Are Complex A and the Orphan Stream related?

Abstract

We consider the possibility that the Galactic neutral hydrogen stream Complex A and the stellar Orphan stream are related, and use this hypothesis to determine possible distances to Complex A and the Orphan stream, and line-of-sight velocities for the latter. The method presented uses our current knowledge of the projected positions of the streams, as well as line-of-sight velocities for Complex A, and we show that a solution exists in which the two streams share the same orbit. If Complex A and the Orphan stream are on this orbit, our calculations suggest the Orphan stream to be at an average distance of 20 kpc, with heliocentric radial velocities of approximately -110 km/s. Complex A would be ahead of the Orphan stream in the same wrap of the orbit, with an average distance of 10 kpc, which is consistent with the distance constraints determined through interstellar absorption line techniques.

4 pages, 2 figures; typos corrected, fig 2 and numerical predictions updated; accepted for publication in MNRAS Letters

References in corpus (2)

• An Orphan in the "Field of Streams"
• Is Ursa Major II the Progenitor of the Orphan Stream?

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• Hunting the Parent of the Orphan Stream II: The First High-Resolution Spectroscopic Study
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• Finding halo streams with a pencil-beam survey: new wraps in the Sagittarius stream
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• Inferring the dynamics of stellar streams via distance gradients