Largest dataset of its kind could clarify how massive stars shaped early galaxies

A new survey called TEMPOS, led by the University of Utah, has collected the largest dataset of its kind to study massive stars in nearby dwarf galaxies. The survey used Hubble's Cosmic Origins Spectrograph (COS) to observe 29 massive stars across six local dwarf galaxies with metallicities below one-fifth that of the sun. The dataset reveals how massive stars lose mass through stellar winds, with lower metallicity stars losing less mass and having weaker winds. The study found that as metallicity decreases, the maximum speed of the stellar winds decreases, but at the lowest metallicities, the wind speeds decline much more sharply. This suggests that extremely metal-poor stars may retain more of their original mass, affecting their evolution and how they shape their host galaxies.

The survey observed that massive stars in more oxygen-rich, high-metallicity galaxies tend to have much stronger iron absorption in their UV spectra than stars in oxygen-poor, low-metallicity galaxies. This variation in iron absorption strengths suggests that these metal-poor stars span a wide range of iron abundances. The study found that the trend in iron absorption strengths across a large sample of stars in six galaxies provides the first statistical power to see that trend in the low-metallicity regime. The findings could help astronomers build better models of massive stars to understand how they shaped galaxies when the universe was young.

The survey's results are significant because they offer insights into the evolution of massive stars and their role in shaping galaxies. The study's findings could help interpret observations from the James Webb Space Telescope, which launched in 2021. The TEMPOS dataset will be made publicly available through the Mikulski Archive for Space Telescopes, providing a resource for researchers to pursue additional questions about massive stars and their role in galaxy evolution. The study is part of a larger effort to understand the astrophysics operating in early galaxies and how massive stars contributed to their formation.

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