NOAO >   Observing Info >   Approved Programs >   2010B-0228

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Proposal Information for 2010B-0228


PI: Sarah Martell, Universitat Heidelberg, martell@ari.uni-heidelberg.de
Address: ZAH/ARI, Monchhofstrasse 12-14, Heidelberg, Baden-W\"{u}rttemberg 69120, Germany

CoI: Eva Grebel, ZAH/ARI, Universitat Heidelberg
CoI: David Lai, NSF Postdoctoral Fellow, UC Santa Cruz

Title: Globular Cluster Contributions to the Galactic Halo

Abstract: The goal of this project is to confirm chemically that globular clusters are the source of as much as half the population of the Galactic halo. Using moderate-resolution spectroscopy from the SEGUE survey, we have identified a previously unknown population of halo field giants with distinctly strong CN features. CN variations are typically only observed in globular clusters, so these stars are interpreted as immigrants to the halo that originally formed in globular clusters. In one night of Keck/HIRES time, we will obtain high-quality, high- resolution spectra for five such stars, and determine abundances of O, Na, Mg, Al, alpha, iron-peak and neutron-capture elements. With this information we can state clearly whether these unusual CN-strong halo stars carry the full abundance pattern seen in CN-strong globular cluster stars, with depleted C, O, and Mg and enhanced N, Na, and Al. This type of coarse ``chemical tagging'' will allow a clearer division of the Galactic halo into contributions from globular clusters and from dwarf galaxies, and will place constraints on theoretical models of globular cluster formation and evolution.


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 >   2010B-0228

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