The Edinburgh-Durham Southern Galaxy Catalogue - VII. The Edinburgh-Milano cluster redshift survey

In this paper, we present the redshifts of the galaxies and galaxy clusters which form the Edinburgh-Milano (EM) cluster redshift survey. A total of 777 galaxy redshifts have been measured in 94 clusters extracted from the digitized Edinburgh-Durham Cluster Catalogue. We also present the radial velocity dispersions for 37 clusters. Observational and data reduction techniques are discussed in detail, together with the strategy adopted to determine the mean redshift of a cluster and to identify and discard plausible phantom clusters. Some 10 per cent of our clusters show heavy contamination, indicating that projection is a serious problem for optically selected, rich clusters. The median velocity dispersion estimated for a subsample of richness $$R\ge1$$ clusters is $$742\pm63\enspace\text{km s}^{-1}$$. From a simple comparison with Ω=1 cold dark matter models of structure formation, these results favour a biasing parameter b=1.6–2.0 and are inconsistent with a bias outside of the range b=1.3-2.5.