Radio identification of submillimeter sources in the Hubble Deep Field

Determination of the epoch-dependent star formation rate of field galaxies is one of the principal goals of observational cosmology. Recently, Hughes et al., using the Submillimeter Common-User Bolometer Array instrument on the James Clerk Maxwell Telescope, reported the detection of a new population of heavily dust enshrouded. star-forming galaxies at high redshifts (z > 2), dramatically altering the picture of galaxy evolution. However, we show that this interpretation must be treated with caution because of ambiguities in the identification of the host galaxies. Based on our deep, high-resolution 1.4 GHz observations of the Hubble Deep Field, we suggest alternate identifications to the submillimeter detections. These identifications argue for a lower redshift to the submillimeter population with a consequential lowering of the z > 2 submillimeter/far-infrared luminosity density and global star formation rate.