Astronomy & Astrophysics

A&A 468, 803-805 (2007)
DOI: 10.1051/0004-6361:20077372

Jeans instability of a galactic disk embedded in a live dark halo

O. Esquivel and B. Fuchs

Astronomisches Rechen-Institut am Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
e-mail: esquivel@ari.uni-heidelberg.de

(Received 28 February 2007 / Accepted 3 April 2007)

Abstract
We investigate the Jeans instability of a galactic disk embedded in a dynamically responsive dark halo. It is shown that the disk-halo system becomes nominally Jeans unstable. On small scales the instability is suppressed, if the Toomre stability index $Q_{\rm T}$ is higher than a certain threshold, but on large scales the Jeans instability sets invariably in. However, using a simple self-consistent disk-halo model it is demonstrated that this occurs on scales which are much larger than the system so that this is indeed only a nominal effect. From a practical point of view the Jeans instability of galactic disks is not affected by a live dark halo.

Key words: galaxies: kinematics and dynamics -- galaxies: halos