Post-galactic-shock dust distribution: one-dimensional model

The aim of the paper is to study whether the dust lanes in the interstellar gas and the shock front in the galactic shock wave can be well spatially separated. A one-dimensional model of the steady state gas-dust flow through the gravitational potential well of the spiral arm is analyzed. The model considers gas and dust as two interpenetrating fluids with two different velocities. Friction is adopted as the only kind of interaction between dust and gas; dust pressure from gas as well as internal pressure inside dust fluid are not allowed for. Dust is considered as a light component dragged by gas, the opposite influence of dust on gas motion is neglected. Turbulent diffusion of dust particles is also ignored. The dust component is considered as a monodisperse mixture of identical particles whose sizes remain constant. Dust streams into the computational domain together with gas, no dust production inside the spiral arm is taken into account. The calculations show that dust has a tendency to concentrate at the rear side of the spiral arm whereas the shock front is set up on the front side. It is concluded that the areas of dust concentration within the arm can be significantly spatially separated from the galactic shock front and thus may not serve as tracers of the shock front. Furthermore, the dust lanes arise even in the subsonic gas flow through the spiral arm when the shock front never forms and thus the dust lanes presence may be not related to the presence or absence of the shock front.