Dissertations / Theses on the topic 'Black holes (Astronomy) Black holes (Astronomy) Active galactic nuclei'
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1
Denney, Kelly D. "Black Hole Masses in Active Galactic Nuclei." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1274716921.
2
Ghosh, Himel. "A Search for the Smallest Supermassive Black Holes." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253492291.
3
Fausnaugh, Michael Martin. "Reverberation Mapping of the Continuum Source in Active Galactic Nuclei." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1494244528720735.
4
Bentz, Misty C. "Black hole scaling relationships new results from reverberation mapping and Hubble Space Telescope imaging /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180453426.
5
Grier, Catherine J. "Active Galactic Nuclei: Masses and Dynamics." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1372681067.
6
Blecha, Laura Elizabeth. "The Dynamics and Evolution of Supermassive Black Holes in Merging Galaxies." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10257.
Abstract:
This thesis is a theoretical study of supermassive black holes (SMBHs) in merging galaxies. We consider the dynamics that govern inspiralling SMBH pairs and gravitational-wave (GW) recoiling SMBHs, as well as the fueling of active galactic nuclei (AGN) during galaxy mergers. In particular, we focus on the observable signatures that could distinguish dual or recoiling AGN from those in isolated galaxies, and we explore the implications of these events for the coordinated evolution of SMBHs and galaxies. In the second and third chapters, semi-analytical models for GW-recoiling SMBHs are developed. The second chapter illustrates that bound recoiling SMBHs may have long wandering timescales and that recoil events can self-regulate SMBH growth. In the third chapter, we study the evolution of recoiling SMBHs in evolving, gaseous merger remnants. We find that the presence of gas greatly influences recoiling SMBH trajectories and may partially suppress even large recoil kicks in some cases. We also show that kinematically- and spatially-offset AGN can have substantial lifetimes for a wide range in kick speeds. Finally, this chapter illustrates that GW recoil influences the observed SMBH-galaxy relations as well as central star formation in the merger remnant. In the fourth chapter we turn our attention to inspiralling SMBH pairs with kiloparsec-scale separations. We use a novel approach to model the narrow-line emission from these SMBH pairs, in order to understand their relationship to observations of double-peaked narrow-line AGN. Our results indicate that double-peaked narrow-line AGN often arise from gas kinematics rather than from dual SMBH motion, but that the latter are a generic, short-lived phase of SMBH inspiral in gaseous mergers. We identify several diagnostics that could aid in distinguishing the true AGN pairs in the double-peaked sample. Finally, the fifth chapter examines a particular galaxy that exhibits signatures of both a recoiling AGN and an AGN pair. Applying methods developed throughout this thesis, we design models for both scenarios that are well-matched to the available data. Currently, neither possibility can be excluded for this object, but our models constrain the most relevant parameters for etermining its nature and for the design of future observations.Astronomy
7
Fukumura, Keigo. "Relativistic Accretion Flows onto Supermassive Black Holes: Shock Formation and Iron Fluorescent Emission Lines in Active Galactic Nuclei." Thesis, Montana State University, 2005. http://etd.lib.montana.edu/etd/2005/fukumura/FukumuraK0505.pdf.
Abstract:
One of the exciting discoveries from the recent X-ray spectroscopic studies of active galactic nuclei (AGNs) is the so called "relativistically-broadened iron fluorescent emission line" often detected in the hard X-ray spectra. It is generally believed to originate from the inner part of the accretion disk surrounding a supermassive black hole (BH) at the center. Although we have begun to obtain some physical insight regarding such emission lines supported by theoretical models (e.g., disk-corona model), exactly how and where the observed fluorescence may take place is still disputable. Here, an X-ray data with XMM-Newton Observatory of a typical narrow-line Seyfert 1 galaxy, NGC 4051, is analyzed based on a partial covering model to consistently explain the observed time-resolved temporal/spectral variations. This model implies that the intrinsic emission varies significantly in the presence of the covering cloud. We often detect a hard X-ray continuum originating from a hot region close to the central engines of AGNs. As a promising X-ray source candidate, relativistic hydrodynamic (HD) shocks are investigated systematically and then extended to the magnetohydrodynamic (MHD) shocks, given the widely accepted suggestion that the presence of the magnetic fields could play an important role in the accreting flows. I show that both HD and MHD shocks can form in the vicinity of the BH, perhaps responsible for creating such a high temperature region where hard X-rays are produced. Particularly in the MHD shocked plasma, the hydro/magneto-dominated states are found. Considering the effect of such magnetic fields in the accretion disk, I calculate nonstandard iron fluorescent line profiles in the presence of spiral density waves and find multiple sharp sub-peak structures in extremely skewed line profiles, which will be detectable with upcoming X-ray satellites such as Astro-E2 XRS for testing the model. This dissertation is the result of my own work and also includes some work done in collaboration. Parts of this dissertation have been either already published in or submitted to the Astrophysical Journal and presented at conferences, while some are still in progress.
