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Weak Shear Study Of Galaxy Clusters By Simulated Gravitational Lensing
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Book Synopsis Weak Shear Study of Galaxy Clusters by Simulated Gravitational Lensing by : David Coss
Download or read book Weak Shear Study of Galaxy Clusters by Simulated Gravitational Lensing written by David Coss and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Gravitational lensing has been simulated for numerical galaxy clusters in order to characterize the effects of substructure and shape variations of dark matter halos on the weak lensing properties of clusters. In order to analyze realistic galaxy clusters, 6 high-resolution Adaptive Refinement Tree N-body simulations of clusters with hydrodynamics are used, in addition to a simulation of one group undergoing a merger. For each cluster, the three-dimensional particle distribution is projected perpendicular to three orthogonal lines of sight, providing 21 projected mass density maps. The clusters have representative concentration and mass values for clusters in the concordance cosmology. Two gravitational lensing simulation methods are presented. In the first method, direct integration is used to calculate deflection angles. To overcome computational constraints inherent in this method, a distributed computing project was created for parallel computation. In addition to its use in gravitational lensing simulation, a description of the setup and function of this distributed computing project is presented as an alternative to in-house computing clusters, which has the added benefit of public enrollment in science and low cost. In the second method, shear maps are created using a fast Fourier transform method. From these shear maps, the effects of substructure and shape variation are related to observational gravitational lensing studies. Average shear in regions less than and greater than half of the virial radius demonstrates distinct dispersion, varying by 24% from the mean among the 21 maps. We estimate the numerical error in shear calculations to be of the order of 5%. Therefore, this shear dispersion is a reliable consequence of shape dispersion, correlating most strongly with the ratio of smallest-to-largest principal axis lengths of a cluster isodensity shell. On the other hand, image ellipticities, which are of great importance in mass reconstruction, are shown to have very little variance. However, tangential alignment of average image distortion is quite strong, making mass density peak locations easily resolvable"--Abstract, leaf iii
Book Synopsis Weak Shear Study of Galaxy Clusters by Simulated Gravitational Lensing by : David Raymond Coss
Download or read book Weak Shear Study of Galaxy Clusters by Simulated Gravitational Lensing written by David Raymond Coss and published by . This book was released on 2010 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Gravitational lensing has been simulated for numerical galaxy clusters in order to characterize the effects of substructure and shape variations of dark matter halos on the weak lensing properties of clusters. In order to analyze realistic galaxy clusters, 6 high-resolution Adaptive Refinement Tree N-body simulations of clusters with hydrodynamics are used, in addition to a simulation of one group undergoing a merger. For each cluster, the three-dimensional particle distribution is projected perpendicular to three orthogonal lines of sight, providing 21 projected mass density maps. The clusters have representative concentration and mass values for clusters in the concordance cosmology. Two gravitational lensing simulation methods are presented. In the first method, direct integration is used to calculate deflection angles. To overcome computational constraints inherent in this method, a distributed computing project was created for parallel computation. In addition to its use in gravitational lensing simulation, a description of the setup and function of this distributed computing project is presented as an alternative to in-house computing clusters, which has the added benefit of public enrollment in science and low cost. In the second method, shear maps are created using a fast Fourier transform method. From these shear maps, the effects of substructure and shape variation are related to observational gravitational lensing studies. Average shear in regions less than and greater than half of the virial radius demonstrates distinct dispersion, varying by 24% from the mean among the 21 maps. We estimate the numerical error in shear calculations to be of the order of 5%. Therefore, this shear dispersion is a reliable consequence of shape dispersion, correlating most strongly with the ratio of smallest-to-largest principal axis lengths of a cluster isodensity shell. On the other hand, image ellipticities, which are of great importance in mass reconstruction, are shown to have very little variance. However, tangential alignment of average image distortion is quite strong, making mass density peak locations easily resolvable"--Abstract, leaf iii.
