{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/117782"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/117782","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Mass Assembly in Protoplanetary Disks: Polarimetry as a Probe of Dust Growth and Accretion","abstract":"Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-04-12 without embargo terms","abstract_html":"Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-04-12 without embargo terms","abstract_has_math":false,"creators":["Harrison, Rachel Elizabeth"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Astronomy","degree_department":null,"school":null,"contributors":["Looney, Leslie","Li, Zhi-Yun","Gammie, Charles","Fields, Brian"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2022,"date_issued":"2022-12","date_published":"2022-12","updated_at":"2026-07-22T22:24:56Z","subjects":["Protoplanetary Disks","Star Formation","Planet Formation","Polarization","Interferometry"],"languages":["en","eng"],"rights":["Copyright 2022 Rachel Harrison"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2142/117782","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Looney, Leslie","Li, Zhi-Yun","Gammie, Charles","Fields, Brian"]},{"key":"dc:creator","label":"Author","values":["Harrison, Rachel Elizabeth"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2022-12","2022-11-30"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Astronomy"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Protoplanetary Disks","Star Formation","Planet Formation","Polarization","Interferometry"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en","eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2022 Rachel Harrison"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2142/117782"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-04-12 without embargo terms","The student, Rachel Harrison, accepted the attached license on 2022-11-28 at 10:52.","The student, Rachel Harrison, submitted this Dissertation for approval on 2022-11-28 at 11:00.","This Dissertation was approved for publication on 2022-11-30 at 15:43.","DSpace SAF Submission Ingestion Package generated from Vireo submission #18637 on 2023-04-12 at 07:33:01","Circumstellar disks are the formation sites of planets, and their physical and chemical characteristics affect the masses and compositions of planets, as well as planet formation timescales and protostellar accretion rates. Millimeter and submillimeter interferometry with instruments like the Atacama Large Millimeter/submillimeter Array (ALMA) gives us a detailed look at the gas and dust in disks, particularly dust near the midplane of the disk where planet formation takes place. There is now evidence that planet formation is well under way by the Class II phase of disk evolution, when the envelope has dissipated but a significant amount of gas and dust remains in the disk. In fact, there is now evidence that planet formation starts even earlier than Class II (Segura-Cox et al., 2020). Open questions remaining about propoplanetary disk evolution include the sizes of the dust grains in disks and the exact role of the magnetic field in accretion. Through observational studies of protoplanetary disks, this dissertation examines the roles of dust grain growth and magnetically-driven protostellar accretion in disk evolution. We first present a study of the polarized emission from four Class II protoplanetary disks at 3 mm. We find that otherwise similar disks can exhibit different polarization morphologies at the same wavelength, which provides evidence that multiple processes can produce polarized emission in protoplanetary disks at millimeter wavelengths. We then present a survey of disk polarization at 870 μm and 3 mm, which includes the sources observed in the previous chapter. We find that disks can exhibit different transitions between polarization morphologies at different wavelengths. We explore possible reasons for these differences, including differences in the disks’ dust populations and radiation environments. For two of the disks in the survey, we present models of the polarization that would be produced via self-scattering for several dust grain populations. Our modeling results indicate that optical depth effects and vertical dust settling should be taken into account when using polarization observations to constrain dust grain sizes. Then, we show the results of Zeeman splitting observations of nine hyperfine lines in the CN (N=2-1) in the Class II protoplanetary disk AS 209. These observations aimed to measure or set upper limits on the magnetic field strengths in these disks. Magnetic fields are thought to be crucial to the protostellar accretion process, and my constraining magnetic field strengths, we can constrain the mass accretion rate and the mechanisms driving accretion. We derive 3σ upper limits on the poloidal and vertical magnetic field strengths of ∼5-9 mG. If accretion in the disk is driven primarily by magnetic disk winds, then magnetic fields with strengths near these upper limits could drive the accretion rate derived from previous observations of AS 209. We also present the results of Zeeman splitting observations of several hyperfine lines in the CN (N=2-1) and (N=1-0) transitions in the Class II circumbinary disk V4046 Sgr. We find that the CN (2-1) observations provide stricter constraints on the magnetic field strength in the disk than the CN (1-0) observations (3σ upper limits on the line-of-sight magnetic field of ∼2 mG vs. ∼20 mG). From the upper limits on the field strengths provided by the (2-1) observations, we estimate that these magnetic field strengths could drive the accretion rate previously observed in V4046 Sgr if accretion is driven by the magnetorotational instability or magnetic disk winds. Finally, we detail improvements to the error calculation process in the SOFIA (Stratospheric Observatory for Infrared Astronomy) HAWC+ (High-resolution Airborne Wide-band Camera Plus) data reduction pipeline. We present polarimetric observations of the protostars HL Tau and L1527 to demonstrate the importance of these improvements when imaging and analyzing low signal-to-noise polarization data."