2005ApJ...618..817P

We present new velocity-resolved spectra of the [Fe II] λ1.644 µm line emission toward the L1551 IRS 5 outflow. The spectra were taken toward the bright [Fe II] knots PHK 1 and PHK 2 with the slit positions perpendicular to the northern jet. We have two major conclusions: (1) At PHK 1, located 1".2 away from the L1551 IRS 5 VLA sources, the spatial profile of the low radial velocity component at V_LSR~-110 km/s shows two spatial subcomponents with their FWHMs of 0".83 and 2".84. The wide subcomponent has an wide opening angle of ∼100°, which is consistent with the opening angle suggested by the broad velocity width of the narrow one. It favors the interpretation that both subcomponents of the low-velocity component arise from the same outflow. The gas corresponding to the wide subcomponent fills the space between the optical jet and the shell of the CO molecular outflow and may be sweeping up envelope material in the vicinity of the protostars. (2) At PHK 2, located ∼4".2 away from the VLA sources, we confirmed that the northern jet has two radial velocity components: V_LSR~-270 and -140 km/s. The former velocity component is highly collimated because it has the same spatial width of 0".78 at both of the two [Fe II] knots.