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Published May 1, 2015 | Published + Submitted
Journal Article Open

Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history

Abstract

We use high-resolution cosmological zoom-in simulations from the FIRE (Feedback in Realistic Environments) project to make predictions for the covering fractions of neutral hydrogen around galaxies at z = 2–4. These simulations resolve the interstellar medium of galaxies and explicitly implement a comprehensive set of stellar feedback mechanisms. Our simulation sample consists of 16 main haloes covering the mass range M_h ≈ 10^9–6 × 10^(12) M_⊙ at z = 2, including 12 haloes in the mass range M_h ∼ 10^(11)–10^(12) M_⊙ corresponding to Lyman break galaxies (LBGs). We process our simulations with a ray tracing method to compute the ionization state of the gas. Galactic winds increase the H i covering fractions in galaxy haloes by direct ejection of cool gas from galaxies and through interactions with gas inflowing from the intergalactic medium. Our simulations predict H i covering fractions for Lyman limit systems (LLSs) consistent with measurements around z ∼ 2–2.5 LBGs; these covering fractions are a factor ∼2 higher than our previous calculations without galactic winds. The fractions of H i absorbers arising in inflows and in outflows are on average ∼50 per cent but exhibit significant time variability, ranging from ∼10 to ∼90 per cent. For our most massive haloes, we find a factor ∼3 deficit in the LLS covering fraction relative to what is measured around quasars at z ∼ 2, suggesting that the presence of a quasar may affect the properties of halo gas on ∼100 kpc scales. The predicted covering fractions, which decrease with time, peak at M_h ∼ 10^(11)–10^(12) M_⊙, near the peak of the star formation efficiency in dark matter haloes. In our simulations, star formation and galactic outflows are highly time dependent; H i covering fractions are also time variable but less so because they represent averages over large areas.

Additional Information

© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 February 16. Received 2015 February 13; in original form 2014 September 5. First published online March 20, 2015. We acknowledge useful discussions with Gwen Rudie, Xavier Prochaska, Joe Hennawi, Kate Rubin, Joop Schaye, Michele Fumagalli and Freeke van de Voort. We also thank the anonymous referee for a constructive review. CAFG was supported by a fellowship from the Miller Institute for Basic Research in Science, by NASA through Einstein Postdoctoral Fellowship Award PF3-140106 and grant 10-ATP10-0187, by NSF through grant AST-1412836, and by Northwestern University funds. Support for PFH was provided by the Gordon and Betty Moore Foundation through Grant 776 to the Caltech Moore Center for Theoretical Cosmology and Physics, by the Alfred P. Sloan Foundation through Sloan Research Fellowship BR2014-022, and by NSF through grant AST-1411920. DK was supported by an Hellman Fellowship and NSF grant AST-1412153. EQ was supported by NASA ATP grant 12-APT12-0183, a Simons Investigator award from the Simons Foundation, the David and Lucile Packard Foundation, and the Thomas Alison Schneider Chair in Physics at UC Berkeley. The simulations analysed in this paper were run on XSEDE computational resources (allocations TG-AST120025, TG-AST130039 and TG-AST140023).

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Published - MNRAS-2015-Faucher-Giguère-987-1003.pdf

Submitted - 1409.1919v1.pdf

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August 20, 2023
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October 18, 2023