A 10,000 star spectroscopic survey of the thick disk-halo interface :
  Phase-space sub-structure in the thick disk
  We analyse a 10,000 star spectroscopic survey, focused on Galactic thick disk
stars typically 2-5 kpc from the Sun, carried out using the AAOmega
Spectrograph on the AAT. We develop methods for completeness-correction of the
survey based on SDSS photometry, and we derive star distances using an improved
isochrone-fitting method with accuracies better than 10%. We determine the
large-scale kinematic (Vphi=172 km/s and sigma(phi,r,z) = (49,51,40) km/s), and
abundance properties of the thick disk, showing these representative values are
a fair description within about 3 kpc of the sun, and in the range 1-3 kpc from
the Galactic Plane. We identify a substantial overdensity in lines of sight
towards the inner Galaxy, with metallicity [Fe/H] -1 dex, and higher line of
sight velocities than the thick disk, localised along the direction
(l,b)=(48,-26). This overdensity appears to be towards, but closer than, the
known Hercules-Aquila halo overdensity and may be related to the
Humphreys-Larsen inner galaxy thick disk asymmetry.
