Kinematics of Tidal Debris from Centauri's Progenitor Galaxy

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Abstract
We present the kinematic properties of a tidally disrupted dwarf galaxy in the Milky Way, based on the hypothesis that its central part once contained the most massive Galactic globular cluster, ω Cen. Dynamical evolution of a self-gravitating progenitor galaxy that follows the present-day and likely past orbits of ω Cen is calculated numerically and the kinematic nature of their tidal debris is analyzed, combined with randomly generated stars comprising spheroidal halo and flat disk components. We show that the retrograde rotation of the debris stars at ~-100 km s-1 accords with a recently discovered large radial velocity stream at ~300 km s-1 toward the Galactic longitude of ~270°. These stars also contribute, only in part, to a reported retrograde motion of the outer halo at the north Galactic pole. The prospects for future debris searches and the implications for the early evolution of the Galaxy are briefly presented.