UCLA UCLA Electronic Theses and Dissertations Title Galaxies at the Epoch of Reionization Permalink https://escholarship.org/uc/item/39t4d9qg Author Mason, Charlotte Publication Date 2018 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA Los Angeles Galaxies at the Epoch of Cosmic Reionization A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Astronomy by Charlotte Ann Mason 2018 © Copyright by Charlotte Ann Mason 2018 ABSTRACT OF THE DISSERTATION Galaxies at the Epoch of Cosmic Reionization by Charlotte Ann Mason Doctor of Philosophy in Astronomy University of California, Los Angeles, 2018 Professor Tommaso L. Treu, Chair The reionization of intergalactic hydrogen in the universe's first billion years was likely driven by the first stars and galaxies, so its history encodes information about their prop- erties. But the timeline of reionization is not well-measured and it is still unclear whether galaxies alone can produce the required ionizing photons. In my thesis I have focused on two ways to use galaxies at our current observational frontiers to constrain reionization and high redshift galaxy evolution. One tool is the UV luminosity function (LF), which traces the evolution of star-forming galaxies and their ionizing photons. Accurately measuring LFs and understanding their evolution are important for understanding the connections between galaxies and their dark matter halos. I developed a simple, but powerful, semi-analytic model for LF evolution assuming star formation is driven by dark matter accretion. This has proved remarkably consistent with observations, and implies the majority of star formation at high redshifts occurs in low mass galaxies. I also developed a technique to improve the accuracy of LF by accounting for gravitational lensing magnification bias. Secondly, Lyman alpha (Lyα) emission from galaxies can probe the intergalactic medium (IGM) ionization state as Lyα photons are strongly attenuated by neutral hydrogen, but this requires disentangling physics on pc to Gpc scales. I developed a new forward-modeling Bayesian framework combining cosmological IGM simulations with interstellar medium mod- els to infer the IGM neutral hydrogen fraction from observations of Lyα emission. My thesis ii presents new measurements of the neutral fraction at z 7 and z 8, which, along with ∼ ∼ other independent constraints, provide increasing evidence for the bulk of reionization oc- curring at z 6 8. This is consistent with reionization being driven by ultra-faint galaxies ∼ − with a low average ionizing photon escape fraction. We also show that reionization impacts Lyα emission from different galaxy populations in different ways: UV bright galaxies living in overdense regions that reionize early have potentially visible Lyα even in a highly neutral IGM. The upcoming James Webb Space Telescope was designed to observe galaxies at Cosmic Dawn. Throughout this thesis I have made predictions for what JWST may observe in the context of high redshift galaxy evolution. iii The dissertation of Charlotte Ann Mason is approved. Steven R. Furlanetto Matthew A. Malkan Smadar Naoz Tommaso L. Treu, Committee Chair University of California, Los Angeles 2018 iv TABLE OF CONTENTS 1 Introduction :::::::::::::::::::::::::::::::::::::: 1 1.1 Galaxy UV luminosity functions . .2 1.2 Lyman alpha emission from galaxies as a probe of reionization . .4 2 The Galaxy UV Luminosity Function Before the Epoch of Reionization 8 2.1 Introduction . .9 2.2 Model Description . 12 2.2.1 Star formation prescription . 13 2.2.2 Dust extinction . 15 2.2.3 Calibration . 17 2.3 Results . 17 2.3.1 Stellar masses and ages . 17 2.3.2 Luminosity functions and SFR density . 20 2.3.3 Forecasts for JWST and WFIRST ................... 22 2.3.4 Implications for reionization . 26 2.4 Summary and Conclusions . 31 3 Correcting the z 8 Galaxy Luminosity Function for Gravitational Lensing ∼ Magnification Bias :::::::::::::::::::::::::::::::::::: 34 3.1 Introduction . 35 3.2 Data . 38 3.2.1 The BoRG Survey . 38 3.2.2 Massive Foreground Galaxies Acting as Deflectors . 39 3.2.3 The Millennium Simulation . 40 v 3.3 Theoretical Background . 