Results appearing since the last APN meeting on the relation between abundances and PNe morphological features are reviewed here. Statistical analyses of round, elliptical, and bipolar PNe clearly separate the latter group as having larger He and N/O abundances. Studies of individual PNe, including the UV and IR domains, allow a detailed comparison with evolutionary models for the AGB phase; the abundances of the most important elements can be matched but an `age-metallicity' problem for the progenitors of He-rich PNe is implied. Halo abundances do not show strong chemical differences with respect to the PN rims, but the halos' faintness requires deeper data to confirm it. Data on the chemistry of microstructures of normal (non H-deficient) PNe are scarce and generally indicate similar abundances to those in the rims. The exception is the high nitrogen overabundance claimed for FLIERS; preliminary modeling on new observational data of the microstructures of NGC 7009 indicates that a moderate enrichment of nitrogen can be real.
Asymmetrical Planetary Nebulae III: Winds, Structure and the Thunderbird
- Pub Date:
- July 2004
- 7 pages including 1 table and 1 figure. Invited review given at Asymmetric Planetary Nebulae III, eds. M. Meixner, J. Kastner, N.Soker and B. Balick (ASP Conf. Ser.)