The Transformation of Cluster Galaxies at Intermeidate Redshift

N. L. Homeier, R. Demarco, P. Rosati, M. Postman, J. P. Blakeslee, R. J. Bouwens, L. D. Bradley, H. C. Ford, T. Goto, C. Gronwall, B. Holden, G. D. Illingworth, M. J. Jee, A. R. Martel, S. Mei, F. Menanteau, A. Zirm, M. Clampin, G. F. Hartig, the ACS Team

Published 2004-12-03Version 1

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 $r_{625}-i_{775}$ colors bluer than 1.0, eight are in the red cluster sequence. Among the star-forming 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 $R\sim 500$ Mpc of the cluster center, which is highly suggestive of an intracluster medium interaction. We derive star formation rates from [OII] $\lambda\lambda 3727$ 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 $T_{X}$, 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.