Environmental Mechanisms Shaping the Nature of Dwarf Spheroidal Galaxies: The View of Computer Simulations
Figure 4
Time evolution of the bound gas mass for a disky dwarf galaxy model(initial ) km/s within a Milky-Way-sized dark matter halo having a hot gaseous halo about 1% of its total mass (see [20] for details on the modeling). The dwarf's orbit has an apocenter of kpc and a pericenter of kpc. The same model has been run with adiabatic gas conditions (thin solid line), radiative cooling with no heating (thick solid line), and radiative cooling plus heating by the cosmic ionizing UV background (dashed line), assuming that when the simulation is started, the time corresponds to . The long-dashed line shows the results for a run in which the hot gaseous halo of the Milky Way was absent to isolate the effect of tides from that of ram pressure. Stripping from ram pressure only is instead shown by the thick solid with dots; in this run, the same dwarf model was evolved in a “wind tunnel”, moving with a speed comparable to the orbital velocity at pericenter in the other runs. In the “wind tunnel” the dwarf moves within a static gas distribution along a straight trajectory withe specified velocity (periodic boundary conditions are used for the gaseous background), but responds only to the ram-pressure force. The latter curve spans less than a Gyr of evolution since ram-pressure stripping saturates quickly without tidal mass loss.
