Following the Cosmic Evolution of Pristine Gas III: The Observational
  Consequences of the Unknown Properties of Population III Stars
  We study the observational consequences of several unknown properties of
Population III (Pop III) stars using large-scale cosmological simulations that
include a subgrid model to track the unresolved mixing of pollutants. Varying
the value of the critical metallicity that marks the boundary between Pop III
and Population II (Pop II) star formation across 2 dex has a negligible effect
on the fraction of Pop III stars formed and the subsequent fraction of Pop III
flux from high-redshift galaxies. However, adopting a log normal initial mass
function (IMF) for Pop III stars, in place of a baseline Salpeter IMF, results
in a Pop III star formation rate density (SFRD) that is 1/4 of the baseline
rate. The flux from high-redshift galaxies modeled with this IMF is highly
bimodal, resulting in a tiny fraction of $z \leq 8$ galaxies with more than
75\% of their flux coming from Pop III stars. However, at $z=9$, right before
reionization in our simulations, $\approx$ 20\% of galaxies are Pop III-bright
with $m_{\rm UV} \le 31.4$ mag and at least 75\% of their flux generated by Pop
III stars . Additionally, the log normal Pop III IMF results in a population of
carbon enhanced, metal poor stars in reasonable agreement with MW halo
observations. Our analysis supports the conclusion that the Pop III IMF was
dominated by stars in the 20-120$M_{\odot}$ range that generate SN with
carbon-enhanced ejecta.
