Cosmological and Environmental Influences on Hot Gas Observed in Elliptical Galaxies

The variation of temperature and density in the hot, X-ray emitting gasaround massive, group dominant elliptical galaxies can be understood as acombination of gas ejected from evolving galactic stars and gas thataccumulates in the outer halo by secondary cosmic infall. Beginning with anoverdensity perturbation in a simple flat cosmology, we can duplicate observedproperties of the hot gas. At some early time we form the stellar galaxy andrelease supernova energy, conserving dark and baryonic matter. Using apotential appropriate to the large elliptical NGC 4472, we follow the evolutionof intergalactic and interstellar gas to the present time when the computed gasdensity and temperature agree with X-ray observations of NGC 4472. If the hotgas and dark matter halos are subject to differential tidal truncations or massexchanges between group members, then the correlation between $L_x/L_B$ and therelative sizes of galactic X-ray images can be generated. The physicalproperties of hot interstellar gas observed in bright ellipticals today aresensitive to the cosmic baryon fraction, the time of maximum star formation andthe amount of ``feedback'' energy delivered to the gas by Type II supernovae atthe epoch of galaxy formation.Comment: 5 pages in AASTEX LaTeX including 3 figures; accepted by Astrophysical Journal Letter