Dust delivery and entrainment in photoevaporative winds

Hutchison, Mark A. und Clarke, Cathie J. (2021): Dust delivery and entrainment in photoevaporative winds. In: Monthly Notices of the Royal Astronomical Society, Bd. 501, Nr. 1: S. 1127-1142

Abstract

We model the gas and dust dynamics in a turbulent protoplanetary disc undergoing extreme-UV photoevaporation in order to better characterize the dust properties in thermal winds (e.g. size distribution, flux rate, trajectories). Our semi-analytic approach allows us to rapidly calculate these dust properties without resorting to expensive hydrodynamic simulations. We find that photoevaporation creates a vertical gas flow within the disc that assists turbulence in supplying dust to the ionization front. We examine both the delivery of dust to the ionization front and its subsequent entrainment in the overlying wind. We derive a simple analytic criterion for the maximum grain size that can be entrained and show that this is in good agreement with the results of previous simulations where photoevaporation is driven by a range of radiation types. We show that, in contrast to the case for magnetically driven winds, we do not expect large-scale dust transport within the disc to be effected by photoevaporation. We also show that the maximum size of grains that can be entrained in the wind (s(max)) is around an order of magnitude larger than the maximum size of grains that can be delivered to the front by advection alone (s(crit) less than or similar to 1 mu m for Herbig Ae/Be stars and less than or similar to 0.01 mu m for T Tauri stars). We further investigate how larger grains, up to a limiting size s(limit), can be delivered to the front by turbulent diffusion alone. In all cases, we find s(max) greater than or similar to s(limit) so that we expect that any dust that is delivered to the front can be entrained in the wind and that most entrained dust follows trajectories close to that of the gas.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 0035-8711
• Sprache: Englisch