2021MNRAS.507.4409M

A model of the Galaxy with the outer ring R₁R₂ can explain the observed distribution of the radial, V_R, and azimuthal, V_T, velocity components along the Galactocentric distance, R, derived from the Gaia EDR3 data. We selected stars from the Gaia EDR3 catalogue with reliable parallaxes, proper motions, and line-of-sight velocities lying near the Galactic plane, |z| < 200 pc, and in the sector of the Galactocentric angles |θ| < 15° and calculated the median velocities V_R and V_T in small bins along the distance R. The distribution of observed velocities appears to have some specific features: the radial velocity V_R demonstrates a smooth fall from +5 km s^–1 at the distance of R ≃ R₀ - 1.5 kpc to -3 km s^–1 at R ≃ R₀ + 1.0 kpc while the azimuthal velocity V_T shows a sharp drop by 7 km s^–1 in the distance interval R₀ < R < R₀ + 1.0 kpc, where R₀ is the solar Galactocentric distance. We build a model of the Galaxy including bulge, bar, disc, and halo components, which reproduces the observed specific features of the velocity distribution in the Galactocentric distance interval |R - R₀| < 1.5 kpc. The best agreement corresponds to the time 1.8 ± 0.5 Gyr after the start of the simulation. A model of the Galaxy with the bar rotating at the angular velocity of Ω_b = 55 ± 3 km s^–1 kpc^–1, which sets the OLR of the bar at the distance of R₀ - 0.5 ± 0.4 kpc, provides the best agreement between the model and observed velocities. The position angle of the bar, θ_b, corresponding to the best agreement between the model and observed velocities is θ_b = 45 ± 15°.