A new discovery space opened by eROSITA

Ionised AGN outflows from X-ray selected samples

¹ Dipartimento di Fisica e Astronomia “Augusto Righi”, Alma Mater Studiorum – Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
e-mail: blessing.musiimenta2@unibo.it
² INAF-Osservatorio di Astrofisica e Scienza dello Spazio, Via Gobetti 93/3, 40129 Bologna, Italy
³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching bei München, Germany
⁴ Institute for Astronomy and Astrophysics, National Observatory of Athens, V. Paulou and I. Metaxa, Athens 11532, Greece
⁵ Leibniz-Institut fũr Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁶ Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502, Japan
⁷ Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU, No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan
⁸ Research Center for Space and Cosmic Evolution, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
⁹ Graduate School of Science and Engineering, Ehime University, 2-5 Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
¹⁰ SISSA, Via Bonomea 265, 34136 Trieste, Italy
¹¹ Instituto de Astrofísica de Canarias, Calle Vía Láctea, s/n, 38205 La Laguna, Tenerife, Spain
¹² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹³ Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
¹⁴ School of Physics and Astronomy, University of Southampton, Highfield SO17 1BJ, UK
¹⁵ Kavli Institute for the Physics and Mathematics of the Universe, The University of Tokyo (Kavli IPMU, WPI), Kashiwa, 277-8583 Tokyo, Japan
¹⁶ School of Astronomy and Space Science, University of Science and Technology of China, Hefei 230026, PR China
¹⁷ Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
¹⁸ Center for AstroPhysical Surveys, National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
¹⁹ National Center for Supercomputing Applications, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA

Received: 25 November 2022
Accepted: 11 September 2023

Abstract

Context. In the context of an evolutionary model, the outflow phase of an active galactic nucleus (AGN) occurs at the peak of its activity, once the central supermassive black hole (SMBH) is massive enough to generate sufficient power to counterbalance the potential well of the host galaxy. This outflow feedback phase plays a vital role in galaxy evolution.

Aims. Our aim in this paper is to apply various selection methods to isolate powerful AGNs in the feedback phase, trace and characterise outflows in these AGNs, and explore the link between AGN luminosity and outflow properties.

Methods. We applied a combination of methods to the Spectrum Roentgen Gamma (SRG) eROSITA Final Equatorial Depth survey (eFEDS) catalogue and isolated ∼1400 candidates at z > 0.5 out of ∼11 750 AGNs (∼12%). Furthermore, we narrowed down our selection to 427 sources that have 0.5 < z < 1. We tested the robustness of our selection on the small subsample of 50 sources with available good quality SDSS spectra at 0.5 < z < 1 and, for which we fitted the [OIII] emission line complex and searched for the presence of ionised gas outflow signatures.

Results. Out of the 50 good quality SDSS spectra, we identified 23 quasars (∼45%) with evidence of ionised outflows based on the presence of significant broad and/or shifted components in [OIII]λ5007 Å. They are on average more luminous (log L_bol ∼ 45.2 erg s⁻¹) and more obscured (N_H ∼ 10²² cm⁻²) than the parent sample of ∼427 candidates, although this may be ascribed to selection effects affecting the good quality SDSS spectra sample. By adding 118 quasars at 0.5 < z < 3.5 with evidence of outflows reported in the literature, we find a weak correlation between the maximum outflow velocity and the AGN bolometric luminosity. On the contrary, we recovered strong correlations between the mass outflow rate and outflow kinetic power with the AGN bolometric luminosity.

Conclusions. About 30% of our sample have kinetic coupling efficiencies, Ė/L_bol > 1%, suggesting that the outflows could have a significant effect on their host galaxies. We find that the majority of the outflows have momentum flux ratios lower than 20 which rules out an energy-conserving nature. Our present work points to the unequivocal existence of a rather short AGN outflow phase, paving the way towards a new avenue to dissect AGN outflows in large samples within eROSITA and beyond.