Suppression of dwarf galaxy formation by cosmic shocks

We carry out a numerical study of the effects of supernova (SN)-driven shocks on galaxy formation at z = 9. These cosmic explosions can have a significant impact on galaxies forming nearby. We study such interactions in two key cases. In the first case in which the forming galaxy has already virialized, the impinging shock has only a small effect (≲1 per cent of the gas is removed) and star formation continues relatively unimpeded. However, in the second case in which the nearby forming galaxy is at the more diffuse turnaround stage, a large fraction (≈70 per cent) of the gas is stripped away from the host dark matter halo and ejected into the intergalactic medium (IGM). As the time spent near turnaround is much longer than the interval from virialization to galaxy formation as a result of strong radiative losses, we expect the second case to be more representative of the majority of outflow-galaxy interactions. Thus, SN-driven pre-galactic outflows may be an efficient mechanism for inhibiting the formation of neighbouring galaxies at high redshift. We briefly outline the possible cosmological consequences of this effect.