Radio-Optical Studies of a Complete Sample of Abell Clusters

Abstract

Study of the properties of radio galaxies in clusters is beset with problems of selection and identification. To reduce these problems we have selected a complete sample of Abell clusters and are using optical spectra of identified galaxies to determine their cluster membership. The sample is in a volume of space defined by the limits of coverage and sensitivity of the two Sydney University radiotelescopes and the Anglo-Australian Telescope; it comprises the 42 clusters with δ≤-8° and distance class 4 or closer. Radio maps have been prepared using archive 408 MHz data from the Molonglo Cross. Possible optical identifications have been selected from the Palomar Sky Survey and low-dispersion optical spectra have been taken of these and sometimes other galaxies or stellar objects within the cluster area. When needed, maps of the cluster areas have been produced at 1415 MHz using the Fleurs Synthesis Telescope. Some details of our early results have been published (Mills et al. 1978, 1979) and here a brief summary of the overall statistics is presented. Observations on five clusters remain to be completed but should not greatly affect the present conclusions.