Issue |
A&A
Volume 449, Number 2, April II 2006
|
|
---|---|---|
Page(s) | 631 - 639 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20054420 | |
Published online | 21 March 2006 |
Modeling the ortho-to-para abundance ratio of cyclic C3H2 in cold dense cores
1
Chemical Physics Program, The Ohio State University, Columbus, OH 43210, USA e-mail: ihpark@mps.ohio-state.edu
2
Department of Physics, The Ohio State University, Columbus, OH 43210, USA e-mail: wakelam@mps.ohio-state.edu
3
Departments of Physics, Chemistry and Astronomy, The Ohio State University, Columbus, OH 43210, USA e-mail: herbst@mps.ohio-state.edu
Received:
26
October
2005
Accepted:
7
December
2005
Aims.We report a detailed attempt to model the ortho-to-para abundance ratio of c-C3H2 so as to reproduce observed values in the cores of the well-known source TMC-1. According to observations, the ortho-to-para ratios vary, within large uncertainties, from a low of near unity to a high of approximately three depending on the core. Methods.We used the osu.2003 network of gas-phase chemical reactions augmented by reactions that specifically consider the formation, depletion, and interconversion of the ortho and para forms of c-C3H2 and its precursor ion c-C3H. We investigated the sensitivity of the calculated ortho-to-para ratio for c-C3H2 to a large number of factors. Results.For the less evolved cores C, CP, and D, we had no difficulty reproducing the observed ortho-to-para ratios of 1–2. In order to reproduce observed ortho-to-para ratios of near three, observed for the evolved cores A and B, it was necessary to include rapid ion-catalyzed interconversion processes.
© ESO, 2006
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