Dark Galaxies in the A1367 Galaxy Cluster

Abstract

We have characterized a sample of extended X-ray sources in the A1367 galaxy cluster that lack optical counterparts. The sources are galaxy size and have an average total mass of $1.3\times10^{11}$ solar masses. The average hot gas mass is $3.0\times10^{9}$ solar masses and the average X-ray luminosity is $4.3\times10^{41}$ erg cm$^{-2}$ s$^{-1}$. Analysis of a composite source spectrum indicates the X-ray emission is thermal, with temperature of 1.25 - 1.45 keV and has low metallicity, 0.026 - 0.067 solar. The average hot gas radius (12.7 kpc) is well matched to nominal stripping radius. We argue that this optically dark, X-ray bright galaxy population forms by a sequence of stripping followed by heating and mixing with the intracluster medium.