NOAO >   Observing Info >   Approved Programs >   2013A-0306

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Proposal Information for 2013A-0306


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

CoI: R. Michael Rich, University of California, Los Angeles
CoI: Catherine Pilachowski, Indiana University
CoI: Christopher Sneden, University of Texas--Austin

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 obtain WIYN-Hydra Echelle spectra for >20 RGB stars in the GCs NGC 6712 ([Fe/H]=-1) and NGC 6342 ([Fe/H]=-0.55). 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. The final data set, which already includes WIYN- Hydra observations of the bulge GCs NGC 6333 and 6366, will contain 12 bulge GCs with [Fe/H]=-1.8 to -0.3 and span a variety of horizontal branch morphologies.


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 >   2013A-0306

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