Dr. Brodie and her team study globular clusters of stars, which are more complicated objects than previously thought. These relatively isolated, self-gravitating systems are partially shielded from the many factors such as mergers, feedback, and energetic flows of baryons, which affect the formation and assembly of galaxies. Thus these objects traditionally were regarded as representative of simple stellar populations which consist of stars with a single age and metallicity. Under this assumption, globular cluster properties were used to place constraints in a variety of contexts such as calibrations for stellar population models, chronometers of the early history of the universe, and luminous fossils of galaxy formation. However, even while isolated, there are internal processes, such as self-enrichment in chemical elements, which influence the evolution of globular clusters. The goal of this work is understand how and why globular clusters deviate from the ideal of being simple stellar populations with a single age and metallicity. This program studies of both extragalactic and Galactic globular clusters, and integrates chemical and dynamical constraints obtained from observation and theoretical modeling. Photometric and spectroscopic observations of individual globular clusters with the Multiple-Mirror Telescope (MMT), and the Keck and Magellan telescopes are used to derive quantities such as the mass-to-light ratios and abundance anomalies, and to investigate factors such as age, metallicity, initial mass function, dynamical evolution, and feedback from evolved stars in the clusters. The major effort is to develop a unified scenario for self-enrichment among massive star clusters; to better understand the stellar content of globular clusters through dynamical and stellar population investigations; and to study the relationship between globular clusters and galaxies at the extreme upper limit of the globular clusters mass function. The properties of globular clusters have wide implications in astrophysics; inferences drawn from stellar populations in globular clusters inform theories of the formation and evolution of stars. These in turn have implications on issues such as the assembly histories of galaxies and the distribution of dark matter within galaxies. This research supports the training of a postdoctoral researcher. The research team has an ongoing partnership with the national, non-profit educational organization called Science Buddies, which is an online resource for K-12 science projects. Results from the research here will be incorporated into age-appropriate, hands-on learning activities (primarily through science fairs) to inspire further study and encourage taking careers in science.

National Science Foundation (NSF)
Division of Astronomical Sciences (AST)
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James Neff
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University of California Santa Cruz
Santa Cruz
United States
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