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Dark matter dominated dwarf disc galaxy Segue 1

Authors

  • Meng Xiang-Gruess,

    1. Christian-Albrechts-Universität zu Kiel, Institut für Theoretische Physik und Astrophysik, Leibnizstr. 15, 24118 Kiel, Germany
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  • Yu-Qing Lou,

    1. Physics Department and Tsinghua Centre for Astrophysics (THCA), Tsinghua University, Beijing, 100084, China
    2. National Astronomical Observatories, Chinese Academy of Sciences, A20, Datun Road, Beijing 100012, China
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  • Wolfgang J. Duschl

    1. Christian-Albrechts-Universität zu Kiel, Institut für Theoretische Physik und Astrophysik, Leibnizstr. 15, 24118 Kiel, Germany
    2. Steward Observatory, The University of Arizona, 933 North Cherry Ave, Tucson, AZ 85721, USA
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E-mail: louyq@mail.tsinghua.edu.cn

ABSTRACT

Several observations reveal that dwarf galaxy Segue 1 has a dark matter (DM) halo at least ∼200 times more massive than its visible baryon mass of only ∼103 M. The baryon mass is dominated by stars with perhaps an interstellar gas mass of ≲13 M. Regarding Segue 1 as a dwarf disc galaxy by its morphological appearance of long stretch, we invoke the dynamic model of Xiang-Gruess, Lou & Duschl (XLD) to estimate its physical parameters for possible equilibria with and without an isopedically magnetized gas disc. We estimate the range of DM mass and compare it with available observational inferences. Due to the relatively high stellar velocity dispersion compared to the stellar surface mass density, we find that a massive DM halo would be necessary to sustain disc equilibria. The required DM halo mass agrees grossly with observational inferences so far. For an isopedic magnetic field in a gas disc, the ratio f between the DM and baryon potentials depends strongly on the magnetic field strength. Therefore, a massive DM halo is needed to counteract either the strong stellar velocity dispersion and rotation of the stellar disc or the magnetic Lorentz force in the gas disc. By the radial force balances, the DM halo mass increases for faster disc rotation.

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