Inferring Host Dark Matter Halo Masses of Individual Galaxies from
  Neighboring Galaxy Counts
  How well can we infer host dark matter halo masses of individual galaxies?
Based on the halo occupation distribution (HOD) framework, we analytically
compute the number of neighboring galaxies within a cylinder of some redshift
interval and radius in transverse comoving distance. The result is used to
derive the conditional probability distribution function (PDF) of the host halo
mass of a galaxy, given the neighboring galaxy counts. We compare our analytic
results with those obtained using a realistic mock galaxy catalog, finding
reasonable agreements. We find the optimal cylinder radius to be $\sim
0.5-1h^{-1}{\rm Mpc}$ for the inference of halo masses. The PDF is generally
broad, and sometimes has two peaks at low- and high-mass regimes, because of
the effect of chance projection along the line-of-sight. Potential applications
and extensions of the new theoretical framework developed herein are also
discussed.
