HIGH-SENSITIVITY RADIO OBSERVATIONS OF THE COMA CLUSTER OF GALAXIES

We present radio observations of the Coma cluster of galaxies, performed at 326 MHz with the Westerbork Synthesis Radio Telescope and at 1.4 GHz with the Very Large Array. Owing to the large field of view and the high sensitivity, 31 radio sources are identified with bright galaxies (mpg≤15.7), six of them for the first time. Of the 31 radio-emitting galaxies, 29 belong to the Coma cluster. Detailed maps are given of the extended low-brightness structures present in the Coma cluster, i.e., the central halo source Coma C and the peripheral extended source 1253 + 275. A very low brightness bridge connecting them is revealed for the first time. CCD images, obtained with the Loiano telescope, are presented for 12 galaxies, 11 of which are radio emitting, and optical core radii are derived for the ellipticals and cD's. The bivariate radio luminosity function is computed to find out if the probability of radio emission of the galaxies correlates with their position within the cluster. It turns out that the probability of forming radio-emitting E galaxies is not related to their radial distance, while S galaxies within 0.5R A of the center have a larger probability of showing radio activity. A statistical analysis of the spectral index distribution α326 MHz1.4 GHZ of the field radio sources is performed to search for steep-spectrum sources. No candidate for the class of "relic" radio sources is found.