Properties of High Redshift Cluster Ellipticals

Abstract

Cluster ellipticals are often thought to be among the oldest galaxies in the universe, with the bulk of their stellar mass formed at early cosmic epochs. I review recent observations of color evolution in early-type cluster galaxies at high redshift, which show remarkably little change in the color-magnitude relation out to z = 1. Spectra of elliptical galaxies from 1.15 < z < 1.41 demonstrate the presence of a dominant old stellar population even at these large lookback times, although there is some evidence for a tail of later star formation. The Kormendy relation, a photometric/morphological scaling law for elliptical galaxies, is used to extend fundamental plane investigations to z = 1.2 and to test for luminosity evolution. While the evidence, overall, is consistent with simple and mild passive evolution, I review some caveats and briefly consider the data in the light of hierarchical galaxy formation models.