Velocity-Anisotropy-Driven Bending Instability in the Galactic Stellar Disk
Resource
CHINESE JOURNAL OF PHYSICS, VOL. 38, NO. 2-I
Journal
Chinese Journal of Physics
Journal Volume
VOL. 38
Journal Issue
NO. 2-I
Pages
-
Date Issued
2000-04
Date
2000-04
Author(s)
Chiueh, Tzihong
Wu, Jun-Mein
Tseng, Yao-Huan
DOI
20060927120019929879
Abstract
Motivated by the results of a recent ultra-high-resolution simulation, which discovers
the disk bending instability in a regime conventional thought to be stable, we analyze an
idealized galactic stellar disk against such an instability, and obtain a reasonable agreement
with the simulation results. The nature of this unstable bending perturbations differs from
that predicted by Toomre, in that they tend to be of long wavelength. The success of our
analysis relies fundamentally on the determination of two equations of states pertaining to
two adiabatic invariants of the three-dimensional stellar motion in a disk. We find that the
disk can be subject to the bending instability when ¯=Q is greater than unity, where ¯ is the
velocity anisotropy and the Toomre Q represents the ratio of disk kinetic energy to gravitational
potential energy.
Publisher
臺北市:國立臺灣大學物理系所
Type
journal article
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