Determination of the Spiral Pattern Speed in the Milky Way from Young Open Star Clusters
В. В. Бобылев, A. T. Bajkova
Abstract
We have estimated the spiral pattern speed in the Galaxy $$\Omega_{p}$$ from a large sample of young open star clusters (OSCs). For this purpose, we have used 2494 OSCs younger than 50 Myr. Their mean proper motions, line-of-sight velocities, and distances were calculated by Hunt and Reffert (2023) based on data from the Gaia DR3 catalogue. Three methods have been applied to estimate $$\Omega_{p}$$ . They all are based on the linear Lin–Shu spiral density wave theory. We have obtained an estimate of $$\Omega_{p}=24.26\pm 0.52$$ km s $${}^{-1}$$ kpc $${}^{-1}$$ by the first method, which is most reliable in our view, using the velocity perturbations $$f_{R}$$ and $$f_{\theta}$$ found through a spectral analysis of the radial, $$V_{R}$$ , and residual rotation, $$\Delta V_{\rm circ}$$ , velocities. Using the second method, we have found the velocity perturbations $$f_{R}$$ and $$f_{\theta}$$ by solving the basic kinematic equations together with the Galactic rotation parameters and obtained an estimate of $$\Omega_{p}=23.45\pm 0.53$$ km s $${}^{-1}$$ kpc $${}^{-1}$$ . We have found $$\Omega_{p}=28.9\pm 2.8$$ km s $${}^{-1}$$ kpc $${}^{-1}$$ by the third method based on an analysis of the position angles of OSCs at their birth time $$\theta_{\rm birth}$$ .