Motion of A Stars Perpendicular to the Galactic Plane-II

The analysis of the motion of A-type stars perpendicular to the galactic plane given by one of us in 1957 is repeated, the approximate solutions of the differential equations then given being replaced by numerical solutions obtained with an ICT 1900. It is recognized, following unpublished observations carried out at Kottamia, that there is an increase in the velocity dispersion of A stars near the galactic pole, with increasing magnitude, and it is shown that the presence of a non (single) Gaussian distribution of velocities affects substantially the value of the mean density in the solar neighbourhood deduced from the velocity dispersion and a measure of the average distance from the galactic plane. The calculations here given result in a density of 0.11 solar masses per cubic parsec.