Selecting Sagittarius: Identification and Chemical Characterization of
  the Sagittarius Stream
  Wrapping around the Milky Way, the Sagittarius stream is the dominant
substructure in the halo. Our statistical selection method has allowed us to
identify 106 highly likely members of the Sagittarius stream. Spectroscopic
analysis of metallicity and kinematics of all members provides us with a new
mapping of the Sagittarius stream. We find correspondence between the velocity
distribution of stream stars and those computed for a triaxial model of the
Milky Way dark matter halo. The Sagittarius trailing arm exhibits a metallicity
gradient, ranging from $-0.59$ dex to $-0.97$ dex over 142$^{\circ}$. This is
consistent with the scenario of tidal disruption from a progenitor dwarf galaxy
that possessed an internal metallicity gradient. We note high metallicity
dispersion in the leading arm, causing a lack of detectable gradient and
possibly indicating orbital phase mixing. We additionally report on a potential
detection of the Sextans dwarf spheroidal in our data.
