A Multi-Wavelength Study of Low Redshift Cluster of Galaxies II.
  Environmental Impact on Galaxy Growth
  Galaxy clusters provide powerful laboratories for the study of galaxy
evolution, particularly the origin of correlations of morphology and star
formation rate (SFR) with density. We construct visible to MIR spectral energy
distributions (SEDs) of cluster galaxies and use them to measure stellar masses
and SFRs in eight low redshift clusters, which we examine as a function of
environment. A partial correlation analysis indicates that SFR depends strongly
on R/R200 (>99.9% confidence) and is independent of projected local density at
fixed radius. SFR also shows no residual dependence on stellar mass. We
therefore conclude that interactions with the intra-cluster medium drive the
evolution of SFRs in cluster galaxies. A merged sample of galaxies from the
five most complete clusters shows <SFR>\propto(R/R200)^(1.3+/-0.7) for galaxies
with R/R200<0.4. A decline in the fraction of SFGs toward the cluster center
contributes most of this effect, but it is accompanied by a reduction in SFRs
among star-forming galaxies (SFGs) near the cluster center. The increase in the
fraction of SFGs toward larger R/R200 and the isolation of SFGs with reduced
SFRs near the cluster center are consistent with ram pressure stripping as the
mechanism to truncate star formation in galaxy clusters. We conclude that
stripping drives the properties of SFGs over the range of radii we examine. We
also find that galaxies near the cluster center are more massive than galaxies
farther out in the cluster at ~3.5\sigma, which suggests that cluster galaxies
experience dynamical relaxation during the course of their evolution.
