Decoupled and Inhomogeneous Gas Flows in S0 Galaxies

Abstract

A recent analysis of the Einstein sample of early-type galaxies has revealed that at any Ðxed optical luminosity S0 galaxies have lower mean X-ray luminosity per unit than elliptical galaxies. L B , L X L B Following a previous analytical investigation of this problem (Ciotti & Pellegrini), we have performed two-dimensional numerical simulations of the gas Ñows inside S0 galaxies in order to ascertain the e †ec-tiveness of rotation and/or galaxy Ñattening in reducing the ratio. L X /L B The Ñow in models without supernova (SNIa) heating is considerably ordered, and essentially all the gas lost by the stars is cooled and accumulated in the galaxy center. If rotation is present, the cold material settles in a disk on the galactic equatorial plane. Models with a time-decreasing SNIa heating host gas Ñows that can be much more complex. After an initial wind phase, gas Ñows in energetically strongly bound galaxies tend to reverse to inÑows. This occurs in the polar regions, while the disk is still in the outÑow phase. In this phase of strong decoupling, cold Ðlaments are created at the interface between inÑowing and outÑowing gas. Models with more realistic values of the dynamical quantities are preferentially found in the wind phase with respect to their spherical counterparts of equal The L B . resulting of this class of models is lower than in spherical models with the same and SNIa L X L B heating. At variance with cooling Ñow models, rotation is shown to have only a marginal e †ect in this reduction, while the Ñattening is one of the driving parameters for such underluminosity, in accordance with the analytical investigation.

Heated Cooling Flows

“…D'Ercole in Bologna (e.g., D'Ercole & Ciotti 1998). Finally, we have successfully checked the two-dimensional ZEUS code against analytic expressions for nonsteady inflow in hypothetical galaxies of uniform density (Appendix of Brighenti & Mathews 1996).…”

“…The cooling is more chaotic in two dimensions, and coherent inward-moving drip waves do not form. In principle, gas can also cool at intermediate radii in unheated galactic cooling flows provided that the galaxy is rotating (Brighenti & Mathews 1997b, 2000bD'Ercole & Ciotti 1998); in this case an extended disk of cooling gas is formed, but there is no observational evidence for this in the X-ray images. We have shown that cooling disks can be avoided if the flow is turbulent or convective (Brighenti & Mathews 2000b), and there is considerable observational evidence for this (e.g., Caon et al 2000).…”

Galactic winds and circulation of the interstellar medium in dwarf galaxies

“…This code and its successive extensions have been applied to a variety of astrophysical problems (e.g. Brighenti & D’Ercole 1997; D’Ercole & Ciotti 1998). The second code employed is zeus‐2d , a widely used, well‐tested scheme developed by M. Norman and collaborators at LCSA (Stone & Norman 1992).…”

The HI content of early-type galaxies from the ALFALFA survey

“…Furthermore D 'Ercole et al (2000) investigated the effect of tidal encounters on hot gas flows, and found the creation of dense, cold filaments. However, in a previous set of simulations D'Ercole & Ciotti (1998) have studied hot gas flows in quite flattened galaxies (S0 or flat Ellipticals), and found that cold filaments are also created at the interface between inflowing and outflowing gas.…”