Calibrating the Radio-Submillimetre Redshift Indicator

Many of the faint submm sources uncovered by deep SCUBA surveys still remain unidentified at most, if not all other wavelengths. The most successful method so far of obtaining accurate positions and hence allowing more secure identifications has been to use centimetre wavelength imaging with the VLA. This has led to a tempting approach for obtaining redshift estimates for this population (Carilli & Yun 1999,2000), which relies on the tight FIR–radio relationship and takes advantage of the steep spectral slope in the submm. In this paper we use the submm data from the SCUBA Local Universe Galaxy Survey (SLUGS) to estimate the usefulness of, and the uncertainties in, the radio–submm redshift estimator.