Exploring Simulated Early Star Formation in the Context of the
  Ultrafaint Dwarf Galaxies
  Ultrafaint dwarf galaxies (UFDs) are typically assumed to have simple,
stellar populations with star formation ending at reionization. Yet as the
observations of these galaxies continue to improve, their star formation
histories (SFHs) are revealed to be more complicated than previously thought.
In this paper, we study how star formation, chemical enrichment, and mixing
proceed in small, dark matter halos at early times using a high-resolution,
cosmological, hydrodynamical simulation. The goals are to inform the future use
of analytic models and to explore observable properties of the simulated halos
in the context of UFD data. Specifically, we look at analytic approaches that
might inform metal enrichment within and beyond small galaxies in the early
Universe. We find that simple assumptions for modeling the extent of
supernova-driven winds agree with the simulation on average whereas
inhomogeneous mixing and gas flows have a large effect on the spread in
simulated stellar metallicities. In the context of the UFDs, this work
demonstrates that simulations can form halos with a complex SFH and a large
spread in the metallicity distribution function within a few hundred Myr in the
early Universe. In particular, bursty and continuous star formation are seen in
the simulation and both scenarios have been argued from the data. Spreads in
the simulated metallicities, however remain too narrow and too metal-rich when
compared to the UFDs. Future work is needed to help reduce these discrepancies
and advance our interpretation of the data.
