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oai:www.repository.cam.ac.uk:1810/3894652025-09-17T01:41:24Zcom_1810_214758com_1810_256064col_1810_219492

Lyα emission as a sensitive probe of galactic mergers and reionization https://doi.org/10.17863/CAM.121337 Yuan, Yuxuan 0000000168160682 Haehnelt, Martin Lyα emission has emerged as a powerful probe of the epoch of reionization. This thesis investigates how various physical processes shape Lyα emission and its connection to cosmic reionization, using state-of-the-art cosmological zoom-in simulations. By post-processing these simulations, we generate synthetic Lyα spectra for comparison with observed Lyα emitter (LAE) populations across cosmic time. Specifically, we address the following key questions: • How can Lyα emission be used to probe LyC escape? We systematically explore the spatial and spectral properties of Lyα emission, finding them to be highly sensitive to feedback physics and the structure of the interstellar medium (ISM). We identify several Lyα parameters that reliably predict the escape fraction of Lyman continuum (LyC) photons. • What governs the visibility of high-redshift LAEs? We show that galaxy mergers trigger intense starbursts, significantly boosting Lyα luminosity. Additionally, resonant scattering produces extended red wings in the line profiles, which enhance transmission through the neutral intergalactic medium (IGM). Our simulations successfully reproduce several JWST observations with the assumption of minimal interstellar dust content. • How can we interpret the detection of a LAE at z ∼ 13? We identify two critical factors influencing the detectability of such early galaxies: (1) how far the red wing in the Lyα profile can extend, and (2) the reionization history and scatter in IGM transmission. We conclude by summarizing the main findings of this thesis and outlining promising directions for future research in the era of JWST and beyond. University of Cambridge 2025-05-06 Thesis Doctoral Doctor of Philosophy (PhD) eng https://www.repository.cam.ac.uk/handle/1810/389465 embargo 2026-09-16 https://www.repository.cam.ac.uk/bitstreams/f5a05348-8b17-4ba6-95a5-e49b0924dccc/download 745581a2a4d93870f535ae4f8012da5b https://www.repository.cam.ac.uk/bitstreams/6edb9b93-f895-425f-89b0-14b3c3c7b791/download 87eda9de84448d1f82354d60eee3eb5f https://creativecommons.org/licenses/by/4.0/ Cosmology Emission line Galaxy