{"id":{"repo_id":"texas","oai_identifier":"oai:repositories.lib.utexas.edu:2152/12950"},"canonical_url":"https://search.dev.ndltd.org/etd/texas/oai:repositories.lib.utexas.edu:2152/12950","repository":{"repo_id":"texas","name":"University of Texas","base_url":"https://repositories.lib.utexas.edu/server/oai/request"},"display":{"title":"Unification of QSOs via black hole and accretion properties","abstract":"Although the orientation-based AGN unification scheme can successfully explain many QSO observational phenomena, orientation does not address all the object-to-object differences in QSOs. Physical differences of the underlying engine, such as luminosity, black hole mass (MBH) and Eddington ratio (L/LEdd), are crucial to our understanding of QSO central engines. Broad Absorption Line (BAL) QSOs are a particularly interesting type of QSO that exhibits both orientation and intrinsic property-related observational features. In this thesis, I studied a large QSO sample, including 16 BAL QSOs at z ∼ 2, with new spectroscopy data for the Hβ region. This sample covers a luminosity range substantially wider than similar studies in the past and hence enables us to differentiate luminosity from other underlying mechanisms driving QSO observational properties. I found that overall, QSOs accrete at close to Eddington rate. Due to the narrow range of L/LEdd, the QSO luminosity is almost directly proportional to the MBH. The slight increase of L/LEdd at high luminosity suggests that the QSO MBH distribution has a high mass cut-off near 109M¯. Compared with radio quiet QSOs, radio loud QSOs tend to have higher MBH for the same luminosity. The [O iii] versus Fe ii anti-correlation discovered from low luminosity QSOs (BGEV1) extends to high luminosity objects with BAL QSOs at the weak [O iii] strong Fe ii end of the trend, and radio loud QSOs at strong [O iii] weak Fe ii end of the trend. Both [O iii] and Fe ii strengths are well correlated with L/LEdd over the entire luminosity range, indicating that L/LEdd is the physical driver behind the BGEV1 correlations. Although BAL QSOs have higher L/LEdd than most QSOs, they do not stand out when compared with high luminosity non-BAL QSOs. One interpretation is that [O iii] and Fe ii are indirectly linked to L/LEdd via the availability of accretion fuel. Even with the expanded luminosity coverage, I could not confirm the existence of an Hβ Baldwin Effect. An [O iii] ”Baldwin Effect” is observed, suggesting a limited amount of [O iii] NLR gas in all QSO systems.","abstract_html":"Although the orientation-based AGN unification scheme can successfully explain many QSO observational phenomena, orientation does not address all the object-to-object differences in QSOs. Physical differences of the underlying engine, such as luminosity, black hole mass (MBH) and Eddington ratio (L/LEdd), are crucial to our understanding of QSO central engines. Broad Absorption Line (BAL) QSOs are a particularly interesting type of QSO that exhibits both orientation and intrinsic property-related observational features. In this thesis, I studied a large QSO sample, including 16 BAL QSOs at z ∼ 2, with new spectroscopy data for the Hβ region. This sample covers a luminosity range substantially wider than similar studies in the past and hence enables us to differentiate luminosity from other underlying mechanisms driving QSO observational properties. I found that overall, QSOs accrete at close to Eddington rate. Due to the narrow range of L/LEdd, the QSO luminosity is almost directly proportional to the MBH. The slight increase of L/LEdd at high luminosity suggests that the QSO MBH distribution has a high mass cut-off near 109M¯. Compared with radio quiet QSOs, radio loud QSOs tend to have higher MBH for the same luminosity. The [O iii] versus Fe ii anti-correlation discovered from low luminosity QSOs (BGEV1) extends to high luminosity objects with BAL QSOs at the weak [O iii] strong Fe ii end of the trend, and radio loud QSOs at strong [O iii] weak Fe ii end of the trend. Both [O iii] and Fe ii strengths are well correlated with L/LEdd over the entire luminosity range, indicating that L/LEdd is the physical driver behind the BGEV1 correlations. Although BAL QSOs have higher L/LEdd than most QSOs, they do not stand out when compared with high luminosity non-BAL QSOs. One interpretation is that [O iii] and Fe ii are indirectly linked to L/LEdd via the availability of accretion fuel. Even with the expanded luminosity coverage, I could not confirm the existence of an Hβ Baldwin Effect. An [O iii] ”Baldwin Effect” is observed, suggesting a limited amount of [O iii] NLR gas in all QSO systems.","abstract_has_math":false,"creators":["Yuan, Michael Juntao"],"institution":"The University of Texas at Austin","degree_name":"Doctor of Philosophy","degree_level":"Doctoral","degree_discipline":"Astronomy","degree_department":null,"school":null,"contributors":[],"advisors":["Wills, Beverley J.","Evans, Neal J."],"committee_chairs":[],"committee_members":[],"year":2004,"date_issued":"2004-08","date_published":"2004-08","updated_at":"2026-07-24T05:01:18Z","subjects":["Quasars","Stars--Luminosity function","Accretion (Astrophysics)","Black holes (Astronomy)"],"languages":["eng"],"rights":["Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2152/12950","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Wills, Beverley J.","Evans, Neal J."]