Collaborative Research: Characterizing Metal-Poor Stars in the APOGEE Survey

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A survey being conducted at the Apache Point Observatory known as APOGEE has, over the last decade, collected thousands of spectra of stars in the Milky Way. This legacy data set is used for many purposes. A team from San Francisco State University and the University of California Santa-Cruz will now use the data to look for a type of very old star known as “metal poor”. These very small stars are mostly made of hydrogen and helium, and contain almost no larger atoms. They are important because they formed when the Milky Way – and indeed the universe – was very young. These stars can therefore be used to study our galaxy just after it was formed. The team expects to find over 300 metal-poor stars from all over the Milky Way in the APOGEE data. They will re-observe these stars using the Lick and Keck telescopes to learn more about the stars themselves and the history of the Milky Way. The data collected will be used by students from both San Francisco State University and the University of California at Santa Cruz, a Hispanic-Serving Institution. Two major outreach programs, Astronomers for Planet Earth and La Noche Plus, will also be pursued. The former educates the public on climate change, while the latter brings families from Latinx-dominated high schools to Lick Observatory for observing sessions. New educational videos will also be developed.The project will find, analyze, and conduct follow-up observations of over 300 metal-poor star candidates that have been observed in the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. The team will determine stellar parameters and abundances of various elements using follow-up observations at Lick and Keck. The chemical compositions of metal-poor stars reflect the earliest stages of nucleosynthesis and galaxy assembly. The near-infrared APOGEE data allow the team to probe regions in the Milky Way that are not as accessible in the optical, such as the bulge. Characterizations of the numbers and properties of metal-poor stars in different regions of the galaxy are essential for understanding the assembly history of the Milky Way.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.