AAS 196th Meeting, June 2000
Session 29. Dwarf Galaxies, Galaxy Structure and Kinematics
Display, Tuesday, June 6, 2000, 10:00am-6:30pm, Empire Hall South

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[29.02] Abundance Patterns of Nearby Dwarf Spheroidal Galaxies

M.D. Shetrone (University of Texas, McDonald Observatory), P. Cote, W.L.W. Sargent (California Institute of Technology)

We have observed 14 giants in the Draco, Sextans and Ursa Minor dwarf spheroidal galaxies using HIRES on the Keck I telescope. Detailed abundances are derived for these giants and are compared with the Milky Way halo and globular cluster abundances. We find 3 giants with significantly unusual abundances. Two of these Draco J and Ursa Minor K have strong C2 bands indicating they are carbon stars. Ursa Minor 199 and Ursa Minor K have rare earth abundance patterns suggesting they are r-process enhanced.

Excluding these 3 giants the abundance patterns found in the dwarf spheroidals match the canonical Population II abundance patterns found in the halo. Metallicities range from -1.5 to -3.0. The \alpha-elements are enhanced relative to the iron peak elements. The [Cr/Fe] abundances decline with decreasing metallicity, and the s-process abundances drop rapidly at low metallicities.

This work was based on observations obtained at the W.M. Keck Observatory, which is operated jointly by the California Institute of Technology and the University of California. We are grateful to the W.M. Keck Foundation for their vision and generosity. PC acknowledges support provided by the Sherman M. Fairchild Foundation. WLWS was supported by grant AST 99-00733 from the National Science Foundation.

The author(s) of this abstract have provided an email address for comments about the abstract: shetrone@astro.as.utexas.edu

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