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Showing 1 to 20 of 63 for “"gravitational lensing"”.
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Gravitational lensing
Gravitational lensing derives its simplicity from some basic assumptions that are satisfied by most physical situations.The thin lens approximation and weak field approximations were used to build the whole theory and explain the phenomenology up to today. We review the gravitational lensing …
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Cosmological applications of gravitational lensing
In dieser Arbeit benutze ich den Gravitationslinseneffekt als ein Werkzeug, um zwei recht unterschiedliche kosmologische Fragestellungen zu bearbeiten: die Natur der dunklen Materie in Galaxienhalos und die Rotation des Universums. Zuerst untersuche ich den Mikrolinseneffekt in den …
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Gravitational Lensing and Telescope Aberrations
… each of which addresses challenges to weak gravitational lensing flexion measurements. Part one is a derivation and analysis of the aberration shapes and patterns imparted onto images by misaligned telescopes. As telescope aberrations will generally interfere with lensing measurements, it is …
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A covariant approach to gravitational lensing
… of null geodesics and their applications to gravitational lensing. The dynamics of the null congruence can be better understood through the propagation and constraint equations in the direction of the congruence. Thus, we derive these equations after describing the geomentry of a ray. We also …
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Galactic dynamics : multiple tracers and gravitational lensing
… dynamical probes (multiple populations, gravitational lensing) to infer the prope1ties of Dark Matter (DM) haloes and investigate scenarios of galaxy formation. It begins with a study of the virial properties (flattening and global anisotropy) of stellar populations in different DM …
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Gravitational Lensing and the Maximum Number of Images
Gravitational lensing, initially a phenomenon used as a solid confirmation of General Relativity, has defined itself in the past decade as a standard astrophysical tool. The ability of a lensing system to produce multiple images of a luminous source is one of the aspects of gravitational lensing …
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New results from the gravitational lensing of galaxies
… use a sample of 53 elliptical galaxies which are lensing background emission-line galaxies and have been observed by the SLACS collaboration using HST and SDSS to place constraints on the post-Newtonian parameter 7 and the cosmological parameter A. We find y = 1.00 ± 0.04 on kiloparsec scales, …
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Finding fossil galaxy system progenitors using strong gravitational lensing
… progenitors in the CASSOWARY catalog of strong gravitational lensing demonstrates that not all fossils are old, and their formation histories are more complex than originally thought. These progenitors have optical characteristics consistent with them being the transition phase between …
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Gravitational lensing of quasars by edge-on spiral galaxies
… images of the system offers an intriguing lensing system for study-the two images straddle the lensing galaxy's visible disk, but are off to one side of the light centroid. Based on mass models for the lens that are constrained by the visible disk of the galaxy, the quadrupole of the disk …
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Constraining the QSO luminosity function using gravitational lensing statistics
In this thesis we use gravitational lensing statistics to constrain the QSO luminosity function at a variety of redshifts. We present a theoretical discussion of gravitational lensing statistics and illustrate how high resolution QSO imagery can be used to constrain the QSO luminosity function. We …
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Investigating strong gravitational lensing with infrared space missions : AKARA, Spitzer and Herschel
This thesis addresses the use of strong gravitational lensing to facilitate deep midinfrared observations of star-forming galaxies and to study highly dust obscured sub-millimetre galaxies (SMG). 15 <i>u</i>m extragalactic number counts were taken from ultra deep AKARI mapping of the gravitational …
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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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Gravitational Lensing in the Solar Neighbourhood and Towards the Milky Way Bulge
… with looking for and characterizing microlensing events in two places that are relatively unexplored. Leveraging astrometry from the Gaia satellite, I search for predicted close stellar alignments by lenses in the solar neighbourhood that will give rise to a microlensing event. Using …
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1+1+2 covariant approach to gravitational lensing in f(R) gravity
… Additionally, we derive a covariant form of the lensing angle for a specific spherically symmetric solution in f(R) = Rn gravity.
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STRONG GRAVITATIONAL LENSING MODELLING OF GALAXY CLUSTERS IN THE ERA OF BIG DATA
… surveys are revolutionizing the field of strong lensing (SL) by galaxy clusters. Remarkably, the Euclid Survey will cover approximately 15,000 square degrees of the sky, detecting SL features in thousands of massive clusters. Complementarily, the James Webb Space Telescope (JWST) is providing …
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Imaging the invisible : constraining dark matter distributions in galaxy clusters using strong gravitational lensing
… thesis, I design and construct a Monte-Carlo gravitational lensing simulation that statistically studies the strong lensing of extended galactic sources by dark matter distributions in galaxy clusters, using recent work on cluster Abell 1689 as an empirical guide. By quantitatively comparing …
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Polishing the Lenses: Refined Modelling of Gravitational Lensing and Delensing of the Cosmic Microwave Background
… however, the photons' paths are deflected by the gravitational influence of the matter distribution of the Universe --- an effect known as `gravitational lensing'. Though the deflections are small, they can affect the statistical properties of the ensemble in crucial ways. Lensing converts part of …
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