| Protostellar jets and molecular outflows associated with young stellar objects (YSOs) are amongst the most spectacular manifestations of star formation. They indicate that forming stars not only accrete mass from the surrounding but also eject mass violently into the ambient material. Molecular outflows are generally seen in CO and currently thought to be driven either by a collimated protostellar jet or an unseen wide-angle wind with a high density "jet-like" core. In this thesis, we investigate the structure and kinematics of molecular outflows and their physical connection with protostellar jets through observations and hydrodynamical simulations. The goal is to understand the dynamics of the molecular outflows and to gain insight into the mass ejection mechanism which powers these outflows.; We have mapped the CO J = 1 - 0 emission from molecular outflows associated with ten nearby young stellar systems using the BIMA array and FCRAO 14-m antenna. CO outflow generally forms a shell structure around the outflow axis with the higher velocity emission further out from the source. Two distinctive kinematic features are evident in position-velocity (PV) diagrams cut along the outflow axis: a parabolic structure originating at the driving source and a convex spur structure with the high velocity tip near known H 2 bow shocks and CO bow-like structures.; We have also performed two-dimensional hydrodynamical simulations of both jet- and wind driven models in order to make detailed comparisons to the kinematics of the observed molecular outflows. The simulations are performed with the ZEUS-2D hydrodynamical code using a simplified equation of state, simplified cooling and no external heating, and no self gravity.; Comparing the simulations with observations, we have found that the parabolic PV structure and the spur PV structure can be modeled with the wind-driven model and jet-driven model, respectively. However, the jet-driven model may have difficulty producing the outflow widths, while the wind-driven model may have difficulty producing highly collimated outflows and internal bow shocks. We have concluded that the "jet-driven" or "wind-driven" dichotomy is insufficient to explain the range of kinematic and structural features evident in the observed molecular outflows. |
