An orphan in the "field of streams"

V. Belokurov*, N. W. Evans, M. J. Irwin, D. Lynden-Bell, B. Yanny, S. Vidrih, G. Gilmore, G. Seabroke, D. B. Zucker, M. I. Wilkinson, P. C. Hewett, D. M. Bramich, M. Fellhauer, H. J. Newberg, R. F G Wyse, T. C. Beers, E. F. Bell, J. C. Barentine, J. Brinkmann, N. ColeK. Pan, D. G. York

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

228 Citations (Scopus)


We use Sloan Digital Sky Survey Data Release 5 photometry and spectroscopy to study a tidal stream that extends over ∼50° in the north Galactic cap. From the analysis of the path of the stream and the colors and magnitudes of its stars, the stream is ∼20-5 +7 kpc away at its nearest detection (the celestial equator). We detect a distance gradient: the stream is farther away from us at higher declination. The contents of the stream are made up from a predominantly old and metal-poor population that is similar to the globular clusters M13 and M92. The integrated absolute magnitude of the stream stars is estimated to be Mr ∼ -7.5. There is tentative evidence for a velocity signature, with the stream moving at ∼-40 km s -1 at low declinations and ∼+100 km s-1 at high declinations. The stream lies on the same great circle as Complex A, a roughly linear association of H I high-velocity clouds stretching over ∼30° on the sky, and as Ursa Major II, a recently discovered dwarf spheroidal galaxy. Lying close to the same great circle are a number of anomalous, young, and metal-poor globular clusters, including Palomar 1 and Ruprecht 106.

Original languageEnglish
Pages (from-to)337-344
Number of pages8
JournalAstrophysical Journal
Issue number1 I
Publication statusPublished - 20 Mar 2007
Externally publishedYes


  • Galaxies: kinematics and dynamics
  • Galaxies: structure
  • Local group


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