NOAO >   Observing Info >   Approved Programs >   2011A-0352

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Proposal Information for 2011A-0352


PI: Michael Briley, University of Wisconsin Oshkosh, mike@maxwell.phys.uwosh.edu
Address: Department of Physics and Astronomy, 800 Algoma Blvd., Oshkosh, WI 54956, USA

CoI: Graeme Smith, UC Observatories/Lick Observatory

Title: Deep Mixing in the Most Metal-Rich Globular Red Giants

Abstract: Over the past 30 years it has become apparent the Galactic globular clusters are not chemically homogeneous collections of stars. The observed abundance patterns in light elements (C, N, O, Na, Mg, and Al) continue to defy explanation although it has become clear we are seeing the effects of two process - a deep mixing of CNO-cycle material to the surface in evolving giants, and a primordial variation incorporated early in the cluster history. Here we focus on deep mixing, the efficiency of which is expected to be a function of metallicity. We have recently tested this using a handful of nearby clusters with the Lick 3-m and the results are promising. However, the high metallicity end of our sample (which includes new spectra obtained in June with the KPNO 4-m) is poorly constrained. Here we request SOAR time to secure Goodman spectrograph observations that will robustly establish the behavior of deep mixing at metallicities of \rm [Fe/H] > -0.7, which in turn will provide observational constraints on competing theories of the underlying mixing mechanism.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



NOAO >   Observing Info >   Approved Programs >   2011A-0352

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