Star formation in local spiral arms

Abstract

We analyze the dynamics of the young stellar clusters belonging to the local spiral arms, based on the proper motions, radial velocities and ages of the clusters, that are compiled in our Catalog of Open Clusters. We find the bitrthplaces of the clusters, and as a first result, we confirm that almost all the clusters are born the spiral arms. This allows us to measure the velocity of the spiral pattern, and to determine the position of the corotation radius, where the spiral pattern and the galactic marerial rotate at the same velocity. The corotation radius is Rc = 1.08 ± 0.08 R0 , that is, very close to the Sun at R0. The direction of the velocity perturbation of the clusters (velocity excess with respect to circular rotation) shows a linear variatin as a function of age, at least for a fraction of the clusters. This is interpreted in terms of a common initial direction dictated by the star‐formation process in the spiral arms, followed by rotation of the velocity vector, according to the epicycle approximation.We analyze the dynamics of the young stellar clusters belonging to the local spiral arms, based on the proper motions, radial velocities and ages of the clusters, that are compiled in our Catalog of Open Clusters. We find the bitrthplaces of the clusters, and as a first result, we confirm that almost all the clusters are born the spiral arms. This allows us to measure the velocity of the spiral pattern, and to determine the position of the corotation radius, where the spiral pattern and the galactic marerial rotate at the same velocity. The corotation radius is Rc = 1.08 ± 0.08 R0 , that is, very close to the Sun at R0. The direction of the velocity perturbation of the clusters (velocity excess with respect to circular rotation) shows a linear variatin as a function of age, at least for a fraction of the clusters. This is interpreted in terms of a common initial direction dictated by the star‐formation process in the spiral arms, followed by rotation of the velocity vector, according to the epicycle appro...