Search for age pattern across spiral arms of the Milky Way

Abstract

The age pattern across spiral arms is one of the key observational features utilised to study the dynamic nature of the Galaxy’s spiral structure. With the most updated samples of high-mass star formation region (HMSFR) masers, O stars and open clusters, we investigated their distributions and kinematic properties in the vicinity of the Sun. We found that the Sagittarius-Carina Arm traced by HMSFRs, O stars (≲ 10 Myr) and young open clusters (<30 Myr) seem to deviate gradually towards the Galactic Anticenter (GAC) direction. The Local Arm traced by HMSFRs, O stars, young clusters and also medium-young clusters (30–100 Myr) are inclined to gradually deviate toward the Galactic Center (GC) direction. The properties for the Local Arm are supported by a simplified simulation of cluster motions in the Galaxy. Indications of systematic motions in the circular and radial velocities are noticed for the old open clusters (>200 Myr). These results are consistent with the idea that star formation can be triggered by spiral shocks of density waves, and indicate that the corotation radius of the Galaxy is located between the Sagittarius-Carina Arm and the Local Arm, close to the Solar circle.