Mapping the Asymmetric Thick Disk: III. The Kinematics and Interaction
  with the Galactic Bar
  In the first two papers of this series, Larsen et al (2010a,b) describe our
faint CCD survey in the inner Galaxy and map the over-density of Thick Disk
stars in Quadrant I (Q1) to 5 kpc or more along the line of sight. The regions
showing the strongest excess are above the density contours of the bar in the
Galactic disk. In this third paper on the asymmetric Thick Disk, we report on
radial velocities and derived metallicity parameters for over 4000 stars in Q1,
above and below the plane and in Q4 above the plane. We confirm the
corresponding kinematic asymmetry first reported by Parker et al. (2004),
extended to greater distances and with more spatial coverage. The Thick Disk
stars in Q1 have a rotational lag of 60 -- 70 km/s relative to circular
rotation, and the Metal-Weak Thick Disk stars have an even greater lag of 100
km/s. Both lag their corresponding populations in Q4 by approximately 30 km/s.
Interestingly, the Disk stars in Q1 also appear to participate in the
rotational lag by about 30 km/s. The enhanced rotational lag for the Thick Disk
in Q1 extends to 4 kpc or more from the Sun. At 3 to 4 kpc, our sight lines
extend above the density contours on the near side of the bar, and as our lines
of sight pass directly over the bar the rotational lag appears to decrease.
This is consistent with a "gravitational wake" induced by the rotating bar in
the Disk which would trap and pile up stars behind it. We conclude that a
dynamical interaction with the stellar bar is the most probable explanation for
the observed kinematic and spatial asymmetries.
