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Ellipticity of Outer Regions of Galactic Disks

Published online by Cambridge University Press:  25 May 2016

Urmas Haud
Urmas Haud*
Affiliation:
Tartu Astrophysical Observatory, EE2444 Toravere, Estonia

Extract

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In hierarchical cosmologies, dark matter coronas arise from the gravitational collapse of density peaks in a random perturbation field. The result is a triaxial, slowly rotating, centrally concentrated dark corona (Dubinski and Carlberg, 1991; Dubinski, 1992). Binney (1978) was the first to consider the effects of triaxial coronas around disk galaxies, showing that they might explain the observed warps and apparent twists seen in many disks. In external galaxies these deformations of density and velocity fields are modeled with a system of circular annuli, each of which has its own inclination and line of nodes (LON). By examining warped systems in a variety of reference frames, Briggs (1990) has mentioned that galaxy kinematics uniquely specifies a new reference frame in which there is a common LON for orbits within the transition radius and also a differently oriented straight LON for the gas outside the transition radius, which is approximately equal to the Holmberg radius of the galaxy.

Type
Chapter 1: Are the Disk and Halo Axisymmetric?
Information
Symposium - International Astronomical Union , Volume 169: Unsolved Problems of the Milky Way , 1996 , pp. 57 - 58
Copyright
Copyright © Kluwer 1996 

References

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