8
McGraw, Sean Michael. "Outflow and Accretion Physics in Active Galactic Nuclei." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1469701247.
9
Down, Emily. "The orientation of accretion disks and jets in quasars." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.572597.
Abstract:
All massive nearby galaxies, including our own, host supermassive black holes. Active galactic nuclei (AGN) are seen when such black holes accrete, and when they produce powerful jets of synchrotron-emitting plasma, they are termed radio-loud AGN. The close correlation between black hole mass and galaxy bulge mass in elliptical galaxies indicates that AGN feedback may be the key to the regulation of galaxy formation. It is thus necessary to fully understand the structure of AGN, the way that they are fuelled, and their duty cycle, in order to study the feedback processes and get a clear picture of galaxy formation. In this thesis, independent methods are developed to constrain the accretion disk and radio jet angles to the line of sight. H IX emission from a sub-sample of high-redshift quasars is measured from near-infrared spectroscopy and modelled as sums of different components, including the characteristic double-peaked profile which results from a thin, rotating accretion disk. Comparing the models using Bayesian evidence, almost all quasars were found to have infrared spectra consistent with the presence of a disk. The jet inclination angles of the same set of quasars were constrained by fitting a model, including the effect of Doppler boosting and the receding torus model for dust obscuration, to the radio \ spectral energy distribution. The fitted disk and jet angles correlate strongly, and are consistent with a model in which the radio jets are launched orthogonally to the plane of the accretion disk, as expected if the jet is powered by energy drawn from the spin of the black hole. Both disk and jet angles correlate with the observed linear source size, which is a projection effect; when deprojected using the fitted angles, the distribution of source sizes agrees with a scenario in which the sources expand into the surrounding medium at a constant rate up to ~ 1 Mpc and then shut off, probably as the nuclei become quiescent. The accretion disk angle was found to correlate weakly with the low-frequency radio luminosity, which provides direct, albeit tenuous, evidence for the receding torus model.
10
Carroll, Carla June. "A Feasibility Study of Photometric Reverberation Mapping with Meter-Class Telescopes." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5469.
Abstract:
For the past several decades, mass estimates for supermassive black holes hosted by active galactic nuclei (AGN) have been made with the reverberation mapping (RM) technique. This methodology has produced consistent results and has been used to establish several relations that link the characteristics of the host galaxy to the mass of the central black hole. Despite this success, there are less than 50 AGN with black hole masses derived from RM. This low number is generally attributed to the difficulties in coordinating large blocks of telescope time for making simultaneous photometric and spectroscopic observations. Spectroscopic observations also generally require several months of nightly observations with moderate to large size telescopes as the signal-to-noise ratio is too low for smaller telescopes. We have made photometric observations of NGC 5548 in four filters (a custom-made Hα10 filter, the Strömgren y filter, the Johnson/Cousins V filter and the Johnson/Cousins R filter) in order to evaluate a photometric methodology for determining the lag time between the variations observed in the continuum and the Hα emission from the broad-line region (BLR) gas. This time delay represents the mean light travel time to the BLR and is therefore a measurement of the mean BLR radius. Multiple JAVELIN analyses of the three continuum light curves (y, V, and R), relative to the light curve from the Hα10 filter yields a value for τ = 3.3 ± 0.1 days. Adopting a value of f = 5.5, along with a single-epoch spectroscopic measurement from Park et of Δv = 4354±25 km/s, enables us to estimate a black hole mass of M_BH = 67.2±2.2x10^6 M_sun.
