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New stellar velocity substructures from Gaia DR3 proper motions

Mikkola, Daniel LU ; McMillan, Paul J. LU orcid and Hobbs, David LU orcid (2023) In Monthly Notices of the Royal Astronomical Society 519(2). p.1989-2003
Abstract

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... (More)

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.

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author
; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: kinematics and dynamics, Galaxy: Solar neighbourhood, Galaxy: structure, methods: data analysis, methods: statistical, stars: kinematics and dynamics
in
Monthly Notices of the Royal Astronomical Society
volume
519
issue
2
pages
15 pages
publisher
Oxford University Press
external identifiers
  • scopus:85159158875
ISSN
0035-8711
DOI
10.1093/mnras/stac3649
language
English
LU publication?
yes
id
fc7395fd-77a4-45e3-ba0d-2e3a4b4f7fe5
date added to LUP
2023-08-14 08:48:00
date last changed
2023-08-14 08:48:00
@article{fc7395fd-77a4-45e3-ba0d-2e3a4b4f7fe5,
  abstract     = {{<p>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 (v<sub>r</sub>, v<sub>φ</sub>, and v<sub>θ</sub>) 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<sup>−1</sup> 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 (v<sub>r</sub>, v<sub>φ</sub>, v<sub>θ</sub>) = (−150, −300, and −100) km s<sup>−1</sup> appears more prominent than previously claimed. Furthermore, we also identify two new structures near (v<sub>r</sub>, v<sub>φ</sub>, and v<sub>θ</sub>) = (225, 25, and 325) km s<sup>−1</sup> and (0, 150, and −125) km s<sup>−1</sup>, 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.</p>}},
  author       = {{Mikkola, Daniel and McMillan, Paul J. and Hobbs, David}},
  issn         = {{0035-8711}},
  keywords     = {{Galaxy: kinematics and dynamics; Galaxy: Solar neighbourhood; Galaxy: structure; methods: data analysis; methods: statistical; stars: kinematics and dynamics}},
  language     = {{eng}},
  month        = {{02}},
  number       = {{2}},
  pages        = {{1989--2003}},
  publisher    = {{Oxford University Press}},
  series       = {{Monthly Notices of the Royal Astronomical Society}},
  title        = {{New stellar velocity substructures from Gaia DR3 proper motions}},
  url          = {{http://dx.doi.org/10.1093/mnras/stac3649}},
  doi          = {{10.1093/mnras/stac3649}},
  volume       = {{519}},
  year         = {{2023}},
}