Nebular Density Distributions; A Critical Look

Abstract

The symmetry of planetary nebulae demands an explanation. Underlying previous attempts to explain these objects is the inferred density distribution based on spatio-kinematic models such as those of Weedman (1968), Reay et al. (1983) and others. Although some observations suggest a linear velocity-radius relationship for planetaries, plausible hypothetical examples may be constructed which greatly violate a linear relationship, and hydrodynamic theory (Schmalz 1986) suggests it may not hold even when observations may be most easily interpreted as supporting a linear relationship. Therefore, an independent assessment of the nebular density distribution is needed.