A super-linear ‘radio-AGN main sequence’ links mean radio-AGN power and galaxy stellar mass since z ∼ 3

¹ INAF – Osservatorio Astronomico di Brera, Via Brera 28, 20121, Milano, Italy and Via Bianchi 46, 23807 Merate, Italy
e-mail: ivan.delvecchio@inaf.it
² Université Paris-Saclay, Université Paris-Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
³ International Space Science Institute (ISSI), Hallerstrasse 6, 3012 Bern, Switzerland
⁴ Astronomy Centre, Department of Physics & Astronomy, University of Sussex, Brighton BN1 9QH, UK
⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK
⁶ School of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RJ, UK
⁷ Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
⁸ Department of Physics and Astronomy, Universitá degli Studi di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁹ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹⁰ INAF – Osservatorio Astronomico di Bologna, Via P. Gobetti 93/3, 40129 Bologna, Italy
¹¹ Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
¹² Cosmic Dawn Center (DAWN), Rådmandsgade 62, 2200 Copenhagen, Denmark
¹³ DTU-Space, Technical University of Denmark, Elektrovej 327, 2800 Kgs. Lyngby, Denmark
¹⁴ Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching, Germany
¹⁵ Independent researcher, formerly at Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
¹⁶ INAF – Istituto di Radioastronomia, Via P. Gobetti 101, 40129 Bologna, Italy
¹⁷ Department of Physics, University of Pretoria, Lynnwood Road, Hatfield, Pretoria 0083, South Africa
¹⁸ Jodrell Bank Centre for Astrophysics, University of Manchester, Oxford Road, Manchester M13 9PL, UK
¹⁹ National Institute for Theoretical and Computational Sciences (NITheCS), Matieland, Stellenbosch 7602, South Africa
²⁰ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 30131 Naples, Italy
²¹ Department of Physics, University of Zagreb, Bijenička cesta 32, 10002 Zagreb, Croatia

Received: 29 July 2022
Accepted: 26 September 2022

Abstract

Mapping the average active galactic nucleus (AGN) luminosity across galaxy populations and over time reveals important clues regarding the interplay between supermassive black hole and galaxy growth. This paper presents the demography, mean power, and cosmic evolution of radio AGN across star-forming galaxies (SFGs) of different stellar masses (ℳ_*). We exploit deep VLA-COSMOS 3 GHz data to build the rest-frame 1.4 GHz AGN luminosity functions at 0.1 ≤ z ≤ 4.5 hosted in SFGs. Splitting the AGN luminosity function into different ℳ_* bins reveals that, at all redshifts, radio AGN are both more frequent and more luminous in higher ℳ_* than in lower ℳ_* galaxies. The cumulative kinetic luminosity density exerted by radio AGN in SFGs peaks at z ∼ 2, and it is mostly driven by galaxies with 10.5 ≤ log(ℳ_*/ℳ_⊙) < 11. Averaging the cumulative radio AGN activity across all SFGs at each (ℳ_*,z) results in a ‘radio-AGN main sequence’ that links the time-averaged radio-AGN power ⟨L_1.4^AGN⟩ and galaxy stellar mass, in the form: log ⟨[L_1.4^AGN/ W Hz⁻¹]⟩ = (20.97 ± 0.16) + (2.51 ± 0.34)⋅ log(1+z) + (1.41 ± 0.09)⋅(log[ℳ_*/ℳ_⊙] – 10). The super-linear dependence on ℳ_*, at fixed redshift, suggests enhanced radio-AGN activity in more massive SFGs as compared to star formation. We ascribe this enhancement to both a higher radio AGN duty cycle and a brighter radio-AGN phase in more massive SFGs. A remarkably consistent ℳ_* dependence is seen for the evolving X-ray AGN population in SFGs. This similarity is interpreted as possibly driven by secular cold gas accretion fuelling both radio and X-ray AGN activity in a similar fashion over the galaxy’s lifetime.