HDO abundance in the envelope of the solar-type protostar IRAS 16293–2422*
Centre d'Étude Spatiale des Rayonnements, BP 4346, 31028 Toulouse Cedex 04, France e-mail: email@example.com
2 Observatoire de Bordeaux, BP 89, 33270 Floirac, France
3 Laboratoire d'Astrophysique de l'Observatoire de Grenoble, BP 53, 38041 Grenoble Cedex 9, France
4 Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apartado Postal 72-3 (Xangari), 58089 Morelia, Michoacán, Mexico
5 Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
6 INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
7 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
8 SRON National Institute for Space Research, Landleven 12, 9747 AD Groningen, The Netherlands
9 Leiden Observatory, PO Box 9513, 2300 RA Leiden, The Netherlands
Accepted: 14 October 2004
We present IRAM 30 m and JCMT observations of HDO lines towards the solar-type protostar IRAS 16293-2422. Five HDO transitions have been detected on-source, and two were unfruitfully searched for towards a bright spot of the outflow of IRAS 16293-2422. We interpret the data by means of the Ceccarelli et al. ([CITE]) model, and derive the HDO abundance in the warm inner and cold outer parts of the envelope. The emission is well explained by a jump model, with an inner abundance and an outer abundance (3σ). This result is in favor of HDO enhancement due to ice evaporation from the grains in the inner envelope. The deuteration ratio HDO/H2O is found to be and (3σ) in the inner and outer envelope respectively and therefore, the fractionation also undergoes a jump in the inner part of the envelope. These results are consistent with the formation of water in the gas phase during the cold prestellar core phase and storage of the molecules on the grains, but do not explain why observations of H2O ices consistently derive a H2O ice abundance of several 10-5 to 10-4, some two orders of magnitude larger than the gas phase abundance of water in the hot core around IRAS 16293-2422.
Key words: ISM: molecules / stars: formation / stars: individual: IRAS 16293-2422
Based on observations with the IRAM 30 m telescope in Spain and with The James Clerk Maxwell Telescope, operated by The Joint Astronomy Centre on behalf of the Particle Physics and Astronomy Research Council of the United Kingdom, the Netherlands Organisation of Scientific Research, and the National Research Council of Canada.
© ESO, 2005