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Showing 1 to 20 of 108 for “"Active Galactic Nuclei"”.
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Dual active galactic nuclei within Romulus25
Dual active galactic nuclei (DAGN) trace the growth of supermassive black holes (SMBHs) during galaxy interactions, while also being an important electromagnetic precursor of SMBH mergers which are important for missions such as LISA. In this thesis, we aim to study the properties of DAGN within …
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The Environments of Active Galactic Nuclei
Near-infrared and optical CCD images of radio-loud quasars, radio-quiet quasars and radio galaxies (RLQs, RQQs, and RGs respectively) are presented. The quasar samples are chosen such that they are well matched in the V-z plane, whilst the RGs are selected so that their radio properties (5 GHz …
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Reverberation mapping of Active Galactic Nuclei
… aimed at contributing to the overall sample of active galactic nuclei (AGNs) with central super-massive black hole (SMBH) mass estimates using reverberation mapping (RM) technique. RM makes use of the time variability of the broad emission lines from the nearby broad-line region (BLR) to measure …
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Imagining active galactic nuclei with 3mm-VLBI
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1995.
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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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Models of Dust and Gas Tori in Active Galactic Nuclei
… of dust and gas in the innermost parsecs of Active Galactic Nuclei. Unified schemes demand a circum-nuclear disk or "torus" to geometrically unify two separate classes of observed objects (face-on and edge-on view onto the torus). In a multi-step approach, we work towards the establishment of …
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Astrophysical maser radiation from Keplerian disks near active galactic nuclei
… radiation emerging from gaseous disks at the nuclei of active galaxies. In at least one galaxy (NGC 4258), such maser radiation is observed and arises from a disk around a presumed massive black hole. The heating, cooling, and excitation mechanisms necessary for creating the physical …
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A Spitzer Mid-Infrared Study of Active Galactic Nuclei with Outflows
… code to create models of the tori that surround Active Galactic Nuclei. We compare these models to mid-infrared spectra of both BAL and non-BAL quasars obtained with the Spitzer Space Telescope. We find the BALQSOs have an average equivalent width 40% larger and an average MIR-optical luminosity …
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X-ray and optical properties of X-ray luminous active galactic nuclei
… below 2 keV into single point sources, mainly active galaxies. The cosmic X-ray background is the integration of all accreting super-massive (several million solar masses) black holes in the centre of active galaxies over cosmic time. Synthesis models need further populations of X-ray absorbed …
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Towards a complete census of active galactic nuclei in the nearby Universe
… is natural to ask, how many of these SMBHs are actively accreting? Studies aimed at answering this question can better define the fraction of nearby galaxies that harbour active galactic nuclei (AGNs), provide constraints on the growth of local SMBHs, and further our understanding towards the …
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The Relationship of Active Galactic Nuclei & Quasars With Their Local Galaxy Environment
… local environment is related to properties of active galactic nuclei (AGNs) of various luminosities. Recent simulations and observations are converging on the view that the extreme luminosity of quasars, the brightest of AGNs, is fueled in major mergers of gas-rich galaxies. In such a picture, …
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Self-consistent dynamical and radiative models of low-luminosity active galactic nuclei
… physical characteristics of these low-luminosity active galactic nuclei (LLAGN) allow a unique opportunity to build and test nearly \emph{ab initio} models of black hole accretion. To that end, I describe numerical techniques we have developed to build self-consistent dynamical and radiative …
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Black Hole Feedback in New Regimes: Modelling Dwarf Galaxies with Active Galactic Nuclei
… observational evidence that feedback from active galactic nuclei (AGN) may also play a role at the low-mass end of the galaxy population. In this thesis, I explore that possibility employing both isolated and cosmological simulations of dwarf galaxies. Firstly, I perform high-resolution …
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Unveiling fundamental physics with high-resolution X-ray spectroscopy of Active Galactic Nuclei.
… the use of high-resolution spectroscopy of active galactic nuclei (AGNs) to probe fundamental physics. It focuses on the study of axion-like particles (ALPs) and the spin of supermassive black holes (SMBHs). Chapter 1 starts with a review of black holes as mathematical and astronomical …
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A multi-frequency study of an X-ray selected sample of active galactic nuclei
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1992.
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The development of new methods for high resolution radio astronomy imaging
… observations of the relativistic jets from Active Galactic Nuclei (AGN) allow the magnetic field environment around the jet to be probed. In particular, multi-wavelength observations of AGN jets allow the creation of Faraday rotation measure maps which can be used to gain an insight into the …
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