Persistent Link:
http://hdl.handle.net/10150/289835
Title:
Properties of galactic nuclei inferred from line spectra
Author:
Fromerth, Michael
Issue Date:
2002
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
This work explores how certain properties of galactic nuclei can be understood on the basis of the available data. Current evidence for the presence of large central masses in these regions, believed to be supermassive black holes, is first reviewed. Methods for estimating the mass are discussed, and a new algorithm is presented for implementing reverberation techniques with time-variable broad line data from active nuclei. The effectiveness of this new algorithm is first tested on sample data sets; it is then applied to actual data. Next, a model is presented for the formation of the cool, dense clouds responsible for the broad line emission, involving the rapid cooling of shocked gas embedded in a quasi-spherical, turbulent accretion flow. As an illustrative example, fitting of the model (with simplify assumptions) is performed on data pertaining to the Seyfert nucleus NGC 5548. Accretion flows in two specific objects are then discussed. First, a cool, spherical accretion flow is argued for the non-active nucleus of M31 on the basis of the observed broad-band spectrum. In addition to comparisons of the model with the currently available data, we provide detailed predictions of the UV and optical line spectra, correcting for extinction due to intervening dust and cold gas. Then, a turbulent disk structure is argued for the weakly-active nucleus in the radio galaxy NGC 4261. This structure is capable of producing both the observed broad line spectrum and radio absorption, and may have application to the nuclei of other radio galaxies. Finally, the iron Kalpha emission from Sgr B2, a giant molecular cloud located in the Galactic Center region, is reviewed. While many argue that this suggests recent activity associated with the radio source Sgr A*, our modeling indicates that the data are also consistent with a time-variable illuminator embedded within the cloud. The observations and modeling suggest that turbulence may be a key component to accretion in active nuclei, facilitating the transfer of angular momentum and allowing the greater accretion rates needed to fuel the central engines. Future 3D-hydrodynamical simulations are required to test this assertion.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Physics, Astronomy and Astrophysics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Physics
Degree Grantor:
University of Arizona
Advisor:
Melia, Fulvio

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleProperties of galactic nuclei inferred from line spectraen_US
dc.creatorFromerth, Michaelen_US
dc.contributor.authorFromerth, Michaelen_US
dc.date.issued2002en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThis work explores how certain properties of galactic nuclei can be understood on the basis of the available data. Current evidence for the presence of large central masses in these regions, believed to be supermassive black holes, is first reviewed. Methods for estimating the mass are discussed, and a new algorithm is presented for implementing reverberation techniques with time-variable broad line data from active nuclei. The effectiveness of this new algorithm is first tested on sample data sets; it is then applied to actual data. Next, a model is presented for the formation of the cool, dense clouds responsible for the broad line emission, involving the rapid cooling of shocked gas embedded in a quasi-spherical, turbulent accretion flow. As an illustrative example, fitting of the model (with simplify assumptions) is performed on data pertaining to the Seyfert nucleus NGC 5548. Accretion flows in two specific objects are then discussed. First, a cool, spherical accretion flow is argued for the non-active nucleus of M31 on the basis of the observed broad-band spectrum. In addition to comparisons of the model with the currently available data, we provide detailed predictions of the UV and optical line spectra, correcting for extinction due to intervening dust and cold gas. Then, a turbulent disk structure is argued for the weakly-active nucleus in the radio galaxy NGC 4261. This structure is capable of producing both the observed broad line spectrum and radio absorption, and may have application to the nuclei of other radio galaxies. Finally, the iron Kalpha emission from Sgr B2, a giant molecular cloud located in the Galactic Center region, is reviewed. While many argue that this suggests recent activity associated with the radio source Sgr A*, our modeling indicates that the data are also consistent with a time-variable illuminator embedded within the cloud. The observations and modeling suggest that turbulence may be a key component to accretion in active nuclei, facilitating the transfer of angular momentum and allowing the greater accretion rates needed to fuel the central engines. Future 3D-hydrodynamical simulations are required to test this assertion.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectPhysics, Astronomy and Astrophysics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplinePhysicsen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMelia, Fulvioen_US
dc.identifier.proquest3061004en_US
dc.identifier.bibrecord.b43042314en_US
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