Neutron-capture elements in dwarf galaxies II: Challenges for the s- and i-processes at low metallicity
| Autor: | Arthur Choplin, A. Skuladottir, Camilla Juul Hansen, Stefania Salvadori, Simon Campbell, Melanie Hampel |
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| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Physics
010308 nuclear & particles physics Metallicity Milky Way FOS: Physical sciences Astronomy and Astrophysics Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics 01 natural sciences Astrophysics - Astrophysics of Galaxies Dwarf spheroidal galaxy Stars 13. Climate action Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) 0103 physical sciences Galaxy formation and evolution Asymptotic giant branch CH star Astrophysics::Solar and Stellar Astrophysics Astrophysics::Earth and Planetary Astrophysics 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Dwarf galaxy |
| Popis: | The slow ($s$) and intermediate ($i$) neutron ($n$) capture processes occur both in asymptotic giant branch (AGB) stars, and in massive stars. To study the build-up of the $s$- and $i$-products at low metallicity, we investigate the abundances of Y, Ba, La, Nd, and Eu in 98 stars, at $-2.4+0.7$ is best fit with a model of a rapidly-rotating massive star, the second (likely CH star) with the $i$-process, while the third has no satisfactory fit. For a more general understanding of the build-up of the heavy elements, we calculate for the first time the cumulative contribution of the $s$- and $i$-processes to the chemical enrichment in Sculptor, and compare with theoretical predictions. By correcting for the $r$-process, we derive $\text{[Y/Ba]}_{s/i}=-0.85\pm0.16$, $\text{[La/Ba]}_{s/i}=-0.49\pm0.17$, and $\text{[Nd/Ba]}_{s/i}=-0.48\pm0.12$, in the overall $s$- and/or $i$-process in Sculptor. These abundance ratios are within the range of those of CEMP stars in the Milky Way, which have either $s$- or $i$-process signatures. The low $\text{[Y/Ba]}_{s/i}$ and $\text{[La/Ba]}_{s/i}$ that we measure in Sculptor are inconsistent with them arising from the $s$-process only, but are more compatible with models of the $i$-process. Thus we conclude that both the $s$- and $i$-processes were important for the build-up of $n$-capture elements in the Sculptor dwarf spheroidal galaxy. Comment: Accepted in A&A, 16 pages, 10 figures, Paper II in series |
| Databáze: | OpenAIRE |
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