Published in

Oxford University Press (OUP), Monthly Notices of the Royal Astronomical Society, 4(491), p. 5911-5924, 2019

DOI: 10.1093/mnras/stz3401

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

This paper was not found in any repository, but could be made available legally by the author.
This paper was not found in any repository, but could be made available legally by the author.

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Data provided by SHERPA/RoMEO

Abstract

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 $\rm {\mathit{ q}_{IR}}$, decreases with increasing redshift: $\rm {\mathit{ q}_{IR}\, =\, 2.86± 0.04(1\, +\, \mathit{ z})^{-0.20± 0.02}}$ out to z ∼ 1.8. We use the $\rm {\mathit{ V}/\mathit{ V}_{max}}$ statistic to quantify the evolution of the comoving space density of the SFG sample. Averaged over luminosity our results indicate $\rm {〈 \mathit{ V}/\mathit{ V}_{max} 〉 }$ to be $\rm {0.51\, ± \, 0.06}$, which is consistent with no evolution in overall space density. However, we find $\rm \mathit{ V}/\mathit{ V}_{max}$ to be a function of radio luminosity, indicating strong luminosity evolution with redshift. We explore the evolution of the SFGs radio luminosity function by separating the source into five redshift bins and comparing to theoretical model predictions. We find a strong redshift trend that can be fitted with a pure luminosity evolution of the form $\rm {\mathit{ L}_{610\, MHz}\, ∝ \, (\, 1+\, \mathit{ z})^{(2.95± 0.19)-(0.50± 0.15)z}}$. We calculate the cosmic SFR density since $\rm {\mathit{ z} ∼ 1.5}$ by integrating the parametric fits of the evolved 610 MHz luminosity function. Our sample reproduces the expected steep decline in the star formation rate density since $\rm {\mathit{ z}\, ∼ \, 1}$.

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