X-ray scaling properties of early-type galaxies

We present an analysis of 39 X-ray luminous early-type galaxies observed with the ROSAT PSPC. Using multicomponent spectral and spatial fits to these data, we have measured halo abundance, temperature, luminosity and surface brightness profile. We compare these measurements to similar results from galaxy groups and clusters, fitting a number of relations commonly used in the study of these larger objects. In particular, we find that the σ−TX relation for our sample is similar to that reported for clusters, consistent with βspec= 1, and that the LX-TX relation has a steep slope (gradient 4.8 ± 0.7) comparable with that found for galaxy groups. Assuming isothermality, we construct three-dimensional models of our galaxies, allowing us to measure gas entropy. We find no correlation between gas entropy and system mass, but do find a trend for low-temperature systems to have reduced gas fractions. We conclude that the galaxies in our sample are likely to have developed their haloes through galaxy winds, influenced by their surrounding environment.