2009ApJ...698..184W

The multiple protostellar system L1551 IRS5 exhibits a large-scale bipolar molecular outflow that spans ∼1.5 pc on both the northeast (redshifted) and southwest (blueshifted) sides of the system. We have studied this outflow within ∼4000 AU of its driving source(s) with the Submillimeter Array. Our CO(2-1) image at ∼4'' (∼560 AU) resolution reveals three distinct components: (1) an X-shaped structure spanning ∼20'' from center with a similar symmetry axis and velocity pattern as the large-scale outflow; (2) an S-shaped structure spanning ∼10'' from center also with a similar symmetry axis but opposite velocity pattern to the large-scale outflow; and (3) a compact central component spanning ∼1".4 from center again with a similar symmetry axis and velocity pattern as the large-scale outflow. The X-shaped component likely comprises the limb-brightened walls of a cone-shaped cavity excavated by the outflows from the two main protostellar components. The compact central component likely comprises material within this cavity newly entrained by one or both outflows from the two main protostellar components. The S-shaped component mostly likely comprises a precessing outflow with its symmetry axis inclined in the opposite sense to the plane of the sky than the other two components, taking the S-shaped component out of the cone-shaped cavity along most, if not all, of its entire length. This outflow may be driven by a recently reported candidate third protostellar component in L1551 IRS5, whose circumstellar disk is misaligned relative to the two main protostellar components. Gravitational interactions between this protostellar component and its more massive northern (and perhaps also southern) neighbor(s) may be causing the circumstellar disk and hence outflow of this component to precess.