On the genealogy of the Orphan Stream

Laura V. Sales, Amina Helmi, Else Starkenburg, Heather L. Morrison, Ethan Engle, Paul Harding, Mario Mateo, Edward W. Olszewski, Thirupathi Sivarani

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


We use N-body simulations to explore the origin and a plausible orbit for the Orphan Stream, one of the faintest substructures discovered so far in the outer halo of our Galaxy. We are able to reproduce its position, velocity and distance measurements by appealing to a single wrap of a double-component satellite galaxy. We find that the progenitor of the Orphan Stream could have been an object similar to today's Milky Way dwarfs, such as Carina, Draco, Leo II or Sculptor; and unlikely to be connected to Complex A or Ursa Major II. Our models suggest that such progenitors, if accreted on orbits with apocentres smaller than ∼35 kpc, are likely to give rise to very low surface brightness streams, which may be hiding in the outer halo and remain largely undetected with current techniques. The systematic discovery of these ghostly substructures may well require wide field spectroscopic surveys of the Milky Way's outer stellar halo.

Original languageEnglish (US)
Pages (from-to)1391-1398
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Sep 2008


  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: haloes
  • Galaxies: kinematics and dynamics

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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