2009/03/31 by Ryo Nagino, Kyoko Matsushita
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph.CO
paper · pdf · doi:10.1051/0004-6361/200810978
22 pages, 18 figures, 6 tables, accepted for publication in A&A
arxiv created 2009/03/31 · openalex publication_date 2009/04/29 · arxiv updated 2015/05/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
<i>Aims. <i/>We study the dark matter content in early-type galaxies and investigate whether X-ray luminosities of early-type galaxies are determined by the surrounding gravitational potential.<i>Methods. <i/>We derived gravitational mass profiles of 22 early-type galaxies observed with XMM-Newton and Chandra.<i>Results. <i/>Sixteen galaxies show constant or decreasing radial temperature profiles, and their X-ray luminosities are consistent with kinematical energy input from stellar mass loss. The temperature profiles of the other 6 galaxies increase with radius, and their X-ray luminosities are significantly higher. The integrated mass-to-light ratio of each galaxy is constant at that of stars within 0.5–, and increases with radius, where <i>r<i/><sub>e<sub/> is the effective radius of a galaxy. The scatter of the central mass-to-light ratio of galaxies was less in <i>K<i/>-band light. At , the integrated mass-to-light ratios of galaxies with flat or decreasing temperature profiles are twice the value at , where the stellar mass dominates, and at , these increase to three times the value at .<i>Conclusions. <i/>This feature should reflect common dark and stellar mass distributions in early-type galaxies: within , the mass of dark matter is similar to the stellar mass, while within , the former is larger than the latter by a factor of two. In contrast, X-ray luminous galaxies have higher gravitational mass in the outer regions than X-ray faint galaxies. We describe these X-ray luminous galaxies as the central objects of large potential structures; the presence or absence of this potential is the main source of the large scatter in the X-ray luminosity.