uncertainties in the catalog, as well as the completeness and reliability considering our source finding strategy. We determine the 90% completeness levels within the MVF to be 100 mJy at 135 MHz with 108" resolution, and 550 mJy at 50 MHz with 166" resolution. Images and catalogs for the full survey, expected to contain 150,000-200,000 sources, will be released to a public web server. We outline the plans for the ongoing production of the final survey products, and the ultimate public release of images and source catalogs., Comment: 23 pages, 19 figures. Accepted for publication in Astronomy & Astrophysics. MSSS Verification Field images and catalog data may be downloaded from http://vo.astron.nl
Published: 2015
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11. 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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12. 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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13. Discovery of carbon radio recombination lines in absorption towards Cygnus A

Author: J. van Enst, D. Engels, J. B. R. Oonk, S. ter Veen, Tim Hassall, Leah K. Morabito, M. A. Garrett, Alexander G. G. M. Tielens, Ashish Asgekar, J. M. Anderson, Rainer Beck, D. D. Mulcahy, Neal Jackson, Frank Breitling, Vishambhar Pandey, Harvey Butcher, Rob Fender, James Miller-Jones, M. Pandey-Pommier, Sarod Yatawatta, Giulia Macario, Michel Tagger, J. Kohler, Anton Zensus, John Conway, H. J. A. Röttgering, Heino Falcke, H. Munk, Marcus Brüggen, A. Horneffer, Richard Fallows, Jochen Eislöffel, E. Juette, Olaf Wucknitz, P. Maat, M. J. Norden, A. Alexov, C. Vogt, Aris Karastergiou, Maaijke Mevius, G. Kuper, S. Duscha, V. I. Kondratiev, Michael W. Wise, Gianni Bernardi, Philip Best, Benjamin Stappers, Dominik J. Schwarz, Wilfred Frieswijk, Y. Tang, A. Shulevski, Anna M. M. Scaife, Chiara Ferrari, Glenn J. White, B. Ciardi, Marco Iacobelli, M. de Vos, Jean-Mathias Grießmeier, A. G. Polatidis, Arthur Corstanje, Matthias Hoeft, J. Sluman, John McKean, C. Tasse, John D. Swinbank, Francisco Salgado, J. W. Broderick, Roberto Pizzo, E. de Geus, Satyendra Thoudam, Ralph A. M. J. Wijers, Christian Vocks, Sera Markoff, C. Toribio, J. D. Mol, M. Kuniyoshi, Annalisa Bonafede, Jason W. T. Hessels, Michiel A. Brentjens, Mark J. Bentum, George Heald, Michael Kramer, J. van Leeuwen, Philippe Zarka, R. van Nieuwpoort, J. P. Hamaker, Charlotte Sobey, Emanuela Orrú, H. Paas, F. Batejat, W. Reich, Oleg Smirnov, F. de Gasperin, I. van Bemmel, Martin Bell, Gottfried Mann, Matthias Steinmetz, I. M. Avruch, R. J. van Weeren, Rene C. Vermeulen, Wouter Klijn, A. J. van der Horst, A. P. Schoenmakers, Netherlands Institute for Radio Astronomy (ASTRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden, Department of Physics and Astronomy [Milton Keynes], The Open University [Milton Keynes] (OU), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, SRON Netherlands Institute for Space Research (SRON), Max-Planck-Institut für Radioastronomie (MPIFR), Sydney Institute for Astronomy (SIfA), The University of Sydney, Department of Physics-Electronics, Rhodes University, Grahamstown, University of Edinburgh, Universität Hamburg (UHH), Leibniz-Institut für Astrophysik Potsdam (AIP), School of Physics and Astronomy [Southampton], University of Southampton, Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Radboud University [Nijmegen], Medstar Research Institute, Thüringer Landessternwarte Tautenburg (TLS), Hamburger Sternwarte/Hamburg Observatory, 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), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford, Karlsruhe Institute of Technology (KIT), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), 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, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], 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), 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), Oonk, J.B.R., van