Skip to main content

Research Repository

Advanced Search

SMBH accretion properties of radio-selected AGN out to z ∼ 4

Delvecchio, I; Smolčić, V; Zamorani, G; Rosario, DJ; Bondi, M; Marchesi, S; Miyaji, T; Novak, M; Sargent, MT; Alexander, DM; Delhaize, J

SMBH accretion properties of radio-selected AGN out to z ∼ 4 Thumbnail


I Delvecchio

V Smolčić

G Zamorani

DJ Rosario

M Bondi

S Marchesi

T Miyaji

M Novak

MT Sargent

J Delhaize


Exploring how radio-emitting active galactic nuclei (AGNs) behave and evolve with time is critical for understanding how AGN feedback impacts galaxy evolution. In this work, we investigate the relationship between 1.4 GHz radio continuum AGN luminosity (⁠LAGN1.4⁠), specific black hole accretion rate (s-BHAR, defined as the accretion luminosity relative to the galaxy stellar mass), and redshift, for a luminosity-complete sample of radio-selected AGNs in the VLA COSMOS 3 GHz Large Project. The sample was originally selected from radio-continuum observations at 3 GHz, and includes about 1800 radio AGNs identified via (>2 σ) radio-excess relative to the infrared-radio correlation of star-forming galaxies. We further select a subsample of over 1200 radio AGNs that is complete in LAGN1.4 over different redshift ranges, out to z ∼ 4, and use X-ray stacking to calculate the average s-BHAR in each LAGN1.4–z bin. We find that the average s-BHAR is independent of LAGN1.4⁠, at all redshifts. However, we see a strong increase of s-BHAR with redshift, at fixed LAGN1.4⁠. This trend resembles the strong increase in the fraction of star-forming host galaxies [based on the (NUV − r)/(r − J) colours] with redshift, at fixed LAGN1.4⁠. A possible explanation for this similarity might imply a link between average AGN radiative power and availability of cold gas supply within the host galaxy. This study corroborates the idea that radio-selected AGNs become more radiatively efficient towards earlier epochs, independently of their radio power.

Journal Article Type Article
Acceptance Date Sep 14, 2018
Online Publication Date Sep 24, 2018
Publication Date Sep 24, 2018
Deposit Date Jan 17, 2019
Publicly Available Date Jan 17, 2019
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 481
Issue 4
Pages 4971-4983
Public URL


Published Journal Article (1.4 Mb)

Copyright Statement
© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.

You might also like

Downloadable Citations