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

Journal
Date Issued
2018
Author(s)
•
Smolčić, V.
•
Zamorani, G.
•
Rosario, D. J.
•
•
•
Miyaji, T.
•
Novak, M.
•
Sargent, M. T.
•
Alexander, D. M.
•
Delhaize, J.
DOI
Description
The authors are grateful to the anonymous referee for his/her constructive comments that improved the content of this manuscript. ID is grateful to Fabio La Franca and Giorgio Lanzuisi for useful discussions. ID, VS, MN, and JD acknowledge the European Union’s Seventh Framework programme under grant agreement 337595 (ERC Starting Grant, ‘CoSMass’). TM and CSTACK are supported by UNAM DGAPA PAPIIT IN104216 and CONACyT 252531. DR and DMA acknowledge the support of the Science and Technology Facilities Council (STFC) through grant ST/P000541/1.
Abstract
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 (L^AGN_1.4), 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 L^AGN_1.4 over different redshift ranges, out to z ∼ 4, and use X-ray stacking to calculate the average s-BHAR in each L^AGN_1.4-z bin. We find that the average s-BHAR is independent of L^AGN_1.4, at all redshifts. However, we see a strong increase of s-BHAR with redshift, at fixed L^AGN_1.4. 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 L^AGN_1.4. 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.
Volume
481
Issue
4
Start page
4971
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2018MNRAS.481.4971D
Rights
open.access
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