Weeren, R.J., salgado, F., Morabito, L.K., Tielens, A.G.G.M., Rottgering, H.J.A., Asgekar, A., White, G.J., Alexov, A., Anderson, J., Avruch, I.M., Batejat, F., Beck, R., Be, M.E., van Bemmel, I., Bentum, M.J., Bernardi, G., Best, P., Bonafede, A., Breitling, F., Brentjens, M., Broderick, J., Brüggen, M., Butcher, H.R., Ciardi, B., Conway, J.E., Corstanje, A., de Gasperin, F., de Geus, E., de Vos, M., Duscha, S., Eislöffel, J., Engels, D., van Enst, J., Falcke, H., Fallows, R.A., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., Griemeier, J., Hamaker, J.P., Hassa, T.E., Heald, G., Hessels, J.W.T., Hoeft, M., Horneffer, A., van der Horst, A., Iacobelli, M., Jackson, N.J., Juette, E., Karastergiou, A., Klijn, W., Kohler, J., Kondratiev, V.I., Kramer, M., Kuniyoshi, M., Kuper, G., van Leeuwen, J., Maat, P., Macario, G., Mann, G., Markoff, S., McKean, J.P., Mevius, M., Miller-Jones, J.C.A., Mol, J.D., Mulcahy, D.D., Munk, H., Norden, M.J., Orru, E., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A.G., Reich, W., scaife, A.M.M., schoenmakers, A., schwarz, D., shulevski, A., sluman, J., smirnov, O., Sobey, C., Stappers, B.W., steinmetz, M., swinbank, J., Tagger, M., Tang, Y., Tasse, C., ter Veen, S., Thoudam, S., Toribio, C., van Nieuwpoort, R., Vermeulen, R., Vocks, C., Vogt, C., Wijers, R.A.M.J., Wise, M.W., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., 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), University of Oxford [Oxford], 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, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
Subjects: [SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], Astronomy, ISM: structure, Interstellar cloud, EWI-24499, FOS: Physical sciences, Astrophysics, structure-local interstellar matter-radio line, ISM [radio lines], Cygnus A, Absorption (electromagnetic radiation), Optical depth, Astrophysics::Galaxy Astrophysics, ISM, Line (formation), ISM: general, Physics, IsM, radio lines, radio lines: ISM, general [ISM], local interstellar matter, Local standard of rest, Astronomy and Astrophysics, METIS-302715, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Galaxy, Cassiopeia A, Space and Planetary Science, Astrophysics of Galaxies (astro-ph.GA), ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, General-IsM, structure [ISM], IR-89519, ISM: general ISM: structure local interstellar matter radio lines: ISM
Abstract: We present the first detection of carbon radio recombination line absorption along the line of sight to Cygnus A. The observations were carried out with the LOw Frequency ARray in the 33 to 57 MHz range. These low frequency radio observations provide us with a new line of sight to study the diffuse, neutral gas in our Galaxy. To our knowledge this is the first time that foreground Milky Way recombination line absorption has been observed against a bright extragalactic background source. By stacking 48 carbon $\alpha$ lines in the observed frequency range we detect carbon absorption with a signal-to-noise ratio of about 5. The average carbon absorption has a peak optical depth of 2$\times$10$^{-4}$, a line width of 10 km s$^{-1}$ and a velocity of +4 km s$^{-1}$ with respect to the local standard of rest. The associated gas is found to have an electron temperature $T_{e}\sim$ 110 K and density $n_{e}\sim$ 0.06 cm$^{-3}$. These properties imply that the observed carbon $\alpha$ absorption likely arises in the cold neutral medium of the Orion arm of the Milky Way. Hydrogen and helium lines were not detected to a 3$\sigma$ peak optical depth limit of 1.5$\times$10$^{-4}$ for a 4 km s$^{-1}$ channel width. Radio recombination lines associated with Cygnus A itself were also searched for, but are not detected. We set a 3$\sigma$ upper limit of 1.5$\times$10$^{-4}$ for the peak optical depth of these lines for a 4 km s$^{-1}$ channel width., Comment: In press
Published: 2014
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14. LOFAR Low-band Antenna Observations of the 3C 295 and Boötes Fields: Source Counts and Ultra-steep Spectrum Sources

