Hunting The Most Distant Stars in the Milky Way: Methods and Initial
  Results
  We present a new catalog of 404 M giant candidates found in the UKIRT
Infrared Deep Sky Survey (UKIDSS). The 2,400 deg$^2$ available in the UKIDSS
Large Area Survey Data Release 8 resolve M giants through a volume four times
larger than that of the entire Two Micron All Sky Survey. Combining
near-infrared photometry with optical photometry and proper motions from the
Sloan Digital Sky Survey yields an M giant candidate catalog with less M dwarf
and quasar contamination than previous searches for similarly distant M giants.
Extensive follow-up spectroscopy of this sample will yield the first map of our
Galaxy's outermost reaches over a large area of sky. Our initial spectroscopic
follow-up of $\sim$ 30 bright candidates yielded the positive identification of
five M giants at distances $\sim 20-90$ kpc. Each of these confirmed M giants
have positions and velocities consistent with the Sagittarius stream. The
fainter M giant candidates in our sample have estimated photometric distances
$\sim 200$ kpc (assuming $[Fe/H]$ = 0.0), but require further spectroscopic
verification. The photometric distance estimates extend beyond the Milky Way's
virial radius, and increase by $\sim 50\%$ for each 0.5 dex decrease in assumed
$[Fe/H]$. Given the number of M giant candidates, initial selection efficiency,
and volume surveyed, we loosely estimate that at least one additional
Sagittarius-like accretion event could have contributed to the hierarchical
build-up of the Milky Way's outer halo.
