PECULIAR VELOCITIES OF CLUSTERS IN COLD DARK-MATTER MODELS

Recently, peculiar velocity measurements became available for a new sa mple of galaxy clusters, hereafter the SCI sample. From an accurately calibrated Tully-Fisher relation for spiral galaxies, we compute the r ms peculiar velocity, V-rms and compare it with the linear theory pred ictions of COBE-normalized low-density and open cold dark matter model s (Lambda CDM and OCDM, respectively). Confidence levels for model rej ection are estimated using a Monte Carlo procedure in order to generat e a large ensemble of artificial data sets for each model. Following Z aroubi et al., we express our results in terms of constraints on the ( Omega(0), n(pr), h) parameter space. Such constraints turn into sigma( 8) Omega(0)(0.6) = 0.50(-0.14)(+0.25) at the 90% confidence level, thu s in agreement with results from cluster abundance. We show that our c onstraints 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 sigma level with respect to those by Zaroubi et al., base d on the Mark III catalog, which tend to prefer larger Omega(0) values within the CDM class of models.