18 results on '"Rafferty, D.A."'
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2. Radio observations of the merging galaxy cluster Abell 520
- Author
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Hoang, D.N., Shimwell, T.W., Van Weeren, R.J., Brunetti, G., Röttgering, H.J.A., Andrade-Santos, F., Botteon, A., Brüggen, M., Cassano, R., Drabent, A., De Gasperin, F., Hoeft, M., Intema, Huib, Rafferty, D.A., Shweta, A., Stroe, A., Hoang, D.N., Shimwell, T.W., Van Weeren, R.J., Brunetti, G., Röttgering, H.J.A., Andrade-Santos, F., Botteon, A., Brüggen, M., Cassano, R., Drabent, A., De Gasperin, F., Hoeft, M., Intema, Huib, Rafferty, D.A., Shweta, A., and Stroe, A.
- Abstract
Context. Extended synchrotron radio sources are often observed in merging galaxy clusters. Studies of the extended emission help us to understand the mechanisms in which the radio emitting particles gain their relativistic energies. Aims. We examine the possible acceleration mechanisms of the relativistic particles that are responsible for the extended radio emission in the merging galaxy cluster Abell 520. Methods. We performed new 145 MHz observations with the LOw Frequency ARay (LOFAR) and combined these with archival Giant Metrewave Radio Telescope (GMRT) 323 MHz and Very Large Array (VLA) 1.5 GHz data to study the morphological and spectral properties of extended cluster emission. The observational properties are discussed in the framework of particle acceleration models associated with cluster merger turbulence and shocks. Results. In Abell 520, we confirm the presence of extended (760 × 950 kpc 2 ) synchrotron radio emission that has been classified as a radio halo. The comparison between the radio and X-ray brightness suggests that the halo might originate in a cocoon rather than from the central X-ray bright regions of the cluster. The halo spectrum is roughly uniform on the scale of 66 kpc. There is a hint of spectral steepening from the SW edge towards the cluster centre. Assuming diffusive shock acceleration (DSA), the radio data are suggestive of a shock Mach number of SW = 2.6-0.2 +0.3 that is consistent with the X-ray derived estimates. This is in agreement with the scenario in which relativistic electrons in the SW radio edge gain their energies at the shock front via acceleration of either thermal or fossil electrons. We do not detect extended radio emission ahead of the SW shock that is predicted if the emission is the result of adiabatic compression. An X-ray surface brightness discontinuity is detected towards the NE region that may be a counter shock of Mach number NE X = 1.52±0.05. This is lower than the value predicted from the radio emission
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- 2019
3. Corrigendum: Radio observations of the merging galaxy cluster Abell 520 (Astronomy and Astrophysics (2019) 622 (A20) DOI: 10.1051/0004-6361/201833900)
- Author
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Hoang, D.N., Shimwell, T.W., Van Weeren, R.J., Brunetti, G., Röttgering, H.J.A., Andrade-Santos, F., Botteon, A., Brüggen, M., Cassano, R., Drabent, A., De Gasperin, F., Hoeft, M., Intema, Huib, Rafferty, D.A., Shweta, A., Stroe, A., Hoang, D.N., Shimwell, T.W., Van Weeren, R.J., Brunetti, G., Röttgering, H.J.A., Andrade-Santos, F., Botteon, A., Brüggen, M., Cassano, R., Drabent, A., De Gasperin, F., Hoeft, M., Intema, Huib, Rafferty, D.A., Shweta, A., and Stroe, A.
- Abstract
© ESO 2019. Some errors have occurred during the production of the original article. The left panel of Fig. 8 was incomplete. Here we publish the correct Fig. 8. Also, Eq. (5) was incorrect, it should read: (Figure Presented).
