Cluster Galaxy Evolution from a New Sample of Galaxy Clusters at 0.3 < Z < 0.9

We analyze photometry and spectroscopy of a sample of 63 clusters at 0.3 ≤ z ≤ 0.9 drawn from the Las Campanas Distant Cluster Survey to empirically constrain models of cluster galaxy evolution. Specifically, 1) by combining I−band photometry of 44 of our clusters with that of 19 clusters from the literature (Aragon-Salamanca et al. ; Smail et al. ; Stanford et al. ) we parameterize the redshift dependence of M I in the observed frame as M ∗ I = (−21.74±0.12)−(0.88±0.24)z−5 logh (rms deviation = 0.34) for 0.3 ≤ z ≤ 0.9 (Ω0 = 0.2, ΩΛ = 0)); 2) by combining 30 of our clusters and 14 clusters from the literature (Aragon-Salamanca et al. ; Smail et al. ; Stanford et al. ) with V and I data we parameterize the redshift dependence of the V − I color of the E/S0 red sequence in the observed frames as V −I = (−0.24±0.28)+(7.42±1.03)z−(4.61±0.91)z (rms deviation = 0.16) for 0.3 ≤ z ≤ 0.9; and 3) by combining 13 of our clusters with 15 clusters from the literature (Aragon-Salamanca et al. ; Stanford et al. ) with I and K ′ data we parameterize the redshift dependence of the I−K ′ color of the E/S0 red sequence in the observed frames as I−K ′ = (0.66±0.65)+(9.50±3.72)z−(14.72±7.01)z+(8.72±4.29)z (rms deviation = 0.18) for 0.3 ≤ z ≤ 0.9. Using the peak surface brightness of the cluster detection, Σ, as a proxy for cluster mass (Gonzalez et al. ), we find no correlation between Σ and M∗I or the location of the red envelope in V − I. We suggest that these observations can be explained with a model in which luminous early type galaxies (or more precisely, the progenitors of current day luminous early type galaxies) form the bulk of their stellar populations at high redshifts (∼> 5) and in which many of these galaxies, if not all, accrete mass either in the form of evolved stellar populations or gas that causes only a short term episode of star formation at lower redshifts (1.5 < z < 2). Our data are too crude to reach conclusions regarding the evolutionary state of any particular cluster or to investigate whether the morphological evolution of galaxies matches the simple scenario we discuss, but the statistical nature of this study suggests that the observed evolutionary trends are universal in massive clusters. Subject headings: galaxies: clusters: general — galaxies: evolution — galaxies: formation — galaxies: photometry — surveys