2001ApJ...552L..63G

We report the first measurements of proper motions in a molecular outflow by using interferometric rotational line observations. We observed and mapped with the BIMA millimeter array the extremely high velocity (EHV) SiO J=2⟶1 emission associated with the L1448 molecular outflow. Comparisons were made with the Plateau de Bure interferometer maps carried out 8.5 yr earlier. We obtained proper motions of up to 0".12 yr^–1, which imply absolute velocities of 180 km.s^–1 and an outflow inclination of 21° to the plane of the sky, in agreement with previous modeling of the CO emission. These proper motions suggests that the EHV emission in L1448 has a short timescale. These results strongly suggest that with the new generation of powerful interferometric arrays, the combination of high spectral and angular resolution with high sensitivity will permit a detailed three-dimensional picture of the kinematics of molecular outflows.