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- 2019
4. LOFAR MSSS: The scaling relation between AGN cavity power and radio luminosity at low radio frequencies
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Kokotanekov, G., Wise, M., Heald, G.H., McKean, J.P., Birzan, L., Rafferty, D.A., Godfrey, L.E.H., Vries, M de, Intema, H.T., Broderick, J.W., Hardcastle, M.J., Bonafede, A., Clarke, A.O., Weeren, R.J. van, Rottgering, H.J.A., Pizzo, R., Iacobelli, M., Orru, E., Shulevski, A., Riseley, C.J., Breton, R.P., Nikiel-Wroczynski, B., Sridhar, S.S., Stewart, A.J., Rowlinson, A., Horst, A.J. van der, Harwood, J.J., Gurkan, G., Carbone, D., Pandey-Pommier, M., Tasse, C., Scaife, A.M.M., Pratley, L., Ferrari, C., Croston, J.H., Pandey, V.N., Jurusik, W., Mulcahy, D.D., Kokotanekov, G., Wise, M., Heald, G.H., McKean, J.P., Birzan, L., Rafferty, D.A., Godfrey, L.E.H., Vries, M de, Intema, H.T., Broderick, J.W., Hardcastle, M.J., Bonafede, A., Clarke, A.O., Weeren, R.J. van, Rottgering, H.J.A., Pizzo, R., Iacobelli, M., Orru, E., Shulevski, A., Riseley, C.J., Breton, R.P., Nikiel-Wroczynski, B., Sridhar, S.S., Stewart, A.J., Rowlinson, A., Horst, A.J. van der, Harwood, J.J., Gurkan, G., Carbone, D., Pandey-Pommier, M., Tasse, C., Scaife, A.M.M., Pratley, L., Ferrari, C., Croston, J.H., Pandey, V.N., Jurusik, W., and Mulcahy, D.D.
- Abstract
Contains fulltext : 178435.pdf (preprint version ) (Open Access)
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- 2017
5. The duty cycle of radio mode feedback
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Bîrzan, L., Rafferty, D.A., Nulsen, P.E.J., McNamara, B.R., Röttgering, H.J.A., Wise, M.W., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Cosmology and Extragalactic Astrophysics - Abstract
The Chandra X-ray Observatory has revealed X-ray bubbles in the intracluster medium (ICM) of many nearby clusters, which are thought to be created by the central active galactic nucleus (AGN). However, the duty cycle of such AGN outbursts is not well understood. In order to further understand how cooling is balanced by bubble heating we studied complete samples of cooling flow clusters (from the Brightest 55 clusters of galaxies sample, B55, and the HIghest X-ray FLUx Galaxy Cluster Sample, HIFLUGCS). We found that there is a radio luminosity cut-off of 2.5×1030 erg s-1 Hz-1 for the cooling flow clusters. Furthermore, we find a duty cycle for radio mode feedback, the fraction of time that a system possesses bubbles inflated by its central radio source, of ≳ 69 % for the B55 sample and ≳ 63 % for the HIFLUGCS sample. These duty cycles are lower limits since some bubbles are likely missed in existing images. We used simulations to constrain the bubble power that might be present and remain undetected in the cooling flow systems without detected bubbles. Among theses systems, almost all could have significant bubble power. Therefore, our results imply that the duty cycle of AGN outbursts with the potential to heat the gas significantly in cooling flow clusters is at least 60% and could approach 100 %.
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- 2013
6. First LOFAR results on galaxy clusters
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Ferrari, C., van Bemmel, I., Bonafede, A., Bîrzan, L., Brüggen, M., Brunetti, G., Cassano, R., Conway, J., De Gasperin, F., Heald, G., Jackson, N., Macario, G., McKean, J., Offringa, A.R., Orrù, E., Pizzo, R., Rafferty, D.A., Röttgering, H.J.A., Shulevski, A., Tasse, C., van der Tol, S., van Weeren, R.J., Wise, M., van Zwieten, J.E., LOFAR Collaboration, [Unknown], Boissier, S., de Laverny, P., Nardetto, N., Samadi, R., Valls-Gabaud, D., Wozniak, H., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Deep radio observations of galaxy clusters have revealed the existence of diffuse radio sources related to the presence of relativistic electrons and weak magnetic fields in the intracluster volume. The role played by this non-thermal intracluster component on the thermodynamical evolution of galaxy clusters is debated, with important implications for cosmological and astrophysical studies of the largest gravitationally bound structures of the Universe. The low surface brightness and steep spectra of diffuse cluster radio sources make them more easily detectable at low-frequencies. LOFAR is the first instrument able to detect diffuse radio emission in hundreds of massive galaxy clusters up to their formation epoch (z ˜ 1). We present the first observations of clusters imaged by LOFAR and the huge perspectives opened by this instrument for non-thermal cluster studies.
