EDP Sciences
Free Access
Volume 399, Number 1, February III 2003
Page(s) 197 - 210
Section Formation, structure and evolution of stars
DOI https://doi.org/10.1051/0004-6361:20021773
Published online 05 February 2003

A&A 399, 197-210 (2003)
DOI: 10.1051/0004-6361:20021773

Reduction of chemical networks

I. The case of molecular clouds
D. Wiebe1, D. Semenov2 and Th. Henning3

1  Institute of Astronomy of the RAS, Pyatnitskaya St. 48, 119017 Moscow, Russia
    e-mail: dwiebe@inasan.rssi.ru
2  Astrophysical Institute and University Observatory, Schillergäßchen 2-3, 07745 Jena, Germany
    e-mail: dima@astro.uni-jena.de
3  Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: henning@mpia.de

(Received 20 September 2002 / Accepted 27 November 2002)

We present a new method to analyse and reduce chemical networks and apply this technique to the chemistry in molecular clouds. Using the technique, we investigated the possibility of reducing the number of chemical reactions and species in the UMIST 95 database simultaneously. In addition, we did the same reduction but with the "objective technique" in order to compare both methods. We found that it is possible to compute the abundance of carbon monoxide and fractional ionisation accurately with significantly reduced chemical networks in the case of pure gas-phase chemistry. For gas-grain chemistry involving surface reactions reduction is not worthwhile. Compared to the "objective technique" our reduction method is more effective but more time-consuming as well.

Key words: astrochemistry -- stars: formation -- molecular processes -- ISM: molecules -- ISM: abundances

Offprint request: D. Wiebe, dwiebe@inasan.rssi.ru

© ESO 2003

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