Description:

JWST has transformed our ability to understand the properties of the first stars and galaxies that formed in the universe following the Big Bang. These objects are important because they provide the first ionizing radiation in the universe. As this radiation permeates from the galaxies into the intergalactic medium it ionizes the surrounding gas. This process is called “reionization”, and it corresponds to the last major phase transition in cosmology whereby all the intergalactic medium is fully ionized, where it has remained to the present day.

I will provide a brief history of our understanding of reionization in the universe. I will discuss how we have come to understand the evolving properties of galaxies, and how this connects to the reionization process. I will discuss observations from JWST that provide measurements of the physical conditions and formation histories of galaxies that exist during the epoch of reionization. These observations show the galaxies produce copious amounts of ionizing radiation, exceeding predictions based on stellar populations in galaxies that form later in the universe.  I will also discuss analyses of JWST data that constrain how much of this radiation escapes from galaxies.  I will also discuss JWST observations that constrain the physical properties of these early galaxies and how they may differ from galaxies that form later in the universe. 

Speaker: Casey Papovich, Texas A&M University

Host: Allison Strom