MUSE Analysis of Gas around Galaxies (MAGG) -- III: The gas and galaxy environment of z = 3-4.5 quasars

TL;DR

This study investigates the environment of high-redshift quasars using MUSE data, revealing extended Lyalpha emission, metal-enriched gas, and galaxy overdensities, suggesting quasars reside in massive haloes with minimal impact on nearby galaxy properties.

Contribution

First detailed analysis of gas and galaxy environments around z=3-4.5 quasars using MUSE, showing extended emission and galaxy overdensities with implications for quasar host halo masses.

Findings

Extended Lyalpha emission detected around all quasars up to 100 kpc.

Gas is metal enriched, with CIV detected and HeII marginally detected.

Overdensity of LAEs near quasars indicates massive host haloes.

Abstract

We present a study of the environment of 27 z=3-4.5 bright quasars from the MUSE Analysis of Gas around Galaxies (MAGG) survey. With medium-depth MUSE observations (4 hours on target per field), we characterise the effects of quasars on their surroundings by studying simultaneously the properties of extended gas nebulae and Lyalpha emitters (LAEs) in the quasar host haloes. We detect extended (up to ~ 100 kpc) Lyalpha emission around all MAGG quasars, finding a very weak redshift evolution between z=3 and z=6. By stacking the MUSE datacubes, we confidently detect extended emission of CIV and only marginally detect extended HeII up to ~40 kpc, implying that the gas is metal enriched. Moreover, our observations show a significant overdensity of LAEs within 300 km/s from the quasar systemic redshifts estimated from the nebular emission. The luminosity functions and equivalent width distributions of these LAEs show similar shapes with respect to LAEs away from quasars suggesting that the Lyalpha emission of the majority of these sources is not significantly boosted by the quasar radiation or other processes related to the quasar environment. Within this framework, the observed LAE overdensities and our kinematic measurements imply that bright quasars at z=3-4.5 are hosted by haloes in the mass range ~ 10^{12.0}-10^{12.5} Msun.