"Numerical Simulations of Protoplanetary Disks Using the Antares Code" Project

ASIAA Summer student report : Link

In 2016, I worked as a summer student with researchers Dr. Chun-Fan Liu, Dr. Wing-Kit Lee, Dr. Hsien Shang, and Dr. Chien-Chang Yen at ASIAA on planet formation. We ran various simulations using Antares code, simulating protoplanetary disk dynamics with a planet.

I wrote various codes to visualize the simulated data and produce time dynamical movies. From the streamline plots and vector plots, it was observed that vortices evolve naturally in the process of planet formation (Figure 1). The relationship between vortices and the asymmetrical dust emission in observation due to dust trapping can be explored further.

Figure 1. Stream line plot for 200 orbits in vortex’s rotating frame. The parameters used are density∝ r^-1; Temperature∝ r^-1; q = 10^-3 (central star to planet mass ratio). Note that the planet is located at (0,0). Created by Cheng-Han Hsieh 2016.8.

On close inspection of data, I also found that the directional velocity change, θ, has a strong dependence on the density profile generated by the planets (Figure 2). The most interesting observation is the slight offset between the peaks of θ directional velocity change and the gap created by a planet. Further studies on how they are out of phase would give insights of how angular momentum and materials are transferred along the gap.

Figure 2. Red: θ direction velocity percentage change vertically shifted 2 units (with respect to the Keplerian motion) for 200 orbits. Blue: θ direction velocity percentage change vertically shifted 2 units for 0 orbit. Green: density profile. The parameters used are d∝r^(-1),T∝r^(-1),q=10^(-4). Note that the planet is located at (1,0). Created by Cheng-Han Hsieh 2016.8.

Besides identifying the kinetic features of planet disk interactions such as time evolution of momentum and density by using the Antares Code, I also developed my own LTE radiative code to create synthetic images for observation. I used my own radiative transfer code and found that planets would create special features on 13CO line spectrum (Figure 3,4). The feature consists of a peak inside the gap. The peak corresponds to the gas accretion around the planet. These features generated by spirals and gaps would be an indirect method to detect young exoplanets.

Figure 3. 13CO J=2-1 line spectrum plot without planet. The parameters used are d∝r^(-1),T∝r^(-0.5),q=10^(-3). Created by Cheng-Han Hsieh 2016.8.

Figure 4. 13CO J=2-1 line spectrum plot for 100 orbits. The parameters used are d∝r^(-1),T∝r^(-0.5),q=10^(-3).Created by Cheng-Han Hsieh 2016.8.

Possible future directions are listed as the following:

1. Correlation between θ direction velocity percentage change and density profile. Are they in phase? How does the planet affect materials moving along the gap? (Figure 2)

2. How does materials and momentum transfer across the gap? What are the implications? How does it affect planet dynamics (eg. Planet migration)?

3. Vortex dynamics study. How does vortex evolve? Where does it locate across the disk? What is its role in planet formation? Does it cause the asymmetrical dust emission in observation due to dust trapping? (Figure 1)

4. Can we actually use 13CO line spectrum to detect planets that are deeply embedded in protoplanetary disks? This would be an interesting question to be further look at from observation point of view. (Figure 3,4)

For more details please see Publication "ASIAA Summer student report".

Supervisors: Dr. Chun-Fan Liu, Dr. Wing-Kit Lee, Dr. Hsien Shang, and Dr. Chien-Chang Yen (Academy Sinica Institute of Astronomy and Astrophysics)

Updated 2017.11.26. by Chengh-Han