Sulphur in the Sculptor dwarf spheroidal galaxy - Including NLTE
  corrections
  In Galactic halo stars, sulphur has been shown to behave like other
$\alpha$-elements, but until now, no comprehensive studies have been done on
this element in stars of other galaxies. Here, we use high-resolution ESO
VLT/FLAMES/GIRAFFE spectra to determine sulphur abundances for 85 stars in the
Sculptor dwarf spheroidal galaxy, covering the metallicity range $-2.5\leq
\text{[Fe/H]} \leq-0.8$. The abundances are derived from the S~I triplet at
9213, 9228, and 9238~\AA. These lines have been shown to be sensitive to
departure from local thermodynamic equilibrium, i.e. NLTE effects. Therefore,
we present new NLTE corrections for a grid of stellar parameters covering those
of the target stars. The NLTE-corrected sulphur abundances in Sculptor show the
same behaviour as other $\alpha$-elements in that galaxy (such as Mg, Si, and
Ca). At lower metallicities ($\text{[Fe/H]}\lesssim-2$) the abundances are
consistent with a plateau at $\text{[S/Fe]}\approx+0.16$, similar to what is
observed in the Galactic halo, $\text{[S/Fe]}\approx+0.2$. With increasing
[Fe/H], the [S/Fe] ratio declines, reaching negative values at
$\text{[Fe/H]}\gtrsim-1.5$. The sample also shows an increase in [S/Mg] with
[Fe/H], most probably because of enrichment from Type Ia supernovae.
