Speaker: PAGS Alumna '19, Kelsey Glazer, PhD Candidate, University of California at Davis

Abstract: Young star-forming galaxies are believed to be the main contributors to the process of cosmic reionization which completed roughly 1 billion years after the big bang, at a redshift z~6. However, it is unclear whether such galaxies actually had sufficient ionizing escape fractions, as direct measurements are impossible due to the neutral intergalactic medium at this epoch. Indirect measurements of the HI gas covering fraction via low-ionization interstellar (LIS) absorption lines offers a promising means to constrain the escape fraction. While reionization-era galaxies are typically too faint for absorption line measurements, I use stacking analysis of JWST/NIRSpec data to determine the LIS absorption properties of galaxies at z>6, representing the first such measurements in the epoch of reionization. I will also discuss complementary measurements of the interstellar gas content of faint z~7 galaxies from ALMA observations.