The origin of the bifurcation in the Sagittarius stream

M. Fellhauer*, V. Belokurov, N. W. Evans, M. I. Wilkinson, D. B. Zucker, G. Gilmore, M. J. Irwin, D. M. Bramich, S. Vidrih, R. F G Wyse, T. C. Beers, J. Brinkmann

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

197 Citations (Scopus)


The latest Sloan Digital Sky Survey data reveal a prominent bifurcation in the distribution of debris of the Sagittarius dwarf spheroidal (Sgr) beginning at a right ascension of α ≈ 190°. Two branches of the stream (A and B) persist at roughly the same heliocentric distance over at least 50° of arc. There is also evidence for a more distant structure (C) well behind the A branch. This paper provides the first explanation for the bifurcation. It is caused by the projection of the young leading (A) and old trailing (B) tidal arms of the Sgr, while the old leading arm (C) lies well behind A. This explanation is only possible if the halo is close to spherical, as the angular difference between the branches is a measure of the precession of the orbital plane.

Original languageEnglish
Pages (from-to)167-173
Number of pages7
JournalAstrophysical Journal
Issue number1 I
Publication statusPublished - 1 Nov 2006
Externally publishedYes


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