{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/109560"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/109560","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Mapping the interstellar magnetic field: Observations of the Goldreich-Kylafis effect towards late-type evolved stars and star-forming regions","abstract":"Mapping magnetic fields is the key to resolving the yet unclear physical picture of circumstellar magnetic fields in both late-type evolved stars and star-forming regions. Observations of linearly polarized molecular line transitions arising from the Goldreich-Kylafis (G-K) effect provide valuable insight into the magnetic field geometry in these sources. Through observing with CARMA, the VLA, and ALMA, this dissertation addresses the questions concerning the dynamical role of magnetic fields in the environment of both the young and the late-type evolved stars. In the circumstellar envelope (CSE) of AGB stars, the uncertainties concerning both the morphology and magnitude of circumstellar magnetic fields and the relative dynamical influence of magnetic fields in shaping AGB mass-loss outflows relative to other proposed mechanisms such as wind interaction models and binarity remain important open astrophysical questions. We examined the magnetic field morphology in the CSE of two Thermal Pulsating (TP-) AGB stars, R Crt and R Leo, revealed by the detected linear polarization of both thermal and maser lines with CARMA and VLA observations to understand the field morphology on multiple scales in the CSE. We detected both thermal (CO J=2-1) and maser (SiO v=1, J=5-4 and SiO v=0,1,2; J=1-0) line polarizations in these two TP-AGB stars. The observed fractional linear polarization due to the G-K effect in the CO emission is measured as $m_{\\ell,p}$ ∼ 3% and $m_{\\ell,p}$ ∼ 9% for R Crt and R Leo, respectively. We utilize a model of the CSE to estimate both circumstellar envelope (CSE) temperature and density profile to yield an estimated linear polarization from G-K modeling (Yang and Lai, 2010) and compare it with the detected CO J = 2 − 1 linear polarization signal. The observed thermal line polarization level is consistent with the predicted results from the model in the case of R Crt, and the missing flux density due to spatial filtering by the interferometer may explain the higher fractional linear polarization in R Leo if the polarized emission originates from a region of smaller spatial extent than the Stokes I emission. The compiled comparison between the inferred magnetic field orientation from our G-K mapping using the polarized J = 2 − 1 CO transition and other intrinsic alignments published for these sources in the literature suggested that there is a more confined magnetic field geometry in R Crt. In star-forming regions, both the magnetic field and turbulence are considered the main agents that support the cloud from collapsing against self gravity (Krumholz and Tan, 2007). We studied the massive star-forming region G10.6-0.4 in ALMA Band 3 polarization observation. G10.6-0.4 is one of the most luminous HII regions with embedded OB stars and thus is a good template for investigating massive star formation processes. In this dissertation, the observed dust continuum polarization mapping and G-K polarization mapping of the CO J = 1−0 transition are presented. The detected dust continuum polarization is at $m_{\\ell,p}$ ∼ 1.52% with a fairly concentrated spatial structure and with an error-weighted PA ∼ 7.1◦. The peak fractional linear polarization measured in the J = 1 − 0 CO line ($m_{\\ell,p}$ ∼ 2.28%) is broadly consistent with the predicted signal strength from detailed G-K modeling. We also found a detailed spatial structure of emission and absorption features across this massive star-forming region, where the absorption region tends to concentrate at the phase center, with the emission originating prominently in the outer region. We discuss future avenues of investigation arising out of the work in this dissertation.","abstract_html":"Mapping magnetic fields is the key to resolving the yet unclear physical picture of circumstellar magnetic fields in both late-type evolved stars and star-forming regions. Observations of linearly polarized molecular line transitions arising from the Goldreich-Kylafis (G-K) effect provide valuable insight into the magnetic field geometry in these sources. Through observing with CARMA, the VLA, and ALMA, this dissertation addresses the questions concerning the dynamical role of magnetic fields in the environment of both the young and the late-type evolved stars. In the circumstellar envelope (CSE) of AGB stars, the uncertainties concerning both the morphology and magnitude of circumstellar magnetic fields and the relative dynamical influence of magnetic fields in shaping AGB mass-loss outflows relative to other proposed