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 23 for “"Overdensity"”.
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No evidence for millimeter continuum source overdensities in the environments of z [greater than approximately] 6 quasars
… the quasars themselves), corresponding to an overdensity δ [subscript gal] [triple bar] (N [subscript gal] – N [subscript exp]) / N [subscript exp] = -0.07 ± 0.56, consistent with no detected overdensity of dusty galaxies within 140 physical kpc of the quasars. However, the apparent lack of …
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The Relationship of Active Galactic Nuclei & Quasars With Their Local Galaxy Environment
… themselves and find that the increased overdensity of early-type galaxies in the environments of bright type I sources suggests that they are located in richer cluster environments than dim sources. We measure increased environment overdensity with increased quasar black hole mass, …
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The integrated Sachs-Wolfe effect with Planck and the 2Mass Photometric Redshift Catalogue
… the CMB temperature anisotropies and the galaxy overdensity. The linear galaxy bias, relating the galaxy density distribution to the underlying matter density distribution, was measured through least squares fitting of the theoretical prediction of the galaxy auto-correlation function in each …
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Detecting the invisible universe with neutrinos and dark matter
… KATRIN of about 10⁴ events per year, or a local overdensity of relic neutrinos of about 3 x 10⁹ is found. Directional detection of cold dark matter provides a unique way to distinguish a dark matter signal from terrestrial backgrounds, using the expected direction of a dark matter wind based on …
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Star-forming Galaxies and Quenched Systems throughout Cosmic Time
… photometric redshifts, I identify a galaxy overdensity near the location of the target (5-σ above the background level at this redshift). The overdensity contains three spectroscopically confirmed, massive, old galaxies. The presence of these evolved systems points to accelerated galaxy …
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First MeerKAT HI survey results mapping large scale structures hidden behind the Milky Way out to z = 0.08
… encompasses the Great Attractor (GA) — a massive overdensity highly influential to the local flow of galaxies. Aided by the newer version of SoFiA (v2.3.1), we found 477 galaxy candidates, most of which are new discoveries, and performed an in-depth comparison against the largest systematic HI …
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A Westerbork blind HI imaging survey of the Perseus-Pisces filament in the Zone of Avoidance
… it at cz ~ 8000 − 12000 km s−1. The galaxy overdensity associated with the PPS is used to demonstrate how this supercluster connects across the ZoA and confirms earlier indications of a filamentary connection between Perseus, Pisces and the A569 clusters through this region of the sky. …
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Spatially resolved spectroscopy of faint star-forming galaxies & their environments in the high redshift universe
… are apparent. We also present evidence for an overdensity of neutral hydrogen in the vicinity of a galaxy at z = 4:9, which we interpret as gas infall onto an object which still has yet to accumulate the bulk of its gas mass. A study of the field of the lensing cluster Abell 1689 is presented, …
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EoR in alternative cosmological scenarios
… assumed is a LCDM characterized by a primordial overdensity field having a non-Gaussian probability distribution. The reionization scenario have been investigated, in this Thesis, through semi-analytic approaches based on the hierarichic growth of the matter uctuations and on suitable assumptions …
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Large Quasar Groups at Redshift ~ 2
… using a convex hull approach, to calculate the overdensity. Each group was submitted to 1000 random simulations, no comparable structure was found from the random simulations. The algorithm was then applied to a greater redshift range of 0.6 - 2.5. The total number of groups found was 36, each …
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The distance to the Norma cluster and its relation to the great attractor region
… the fractional contribution of the local mass overdensity, particularly in the Great Attractor region and the more distant Shapley Supercluster, remain contradictory. This work is an attempt to disentangle these contributions by measuring a redshift-independent distance to the Norma cluster, …
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Optimisation of galaxy identification methods on large interferometric surveys
… Radio Telescope (WSRT). The survey mapped the overdensity corresponding to the Perseus-Pisces Supercluster filament crossing the Zone-of-Avoidance (ZoA), at (`, b) ≈ (160◦ , 0.5◦ ). A total of 211 galaxies detected using the semi-automated method by Ramatsoku et al. [2016]. In this work, I …
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The high-redshift clusters occupied by bent radio AGN (COBRA) survey
… By measuring the color of each galaxy and the overdensity of galaxies surrounding each AGN, I identify 39 red sequence cluster candidates, 17 of which are at redshifts of z > 1.0. Using my red sequence surface density measurement, I show that each bent AGN is not necessarily centrally located, …
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Testing General Relativity with the next generation of cosmological surveys
… full relativistic corrections in the observed overdensity and convergence. This yield new observables which gives independent insights regarding the peculiar velocity of galaxies, the growth of structure of the Universe etc.
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Unveiling the Primary Quenching Mechanisms in Galaxies through Large Spectroscopic Surveys
… show only a weak dependence on halo mass, local overdensity and projected distance from their central. Finally, we find, using integral field spectroscopy from the SDSS-IV MaNGA galaxy survey, that passive galaxies are substantially more metal-rich than star-forming galaxies at all radii, with …
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Tracer populations in the local group
… were already known to exist, and the Pisces Overdensity, which was previously undetected. It is a faint, extended structure found at ~80 kpc and is of unknown origin. Altogether, I find that nearly 80% of the RR Lyraes are associated with substructures, consistent with the theory that galaxy …
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Projected Angular Statistics for Large-scale Structure Cosmology
… The natural observables are maps of the galaxy overdensity, projected in redshift bins. Similarly, line-intensity mapping (LIM) surveys measure fluctuations in the sky brightness in narrow frequency bands. This thesis considers the statistics of such projected observables, spanning theoretical …
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Numerical modelling of low temperature plasma
… of ionisation. The evolution of such an electron overdensity is simulated and their energy gain under different density and magnetic field conditions is calculated. The results from the simulation may explain the discrepancy between laboratory and space experiments.
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Magnetic Field Evolution in Black Hole Accretion Disks and Relativistic Jets
… by caution on the resolution, as an m = 1 mode overdensity is created at the crossroads of a weak field, moderate resolution, and resolution step-change. I additionally perform a minor study of the disk dynamo, covered in Chapter 3. Using mean-field dynamo theory, I calculate the diagonal, …
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Galaxy groups from observations and simulations
… the group luminosity functions using the overdensity radii, with the extracted colour-magnitude relation from the spectroscopic observations, and find that the luminosity function of optically selected groups are very similar to that of X-ray selected groups.
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