Elemental abundance survey of the Galactic thick disc

摘要: We have performed an abundance analysis for F- and G- dwarfs of the Galactic thick-disc component. A sample 176 nearby (d≤ 150 pc) candidate stars was chosen from Hipparcos catalogue subjected to a high-resolution spectroscopic analysis. Using accurate radial velocities combined with astrometry, kinematics (U, V W) orbital parameters were computed. estimate probability star belong thin disc, thick disc or halo. With P≥ 70 per cent taken as certain membership, we assigned 95 13 20 The remaining 48 in cannot be reasonable certainty one three components. Abundances C, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Ba, Ce, Nd Eu been obtained. abundances are compared those thin-disc members Reddy et al. ratios α-elements (O, Ca Ti) iron show clear enhancement range −0.3 < [Fe/H] −1.2. There also other elements – possibly Zn which enhanced relative disc. Ni Cu (relative Fe) very similar thin- stars. dispersion [X/Fe] at given is consistent expected scatter due measurement errors, suggesting lack ‘cosmic’ scatter. A few classified by our kinematic criteria abundances. These stars, appear older than most also, on average, younger population. They may originated early history, subsequently scattered hotter orbits collisions. not include > −0.3. observed compositions discs seem models galaxy formation hierarchical clustering Lambda cold dark matter (ΛCDM) universe.