Sensitive Radio and Optical Observations of z ∼ 0.2 Rich Abell Clusters

Abstract

We present optical observations and radio continuum imaging data for a sample of rich, X-ray–bright Abell clusters at intermediate (z ~ 0.2) redshifts. We find that the radio galaxy population varies substantially from cluster to cluster within this homogeneous sample. The spatial distribution of the high-luminosity radio galaxies (HLRGs; L1.4 > 1023 W Hz-1) is very different from the low-luminosity radio galaxies (LLRGs; L1.4 ≤ 1022.75 W Hz-1), with the LLRGs displaying a flat spatial distribution in contrast to the centrally peaked HLRGs. A color-morphology classification shows that the HLRGs are composed primarily of galaxies with old stellar populations, whereas the LLRGs have a much more diverse composition. We do not see a correlation between the cluster radio fraction and cluster blue fraction. However, there is a moderate anticorrelation with richness, suggesting that a rich cluster is less likely to have radio-bright galaxies, whether the radio emission is due to active galactic nuclei or star formation.