Author: Stappers, Benjamin, {van Weeren}, R J, {Williams}, W L, {Tasse}, C, {Röttgering}, H J A, {Rafferty}, D A, {van der Tol}, S, {Heald}, G, {White}, G J, {Shulevski}, A, {Best}, P, {Intema}, H T, {Bhatnagar}, S, {Reich}, W, {Steinmetz}, M, {van Velzen}, S, {En{\ss}lin}, T A, {Prandoni}, I, {de Gasperin}, F, {Jamrozy}, M, {Brunetti}, G, {Jarvis}, M J, {McKean}, J P, {Wise}, M W, {Ferrari}, C, {Harwood}, J, {Oonk}, J B R, {Hoeft}, M, {Kunert-Bajraszewska}, M, {Horellou}, C, {Wucknitz}, O, {Bonafede}, A, {Mohan}, N R, {Scaife}, A M M, {Klöckner}, H-R, {van Bemmel}, I M, {Merloni}, A, {Chyzy}, K T, {Engels}, D, {Falcke}, H, {Pandey-Pommier}, M, {Alexov}, A, {Anderson}, J, {Avruch}, I M, {Beck}, R, {Bell}, M E, {Bentum}, M J, {Bernardi}, G, {Breitling}, F, {Broderick}, J, {Brouw}, W N, {Brüggen}, M, {Butcher}, H R, {Ciardi}, B, {de Geus}, E, {de Vos}, M, {Deller}, A, {Duscha}, S, {Eislöffel}, J, {Fallows}, R A, {Frieswijk}, W, Garrett, Michael, {Grie{\ss}meier}, J, {Gunst}, A W, {Hamaker}, J P, {Hassall}, T E, {Hörandel}, J, {van der Horst}, A, {Iacobelli}, M, {Jackson}, N J, {Juette}, E, {Kondratiev}, V I, {Kuniyoshi}, M, {Maat}, P, {Mann}, G, {McKay-Bukowski}, D, {Mevius}, M, {Morganti}, R, {Munk}, H, {Offringa}, A R, {Orrù}, E, {Paas}, H, {Pandey}, V N, {Pietka}, G, {Pizzo}, R, {Polatidis}, A G, {Renting}, A, {Rowlinson}, A, {Schwarz}, D, {Serylak}, M, {Sluman}, J, {Smirnov}, O, {Stappers}, B W, {Stewart}, A, {Swinbank}, J, {Tagger}, M, {Tang}, Y, {Thoudam}, S, {Toribio}, C, {Vermeulen}, R, {Vocks}, C, {Zarka}, P, Astronomy, Netherlands Institute for Radio Astronomy (ASTRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Leiden Observatory [Leiden], Universiteit Leiden [Leiden], SKA South Africa, Ska South Africa, Rhodes University, Grahamstown, 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), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, SLAC National Accelerator Laboratory (SLAC), Stanford University, University of Edinburgh, Department of Computer Science and Automation [Bangalore] (CSA), Indian Institute of Science [Bangalore] (IISc Bangalore), Max-Planck-Institut für Radioastronomie (MPIFR), Charles Darwin University, Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Thüringer Landessternwarte Tautenburg (TLS), Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, Jacobs University [Bremen], School of Physics and Astronomy [Southampton], University of Southampton, Radboud university [Nijmegen], 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 für Astrophysik Potsdam (AIP), SRON Netherlands Institute for Space Research (SRON), Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medstar Research Institute, Institute of Mathematical and Physical Sciences, 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, 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, University of Manchester [Manchester], Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), Ruhr-Universität Bochum [Bochum], University of Oulu, Applied Stochastics (IMAPP), Oxford Astrophysics, University of Oxford [Oxford], 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), 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, ANR-09-JCJC-0001,OPALES(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Van Weeren, R.J., Williams, W.L., Tasse, C., Röttgering, H.J.A., Rafferty, D.A., Van Der Tol, S., Heald, G., White, G.J., Shulevski, A., Best, P., Intema, H.T., Bhatnagar, S., Reich, W., Steinmetz, M., Van Velzen, S., Enßlin, T.A., Prandoni, I., De Gasperin, F., Jamrozy, M., Brunetti, G., Jarvis, M.J., McKean, J.P., Wise, M.W., Ferrari, C., Harwood, J., Oonk, J.B.R., Hoeft, M., Kunert-Bajraszewska, M., Horellou, C., Wucknitz, O., Bonafede, A., Mohan, N.R., Scaife, A.M.M., Klöckner, H.-R., Van Bemmel, I.M., Merloni, A., Chyzy, K.T., Engels, D., Falcke, H., Pandey-Pommier, M., Alexov, A., Anderson, J., Avruch, I.M., Beck, R., Bell, M.E., Bentum, M.J., Bernardi, G., Breitling, F., Broderick, J., Brouw, W.N., Brüggen, M., Butcher, H.R., Ciardi, B., De Geus, E., De Vos, M., Deller, A., Duscha, S., Eislöffel, J., Fallows, R.A., Frieswijk, W., Garrett, M.A., Grießmeier, J., Gunst, A.W., Hamaker, J.P., Hassall, T.E., Hörandel, J., Van Der Horst, A., Iacobelli, M., Jackson, N.J., Juette, E., Kondratiev, V.I., Kuniyoshi, M., Maat, P., Mann, G., McKay-Bukowski, D., Mevius, M., Morganti, R., Munk, H., Offringa, A.R., Orrù, E., Paas, H., Pandey, V.N., Pietka, G., Pizzo, R., Polatidis, A.G., Renting, A., Rowlinson, A., Schwarz, D., Serylak, M., Sluman, J., Smirnov, O., Stappers, B.W., Stewart, A., Swinbank, J., Tagger, M., Tang, Y., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Zarka, P., Harvard University-Smithsonian Institution, Universiteit Leiden, Radboud University [Nijmegen], 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), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), and University of Oxford
Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO), general, surveys [radio continuum], EWI-25425, Radio galaxy, Astronomy, techniques, galaxies: active, radio continuum: general, FOS: Physical sciences, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, METIS-309728, surveys, survey, Source counts, Astrophysics::Galaxy Astrophysics, Physics, Spectral index, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Astronomy and Astrophysics, BOOTES, LOFAR, Astronomy and Astrophysic, Astrophysics - Astrophysics of Galaxies, Redshift, interferometric [techniques], IR-93230, Space and Planetary Science, [SDU]Sciences of the Universe [physics], techniques: interferometric, Astrophysics of Galaxies (astro-ph.GA), interferometric, active [galaxies], ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, Spectral energy distribution, general [radio continuum], Noise (radio), Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract: We present LOFAR Low Band observations of the Bootes and 3C295 fields. Our images made at 34, 46, and 62 MHz reach noise levels of 12, 8, and 5 mJy beam$^{-1}$, making them the deepest images ever obtained in this frequency range. In total, we detect between 300 and 400 sources in each of these images, covering an area of 17 to 52 deg$^{2}$. From the observations we derive Euclidean-normalized differential source counts. The 62 MHz source counts agree with previous GMRT 153 MHz and VLA 74 MHz differential source counts, scaling with a spectral index of $-0.7$. We find that a spectral index scaling of $-0.5$ is required to match up the LOFAR 34 MHz source counts. This result is also in agreement with source counts from the 38 MHz 8C survey, indicating that the average spectral index of radio sources flattens towards lower frequencies. We also find evidence for spectral flattening using the individual flux measurements of sources between 34 and 1400 MHz and by calculating the spectral index averaged over the source population. To select ultra-steep spectrum ($\alpha < -1.1$) radio sources, that could be associated with massive high redshift radio galaxies, we compute spectral indices between 62 MHz, 153 MHz and 1.4 GHz for sources in the Bo\"otes field. We cross-correlate these radio sources with optical and infrared catalogues and fit the spectral energy distribution to obtain photometric redshifts. We find that most of these ultra-steep spectrum sources are located in the $ 0.7 \lesssim z \lesssim 2.5$ range., Comment: 26 pages, 20 figures, ApJ in press
Published: 2014
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15. The LOFAR pilot surveys for pulsars and fast radio transients

