Astron. Astrophys. 315, L377-L380 (1996)
Solid methane toward deeply embedded protostars*
A.C.A. Boogert1, W.A. Schutte2, A.G.G.M. Tielens3, D.C.B. Whittet4, F.P. Helmich2, P. Ehrenfreund2, P.R. Wesselius1,5, Th. de Graauw1,5, and T. Prusti6
1 Kapteyn Astronomical Institute, P.O. Box 800,
9700 AV Groningen, The Netherlands
Received 16 July 1996 / Accepted 22 August 1996
Abstract. We report on the detection of an absorption feature near 7.67 toward the deeply embedded protostellar objects W 33A and NGC 7538 : IRS9. Comparison with laboratory spectra shows that this feature can be identified as the (`deformation') mode of solid state embedded in polar molecules (i.e., ) in icy grain mantles. The solid column density relative to solid is 0.4-1.9%. Unlike solid CO, solid does not seem to be subjected to out-gassing toward the warm source W 33A. The low gas-to-solid ratio for argues that is formed on grains either by hydrogenation of accreted C or by ultraviolet processing of -rich ices.
Key words: ISM: dust, extinction - ISM: molecules - ISM: abundances - infrared: ISM: lines and bands - stars: individual: NGC 7538: IRS9 - stars: individual: W 33A
* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.
Last change: December 16, 1996