A Local View of Stellar Astrophysics in the Early Universe

Energetic feedback from low-metallicity massive stars regulates the evolution of low-mass galaxies, both nearby and in the early Universe. To understand those processes requires robust models of massive star formation, evolution, and ionizing photon production at low metallicity. Yet, these models remain largely theoretical and uncertain due to a lack of observational constraints in metal-poor galaxies close enough that individual stars and star-forming gas can be spatially resolved.

I will present new insights into the astrophysics of metal-poor stars in the nearby Universe using HST far-ultraviolet and ground-based optical spectroscopy of individual massive stars. Atmosphere models fit to these observations favor weaker winds than predicted by widely adopted theoretical wind recipes at very low metallicities. I will then describe the recent discovery of molecular gas in a 3% Solar metallicity star-forming galaxy with JWST, which provides a novel constraint on the nature of the metal-poor gas from which stars formed in the early Universe. These detailed observations that can only be made in very nearby dwarf galaxies are essential to guide the massive-star models that are required to interpret observations of distant, metal-poor galaxies and their impact on the evolution of the early Universe.

Biography: Grace's research focus is on the interplay between star formation, stellar feedback, and galaxy evolution, particularly under the conditions typical in both low-mass galaxies and young galaxies in the early universe that are too distant to study in detail. Grace observes individual stars and the interstellar medium in nearby galaxies using telescopes on the ground and in space, and models those observations to characterize massive stars and how they impact their host galaxies' evolution. (Credit: https://www.physics.utah.edu/research/astronomy/)