Radio Identification of Sub-mm Sources in the Hubble Deep Field

Determination of the epoch dependent star-formation rate of field galaxies is one of the principal goals of modern observational cosmology. Recently, Hughes et al. (1998) using the SCUBA instrument on the James Clerk Maxwell Telescope, report 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 obervations of the Hubble Deep Field, we suggest alternate identifications to the sub-mm detections. These identifications argue for a substantially lower redshift to the sub-mm population with a consequential lowering of the z > 2 sub-mm/far infrared luminosity density and global star-formation rate.

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The SCUBA positions are given after translation to the VLA coordinate frame. 2 The most probable optical identi cation of the radio source in the HDF catalog Williams et al. 1996) based on positional coincidece. 3 The integrated ux density corrected for the attenuation of the VLA primary beam. In a few places upperlimits are given. 4 The integrated I magnitude of the identi cation as taken from the HDF catalog Cohen et al. 1996). We have transformed to the AB system using the convention (HDF magnitude { AB) = 0.8. 5 The spectroscopic redshift Lowenthal et al. 1996 Fernandez-Soto et al. 1997) of the identi cation. Values within parentheses are photometric estimates of the redshift

Williams