Constraining Cosmology with Weak Gravitational Lensing PDF Download
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Author: Kellen J. Murphy
Publisher:
ISBN:
Category : Astrotomography
Languages : en
Pages : 189
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Author: Kellen J. Murphy
Publisher:
ISBN:
Category : Astrotomography
Languages : en
Pages : 189
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Book Description
Author: Marc Gentile
Publisher:
ISBN:
Category :
Languages : en
Pages : 196
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Author: Masato Shirasaki
Publisher: Springer
ISBN: 9812877967
Category : Science
Languages : en
Pages : 144
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Book Description
In this book the applicability and the utility of two statistical approaches for understanding dark energy and dark matter with gravitational lensing measurement are introduced. For cosmological constraints on the nature of dark energy, morphological statistics called Minkowski functionals (MFs) to extract the non-Gaussian information of gravitational lensing are studied. Measuring lensing MFs from the Canada–France–Hawaii Telescope Lensing survey (CFHTLenS), the author clearly shows that MFs can be powerful statistics beyond the conventional approach with the two-point correlation function. Combined with the two-point correlation function, MFs can constrain the equation of state of dark energy with a precision level of approximately 3–4 % in upcoming surveys with sky coverage of 20,000 square degrees. On the topic of dark matter, the author studied the cross-correlation of gravitational lensing and the extragalactic gamma-ray background (EGB). Dark matter annihilation is among the potential contributors to the EGB. The cross-correlation is a powerful probe of signatures of dark matter annihilation, because both cosmic shear and gamma-ray emission originate directly from the same dark matter distribution in the universe. The first measurement of the cross-correlation using a real data set obtained from CFHTLenS and the Fermi Large Area Telescope was performed. Comparing the result with theoretical predictions, an independent constraint was placed on dark matter annihilation. Future lensing surveys will be useful to constrain on the canonical value of annihilation cross section for a wide range of mass of dark matter annihilation. Future lensing surveys will be useful to constrain on the canonical value of annihilation cross section for a wide range of mass of dark matter.
Author: Jia Liu
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Thus we need higher order (non-Gaussian) statistics to utilize these features in the nonlinear regime. In this thesis, we study the constraining power on cosmology and relevant systematics of non-Gaussian statistics, with a focus on convergence peaks. We present the first cosmological constraints using peak counts of the CFHTLenS survey. We also quantify the impact of magnification and size bias, one type of lensing systematics, on the lensing power spectrum and peaks. Finally, going beyond galaxy lensing, we cross-correlate Planck CMB lensing maps with CFHTLenS galaxy lensing maps, to investigate various WL systematics.
Author: Miyoung Choi
Publisher:
ISBN:
Category : Astrophysics
Languages : en
Pages :
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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.
Author: Ivan Debono
Publisher: LAP Lambert Academic Publishing
ISBN: 9783843361002
Category :
Languages : en
Pages : 204
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Book Description
Modern concordance cosmology is faced with two tasks: Accounting for the abundance of the known constituents, and determining the nature of the unknown components - dark matter and dark energy. The initial conditions which led to structure formation pose another important question. This work studies the potential of weak gravitational lensing to determine the nature of dark energy through its equation of state and its evolution, and to advance our understanding of the distribution of the primordial density fluctuations. We show how a future all-sky tomographic weak lensing survey in conjunction with expected results from CMB anisotropy probes could provide constraints on the dark energy equation of state as well as neutrino and primordial power spectrum parameters. We also examine how the parameter precision depends on the cosmological model used in our calculations, and discuss the significance of our results to survey optimisation. This work should be helpful to astrophysicists working in the field of weak lensing, and to the wider community of observational cosmologists.
Author: Julia Young
Publisher:
ISBN:
Category :
Languages : en
Pages : 106
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Book Description
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: J. A. Peacock
Publisher: Cambridge University Press
ISBN: 9780521422703
Category : Science
Languages : en
Pages : 700
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Book Description
A comprehensive and authoritative introduction to contemporary cosmology for advanced undergraduate and graduate students.
Author: Peter Schneider
Publisher: Springer Science & Business Media
ISBN: 3540303103
Category : Science
Languages : en
Pages : 565
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Book Description
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: N. Kaiser
Publisher: Springer Science & Business Media
ISBN: 9400930356
Category : Science
Languages : en
Pages : 361
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Book Description
This volume consists of invited talks and contributed papers presented at the NATO Advanced Study Institute "The Post Recombination Universe" which was held in Cambridge in the summer of 1987. There have, in recent years, been numerous meetings devoted to problems in observational cosmology. The attention given reflects the exciting rate of de velopment of the subject, and a survey of the proceedings from these symposia reveals that a great deal of emphasis has been given to consideration of the very early universe on the one hand, and to large scale structure in the universe at the present epoch on the other. The theme of this meeting was chosen to comple ment these efforts by focussing on the state of the universe at quite early times, but at those epochs which are still accessible to direct observations. The meet ing provided a broad coverage of the post recombination universe by drawing on experts from a wide variety of fields covering theory, background radiation fields and discrete sources at high redshift. Events in the moderately early universe will have left their mark in a great range of wavebands, from X-rays to the microwave region, and the evolution of the universe can be revealed by studies of the inter galactic medium, gravitational lensing and the abundance and clustering of high redshift sources. All of these subjects received much attention at the meeting, and the papers demonstrate the rich interplay between these areas in the rapidly expanding world of observational cosmology.
