Coupling Galaxy Evolution and the Epoch of Reionization
The Epoch of Reionization is a pivotal period in our cosmic history, representing the transition from a neutral post-recombination Universe into the fully ionized one we observe today. The procession of reionization is dictated by the fraction of ionizing photons, fesc, that escapes from galaxies to ionize the inter-galactic medium, with the exact value and functional form still an open question. I explore this question using the Semi-Analytic Galaxy Evolution (SAGE) model to generate galaxy properties, such as the number of ionizing photons emitted, and follow different possible Epoch of Reionization scenarios with a semi-numerical scheme. Specifically, I consider physically motivated forms of fesc, testing dependencies upon parameters such as the halo mass (both positively and negatively correlated), the fraction of gas ejected from the galaxy compared to the hot halo, specific star formation rate and quasar activity. I measure how these prescriptions impact important properties including the duration of reionization, the size of ionized bubbles and the integrated optical depth. Such predictions, when combined with future observations, will provide powerful constraints on the early evolution of gas and galaxies in the Universe.