Astron. Astrophys. Suppl. Ser. 145, 467-472
Dredge-up effects in galactic and magellanic
R.D.D. Costa1 - J.A. de Freitas Pacheco2 - T.P.
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1 - Instituto Astronômico e Geofísico, Av. Miguel Stéfano
4200, 04301-904 São Paulo, Brazil
Observatoire de la Côte d'Azur, BP. 4229, 06304 Nice Cedex 4, France
Received February 14; accepted June 29, 2000
Chemical abundances are reported for 23 planetary nebulae
in the Small Magellanic Cloud. Average abundances agree with values found
for HII regions, suggesting that progenitors of most of these objects have
been formed in the last 1-2 Gyr. The N/O vs. O/H anticorrelation is
confirmed for Magellanic and galactic planetaries, and a more robust
result is obtained if objects of similar ages (or masses) are grouped
together. For a given class, such a negative correlation suggests that the
surface enrichment due to dredge-up episodes is more efficient at lower
metallicities, in agreement with recentcomputations.
Key words: galaxies: Magellanic Clouds, abundances -- Planetary Nebulae
Copyright The European Southern Observatory (ESO)
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