1.2 Dark Matter in the Solar Neighbourhood

Oort (1932, 1960) was the first to perform an analysis of the vertical equilibrium of the stellar distribution in the solar neighbourhood. He found that there is more mass in the galactic disk than can be accounted for by star counts. A reanalysis of this problem by Bahcall (1984a, b, c) argued for the presence of a dark ``disk'' of a scaleheight of 700 pc. This was called into question by Bienaymé et al. (1987), and by Kuijken & Gilmore (1989a, b, 1991). The newest result is based on a sample of stars with HIPPARCOS distances and Coravel radial velocities, within 125 pc of the Sun. Crézé et al. (1998) find that there is no evidence for dark matter in the disk : all the matter is accounted for by adding up the contributions of gas, young stars and old stars.