Evidence for IMF Variations from the Integrated Light of SDSS Galaxies
  The H alpha equivalent width (EW) is the ratio of the H alpha flux to the
continuum at 6565{\AA}. In normal star forming galaxies the H alpha flux is
dominated by reprocessed photons from stars with masses greater than 10 M_o and
the 6565{\AA} continuum is predominantly due to 0.7-3.0 M_o red giant stars. In
these galaxies the H alpha EW is effectively the ratio of high mass to low mass
stars and is thus sensitive to the stellar initial mass function (IMF). In
Hoversten & Glazebrook 2008 we used ~131,000 galaxies from the Sloan Digital
Sky Survey to show evidence for systematic variations in the IMF with galaxy
luminosity. In this proceeding we use that sample, with the addition of H
delta_A measurements, to investigate other parameterizations of the IMF. We
find evidence for IMF variations with surface brightness, and also show that,
modulo uncertainties in spectral synthesis models, that 120 M_o stars are
important in accounting for the observed H alpha EW distribution.
