A search for (H O) in the Galaxy and toward comet Hale-Bopp

M. Scherer - M. Havenith - R. Mauersberger - T.L. Wilson
Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, D-53115 Bonn, Germany
Steward Observatory, The University of Arizona, Tucson, AZ85721, U.S.A.
Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
Submillimeter Telescope Observatory, The University of Arizona, Tucson, AZ85721, U.S.A.
Abstract: The MPIfR 100m telescope, the NRAO 12m telescope, and the IRAM 30m telescope were used to search for low lying rotational transitions of the water dimer, (H O) , toward the Galactic cloud cores Orion-KL, W51d, W51e1e2, NGC7538, SgrB2(M) and L134N, and toward comet Hale-Bopp. The comet was observed on December 20, 1996 and March 25/26, 1997 (i.e. near perihelion on April 1) at 24GHz. No lines of (H O) were found. Our limit for the abundance of (H O) relative to that of water (from H O data) is typically toward dense cloud cores. Toward Orion-KL an even more stringent limit of <810 is derived. The abundance of (H O) relative to H is typically . Our data show that at perihelion the production rate of the water dimer of comet C/1995 O1 (Hale-Bopp) was . This is less than 6% the production rate of H O.

Submitted to Astronomy & Astrophysics e-mail contact: mauers@as.arizona.edu