Chemically-dissected rotation curves of the Galactic Bulge from Main
  Sequence proper motions
  We report results from an exploratory study implementing a new probe of
Galactic evolution using archival Hubble Space Telescope imaging observations.
Precise proper motions are combined with photometric relative metallicity and
temperature indices, to produce the proper motion rotation curves of the
Galactic bulge separately for metal-poor and metal-rich Main Sequence samples.
This provides a "pencil-beam" complement to large-scale wide-field surveys,
which to-date have focused on the more traditional bright Giant Branch tracers.
  We find strong evidence that the Galactic bulge rotation curves drawn from
"Metal-rich" and "Metal-poor" samples are indeed discrepant. The "Metal-rich"
sample shows greater rotation amplitude and a steeper gradient against line of
sight distance, as possibly a stronger central concentration along the line of
sight. This may represent a new detection of differing orbital anisotropy
between metal-rich and metal-poor bulge objects. We also investigate selection
effects that would be implied for the longitudinal proper motion cut often used
to isolate a "pure-bulge" sample. Extensive investigation of synthetic stellar
populations suggest that instrumental and observational artifacts are unlikely
to account for the observed rotation curve differences. Thus, proper
motion-based rotation curves can be used to probe chemo-dynamical correlations
for Main Sequence tracer stars, which are orders of magnitude more numerous in
the Galactic Bulge than the bright Giant Branch tracers. We discuss briefly the
prospect of using this new tool to constrain detailed models of Galactic
formation and evolution.
