The local star formation rate and radio luminosity density

We present a new determination of the local volume-averaged star formation rate from the 1.4 GHz luminosity function of star forming galaxies. Our sample, taken from the B<=12 Revised Shapley-Ames catalogue has around 100% complete radio detections and is insensitive to dust obscuration and cirrus contamination. After removal of known active galaxies, the best-fit Schechter function has a faint-end slope of -1.27+/-0.07 in agreement with the local Halpha luminosity function, characteristic luminosity L*=(2.6+/-0.7)*10^{22} W/Hz and density phi*=(4.8+/-1.1)*10^{-4} Mpc^{-3}. The inferred local radio luminosity density of (1.72+/-0.37)*10^{19} W/Hz/Mpc^3 implies a volume averaged star formation rate around 2-3x larger than the Gallego et al. Halpha estimate, i.e. rho(1.4 GHz)=(2.26+/-0.48)*10^{-2} Msun/yr/Mpc^3 for a Salpeter initial mass function from 0.1-125 Msun and Hubble constant of 50 km/s/Mpc. We conclude that unlike mid-IR, far-IR and radio estimates, the de-reddened UV and Halpha estimates of star formation rates are significant underestimates. This adds further evidence that claims of a redshift cut-off in the comoving star formation density are premature