Book Synopsis The Signal of Weak Gravitational Lensing from Galaxy Groups and Clusters by : Sean Markert
Download or read book The Signal of Weak Gravitational Lensing from Galaxy Groups and Clusters written by Sean Markert and published by . This book was released on 2017 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: The weak gravitational lensing of galaxy clusters is a valuable tool. The deflection of light around a lens is solely dependent on the underlying distribution of foreground mass, and independent of tracers mass such as the mass to light ratio and kinematics. As a direct probe of mass, weak lensing serves as an independent calibration of mass-observable relationships. These massive clusters are objects of great interest to astronomers, as their abundance is dependent on the conditions of the early universe, and accurate counts of clusters serve as a test of cosmological model. Upcoming surveys, such as LSST and DES, promise to push the limit of observable weak lensing, detecting clusters and sources at higher redshift than has ever been detected before. This makes accurate counts of clusters of a given mass and redshift, and proper calibration of mass-observable relationships, vital to cosmological studies. We used M> 10 [superscript 13.5] h−1M[sun] halos from the MultiDark Planck simulation at z~0.5 to study the behavior of the reduced shear in clusters. We generated 2D maps of convergence and shear the halos using the GLAMER lensing library. Using these maps, we simulated observations of randomly placed background sources, and generated azimuthal averages of the shear. This reduced shear profile, and the true reduced shear profile of the halo, is fit using analytical solutions for shear of the NFW, Einasto, and truncated NFW density profile. The masses of these density profiles are then compared to the total halo masses from the halo catalogs. We find that fits to the reduced shear for halos extending past [approximately equal] 2h−1Mpc are fits to the noise of large scale structure along the line of sight. This noise is largely in the 45° rotated component to the reduced tangential shear, and is a breakdown in the approximation of g[subscript tan][approximately equal]g[subscript tot] required for density profile fitting of clusters. If fits are constrained to a projected radii of
Book Synopsis Weak Gravitational Lensing Shear and Magnification Analysis of Hydrodynamic Simulations and Application to Weak Lensing Data by : Miyoung Choi
Download or read book Weak Gravitational Lensing Shear and Magnification Analysis of Hydrodynamic Simulations and Application to Weak Lensing Data written by Miyoung Choi and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the main part of this dissertation we study the impact of baryonic processes and massive neutrinos on weak lensing peak statistics that can be used to constrain cosmological parameters. We use the BAHAMAS simulations, which self-consistently include baryonic processes and the effect of massive neutrino free-streaming on the evolution of structure formation. We construct synthetic weak lensing maps by ray-tracing through light-cones, specifically using the so-called aperture mass statistic. The peaks detected on the maps reflect the cumulative lensing signal from massive bound objects and general large scale structure of the Universe. In particular, we quantify the impact of the prescription for baryonic physics and a range of summed neutrino masses {0.06, 0.12, 0.24, 0.48} eV on the detected peaks, so that in future this uncertainty can be factored into studies using lensing peaks to constrain cosmological models. As higher neutrino mass tends to suppress the formation of massive structures in the Universe, the halo mass function and lensing peak counts are therefore modified as a function of M.,,, . Both baryonic physics and massive neutrinos impact on weak lensing peaks, depending on the mass range under consideration, and should be accounted for when deriving cosmological parameters from weak lensing observations. For example, baryonic physics is less important for the most massive haloes. We also present a study of the cluster merger system Abell 2146. We make new aperture mass maps by applying the aperture mass statistic to Hubble Space Telescope data of the system, using different size apertures. These maps directly show the signal-to-noise with which lensing detects features in the system. We also develop a pipeline that can in general be applied to snapshots from computer simulations of cluster merger systems. This pipeline produces maps of lensing observables that would be measured at different times during the merger process. In particular the lensing distortion field or so-called shear field can be compared with the shear field that we have estimated from Hubble Space Telescope observations, in order to find the best description of the cluster and merger parameters of the system. Finally we develop a pipeline to measure the stacked weak lensing shear and magnification signatures of galaxy clusters. We apply this pipeline to analytic models of clusters, and conclude that the shear information gives better constraints on mass models, even though the number of sources from which the shear can be measured is lower than for the magnification. In future this can be applied to synthetic catalogues for example from the BAHAMAS simulation or to real data for example from LSST or Euclid.
