Astronomy and Astrophysics Letters dedicated to ISO

Detection of hot, abundant water toward AFGL 2591

F.P. Helmich E.F. van Dishoeck J.H. Black Th. de Graauw D.A. Beintema A.M. Heras F. Lahuis P.W. Morris E.A. Valentijn


We present the first detection of absorption lines within the bending vibration of water in the interstellar medium using the ISO-SWS. More than 30 lines between 5.5 and 6.6 microns are detected toward the bright infrared source GL 2591, which arise most likely in the dense molecular cloud core surrounding the young stellar object. Comparison with model spectra indicates a high excitation temperature (Tex > 200K) and a high abundance [H2O]/[H2] ~ (2 -6) 10-3. We speculate on the origin of the hot water, and the consequences for the chemistry.

ISM: abundances - ISM: molecules - ISM: clouds - ISM: individual: AFGL~2591

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