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Astron. Astrophys. 321, 293-304 (1997)

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SiO production in interstellar shocks *

P. Schilke 1, C.M. Walmsley 2, G. Pineau des Forêts 3 and D.R. Flower 4

1 I. Physikalisches Institut der Universität zu Köln, Zülpicher Str. 77, D-50937 Köln, Germany
2 Osservatorio di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy
3 DAEC, Observatoire de Paris, F-92195 Meudon Principal Cedex, France
4 Physics Department, The University, Durham DH1 3LE, UK

Received 22 April 1996 / Accepted 19 August 1996


We study the production of SiO in the gas phase of molecular outflows, through the sputtering of Si-bearing material in grains. The sputtering is driven by neutral particle impact on charged grains in C-type shocks, at the speed corresponding to ambipolar diffusion. Shock speeds in the range [FORMULA] and preshock densities [FORMULA] have been investigated. Sputtering of Si-bearing material in both the cores and the mantles of the grains is considered. We find that, for [FORMULA] of approximately 25 km s-1 and [FORMULA] of the order [FORMULA] cm-3, column densities of SiO similar to those observed in molecular outflow regions can be generated by either mechanism. Impact by particles heavier than helium dominates the core-sputtering process for shock velocities of this order. The profiles of rotational transitions of SiO are computed and compared with observations of molecular outflows.

Key words: molecular processes – shock waves – ISM: abundances; jets and outflows; molecules

* Tables 1 and 2 are available in electronic form at CDS via ftp or http://cdsweb.u-strasbg.fr/Abstract.html

Send offprint requests to: G. Pineau des Forêts

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998