All-sky Medium Energy Gamma-ray Observatory: Exploring the Extreme Multimessenger Universe

Ionizing photons produced by massive stars play a key role in galaxy evolution and in ending the dark ages. Fundamental unsolved questions about the production and escape of ionizing photons, and how ionizing galaxy populations evolve through cosmic time, can be definitively answered with next-gen UV spectroscopy, in concert with JWST and the ELTs.