Quantifying the abundance of faint, low-redshift satellite galaxies in
  the COSMOS survey
  Faint dwarf satellite galaxies are important as tracers of small-scale
structure, but remain poorly characterized outside the Local Group, due to the
difficulty of identifying them consistently at larger distances. We review a
recently proposed method for estimating the average satellite population around
a given sample of nearby bright galaxies, using a combination of size and
magnitude cuts (to select low-redshift dwarf galaxies preferentially) and
clustering measurements (to estimate the fraction of true satellites in the cut
sample). We test this method using the high-precision photometric redshift
catalog of the COSMOS survey, exploring the effect of specific cuts on the
clustering signal. The most effective of the size-magnitude cuts considered
recover the clustering signal around low-redshift primaries (z < 0.15) with
about two-thirds of the signal and 80\%\ of the signal-to-noise ratio
obtainable using the full COSMOS photometric redshifts. These cuts are also
fairly efficient, with more than one third of the selected objects being
clustered satellites. We conclude that structural selection represents a useful
tool in characterizing dwarf populations to fainter magnitudes and/or over
larger areas than are feasible with spectroscopic surveys.} In reviewing the
low-redshift content of the COSMOS field, we also note the existence of several
dozen objects that appear resolved or partially resolved in the HST imaging,
and are confirmed to be local (at distances of $\sim$250 Mpc or less) by their
photometric or spectroscopic redshifts. This underlines the potential for
future space-based surveys to reveal local populations of intrinsically faint
galaxies through imaging alone.
