Probing Circumstellar Disk Properties with Polarization

Circumstellar disks surrounding nearly all newly formed stars are the birthplaces of planets, and the physical conditions within the disks govern the formation of planets. This project will use high quality polarization observations from the Atacama Large Millimeter/submillimeter Array (ALMA) to study nearby circumstellar disks in detail. Because polarization mechanisms depend strongly on wavelength, polarization observations are a sensitive means to probe the substructures and magnetic fields within circumstellar disks. Using polarization models, the investigators will explore how disk polarization and the properties inferred from it evolve over time. Results from this project will advance astronomers’ understanding of star and planet formation. The project will train a graduate student in advanced astronomical techniques and applications, provide research experience to an undergraduate student, and conduct science outreach to a Native American tribe. The research team will undertake polarization observations using ALMA to measure the properties of circumstellar disks, placing them within the context of exoplanet detections. The research program seeks to: (1) address the discrepancy between maximum dust grain sizes measured by polarization scattering (~75 micron) and ones inferred from spectral indices (~millimeter); (2) characterize the differences in observed polarization morphology and intensity with wavelength for a large sample of sources; (3) measure polarization in an enlarged sample of young disks to compare their properties to the older T Tauri disks; and (4) detect disk magnetic fields or place stringent observational constraints on them. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.