paper

Deep uGMRT observations of the ELAIS-North 1 field: statistical properties of radio--infrared relations up to 2

arXiv:2111.08336 · doi:10.1093/mnras/stac1504

Abstract

Comprehending the radio--infrared (IR) relations of the faint extragalactic radio sources is important for using radio emission as a tracer of star-formation in high redshift () star-forming galaxies (SFGs). Using deep uGMRT observations of the ELAIS-N1 field in the 0.3--0.5\,GHz range, we study the statistical properties of the radio--IR relations and the variation of the `-parameter' up to after broadly classifying the faint sources as SFGs and AGN. We find the dust temperature ($\tdust$) to increase with . This gives rise to $\qmir$, measured at $24\,\upmu$m, to increase with as the peak of IR emission shifts towards shorter wavelengths, resulting in the largest scatter among different measures of -parameters. $\qfir$ measured at $70\,\upmu$m, and using total-IR (TIR) emission are largely unaffected by $\tdust$. We observe strong, non-linear correlations between the radio luminosities at 0.4 and 1.4\,GHz with $70\,\upmu$m luminosity and TIR luminosity($\ltir$). To assess the possible role of the radio-continuum spectrum in making the relations non-linear, for the first time we study them at high using integrated radio luminosity ($\lrc$) in the range 0.1--2\,GHz. In SFGs, the $\lrc$--$\ltir$ relation remains non-linear with a slope of , has a factor of 2 lower scatter compared to monochromatic radio luminosities, and $\qtirbol$ decreases with as $\qtirbol = (2.27 \pm 0.03)\,(1+z)^{-0.12 \pm 0.03}$. A redshift variation of is a natural consequence of non-linearity. We suggest that a redshift evolution of magnetic field strengths and/or cosmic ray acceleration efficiency in high- SFGs could give rise to non-linear radio--IR relations.

arXiv commentAccepted for publication in MNRAS (20 pages, 20 Figures and one Appendix)

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