11
Romano, Patrizia. "Multi-Wavelength Study of Narrow-Line Seyfert 1 Galaxies." The Ohio State University, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=osu1028570377.
12
Reza, Katebi. "Nuclear Outbursts in the Centers of Galaxies." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1573031465540983.
13
Onken, Christopher Alan. "Measurement of black hole masses in active Galactic Nuclei." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1125427208.
14
Stone, Nicholas Chamberlain. "Tidal Disruption of Stars by Supermassive Black Holes." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10998.
Abstract:
This thesis presents theoretical results on the tidal disruption of stars by supermassive black holes (SMBHs). The multiwavelength ares produced by tidal disruption events (TDEs) have supernova-like luminosities, and associated relativistic jets can be visible to cosmological distances. TDEs probe the demography of quiescent SMBHs, and are natural laboratories for jet launching mechanisms and super-Eddington accretion. The first chapter broadly surveys TDE physics. The second and third chapters estimate the TDE rate following gravitational wave (GW) recoil of a SMBH (after a SMBH binary merger). Immediately after GW recoil, the TDE rate increases, sometimes to \(~10^{-1}\) TDEs per year. This "burst" of TDE flares can provide an electromagnetic counterpart to low frequency GW signals, localizing sources and measuring cosmological parameters. Millions of years later, recoiled SMBHs wandering through their host galaxies will produce spatially offset TDEs at a rate which is likely detectable with the LSST. In the fourth chapter, we show that standard estimates for \(\Delta\epsilon\), the energy spread of TDE debris, are wrong, sometimes by orders of magnitude. Correcting this error reduces the observability of many TDEs. We introduce a new analytic model for tidal disruption, calculate \(\Delta\epsilon\)'s dependence on stellar spin, estimate general relativistic corrections to \(\Delta\epsilon\), and quantify the GW signal generated from tidal compression. The fifth chapter presents hydrodynamical simulations of TDE debris circularization, focusing on eccentric, rather than parabolic, orbits. General relativistic precession drives debris circularization, in contrast to past simulations using smaller black holes. In the sixth chapter, we show that TDE light curves can constrain or measure SMBH spins, as Lense-Thirring torques produce quasiperiodic variability in disk emission. Precession of a relativistic jet could also measure SMBH spin, and we apply our model to the relativistic Swift 1644+57 TDE. The seventh chapter considers the disruption of neutron stars (NSs) by stellar mass black holes (BHs) or other NSs. Jet precession in associated short-hard gamma ray bursts is uniquely possible for NS-BH (not NS-NS) mergers. We quantify typical precession amplitudes and periods, and calculate their time evolution. If disk viscosities are relatively low, electromagnetic observations alone could distinguish NS-BH from NS-NS mergers.Astronomy
15
Assef, Roberto Jose. "Properties of Active Galactic Nuclei and Galaxies: Spectral Energy Distributions, Luminosity Functions and Black Hole Masses." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281369360.
16
Hall, Jimmy Clyde 1952. "A general relativistic study of the infrared emission from massive black holes in the nuclei of active galaxies." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/290598.
