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Durham University

Department of Physics

Staff profile

Publication details for Prof Richard Bower

Rahmati, A., Schaye, J., Bower, R. G., Crain, R. A., Furlong, M., Schaller, M. & 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): 2034-2056.

Author(s) from Durham


The observed high covering fractions of neutral hydrogen (HI
) 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 HI
around high-redshift galaxies. We predict the covering fractions of strong HI
absorbers (N HI ≳10 17 cm −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 HI
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 HI
distribution is highly sensitive to the feedback efficiency. The fiducial EAGLE simulation reproduces both the observed global column density distribution function of HI
and the observed radial covering fraction profiles of strong HI
absorbers around LBGs and bright quasars.