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The VLA-cosmos perspective on the infrared-radio relation. I. New constraints on selection biases and the non-evolution of the infrared/radio properties of star-forming and active galactic nucleus galaxies at intermediate and high redshift

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posted on 2023-06-08, 15:41 authored by Mark Sargent, et al
VLA 1.4 GHz (s~0.012 mJy) and MIPS 24 and 70 µm (s~0.02 and 1.7 mJy, respectively) observations covering the 2 sqdeg COSMOS field are combined with an extensive multiwavelength data set to study the evolution of the infrared (IR)-radio relation at intermediate and high redshift. With ~4500 sources—of which ~30% have spectroscopic redshifts—the current sample is significantly larger than previous ones used for the same purpose. Both monochromatic IR/radio flux ratios (q24 and q70), as well as the ratio of the total IR and the 1.4 GHz luminosity (qTIR), are used as indicators for the IR/radio properties of star-forming galaxies and active galactic nuclei (AGNs). Using a sample jointly selected at IR and radio wavelengths in order to reduce selection biases, we provide firm support for previous findings that the IR-radio relation remains unchanged out to at least z~1.4. Moreover, based on data from ~150 objects we also find that the local relation likely still holds at zin [2.5, 5]. At redshift z<1.4, we observe that radio-quiet AGNs populate the locus of the IR-radio relation in similar numbers as star-forming sources. In our analysis, we employ the methods of survival analysis in order to ensure a statistically sound treatment of flux limits arising from non-detections. We determine the observed shift in average IR/radio properties of IR- and radio-selected populations and show that it can reconcile apparently discrepant measurements presented in the literature. Finally, we also investigate variations of the IR/radio ratio with IR and radio luminosity and find that it hardly varies with IR luminosity but is a decreasing function of radio luminosity.

History

Publication status

  • Published

File Version

  • Accepted version

Journal

Astrophysical Journal Supplement Series

ISSN

0067-0049

Publisher

American Astronomical Society

Issue

2

Volume

186

Page range

341-377

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2013-09-12

First Open Access (FOA) Date

2013-09-12

First Compliant Deposit (FCD) Date

2013-09-12

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