The Edinburgh-Durham Southern Galaxy Catalogue. 5. The cluster correlation function

The spatial cluster correlation function for a 90 per cent complete sample of 79 clusters from the Edinburgh-Durham Southern Galaxy Catalogue is presented. These clusters are selected in an objective manner using an automated cluster-finding algorithm and correspond to a richness mid-way between the Abell richness classes RC = 0 and 1. Projection effects in this sample have been reduced by using a small cluster radius and deblending overlapping clusters. For 80 per cent of the sample we have observed congruent-to 10 galaxies in the direction of each cluster core. For these reasons this work supersedes previous determinations of the cluster correlation function. We derive a correlation length for the sample of r0 = 16.4 +/- 4.0 h-1 Mpc, a value systematically smaller than that calculated from Abell cluster samples. On scales congruent-to r0, the anisotropy in the correlation function between the redshift and transverse components is the lowest of any xi(cc) yet published. It is therefore unlikely that the strong anisotropy seen in previous correlation determinations is the result of real line-of-sight clustering or large cluster peculiar velocities.