The X-ray emission from bright early-type galaxies is thought to be thermal emission from diffuse hot gas. The hot gas is likely to be from the accumulation of stellar mass loss within the galaxies. While the total X-ray luminosities L(X) of early-type galaxies are correlated with the galaxies' optical (e.g., blue) luminosities L(B) (L(X) proportional L(B)1.5-2.3), the X-ray luminosities exhibit considerable dispersion for a given optical luminosity. This dispersion in L(X) for a given L(B) is much greater than that in any of the usual optical observables (e.g., size, surface brightness, velocity dispersion, color, metallicity). We consider several possible causes for this dispersion in X-ray luminosity: stellar population variations, which may lead to differences in stellar mass-loss rates or supernova rates; the presence of cool gas in some early-type galaxies, which may provide a heat sink for the hot coronae; velocity dispersion differences, which would lead to differing heating rates (due to stellar mass-loss shocking with the random velocities of the stars) and may reflect differences in the total masses of the galaxies; environmental influences, such as varying degrees of ram-pressure stripping of the gaseous halos or (if many ellipticals are merger remnants) differing merger characteristics. The effectiveness of ram-pressure stripping may also be modulated by variations in total galactic masses for a given L(B). To determine which of these possible causes are tenable, we search for a correlation between L(X) residuals (from the mean L(X) - L(B) relation) and the variations in the other galactic properties mentioned above. We are unable to find any intrinsic galaxy property which significantly reduces the dispersion in X-ray luminosities when correlated with L(X). However, we find that early-type galaxies with relatively low L(X) for a given L(B) have approximately 50% more neighbors than galaxies with relatively high L(X). We conclude that the large dispersion in X-ray luminosity (for a given L(B)) is likely to be environmentally induced, caused either by ram-pressure stripping of the gaseous halos or by mergers.
