We present a numerical tool Shiva designed to simulate the dust destruction in warm neutral, warm ionized, and hot ionized media under the influence of photo-processing, sputtering, and shattering. The tool is designed primarily to study the evolution of hydrogenated amorphous carbons (HACs), but options to simulate polycyclic aromatic hydrocarbons (PAHs), silicate and graphite grains are also implemented. HAC grain photo-processing includes both dehydrogenation and carbon atom loss. Dehydrogenation leads to material transformation from aliphatic to aromatic structure. Simultaneously, some other physical properties (band gap energy, optical properties, etc.) of the material change as well. The Shiva tool allows calculating the time-dependent evolution of the dust size distribution depending on hydrogen, helium, and carbon number densities and ionization state, gas temperature, radiation flux, relative gasdust and grain-grain velocities. For HAC grains the evolution of band gap energy distribution is also computed. We describe a dust evolution model, on which the tool relies, and present evolutionary time-scales for dust grains of different sizes depending on external conditions. This allows a user to estimate quickly a lifetime of a specific dust grain under relevant conditions. As an example of the tool usage, we demonstrate how grain properties and corresponding infrared spectra evolve in photo-dissociation regions, HII regions, and supernova remnant shocks.

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Abstract— We consider the drift of dust grains of various sizes and chemical compositions caused by the stellar radiation pressure in the vicinity of the Milky Way. When integrating the equations of motion, in addition to the radiation pressure, we consider the gravitational attraction from various components of the Galaxy and the gas drag. It has been shown that carbonaceous grains of medium sizes (~0.01 μm) are swept out of the galactic disc most effectively. Smaller dust grains are swept out to a substantially lesser extent, or they are not swept out at all. We also consider the motion of silicate dust grains, including those with porous structure. It has been shown that silicate grains experience a considerably weaker impact of the radiation pressure. The simulation result of their motion does not essentially depend on whether their porosity is accounted for or ignored. The total rate of the Galaxy’s dust loss has turned out to be high—approximately 0.03 M⊙ per year, which is comparable to the effect produced by the other mechanisms ejecting heavy elements to the circumgalactic space. We discuss the potential of the sweeping of dust out of the Galaxy in formation of the radial metallicity gradient, as well as the prospects of detecting extensive dust structures in elliptical galaxies.