Sulfur, Chlorine, and Argon in Planetary Nebulae. I. Observations and Abundances in a Northern Sample

Abstract

This paper is the first of a series specifically studying the abundances of sulfur, chlorine, and argon in type II planetary nebulae (PNe) in the Galactic disk. Ratios of S/O, Cl/O, and Ar/O constitute important tests of differential nucleosynthesis of these elements and serve as strict constraints on massive star yield predictions. We present new ground-based optical spectra extending from 3600-9600 A for a sample of 19 type II northern PNe. This range includes the strong near-infrared lines of [S III] λλ9069,9532, which allows us to test extensively their effectiveness as sulfur abundance indicators. We also introduce a new, model-tested ionization correction factor for sulfur. For the present sample, we find average values of S/O = 1.2 × 10-2 ± 0.71 × 10-2, Cl/O = 3.3 × 10-4 ± 1.6 × 10-4, and Ar/O = 5.0 × 10-3 ± 1.9 × 10-3.