GALEX-SDSS-WISE Legacy Catalog (GSWLC): Star Formation Rates, Stellar
  Masses and Dust Attenuations of 700,000 Low-redshift Galaxies
  In this paper, we present GALEX-SDSS-WISE Legacy Catalog (GSWLC), a catalog
of physical properties (stellar masses, dust attenuations and star formation
rates (SFRs)) of ~700,000 galaxies with SDSS redshifts below 0.3. GSWLC
contains galaxies within the GALEX footprint, regardless of a UV detection,
covering 90% of SDSS. The physical properties were obtained from UV/optical SED
fitting following Bayesian methodology of Salim et al. (2007), with
improvements such as blending corrections for low-resolution UV photometry,
flexible dust attenuation laws, and emission line corrections. GSWLC includes
mid-IR SFRs derived from IR templates based upon 22 micron WISE observations.
These estimates are independent of UV/optical SED fitting, in order to separate
possible systematics. The paper argues that the comparison of specific SFRs
(SSFRs) is more informative and physically motivated than the comparison of
SFRs. SSFRs resulting from the UV/optical SED fitting are compared to the
mid-IR SSFRs, and to SSFRs from three published catalogs. For "main sequence"
galaxies with no AGN contribution all SSFRs are in very good agreement (within
0.1 dex on average). In particular, the widely-used aperture-corrected SFRs
from MPA/JHU catalog show no systematic offsets, in contrast to some
integral-field spectroscopy results. For galaxies below the main sequence (log
SSFR<-11), mid-IR (S)SFRs based on fixed luminosity-SFR conversion are severely
biased (up to 2 dex) because the dust is primarily heated by old stars.
Furthermore, mid-IR (S)SFRs are overestimated by up to 0.6 dex for galaxies
with AGN, presumably due to non-stellar dust heating. UV/optical (S)SFRs are
thus preferred to IR-based (S)SFRs for quenched galaxies and those which host
AGN.
