An elementary model for the dust cycle in galaxies

We give an elementary model for the evolution of dust in galaxies, based on abundance arguments. The model takes account of grain core production in b oth supernovae and giant stars, and includes mantle growth in the interstel lar medium. Destruction of grain cores does not appear to be a dominant eff ect. We show that a self-consistent picture can be made in which the inters tellar dust mass is an approximately constant fraction of the heavy element mass in the interstellar medium. This result is demonstrated to be essenti ally independent of outflow or inflow of interstellar material.