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Book Improving Accuracy in Gravitational Weak Lensing Measurements of Clusters

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 Gravitational Lensing  Strong  Weak and Micro

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 Cosmology and Astrophysics from Relaxed Galaxy Clusters   IV

Download or read book Cosmology and Astrophysics from Relaxed Galaxy Clusters IV written by and published by . This book was released on 2016 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the fourth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here, we use measurements of weak gravitational lensing from the Weighing the Giants project to calibrate Chandra X-ray measurements of total mass that rely on the assumption of hydrostatic equilibrium. This comparison of X-ray and lensing masses measures the combined bias of X-ray hydrostatic masses from both astrophysical and instrumental sources. While we cannot disentangle the two sources of bias, only the combined bias is relevant for calibrating cosmological measurements using relaxed clusters. Assuming a fixed cosmology, and within a characteristic radius (r2500) determined from the X-ray data, we measure a lensing to X-ray mass ratio of 0.96 ± 9% (stat) ± 9% (sys). We find no significant trends of this ratio with mass, redshift or the morphological indicators used to select the sample. Our results imply that any departures from hydrostatic equilibrium at these radii are offset by calibration errors of comparable magnitude, with large departures of tens-of-percent unlikely. In addition, we find a mean concentration of the sample measured from lensing data of c200 = 3.0+4.4-1.8. In conclusion, anticipated short-term improvements in lensing systematics, and a modest expansion of the relaxed lensing sample, can easily increase the measurement precision by 30-50%, leading to similar improvements in cosmological constraints that employ X-ray hydrostatic mass estimates, such as on [Omega]m from the cluster gas mass fraction.

Book Cosmic Stellar Explosions and Galaxy Cluster Weak Gravitational Lensing

Download or read book Cosmic Stellar Explosions and Galaxy Cluster Weak Gravitational Lensing written by Patrick Laughlin Kelly and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Observations of supernova (SN) explosions and galaxy clusters have been essential to the construction of the standard $\Lambda$-CDM cosmological model. Type Ia SN are powerful probes of the cosmic expansion history and were the tools used to discover cosmic acceleration more than a decade ago. They are the thermonuclear explosions of white dwarf stars, and regular patterns in their light curves and luminosities enable distance measurements with a precision of ~10%. Core-collapse SN, which signal instead the deaths of young, massive stars, also have use as cosmological distance indicators and can be detected, when accompanied by a GRB, to very high redshift. A very different technique for constraining cosmological parameters is to measure the distribution of galaxy clusters as a function of mass and redshift within well-defined X-ray or optical surveys. For this method, the current limiting systematic uncertainty is the calibration of galaxy-cluster mass proxies such as total X-ray luminosity or cluster richness. In this thesis, I discuss the discovery that SNe Ia found in more massive host galaxies are ~10% brighter, after light curve corrections for stretch and color, than those in less massive galaxies. I also demonstrate the existence of strong patterns among the explosion environments of core-collapse SN which point to the effects of progenitor mass and metallicity on massive stellar evolution. Finally, I present a weak-lensing mass analysis of 51 X-ray--luminous galaxy clusters. The inclusion of these lensing mass estimates in current cosmological analyses will improve significantly the calibration of X-ray mass proxies and increase both the accuracy and precision of galaxy cluster cosmological constraints.

Book Numerical Methods for the Prediction of Gravitational Lensing Signal as a Probe of the Mass Content on the Universe

