NASA Astrophysics Data System (ADS)
Pires, Sandrine; Starck, Jean-Luc; Leonard, Adrienne; Réfrégier, Alexandre
2012-03-01
This chapter reviews the data mining methods recently developed to solve standard data problems in weak gravitational lensing. We detail the different steps of the weak lensing data analysis along with the different techniques dedicated to these applications. An overview of the different techniques currently used will be given along with future prospects. Until about 30 years ago, astronomers thought that the Universe was composed almost entirely of ordinary matter: protons, neutrons, electrons, and atoms. The field of weak lensing has been motivated by the observations made in the last decades showing that visible matter represents only about 4-5% of the Universe (see Figure 14.1). Currently, the majority of the Universe is thought to be dark, that is, does not emit electromagnetic radiation. The Universe is thought to be mostly composed of an invisible, pressure less matter - potentially relic from higher energy theories - called "dark matter" (20-21%) and by an even more mysterious term, described in Einstein equations as a vacuum energy density, called "dark energy" (70%). This "dark" Universe is not well described or even understood; its presence is inferred indirectly from its gravitational effects, both on the motions of astronomical objects and on light propagation. So this point could be the next breakthrough in cosmology. Today's cosmology is based on a cosmological model that contains various parameters that need to be determined precisely, such as the matter density parameter Omega_m or the dark energy density parameter Omega_lambda. Weak gravitational lensing is believed to be the most promising tool to understand the nature of dark matter and to constrain the cosmological parameters used to describe the Universe because it provides a method to directly map the distribution of dark matter (see [1,6,60,63,70]). From this dark matter distribution, the nature of dark matter can be better understood and better constraints can be placed on dark energy, which affects the evolution of structures. Gravitational lensing is the process by which light from distant galaxies is bent by the gravity of intervening mass in the Universe as it travels toward us. This bending causes the images of background galaxies to appear slightly distorted, and can be used to extract important cosmological information. In the beginning of the twentieth century, A. Einstein predicted that massive bodies could be seen as gravitational lenses that bend the path of light rays by creating a local curvature in space time. One of the first confirmations of Einstein's new theory was the observation during the 1919 solar eclipse of the deflection of light from distant stars by the sun. Since then, a wide range of lensing phenomena have been detected. The gravitational deflection of light by mass concentrations along light paths produces magnification, multiplication, and distortion of images. These lensing effects are illustrated by Figure 14.2, which shows one of the strongest lenses observed: Abell 2218, a very massive and distant cluster of galaxies in the constellation Draco. The observed gravitational arcs are actually the magnified and strongly distorted images of galaxies that are about 10 times more distant than the cluster itself. These strong gravitational lensing effects are very impressive but they are very rare. Far more prevalent are weak gravitational lensing effects, which we consider in this chapter, and in which the induced distortion in galaxy images is much weaker. These gravitational lensing effects are now widely used, but the amplitude of the weak lensing signal is so weak that its detection relies on the accuracy of the techniques used to analyze the data. Future weak lensing surveys are already planned in order to cover a large fraction of the sky with high accuracy, such as Euclid [68]. However, improving accuracy also places greater demands on the methods used to extract the available information.
Simulations of weak gravitational lensing
Martin White; Chris Vale
2004-05-13
We describe the simulation data produced by a pilot programme to compute mock weak gravitational lensing maps for a range of currently popular cosmological models by ray tracing through high-resolution N-body simulations. The programme required only a modest investment in computer time to produce maps accurate to arcminute scales covering hundreds of square degrees of sky for 4 cosmological models.
Instrumental systematics and weak gravitational lensing
NASA Astrophysics Data System (ADS)
Mandelbaum, R.
2015-05-01
We present a pedagogical review of the weak gravitational lensing measurement process and its connection to major scientific questions such as dark matter and dark energy. Then we describe common ways of parametrizing systematic errors and understanding how they affect weak lensing measurements. Finally, we discuss several instrumental systematics and how they fit into this context, and conclude with some future perspective on how progress can be made in understanding the impact of instrumental systematics on weak lensing measurements.
Image processing challenges in weak gravitational lensing
Amara, Adam
2011-01-01
The field of weak gravitational lensing, which measures the basic properties of the Universe by studying the way that light from distant galaxies is perturbed as it travels towards us, is a very active field in astronomy. This short article presents a broad overview of the field, including some of the important questions that cosmologists are trying to address, such as understanding the nature of dark energy and dark matter. To do this, there is an increasing feeling within the weak lensing community that other disciplines, such as computer science, machine learning, signal processing and image processing, have the expertise that would bring enormous advantage if channelled into lensing studies. To illustrate this point, the article below outlines some of the key steps in a weak lensing analysis chain. The challenges are distinct at each step, but each could benefit from ideas developed in the signal processing domain. This article also gives a brief overview of current and planned lensing experiments that wi...
Weak gravitational lensing with DEIMOS
Melchior, Peter; Schäfer, Björn Malte; Bartelmann, Matthias
2010-01-01
We introduce a novel method for weak-lensing measurements, which is based on a mathematically exact deconvolution of the moments of the apparent brightness distribution of galaxies from the telescope's PSF. No assumptions on the shape of the galaxy or the PSF are made. The (de)convolution equations are exact for unweighted moments only, while in practice a compact weight function needs to be applied to the noisy images to ensure that the moment measurement yields significant results. We employ a Gaussian weight function, whose centroid and ellipticity are iteratively adjusted to match the corresponding quantities of the source. The change of the moments caused by the application of the weight function can then be corrected by considering higher-order weighted moments of the same source. Because of the form of the deconvolution equations, even an incomplete weighting correction leads to an excellent shear estimation if galaxies and PSF are measured with a weight function of identical size. We demonstrate the a...
