Optical and X-Ray Properties of Elliptical Galaxies

We compare and correlate the x-ray properties of early-type galaxies with their optical properties, using the data from extensive, homogeneous optical photometry surveys. Bivariate scaling solutions are found for the x-ray luminosities in terms of the optical surface brightness and velocity dispersion. A new quantity, the anisotropy index (AI) is defined. X-ray luminosities are found to correlate well with the AI. This is tentatively interpreted as a suggestion that mergers and tidal interactions played an important role in generation of the x-ray coronae in elliptical galaxies