Possible evidence for a large-scale enhancement in the Lyman-α forest power spectrum at redshift z ≥ 4

Molaro, Margherita; Iršič, Vid; Bolton, James S.; Lieu, Maggie; Keating, Laura C.; Puchwein, Ewald; Haehnelt, Martin G; Viel, Matteo

Abstract

Inhomogeneous reionization enhances the 1D Ly α forest power spectrum on large scales at redshifts z ≥ 4. This is due to coherent fluctuations in the ionized hydrogen fraction that arise from large-scale variations in the post-reionization gas temperature, which fade as the gas cools. It is therefore possible to use these relic fluctuations to constrain inhomogeneous reionization with the power spectrum at wavenumbers log10(k/km−1 s) ≾ −1.5. We use the Sherwood-Relics suite of hybrid radiation hydrodynamical simulations to perform a first analysis of new Ly α forest power spectrum measurements at 4.0 ≤ z ≤ 4.6. These data extend to wavenumbers log10(k/km−1 s) ≃ −3, with a relative uncertainty of 10–20 per cent in each wavenumber bin. Our analysis returns a 2.7σ preference for an enhancement in the Ly α forest power spectrum at large scales, in excess of that expected for a spatially uniform ultraviolet background. This large-scale enhancement could be a signature of inhomogeneous reionization, although the statistical precision of these data is not yet sufficient for obtaining a robust detection of the relic post-reionization fluctuations. We show that future power spectrum measurements with relative uncertainties of ≾ 2.5 per cent should provide unambiguous evidence for an enhancement in the power spectrum on large scales.

Citation

Molaro, M., Iršič, V., Bolton, J. S., Lieu, M., Keating, L. C., Puchwein, E., …Viel, M. (2023). Possible evidence for a large-scale enhancement in the Lyman-α forest power spectrum at redshift z ≥ 4. Monthly Notices of the Royal Astronomical Society, 521(1), 1489–1501. https://doi.org/10.1093/mnras/stad598

• Journal Article Type: Article
• Acceptance Date: Feb 22, 2023
• Online Publication Date: Mar 2, 2023
• Publication Date: May 1, 2023
• Deposit Date: Mar 6, 2023
• Publicly Available Date: Mar 2, 2023
• 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: 521
• Issue: 1
• Pages: 1489–1501
• DOI: https://doi.org/10.1093/mnras/stad598
• Keywords: Methods: numerical, intergalactic medium, quasars: absorption lines, large-scale structure of Universe
• Public URL: https://nottingham-repository.worktribe.com/output/18200583
• Publisher URL: https://academic.oup.com/mnras/article/521/1/1489/7068093
• Additional Information: ©The Author(s) 2023. Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( https://cr eativecommons.or g/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.