Abstract:
The possibility that some portion of the infrared (IR) radiation emanating from Active Galactic Nuclei (AGN's) may arise from disklike structures of ionized plasma accreting onto massive or supermassive black holes motivates the investigation of the effects on the observed radiation of the strong gravitational fields in the vicinity of the emitting particles. Numerous previous studies have been incomplete in several respects: (a) they have neglected to take into account the contribution to the observed specific power flux of radiation emitted from the underside of the disk and gravitationally lensed into the upper half-hemisphere; (b) they have considered only a limited range of observing positions and hole spins; (c) many have been restricted to examination of the steady state flux arising from homogeneous disks; (d) they have employed a methodology not readily extendible to the analysis of gravitational effects on radiation arising from more complicated physical systems (e.g., nonplanar ensembles of gaseous clouds). The present study develops, within the context of the optically thick, geometrically thin accretion disk model, a new method of complementary images. Fully taking into account the so-called first-orbit disk images, including the effects of disk self-occlusion, for the entire range of observing positions and hole spins, and for both homogeneous and thermally inhomogeneous disks, it applies this method to both steady state and time-dependent analyses in the paradigm case of the Galactic Center black hole candidate Sagittarius A*. Completely general results applicable to any similar black hole-accretion disk system are presented. An illustration is given of how the basic method, along with ancillary analytical devices such as that of extended images and computationally efficient techniques based on their properties, may be extended to the analysis of considerably more complicated physical systems, and tentative results for the case of the Broad Line Region (BLR) of quasar spectra are presented.
17
Ryle, Wesley Thomas. "Investigation of Fundamental Black Hole Properties of AGN through Optical Variability." Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/phy_astr_diss/25.
Abstract:
Active galactic nuclei (AGN) are known to vary in brightness in all regions of the electromagnetic spectrum and over a wide range of timescales. Many methods have been utilized to transform this observed variability into meaningful information about the central engines of AGN. One such technique, adapted from time series analysis of galactic x-ray binary systems, has been used to detect a characteristic break timescale in the power density spectra of x-ray variability in Seyfert galaxies. This timescale, thought to be related to instabilities in the accretion disk, appears to scale with black hole mass over many orders of magnitude. This dissertation performs similar time series analyses with the optical data of eight blazars. The majority of these objects also display a characteristic break timescale. In cases where a black hole estimate is known, the timescales are in good agreement with the relationship observed for galactic x-ray binary systems and Seyfert galaxies. For objects of unknown mass, this relationship can be used to provide a mass estimate of the supermassive black hole. Comparisons are made between the structure function and power density spectrum for each object, and the implications for the connection between the accretion disk and the relativistic jet in AGN are discussed.
18
Cole, Robert Harry. "Gravitational waves from extreme-mass-ratio inspirals." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709066.
19
Savić, Đorđe. "Measuring black hole masses in active galactic nuclei using the polarization of broad emission lines." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAE034.
Abstract:
Les trous noirs supermassifs (SMBH) se trouvent au coeur de presque toutes les galaxies massives dans l’Univers. La plupart sont en sommeil, mais lorsqu’il y a assez de gaz à proximité, ils entrent dans une phase active et forment ce qu’on appelle un noyau actif de galaxie (AGN). Ils ont alors un effet profond sur l'évolution de la galaxie hôte et jouent un rôle important sur leur environnement. La mesure fiable de la masse des SMBH est donc une tâche importante dans l'astronomie moderne. À cette fin, Afanasiev et Popovic (2015) ont récemment proposé une méthode qui utilise la rotation de l'angle de position du plan de polarisation sur le profil en fréquence des raies d'émission larges afin de tracer le mouvement Keplerien et de déterminer la masse du SMBH. Le but de la thèse est d'explorer théoriquement les possibilités de cette méthode. Pour ce faire, nous avons dans une première partie effectué de nombreuses simulations de transfert radiatif pour la modélisation de la diffusion équatoriale dans AGN à l'aide