The Type II AGN-host galaxy connection

Insights from the VVDS and VIPERS surveys

¹ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Milano, Via A. Corti 12, 20133 Milano, Italy
e-mail: giustina.vietri@inaf.it
² OmegaLambdaTec GmbH, Lichtenbergstraße 8, 85748 Garching, Germany
³ National Centre for Nuclear Research, ul. Hoza 69, 00-681 Warsaw, Poland
⁴ Aix Marseille Univ., CNRS, CNES, LAM Marseille, France
⁵ Institute for Computational Cosmology (ICC), Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁶ Centre for Extragalactic Astronomy (CEA), Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁷ Institute for Data Science (IDAS), Durham University, South Road, Durham DH1 3LE, UK
⁸ Astronomical Observatory of the Jagiellonian University, ul. Orla 171, 30-244 Kraków, Poland
⁹ Institut de Física d’Altes Energies (IFAE), The Barcelona Institute of Science and Technology, 08193 Bellaterra (Barcelona), Spain
¹⁰ National Centre for Nuclear Research, ul. Pasteura 7, 02-093 Warsaw, Poland
¹¹ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica Bologna, Via Gobetti 101, 40129 Bologna, Italy
¹² INAF – Istituto di Radioastronomia, Via Gobetti 101, 40129 Bologna, Italy

Received: 13 April 2021
Accepted: 4 November 2021

Abstract

We present a study of optically selected Type II active galactic nuclei (AGN) at 0.5 < z < 0.9 from the VIPERS and VVDS surveys, to investigate the connection between AGN activity and the physical properties of their host galaxies. The host stellar mass is estimated through spectral energy distribution fitting with the CIGALE code, and star formation rates are derived from the [OII]λ3727 Å line luminosity. We find that 49% of the AGN host galaxies are on or above the main sequence (MS), 40% lie in the sub-MS locus, and 11% in the quiescent locus. Using the [OIII]λ5007 Å line luminosity as a proxy of the AGN power, we find that at fixed AGN power Type II AGN host galaxies show a bimodal behaviour: systems with host galaxy stellar mass < 10¹⁰ M_⊙ reside along the MS or in the starbursts locus (high-SF Type II AGN), while systems residing in massive host galaxies (> 10¹⁰ M_⊙) show a lower level of star formation (low-SF Type II AGN). At all stellar masses the offset from the MS is positively correlated with the AGN power. We interpret this correlation as evidence of co-evolution between the AGN and the host, possibly due to the availability of cold gas. In the most powerful AGN with host galaxies below the MS we find a hint, though weak, of asymmetry in the [OIII] line profile, likely due to outflowing gas, consistent with a scenario in which AGN feedback removes the available gas and halts the star formation in the most massive hosts.