Download or read book Numerical Methods for the Prediction of Gravitational Lensing Signal as a Probe of the Mass Content on the Universe written by Céline Gouin and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Upcoming weak lensing surveys such as Euclid, LSST and WFIRST will provide an unprecedented opportunity to investigate the dark Universe. Through these large scale surveys, gravitational lensing is an indispensable cosmological probe to investigate the dark energy and the dark matter. Due to the new level of accuracy in observations, we must perform cosmological predictions in state-of-art simulations, to precisely quantify its variances, biases and potential degeneracies coming from baryonic physics. In this context, my thesis focuses on the construction of accurate weak lensing observables. The first part of my PhD work characterises the geometry of large-scale structure through weak lensing (Gouin et al. 2017). I relied on multipolar decomposition of weak lensing signal to quantify the azimuthal distribution of dark matter centred on galaxy clusters. The statistical properties of these moments are estimated from a large N-body simulation. The harmonic distortions computed in the vicinity of clusters appear to trace the filamentary structure. Larger number of filaments seem to be connected to high-mass clusters.The detection level of this statistical estimator is estimated. In the last part of my thesis, I mock the weak gravitational lensing signal in the light-cone of the Horizon-AGN simulation (Gouin et al. 2019). To do so, I propagate light-rays along the light-cone in the multiple-lens-plane approximation. The impact of baryons is significant in cosmic shear statistics for angular scales below a few arcmins. In addition, the galaxy-galaxy lensing signal is compared to current observational measurements (Leauthaud et al. 2017), and seems in good agreement.

Book Gravitational Lensing And Microlensing

Download or read book Gravitational Lensing And Microlensing written by Silvia Mollerach and published by World Scientific. This book was released on 2002-01-15 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive and self-contained exposition of gravitational lensing phenomena. It presents the up-to-date status of gravitational lensing and microlensing, covering the cosmological applications of the observed lensing by galaxies, clusters and the large scale structures, as well as the microlensing searches in the Local Group and its applications to unveil the nature of the galactic dark matter, the search for planetary objects and the distribution of faint stars in our galaxy.Gravitational Lensing and Microlensing is pitched at the level of the graduate student interested in the issues of astrophysics and cosmology, and should be useful for specialist researchers as well.

Book Modified Gravity  Progresses And Outlook Of Theories  Numerical Techniques And Observational Tests

Download or read book Modified Gravity Progresses And Outlook Of Theories Numerical Techniques And Observational Tests written by Baojiu Li and published by World Scientific. This book was released on 2019-10-10 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modified gravity theories have been a main focus of theoretical cosmology research in the past decade or so, and have been quickly developing into a mature research field that attracts attention, interest and effort from both theoretical and observational cosmologists. To be prepared for fully exploiting the future observational data, and to provide a guidance for people who are new to this field, it is useful to have a comprehensive review to summarise the current state of knowledge and to foresee the future developments.This book presents expert reviews on different topics in the field, which are then coordinated and organised in a self-consistent and self-contained manner. It is suitable for graduate students and researchers interested in the frontier research of gravity theories.

Book Gravitational Lensing  An Astrophysical Tool

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 The Shapes of Galaxies and Their Dark Halos

Download or read book The Shapes of Galaxies and Their Dark Halos written by Priyamvada Natarajan and published by World Scientific. This book was released on 2002 with total page 286 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 The Extragalactic Distance Scale

    Book Details:
  • Author : Space Telescope Science Institute (U.S.). Symposium
  • Publisher : Cambridge University Press
  • Release : 1997-06-28
  • ISBN : 9780521591645
  • Pages : 354 pages

Download or read book The Extragalactic Distance Scale written by Space Telescope Science Institute (U.S.). Symposium and published by Cambridge University Press. This book was released on 1997-06-28 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the hottest debates in astronomy and cosmology today concerns the value of the Hubble constant. This constant is of paramount importance since it fixes the size and age of the Universe. At a symposium at the Space Telescope Science Institute, experts from around the world presented the latest results from a plethora of techniques for determining the Hubble constant. The value has always been controversial, but at this meeting experts' results agreed for the first time to within about 20%. Based on the meeting, this book presents twenty-three specially written review articles. They provide a comprehensive account of the Hubble-constant debate with the latest results from gravitational lensing, supernovae and novae, the Tully-Fisher relation, the Sunyaev-Zeldovich effect, globular clusters, planetary nebulae, light echoes, and the Hubble Space Telescope Key Project. This timely volume provides a standard reference for graduate students and researchers in astronomy and cosmology.

