Cosmic evolution of star-forming galaxies to z 1.8 in the faint low-frequency radio source population

Abstract

We study the properties of star-forming galaxies selected at 610 MHz with the GMRT in a survey covering ∼1.86 deg2 down to a noise of ∼7.1 μJy beam−1. These were identified by combining multiple classification diagnostics: optical, X-ray, infrared, and radio data. Of the 1685 SFGs from the GMRT sample, 496 have spectroscopic redshifts whereas 1189 have photometric redshifts. We find that the IRRC of star-forming galaxies, quantified by the infrared-to-1.4 GHz radio luminosity ratio qIR⁠, decreases with increasing redshift: qIR=2.86±0.04(1+z)−0.20±0.02 out to z ∼ 1.8. We use the V/Vmax statistic to quantify the evolution of the comoving space density of the SFG sample. Averaged over luminosity our results indicate ⟨V/Vmax⟩ to be 0.51±0.06⁠, which is consistent with no evolution in overall space density. However, we find V/Vmax to be a function of radio luminosity, indicating strong luminosity evolution with redshift.