Molecular gas mass functions of normal star-forming galaxies since z 3

We used deep far-infrared data from the PEP/GOODS-Herschel surveys and restframe ultraviolet photometry to study the evolution of the molecular gas mass function of normal star-forming galaxies. Computing the molecular gas mass, Mmol, by scaling star formation rates through depletion timescales, or combining infrared (IR) luminosity and obscuration properties as described in the literature, we obtained Mmol for roughly 700, z = 0.2−3.0 galaxies near the star-forming main sequence. The number density of galaxies follows a Schechter function of Mmol. The characteristic mass M ∗ is found to strongly evolve up to z ~ 1 and then flatten at earlier epochs, resembling the IR luminosity evolution of similar objects. At z ~ 1, our result is supported by an estimate based on the stellar mass function of star-forming galaxies and gas fraction scalings from the PHIBSS survey. We compared our measurements with results from current models, finding better agreement with those that are treating star formation laws directly rather than in post-processing. Integrating the mass function, we studied the evolution of the Mmol density and its density parameter Ωmol.