Author: K. Zagkouris, Stefan Oslowski, C. Schrijvers, Michel Tagger, A. Noutsos, Jean-Mathias Grießmeier, John D. Swinbank, Simon Cooper, Dominik J. Schwarz, Rob Fender, P. Zarka, Heino Falcke, Philip Best, V. I. Kondratiev, D. McKay-Bukowski, Charlotte Sobey, Arthur Corstanje, Gerard H. Kuper, Christian Vocks, T. Coenen, M. A. Garrett, Y. Tang, M. Serylak, T. E. Hassall, Oleg Smirnov, Gottfried Mann, Olaf Wucknitz, Anna M. M. Scaife, Jason W. T. Hessels, J. Sluman, Aris Karastergiou, Gianni Bernardi, Mark J. Bentum, Michael Kramer, M. Pilia, George Heald, S. ter Veen, A. W. Gunst, H. Munk, H. J. A. Röttgering, A. S. van Amesfoort, E. de Geus, Satyendra Thoudam, Marcus Brüggen, C. Tasse, Harvey Butcher, John McKean, Emanuela Orru, Casey J. Law, M. Kuniyoshi, Chiara Ferrari, F. Breitling, Annalisa Bonafede, Joeri van Leeuwen, M. Pandey-Pommier, A. Zensus, James M. Anderson, Antonia Rowlinson, Ashish Asgekar, C. Toribio, R. Vermeulen, Joris P. W. Verbiest, Evan Keane, Matthias Hoeft, Vishal Gajjar, Jochen Eislöffel, S. Duscha, H. Paas, A. G. Polatidis, A. Alexov, Rebecca McFadden, Benedetta Ciardi, Stefan J. Wijnholds, J. W. Broderick, Richard Fallows, Wolfgang Reich, B. W. Stappers, A. Renting, F. de Gasperin, Adam T. Deller, W. Frieswijk, Martin Bell, Anna V. Bilous, R. J. van Weeren, I. M. Avruch, E. Juette, Patrick Weltevrede, J. P. Hamaker, A. J. van der Horst, Rene P. Breton, Kapteyn Astronomical Institute, Astronomy, Netherlands Institute for Radio Astronomy (ASTRON), University of Amsterdam [Amsterdam] (UvA), Jodrell Bank Centre for Astrophysics (JBCA), University of Manchester [Manchester], University of Southampton, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Radboud University [Nijmegen], Max-Planck-Institut für Radioastronomie (MPIFR), 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), University of Oxford, Universität Bielefeld, Leibniz-Institut für Astrophysik Potsdam (AIP), SRON Netherlands Institute for Space Research (SRON), Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University-Smithsonian Institution, University of Edinburgh, Jacobs University [Bremen], Universität Hamburg (UHH), Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, 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), Leiden Observatory [Leiden], Universiteit Leiden, Ruhr-Universität Bochum [Bochum], Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Oulu, 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), School of Physics and Astronomy [Southampton], Rhodes University, Grahamstown, 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), ANR-09-JCJC-0001,OPALES(2009), European Project: 224838,EC:FP7:PEOPLE,FP7-PEOPLE-2007-4-3-IRG,PULSARS WITH LOFAR(2008), High Energy Astrophys. & Astropart. Phys (API, FNWI), 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), University of Oxford [Oxford], 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), 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), Jodrell Bank Centre for Astrophysics, 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], 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), 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), ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), Coenen, Thij, Van Leeuwen, Joeri, Hessels, Jason W. T., Stappers, Ben W., Kondratiev, Vladislav I., Alexov, A., Breton, R.P., Bilous, A., Cooper, S., Falcke, H., Fallows, R.A., Gajjar, V., Grießmeier, J.-M., Hassall, T.E., Karastergiou, A., Keane, E.F., Kramer, M., Kuniyoshi, M., Noutsos, A., Osłowski, S., Pilia, M., Serylak, M., Schrijvers, C., Sobey, C., Ter Veen, S., Verbiest, J., Weltevrede, P., Wijnholds, S., Zagkouris, K., Van Amesfoort, A.S., Anderson, J., Asgekar, A., 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., Corstanje, A., Deller, A., Duscha, S., Eislöffel, J., Fender, R., Ferrari, C., Frieswijk, W., Garrett, M.A., De Gasperin, F., De Geus, E., Gunst, A.W., Hamaker, J.P., Heald, G., Hoeft, M., Van Der Horst, A., Juette, E., Kuper, G., Law, C., Mann, G., McFadden, R., McKay-Bukowski, D., McKean, J.P., Munk, H., Orru, E., Paas, H., Pandey-Pommier, M., Polatidis, A.G., Reich, W., Renting, A., Röttgering, H., Rowlinson, A., Scaife, A.M.M., Schwarz, D., Sluman, J., Smirnov, O., Swinbank, J., Tagger, M., Tang, Y., Tasse, C., Thoudam, S., Toribio, C., Vermeulen, R., Vocks, C., Van Weeren, R.J., Wucknitz, O., Zarka, P., and Zensus, A.
Subjects: EWI-25426, Aperture array, media_common.quotation_subject, Astronomy, Pilot survey, SPECTRAL INDEX, FOS: Physical sciences, Astrophysics, general [pulsars], METIS-309729, MHZ, Pulsar, surveys, pulsars: general, BURSTS, Survey, Telescope, POPULATION, Solar and Stellar Astrophysics (astro-ph.SR), media_common, Physics, High Energy Astrophysical Phenomena (astro-ph.HE), [PHYS]Physics [physics], ORIGIN, [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Astronomy and Astrophysics, telescopes, BINARY, LOFAR, Astronomy and Astrophysic, IR-93231, Astrophysics - Solar and Stellar Astrophysics, Sky, Space and Planetary Science, DISCOVERY, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, STATE CHANGE, Antenna (radio), ALLEN TELESCOPE ARRAY, EMISSION, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], Astrophysics - High Energy Astrophysical Phenomena
Abstract: We have conducted two pilot surveys for radio pulsars and fast transients with the Low-Frequency Array (LOFAR) around 140 MHz and here report on the first low-frequency fast-radio burst limit and the discovery of two new pulsars. The first survey, the LOFAR Pilot Pulsar Survey (LPPS), observed a large fraction of the northern sky, ~1.4 x 10^4 sq. deg, with 1-hr dwell times. Each observation covered ~75 sq. deg using 7 independent fields formed by incoherently summing the high-band antenna fields. The second pilot survey, the LOFAR Tied-Array Survey (LOTAS), spanned ~600 sq. deg, with roughly a 5-fold increase in sensitivity compared with LPPS. Using a coherent sum of the 6 LOFAR "Superterp" stations, we formed 19 tied-array beams, together covering 4 sq. deg per pointing. From LPPS we derive a limit on the occurrence, at 142 MHz, of dispersed radio bursts of < 150 /day/sky, for bursts brighter than S > 107 Jy for the narrowest searched burst duration of 0.66 ms. In LPPS, we re-detected 65 previously known pulsars. LOTAS discovered two pulsars, the first with LOFAR or any digital aperture array. LOTAS also re-detected 27 previously known pulsars. These pilot studies show that LOFAR can efficiently carry out all-sky surveys for pulsars and fast transients, and they set the stage for further surveying efforts using LOFAR and the planned low-frequency component of the Square Kilometer Array., 18 pages, 10 figures, accepted for A&A
Published: 2014
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16. 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

