Multi-phase investigation of outflows in the circumgalactic and interstellar media of luminous quasars at z ∼ 5

¹ Department of Physics, Astronomy Section, University of Trieste, Via G.B. Tiepolo, 11, I-34143 Trieste, Italy
² INAF – Osservatorio Astronomico di Trieste, Via G. B. Tiepolo 11, I-34143 Trieste, Italy
³ IFPU – Institute for Fundamental Physics of the Universe, Via Beirut 2, I-34014 Trieste, Italy
⁴ Scuola Normale Superiore, P.zza dei Cavalieri, I-56126 Pisa, Italy
⁵ Department of Physics & Astronomy, University of California, Riverside, CA 92512, USA
⁶ Faculty of Mathematics and Physics, University of Ljubljana, 19 Jadranska ulica, Ljubljana 1000, Slovenia

^⋆ Corresponding author: matilde.brazzini@phd.units.it; matilde.brazzini@inaf.it

Received: 3 February 2025
Accepted: 14 April 2025

Abstract

Aims. Outflows from active galactic nuclei are invoked as the principal feedback process regulating the co-evolution of supermassive black holes and their host galaxies. Because of their multi-phase and multi-scale nature, an exhaustive description of these winds should exploit multiple tracers. However, connecting various outflow features remains a challenge. The aim of this work is to provide a complete characterisation of outflows in a sample of z ∼ 5 quasars, by exploiting the combination of different emission and absorption tracers.

Methods. We analysed the UV/optical and FIR continuum, line emission, and absorption in a sample of 39 z ∼ 5 quasars observed with VLT/X-Shooter and ALMA (available for six objects). We identified broad and narrow absorption lines associated with the quasar and emission lines to determine black hole masses and bolometric luminosities.

Results. Our sample encompasses massive (M_BH,Mg II = 10^8.5−10 M_⊙) and luminous (L_bol = 10^{46.9 − 48} erg/s) quasars at redshift 5 − 5.7. They display powerful ionised outflows detected in both emission and absorption, with velocities exceeding 48 000 km s⁻¹ in some cases, and lie above the local black hole – host galaxy mass relation, exhibiting a behaviour similar to that of z ≳ 6 quasars. These findings suggest a phase of efficient black hole feedback occurring at redshift z ≳ 6 and likely persisting down to z ∼ 5, characterised by rapid black hole growth exceeding that of the host galaxy. The fraction of quasars with outflow detections in absorption is higher for larger C IV-Mg II velocity shifts, suggesting that while the physical mechanisms powering the two outflow phenomena detected in emission and absorption may differ, a correlation exists between them.