VLA1623A Class 0 Keplerian Disk

Poster: Link

About VLA1623A, the extremely rare Class 0 Keplerian Disk

VLA1623 is a triple star system. It is composed of 3 extremely young stars, VLA1623A (Class 0), VLA1623B (Class 0) and VLA1623W (Class 1). In the traditional star formation theory, Keplerian Disks is expected to be found for Class 1 star. What is special about VLA1623A is that a very embedded disk is found around it, and it is Class 0! And surprisingly that it is a Keplerian Disk!!

Finding an extremely young Keplerian Disk shakes our understanding in star formation. It is suggested that the starting time for planet and star formation might be earlier than what we currently think. Also, a Keplerian Disk suggests that the effect of magnetic breaking is small. This further suggests magnetic field is misaligned with rotating axis or B field is weak and it is dissipated in an early stage of star formation.

Previous ALMA data of VLA1623 have been fitted with a flat disk model developed by Nadia Murillo (see 2013 Nadia A&A 560, A103). Recent close inspection of new ALMA data reveals a rich vertical structure that can no longer be fitted appropriately with flat disk model, so I have worked to independently develop both flat and flared Keplerian 3D disk models. This will help us unlock the mysteries behind the vertical structure of extremely early Keplerian disks.

What is the vertical structure of Class 0 Keplerian Disk? What is the density, temperature distribution?

These are extremely important questions to answer. In my project my goal is to

Developed a 3D flared/flat Keplerian disk model to constrain the vertical structure, temperature, density distribution of VLA1623A disk.

I used my own python and I developed my own radiative transfer code and output as fits file. I then use the standard analyzing software, CASA to compare with the ALMA Cycle 2 data. Below is my comparison results.

Figure 1. C18O PV diagram along angle 135 degrees of VLA1623A Keplerian Disk. Color: ALMA Cycle 2 data; Black Contour: 3D Flared Disk Simulation model (Chenghan Hsieh in prep.)

Figure 2. C18O PV diagram along angle 135 degrees of VLA1623A Keplerian Disk. Color: ALMA Cycle 2 data; Black Contour: 2D Flat Disk Simulation model (Chenghan Hsieh in prep.)

Figure 3. 3D Flared Disk Model Density Demonstration Figure (Chenghan Hsieh in prep.)

Figure 4. theta direction velocity on the disk (Chenghan Hsieh in prep.)

By comparing with the ALMA data, I was able to constrain the density profile, temperature profile, and the vertical structure of the protoplanet disk around VLA1623. I participated as a Co-PI in 2017 ALMA proposal “Disk formation in extremely young protostars VLA1623: from the accretion flows to the disk”. I will publish my research results in my “first author” paper before I graduate.

Supervisor: Prof. Shih-Ping Lai (NTHU)

Updated: 2017.11.24 Chenghan Hsieh