The imprint of AGN-driven outflows on the Circumgalactic Medium: The case of Lyα nebulae around high-z quasars

¹ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
² Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße 1, 85748 Garching bei München, Germany
³ Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK
⁴ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching bei München, Germany
⁵ School of Mathematics, Statistics and Physics, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
⁶ International Gemini Observatory/NSF NOIRLab, 670 N A’ohoku Place, Hilo Hawai’i 96720, USA
⁷ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, I-40129 Bologna, Italy

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Received: 27 October 2025
Accepted: 3 February 2026

Abstract

Some cosmological hydrodynamical simulations predict that outflows driven by active galactic nuclei (AGN) play a key role in powering the Lyα nebulae observed around high-redshift quasars. In such simulations, AGN feedback seeded as powerful outflows leads to extended and luminous nebulae whose morphology and surface-brightness profiles accurately reproduce the observations, while suppressing AGN feedback leads to compact and faint nebulae. This link might arise from outflows opening up a channel for Lyα photons to escape from the galactic nucleus to the circumgalactic medium (CGM). The main aim of this paper is to test this theoretical prediction using observations, by comparing the physical properties of outflows and Lyα nebulae. We analyze integral-field unit data obtained with VLT/ERIS and GEMINI/GNIRS to trace the ionized gas in the interstellar medium (ISM) of a sample of six quasars at z ∼ 2 − 3, using the [O III] emission line. We detect powerful outflows in all the quasars of our sample, with velocities > 1500 km s⁻¹ and kinetic energies ≳2 × 10⁴³ erg s⁻¹. Four of our quasars are spatially resolved and show signs of extended [O III] emission out to distances > 2 kpc from the central supermassive black hole. When excluding one outlier, we find a positive monotonic correlation between the outflow power and the Lyα nebulae size (ρ = 0.89, p = 0.03) and luminosity (ρ = 0.6, p = 0.28). Additionally, we find evidence of spatial alignment between the ionization cone and the inner and brightest regions of the Lyα nebula. Our results provide tentative evidence in support of the theoretical prediction that AGN-driven outflows at ISM scales open a low-optical-depth path for central Lyα photons to reach the CGM and create extended nebulae.