Journal article
Galactic Bar Resonances with Diffusion: An Analytic Model with Implications for Bar-Dark Matter Halo Dynamical Friction
The Astrophysical journal, Vol.954(1), 12
09/01/2023
DOI: 10.3847/1538-4357/acd69b
Abstract
The secular evolution of disk galaxies is largely driven by resonances between the orbits of "particles" (stars or dark matter) and the rotation of non-axisymmetric features (spiral arms or a bar). Such resonances may also explain kinematic and photometric features observed in the Milky Way and external galaxies. In simplified cases, these resonant interactions are well understood: for instance, the dynamics of a test particle trapped near a resonance of a steadily rotating bar is easily analyzed using the angle-action tools pioneered by Binney, Monari, and others. However, such treatments do not address the stochasticity and messiness inherent to real galaxies-effects that have, with few exceptions, been previously explored only with complex N-body simulations. In this paper, we propose a simple kinetic equation describing the distribution function of particles near an orbital resonance with a rigidly rotating bar, allowing for diffusion of the particles' slow actions. We solve this equation for various values of the dimensionless diffusion strength & UDelta;, and then apply our theory to the calculation of bar-halo dynamical friction. For & UDelta; = 0, we recover the classic result of Tremaine and Weinberg that friction ultimately vanishes, owing to the phase mixing of resonant orbits. However, for & UDelta; > 0, we find that diffusion suppresses phase mixing, leading to a finite torque. Our results suggest that stochasticity-be it physical or numerical-tends to increase bar-halo friction, and that bars in cosmological simulations might experience significant artificial slowdown, even if the numerical two-body relaxation time is much longer than a Hubble time.
Details
- Title: Subtitle
- Galactic Bar Resonances with Diffusion: An Analytic Model with Implications for Bar-Dark Matter Halo Dynamical Friction
- Creators
- Chris Hamilton - Institute for Advanced StudyElizabeth A. Tolman - Institute for Advanced StudyLev Arzamasskiy - Institute for Advanced StudyVinicius N. Duarte - Princeton Plasma Physics Laboratory
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.954(1), 12
- DOI
- 10.3847/1538-4357/acd69b
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Publisher
- IOP Publishing Ltd
- Number of pages
- 21
- Grant note
- Institute for Advanced Study PHY-1607611 / National Science Foundation; National Science Foundation (NSF) DE-AC02-09CH11466 / U.S. Department of Energy; United States Department of Energy (DOE) W.M. Keck Foundation Fund at the Institute for Advanced Study; W.M. Keck Foundation 816048 / Simons Foundation
- Language
- English
- Date published
- 09/01/2023
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9985113756802771
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