Award Date

12-1-2020

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics and Astronomy

First Committee Member

Zhaohuan Zhu

Second Committee Member

Rebecca Martin

Third Committee Member

Jason Steffen

Fourth Committee Member

Shichun Huang

Number of Pages

49

Abstract

Recent molecular line observations by ALMA have revealed the 3D velocity structure of protoplanetary disks, providing new insight on the mechanisms of disk accretion and ring/gap formation. Although the constant α viscous disk model has been widely used to describe the disk surface density evolution, it may not adequately describe the gas velocity at different disk heights. By carrying out viscous hydrodynamic simulations, we confirm that the vertical velocity structure varies considerably between these models. On the other hand, the surface density evolution of the disk is only dependent on the vertically integrated stress, and does not depend on a particular vertical stress profile. We also include a planet in the 3D simulation to study the kinematic signatures of a young protoplanet. The planet-induced gap causes gas at the gap edge to deviate from Keplerian velocity. This deviation is constant in the vertical direction up to three scale heights in the disk, and the relation between the amplitude of the deviation and the planet mass is consistent with previous relationships derived in 2D simulations. Finally, by removing the planet from the simulation, most of the velocity structure is unchanged and is thus a product of the gap and not the planet. The only notable velocity flows induced by the planet appear in the radial velocity component, away from the planet at the midplane. Overall, axisymmetric observations of the disk can sensitively probe the structure of the rings and gaps, but they cannot exclude other mechanisms besides planets as a process for ring/gap formation

Keywords

Accretion disks; Dynamo; Magnetohydrodynamics (MHD); Turbulence

Disciplines

Astrophysics and Astronomy | Physics

File Format

pdf

File Size

6100 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/


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