Issue |
A&A
Volume 395, Number 3, December I 2002
|
|
---|---|---|
Page(s) | 853 - 862 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20021300 | |
Published online | 18 November 2002 |
The 2-D structure of dusty disks around Herbig Ae/Be stars
I. Models with grey opacities
Max Planck Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany e-mail: dullemon@mpa-garching.mpg.de
Accepted: 16 August 2002
In this paper the two-dimensional structure of protoplanetary disks around
Herbig Ae/Be stars is studied. This is done by constructing a
self-consistent model based on 2-D radiative transfer coupled to the
equation of vertical hydrostatics. As a simplifying assumption a grey
opacity is used. It is found that the disk can adopt four different
structures, dependent on the surface density distribution as a
function of radius, i.e. on radial- and vertical optical depth of the
disk. For the case of high to intermediate vertical optical depth, the
temperature and density structures are in agreement with the simple “disk
with inner hole” model of Dullemond et al. (2001, henceforth
DDN01). At large radii the disk adopts a flaring shape as expected, and near
the dust destruction radius (located at about
for most Herbig Ae
stars) the disk is superheated and puffs up. The region directly behind this
“puffed-up inner dust wall” is shadowed, as predicted by DDN01. For the
case of intermediate to low vertical optical depth, but still high radial
optical depth, the 2-D models show that the shadow can cover the entire
disk. For such competely self-shadowed disks the inner rim emission in the
near infrared constitutes the dominant part of the SED, since the flaring
component in the mid- and far infrared is suppressed by the self-shadowing
effect. When the disk is optically thin even in radial direction, it becomes
unshadowed again because the inner rim can no longer block the stellar
light. Such disks have relatively weak infrared excess compared to the
stellar flux. Finally, for disks that flare at intermediate radii, but
become too optically thin at large radii, the outer parts once again become
shadowed. But this time the shadowing is caused by the flaring part of the
disk, instead of the inner rim. The disk then consists of a bright inner rim,
a shadow, a flaring part and finally a (dim) shadowed outer part. Different
observational methods of determining the size of the disk (e.g. from the SED,
from continuum mapping or from CO mapping) may yield different results.
Key words: accretion, accretion disks / stars: circumstellar matter / stars: formation / stars: pre-main-sequence / infrared: stars
© ESO, 2002
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