Collaborative Research: Beyond O/H: Fundamental Astrophysics with HII Region Abundances

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Galaxies contain gas and stars. The chemicals in the gas leave fingerprints in the form of emission lines. The chemical abundances can be measured by studying the emission lines. These studies show trends between the abundances and the stellar mass of a galaxy. They also show trends in the abundances between the inner and outer regions of a galaxy. Such trends carry important clues about how galaxies form and evolve. But the clues are muddled because the absolute scales for the trends are uncertain. To make progress, the team will observe galaxies at optical wavelengths with the Large Binocular Telescope. They will use a new, NSF-enabled instrument to study the galaxies' emission lines. The team will then analyze the emission lines to determine absolute abundances. Senior team members will train junior team members. The team will partner with the State Parks of Minnesota to give public talks in novel settings. They will also use a planetarium to reach K-12 students in low-income areas of Ohio.The team will analyze cutting-edge emission line spectra of HII regions in 13 spiral galaxies. Their goals are to (1) solve the decades-old discrepancy between abundances based on collisionally-excited forbidden lines and those based on optical recombination lines, (2) conduct a definitive study the abundance gradients in spiral galaxies, and (3) design a calibration of strong-line abundances appropriate to both unresolved global spectra and spatially-resolved spectra from the next generation of surveys with integral field units.