Abundance Analyses of Extreme Metal-Poor Stars

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Date/Time:Friday, 06 Nov 2009 from 4:10 pm to 5:10 pm
Location:Physics Hall 3
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Sung-Ju Kang, Iowa State University

The chemical evolution of the Galaxy and the early Universe is a key topic in modern astrophysics. The most metal-poor Galactic halo stars are now frequently used in an attempt to reconstruct the onset of the
chemical and dynamical formation processes of the Galaxy. These stars are an easily-accessible local equivalent of the high-redshift Universe, and are used to carry out near-field cosmology. We present an abundance analysis of ~20 metal-poor stars selected from
the bright sample of the Hamburg/ESO survey. Three stars have Fe abundances of [Fe/H]<-3.0, the lowest one having [Fe/H]~-3.8, which allows us to probe the earliest times of the chemical history of the Galaxy. We find scaled solar abundances down to [Fe/H]=-3.8, in line with previous results that the ISM was well-mixed already at the earliest times. We also focus on particularly carbon-poor metal-poor stars to test a recent fine-structure line cooling theory for the
formation of the very first-low mass stars (M<1Msun) in the Universe. We find that our low carbon abundances thus far support this theory.