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- 2012
7. Jet interactions with the hot halos of clusters and galaxies
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McNamara, B.R., Bîrzan, L., Rafferty, D.A., Nulsen, P.E.J., Carilli, C., Wise, M.W., Rector, T.A., De Young, D.S., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
X-ray observations of cavities and shock fronts produced by jets streaming through hot halos have significantly advanced our understanding of the energetics and dynamics of extragalactic radio sources. Radio sources at the centers of clusters have dynamical ages between ten and several hundred million years. They liberate between 1058−62 erg per outburst, which is enough energy to regulate cooling of hot halos from galaxies to the richest clusters. Jet power scales approximately with the radio synchrotron luminosity to the one half power. However, the synchrotron efficiency varies widely from nearly unity to one part in 10,000, such that relatively feeble radio source can have quasar-like mechanical power. The synchrotron ages of cluster radio sources are decoupled from their dynamical ages, which tend to be factors of several to orders of magnitude older. Magnetic fields and particles in the lobes tend to be out of equipartition. The lobes may be maintained by heavy particles (e.g., protons), low energy electrons, a hot, diffuse thermal gas, or possibly magnetic (Poynting) stresses. Sensitive X-ray images of shock fronts and cavities can be used to study the dynamics of extragalactic radio sources.
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- 2008
8. AGN Heating through Cavities and Shocks
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Nulsen, P.E.J., Jones, C., Forman, W.R., David, L.P., McNamara, B.R., Rafferty, D.A., Bîrzan, L., Wise, M., and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics (astro-ph) ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
Three comments are made on AGN heating of cooling flows. A simple physical argument is used to show that the enthalpy of a buoyant radio lobe is converted to heat in its wake. Thus, a significant part of ``cavity'' enthalpy is likely to end up as heat. Second, the properties of the repeated weak shocks in M87 are used to argue that they can plausibly prevent gas close to the AGN from cooling. As the most significant heating mechanism at work closest to the AGN, shock heating probably plays a critical role in the feedback mechanism. Third, results are presented from a survey of AGN heating rates in nearby giant elliptical galaxies. With inactive systems included, the overall AGN heating rate is reasonably well matched to the total cooling rate for the sample. Thus, intermittent AGN outbursts are energetically capable of preventing the hot atmospheres of these galaxies from cooling and forming stars., 6 pages, 2 figures, for proceedings of "Heating vs. Cooling in Galaxies and Clusters of Galaxies," eds H. Boehringer, P. Schuecker, G. W. Pratt & A. Finoguenov, in Springer-Verlag series "ESO Astrophysics Symposia."
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- 2006
9. The duty cycle of the radio mode feedback
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Bîrzan, L., primary, Rafferty, D.A., additional, Nulsen, P.E.J., additional, McNamara, B.R., additional, Röttgering, H.J.A., additional, and Wise, M.W., additional
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- 2013
- Full Text
- View/download PDF
10. AGN Heating Through Cavities and Shocks.
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Leibundgut, Bruno, Böhringer, H., Pratt, G.W., Finoguenov, A., Schuecker, P., Nulsen, P.E.J., Jones, C., Forman, W.R., David, L.P., McNamara, B.R., Rafferty, D.A., Bîrzan, L., and Wise, M.W.
