The planar age-velocity dispersion relation from a polar sample of F stars with solar composition

Details The planar age-velocity dispersion relation from a polar sample of F stars with solar composition The planar age-velocity dispersion relation from a polar sample of F stars with solar composition

Jun 1987

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987a%26a...179..115k&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 179, no. 1-2, June 1987, p. 115-126. Research supported by the Statens Naturvi

Astronomy and Astrophysics

Astrophysics

20

Early Stars, F Stars, Milky Way Galaxy, Radial Velocity, Star Distribution, Stellar Motions, Galactic Evolution, Galactic Structure, Stellar Composition

Scientific paper

A photometric catalog of A and F stars at the North Galactic Pole is compared to the AGK 3. The intersection contains 2359 stars. Due to the high latitude of these stars, b > +70°, an accurate estimate of the plane parallel velocities U and V is obtainable from proper motions and distances alone. Complete subsamples of unevolved and slightly evolved F stars of solar composition are used to study the variation of the velocity dispersions σU and σV with time. Both dispersions are found to follow power laws very closely but the two laws have significantly different powers. The axial ratio σV/σU is found to change from 1 to about 0.5 during a period lasting five billion years signifying a changing shape of the velocity ellipsoid. The age variation's power may discriminate between disk heating mechanisms. It is therefore interesting that the two resulting powers almost are identical to those suggested for spiral wave heating (+1/2) and heating by gravitational collisions with giant molecular clouds (+1/4) respectively. The dispersion of the velocity parallel to the plane is found to obey a law with power ≈1/2.

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