THE 2-POINT CORRELATION-FUNCTION OF RICH CLUSTERS OF GALAXIES - RESULTS FROM AN EXTENDED APM CLUSTER REDSHIFT SURVEY

We present new estimates of the spatial two-point correlation function of rich clusters of galaxies selected from the APM Galaxy Survey. We have measured redshifts for a sample of 364 clusters out to a depth of similar to 450 h(-1) Mpc.(1) The clusters have a mean space density of ($) over bar n=3.4 x 10(-5) h(3) Mpc(-3). The two-point correlation function in redshift space, xi(cc)(s), for this sample is equal to unity at a pair separation of r(0)=14.3 +/- 2.35 h(-1) Mpc (2 sigma errors), consistent with our earlier results from a smaller sample. The new observations provide an accurate determination of the shape of xi(cc) to pair separations of about 50 h(-1) Mpc. Our results show that xi(cc) has a higher amplitude than expected according to the standard Omega=1 cold dark matter (CDM) model on spatial scales of 2 less than or similar to s less than or similar to 50 h(-1) Mpc, but are in good agreement with scale-invariant fluctuations in either a low-density CDM model or a critical-density universe made up of a mixture of hot and cold dark matter. Our results provide strong constraints on so-called 'cooperative' models of galaxy formation, in which the galaxy formation process introduces large-scale structure into the galaxy distribution.