The Role of Magnetic Fields in Forming Stars, Disks, and Planets

从星系的形成和演化到行星的诞生和生命的起源，恒星的形成在天文学的大多数方面都起着举足轻重的作用。恒星形成背后的物理学，特别是磁场在这一过程中的关键作用，人们知之甚少。磁场的观测限制相对较少，因为它们很难直接观测到。磁场通常是从星际尘埃颗粒的极化发射推断出来的，但这些研究受到未知尘埃特性和与非磁性特征混淆的阻碍。结合新技术和新的数据分析技术，我的研究团队将绕过这些限制，更可靠地探测磁场在恒星和行星形成中的作用。首先，我的团队将利用詹姆斯·克拉克·麦克斯韦望远镜（JCMT）和平流层红外天文观测台（SOFIA）之间的多波长协同作用，推断这些望远镜追踪到的不同尘埃群的磁场。理论研究预测极化特征随尘埃颗粒大小而变化。超过10个附近的恒星形成云已经或将从这两个大型调查设施中进行观测（我是其中的一员）。有了这些数据，我的团队将领导数据分析，通过测量几个恒星形成云的磁场强度和尘埃演化来测试理论预测。对这些预测的确认将使我们能够更深入地了解云中的尘埃和磁场，而矛盾则表明当前的尘埃模型是错误的。其次，我的团队将使用阿塔卡马大型毫米波阵列（ALMA）的高分辨率尘埃偏振观测，追踪年轻恒星（~ 10天文单位）周围星周盘的磁场，行星就是在这里形成的。ALMA最近的结果表明，磁盘中的极化特征可以由非磁性机制主导。为了约束这些非磁性特征，我的团队将使用存档数据和新的ALMA数据，包括我领导的极化调查数据，来模拟磁盘属性和非磁性极化机制。该项目将测试关于行星盘形成的理论预测，并提供关于行星盘尘埃大小的可靠约束，将行星盘的性质与行星形成的开始联系起来。总之，偏振测量的最新进展提供了探测从大云到小行星形成盘的尘埃偏振的机会。通过开发新的探测器，我的研究小组将绕过目前使用尘埃极化来推断磁场性质的限制。我们将在云和盘之间架起磁场的桥梁，并确定它们如何支持云不碎裂，支持云中的致密核心不坍缩成原恒星，以及抑制盘的形成。这些结果直接影响恒星形成过程中产生的恒星和行星的类型。

Star formation plays a pivotal role in most aspects of astronomy, from the formation and evolution of galaxies to the birth of planets and the origins of life. The physics behind star formation and, in particular, the critical role of magnetic fields in this process is poorly understood. There are relatively few observational constraints on magnetic fields because they are difficult to observe directly. Magnetic fields are generally inferred from polarized emission from interstellar dust grains, but these studies are hampered by unknown dust properties and confusion with non-magnetic signatures. Using a combination of new technologies and new data analysis techniques, my research team will circumvent these limitations to more reliably probe the role of magnetic fields in the formation of stars and planets. First, my team will use multi-wavelength synergy between the James Clerk Maxwell Telescope (JCMT) and Statospheric Observatory for Infrared Astronomy (SOFIA) to infer magnetic fields for different dust populations traced by these telescopes. Theoretical studies predict that polarization signatures vary with dust grain size. Over 10 nearby star-forming clouds have or will have observations from both facilities from large surveys (of which I am a member). With these data, my team will lead the data analyses to test theoretical predictions by measuring magnetic field strengths and dust evolution across several star-forming clouds. Confirmation of these predictions will enable a deeper understanding of both dust and magnetic fields in clouds, whereas a contradiction would indicate that current dust models are wrong. Second, my team will use high-resolution dust polarization observations from the Atacama Large Millimeter Array (ALMA) to trace magnetic fields down to scales of circumstellar disks around young stars (~ 10 AU), where planets form. Recent results from ALMA have shown that polarization signatures in disks can be dominated by non-magnetic mechanisms. To constrain these non-magnetic signatures, my team will use archival and new ALMA data, including data from a polarization survey that I led, to model disk properties and the non-magnetic polarization mechanisms. This project will test theoretical predictions of disk formation and provide robust constraints on dust sizes in disks, connecting disk properties to the onset of planet formation. In summary, recent advances in polarimetry provide the opportunity to probe dust polarization from large clouds to small planet-forming disks. By exploiting new detectors, my research team will circumvent current limitations in using dust polarization to infer magnetic field properties. We will bridge magnetic fields from clouds to disks and determine how they support clouds against fragmentation, support dense cores in clouds against collapse into protostars, and suppress the formation of disks. These outcomes directly affect the types of stars and planets produced during the star formation process.