Evolution of Hot Gas and Dark Halos in Group‐dominant Elliptical Galaxies: Influence of Cosmic Inflow

We study the complete dynamical evolution of hot interstellar gas in massiveelliptical galaxies born into a simple flat universe beginning with anoverdense perturbation. Within the turn-around radius dark matter flows in aself-similar fashion into a stationary Navarro-Frenk-White halo and thebaryonic gas shocks. After a few gigayears, when enough gas accumulates withinthe accretion shock, the de Vaucouleurs stellar system is constructed and theenergy from Type II supernovae is released. The stars and dark halo are matchedto NGC 4472. Gas continues to enter the galaxy by secondary infall and bystellar mass loss based on a Salpeter IMF. After about 13 Gyrs the temperatureand density distribution in the hot gas agree quite well with the hotinterstellar gas observed in NGC 4472. As a result of supernova-driven outflow,the present day baryonic fraction has a deep minimum in the outer galactichalo. When relatively gas-rich, X-ray luminous models are spatially truncatedat early times, simulating tidal events that may have occurred during galaxygroup dynamics, the current locus of truncated models lies just along the$L_x$, X-ray size correlation among well-observed ellipticals, providinganother striking confirmation of our simple model of elliptical evolution.Comment: 16 pages in AASTEX LaTeX with 14 figures; accepted by Astrophysical Journa