Who reionized the Universe ? : dermining the photon budget of galaxies during reionization with numerical simulations, and studying the impact of dust Joseph Lewis To cite this version: Joseph Lewis. Who reionized the Universe ? : dermining the photon budget of galaxies during reioniza- tion with numerical simulations, and studying the impact of dust. Astrophysics [astro-ph]. Université de Strasbourg, 2020. English. NNT : 2020STRAE041. tel-03199136 HAL Id: tel-03199136 https://tel.archives-ouvertes.fr/tel-03199136 Submitted on 15 Apr 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. UNIVERSITÉ DE STRASBOURG ÉCOLE DOCTORALE 182 UMR 7550, Observatoire astronomique de Strasbourg THÈSE présentée par : Joseph Lewis soutenue le : 25 septembre 2020 pour obtenir le grade de : Docteur de l’université de Strasbourg Discipline/ Spécialité : Astrophysique Qui a réionisé l’Univers ? Détermination par la simulation numérique du budget de photons des galaxies pendant l’époque de la Réionisation, et étude de l’impact des poussières THÈSE dirigée par : M. AUBERT Dominique Professeur des universités, Université de Strasbourg RAPPORTEURS : M. GONZALES Mathias Maître de conférences, Université de Paris M. LANGER Mathieu Professeur des universités, Université Paris-Saclay AUTRES MEMBRES DU JURY : M. SEMELIN Benoît Professeur des universités, Sorbonne Université Mme. LANCON Ariane Professeur des universités, Université de Strasbourg M. OCVIRK Pierre Astronome adjoint, Université de Strasbourg ACKNOWLEDGEMENT First and foremost, I’d like to express my deepest gratitude and respect to Pierre and Dominique. Though they will definitely be humble about the quality of their supervision, I am thoroughly impressed by their availability and readiness to lend a hand, explain something or just have a chat. From the start, I found them very easy to work with, their laid back and informal but involved and supportive style is un-intimidating, pleasant, and productive. This, combined with a hands on approach provided me with a fantastic learning opportunity. I look forward to continue working and interacting with them whenever possible. I also want to thank Timothé and Federico, who both endured my loud keystrokes, sporadic ranting, and extensive kettle usage with a smile. I couldn’t have hoped for better office mates. Hopefully, the next generation can continue to annoy each other with the office nerf gun. On the whole, I feel hugely indebted to everyone at the Observatoire for their warm and friendly they help maintain, it made me feel welcome, and at home in Strasbourg. In fact I hadn’t antici- pated making so many friends and memories here, both of which I’ll be clinging to dearly. Thus, for (heavy)lifting my spirits I’d like to mention JB, Jérôme, Jonathan, Julie, Julien, Lucie, Mathieu, the Nicolas (D., G., and L.), Paolo, and Timothé; but also Ada, Katarina, Lorenzo, Mari, Oliver, and Yelena. I’d also like to thank Aline, Elena, Ludmilla, Melchior, and Orlane for putting up with me at home (and the amount of dirty dishes I produce). In particular, thank-you Orlane and Elena for making writing in quarantine bearable. A special mention goes out to François and Raphael for the hours of fun over discord, as well as to Benoît and to Cyril who also continue to enjoy my company, which is no mean feat. Naturally, I want to say to my parents how much I appreciate their enduring support and love, enabling me on all possible fronts. Finally, I’d like to renew my expression of gratitude to Roser, for turning me on to astrophysics all the way back in 2014. 3 TABLE OF CONTENTS Foreword 9 Avant-propos 14 Introduction 17 A brief note on cosmology . 17 Epoch of Reionization . 20 Sources of ionisation . 22 Constraints on Reionization . 31 Simulating the Epoch of Reionization with RAMSES-CUDATON . 34 RAMSES ........................................... 34 ATON............................................. 36 Coupling of RAMSES and ATON . 38 1 Photon budget in CoDa II 47 1.1 Presenting Cosmic Dawn II . 47 1.1.1 RAMSES-CUDATON . 47 1.1.2 Simulation set-up . 47 1.1.3 Results . 48 1.1.4 Galaxy sample . 50 1.1.5 Ocvirk et al. 2020 . 53 1.2 Galactic ionising photon budget in CoDa II . 80 1.2.1 Why study the photon budget in CoDa II? . 80 1.2.2 Escape fractions . 80 1.2.3 Escaping luminosities . 82 1.2.4 Ionising photon budget of galaxies . 82 1.2.5 Lewis et al. 2020 . 85 1.2.6 The limits of the definition of galaxies in CoDa II . 101 1.2.7 On the computation of the escape fraction . 101 1.2.8 SFR weighted average escape fractions . 