York University
Detecting the Ultra-Faint Galaxies Responsible for Cosmic Reionization with Gravitational Lensing and JWST Medium Bands — Most of the hydrogen gas in the Universe is ionized, but prior to the formation of galaxies, the Universe was neutral. Once stars started forming, a significant phase change occurred in the universe, a process known as “Reionization”.  This project will look for the faintest possible sources of Reionization, tiny dwarf galaxies. The project targets strong-lensing clusters which provide a factor of 3 - 50 boost in the brightness of background sources. This increase in sensitivity allows the detection of extraordinarily low-mass galaxies (the equivalent of large star-clusters) during the reionization epoch and quantify their role in this process.