du code STOKES. Nous avons inclus les mouvements complexes présents dans le système sous forme d’accrétion et d’éjection, et nous avons également comparé nos résultats aux observations. Notre travail est important car nous avons démontré dans quelles circonstances cette méthode peut être utilisée pour mesurer la masse du trou noir de manière indépendante. La deuxième partie de ce travail consiste à prédire la polarisation des raies larges au cas où les AGN seraient alimentés par des trous noirs binaires supermassifs (SMBBH). Nous avons traité quatre cas différents avec des binaires de trous noirs séparés de moins d’un parsec, et modélisé à nouveau la diffusion équatoriale. Nous avons obtenu une signature de polarisation unique sur les raies larges. Nous avons montré que la spectropolarimétrie pouvait constituer un outil puissant et une première étape pour la recherche de SMBBH dans les futurs levés spectropolarimétriques systématiquesSupermassive black holes (SMBHs) reside in the heart of nearly every massive galaxy in the Universe. Most of them lie dormant, but when the nearby gas is abundant, it will enter an active phase and form an active galactic nucleus (AGN). When in their active phase, SMBHs have a profound effect on the host galaxy evolution and play an important role in shaping their environment. Reliable SMBH mass measuring is therefore an important task in modern astronomy. For that purpose, a method has been recently proposed by Afanasiev & Popovic (2015) that uses the rotation of the polarization plane position angle across the broad emission line profile in order to trace the Keplerian motion and determine the SMBH mass. The goal of the thesis is to theoretically explore the possibilities of this method. In order to do that, we performed numerous radiative transfer simulations for modeling equatorial scattering in AGNs using the code STOKES. We included complex motions present in the system in the form of inflows and outflows, and we also compared our results with observations. We have demonstrated under which circumstances this method can be used to measure the SMBH mass in a new independent way. The second part of this work involves predicting the broad lines polarization when AGNs are powered by supermassive binary black holes (SMBBHs). We treated four different cases with sub-pc SMBBHs, and again modeled equatorial scattering. We obtained a unique polarization signature across the broad lines. We have shown that spectropolarimetry could be a powerful tool and a first step for searching SMBBHs in the future systematic spectropolarimetric surveys
20
Salow, Robert M. "Self-Gravitating Eccentric Disk Models for the Double Nucleus of Μ31." Ohio University / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1088521276.
21
Ursini, Francesco. "Constraining the high energy emission sources in the environment of supermassive black holes." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY062/document.
Abstract:
Des trous noirs supermassifs de plusieurs centaines de millions de masses solaires résident au centre de la plupart des galaxies massives. Dans 90% des cas, ces trous noirs sont dans état quiescent, très peu lumineux. Cependant, dans les 10% restant, des processus extrêmement violents sont observés, avec la libération d'énorme quantités d'énergie no- tamment en UV, X et gamma. On observe aussi parfois des jets puissants de matière pouvant s'étendre sur plusieurs centaines de kpc. Le coeur de ces galaxies sont appelés Noyaux Actifs de Galaxie (NAG). Ce sont parmis les objets les plus lumineux de l'univers. L'accrétion de la matière environnante sur le trou noir supermassif central est unanimement reconnue comme la source d'énergie la plus plausible pour expliquer la puissance phénoménale observée. L'énergie gravitationelle serait ainsi en partie libérée dans un disque d'accrétion, sous forme de rayonnement thermique piquant dans l'optique/UV, et en partie rayonnée en X/gamma par une couronne de plasma chaud présente dans l'environnement proche du trou noir.De nombreux phénomènes sont néanmoins encore très mal connus et beaucoup de ques- tions n'ont toujours pas de réponses satisfaisantes: quelles sont la dynamique et la structure des flots d'accrétion et d'éjection dans les NAG? Quels sont les processus radiatifs produisant le rayonnement UV/X? Quelle est l'origine des différentes composantes spectrales présentes dans ces domaines d'énergie? Cette thèse a pour objectif d'apporter de nouvelles contraintes observationnelles pour meux répondre à ces questions. Son originalité réside dans le développement et l'utilisation de modèles réalistes de Comptonisation thermique permettant d'une part de mieux contraindre les propriétés physiques et géométriques des régions d'émission UV/X et d'autre part de mieux comprendre l'origine des différentes composantes spectrales observées. Nous nous sommes notamment intéressés, au