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 100 for “"quasars"”.
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Quasars, clusters and cosmology
Thesis (Ph. D.)--Michigan State University. Physics and Astronomy, 2010
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Outflows and Dust in Quasars
… 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 properties in quasars at 1<z<3, corresponding to the peak epoch of …
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Outflow properties of luminous quasars
Quasars, powered by accretion onto the super-massive black holes at their galaxies' centres, are capable of ejecting highly energetic outflows of gas, which can suppress star formation in the host galaxy, thereby impacting its evolution. Quasar-driven outflows are widely invoked in galaxy formation …
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Star formation in unobscured quasars
… In the first, we assemble a sample of 513 quasars identified by the Sloan Digital Sky Survey with detections by Herschel. These objects span a redshift range of 0 < z < 4, and their SEDs give a mean SFR of ~1000M☉/year. When comparing these SFRs to the intrinsic properties of the quasars, …
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Quasars at the High Redshift Frontier
… powerful numerical simulations. High-redshift quasars have become a ubiquitous tool in the study of this era with more than 115 quasars now spectroscopically confirmed at z>6.0. In this thesis, I use spectra of high-redshift quasars to provide improved observational constraints through a …
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New optical surveys for gravitationally lensed quasars
… new optical surveys for gravitationally lensed quasars. The goal of this work has been to (1) explore new strategies for conducting optical surveys, especially in the southern hemisphere, in the hopes of "fine-tuning" the survey techniques toward finding systems of particular scientific …
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Optical variability of radio-luminous palomar-green quasars
… variability at optical wavelengths. The ten quasars with the highest radio core luminosity at 5 GHz in the Palomar Bright Quasar Survey were selected for this monitoring program; Seven out of the ten radio-luminous quasars exhibited signs of short-term variability, and all ten radio-luminous …
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Investigating the evolution of red and blue quasars
… of a sample of 218 red and blue broadline quasars (AGN with Lₓ > 10⁴⁴ erg/s) to test the predictions of the major merger-driven evolutionary model. Using rich multiwavelength data, we analyze differences in bolometric luminosity, specific star formation rate (sSFR), black hole mass, and …
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Probing the Intergalactic Medium with high-redshift quasars
Clues about the timing of reionization and the nature of the ionizing sources responsible are imprinted in the ionization and thermal state of the IGM. In this thesis, I use high-resolution quasar spectra in conjunction with state-of-the-art hydrodynamical simulations to probe the IGM at high …
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The Optical Variability of Quasars as Seen by SDSS
… for 80,000 spectroscopically confirmed quasars recently assembled by the Sloan Digital Sky Survey (SDSS). This database is an excellent data set to study quasar variability, and includes 9,000 well-sampled light curves from Stripe 82 and a 25,000-object two-epoch sample from the northern …
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Large groups of quasars in an ultraviolet-excess survey
… of a large, homogeneous catalogue of quasars with redshifts 0.4 < z < 2.2, and the use of the catalogue to investigate the large-scale structure of the early Universe, particularly at large scales ('.-' 100 h' Mpc). The survey covers 140 deg 2 , with a 100 x 100 programme area centred …
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Gravitational lensing of quasars by edge-on spiral galaxies
In this thesis, I studied the lensed quasar CX2201-3201, which is lensed by an edge-on spiral galaxy. The unusually high tilt of the spiral galaxy provides us with a rare opportunity for mass modeling. In addition, the unusual placement of the two visible images of the system offers an intriguing …
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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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The Host Galaxies of Luminous Reddened Quasars at z~2
… of a class of luminous, yet heavily-obscured, quasars at z$\sim$2 - a peak epoch of both star formation and black hole accretion. Here, we seek to characterise the star-forming properties of these obscured quasars to improve our understanding of galaxy-quasar coevolution. A key issue facing …
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Properties of Galaxies Detected in Emission and Absorption with Background Quasars
<p>The question of how galaxies evolve is a difficult one to answer. By studying galaxies hosting Damped (DLA) and sub-Damped Lyman-alpha (sub-DLA) systems, we hope to shed some light on the subject. DLA and sub-DLA systems contain the vast majority of neutral gas in the universe, making them ideal …
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The Cluster and Large Scale Environments of Quasars at z < 0.9.
… an investigation into the environments of quasars with respect to galaxy clus- ters, and environment evolution with redshift and luminosity. The positions of quasars with respect to clusters have been studied using cluster and quasar catalogues available, covering the redshift range 0.2 < z …
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Discovery and Characterisation of Gravitationally Lensed Quasars in Wide-field Surveys
… predictions suggest there are many bright lensed quasars hidden in these datasets. This thesis presents several new techniques to mine these rare systems from whole-sky photometric datasets. We use the excellent resolving ability of Gaia, coupled with other wide-field surveys such as the Dark …
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Theoretical studies of gravitational lensing phenomena: the case of multiply imaged quasars
In the early 1960s, gravitational lensing has received a special attention when S. Liebes and S. Refsdal have derived in detail some of the basic equations of the theory. While Liebes (1964) discussed the probability of detecting these effects and considered several astrophysical applications, …
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