Book Synopsis Improving Accuracy in Gravitational Weak Lensing Measurements of Clusters by : Julia Young
Download or read book Improving Accuracy in Gravitational Weak Lensing Measurements of Clusters written by Julia Young and published by . This book was released on 2013 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Measuring the distribution of galaxy clusters provides a powerful constraint on cosmological parameters. Currently, the largest challenge for using the observed abundance of clusters to constrain cosmology is to measure their mass accurately. The best tool to measure the mass of clusters is weak gravitational lensing, which measures the baryonic and dark matter present in galaxy clusters by observing the distortion of the shape of sources behind the gravitational lens called shear. Weak lensing measurements are technically challenging to measure due to the distortion in the shape of sources from the atmosphere and telescope optics called the Point Spread Function or PSF. To measure shear, images are processed by various software programs called lensing pipelines which correct for the distortion due to the PSF. Using image simulations with sources of known characteristics and known shear the systematic error of different lensing pipelines can be compared. In this dissertation the results of the Cluster Shear TEsting Program (CSTEP), a test of lensing pipelines on simulated images, is presented. CSTEP was developed to accurately measure the systematic bias on weak lensing measurements of clusters expected by the Dark Energy Survey (DES). The systematic error from lensing pipelines is then used to predict the error on mass measurements of galaxy clusters observed by DES.
Book Synopsis Gravitational Lensing: An Astrophysical Tool by : Frederic Courbin
Download or read book Gravitational Lensing: An Astrophysical Tool written by Frederic Courbin and published by Springer. This book was released on 2008-01-11 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gravitational lensing is by now sufficiently well understood that it can be used as a tool of investigation in other astrophysical areas. Applications include the determination of the Hubble constant, probing the dark matter context of galaxies and the mapping of the universe to the identification of otherwise invisible large-scale structures. Each chapter of the book covers in a self-contained manner a subfield of gravitational lensing, with the double aim of describing in a simple way the basics of the theory and of reviewing the most recent developments as well as applications foreseen in the near future. The book will thus be particularly useful as a high-level textbook for nonspecialist researchers and advanced students wishing to become familiar with the field all the way up to the forefront of research.
Book Synopsis A Pan-Chromatic View of Clusters of Galaxies and the Large-Scale Structure by : Manolis Plionis
Download or read book A Pan-Chromatic View of Clusters of Galaxies and the Large-Scale Structure written by Manolis Plionis and published by Springer. This book was released on 2008-02-17 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reviews presented in this volume cover a huge range of cluster of galaxies topics. Readers will find the book essential reading on subjects such as the physics of the ICM gas, the internal cluster dynamics, and the detection of clusters using different observational techniques. The expert chapter authors also cover the huge advances being made in analytical or numerical modeling of clusters, weak and strong lensing effects, and the large scale structure as traced by clusters.
Book Synopsis Gravitational Lensing: Strong, Weak and Micro by : Peter Schneider
Download or read book Gravitational Lensing: Strong, Weak and Micro written by Peter Schneider and published by Springer Science & Business Media. This book was released on 2006-12-30 with total page 565 pages. Available in PDF, EPUB and Kindle. Book excerpt: The observation, in 1919 by A.S. Eddington and collaborators, of the gra- tational de?ection of light by the Sun proved one of the many predictions of Einstein’s Theory of General Relativity: The Sun was the ?rst example of a gravitational lens. In 1936, Albert Einstein published an article in which he suggested - ing stars as gravitational lenses. A year later, Fritz Zwicky pointed out that galaxies would act as lenses much more likely than stars, and also gave a list of possible applications, as a means to determine the dark matter content of galaxies and clusters of galaxies. It was only in 1979 that the ?rst example of an extragalactic gravitational lens was provided by the observation of the distant quasar QSO 0957+0561, by D. Walsh, R.F. Carswell, and R.J. Weymann. A few years later, the ?rst lens showing images in the form of arcs was detected. The theory, observations, and applications of gravitational lensing cons- tute one of the most rapidly growing branches of astrophysics. The gravi- tional de?ection of light generated by mass concentrations along a light path producesmagni?cation,multiplicity,anddistortionofimages,anddelaysp- ton propagation from one line of sight relative to another. The huge amount of scienti?c work produced over the last decade on gravitational lensing has clearly revealed its already substantial and wide impact, and its potential for future astrophysical applications.
Book Synopsis Merging Processes in Galaxy Clusters by : L. Feretti
Download or read book Merging Processes in Galaxy Clusters written by L. Feretti and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mergers are the mechanisms by which galaxy clusters are assembled through the hierarchical growth of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. Many of the observed properties of clusters depend on the physics of the merging process. These include substructure, shock, intra cluster plasma temperature and entropy structure, mixing of heavy elements within the intra cluster medium, acceleration of high-energy particles, formation of radio halos and the effects on the galaxy radio emission. This book reviews our current understanding of cluster merging from an observational and theoretical perspective, and is appropriate for both graduate students and researchers in the field.
