0 Cluster Correlation in Mixed Models

Received ; accepted – 2 – ABSTRACT We evaluate the dependence of the cluster correlation length r c on the mean intercluster separation D c , for three models with critical matter density, vanishing vacuum energy (Λ = 0) and COBE normalized: a tilted CDM (tCDM) model (n = 0.8) and two blue mixed models with two light massive neutrinos yielding Ω h = 0.26 and 0.14 (MDM1 and MDM2, respectively). All models approach the observational value of σ 8 (and, henceforth, the observed cluster abundance) and are consistent with the observed abundance of Damped Lymanα systems. Mixed models have a motivation in recent results of neutrino physics; they also agree with the observed value of the ratio σ 8 /σ 25 , yielding the spectral slope parameter Γ, and nicely fit LCRS reconstructed spectra. We use parallel AP3M simulations, performed in a wide box (side 360 h −1 Mpc) and with high mass and distance resolution, enabling us to build artificial samples of clusters, whose total number and mass range allow to cover the same D c interval inspected through APM and Abell cluster clustering data. We find that the tCDM model performs substantially better than n = 1 critical density CDM models. Our main finding, however, is that mixed models provide a surprisingly good fit of cluster clustering data.