Evolution of Dust Grains through a Hot Gaseous Halo

The evolution of bare spherical dust grains in the halo of spiral galaxies is analyzed. Two different grain compounds, graphites and astronomical silicates, are considered. The detailed mass and luminosity distributions for the Milky Way and NGC 3198 (considered as representative of the Sb and Sc types, respectively) are used to evaluate the range of possible evolutionary tracks. Aside from radiative and gravitational forces, the effects of drag and sputtering from a gaseous halo are included. A simple isothermal and hydrostatic density structure, with temperatures in the range 3 × 10 5 -10 6 K, has been used for this gaseous halo