Weak gravitational lensing of intrinsically aligned galaxies
NASA Astrophysics Data System (ADS)
Giahi-Saravani, Aram; Schäfer, Björn Malte
2014-01-01
Subject of this paper is the weak lensing effect on galaxies that show intrinsically correlated ellipticities. In our model, we investigate the distortion of the ellipticity field if the galaxies experience an apparent shift in their position by weak lensing deflection and compare this effect to the shearing effect induced by tidal fields. Starting with a derivation of intrinsic ellipticity spectra by employing a tidal torquing model generating galactic angular momenta, we model the galaxy ellipticity by assuming that the galactic disc forms perpendicularly to the host halo angular momentum direction and derives intrinsic ellipticity E-mode and B-mode spectra from the angular momentum statistics. The lensing effect on the ellipticity field is modelled by employing the methodology developed in the framework of lensing of the cosmic microwave background polarization. For Euclid, ellipticity correlations are altered by lensing deflection on multipoles ? ? 1000 by ˜5 per cent for the ellipticity E modes and ˜30 per cent for the B modes, while a shallower survey would exhibit larger changes on larger angular scales. In addition to the convolving effect of lensing on the ellipticity spectra, we investigate the E/B-mode conversion and discuss the possibility of measuring correlations between different multipoles, which is evoked by the homogeneity breaking effect of the lensing displacement. Our conclusion is that although shape correlations generated by weak gravitational shear is dominant, the shifting effect due to lensing is shaping the ellipticity spectra on small angular scales and causing a number of interesting phenomena, which might be observable by future surveys.
Baryons, neutrinos, feedback and weak gravitational lensing
NASA Astrophysics Data System (ADS)
Harnois-Déraps, Joachim; van Waerbeke, Ludovic; Viola, Massimo; Heymans, Catherine
2015-06-01
The effect of baryonic feedback on the dark matter mass distribution is generally considered to be a nuisance to weak gravitational lensing. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arcminutes. Recent progress on the numerical modelling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current weak lensing surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform our analysis, we construct an analytic fitting formula that describes the effect of the baryons on the mass power spectrum. This fitting formula is based on three scenarios of the OverWhelmingly Large hydrodynamical simulations. It is specifically calibrated for z < 1.5, where it models the simulations to an accuracy that is better than 2 per cent for scales k < 10 h Mpc-1 and better than 5 per cent for 10 < k < 100 h Mpc-1. Equipped with this precise tool, this paper presents the first constraint on baryonic feedback models using gravitational lensing data, from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). In this analysis, we show that the effect of neutrino mass on the mass power spectrum is degenerate with the baryonic feedback at small angular scales and cannot be ignored. Assuming a cosmology precision fixed by WMAP9, we find that a universe with massless neutrinos is rejected by the CFHTLenS lensing data with 85-98 per cent confidence, depending on the baryon feedback model. Some combinations of feedback and non-zero neutrino masses are also disfavoured by the data, although it is not yet possible to isolate a unique neutrino mass and feedback model. Our study shows that ongoing weak gravitational lensing surveys (KiDS, HSC and DES) will offer a unique opportunity to probe the physics of baryons at galactic scales, in addition to the expected constraints on the total neutrino mass.
Baryons, Neutrinos, Feedback and Weak Gravitational Lensing
Harnois-Déraps, Joachim; Viola, Massimo; Heymans, Catherine
2014-01-01
(Abridged) The effect of baryonic feedback on the dark matter mass distribution is generally considered to be a nuisance to weak gravitational lensing. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arcminutes. Recent progress on the numerical modelling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current weak lensing surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform our analysis, we construct an analytic fitting formula that describes the effect of the baryons on the mass power spectrum. This fitting formula is based on three scenarios of the OWL hydrodynamical simulations. It is specifically calibrated for $z<1.5$, where it models the simulations to an accuracy that is better than $2\\%$ for scales $k<10 h\\mbox{Mpc}^{-1}$ and better than ...
Atomic Inference from Weak Gravitational Lensing Data
Marshall, Phil; /KIPAC, Menlo Park
2005-12-14
We present a novel approach to reconstructing the projected mass distribution from the sparse and noisy weak gravitational lensing shear data. The reconstructions are regularized via the knowledge gained from numerical simulations of clusters, with trial mass distributions constructed from n NFW profile ellipsoidal components. The parameters of these ''atoms'' are distributed a priori as in the simulated clusters. Sampling the mass distributions from the atom parameter probability density function allows estimates of the properties of the mass distribution to be generated, with error bars. The appropriate number of atoms is inferred from the data itself via the Bayesian evidence, and is typically found to be small, reecting the quality of the data. Ensemble average mass maps are found to be robust to the details of the noise realization, and succeed in recovering the demonstration input mass distribution (from a realistic simulated cluster) over a wide range of scales. As an application of such a reliable mapping algorithm, we comment on the residuals of the reconstruction and the implications for predicting convergence and shear at specific points on the sky.
Studying the LSS through weak gravitational lensing maps
Antonio C. C. Guimarães
2001-12-10
Weak gravitational lensing is a promising tool for the study of the mass distribution in the Universe. Here we report some partial results that show how lensing maps can be used to differentiate between cosmological models. We pay special attention to the role of noise and smoothing. As an application, we use mock convergence fields constructed from N-body simulations of the large-scale structure for three historically important cosmological models. Various map analyses are used, including Minkowski functionals, and their ability to differentiate the models is calculated and discussed.
Weak gravitational lensing by compact objects in fourth order gravity
NASA Astrophysics Data System (ADS)
Horváth, Zsolt; Gergely, László Á.; Hobill, David; Capozziello, Salvatore; De Laurentis, Mariafelicia
2013-09-01
We discuss weak lensing characteristics in the gravitational field of a compact object in the low-energy approximation of fourth order f(R)-gravity theory. The particular solution is characterized by a gravitational strength parameter ? and a distance scale rc much larger than the Schwarzschild radius. Above rc gravity is strengthened and as a consequence weak lensing features are modified compared to the Schwarzschild case. We find a critical impact parameter (depending upon rc) for which the behavior of the deflection angle changes. Using the Virbhadra-Ellis lens equation we improve the computation of the image positions, Einstein ring radii, magnification factors and the magnification ratio. We demonstrate that the magnification ratio as function of image separation obeys a power law depending on the parameter ?, with a double degeneracy. No ??0 value gives the same power as the one characterizing Schwarzschild black holes. As the magnification ratio and the image separation are the lensing quantities most conveniently determined by direct measurements, future lensing surveys will be able to constrain the parameter ? based on this prediction.
