W. J. Maciel -
Abstract #103
PLANETARY NEBULAE AS A CHEMICAL EVOLUTION TOOL: ABUNDANCE GRADIENTS
W. J. Maciel, L. G. Lago, R. D. D. Costa
Planetary Nebulae as Astronomical Tools, ed. R. Szczerba, G. Stasinska, S. K. Gorny, AIP, 246-249 (2005) We have studied the time variation of the radial abundance gradients using samples of planetary nebulae, open clusters, cepheids and other young objects. Based on the analysis of O/H and S/H abundances for planetary nebulae and metallicities of the remaining objects, we concluded that the gradients have been flattening out in the last 8 Gyr with an average rate of the order of 0.005 - 0.010 dex/kpcGyr. We have estimated the errors involved in the determination of the gradients, and concluded that the existence of systematic abundance variations is more likely than a simple statistical dispersion around a mean value.
