On the maximum grain size entrained by photoevaporative winds

TL;DR

This paper develops an analytic model for the maximum dust grain size that photoevaporative winds can entrain from protoplanetary discs, validated by hydrodynamic simulations, revealing size limits influenced by disc mass loss and dust settling.

Contribution

It provides a new analytic expression for maximum entrainable grain size in photoevaporative winds, linking it to disc mass loss rate and validating it with simulations.

Findings

Maximum grain size proportional to disc mass loss rate.

Hydrodynamic simulations confirm the analytic model.

Dust settling reduces entrainable grain sizes in turbulent discs.

Abstract

We model the behaviour of dust grains entrained by photoevaporation-driven winds from protoplanetary discs assuming a non-rotating, plane-parallel disc. We obtain an analytic expression for the maximum entrainable grain size in extreme-UV radiation-driven winds, which we demonstrate to be proportional to the mass loss rate of the disc. When compared with our hydrodynamic simulations, the model reproduces almost all of the wind properties for the gas and dust. In typical turbulent discs, the entrained grain sizes in the wind are smaller than the theoretical maximum everywhere but the inner disc due to dust settling.