mechanisms such as wind interaction models and binarity remain important open astrophysical questions. We examined the magnetic field morphology in the CSE of two Thermal Pulsating (TP-) AGB stars, R Crt and R Leo, revealed by the detected linear polarization of both thermal and maser lines with CARMA and VLA observations to understand the field morphology on multiple scales in the CSE. We detected both thermal (CO J=2-1) and maser (SiO v=1, J=5-4 and SiO v=0,1,2; J=1-0) line polarizations in these two TP-AGB stars. The observed fractional linear polarization due to the G-K effect in the CO emission is measured as <span class=\"etd-inline-math\">m<sub>\\ell,p</sub></span> ∼ 3% and <span class=\"etd-inline-math\">m<sub>\\ell,p</sub></span> ∼ 9% for R Crt and R Leo, respectively. We utilize a model of the CSE to estimate both circumstellar envelope (CSE) temperature and density profile to yield an estimated linear polarization from G-K modeling (Yang and Lai, 2010) and compare it with the detected CO J = 2 − 1 linear polarization signal. The observed thermal line polarization level is consistent with the predicted results from the model in the case of R Crt, and the missing flux density due to spatial filtering by the interferometer may explain the higher fractional linear polarization in R Leo if the polarized emission originates from a region of smaller spatial extent than the Stokes I emission. The compiled comparison between the inferred magnetic field orientation from our G-K mapping using the polarized J = 2 − 1 CO transition and other intrinsic alignments published for these sources in the literature suggested that there is a more confined magnetic field geometry in R Crt. In star-forming regions, both the magnetic field and turbulence are considered the main agents that support the cloud from collapsing against self gravity (Krumholz and Tan, 2007). We studied the massive star-forming region G10.6-0.4 in ALMA Band 3 polarization observation. G10.6-0.4 is one of the most luminous HII regions with embedded OB stars and thus is a good template for investigating massive star formation processes. In this dissertation, the observed dust continuum polarization mapping and G-K polarization mapping of the CO J = 1−0 transition are presented. The detected dust continuum polarization is at <span class=\"etd-inline-math\">m<sub>\\ell,p</sub></span> ∼ 1.52% with a fairly concentrated spatial structure and with an error-weighted PA ∼ 7.1◦. The peak fractional linear polarization measured in the J = 1 − 0 CO line (<span class=\"etd-inline-math\">m<sub>\\ell,p</sub></span> ∼ 2.28%) is broadly consistent with the predicted signal strength from detailed G-K modeling. We also found a detailed spatial structure of emission and absorption features across this massive star-forming region, where the absorption region tends to concentrate at the phase center, with the emission originating prominently in the outer region. We discuss future avenues of investigation arising out of the work in this dissertation.","abstract_has_math":true,"creators":["Huang, Ko-Yun"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Astronomy","degree_department":null,"school":null,"contributors":["Kemball, Athol J","Looney, Leslie W","Wong, Tony","Ricker, Paul M."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-03-05T21:45:09Z","date_published":"2021-03-05T21:45:09Z","updated_at":"2026-07-22T22:24:50Z","subjects":["Stellar magnetic fields","polarimetry","asymptotic giant branch stars","star formation"],"languages":["en"],"rights":["Copyright 2020 Ko-Yun Huang"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/109560","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Kemball, Athol J","Looney, Leslie W","Wong, Tony","Ricker, Paul M."]},{"key":"dc:creator","label":"Author","values":["Huang, Ko-Yun"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2021-03-05T21:45:09Z","2023-03-05T21:47:41Z","2020-09-08","2020-12"]},{"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":["Stellar magnetic fields","polarimetry","asymptotic giant branch stars","star formation"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2020 Ko-Yun Huang"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/109560"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Mapping magnetic fields is the key to resolving the yet unclear physical picture of circumstellar magnetic fields in both late-type evolved stars and star-forming regions. Observations of linearly polarized molecular line transitions arising from the Goldreich-Kylafis (G-K) effect provide valuable insight into the magnetic field geometry in these sources. Through observing with CARMA, the VLA, and ALMA, this dissertation addresses the questions concerning the dynamical role of magnetic fields in the environment of both the young and the late-type evolved stars. In the circumstellar