Issue |
A&A
Volume 418, Number 3, May II 2004
|
|
---|---|---|
Page(s) | 1021 - 1034 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20034476 | |
Published online | 16 April 2004 |
Physical-chemical modeling of the low-mass protostar IRAS 16293-2422
1
Department of Physics and Astronomy, Denison University, Granville, OH 43023, USA
2
Stockholm Observatory, AlbaNova, 10691 Stockholm, Sweden
3
Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
Corresponding author: S. Doty, doty@cc.denison.edu
Received:
8
October
2003
Accepted:
29
January
2004
We present detailed gas-phase chemical models for the
envelope of the low-mass star-forming region IRAS 16293-2422. By
considering both time- and space-dependent chemistry, these models
are used to study both the physical structure proposed by Schöier
et al. ([CITE]), as well as the chemical
evolution of this region. A new feature of our study is the use of
a detailed, self-consistent radiative transfer model to translate
the model abundances into line strengths and compare them directly with
observations of a total of 76 transitions for 18 chemical species,
and their isotopes. The model can reproduce many of the line
strengths observed within 50%.
The best fit is for times
in the range of yrs and requires
only minor modifications to our model for the high-mass star-forming
region AFGL 2591. The ionization rate for the source may be higher than
previously expected – either due to an enhanced cosmic-ray
ionization rate, or, more probably, to the presence of X-ray induced
ionization from the center. A significant fraction of the CO is found
to desorb in the temperature range of 15-40 K; below this temperature ~90% or more of the CO is frozen out. The inability of the
model to explain the HCS+, C2H, and OCS abundances suggests the importance of
further laboratory studies of basic reaction rates. Finally,
predictions of the abundances and spatial distributions
of other species which could be observed by future
facilities (e.g. Herschel-HIFI, SOFIA, millimeter arrays) are
provided.
Key words: stars: formation / stars: individual: IRAS 16293-2422 / ISM: molecules
© ESO, 2004
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