Bibcode
Gonçalves, Denise R.; Ercolano, Barbara; Carnero, A.; Mampaso, A.; Corradi, R. L. M.; Barlow, M. J.
Bibliographical reference
Planetary Nebulae in our Galaxy and Beyond, Proceedings of the International Astronomical Union, Symposium #234. Edited by Michael J. Barlow and Roberto H. Méndez. Cambridge: Cambridge University Press, 2006., pp.405-406
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2006
Citations
1
Refereed citations
1
Description
We have recently (Gonçalves et al. 2006) shown that previously
reported enhanced N abundances in fast, low-ionization emission regions
(FLIERs) of PNe, particularly in NGC 7009, may be due to ionization
effects. We reached this conclusion through the 3D MOCASSIN
photoionization modeling of the bright inner rim of NGC 7009 and its
pair of FLIERs, assuming homogeneous elemental abundances throughout the
nebula, for N as well as other elements. The (N^+/N)/(O^+/O) ratio
predicted by our models is 0.60 for the rim and 0.72 for the knots,
clearly in disagreement with the N^+/N=O^+/O assumption of the
ionization correction factors (ICF) method. Therefore the ICFs are
underestimated in both components, rim and knots, but more so in the
knots. This effect is partly responsible for the apparent N
overabundance claimed for FLIERs.Based on the above results we are also
investigating what would be the effect of the N/O ICF overestimation on
the definition of Type I PNe which do not have FLIERs-like structures.