The Transformation of Cluster Galaxies at Intermediate Redshift

We combine imaging data from the Advanced Camera for Surveys (ACS) with VLT/FORS optical spectroscopy to study the properties of star-forming galaxies in the z = 0.837 cluster CL0152-1357. We have morphological information for 24 star-forming cluster galaxies, which range in morphology from late-type and irregular to compact early-type galaxies. We find that while most star-forming galaxies have r625 − i775 colors bluer than 1.0, eight are in the red cluster sequence. Among the starforming cluster population we find five compact early-type galaxies which have properties consistent with their identification as progenitors of dwarf elliptical galaxies. The spatial distribution of the star-forming cluster members is nonuniform. We find none within R ∼ 500 Mpc of the cluster center, which is highly suggestive of an intracluster medium interaction. We derive star formation rates from [OII] λλ3727 line fluxes, and use these to compare the global star formation rate of CL0152-1357 to other clusters at low and intermediate redshifts. We find a tentative correlation between integrated star formation rates and TX , in the sense that hotter clusters have lower integrated star formation rates. Additional data from clusters with low X-ray temperatures is needed to confirm this trend. We do not find a significant correlation with redshift, suggesting that evolution is either weak or absent between z = 0.2− 0.8. Subject headings: galaxies: clusters: general, galaxies: clusters: individual (CL0152-1357), galaxies: evolution, galaxies: interactions, galaxies: high-redshift