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

Keating, Laura C. and Haehnelt, Martin G. and Becker, George D. and Bolton, James 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). pp. 1820-1831. ISSN 1365-2966

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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.

Item Type: Article
Additional Information: his 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.
Keywords: Galaxies: high-redshift, Intergalactic medium, Quasars, Absorption lines, Reionization, First stars
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
Identification Number: 10.1093/mnras/stt2324
Depositing User: Bolton, James
Date Deposited: 04 May 2017 12:32
Last Modified: 05 May 2017 13:57
URI: http://eprints.nottingham.ac.uk/id/eprint/42496

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