The Effect of Environment on the X‐Ray Emission from Early‐Type Galaxies

In order to help understand the phenomena of X-ray emission from early-typegalaxies, we obtained an optically flux-limited sample of 34 early-typegalaxies, observed with ROSAT. A previous analysis of this sample suggestedthat the most X-ray luminous galaxies were in rich environments. Here weinvestigate environmental influences quantitatively, and find a positivecorrelation between L_B/L_X and the local galaxy density. We suggest that thiscorrelation occurs because the X-ray luminosity is enhanced either throughaccretion of the intergalactic gas or because the ambient medium stiflesgalactic winds. When the ambient medium is unimportant, partial or globalgalactic winds can occur, reducing L_B/L_X. These effects lead to the largeobserved dispersion in L_X at fixed L_B. We argue that the transition fromglobal winds to partial winds is one of the principle reasons for the steeprelationship between L_X and L_B. We discuss details of the data reduction notpreviously presented, and examine the dependence of L_X on the choice of outersource radius and background location. Effects of Malmquist bias are shown notto be important for the issues addressed. Finally, we compare the temperaturededuced for these galaxies from different analyses of ROSAT and ASCA data.Comment: 29 pages, including 6 figures (ps); AASTeX 12pt,aaspp4 format; submitted to Ap