1996/06/17 by Dario Fadda, D.M.G.F. Fadda, M. Girardi +7 · 287 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Brightest cluster galaxy #Cluster (spacecraft) #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy cluster #Galaxy groups and clusters #Redshift #Scientific Research and Discoveries #Velocity dispersion #astro-ph
paper · pdf · doi:10.1086/178180
published in The Astrophysical Journal 473(2), 670-686 (IOP Publishing) · 18 pages, latex file with macros included, 9 figures and 6 tables (automatically included), ApJ in press
arxiv created 1996/06/17 · openalex publication_date 1996/12/20 · arxiv updated 2010/04/06 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We analyze the internal velocity dispersion σ of a sample of 172 nearby galaxy clusters (z ≤ 0.15), each of which has at least 30 available galaxy redshifts and spans a large richness range. Cluster membership selection is based on nonparametric methods. In the estimate of galaxy velocity dispersion, we consider the effects of possible velocity anisotropies in galaxy orbits, the infall of late-type galaxies, and velocity gradients. The dynamical uncertainties due to the presence of substructures are also taken into account. Previous σ-distributions, based on smaller cluster samples, are complete for the Abell richness class R ≥ 1. In order to improve σ completeness, we enlarge our sample by also including poorer clusters. By resampling 153 Abell—Abell-Corwin-Olowin clusters, according to the richness class frequencies of the Edinburgh-Durham Cluster Catalog, we obtain a cluster sample which can be taken as representative of the nearby universe. Our cumulative σ-distribution agrees with previous distributions within their σ completeness limit (σ ≳ 800 km s –1 ). We estimate that our distribution is complete for at least σ ≥ 650 km s –1 . In this completeness range, a fit of the form dN ∝ σ α d σ gives α = -(7.4 –0.8 +0.7 in fair agreement with results coming from the X-ray temperature distributions of nearby clusters. We briefly discuss our results with respect to p-distributions for galaxy groups and to theories of large-scale structure formation.