Title: Planet formation in a polarized view

Speaker: 杨海峰

Institute: 浙江大学

Host: 方陶陶

Time: 2024.9.19 周四 14:30

Location: 物理楼 552

Abstract:

(Sub)millimeter disk polarization is an exciting new field of research that has been revolutionized by ALMA. In contrast to its canonical picture, the polarization on the disk scale revealed by radio interferometry does not come from irregular dust grains aligned with magnetic fields but mostly from scattering. This scattering-induced polarization is very sensitive to the sizes of dust grains and local radiation fields. It is a powerful tool for studying grain growth and dust settling. I will discuss how the polarization signatures depends on the dust scale height and present detailed modeling on protoplanetary disks and constraints on the dust settling. Theoretically, the large (mm-sized) grains in protoplanetary disks can not be aligned by magnetic fields due to their long Larmor precision timescale and short gas-damping timescale, which agrees with ALMA’s non-detection of magnetic fields. The magnetic alignment conditions are much better in the disk atmosphere, inhabited by micron-sized dust grains. We show that the near-IR scattered light may trace magnetic fields in the disk atmosphere. If time permits, I will discuss the disk polarization at longer wavelengths that are not due to scattering, introduce our recent development of a Neural-Network aided GPU MCRT code to solve scattering by large aligned dust grains.

Bio：

Dr. Haifeng Yang is a Bairen Research Professor at Institute for Astronomy, Zhejiang University. He got his Ph.D. from the University of Virginia in 2018. Before joining ZJU, he worked as a C.N. Yang Junior Fellow at the Institute of Advanced Study at Tsinghua University and worked as a Boya Fellow at the Kavli Institute for Astrophysics and Astronomy at Peking University. Haifeng’s primary research focuses on studying the protoplanetary disks, using (sub)millimeter polarimetric observations, Radiative Transfer modelings, and magneto-hydrodynamical simulations.

Related paper:

https://ui.adsabs.harvard.edu/abs/2016MNRAS.456.2794Y/abstract

https://ui.adsabs.harvard.edu/abs/2017MNRAS.472..373Y/abstract