The infrared–radio correlation of spheroid- and disc-dominated star-forming galaxies to z ∼ 1.5 in the COSMOS field

Molinár, Dániel Cs. and Sargent, Mark T. and Delhaize, Jacinta and Delvecchio, Ivan and Smolčić, Vernesa and Novak, Mladen and Schinnerer, Eva and Zamorani, Giovanni and Bondi, Marco and Herrera-Ruiz, Noelia and Murphy, Eric J. and Vardoulaki, Eleni and Karim, Alexander and Leslie, Sarah and Magnelli, Benjamin and Carollo, C. Marcella and Middleberg, Enno (2018) The infrared–radio correlation of spheroid- and disc-dominated star-forming galaxies to z ∼ 1.5 in the COSMOS field. Monthly Notices of the Royal Astronomical Society, 475. pp. 827-838. ISSN 0035-8711

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Using infrared data from the Herschel Space Observatory and Karl G. Jansky Very Large Array 3 GHz observations in the COSMOS field, we investigate the redshift evolution of the infrared–radio correlation (IRRC) for star-forming galaxies (SFGs) we classify as either spheroid- or disc-dominated based on their morphology. The sample predominantly consists of disc galaxies with stellar mass ≳ 10^10M_⊙, and residing on the star-forming main sequence (MS). After the removal of AGN using standard approaches, we observe a significant difference between the redshift evolution of the median IR/radio ratio q¯¯_TIR of (i) a sample of ellipticals, plus discs with a substantial bulge component (‘spheroid-dominated’ SFGs) and, (ii) virtually pure discs and irregular systems (‘disc-dominated’ SFGs). The spheroid-dominated population follows a declining q_TIR versus z trend similar to that measured in recent evolutionary studies of the IRRC. However, for disc-dominated galaxies, where radio and IR emission should be linked to star formation in the most straightforward way, we measure very little change in q¯¯_TIR. This suggests that low-redshift calibrations of radio emission as a star formation rate (SFR) tracer may remain valid out to at least z ≃ 1–1.5 for pure star-forming systems. We find that the different redshift evolution of q¯¯_TIR for the spheroid- and disc-dominated sample is mainly due to an increasing radio excess for spheroid-dominated galaxies at z≳ 0.8, hinting at some residual AGN activity in these systems. This finding demonstrates that in the absence of AGN, the IRRC is independent of redshift, and that radio observations can therefore be used to estimate SFRs at all redshifts for genuinely star-forming galaxies.

Item Type: Article
Keywords: galaxies: evolution; infrared: galaxies; radio continuum: galaxies
Date: 2018
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2017 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2017 December 10. Received 2017 November 17; in original form 2017 June 26; published 14 December 2017
Divisions: Faculty of Science > Department of Physics
Publisher: Oxford University Press
Depositing User: Vernesa Smolčić
Date Deposited: 03 May 2019 13:11
Last Modified: 13 Jul 2019 17:54

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