Influence of growth on dust settling and migration in protoplanetary discs

Abstract

To form meter-sized pre-planetesimals in protoplanetary discs, dust aggregates have to decouple from the gas at a distance far enough from the central star so they are not accreted. Dust grains are affected by gas drag, which results in a vertical settling towards the mid-plane, followed by radial migration. To have a better understanding of the influence of growth on the dust dynamics, we use a simple grain growth model to determine the dust distribution in observed discs. We implement a constant growth rate into a gas+dust hydrodynamics SPH code and vary the growh rate to study the resulting effect on dust distribution. The growth rate allows us to determine the relative importance between friction and growth.We show that depending on the growth rate, a range of dust distribution can result. For large enough growth rates, grains can decouple from the gas before being accreted onto the central star, thus contributing as planetary building rocks.