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

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, Richard D.E. Saunders

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


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 mergerinduced 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.

Original languageEnglish
Pages (from-to)2402-2416
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date21 Nov 2015
Publication statusPublished - 21 Jan 2016


  • Acceleration of particles
  • Galaxies: clusters: individual: 1RXS j0603.3+4214
  • Galaxies: clusters: individual: CIZA j2242.8+5301
  • Radiation mechanisms: non-thermal
  • Radio continuum: general
  • Shock waves


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