NOAO >   Observing Info >   Approved Programs >   2011B-0106

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Proposal Information for 2011B-0106


PI: Timothy Beers, Michigan State University, beers@pa.msu.edu
Address: Department of Physics and Astronomy, East Lansing, MI, 48824-1116, USA

CoI: Vinicius Placco, Universidade de Sao Paulo
CoI: Catherine Kennedy, Michigan State University
CoI: Silvia Rossi, Universidade de Sao Paulo
CoI: Norbert Christlieb, University of Heidelberg
CoI: Young Sun Lee, Michigan State University
CoI: Thirupathi Sivarani, Indian Institute of Astrophysics

Title: A Survey for Unrecognized Carbon-Enhanced Metal-Poor Stars in the Galaxy

Abstract: Carbon-Enhanced Metal-Poor (CEMP) stars are of great astrophysical interest for a host of reasons. Although the majority (80%) of such stars are known to be associated with mass-transfer events from a companion star that has evolved to the AGB stage (the CEMP-s stars), 20% of these stars do not exhibit enhanced s-process elements (the CEMP-no stars), and hence may be associated with a variety of other carbon-production mechanisms in the early Universe. A list of previously unidentified candidate CEMP stars from the Hamburg/ESO prism survey has been compiled, based on the strength of a new extended CH G-band index. Follow-up spectroscopy for a pilot sample of 132 candidates was obtained with SOAR; results show that the majority of candidates possess prominent carbon absorption features at 4300A. We propose to acquire additional spectroscopic data for this sample of CEMP candidates, using GMOS-S observations. This will enable the identification of new CEMP stars over a wide range of [Fe/H], which includes representatives of the inner- and outer-halo populations, as well as the metal-weak thick disk and thick disk. Metallicities and carbon abundances for such stars will serve as probes of the stellar populations in the Galaxy and its nearby satellites.


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