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。对磁场的观测限制相对较少，因为它们很难直接观察到。磁场通常是从星际尘埃颗粒的极化发射中推断出来的，但这些研究受到未知尘埃性质和与非磁性特征的混淆的阻碍。使用新技术和新数据分析技术的组合，我的研究团队将绕过这些限制，更可靠地探索磁场在恒星和行星形成中的作用。首先，我的团队将使用James Clerk Maxwell望远镜(JCMT)和红外天文台(SOFIA)之间的多波长协同效应来推断这些望远镜跟踪的不同尘埃种群的磁场。理论研究预测了极化特征随尘埃颗粒尺寸的不同而变化。超过10个附近的恒星形成云已经或将从这两个设施通过大型调查(我是其中的一员)进行观测。有了这些数据，我的团队将领导数据分析，通过测量磁场强度和几个恒星形成星云中的尘埃演化来验证理论预测。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，我的团队将使用来自阿塔卡马大毫米阵列(ALMA)的高分辨率尘埃偏振观测来追踪磁场，直到年轻恒星(~10AU)周围的恒星圆盘尺度，行星就是在那里形成的。ALMA的最新结果表明，磁盘中的极化特征可以由非磁机制主导。为了限制这些非磁性签名，我的团队将使用档案和新的ALMA数据，包括来自我领导的极化调查的数据，来模拟磁盘属性和非磁性极化机制。该项目将测试盘状物质形成的理论预测，并提供对盘状物中尘埃大小的强有力的约束，将盘状物的性质与行星形成的开始联系起来。总而言之，旋光测量的最新进展为探测从大型云团到小型行星形成盘的尘埃极化提供了机会。通过开发新的探测器，我的研究团队将绕过目前使用尘埃极化来推断磁场性质的限制。我们将从云到盘之间架起磁场的桥梁，并确定它们如何支持云的碎裂，支持云中的致密核心防止塌缩成原恒星，并抑制盘的形成。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.