17. LOFAR: The LOw-Frequency ARray

Author: M. P. van Haarlem, M. W. Wise, A. W. Gunst, G. Heald, J. P. McKean, J. W. T. Hessels, A. G. de Bruyn, R. Nijboer, J. Swinbank, R. Fallows, M. Brentjens, A. Nelles, R. Beck, H. Falcke, R. Fender, J. Hörandel, L. V. E. Koopmans, G. Mann, G. Miley, H. Röttgering, B. W. Stappers, R. A. M. J. Wijers, S. Zaroubi, M. van den Akker, A. Alexov, J. Anderson, K. Anderson, A. van Ardenne, M. Arts, A. Asgekar, I. M. Avruch, F. Batejat, L. Bähren, M. E. Bell, M. R. Bell, I. van Bemmel, P. Bennema, M. J. Bentum, G. Bernardi, P. Best, L. Bîrzan, A. Bonafede, A.-J. Boonstra, R. Braun, J. Bregman, F. Breitling, R. H. van de Brink, J. Broderick, P. C. Broekema, W. N. Brouw, M. Brüggen, H. R. Butcher, W. van Cappellen, B. Ciardi, T. Coenen, J. Conway, A. Coolen, A. Corstanje, S. Damstra, O. Davies, A. T. Deller, R.-J. Dettmar, G. van Diepen, K. Dijkstra, P. Donker, A. Doorduin, J. Dromer, M. Drost, A. van Duin, J. Eislöffel, J. van Enst, C. Ferrari, W. Frieswijk, H. Gankema, M. A. Garrett, F. de Gasperin, M. Gerbers, E. de Geus, J.-M. Grießmeier, T. Grit, P. Gruppen, J. P. Hamaker, T. Hassall, M. Hoeft, H. A. Holties, A. Horneffer, A. van der Horst, A. van Houwelingen, A. Huijgen, M. Iacobelli, H. Intema, N. Jackson, V. Jelic, A. de Jong, E. Juette, D. Kant, A. Karastergiou, A. Koers, H. Kollen, V. I. Kondratiev, E. Kooistra, Y. Koopman, A. Koster, M. Kuniyoshi, M. Kramer, G. Kuper, P. Lambropoulos, C. Law, J. van Leeuwen, J. Lemaitre, M. Loose, P. Maat, G. Macario, S. Markoff, J. Masters, R. A. McFadden, D. McKay-Bukowski, H. Meijering, H. Meulman, M. Mevius, E. Middelberg, R. Millenaar, J. C. A. Miller-Jones, R. N. Mohan, J. D. Mol, J. Morawietz, R. Morganti, D. D. Mulcahy, E. Mulder, H. Munk, L. Nieuwenhuis, R. van Nieuwpoort, J. E. Noordam, M. Norden, A. Noutsos, A. R. Offringa, H. Olofsson, A. Omar, E. Orrú, R. Overeem, H. Paas, M. Pandey-Pommier, V. N. Pandey, R. Pizzo, A. Polatidis, D. Rafferty, S. Rawlings, W. Reich, J.-P. de Reijer, J. Reitsma, G. A. Renting, P. Riemers, E. Rol, J. W. Romein, J. Roosjen, M. Ruiter, A. Scaife, K. van der Schaaf, B. Scheers, P. Schellart, A. Schoenmakers, G. Schoonderbeek, M. Serylak, A. Shulevski, J. Sluman, O. Smirnov, C. Sobey, H. Spreeuw, M. Steinmetz, C. G. M. Sterks, H.-J. Stiepel, K. Stuurwold, M. Tagger, Y. Tang, C. Tasse, I. Thomas, S. Thoudam, M. C. Toribio, B. van der Tol, O. Usov, M. van Veelen, A.-J. van der Veen, S. ter Veen, J. P. W. Verbiest, R. Vermeulen, N. Vermaas, C. Vocks, C. Vogt, M. de Vos, E. van der Wal, R. van Weeren, H. Weggemans, P. Weltevrede, S. White, S. J. Wijnholds, T. Wilhelmsson, O. Wucknitz, S. Yatawatta, P. Zarka, A. Zensus, J. van Zwieten, Netherlands Institute for Radio Astronomy (ASTRON), Astronomical Institute Anton Pannekoek (AI PANNEKOEK), University of Amsterdam [Amsterdam] (UvA), Institute of Mathematical and Physical Sciences, Radboud university [Nijmegen], Laboratoire de Chimie Physique Moléculaire (LCPM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Max-Planck-Institut für Radioastronomie (MPIFR), University of Southampton, Leibniz-Institut für Astrophysik Potsdam (AIP), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, Medical Center Haaglanden, SRON Netherlands Institute for Space Research (SRON), University of Edinburgh, Jacobs University [Bremen], Technische Universität Dresden = Dresden University of Technology (TU Dresden), Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Department of Reproduction and Development, Erasmus University Rotterdam, London Institute for Mathematical Sciences, Netherlands Centre for Biodiversity, Leiden, The Netherlands, Thüringer Landessternwarte Tautenburg (TLS), Laboratoire Réactions et Génie des Procédés (LRGP), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), Medstar Research Institute, 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), Plant Research International, Business Unit Bioscience, Wageningen University and Research [Wageningen] (WUR), Dipartimento di Matematica 'Guido Castelnuovo' [Roma I] (Sapienza University of Rome), Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome], Centre de Mathématiques Laurent Schwartz (CMLS), Centre National de la Recherche Scientifique (CNRS)-École polytechnique (X), 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), Ruhr-Universität Bochum [Bochum], Oxford Astrophysics, University of Oxford [Oxford], Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam [Amsterdam] (VU), Vrije Universiteit Medical Centre (VUMC), Queen's Medical Centre, National Radio Astronomy Observatory (NRAO), University of Oulu, Department of Economics, Bryant University, Center for Agricultural Research in Suriname CELOS and Department of Biology, Anton de Kom Universiteit van Suriname - Anton de Kom University of Suriname [Paramaribo] (UVS), DLR