Weak shear study of galaxy clusters by simulated gravitational lensing
NASA Astrophysics Data System (ADS)
Coss, David
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.
Weak Gravitational Lensing around Field Galaxies in HST Survey Images
R. E. Griffiths; S. Casertano; M. Im; K. U. Ratnatunga
1996-05-17
Using data from the HST Medium Deep Survey, a long-term Key Project, together with generically similar archived data, we have discovered evidence for weak gravitational `shear' of background field galaxies (I = 22 -- 26) in the vicinity of isolated, foreground galaxies ( I = 15 -- 22), especially those of early type. The statistical lensing is demonstrated by the slight preferential orientation of the major axes of the background galaxies in directions at right angles to the lines joining them to the foreground ones. The detected shear is at the level of $\\delta\\phi = 2.5^{o}\\pm 1.2^{o}$ averaged over the background galaxies at about ~10 half-light radii from 400 foreground ellipticals, corresponding to a polarization of about 0.04. A positive but less significant result is also reported for foreground spirals. This result excludes the de Vaucouleurs model for the mass distribution of ellipticals, but is consistent with elliptical galaxies having total M/L ~ 100 and extensive dark halos.
Weak Gravitational Lensing with COSMOS: Galaxy Selection and Shape Measurements
A. Leauthaud; R. Massey; J. P. Kneib; J. Rhodes; D. E. Johnston; P. Capak; C. Heymans; R. S. Ellis; A. M. Koekemoer; O. Le Fevre; Y. Mellier; A. Refregier; A. C. Robin; N. Scoville; L. Tasca; J. E. Taylor; L. Van Waerbeke
2007-02-13
With a primary goal of conducting precision weak lensing measurements from space, the COSMOS survey has imaged the largest contiguous area observed by the Hubble Space Telescope (HST) to date using the Advanced Camera for Surveys (ACS). This is the first paper in a series where we describe our strategy for addressing the various technical challenges in the production of weak lensing measurements from the COSMOS data. The COSMOS ACS catalog is constructed from 575 ACS/WFC tiles (1.64 deg^2) and contains a total 1.2x10^6 objects to a limiting magnitude of F814W=26.5. This catalog is made publicly available. The shapes of galaxies have been measured and corrected for the distortion induced by the time varying ACS Point Spread Function and for Charge Transfer Efficiency effects. Next, simulated images are used to derive the shear susceptibility factors that are necessary in order to transform shape measurements into unbiased shear estimators. Finally, for each galaxy, we derive a shape measurement error and utilize this quantity to extract the intrinsic shape noise of the galaxy sample. Interestingly, our results indicate that the intrinsic shape noise varies little with either size, magnitude or redshift. Representing a number density of 66 galaxies per arcmin^2, the final COSMOS weak lensing catalog contains 3.9x10^5 galaxies with accurate shape measurements. The properties of the COSMOS weak lensing catalog described throughout this paper will provide key input numbers for the preparation and design of next-generation wide field space missions.
J. Anthony Tyson; David Kirkman; Ian Dell'Antonio; Gary Bernstein; David M. Wittman
2000-01-01
Most of the matter in the Universe is not luminous, and can be observed only through its gravitational influence on the appearance of luminous matter. Weak gravitational lensing is a technique that uses the distortions of the images of distant galaxies as a tracer of dark matter: such distortions are induced as the light passes through large-scale distributions of dark
Testing dark energy paradigms with weak gravitational lensing R. Ali Vanderveld,1
Hu, Wayne
Testing dark energy paradigms with weak gravitational lensing R. Ali Vanderveld,1 Michael J all quintessence models, with or without early dark energy. We further explore how uncertainties a given dark energy paradigm, such as the standard CDM model of cold dark matter and a cosmological
Detection of Weak Gravitational Lensing by Large-scale Structure
David Bacon; Alexandre Refregier; Richard Ellis
2000-07-17
We report a detection of the coherent distortion of faint galaxies arising from gravitational lensing by foreground structures. This ``cosmic shear'' is potentially the most direct measure of the mass power spectrum, as it is unaffected by poorly-justified assumptions made concerning the biasing of the distribution. Our detection is based on an initial imaging study of 14 separated 8' x 16' fields observed in good, homogeneous conditions with the prime focus EEV CCD camera of the 4.2m William Herschel Telescope. We detect an rms shear of 1.6% in 8' x 8' cells, with a significance of 3.4 sigma. We carefully justify this detection by quantifying various systematic effects and carrying out extensive simulations of the recovery of the shear signal from artificial images defined according to measured instrument characteristics. We also verify our detection by computing the cross-correlation between the shear in adjacent cells. Including (gaussian) cosmic variance, we measure the shear variance to be (0.016)^2 plus/minus (0.012)^2 plus/minus (0.006)^2, where these 1 sigma errors correspond to statistical and systematic uncertainties, respectively. Our measurements are consistent with the predictions of cluster-normalised CDM models (within 1 sigma) but a COBE-normalised SCDM model is ruled out at the 3.0 sigma level. For the currently-favoured Lambda-CDM model (with Omega_m = 0.3), our measurement provides a normalisation of the mass power spectrum of sigma_8 = 1.5 plus/minus 0.5, fully consistent with that derived from cluster abundances. Our result demonstrates that ground-based telescopes can, with adequate care, be used to constrain the mass power spectrum on various scales. The present results are limited mainly by cosmic variance, which can be overcome in the near future with more observations.
Weak gravitational lensing as a method to constrain unstable dark matter
Wang Meiyu; Zentner, Andrew R. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)
2010-12-15
The nature of the dark matter remains a mystery. The possibility of an unstable dark matter particle decaying to invisible daughter particles has been explored many times in the past few decades. Meanwhile, weak gravitational lensing shear has gained a lot of attention as a probe of dark energy, though it was previously considered a dark matter probe. Weak lensing is a useful tool for constraining the stability of the dark matter. In the coming decade a number of large galaxy imaging surveys will be undertaken and will measure the statistics of cosmological weak lensing with unprecedented precision. Weak lensing statistics are sensitive to unstable dark matter in at least two ways. Dark matter decays alter the matter power spectrum and change the angular diameter distance-redshift relation. We show how measurements of weak lensing shear correlations may provide the most restrictive, model-independent constraints on the lifetime of unstable dark matter. Our results rely on assumptions regarding nonlinear evolution of density fluctuations in scenarios of unstable dark matter and one of our aims is to stimulate interest in theoretical work on nonlinear structure growth in unstable dark matter models.
Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements
NASA Astrophysics Data System (ADS)
Seshadri, S.; Shapiro, C.; Goodsall, T.; Fucik, J.; Hirata, C.; Rhodes, J. D.; Rowe, B. T. P.; Smith, R. M.
2013-09-01
Weak gravitational lensing observations are a key science driver for the NASA Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of the WFIRST infrared detectors, we have performed a laboratory emulation of weak gravitational lensing measurements. Our experiments used a custom precision projector system to image a target mask composed of a grid of pinholes, emulating stellar point sources, onto a 1.7 ?m cut-off Teledyne HgCdTe/H2RG detector. We used a 0.88 ?m LED illumination source and f/22 pupil stop to produce undersampled point spread functions similar to those expected from WFIRST. We also emulated the WFIRST image reconstruction strategy, using the image combination (IMCOM) algorithm to derive oversampled images from dithered, undersampled input images. We created shear maps for this data and computed shear correlation functions to mimic a real weak lensing analysis. After removing only second-order polynomial fits to the shear maps, we found that the correlation functions could be reduced to O(10-6). This places a conservative upper limit on the detector-induced bias to the correlation function (under our test conditions). This bias is two orders of magnitude lower than the expected weak lensing signal. Restricted to scales relevant to dark energy analyses (sky separations >0.5'), the bias is O(10-7) - comparable to the requirement for future weak lensing missions to avoid biasing cosmological parameter estimates. Our experiment will need to be upgraded and repeated under different configurations to fully characterize the shape measurement performance of WFIRST IR detectors.
Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit
NASA Astrophysics Data System (ADS)
Gyulchev, G. N.; Yazadjiev, S. S.
2010-11-01
We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r?/b, where M is the black hole mass, a is the angular momentum, r? = Q2/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.
A step towards testing general relativity using weak gravitational lensing and redshift surveys
Yong-Seon Song; Olivier Doré
2009-08-24
Using the linear theory of perturbations in General Relativity, we express a set of consistency relations that can be observationally tested with current and future large scale structure surveys. We then outline a stringent model-independent program to test gravity on cosmological scales. We illustrate the feasibility of such a program by jointly using several observables like peculiar velocities, galaxy clustering and weak gravitational lensing. After addressing possible observational or astrophysical caveats like galaxy bias and redshift uncertainties, we forecast in particular how well one can predict the lensing signal from a cosmic shear survey using an over-lapping galaxy survey. We finally discuss the specific physics probed this way and illustrate how $f(R)$ gravity models would fail such a test.
EDITORIAL: Focus on Gravitational Lensing
Bhuvnesh Jain
2007-01-01
Gravitational lensing emerged as an observational field following the 1979 discovery of a doubly imaged quasar lensed by a foreground galaxy. In the 1980s and '90s dozens of other multiply imaged systems were observed, as well as time delay measurements, weak and strong lensing by galaxies and galaxy clusters, and the discovery of microlensing in our galaxy. The rapid pace
M. A. Troxel; Mustapha Ishak
2014-12-07
The wealth of incoming and future cosmological observations will allow us to map out the structure and evolution of the observable universe to an unprecedented level of precision. Among these observations is the weak gravitational lensing of galaxies, e.g., cosmic shear that measures the minute distortions of background galaxy images by intervening cosmic structure. Weak lensing and cosmic shear promise to be a powerful probe of astrophysics and cosmology, constraining models of dark energy, measuring the evolution of structure in the universe, and testing theories of gravity on cosmic scales. However, the intrinsic alignment of galaxies -- their shape and orientation before being lensed -- may pose a great challenge to the use of weak gravitational lensing as an accurate cosmological probe, and has been identified as one of the primary physical systematic biases in cosmic shear studies. Correlations between this intrinsic alignment and the lensing signal can persist even for large physical separations, and isolating the effect of intrinsic alignment from weak lensing is not trivial. A great deal of work in the last two decades has been devoted to understanding and characterizing this intrinsic alignment, which is also a direct and complementary probe of structure formation and evolution in its own right. In this review, we report in a systematic way the state of our understanding of the intrinsic alignment of galaxies, with a particular emphasis on its large-scale impact on weak lensing measurements and methods for its isolation or mitigation. (Abridged)
NASA Astrophysics Data System (ADS)
Harnois-Déraps, Joachim; van Waerbeke, Ludovic
2015-07-01
Numerical N-body simulations play a central role in the assessment of weak gravitational lensing statistics, residual systematics and error analysis. In this paper, we investigate and quantify the impact of finite simulation volume on weak lensing two- and four-point statistics. These finite support (FS) effects are modelled for several estimators, simulation box sizes and source redshifts, and validated against a new large suite of 500 N-body simulations. The comparison reveals that our theoretical model is accurate to better than 5 per cent for the shear correlation function ?+(?) and its error. We find that the most important quantities for FS modelling are the ratio between the measured angle ? and the angular size of the simulation box at the source redshift, ?box(zs), or the multipole equivalent ?/?box(zs). When this ratio reaches 0.1, independently of the source redshift, the shear correlation function ?+ is suppressed by 5, 10, 20 and 25 per cent for Lbox = 1000, 500, 250 and 147 h-1 Mpc, respectively. The same effect is observed in ?-(?), but at much larger angles. This has important consequences for cosmological analyses using N-body simulations and should not be overlooked. We propose simple semi-analytic correction strategies that account for shape noise and survey masks, generalizable to any weak lensing estimator. From the same simulation suite, we revisit the existing non-Gaussian covariance matrix calibration of the shear correlation function, and propose a new one based on the 9-year Wilkinson Microwave Anisotropy Probe)+baryon acoustic oscillations+supernova cosmology. Our calibration matrix is accurate at 20 per cent down to the arcminute scale, for source redshifts in the range 0 < z < 3, even for the far off-diagonal elements. We propose, for the first time, a parametrization for the full ?- covariance matrix, also 20 per cent accurate for most elements.
Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit
Gyulchev, G. N. [Department of Physics, Biophysics and Roentgenology, Faculty of Medicine, St. Kliment Ohridski, University of Sofia, 1 Kozyak str., 1407 Sofia (Bulgaria); Yazadjiev, S. S. [Department of Theoretical Physics, Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia (Bulgaria)
2010-11-25
We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r{sub {alpha}}/b, where M is the black hole mass, a is the angular momentum, r{sub {alpha}}= Q{sup 2}/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.
Weak Gravitational Lensing S. Pires, J.-L. Starck, A. Leonard and A. Refregier
Starck, Jean-Luc
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 4 2D mapping of the dark matter 14 4.1 Inversion problem. Figure 2: Strong Gravitational Lensing effect observed in the Abell 2218 cluster (W. Couch et al, 1975
NASA Astrophysics Data System (ADS)
Troxel, M. A.; Ishak, Mustapha
2015-02-01
The wealth of incoming and future cosmological observations will allow us to map out the structure and evolution of the observable universe to an unprecedented level of precision. Among these observations is the weak gravitational lensing of galaxies, e.g., cosmic shear that measures the minute distortions of background galaxy images by intervening cosmic structure. Weak lensing and cosmic shear promise to be a powerful probe of astrophysics and cosmology, constraining models of dark energy, measuring the evolution of structure in the universe, and testing theories of gravity on cosmic scales. However, the intrinsic alignment of galaxies-their shape and orientation before being lensed-may pose a great challenge to the use of weak gravitational lensing as an accurate cosmological probe, and has been identified as one of the primary physical systematic biases in cosmic shear studies. Correlations between this intrinsic alignment and the lensing signal can persist even for large physical separations, and isolating the effect of intrinsic alignment from weak lensing is not trivial. A great deal of work in the last two decades has been devoted to understanding and characterizing this intrinsic alignment, which is also a direct and complementary probe of structure formation and evolution in its own right. In this review, we report in a systematic way the state of our understanding of the intrinsic alignment of galaxies, with a particular emphasis on its large-scale impact on weak lensing measurements and methods for its isolation or mitigation. We begin with an introduction to the use of cosmic shear as a probe for cosmology and describe the various physical contributions by intrinsic alignment to the shear or convergence 2- and 3-point correlations. We then review developments in the modeling of the intrinsic alignment signal, including a trend toward attempting to incorporate more accurate nonlinear and single halo effects. The impact on cosmological constraints by the intrinsic alignment of galaxies is also outlined based on these models. We then summarize direct measurements of the large-scale intrinsic alignment signal in various surveys and discuss their constraints on models of intrinsic alignment, as well as progress in utilizing numerical simulations of structure formation to further our understanding of intrinsic alignment. Finally, we outline the development of a variety of mitigation techniques for reducing the impact of the intrinsic alignment contamination on weak lensing signals both within a galaxy data set and between complementary probes of gravitational lensing. The methodology and projected impact of these techniques are discussed for both 2- and 3-point correlations. We conclude by presenting a summary and outlook on the state of intrinsic alignment study and its impact on ongoing and planned weak lensing surveys.
Probing Dark Energy via Weak Gravitational Lensing with the Supernova Acceleration Probe (SNAP)
Albert, J.; Aldering, G.; Allam, S.; Althouse, W.; Amanullah, R.; Annis, J.; Astier, P.; Aumeunier, M.; Bailey, S.; Baltay, C.; Barrelet, E.; Basa, S.; Bebek, C.; Bergstom, L.; Bernstein, G.; Bester, M.; Besuner, B.; Bigelow, B.; Blandford, R.; Bohlin, R.; Bonissent, A.; /Caltech /LBL, Berkeley /Fermilab /SLAC /Stockholm U. /Paris, IN2P3
2005-08-08
SNAP is a candidate for the Joint Dark Energy Mission (JDEM) that seeks to place constraints on the dark energy using two distinct methods. The first, Type Ia SN, is discussed in a separate white paper. The second method is weak gravitational lensing, which relies on the coherent distortions in the shapes of background galaxies by foreground mass structures. The excellent spatial resolution and photometric accuracy afforded by a 2-meter space-based observatory are crucial for achieving the high surface density of resolved galaxies, the tight control of systematic errors in the telescope's Point Spread Function (PSF), and the exquisite redshift accuracy and depth required by this project. These are achieved by the elimination of atmospheric distortion and much of the thermal and gravity loads on the telescope. The SN and WL methods for probing dark energy are highly complementary and the error contours from the two methods are largely orthogonal. The nominal SNAP weak lensing survey covers 1000 square degrees per year of operation in six optical and three near infrared filters (NIR) spanning the range 350 nm to 1.7 {micro}m. This survey will reach a depth of 26.6 AB magnitude in each of the nine filters and allow for approximately 100 resolved galaxies per square arcminute, {approx} 3 times that available from the best ground-based surveys. Photometric redshifts will be measured with statistical accuracy that enables scientific applications for even the faint, high redshift end of the sample. Ongoing work aims to meet the requirements on systematics in galaxy shape measurement, photometric redshift biases, and theoretical predictions.
