Kinematics of Molecular Clouds. II. New Data on Nearby GMCs.

The best currently available data on positions, distances and velocities of Giant Molecular Clouds within 3 kpc of the sun are analyzed to yield a one-dimensional rms velocity dispersion sigma sub v = 7.8 sup (+0.6) sub (-0.5). Velocity dispersion is defined here as the root-mean-square of cloud peculiar velocities, a quanity which includes small-scale streaming. Some clouds have velocities forbidden by galactic rotation; also, there exist pairs of clouds in close proximity to each other having very different velocities: these can be explained by the calculated value of sigma sub v, but substantially smaller values are unlikely. The mean motion of nearby molecular clouds is drifting by ~4km s sup (-1) with respect to the LSR.