The Peculiar Velocity Function of Galaxy Clusters

This is the authors' abstract. We don't add key points for this paper.

The peculiar velocity function of clusters of galaxies is determined using an accurate sample of cluster velocities based on Tully-Fisher distances of Sc galaxies. In contrast to previous results based on samples with considerably larger velocity uncertainties, the observed velocity function does not exhibit a tail of high peculiar velocity clusters. The results indicate a low probability of ≲5% of finding clusters with one-dimensional peculiar velocities greater than ~600 km s -1 . The rms one-dimensional cluster peculiar velocity is 293 ± 28 km s -1 . The observed cluster velocity function is compared with expectations from different cosmological models. The absence of a high-velocity tail in the observed function is most consistent with a low-mass-density (Ω ~ 0.3) CDM model and is inconsistent at the ≳3 σ level with Ω = 1.0 CDM and HDM models. The rms one-dimensional cluster peculiar velocities in these models correspond, respectively, to 314, 516, and 632 km s -1 (when convolved with the observational uncertainties). Comparison with the observed rms cluster velocity of 293 ± 28 km s -1 further supports the low-density CDM model.