Book Synopsis A Detailed Study of Galaxy Clusters with Weak Gravitational Lensing and X-rays by : Jennifer Miriam Piel
Download or read book A Detailed Study of Galaxy Clusters with Weak Gravitational Lensing and X-rays written by Jennifer Miriam Piel and published by . This book was released on 2012 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Shapes Of Galaxies And Their Dark Halos, The - Proceedings Of The Yale Cosmology Workshop by : Priyamvada Natarajan
Download or read book Shapes Of Galaxies And Their Dark Halos, The - Proceedings Of The Yale Cosmology Workshop written by Priyamvada Natarajan and published by World Scientific. This book was released on 2002-03-28 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book constitutes the proceedings of a very topical workshop aimed at understanding the shapes of the baryonic and dark matter components of galaxies. Several groups presented their recent results from observations and numerical N-body simulations.
Book Synopsis Probabilistic Inference of Dark Matter Properties in Galaxy Clusters and the Cosmic Web by : Yin-Yee Ng
Download or read book Probabilistic Inference of Dark Matter Properties in Galaxy Clusters and the Cosmic Web written by Yin-Yee Ng and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Mass tells spacetime how to curve, spacetime tells mass how to move". This famous quote by physicist John Archibald Wheeler succinctly summarizes General Relativity, the most successful theory that describes our universe at large scale. However, most of the mass that General Relativity describes, namely dark matter (DM), remains a mystery. We have solid evidence of the existence of DM from various observations, but we know little or nothing about the particle nature of DM and how DM particles interact with different particles. Completing this knowledge gap would improve or revolutionize our established cosmological model, the Lambda Cold-Dark Matter (CDM) model, and give directions to theories beyond the standard particle physics model.This work attempts to study DM by examining and extending existing modeling approaches of DM and its visible tracers in a probabilistic way. The single verified form of DM interaction is gravitational. Currently, the only way to infer the properties of DM is through visible tracers. Most of these indirect detections either have low signal-to-noise, sparse coverage, or missing variables. These limitations introduce additional modeling choices and uncertainties. A probabilistic approach allows us to propagate the uncertainties appropriately and marginalize any missing variables. There are two recurring types of visible tracers that my work uses. The first type of tracers are galaxies and observables in the overdense regions of DM. These tracers allow usto infer the macroscopic dynamical properties of DM distribution that we want to study. The second type of tracers, on the hand, are in the background, i.e. further away than the foreground dark matter, from us observers. The gravity of DM can bend spacetime such that the path of light traveling in the vicinity would also curve, leaving distortions in the galaxy images. The gravitational distortion of the images of the background galaxies is also known as gravitational lensing. In the introduction (first chapter) of this thesis, I will layout the technical history, terminology and the reasons behind choosing the various data sets and give an overview of the analysis methods for my thesis work. In chapter two, I will present the study based on the observational data of El Gordo, one of the most massive, most ancient, merging galaxy clusters. Under the extreme collision speeds during a merger of a galaxy cluster, it is more probable for DM particles in the cluster to manifest eects of self-interaction. Thus, if DM particles can interact with one another, some preliminary simulations have shown that large-scale spatial distribution of DM can show discrepancies from its galaxy-counterparts. This discrepancy is also known as the galaxy-DM offset, with a caveat. The long duration (millions of years) of a merger means that we cannot detect the direction of motions of the components directly to confirm the offset as a lag. My work on El Gordo was the first to show a quantitative method of estimating how likely the DM components of El Gordo are to be moving in a certain direction. This study was made possible by utilizing informative observables in various wavelengths, including a pair of radio shockwaves on the outer skirt of the cluster, enhanced X-ray emissivity and the decrement of the Sunyaev-Zel'Dovich effect for the infra-red observations. This comprehensive set of observables allowed us to formulate probabilistic constraints in our Monte Carlo simulation of El Gordo. Furthermore, the study also brought up several questions about the modeling choices for comparing the DM and the member-galaxy distributions of a cluster. For instance, do the DM maps and the galaxy maps have high enough resolution to show the