Kinematics of the outer pseudorings and the spiral structure of the Galaxy

TL;DR

This paper investigates the kinematics of outer pseudorings and spiral structures in the Galaxy, attributing observed motions to resonance effects and gas outflows, and models these dynamics to explain stellar residual velocities.

Contribution

It provides new models that reproduce the residual velocities of young stars in various Galactic regions, linking them to the Galaxy's pseudoring structure and resonance dynamics.

Findings

Residual velocities are explained by the outer pseudoring structure.

Models accurately reproduce observed stellar motions.

The solar position angle is constrained to 45 degrees.

Abstract

The kinematics of the outer rings and pseudorings is determined by two processes: the resonance tuning and the gas outflow. The resonance kinematics is clearly observed in the pure rings, while the kinematics of the gas outflow is manifested itself in the pseudorings. The direction of systematical motions in the pure rings depends on the position angle of a point with respect to the bar major axis and on the class of the outer ring. The direction of the radial and azimuthal components of the residual velocities of young stars in the Perseus, Carina, and Sagittarius regions can be explained by the presence of the outer pseudoring of class R1R2' in the Galaxy. We present models, which reproduce the directions and values of the residual velocities of OB-associations in the Perseus and Sagittarius regions, and also model reproducing the directions of the residual velocities in the Perseus, Sagittarius, and Carina regions. The kinematics of the Sagittarius region accurately defines the solar position angle with respect to the bar elongation, theta_b=45 (+/-5) deg.