近日，美国伍斯特州立大学的Ian W. Stephens与弗吉尼亚大学的Zhe-Yu Daniel Lin以及北京大学的仰海峰等人合作并取得一项新进展。经过不懈努力，他们在行星形成盘间隙中发现对齐颗粒和散射光。相关研究成果发表已于2023年11月15日在国际权威学术期刊《自然》上发表。

该研究团队对HL Tau进行了870μm波长的高分辨率深度极化观测，成功解析了环和间隙中的极化现象。研究结果显示，与环相比，间隙区域的极化角呈现出明显的方位角分量，并且具有更高的极化分数。研究人员通过提出的模型解释了行星盘极化的成因，认为是由有效延长的对齐颗粒散射和辐射所导致。这些对齐尘埃颗粒的本征极化率可能超过10%，这一数值远高于低分辨率观测时的预期值（约1%）。此外，研究还发现，在非极化观测中难以察觉的不对称性和尘埃特征在极化观测中变得清晰可见。

据悉，最初人们认为星周盘中尘埃颗粒的极化(亚)毫米辐射是由于颗粒与磁场对齐所产生的。然而，随着多波长观测分辨率的提高和模型的改进，人们发现这种极化实际上主要由短波长（例如870μm）的自散射和长波长（例如3mm）与磁场外其他物质对齐的颗粒所主导。值得注意的是，极化信号可能受到潜在子结构的影响，而目前的观测结果尚无法解析多环和间隙中的极化情况。HL Tau是一个原行星盘，距离地球147.3±0.5光年，是在毫米-亚毫米波段最亮的I类或II类行星盘之一。

附：英文原文

Title: Aligned grains and scattered light found in gaps of planet-forming disk

Author: Stephens, Ian W., Lin, Zhe-Yu Daniel, Fernndez-Lpez, Manuel, Li, Zhi-Yun, Looney, Leslie W., Yang, Haifeng, Harrison, Rachel, Kataoka, Akimasa, Carrasco-Gonzalez, Carlos, Okuzumi, Satoshi, Tazaki, Ryo

Issue&Volume: 2023-11-15

Abstract: Polarized (sub)millimetre emission from dust grains in circumstellar disks was initially thought to be because of grains aligned with the magnetic field. However, higher-resolution multi-wavelength observations and improved models found that this polarization is dominated by self-scattering at shorter wavelengths (for example, 870μm) and by grains aligned with something other than magnetic fields at longer wavelengths (for example, 3mm). Nevertheless, the polarization signal is expected to depend on the underlying substructure, and observations until now have been unable to resolve polarization in multiple rings and gaps. HL Tau, a protoplanetary disk located 147.3±0.5pc away, is the brightest class I or class II disk at millimetre–submillimetre wavelengths. Here we show deep, high-resolution polarization observations of HL Tau at 870μm, resolving polarization in both the rings and the gaps. We find that the gaps have polarization angles with a notable azimuthal component and a higher polarization fraction than the rings. Our models show that the disk polarization is due to both scattering and emission from the aligned effectively prolate grains. The intrinsic polarization of aligned dust grains is probably more than 10%, which is much higher than that expected in low-resolution observations (about 1%). Asymmetries and dust features that are not seen in non-polarimetric observations are seen in the polarization observations.

DOI: 10.1038/s41586-023-06648-7

Source: https://www.nature.com/articles/s41586-023-06648-7