Chemical Evolution of the Galaxy's Dwarf Satellites: Revising Observations Using NLTE Methods
Abstract
We review our recent abundance results for very metal-poor stars in seven dwarf spheroidal galaxies (dSphs) and in the Milky Way (MW) halo comparison sample that were obtained based on high-resolution spectroscopic datasets, homogeneous and accurate atmospheric parameters, and the NLTE line formation for 10 chemical species. We show that all massive galaxies (the MW halo and the classical dSphs Sculptor, Ursa Minor, Sextans, and Fornax) reveal a similar plateau at [α/Fe] ≃ 0.3 for each of the α-process elements: Mg, Ca, and Ti. The evidence is provided for a decline in α/Fe with increasing metallicity in the Boötes I ultra-faint dwarf galaxy (UFD) that is most probably due to the ejecta of SNeIa. In our classical dSphs, we observe the dichotomy in the [Sr/Ba] versus [Ba/H] diagram, similarly to the MW halo, calling for two different nucleosynthesis channels for Sr at the earliest evolution stages of these galaxies. The subsolar Sr/Ba ratios of Boötes I and UMa II indicate a common r-process origin of Sr and Ba.
- Publication:
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Modern Star Astronomy
- Pub Date:
- September 2018
- DOI:
- 10.31361/eaas.2018-1.050
- Bibcode:
- 2018msa..conf..228M
- Keywords:
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- NLTE METHODS