Dust distribution in protoplanetary disks

Vertical settling and radial migration

¹ Centre de Recherche Astronomique de Lyon (CNRS-UMR 5574), École Normale Supérieure de Lyon, 46 allée d'Italie, 69364 Lyon Cedex 07, France e-mail: [Laure.Barriere;Jean-Francois.Gonzalez]@ens-lyon.fr
² Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC 3122, Australia e-mail: [jmurray;smaddison]@swin.edu.au
³ Canadian Institute for Theoretical Astrophysics, University of Toronto, 60, St. George Street, Toronto, ON M5S 3H8, Canada e-mail: rjh@cita.utoronto.ca

Received: 25 October 2004
Accepted: 3 August 2005

Abstract

We present the results of a three dimensional, locally isothermal, non-self-gravitating SPH code which models protoplanetary disks with two fluids: gas and dust. We ran simulations of a 1  star surrounded by a 0.01  disk comprising 99% gas and 1% dust in mass and extending from 0.5 to  AU. The grain size ranges from 10^-6 m to 10 m for the low resolution ( SPH particles) simulations and from 10^-4 m to 10 cm for the high resolution ( SPH particles) simulations. Dust grains are slowed down by the sub-Keplerian gas and lose angular momentum, forcing them to migrate towards the central star and settle to the midplane. The gas drag efficiency varies according to the grain size, with the larger bodies being weakly influenced and following marginally perturbed Keplerian orbits, while smaller grains are strongly coupled to the gas. For intermediate sized grains, the drag force decouples the dust and gas, allowing the dust to preferentially migrate radially and efficiently settle to the midplane. The resulting dust distributions for each grain size will indicate, when grain growth is added, the regions when planets are likely to form.