On The Characteristics of the Velocity Field of Young Stars in the Solar Neighbourhood

Extract

The analysis of stellar kinematics of the local system of young stars from Hipparcos data offers an excellent opportunity to revise models accounting for the origin of the observed deviations from circular motions, and to give new hints on the history of star formation and the dynamical processesinvolved in the evolution of our Galaxy. We have complemented the astrometric Hipparcos data with a careful compilation of available radial velocitiesand Strömgren photometry, information which enables us to obtain reliable space velocities and individual ages for a large number of stars. Thevelocity field has been studied by means of the classical first order approach, interpreting the trends observed in the Oort’s contants in terms of the local expansion of the Gould’s Belt (stars with ages less than 30-50 Myr, at heliocentric distances ρ < 400 — 600 pc). The fundamental geometric parameters of such structure have been determined. Several statistical methods have been applied to identify moving groups in the 4-dimensional space of (U,V,W, age). Our results definitively confirm their existence with mean velocity dispersions of the order of 5-7 km/s. Theobtained results will be published in Astronomy & Astrophysics.