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dc.contributor.advisorWills, Beverley J.en
dc.contributor.advisorEvans, Neal J.en
dc.creatorYuan, Michael Juntaoen
dc.date.accessioned2011-08-08T21:53:49Zen
dc.date.available2011-08-08T21:53:49Zen
dc.date.issued2004-08en
dc.identifier.urihttp://hdl.handle.net/2152/12950en
dc.descriptiontexten
dc.description.abstractAlthough 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.mediumelectronicen
dc.language.isoengen
dc.rightsCopyright 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.en
dc.subjectQuasarsen
dc.subjectStars--Luminosity functionen
dc.subjectAccretion (Astrophysics)en
dc.subjectBlack holes (Astronomy)en
dc.titleUnification of QSOs via black hole and accretion propertiesen
dc.description.departmentAstronomyen
thesis.degree.departmentAstronomyen
thesis.degree.disciplineAstronomyen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen


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