Models of planetary nebulae with dust

Abstract

Computer models have been constructed of planetary nebulae of 0.15 and 0.5 Msun total mass, containing varying amounts of absorption dust grains. In all cases the dust remained well mixed with the gas, and was responsible for the maintenance of a well-defined inner edge for the nebular shell. Once the nebula was ionized, the expansion in the outer regions accelerated due to pressure gradients, so that the observed mass decreased with time. The more massive nebulae were found to expand more slowly. Even when all of the Lα radiation was absorbed by grains, it was not as important for grain heating and acceleration as the direct stellar radiation. Agreement with several aspects of recent infrared observations was obtained.