KINEMATICAL SEARCH IN THE OPTICAL FOR LOW-MASS STARS OF THE GOULD BELT SYSTEM

The peculiar kinematics of the Gould Belt system is modeled as an expa nsion wave of 3.6 km s(-1) velocity, when analyzing the phase space of a set of 9 x 10(4) nearby A, F, G disk dwarfs. The shock front distan ce of 315 pc from the Cas-Tau association reads to a kinematical time scale of 85 Myr, suggesting an expansion induced by the compression of a spiral density wave in the Carina Arm. Post-shock kinetic temperatu re of the cold neutral phase of the ISM and mass stratification of the gravitational instability favor a possible formation of the Could Bel t system through a Parker-Jeans instability. The instability time scal e is on the order of 12 Myr with a characteristic length of 1.4 kpc in the galactic plane and a scale height of 200 pc. The model of the mag netic field instability in the ISM is used to identify stars of spectr al types later than AO whose orbits mimic the gas motion, Formation ca used by the impact of a high velocity cloud in the gas of the galactic disk cannot be ruled out in view of the mainly illustrative aspect of the interstellar shock wave suggested picture, A system of 1.2 x 10(3 ) candidates out of the sample of 9 x 10(4) stars has been segregated for tracking genuine tracers of the Gould Belt system for follow-up sp ectroscopic observations. An analysis of the spectra of 55 stars confi rms F and G core hydrogen-burning stars whose observed line-of-sight v elocity fits the model associated with the Gould Belt system formation at a mms scatter of 7 kms s(-1). A set of ten candidates with Lithium abundance similar to the Hyades late F-type stars suggests a success rate of 20% for the kinematical search. (C) 1996 American Astronomical Society.