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MUSE analysis of gas around galaxies (MAGG) – III. The gas and galaxy environment of z = 3–4.5 quasars

Fossati, M; Fumagalli, M; Lofthouse, EK; Dutta, R; Cantalupo, S; Arrigoni Battaia, F; Fynbo, JPU; Lusso, E; Murphy, MT; Prochaska, JX; Theuns, T; Cooke, RJ

MUSE analysis of gas around galaxies (MAGG) – III. The gas and galaxy environment of z = 3–4.5 quasars Thumbnail


M Fossati

M Fumagalli

EK Lofthouse

R Dutta

S Cantalupo

F Arrigoni Battaia

JPU Fynbo

E Lusso

MT Murphy

JX Prochaska


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 Multi Unit Spectroscopic Explorer (MUSE) observations (4 h on target per field), we characterize the effects of quasars on their surroundings by studying simultaneously the properties of extended gas nebulae and Ly α emitters (LAEs) in the quasar host haloes. We detect extended (up to ≈100 kpc) Ly α 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 C IV and only marginally detect extended He II up to ≈40 kpc, implying that the gas is metal enriched. Moreover, our observations show a significant overdensity of LAEs within 300 km s−1 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 Ly α 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 ≈1012.0−−1012.5 M⊙⁠.

Journal Article Type Article
Acceptance Date Mar 1, 2021
Online Publication Date Mar 8, 2021
Publication Date 2021-05
Deposit Date Jul 14, 2021
Publicly Available Date Jul 14, 2021
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 503
Issue 2
Pages 3044-3064
Public URL


Published Journal Article (7.4 Mb)

Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2021 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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