Adaptive Optics Imaging of a Massive Galaxy Associated with a Metal-rich
  Absorber
  The damped and sub-damped Lyman-alpha absorption line systems in quasar
spectra are believed to be produced by intervening galaxies. However, the
connection of quasar absorbers to galaxies is not well-understood, since
attempts to image the absorbing galaxies have often failed. While most DLAs
appear to be metal-poor, a population of metal-rich absorbers, mostly sub-DLAs,
has been discovered in recent studies. Here we report high-resolution K-band
imaging with the Keck Laser Guide Star Adaptive Optics (LGSAO) system of the
field of quasar SDSSJ1323-0021 in search of the galaxy producing the z = 0.72
sub-DLA absorber. With a metallicity of 2-4 times the solar level, this
absorber is of the most metal-rich systems found to date. Our data show a large
bright galaxy with an angular separation of only 1.25" from the quasar,
well-resolved from the quasar at the high resolution of our data. The galaxy
has a magnitude of K = 17.6-17.9, which corresponds to a luminosity of ~ 3-6
L*. Morphologically, the galaxy is fit with a model with an effective radius,
enclosing half the total light, of R_e = 4 kpc and a bulge-to-total ratio of
0.4-1.0, indicating a substantial bulge stellar population. Based on the
mass-metallicity relation of nearby galaxies, the absorber galaxy appears to
have a stellar mass > 10^{11} M_sun. Given the small impact parameter, this
massive galaxy appears to be responsible for the metal-rich sub-DLA. The
absorber galaxy is consistent with the metallicity-luminosity relation observed
for nearby galaxies, but is near the upper end of metallicity. Our study marks
the first application of LGSAO for study of structure of galaxies producing
distant quasar absorbers. Finally, this study offers the first example of a
massive galaxy with a substantial bulge producing a metal-rich absorber.
