Surface-brightness Evolution of Cluster Galaxies

Surface brightness evolution has been detected in elliptical galaxies (consistent with passive evolution models of old stellar populations) and in disk galaxies (presumably due to enhanced star-formation rates). The rates of evolution in clusters and the field are not measurably different. In addition to this similarity, the high-redshift populations in both environments exhibit a “blue-excess” population, increased rates of star formation, and high frequency of peculiar structure. Thus, there are several parallels between evolving cluster and field galaxies and the highredshift cluster environment will be understood only by comparison with the field population at the same epoch.