Abstract
The orbits of over 10000 stars are integrated in a steady-state model of the Galaxy for a time 6.0×108 yr. Initially, the stars are placed randomly inside spheres of 500 pc and 50 pc radius and are given random velocities, such that the sample has a Maxwellian or a spheroidal velocity distribution. The spheres are placed at the Sun's distance from the galactic centre (10 kpc) and are given a circular velocity of 250 km s−1. The mean velocities and dispersions of stars within 1 kpc of an ‘observer’ moving at the circular velocity are calculated as functions of time. The quantities show a strong time-dependence with oscillations of period 108 yr. The oscillations are independent of the mass model and occur also in an inverse square force field. A vertex deviation of the velocity ellipsoid, an asymmetric drift and aK-effect occur as natural consequences of the oscillations. Attempts to apply the Oort method for density determinations in the galactic plane are also influenced by the oscillations. Spiral density waves appear to have a small effect on the motions of the test stars.
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House, F.C., Innanen, K.A. A numerical study of local stellar motions. Astrophys Space Sci 32, 139–151 (1975). https://doi.org/10.1007/BF00646221
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DOI: https://doi.org/10.1007/BF00646221