Periodic Pattern in the Residual-Velocity Field of OB Associations

TL;DR

This study uncovers periodic variations in the residual-velocity field of OB associations near the Sun, revealing insights into Galactic structure and dynamics, including the locations of spiral arms and the corotation radius.

Contribution

It presents the first detailed analysis of periodic residual-velocity patterns in OB associations, linking these to Galactic spiral arms and the corotation radius.

Findings

Radial residual velocities show a periodic pattern with a 2.0 kpc scale.

Azimuthal residual velocities exhibit a pattern in 0<l<180° but not in 180<l<360°.

The Cygnus and Perseus arms coincide with velocity pattern features.

Abstract

An analysis of the residual-velocity field of OB associations within 3 kpc of the Sun has revealed periodic variations in the radial residual velocities along the Galactic radius vector with a typical scale length of lambda=2.0(+/-0.2) kpc and a mean amplitude of fR=7(+/-1) km/s. The fact that the radial residual velocities of almost all OB-associations in rich stellar-gas complexes are directed toward the Galactic center suggests that the solar neighborhood under consideration is within the corotation radius. The azimuthal-velocity field exhibits a distinct periodic pattern in the region 0<l<180 degrees, where the mean azimuthal-velocity amplitude is ft=6(+/-2) km/s. There is no periodic pattern of the azimuthal-velocity field in the region 180<l<360 degrees. The locations of the Cygnus arm, as well as the Perseus arm, inferred from an analysis of the radial- and azimuthal-velocity fields coincide. The periodic patterns of the residual-velocity fields of Cepheids and OB associations share many common features.