Astrophys. J., 636, 698-711 (2006/January-2)
Scaling mass profiles around elliptical galaxies observed with Chandra and XMM-Newton.
FUKAZAWA Y., BOTOYA-NONESA J.G., PU J., OHTO A. and KAWANO N.
Abstract (from CDS):
We investigated the dynamical structure of 53 elliptical galaxies using the Chandra archival X-ray data. In X-ray-luminous galaxies, temperature increases with radius and gas density is systematically higher at the optical outskirts, indicating the presence of a significant amount of the group-scale hot gas. In contrast, X-ray-dim galaxies show a flat or declining temperature profile against radius and the gas density is relatively lower at the optical outskirts. Thus, it is found that X-ray-bright and faint elliptical galaxies are clearly distinguished by the temperature and gas density profile. The mass profile is well scaled by a virial radius r200rather than an optical half-radius re, is quite similar at (0.001-0.03)r200between X-ray-luminous and dim galaxies, and smoothly connects to those profiles of clusters of galaxies. At the inner region of (0.001-0.01)r200or (0.1-1)re, the mass profile well traces a stellar mass with a constant mass-to-light ratio of M/LB=3-10 M☉/L☉. The M/LBratio of X-ray-bright galaxies rises up steeply beyond 0.01r200and thus requires a presence of massive dark matter halo. From the deprojection analysis combined with the XMM-Newton data, we found that X-ray-dim galaxies NGC 3923, NGC 720, and IC 1459 also have a high M/LBratio of 20-30 at 20 kpc, comparable to that of X-ray-luminous galaxies. Therefore, dark matter is indicated to be common in elliptical galaxies; their dark matter distribution, as well as that of galaxy clusters, almost follows the NFW profile.
Galaxies: Elliptical and Lenticular, cD - Galaxies: ISM - X-Rays: Galaxies
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