Refinement of the parameters of three selected model Galactic potentials based on the velocities of objects at distances up to 200 kpc

Abstract

This paper is a continuation of our recent paper devoted to refining the parameters of threecomponent (bulge, disk, halo) axisymmetric model Galactic gravitational potentials differing by the expression for the dark matter halo using the velocities of distant objects. In all models the bulge and disk potentials are described by the Miyamoto–Nagai expressions. In our previous paper we used the Allen–Santillán (I), Wilkinson–Evans (II), and Navarro–Frenk–White (III) models to describe the halo. In this paper we use a spherical logarithmic Binney potential (model IV), a Plummer sphere (model V), and a Hernquist potential (model VI) to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of the listed models, which are employed most commonly at present. The model rotation curves are fitted to the observed velocities by taking into account the constraints on the local matter density ρ_⊙= 0.1 M_⊙pc⁻³ and the force K_z=1.1/2πG = 77M_⊙pc⁻² acting perpendicularly to the Galactic plane. The Galactic mass within spheres of radius 50 and 200 kpc are shown to be, respectively, M₅₀ = (0.409 ± 0.020) × 10¹²M_⊙ and M₂₀₀ = (1.395 ± 0.082) × 10¹²M_⊙ in model IV, M₅₀ = (0.417 ± 0.034) × 10¹²M_⊙ and M₂₀₀ = (0.469 ± 0.038) × 10¹²M_⊙in model V, and M₅₀ = (0.417 ± 0.032) × 10¹²M_⊙ and M₂₀₀ = (0.641 ± 0.049)× 10¹²M_⊙ in model VI. Model VI looks best among the three models considered here from the viewpoint of the achieved accuracy of fitting the model rotation curves to the measurements. This model is close to the Navarro–Frenk–White model III refined and considered best in our previous paper, which is shown using the integration of the orbits of two globular clusters, Lynga 7 and NGC 5053, as an example.