Spectroscopic Follow-Up of the Hercules Aquila Cloud
  We designed a follow-up program to find the spectroscopic properties of the
Hercules-Aquila Cloud (HAC) and test scenarios for its formation. We measured
the radial velocities (RVs) of 45 RR Lyrae in the southern portion of the HAC
using the facilities at the MDM observatory, producing the first large sample
of velocities in the HAC. We found a double-peaked distribution in RVs, skewed
slightly to negative velocities. We compared both the morphology of HAC
projected onto the plane of the sky and the distribution of velocities in this
structure outlined by RR Lyrae and other tracer populations at different
distances to N-body simulations. We found that the behaviour is characteristic
of an old, well-mixed accretion event with small apo-galactic radius. We cannot
yet rule out other formation mechanisms for the HAC. However, if our
interpretation is correct, HAC represents just a small portion of a much larger
debris structure spread throughout the inner Galaxy whose distinct kinematic
structure should be apparent in RV studies along many lines of sight.