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Mass Assembly in Protoplanetary Disks: Polarimetry as a Probe of Dust Growth and Accretion"]}]}],"canonical_facts":{"dc:contributor":["Looney, Leslie","Li, Zhi-Yun","Gammie, Charles","Fields, Brian"],"dc:creator":["Harrison, Rachel Elizabeth"],"dc:date":["2022-12","2022-11-30"],"dc:description":["Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2023-04-12 without embargo terms","The student, Rachel Harrison, accepted the attached license on 2022-11-28 at 10:52.","The student, Rachel Harrison, submitted this Dissertation for approval on 2022-11-28 at 11:00.","This Dissertation was approved for publication on 2022-11-30 at 15:43.","DSpace SAF Submission Ingestion Package generated from Vireo submission #18637 on 2023-04-12 at 07:33:01","Circumstellar disks are the formation sites of planets, and their physical and chemical characteristics affect the masses and compositions of planets, as well as planet formation timescales and protostellar accretion rates. Millimeter and submillimeter interferometry with instruments like the Atacama Large Millimeter/submillimeter Array (ALMA) gives us a detailed look at the gas and dust in disks, particularly dust near the midplane of the disk where planet formation takes place. There is now evidence that planet formation is well under way by the Class II phase of disk evolution, when the envelope has dissipated but a significant amount of gas and dust remains in the disk. In fact, there is now evidence that planet formation starts even earlier than Class II (Segura-Cox et al., 2020). Open questions remaining about propoplanetary disk evolution include the sizes of the dust grains in disks and the exact role of the magnetic field in accretion. Through observational studies of protoplanetary disks, this dissertation examines the roles of dust grain growth and magnetically-driven protostellar accretion in disk evolution. We first present a study of the polarized emission from four Class II protoplanetary disks at 3 mm. We find that otherwise similar disks can exhibit different polarization morphologies at the same wavelength, which provides evidence that multiple processes can produce polarized emission in protoplanetary disks at millimeter wavelengths. We then present a survey of disk polarization at 870 μm and 3 mm, which includes the sources observed in the previous chapter. We find that disks can exhibit different transitions between polarization morphologies at different wavelengths. We explore possible reasons for these differences, including differences in the disks’ dust populations and radiation environments. For two of the disks in the survey, we present models of the polarization that would be produced via self-scattering for several dust grain populations. Our modeling results indicate that optical depth effects and vertical dust settling should be taken into account when using polarization observations to constrain dust grain sizes. Then, we show the results of Zeeman splitting observations of nine hyperfine lines in the CN (N=2-1) in the Class II protoplanetary disk AS 209. These observations aimed to measure or set upper limits on the magnetic field strengths in these disks. Magnetic fields are thought to be crucial to the protostellar accretion process, and my constraining magnetic field strengths, we can constrain the mass accretion rate and the mechanisms driving accretion. We derive 3σ upper limits on the poloidal and vertical magnetic field strengths of ∼5-9 mG. If accretion in the disk is driven primarily by magnetic disk winds, then magnetic fields with strengths near these upper limits could drive the accretion rate derived from previous observations of AS 209. We also present the results of Zeeman splitting observations of several hyperfine lines in the CN (N=2-1) and (N=1-0) transitions in the Class II circumbinary disk V4046 Sgr. We find that the CN (2-1) observations provide stricter constraints on the magnetic field strength in the disk than the CN (1-0) observations (3σ upper limits on the line-of-sight magnetic field of ∼2 mG vs. ∼20 mG). From the upper limits on the field strengths provided by the (2-1) observations, we estimate that these magnetic field strengths could drive the accretion rate previously observed in V4046 Sgr if accretion is driven by the magnetorotational instability or magnetic disk winds. Finally, we detail improvements to the error calculation process in the SOFIA (Stratospheric Observatory for Infrared Astronomy) HAWC+ (High-resolution Airborne Wide-band Camera Plus) data reduction pipeline. We present polarimetric observations of the protostars HL Tau and L1527 to demonstrate the importance of these improvements when imaging and analyzing low signal-to-noise polarization data."],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2142/117782"],"dc:language":["en","eng"],"dc:rights":["Copyright 2022 Rachel Harrison"],"dc:subject":["Protoplanetary Disks","Star Formation","Planet Formation","Polarization","Interferometry"],"dc:title":["Mass Assembly in Protoplanetary Disks: Polarimetry as a Probe of Dust Growth and Accretion"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Astronomy"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:56Z"}