Crain, R.A. and Bahé, Y.M. and Lagos, C.d.P. and Rahmati, A. and Schaye, J. and McCarthy, I.G. and Marasco, A. and Bower, R.G. and Schaller, M. and Theuns, T. and van der Hulst, T. (2017) 'The EAGLE simulations : atomic hydrogen associated with galaxies.', Monthly notices of the Royal Astronomical Society., 464 (4). pp. 4204-4226.
We examine the properties of atomic hydrogen (H i) associated with galaxies in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations of galaxy formation. EAGLE's feedback parameters were calibrated to reproduce the stellar mass function and galaxy sizes at z = 0.1, and we assess whether this calibration also yields realistic H i properties. We estimate the self-shielding density with a fitting function calibrated using radiation transport simulations, and correct for molecular hydrogen with empirical or theoretical relations. The ‘standard-resolution’ simulations systematically underestimate H i column densities, leading to an H i deficiency in low-mass (M⋆ < 1010 M⊙) galaxies and poor reproduction of the observed H i mass function. These shortcomings are largely absent from EAGLE simulations featuring a factor of 8 (2) better mass (spatial) resolution, within which the H i mass of galaxies evolves more mildly from z = 1 to 0 than in the standard-resolution simulations. The largest volume simulation reproduces the observed clustering of H i systems, and its dependence on H i richness. At fixed M⋆, galaxies acquire more H i in simulations with stronger feedback, as they become associated with more massive haloes and higher infall rates. They acquire less H i in simulations with a greater star formation efficiency, since the star formation and feedback necessary to balance the infall rate is produced by smaller gas reservoirs. The simulations indicate that the H i of present-day galaxies was acquired primarily by the smooth accretion of ionized, intergalactic gas at z ≃ 1, which later self-shields, and that only a small fraction is contributed by the reincorporation of gas previously heated strongly by feedback. H i reservoirs are highly dynamic: over 40 per cent of H i associated with z = 0.1 galaxies is converted to stars or ejected by z = 0.
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|Publisher Web site:||https://doi.org/10.1093/mnras/stw2586|
|Publisher statement:||This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2016 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.|
|Date accepted:||06 October 2016|
|Date deposited:||02 March 2017|
|Date of first online publication:||08 October 2016|
|Date first made open access:||02 March 2017|
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