Astronomy and Astrophysics, volume 626A, 15-15 (2019/6-1)
VLT/FLAMES high-resolution chemical abundances in Sculptor: a textbook dwarf spheroidal galaxy.
HILL V., SKULADOTTIR A., TOLSTOY E., VENN K.A., SHETRONE M.D., JABLONKA P., PRIMAS F., BATTAGLIA G., DE BOER T.J.L., FRANCOIS P., HELMI A., KAUFER A., LETARTE B., STARKENBURG E. and SPITE M.
Abstract (from CDS):
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 ∼12Gyr 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]>-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 ∼12Gyr ago.
© V. Hill et al. 2019
stars: abundances - galaxies: abundances - galaxies: evolution - galaxies: dwarf - galaxies: individual: Sculptor - Local Group
VizieR on-line data:
<Available at CDS (J/A+A/626/A15): tablec1.dat tablec2.dat tablec3.dat tablec4.dat tablec5.dat>
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