Cosmology with weak lensing surveys
NASA Astrophysics Data System (ADS)
Munshi, Dipak; Valageas, Patrick; van Waerbeke, Ludovic; Heavens, Alan
2008-06-01
Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening matter. The distortions are due to fluctuations in the gravitational potential, and are directly related to the distribution of matter and to the geometry and dynamics of the Universe. As a consequence, weak gravitational lensing offers unique possibilities for probing the Dark Matter and Dark Energy in the Universe. In this review, we summarise the theoretical and observational state of the subject, focussing on the statistical aspects of weak lensing, and consider the prospects for weak lensing surveys in the future. Weak gravitational lensing surveys are complementary to both galaxy surveys and cosmic microwave background (CMB) observations as they probe the unbiased non-linear matter power spectrum at modest redshifts. Most of the cosmological parameters are accurately estimated from CMB and large-scale galaxy surveys, so the focus of attention is shifting to understanding the nature of Dark Matter and Dark Energy. On the theoretical side, recent advances in the use of 3D information of the sources from photometric redshifts promise greater statistical power, and these are further enhanced by the use of statistics beyond two-point quantities such as the power spectrum. The use of 3D information also alleviates difficulties arising from physical effects such as the intrinsic alignment of galaxies, which can mimic weak lensing to some extent. On the observational side, in the next few years weak lensing surveys such as CFHTLS, VST-KIDS and Pan-STARRS, and the planned Dark Energy Survey, will provide the first weak lensing surveys covering very large sky areas and depth. In the long run even more ambitious programmes such as DUNE, the Supernova Anisotropy Probe (SNAP) and Large-aperture Synoptic Survey Telescope (LSST) are planned. Weak lensing of diffuse components such as the CMB and 21 cm emission can also provide valuable cosmological information. Finally, we consider the prospects for joint analysis with other probes, such as (1) the CMB to probe background cosmology (2) galaxy surveys to probe large-scale bias and (3) Sunyaev Zeldovich surveys to study small-scale baryonic physics, and consider the lensing effect on cosmological supernova observations.
Detection of a filament connected to CL0016 with weak gravitational lensing
Higuchi, Yuichi; Tanaka, Masayuki; Sakurai, Junya
2015-01-01
We report on the weak lensing detection of a filament between two galaxy clusters at $z=0.55$, CL0015.9+1609 and RX J0018.3+1618. We conduct weak lensing analysis of deep multi-band Subaru/Suprime-Cam images with $Lensfit$. The weak lensing signals from the filament are contaminated by signals from the adjacent massive clusters and we statistically subtract the cluster component using two different methods. Both methods yield consistent shear profiles on the filament with $\\gtrsim2\\sigma$ significance and the average surface mass density of the filament is $=(3.20\\pm0.10)\\times10^{14}h$ M$_\\odot$Mpc$^{-2}$, which is in broad agreement with previous studies. On-going surveys such as Hyper Suprime-Cam will identify more filaments, which will serve as a new probe of structure formation in the Universe.
Pengjie Zhang
2010-07-14
The galaxy intrinsic alignment is a severe challenge to precision cosmic shear measurement. We propose to self-calibrate the induced gravitational shear-galaxy intrinsic ellipticity correlation (the GI correlation, \\citealt{Hirata04b}) in weak lensing surveys with photometric redshift measurement. (1) We propose a method to extract the intrinsic ellipticity-galaxy density cross correlation (I-g) from the galaxy ellipticity-density measurement in the same redshift bin. (2) We also find a generic scaling relation to convert the extracted I-g correlation to the demanded GI correlation. We perform concept study under simplified conditions and demonstrate its capability to significantly reduce the GI contamination. We discuss the impact of various complexities on the two key ingredients of the self-calibration technique, namely the method to extract the I-g correlation and the scaling relation between the I-g and the GI correlation. We expect none of them is likely able to completely invalidate the proposed self-calibration technique.
Cosmology with weak lensing surveys.
Munshi, Dipak; Valageas, Patrick
2005-12-15
Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening mass. Since the lensing effects arise from deflections of the light rays due to fluctuations of the gravitational potential, they can be directly related to the underlying density field of the large-scale structures. Weak gravitational surveys are complementary to both galaxy surveys and cosmic microwave background observations as they probe unbiased nonlinear matter power spectra at medium redshift. Ongoing CMBR experiments such as WMAP and a future Planck satellite mission will measure the standard cosmological parameters with unprecedented accuracy. The focus of attention will then shift to understanding the nature of dark matter and vacuum energy: several recent studies suggest that lensing is the best method for constraining the dark energy equation of state. During the next 5 year period, ongoing and future weak lensing surveys such as the Joint Dark Energy Mission (JDEM; e.g. SNAP) or the Large-aperture Synoptic Survey Telescope will play a major role in advancing our understanding of the universe in this direction. In this review article, we describe various aspects of probing the matter power spectrum and the bi-spectrum and other related statistics with weak lensing surveys. This can be used to probe the background dynamics of the universe as well as the nature of dark matter and dark energy. PMID:16286284
Optimal weak lensing tomography for CFHTLenS
Grocutt, Emma Liana
2012-11-28
Weak gravitational lensing is a powerful astronomical tool for constraining cosmological parameters that is entering its prime. Lensing occurs because gravitational fields deflect light rays and measuring this deflection ...
Simulating weak lensing by large scale structure
Chris Vale; Martin White
2003-03-25
We model weak gravitational lensing of light by large-scale structure using ray tracing through N-body simulations. The method is described with particular attention paid to numerical convergence. We investigate some of the key approximations in the multi-plane ray tracing algorithm. Our simulated shear and convergence maps are used to explore how well standard assumptions about weak lensing hold, especially near large peaks in the lensing signal.
GaBoDS: The Garching-Bonn Deep Survey: VII. Probing galaxy bias using weak gravitational lensing
P. Simon; M. Hetterscheidt; M. Schirmer; T. Erben; P. Schneider; C. Wolf; K. Meisenheimer
2006-01-01
[ABRIDGED] The weak gravitational lensing effect is used to infer matter\\u000adensity fluctuations within the field-of-view of the Garching-Bonn Deep Survey\\u000a(GaBoDS). This information is employed for a statistical comparison of the\\u000agalaxy distribution to the total matter distribution. The result of this\\u000acomparison is expressed by means of the linear bias factor, b, the ratio of\\u000adensity fluctuations, and
Mischa Schirmer; Thomas Erben; Peter Schneider; Christian Wolf; Klaus Meisenheimer
2004-01-12
We report the first confirmation of colour-selected galaxy cluster candidates by means of weak gravitational lensing. Significant lensing signals were identified in the course of the shear-selection programme of dark matter haloes in the Garching-Bonn Deep Survey, which currently covers 20 square degrees of deep, high-quality imaging data on the southern sky. The detection was made in a field that was previously covered by the ESO Imaging Survey (EIS) in 1997. A highly significant shear-selected mass-concentration perfectly coincides with the richest EIS cluster candidate at z~0.2, thus confirming its cluster nature. Several other shear patterns in the field can also be identified with cluster candidates, one of which could possibly be part of a filament at z~0.45.
