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Deep learning the intergalactic medium using Lyman-alpha forest at 4 ≤ z ≤ 5

Nasir, Fahad; Gaikwad, Prakash; Davies, Frederick B.; Bolton, James S.; Puchwein, Ewald; Bosman, Sarah E.I.

Deep learning the intergalactic medium using Lyman-alpha forest at 4 ≤ z ≤ 5 Thumbnail


Authors

Fahad Nasir

Prakash Gaikwad

Frederick B. Davies

Profile image of JAMES BOLTON

JAMES BOLTON James.Bolton@nottingham.ac.uk
Professor of Astrophysics

Ewald Puchwein

Sarah E.I. Bosman



Abstract

Unveiling the thermal history of the intergalactic medium (IGM) at 4 ≤ z ≤ 5 holds the potential to reveal early onset He II reionization or lingering thermal fluctuations from H I reionization. We set out to reconstruct the IGM gas properties along simulated Lyman-alpha (Lyα) forest data on pixel-by-pixel basis, employing deep neural networks. Our approach leverages the Sherwood-Relics simulation suite, consisting of diverse thermal histories, to generate mock spectra. Our convolutional and residual networks with likelihood metric predict the Lyα optical depth-weighted density or temperature for each pixel in the Lyα forest skewer. We find that our network can successfully reproduce IGM conditions with high fidelity across range of instrumental signal-to-noise ratio. These predictions are subsequently translated into the temperature–density plane, facilitating the derivation of reliable constraints on thermal parameters. This allows us to estimate temperature at mean cosmic density, T0, with 1σ confidence, δT0 ≲ 1000 K, using only one 20 h−1 cMpc sightline (∆z ≃ 0.04) with a typical reionization history. Existing studies utilize redshift path-length comparable to ∆z ≃ 4 for similar constraints. We can also provide more stringent constraints on the slope (1σ confidence interval, δγ ≲ 0.1) of the IGM temperature–density relation as compared to other traditional approaches. We test the reconstruction on a single high signal-to-noise observed spectrum (20 h−1 cMpc segment) and recover thermal parameters consistent with current measurements. This machine learning approach has the potential to provide accurate yet robust measurements of IGM thermal history at the redshifts in question.

Citation

Nasir, F., Gaikwad, P., Davies, F. B., Bolton, J. S., Puchwein, E., & Bosman, S. E. (2024). Deep learning the intergalactic medium using Lyman-alpha forest at 4 ≤ z ≤ 5. Monthly Notices of the Royal Astronomical Society, 534(2), 1299-1316. https://doi.org/10.1093/mnras/stae2153

Journal Article Type Article
Acceptance Date Sep 13, 2024
Online Publication Date Sep 17, 2024
Publication Date Oct 1, 2024
Deposit Date Oct 8, 2024
Publicly Available Date Sep 17, 2024
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 534
Issue 2
Pages 1299-1316
DOI https://doi.org/10.1093/mnras/stae2153
Keywords methods: numerical
Public URL https://nottingham-repository.worktribe.com/output/39730996
Publisher URL https://academic.oup.com/mnras/article/534/2/1299/7759720?login=true

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