The problem of sulfur abundance determination in gaseous nebulae

Abstract

The problem of the ionization equilibrium and the abundance determination of sulfur is discussed. It is found that the commonly used ionization-correction-factor procedure can overestimate the S(3+) abundance by a factor of about 10 for most planetary nebulae and usually more than 3 for H II regions. A method for deriving S(3+) abundance in medium- and high-excitation objects is presented and applied to 41 planetary nebulae in order to get total sulfur abundances. The derived average value is log (S/H) + 12 = 6.8 + or - 0.28.