Weak lensing and gravity theories
Viviana Acquaviva; Carlo Baccigalupi; Francesca Perrotta
2004-09-05
We present the theory of weak gravitational lensing in cosmologies with generalized gravity, described in the Lagrangian by a generic function depending on the Ricci scalar and a non-minimally coupled scalar field. We work out the generalized Poisson equations relating the dynamics of the fluctuating components to the two gauge invariant scalar gravitational potentials, fixing the new contributions from the modified background expansion and fluctuations. We show how the lensing observables are affected by the cosmic expansion as well as by the presence of the anisotropic stress, which is non-null at the linear level both in scalar-tensor gravity and in theories where the gravitational Lagrangian term features a non-minimal dependence on the Ricci scalar. We derive the generalized expressions for the convergence power spectrum, and illustrate phenomenologically the new effects in Extended Quintessence scenarios, where the scalar field coupled to gravity plays the role of the dark energy.
Cosmology with Weak Lensing Surveys
Dipak Munshi; Patrick Valageas
2005-09-27
Weak gravitational lensing surveys measure the distortion of the image of distant sources due to the deflections of light rays by the fluctuations of the gravitational potential along the line of sight. Since they probe the non-linear matter power spectrum itself at medium redshift such surveys are complimentary to both galaxy surveys (which follow stellar light) and cosmic microwave background observations (which probe the linear regime at high redshift). Ongoing CMB experiments such as WMAP and the future Planck satellite mission will measure the standard cosmological parameters with unprecedented accuracy. The focus of attention will then shift to understanding the nature of dark matter and vacuum energy: several recent studies suggest that lensing is the best method for constraining the dark energy equation of state. During the next 5 year period ongoing and future weak lensing surveys such as the Joint Dark Energy Mission (JDEM, e.g. SNAP) or the Large-aperture Synoptic Survey Telescope (LSST) will play a major role in advancing our understanding of the universe in this direction. In this review article we describe various aspects of weak lensing surveys and how they can help us in understanding our universe.
Aberration in gravitational lensing
Sereno, M. [Institut fuer Theoretische Physik, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)
2008-10-15
It is known that a relative translational motion between the deflector and the observer affects gravitational lensing. In this paper, a lens equation is obtained to describe such effects on actual lensing observables. Results can be easily interpreted in terms of aberration of light rays. Both radial and transverse motions with relativistic velocities are considered. The lens equation is derived by first considering geodesic motion of photons in the rest-frame Schwarzschild space-time of the lens, and, then, light-ray detection in the moving observer's frame. Because of the transverse motion images are displaced and distorted in the observer's celestial sphere, whereas the radial velocity along the line of sight causes an effective rescaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still pointlike. Either for null transverse motion or up to linear order in velocities, the critical curve is still a circle with its radius corrected by a factor (1+z{sub d}) with respect to the static case, z{sub d} being the relativistic Doppler shift of the deflector. From the observational point of view, the orbital motion of the Earth can cause potentially observable corrections of the order of the {mu}arcsec in lensing towards the supermassive black hole at the Galactic center. On a cosmological scale, tangential peculiar velocities of a cluster of galaxies bring about a typical flexion in images of background galaxies in the weak lensing regime but future measurements seem to be too challenging.
Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Massey, Richard J. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Rhodes, Jason; Ellis, Richard; Scoville, Nick [California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kitching, Thomas D. [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Ilbert, Olivier; Kneib, Jean-Paul [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Jullo, Eric [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Koekemoer, Anton M., E-mail: taylor@uwaterloo.ca [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2012-04-20
Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component {Omega}{sub X} at greater than 99% confidence for an equation-of-state parameter -2.5 {<=} w {<=} -0.1. For the case w = -1, we find a value for the cosmological constant density parameter {Omega}{sub {Lambda}} = 0.85{sup +0.044}{sub -}0{sub .19} (68% CL) and detect cosmic acceleration (q{sub 0} < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys.
What is Gravitational Lensing?
Alexie Leauthaud and Reiko Nakajima
2009-07-31
July 28, 2009 Berkeley Lab summer lecture: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
Influence of gravitational lensing on gravitational radiation
NASA Astrophysics Data System (ADS)
Zakharov, Alexander F.
In a paper by [Wang, Y., Stebbins, A., Turner, E.L. Gravitational lensing of gravitational waves from merging neutron star binaries. Phys. Rev. Lett. 77, 2875 2878, 1996] an influence of gravitational lensing on increasing an estimated rate of gravitational radiation sources was considered. We show that the authors used the geometrical optics approximation model for gravitational lensing and thus they gave an overestimated rate of possible events for possible sources of gravitational radiation for the advanced LIGO detector. We show also that if we would use a more correct model of gravitational lensing, one could conclude that a more strong influence on increasing rate of estimated events of gravitational radiation for advanced LIGO detector could give gravitational lenses of galactic masses but not gravitational lenses of stellar masses as [Wang, Y., Stebbins, A., Turner, E.L. Gravitational lensing of gravitational waves from merging neutron star binaries. Phys. Rev. Lett. 77, 2875 2878, 1996] concluded.
D. J. Bacon; D. M. Goldberg; B. T. P. Rowe; A. N. Taylor
2005-04-21
Flexion is the significant third-order weak gravitational lensing effect responsible for the weakly skewed and arc-like appearance of lensed galaxies. Here we demonstrate how flexion measurements can be used to measure galaxy halo density profiles and large-scale structure on non-linear scales, via galaxy-galaxy lensing, dark matter mapping and cosmic flexion correlation functions. We describe the origin of gravitational flexion, and discuss its four components, two of which are first described here. We also introduce an efficient complex formalism for all orders of lensing distortion. We proceed to examine the flexion predictions for galaxy-galaxy lensing, examining isothermal sphere and Navarro, Frenk & White (NFW) profiles and both circularly symmetric and elliptical cases. We show that in combination with shear we can precisely measure galaxy masses and NFW halo concentrations. We also show how flexion measurements can be used to reconstruct mass maps in 2-D projection on the sky, and in 3-D in combination with redshift data. Finally, we examine the predictions for cosmic flexion, including convergence-flexion cross-correlations, and find that the signal is an effective probe of structure on non-linear scales.
