A Total Molecular Gas Mass Census in z~2-3 Star-forming Galaxies: Low-J
  CO Excitation Probes of Galaxies' Evolutionary States
  We present CO(1-0) observations obtained at the Karl G. Jansky Very Large
Array (VLA) for 14 z~2 galaxies with existing CO(3-2) measurements, including
11 galaxies which contain active galactic nuclei (AGN) and three submillimeter
galaxies (SMGs). We combine this sample with an additional 15 z~2 galaxies from
the literature that have both CO(1-0) and CO(3-2) measurements in order to
evaluate differences in CO excitation between SMGs and AGN host galaxies,
measure the effects of CO excitation on the derived molecular gas properties of
these populations, and to look for correlations between the molecular gas
excitation and other physical parameters. With our expanded sample of
CO(3-2)/CO(1-0) line ratio measurements, we do not find a statistically
significant difference in the mean line ratio between SMGs and AGN host
galaxies as found in the literature, instead finding r_3,1=1.03+/-0.50 for AGN
host galaxies and r_3,1=0.78+/-0.27 for SMGs (or r_3,1=0.90+/-0.40 for both
populations combined). We also do not measure a statistically significant
difference between the distributions of the line ratios for these populations
at the p=0.05 level, although this result is less robust. We find no excitation
dependence on the index or offset of the integrated Schmidt-Kennicutt relation
for the two CO lines, and obtain indices consistent with N=1 for the various
sub-populations. However, including low-z "normal" galaxies increases our
best-fit Schmidt-Kennicutt index to N~1.2. While we do not reproduce
correlations between the CO line width and luminosity, we do reproduce
correlations between CO excitation and star formation efficiency.
