2006ApJ...642L.123H

We examine the distribution of stellar masses of galaxies in MS 1054.4-0321 and Cl 0152.7-1357, two X-ray-selected clusters of galaxies at z=0.83. Our stellar mass estimates, from spectral energy distribution fitting, reproduce the dynamical masses as measured from velocity dispersions and half-light radii with a scatter of 0.2 dex in the mass for early-type galaxies. When we restrict our sample of members to high stellar masses, those over 10^11.1 M_☉(M* in the Schechter mass function for cluster galaxies), we find that the fraction of early-type galaxies is 79%±6% at z=0.83 and 87%±6% at z=0.023 for the Coma Cluster, consistent with no evolution. Previous work with luminosity-selected samples has found that the early-type fraction in rich clusters declines from ≃80% at z=0 to ≃60% at z=0.8. The observed evolution in the early-type fraction from luminosity-selected samples must predominantly occur among sub-M* galaxies. As M* for field and group galaxies, especially late types, is below M* for cluster galaxies, infall could explain most of the recent growth in the early-type fraction. Future surveys could determine the morphological distributions of lower mass systems, which would confirm or refute this explanation.