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Velocity Dispersions of CNOC Clusters and the Evolution of the Cluster Abundance

S. Borgani·M. Girardi·R. G. Carlberg·H. K. C. Yee·E. Ellingson
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Abstract

We present the results of the analysis of the internal velocity dispersions, σ_v, for the CNOC sample of distant galaxy clusters, based on an interlopers removal algorithm, which is different from that originally applied by Carlberg et al. (1996, C96). We find that the resulting σ_v values are consistent within <10% with the original C96 estimates. This result points in favor of a substantial robustness of currently applied methods for optical studies of the internal cluster dynamics. The resulting distribution of velocity dispersions is used to trace the redshift evolution of the cluster abundance with the aim of constraining the matter density parameter, Ω_m. We find that constraints on Ω_m are very sensitive to the adopted value of σ_8, as obtainable from the local cluster abundance: as σ_8 varies from 0.5 to 0.6 (for Omega_m=1), the best fitting Omega_m varies in the range 0.3-1.0.

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S. Borgani, M. Girardi, R. G. Carlberg, H. K. C. Yee, E. Ellingson. 1999-07-27. Velocity Dispersions of CNOC Clusters and the Evolution of the Cluster Abundance. https://doi.org/10.1086/308130

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