Redshift evolution of the 1.4 GHz volume averaged radio luminosity function in clusters of galaxies

¹ Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
e-mail: mnord@astro.uni-bonn.de
² Max Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received: 15 November 2010
Accepted: 15 March 2011

Abstract

By cross-correlating large samples of galaxy clusters with publicly available radio source catalogs, we construct the volume-averaged radio luminosity function (RLF) in clusters of galaxies, and investigate its dependence on cluster redshift and mass. In addition, we determine the correlation between the cluster mass and the radio luminosity of the brightest source within 50 kpc from the cluster center. We use two cluster samples: the optically selected maxBCG cluster catalog and a composite sample of X-ray selected clusters. The radio data come from the VLA NVSS and FIRST surveys. We use scaling relations to estimate cluster masses and radii to get robust estimates of cluster volumes. We determine the projected radial distribution of sources, for which we find no dependence on luminosity or cluster mass. Background and foreground sources are statistically accounted for, and we account for confusion of radio sources by adaptively degrading the resolution of the radio source surveys. We determine the redshift evolution of the RLF under the assumption that its overall shape does not change with redshift. Our results are consistent with a pure luminosity evolution of the RLF in the range 0.1 ≤ z ≤ 0.3 from the optical cluster sample. The X-ray sample extends to higher redshift and yields results also consistent with a pure luminosity evolution. We find no direct evidence of a dependence of the RLF on cluster mass from the present data, although the data are consistent with the most luminous sources only being found in high-mass systems.