Zinc in the Sculptor dwarf spheroidal galaxy

Abstract

From ESO VLT/FLAMES/GIRAFFE spectra, abundance measurements of Zn have been made in $\approx$100 individual red giant branch (RGB) stars in the Sculptor dwarf spheroidal galaxy. This is the largest sample of individual Zn abundance measurements within a stellar system beyond the Milky Way. In the observed metallicity range, $-2.7\leq\text{[Fe/H]}\leq-0.9$, the general trend of Zn abundances in Sculptor is similar to that of $\alpha$-elements. That is, super-solar abundance ratios of [Zn/Fe] at low metallicities, which decrease with increasing [Fe/H], eventually reaching subsolar values. However, at the higher metallicities in Sculptor, $\text{[Fe/H]}\gtrsim-1.8$, we find a significant scatter, $-0.8\lesssim\text{[Zn/Fe]}\lesssim+0.4$, which is not seen in any $\alpha$-element. Our results are consistent with previous observations of a limited number of stars in Sculptor and in other dwarf galaxies. These results suggest that zinc has a complex nucleosynthetic origin, behaving neither completely like an $\alpha$- nor an iron-peak element.