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 \leq 12 Revised Shapley-Ames catalogue ( 231 normal spiral galaxies over effective area 7.1 sr ) has \simeq 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 \pm 0.07 in agreement with the local H \alpha luminosity function , characteristic luminosity L _ { * } = ( 2.6 \pm 0.7 ) \times 10 ^ { 22 } W Hz ^ { -1 } and density \phi _ { * } = ( 4.8 \pm 1.1 ) \times 10 ^ { -4 } Mpc ^ { -3 } .
The inferred local radio luminosity density of ( 1.73 \pm 0.37 \pm 0.03 ) \times 10 ^ { 19 } W Hz ^ { -1 } Mpc ^ { -3 } ( Poisson noise , large scale structure fluctuations ) implies a volume averaged star formation rate \sim 2 \times larger than the Gallego et al .
H \alpha estimate , i.e . \rho _ { 1.4 { GHz } } = ( 2.10 \pm 0.45 \pm 0.04 ) \times 10 ^ { -2 } M _ { \odot } yr ^ { -1 } Mpc ^ { -3 } for a Salpeter initial mass function from 0.1 - 125 M _ { \odot } and Hubble constant of 50 km s ^ { -1 } Mpc ^ { -1 } .
We demonstrate that the Balmer decrement is a highly unreliable extinction estimator , and argue that optical-UV SFRs are easily underestimated , particularly at high redshift .