The Star Formation Histories Of Galaxies In Distant Clusters

Abstract

We present a detailed analysis of the spectroscopic catalog of galaxies in 10 distant clusters from Dressler et al. (1999, D99). We investigate the nature of the different spectral classes defined by D99 including star forming, post--starburst and passive galaxy populations, and reproduce their basic properties using our spectral synthesis model. We attempt to identify the evolutionary pathways between the various spectral classes in order to search for the progenitors of the numerous post--starburst galaxies. The comparison of the spectra of the distant galaxy populations with samples drawn from the local Universe leads us to identify a significant population of dust-- enshrouded starburst galaxies, showing both strong Balmer absorption and relatively modest [OII] emission, that we believe are the most likely progenitors of the post--starburst population. We present the differences between the field and cluster galaxies at z = 0:4--0.5. We then compare the spectral and the morphologic..