The Edinburgh-Durham Southern Galaxy Catalogue. 4. The Cluster Catalogue

We present the Edinburgh-Durham Cluster Catalogue (EDCC). This is the first machine-based, objectively selected sample of clusters of galaxies. It consists of 737 clusters or groups of all richnesses, over 0.5 sr of sky, centred on the South Galactic Pole (SGP). The primary galaxy data set for the cluster survey is the Edinburgh-Durham Souther D Galaxy Catalogue (EDSGC). The EDCC was constructed using an automatic peak-finding algorithm and is complete to m10(b(j)) = 18.75. In a comparison with the Abell clusters in the same region, we detect 80 per cent of their rich clusters nominally brighter than our completion limit in addition to many new systems, This suggests that the EDCC is 90 per cent complete for Abell-type clusters. We also conclude that the Abell magnitude system is biased towards bright magnitudes for most of their clusters, and that their richness estimates are prone to a larger uncertainty than they suggest. The EDCC therefore supersedes the Abell catalogue as a data base for statistical studies of cluster properties.