Friday, November 13, 2026 at 12:15 pm

JILA Foothills Room

Loraine Sandoval Ascencio ,

"Caught in Transition: Tracing the Evolution of Ultra-Diffuse Galaxies"

Abstract:

Ultra-diffuse galaxies (UDGs) are low-surface-brightness systems with unusually large sizes whose formation and evolution remain poorly understood. Observationally, star-forming UDGs are typically found in relatively isolated environments, whereas quiescent UDGs are preferentially located in groups and clusters. However, it remains unclear whether quenching in UDGs requires environmental processes or can also occur in isolation. In this talk, I will present spectroscopic observations of 44 UDG candidates from the Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) survey using the Keck Cosmic Web Imager (KCWI). Spectroscopic redshifts confirm that approximately 80% of the sample are true UDGs. Among these galaxies, we identify a subset exhibiting post-starburst spectral features, indicating a recent episode of star formation followed by its rapid suppression. Interestingly, nearly half of these post- starburst UDGs are found in relatively isolated environments, suggesting that environmental processes may not fully explain their recent suppression of star formation. I will also discuss follow-up neutral hydrogen (HI) observations with the Green Bank Telescope, which allow us to investigate whether these galaxies have depleted their star-forming fuel or retain substantial atomic gas reservoirs despite their recently suppressed star formation. Together, these observations provide new insights into the diverse evolutionary pathways of UDGs and the mechanisms responsible for quenching in low- mass galaxies.

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