UCLA

Understanding the ionizing radiation field in intergalactic space is crucial for studying the intergalactic medium (IGM). The ionizing background naturally fluctuates in space due to the discrete nature of ionizing sources (i.e. individual galaxies and quasars) and their clustering due to the cosmic growth of structure. These fluctuations are typically ignored in cosmological simulations, but they may be required to explain recent observations of the hydrogen and helium Lyman-alpha forests. For my thesis, I have developed novel physically-motivated models of the large-scale fluctuations in the ionizing background and the mean free path of ionizing photons which compare favorably to the latest observations. I have also re-investigated a once promising idea to directly observe the ionization of the IGM by quasars during the epoch of reionization through Lyman-alpha emission from the ionization front.