41 3.3.1 Galaxy Luminosity Function . 41 3.3.2 Strong Lensing . 41 3.3.3 Weak Lensing . 42 3.3.4 Magnification Bias . 43 3.4 Strong and Intermediate Lensing . 45 3.4.1 Strong Lensing by an Evolving Deflector Population . 45 3.4.2 Identifying Significantly Magnified Sources . 53 3.5 Weak Lensing . 58 3.5.1 Estimating Magnification from Simulation Catalogs . 58 3.5.2 BoRG Weak Lensing Magnification PDFs . 60 3.6 Recomputing the LF . 60 3.6.1 Bayesian Estimation of the LF . 61 3.6.2 Including the Lensing Corrections . 62 3.7 Results . 63 3.7.1 Strong and Intermediate Lensing Events in the BoRG Survey . 64 3.7.2 Inference of the Intrinsic z 8LF.................... 64 ∼ 3.7.3 Predictions for z > 8 and Future Surveys . 66 3.8 Summary and Conclusion . 68 3.9 Appendix: Bayesian Framework for Estimating the luminosity function . 70 4 The Universe is Reionizing at z 7: Bayesian Inference of the IGM Neutral ∼ Fraction Using Lyα Emission from Galaxies :::::::::::::::::::: 80 4.1 Introduction . 81 4.2 ISM, CGM, and IGM Radiative Transfer Modeling . 85 vi 4.2.1 ISM Lyα radiative transfer . 85 4.2.2 IGM and CGM Lyα Radiative Transfer . 95 4.3 Bayesian Inference . 102 4.3.1 Generating the likelihood . 104 4.4 Results . 106 4.4.1 Large samples of galaxies can accurately constrain the neutral fraction 107 4.4.2 Inference from current data . 108 4.4.3 Predictions for JWST . 114 4.5 Discussion . 117 4.5.1 The global reionization history . 117 4.5.2 A sudden drop in Lyα emission { redshift evolution of ∆v?...... 119 4.5.3 Lyα from UV bright galaxies { redshifted away from resonance? . 120 4.6 Summary and Conclusions . 121 5 Beacons into the Cosmic Dark Ages: Boosted transmission of Lyα from UV bright galaxies at z > 7 ::::::::::::::::::::::::::::::: 124 ∼ 5.1 Introduction . 125 5.2 Method . 126 5.3 Results . 128 5.3.1 Boosted transmission of Lyα from massive halos . 128 5.3.2 Evolving Lyα fraction for UV bright galaxies . 132 5.3.3 UV bright galaxies as probes of reionization . 133 5.4 Discussion . 135 5.5 Summary and Conclusions . 136 6 First Results from the KMOS Lens-Amplified Spectroscopic Survey (KLASS): vii Kinematics of Lensed Galaxies at Cosmic Noon ::::::::::::::::: 138 6.1 Introduction . 139 6.2 The KMOS Lens-Amplified Spectroscopic Survey . 142 6.3 Observations and Data . 143 6.3.1 Target selection . 143 6.3.2 Observations and data reduction . 144 6.4 Analysis and Results . 144 6.4.1 Comparison of HST grism and ground-based flux measurements . 145 6.4.2 Photometric properties and gravitational lens modeling . 148 6.4.3 Kinematics . 153 6.4.4 Star formation drivers . 159 6.4.5 Kinematic trends . 163 6.5 Discussion . 167 6.5.1 What is the dynamical nature of galaxies at z > 1? . 167 ∼ 6.5.2 Revealing the kinematics of low mass galaxies . 168 6.5.3 What are dispersion dominated galaxies? . 169 6.6 Conclusions . 170 6.7 Appendix: Kinematic Maps . 172 6.8 Appendix: Rotation Curves . 178 7 Inferences on the Timeline of Reionization at z 8 From the KMOS Lens- ∼ Amplified Spectroscopic Survey ::::::::::::::::::::::::::: 181 7.1 Introduction . 182 7.2 Observations . 184 7.2.1 The KMOS Lens-Amplified Spectroscopic Survey . 184 viii 7.2.2 Target selection . 186 7.2.3 KLASS observing strategy and reduction . 189 7.2.4 Reduction . 189 7.3 Emission Line Search, Purity and Completeness . 191 7.3.1 Emission line detection technique . 191 7.3.2 Candidate emission lines and sample purity . 192 7.3.3 Completeness . 194 7.3.4 Flux and equivalent width limits . 198 7.4 Reionization inference . 199 7.4.1 Bayesian inference framework . 199 7.4.2 Defining a selection function for a photometric sample . 202 7.4.3 Inference on the IGM neutral fraction . 209 7.5 Discussion . 210 7.5.1 The timeline of reionization . 214 7.5.2 M1149 JD1 { Lyα emission at z = 9:11? . 217 7.5.3 Other UV emission lines at z 8.................... 219 ∼ 7.5.4 Background limited observations with KMOS . 220 7.6 Summary and Conclusions . 223 7.7 Independent confirmation of CIV emission at z = 6:11 . 225 7.8 Testing the selection function of our final sub-sample . 227 7.9 Reionization Inference . 231 7.9.1 Likelihood at one.