The peculiar velocity function of galaxy clusters

Neta A. Bahcall, O. H. Siang Peng

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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) COM 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.

Original languageEnglish (US)
Pages (from-to)l49-l52
JournalAstrophysical Journal
Issue number2 PART II
StatePublished - 1996

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: observations
  • Cosmology: theory
  • Dark matter
  • Galaxies: clusters: general
  • Large-scale structure of universe


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