Galaxies and Cosmology Seminar
Mar
9
2026
Mar
9
2026
Description
Michelle Jecmen, The University of Texas at Austin
A GLIMPSE into the UV Slopes of the Faintest Galaxies: Implications for Cosmic Reionization
The first structures in the universe produced enough ionizing photons to drive cosmic reionization. Since observations have yet to probe the faintest galaxies, it remains unclear whether bright or faint galaxies dominated this process. In this talk, I will present results from GLIMPSE, a JWST program which combines ultra-deep imaging with strong gravitational lensing to probe the faintest galaxies (MUV ~ -12) in the Epoch of Reionization. Over the past two years, I have analyzed the UV continuum slopes of 553 galaxies in GLIMPSE as a diagnostic of stellar populations and a tracer of Lyman continuum (LyC) escape. The faintest galaxies are a diverse population which do not exhibit the bluest UV slopes expected with high LyC escape fractions. Incorporating these constraints with other GLIMPSE results produces a reionization history consistent with independent constraints and suggests that galaxies with -18 < MUV < -14 emitted ~60% of the cosmic ionizing photons.
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