Faint radio sources and star formation history

The centimeter-wave luminosity of local radio galaxies correlates well with their star formation rate. We extend this correlation to surveys of high-r edshift radio sources to estimate the global star formation history. The st ar formation rate found from radio observations needs no correction for dus t obscuration, unlike the values calculated from optical and ultraviolet da ta. Three deep radio surveys have provided catalogs of sources with nearly complete optical identifications and nearly 60% complete spectroscopic reds hifts: the Hubble Deep Field and Flanking Fields at 12(h) + 62 degrees, the SSA13 field at 13(h) + 42 degrees, and the V15 field at 14(h) + 52 degrees . We use the redshift distribution of these radio sources to constrain the evolution of their luminosity function. The epoch-dependent luminosity func tion is then used to estimate the evolving global star formation density. A t redshifts less than 1, our calculated star formation rates are significan tly larger than even the dust-corrected optically selected star formation r ates; however, we confirm the rapid rise from z = 0 to z = 1 seen in those surveys.