Molecular gas kinematics and high-mass star formation in the spiral arms of the milky way

We-study the kinematic of the molecular gas using observations of the rotational line (CO)-C-12(J=1-->0), and also the star formation traced by Ultra-Compact HII regions in the IV galactic quadrant (270degrees less than or equal to l less than or equal to 360degrees). Our results. show that there is a connection between 1) high-mass star formation in the spiral arms of the Milky Way, 2) molecular gas of high column density, and 3) the large-scale rigid-body-like motion of the gas. The large-scale rigid-body-like motions observed in the arms imply that there is less angular momentum to dissipate in the formation processes of stellar systems. We show a multiple stellar system under study, embedded in its parent molecular-cloud in the Carina arm region.