DENSITY OF MATTER IN THE GALACTIC DISC

We determine abundances, luminosities and space motions for a sample o f nearby K giants. We analyse their kinematics and argue that we have isolated the local counterpart of the K giants found in a cone at the South Galactic Pole by Bahcall, Flynn and Gould (BFG). For a given des cription of the vertical potential of the local disc, constructed from the known matter and possible dark matter components, the velocity di stribution and space density of these nearby K giants can be calculate d as a function of height z above the Galactic plane. Comparison with the BFG observations then allows us to solve for the best-fitting pote ntial. The major result is that the observations can be quite well fit ted by the potential due to known matter only. The fit can be improved by invoking dark matter in the disc, but only a small amount is requi red: if such dark matter is distributed proportionately to the known m atter (following Bahcall) our best-fitting model has a disc surface de nsity of Sigma. = 52 +/- 13 M. pc(-2), compared to Sigma. = 49 +/- 9 M . pc(-2) for the known disc matter. This determination is in good acco rd with the Kuijken and Gilmore analysis of disc dark matter from K dw arfs.