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Astron. Astrophys. 340, 103-116 (1998)

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Radiative transfer in the clumpy environment of young stellar objects

S. Wolf 1, O. Fischer 2 and W. Pfau 2

1 Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany
2 Astrophysikalisches Institut und Universitäts-Sternwarte, Schillergässchen 2, D-07745 Jena, Germany

Received 8 May 1998 / Accepted 27 July 1998

Abstract

We developed a Monte-Carlo code for the treatment of the radiative transfer in arbitrary clumpy dust configurations. Both the radiation of the (central) energy source(s) and the thermal emission of the dust are considered. Intensity and polarization maps of the modelled objects can be computed.

As the first application of our code we studied the radiative transfer in a spherical two-phase clumpy dust shell containing a single star. The structure of the circumstellar dust density distribution is characterized by the filling factor of high-density clumps, the density ratio between the low and the high density phases and the size of the smallest individual clumps.

Firstly, we considered the properties of the clumpy structures of that model using the percolation theory. Particularly, we checked different ways to describe the optical depth. Secondly, we investigated the total stellar flux, the mean scattering number and the absorption of the stellar radiation depending on the filling factor, the density ratio, the optical depth, the dust grain size and the smallest clump size. Thirdly, we compared the polarizing influence of a clumpy and an homogeneous dust shell. Fourthly, we investigated the influence of a clumpy density structure on the surface brightness distribution.

First results show significant changes in the spectral energy distribution as well as in images of clumpy dust configurations in comparison to their homogeneous counterparts.

Key words: radiative transfer – methods: numerical – methods: statistical – reflection nebulae – ISM: structure

Send offprint requests to: S. Wolf, (wolf@tls-tautenburg.de)

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© European Southern Observatory (ESO) 1998

Online publication: November 3, 1998
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