Can Massive Dark Haloes Destroy the Disks of Dwarf Galaxies?

TL;DR

This paper investigates how massive dark haloes influence the stability of dwarf galaxy disks, revealing that overly massive and cold haloes can induce local instabilities, but realistic haloes generally do not destabilize disks.

Contribution

It generalizes Toomre's Q parameter for disk-halo systems and demonstrates conditions under which dark haloes can destabilize dwarf galaxy disks.

Findings

Massive, cold haloes can cause local Jeans instability in disks.

Realistic dark haloes in equilibrium do not destabilize disks.

Low-mass disks remain stable despite halo effects.

Abstract

Recent high-resolution simulations together with theoretical studies of the dynamical evolution of galactic disks have shown that contrary to wide-held beliefs a `live', dynamically responsive, dark halo surrounding a disk does not stabilize the disk against dynamical instabilities. We generalize Toomre's Q stability parameter for a disk-halo system and show that if a disk, which would be otherwise stable, is embedded in a halo, which is too massive and cold, the combined disk-halo system can become locally Jeans unstable. The good news is, on the other hand, that this will not happen in real dark haloes, which are in radial hydrostatic equilibrium. Even very low-mass disks are not prone to such dynamical instabilities.