Interstellar water and interstellar ice
Authors: O'neill, P.T.; Williams, D.A.
Source: Astrophysics and Space Science, Volume 266, Number 4, 1999 , pp. 539-548(10)
Abstract:There are two ways that water ice can form in the interstellar medium: H_2O molecules can form in the gas phase and then freeze out onto dust grain surfaces, or O and OH can be converted at the surfaces of grains to form H_2O, which is then retained. Bergin et al. (1998) have recently shown that shocks passing through interstellar clouds sufficiently frequently can make the first method effective. However, we present results from a similar chemical model which indicate that this requires significant optical shielding because of the high ionization fraction in regions exposed to a high UV flux. We deduce, therefore, that grain surface reactions probably represent the main source of H_2O ice on lines of sight with visual extinction up to about 6 magnitudes to an embedded source or 12 magnitudes to a background object.
Document Type: Regular Paper
Affiliations: Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT
Publication date: January 1, 1999