Stellar Masses and SFRs for 1M Galaxies from SDSS and WISE

We combine Sloan Digitital Sky Survey ( SDSS ) and WISE photometry for the full SDSS spectroscopic galaxy sample, creating spectral energy distributions ( SEDs ) that cover λ = 0.4 – 22 μ m for an unprecedentedly large and comprehensive sample of 858,365 present-epoch galaxies. Using MAGPHYS, we then simultaneously and consistently model both the attenuated stellar SED and the dust emission at 12 and 22 μ m, producing robust new calibrations for monochromatic mid-IR star formation rate ( SFR ) proxies. These modeling results provide the fi rst mid-IR-based view of the bimodality in star formation activity among galaxies, exhibiting the sequence of star- forming galaxies ( “ main sequence ” ) with a slope of = d dM log SFR log * 0.80 and a scatter of 0.39 dex. We fi nd that these new SFRs along the SF main sequence are systematically lower by a factor of 1.4 than those derived from optical spectroscopy. We show that for most present-day galaxies, the 0.4 – 22 μ m SED fi ts can exquisitely predict the fl uxes measured by Herschel at much longer wavelengths. Our analysis also illustrates that the majority of stars in the present-day universe are formed in luminous galaxies ( ~ L * ) in and around the “ green valley ” of the color – luminosity plane. We make publicly available the matched photometry catalog and SED modeling results