Mechanisms of the Vertical Secular Heating of a Stellar Disk

Astrophysics, abstract
astro-ph/0304215

From: Natalia Sotnikova <nsot@astro.spbu.ru>

Date: Fri, 11 Apr 2003 12:39:54 GMT   (571kb)

Authors:
N.Ya.Sotnikova,
S.A.Rodionov

Comments: 22 pages including 8 figures. To be published in Astronomy Letters
(v.29, 2003)

We investigate the nonlinear growth stages of bending instability in stellar
disks with exponential radial density profiles.We found that the unstable modes
are global (the wavelengths are larger than the disk scale lengths) and that
the instability saturation level is much higher than that following from a
linear criterion. The instability saturation time scales are of the order of
one billion years or more. For this reason, the bending instability can play an
important role in the secular heating of a stellar disk in the $z$ direction.
In an extensive series of numerical $N$-body simulations with a high spatial
resolution, we were able to scan in detail the space of key parameters (the
initial disk thickness $z_0$, the Toomre parameter $Q$, and the ratio of dark
halo mass to disk mass $M_{
m h} / M_{
m d}$). We revealed three distinct
mechanisms of disk heating in the $z$ direction: bending instability of the
entire disk, bending instability of the bar, and heating on vertical
inhomogeneities in the distribution of stellar matter.

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