SIGNIFICANT CLUSTER CORRELATIONS AT 30 H(-1) MPC - CAN STANDARD MODELS BE RULED OUT

We compute the cluster autocorrelation function, xi(c)(r), of an exten ded, complete sample of 220 rich (R greater-than-or-equal-to 1) Abell clusters with measured redshifts. We correct for projection contaminat ion and pay special attention to estimating the random errors, aiming at rejecting certain theoretical models. While the observed xi(c) in t he range r < 20 h-1 Mpc is in agreement with the predictions of CDM an d textures models, we find an excess over both theories in the range 2 0 h-1 M pc less-than-or-equal-to r less-than-or-equal-to 40 h-1 Mpc, s ignificant at beyond the 3 sigma level. Assuming that the observed xi( c) below 30 h-1 Mpc represents the true correlations, the hypothesis t hat xi(c) vanishes right beyond this scale can be rejected with simila r confidence. These results are in agreement with our earlier findings from the angular correlation function of the complete Abell and ACO c atalogs. Possible remaining biases and ways out for these models are d iscussed.