On the validity of grey radiation transfer in dusty envelopes
Thomas Preibisch, Cordula Sonnhalter & Harold W. Yorke
Astronomy and Astrophysics 299, 144, (1995)
Radiative transfer calculations in dusty protostellar envelopes have
been performed to test the validity of the grey approximation
which is often used in radiation hydrodynamic calculations.
In the spherical symmetric (1D) case we compare grey calculations with
the frequency dependent exact solution of radiation transport.
In the 2D case we use the flux-limited diffusion approximation to solve
the radiation transport equation in grey and frequency dependent form.
In all cases the dust temperature distributions are determined
Model envelopes are considered with a density peaked structure
and with different total optical depths in
the 1D case. In the 2D case we use the density distributions of
various disk models. A dust model consisting of amorphous carbon and
silicate grains, partially coated with `dirty ice', is assumed.
We find that the dust temperatures are generally underestimated in the
grey approximation (by factors up to three) and that the radiative
acceleration can be underestimated by orders of magnitude. The
importance of efficient but more accurate algorithms than the usual
grey approximation is stressed.
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