Date of Award

Spring 1-1-2011

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Astrophysical & Planetary Sciences

First Advisor

Philip J. Armitage

Second Advisor

John Bally

Third Advisor

Stephen J. Mojzsis

Abstract

Understanding the small-dust component of protoplanetary disks is key to understanding the conditions for planet formation. Small dust grains, particularly at large distances, provide our primary observational window into the physics of protoplanetary disks, being much more easily observed than the gas component. Furthermore, the distribution of these grains must ultimately control the timing and locations for planetesimal formation, the first major step toward planet formation. For my thesis work, I have used numerical simulations to model the radial distribution of dust grains as they are acted upon by the gas disk, including the evolution of the disk (outward expansion and inward accretion), radial and azimuthal drag of the gas flow on the particle orbits, and turbulent mixing of the particle ensemble radially within the disk. I have run simulations using a range of particle sizes and disk-model parameters and consider primarily two phenomena: the radial diffusion of hot, inner disk particles outward to large AU, relevant to the compositional makeup of bodies within our own solar system, and the time evolution of the global dust-to-gas ratio, which dictates the supply of solid material to the planetesimal- and planet-forming regions. I find that, while the degree out outward mixing depends sensitively on a number of disk-model parameters, the behavior of the global dust-to-gas distribution is relatively uniform between different disk-model simulations, suggesting that, while still mysterious, the conditions for planetesimal formation are commonly met across a range of disk configurations. Observed disk compositions correlate poorly with most observable disk parameters. However, my simulations suggest compositional properties are most-strongly controlled by the initial conditions of young disk systems.

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