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- 2007
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11. Feedback at the Working Surface: A Joint X-ray and Low-Frequency Radio Spectral Study of the Cocoon Shock in Cygnus A
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Wise, M.W., Rafferty, D.A., McKean, J.P., Astronomy, and High Energy Astrophys. & Astropart. Phys (API, FNWI)
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Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics::Galaxy Astrophysics - Abstract
We report on preliminary results from a joint spectral analysis of the cocoon shock region in Cygnus A using deep archival Chandra data and new low-frequency radio data from LOFAR. Being both bright in X-rays and the most powerful radio source in the local universe, the FRII radio galaxy Cygnus A represents an ideal opportunity to study the interaction between the jets produced by the central AGN and the surrounding intracluster medium (ICM) in which that AGN is embedded. Using the entire 235 ksec archival Chandra exposure, we have performed a spatially resolved, X-ray spectral analysis of the ICM in Cygnus A. By combining the resulting X-ray images and temperature maps with spectral index maps between 30-80 MHz and 120-180 MHz calculated from a recent, deep LOFAR observation, we can resolve the X-ray and radio emitting plasmas in any given region on spatial scales of 3-4 kpc over the central 100 kpc. We clearly resolve the cocoon shock surrounding Cygnus A and determine the Mach number of the shock as a function of position angle. Temperature jumps associated with this shock are detected over a large fraction of the total shock circumference. Significant non-thermal emission is also detected in the regions surrounding the SE and NW leading edges of the shock near the hotspots. In this talk, we will present a detailed analysis of the energetics of this interface region between the radio plasma inside the cocoon shock and the X-ray emitting gas outside the shock. Inside the shock, we will present constraints on the emission mechanisms in the jet, counter-jet, and hotspots based on the combined radio and X-ray spectra. Using maps of the spectral age derived from the LOFAR data and independent age estimates based on various cavity features seen in the X-ray image, we will present a picture of the evolution of the shock region in Cygnus A over the past 50 Myr. Finally, we will discuss the implications these observations have for AGN feedback models as well as the energy transfer mechanism itself.
12. A Massive Cluster at z = 0.288 Caught in the Process of Formation: The Case of Abell 959
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Bîrzan, L., Rafferty, D.A., Cassano, R., Brunetti, G., Weeren, RJ van, Brüggen, M., Intema, Huib, Gasperin, F de, Andrade-Santos, F., Botteon, A., Röttgering, H.J.A., Shimwell, T.W., Bîrzan, L., Rafferty, D.A., Cassano, R., Brunetti, G., Weeren, RJ van, Brüggen, M., Intema, Huib, Gasperin, F de, Andrade-Santos, F., Botteon, A., Röttgering, H.J.A., and Shimwell, T.W.
- Abstract
The largest galaxy clusters are observed still to be forming through major cluster-cluster mergers, often showing observational signatures such as radio relics and giant radio haloes. Using LOFAR Two-meter Sky Survey data, we present new detections of both a radio halo (with a spectral index of $\alpha_{143}^{1400}=1.48^{+0.06}_{-0.23}$) and a likely radio relic in Abell 959, a massive cluster at a redshift of z=0.288. Using a sample of clusters with giant radio haloes from the literature (80 in total), we show that the radio halo in A959 lies reasonably well on the scaling relations between the thermal and non-thermal power of the system. Additionally, we find evidence that steep-spectrum haloes tend to reside in clusters with high X-ray luminosities relative to those expected from cluster LM scaling relations, indicating that such systems may preferentially lie at an earlier stage of the merger, consistent with the theory that some steep-spectrum haloes result from low-turbulence mergers. Lastly, we find that halo systems containing radio relics tend to lie at lower X-ray luminosities, relative to those expected from cluster LM scaling relations, for a given halo radio power than those without relics, suggesting that the presence of relics indicates a later stage of the merger, in line with simulations.
13. LOFAR, VLA, and Chandra Observations of the Toothbrush Galaxy Cluster
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H. J. A. Röttgering, Christine Jones, Laura Birzan, William A. Dawson, Georgiana A. Ogrean, J. Sabater, Judith H. Croston, Torsten A. Ensslin, S. S. Murray, T. J. Dijkema, Martin J. Hardcastle, S. S. Sridhar, S. van der Tol, Lawrence Rudnick, Roberto Pizzo, Marcus Brüggen, Rossella Cassano, Cathy Horellou, Maaijke Mevius, Aurora Simionescu, William R. Forman, Craig L. Sarazin, George Heald, Glenn J. White, Krzysztof T. Chyzy, Emanuela Orrú, Andra Stroe, G. K. Miley, Annalisa Bonafede, Wendy L. Williams, D. A. Rafferty, Hubertus Intema, G. Brunetti, Timothy W. Shimwell, Felipe Andrade-Santos, R. J. van Weeren, Philip Best, Chiara Ferrari, Matthias Hoeft, Ralph P. Kraft, Matt J. Jarvis, F. de Gasperin, Astronomy, Van Weeren, R.J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G.A., Williams, W.L., Röttgering, H.J.A., Dawson, W.A., Forman, W.R., Gasperin, F. De, Hardcastle, M.J., Jones, C., Miley, G.K., Rafferty, D.A., Rudnick, L., Sabater, J., Sarazin, C.L., Shimwell, T.W., Bonafede, A., Best, P.N., Birzan, L., Cassano, R., Chyzy, K.T., Croston, J.H., Dijkema, T.J., Enßlin, T., Ferrari, C., Heald, G., Hoeft, M., Horellou, C., Jarvis, M.J., Kraft, R.P., Mevius, M., Intema, H.T., Murray, S.S., Orrú, E., Pizzo, R., Sridhar, S.S., Simionescu, A., Stroe, A., Tol, S. Van Der, and White, G.J.
