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Astron. Astrophys. 352, 297-307 (1999)

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The dust content of planetary nebulae: a reappraisal *

Grayna Stasiska 1 and Ryszard Szczerba 2

1 DAEC, Observatoire de Paris-Meudon, 92195 Meudon Cedex, France (grazyna@obspm.fr)
2 N. Copernicus Astronomical Center, Rabiaska 8, 87-100 Toru, Poland (szczerba@ncac.torun.pl)

Received 2 June 1999 / Accepted 4 October 1999

Abstract

We have performed a statistical analysis using broad band IRAS data on about 500 planetary nebulae with the aim of characterizing their dust content. Our approach is different from previous studies in that it uses an extensive grid of photoionization models to test the methods for deriving the dust temperature, the dust-to-gas mass ratio and the average grain size. In addition, we use only distance independent diagrams.

With our models, we show the effect of contamination by atomic lines in the broad band IRAS fluxes during planetary nebula evolution. We find that planetary nebulae with very different dust-to-gas mass ratios exist, so that the dust content is a primordial parameter for the interpretation of far infrared data of planetary nebulae. In contrast with previous studies, we find no evidence for a decrease in the dust-to-gas mass ratio as the planetary nebulae evolve. We also show that the decrease in grain size advocated by Natta & Panagia (1981) and Lenzuni et al. (1989) is an artefact of their method of analysis. Our results suggest that the timescale for destruction of dust grains in planetary nebulae is larger than their lifetime.

Key words: ISM: planetary nebulae: general – infrared: stars – stars: AGB and post-AGB – stars: circumstellar matter – radiative transfer

* Table 1 is only accessible in electronic form at the CDS via anonymous ftp to ftp://cdsarc.u-strasbg.fr//pub/cats/J/A+A/351/297 (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/352/297

Send offprint requests to: Grayna Stasiska (grazyna@obspm.fr)

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© European Southern Observatory (ESO) 1999

Online publication: November 23, 1999
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