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

Journal Article · 01 June 2022 · Monthly Notices of the Royal Astronomical Society

DOI: https://doi.org/10.1093/mnras/stac1504 · OSTI ID:1874508

Sinha, Akriti ; Basu, Aritra ; Datta, Abhirup; Chakraborty, Arnab

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 (z) 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 ‘q-parameter’ up to z = 2 after broadly classifying the faint sources as SFGs and AGN. We find the dust temperature (Tdust) to increase with z. This gives rise to $$q_{\rm 24\,\mu m}$$, measured at $$24\, \mu$$m, to increase with z as the peak of IR emission shifts towards shorter wavelengths, resulting in the largest scatter among different measures of q-parameters. $$q_{\rm 70\,\mu m}$$ measured at $$70\, \mu$$m, and qTIR 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 $$70\, \mu$$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 z 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 1.07 ± 0.02, has a factor of 2 lower scatter compared to monochromatic radio luminosities, and $$q^{\rm RC}_{\rm TIR}$$ decreases with z as $$q^{\rm RC}_{\rm TIR}= (2.27 \pm 0.03)\, (1+z)^{-0.12 \pm 0.03}$$. A redshift variation of q 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-z SFGs could give rise to non-linear radio–IR relations.

• Research Organization: US Department of Energy (USDOE), Washington, DC (United States). Office of Science, Sloan Digital Sky Survey (SDSS)
• Sponsoring Organization: Alfred P. Sloan Foundation; National Science Foundation (NSF); USDOE; USDOE Office of Science (SC)
• Contributing Organization: Brookhaven National Laboratory (BNL); Lawrence Berkeley National Laboratory (LBNL)
• OSTI ID: 1874508
• Journal Information: Monthly Notices of the Royal Astronomical Society, Journal Name: Monthly Notices of the Royal Astronomical Society Journal Issue: 3 Vol. 514; ISSN 0035-8711
• Publisher: Oxford University PressCopyright Statement
• Country of Publication: United Kingdom
• Language: English