},{"key":"dc:creator","label":"Author","values":["Yuan, Michael Juntao"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2011-08-08T21:53:49Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2011-08-08T21:53:49Z"]},{"key":"dc:date.issued","label":"Date","values":["2004-08"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Astronomy"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["The University of Texas at Austin"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Quasars","Stars--Luminosity function","Accretion (Astrophysics)","Black holes (Astronomy)"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/2152/12950"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["text"]},{"key":"dc:description.abstract","label":"Abstract","values":["Although the orientation-based AGN unification scheme can successfully explain many QSO observational phenomena, orientation does not address all the object-to-object differences in QSOs. Physical differences of the underlying engine, such as luminosity, black hole mass (MBH) and Eddington ratio (L/LEdd), are crucial to our understanding of QSO central engines. Broad Absorption Line (BAL) QSOs are a particularly interesting type of QSO that exhibits both orientation and intrinsic property-related observational features. In this thesis, I studied a large QSO sample, including 16 BAL QSOs at z ∼ 2, with new spectroscopy data for the Hβ region. This sample covers a luminosity range substantially wider than similar studies in the past and hence enables us to differentiate luminosity from other underlying mechanisms driving QSO observational properties. I found that overall, QSOs accrete at close to Eddington rate. Due to the narrow range of L/LEdd, the QSO luminosity is almost directly proportional to the MBH. The slight increase of L/LEdd at high luminosity suggests that the QSO MBH distribution has a high mass cut-off near 109M¯. Compared with radio quiet QSOs, radio loud QSOs tend to have higher MBH for the same luminosity. The [O iii] versus Fe ii anti-correlation discovered from low luminosity QSOs (BGEV1) extends to high luminosity objects with BAL QSOs at the weak [O iii] strong Fe ii end of the trend, and radio loud QSOs at strong [O iii] weak Fe ii end of the trend. Both [O iii] and Fe ii strengths are well correlated with L/LEdd over the entire luminosity range, indicating that L/LEdd is the physical driver behind the BGEV1 correlations. Although BAL QSOs have higher L/LEdd than most QSOs, they do not stand out when compared with high luminosity non-BAL QSOs. One interpretation is that [O iii] and Fe ii are indirectly linked to L/LEdd via the availability of accretion fuel. Even with the expanded luminosity coverage, I could not confirm the existence of an Hβ Baldwin Effect. An [O iii] ”Baldwin Effect” is observed, suggesting a limited amount of [O iii] NLR gas in all QSO systems."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["electronic"]},{"key":"dc:title","label":"Title","values":["Unification of QSOs via black hole and accretion properties"]}]}],"canonical_facts":{"dc:contributor.advisor":["Wills, Beverley J.","Evans, Neal J."],"dc:creator":["Yuan, Michael Juntao"],"dc:date.accessioned":["2011-08-08T21:53:49Z"],"dc:date.available":["2011-08-08T21:53:49Z"],"dc:date.issued":["2004-08"],"dc:description":["text"],"dc:description.abstract":["Although the orientation-based AGN unification scheme can successfully explain many QSO observational phenomena, orientation does not address all the object-to-object differences in QSOs. Physical differences of the underlying engine, such as luminosity, black hole mass (MBH) and Eddington ratio (L/LEdd), are crucial to our understanding of QSO central engines. Broad Absorption Line (BAL) QSOs are a particularly interesting type of QSO that exhibits both orientation and intrinsic property-related observational features. In this thesis, I studied a large QSO sample, including 16 BAL QSOs at z ∼ 2, with new spectroscopy data for the Hβ region. This sample covers a luminosity range substantially wider than similar studies in the past and hence enables us to differentiate luminosity from other underlying mechanisms driving QSO observational properties. I found that overall, QSOs accrete at close to Eddington rate. Due to the narrow range of L/LEdd, the QSO luminosity is almost directly proportional to the MBH. The slight increase of L/LEdd at high luminosity suggests that the QSO MBH distribution has a high mass cut-off near 109M¯. Compared with radio quiet QSOs, radio loud QSOs tend to have higher MBH for the same luminosity. The [O iii] versus Fe ii anti-correlation discovered from low luminosity QSOs (BGEV1) extends to high luminosity objects with BAL QSOs at the weak [O iii] strong Fe ii end of the trend, and radio loud QSOs at strong [O iii] weak Fe ii end of the trend. Both [O iii] and Fe ii strengths are well correlated with L/LEdd over the entire luminosity range, indicating that L/LEdd is the physical driver behind the BGEV1 correlations. Although BAL QSOs have higher L/LEdd than most QSOs, they do not stand out when compared with high luminosity non-BAL QSOs. One interpretation is that [O iii] and Fe ii are indirectly linked to L/LEdd via the availability of accretion fuel. Even with the expanded luminosity coverage, I could not confirm the existence of an Hβ Baldwin Effect. An [O iii] ”Baldwin Effect” is observed, suggesting a limited amount of [O iii] NLR gas in all QSO systems."],"dc:format.medium":["electronic"],"dc:identifier.uri":["http://hdl.handle.net/2152/12950"],"dc:language.iso":["eng"],"dc:rights":["Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works."],"dc:subject":["Quasars","Stars--Luminosity function","Accretion (Astrophysics)","Black holes (Astronomy)"],"dc:title":["Unification of QSOs via black hole and accretion properties"],"thesis:degree_discipline":["Astronomy"],"thesis:degree_level":["Doctoral"],"thesis:degree_name":["Doctor of Philosophy"],"thesis:institution_name":["The University of Texas at Austin"]},"updated_at":"2026-07-24T05:01:18Z"}