envelope (CSE) of AGB stars, the uncertainties concerning both the morphology and magnitude of circumstellar magnetic fields and the relative dynamical influence of magnetic fields in shaping AGB mass-loss outflows relative to other proposed mechanisms such as wind interaction models and binarity remain important open astrophysical questions. We examined the magnetic field morphology in the CSE of two Thermal Pulsating (TP-) AGB stars, R Crt and R Leo, revealed by the detected linear polarization of both thermal and maser lines with CARMA and VLA observations to understand the field morphology on multiple scales in the CSE. We detected both thermal (CO J=2-1) and maser (SiO v=1, J=5-4 and SiO v=0,1,2; J=1-0) line polarizations in these two TP-AGB stars. The observed fractional linear polarization due to the G-K effect in the CO emission is measured as $m_{\\ell,p}$ ∼ 3% and $m_{\\ell,p}$ ∼ 9% for R Crt and R Leo, respectively. We utilize a model of the CSE to estimate both circumstellar envelope (CSE) temperature and density profile to yield an estimated linear polarization from G-K modeling (Yang and Lai, 2010) and compare it with the detected CO J = 2 − 1 linear polarization signal. The observed thermal line polarization level is consistent with the predicted results from the model in the case of R Crt, and the missing flux density due to spatial filtering by the interferometer may explain the higher fractional linear polarization in R Leo if the polarized emission originates from a region of smaller spatial extent than the Stokes I emission. The compiled comparison between the inferred magnetic field orientation from our G-K mapping using the polarized J = 2 − 1 CO transition and other intrinsic alignments published for these sources in the literature suggested that there is a more confined magnetic field geometry in R Crt. In star-forming regions, both the magnetic field and turbulence are considered the main agents that support the cloud from collapsing against self gravity (Krumholz and Tan, 2007). We studied the massive star-forming region G10.6-0.4 in ALMA Band 3 polarization observation. G10.6-0.4 is one of the most luminous HII regions with embedded OB stars and thus is a good template for investigating massive star formation processes. In this dissertation, the observed dust continuum polarization mapping and G-K polarization mapping of the CO J = 1−0 transition are presented. The detected dust continuum polarization is at $m_{\\ell,p}$ ∼ 1.52% with a fairly concentrated spatial structure and with an error-weighted PA ∼ 7.1◦. The peak fractional linear polarization measured in the J = 1 − 0 CO line ($m_{\\ell,p}$ ∼ 2.28%) is broadly consistent with the predicted signal strength from detailed G-K modeling. We also found a detailed spatial structure of emission and absorption features across this massive star-forming region, where the absorption region tends to concentrate at the phase center, with the emission originating prominently in the outer region. We discuss future avenues of investigation arising out of the work in this dissertation.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01","The student, Ko-Yun Huang, accepted the attached license on 2020-09-02 at 20:20.","The student, Ko-Yun Huang, submitted this Dissertation for approval on 2020-09-02 at 20:40.","This Dissertation was approved for publication on 2020-09-08 at 08:41.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15796 on 2021-03-04 at 16:30:12","Made available in DSpace on 2021-03-05T21:45:09Z (GMT). No. of bitstreams: 3 HUANG-DISSERTATION-2020.pdf: 14698942 bytes, checksum: 6934c73c194aa9ca4f32f1c777598b4e (MD5) LICENSE.txt: 4209 bytes, checksum: 4caf5ea4b8b666ab27c3084d4b6240b3 (MD5) PROQUEST_LICENSE.txt: 4555 bytes, checksum: 4ad3b0d4318a93a9324f7c9664f4c850 (MD5) Previous issue date: 2020-09-08","Embargo set by: Seth Robbins for item 117265 Lift date: 2023-03-05T21:45:47Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 117265 Lift date: 2023-03-05T21:47:41Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Mapping the interstellar magnetic field: Observations of the Goldreich-Kylafis effect towards late-type evolved stars and star-forming regions"]}]}],"canonical_facts":{"dc:contributor":["Kemball, Athol J","Looney, Leslie W","Wong, Tony","Ricker, Paul M."],"dc:creator":["Huang, Ko-Yun"],"dc:date":["2021-03-05T21:45:09Z","2023-03-05T21:47:41Z","2020-09-08","2020-12"],"dc:description":["Mapping magnetic fields is the key to resolving the yet unclear physical picture of circumstellar magnetic fields in both late-type evolved stars and star-forming regions. Observations of linearly polarized molecular line transitions arising from the Goldreich-Kylafis (G-K) effect provide valuable insight into the magnetic field geometry in these sources. Through observing with CARMA, the VLA, and ALMA, this