Two-size approximation: a simple way of treating the evolution of grain size distribution in galaxies

Understand

Full calculations of the evolution of grain size distribution in galaxies are in general computationally heavy.

• In this paper, we propose a simple model of dust enrichment in a galaxy with a simplified treatment of grain size distribution by imposing a `two-size approximation'; that is, all the grain population is represented by small (grain radius a < 0.03 micron) and large (a > 0.03 micron) grains.
• We include in the model dust supply from stellar ejecta, destruction in supernova shocks, dust growth by accretion, grain growth by coagulation and grain disruption by shattering, considering how these processes work on the small and large grains.
• We show that this simple framework reproduces the main features found in full calculations of grain size distributions as follows.