Champagne Flutes and Brandy Snifters: Modelling Protostellar Outflow-Cloud Chemical Interfaces

摘要

A rich variety of molecular species has now been observed towards hot coresin star forming regions and in the interstellar medium. An increasing body ofevidence from millimetre interferometers suggests that many of these form atthe interfaces between protostellar outflows and their natal molecular clouds.However, current models have remained unable to explain the origin of theobservational bias towards wide-angled "brandy snifter" shaped outflows overnarrower "champagne flute" shapes in carbon monoxide imaging. Furthermore,these wide-angled systems exhibit unusually high abundances of the molecularion HCO$^+$. We present results from a chemo-dynamic model of such regionswhere a rich chemistry arises naturally as a result of turbulent mixing betweencold, dense molecular gas and the hot, ionized outflow material. The injectadrives a rich and rapid ion-neutral chemistry in qualitative and quantitativeagreement with the observations. The observational bias towards wide-angledoutflows is explained naturally by the geometry-dependent ion injection ratecausing rapid dissociation of CO in the younger systems.