Herschelobservations of deuterated water towards Sgr B2(M)

C Comito,The Hexos Team ,E.A Bergin,D.C Lis,P Schilke,R Rolffs

doi:10.1051/eas/1152048

Abstract

Observations of HDO are an important complement for studies of water, because they give strong constraints on the formation processes – grain surfaces versus energetic process in the gas phase, e.g. in shocks. The HIFI observations of multiple transitions of HDO in Sgr B2(M) presented here allow the determination of the HDO abundance throughout the envelope, which has not been possible before with ground-based observations only. For more details, see Comito et al. (2010).

Highlights

Water is known to be a fundamental ingredient of the interstellar medium
Water can be formed in the gas phase through an ionmolecule channel that is initiated by a reaction of H+ or H+3 with atomic oxygen
Water can be formed through highly endothermic reactions that involve atomic oxygen, which reacts with molecular hydrogen to form OH, which in turn can react with molecular hydrogen to form H2O

Summary

Introduction

Water is known to be a fundamental ingredient of the interstellar medium It is a major coolant of star-forming clouds, but, apart from some high-lying maser transitions, is unobservable from the ground because of the atmospheric absorption. There it is assumed that water is formed on grain surfaces, where oxygen can react with atomic hydrogen. These icy grain mantles can be studied through observations of the water stretching bands in ice in the infrared (e.g., Gibb et al 2000), by which the existence of water ice is a well established observational fact. I.e. the enrichment of the deuterated counterpart of a molecular species much above the cosmic [D]/[H] ratio, is a process that is caused by the zero-point energy difference of the vibrational potential.

42.9 IRAM 30-m b

Observations

Results

Discussion