Resonant thickening of self-gravitating discs: imposed or self-induced orbital diffusion in the tightly wound limit - Sorbonne Université Accéder directement au contenu
Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2017

Resonant thickening of self-gravitating discs: imposed or self-induced orbital diffusion in the tightly wound limit

Jean-Baptiste Fouvry
Christophe Pichon
Laura Monk

Résumé

The secular thickening of a self-gravitating stellar galactic disc is investigated using the dressed collisionless Fokker–Planck equation and the inhomogeneous multicomponent Balescu–Lenard equation. The thick WKB limits for the diffusion fluxes are found using the epicyclic approximation, while assuming that only radially tightly wound transient spirals are sustained by the disc. This yields simple quadratures for the drift and diffusion coefficients, providing a clear understanding of the positions of maximum vertical orbital diffusion within the disc, induced by fluctuations either external or due to the finite number of particles. These thick limits also offer a consistent derivation of a thick disc Toomre parameter, which is shown to be exponentially boosted by the ratio of the vertical to radial scaleheights. Dressed potential fluctuations within the disc statistically induce a vertical bending of a subset of resonant orbits, triggering the corresponding increase in vertical velocity dispersion. When applied to a tepid stable tapered disc perturbed by shot noise, these two frameworks reproduce qualitatively the formation of ridges of resonant orbits towards larger vertical actions, as found in direct numerical simulations, but overestimates the time-scale involved in their appearance. Swing amplification is likely needed to resolve this discrepancy, as demonstrated in the case of razor-thin discs. Other sources of thickening are also investigated, such as fading sequences of slowing bars, or the joint evolution of a population of giant molecular clouds within the disc.

Dates et versions

hal-01613332 , version 1 (09-10-2017)

Identifiants

Citer

Jean-Baptiste Fouvry, Christophe Pichon, Pierre-Henri Chavanis, Laura Monk. Resonant thickening of self-gravitating discs: imposed or self-induced orbital diffusion in the tightly wound limit. Monthly Notices of the Royal Astronomical Society, 2017, 471 (3), pp.2642 - 2673. ⟨10.1093/mnras/stx1625⟩. ⟨hal-01613332⟩
96 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More