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clusters: individual: RX J0603.3+4214 [galaxies] ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,galaxies: clusters: intracluster medium ,Radio galaxy ,Astrophysics::High Energy Astrophysical Phenomena ,Population ,FOS: Physical sciences ,galaxies: clusters: individual: RX J0603.3+4214 ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Radio relics ,0103 physical sciences ,education ,010303 astronomy & astrophysics ,Galaxy cluster ,Astrophysics::Galaxy Astrophysics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,large-scale structure of universe ,education.field_of_study ,Spectral index ,010308 nuclear & particles physics ,galaxies: clusters: individual (RX J0603.3+4214) ,largescale structure of universe ,Astronomy and Astrophysics ,LOFAR ,Astronomy and Astrophysic ,radiation mechanisms: non-thermal ,non-thermal [radiation mechanisms] ,X-rays: galaxies: cluster ,Particle acceleration ,Radio halo ,clusters: intracluster medium [galaxies] ,Space and Planetary Science ,X-rays: galaxies: clusters ,large-scale structure of Universe ,galaxies: clusters [X-rays] ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
著者人数: 42名, Accepted: 2016-01-18, 資料番号: SA1160090000
- Published
- 2016
14. LOFAR FACET CALIBRATION
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Chiara Ferrari, Craig L. Sarazin, Rossella Cassano, Ralph P. Kraft, Matthias Hoeft, George Heald, R. Pizzo, Gianfranco Brunetti, Lawrence Rudnick, J. Sabater, Laura Birzan, S. S. Murray, William A. Dawson, Huub Röttgering, Glenn J. White, Aurora Simionescu, George K. Miley, Huib Intema, Andra Stroe, Matt J. Jarvis, D. A. Rafferty, Felipe Andrade-Santos, Philip Best, Cathy Horellou, F. de Gasperin, R. J. van Weeren, Krzysztof T. Chyzy, M. Mevius, Wendy L. Williams, Judith H. Croston, Martin J. Hardcastle, Marcus Brüggen, S. S. Sridhar, William R. Forman, S. van der Tol, T. J. Dijkema, Timothy W. Shimwell, Georgiana A. Ogrean, Annalisa Bonafede, Torsten A. Ensslin, Emanuela Orru, Christine Jones, Ferrari, Chiara, Harvard-Smithsonian Center for Astrophysics (CfA), Harvard University [Cambridge]-Smithsonian Institution, Leiden University, Netherlands Institute for Radio Astronomy (ASTRON), University of Hertfordshire [Hatfield] (UH), Hamburger Sternwarte/Hamburg Observatory, Universität Hamburg (UHH), Institute for Astronomy [Edinburgh] (IfA), University of Edinburgh, Kapteyn Astronomical Institute [Groningen], University of Groningen [Groningen], Istituto di Radioastronomia [Bologna] (IRA), Istituto Nazionale di Astrofisica (INAF), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], Lawrence Livermore National Laboratory (LLNL), University of Minnesota [MN, USA], University of Virginia, Uniwersytet Jagielloński w Krakowie = Jagiellonian University (UJ), University of Southampton, Max Planck Institute for Astrophysics, Max-Planck-Gesellschaft, 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), Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA), Thüringer Landessternwarte Tautenburg (TLS), Chalmers University of Technology [Gothenburg, Sweden], Oxford Astrophysics, University of Oxford, University of the Western Cape, National Radio Astronomy Observatory [Socorro] (NRAO), National Radio Astronomy Observatory (NRAO), Johns Hopkins University (JHU), Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency [Sagamihara] (JAXA), The Open University [Milton Keynes] (OU), STFC Rutherford Appleton Laboratory (RAL), Science and Technology Facilities Council (STFC), Astronomy, Smithsonian Institution-Harvard University [Cambridge], University of Virginia [Charlottesville], 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, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), University of Oxford [Oxford], Weeren, R. J. Van, Williams, W.L., Hardcastle, M.J., Shimwell, T.W., Rafferty, D.A., Sabater, J., Heald, G., Sridhar, S.S., Dijkema, T.J., Brunetti, G., Brüggen, M., Andrade-Santos, F., Ogrean, G.A., Röttgering, H.J.A., Dawson, W.A., Forman, W.R., Gasperin, F. De, Jones, C., Miley, G.K., Rudnick, L., Sarazin, C.L., Bonafede, A., Best, P.N., Birzan, L., Cassano, R., Chyzy, K.T., Croston, J.H., Ensslin, T., Ferrari, C., Hoeft, M., Horellou, C., Jarvis, M.J., Kraft, R.P., Mevius, M., Intema, H.T., Murray, S.S., Orrú, E., Pizzo, R., Simionescu, A., Stroe, A., Tol, S. Van Der, and White, G.J.
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Facet (geometry) ,Computer science ,[SDU.ASTR.CO]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] ,media_common.quotation_subject ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,FOS: Physical sciences ,Field of view ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Radio telescope ,[SDU.ASTR.IM] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM] ,0103 physical sciences ,Calibration ,010303 astronomy & astrophysics ,Instrumentation and Methods for Astrophysics (astro-ph.IM) ,media_common ,Remote sensing ,[SDU.ASTR.CO] Sciences of the Universe [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO] ,010308 nuclear & particles physics ,Astrophysics::Instrumentation and Methods for Astrophysics ,Astronomy and Astrophysics ,LOFAR ,technique ,Astronomy and Astrophysic ,interferometric [techniques] ,[SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM] ,Space and Planetary Science ,Sky ,techniques: interferometric ,interferometric ,Ionosphere ,Antenna (radio) ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
著者人数: 42名, Accepted: 2016-01-18, 資料番号: SA1160093000
- Published
- 2016
- Full Text
- View/download PDF
15. LOFAR Low-band Antenna Observations of the 3C 295 and Boötes Fields: Source Counts and Ultra-steep Spectrum Sources
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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
- Full Text
- View/download PDF
16. First LOFAR observations at very low frequencies of cluster-scale non-thermal emission: the case of Abell 2256
- Author
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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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- View/download PDF
17. Revealing a population of heavily obscured active galactic nuclei at z ≈ 0.5-1 in the Chandra deep field-south
- Author
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Franz E. Bauer, W. N. Brandt, Donald P. Schneider, Yongquan Xue, Andrew C. Fabian, Cristian Vignali, Bret D. Lehmer, Marcella Brusa, D. A. Rafferty, Roberto Gilli, Andrea Comastri, David M. Alexander, Bin Luo, Luo B., Brandt W.N., Xue Y.Q., Alexander D.M., Brusa M., Bauer F.E., Comastri A., Fabian A.C., Gilli R., Lehmer B.D., Rafferty D.A., Schneider D.P., and Vignali C.
