The Cluster Velocity Field in Dark Matter Models

Abstract

The study of large—scale flows is potentially one of the most powerful tools with which to understand the structure of the universe on large (≳ 50 h -1 Mpc) scales (Dekel 1994; Strauss & Willick 1995 and references therein). Clusters of galaxies provide a particularly efficient and precise way to estimate peculiar motions, since the determination of many redshift—independent distances of cluster members leads to a substantial reduction in the statistical errors compared to studies of isolated galaxies. On large scales, fluctuations are largely in the linear regime and are, therefore, more closely related to the “initial conditions” from which large—scale structure developed. We present here a comparison between available observational data on cluster velocities and an extended set of numerical simulations based on the Zel’dovich approximation (see Moscardini et al. 1996, and references therein) of different cosmological models. Our main aim here is to investigate whether the cluster velocity field can constrain the values of the density parameter Ω0 and of the cosmological constant term ΩΛ.