Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 46 for “"Active Galactic Nuclei (agn)"”.
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Infrared-Bright Active Galactic Nuclei in Massive Galaxy Clusters
The number of active galactic nuclei (AGN) in galaxy clusters has been observed to grow by nearly two orders of magnitude from the local universe to z ~ 1.5. Star formation rates in clusters have also been observed to rise rapidly over this redshift interval. These trends, along with several other …
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The variability of warm absorbers in Active Galactic Nuclei
… of warm (photoionized) absorber variability in Active Galactic Nuclei (AGN) using high-resolution X-ray spectra provided by the Chandra High Energy Transmission Grating (HETG). The first study is a single observation of the AGN MR 2251-178, which is known to have a highly variable warm absorber …
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Statistiškai reiškmingi skirtumai tarp aktyvių ir fosilinių tėkmių parametrų /
Active galactic nuclei (AGN) may cause gas outflows which can impede star formation and even eject gas from the galaxy. The majority of observed outflows may be made up of fossil outflows, which persist after the conclusion of an AGN episode. The aim of this work is to compile histories of fossil …
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Radiative signatures of the jet launching region in astronomical objects
… binaries (XRBs), to supermassive black holes in active galactic nuclei (AGN). However, despite decades of observational and theoretical research, the mechanism by which relativistic jets are launched in nature remains one of the most important unanswered questions in high-energy astrophysics. In …
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Searching for Extreme-BCG Clusters at 0.2 < z < 1.3
Active galactic nuclei (AGN) feedback is believed to be responsible for counteracting the formation of the classical “cooling flow”, predicted to be associated with most “cool core” clusters of galaxies. Several studies have shown that many phenomena found in galaxy clusters can be neatly explained …
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Evolution of Supermassive Black Hole Feedback in Galaxy Clusters
… galaxies. The outer boundary of a galaxy’s circumgalactic medium (CGM) should be the most sensitive probe of inflowing and outflowing material, but it is difficult to observe. Only in galaxy clusters, where the CGM gets hot enough to glow in X-rays, can the entire baryon cycle be observed– from …
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Time-dependent Accretion Flows onto Black Holes
… role in a number of astrophysical systems like active galactic nuclei (AGN) and black hole X-ray binaries (BHXB). The standard thin disk model fails to reproduce the spectra of these systems. They exhibit a blackbody-like component, generally attributed to the cold standard disk, and a hard …
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Estimating the stellar masses of NLS1 galaxies using multifrequency data
… narrow-line Seyfert 1 (NLS1) galaxies. NLS1s are active galactic nuclei (AGN) known for their relatively low black hole masses, disk-like host galaxies, high accretion rates and their ability to host powerful relativistic jets. The stellar masses are derived using the Code Investigating GALaxy …
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Modelling the Epoch of Reionization with Cosmological Radiative Transfer Simulations
… the timeline and contributing sources remain active research areas. In this thesis, I model reionization by post-processing a hydrodynamical simulation using aton-he, a radiative transfer code I developed for this purpose. The thesis is structured into four sections. The first section details …
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Outflows and Dust in Quasars
… (SMBHs) at the centres of galaxies are known to actively accrete, forming so-called `active galactic nuclei' (AGN) or `quasars'. These AGN are believed to feed back energy into their host galaxies, regulating star formation and the growth of the SMBH itself. This thesis investigates the outflow …
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X-ray Studies of the Innermost Regions of Black Hole Accretion
… and Chapter 4-6 for supermassive black holes in active galactic nuclei (AGN). This work mainly focuses on the X-ray spectral shape and the spectral variability of these accreting black hole systems. By studying the broad band spectra of XRBs and AGN, we are able to extract some information about …
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Quasar Outflows: Their Scale, Behavior and Influence in the Host Galaxy
Quasar outflows are a major candidate for Active Galactic Nuclei (AGN) feedback, and their capacity to influence the evolution of their host galaxy depends on the mass-flow rate (M) and kinetic luminosity (E) of the outflowing material. Both quantities require measurement of the distance (R) to the …
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On the Distances and Energetics of AGN Outflows
Active galactic nuclei (AGN) ubiquitously show outflows. It is now widely recognized that these outflows are key components in the evolution of super-massive black holes and their host galaxies. As important as these outflows are, we still lack sufficient understanding of their structure and …
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Probing Galaxy Evolution with AKARI
… the first detailed analysis of three extragalactic fields observed by the infrared satellite, AKARI. AKARI is the only telescope able to observe deeply in the Spitzer/IRAC - Spitzer/MIPS band gap of 8-24 microns. The first analysis of these extragalactic fields, was to perform galaxy number …
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A new twist on black holes: the role of black hole spin in galaxy formation.
… Seyferts, suggesting that the jet properties of active galactic nuclei (AGN) are a natural consequence of both the accretion rate onto and the spin of the central BH. The model also reproduces the observed luminosity functions (LF) of AGN (optical, soft and hard X-ray, and bolometric) for a wide …
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Detectability of Self-Lensing Supermassive Black Hole Binaries in Quasars
Active galactic nuclei (AGN) or quasars are distant and luminous objects thought to be powered accretion into supermassive black holes (SMBHs) whose luminosity rivals that of their local galaxy. Since most galaxies are thought to contain SMBHs and galaxies commonly merge, it is likely that some AGN …
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Multifrequency observations of blazars
Blazars are a class of active galactic nuclei (AGN). Active galaxies are those that host compact sources of non-thermal radiation in their nuclear regions and are usually classified as being radio-loud or radio-quiet. The nature of the central source is ullcertain, but arguments based on energy …
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The Influence of Physical Processes in Galaxy Clusters on Observable Cluster Scaling Relations
… gravity, radiative cooling, and heating from active galactic nuclei (AGN), on cluster mass-observable relations. In particular, we investigate the physical origin of the intrinsic scatter around the best-fit relations by correlating it with measures of cluster structure, dynamical state, and …
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Spectral Energy Distribution Modelling of X-ray Selected AGNs and Their Host Galaxies
The nature of the relation between active galactic nuclei (AGN), and their host galaxies have been observed in detail throughout the Universe. Such work has found an intrinsic link between central supermassive black hole (SMBH) masses, and host galaxy properties such as the velocity dispersion of …
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The Role of Baryons and Neutrinos in the Evolution of Large-Scale Structure
… of baryon physics (particularly feedback from active galactic nuclei, AGN) and the free-streaming of massive neutrinos on large-scale structure. I focus on five diagnostics: i) the halo mass function; ii) halo mass density profiles; iii) the halo mass concentration relation; iv) the clustering …
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