Galaxy population properties in the rich clusters MS0839.8+2938, 1224.7+2007 and 1231.3+1542

Abstract

This paper discusses the galaxy populations of three rich clusters, with redshift 0.19 (0839+29), 0.24 (1231+15), and 0.32 (1224+20), from the database of the CNOC1 consortium. The data consist of spectra of 52 cluster members for 0839+29, 30 members for 1224+15, and 82 members for 1231+15, and there are comparable numbers of field galaxy spectra. 0839+29 is compact with no strong radial gradients, and possibly dusty. 1224+20 is isolated in redshift, has low velocity dispersion around the cD galaxy, and low 4000A break. 1231+15 is asymmetrical and we discuss the possibility that it may be a recent merger of two old clusters. We find few galaxies in 0839+29 and 1231+15 with ongoing or recently truncated star-formation.