2022MNRAS.511.4377D

²⁺We present a methodology for the use of sulphur as global metallicity tracer in galaxies, allowing performing a complete abundance analysis using only the red-to-near-infrared spectral region. We have applied it to a compilation of high-quality data split into two samples: H II regions (DHR) in spiral and irregular galaxies, and dwarf galaxies dominated by a strong starburst (H II Gal). Sulphur abundances have been derived by direct methods under the assumption of an ionization structure composed of two zones: an intermediate-ionization one where S⁺⁺ is originated, and a low-ionization one where S⁺ is formed. Ionization correction factors (ICF) have been calculated from the Ar/Ar³⁺ratio and are shown to correlate with the hardness of the radiation field. Only about 10 per cent of the objects show S³⁺ contributions to the total abundance larger than 30 per cent. A good correlation exists between sulphur abundance and ionizing temperature with low-metallicity objects being ionized by hotter stars. No correlation is found between ionization parameter and total S/H abundance. Most of the H II Gal objects show S/O ratios below the solar value and a trend for increasing S/O ratios with increasing sulphur abundances, while DHR objects show S/O ratios larger than solar and a tendency for lower S/O ratios for higher metallicities. Finally, we present a calibration of the sulphur abundance through the S₂₃ parameter that remains single valued up to sulphur abundances well beyond the solar value. S₂₃ is independent of the ionization parameter and only weakly dependent on ionizing temperature.