Periodic pattern in the residual-velocity field of OB associations

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 f(R) = 7 +/- 1 km s(-1). 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 0 degrees < l < 180 degrees region, where the mean azimuthal-velocity amplitude is f(theta) = 6 +/- 2 km s(-1). There is no periodic pattern of the azimuthal-velocity field in the 180 degrees < l < 360 degrees region. 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. (C) 2001 MAIK Nauka/Interperiodica.