The Inner Rim of YSO Disks: Effects of Dust Grain Evolution

Dust-grain growth and settling are the first steps toward planet formation. An understanding of dust physics is therefore integral to a complete theory of the planet formation process. In this paper we explore the possibility of using the dust evaporation front in YSO disks ("the inner rim") as a probe of the dust physics operating in circumstellar disks. The geometry of the rim depends sensitively on the composition and spatial distribution of dust. Using radiative transfer and hydrostatic equilibrium calculations we demonstrate that dust growth and settling can curve the evaporation front dramatically (from a cylindrical radius of about 0.5 AU in the disk midplane to 1.2 AU in the disk upper layers for an A0 star). We compute synthetic images and interferometric visibilities for our representative rim models and show that the current generation of near-IR long-baseline interferometers (VLTI, CHARA) can strongly constrain the dust properties of circumstellar disks, shedding light on the relatively poorly understood processes of grain growth, settling and turbulent mixing.