NOAO >   Observing Info >   Approved Programs >   2012A-0428

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Proposal Information for 2012A-0428


PI: Christian Johnson, University of California, Los Angeles, cijohnson@astro.ucla.edu
Address: Physics Department, 430 Portoloa Plaza, Box 951547, Los Angeles, CA 90095--1547, USA

CoI: R. Michael Rich, University of California, Los Angeles
CoI: Andrea Kunder, Cerro Tololo Inter--American Observatory

Title: Exploring the Population of Galactic Bulge Globular Clusters

Abstract: While the chemical composition of halo globular cluster (GC) stars has received renewed interest in the last ten years, the bulge GC system has not received the same attention. Very few chemical abundance determinations are available for these objects even though some age determinations suggest they may be at least 1 Gyr older than the average halo GC. Interestingly, many clusters host very extended blue horizontal branches despite their relatively high metallicities. With the limited data available, there is already some evidence that the bulge GCs exhibit unusual enhancements in certain abundance ratios and extraordinarily large dispersions in their neutron-capture element abundances. Additionally, these objects may yield insight into the formation conditions and timescales of the very early bulge. This is particularly important because metal-poor bulge field stars are relatively rare. In order to significantly increase the number of bulge GC stars analyzed via high-resolution spectroscopy, we are proposing to observe >20 RGB stars each in six different bulge GCs spanning a range of horizontal branch morphologies and [Fe/H]=-1.7 to -0.6, using the Hydra multi-fiber spectrographs on the Blanco 4m and WIYN 3.5m telescopes. These data will compliment our existing large sample survey of the bulge field population and allow for a direct comparison between field and GC stars at a given metallicity.


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