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asymmetric drift

  1. The tendency of a population of stars to have a mean rotation velocity around the galactic center that lags behind that of the local standard of rest.

  2. The negative of the mean V velocity (one of the components of space velocity) of a stellar population. In general, it increases with random motion within the population, so that the older the population, the more negative the V velocity. For example, the young thin disk population has an asymmetric drift of 0 km/s, whereas the halo population has an asymmetric drift of about 200 km/s.

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