Award Date

May 2024

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

First Committee Member

Zhaohuan Zhu

Second Committee Member

Rebecca Martin

Third Committee Member

Daniel Proga

Fourth Committee Member

Amei Amei

Number of Pages

492

Abstract

Protoplanetary disks are birthplaces of planets. The past decade witnessed a great advance- ment in disk observations by Atacama Large Millimeter Array (ALMA) and extreme adaptive optics (ExAOs). Hundreds of disks have been observed at high angular resolutions and revealed rich substructures (e.g., gaps/rings) at midplane and atmosphere, at least part of which are per- turbed by planets. Deep understanding of disk physics has a great potential to unveil more young planets from substructures and distinguish those that are not caused by planets. I worked on con- straining young planet populations using planet-disk interaction simulations and substructures and self-consistent treatment of thermal structures of protoplanetary disks. I developed the tool to infer planet mass by fitting the relationship between the gap width, planet mass, disk viscosity, grain size, and gas surface density using planet-disk interactions simulations. Then I used substructures found in DSHARP (Disk Substructures at High Angular Resolution Project) to infer a population of young planets at 10-100 au with 10-100 Earth masses, which is at a different regime from detected mature exoplanets. To improve the tool, I used an additional set of simulations to demonstrate the effectiveness of deep learning in obtaining planet and disk properties. To improve the statis- tics, I subsequently used a more uniformly selected Taurus sample to infer the planet occurrence rates considering selection and detection biases. However, these results are based on isothermal simulations commonly adopted in the field. Dust and thermal structures in disks can affect these interpretations. By changing the disk cooling rate, I found a certain regime that planet-launched spirals can be damped, leading to narrower and shallower gaps. Focusing on the rings, I showed that the concentration of large grains at the ring can lead to a drop of temperature, which changes the shape of the ring and may even lead to more rings. Radiation hydrodynamic simulations can capture the thermal structure in a time-dependent manner, improving self-consistency. I used rad- hydro to study a hydrodynamic instability, vertical shear instability (VSI) that operates in the outer disk. VSI can lead to kinematic and morphological substructures that can be misinterpreted as planet origin. I found that when considering realistic temperatures, the kinematics change signif- icantly compared to previous isothermal simulations, resulting in entirely different observational signatures. The cool midplane becomes quiescent whereas the atmosphere becomes turbulent. The classical radially narrow, vertically extended circulation pattern disappears and becomes more isotropic turbulence. These are consistent with existing ALMA observations and can be tested for the ongoing ALMA large program exoALMA. Zonal flows and substructures can develop depend- ing on the disk inner cavity size. A strong shear flow occurs at the boundary between the cool midplane and superheated atmosphere, leading to layered accretion.

Disciplines

Astrophysics and Astronomy

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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