Large-Scale Simulations of Hydrogen and Helium Reionization

I present here discussion and results of large-scale simulations of cosmic reionization, both hydrogen and helium. For hydrogen reionization, I have focused on the impact that the light cone effect has on observables related to the 21 cm hyperfine signal, with specific attention given to how the duration of reionization affects the results. I show that the light cone effect can introduce significant anisotropy in the detected signal, especially for (cosmically) brief reionization scenarios. Following this, I discuss a series of simulations of helium reionization, focusing this time on observables related to the Lyman- forest. First I present a method by which dark matter halos from simulations can be populated with quasars to match the latest quasar luminosity function and clustering measurements. Then I discuss a suite of simulations of helium reionization where the quasar model is modified to explore the impact on the timing and duration of reionization, as well as related measurements of the Lyman- forest. I show that many of the statistical features from the H i Lyman- forest are similar once the global optical depth is the same across simulations. However, differences of up to a factor of two remain, which might facilitate detection in the future. Finally, I show that differences in the He ii Lyman- forest are significant, and provide a promising way forward for determining the helium reionization history of the Universe.