Institute of Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt [Köln] (DLR), Onsala Space Observatory (OSO), Chalmers University of Technology [Göteborg], Geophysical Institute [Bergen] (GFI / BiU), University of Bergen (UiB), 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), Department of Astronomy and Astrophysics [PennState], Pennsylvania State University (Penn State), Penn State System-Penn State System, Academic Medical Center - Academisch Medisch Centrum [Amsterdam] (AMC), School of Physics and Astronomy [Southampton], 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), Rhodes University, Grahamstown, Center for Information Technology CIT, Université de Groningen, Processus d'Activation Sélective par Transfert d'Energie Uni-électronique ou Radiatif (UMR 8640) (PASTEUR), Université Pierre et Marie Curie - Paris 6 (UPMC)-Département de Chimie - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut de Chimie du CNRS (INC)-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), Center for Operations and Econometrics, Center of Operation Research and Econometrics [Louvain] (CORE), Université Catholique de Louvain = Catholic University of Louvain (UCL)-Université Catholique de Louvain = Catholic University of Louvain (UCL), Finca El Encin, Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario (IMIDRA), Department of Surgery (EINDHOVEN - Surgery), Catharina Hospital, Institute for Mathematics, Astrophysics and Particle Physics (IMAPP), Harvard-Smithsonian Center for Astrophysics (CfA), Smithsonian Institution-Harvard University [Cambridge], Argelander-Institut für Astronomie (AlfA), Rheinische Friedrich-Wilhelms-Universität Bonn, ANR-09-JCJC-0001,OPALES(2009), Astronomy, KVI - Center for Advanced Radiation Technology, Radboud University [Nijmegen], Universiteit Leiden, Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome] (UNIROMA), École polytechnique (X)-Centre National de la Recherche Scientifique (CNRS), University of Oxford, 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), Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Harvard University-Smithsonian Institution, UMR Peuplement Végétaux et Bioagresseurs en Milieu Tropical (UMR PVBMT - INRA), Institut National de la Recherche Agronomique (INRA), 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), Technische Universität Dresden (TUD), university Rotterdam, 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)-PSL Research University (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Centre National d’Études Spatiales [Paris] (CNES), Wageningen University and Research Centre [Wageningen] (WUR), Università degli Studi di Roma 'La Sapienza' [Rome], Department of Physics, University of Crete [Heraklion] (UOC), Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas (FORTH), Anton de Kom University of Suriname, Geophysical Institute [Bergen], University of Bergen (UIB), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), Rhodes University, École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)-Centre National de la Recherche Scientifique (CNRS), SKA South Africa, Ska South Africa, Center for Operations and Econometrics, Universit´e catholique de Louvain and Fonds National de la Recherche Scientifique, Harvard University [Cambridge]-Smithsonian Institution, Observatoire de Paris - Site de Paris (OP), PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), ANR-09-JCJC-0001,OPALES,nOn-thermal Processes in gALaxy cluStErs(2009), High Energy Astrophys. & Astropart. Phys (API, FNWI), Van Haarlem, M.P., Wise, M.W., Gunst, A.W., Heald, G., McKean, J.P., Hessels, J.W.T., De Bruyn, A.G., Nijboer, R., Swinbank, J., Fallows, R., Brentjens, M., Nelles, A., Beck, R., Falcke, H., Fender, R., Hörandel, J., Koopmans, L.V.E., Mann, G., Miley, G., Röttgering, H., Stappers, B.W., Wijers, R.A.M.J., Zaroubi, S., Van Den Akker, M., Alexov, A., Anderson, J., Anderson, K., Van Ardenne, A., Arts, M., Asgekar, A., Avruch, I.M., Batejat, F., Bähren, L., Bell, M.E., Bell, M.R., Van Bemmel, I., Bennema, P., Bentum, M.J., Bernardi, G., Best, P., Bîrzan, L., Bonafede, A., Boonstra, A.-J., Braun, R., Bregman, J., Breitling, F., Van De Brink, R.H., Broderick, J., Broekema, P.C., Brouw, W.N., Brüggen, M., Butcher, H.R., Van Cappellen, W., Ciardi, B., Coenen, T., Conway, J., Coolen, A., Corstanje, A., Damstra, S., Davies, O., Deller, A.T., Dettmar, R.-J., Van Diepen, G., Dijkstra, K., Donker, P., Doorduin, A., Dromer, J., Drost, M., Van Duin, A., Eislöffel, J., Van Enst, J., Ferrari, C., Frieswijk, W., Gankema, H., Garrett, M.A., De Gasperin, F., Gerbers, M., De Geus, E., Grießmeier, J.