Precision Cosmology with Weak Gravitational Lensing and Galaxy Populations PDF Download
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Author: Jenna Freudenburg
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 120
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Author: Jenna Freudenburg
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 120
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Author: Hao-Yi Wu
Publisher: Stanford University
ISBN:
Category :
Languages : en
Pages : 234
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The acceleration of the universe, which is often attributed to "dark energy, " has posed one of the main challenges to fundamental physics. Galaxy clusters provide one of the most sensitive probes of dark energy because their abundance reflects the growth rate of large-scale structure and the expansion rate of the universe. Several large galaxy cluster surveys will soon provide tremendous statistical power to constrain the properties of dark energy; however, the constraining power of these surveys will be determined by how well systematic errors are controlled. Of these systematic errors, the dominant one comes from inferring cluster masses using observable signals of clusters, the so-called "observable--mass distribution." This thesis focuses on extracting dark energy information from forthcoming large galaxy cluster surveys, including how we maximize the cosmological information, how we control important systematics, and how precisely we need to calibrate theoretical models. We study how multi-wavelength follow-up observations can improve cluster mass calibration in optical surveys. We also investigate the impact of theoretical uncertainties in calibrating the spatial distributions of galaxy clusters on dark energy constraints. In addition, we explore how the formation history of galaxy clusters impacts the self-calibration of cluster mass. In addition, we use N-body simulations to develop a new statistical sample of cluster-size halos in order to further understand the observable--mass distribution. We study the completeness of subhalos in our cluster sample by comparing them with the satellite galaxies in the Sloan Digital Sky Survey. We also study how subhalo selections impact the inferred correlation between formation time and optical mass tracers, including cluster richness and velocity dispersion.
Author: Michael A. Troxel
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 576
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Gravitational lensing has been identified as a critical cosmological tool in studying the evolution of large scale structure in the universe as well as the nature of dark matter and dark energy. One of the primary physical systematics of weak lensing due to large scale structure (cosmic shear) is the intrinsic alignment (IA) of galaxies, which poses a barrier to precision weak lensing measurements. Methods for identifying and removing its effects on cosmological information are key to the success of weak lensing survey science goals. We have expanded model-independent techniques to isolate and remove the IA contamination from the lensing signal. These self-calibration techniques take advantage of complementary survey information to self-calibrate the lensing signal, which along with unique lensing and IA geometry and separation dependencies, allow us to reconstruct the IA correlations at the level of the spectrum and bispectrum. We have demonstrated that the self-calibration approach can reduce the IA bias over most relevant scale and redshift ranges by up to a factor of 10 or more. This could reduce a potential 10-20% bias in some cosmological information down to the 1-2% level. The self-calibration techniques have the added benefit of preserving the IA signal, which itself provides additional information that can be used in studying the formation and evolution of large scale structure in the universe. We have also identified a new source of intrinsic alignment contamination in cross-correlations with cosmic microwave background lensing and proposed a method to calibrate it, and we explored the potential of future surveys to measure directly various 2- and 3-point intrinsic alignment correlations. Finally, we have investigated the use of exact anisotropic and inhomogeneous models in general relativity for large- and small-scale structures in the universe, developing the frameworks necessary to analyze gravitational lensing in such models, and have compared them to observations, identifying potential sources of bias. We have found, for example, that ignoring substructure level anisotropies in structures could bias the lensing convergence, shear, and kinematic mass estimates by up to 10% or more. We conclude by presenting a numerical code package for calculations in such exact anisotropic and inhomogeneous models.
Author: Robin Upham
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Peter Schneider
Publisher: Springer Science & Business Media
ISBN: 3540303103
Category : Science
Languages : en
Pages : 552
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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.
Author: International Astronomical Union. Symposium
Publisher: Cambridge University Press
ISBN: 9780521851961
Category : Science
Languages : en
Pages : 478
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This book contains the proceedings of the International Astronomical Union Symposium no. 225, held in July 2004 at the Ecole Polytechnique Federale de Lausanne (EPFL), in Lausanne, Switzerland. The meeting focused on the applications of gravitational lensing to cosmological physics, and this book summarizes the most recent theoretical and observational developments. With chapters written by leading scientists in the field, this is a valuable resource for professional astronomers and graduate students in astronomy, physics and astro-particle physics.
Author: Jaiyul Yoo
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages : 163
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Abstract: Galaxy clustering measurement has been one of the leading tools in cosmology for estimating a more fundamental quantity, the clustering of the underlying dark matter distribution. With the recent advances in galaxy redshift surveys, and hence dramatic improvement in observational data, the main obstacle to achieving this goal has become the theoretical uncertainty of galaxy bias, the difference between the galaxy and the matter distributions. The halo occupation distribution (HOD) program has emerged as a powerful tool to overcome the difficulty in inferring dark matter clustering by providing a theoretical framework that describes statistical properties of galaxy populations in individual dark matter halos. Moreover, gravitational lensing depends only on gravity, regardless of whether it is produced by dark or luminous matter, thus providing an observational method to break the degeneracy between the galaxy bias and underlying cosmology. In particular, weak gravitational lensing uses the subtle distortion of background galaxy shapes to measure how foreground lensing matter is statistically distributed, making its method well suited to the HOD description. In this thesis, I describe three methods to quantify dark matter clustering based on the HOD framework, making full use of precision measurements of galaxy clustering and weak lensing from recent galaxy redshift surveys. First, using galaxy clustering measurements on small scales, I infer the scale-dependent bias function, which makes it possible to extend the recovery of the primordial matter power spectrum over a large dynamic range, and thereby tighten constraints on cosmological parameters obtainable from the galaxy samples of the Sloan Digital Sky Survey. Second, I develop an analytic model for combining galaxy-galaxy lensing and galaxy clustering to constrain the matter density parameter and the matter fluctuation amplitude. Finally, I present a novel method to constrain dark energy models using cluster-galaxy weak lensing and apply our method to the planned Dark Energy Survey (DES), forecasting our ability to measure cosmological parameters. Comprehensive analysis of galaxy clustering measurements with these complementary approaches will provide a unique opportunity for a complete description of dark matter clustering.
Author: J. A. Peacock
Publisher: Cambridge University Press
ISBN: 9780521422703
Category : Science
Languages : en
Pages : 700
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A comprehensive and authoritative introduction to contemporary cosmology for advanced undergraduate and graduate students.
Author: Julia Young
Publisher:
ISBN:
Category :
Languages : en
Pages : 106
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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.
Author: Kellen J. Murphy
Publisher:
ISBN:
Category : Astrotomography
Languages : en
Pages : 189
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