The Influence of Galactic Outflows on the Formation of Nearby Dwarf Galaxies

Abstract

We show that the gas in growing density perturbations is vulnerable to the influence of winds outflowing from nearby collapsed galaxies that have already formed stars. This suggests that the formation of nearby galaxies with masses less than 10^9 solar masses is likely to be suppressed, irrespective of the details of galaxy formation. An impinging wind may shock heat the gas of a nearby perturbation to above the virial temperature, thereby mechanically evaporating the gas, or the baryons may be stripped from the perturbation entirely if they are accelerated to above the escape velocity. We show that baryonic stripping is the most effective of these two processes, because shock-heated clouds that are too large to be stripped are able to radiatively cool within a sound-crossing time, limiting evaporation. The intergalactic medium temperatures and star-formation rates required for outflows to have a significant influence on the formation of low-mass galaxies are consistent with current observations, but may soon be examined directly via associated distortions in the cosmic microwave background, and with near-infrared observations from the Next Generation Space Telescope, which may detect the supernovae from early-forming stars.