Absolute Proper Motions and the Kinematics of Globular Clusters

Abstract

Position data for stars in the vicinities of 119 Galactic globular clusters from the USNOB1, 2MASS, URAT1, and ALLWISE catalogs have been reduced in the system of the UCAC5 reference catalog. The published positions are used together with positions from the UCAC5 and Gaia DR1 catalogs (with a difference in their epochs of 65 years) and photometric data from the 2MASS survey to distinguish cluster members, determine their absolute proper motions with an accuracy of 1–2 milliarcseconds/year (mas/year), and calculate the mean absolute proper motions of the clusters with accuracies of about 0.4 mas/year. The derived proper motions and published distances and radial velocities for the clusters are used to establish the absence of rotation for a sample of metal-poor clusters in the Galactic halo. The mean velocity of the Sun relative to this sample is found to be (V_x(0), V_y(0), V_z(0)) = (−16 ± 16, −231 ± 19, +2± 16) km/s, and the distance of the Sun fromthe Galactic center is estimated to be R₀ = 7.6 ±0.7 kpc. This paper is based on a presentation made at the conference “Modern Astrometry 2017,” dedicated to the memory of K.V. Kuimov (Sternberg Astronomical Institute,Moscow State University, October 23–25, 2017).