Estimating the baryonic masses of face-on spiral galaxies from stellar
  kinematics
  The kinematic dispersions of disc stars can be used to measure the dynamic
contributions of baryons to the rotation curves of spiral galaxies and hence to
trace the amount and distribution of the remaining dark matter. However, the
simple single-component infinite disc model traditionally used to convert
stellar dispersions to mass-densities is no longer adequate. The dark matter
halo has a significant effect upon the stellar dispersions for any non-maximal
disc. The correction for cuspy dark matter halos is particularly large,
suggesting that such models are not consistent with the observed stellar
dispersions. When a more realistic model for the vertical gravity of the disc
is used, the derived stellar surface densities are generally larger (smaller)
for disc radii smaller (larger) than 2.3 times the radial scale-length. When
the vertical gravity correction is applied to the radially resolved stellar
mass-to-light ratios derived by the DiskMass consortium, the true values are
not constant but decrease with radius, as expected from photometric colour
gradients, and the true mass scale-lengths are about 80% of the photometric
scale-lengths. The effects of a thin gaseous disc are larger than expected,
especially when an allowance is made for optically thick or CO-dark gas. The
presence of a thick-disc stellar component has severe consequences,
particularly if its radial scale-length is smaller than that of the thin disc,
as it appears to be in the Milky Way.
