2013ApJ...767...73R

We demonstrate estimating the total infrared luminosity, L(TIR), and star formation rates (SFRs) of star-forming galaxies at redshift 0 < z < 2.8 from single-band 24 µm observations, using local spectral energy distribution (SED) templates without introducing additional free parameters. Our method is based on characterizing the SEDs of galaxies as a function of their L(TIR) surface density, which is motivated by the indications that the majority of IR luminous star-forming galaxies at 1 < z < 3 have extended star-forming regions, in contrast to the strongly nuclear concentrated, merger-induced starbursts in local luminous and ultraluminous IR galaxies. We validate our procedure for estimating L(TIR) by comparing the resulting L(TIR) with those measured from far-IR observations, such as those from Herschel in the Extended Chandra Deep Field South (ECDFS) and Hubble Deep Field North (HDFN), as well as L(TIR) measured from stacked far-IR observations at redshift 0 < z < 2.8. Active galactic nuclei were excluded using X-ray and 3.6-8.0 µm observations, which are generally available in deep cosmological survey fields. The Gaussian fits to the distribution of the discrepancies between the L(TIR) measurements from single-band 24 µm and Herschel observations in the ECDFS and HDFN samples have σ < 0.1 dex, with ∼10% of objects disagreeing by more than 0.2 dex. Since the 24 µm estimates are based on SEDs for extended galaxies, this agreement suggests that ∼90% of IR galaxies at high z are indeed much more physically extended than local counterparts of similar L(TIR), consistent with recent independent studies of the fractions of galaxies forming stars in the main-sequence and starburst modes, respectively. Because we have not introduced empirical corrections to enhance these estimates, in principle, our method should be applicable to lower luminosity galaxies. This will enable use of the 21 µm band of the Mid-Infrared Instrument on board the James Webb Space Telescope to provide an extremely sensitive tracer of obscured SFR in individual star-forming galaxies across the peak of the cosmic star formation history.