Molecular Entrainment by Optical Jets

Molecular outflows around young stellar objects (YSOs) have been studied extensively. Many models have tried to explain their appearance, and currently the most popular are those which invoke momentum-conserving collimated jets, emanating from the YSO. Two competing models describe the mechanism by which the jet sets the molecular cloud in motion: `prompt' entrainment and `turbulent' entrainment. We present a method for distinguishing between the two cases by examining the velocity structure and the morphology of outflows. We also examine the effects on the observations of viewing angle and show how two well-studied outflows fit into the global picture of jet-molecular cloud interaction. Finally we show evidence for time-dependent ejection of the jet.