On the settling of small grains in dusty discs: analysis and formulas

Guillaume Laibe , Charles-Edouard Bréhier (1, 2) , Maxime Lombart

1 PSPM - Probabilités, statistique, physique mathématique
2 ICJ - Institut Camille Jordan

Instruments achieve sharper and finer observations of micron-in-size dust grains in the top layers of young stellar discs. To provide accurate models, we revisit the theory of dust settling for small grains, when gas stratification, dust inertia and finite correlation times for the turbulence should be handled simultaneously. We start from a balance of forces and derive distributions at steady-state. Asymptotic expansions require caution since limits do not commute. In particular, non-physical bumpy distributions appear when turbulence is purely diffusive. This excludes very short correlation times for real discs, as predicted by numerical simulations.

Mots clés: Planets and satellites: formation; Diffusion; Turbulence; Methods: analytical; Methods: numerical

Domaines: Astrophysique [astro-ph]

Guillaume Laibe, Charles-Edouard Bréhier, Maxime Lombart. On the settling of small grains in dusty discs: analysis and formulas. Monthly Notices of the Royal Astronomical Society, 2020, ⟨10.1093/mnras/staa994⟩. ⟨hal-03020151⟩