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Low-redshift Lyman limit systems as diagnostics of cosmological inflows and outflows


Hafen, Zachary; Faucher-Giguère, Claude-André; Anglés-Alcázar, Daniel; Kereš, Dušan; Feldmann, Robert; Chan, T. K; Quataert, Eliot; Murray, Norman; Hopkins, Philip F (2017). Low-redshift Lyman limit systems as diagnostics of cosmological inflows and outflows. Monthly Notices of the Royal Astronomical Society, 469(2):2292-2304.

Abstract

We use cosmological hydrodynamic simulations with stellar feedback from the FIRE (Feedback In Realistic Environments) project to study the physical nature of Lyman limit systems (LLSs) at z ≤ 1. At these low redshifts, LLSs are closely associated with dense gas structures surrounding galaxies, such as galactic winds, dwarf satellites and cool inflows from the intergalactic medium. Our analysis is based on 14 zoom-in simulations covering the halo mass range Mh ≈ 109–1013 M⊙ at z = 0, which we convolve with the dark matter halo mass function to produce cosmological statistics. We find that the majority of cosmologically selected LLSs are associated with haloes in the mass range 1010 ≲ Mh ≲ 1012 M⊙. The incidence and H i column density distribution of simulated absorbers with columns in the range 1016.2≤NHI≤2×1020 cm−2 are consistent with observations. High-velocity outflows (with radial velocity exceeding the halo circular velocity by a factor of ≳ 2) tend to have higher metallicities ([X/H] ∼ −0.5) while very low metallicity ([X/H] < −2) LLSs are typically associated with gas infalling from the intergalactic medium. However, most LLSs occupy an intermediate region in metallicity-radial velocity space, for which there is no clear trend between metallicity and radial kinematics. The overall simulated LLS metallicity distribution has a mean (standard deviation) [X/H] = −0.9 (0.4) and does not show significant evidence for bimodality, in contrast to recent observational studies, but consistent with LLSs arising from haloes with a broad range of masses and metallicities.

Abstract

We use cosmological hydrodynamic simulations with stellar feedback from the FIRE (Feedback In Realistic Environments) project to study the physical nature of Lyman limit systems (LLSs) at z ≤ 1. At these low redshifts, LLSs are closely associated with dense gas structures surrounding galaxies, such as galactic winds, dwarf satellites and cool inflows from the intergalactic medium. Our analysis is based on 14 zoom-in simulations covering the halo mass range Mh ≈ 109–1013 M⊙ at z = 0, which we convolve with the dark matter halo mass function to produce cosmological statistics. We find that the majority of cosmologically selected LLSs are associated with haloes in the mass range 1010 ≲ Mh ≲ 1012 M⊙. The incidence and H i column density distribution of simulated absorbers with columns in the range 1016.2≤NHI≤2×1020 cm−2 are consistent with observations. High-velocity outflows (with radial velocity exceeding the halo circular velocity by a factor of ≳ 2) tend to have higher metallicities ([X/H] ∼ −0.5) while very low metallicity ([X/H] < −2) LLSs are typically associated with gas infalling from the intergalactic medium. However, most LLSs occupy an intermediate region in metallicity-radial velocity space, for which there is no clear trend between metallicity and radial kinematics. The overall simulated LLS metallicity distribution has a mean (standard deviation) [X/H] = −0.9 (0.4) and does not show significant evidence for bimodality, in contrast to recent observational studies, but consistent with LLSs arising from haloes with a broad range of masses and metallicities.

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Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute for Computational Science
Dewey Decimal Classification:530 Physics
Language:English
Date:April 2017
Deposited On:09 Jan 2018 21:02
Last Modified:19 Feb 2018 09:50
Publisher:Oxford University Press
ISSN:0035-8711
Additional Information:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2017 The Authors Published by Oxford University Press on behalf of Royal Astronomical Society. All rights reserved.
OA Status:Green
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1093/mnras/stx952

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