delicate offset signal produced by the possible self-interaction of DM (SIDM)? To address my concerns from the study of El Gordo, I conducted a second investigation of galaxy clusters in a cosmological simulation, which is described in chapter 3. The dataset I chose was from the Illustris simulation. As this simulation assumes a Cold-Dark-Mattermodel (CDM) without requiring an SIDM model, any offset between DM and the member galaxies in a galaxy cluster provides an estimate of the variability of the galaxy-DM offset. My study shows that the variability in this setting is non-negligible compared to the small observed offsets, it is likely that random variation can account for the galaxy-DM offsets inobservations. The result weakens our belief that SIDM is the cause of the offsets. The fourth chapter of my dissertation builds on top of my previous experience with analyzing the weak lensing data for El Gordo. This time, I performed the weak lensing study for a dataset of a much larger spatial scale, such that, galaxy clusters look like parts of a homogeneous and isotropic DM web. At this scale, it is possible to compare the spatial distribution of DM to simulations to give competitive constraints on cosmological parameters. Using weak lensing signals for estimating cosmological parameters is also known as cosmic shear inference. While I used a parametric technique to estimate the mass of El Gordo in chapter 2, my work in chapter 4 introduces a new non-parametric model using a Gaussian Process. A Gaussian Process is a generalization of the multivariate normal distribution to higher dimensions. We can draw functional models from a Gaussian Process to describe our data. While the realizations are drawn from a multivariate normal distribution, we can specify the parameters and the functional structure of the covariance (kernel) matrix of the underlying distribution. This generative model gives us the ability to put probabilistic estimates of DM density in regions without any background galaxies. As I have built the lensing physics into the very core of the covariance kernel matrix, we can also simultaneously infer the several important lensing observables, such as shear and convergence, given some lensed galaxy shapes. More importantly, this technique relies on fewer assumptions about the photometric redshift than traditional cosmic shear analysis technique. This may reduce the bias towards a ducial cosmology and lead to interesting discoveries. However, this new technique is not without its challenges. Computationally, this technique requires an O(n3) runtime. Despite my best attempts to parallelize the computation, the algorithm takes longer for generating DM mass maps than traditional approaches. My work here marks the beginning of an alternative method for cosmic shear inference. Many promising approximation techniques have emerged to drastically speed up the runtime of doing inference with a Gaussian Process. Incorporating these approximations may make it possible to use this method to give tighter cosmological constraints from future sky surveys such as the Large Synoptic Survey Telescope. I conclude my work in Chapter 5 and discuss the implications of my work. This includes some future directions for analyzing DM by using simulations with different underlying DM models and real data.
Book Synopsis Galaxy Cluster Studies with Weak Lensing Magnification & Shear by : Jessica Lange Ford
Download or read book Galaxy Cluster Studies with Weak Lensing Magnification & Shear written by Jessica Lange Ford and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Introduction to Gravitational Lensing by : Massimo Meneghetti
Download or read book Introduction to Gravitational Lensing written by Massimo Meneghetti and published by Springer Nature. This book was released on 2021-12-10 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces the phenomenology of gravitational lensing in an accessible manner and provides a thorough discussion of the related astrophysical applications. It is intended for advanced undergraduates and graduate students who want to start working in this rapidly evolving field. This includes also senior researchers who are interested in ongoing or future surveys and missions such as DES, Euclid, WFIRST, LSST. The reader is guided through many fascinating topics related to gravitational lensing like the structure of our galaxy, the searching for exoplanets, the investigation of dark matter in galaxies and galaxy clusters, and several aspects of cosmology, including dark energy and the cosmic microwave background. The author, who has gained valuable experience as academic teacher, guides the readers towards the comprehension of the theory of gravitational lensing and related observational techniques by using simple codes written in python. This approach, beyond facilitating the understanding of gravitational lensing, is preparatory for learning the python programming language which is gaining large popularity both in academia and in the private sector.
