Determination of the Spiral Pattern Speed in the Milky Way from Young Open Star Clusters

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, $\Delta V_{\mathrm{circ}},$ 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 ${\theta }_{\mathrm{birth}}$.

15 pages, 5 figures, 1 table. arXiv admin note: text overlap with arXiv:2203.12902, arXiv:1903.09313, arXiv:2207.03412

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Cited by in corpus (1)

• The Spiral Pattern Speed in the Milky Way Galaxy