Journal Article

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 and Thirupathi Sivarani

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 389, issue 3, pages 1391-1398
Published in print September 2008 | ISSN: 0035-8711
Published online September 2008 | e-ISSN: 1365-2966 | DOI:
On the genealogy of the Orphan Stream

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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.

Keywords: galaxies: evolution; galaxies: formation; galaxies: haloes; galaxies: kinematics and dynamics

Journal Article.  7234 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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