Mass Distributions in Elliptical Galaxies at Large Radii

Abstract

Recently, x-ray observations have shown that elliptical galaxies generally contain large quantities of hot gas. Central dominant cluster ellipticals have even more gas, which they have accreted from the surrounding clusters. The mass distributions in these galaxies can be derived from the condition of hydrostatic equilibrium. M87, the best studied central dominant galaxy, has a massive, dark halo with a total mass of about 4 x 1012 M⊙ within a radius of 300 kpc. The total mass-to-light ratio within this radius is at least 150 M⊙/L⊙. The x- ray observations of normal ellipticals also strongly suggest that they have heavy haloes, although the distribution of the mass is much less certain than in M87.