- Subjects
Active galactic nucleus ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Population ,Extinction (astronomy) ,galaxies: active ,FOS: Physical sciences ,galaxies: starburst ,Starburst ,Astrophysics ,cosmic background radiation ,Cosmic background radiation ,Luminosity ,Photometry ,X-rays ,education ,Luminous infrared galaxy ,Physics ,High Energy Astrophysical Phenomena (astro-ph.HE) ,education.field_of_study ,infrared: galaxie ,Astronomy ,Astronomy and Astrophysics ,Extragalactic astronomy ,Galaxies ,Galaxy ,galaxies: photometry ,X-rays: galaxies ,Space and Planetary Science ,Chandra Deep Field South ,Astrophysics - High Energy Astrophysical Phenomena ,Infrared ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
(abridged) We identify a numerically significant population of heavily obscured AGNs at z~0.5-1 in the Chandra Deep Field-South (CDF-S) and Extended Chandra Deep Field-South by selecting 242 X-ray undetected objects with infrared-based star formation rates (SFRs) substantially higher (a factor of 3.2 or more) than their SFRs determined from the UV after correcting for dust extinction. An X-ray stacking analysis of 23 candidates in the central CDF-S region using the 4 Ms Chandra data reveals a hard X-ray signal with an effective power-law photon index of Gamma=0.6_{-0.4}^{+0.3}, indicating a significant contribution from obscured AGNs. Based on Monte Carlo simulations, we conclude that 74+-25% of the selected galaxies host obscured AGNs, within which ~95% are heavily obscured and ~80% are Compton-thick (CT; NH>1.5x10^{24} cm^{-2}). The heavily obscured objects in our sample are of moderate intrinsic X-ray luminosity [ ~ (0.9-4)x10^{42} erg/s in the 2-10 keV band]. The space density of the CT AGNs is (1.6+-0.5)x10^{-4} Mpc^{-3}. The z~0.5-1 CT objects studied here are expected to contribute ~1% of the total XRB flux in the 10-30 keV band, and they account for ~5-15% of the emission in this energy band expected from all CT AGNs according to population-synthesis models. In the 6--8 keV band, the stacked signal of the 23 heavily obscured candidates accounts for, 17 pages, 7 figures. ApJ in press
- Published
- 2011
18. Identifications and Photometric Redshifts of the 2 Ms Chandra Deep Field-South Sources
- Author
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Andrea Comastri, Anton M. Koekemoer, Bret D. Lehmer, Marcella Brusa, Donald P. Schneider, Yongquan Xue, Cristian Vignali, David Rafferty, V. Mainieri, John D. Silverman, David M. Alexander, W. N. Brandt, Bin Luo, Franz E. Bauer, Luo B., Brandt W.N., Xue Y., Brusa M., Alexander D.M., Bauer F.E., Comastri A., Koekemoer A., Lehmer B.D., Mainieri V., Rafferty D.A., Schneider D.P., Silverman J.D., and Vignali C.
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,Cosmology and Nongalactic Astrophysics (astro-ph.CO) ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astronomy and Astrophysics ,cosmology: observations – galaxies: active – galaxies: distances and redshifts – galaxies: photometry – X-rays: galaxies ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Redshift ,Space and Planetary Science ,Outlier ,Chandra Deep Field South ,Astrophysics - High Energy Astrophysical Phenomena ,Astrophysics::Galaxy Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics - Abstract
[Abridged] We present reliable multiwavelength identifications and high-quality photometric redshifts for the 462 X-ray sources in the ~2 Ms Chandra Deep Field-South. Source identifications are carried out using deep optical-to-radio multiwavelength catalogs, and are then combined to create lists of primary and secondary counterparts for the X-ray sources. We identified reliable counterparts for 446 (96.5%) of the X-ray sources, with an expected false-match probability of ~6.2%. A likelihood-ratio method is used for source matching, which effectively reduces the false-match probability at faint magnitudes compared to a simple error-circle matching method. We construct a master photometric catalog for the identified X-ray sources including up to 42 bands of UV-to-infrared data, and then calculate their photometric redshifts (photo-z's). The reliability of the photo-z's is evaluated using the subsample of 220 sources with secure spectroscopic redshifts. We achieve an accuracy of ~1% [|Delta z|/(1+z)] and an outlier fraction of ~1.4% for sources with spectroscopic redshifts. We performed blind tests to derive a more realistic estimate of the photo-z quality for sources without spectroscopic redshifts. We expect there are ~9% outliers for the relatively brighter sources (R26). The typical photo-z accuracy is ~6-7%. The outlier fraction and photo-z accuracy do not appear to have a redshift dependence (for z~0-4). These photo-z's appear to be the best obtained so far for faint X-ray sources, and they have been significantly (>50%) improved compared to previous estimates of the photo-z's for the X-ray sources in the ~2 Ms Chandra Deep Field-North and ~1 Ms Chandra Deep Field-South., ApJS accepted. Minor updates compared to the submitted version. 22 pages, 15 figures. Catalogs may be requested from lbin@astro.psu.edu
- Published
- 2010
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