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Astron. Astrophys. 325, 269-276 (1997)

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IR emission from carbon-dust in nebulae

Cesare Cecchi-Pestellini 1, Luigi Colangeli 1, Vito Mennella 1, Pasquale Palumbo 2, Alessandra Rotundi 2 and Ezio Bussoletti 2

1 Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131 Napoli, Italy
2 Istituto di Fisica Sperimentale, Istituto Universitario Navale, via A. De Gasperi 5, I-80133 Napoli, Italy

Received 30 July 1996 / Accepted 10 March 1997

Abstract

The relevance of dust in circumstellar emission has to be carefully considered in order to properly interpret astronomical observations. In this work we focus on carbon-rich planetary nebulae in order to produce models able to account for IR and submillimeter dust emission. The effects of dust selective absorption on the ionization structure are investigated by means of dust opacities measured in laboratory experiments. The infrared spectrum emitted by dust present in both ionized and neutral circumstellar regions is calculated for various choices of the model parameters. The IR dust continuum emission in planetary nebula NGC 7027 is also modelled on the basis of a possible evolutionary scenario for carbon dust grains. Our results provide evidence that by means of UV dust processing it is possible to account for most of the spectral distribution of carbon-rich planetary nebulae. However, non-equilibrium emission is needed to explain near-IR bands and part of the underlying continuum.

Key words: ISM: dust – ISM: planetary nebulae

Send offprint requests to: C. Cecchi-Pestellini

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© European Southern Observatory (ESO) 1997

Online publication: May 5, 1998

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