Where are All the Gas-Bearing Local Dwarf Galaxies? Quantifying Possible
  Impacts of Reionization
  We present an approach for comparing the detections and non-detections of
Local Group (LG) dwarf galaxies in large HI surveys to the predictions of a
suite of n-body simulations of the LG. This approach depends primarily on a set
of empirical scaling relations to connect the simulations to the observations,
rather than making strong theoretical assumptions. We then apply this
methodology to the Galactic Arecibo L-band Feed Array HI Compact Cloud Catalog
(GALFA-HI CCC), and compare it to the ELVIS suite of simulations. This approach
reveals a strong tension between the na\"ive results of the model and the
observations: while there are no LG dwarfs in the GALFA-HI CCC, the simulations
predict $\sim 10$. Applying a simple model of reionization can resolve this
tension by preventing low-mass halos from forming gas. However, and if this
effect operates as expected, the observations provide a constraint on the mass
scale of dwarf galaxy that reionization impacts. Combined with the observed
properties of Leo T, the halo virial mass scale at which reionization impacts
dwarf galaxy gas content is constrained to be $\sim 10^{8.5} M_\odot$,
independent of any assumptions about star formation.
