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Theses

Étude des sources de la réionisation dans la simulation SPHINX

Abstract : The epoch of reionisation is the transition from a neutral hydrogen Universe to a fully reionised one. It starts with the formation of the first galaxies, whose stars produce the energy responsible for the reionisation of the hydrogen, and last until one billion years after the beginning of the Universe. The high-redshift of the reionisation era makes that it is very challenging to observe galaxies from this epoch, which are, however, the sources of reionisation. In order to solve this issue and complete the observational results, numerical simulations are often used to study the sources of reionisation. This is the work I propose to carry out in this thesis. Using the SPHINX radiative hydrodynamical simulation, which simulates thousands of galactic haloes at the epoch of reionisation, I focused on the escape fraction of the ionising photons from haloes into the inter-galactic medium. I first focused on the entire halo population at different redshifts in order to statistically study the role and the characteristics of haloes during the reionisation. This allowed us to put forward the major role of the numerous small haloes during reionisation. Then I studied the most massive halo of our simulation in order to understand the physical mechanisms behind the escape of ionising photons. More specifically, I focused on the duty cycle of the escape fraction, related to the stellar formation, and the critical role of supernovae concerning the escape of ionising photons. Finally, I worked on the observability of the escape fraction by studying the anisotropy of the escape of ionising photons and the relation between the UV magnitude and the escape fraction. The principal result is that when a UV selection is made on galaxies or on lines-of-sight, it leads to an overestimation of the escape fraction.
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Submitted on : Monday, December 20, 2021 - 2:40:08 PM
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Mathieu Chuniaud. Étude des sources de la réionisation dans la simulation SPHINX. Astrophysique [astro-ph]. Université de Lyon, 2021. Français. ⟨NNT : 2021LYSE1157⟩. ⟨tel-03496560⟩

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