The destruction of cosmological minihalos by primordial supernovae

Abstract

We present numerical simulations of primordial supernovae in cosmological minihalos at z ~ 20. We consider Type II supernovae, hypernovae, and pair instability supernovae (PISN) in halos from 6.9 × 105 to 1.2 × 107 M, those in which Population III stars are expected to form via H2 cooling. Our simulations are the first to follow the evolution of the blast from a free expansion on spatial scales of 10−4 pc until its approach to pressure equilibrium in the relic H II region of the progenitor, ~1000 pc. Supernovae in H II regions first expand adiabatically and then radiate strongly upon collision with baryons ejected from the halo during its photoevaporation by the progenitor. In contrast to previous findings, supernovae in neutral halos promptly emit most of their kinetic energy as X-rays, but retain enough momentum to seriously disrupt the halo. Explosions in H II regions escape into the IGM, but neutral halos confine the blast and its metals. In H II regions, a prompt second generation of stars may form in the remnant at radii of 100-200 pc. Explosions confined by massive halos instead recollapse, with infall rates in excess of 10−2 M yr−1 that heavily contaminate their interior. This fallback may either fuel massive black hole growth at very high redshifts or create the first globular clusters with radii of 10-20 pc at the center of the halo. Our findings suggest that the first primitive galaxies may therefore have formed sooner, with greater numbers of stars and distinct chemical signatures, than in current models.