The Star Formation & Chemical Evolution History of the Sculptor Dwarf
  Spheroidal Galaxy
  We have combined deep photometry in the B,V and I bands from CTIO/MOSAIC of
the Sculptor dwarf spheroidal galaxy, going down to the oldest Main Sequence
Turn-Offs, with spectroscopic metallicity distributions of Red Giant Branch
stars. This allows us to obtain the most detailed and complete Star Formation
History to date, as well as an accurate timescale for chemical enrichment. The
Star Formation History shows that Sculptor is dominated by old ($>$10 Gyr),
metal-poor stars, but that younger, more metal-rich populations are also
present. Using Star Formation Histories determined at different radii from the
centre we show that Sculptor formed stars with an increasing central
concentration with time. The old, metal-poor populations are present at all
radii, while more metal-rich, younger stars are more centrally concentrated. We
find that within an elliptical radius of 1 degree, or 1.5 kpc from the centre,
a total mass in stars of 7.8$\times10^{6}$ M$_{\odot}$ was formed, between 14
and 7 Gyr ago, with a peak at 13$-$14 Gyr ago. We use the detailed Star
Formation History to determine age estimates for individual Red Giant Branch
stars with high resolution spectroscopic abundances. Thus, for the first time,
we can directly determine detailed timescales for the evolution of individual
chemical elements. We find that the trends in alpha-elements match what is
expected from an extended, relatively uninterrupted period of star formation
continuing for 6$-$7 Gyr. The knee in the alpha-element distribution occurs at
an age of 10.9$\pm$1Gyr, suggesting that SNe Ia enrichment began
$\approx2\pm$1Gyr after the start of star formation in Sculptor.
