Signatures of minor mergers in the Milky Way disc – I. The SEGUE stellar sample

Authors

  • Facundo A. Gómez,

    Corresponding author
    1. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
    2. Institute for Cyber-Enabled Research, Michigan State University, East Lansing, MI 48824, USA
      E-mail: fgomez@pa.msu.edu
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  • Ivan Minchev,

    1. Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany
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  • Brian W. O’Shea,

    1. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
    2. Institute for Cyber-Enabled Research, Michigan State University, East Lansing, MI 48824, USA
    3. Lyman Briggs College, Michigan State University, East Lansing, MI 48825, USA
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  • Young Sun Lee,

    1. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
    2. Joint Institute for Nuclear Astrophysics (JINA), Michigan State University, East Lansing, MI 48824, USA
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  • Timothy C. Beers,

    1. Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
    2. National Optical Astronomy Observatory, Tucson, AZ 85719, USA
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  • Deokkeun An,

    1. Department of Science Education, Ewha Womans University, Seoul 120-750, Republic of Korea
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  • James S. Bullock,

    1. Center for Cosmology, Department of Physics and Astronomy, The University of California, Irvine, CA 92697, USA
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  • Chris W. Purcell,

    1. Center for Cosmology, Department of Physics and Astronomy, The University of California, Irvine, CA 92697, USA
    2. Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260, USA
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  • Álvaro Villalobos

    1. INAF – Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34143 Trieste, Italy
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E-mail: fgomez@pa.msu.edu

ABSTRACT

It is now known that minor mergers are capable of creating structure in the phase-space distribution of their host galaxy’s disc. In order to search for such imprints in the Milky Way, we analyse the Sloan Extension for Galactic Understanding and Exploration (SEGUE) F/G dwarf and the Schuster et al. stellar samples. We find similar features in these two completely independent stellar samples, consistent with the predictions of a Milky Way minor-merger event. We next apply the same analyses to high-resolution, idealized N-body simulations of the interaction between the Sagittarius dwarf galaxy and the Milky Way. The energy distributions of stellar particle samples in small spatial regions in the host disc reveal strong variations of structure with position. We find good matches to the observations for models with a mass of Sagittarius’ dark matter halo progenitor less-than or approximately equal-to1011 M. Thus, we show that this kind of analysis could be used to provide unprecedentedly tight constraints on Sagittarius’ orbital parameters, as well as place a lower limit on its mass.

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