  The stellar initial mass function (IMF) is predicted to depend upon the
temperature of gas in star-forming molecular clouds. The introduction of an
additional parameter, $T_{IMF}$ , into photometric template fitting, allows
galaxies to be fit with a range of IMFs. Three surprising new features appear:
(1) most star-forming galaxies are best fit with a bottom-lighter IMF than the
Milky Way; (2) most star-forming galaxies at fixed redshift are fit with a very
similar IMF; and (3) the most massive star-forming galaxies at fixed redshift
instead exhibit a less bottom-light IMF, similar to that measured in quiescent
galaxies. Additionally, since stellar masses and star formation rates both
depend on the IMF, these results slightly modify the resulting relationship,
while yielding similar qualitative characteristics to previous studies.
