2012ApJ...747L..37M

We present the latitude-normalized radial velocity (v_b) 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° and extended, retrograde "streams" visible as relatively tight l-v_bsequences. One sequence in the fourth Galactic quadrant lies within the l-v_b space expected to contain tidal debris from the "star cluster" ω Centauri. Not only does ω Cen lie precisely in this l-v_bsequence, but the positions and v_b of member stars match those of N-body simulations of tidally disrupting dwarf galaxies on orbits ending with ω Cen's current position and space motion. But the ultimate proof that we have very likely found extended parts of the ω Cen 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 ω Cen. The newly discovered ω Cen debris accounts for almost all fourth Galactic quadrant retrograde stars in the southern GGSS, which suggests ω Cen %%%% Already done %%%% is a dominant contributor of retrograde giant stars in the inner Galaxy.