ON THE G-DWARF ABUNDANCE DISTRIBUTION IN THE SOLAR CYLINDER

The oxygen abundance distribution of G-dwarfs in the solar cylinder is obtained using the G-dwarf data of Pagel & Patchett as local normalization and two different types of models of the local, vertical structure of the galactic disc. One is the model of Norris & Ryan and the other is obtained using the Polak-Ribiere method to fit the data of Kuijken & Gilmore. The results are compared to simple, chemical evolution models characterized by an exponentially decreasing infall rate, simple star-formation laws of the type d-SIGMA-*/dt proportional SIGMA-g(N) and no radial flows. Infall time-scales of t(i) = 3-4.5 and 4-6 Gyr are deduced from the comparison for the two sets of models with an estimated uncertainty on t(i) of approximately 1.5 Gyr. The infall time-scales obtained in the analysis compare well with the empirically determined halo formation time-scale of approximately 3 Gyr found by Schuster & Nissen, strongly suggesting that the formation of the halo and disc were coupled processes in the sense that the halo stars formed out of the gas, which later became the galactic disc.