cours de cette thèse, à l'excès d'émission X-mou (<2 keV), présent dans un grand nombre de NAG, et dont l'origine est toujours inconnue.Ces travaux s'articulent autour de deux axes principaux. Le premier est l'étude spectrale détaillée de longues campagnes d'observation multi-longueur d'ondes de trois galaxies de Seyfert (NGC 5548, NGC 7213 et NGC 4593). La qualité des données ont ainsi permis de révéler les paramètres physiques (notamment la température et la profondeur optique) et géométriques de la couronne thermique à l'origine du continuum X. Le second axe porte sur l'analyse de données d'archives (en provenance du satellite XMM-Newton) d'un échantillon important de galaxies de Seyfert. Cela a permis d'apporter, cette fois ci, des contraintes plus générales sur les processus d'émission haute énergie observés dans ces objets. Ces deux approches ont notamment montré que l'exces d'émission X-mou pouvait provenir des couches supérieures chaudes du disque d'accrétion, suggérant un chauffage plus efficace en surface plutôt que dans les régions internesSupermassive black holes of several hundred million solar masses lie at the centre of most massive galaxies. In 90% of cases, these black holes are in quiescent, very low luminous states. Nevertheless, in the remaining 10%, extremely violent processes are seen, with the liberation of huge amounts of energy especially in the UV, X-ray and gamma-ray bands. We also sometimes observe powerful jets, extending up to several hundred kpc scales. The cores of these galaxies are called Active Galactic Nuclei (AGNs). These are among the most luminous objects in the Universe. The accretion of surrounding matter onto the central supermassive black hole is generally considered as the most likely energy source to explain the extraordinary observed luminosity. The gravitational energy would be partly liberated into an accretion disc as thermal radiation peaking in the optical/UV band, and partly radiated in the X-ray/gamma-ray band by a corona of hot plasma lying in the environment close to the black hole.However, several phenomena are still poorly understood and a number of questions lacks satisfactory answers: what are the dynamics and the structure of the accretion and ejection flows in AGNs? What are the radiative processes producing the UV/X-ray radiation? What is the origin of the different spectral components present in those energy bands? The goal of this thesis is to derive new observational constraints to better answer to these questions. Its originality resides in the development and application of realistic models of thermal Comptonization, allowing on the one hand to better constrain the physical and geometrical properties of the UV and X-ray-emitting regions, and on the other hand to better understand the origin of the different observed spectral components. In particular, we studied the excess of the soft (<2 keV) X-ray emission, seen in a great number of AGNs, and whose origin is still unknown.This work is structured along two main branches. One is the detailed spectral analysis of long, multiwavelength observational campaigns on three Seyfert galaxies (NGC 5548, NGC 7213 and NGC 4593). The quality of the data permitted to reveal the geometrical and physical parameters (in particular the temperature and optical depth) of the thermal corona producing the X-ray continuum. The second branch is based on the analysis of archival data (from the XMM-newton satellite) of a large sample of Seyfert galaxies. This allowed us to derive more general constraints on the high-energy emission processes observed in these objects. These two approaches have shown, in particular, that the soft X-ray emission excess may arise in the warm upper layers of the accretion disc, suggesting a more effective heating of the surface rather than the inner regions
22
Jonic, Sanja [Verfasser], Lutz [Akademischer Betreuer] Wisotzki, Jakob C. [Akademischer Betreuer] Walcher, Lutz [Gutachter] Wisotzki, Philipp [Gutachter] Richter, and Amy [Gutachter] Reines. "Constraining black hole growth across cosmic time : the faintest active galactic nuclei / Sanja Jonic ; Gutachter: Lutz Wisotzki, Philipp Richter, Amy Reines ; Lutz Wisotzki, Jakob C. Walcher." Potsdam : Universität Potsdam, 2021. http://d-nb.info/1236786661/34.
23
Overkemping, Ann-Kristin [Verfasser], Wolfgang [Akademischer Betreuer] Rhode, and Joachim [Gutachter] Stolze. "Messages from a Black Hole : a long term analysis of the Active Galactic Nucleus Markarian 421 in the light of γ-rays measured by MAGIC-I / Ann-Kristin Overkemping. Betreuer: Wolfgang Rhode. Gutachter: Joachim Stolze." Dortmund : Universitätsbibliothek Dortmund, 2015. http://d-nb.info/110160641X/34.
24
Gavignaud, Isabelle. "Propriétés statistiques des AGN de faibles luminositées." Phd thesis, Université Paul Sabatier - Toulouse III, 2006. http://tel.archives-ouvertes.fr/tel-00123824.
