EVOLUTION OF GROUP GALAXIES FROM THE FIRST RED-SEQUENCE CLUSTER SURVEY

We study the evolution of the red-galaxy fraction ([functionof] sub(red)) in 905 galaxy groups with 0.15 [< or =, slant] z < 0.52. The galaxy groups are identified by the "probability friends-of-friends" algorithm from the first Red-Sequence Cluster Survey (RCS1) photometric-redshift sample. There is a high degree of uniformity in the properties of the red sequence of the group galaxies, indicating that the luminous red-sequence galaxies in the groups are already in place by z ~ 0.5 and that they have a formation epoch of z [> ~] 2. In general, groups at lower redshifts exhibit larger [functionof] sub(red) than those at higher redshifts, showing a group Butcher-Oemler effect. We investigate the evolution of [functionof] sub(red) by examining its dependence on four parameters, one of which can be classified as intrinsic and three of which can be classified as environmental: galaxy stellar mass (M[low *]), total group stellar mass (M[low *] sub(, grp), a proxy for group halo mass), normalized group-centric radius (r sub(grp)), and local galaxy density ([summationoperator] sub(5)). We find that M[low *] is the dominant parameter such that there is a strong correlation between [functionof] sub(red) and galaxy stellar mass. Furthermore, the dependence of [functionof] sub(red) on the environmental parameters is also a strong function of M[low *]. Massive galaxies (M[low *] [> ~] 10 super(11) M sub([middot in circle])) show little dependence of [functionof] sub(red) on r sub(grp), M[low *] sub(, grp), and [summationoperator] sub(5) over the redshift range. The dependence of [functionof] sub(red) on these parameters is primarily seen for galaxies with lower masses, especially for M[low *] [