104 1.2.9 Scatter of fesc values around the mass averages . 105 1.2.10 Time integrated ionising photon budget . 108 1.3 Résumé des résultats . 109 5 TABLE OF CONTENTS 2 Towards Cosmic Dawn III : Evolving RAMSES-CUDATON 115 2.1 Beyond CoDa II and missing physics . 115 2.2 Standard RAMSES chemical enrichment . 117 2.3 Evolving stellar emissivities . 117 2.4 Metal and Helium line cooling . 120 2.4.1 Implementing metal line cooling . 120 2.4.2 Implementing Helium line cooling . 120 2.4.3 New cooling rates . 121 2.4.4 Effects of He and Metal cooling on the temperature-density relation . 124 2.4.5 Effects of new cooling on star formation . 126 2.5 Dust model . 127 2.5.1 With a semi-analytical fit . 127 2.5.2 With a physical model . 128 2.6 Radiative transfer through dust . 137 2.6.1 LyC photon absorption by dust in ATON . 137 2.6.2 Post-processing with dust . 138 2.7 Evaluating the validity of the physical dust model : comparison to observations and semi-analytical models . 140 2.7.1 Dust mass to stellar mass . 140 2.7.2 Dust to metals and dust to gas . 141 2.7.3 Dust mass function . 143 2.7.4 UV continuum slopes . 144 2.8 Dusty massive haloes . 146 2.9 Résumé des résultats . 150 3 Towards Cosmic Dawn III : Recalibration 155 3.1 Beyond CoDa II and Ly α forest constraints . 155 3.2 The new calibration . 156 3.2.1 New parametrisation . 156 3.2.2 Matching the Ly α forest . 156 3.2.3 UVLF . 159 3.2.4 Further constraints on sources . 160 3.2.5 Further constraints on ionisation . 162 3.3 Résumé des résultats . 164 4 Dusty late Reionization photon budget 169 4.1 Escape fraction . 169 4.1.1 Escape fraction versus mass . 169 4.1.2 Average escape fraction versus mass . 172 ray 4.1.3 Total average fesc ................................... 172 ray 4.2 Gas fesc ............................................ 174 6 TABLE OF CONTENTS ray 4.2.1 Average gas fesc versus mass . 174 ray 4.2.2 Effect of T ⋆ on gas fesc ............................... 174 ray 4.3 Dust fesc ............................................ 176 ray 4.3.1 Average dust fesc versus mass . 176 4.4 Escaping luminosities in CoDa 2.5 . 177 4.5 Galactic ionising photon budget in CoDa 2.5 . 178 4.5.1 Photon budget . 178 4.5.2 Ionising emissivities . 182 4.6 Discussion . 183 4.7 Résumé des résultats . 184 Conclusions and perspectives 189 Conclusions et perspectives 192 List of figures 202 List of tables 203 Glossary 205 7 FOREWORD Hierarchical structure formation has enjoyed much success in explaining the gradual bottom up for- mation of the large scale structure of the Universe, and galaxies. However, because it is extremely difficult to observationally constrain the formation of the first structures, a large gap in our knowl- edge persists. One possible avenue of investigation is to study the Epoch of Reionization(EoR): When the first ionising sources formed in the first galaxies a few hundred million years after the Big Bang, they ionised the intergalactic Hydrogen gas over the next several hundred million years. During this process, and as time went by, and the number of ionising sources grew, so did the ionised regions surrounding galaxies, until eventually the intergalactic matter (IGM) was fully ionised. Evidently, the EoR is directly connected to the build up of structure. Therefore, following the density and luminos- ity of ionising sources, as well as the growth and distribution of ionised regions in the IGM at very high redshift gives a window into the formation of the first structure, its spatial distribution, and its evolution. In fact, the study of the EoR, the main topic of interest in this thesis, is timely. Indeed, over the next decades a new generation of instruments is set to revolutionise our observations of Reionization. First, new facilities capable of targetting reionising galaxies such as the James Webb Space Telescope (JWST) 1, or the Extremely Large Telescope (ELT) 2 will see first light. Second, new radio experiments such as the Square Kilometre Array (SKA) 3 or the Low Frequency Array (LOFAR) 4 will allow us to directly probe the density and distribution of neutral Hydrogen gas. Interpreting these new datasets will require extensive modelling and simulating, to retrieve physical constraints on Reionization. Understanding how Reionization unfolds requires understanding the relative contribution of the various ionising sources to Reionization, and how it evolved. Therefore, one question at the heart of my work is "Which ionising sources drove Reionization?". This has proved a difficult question to answer using observations, as it requires extensive assumptions and modelling.