An empirical calibration of sulphur abundance in ionised gaseous nebulae

We have derived an empirical calibration of the abundance of S/H as a function of the S23 parameter, defined using the bright sulphur lines of [SII] and [SIII]. Contrary to what is the case for the widely used O23 parameter, the calibration remains single valued up to the abundance values observed in the disk HII regions. The calibration is based on a large sample of nebulae for which direct determinations of electron temperatures exist and the sulphur chemical abundances can be directly derived. ICFs, as derived from the [SIV] 10.52 μ emission line (ISO observations), are shown to be well reproduced by Barker’s formula for a value of α = 2.5. At any rate, only about 30 % of the objects in the sample require ICFs larger than 1.2. The use of the proposed calibration opens the possibility of performing abundance analysis with red to IR spectroscopic data using S/H as a metallicity tracer.