Computer Science
Scientific paper
Mar 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999esasp.427..565c&link_type=abstract
The Universe as Seen by ISO. Eds. P. Cox & M. F. Kessler. ESA-SP 427., p. 565
Computer Science
9
Molecular Clouds, Orion-Irc2, Sgr B2, Molecules, Molecular Abundances
Scientific paper
We present our ISO open time results concerning the water vapour abundance and its spatial distribution in Orion-IRc2 and SgrB2. LWS grating and FP data have been obtained in both sources for H2O and for the H218O and H217O rare isotopes. In Orion IRC2 we have observed more than 70 lines from the different isotopes of water vapour. As already probed by Cernicharo et al. in 1994 from ground based observations at 183.3 GHz, our LWS FP and grating maps of Orion show that water vapour is spatially extended in this cloud and has an abundance around 10-5 at large scale (ridge molecular cloud). The same abundance has been found for the extended water vapour absorption in the direction of SgrB2 where the 179.5 μm line of H2O is detected over a region having a size of 80 pc. In the direction of Orion IRC2 the data contain information on the different gas components associated to this prominent molecular cloud. The water vapour lines with wavelengths above 100 μm are in emission. However, for shorter wavelengths the lines arising from energy levels below 500 K present P-Cygni profiles while those arising from higher energies are in emission. All the lines observed with the SWS spectrometer are in absorption. The interpretation of the data is not obvious in view of the extremely large opacities of the water vapour lines and of the complex line profiles. We present radiative transfer models including dust and molecules simultaneously that predict several important effects in the water vapour lines intensities and line profiles. These models reproduce qualitatively and quantitatively the observed water vapour lines with the SWS and the LWS ISO spectrometers. A detailed fit to the data will require a more detailed knowledge of the geometry of the region and of the relative distribution of dust and H2O. Water vapour abundances around 10-4 have been estimated for the shocked gas in IRC2.
Cernicharo Jose
Cox Pierre
Gonzalez-Alfonso Eduardo
Leeks Sarah J.
Lim Tanya
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