Galaxies Science Interest Group Seminar, May 6, 2026
6 May 2026
Advancements in Exploring the Early Universe: Unlocking the Mysteries of Galaxies During the First Billion Years
Speaker: Rebecca Larson | STSci
Abstract:
The history of galaxies in the early Universe remains substantially unknown. The mystery surrounding these galaxies is primarily due to the epoch in which they existed. During the epoch of reionization (z>6), the Universe experienced its last major phase change, where the neutral gas permeating the intergalactic medium [IGM] became ionized. Light emitted by early galaxies was often blocked by this neutral gas (or "cosmic fog"), preventing rest-frame ultraviolet [UV] spectroscopic studies of this epoch, except for faint traces detectable in the near-infrared [NIR] from the brightest sources. Before 2022, the high-redshift field was limited by the availability of ground- and space-based instrumentation probing NIR wavelengths and beyond. Much of what we learned spectroscopically about these galaxies during this time came from a handful of bright UV metal emission lines or far-infrared [FIR] emission (generally with only 1-2 lines detected in individual galaxies). These data came only after hours of fighting with the most massive telescopes on the ground and in space.
Since the advent of JWST, the high-redshift field has exploded with new science probing wavelengths and redshifts previously inaccessible. Using the advanced spectroscopic NIR capabilities of the JWST, we have found increasingly distant galaxies and characterized these sources within the heart of the epoch of reionization [EoR] for the first time. In this talk, I will discuss the state of the high-redshift field before and after the launch of JWST -- highlighting our work from the Cosmic Evolution and Early Release Science [CEERS] survey, among other key early release science [ERS] & Cycle 1-3 programs. These new data have led to the discovery of an unexpected abundance of bright galaxies and active galactic nuclei [AGN] in the EoR and before, pushing detailed studies of galaxies into the first 500Myr after the Big Bang.