paper

Are galactic disks dynamically influenced by dust?

arXiv:astro-ph/0405331 · doi:10.1051/0004-6361:20034047

Abstract

Dynamically cold components are well known to destabilize hotter, even much more massive components. In this paper we studied the dynamical influence of a cold dust component on the gaseous phase in the central regions of galactic disks. We performed two-dimensional hydrodynamical simulations for flat multi-component disks embedded in a combined static stellar and dark matter potential. The pressure-free dust component is coupled to the gas by a drag force depending on their velocity difference. It turned out that the most unstable regions are those with either a low or near to minimum Toomre parameter or with rigid rotation, i.e. the central area. In that regions the dust-free disks become most unstable for high azimuthal modes (m~8), whereas in dusty disks all modes have a similar amplitude resulting in a patchy appearance. The structures in the dust have a larger contrast between arm and inter-arm regions than those of the gas. The dust peaks are frequently correlated with peaks of the gas distribution, but they do not necessarily coincide with them. Therefore, a large scatter in the dust-to-gas ratios is expected. The appearance of the dust is more cellular (i.e. sometimes connecting different spiral features), whereas the gas is organized in a multi-armed spiral structure. An admixture of 2% dust destabilizes gaseous disks substantially, whereas dust-to-gas ratios below 1% have no influence on the evolution of the gaseous disk. For a high dust-to-gas ratio of 10% the instabilities reach a saturation level already after 30 Myr.

21 pages including 24 figures (some figures degraded in quality), in press in Astronomy & Astrophysics 418, 959(2004), A&A version available at http://www.edpsciences.org/articles/aa/full/2004/18/aa0047/aa0047.html

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