dissertation addresses the questions concerning the dynamical role of magnetic fields in the environment of both the young and the late-type evolved stars. In the circumstellar envelope (CSE) of AGB stars, the uncertainties concerning both the morphology and magnitude of circumstellar magnetic fields and the relative dynamical influence of magnetic fields in shaping AGB mass-loss outflows relative to other proposed mechanisms such as wind interaction models and binarity remain important open astrophysical questions. We examined the magnetic field morphology in the CSE of two Thermal Pulsating (TP-) AGB stars, R Crt and R Leo, revealed by the detected linear polarization of both thermal and maser lines with CARMA and VLA observations to understand the field morphology on multiple scales in the CSE. We detected both thermal (CO J=2-1) and maser (SiO v=1, J=5-4 and SiO v=0,1,2; J=1-0) line polarizations in these two TP-AGB stars. The observed fractional linear polarization due to the G-K effect in the CO emission is measured as $m_{\\ell,p}$ ∼ 3% and $m_{\\ell,p}$ ∼ 9% for R Crt and R Leo, respectively. We utilize a model of the CSE to estimate both circumstellar envelope (CSE) temperature and density profile to yield an estimated linear polarization from G-K modeling (Yang and Lai, 2010) and compare it with the detected CO J = 2 − 1 linear polarization signal. The observed thermal line polarization level is consistent with the predicted results from the model in the case of R Crt, and the missing flux density due to spatial filtering by the interferometer may explain the higher fractional linear polarization in R Leo if the polarized emission originates from a region of smaller spatial extent than the Stokes I emission. The compiled comparison between the inferred magnetic field orientation from our G-K mapping using the polarized J = 2 − 1 CO transition and other intrinsic alignments published for these sources in the literature suggested that there is a more confined magnetic field geometry in R Crt. In star-forming regions, both the magnetic field and turbulence are considered the main agents that support the cloud from collapsing against self gravity (Krumholz and Tan, 2007). We studied the massive star-forming region G10.6-0.4 in ALMA Band 3 polarization observation. G10.6-0.4 is one of the most luminous HII regions with embedded OB stars and thus is a good template for investigating massive star formation processes. In this dissertation, the observed dust continuum polarization mapping and G-K polarization mapping of the CO J = 1−0 transition are presented. The detected dust continuum polarization is at $m_{\\ell,p}$ ∼ 1.52% with a fairly concentrated spatial structure and with an error-weighted PA ∼ 7.1◦. The peak fractional linear polarization measured in the J = 1 − 0 CO line ($m_{\\ell,p}$ ∼ 2.28%) is broadly consistent with the predicted signal strength from detailed G-K modeling. We also found a detailed spatial structure of emission and absorption features across this massive star-forming region, where the absorption region tends to concentrate at the phase center, with the emission originating prominently in the outer region. We discuss future avenues of investigation arising out of the work in this dissertation.","Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01","The student, Ko-Yun Huang, accepted the attached license on 2020-09-02 at 20:20.","The student, Ko-Yun Huang, submitted this Dissertation for approval on 2020-09-02 at 20:40.","This Dissertation was approved for publication on 2020-09-08 at 08:41.","DSpace SAF Submission Ingestion Package generated from Vireo submission #15796 on 2021-03-04 at 16:30:12","Made available in DSpace on 2021-03-05T21:45:09Z (GMT). No. of bitstreams: 3 HUANG-DISSERTATION-2020.pdf: 14698942 bytes, checksum: 6934c73c194aa9ca4f32f1c777598b4e (MD5) LICENSE.txt: 4209 bytes, checksum: 4caf5ea4b8b666ab27c3084d4b6240b3 (MD5) PROQUEST_LICENSE.txt: 4555 bytes, checksum: 4ad3b0d4318a93a9324f7c9664f4c850 (MD5) Previous issue date: 2020-09-08","Embargo set by: Seth Robbins for item 117265 Lift date: 2023-03-05T21:45:47Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Embargo set by: Seth Robbins for item 117265 Lift date: 2023-03-05T21:47:41Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system","Author requested closed access (OA after 2yrs) in Vireo ETD system","Limited"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/109560"],"dc:language":["en"],"dc:rights":["Copyright 2020 Ko-Yun Huang"],"dc:subject":["Stellar magnetic fields","polarimetry","asymptotic giant branch stars","star formation"],"dc:title":["Mapping the interstellar magnetic field: Observations of the Goldreich-Kylafis effect towards late-type evolved stars and star-forming regions"],"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":"2026-07-22T22:24:50Z"}