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VLT/FLAMES high-resolution chemical abundances in Sculptor: a textbook dwarf spheroidal galaxy

MPS-Authors

Hill,  V.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Skúladóttir,  Á.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Tolstoy,  E.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Venn,  K. A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Shetrone,  M. D.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Jablonka,  P.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Primas,  F.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Battaglia,  G.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

de Boer,  T. J. L.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

François,  P.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Helmi,  A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Kaufer,  A.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Letarte,  B.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Starkenburg,  E.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

Spite,  M.
Max Planck Institute for Astronomy, Max Planck Society and Cooperation Partners;

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Citation

Hill, V., Skúladóttir, Á., Tolstoy, E., Venn, K. A., Shetrone, M. D., Jablonka, P., et al. (2019). VLT/FLAMES high-resolution chemical abundances in Sculptor: a textbook dwarf spheroidal galaxy. Astronomy and Astrophysics, 626.


Cite as: https://hdl.handle.net/21.11116/0000-0005-D0F8-8
Abstract
We present detailed chemical abundances for 99 red-giant branch stars in the centre of the Sculptor dwarf spheroidal galaxy, which have been obtained from high-resolution VLT/FLAMES spectroscopy. The abundances of Li, Na, α-elements (O, Mg, Si, Ca Ti), iron-peak elements (Sc, Cr, Fe, Co, Ni, Zn), and r- and s-process elements (Ba, La, Nd, Eu) were all derived using stellar atmosphere models and semi-automated analysis techniques. The iron abundances populate the whole metallicity distribution of the galaxy with the exception of the very low metallicity tail, -2.3 ≤ [Fe/H] ≤ -0.9. There is a marked decrease in [α/Fe] over our sample, from the Galactic halo plateau value at low [Fe/H] and then, after a "knee", a decrease to sub-solar [α/Fe] at high [Fe/H]. This is consistent with products of core-collapse supernovae dominating at early times, followed by the onset of supernovae type Ia as early as ̃12 Gyr ago. The s-process products from low-mass AGB stars also participate in the chemical evolution of Sculptor on a timescale comparable to that of supernovae type Ia. However, the r-process is consistent with having no time delay relative to core-collapse supernovae, at least at the later stages of the chemical evolution in Sculptor. Using the simple and well-behaved chemical evolution of Sculptor, we further derive empirical constraints on the relative importance of massive stars and supernovae type Ia to the nucleosynthesis of individual iron-peak and α-elements. The most important contribution of supernovae type Ia is to the iron-peak elements: Fe, Cr, and Mn. There is, however, also a modest but non- negligible contribution to both the heavier α-elements: S, Ca and Ti, and some of the iron-peak elements: Sc and Co. We see only a very small or no contribution to O, Mg, Ni, and Zn from supernovae type Ia in Sculptor. The observed chemical abundances in Sculptor show no evidence of a significantly different initial mass function, compared to that of the Milky Way. With the exception of neutron-capture elements at low [Fe/H], the scatter around mean trends in Sculptor for [Fe/H] &gt; -2.3 is extremely low, and compatible with observational errors. Combined with the small scatter in the age-elemental abundances relation, this calls for an efficient mixing of metals in the gas in the centre of Sculptor since ̃12 Gyr ago. Tables C.1-C.5 are only available at the CDS via anonymous ftp to <A href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A> (ftp://130.79.128.5) or via <A href="http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/626/A15">http://cdsarc.u-strasbg.fr/viz- bin/qcat?J/A+A/626/A15</A>Based on VLT/FLAMES observations collected at the European Organisation for Astronomical Research (ESO) in the Southern Hemisphere under programmes 71.B-0641 and 171.B-0588.