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Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six

Becker, George D.; Bolton, James S.; Madau, Piero; Pettini, Max; Ryan-Weber, Emma V.; Venemans, Bram P.

Authors

George D. Becker

Piero Madau

Max Pettini

Emma V. Ryan-Weber

Bram P. Venemans



Abstract

We report the discovery of an extremely long (∼110 Mpc/h) and dark (τeff≳7) Lyα trough extending down to z≃5.5 towards the zem≃6.0 quasar ULAS J0148+0600. We use these new data in combination with Lyα forest measurements from 42 quasars at 4.5≤zem≤6.4 to conduct an updated analysis of the line-of-sight variance in the intergalactic Lyα opacity over 4≤z≤6. We find that the scatter in transmission among lines of sight near z∼6 significantly exceeds theoretical expectations for either a uniform ultraviolet background (UVB) or simple fluctuating UVB models in which the mean free path to ionizing photons is spatially invariant. The data, particularly near z≃5.6-5.8, instead require fluctuations in the volume-weighted hydrogen neutral fraction that are a factor of 3 or more beyond those expected from density variations alone. We argue that these fluctuations are most likely driven by large-scale variations in the mean free path, consistent with expectations for the final stages of inhomogeneous hydrogen reionization. Even by z≃5.6, however, a large fraction of the data are consistent with a uniform UVB, and by z∼5 the data are fully consistent with opacity fluctuations arising solely from the density field. This suggests that while reionization may be ongoing at z∼6, it has fully completed by z∼5.

Journal Article Type Article
Publication Date Mar 11, 2015
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 0035-8711
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 447
Issue 4
Pages 3402-3419
APA6 Citation Becker, G. D., Bolton, J. S., Madau, P., Pettini, M., Ryan-Weber, E. V., & Venemans, B. P. (2015). Evidence of patchy hydrogen reionization from an extreme Lyα trough below redshift six. Monthly Notices of the Royal Astronomical Society, 447(4), 3402-3419. https://doi.org/10.1093/mnras/stu2646
DOI https://doi.org/10.1093/mnras/stu2646
Keywords Intergalactic Medium, Quasars, Absorption Lines, Cosmology, Observations, Dark Ages, Reionization, First Stars, Large-scale Structure of the Universe
Publisher URL http://mnras.oxfordjournals.org/content/447/4/3402
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 published in Monthly Notices of the Royal Astronomical Society © 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

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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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