M.L. Turner
Observations of metals in the z ≈ 3.5 intergalactic medium and comparison to the EAGLE simulations
Turner, M.L.; Schaye, J.; Crain, R.A.; Theuns, T.; Wendt, M.
Abstract
We study the z ≈ 3.5 intergalactic medium (IGM) by comparing new, high-quality absorption spectra of eight QSOs with 〈zQSO〉 = 3.75, to virtual observations of the Evolution and Assembly of Galaxies and their Environments (EAGLE) cosmological hydrodynamical simulations. We employ the pixel optical depth method and uncover strong correlations between various combinations of H I, C III, C IV, Si III, Si IV, and O VI. We find good agreement between many of the simulated and observed correlations, including τOvi(τHi)τOvi(τHi). However, the observed median optical depths for the τCiv(τHi)τCiv(τHi) and τSiiv(τHi)τSiiv(τHi) relations are higher than those measured from the mock spectra. The discrepancy increases from up to ≈0.1 dex at τHi=1τHi=1 to ≈1 dex at τHi=102τHi=102, where we are likely probing dense regions at small galactocentric distances. As possible solutions, we invoke (a) models of ionizing radiation softened above 4 Ryd to account for delayed completion of He II reionization; (b) simulations run at higher resolution; (c) the inclusion of additional line broadening due to unresolved turbulence; and (d) increased elemental abundances; however, none of these factors can fully explain the observed differences. Enhanced photoionization of H I by local sources, which was not modelled, could offer a solution. However, the much better agreement with the observed O VI(H I) relation, which we find probes a hot and likely collisionally ionized gas phase, indicates that the simulations are not in tension with the hot phase of the IGM, and suggests that the simulated outflows may entrain insufficient cool gas.
Journal Article Type | Article |
---|---|
Acceptance Date | Jul 21, 2016 |
Online Publication Date | Jul 28, 2016 |
Publication Date | Jul 28, 2016 |
Deposit Date | Sep 28, 2016 |
Publicly Available Date | Oct 6, 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 | 462 |
Issue | 3 |
Pages | 2440-2464 |
DOI | https://doi.org/10.1093/mnras/stw1816 |
Public URL | https://durham-repository.worktribe.com/output/1396468 |
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Copyright Statement
This article has been published 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.
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