A Kinematically-Distinct RR-Lyrae Overdensity in the Inner Regions of
  the Milky Way
  We combine the Siding Spring Survey of RR Lyrae stars with the Southern
Proper Motion Catalog 4, in order to detect and kinematically characterize
overdensities in the inner halo of the Milky Way. We identify one such
overdensity above the Galactic plane, in quadrant 4 of the Galaxy. The
overdensity extends at least 20 degrees in longitude, has an average
heliocentric distance of 8 kpc with a depth of 4 kpc, and is confined within 4
kpc of the Galactic plane. Its metallicity distribution is distinct from that
of the field population having a peak at -1.3 and a pronounced tail to -2.0.
Proper motions indicate a net vertical motion away from the plane, and a low
orbital angular momentum. Qualitatively, these orbit properties suggest a
possible association with omega Centauri's parent satellite. However,
comparison to a specific omega Cen N-body disruption model does not give a good
match with observations. Line-of-sight velocities, and more extensive N-body
modelling will help clarify the nature of this overdensity.
