The Spiral Pattern Speed in the Milky Way Galaxy

For a sample of masers, the basic kinematic equations were solved by including the Galactic rotation parameters and the peculiar velocity of the Sun as the unknown variables. Based on spectral analysis, the following estimates were obtained: $\mathrm{\mid }f{\mathrm{\mid }}_{R,\theta }=(7.0,5.1)\pm (1.2,1.4)$ km s${}^{-1}$ and the corresponding wavelengths ${\lambda }_{R,\theta }=(1.9,1.7)\pm (0.4,0.7)$ kpc, as well as ${\chi }_{\odot }=-{140}^{\circ }\pm {15}^{\circ }$. The presence of periodic perturbations in the vertical velocities of masers with an amplitude of $\mathrm{\mid }f{\mathrm{\mid }}_W=3.1\pm 1.4$ km s${}^{-1}$ and a wavelength of $\lambda =1.9\pm 0.8$ kpc was confirmed. It is shown that the velocities $f_R$ and $f_{\theta }$ can have both the same and different signs. Therefore, we obtained a large scatter of estimates. Thus, if $f_R$ and $f_{\theta }$ have the same signs, then ${\mathrm{\Omega }}_p=25.8\pm 2.0$ km s${}^{-1}$ kpc${}^{-1}$ and $R_{cor}=9.1\pm 0.8$ kpc. And when $f_R$ and $f_{\theta }$ have different signs, then ${\mathrm{\Omega }}_p=35.4\pm 2.0$ km s${}^{-1}$ kpc${}^{-1}$ and $R_{cor}=6.8\pm 0.8$ kpc.