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The widest frequency radio relic spectra: observations from 150 MHz to 30 GHz

Stroe, Andra and Shimwell, Timothy and Rumsey, Clare and van Weeren, Reinout and Kierdorf, Maja and Donnert, Julius and Jones, Thomas W. and Röttgering, Huub J. A. and Hoeft, Matthias and Rodríguez-Gonzálvez, Carmen and Harwood, Jeremy J. and Saunders, Richard D. E. (2015) The widest frequency radio relic spectra: observations from 150 MHz to 30 GHz. Monthly Notices of the Royal Astronomical Society, 455 (3). pp. 2402-2416. ISSN 0035-8711.

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Radio relics are patches of diffuse synchrotron radio emission that trace shock waves. Relics are thought to form when intracluster medium electrons are accelerated by cluster merger-induced shock waves through the diffusive shock acceleration mechanism. In this paper, we present observations spanning 150 MHz to 30 GHz of the ‘Sausage’ and ‘Toothbrush’ relics from the Giant Metrewave and Westerbork telescopes, the Karl G. Jansky Very Large Array, the Effelsberg telescope, the Arcminute Microkelvin Imager and Combined Array for Research in Millimeter-wave Astronomy. We detect both relics at 30 GHz, where the previous highest frequency detection was at 16 GHz. The integrated radio spectra of both sources clearly steepen above 2 GHz, at the ≳6σ significance level, supporting the spectral steepening previously found in the ‘Sausage’ and the Abell 2256 relic. Our results challenge the widely adopted simple formation mechanism of radio relics and suggest more complicated models have to be developed that, for example, involve re-acceleration of aged seed electrons.

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Additional Information:© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 October 22. Received 2015 October 13; in original form 2015 July 20. First published online November 23, 2015. We would like to thank the anonymous referee for her/his useful comments which helped improve the clarity of the paper. We thank the staff of the Mullard Radio Astronomy Observatory for their invaluable assistance in the operation of AMI, which is supported by Cambridge University. Support for CARMA construction was derived from the states of California, Illinois and Maryland, the James S. McDonnell Foundation, the Gordon and Betty Moore Foundation, the Kenneth T. and Eileen L. Norris Foundation, the University of Chicago, the Associates of the California Institute of Technology and the National Science Foundation. This work is based in part on observations with the 100 m telescope of the MPIfR (Max-Planck-Institut für Radioastronomie) at Effelsberg. The Westerbork Synthesis Radio Telescope is operated by the ASTRON (Netherlands Institute for Radio Astronomy) with support from the Netherlands Foundation for Scientific Research (NWO). We thank the staff of the GMRT who have made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This research has made use of NASA's Astrophysics Data System. AS and HR acknowledge financial support from NWO (grant number: NWO-TOP LOFAR 614.001.006). TS and HR acknowledge support from the ERC Advanced Investigator programme NewClusters 321271. CR acknowledges the support of STFC studentships. RJvW is supported by NASA through the Einstein Postdoctoral grant number PF2-130104 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. TWJ acknowledges support from NSF (USA) grant AST1211595. MH acknowledges support by the research group FOR 1254 founded by the Deutsche Forschungsgemeinschaft. JJH wishes to thank the Netherlands Institute for Radio Astronomy (ASTRON) for a postdoctoral fellowship.
Funding AgencyGrant Number
states of California, Illinois, and MarylandUNSPECIFIED
James S. McDonnell FoundationUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Kenneth T. and Eileen L. Norris FoundationUNSPECIFIED
University of ChicagoUNSPECIFIED
Caltech AssociatesUNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)614.001.006
European Research Council (ERC)321271
Science and Technology Facilities Council (STFC)UNSPECIFIED
NASA Einstein Fellowship ProgramPF2-130104
Deutsche Forschungsgemeinschaft (DFG)UNSPECIFIED
Netherlands Institute for Radio Astronomy (ASTRON)UNSPECIFIED
Subject Keywords:acceleration of particles – radiation mechanisms: non-thermal – shock waves – galaxies: clusters: individual: 1RXS J0603.3+4214 – galaxies: clusters: individual: CIZA J2242.8+5301 – radio continuum: general
Issue or Number:3
Record Number:CaltechAUTHORS:20160204-143736957
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Official Citation:Andra Stroe, Timothy Shimwell, Clare Rumsey, Reinout van Weeren, Maja Kierdorf, Julius Donnert, Thomas W. Jones, Huub J. A. Röttgering, Matthias Hoeft, Carmen Rodríguez-Gonzálvez, Jeremy J. Harwood, and Richard D. E. Saunders The widest frequency radio relic spectra: observations from 150 MHz to 30 GHz MNRAS (January 21, 2016) Vol. 455 2402-2416 doi:10.1093/mnras/stv2472 First published online November 23, 2015
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:64242
Deposited By: Ruth Sustaita
Deposited On:04 Feb 2016 23:50
Last Modified:03 Oct 2019 09:36

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