SIMBAD references

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 Å 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=1.2x10^–2±0.71x10^–2, Cl/O=3.3x10^–4±1.6x10^–4, and Ar/O=5.0x10^–3±1.9x10^–3.