Book Weak Gravitational Lensing Shear and Magnification Analysis of Hydrodynamic Simulations and Application to Weak Lensing Data

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 Probing Large scale Structure with Intrinsic Alignments and Galaxy Clustering

Download or read book Probing Large scale Structure with Intrinsic Alignments and Galaxy Clustering written by Jonathan Andrew Blazek and published by . This book was released on 2013 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of large-scale structure aims to describe the distribution of matter in the universe. This thesis examines two important topics in this field: intrinsic alignments and anisotropic galaxy clustering. Intrinsic alignments of galaxies are correlations between galaxy shapes and the surrounding density field and are a significant systematic uncertainty in weak gravitational lensing measurements. We examine intrinsic alignments from both theoretical and observational perspectives. First, the most commonly used model for intrinsic alignments, the tidal (linear) alignment model, is tested and developed in the context of recent measurements. The model is found to provide a reasonably accurate description of observations on large scales, particularly for luminous red galaxies. We raise unresolved issues with the model and explore several ways in which it could be improved and expanded. Second, we develop a technique to separate intrinsic alignments from galaxy-galaxy lensing measurements. This technique allows the removal of contamination from the desired lensing signal while also providing a probe of intrinsic alignments in different galaxy populations. Using data from the Sloan Digital Sky Survey (SDSS), we use this method to place the tightest current constraints on intrinsic alignment strength for the SDSS lensing sample, finding that it is a subdominant source of uncertainty at the current level of statistical precision. The measured galaxy clustering signal in redshift surveys is anisotropic due to both geometric and dynamic distortions. We discuss the nature of these distortions and examine their information content in the context of future redshift surveys. We employ a model for the galaxy power spectrum in redshift space, based on an expansion in velocity moments of the phase-space distribution function of matter. This model includes nonlinear treatment of matter clustering, galaxy bias, shot noise, and redshift-space distortions. Comparing with numerical simulations, we find that this model is able to describe halo clustering with sufficient accuracy to allow the inclusion of broadband information on small scales, thus significantly improving constraints on both geometry and growth of structure in the universe.

Book Optimizing Weak Lensing Mass Estimates for Cluster Profile Uncertainty

Download or read book Optimizing Weak Lensing Mass Estimates for Cluster Profile Uncertainty written by and published by . This book was released on 2011 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Weak lensing measurements of cluster masses are necessary for calibrating mass-observable relations (MORs) to investigate the growth of structure and the properties of dark energy. However, the measured cluster shear signal varies at fixed mass M200m due to inherent ellipticity of background galaxies, intervening structures along the line of sight, and variations in the cluster structure due to scatter in concentrations, asphericity and substructure. We use N-body simulated halos to derive and evaluate a weak lensing circular aperture mass measurement Map that minimizes the mass estimate variance (Map - M200m)2 in the presence of all these forms of variability. Depending on halo mass and observational conditions, the resulting mass estimator improves on Map filters optimized for circular NFW-profile clusters in the presence of uncorrelated large scale structure (LSS) about as much as the latter improve on an estimator that only minimizes the influence of shape noise. Optimizing for uncorrelated LSS while ignoring the variation of internal cluster structure puts too much weight on the profile near the cores of halos, and under some circumstances can even be worse than not accounting for LSS at all. As a result, we discuss the impact of variability in cluster structure and correlated structures on the design and performance of weak lensing surveys intended to calibrate cluster MORs.

Book Weak Lensing PSF Correction of Wide field CCD Mosaic Images  SULI Paper

Download or read book Weak Lensing PSF Correction of Wide field CCD Mosaic Images SULI Paper written by Marissa Cevallos and published by . This book was released on 2006 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gravitational lensing provides some of the most compelling evidence for the existence of dark matter. Dark matter on galaxy cluster scales can be mapped due to its weak gravitational lensing effect: a cluster mass distribution can be inferred from the net distortion of many thousands of faint background galaxies that it induces. Because atmospheric aberration and defects in the detector distort the apparent shape of celestial objects, it is of great importance to characterize accurately the point spread function (PSF) across an image. In this research, the PSF is studied in images from the Canada-France-Hawaii Telescope (CFHT), whose camera is divided into 12 CCD chips. Traditional weak lensing methodology involves averaging the PSF across the entire image: in this work we investigate the effects of measuring the PSF in each chip independently. This chip-by-chip analysis was found to reduce the strength of the correlation between star and galaxy shapes, and predicted more strongly the presence of known galaxy clusters in mass maps. These results suggest correcting the CFHT PSF on an individual chip basis significantly improves the accuracy of detecting weak lensing.

