ESO distant cluster survey: spectroscopy

We present first results for spectroscopic observations of galaxies in 4 clusters at z=0.7-0.8 and one cluster at z=0.5 observed by the ESO Distant Cluster Survey (EDisCS). Our spectroscopic catalogues contain 236 cluster members of our 5 clusters, and the number of members per cluster ranges from 30 to 67. Our cluster velocity dispersions are between ∼400 and over 1000 km s^-1. Galaxy redshift distributions are found to be non-Gaussian and we find evidence for significant substructure in two clusters, one at z ∼ 0.79 and another at z ∼ 0.54; both clusters have velocity dispersions exceeding 1000 km s^-1. These systems have clearly not yet virialised at these epochs in qualitative agreement with CDM scenarios and their cluster velocity dispersions should not be used in the measurement of cluster mass. Our clusters have a wide range of different cluster velocity dispersions, richnesses and substructuring, and our spectroscopic data set is allowing a comprehensive insight into cluster galaxy evolution as a function of redshift and environment.