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

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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.