Abundances of the volatile elements S and Zn have now been measured in around 80 individual stars in the Sculptor dwarf spheroidal galaxy , covering the metallicity range -2.4 \leq \text { [ Fe / H ] } \leq - 0.9 .
These two elements are of particular interest as they are not depleted onto dust in gas , and their ratio , [ S/Zn ] , has thus commonly been used as a proxy for [ \alpha /Fe ] in Damped Lyman- \alpha systems ( DLAs ) .
The S abundances in Sculptor are similar to other \alpha -elements in this galaxy , consistent with S being mainly created in core-collapse supernovae , but also having some contribution from type Ia supernovae .
However , our results show that Zn and Fe do not trace all the same nucleosynthetic production channels .
In particular , ( contrary to Fe ) Zn is not significantly produced by type Ia supernovae .
Thus , [ S/Zn ] can not be reliably used as a proxy for [ \alpha /Fe ] .
We propose [ O/S ] as a function of [ S/H ] as a possible alternative .
At higher metallicities , the values of [ S/Zn ] measured in DLAs are inconsistent with those in local dwarf galaxies , and are more compatible with the Milky Way disk .
Low-metallicity DLAs are , however , consistent with the most metal-poor stars in Local Group dwarf spheroidal galaxies .
Assuming that the dust depletions of S and Zn are negligible , our comparison indicates that the star formation histories of DLAs are on average different from both the Milky Way and the Sculptor dwarf spheroidal galaxy .