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Title:
Residual Gas Motions in the Intracluster Medium and Bias in Hydrostatic Measurements of Mass Profiles of Clusters
Authors:
Lau, Erwin T.; Kravtsov, Andrey V.; Nagai, Daisuke
Affiliation:
AA(Department of Astronomy & Astrophysics, 5640 South Ellis Ave., The University of Chicago, Chicago, IL 60637, USA ), AB(Department of Astronomy & Astrophysics, 5640 South Ellis Ave., The University of Chicago, Chicago, IL 60637, USA ; Kavli Institute for Cosmological Physics and Enrico Fermi Institute, 5640 South Ellis Ave., The University of Chicago, Chicago, IL 60637, USA ), AC(Department of Physics, Yale University, New Haven, CT 06520, USA ; Yale Center for Astronomy & Astrophysics, Yale University, New Haven, CT 06520, USA)
Publication:
The Astrophysical Journal, Volume 705, Issue 2, pp. 1129-1138 (2009). (ApJ Homepage)
Publication Date:
11/2009
Origin:
IOP
ApJ Keywords:
cosmology: theory, galaxies: formation, methods: numerical
DOI:
10.1088/0004-637X/705/2/1129
Bibliographic Code:
2009ApJ...705.1129L

Abstract

We present analysis of bulk and random gas motions in the intracluster medium using high-resolution Eulerian cosmological simulations of 16 simulated clusters, including both very relaxed and unrelaxed systems and spanning a virial mass range of 5 × 1013-2\times 10^{15}\,h^{-1}\,{\it\, M_{\odot }}. We investigate effects of the residual subsonic gas motions on the hydrostatic estimates of mass profiles and concentrations of galaxy clusters. In agreement with previous studies, we find that the gas motions contribute up to ≈5%-15% of the total pressure support in relaxed clusters with contribution increasing with the cluster-centric radius. The fractional pressure support is higher in unrelaxed systems. This contribution would not be accounted for in hydrostatic estimates of the total mass profile and would lead to systematic underestimate of mass. We demonstrate that total mass can be recovered accurately if pressure due to gas motions measured in simulations is explicitly taken into account in the equation of hydrostatic equilibrium. Given that the underestimate of mass is increasing at larger radii, where gas is less relaxed and contribution of gas motions to pressure is larger, the total density profile derived from hydrostatic analysis is more concentrated than the true profile. This may at least partially explain some high values of concentrations of clusters estimated from hydrostatic analysis of X-ray data.
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