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