First Connection between Cold Gas in Emission and Absorption: CO
  Emission from a Galaxy-Quasar Pair
  We present the first detection of molecular emission from a galaxy selected
to be near a projected background quasar using the Atacama Large
Millimeter/submillimeter Array (ALMA). The ALMA detection of CO(1$-$0) emission
from the $z=0.101$ galaxy toward quasar PKS 0439-433 is coincident with its
stellar disk and yields a molecular gas mass of $M_{\rm mol} \approx 4.2 \times
10^9 M_\odot$ (for a Galactic CO-to-H$_2$ conversion factor), larger than the
upper limit on its atomic gas mass. We resolve the CO velocity field, obtaining
a rotational velocity of $134 \pm 11$ km s$^{-1}$, and a resultant dynamical
mass of $\geq 4 \times 10^{10} M_\odot$. Despite its high metallicity and large
molecular mass, the $z=0.101$ galaxy has a low star formation rate, implying a
large gas consumption timescale, larger than that typical of late-type
galaxies. Most of the molecular gas is hence likely to be in a diffuse extended
phase, rather than in dense molecular clouds. By combining the results of
emission and absorption studies, we find that the strongest molecular
absorption component toward the quasar cannot arise from the molecular disk,
but is likely to arise from diffuse gas in the galaxy's circumgalactic medium.
Our results emphasize the potential of combining molecular and stellar emission
line studies with optical absorption line studies to achieve a more complete
picture of the gas within and surrounding high-redshift galaxies.
