2007A&A...476...99G

We present a radio morphological study and spectral analysis of a sample of 13 cD galaxies in rich and poor clusters of galaxies. Our study is based on new high sensitivity Giant Metrewave Radio Telescope (GMRT) observations at 1.28GHz, 610MHz and 235MHz, and on archival data. From a statistical sample of cluster cD galaxies we selected those sources with little information available in the literature and promising for the detection of aged radio emission. As well as the high sensitivity images for all 13 radio galaxies, we present also a detailed spectral analysis for 7 of them. We found a variety of morphologies and linear sizes, as typical for radio galaxies in the radio power range sampled here (low to intermediate power radio galaxies). The spectral analysis shows that 10/13 radio galaxies have a steep radio spectrum, with spectral index α≥1. In general, the radiative ages and growth velocities are consistent with previous findings that the evolution of radio galaxies at cluster centres is affected by the dense external medium (i.e. low growth velocities and old ages). We suggest that the dominant galaxies in A2622 and MKW03s are dying radio sources, which at present are not fed by nuclear activity. On the other hand, the spectacular source at the centre of A2372 might be a very interesting example of a restarted radio galaxy. For this source we estimated a life cycle of the order of 10⁶yr.