Infrared-Faint Radio Sources (IFRSs) are an important class of high-redshift active galaxy, and potentially important as a means of discovering more high-redshift radio sources, but only 25 IFRSs had redshifts prior to this paper. Here we increase the number of IFRSs with known spectroscopic redshifts by a factor of about 5 to 131, with redshifts up to z=4.387, and a median redshift of z = 2.68. The IFRS redshift distribution overlaps with the high-z radio galaxy (HzRG) redshift distribution but is significantly narrower, suggesting that the IFRSs are a subset of the larger class of HzRGs. We also confirm and measure the proposed correlation between redshift and 3.6 μm flux density, making it possible to use this correlation to find even higher redshift radio sources. Many more high-redshift sources are probably present in existing radio survey catalogues.
@article{arxiv.1811.11957,
title = {The Redshift Distribution of Infrared-Faint Radio Sources},
author = {Brendan J. Orenstein and Jordan D. Collier and Ray P. Norris},
journal= {arXiv preprint arXiv:1811.11957},
year = {2018}
}