1993/09/14 by Ray Carlberg, Carlberg, Ray
Physics and Astronomy · #Advanced Mathematical Theories and Applications #Astrophysics (astro-ph) #Cosmology and Gravitation Theories #FOS: Physical sciences #Relativity and Gravitational Theory #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9309021
10pages (0.5Mbyte .ps.Z.uu file) in proceedings of IAP Colloq 9, Cosmological Velocity Fields ed F Bouchet & M. Lachieze-Rey (revised--typo in eq.4, numerical value correct)
openalex publication_date 1993/09/14 · arxiv created 1993/09/16 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Velocity bias is a reduction of the velocity dispersion of tracer galaxies in comparison to the velocity dispersion of the underlying mass field. There are two distinct forms of velocity bias. The single particle velocity reduction, bv(1), is the result of energy loss of a tracer population, and in virialized regions, such as galaxy clusters, is intimately associated with mass segregation which together lead to cluster mass underestimates. The pairwise velocity bias, bv(2), has an additional statistical reduction if the total mass per galaxy rises with velocity dispersion of the virialized cluster. Values of the velocity bias are estimated from n-body simulations, finding bv(1)≃ 0.85±0.1 and bv(2)≃ 0.6±0.2. The value of bv(1) is relatively secure and predicts that the virial radius of the cluster light is about 20% of the cluster mass, which can be tested with observations of cluster mass profiles beyond the apparent virial radius. The value of bv(2) is sensitive to the formation efficiency of galaxies over environments ranging from voids to rich clusters, the latter of which are not yet well resolved in simulations. An n=1, Ω=1, COBE normalized CDM spectrum requires bv(2)≃0.20(15μK/Q)(σ12/317 \kms) which is well below the measured range of bv(2). The pairwise velocities at 1 \hmpc allow Ω=1 for a galaxy clustering bias near unity if bv(2)≃0.6.