Winds, outflows, and inflows in X-ray elliptical galaxies. I

A new class of one-dimensional hydrodynamical evolutionary sequences for the gas flows in elliptical galaxies is presented. The model galaxies are described by either King's or de Vaucouleurs's virialized density distributions, constrained to lie on the fundamental plane of elliptical galaxies, and are surrounded by variable amounts of dark matter. Two source terms operate: mass loss from evolving stars, and a secularly declining heating by Type I supernovae. The resulting models evolve through up to three consecutive evolutionary stages: the wind, outflow, and inflow phases. Agreement with the observed trends of the X-ray luminosity Lx, with the optical characteristics of the galaxies, is achieved for dark-to-visible mass ratios of ∼ 10, when the standard SN I rate is assumed. Also the large dispersion of Lx for given optical luminosity is easily accounted for. These sequences indicate that the X-ray faint galaxies are still in their wind phase, while the bulk of ellipticals are in the outflow phase, and a few of the brightest galaxies may have already experienced their transition to the inflow regime. In models with a de Vaucouleurs distribution small mini-inflows can be present in the central regions long before the global transition to the main inflow regime. The effects of interactions with the intracluster medium, ram pressure, encounters, and merging events are qualitatively discussed. We argue that the iron abundance in the flows can constrain the SN I heating rate in the galaxies, while the total mass of iron in the intracluster medium provides a constraint on the total number of Type I SNs so far exploded in cluster galaxies. Our adopted SN I rate implies a total iron mass in excellent agreement with current estimates for nearby clusters. Finally, the Lx - LB correlation is seen as an ongoing manifestation of the fact that brighter galaxies are characterized by a larger binding energy per unit mass, i.e., as an implication of the Faber-Jackson LB - σ* relation, not unlike the LB-metallicity correlation established at the formation epoch of elliptical galaxies.