The global star formation rate from the 1.4 GHz luminosity function

The decimetric luminosity of many galaxies appears to be dominated by synchrotron emission excited by supernova explosions. Simple models suggest that the luminosity is directly proportional to the rate of the supernova explosions of massive stars averaged over the past approximate to 3 x 10(7) yr. The proportionality may be used, together with models of the evolving 1.4 GHz luminosity function, to estimate the global star formation rate density in the era z less than or similar to 1. The local value is estimated to be 0.026 M(circle dot) yr(-1) Mpc(-3), twice the value inferred from the H alpha luminosity density. The value at z approximate to 1 is found to be 0.30 M(circle dot) yr(-1) Mpc(-3). The tenfold increase in the star formation rate density is consistent with the increase inferred from millimeter-wave, far-infrared, ultraviolet, and H alpha observations.