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The shape of the dark matter halo revealed from a hypervelocity star

Published online by Cambridge University Press:  14 May 2020

Kohei Hattori Open the ORCID record for Kohei Hattori [Opens in a new window]  and
Monica Valluri
Kohei Hattori
Affiliation:
Deptartment of Astronomy, University of Michigan, 1085 S University Ave, Ann Arbor, MI48109, USA email: khattori@umich.edu Deptartment of Physics, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA15213, USA
Monica Valluri
Affiliation:
Deptartment of Astronomy, University of Michigan, 1085 S University Ave, Ann Arbor, MI48109, USA email: khattori@umich.edu
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Abstract

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A recently discovered young, high-velocity giant star J01020100-7122208 is a good candidate of hypervelocity star ejected from the Galactic center, although it has a bound orbit. If we assume that this star was ejected from the Galactic center, it can be used to constrain the Galactic potential, because the deviation of its orbit from a purely radial orbit informs us of the torque that this star has received. Based on this assumption, we estimate the flattening of the Galactic dark matter halo by using the Gaia DR2 data and the circular velocity data. Our Bayesian analysis shows that the orbit of J01020100-7122208 favors a prolate halo within ~ 10 kpc from the Galactic center. The posterior distribution of the density flattening q shows a broad distribution at q ≳ 1 and peaks at q ≃ 1.5. Also, 98.5% of the posterior distribution is located at q > 1, highly disfavoring an oblate halo.

Keywords

Galaxy: haloGalaxy: structureGalaxy: kinematics and dynamics
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 14 , Symposium S353: Galactic Dynamics in the Era of Large Surveys , June 2019 , pp. 96 - 100
Copyright
© International Astronomical Union 2020

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