Galactic resonance rings. Modelling of motions in the wide solar neighborhood

Abstract

Models of the Galaxy with analytical Ferrers bars can reproduce the residual velocities of OB-associations in the Sagittarius, Perseus and Local System stellar-gas complexes located within 3 kpc solar neighborhood. Ferrers ellipsoids with density distribution defined by power indices n=1 and 2 are considered. The success in the reproduction of the velocity in the Local System is due to the large velocity dispersion which weakens the resonance effects by producing smaller systematic motions. Model galaxies form nuclear, inner and outer resonance rings R1 and R2. The outer rings R2 manage to catch twice more particles than the rings R1. The outer Lindblad resonance of the bar (OLR) is located 0.4 kpc beyond the solar circle, R_OLR=R0+0.4 kpc, corresponding to the bar angular velocity of Omega_b=50 km s-1 kpc-1. The solar position angle with respect to the bar, theta_b, providing the agreement between model and observed velocities is 40-52 degrees. Unfortunately, models considered cannot reproduce the residual velocities in the Carina and Cygnus stellar-gas complexes. The redistribution of the specific angular momentum, L, is found near the Lindblad resonances of the bar (ILR and OLR): the average value of L increases (decreases) at the radii a bit smaller (larger) than those of the resonances that can be connected with the existence of two types of periodic orbits elongated perpendicular to each other there.

20 pages, 15 figures, accepted for publication in MNRAS

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