Princeton University Star Formation/ISM Rendezvous (SFIR)

Low-metallicity massive stars shape the ISM and evolution of dwarf galaxies. Theory predicts that the evolution of these stars diverges significantly from their higher-metallicity counterparts, with important implications for stellar feedback and the drivers of cosmic reionization at high redshift. However, few observations of individual, metal-poor O stars exist to validate widely adopted models of stellar winds and ionizing photon production due to the large distance of even the closest galaxies more metal-poor than the Small Magellanic Cloud (20% Z_sun). I will present new HST/COS FUV spectra of three late-type O dwarf stars in the metal-poor galaxies WLM (14% Z_sun), Sextans A (6% Z_sun), and Leo P (3% Z_sun). These data reveal that the two most metal-poor stars are both driving weak stellar winds and are rotating faster than 290 km/s, which suggest longer lifetimes and higher ionizing photon production than standard stellar model predictions. I will then present new Keck/KCWI optical IFU spectroscopy of the HII region being powered by the only O star in Leo P and compare the observed nebular emission to the expectations from purely theoretical ionizing stellar spectra. These rare observations of metal-poor O stars enable a unique test of stellar models that are essential to model feedback processes in dwarf galaxies, both locally and in the early universe.