A New Study of Some Galactic Planetary Nebulae
Expansion velocities ([O III], [O II], and He II) have been measured for a sample of 64 Southern Planetary Nebulae (PN). The ratio of [O III] to [O II] expansion velocities is used to derive a typical ionized shell thickness of order ΔR/Rneb ≈ 0.12. Nebular electronic densities have been determined from the [O II]λλ3727, 3729 A doublet for 23 of these objects. These data are compared with previously published values. The Dopita et al. (1987) distance scale for Magellanic Cloud PN based on a correlation between observable nebular parameters is used to derive distances to 32 Galactic nebulae. These distances are compared with published values, and lead to the conclusion that the Dopita et al., Daub (1982) and Maciel (1984) distance scales agree well, but that the Shklovsky (1956) method yields distances that are too large. Nebular ionized masses are also calculated for a subset of 30 objects.