Cosmic Reionization

Reionization and Cosmology with 21 cm Fluctuations

Three major stages in the evolution of our universe are written in the phases of hydrogen. After nucleosynthesis the universe was an ionized plasma of hydrogen and helium. As expansion cooled the universe, hydrogen went through a phase transition, rapidly becoming neutral and releasing the Cosmic Microwave Background light at a redshift of ~1089. High energy photons produced by the firrst stars and quasars later reionized the hydrogen in the inter galactic medium (IGM), forcing the universe back through a second extended and patchy phase transition referred to as the epoch of reionization (EoR).