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Astron. Astrophys. 322, 296-301 (1997)

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Grain-grain collisions and sputtering in oblique C-type shocks

P. Caselli 1, 2, T.W. Hartquist 2 and O. Havnes 3

1 Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
2 Max-Planck-Institut für extraterrestrische Physik, D-85740 Garching, Germany
3 Auroral Observatory, University of Tromso, N-9037 Tromso, Norway

Received 29 August 1996 / Accepted 13 November 1996

Abstract

We use a model of the dissipation regions in C-type shocks in which two grain fluids are included to evaluate the rates at which grain-grain collisions and sputtering inject elemental silicon and water into the gas phase. For physical parameters typical of star forming regions, and on the assumption that a substantial fraction of the evaporated silicon is efficiently converted in SiO, the two grain destruction mechanisms lead to gas phase SiO abundances larger than those in the quiescent gas by more than three orders of magnitude. This result is in good agreement with recent observations of SiO near stellar jets. Grain-grain collisions will dominate the return of elemental silicon to the gas phase when the hydrogen nuclei number density of the region into which the shock is propagating is [FORMULA] and the shock speed is between about [FORMULA] and [FORMULA]. Grain-grain collisions dominate over sputtering in the return of water to the gas phase when [FORMULA] and at some shock speeds below about 15 [FORMULA].

Key words: interstellar medium: clouds – interstellar medium: dust, extinction – physical processes: shock waves – interstellar medium: jets and outflows

Send offprint requests to: P. Caselli

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© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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