CO Observations of High Redshift Galaxies with the Owens Valley Millimeter Array

The peaking of quasar density at z ∼ 2 as well as the stellar population analysis of galaxies in the local universe suggest that galaxies were formed near or prior to the redshift of 2. The identification of IRAS FSC 10214+4724 with a z = 2.3 galaxy (Rowan-Robinson et al. 1991) and the detection of CO emission (Brown & Vanden Bout 1991, Solomon et al. 1992) have substantiated the hypothesized existence of luminous gas-rich galaxies in the early epochs forming stars at prodigious rates. Given that there has been reasonable heavy element production, CO rotational transitions are excellent probes of cold interstellar medium in very distant galaxies. For objects of constant intrinsic CO brightness temperature, the observed line flux is almost independent of redshift at z = 1-6 due to the factor (1 + z)² in angular size distance. These molecular transitions are also unambiguous tracers of cold, dense molecular gas where stars are forming.