Book Weak Gravitational Lensing Uncertainties

Download or read book Weak Gravitational Lensing Uncertainties written by Tingting Lu and published by . This book was released on 2006 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dark matter dominates the mass distribution of the universe, and dark energy determines its expansion. The two are the most mysterious and attractive subjects in modern cosmology, because they provide an opportunity to discover new fundamental physics.Cosmological weak gravitational lensing, which describes the deflection of photons by the gravitational force from large-scale structure in the universe, has been an active area of research in the past decade with many completed, ongoing, and upcoming surveys. Because weak lensing is sensitive to the growth of structure and expansion history of the universe, it is a great tool for improving our understanding of both dark matter and dark energy problems.We show that the non-Gaussianity nature of lensing decreases the dark energy figure of merit by a factor of 1.3 to 1.6 for a few future surveys. We also find that the non-Gaussianity nature of the 21-cm sources reduces the signal to noise ratio by several orders of magnitude. The reconstruction noise saturates at mildly non-linear scales, where the linear power spectrum of the source is Delta2 ∼ 0.2 -- 0.5. For 21-cm sources at z ∼ 2 -- 4, the lensing reconstruction is limited by cosmic variance at ℓ ≲ 100, which is in the linear regime of gravitational growth, and robustly predicted by theory. This allows promising constraints to various modified gravity and dark energy models.Cosmic structures have become non-linear by gravitational clustering. The non-linear structures are important to weak lensing, and cause non-Gaussianity in the lensing maps. In this thesis, I study the influence of non-linearity and non-Gaussianity on the uncertainty of lensing measurements. I develop a new method to robustly measure the co-variance matrix of the lensing convergence power spectrum, from simulations. Because 21-cm intensity map may soon cover half sky at redshift 1-4, I build optimal estimators for reconstructing lensing from the 21-cm sources. I develop Gaussian optimal estimators which can be derived analytically, and non-Gaussian optimal estimators which can be constructed numerically from simulation data. I then run a large number of N-body simulations. For both lenses and 21-cm sources, I explore the statistical uncertainties in the simulation data.

Book Modern Cosmology

    Book Details:
  • Author : Scott Dodelson
  • Publisher : Academic Press
  • Release : 2003-03-13
  • ISBN : 0122191412
  • Pages : 462 pages

Download or read book Modern Cosmology written by Scott Dodelson and published by Academic Press. This book was released on 2003-03-13 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: An advanced text for senior undergraduates, graduate students and physical scientists in fields outside cosmology. This is a self-contained book focusing on the linear theory of the evolution of density perturbations in the universe, and the anisotropiesin the cosmic microwave background.

Book Weak Lensing Flexion as a Probe of Galaxy Cluster Substructure

Download or read book Weak Lensing Flexion as a Probe of Galaxy Cluster Substructure written by Benjamin Martin Cain and published by . This book was released on 2011 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: Measuring galaxy cluster total masses and the amount of dark matter substructure within galaxy cluster haloes is a fundamental probe of the ACDM model of structure formation, as well as the interactions between baryonic and non-baryonic matter. In this thesis I approach the topic of cluster mass structure in two ways. With a combination of optical imaging, spectroscopy, and X-ray observations I determine that the cluster RCS043938-2904.7, while apparently anomalous initially due to its high optical richness and low X-ray surface brightness, is in fact an association of structures along the line of sight. Accounting for this structure brings the observed cluster properties into agreement with known scaling relations. I also present a novel method for measuring weak gravitational lensing flexion to inform mass measurements on small scales. While previously published methods for measuring flexion focus on measuring derived properties of the lensed images, such as shapelet coefficients or surface brightness moments, my method fits a fully mass-sheet-invariant parametrized Analytic Image Model (AIM) to the each galaxy image. This simple parametric model traces the distortion of lensed image isophotes. I tested the AIM method using simulated data images with realistic noise and a variety of input image properties, and I show that it successfully reproduces the input lensing fields. I also apply the AIM method for flexion measurement to Hubble Space Telescope observations of Abell 1689, and detect mass structure in that cluster using only flexion measured with the AIM method.