The relation between velocity dispersion and temperature in clusters - Limiting the velocity bias

Abstract

view Abstract Citations (122) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Relation between Velocity Dispersion and Temperature in Clusters: Limiting the Velocity Bias Lubin, Lori M. ; Bahcall, Neta A. Abstract The observed galaxy velocity dispersion in clusters of galaxies is compared with the X-ray temperature of the intracluster gas for a large sample of clusters. A strong correlation is found between the observables which is best fitted by the relation σ = 332 + 52(kT)^0.6+/-0.1^ km s^-1^; here σ is the rms radial velocity dispersion in the cluster, and kT is the gas temperature in keV. The relation is consistent with that expected from an isothermal model where both the gas and the galaxies are in hydrostatic equilibrium with the binding cluster potential, i.e., σ is proportional to T^0.5^. The observed relation is used to determine the best-fit average β parameter for clusters, β = σ^2^/(kT/μm_p_), which describes the ratio of energy per unit mass in the galaxies to that in the gas (where μm_p_ is the mean particle mass); we find β = 0.94 +/- 0.08 [ and β(median) = 0.98]. This implies that the galaxies and the gas trace the same cluster potential with approximately equal energy per unit mass (i.e., β = 1). The best-fit observed β also suggests that no significant velocity bias exists in clusters of galaxies, i.e., the galaxy velocity dispersion in clusters is a fair tracer of the dark matter velocity dispersion. The best-fit velocity bias is bnu = σ_gal_/σ_DM_ ~ β^0.5^ = 0.97 +/- 0.04 (with bnu_ = 1 corresponding to no bias). Publication: The Astrophysical Journal Pub Date: September 1993 DOI: 10.1086/187022 Bibcode: 1993ApJ...415L..17L Keywords: Dark Matter; Galactic Clusters; Radial Velocity; X Ray Astronomy; Gas Temperature; Particle Mass; Velocity Distribution; Astrophysics; GALAXIES: CLUSTERING; COSMOLOGY: DARK MATTER; X-RAYS: GALAXIES full text sources ADS | data products SIMBAD (42) NED (41)