Book Synopsis Principles of Gravitational Lensing by : Arthur B. Congdon
Download or read book Principles of Gravitational Lensing written by Arthur B. Congdon and published by Springer. This book was released on 2018-12-01 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook provides an introduction to gravitational lensing, which has become an invaluable tool in modern astrophysics, with applications that range from finding planets orbiting distant stars to understanding how dark matter and dark energy conspired to form the cosmic structures we see today. Principles of Gravitational Lensing begins with Einstein’s prediction that gravity bends light, and shows how that fundamental idea has spawned a rich field of study over the past century. The gravitational deflection of light was first detected by Eddington during a solar eclipse in May 1919, launching Einstein and his theory of relativity into public view. Yet the possibility of using the phenomenon to unlock mysteries of the Universe seemed remote, given the technology of the day. Theoretical work was carried out sporadically over the next six decades, but only with the discovery of the system Q0957+561 in 1979 was gravitational lensing transformed from a curiosity of general relativity into a practical observational tool. This book describes how the three subfields known as strong lensing, weak lensing, and microlensing have grown independently but become increasingly intertwined. Drawing on their research experience, Congdon and Keeton begin with the basic physics of light bending, then present the mathematical foundations of gravitational lensing, building up to current research topics in a clear and systematic way. Relevant background material from physics and mathematics is included, making the book self-contained. The derivations and explanations are supplemented by exercises designed to help students master the theoretical concepts as well as the methods that drive current research. An extensive bibliography guides those wishing to delve more deeply into particular areas of interest. Principles of Gravitational Lensing is ideal for advanced students and seasoned researchers looking to penetrate this thriving subject and even contribute research of their own.
Book Synopsis Optical Galaxy Cluster Detection and Weak Gravitational Lensing Derived Galaxy Cluster Mass Functions by : Martha Milkeraitis
Download or read book Optical Galaxy Cluster Detection and Weak Gravitational Lensing Derived Galaxy Cluster Mass Functions written by Martha Milkeraitis and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Weak Lensing by Galaxy Clusters by :
Download or read book Weak Lensing by Galaxy Clusters written by and published by . This book was released on 2015 with total page 249 pages. Available in PDF, EPUB and Kindle. Book excerpt: The story of the origin and evolution of our Universe is told, equivalently, by space-time itself and by the structures that grow inside of it. Clusters of galaxies are the frontier of bottom-up structure formation. They are the most massive objects to have collapsed at the present epoch. By that virtue, their abundance and structural parameters are highly sensitive to the composition and evolution of the Universe. The most common probe of cluster cosmology, abundance, uses samples of clusters selected by some observable. Applying a mass-observable relation (MOR), cosmological parameters can be constrained by comparing the sample to predicted cluster abundances as a function of observable and redshift. Arguably, however, cluster probes have not yet entered the era of per cent level precision cosmology. The primary reason for this is our imperfect understanding of the MORs. The overall normalization, the slope of mass vs. observable, the redshift evolution, and the degree and correlation of intrinsic scatters of observables at fixed mass have to be constrained for interpreting abundances correctly. Mass measurement of clusters by means of the differential deflection of light from background sources in their gravitational field, i.e. weak lensing, is a powerful approach for achieving this. This thesis presents new methods for and scientific results of weak lensing measurements of clusters of galaxies. The former include, on the data reduction side, (i) the correction of CCD images for non-linear effects due to the electric fields of accumulated charges (Chapter 2, Gruen et al. 2015a) and (ii) a method for masking artifact features in sets of overlapping images of the sky by comparison to the median image (Chapter 3, Gruen et al. 2014a). Also, (iii) I develop a method for the selection of background galaxy samples based on their color and apparent magnitude that includes a new correction for contamination with cluster member galaxies (Section 5.3.1). The main scientific results are the following. (i) For th! e Hubble Frontier Field cluster RXC J2248.7--4431 our lensing analysis constrains mass and concentration of the cluster halo and we confirm the large mass predicted by X-ray and Sunyaev-Zel'dovich (SZ) observations. The study of cluster members shows the relation of galaxy morphology to luminosity and environment (Chapter 4, Gruen et al. 2013). (ii) Our lensing mass measurements for 12 clusters are consistent with X-ray masses derived under the assumption of hydrostatic equilibrium of the intra-cluster gas. We confirm the MORs derived by the South Pole Telescope collaboration for the detection significance of the cluster SZ signal in their survey. We find discrepancies, however, with the Planck SZ MOR. We hypothesize that these are related either to a shallower slope of the MOR or a size, redshift or noise dependent bias in SZ signal extraction (Chapter 5, Gruen et al. 2014b). (iii) Finally, using a combination of simulations and theoretical models for the variation of cluster profiles at fixed mass, we find that the latter is a significant contribution to the uncertainty of cluster lensing mass measurements. A cosmic variance model, such as the one we develop, is necessary for MOR constraints to be accurate at the level required for future surveys (Chapter 6, Gruen et al. 2015b).
