Cross-correlating Carbon Monoxide Line-intensity Maps with Spectroscopic
  and Photometric Galaxy Surveys
  Line-intensity mapping (LIM or IM) is an emerging field of observational
work, with strong potential to fit into a larger effort to probe large-scale
structure and small-scale astrophysical phenomena using multiple complementary
tracers. Taking full advantage of such complementarity means, in part,
undertaking line-intensity surveys with galaxy surveys in mind. We consider the
potential for detection of a cross-correlation signal between COMAP and blind
surveys based on photometric redshifts (as in COSMOS) or based on spectroscopic
data (as with the HETDEX survey of Lyman-$\alpha$ emitters). We find that
obtaining $\sigma_z/(1+z)\lesssim0.003$ accuracy in redshifts and
$\gtrsim10^{-4}$ sources per Mpc$^3$ with spectroscopic redshift determination
should enable a CO-galaxy cross spectrum detection significance at least twice
that of the CO auto spectrum. Either a future targeted spectroscopic survey or
a blind survey like HETDEX may be able to meet both of these requirements.
