The contribution of starbursts and normal galaxies to infrared
  luminosity functions at z < 2
  We present a parameter-less approach to predict the shape of the infrared
(IR) luminosity function (LF) at redshifts z < 2. It requires no tuning and
relies on only three observables: (1) the redshift evolution of the stellar
mass function for star-forming galaxies, (2) the evolution of the specific star
formation rate (sSFR) of main-sequence galaxies, and (3) the double-Gaussian
decomposition of the sSFR-distribution at fixed stellar mass into a
contribution (assumed redshift- and mass-invariant) from main-sequence and
starburst activity. This self-consistent and simple framework provides a
powerful tool for predicting cosmological observables: observed IR LFs are
successfully matched at all z < 2, suggesting a constant or only weakly
redshift-dependent contribution (8-14%) of starbursts to the star formation
rate density. We separate the contributions of main-sequence and starburst
activity to the global IR LF at all redshifts. The luminosity threshold above
which the starburst component dominates the IR LF rises from log(LIR/Lsun) =
11.4 to 12.8 over 0 < z < 2, reflecting our assumed (1+z)^2.8-evolution of sSFR
in main-sequence galaxies.
