Exploring Halo Substructure with Giant Stars: Substructure in the Local
  Halo as Seen in the Grid Giant Star Survey Including Extended Tidal Debris
  from Omega Centauri
  We present the latitude-normalized radial velocity (vb) distribution of 3318
subsolar metallicity, V<13.5 stars from the Grid Giant Star Survey (GGSS) in
Southern Hemisphere fields. The sample includes giants mostly within ~5 kpc
from the Galactic disks and halo. The nearby halo is found to (1) exhibit
significant kinematical substructure, and (2) be prominently represented by
several velocity coherent structures, including a very retrograde "cloud" of
stars at l~285 deg and extended, retrograde "streams" visible as relatively
tight l-vb sequences. One sequence in the fourth Galactic quadrant lies within
the l-vb space expected to contain tidal debris from the "star cluster"
wCentauri. Not only does wCen lie precisely in this l-vb sequence, but the
positions and vb of member stars match those of N-body simulations of tidally
disrupting dwarf galaxies on orbits ending with wCen's current position and
space motion. But the ultimate proof that we have very likely found extended
parts of the wCen tidal stream comes from echelle spectroscopy of a subsample
of the stars that reveals a very particular chemical abundance signature known
to occur only in wCen. The newly discovered wCen debris accounts for almost all
fourth Galactic quadrant retrograde stars in the southern GGSS, which suggests
wCen is a dominant contributor of retrograde giant stars in the inner Galaxy.
