An empirical calibration of sulphur abundance in ionised gaseous nebulae

Abstract

We have derived an empirical calibration of the abundance of S/H as a function of the S{23} parameter, defined using the bright sulphur lines of [SII] and [SIII]. Contrary to the case for the widely used O{23} 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. 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.