POPULATION III STARS AND REMNANTS IN HIGH-REDSHIFT GALAXIES

Recent simulations of Population III star formation have suggested that some fraction form in binary systems, in addition to having a characteristic mass of tens of solar masses. The deaths of metal-free stars result in the initial chemical enrichment of the universe and the production of the first stellar-mass black holes. Here we present a cosmological adaptive mesh refinement simulation of an overdense region that forms a few 10(9) M-circle dot dark matter halos and over 13,000 Population III stars by redshift 15. We find that most halos do not form Population III stars until they reach M-vir similar to 10(7) M-circle dot because this biased region is quickly enriched from both Population III and galaxies, which also produce high levels of ultraviolet radiation that suppress H-2 formation. Nevertheless, Population III stars continue to form, albeit in more massive halos, at a rate of similar to 10(-4) M-circle dot yr(-1) Mpc(-3) at redshift 15. The most massive starless halo has a mass of 7 x 10(7) M-circle dot, which could host massive black hole formation through the direct gaseous collapse scenario. We show that the multiplicity of the Population III remnants grows with halo mass above 10(8) M-circle dot, culminating in 50 remnants located in 10(9) M-circle dot halos on average. This has implications that high-mass X-ray binaries and intermediate-mass black holes that originate from metal-free stars may be abundant in high-redshift galaxies.