Abstract:
Ces dernières années les principaux relevés cosmologiques ont collectés plusieurs dizaines de milliers de spectres de noyaux actifs de galaxies (connus aussi sous l'abréviation anglaise AGN), illustrant ainsi la grande éfficacité des techniques de pré-sélections optiques de candidat AGN. Ils ont ainsi permis une étude statistique détaillée de la population d'AGN.Le revers de ces techniques de pré-sélection est que certaines catégories de la population globale des AGN optiques sont peut-être sous-représentées dans ces échantillons, biaisant notre compréhension actuelle de l'évolution de ces objets.
Cette thèse de doctorat est dédiée à l'étude des propriétés des AGN de type 1 de faible luminosité. Dans ce but nous utilisons un échantillon spectroscopique de 130 AGN à raies
d'émission larges, extrait d'un grand relevé de galaxie: le VIRMOS VLT Deep Survey (VVDS).
Cet échantillon présente un intérêt unique, de part la simplicité des critères de pré-sélection de ces objets (une simple limite en magnitude) ainsi que par la profondeur en magnitude atteinte: il fournit d'une part un aperçu des propriétés des AGN de type 1 à des magnitudes encore peu explorées spectroscopiquement (les AGN étudiés ici sont jusqu'à cent fois plus faibles que ceux du SDSS) et il permet d'autre part de quantifier les biais qui seraient introduits par des critères classiques de sélection.
Nous mesurons une densité sur le ciel d'environ 470 AGN par degré carré à notre magnitude limite (Iab=24). Une fraction importante des AGN que nous observons ne serait pas sélectionée par les techniques de sélections morphologiques et d'excès d'UV classiquement appliquées. Nous attribuons cet effet à la contamination de nos AGN par leur galaxie hôte, vue leur faible luminosité. La fonction de luminosité des AGN montre qu'il y a relativement plus d'AGN de faible luminosité à bas redshift qu'á plus grand redshift. Cette observation corrobore le scénario de croissance anti-hierarchique de trous-noirs galactiques suggéré par les echantillons d'AGN sélectionnés en rayons-X.
Finalement nous nous sommes intéressés à la nature des trous noirs qui sont à l'origine de nos AGN. S'agit-il de petits trous noirs galactiques ou bien, au contraire, de trous noirs de grandes masses accrétant faiblement ?
Nos résultats, encore préliminaires, suggèrent que nos AGN correspondent en moyenne à des trous noirs galactique de masses intermediaires (~100 millions de masses solaires) accrétant à des taux d'Eddington modeste (~< 10%).
25
Dong, Xiaoyi. "Relations between nearby, low-luminosity active galaxies and their central black holes /." 2004.
Abstract:
Thesis (M.Sc.)--York University, 2004. Graduate Programme in Physics and Astronomy.Typescript. Includes bibliographical references (leaves 86-89). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://gateway.proquest.com/openurl?url%5Fver=Z39.88-2004&res%5Fdat=xri:pqdiss &rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:MR11775
26
Salviander, Sarah Triplett 1971. "Demographics and evolution of super massive black holes in quasars and galaxies." 2008. http://hdl.handle.net/2152/17748.
