Molecular Outflows: Observations

Abstract

The wealth of mm-wave observations being provided by large radiotelescopes and interferometers on bipolar molecular outflows are reviewed. The physical outflow parameters are mainly obtained from CO observations, but we also pay attention to more rare and complex molecules such as CH3OH, H2CO, SiO, HCO+, etc. Recent results from chemical surveys of young protostellar outflows show that the peculiarities of the chemical behavior together with other structural parameters (such as the presence of molecular bullets, the flow opening angle, and the mechanical power efficiency) can be used to produce a classification of the observed outflows, and we suggest that this represents a rough time evolutionary sequence. We finally discuss the properties of the underlying primary wind which is assumed to drive the molecular outflows. Recent observations and theoretical work suggest that a primary wind with two components (a highly collimated jet and a wide-angle wind) is needed to explain the observations.