Determination of the Solar Galactocentric Distance from the Kinematics of Masers

Abstract

We determine the parameters of Galactic rotation and the solar galactocentric distance R 0 by simultaneously solving Bottlinger’s kinematic equations using data for masers with known line-of-sight velocities and highly accurate VLBI trigonometric parallaxes and proper motions. Our sample includes 93 masers spanning the range of galactocentric distances R from 3 to 15 kpc. The inferred parameters are Ω 0 = 29.7 ± 0.5 km s −1 kpc −1 , Ω′ 0 = −4.20 ± 0.11 km s −1 kpc −2 , Ω″ 0 = 0.730 ± 0.029 km s −1 kpc −3 , and R 0 = 8.03 ± 0.12 kpc, implying a circular rotation velocity of V 0 = 238 ± 6 km s −1 at the solar distance R 0 .