Abstract:
This dissertation addresses the co-evolutionary relationship between central super-massive black holes and host galaxies. This relationship is suggested by observed correlations between black hole mass (M[subscript BH]) and properties of the host galaxy bulge. We first discuss investigation of the relationship between MBH and host galaxy velocity dispersion, [sigma subscript asterisk], for quasars in the Sloan Digital Sky Survey (SDSS). We derive MBH from the broad emission line width and continuum luminosity, and [sigma subscript asterisk] from the width of narrow forbidden emission lines. For redshifts z < 0.5, our results agree with the locally-observed M[subscript BH]- [sigma subscript asterisk] relationship. For 0.5 < z < 1.2, the M[subscript BH]- [sigma subscript asterisk] relationship appears to evolve with redshift in the sense that bulges are too small for their black holes. Part of this apparent trend can be attributed to observational biases, including a Malmquist bias involving the quasar luminosity. Accounting for these biases, we find approximately a factor of two evolution in the M[subscript BH]- [sigma subscript asterisk] relationship between the present and redshift z [approximately equal] 1. The second topic involves a search for the largest velocity dispersion galaxies in the SDSS. Black holes in quasars can have M[subscript BH]exceeding 5 billion M[mass compared to the sun], implying [sigma subscript asterisk] > 500 km s−1 by the local M[subscript BH]- [sigma subscript asterisk] relationship. We present high signal-to-noise HET observations for eight galaxies at redshift z < 0.3 from the SDSS showing large [sigma subscript asterisk] while appearing to be single galaxies in HST images. The maximum velocity dispersion we find is [sigma subscript asterisk] = 444 km s−1, suggesting either that quasar black hole masses are overestimated or that the black hole - bulge relationship changes at high black hole mass. The third topic involves work contributed to co-authored papers, including: (1) evidence for recoiling black holes in SDSS quasars, (2) the [sigma][O III] - [sigma subscript asterisk] relationship in active galactic nuclei (AGN), and (3) accretion disk temperatures and continuum colors in quasars. Lastly, we discuss research in progress, including: (1) possible physical influences on the width of narrow emission lines of SDSS AGN, including the gravitational effect of the black hole, and (2) a search for binary AGN in the SDSS using double-peaked [O III] emission lines.text
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Bonning, Erin Wells Matzner Richard A. "Computational and astrophysical studies of black hole spacetimes." 2004. http://wwwlib.umi.com/cr/utexas/fullcit?p3139194.
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Bonning, Erin Wells. "Computational and astrophysical studies of black hole spacetimes." Thesis, 2004. http://hdl.handle.net/2152/1212.
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Duţan, Ioana [Verfasser]. "Jets from spinning black holes in active galactic nuclei / vorgelegt von Ioana Duţan." 2010. http://d-nb.info/1013363213/34.
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Latulippe, Myriam. "Influence du trou noir supermassif central dans l’amas de galaxies MACS J1447.4+0827." Thèse, 2017. http://hdl.handle.net/1866/20312.
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Gendron-Marsolais, Marie-Lou. "Observations multi-longueur d’onde d’amas et de groupes de galaxies proches." Thèse, 2018. http://hdl.handle.net/1866/21757.
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D'Orazio, Daniel John. "Predicting Electromagnetic Signatures of Gravitational Wave Sources." Thesis, 2016. https://doi.org/10.7916/D8CC10W8.
Abstract:
This dissertation investigates the signatures of electromagnetic radiation that may accompany two specific sources of gravitational radiation: the inspiral and merger of massive black hole binaries (MBHBs) in galactic nuclei, and the coalescence of black hole neutron star (BHNS) pairs. Part I considers the interaction of MBHBs, at sub-pc separations, with a circumbinary gas disk. Accretion rates onto the MBHB are calculated from two-dimensional hydrodynamical simulations as a function of the relative masses of the black holes. The results are applied to interpretation of the recent, sub-pc separation MBHB candidate in the nucleus of the periodically variable Quasar PG 1302-102. We advance an interpretation of the variability observed in PG 1302-102 as being caused by Doppler-boosted emission sourced by the orbital velocity of the smaller black hole in a MBHB with disparate relative masses. Part II considers BHNS binaries in which the black hole is large enough to swallow the neutron star whole before it is disrupted. As the pair nears merger, orbital motion of the black hole through the magnetosphere of the neutron star generates an electromotive force, a black-hole-battery, which, for the strongest neutron star magnetic field strengths, could power luminosities large enough to make the merging pair observable out to cosmic distances. Relativistic solutions for vacuum fields of a magnetic dipole near a horizon are given, and a mechanism for harnessing the power of the black-hole-battery is put forth in the form of a fireball emitting in hard X-rays to to gamma-rays.
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Richard-Laferrière, Annabelle. "L'impact des trous noirs les plus massifs de l’Univers sur le coeur des amas de galaxies." Thèse, 2019. http://hdl.handle.net/1866/22724.