Molecular gas phase counterparts to solid state grain mantles features: implication for gas/grain chemistry

We present ISO SWS (AOT6) observations of the protostellar object RAFGL 7009S. This source is particularly interesting for the characterisation of chemistry arising from grain surfaces andmantles, since the solid state features ofmany simple molecules such asH2O,CO,CO2, CO2 andCH4 are detected, together with weaker features not yet unambiguously identified. Gas phase H2O, CO2, CH4 and CO can also be seen superimposed on the much broader solid state features. We derive an estimate for the gas phase temperature around 50K. The gas to solid ratios of these simple molecules is found to be≥0.2 for H2O, ∼0.2 for CH4, and an order of magnitude lower for CO2. We discuss the possible implications for interstellar chemistry in such objects.