Cosmos Seminar: The UV Slopes of the Faintest, High-Redshift Galaxies with Glimpse
Event starts on this day
Apr
3
2025
Featured Speaker(s):
Michelle Jecmen - The University of Texas at Austin
Event starts on this day
Apr
3
2025
Cosmos Seminar
Description
The UV Slopes of the Faintest, High-Redshift Galaxies with Glimpse
The first structures in the universe produced enough ionizing photons to drive cosmic reionization. Since observations have yet to probe the faintest galaxies, it is still debated whether faint or bright galaxies produced the required ionizing photons. The rest-frame ultraviolet (UV) continuum slope (beta) is a critical diagnostic of star-forming galaxies and a key indicator of the escape of ionizing photons at high-redshift. We expand upon previous work with data from JWST’s Glimpse, a program leveraging ultra-deep imaging and strong gravitational lensing of massive foreground cluster Abell S1063 to probe the faintest and highest redshift galaxies. We calculate UV slopes of ~200 high-redshift (z > 6) galaxies with absolute magnitudes down to MUV ~ -11. We find that beta decreases with redshift and we uncover a turnover in the beta-MUV relation, where beta gets bluer until MUV ~ -16.5 and then becomes redder towards fainter galaxies. We estimate the Lyman continuum escape fraction (fesc) for each observed beta according to the empirical trend derived at low-redshift, finding fesc peaks at ~10% for these moderately bright galaxies (MUV ~ -16.5) with blue UV-slopes. We fit Bagpipes models which allow for a non-zero fesc to understand the origin and physical conditions which facilitate extremely blue UV-slopes. We provide new constraints on the ionizing photon budget from the faintest galaxies and discuss impacts for cosmic reionization.
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23
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