We present a parameter-less approach capable of predicting
the shape of the infrared luminosity function at redshifts z ≤2. It relies on
three observables: (1) the redshift evolution of the stellar mass function
for star-forming galaxies, (2) the evolution of the specific star formation
rate of main-sequence galaxies, and (3) the double-Gaussian decomposition
of the specific star formation rate distribution at fixed stellar mass
into the contributions (assumed to be redshift- and mass-invariant) from
main-sequence and starburst activity.
Using this self-consistent and simple framework, we identify the contributions
of main-sequence and starburst activity to the global infrared luminosity
function and find a constant or only weakly redshift-dependent
contribution (8–14%) of starbursts to the star formation rate density at
z ≤2. Over the same redshift range, we also infer the evolution of the
cosmic abundance of molecular gas in star-forming galaxies, based on the
relations between star formation rate and molecular gas mass followed by
normal and starburst galaxies
