The imprint of AGN-driven outflows on the CGM: the case of Ly{\alpha} nebulae around high-z quasars

TL;DR

This study investigates the connection between AGN-driven outflows and Lyα nebulae around high-redshift quasars, providing observational evidence that outflows influence nebula size and brightness by facilitating photon escape.

Contribution

It offers the first observational support for the theory that AGN outflows shape Lyα nebulae by opening channels for photon escape, based on integral-field spectroscopy of six quasars.

Findings

Detected powerful outflows in all quasars with velocities >1500 km/s.

Found a strong correlation between outflow power and nebula size and luminosity.

Observed spatial alignment between ionization cones and Lyα nebula regions.

Abstract

Some cosmological hydrodynamical simulations predict that outflows driven by active galactic nuclei (AGN) play a key role in powering the Ly$\alpha$ 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 Ly$\alpha$ 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 Ly$\alpha$ 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 $z\sim2-3$, using the [O III] emission line. We detect powerful outflows in all the quasars of our sample, with velocities $>1500~\mathrm{km~s^{-1}}$ and kinetic energies $ \gtrsim 2\times10^{43}~\mathrm{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 Ly$\alpha$ nebulae size ($\rho=0.89$, $p=0.03$) and luminosity ($\rho=0.6$, $p=0.28$). Additionally, we find evidence of spatial alignment between the ionization cone and the inner and brightest regions of the Ly$\alpha$ 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 Ly$\alpha$ photons to reach the CGM and create extended nebulae.