Galactic Rotation and Solar Motion from Stellar Kinematics
  I present three methods to determine the distance to the Galactic centre R0,
the solar azimuthal velocity in the Galactic rest frame Vg,\odot and hence the
local circular speed Vc at R0. These simple, model-independent strategies
reduce the set of assumptions to near axisymmetry of the disc and are designed
for kinematically hot stars, which are less affected by spiral arms and other
effects. The first two methods use the position-dependent rotational streaming
in the heliocentric radial velocities U. The resulting rotation estimate
{\theta} from U velocities does not depend on Vg,\odot. The first approach
compares this with rotation from the galactic azimuthal velocities to constrain
Vg,\odot at an assumed R0. Both Vg,\odot and R0 can be determined using the
proper motion of Sgr A\ast as a second constraint. The second strategy makes
use of {\theta} being roughly proportional to R0. Therefore a wrong R0 can be
detected by an unphysical trend of Vg,\odot with the intrinsic rotation of
different populations. From these two strategies I estimate R0 = (8.27 \pm
0.29) kpc and Vg,\odot = (250 \pm 9) kms-1 for a stellar sample from SEGUE, or
respectively Vc = (238 \pm 9) kms-1. The result is consistent with the third
estimator, where I use the angle of the mean motion of stars, which should
follow the geometry of the Galactic disc. This method also gives the Solar
radial motion with high accuracy. The rotation effect on U velocities must not
be neglected when measuring the Solar radial velocity U\odot. It biases U\odot
in any extended sample that is lop-sided in position angle {\alpha} by of order
10 kms-1. Combining different methods I find U\odot \sim 14 kms-1, moderately
higher than previous results from the Geneva-Copenhagen Survey.
