2003MNRAS.344L..17S

We use archival Chandra X-Ray Observatory data to investigate X-ray emission from early-type galaxies in the rich z = 0.06 cluster Abell 3128. By combining the X-ray count rates from an input list of optically selected galaxies, we obtain a statistical detection of X-ray flux, unbiased by X-ray selection limits. Using 87 galaxies with reliable Chandra data, X-ray emission is detected for galaxies down to M_B~-19.0, with only an upper limit determined for galaxies at M_B~-18.3. The ratio of X-ray to optical luminosities is consistent with recent determinations of the low-mass X-ray binary content of nearby elliptical galaxies. Taken individually, in contrast, we detect significant (3σ) flux for only six galaxies. Of these, one is a foreground galaxy, whereas two are optically faint galaxies with X-ray hardness ratios characteristic of active galactic nuclei. The remaining three detected galaxies are amongst the optically brightest cluster members, and have softer X-ray spectra. Their X-ray flux is higher than that expected from X-ray binaries, by a factor of 2-10; the excess suggests that these galaxies have retained their hot gaseous haloes. The source with the highest L_X/L_Bratio is of unusual optical morphology with prominent sharp-edged shells. Notwithstanding these few exceptions, the cluster population overall exhibits X-ray properties consistent with its emission being dominated by X-ray binaries. We conclude that in rich cluster environments, interaction with the ambient intracluster medium acts to strip most galaxies of their hot halo gas.