Constraints on the abundance of solid O-2 in dense clouds from ISO-SWS and ground-based observations
Vandenbussche, Bart × Ehrenfreund, P Boogert, ACA van Dishoeck, EF Schutte, WA Gerakines, PA Chiar, J Tielens, AGGM Keane, J Whittet, DCB Breitfellner, M Burgdorf, M #
Astronomy and astrophysics vol:346 issue:3 pages:L57-L60
The Short Wavelength Spectrometer (SWS) onboard the Infrared Space Observatory (ISO) has been used to search for solid O-2 in cold dense clouds at 6.45 mu m. Additional constraints on the O-2 abundance are obtained from analysis of the 4.67 mu m solid CO absorption profile observed from the ground. We derive upper limits of 50% and 100% of solid O-2 relative to solid CO toward the protostellar sources R CrA IRS2 and NGC 7538 IRS9 respectively, corresponding to abundances of 30 x 10(-6) and 15 x 10(-6) relative to n(H). These results indicate that the abundance of solid O-2 in dense clouds accounts for less than 6% of the total oxygen budget in the interstellar medium. The reservoirs of oxygen in dense clouds are discussed, taking into account recent measurements of oxygen-bearing species.