Radial transport of dust in spiral galaxies

Abstract

Motivated by recent observations which detect dust at large galactocentric distances in the disks of spiral galaxies, we propose a mechanism of outward radial transport of dust by spiral stellar density waves. We consider spiral galaxies in which most of dust formation is localized inside the corotation radius. We show that in the disks of such spiral galaxies, the dust grains can travel over radial distances that exceed the corotation radius by roughly 25%. A fraction of the dust grains can be trapped on kidney-shaped stable orbits between the stellar spiral arms and thus can escape the destructive effect of supernova explosions. These grains form diffuse dusty spiral arms, which stretch 4-5 kpc from the sites of active star formation. About 10% of dust by mass injected inside corotation, can be transported over radial distances 3-4 kpc during approximately 1.0 Gyr. This is roughly an order of magnitude more efficient than can be provided by the turbulent motions.