Journal
ASTRONOMY & ASTROPHYSICS
Volume 508, Issue 1, Pages L1-L4Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/200912833
Keywords
galaxies: individual: Bootes I; stars: abundances; galaxies: abundances; galaxies: dwarf; Local Group
Categories
Funding
- Knut and Alice Wallenberg Foundation
- Swedish Research Council
- Royal Society University Research Fellowship
- National Aeronautics and Space Administration
- National Science Foundation
- Science and Technology Facilities Council [ST/H00856X/1, PP/E00119X/1] Funding Source: researchfish
- STFC [ST/H00856X/1] Funding Source: UKRI
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Aims. We establish the mean metallicity from high-resolution spectroscopy for the recently found dwarf spheroidal galaxy Bootes I and test whether it is a common feature for ultra-faint dwarf spheroidal galaxies to show signs of inhomogeneous chemical evolution (e. g. as found in the Hercules dwarf spheroidal galaxy). Methods. We analyse high-resolution, moderate signal-to-noise spectra for seven red giant stars in the Bootes I dSph galaxy using standard abundance analysis techniques. In particular, we assume local thermodynamic equilibrium and employ spherical model atmospheres and codes that take the sphericity of the star into account when calculating the elemental abundances. Results. We confirm previous determinations of the mean metallicity of the Bootes I dwarf spheroidal galaxy to be -2.3 dex. Whilst five stars are clustered around this metallicity, one is significantly more metal-poor, at -2.9 dex, and one is more metal-rich at, -1.9 dex. Additionally, we find that one of the stars, Boo-127, shows an atypically high [Mg/Ca] ratio, indicative of stochastic enrichment processes within the dSph galaxy. Similar results have previously only been found in the Hercules and Draco dSph galaxies and appear, so far, to be unique to this type of galaxy.
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