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Kinematics with GAIA DR2 : The force of a dwarf

Carrillo, I. ; Minchev, I. ; Steinmetz, M. ; Monari, G. ; Laporte, C. F.P. ; Anders, F. ; Queiroz, A. B.A. ; Chiappini, C. ; Khalatyan, A. and Martig, M. , et al. (2019) In Monthly Notices of the Royal Astronomical Society 490(1). p.797-812
Abstract

We use Gaia DR2 astrometric and line-of-sight velocity information combined with two sets of distances obtained with a Bayesian inference method to study the 3D velocity distribution in the Milky Way disc. We search for variations in all Galactocentric cylindrical velocity components (Vφ, VR, and Vz) with Galactic radius, azimuth, and distance from the disc mid-plane. We confirm recent work showing that bulk vertical motions in the R–z plane are consistent with a combination of breathing and bending modes. In the x–y plane, we show that, although the amplitudes change, the structure produced by these modes is mostly invariant as a function of distance from the plane. Comparing to two different Galactic... (More)

We use Gaia DR2 astrometric and line-of-sight velocity information combined with two sets of distances obtained with a Bayesian inference method to study the 3D velocity distribution in the Milky Way disc. We search for variations in all Galactocentric cylindrical velocity components (Vφ, VR, and Vz) with Galactic radius, azimuth, and distance from the disc mid-plane. We confirm recent work showing that bulk vertical motions in the R–z plane are consistent with a combination of breathing and bending modes. In the x–y plane, we show that, although the amplitudes change, the structure produced by these modes is mostly invariant as a function of distance from the plane. Comparing to two different Galactic disc models, we demonstrate that the observed patterns can drastically change in short time intervals, showing the complexity of understanding the origin of vertical perturbations. A strong radial VR gradient was identified in the inner disc, transitioning smoothly from 16 km s−1 kpc−1 at an azimuth of 30 < φ < 45 ahead of the Sun-Galactic centre line to −16 km s−1 kpc−1 at an azimuth of −45 < φ < −30 lagging the solar azimuth. We use a simulation with no significant recent mergers to show that exactly the opposite trend is expected from a barred potential, but overestimated distances can flip this trend to match the data. Alternatively, using an N-body simulation of the Sagittarius dwarf–Milky Way interaction, we demonstrate that a major recent perturbation is necessary to reproduce the observations. Such an impact may have strongly perturbed the existing bar or even triggered its formation in the last 1–2 Gyr.

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publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxy: disc, Galaxy: evolution, Galaxy: kinematics and dynamics, Galaxy: structure
in
Monthly Notices of the Royal Astronomical Society
volume
490
issue
1
pages
16 pages
publisher
Oxford University Press
external identifiers
  • scopus:85075228474
ISSN
1365-2966
DOI
10.1093/mnras/stz2343
language
English
LU publication?
yes
id
c1f32db0-42a6-4da5-b46f-9e406c545a36
date added to LUP
2019-12-10 12:38:26
date last changed
2020-10-07 06:48:58
@article{c1f32db0-42a6-4da5-b46f-9e406c545a36,
  abstract     = {<p>We use Gaia DR2 astrometric and line-of-sight velocity information combined with two sets of distances obtained with a Bayesian inference method to study the 3D velocity distribution in the Milky Way disc. We search for variations in all Galactocentric cylindrical velocity components (V<sub>φ</sub>, V<sub>R</sub>, and V<sub>z</sub>) with Galactic radius, azimuth, and distance from the disc mid-plane. We confirm recent work showing that bulk vertical motions in the R–z plane are consistent with a combination of breathing and bending modes. In the x–y plane, we show that, although the amplitudes change, the structure produced by these modes is mostly invariant as a function of distance from the plane. Comparing to two different Galactic disc models, we demonstrate that the observed patterns can drastically change in short time intervals, showing the complexity of understanding the origin of vertical perturbations. A strong radial V<sub>R</sub> gradient was identified in the inner disc, transitioning smoothly from 16 km s<sup>−1</sup> kpc<sup>−1</sup> at an azimuth of 30<sup>◦</sup> &lt; φ &lt; 45<sup>◦</sup> ahead of the Sun-Galactic centre line to −16 km s<sup>−1</sup> kpc<sup>−1</sup> at an azimuth of −45<sup>◦</sup> &lt; φ &lt; −30<sup>◦</sup> lagging the solar azimuth. We use a simulation with no significant recent mergers to show that exactly the opposite trend is expected from a barred potential, but overestimated distances can flip this trend to match the data. Alternatively, using an N-body simulation of the Sagittarius dwarf–Milky Way interaction, we demonstrate that a major recent perturbation is necessary to reproduce the observations. Such an impact may have strongly perturbed the existing bar or even triggered its formation in the last 1–2 Gyr.</p>},
  author       = {Carrillo, I. and Minchev, I. and Steinmetz, M. and Monari, G. and Laporte, C. F.P. and Anders, F. and Queiroz, A. B.A. and Chiappini, C. and Khalatyan, A. and Martig, M. and McMillan, P. J. and Santiago, B. X. and Youakim, K.},
  issn         = {1365-2966},
  language     = {eng},
  number       = {1},
  pages        = {797--812},
  publisher    = {Oxford University Press},
  series       = {Monthly Notices of the Royal Astronomical Society},
  title        = {Kinematics with GAIA DR2 : The force of a dwarf},
  url          = {http://dx.doi.org/10.1093/mnras/stz2343},
  doi          = {10.1093/mnras/stz2343},
  volume       = {490},
  year         = {2019},
}