TY - JOUR
T1 - The highest frequency detection of a radio relic
T2 - 16 GHz AMI observations of the 'Sausage' cluster
AU - Stroe, Andra
AU - Rumsey, Clare
AU - Harwood, Jeremy J.
AU - Van weeren, Reinout J.
AU - Röttgering, Huub J.A.
AU - Saunders, Richard D.E.
AU - Sobral, David
AU - Perrott, Yvette C.
AU - Schammel, Michel P.
N1 - This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters. © 2014 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
PY - 2014/6/11
Y1 - 2014/6/11
N2 - 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.
AB - 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.
KW - Acceleration of particles
KW - Radiation mechanisms: Non-thermal
KW - Radio continuum: General
KW - Shock waves
UR - http://www.scopus.com/inward/record.url?scp=84899917838&partnerID=8YFLogxK
U2 - 10.1093/mnrasl/slu045
DO - 10.1093/mnrasl/slu045
M3 - Article
AN - SCOPUS:84899917838
SN - 1745-3925
VL - 441
SP - L41–L45
JO - Monthly Notices of the Royal Astronomical Society: Letters
JF - Monthly Notices of the Royal Astronomical Society: Letters
IS - 1
M1 - slu045
ER -