The sources of reionization: new clues from high and low-redshift

Abstract: Early stars and galaxies emitted sufficient ionizing photons to ionize all of the gas between galaxies. This epoch of reionization established the conditions from which modern-day galaxies emerged, but very little, pre-JWST, had been observed about how the Universe became reionized. Here, I present recent results that tie together both local galaxies and galaxies within the epoch of reionization to reveal new constraints on the sources of reionization. I will focus on recent direct observations of galaxies squarely within this time period with NIRSpec on the James Webb Space Telescope. These NIRSpec observations probe both the production and escape of ionizing photons squarely within the epoch of reionization. However, JWST observations cannot directly constrain the sources of ionizing photons. A large sample of local galaxies known to emit ionizing photons, called the Low-Redshift Lyman Continuum Survey, provides the template to constrain how ionizing photons escape distant galaxies. I will present some recent results from this survey that are directly applicable to the high-redshift universe and look forward to upcoming JWST observations that will constrain the sources of cosmic reionization.