Galactic Outflows and Photoionization Heating in the Reionization Epoch
  We carry out a new suite of cosmological radiation hydrodynamic simulations
and explore the relative impacts on reionization-epoch star formation of
galactic outflows and photoionization heating. By itself, an extragalactic
ultraviolet background (EUVB) suppresses the luminosity function by less than
50% at z=6, overproducing the observed galaxy abundance by a factor of 3-5.
Galactic outflows restore agreement with observations without preventing
Population II star formation from reionizing the Universe by z=6. The resulting
EUVB suppresses star formation in halos with virial temperatures below 10^5K
but has a weaker impact in more massive halos. Nonetheless, the low-mass halos
contribute up to 50% of all ionizing photons owing to the EUVB's inhomogeneity.
Overall, star formation rate scales as halo mass M_h to the 1.3-1.4 in halos
with $M_h=10^{8.2--10.2}\msun$. This is a steeper dependence than is often
assumed in reionization models, boosting the expected power spectrum of 21
centimeter fluctuations on large scales. The luminosity function rises steeply
to at least M_1600=-13, indicating that reionization was driven by faint
galaxies (M_1600 >= -15) that have not yet been observed. Our models cannot
simultaneously explain observations of galaxies, the cosmic microwave
background, and the intergalactic medium. Increased dynamic range will
alleviate the existing discrepancies, but observations may still require
additional physics such as a variable ionizing escape fraction (abridged).
