2007MNRAS.376.1327F -
Mon. Not. R. Astron. Soc., 376, 1327-1334 (2007/April-2)
Entropy of gas and dark matter in galaxy clusters.
FALTENBACHER A., HOFFMAN Y., GOTTLOBER S. and YEPES G.
Abstract (from CDS):
On the basis of a large-scale `adiabatic', namely non-radiative and non-dissipative, cosmological smooth particle hydrodynamic simulation we compare the entropy profiles of the gas and the dark matter (DM) in galaxy clusters. We employ the quantity Kg= 3kBTgρ–2/3g/(µmp) = σ2gρ–2/3gas measure for the entropy of the intracluster gas. By analogy the DM entropy is defined as KDM = σ2DMρ–2/3DM(σ2DMis the 3D velocity dispersion of the DM). The DM entropy is related to the DM phase-space density by KDM∝ Q–2/3DM. In accord with other studies, the radial DM phase-space density profile follows a power-law behaviour, QDM ∝ r–1.82, which corresponds to KDM∝ r1.21. The simulated intracluster gas has a flat entropy core within (0.8 ±0.4)Rs, where Rsis the Navarro-Frenk-White scale radius. The outer profile follows the DM behaviour, Kg∝ r1.21, in close agreement with X-ray observations. Upon scaling the DM and gas densities by their mean cosmological values, we find that outside the entropy core a constant ratio of Kg/KDM= 0.71±0.18 prevails. By extending the definition of the gas temperature to include also the bulk kinetic energy the ratio of the DM and gas extended entropy is found to be unity for r ≳ 0.8Rs. The constant ratio of the gas thermal entropy to that of the DM implies that observations of the intracluster gas can provide an almost direct probe of the DM.
Abstract Copyright:
2007 The Authors. Journal compilation © 2007 RAS
Journal keyword(s):
methods: numerical - galaxies: clusters: general
Simbad objects:
2
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