Long Dark Gaps in the Ly β Forest at z < 6: Evidence of Ultra-late Reionization from XQR-30 Spectra
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Author
Zhu, Y.Becker, G.D.
Bosman, S.E.I.
Keating, L.C.
D'Odorico, V.
Davies, R.L.
Christenson, H.M.
Bañados, E.
Bian, F.
Bischetti, M.
Chen, H.
Davies, F.B.
Eilers, A.-C.

Fan, X.
Gaikwad, P.
Greig, B.
Haehnelt, M.G.
Kulkarni, G.
Lai, S.
Pallottini, A.
Qin, Y.
Ryan-Weber, E.V.
Walter, F.
Wang, F.
Yang, J.
Affiliation
Steward Observatory, University of ArizonaIssue Date
2022
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Institute of PhysicsCitation
Zhu, Y., Becker, G. D., Bosman, S. E. I., Keating, L. C., D’Odorico, V., Davies, R. L., Christenson, H. M., Bañados, E., Bian, F., Bischetti, M., Chen, H., Davies, F. B., Eilers, A.-C., Fan, X., Gaikwad, P., Greig, B., Haehnelt, M. G., Kulkarni, G., Lai, S., … Yang, J. (2022). Long Dark Gaps in the Ly β Forest at z < 6: Evidence of Ultra-late Reionization from XQR-30 Spectra. Astrophysical Journal, 932(2).Journal
Astrophysical JournalRights
Copyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
We present a new investigation of the intergalactic medium near reionization using dark gaps in the Lyβ forest. With its lower optical depth, Lyβ offers a potentially more sensitive probe to any remaining neutral gas compared to the commonly used Lyα line. We identify dark gaps in the Lyβ forest using spectra of 42 QSOs at z em > 5.5, including new data from the XQR-30 VLT Large Programme. Approximately 40% of these QSO spectra exhibit dark gaps longer than 10 h -1 Mpc at z ≃ 5.8. By comparing the results to predictions from simulations, we find that the data are broadly consistent both with models where fluctuations in the Lyα forest are caused solely by ionizing ultraviolet background fluctuations and with models that include large neutral hydrogen patches at z < 6 due to a late end to reionization. Of particular interest is a very long (L = 28 h -1 Mpc) and dark (τ eff ≳ 6) gap persisting down to z ≃ 5.5 in the Lyβ forest of the z = 5.85 QSO PSO J025-11. This gap may support late reionization models with a volume-weighted average neutral hydrogen fraction of 〈x H I〉 ≳ 5% by z = 5.6. Finally, we infer constraints on 〈x H I〉 over 5.5 ≲ z ≲ 6.0 based on the observed Lyβ dark gap length distribution and a conservative relationship between gap length and neutral fraction derived from simulations. We find 〈x H I〉 ≤ 0.05, 0.17, and 0.29 at z ≃ 5.55, 5.75, and 5.95, respectively. These constraints are consistent with models where reionization ends significantly later than z = 6. © 2022. The Author(s). Published by the American Astronomical Society.Note
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0004-637XVersion
Final published versionae974a485f413a2113503eed53cd6c53
10.3847/1538-4357/ac6e60
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Except where otherwise noted, this item's license is described as Copyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.