  A universal stellar initial mass function (IMF) should not be expected from
theoretical models of star formation, but little conclusive observational
evidence for a variable IMF has been uncovered. In this paper, a
parameterization of the IMF is introduced into photometric template fitting of
the COSMOS2015 catalog. The resulting best-fit templates suggest systematic
variations in the IMF, with most galaxies exhibiting top-heavier stellar
populations than in the Milky Way. At fixed redshift, only a small range of
IMFs are found, with the typical IMF becoming progressively top-heavier with
increasing redshift. Additionally, subpopulations of ULIRGs, quiescent- and
star-forming galaxies are compared with predictions of stellar population
feedback and show clear qualitative similarities to the evolution of dust
temperatures.
