Accurate Atomic Transition Probabilities in Aid of APOGEE and the Study of Galactic Chemical Evolution

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

Spectroscopy of metal-poor stars – very old stars deficient in elements heavier than helium – is one of the most important means to study the origin of chemical elements in the Milky Way. This research project will primarily generate high quality laboratory measurements of infrared (IR) atomic spectra and transition probabilities that will enable the Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectroscopic survey to accurately determine elemental abundances in metal-poor stars residing in the dusty bulge of the Milky Way. This will allow astronomers to better understand the sites and processes of nucleosynthesis and the chemical enrichment history of the Galaxy. Data generated in this project will also be useful for observations undertaken with the next generation of large IR telescopes. This project will provide opportunities for undergraduate students to be involved in advanced spectroscopic research, as well as opportunities for community engagement with local elementary school teachers and high school students. Using advanced experimental techniques, the research team of the Wisconsin Atomic Transition Probability program (WATP) will measure high resolution near IR spectra of lanthanide and Fe-group elements, and optical and ultraviolet (UV) spectra of key lanthanide elements. This will permit determination of accurate, absolute atomic transition probabilities. WATP personnel are collaborating with some of the leading experts in the study of metal-poor stars, and this project represents the beginning of a focused effort to measure transition data in the near IR wavelength range, specifically targeting several measurements in the H-band, in aid of the large APOGEE survey. The data generated by this project will improve the ability of APOGEE to a) determine the important parameter log(g), or stellar surface gravity, b) discriminate between predominantly r(apid)-process and predominantly s(low)-process n(eutron)-capture nucleosynthesis sites, and c) determine more reliable abundances of several Fe-group species. In addition to these near IR studies, this project will generate optical and UV measurements of important n-capture lanthanide elements. The methods of quantitative atomic spectroscopy developed and applied in this project are also expected to benefit other fields such as analytical chemistry. 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.