KINEMATIC EVIDENCE FOR THE WAVE NATURE OF THE CARINA-SAGITTARIUS ARM

Radial-velocity and (Hipparcos) proper-motion data are used to constru ct the residual space velocity field for OB associations in the Carina -Sagittarius arm. The azimuthal residual velocity component for most s tars in the Sgr OB1, Ser OB1, Cru OB1, Cen OB1, and Car OB2 associatio ns has the direction that is opposite to the Galactic rotation, while in the Car OB1 association this component has the same direction as th e Galactic rotation. The radial residual velocity component for Cru OB 1 and Cen OB1 is directed toward the Galactic center, while for Car OB 2, Car OB1, and Sgr OB1 it is close to zero. We found a residual-veloc ity gradient for Cru OB1, Car OB2, and Car OB1 from the inner edge of the Carina arm (V-theta = -10 km s(-1); V-R = -9 km s(-1)) to its oute r edge (V-theta = +4 km s(-1); V-R = +3 km s(-1)). We argue that the c hange in the residual velocities of the associations from the inner to the outer edges of the Carina arm is accompanied by the stratificatio n of stars in age. Our results are in general agreement with the expec ted residual-velocity distribution due to the spiral density waves wit hin the carotation radius.