Integrated Models of Magnetic Fields and Gas Kinematics in Molecular Clouds

分子云是磁化的、湍流的、自引力的结构，是我们银河系中恒星形成的中心。恒星的形成发生在小尺度上（~0.1 pc），在致密的核心中，重力克服了湍流和向外的磁力。磁力离心力驱动一对射流，将周围的气体扫向一对双极性分子外流。自引力、外流和磁场在恒星形成过程中紧密耦合。综合数据驱动的建模方法，同时考虑到这些组成部分，将提供恒星形成区域的清晰图像。我和我的HQP开发了一个名为PolCat的软件包，它使用一种新颖的方法来搜索潜在密度/磁场配置的巨大空间，以自动找到最适合亚毫米极化和强度图的那些。我们的模型经常是退化的，但我们很容易排除不能解释数据的场几何，并找到有效的几何。PolCat模型是三轴的，不假设详细的平衡。然而，我们将使用张量维里定理来拒绝远离任何主轴平衡的核心模型，从而提供更严格的模型约束。我们还将在MHD自洽场方法的基础上开发一种补充方法，快速计算旋转、磁化、自重岩心的轴对称平衡模型。PolCat最重要的扩展将是一个新的组件来模拟分子外流及其CO（一氧化碳）线排放。我的HPQ和我将开发综合三维建模方法，建立在我的小组开发的技术基础上，利用观测数据生成和约束磁化恒星形成核心及其流出的模型。我们将通过将我们的模型应用于BISTRO调查的数据来探索地核磁场与流出物的结构和方向之间的关系，该调查使用了詹姆斯·克拉克·麦克斯韦望远镜上的新型POL-2偏振计。

Molecular clouds are magnetized, turbulent, self-gravitating structures, and the seat of star formation in our Galaxy. Star formation occurs on small scales (~0.1 pc), in dense cores, where gravity overcomes turbulence and outward magnetic forces. Magneto-centrifugal forces drive a pair of jets, which sweep up surrounding gas into a pair of bipolar molecular outflows. Self-gravity, outflows, and magnetic fields are strongly coupled in star formation. An integrated data-driven modelling approach, which takes into account these components simultaneously, will provide a clear picture of star forming regions. My HQP and I have developed a software package called PolCat, which uses a novel method to search an enormous space of potential density/magnetic field configurations, to automatically find those that best fit sub-millimetre polarization and intensity maps. Our models are often degenerate, but we easily rule out field geometries that cannot explain the data, and find geometries that work. PolCat models are triaxial and do not assume detailed equilibrium. However, we will use the tensor virial theorem to reject core models that are far from equilibrium along any principal axis, thus providing tighter model constraints. We will also develop a complementary method, based on the self-consistent field method of MHD, to rapidly calculate axisymmetric equilibrium models of rotating, magnetized, self-gravitating cores. The most important extension to PolCat will be a new component to model molecular outflows and their CO (carbon monoxide) line emission. My HPQ and I will develop integrated three-dimensional modelling methods, built upon techniques developed by my group, to generate and constrain models of magnetized star-forming cores and their outflows using observational data. We will explore the relationship between a core's magnetic field and the structure and orientation of outflows by applying our models to data from the BISTRO survey, which uses the new POL-2 polarimeter at the James Clerk Maxwell Telescope. A related line of inquiry will investigate the recently discovered phenomenon of molecular tornadoes, which are pressure-bound, rotating, helically-wound molecular filaments near the Galactic Centre. It is believed that their striking helical structure arises from the magnetohydrodynamic instability of a twisted magnetic tube, which is wrapped up by a torsional Alfven wave propagating along the filament. My HQP and I will develop a comprehensive, observationally constrained theory of molecular tornadoes and their stability, which will explain their unusual morphology. We will predict submillimetre polarization maps due to these objects, for comparison with future observations. The overarching goal of this research program is to develop new models and computational tools leading to an improved understanding of magnetic fields in molecular clouds and star formation.