Population III Supernovae and the Assembly of the First Galaxies

Abstract

Current numerical studies suggest that the first galaxies formed a few stars at a time and were enriched only gradually by the first heavy elements. However, the large box sizes in these models cannot resolve primordial supernova explosions or the mixing of their metals with ambient gas, which could result in intervening, prompt generations of low-mass stars. We present multiscale 1D models of Population III supernovae in cosmological halos that evolve the blast from its earliest stages as a free expansion. We find that if the star ionizes the halo, the ejecta strongly interacts with the dense shell swept up by the H II region, potentially cooling and fragmenting it into clumps that are unstable to gravitational collapse. If the star fails to ionize the halo, the explosion propagates metals out to 20 - 40 pc and then collapses, enriching tens of thousands of solar masses of primordial gas, in contrast to previous models that suggest such explosions 'fizzle'. Rapid formation of low-mass stars trapped in the gravitational potential well of the halo appears to be inevitable in such circumstances. Consequently, it is possible that far more stars were swept up into the first galaxies, at earlier times and with distinct chemical signatures, than in present models. Upcoming measurements by JWST and ALMA may discriminate between these two paradigms.