2005A&A...440..867G

We present a new detailed multiband study of the merging cluster A3562, in the core of the Shapley Concentration Supercluster. We analyzed new, low frequency radio data performed at 240MHz, 332MHz and 610MHz with the Giant Metrewave Radio Telescope (GMRT). The new GMRT data allowed us to carry out a detailed study of the radio halo at the centre of A3562, as well as of the head-tail radio galaxy J1333-3141 embedded in it, and of the extended emission around the peripheral cluster galaxy J1332-3146a. Thanks to the present observations we could derive the integrated spectrum of the radio halo with five data points in the frequency range 240MHz-1.4GHz. Our data show a clear steepening of the total spectrum in this frequency range. Furthermore, by comparing the GMRT 332MHz image with a previously published VLA 1.4GHz image, we produced an image of the halo spectral index distribution. The image shows a very complex structure, with an average value of α^1.4GHz_332MHz∼1.5 and a number of knots steepening up to ∼2. We performed a combined morphological and statistical analysis using the radio images and the quantities derived from XMM-Newton and Chandra observations. We discuss our results in the light of particle re-acceleration processes in galaxy clusters. In particular, we outline an overall picture, consistent with the available radio and X-ray data, in which the cluster merger kinematics, the injection of turbulence and B-amplification induced by the merger between A3562 and SC1329-313 are jointly taken into account.