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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 and Fumagalli, M and Lofthouse, E K and Dutta, R and Cantalupo, S and Arrigoni Battaia, F and Fynbo, J P U and Lusso, E and Murphy, M T and Prochaska, J X and Theuns, T and Cooke, R J (2021) 'MUSE analysis of gas around galaxies (MAGG) – III. The gas and galaxy environment of z = 3–4.5 quasars.', Monthly notices of the Royal Astronomical Society, 503 (2). pp. 3044-3064.


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⊙⁠.

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Publisher 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.
Date accepted:01 March 2021
Date deposited:14 July 2021
Date of first online publication:08 March 2021
Date first made open access:14 July 2021

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