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Fitting orbits to tidal streams with proper motions
Article first published online: 10 SEP 2009
DOI: 10.1111/j.1745-3933.2009.00744.x
© 2009 The Authors. Journal compilation © 2009 RAS
Issue
Monthly Notices of the Royal Astronomical Society: Letters
Volume 399, Issue 1, pages L160–L163, October 2009
Additional Information
How to Cite
Eyre, A. and Binney, J. (2009), Fitting orbits to tidal streams with proper motions. Monthly Notices of the Royal Astronomical Society: Letters, 399: L160–L163. doi: 10.1111/j.1745-3933.2009.00744.x
Publication History
- Issue published online: 1 OCT 2009
- Article first published online: 10 SEP 2009
- Accepted 2009 August 18. Received 2009 August 14; in original form 2009 June 27
- Abstract
- Article
- References
- Cited By
Keywords:
- stellar dynamics;
- methods: N-body simulations;
- Galaxy: kinematics and dynamics;
- Galaxy: structure
ABSTRACT
The Galaxy's stellar halo seems to be a tangle of disrupted systems that have been tidally stretched out into streams. Each stream approximately delineates an orbit in the Galactic force-field. In the first paper in this series, we showed that all six phase-space coordinates of each point on an orbit can be reconstructed from the orbit's path across the sky and measurements of the line-of-sight velocity along the orbit. In this paper, we complement this finding by showing that the orbit can also be reconstructed if we know proper motions along the orbit rather than the radial velocities. We also show that accurate proper motions of stream stars would enable distances to be determined to points on the stream that are independent of any assumption about the Galaxy's gravitational potential. Such ‘Galactic parallaxes’ would be as fundamental as conventional trigonometric parallaxes, but measurable to distances ∼70 times further.