Collaborative Research: PNe as Probes of the Early Chemical History of the Galaxy and M31

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In this collaborative effort, Drs Bruce Balick (University of Washington), Richard Henry (University of Oklahoma), and Karen Kwitter (Williams College) will complement extant studies of the least evolved and most extended stellar populations with observations of the metal-enriched gas ejected from early generations of stars in the Milky Way (the "Galaxy") and our nearest sibling neighbor galaxy, M31. The results will constrain and challenge extant models of how all galaxies evolved or merged into others. In addition, the means by which elements such as nitrogen and oxygen have been formed in dying stars will be determined by measuring the historical rates of their production. The data products will include databases of spectra and abundances of planetary nebulae (PNe) in all galactic environments, doubling the size of the present sample derived for of PNe near the Earth.The history of galaxy formation must be read from the shape, dynamics, and chemistry of its oldest and least evolved "fossil" stars. These stars are found throughout the extended, largely undisturbed outer regions of all galaxies, large and small. The chemistry and kinematics of these stars help to constrain the models for the early assembly of galaxies, the role of ongoing assimilation of dwarf galaxies, the ejections of younger stars into the old thick disk and halo, the feedback of heavy elements from the nucleus, supernovae, and AGB mass loss, the influence of dark matter, and the rates and size scales of the formation of structure in the early and highly chaotic universe. As a part of this research, new methods for analyzing the data and measuring chemical abundances will be developed for faint nebulae. These will have application throughout extragalactic astronomy in such areas as element production rates in very early supernovae and the chemical properties of distant quasars. In addition, all of the activities that will take place as a part of this research program have been conceived with the goal of providing research opportunities for undergraduate students, especially those students from underrepresented groups. The students will be direct participants in analyzing the data and developing creative interpretive ideas that form the core motivation for practicing science and research, and for understanding its role in modern society.