Photometric redshifts for the next generation of deep radio continuum
  surveys - I: Template fitting
  We present a study of photometric redshift performance for galaxies and
active galactic nuclei detected in deep radio continuum surveys. Using two
multi-wavelength datasets, over the NOAO Deep Wide Field Survey Bo\"otes and
COSMOS fields, we assess photometric redshift (photo-z) performance for a
sample of $\sim 4,500$ radio continuum sources with spectroscopic redshifts
relative to those of $\sim 63,000$ non radio-detected sources in the same
fields. We investigate the performance of three photometric redshift template
sets as a function of redshift, radio luminosity and infrared/X-ray properties.
We find that no single template library is able to provide the best performance
across all subsets of the radio detected population, with variation in the
optimum template set both between subsets and between fields. Through a
hierarchical Bayesian combination of the photo-z estimates from all three
template sets, we are able to produce a consensus photo-z estimate which equals
or improves upon the performance of any individual template set.
