Collaborative Research: Observational testing of interstellar grain alignment theory

由安德森博士(大学空间研究协会)、琼斯博士(明尼苏达大学)和拉扎里安博士(威斯康星大学麦迪逊分校)领导的合作研究通过新的多波长观测和理论建模提高了我们追踪星际介质和分子云中磁场的能力。通过对星际颗粒排列的有针对性的观测和基于领先理论范式的建模，可以更好地理解宇宙微波背景(CMB)偏振的前景。这项新的量化工作解决了星际颗粒排列的机制。基于辐射取向力矩的定量理论提供了作为环境和谷物特性的函数的颗粒取向的具体的、可测试的预测。利用光学和近红外(NIR)偏振技术的观测，直接探索了从分子云表面到观察到(亚)毫米波偏振发射的深度的颗粒取向效率变化的理论预测。对颗粒排列的广泛模拟，模拟了由排列的颗粒引起的极化，支持了对观察结果的解释。对取向机制的定量理解对于理解磁场的结构和强度(分别通过极化矢量的几何和Chandrasekhar-Fermi方法)很重要。对相关研究的影响从恒星形成的模型(通过可靠的磁场追踪)到早期宇宙的物理(通过可靠地将极化尘埃前景与CMB极化辐射分离)，以及更好地理解星际尘埃颗粒的微观物理。该项目培训年轻研究人员和研究生获取、分析和解释光学和近红外观测数据，以及研究天体物理磁场和星际偏振性质所需的计算模型。

The collaborative research lead by Dr. Andersson (Universities Space Research Association), Dr. Jones (University of Minnesota), and Dr. Lazarian (University of Wisconsin, Madison) advances our ability to trace magnetic fields in the interstellar medium and molecular clouds through new multi-wavelength observations and theoretical modeling. It leads to a better understanding of the foregrounds to the cosmic microwave background (CMB) polarization through targeted observations of interstellar grain alignment and modeling based on the leading theoretical paradigm. The combined new quantitative effort addresses interstellar grain alignment mechanisms. A quantitative theory based on radiative alignment torques provides specific, testable predictions of the grain alignment as functions of the environment and grain characteristics. Observations, employing optical and near-infrared (NIR) polarimetry, directly probe the theoretical predictions of the variations of grain alignment efficiencies from the molecular cloud surfaces to the depths where (sub-)mm wave polarized emission is observed. Extensive modeling of the grain alignment, simulating the polarization arising from aligned grains, supports interpretations of the observations. A quantitative understanding of the alignment mechanism is important to understand the structure and strength of the magnetic field (through the geometry of the polarization vectors and the Chandrasekhar-Fermi method, respectively). The impact on related research ranges from models of star formation (through a reliable magnetic field tracing) to the physics of Early Universe (through a reliable separation of polarized dust foreground from the CMB polarized radiation) as well as a better understandinging micro-physics of interstellar dust grains. This project trains young researchers and graduate students in the acquisition, analysis and interpretation of the optical and NIR observations, and on computational models necessary for the study of astrophysical magnetic fields and the nature of interstellar polarization.