The Impact of Inhomogeneous Reionization on the Satellite Galaxy
  Population of the Milky Way
  We use the publicly available subhalo catalogs from the Via Lactea simulation
along with a Gpc-scale N-body simulation to understand the impact of
inhomogeneous reionization on the satellite galaxy population of the Milky Way.
The large-volume simulation is combined with a model for reionization that
allows us to predict the distribution of reionization times for Milky Way mass
halos. Motivated by this distribution, we identify candidate satellite galaxies
in the simulation by requiring that any subhalo must grow above a specified
mass threshold before it is reionized; after this time the photoionizing
background will suppress both the formation of stars and the accretion of gas.
We show that varying the reionization time over the range expected for Milky
Way mass halos can change the number of satellite galaxies by roughly two
orders of magnitude. This conclusion is in contradiction with a number of
studies in the literature, and we conclude that this is a result of
inconsistent application of the results of Gnedin (2000). We compare our
satellite galaxies to observations using both abundance matching and stellar
population synthesis methods to assign luminosities to our subhalos and account
for observational completeness effects. Additionally, if we assume that the
mass threshold is set by the virial temperature Tvir = 8e3K we find that our
model accurately matches the vmax distribution, radial distribution, and
luminosity function of observed Milky Way satellites for a reionization time
zreion = 9.6^{1.0}_{-2.1}, assuming that the Via Lacteasubhalo distribution is
representative of the Milky Way. This results in the presence of
119^{+202}_{-50} satellite galaxies.
