Chemical abundances and physical conditions in planetary nebulae

Photoelectric scanner observations have been made of the intensities of a number of emission lines between lambda 3400A and lambda 7400A in thirty planetary nebulae. The electron temperatures and densities implied by different forbidden line intensity ratios agree well for most nebulae, although there is evidence for large variations in three self-absorbed nebulae. The relative abundances of H, He, Ne, O, and, less reliably, N and S, were determined for thirty planetaries and for several planetaries observed by others. There is some evidence for a radial galactic abundance gradient in He, N, and possibly O and Ne. All nebulae (except the previously-studied planetary in the galactic halo and the one in the globular cluster M 15) have nearly the same abundances of O and Ne. (U.S.)