Two‐Phase Intracluster Medium in the Centaurus Cluster of Galaxies

Abstract

ASCA and ROSAT data of the Centaurus Cluster, containing a cD galaxy NGC 4696, were analyzed in a partial reanalysis of the work of Fukazawa et al., Fabian et al., and Allen & Fabian. Radial brightness profiles in different energy bands show that the central excess emission of this cluster, seen previously in soft X-rays (ASCA and ROSAT data successfully. The spatial distribution of the dark matter that is derived by subtracting the stellar mass from the calculated total gravitating mass deviates from a King-type profile and exhibits a central excess. Another two-phase cluster model in which the dark matter density profile is given with the universal density profile of Navarro, Frenk, & White also gave a satisfactory account of the data. A detailed comparison of the iron mass distribution with that of the stellar component reveals that the iron is more widely spread than stars, perhaps as a result of energetic supernovae and the motion of the cD galaxy. Since the derived characteristics of the cool phase, including the temperature, angular extent, gas mass, and metallicity, are on a smooth extension of those of the interstellar medium (ISM) of elliptical galaxies, the cool phase can be regarded as the ISM associated with the cD galaxy, while the high X-ray luminosity of the cool phase (1.1 × 10⁴³ ergs s^-1 in 0.5-4.0 keV) is interpreted as a result of compression by the surrounding hot phase. The cool-phase X-ray emission is presumably sustained by energies dissipated by mass infalling to the cD galaxy in the course of cluster evolution.