Understanding the Role of Magnetic Fields in Star and Planet Formation Using Stratospheric Balloon-borne Polarimeters

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Stars form out of large clouds of molecular gas. However, this process is incredibly inefficient, in that typically at most a few percent of the gas in molecular clouds will end up in stars. What causes this inefficiency is a key outstanding question in astrophysics. To answer this question requires understanding the physical processes that regulate star formation: gravity, turbulent gas motions, feedback from young stars, and magnetic fields. Of these processes magnetic fields are the hardest to observe, and therefore the least understood. I propose to quantitatively determine the role of magnetic fields in star formation, over scales ranging from molecular cloud complexes to individual protostars and protoplanetary disks, using observations from our new stratospheric balloon-borne polarimeter BLAST-TNG. BLAST-TNG measures sub-mm polarized light radiated from dust grains aligned relative to their local magnetic field. The Earth's atmosphere absorbs most sub-mm light, so by operating above >99.5% of the atmosphere BLAST-TNG can map magnetic fields in star-forming regions with an unprecedented level of detail. Our research will focus on three topics, each led by an MSc/PhD student: 1)How do magnetic fields in molecular clouds affect the efficiency of star formation? Previous research shows that magnetic fields are generally strong enough to prevent gas from moving across field lines, which should slow down the formation of dense, gravitationally-unstable gas. We will compare our BLAST-TNG maps to maps made from simulations of star forming regions, to determine which clouds are strongly magnetized and whether these clouds are less efficient at forming stars. 2)Do magnetic fields support filaments against gravitational collapse? Dense filaments appear to be preferred sites of star formation. Using BLAST-TNG maps of hundreds of filaments, and detailed maps of seven filaments with the high resolution TolTEC polarimeter, we will test whether magnetic fields support filaments against gravitational collapse. 3)Do magnetic fields inhibit the formation of protoplanetary disks? Disks form as a consequence of angular momentum conservation in collapsing cores, but magnetic fields may reduce core angular momentum and inhibit disk formation. With BLAST-TNG and TolTEC we will study the magnetic fields of hundreds of protostars to determine whether disks with axes aligned with the magnetic field are smaller, and study how magnetic fields affect core collapse. This research will provide the first quantitative measurements of the degree to which magnetic fields regulate star formation efficiency and planet formation. In total 9 students (3 MSc/PhD, 6 undergraduate) trained in this program will gain skills in analyzing big datasets, working as part of large international collaborations, and presenting their research results. Our program will also generate important public legacy datasets and further Canada's leadership in the study of star formation.