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The distribution of neutral hydrogen around high-redshift galaxies and quasars in the EAGLE simulation.

Rahmati, A. and Schaye, J. and Bower, R. G. and Crain, R. A. and Furlong, M. and Schaller, M. and Theuns, T. (2015) 'The distribution of neutral hydrogen around high-redshift galaxies and quasars in the EAGLE simulation.', Monthly notices of the Royal Astronomical Society., 452 (2). pp. 2034-2056.


The observed high covering fractions of neutral hydrogen (HIHI) with column densities above ∼1017 cm−2 around Lyman-Break Galaxies (LBGs) and bright quasars at redshifts z ∼ 2–3 has been identified as a challenge for simulations of galaxy formation. We use the Evolution and Assembly of Galaxies and their Environment (EAGLE) cosmological, hydrodynamical simulation, which has been shown to reproduce a wide range of galaxy properties and for which the subgrid feedback was calibrated without considering gas properties, to study the distribution of HIHI around high-redshift galaxies. We predict the covering fractions of strong HIHI absorbers (NHI≳1017cm−2NHI≳1017cm−2) inside haloes to increase rapidly with redshift but to depend only weakly on halo mass. For massive (M200 ≳ 1012M⊙) haloes, the covering fraction profiles are nearly scale-invariant and we provide fitting functions that reproduce the simulation results. While efficient feedback is required to increase the HIHI covering fractions to the high observed values, the distribution of strong absorbers in and around haloes of a fixed mass is insensitive to factor of 2 variations in the strength of the stellar feedback. In contrast, at fixed stellar mass the predicted HIHI distribution is highly sensitive to the feedback efficiency. The fiducial EAGLE simulation reproduces both the observed global column density distribution function of HIHI and the observed radial covering fraction profiles of strong HIHI absorbers around LBGs and bright quasars.

Item Type:Article
Keywords:Methods: numerical, Galaxies: formation, Galaxies: high-redshift, Intergalactic medium, Quasars: absorption lines.
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Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:23 June 2015
Date deposited:19 February 2016
Date of first online publication:September 2015
Date first made open access:No date available

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