15/03/2006 – 14h – Auditório Principal, Bloco G – IAG/USP

Denise Rocha Gonçalves

IAG/USP

Título/Title: Photo modeling of PNe: Unveiling wrong assumptions of usual empirical analysis

Resumo/Abstract:

How well do we know the chemical properties of planetary nebulae (PNe)? I will discuss this issue, first, commenting on the empirical ICF abundances of a dozen Galactic PNe, computed from spatially resolved long-slit data, and showing that they give important information of these objects, even though with large uncertainties.

Second, describing our recent results (Gonçalves et al. 2006) which strongly suggest that the apparent enhanced nitrogen abundance previously reported in FLIERs of PNe is due to ionization effects. What we pointed out with this study is that a realistic density distribution is essential to the modeling of a non-spherical object, if useful information is to be extracted from spatially resolved observations. The erroneous N/H previously obtained used to be interpreted as an evidence that FLIERs originate from recent high-velocity ejections of the PN central star, perhaps hiding the true nature of these structures.

Finally, it should be noted that the empirical ICF abundance diagnosis are used not only to the analysis of PNe, but also for other ionized nebula, for which less constraints are generally available. For this reason it is of vital importance to verify the reliability of the currently used techniques for the determination of abundances.

 

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