Estimation of the Galactic Spiral Pattern Speed from Cepheids

Abstract

To study the peculiarities of the Galactic spiral density wave, we have analyzed the space velocities of Galactic Cepheids with proper motions from the Hipparcos catalog and line-of-sight velocities from various sources. First, based on the entire sample of 185 stars and taking $R_0=8$ kpc, we have found the components of the peculiar solar velocity $(u_{\odot },v_{\odot },w_{\odot })=(7.6,11.6,6.1)\pm (0.8,1.1,0.6)$ km s${}^{-1}$, the angular velocity of Galactic rotation ${\Omega }_0=-27.4\pm 0.6$ km s${}^{-1}$ kpc${}^{-1}$ and its derivatives ${\Omega }_0^{{}^{\prime }}=+4.07\pm 0.21,$ km s${}^{-1}$ kpc${}^{-2}$ and ${\Omega }_0^{"}=-0.83\pm 0.17,$ km s${}^{-1}$ kpc${}^{-3}$, the amplitudes of the velocity perturbations in the spiral density wave $f_R=-6.7\pm 0.7$ and $f_{\theta }=3.5\pm 0.5$ km s${}^{-1}$, the pitch angle of a two-armed spiral pattern (m = 2) $i=-4.5\pm 0.1^{\circ }$ (which corresponds to a wavelength $\lambda =2.0\pm 0.1$ kpc), and the phase of the Sun in the spiral density wave ${\chi }_{\odot }=-191\pm 5^{\circ }$. The phase ${\chi }_{\odot }$ has been found to change noticeably with the mean age of the sample. Having analyzed these phase shifts, we have determined the mean value of the angular velocity difference ${\Omega }_p-\Omega$, which depends significantly on the calibrations used to estimate the individual ages of Cepheids. When estimating the ages of Cepheids based on Efremov's calibration, we have found $|{\Omega }_p-{\Omega }_0|=9\pm 2$ km s${}^{-1}$ kpc${}^{-1}$. The ratio of the radial component of the gravitational force produced by the spiral arms to the total gravitational force of the Galaxy has been estimated to be $f_{r0}=0.04$.

arXiv comment17 pages, 5 figures, 2 tables

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• Analysis of galaxy kinematics based on Cepheids from the Gaia DR2 Catalogue
• Galactic Kinematics from a Sample of Young Massive Stars
• The local standard of rest from data on young objects with account for the Galactic spiral density wave
• Cepheid Kinematics and the Galactic Warp
• A Galactic Ring of Minimum Stellar Density Near the Solar Orbit Radius
• The Galaxy Kinematics from OB Stars with Proper Motions from the Gaia DR1 Catalog
• Kinematics of the Galaxy from Cepheids with proper motions from the Gaia DR1 catalogue
• Estimation of the SolarGalactocentric Distance and Rotation Velocity from Near-Solar-Circle Objects
• Kinematics of the Galaxy from OB Stars with Data from the Gaia DR2 Catalogue
• Kinematics of the Galaxy from a Sample of Young Open Star Clusters with Data from the Gaia DR2 Catalogue
• 3-D kinematics of classical Cepheids according to Gaia, EDR3 catalog
• Galactic Kinematics from Data on Open Star Clusters from the MWSC Catalogue
• Study of the Galactic Rotation Based on Masers and Radio Stars with VLBI Measurements of Their Parallaxes
• Evidence of the Galactic outer ring R1R2' from young open clusters and OB-associations
• Determination of the Spiral Pattern Speed in the Galaxy from Three Samples of Stars
• Redetermination of the Parameters of the Galactic Spiral Pattern from Classical Cepheids
• Estimation of the Parameters of the Spiral Pattern in the Galaxy Based on a Sample of Classical Cepheids
• Search for Kinematic Siblings of the Sun Based on Data from the XHIP Catalog
• Analysis of the Distance Scales by Cepheids from the Gaia EDR3 Catalogue Data
• A new estimate of the Local Standard of Rest from data on young Galactic objects