Kinematics & Chemistry of Halo Substructures: The Vicinity of the Virgo
  Over-Density
  We present observations obtained with the AAT's 2dF wide field spectrograph
AAOmega of K-type stars located within a region of the sky which contains the
Virgo Over-Density and the leading arm of the Sagittarius Stream. On the basis
of the resulting velocity histogram we isolate halo substructures in these
overlapping regions including Sagittarius and previously discovered Virgo
groups. Through comparisons with N-body models of the Galaxy-Sagittarius
interaction, we find a tri-axial dark matter halo is favoured and we exclude a
prolate shape. This result is contradictory with other observations along the
Sagittarius leading arm, which typically favour prolate models. We have also
uncovered K-giant members of Sagittarius that are notably more metal poor
([Fe/H] = -1.7 +/- 0.3 dex) than previous studies. This suggests a
significantly wider metallicity distribution exists in the Sagittarius Stream
than formerly considered. We also present data on five carbon stars which were
discovered in our sample.
