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Probing the metallicity and ionization state of the circumgalactic medium at z~6 and beyond with OI absorption

Keating, Laura C.; Haehnelt, Martin G.; Becker, George D.; Bolton, James S.

Authors

Laura C. Keating

Martin G. Haehnelt

George D. Becker

James S. Bolton

Abstract

Low-ionization metal absorption due to O I has been identified as an important probe of the physical state of the intergalactic/circumgalactic medium at the tail end of reionization. We use here high-resolution hydrodynamic simulations to interpret the incidence rate of O I absorbers at z ∼ 6 as observed by Becker et al. We infer weak O I absorbers (EW ≳ 0.1 Å) to have typical H I column densities in the range of sub-damped Lyman α systems, densities of 80 times the mean baryonic density and metallicities of about 1/500th solar. This is similar to the metallicity inferred at similar overdensities at z ∼ 3, suggesting that the metal enrichment of the circumgalactic medium around low-mass galaxies has already progressed considerably by z ∼ 6. The apparently rapid evolution of the incidence rates for O I absorption over the redshift range 5 ≲ z ≲ 6 mirrors that of self-shielded Lyman-limit systems at lower redshift and is mainly due to the rapid decrease of the metagalactic photoionization rate at z ≳ 5. We predict the incidence rate of O I absorbers to continue to rise rapidly with increasing redshift as the IGM becomes more neutral. If the distribution of metals extends to lower density regions, O I absorbers will allow the metal enrichment of the increasingly neutral filamentary structures of the cosmic web to be probed.

Journal Article Type Article
Publication Date Dec 31, 2013
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press (OUP)
Peer Reviewed Peer Reviewed
Volume 438
Issue 2
Institution Citation Keating, L. C., Haehnelt, M. G., Becker, G. D., & Bolton, J. S. (2013). Probing the metallicity and ionization state of the circumgalactic medium at z~6 and beyond with OI absorption. Monthly Notices of the Royal Astronomical Society, 438(2), doi:10.1093/mnras/stt2324
DOI https://doi.org/10.1093/mnras/stt2324
Keywords Galaxies: high-redshift, Intergalactic medium, Quasars, Absorption lines, Reionization, First stars
Publisher URL https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stt2324
Copyright Statement Copyright information regarding this work can be found at the following address: http://eprints.nottingh.../end_user_agreement.pdf
Additional Information This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2013 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf




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