For refcode 1996ApJ...473..670F: Retrieve 175 NED objects in this reference. Please click here for ADS abstract
NED Abstract
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1996ApJ...473..670F
THE OBSERVATIONAL DISTRIBUTION OF INTERNAL VELOCITY DISPERSIONS IN
NEARBY GALAXY CLUSTERS
D. FADDA, M. GIRARDI, G. GIURICIN, F. MARDIROSSIAN, M. MEZZETTI
Received 1996 January 5; accepted 1996 June 17
ABSTRACT
We analyze the internal velocity dispersion {sigma} 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 latetype galaxies,
and velocity gradients. The dynamical uncertainties due to the presence
of substructures are also taken into account. Previous {sigma}
distributions, based on smaller cluster samples, are complete for the
Abell richness class R >= 1. In order to improve {sigma} completeness, we
enlarge our sample by also including poorer clusters. By resampling 153
AbellAbellCorwinOlowin clusters, according to the richness class
frequencies of the EdinburghDurham Cluster Catalog, we obtain a cluster
sample which can be taken as representative of the nearby universe. Our
cumulative {sigma}distribution agrees with previous distributions within
their {sigma} completeness limit ({sigma} ~> 800 km s^1^). We estimate
that our distribution is complete for at least {sigma} >= 650 km s^1^.
In this completeness range, a fit of the form dN is proportional to
{sigma}^{alpha}^d{sigma} gives {alpha} = (7.4^+0.7^_0.8_), in fair
agreement with results coming from the Xray temperature distributions of
nearby clusters. We briefly discuss our results with respect to {sigma}
distributions for galaxy groups and to theories of largescale structure
formation.
Subject headings: galaxies: clusters: general galaxies: distances and
redshifts  galaxies: kinematics and dynamics
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