W. J. Maciel -
Abstract #77
ABUNDANCE GRADIENTS IN THE OUTER GALACTIC DISK FROM PLANETARY NEBULAE
W. J. Maciel, C. Quireza
Astronomy and Astrophysics 345, 629-634 (1999) Radial abundance gradients of the element ratios O/H, Ne/H, S/H, and Ar/H are determined on the basis of a sample of disk planetary nebulae. The behaviour of the gradients at large distances from the galactic centre, R > Ro = 7.6 kpc, is emphasized. It is concluded that the derived gradients are consistent with an approximately constant slope in the inner parts of the Galaxy, and some flattening for distances larger than Ro. A comparison is made with previous determinations using both photoionized nebulae and young stars, and some consequences on theoretical models for the chemical evolution of the galactic disk are discussed.