-M., Grit, T., Gruppen, P., Hamaker, J.P., Hassall, T., Hoeft, M., Holties, H.A., Horneffer, A., Van Der Horst, A., Van Houwelingen, A., Huijgen, A., Iacobelli, M., Intema, H., Jackson, N., Jelic, V., De Jong, A., Juette, E., Kant, D., Karastergiou, A., Koers, A., Kollen, H., Kondratiev, V.I., Kooistra, E., Koopman, Y., Koster, A., Kuniyoshi, M., Kramer, M., Kuper, G., Lambropoulos, P., Law, C., Van Leeuwen, J., Lemaitre, J., Loose, M., Maat, P., Macario, G., Markoff, S., Masters, J., McFadden, R.A., McKay-Bukowski, D., Meijering, H., Meulman, H., Mevius, M., Middelberg, E., Millenaar, R., Miller-Jones, J.C.A., Mohan, R.N., Mol, J.D., Morawietz, J., Morganti, R., Mulcahy, D.D., Mulder, E., Munk, H., Nieuwenhuis, L., Van Nieuwpoort, R., Noordam, J.E., Norden, M., Noutsos, A., Offringa, A.R., Olofsson, H., Omar, A., Orrú, E., Overeem, R., Paas, H., Pandey-Pommier, M., Pandey, V.N., Pizzo, R., Polatidis, A., Rafferty, D., Rawlings, S., Reich, W., De Reijer, J.-P., Reitsma, J., Renting, G.A., Riemers, P., Rol, E., Romein, J.W., Roosjen, J., Ruiter, M., Scaife, A., Van Der Schaaf, K., Scheers, B., Schellart, P., Schoenmakers, A., Schoonderbeek, G., Serylak, M., Shulevski, A., Sluman, J., Smirnov, O., Sobey, C., Spreeuw, H., Steinmetz, M., Sterks, C.G.M., Stiepel, H.-J., Stuurwold, K., Tagger, M., Tang, Y., Tasse, C., Thomas, I., Thoudam, S., Toribio, M.C., Van Der Tol, B., Usov, O., Van Veelen, M., Van Der Veen, A.-J., Ter Veen, S., Verbiest, J.P.W., Vermeulen, R., Vermaas, N., Vocks, C., Vogt, C., De Vos, M., Van Der Wal, E., Van Weeren, R., Weggemans, H., Weltevrede, P., White, S., Wijnholds, S.J., Wilhelmsson, T., Wucknitz, O., Yatawatta, S., Zarka, P., Zensus, A., and Van Zwieten, J.
Subjects: instrumentation: interferometers -radio continuum: general -radio lines: general -dark ages, Computer science, Astronomy, INTERPLANETARY SCINTILLATION, radio continuum: general, 7. Clean energy, 01 natural sciences, Precision Array for Probing the Epoch of Reionization, law.invention, Observatory, law, first stars - telescopes, dark ages, instrumentation: interferometers, 010303 astronomy & astrophysics, Telescope, UNDERSTANDING RADIO POLARIMETRY, Instrumentation: Interferometer, SELF-CALIBRATION, Interferometry, ComputingMethodologies_DOCUMENTANDTEXTPROCESSING, reionization, Astrophysics - Instrumentation and Methods for Astrophysics, radio lines: general, first stars, Z-GREATER-THAN-5.7 QUASARS, FOS: Physical sciences, Murchison Widefield Array, 0103 physical sciences, RAY AIR-SHOWERS, Angular resolution, dark ages, reionization, first stars, Instrumentation and Methods for Astrophysics (astro-ph.IM), Remote sensing, 010308 nuclear & particles physics, telescopes, Astronomy and Astrophysics, LOFAR, Astronomy and Astrophysic, Sextant (astronomical), Dark ages, reionization, first star, Space and Planetary Science, [SDU]Sciences of the Universe [physics], PROBE WMAP OBSERVATIONS, DIGITAL SKY SURVEY, HIGH-REDSHIFT, MONTE-CARLO SIMULATIONS, INTERGALACTIC MEDIUM
Abstract: LOFAR, the LOw-Frequency ARray, is a new-generation radio interferometer constructed in the north of the Netherlands and across europe. Utilizing a novel phased-array design, LOFAR covers the largely unexplored low-frequency range from 10-240 MHz and provides a number of unique observing capabilities. Spreading out from a core located near the village of Exloo in the northeast of the Netherlands, a total of 40 LOFAR stations are nearing completion. A further five stations have been deployed throughout Germany, and one station has been built in each of France, Sweden, and the UK. Digital beam-forming techniques make the LOFAR system agile and allow for rapid repointing of the telescope as well as the potential for multiple simultaneous observations. With its dense core array and long interferometric baselines, LOFAR achieves unparalleled sensitivity and angular resolution in the low-frequency radio regime. The LOFAR facilities are jointly operated by the International LOFAR Telescope (ILT) foundation, as an observatory open to the global astronomical community. LOFAR is one of the first radio observatories to feature automated processing pipelines to deliver fully calibrated science products to its user community. LOFAR's new capabilities, techniques and modus operandi make it an important pathfinder for the Square Kilometre Array (SKA). We give an overview of the LOFAR instrument, its major hardware and software components, and the core science objectives that have driven its design. In addition, we present a selection of new results from the commissioning phase of this new radio observatory., Comment: 56 pages, 34 figures, accepted for publication by A&A
Published: 2013
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18. 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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19. 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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19 results on '"Hamaker, J.P."'

