VLT/FLAMES high-resolution chemical abundances in Sculptor: a textbook
  dwarf spheroidal galaxy
  We present detailed chemical abundances for 99 red-giant branch stars in the
centre of the Sculptor dwarf spheroidal galaxy, obtained from high-resolution
VLT/FLAMES spectroscopy. This includes abundances of Li (detected in 1 out of
99 stars), Na, $\alpha$-elements (O, Mg, Si, Ca Ti), iron-peak elements (Sc,
Cr, Fe, Co, Ni, Zn), r- and s-process elements (Ba, La, Nd, Eu). The sample,
covering -2.3< [Fe/H]<-0.9, populates the whole metallicity distribution of the
galaxy with the exception of the very low metallicity tail. There is a marked
decrease in [$\alpha$/Fe] over our sample, from the Galactic halo plateau value
at low [Fe/H] and then, after a `knee', a decrease to sub-solar [$\alpha$/Fe]
at high [Fe/H]. This is consistent with products of core-collapse supernovae
dominating at early times, followed by the onset of supernova type Ia as early
as 12 Gyrs ago. The products from low-mass asymptotic giant branch stars, as
traced by the s-process, also participate in the chemical evolution of Sculptor
with a timescale comparable to that of supernovae type Ia. The r-process is
consistent with having no time delay relative to core-collapse SN at the later
stages of the chemical evolution in Sculptor. We derive empirical constraints
on the relative importance of supernovae type II and Ia to the nucleosynthesis
of individual iron-peak and $\alpha$-elements. The most important contribution
of supernovae type Ia is to the iron-peak elements: Fe, Cr and Mn; but there is
also a modest but non-negligible contribution to both the heavier
$\alpha$-elements: S, Ca and Ti, and some of the iron-peak elements: Sc and Co.
We see only 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.
