The Chemical Evolution of the Ursa Minor Dwarf Spheroidal Galaxy
Judith G. Cohen, Wenjin Huang

TL;DR
This study analyzes the chemical composition of stars in the Ursa Minor dwarf galaxy, revealing its star formation history and chemical evolution patterns, which differ from those of the Milky Way and other dwarf galaxies.
Contribution
It provides detailed abundance measurements for stars across a wide metallicity range in Ursa Minor, highlighting similarities to the Galactic halo at low metallicities and differences at higher metallicities.
Findings
Stars at low metallicity resemble Galactic halo stars in alpha-element ratios.
The galaxy's neutron-capture elements are dominated by the r-process across metallicities.
Star formation in Ursa Minor was shorter and more intense than in other dwarf galaxies.
Abstract
We present an abundance analysis based on high resolution spectra of 10 stars selected to span the full range in metallicity in the Ursa Minor dwarf spheroidal galaxy. We find [Fe/H] for the sample stars ranges from -1.35 to -3.10 dex and establish the trends of the abundance ratios [X/Fe]. In key cases, particularly for the alpha-elements, these resemble those for stars in the outer part of the Galactic halo, especially at the lowest metallicities probed. The n-capture elements show a r-process distribution over the full range of Fe-metallicity. This suggests that the duration of star formation in the UMi dSph was shorter than in other dSph galaxies. The derived ages for a larger sample of UMi stars with more uncertain metallicities also suggest a population dominated by uniformly old (~13 Gyr) stars, with a hint of an age-metallicity relationship. In comparing our results for UMi,…
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