Massachusetts-Stony Brook Galactic plane CO survey - The Galactic disk rotation curve

Abstract

Data from the Massachusetts-Stony Brook Galactic plane CO survey have been analyzed to determine the dependence of CO radial velocity on Galactic longitude along the loci of tangents in the inner Galaxy. These measurements are combined with published data for H I in the nuclear region, outer Galaxy CO-H II regions, and the globular cluster system to yield a rotation curve valid over the northern Galactic disk. Streaming motions characterized by lengths larger than 0.22 R(0) and velocities of 5 km/s have been successfully separated from the smaller scale cloud-cloud motions, which possess linear scale lengths up to 0.015 R(0) and one-dimensional velocity dispersions of 3.0 km/s. The LSR exhibits an azimuthal peculiar velocity of 7 km/s.