The Gaia-ESO Survey: Galactic evolution of sulphur and zinc
  Due to their volatile nature, when sulfur and zinc are observed in external
galaxies, their determined abundances represent the gas-phase abundances in the
interstellar medium. This implies that they can be used as tracers of the
chemical enrichment of matter in the Universe at high redshift. Comparable
observations in stars are more difficult and, until recently, plagued by small
number statistics. We wish to exploit the Gaia ESO Survey (GES) data to study
the behaviour of sulfur and zinc abundances of a large number of Galactic
stars, in a homogeneous way. By using the UVES spectra of the GES sample, we
are able to assemble a sample of 1301 Galactic stars, including stars in open
and globular clusters in which both sulfur and zinc were measured. We confirm
the results from the literature that sulfur behaves as an alpha-element. We
find a large scatter in [Zn/Fe] ratios among giant stars around solar
metallicity. The lower ratios are observed in giant stars at Galactocentric
distances less than 7.5 kpc. No such effect is observed among dwarf stars,
since they do not extend to that radius. Given the sample selection, giants and
dwarfs are observed at different Galactic locations, and it is plausible, and
compatible with simple calculations, that Zn-poor giants trace a younger
population more polluted by SN Ia yields. It is necessary to extend
observations in order to observe both giants and dwarfs at the same Galactic
location. Further theoretical work on the evolution of zinc is also necessary.
