The Star Formation Reference Survey-V: the effect of extinction, stellar
  mass, metallicity, and nuclear activity on star-formation rates based on
  H$\alpha$ emission
  We present new H$\alpha$ photometry for the Star-Formation Reference Survey
(SFRS), a representative sample of star-forming galaxies in the local Universe.
Combining these data with the panchromatic coverage of the SFRS, we provide
calibrations of H$\alpha$-based star-formation rates (SFRs) with and without
correction for the contribution of [$\rm N_{^{II}}$] emission. We consider the
effect of extinction corrections based on the Balmer decrement, infrared excess
(IRX), and spectral energy distribution (SED) fits. We compare the SFR
estimates derived from SED fits, polycyclic aromatic hydrocarbons, hybrid
indicators such as 24 $\mu$m + H$\alpha$, 8 $\mu$m + H$\alpha$, FIR + FUV, and
H$\alpha$ emission for a sample of purely star-forming galaxies. We provide a
new calibration for 1.4 GHz-based SFRs by comparing to the H$\alpha$ emission,
and we measure a dependence of the radio-to-H$\alpha$ emission ratio based on
galaxy stellar mass. Active galactic nuclei introduce biases in the
calibrations of different SFR indicators but have only a minimal effect on the
inferred SFR densities from galaxy surveys. Finally, we quantify the
correlation between galaxy metallicity and extinction.
