On the genealogy of the Orphan Stream
Corresponding Author
Laura V. Sales
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
E-mail: [email protected] LVSSearch for more papers by this authorAmina Helmi
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
Search for more papers by this authorElse Starkenburg
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
Search for more papers by this authorHeather L. Morrison
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106-7215, USA
Search for more papers by this authorEthan Engle
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106-7215, USA
Search for more papers by this authorPaul Harding
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106-7215, USA
Search for more papers by this authorMario Mateo
Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
Search for more papers by this authorEdward W. Olszewski
Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
Search for more papers by this authorThirupathi Sivarani
Department of Physics & Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, MI, USA
Search for more papers by this authorCorresponding Author
Laura V. Sales
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
E-mail: [email protected] LVSSearch for more papers by this authorAmina Helmi
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
Search for more papers by this authorElse Starkenburg
Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700AV Groningen, the Netherlands
Search for more papers by this authorHeather L. Morrison
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106-7215, USA
Search for more papers by this authorEthan Engle
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106-7215, USA
Search for more papers by this authorPaul Harding
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106-7215, USA
Search for more papers by this authorMario Mateo
Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
Search for more papers by this authorEdward W. Olszewski
Steward Observatory, University of Arizona, Tucson, AZ 85721, USA
Search for more papers by this authorThirupathi Sivarani
Department of Physics & Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, MI, USA
Search for more papers by this authorABSTRACT
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.
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