The influence of ice-coated grains on protostellar spectra

Thomas Preibisch, Volker Ossenkopf, Harold W. Yorke & Thomas Henning

Astronomy & Astrophysics, 279, 577-588, (1993)


Information about protostellar sources obtained by fit calculations contain a number of uncertanties due to our poor knowledge of the properties of dust grains in dense clouds. From the results of recent observational and theoretical studies of dust in dense regions we construct a new dust model that consists of amorphous carbon grains and ice-coated silicate grains.

The model is based on new refractive indices of amorphous carbon and ice-coated silicate grains. Our model of the ``dirty ice'' assumes a mixture of H_2O and NH_3 ice with inclusions of amorphous carbon. The optical constants are calculated using effective-medium theory. We determine the opacities of core-mantle-particles with varying mantle thickness and pollution by spherical Mie calculations and investigate the effects on the spectrum of a embedded source.

The different models for the core-mantle-particles are used to fit the observed spectra of two protostellar sources and to determine the envelopes masses of these objects. We find considerable differences in the masses obtained from different dust models.

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