Cake Talk by Christopher Cain
The Epoch of Reionization (EoR) saw the Intergalactic Medium (IGM) transition from being neutral to highly ionized. This process took place during the first billion years after the Big Bang and was driven by the first generation of HI-ionizing sources, likely the first galaxies. Reionization is a complicated process involving a wide range of physical scales. The shapes and sizes of ionized regions during the EoR are driven by the clustering of galaxies on 100-Mpc scales, while the opacity of the intervening IGM is affected by kpc-scale density fluctuations and the processes regulating the escape of ionizing photons from galaxies take place on even smaller scales. Thus, reionization is a challenging problem to solve from a theoretical perspective. I will discuss a radiative transfer code that I developed that is optimized to solve reionization efficiently without sacrificing accuracy. My code uses a novel sub-grid prescription for the opacity of the ionized IGM that is built on high-resolution simulations that resolve the clumping and dynamics of intergalactic gas down to kpc scales. I will also discuss recent results using this code to better understand and interpret reionization observables, with a focus on recent observations of QSO spectra at z = 5-6.