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The distribution of atomic hydrogen in EAGLE galaxies: morphologies, profiles, and HI holes

Bahe, YM and Crain, RA and Kauffmann, G and Bower, RG and Schaye, J and Furlong, M and Lagos, C and Schaller, M and Trayford, JW and Dalla Vecchia, C and Theuns, T (2016) The distribution of atomic hydrogen in EAGLE galaxies: morphologies, profiles, and HI holes. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 456 (1). pp. 1115-1136. ISSN 0035-8711

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Abstract

We compare the mass and internal distribution of atomic hydrogen (H I) in 2200 present-day central galaxies with Mstar > 1010  M⊙ from the 100 Mpc EAGLE ‘Reference’ simulation to observational data. Atomic hydrogen fractions are corrected for self-shielding using a fitting formula from radiative transfer simulations and for the presence of molecular hydrogen using an empirical or a theoretical prescription from the literature. The resulting neutral hydrogen fractions, , agree with observations to better than 0.1 dex for galaxies with Mstar between 1010 and 1011  M⊙. Our fiducial, empirical H2 model based on gas pressure results in galactic H I mass fractions, [Math Processing Error], that agree with observations from the GASS survey to better than 0.3 dex, but the alternative theoretical H2 formula from high-resolution simulations leads to a negative offset in [Math Processing Error] of up to 0.5 dex. Visual inspection of mock H I images reveals that most H I discs in simulated H I-rich galaxies are vertically disturbed, plausibly due to recent accretion events. Many galaxies (up to 80 per cent) contain spuriously large H I holes, which are likely formed as a consequence of the feedback implementation in EAGLE. The H I mass–size relation of all simulated galaxies is close to (but 16 per cent steeper than) observed, and when only galaxies without large holes in the H I disc are considered, the agreement becomes excellent (better than 0.1 dex). The presence of large H I holes also makes the radial H I surface density profiles somewhat too low in the centre, at [Math Processing Error] (by a factor of ≲ 2 compared to data from the Bluedisk survey). In the outer region ([Math Processing Error]), the simulated profiles agree quantitatively with observations. Scaled by H I size, the simulated profiles of H I-rich ([Math Processing Error]) and control galaxies ([Math Processing Error]) follow each other closely, as observed.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: 0201 Astronomical And Space Sciences
Subjects: Q Science > QB Astronomy
Divisions: Astrophysics Research Institute
Publisher: OXFORD UNIV PRESS
Related URLs:
Date Deposited: 12 Feb 2016 14:06
Last Modified: 12 Feb 2016 14:06
DOI or Identification number: 10.1093/mnras/stv2674
URI: http://researchonline.ljmu.ac.uk/id/eprint/2930

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