The SiO and CS emission in the molecular outflow toward L1157

We present observational studies of the molecular outflow associated with t he Class 0 young stellar object toward L1157. The CO emission shows a well- collimated bipolar morphology with rich structure. In addition to the exten ded emission, the CO gas is found in clumps in the vicinity of the near-inf rared H-2 emission. The SiO emission is seen in six prominent condensations , three on each side of the protostar. They appear to be in three pairs; ea ch pair aligns well with the exciting star. The CS emission imaged toward t he blueshifted outflow is well collimated and presents a bow-shaped structu re coincident with the SiO and H-2. A comparison of the outflow in differen t tracers suggests that the molecular gas is entrained at the head of an un derlying jet. The jet seems to be episodic and shows signs of deceleration as it ploughs through the dense core.