The build-up of the red-sequence in galaxy clusters since z~0.8

Abstract

We study the rest-frame (U-V) color-magnitude relation in 4 clusters at redshifts 0.7-0.8, drawn from the ESO Distant Cluster Survey. We confirm that red-sequence galaxies in these clusters can be described as an old, passively-evolving population and we demonstrate, by comparison with the Coma cluster, that there has been significant evolution in the stellar mass distribution of red-sequence galaxies since z~0.75. The EDisCS clusters exhibit a deficiency of low luminosity passive red galaxies. Defining as `faint' all galaxies in the passive evolution corrected range 0.4>~ L/L*>~0.1, the luminous-to-faint ratio of red-sequence galaxies varies from 0.34+/-0.06 for the Coma cluster to 0.81+/-0.18 for the high redshift clusters. These results exclude a synchronous formation of all red-sequence galaxies and suggest that a large fraction of the faint red galaxies in current clusters moved on to the red-sequence relatively recently. Their star formation activity presumably came to an end at z<~0.8.