The highest frequency detection of a radio relic: 16 GHz AMI observations of the 'Sausage' cluster

Andra Stroe, Clare Rumsey, Jeremy J. Harwood, Reinout J. Van weeren, Huub J.A. Röttgering, Richard D.E. Saunders, David Sobral, Yvette C. Perrott, Michel P. Schammel

    Research output: Contribution to journalArticlepeer-review

    30 Citations (Scopus)
    14 Downloads (Pure)


    We observed the cluster CIZA J2242.8+5301 with the Arcminute Microkelvin Imager at 16 GHz and present the first high radio-frequency detection of diffuse, non-thermal cluster emission. This cluster hosts a variety of bright, extended, steep-spectrum synchrotron-emitting radio sources, associated with the intracluster medium, called radio relics. Most notably, the northern, Mpc-wide, narrow relic provides strong evidence for diffusive shock acceleration in clusters. We detect a puzzling, flat-spectrum, diffuse extension of the southern relic, which is not visible in the lower radio-frequency maps. The northern radio relic is unequivocally detected and measures an integrated flux of 1.2 ± 0.3 mJy. While the low-frequency (<2 GHz) spectrum of the northern relic is well represented by a power law, it clearly steepens towards 16 GHz. This result is inconsistent with diffusive shock acceleration predictions of ageing plasma behind a uniform shock front. The steepening could be caused by an inhomogeneous medium with temperature/density gradients or by lower acceleration efficiencies of high energy electrons. Further modelling is necessary to explain the observed spectrum.

    Original languageEnglish
    Article numberslu045
    Pages (from-to)L41–L45
    JournalMonthly Notices of the Royal Astronomical Society: Letters
    Issue number1
    Early online date15 Apr 2014
    Publication statusPublished - 11 Jun 2014


    • Acceleration of particles
    • Radiation mechanisms: Non-thermal
    • Radio continuum: General
    • Shock waves


    Dive into the research topics of 'The highest frequency detection of a radio relic: 16 GHz AMI observations of the 'Sausage' cluster'. Together they form a unique fingerprint.

    Cite this