Solving Reionization with Resolved Lyman-alpha

Reionization was the last great phase transition of the Universe when the first galaxies announced their presence by transforming the vast reservoirs of cold, neutral gas across the cosmos into a hot, ionized state. The most pressing questions around reionization hinge on the unknown ionizing photon escape fractions (LyC fesc) of star-forming galaxies -- i.e., the fraction of photons that evade absorption by gas and dust in galaxies so they may reionize the intergalactic medium (IGM). Direct measurements of LyC fesc are impossible at high redshift (z>3-4) due to the opacity of the intervening IGM. In this talk, I will present recent breakthroughs on the LyC fesc problem. I will describe how high-resolution (R>4000) Lyman-alpha (LyA) line profiles may be used to infer LyC fesc. Based on these findings I will present a LyA-linked framework to understand the cosmic ionizing background from z~2-8. I will end by previewing two Cycle 1 JWST programs I am leading -- these programs perform deep spectroscopy of ionized bubbles towards the beginning and the end of reionization.