UVBY-BETA PHOTOMETRY OF HIGH-VELOCITY AND METAL-POOR STARS .4. DISTANCES, KINEMATICS, AND GALACTIC ORBITS FOR STARS WITH (FE/H)LESS-THAN-OR-EQUAL-TO-2.0

From the catalogue of high-velocity and metal-poor stars of Schuster and Nissen 43 stars with [Fe/H] less-than-or-equal-to - 2.0 were selected as a sample representative of the oldest, most kinematically extreme component of our Galaxy. For these stars, photometric distances were determined. Their galactic orbits were then numerically integrated in the galactic potential model of Allen and Martos. Of the 40 stars with complete data, 27 are found to be in box-orbits, 2 in orbits verging on chaotic, 9 in chaotic, and 2 in tube-like orbits. Four stars attaining R(max) > 50 kpc and five stars with low eccentricities (e < 0.4) are present in the sample. No obvious correlations of ages and/or metallicities with kinematical parameters were found. All stars with R(max) > 20 kpc have h less-than-or-almost-equal-to suggesting different evolutionary scenarios for the inner and outer halo. Two mechanisms for hiding chemical gradients in the halo are shown to be of importance.