SPH simulations of grain growth in protoplanetary disks

¹ Université de Lyon, Lyon, 69003; Université Lyon 1, Villeurbanne, 69622; CNRS, UMR 5574, Centre de Recherche Astrophysique de Lyon; École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France e-mail: [Guillaume.Laibe;Jean-Francois.Gonzalez]@ens-lyon.fr
² Institute of Astronomy, ETH Zürich, Schafmattstrasse 16, HPT D19, 8093 Zürich, Switzerland e-mail: fouchet@phys.ethz.ch
³ Centre for Astrophysics and Supercomputing, Swinburne Institute of Technology, PO Box 218, Hawthorn, VIC 3122, Australia e-mail: smaddison@swin.edu.au

Received: 6 February 2008
Accepted: 5 June 2008

Abstract

Aims. In order to understand the first stages of planet formation, when tiny grains aggregate to form planetesimals, one needs to simultaneously model grain growth, vertical settling and radial migration of dust in protoplanetary disks. In this study, we implement an analytical prescription for grain growth into a 3D two-phase hydrodynamics code to understand its effects on the dust distribution in disks.

Methods. Following the analytic derivation of Stepinski & Valageas (1997, A&A, 319, 1007), which assumes that grains stick perfectly upon collision, we implement a convenient and fast method of following grain growth in our 3D, two-phase (gas+dust) SPH code. We then follow the evolution of the size and spatial distribution of a dust population in a classical T Tauri star disk.

Results. We find that the grains go through various stages of growth due to the complex interplay between gas drag, dust dynamics, and growth. Grains initially grow rapidly as they settle to the mid-plane, then experience a fast radial migration with little growth through the bulk of the disk, and finally pile-up in the inner disk where they grow more efficiently. This results in a bimodal distribution of grain sizes. Using this simple prescription of grain growth, we find that grains reach decimetric sizes in 10⁵ years in the inner disk and survive the fast migration phase.