Local stellar kinematics from RAVE data- V. Kinematic investigation of the Galaxy with red clump stars

Abstract

We investigated the space velocity components of 6610 red clump (RC) stars in terms of vertical distance, Galactocentric radial distance and Galactic longitude. Stellar velocity vectors are corrected for differential rotation of the Galaxy which is taken into account using photometric distances of RC stars. The space velocity components estimated for the sample stars above and below the Galactic plane are compatible only for the space velocity component in the direction to the Galactic rotation of the thin disc stars. The space velocity component in the direction to the Galactic rotation (V) shows a smooth variation relative to the mean Galactocentric radial distance (Rm), while it attains its maximum at the Galactic plane. The space velocity components in the Galactic centre (U) and in the vertical direction (W) show almost flat distributions relative to Rm with small changes in their trends at Rm=7.5 kpc. U values estimated for the RC stars in quadrant 180<l<=270 are larger than the ones in quadrants 0<l<=90 and 270<l<=360. The smooth distribution of the space velocity dispersions reveals that the thin and thick discs are kinematically continuous components of the Galaxy. Based on the W space velocity components estimated in the quadrants 0<l<=90 and 270<l<=360, in the inward direction relative to the Sun, we showed that RC stars above the Galactic plane move towards the North Galactic Pole, whereas those below the Galactic plane move in the opposite direction. In the case of quadrant 180<l<=270, their behaviour is different, i.e. the RC stars above and below the Galactic plane move towards the Galactic plane. We stated that the Galactic long bar is the probable origin of many, but not all, of the detected features.