On Passing of Interstellar Clouds Through a Galactic Spiral Arm

It is believed that the taxonomy of interstellar clouds in their vicinity can serve as an indicator of the features of the geometry and intensity of galactic shock waves. In this paper, the authors present the results of a detailed two-dimensional hydrodynamic simulation of the passage of a cloud through the spiral arm of a galaxy and provide a brief analysis of the effects arising from this motion. The model of interstellar gas used assumes adiabatic flow in the spiral arm. The external gravitational field of the galactic disk and spiral arm is taken into account. The transverse dimensions of the arm in the calculations are taken as follows: the half-width of the arm is 1 kpc along the plane of the disk and 0.6 kpc in the vertical direction. A fragment of the flow is considered near and inside the spiral arm, the effects of the curvature of the arm and theinfluence of the Coriolis forces are neglected. It is shown that clouds passing through the arm are strongly deformed and lose a significant part of the mass or are completely destroyed in the case of low-mass clouds. The boundary value of the cloud mass at which complete destruction occurs lies in the interval between 3 000 and 6 000 M.