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|Title: ||Warping, dust settling and dynamics of protoplanetary disks|
|Authors: ||O'Sullivan, Mark George|
|Supervisors: ||Wood, Kenneth|
|Issue Date: ||2008|
|Abstract: ||The research presented in this thesis investigates several aspects of the evolutionary
processes of T Tauri stars and their accompanying circumstellar disks. The versatile
Monte Carlo radiation transfer technique, with several modifications and extensions, is
used throughout to study the structure and constitution of both the circumstellar disk at
large and the changeable and dynamic inner disk regions.
The photopolarimetric variability of AA Tau in the Taurus star forming region is
modelled in a fully 3D manner. I find that a magnetospherically induced warp in the
accretion disk at roughly the stellar co-rotation radius occults the star and reproduces
both the observed period and duration and the required brightness and polarisation
variations. The model SEDs allow estimates of the disk mass, radial extent and large-
scale density structure. Using a modified SPH code we find the interaction of a 5.2kG
stellar magnetic field inclined at 30° to the rotation axis with the disk, is capable of
generating a warp of the size and shape needed to reproduce the observed variations.
Modified Monte Carlo models capable of incorporating any number of dust particle
grain sizes distributed throughout the disk in vertical and radial distributions, in a fully
3D manner are presented. This versatile tool allows the investigation of evolutionary
processes such as dust settling and grain growth predicted to occur in T Tauri sources as
they age. A Mie Scattering code was also adapted and incorporated into the models
allowing us to determine optical properties for dust grains and distributions of any size.
I present model SEDs fitting the latest publicly available IR data for a number of T
Tauri sources and reproduce the observational effects of dust grain growth and settling
with a high degree of success. The fits are by no means unique and the structural
parameters required to produce them are quite uncertain but it is possible to determine
useful information on the larger scale structure and bulk constituents of these disks.
A fully 3D non-LTE radiative transfer code using CO line emissions as a tracer of the
disk dynamics and able to simulate any disk structure or geometry, either analytical or
imported from a hydrodynamic simulation, is presented. Signatures attributed to the
disk dynamics and spiral density structure derived from hydrodynamic simulations of
massive disks are investigated and resolved. Line profiles and contour maps of the
velocity of the emitting material are generated and compared with observations.|
|Publisher: ||University of St Andrews|
|Appears in Collections:||Physics & Astronomy Theses|
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