INTERNAL AND RELATIVE MOTIONS OF THE TAURUS AND OPHIUCHUS STAR-FORMING REGIONS

We investigate the internal and relative motions of the Taurus and Ophiuchus star-forming regions using a sample of young stars with accurately measured radial velocities and proper motions. We find no evidence for expansion or contraction of the Taurus complex, but a clear indication of global rotation, resulting in velocity gradients of the order of 0.1 km s(-1) pc(-1) across the region. In the case of Ophichus, more data are needed to reliably establish its internal kinematics. Both Taurus and Ophiuchus, have a bulk motion relative to the LSR ( i.e., a non-zero mean peculiar velocity) of the order of 5 km s(-1). Interestingly, these velocities are roughly equal in magnitude, but nearly exactly opposite in direction. Moving back in time, we find that Taurus and Ophiuchus must have been very near each other 20-25 Myr ago. This suggests a common origin, possibly related to that of Gould's Belt.