1999A&AS..135..531T

We have performed a 330-360 GHz molecular line survey of the molecular gas associated with the ultracompact (UC) HII region G5.89-0.39. 142 lines originating from 19 species were detected and a further 6 lines that could not be identified. Over 50% of the identified molecular lines are from sulphur-bearing species, with SO₂ (and its isotopomer ³⁴SO₂) exhibiting the most lines. No emission from heavy organic molecules (e.g. dimethyl ether, ethanol, methyl formate) was detected. The lines can be divided into two types by their profiles: narrow lines with no (or slight) wing emission which probe a molecular envelope surrounding the UC HII region and broad lines with considerable wings which may probe the gas in the bipolar molecular outflow associated with the UC HII region. We discuss the chemical models which may explain the features observed in the survey and outline the strategy for the chemical modelling of the evolution of the molecular gas, to be considered more quantatively in a following paper.