Free access article

A&A 444, 883-891 (2005)
DOI: 10.1051/0004-6361:20053673

Estimation and reduction of the uncertainties in chemical models: application to hot core chemistry

V. Wakelam¹, F. Selsis², E. Herbst^{1, 3} and P. Caselli<sup>4

1</sup>  Department of Physics, The Ohio State University, Columbus, OH 43210, USA
    e-mail: wakelam@mps.ohio-state.edu
²  Centre de Recherche Astronomique de Lyon, École Normale Supérieure, 46 allée d'Italie, 69364 Lyon Cedex 7, France
³  Departments of Astronomy and Chemistry, The Ohio State University, Columbus, OH 43210, USA
⁴  INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 50125 Firenze, Italy

(Received 21 June 2005 / Accepted 25 August 2005 )

Abstract
It is not common to consider the role of uncertainties in the rate coefficients used in interstellar gas-phase chemical models. In this paper, we report a new method to determine both the uncertainties in calculated molecular abundances and their sensitivities to underlying uncertainties in the kinetic data utilized. The method is used in hot core models to determine if previous analyses of the age and the applicable cosmic-ray ionization rate are valid. We conclude that for young hot cores (10⁴ yr), the modeling uncertainties related to rate coefficients are reasonable so that comparisons with observations make sense. On the contrary, the modeling of older hot cores is characterized by strong uncertainties for some of the important species. In both cases, it is crucial to take into account these uncertainties to draw conclusions from the comparison of observations with chemical models.

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

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