Spatiokinematical models of five planetary nebulae

Abstract

The [O III] and Hα expansion velocity fields in the planetary nebulae NGC 6058 and 6804 and the [O III], Hα and [N II] expansion velocity fields in NGC 6309, 6751 and 6818, were obtained from high dispersion spectra. We have derived spatiokinematical models of the nebulae assuming an expansion velocity of the gas proportional to the distance from the central star and using the expansion velocity–radius correlation given by Sabbadin et al. (1984b). The observational parameters of the nebulae (radius, mass and expansion velocity) and of the exciting stars (temperature, radius and luminosity) closely fit the evolutionary model suggested by Sabbadin et al. for this class of objects. NGC 6818 is an optically thick nebula in a rather early evolutionary phase, NGC 6309, 6751 and 6804 are thick nebulae close to the transition from thick to thin; NGC 6058 is an evolved planetary nebula in the thin phase.