Dust-Corrected Star Formation Rates of Galaxies. Ii. Combinations of Ultraviolet and Infrared Tracers

We combine Hα 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 Hα + IR based SFRs are in excellent agreement with attenuation-corrected SFRs derived from integrated spectrophotometry, over the full range of SFRs (0.01 – 80 M ⊙ yr −1) and attenuations (0 – 2.5 mag) studied. We find that the combination of Hα and total infrared luminosities provides the most robust SFR measurements, but combinations of Hα measurements with monochromatic luminosities at 24µm and 8µm 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 1