Chemical Composition of Globular Clusters of Milky Way Subsystems from Gaia DR2 Data

Results of a study of the kinematic and chemical properties of globular clusters of the Milky Way based on data from the Gaia DR2 catalog and meaurements with the Hubble Space Telescope are presented. A new method for dividing globular clusters into Galatic subsystems based on the elements of their Galactic orbits is proposed. Samples of globular clusters belonging to the bar/bulge, thick disk, and halo of the Milky Way are obtained. The mean metallicities of the globular clusters in various subsystems are calculated. The mean metallicities of globular clusters of the thick disk and halo display statistically significant differences. At the same time, no statistically significant differences are present between the mean metallicities of halo globular clusters moving in the direction of rotation of the Galactic disk and those moving in the retrograde direction. This argues against the suggestion that retrograde and prograde globular clusters have different origins.

     

Kinematic control of the inertiality of ICRS catalogs

We perform a kinematic analysis of the Hipparcos and TRC proper motions of stars by using a linear Ogorodnikov-Milne model. All of the distant (r>0.2 kpc) stars of the Hipparcos catalog have been found to rotate around the Galactic y axis with an angular velocity of M ₁₃ ^? =?0.36±0.09 mas yr^?1. One of the causes of this rotation may be an uncertainty in the lunisolar precession constant adopted when constructing the ICRS. In this case, the correction to the IAU (1976) lunisolar precession constant in longitude is shown to be Δp₁=?3.26±0.10 mas yr^?1. Based on the TRC catalog, we have determined the mean Oort constants: A=14.9±1.0 and B=?10.8±0.3 km s^?1 kpc^?1. The component of the model that describes the rotation of all TRC stars around the Galactic y axis is nonzero for all magnitudes, M ₁₃ ^? =?0.86±0.11 mas yr^?1.     

Determination of galactic rotation parameters and the solar galactocentric distance R 0 from 73 masers

We have determined the Galactic rotation parameters and the solar Galactocentric distance R ₀ by simultaneously solving Bottlinger’s kinematic equations using data on masers with known line-of-sight velocities and highly accurate trigonometric parallaxes and proper motions measured by VLBI. Our sample includes 73 masers spanning the range of Galactocentric distances from 3 to 14 kpc. The solutions found are Ω₀ = 28.86 ± 0.45 km s^?1 kpc^?1, Ω′₀ = ?3.96 ± 0.09 km s^?1 kpc^?2, Ω″₀ = 0.790 ± 0.027 km s^?1 kpc^?3, and R ₀ = 8.3 ± 0.2 kpc. In this case, the linear rotation velocity at the solar distance R ₀ is V = 241 ± 7 km s^?1. Note that we have obtained the R ₀ estimate, which is of greatest interest, from masers for the first time; it is in good agreement with the most recent estimates and even surpasses them in accuracy.