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.

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.

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), https://doi.org/10.1093/mnras/stt2324

• Journal Article Type: Article
• Acceptance Date: Nov 29, 2013
• Publication Date: Dec 31, 2013
• Deposit Date: May 4, 2017
• Publicly Available Date: May 4, 2017
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 438
• Issue: 2
• DOI: https://doi.org/10.1093/mnras/stt2324
• Keywords: Galaxies: high-redshift, Intergalactic medium, Quasars, Absorption lines, Reionization, First stars
• Public URL: https://nottingham-repository.worktribe.com/output/720157
• Publisher URL: https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stt2324
• 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.