Local Dwarf Galaxies as Laboratories to Understand Massive Stars and the ISM in the Early Universe
Grace Telford (Princeton University)

Feedback from low-metallicity massive stars regulates the evolution of both dwarf and high-redshift galaxies. To understand those processes requires robust models of the metal-poor ISM in which stars form and of massive stars' winds and ionizing spectra. Yet, these models remain entirely theoretical and uncertain due to a lack of observational constraints in the extremely low-metallicity regime. In this talk, I will present a suite of JWST, HST, and Keck observations of the nearby 3% Solar metallicity galaxy Leo P. First, I will describe novel constraints on the wind properties and ionizing spectrum of the galaxy's only O-type star from modeling HST/COS and Keck/KCWI spectroscopy. This star is part of the Treasury of Extremely Metal-Poor O Stars (TEMPOS), a Large Treasury HST program that will extend this initial analysis to a much larger sample at ~5-10% Solar metallicity. I will then present new JWST/MIRI-MRS observations of Leo P, which enabled the first detection of cold molecular hydrogen at such low metallicity via rotationally excited emission from the photodissociation region illuminated by the O star. Our detailed understanding of that star's UV radiation from the HST data constrains the temperature and mass of the detected molecular hydrogen, providing a benchmark for models of the ISM at the very low metallicities typical at high redshift. Leo P showcases the potential of the metal-poor dwarf galaxies in our backyard to inform models of early galaxies.

Local Dwarf Galaxies as Laboratories to Understand Massive Stars and the ISM in the Early Universe
Grace Telford (Princeton University)

Feedback from low-metallicity massive stars regulates the evolution of both dwarf and high-redshift galaxies. To understand those processes requires robust models of the metal-poor ISM in which stars form and of massive stars' winds and ionizing spectra. Yet, these models remain entirely theoretical and uncertain due to a lack of observational constraints in the extremely low-metallicity regime. In this talk, I will present a suite of JWST, HST, and Keck observations of the nearby 3% Solar metallicity galaxy Leo P. First, I will describe novel constraints on the wind properties and ionizing spectrum of the galaxy's only O-type star from modeling HST/COS and Keck/KCWI spectroscopy. This star is part of the Treasury of Extremely Metal-Poor O Stars (TEMPOS), a Large Treasury HST program that will extend this initial analysis to a much larger sample at ~5-10% Solar metallicity. I will then present new JWST/MIRI-MRS observations of Leo P, which enabled the first detection of cold molecular hydrogen at such low metallicity via rotationally excited emission from the photodissociation region illuminated by the O star. Our detailed understanding of that star's UV radiation from the HST data constrains the temperature and mass of the detected molecular hydrogen, providing a benchmark for models of the ISM at the very low metallicities typical at high redshift. Leo P showcases the potential of the metal-poor dwarf galaxies in our backyard to inform models of early galaxies.

Please join us for the SED Director’s Seminar. Hosted by the Exoplanets and Stellar Astrophysics Laboratory, Code 667!