Abstract

We combine the recent determination of the evolution of the cosmic density of molecular gas (H-2) using deep, volumetric surveys, with previous estimates of the cosmic density of stellar mass, star formation rate and atomic gas (Hi), to constrain the evolution of baryons associated with galaxies averaged over cosmic time and space. The cosmic Hiand H(2)densities are roughly equal atz similar to 1.5. The H(2)density then decreases by a factor