Persistent Link:
http://hdl.handle.net/10150/194982
Title:
Supermassive Black Hole Activity in the Cosmic Evolution Survey
Author:
Trump, Jonathan Russell
Issue Date:
2010
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:
I investigate active supermassive black holes, also called active galactic nuclei (AGNs). My tool for this work is the Cosmic Evolution Survey (COSMOS), a deep multiwavelength survey over 2 deg² of the sky. I describe the COSMOS AGN optical spectroscopy campaign, and present the largest AGN sample to date with full multiwavelength (radio, IR, optical, UV and X-ray) spectral energy distributions. Studying the COSMOS AGN sample reveals a unified model for supermassive black hole activity based on accretion rate, as shown by the following main results. (1) Classically “obscured” (Type 2) AGNs are more prevalent at higher redshifts and lower luminosities, suggesting that these objects accrete through low-level stochastic disk feeding by their hosts. (2) The prescence of broad emission lines in an AGN requires a minimum accretion rate (L/L(Edd) > 0.01). Broad-line (Type 1) AGNs in COSMOS span a large range of accretion rates (0.01 < L/L(Edd) < 1), in contrast to results from previous, shallower surveys, and broad-line AGNs become more optically luminous as accretion rate increases. (3) Lineless, “optically dull” AGNs have very different SEDs than broad-line and narrow-line AGNs, with comparatively brighter X-ray emission, redder optical continua, no infrared hot dust, and stronger radio emission. While up to 2/3 of optically dull AGNs may be “normal” AGNs diluted by extranuclear host galaxy light, at least 1/3 are best described as unobscured, intrinsically weak AGNs. (4) At low accretion rates, material accreting onto an AGN changes from a thin disk to an advection-dominated flow near the black hole, resulting in very different observed properties: the broad-line region disappears, radio jets become more important, and the hot dust signature changes. In contrast to previous unification models, observations indicate that most of the narrow-line and lineless AGNs in COSMOS are best described as weakly accreting AGNs. We conclude by noting a few predictions and observational tests to further investigate our model of AGN unification by accretion rate.
Type:
text; Electronic Dissertation
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Astronomy; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Impey, Christopher D.
Committee Chair:
Impey, Christopher D.

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleSupermassive Black Hole Activity in the Cosmic Evolution Surveyen_US
dc.creatorTrump, Jonathan Russellen_US
dc.contributor.authorTrump, Jonathan Russellen_US
dc.date.issued2010en_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.abstractI investigate active supermassive black holes, also called active galactic nuclei (AGNs). My tool for this work is the Cosmic Evolution Survey (COSMOS), a deep multiwavelength survey over 2 deg² of the sky. I describe the COSMOS AGN optical spectroscopy campaign, and present the largest AGN sample to date with full multiwavelength (radio, IR, optical, UV and X-ray) spectral energy distributions. Studying the COSMOS AGN sample reveals a unified model for supermassive black hole activity based on accretion rate, as shown by the following main results. (1) Classically “obscured” (Type 2) AGNs are more prevalent at higher redshifts and lower luminosities, suggesting that these objects accrete through low-level stochastic disk feeding by their hosts. (2) The prescence of broad emission lines in an AGN requires a minimum accretion rate (L/L(Edd) > 0.01). Broad-line (Type 1) AGNs in COSMOS span a large range of accretion rates (0.01 < L/L(Edd) < 1), in contrast to results from previous, shallower surveys, and broad-line AGNs become more optically luminous as accretion rate increases. (3) Lineless, “optically dull” AGNs have very different SEDs than broad-line and narrow-line AGNs, with comparatively brighter X-ray emission, redder optical continua, no infrared hot dust, and stronger radio emission. While up to 2/3 of optically dull AGNs may be “normal” AGNs diluted by extranuclear host galaxy light, at least 1/3 are best described as unobscured, intrinsically weak AGNs. (4) At low accretion rates, material accreting onto an AGN changes from a thin disk to an advection-dominated flow near the black hole, resulting in very different observed properties: the broad-line region disappears, radio jets become more important, and the hot dust signature changes. In contrast to previous unification models, observations indicate that most of the narrow-line and lineless AGNs in COSMOS are best described as weakly accreting AGNs. We conclude by noting a few predictions and observational tests to further investigate our model of AGN unification by accretion rate.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorImpey, Christopher D.en_US
dc.contributor.chairImpey, Christopher D.en_US
dc.contributor.committeememberImpey, Christopher D.en_US
dc.contributor.committeememberDavé, Romeelen_US
dc.contributor.committeememberGreen, Richard F.en_US
dc.contributor.committeememberZaritsky, Dennisen_US
dc.identifier.proquest10896en_US
dc.identifier.oclc659753817en_US
All Items in UA Campus Repository are protected by copyright, with all rights reserved, unless otherwise indicated.