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The effects of bar-spiral coupling on stellar kinematics in the Galaxy

Monari, G; Famaey, B; Siebert, A; Grand, RJJ; Kawata, D; Boily, C; (2016) The effects of bar-spiral coupling on stellar kinematics in the Galaxy. Monthly Notices of the Royal Astronomical Society , 461 (4) pp. 3835-3846. 10.1093/mnras/stw1564. Green open access

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Abstract

We investigate models of the Milky Way disc taking into account simultaneously the bar and a two-armed quasi-static spiral pattern. Away from major resonance overlaps, the mean stellar radial motions in the plane are essentially a linear superposition of the isolated effects of the bar and spirals. Thus, provided the bar is strong enough, even in the presence of spiral arms, these mean radial motions are predominantly affected by the Galactic bar for large scale velocity fluctuations. This is evident when comparing the peculiar line-of-sight velocity power spectrum of our coupled models with bar-only models. However, we show how forthcoming spectroscopic surveys could disentangle bar-only non-axisymmetric models of the Galaxy from models in which spiral arms have a significant amplitude. We also point out that overlaps of low-order resonances are sufficient to enhance stellar churning within the disc, even when the spirals amplitude is kept constant. Nevertheless, for churning to be truly non-local, stronger or (more likely) transient amplitudes would be needed: otherwise the disc is actually mostly unaffected by churning in the present models. Finally, regarding vertical breathing modes, the combined effect of the bar and spirals on vertical motions is a clear non-linear superposition of the isolated effects of both components, significantly superseding the linear superposition of modes produced by each perturber separately, thereby providing an additional effect to consider when analysing the observed breathing mode of the Galactic disc in the extended Solar neighbourhood.

Type: Article
Title: The effects of bar-spiral coupling on stellar kinematics in the Galaxy
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stw1564
Publisher version: http://dx.doi.org/10.1093/mnras/stw1564
Language: English
Additional information: © 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Galaxy: evolution, Galaxy: kinematics and dynamics, solar neighbourhood, Galaxy: structure, galaxies: spiral.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/1501278
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