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 , \alpha -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 \leq [ Fe/H ] \leq - 0.9 .
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 supernovae type Ia as early as \sim 12 Gyr 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 \alpha -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 \alpha -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 \text { [ 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 \sim 12 Gyr ago .