Statistical Tests for CHDM and ΛCDM Cosmologies

Abstract

We apply several statistical estimators to high-resolution N-body simulations of two currently viable cosmological models: a mixed dark matter model, having ?? = 0.2 contributed by two massive neutrinos (C + 2?DM), and a cold dark matter model with cosmological constant (?CDM) with ?0 = 0.3 and h = 0.7. Our aim is to compare simulated galaxy samples with the Perseus-Pisces redshift survey (PPS). We consider the n-point correlation functions (n = 2-4); the N-count probability functions PN, including the void probability function P0; and the underdensity probability function U (where fixes the underdensity threshold in percentage of the average). We find that P0 (for which PPS and CfA2 data agree) and P1 distinguish efficiently between the models, while U is only marginally discriminatory. On the contrary, the reduced skewness and kurtosis are, respectively, S3 2.2 and S4 6-7 in all cases, quite independent of the scale, in agreement with hierarchical scaling predictions and estimates based on redshift surveys. Among our results, we emphasize the remarkable agreement between PPS data and C + 2?DM in all the tests performed. In contrast, the above ?CDM model has serious difficulties in reproducing observational data if galaxies and matter overdensities are related in a simple way.