[TCA Student Seminar] Model the streamer Structure in Collapsing Prestellar Cores / A Rotation Dip in the Envelope-Disk Transition Region: Evidence of Magnetic Braking
The NCTS Astrophysics group (TG2.3) is holding the monthly student seminar series. These provide opportunities for the domestic students to share their work and practice giving live talks.
Please find the schedule listed in the tabulation below. Each seminar starts at 12 p.m. and takes place in the NCTS Physics 4F Lecture Hall, Cosmology Hall, NTU.
For more detailed information regarding each seminar, please see it in the section below the tabulation a week before the seminar.
| Date | Speaker 1 | Affiliation | Supervisor | Speaker 2 | Affiliation | Supervisor |
| 2025/7/24 | Pon-Yin Wang | TKU | Hsi-An Pan | |||
| 2025/8/22 | Tsung-Han Chuang | NTNU | Yueh-Ning Lee | Jyun-Heng Lin | NTHU/ASIAA | Chin-Fei Lee |
| 2025/9/26 | Chiung-Yin Chang | NTHU | Hsiang-Yi Karen Yang | Huan-Ping Chao | NCKU | Kwan-Lok Li |
| 2025/10/31 | Yi-Yang Lee | NTHU | Hsiang-Yi Karen Yang | Prangsutip Cherdwongsung | NTHU | Ing-Guey Jiang |
| 2025/11/28 | Yu-Xuan Nancy Lin | NYCU | Shih-Ping Lai | Tz-En Gau | NTU | Chia-Yu Hu |
| 2025/12/26 | Szu-Ting Chen | NTHU | Shin-Ping Lai | Afif Ismail | NTNU | Hung-Yi Pu |
Time: 2025/08/22 (Fri.) 12:00-12:30
Place: NCTS Physics 4F Lecture Hall, Cosmology Hall, NTU
Talk Title: Model the streamer Structure in Collapsing Prestellar Cores
Speaker: Tsung-Han Chuang (NTNU)
Register for Lunch Box: https://forms.gle/8MXzPRfRN2qey7eb8
Abstract:
Streamers have been observed with high-resolution ALMA observations around many protoplanetary disks undergoing formation. They have been suggested to dominate the mass accretion budget from the collapsing prestellar core, and have important consequences on the disk dynamics. Understanding the formation of streamers is therefore important for explaining how protoplanetary disks receive mass from the envelope. We propose a model to explain the formation of streamer structures by considering density enhancements due to gravitational instability. We test our model against sources where streamers have been detected (ex. Per-emb-2 and Per-emb-50 observed with NOEMA) and fit for model parameters. This allows us to gain deeper insights into the physical origin of streamers and their role in mass transport from the core to the disk. This model can be applied to analyze new observations as well as archival data that show signs of streamers.
Time: 2025/08/22 (Fri.) 12:30-13:00
Place: NCTS Physics 4F Lecture Hall, Cosmology Hall, NTU
Talk Title: A Rotation Dip in the Envelope-Disk Transition Region: Evidence of Magnetic Braking
Speaker: Jyun-Heng Lin (NTHU/ASIAA)
Register for Lunch Box: https://forms.gle/8MXzPRfRN2qey7eb8
Abstract:
The envelope-disk transition region in protostellar system is key to understanding how angular momentum is removed during star formation. Magnetic braking, predicted to operate in this region, can remove angular momentum and regulate disk growth, but direct observational evidence remains limited. Using ALMA C18O (J = 2–1) data of the HH 111 VLA1 system, we analyzed gas kinematics within 6000 au of the protostar. We find clear deviations from simple free-fall with conserved angular momentum across the transition region (~5200–160 au), which can be divided into three zones: (1) an outer region with reduced infall velocity, likely due to magnetic tension from pinched field lines; (2) a middle region showing a sharp drop in rotation velocity and angular momentum, consistent with strong magnetic braking; and (3) an inner region where rotation rises toward Keplerian velocity and infall ceases, likely due to weaker braking from ambipolar diffusion. The resulting dip in the rotation profile provides observational evidence for magnetic braking.
