Radio Observations of the Cluster of Galaxies in Coma Berenices-- the 5C4 Survey

Abstract

High-resolution observations of the Coma cluster have enabled the detection of 189 radio sources with |${S}_{408}\,\gt\,16\,\times\,{10}^{-29}\,\text{W}\,\text{m}^{-2}\,\text{Hz}^{-1}$|⁠. Twenty-four were also detected at 1407 MHz. Most of them are believed to be field objects unconnected with the cluster. Optical identifications are suggested for many and the counts and spectra are compared with the results of earlier 5C surveys. Two components of the complex of radio sources Coma C coincide with the bright galaxies NGC 4874 and NGC 4869, and about nine other cluster galaxies have radio luminosities |${P}_{408}\,\gtrsim\,{10}^{21}\,\text{W}\,\text{Hz}^{-1}\,\text{sr}^{-1}$|⁠. It is shown that the other component of Coma C, a large diameter source observed at low frequencies, must be intergalactic emission rather than the integrated radiation from normal galaxies. Such extensive sources appear to be a common feature of rich clusters. The extended source, and the emission associated with NGC 4869, may be due to the ejection of relativistic particles from NGC 4874 at a mean rate of |${10}^{51}\,\text{erg}\,\text{yr}^{-1}$| for the past |$3.5\,\times\,{10}^{9}\,\text{yr}$|⁠.