The Star Formation Reference Survey III: A Multi-wavelength View of Star
  Formation in Nearby Galaxies
  We present multi-wavelength global star formation rate (SFR) estimates for
326 galaxies from the Star Formation Reference Survey (SFRS) in order to
determine the mutual scatter and range of validity of different indicators. The
widely used empirical SFR recipes based on 1.4 GHz continuum, 8.0 $\mu$m
polycyclic aromatic hydrocarbons (PAH), and a combination of far-infrared (FIR)
plus ultraviolet (UV) emission are mutually consistent with scatter of
$\raise{-0.8ex}\stackrel{\textstyle <}{\sim }$0.3 dex. The scatter is even
smaller, $\raise{-0.8ex}\stackrel{\textstyle <}{\sim }$0.24 dex, in the
intermediate luminosity range 9.3<log(L(60 $\mu$m/L$_\odot$)<10.7. The data
prefer a non-linear relation between 1.4 GHz luminosity and other SFR measures.
PAH luminosity underestimates SFR for galaxies with strong UV emission. A
bolometric extinction correction to far-ultraviolet luminosity yields SFR
within 0.2 dex of the total SFR estimate, but extinction corrections based on
UV spectral slope or nuclear Balmer decrement give SFRs that may differ from
the total SFR by up to 2 dex. However, for the minority of galaxies with UV
luminosity ${>}5\times10^9$ L$_{\odot}$ or with implied far-UV extinction <1
mag, the UV spectral slope gives extinction corrections with 0.22~dex
uncertainty.
