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Astron. Astrophys. 343, L83-L86 (1999)

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Letter to the Editor

The H2O abundance and star formation history in [FORMULA] Oph *

René Liseau and Göran Olofsson

Stockholm Observatory, S-133 36, Saltsjöbaden, Sweden (rene; olofsson@astro.su.se)

Received 15 December 1998 / Accepted 14 February 1999


ISO -LWS observations towards a large number of different positions in the core of the [FORMULA] are used to place a limit to the abundance of wide spread H2O. From NLTE excitation and radiative transfer modelling the average line spectrum of the [FORMULA], we find X(H2O) [FORMULA] 10[FORMULA] to 10[FORMULA]. We interprete these results within the framework of the dynamical chemistry models by Bergin, Melnick & Neufeld (1998), which describe the time evolution of molecular clouds being shocked by outflowing gas from young stellar objects, and conclude that the [FORMULA] has been forming stars for less than one million years (2 - 5 [FORMULA] yr). Finally, we show that this limiting result can be put to conclusive observational test by the ODIN satellite mission in the near future.

Key words: ISM: individual objects: ae Oph cloud (L 1688) – ISM: clouds – ISM: abundances – ISM: molecules – ISM: jets and outflows – stars: formation

* 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.

Send offprint requests to: R. Liseau

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999