L1527

Sub-arcsecond resolution images of the rotational line emissions of CS and c-C $$_3$$ H $$_2$$ were observed toward the low-mass protostellar core L1527 with the Atacama Large Millimeter/submillimeter Array. The observed lines are investigated to characterize the geometrical configuration of the outflow/envelope system of this source. The CS emission traces both an envelope component extending along the north-south direction and a faint outflow component with a butterfly shape. The observed kinematic structure of the envelope is well explained with the aid of a ballistic model of an infalling-rotating envelope. Although the envelope has a nearly edge-on configuration, the inclination angle of the rotation axis from the plane of the sky is found to be $$85{^\circ }$$ , where the western side of the envelope is found to face the observer. This configuration is opposite to that previously suggested for a larger-scale ( $$\sim 10^4$$ au) outflow based on the $$^{12}$$ CO ( $$J=3-2$$ ) observation, and to the morphology of infrared reflection near the protostar ( $$\sim 200$$ au). The discrepancy with the infrared observation result could originate from high extinction by the outflow cavity on the western side. Alternatively, these discrepancies may indicate that the outflow axis is not perpendicular to the mid-plane of the envelope structure. The acceleration of the gas in the outflow cavity wall is shown in position-velocity diagrams, and the kinematic structure in the 2000 au scale is explained with the aid of a parabolic outflow model with the inclination angle constrained by the analysis of the envelope structure. The difference in the orientation between the small and large scale outflow structures implies a precession of the outflow axis.