Kinematics of T Tauri stars in nearby star forming regions
The kinematics of T Tauri stars in the nearby star forming regions Taurus-Auriga, Chamaeleon, Lupus and Scorpius-Centaurus is studied using proper motions from the Hipparcos, PPM, ACT, TRC and STARNET proper motion catalogues. Especially the STARNET catalogue is very well suited for this purpose as it provides accurate proper motions for about 4.3 million stars, so that a large number of T Tauri stars is included in that catalogue. Where available, Hipparcos parallaxes and radial velocities are combined with the proper motions to calculate space velocities and velocity dispersions. In the Scorpius-Centaurus association, the favourable geometry allows for the determination of kinematical distances. A large fraction of the stars in the samples belongs to the population of weak-line T Tauri stars discovered with the help of the X-ray satellite ROSAT during the last years. In contrast to classical T Tauri stars, which had preferentially been found very close to the densest cores of the cloud material in those star forming regions, weak-line T Tauri stars are distributed over larger regions in space. The kinematic signatures of processes producing such halos of weak-line T Tauri stars should still be visible, and the observed motions of the stars are analyzed in the framework of various star formation scenarios.
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