CO luminosity functions for far-infrared- and B-band-selected galaxies and the first estimate for ΩH I+H2

We derive a nonparametric CO luminosity function using an FIR- and an optical B-band-selected sample of the galaxies included in the FCRAO Extragalactic CO Survey. The FIR- selected sample is defined using the IRAS bright galaxy samples (BGS; IRAS 60 mum flux density greater than or equal to5.24 Jy). Although our CO sample is not complete, the normalization using the BGS reproduces the IRAS 60 mum luminosity function in excellent agreement with those found in the literature. Similarly, a B-band selected sample defined using the Revised Shapley-Ames catalog is used to derive a CO luminosity function for a comparison. A Schechter function describes both the derived CO luminosity functions reasonably well. Adopting the standard CO-to-H-2 conversion factor, we derive a molecular gas density of rho(H2) = (3.1 +/- 1.2) x 10(7) h M. Mpc(-3) for the local volume. Combining with the measurements of the local H I mass density and the helium contribution, we estimate that the total mass density of cold neutral gas in the local universe is Omega(gas) = 4.3 +/- 1.1 x 10(-4) h(-1), which is about 20% of the total stellar mass density Omega(*).