Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG), Universidade de São Paulo, Rua do Matão 1226, 05508-900, São Paulo SP, Brazil e-mail: [roberto;monica;maciel]@astro.iag.usp.br
Accepted: 24 April 2004
In this paper we report new observations and derive chemical abundances for a sample of 26 planetary nebulae (PN) located in the anticenter direction. Most of these nebulae are far away objects, located at Galactocentric distances greater than about 8 kpc, so that they are particularly useful for the determination of the radial gradients at large distances from the galactic center. A comparison of the present results with previously determined abundances suggests that the radial abundance gradients flatten out at distances larger than about 10 kpc from the center.
Key words: ISM: planetary nebulae: general / Galaxy: disk / ISM: abundances
Based on observations made at the European Southern Observatory (Chile) and Laboratório Nacional de Astrofísica (Brazil).
© ESO, 2004