Quasars Probing Galaxies: I. Signatures of Gas Accretion at Redshift
  Approximately 0.2
  We describe the kinematics of circumgalactic gas near the galactic plane,
combining new measurements of galaxy rotation curves and spectroscopy of
background quasars. The sightlines pass within 19--93 kpc of the target galaxy
and generally detect Mg II absorption. The Mg II Doppler shifts have the same
sign as the galactic rotation, so the cold gas co-rotates with the galaxy.
Because the absorption spans a broader velocity range than disk rotation can
explain, we explore simple models for the circumgalactic kinematics. Gas
spiraling inwards (near the disk plane) offers a successful description of the
observations. An Appendix describes the addition of tangential and radial gas
flows and illustrates how the sign of the disk inclination produces testable
differences in the projected line-of-sight velocity range. This inflow
interpretation implies that cold flow disks remain common down to redshift $z
\approx 0.2$ and prolong star formation by supplying gas to the disk.
