Mass profiles and galaxy orbits in nearby galaxy clusters from the analysis of the projected phase space
Abstract
We analyse kinematic data of 41 nearby (z < 0.1) relaxed galaxy clusters in terms of the projected phasespace density using a phenomenological, fully anisotropic model of the distribution function. We apply the Markov Chain Monte Carlo approach to place constraints on total mass distribution approximated by the universal Navarro, Frenk and White (NFW) profile and the profile of the anisotropy of galaxy orbits. We find the normalization of the mean massconcentration relation is c = 6.9^{+0.6}_{0.7} at the virial mass M_{v} = 5 × 10^{14} M_{solar}. By comparison with the calibration from cosmological Nbody simulations it is demonstrated that this result is fully consistent with σ_{8} from 1yr Wilkinson Microwave Anisotropy Probe (WMAP1) data release and agrees at ~ 1σ level with that from WMAP5. Assuming a onetoone correspondence between σ_{8} and the normalization of the massconcentration relation in the framework of the concordance model we estimate the normalization of the linear power spectrum to be σ_{8} = 0.91^{+0.07}_{0.08}. Our constraints on the parameters of the mass profile are compared with estimates from Xray observations and other methods based on galaxy kinematics. We also study correlations between the virial mass and different mass proxies including the velocity dispersion, the Xray temperature and the Xray luminosity. We demonstrate that the mass scaling relations with the velocity dispersion and the Xray temperature are fully consistent with the predictions of the virial theorem.
We show that galaxy orbits are isotropic at the cluster centres (with the mean ratio of the radialtotangential velocity dispersions σ_{r}/σ_{θ} = 0.97 +/ 0.04) and radially anisotropic at the virial sphere (with the mean ratio σ_{r}/σ_{θ} = 1.75^{+0.23}_{0.19}). Although the value of the central anisotropy appears to be universal, the anisotropy at the virial radius differs between clusters within the range 1 <~ (σ_{r}/σ_{θ}) <~ 2.
Utilizing the BautzMorgan morphological classification and information on the prominence of a cool core we select two subsamples of galaxy clusters corresponding to less and more advanced evolutionary states. It is demonstrated that less evolved clusters have shallower mass profiles and their galaxy orbits are more radially biased at the virial sphere. This property is consistent with the expected evolution of the mass profiles as well as with the observed orbital segregation of late and earlytype galaxies.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 November 2010
 DOI:
 10.1111/j.13652966.2010.17297.x
 arXiv:
 arXiv:1004.3771
 Bibcode:
 2010MNRAS.408.2442W
 Keywords:

 galaxies: clusters: general;
 galaxies: kinematics and dynamics;
 dark matter;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 16 pages, 12 figures, accepted for publication in MNRAS