NGC 5466: a unique probe of the Galactic halo shape

Authors

  • H. Lux,

    Corresponding author
    1. School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD
    2. Department of Theoretical Physics, University of Zürich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
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  • J. I. Read,

    1. Institute for Astronomy, Department of Physics, ETH Zürich, Wolfgang-Pauli-Strasse 16, CH-8093 Zürich, Switzerland
    2. Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH
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  • G. Lake,

    1. Department of Theoretical Physics, University of Zürich, Winterthurerstr. 190, CH-8057 Zürich, Switzerland
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  • K. V. Johnston

    1. Department of Astronomy, Columbia University, Pupin Physics Laboratories, 550 West 120th Street, New York, NY 10027, USA
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E-mail: Hanni.Lux@nottingham.ac.uk

ABSTRACT

Stellar streams provide unique probes of galactic potentials, with the longer streams normally providing the cleaner measurements. In this Letter, we show an example of a short tidal stream that is particularly sensitive to the shape of the Milky Way’s dark matter halo: the globular cluster tidal stream NGC 5466. This stream has an interesting deviation from a smooth orbit at its western edge. We show that such a deviation favours an underlying oblate or triaxial halo (irrespective of plausible variations in the Milky Way disc properties and the specific halo parametrization chosen); spherical or prolate halo shapes can be excluded at a high confidence level. Therefore, more extensive data sets along the NGC 5466 tidal stream promise strong constraints on the Milky Way halo shape.

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