The Likelihood Ratio as a tool for Radio Continuum Surveys with SKA
  precursor telescopes
  In this paper we investigate the performance of the likelihood ratio method
as a tool for identifying optical and infrared counterparts to proposed radio
continuum surveys with SKA precursor and pathfinder telescopes. We present a
comparison of the infrared counterparts identified by the likelihood ratio in
the VISTA Deep Extragalactic Observations (VIDEO) survey to radio observations
with 6, 10 and 15 arcsec resolution. We cross-match a deep radio catalogue
consisting of radio sources with peak flux density $>$ 60 $\mu$Jy with deep
near-infrared data limited to $K_{\mathrm{s}}\lesssim$ 22.6. Comparing the
infrared counterparts from this procedure to those obtained when cross-matching
a set of simulated lower resolution radio catalogues indicates that degrading
the resolution from 6 arcsec to 10 and 15 arcsec decreases the completeness of
the cross-matched catalogue by approximately 3 and 7 percent respectively. When
matching against shallower infrared data, comparable to that achieved by the
VISTA Hemisphere Survey, the fraction of radio sources with reliably identified
counterparts drops from $\sim$89%, at $K_{\mathrm{s}}\lesssim$22.6, to 47% with
$K_{\mathrm{s}}\lesssim$20.0. Decreasing the resolution at this shallower
infrared limit does not result in any further decrease in the completeness
produced by the likelihood ratio matching procedure. However, we note that
radio continuum surveys with the MeerKAT and eventually the SKA, will require
long baselines in order to ensure that the resulting maps are not limited by
instrumental confusion noise.
