Satellite galaxies as probes of the gravitational potentials of large spirals

Beckman, J. E.; Varela, A. M.; Cepa, J.
Bibliographical reference

(IAU, European Regional Astronomy Meeting, 11th, La Laguna, Spain, July 3-8, 1989) Astrophysics and Space Science (ISSN 0004-640X), vol. 170, no. 1-2, Aug. 1990, p. 327-335.

Advertised on:
An aspect of the missing mass problem in galaxies, not easy to address, is whether the dynamical mass distribution is spherical or greatly flattened, following the light. Rotation curves of spirals out of the plane of the disk cannot, by definition, be measured. A way around this problem might be to use satellite galaxies orbiting within a few Holmberg radii of their parents. In this paper, the difficulties implied in using a satellite are addressed in this way: to what extent is it possible to solve uniquely for its orbital parameters? A practical set of solutions which can constrain an orbit is derived using the tidal radius of the satellite to scale the gravitational pull of the parent. Although data of the quality needed exist as yet for very few systems, it is shown, using M31, NGC 128, and NGC 1023 and their respective satellites, how the dynamics of the interactions can be explored.