What can Lyα emission from galaxies tell us about reionization?
The reionization of intergalactic hydrogen in the universe’s first billion years was likely driven by the first stars and galaxies. The timeline of reionization is currently uncertain but if it is accurately measured it can unveil properties of ‘first light’ sources. I will describe how we can use galaxies at our current observational frontiers to learn about reionization. In particular, Lyman alpha (Lyα) emission from galaxies can be used to probe the intergalactic medium (IGM) at high redshift, but requires modelling physics from pc to Gpc scales. I will describe a forward-modelling Bayesian approach which combines cosmological IGM simulations with empirical interstellar medium models to constrain reionization from observations of galaxies, focusing on Lyα emission at z>6. I will present new measurements which favour a late and relatively rapid reionization, and place these in the context of high redshift galaxy formation. I will discuss the challenges and future prospects in using Lyα emission as a cosmological tool.