  We investigate the transition from primordial Population III (Pop III) star
formation to normal Pop II star formation in the first galaxies using new
cosmological hydrodynamic simulations. We find that while the first stars seed
their host galaxies with metals, they cannot sustain significant outflows to
enrich the intergalactic medium, even assuming a top-heavy initial mass
function. This means that Pop III star formation could potentially continue
until z~6 in different unenriched regions of the universe, before being
ultimately shut off by cosmic reionization. Within an individual galaxy, the
metal production and stellar feedback from Pop II stars overtake Pop III stars
in 20-200 Myr, depending on galaxy mass.
