The Earliest Stage of Planet Formation: Numerical Simulations of Disk-planet Interaction and Observations of Protoplanetary Disks

Abstract

Planets form in protoplanetary disks. In disks, planets excite structures such as spiral density waves, and may clear material around their orbits to form gaps, through gravitational disk-planet interactions. By identifying these structures and comparing them with disk-planet interaction theory, we can study where, when, and how planets form in disks. In this work, we present studies of disk-planet interactions using numerical hydrodynamic simulations and possible planet-induced signals in protoplanetary disks from direct imaging of disks.

With very high spatial resolution, an accurate numerical solver, and a precise planetary potential, we carry out 2D shearing sheet simulations to provide detailed quantitative comparisons of numerical results with both linear and nonlinear analytical theories of the density waves excited by planets. We achieve excellent agreement with theory for the primary physical variables. Also, we study issues which are ignored by the theories, such as the emerging nonlinear effects in the linear stage. The effects of various numerical parameters are extensively investigated, and we provide a framework for future code testing in this field.

Transitional disks are protoplanetary disks that have depleted inner regions.

We obtain high spatial resolution near-infrared scattered light Subaru images of a sample of transitional disks as part of the SEEDS project, and carry out radiative transfer simulations to study their structure. We find that in some cases cavities are not present in the scattered light, which requires decoupling between the sub-um-sized and mm-sized grains inside the

cavity. For another group of transitional disks in which Subaru does reveal the cavities at NIR, we

focus on whether grains at different sizes have the same spatial distribution or not

(i.e. the cavity size and the depletion factor inside the cavity for different dust

populations). With our modeling results, we

examine various transitional disk formation theories, and in particular, whether their cavities are opened by the forming planets in the systems.