The properties of satellite galaxies in simulations of galaxy formation

We investigate the properties of satellite galaxies in cosmological N-body/smooth particle hydrodynamics simulations of galaxy formation in Milky Way-sized haloes. Because of their shallow potential wells, satellite galaxies are very sensitive to heating processes which affect their gas content. Their properties can therefore be used to constrain the nature of feedback processes that regulate galaxy formation. In our simulations, we assume that all the energy produced by supernovae is used as kinetic energy to drive galactic winds. Several of our simulations produce bright, disc-dominated galaxies. We find that wind models in which the wind speed, v(w), is proportional to the local velocity dispersion of the dark matter, sigma (and thus the wind mass-loading, eta w proportional to sigma(-2)), make star formation in satellites sporadic, reproduce the observed satellite luminosity function reasonably well (down to M-v=-7) and match the luminosity-metallicity relation observed in the Local Group satellites. By contrast, models that assume a constant wind speed overproduce faint satellites and predict an incorrect luminosity-metallicity relation. Our simulations therefore suggest that the feedback processes that operate on the scale of satellite galaxies should generate galactic outflows whose mass-loading varies inversely with the depth of the potential.