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David Hobbs. Photo.

David Hobbs

Professor

David Hobbs. Photo.

New stellar velocity substructures from Gaia DR3 proper motions

Author

  • Daniel Mikkola
  • Paul J. McMillan
  • David Hobbs

Summary, in English

Local stellar motions are expected, and have been shown, to include signatures of the Galaxy’s past dynamical evolution. These are typically divided into the disc, which shows the dynamical effects of spiral arms and the bar, and the stellar halo, with structures thought to be debris from past mergers. We use Gaia Data Release 3 to select large samples of these populations without limiting them to sources with radial velocities. We apply a penalized maximum likelihood method to these samples to determine the full 3D velocity distribution in Cartesian (U, V, and W) or spherical (vr, vφ, and vθ) coordinates. We find that the disc population is dominated by four moving groups and also detect a new moving group at (U, V) = (−10, −15) km s−1 which we call MMH-0. For the stellar halo, we isolate the accreted component with cuts in transverse velocity and the colour–magnitude diagram. In this component, we find several known structures believed to be caused by past mergers, particularly one around (vr, vφ, vθ) = (−150, −300, and −100) km s−1 appears more prominent than previously claimed. Furthermore, we also identify two new structures near (vr, vφ, and vθ) = (225, 25, and 325) km s−1 and (0, 150, and −125) km s−1, which we refer to as MMH-1 and MMH-2, respectively. These results give new insights into local stellar motions and shows the potential of using samples that are not limited to stars with measured line-of-sight velocities, which is key to providing large samples of stars, necessary for future studies.

Department/s

  • Astrophysics

Publishing year

2023-02-01

Language

English

Pages

1989-2003

Publication/Series

Monthly Notices of the Royal Astronomical Society

Volume

519

Issue

2

Document type

Journal article

Publisher

Oxford University Press

Topic

  • Astronomy, Astrophysics and Cosmology

Keywords

  • Galaxy: kinematics and dynamics
  • Galaxy: Solar neighbourhood
  • Galaxy: structure
  • methods: data analysis
  • methods: statistical
  • stars: kinematics and dynamics

Status

Published

ISBN/ISSN/Other

  • ISSN: 0035-8711