Cyclic Changes in Dust-to-Gas Ratio

摘要: We discuss the time variation of dust-to-gas mass ratio in spiral galaxies, using multiphase model interstellar medium. The typical timescale phase change an gas is ~107-8 yr galaxies. Since transition changes filling factor cold where dust growth occurs, rate varies on that timescale. In order to examine response transition, we construct a evolution ratio. adopt three-phase for and Ikeuchi-Tomita exchange between phases. According model, three types solutions are possible: (1) all transformed hot gas; (2) stable stationary state phases realized; (3) each cyclically changes. For solutions, behaves as follows: solution 1, almost destroyed (the becomes ~0); 2, converges state; 3, transition. case amplitude large (nearly magnitude) if shorter than This condition easily satisfied However, it difficult dwarf galaxies realize condition, because their small metallicity makes long.