1. The shape of the radio wavefront of extensive air showers as measured with LOFAR

2. A very brief description of LOFAR -- the Low Frequency Array

3. The synthesis radio telescope at Westerbork.

4. Understanding radio polarimetry

5. Measurement Errors in Rotational Synthesis and their Effects in the Map Plane

6. “Kneading”: The Adjustment of Instrumental Phase and Gain Parameters to Suppress Error Patterns in a Synthesis Map

7. A simple RC realization of the 90° phase-difference network including source and load resistances

8. LOFAR discovery of a quiet emission mode in PSR B0823+26

9. Wide-band, low-frequency pulse profiles of 100 radio pulsars with LOFAR

10. The LOFAR Multifrequency Snapshot Sky Survey (MSSS): I. Survey description and first results

11. The shape of the radio wavefront of extensive air showers as measured with LOFAR

12. Initial LOFAR observations of epoch of reionization windows. II. Diffuse polarized emission in the ELAIS-N1 field

13. Discovery of carbon radio recombination lines in absorption towards Cygnus A

14. LOFAR Low-band Antenna Observations of the 3C 295 and Boötes Fields: Source Counts and Ultra-steep Spectrum Sources

15. The LOFAR pilot surveys for pulsars and fast radio transients

16. Studying Galactic interstellar turbulence through fluctuations in synchrotron emission First LOFAR Galactic foreground detection

17. LOFAR: The LOw-Frequency ARray

18. First LOFAR observations at very low frequencies of cluster-scale non-thermal emission: the case of Abell 2256

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

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19 results on '"Hamaker, J.P."'

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