Dust-Corrected Star Formation Rates of Galaxies. I. Combinations of
  H-alpha and Infrared Tracers
  We combine H-alpha emission-line and infrared continuum measurements of two
samples of nearby galaxies to derive dust attenuation-corrected star formation
rates (SFRs). We use a simple energy balance based method that has been applied
previously to HII regions in the Spitzer Infrared Nearby Galaxies Survey
(SINGS), and extend the methodology to integrated measurements of galaxies. We
find that our composite H-alpha+IR based SFRs are in excellent agreement with
attenuation-corrected SFRs derived from integrated spectrophotometry, over the
full range of SFRs (0.01 -- 80 solar mass per year) and attenuations (0 -- 2.5
mag) studied. We find that the combination of H-alpha and total infrared
luminosities provides the most robust SFR measurements, but combinations of
H-alpha measurements with monochromatic luminosities at 24 micron and 8 micron
perform nearly as well. The calibrations differ significantly from those
obtained for HII regions (Calzetti et al. 2007), with the difference
attributable to a more evolved population of stars heating the dust. Our
results are consistent with a significant component of diffuse dust (the `IR
cirrus' component) that is heated by a non-star-forming population. The same
methodology can be applied to [OII]$\lambda$3727 emission-line measurements,
and the radio continuum fluxes of galaxies can be applied in place of IR fluxes
when the latter are not available. We assess the precision and systematic
reliability of all of these composite methods.
