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 .