High resolution spectra of 34 halo population dwarf and subgiant stars have been obtained with VLT/UVES and used to derive sulphur abundances from the \lambda \lambda 8694.0 , 8694.6 and \lambda \lambda 9212.9 , 9237.5 S i lines .
In addition , iron abundances have been determined from 19 Fe ii lines and zinc abundances from the \lambda \lambda 4722.2 , 4810.5 lines .
The abundances are based on a classical 1D , LTE model atmosphere analysis , but effects of 3D hydrodynamical modelling on the [ S/Fe ] , [ Zn/Fe ] and [ S/Zn ] ratios are shown to be small .
We find that most halo stars with metallicities in the range -3.2 < \mbox { [ Fe / H ] } < -0.8 have a near-constant \mbox { [ S / Fe ] } \simeq + 0.3 ; a least square fit to [ S/Fe ] vs. [ Fe/H ] shows a slope of only -0.04 \pm 0.01 .
Among halo stars with -1.2 < \mbox { [ Fe / H ] } < -0.8 the majority have \mbox { [ S / Fe ] } \simeq + 0.3 , but two stars ( previously shown to have low \alpha /Fe ratios ) have \mbox { [ S / Fe ] } \simeq 0.0 .
For disk stars with \mbox { [ Fe / H ] } > -1 , [ S/Fe ] decreases with increasing [ Fe/H ] .
Hence , sulphur behaves like other typical \alpha -capture elements , Mg , Si and Ca .
Zinc , on the other hand , traces iron over three orders of magnitude in [ Fe/H ] , although there is some evidence for a small systematic Zn overabundance ( \mbox { [ Zn / Fe ] } \simeq + 0.1 ) among metal-poor disk stars and for halo stars with \mbox { [ Fe / H ] } < -2.0 .
Recent measurements of S and Zn in ten damped Ly \alpha systems ( DLAs ) with redshifts between 1.9 and 3.4 and zinc abundances in the range -2.1 < \mbox { [ Zn / H ] } < -0.15 show an offset relative to the [ S/Zn ] – [ Zn/H ] relation in Galactic stars .
Possible reasons for this offset are discussed , including low and intermittent star formation rates in DLAs .