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

Bahé, Y.M.; Crain, R.A.; Kauffmann, G.; Bower, R.G.; Schaye, J.; Furlong, M.; Lagos, C.; Schaller, M.; Trayford, J.W.; Dalla Vecchia, C.; Theuns, T.

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.

Citation

Bahé, Y., Crain, R., Kauffmann, G., Bower, R., Schaye, J., Furlong, M., …Theuns, T. (2016). The distribution of atomic hydrogen in EAGLE galaxies: morphologies, profiles, and H I holes. Monthly Notices of the Royal Astronomical Society, 456(1), 1115-1136. https://doi.org/10.1093/mnras/stv2674

• Journal Article Type: Article
• Acceptance Date: Nov 12, 2015
• Online Publication Date: Dec 19, 2015
• Publication Date: Feb 11, 2016
• Deposit Date: Apr 5, 2016
• Publicly Available Date: Apr 7, 2016
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 456
• Issue: 1
• Pages: 1115-1136
• DOI: https://doi.org/10.1093/mnras/stv2674
• Public URL: https://durham-repository.worktribe.com/output/1407795