Peculiar Velocities of Clusters in Cold Dark Matter Models

Recently, peculiar velocity measurements became available for a new sample of galaxy clusters, hereafter the SCI sample. From an accurately calibrated Tully-Fisher relation for spiral galaxies, we compute the rms peculiar velocity, Vrms, and compare it with the linear theory predictions of COBE-normalized low-density and open cold dark matter models (ΛCDM and OCDM, respectively). Confidence levels for model rejection are estimated using a Monte Carlo procedure in order to generate a large ensemble of artificial data sets for each model. Following Zaroubi et al., we express our results in terms of constraints on the (Ω0, npr, h) parameter space. Such constraints turn into σ8Ω00.6 = 0.50−0.14+0.25 at the 90% confidence level, thus in agreement with results from cluster abundance. We show that our constraints are also consistent with those implied by the shape of the galaxy power spectrum within a rather wide range for the values of the model parameters. Finally, we point out that our findings disagree at about the 3 σ level with respect to those by Zaroubi et al., based on the Mark III catalog, which tend to prefer larger Ω0 values within the CDM class of models.