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Distribution functions for Galactic disc stellar populations in the presence of non-axisymmetric perturbations

Published online by Cambridge University Press:  02 August 2018

B. Famaey Open the ORCID record for B. Famaey [Opens in a new window] ,
G. Monari ,
A. Siebert ,
J.-B. Fouvry  and
J. Binney
B. Famaey
Affiliation:
Université de Strasbourg, CNRS UMR 7550, Observatoire astronomique de Strasbourg 11 rue de l’Université, 67000 Strasbourg, France email: benoit.famaey@astro.unistra.fr
G. Monari
Affiliation:
The Oskar Klein Centre for Cosmoparticle Physics, Dept. of Physics, Stockholm University AlbaNova, 10691 Stockholm, Sweden
A. Siebert
Affiliation:
Université de Strasbourg, CNRS UMR 7550, Observatoire astronomique de Strasbourg 11 rue de l’Université, 67000 Strasbourg, France email: benoit.famaey@astro.unistra.fr
J.-B. Fouvry
Affiliation:
Institute for Advanced Study Einstein Drive, Princeton, NJ 08540, USA
J. Binney
Affiliation:
Rudolf Peierls Centre for Theoretical Physics Keble Road, Oxford OX1 3NP, UK
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Abstract

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The present-day response of a Galactic disc stellar population to a non-axisymmetric perturbation of the potential, in the form of a bar or spiral arms, can be treated, away from the main resonances, through perturbation theory within the action-angle coordinates of the unperturbed axisymmetric system. The first order moments of such a perturbed distribution function (DF) in the presence of spiral arms give rise to non-zero radial and vertical mean stellar velocities, called breathing modes. Such an Eulerian linearized treatment however diverges at resonances. The Lagrangian approach to the impact of non-axisymmetries at resonances avoids this problem. It is based on the construction of new orbital tori in the resonant trapping region, which come complete with a new system of angle-action variables. These new tori can be populated by phase-averaging the unperturbed DF over the new tori. This boils down to phase-mixing the DF in terms of the new angles, such that the DF for trapped orbits only depends on the new set of actions. This opens the way to quantitatively fitting the effects of the bar and spirals to Gaia data with an action-based DF.

Keywords

Galaxy: kinematics and dynamicsGalaxy: diskGalaxy: structure
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 13 , Symposium S334: Rediscovering our Galaxy , July 2017 , pp. 195 - 198
Copyright
Copyright © International Astronomical Union 2018 

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