Integrated Models of Magnetic Fields and Gas Kinematics in Molecular Clouds

分子云是磁化的、湍流的、自引力结构，也是我们银河系恒星形成的所在地。恒星的形成发生在小尺度(约0.1pC)的致密核心中，重力克服了湍流和向外的磁力。磁离心力驱动一对喷流，这些喷流将周围的气体卷成一对双极分子外流。在恒星形成过程中，自重、流出和磁场是强耦合的。一种综合的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景。我和我的HQP开发了一个名为PolCat的软件包，它使用一种新方法来搜索巨大的潜在密度/磁场配置空间，以自动找到最适合亚毫米极化和强度图的配置。我们的模型通常是退化的，但我们很容易排除无法解释数据的现场几何图形，并找到有效的几何图形。PolCat模型是三轴的，不假设详细的均衡。然而，我们将使用张量维里定理来拒绝沿任何主轴远离平衡的核心模型，从而提供更紧密的模型约束。我们还将在MHD自洽场方法的基础上发展一种补充方法，以快速计算轴对称旋转、磁化、自引力磁芯的平衡模型。PolCat最重要的扩展将是一个新的组件，用于模拟分子外流及其一氧化碳(CO)线排放。我和我的HPQ将开发集成的三维建模方法，建立在我的团队开发的技术的基础上，利用观测数据生成和约束磁化恒星形成核心及其外流的模型。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外流结构和方向之间的关系。Bistro调查使用了James Clerk Maxwell望远镜的新POL-2偏振仪。 一条相关的调查路线将调查最近发现的分子龙卷风现象，分子龙卷风是银河系中心附近的压力约束、旋转、螺旋缠绕的分子细丝。人们认为，它们显著的螺旋结构是由扭曲的磁管的磁流体力学不稳定性引起的，扭曲的磁管被沿灯丝传播的扭转阿尔芬波包裹。我和我的HQP将发展一个全面的、受观测约束的分子龙卷风及其稳定性理论，这将解释它们不寻常的形态。我们将预测这些天体的亚毫米偏振图，以便与未来的观测进行比较。 这项研究计划的首要目标是开发新的模型和计算工具，从而更好地理解分子云和恒星形成中的磁场。

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.