  The relationship between the clustering of dark matter and that of luminous
matter is often described using the bias parameter. Here, we provide a new
method to probe the bias of intermediate to high-redshift radio continuum
sources for which no redshift information is available. We matched radio
sources from the Faint Images of the Radio Sky at Twenty centimetres (FIRST)
survey data to their optical counterparts in the Sloan Digital Sky Survey
(SDSS) to obtain photometric redshifts for the matched radio sources. We then
use the publicly available semi-empirical simulation of extragalactic radio
continuum sources (S3) to infer the redshift distribution for all FIRST sources
and estimate the redshift distribution of unmatched sources by subtracting the
matched distribution from the distribution of all sources. We infer that the
majority of unmatched sources are at higher redshifts than the optically
matched sources and demonstrate how the angular scales of the angular two-point
correlation function can be used to probe different redshift ranges. We compare
the angular clustering of radio sources with that expected for dark matter and
estimate the bias of different samples.