N. Padmanabhan; U. Seljak; U. L. Pen
2002-10-21
We present a survey of the cosmological applications of the next generation of weak lensing surveys, paying special attention to the computational challenges presented by the number of galaxies, $N_{gal} ~$ 10$^{5}$. We focus on optimal methods with no pixelization and derive a multigrid $P^3M$ algorithm that performs the relevant computations in $O(N_{gal} \\log N_{gal})$ time. We test the algorithm by studying three applications of weak lensing surveys - convergence map reconstruction, cluster detection and $E$ and $B$ power spectrum estimation using realistic 1 deg^{2} simulations derived from N-body simulations. The map reconstruction is able to reconstruct large scale features without artifacts. Detecting clusters using only weak lensing is difficult because of line of sight contamination and noise, with low completeness if one desires low contamination of the sample. A power spectrum analysis of the convergence field is more promising and we are able to reconstruct the convergence spectrum with no loss of information down to the smallest scales. The numerical methods used here can be applied to other data sets with same $O(N\\log N)$ scaling and can be generalised to a sphere.
On the role of ? in gravitational lensing
Mauro Sereno
2010-01-01
The cosmological constant ? affects gravitational lensing phenomena. Related effect can be studied in the framework of the Schwarzschild-de Sitter space-time in the weak deflection limit. The main contribution of ? can be accounted for by a proper use of angular diameter distances. For near lenses and static observers, unresolved images are slightly de-magnified, the radius of the Einstein ring
Gravitational lenses and particle properties
NASA Technical Reports Server (NTRS)
Turner, Edwin L.
1986-01-01
The potential of observations of gravitational lens systems for the determination of cosmological constants and for tests of the nature and distribution of dark matter is illustrated. The advantages and disadvantages of gravitational lenses as cosmological probes are evaluated.
Unsolved problems in gravitational lensing
R. D. Blandford
1997-01-01
Recent observations of gravitational lenses and their standard theoretical interpretation are briefly reviewed. The prospects for gravitational lenses resolving some of the central questions of cosmology and extragalactic astronomy are assessed. It is suggested that a large enough sample of radio rings could provide a convincing and direct measurement of the Hubble constant, but that it will be very difficult
Gravitational Lensing in the Universe
Xiang-Ping Wu
1995-12-17
This work reviews the basic theoretical aspects, the main observational evidences and the recent applications of gravitational lensing in the Universe. The article is aimed particularly at providing the readers who don't work on gravitational lensing a relatively easy introduction to this active research field in today's astrophysics.
Influence of gravitational lensing on gravitational radiation
NASA Astrophysics Data System (ADS)
Zakharov, A.
In a paper by Wang, Turner and Stebbins (PRL, Phys. Rev. Lett. 77 (1996) p.2875) an influence of gravitational lensing on increasing an estimated rate of gravitational radiation sources was considered. We show that the authors used the incorrect model for this case and thus they gave overestimated rate of possible events for possible sources of gravitational radiation for the advanced LIGO detector. We show also that if we would use a more correct model of gravitational lensing, one could conclude that more strong influence on increasing rate of estimated events of gravitational radiation for advanced LIGO detector could give gravitational lenses of galactic masses but not gravitational lenses of stellar masses as Wang et al. concluded. Moreover, binary gravitational lenses could give essential distortion of gravitational wave form template, especially gravitational wave template of periodic sources and the effect could be significant for templates of quasi-periodic sources which could be detected by a future gravitational wave space detector like LISA. Recently, the Galactic center was considered by Ruffa (ApJ, 1999) as a gravitational lens that focuses a gravitational wave energy to the Earth. The author used the wave optic approximation to solve this problem and concluded that amplification due to the gravitational lens focusing could be very huge. The conclusion is based on the perfect location of the gravitational wave source, namely the source lies very close to the line passing through the Earth and the gravitational lens (the Galactic Center), therefore the probability of the huge magnification of gravitational wave sources is negligible.
Strong Gravitational Lensing with LSST
Philip J. Marshall; M. Bradac; G. Chartas; G. Dobler; A. Eliasdottir; E. Falco; C. D. Fassnacht; M. J. Jee; C. R. Keeton; M. Oguri; J. A. Tyson
2010-01-01
LSST will find more strong gravitational lensing events than any other survey preceding it, and will monitor them all at a cadence of a few days to a few weeks. We can expect the biggest advances in strong lensing science made with LSST to be in those areas that benefit most from the large volume, and the high accuracy multi-filter
Environments of strong gravitational lenses
Ivelina Gospodinova Momcheva
2009-01-01
This dissertation focuses on determining the properties of the environments and the line-of-sight mass distributions for a sample of strong gravitational lenses as well as establishing their effects on the observed lens properties and the Hubble constant. Strong gravitational lenses ought to be able to provide important constraints for cosmology, however the lack of understanding of their large-scale environments has
Numerical Simulations of Weak Lensing Measurements
David Bacon; Alexandre Refregier; Douglas Clowe; Richard Ellis
2000-07-03
(Abridged) Weak gravitational lensing induces distortions on the images of background galaxies, and thus provides a direct measure of mass fluctuations in the universe. Since the distortions induced by lensing on the images of background galaxies are only of a few percent, a reliable measurement demands very accurate galaxy shape estimation and a careful treatment of systematic effects. Here, we present a study of a shear measurement method using detailed simulations of artificial images. The images are produced using realisations of a galaxy ensemble drawn from the HST Groth strip. We consider realistic observational effects including atmospheric seeing, PSF anisotropy and pixelisation, incorporated in a manner to reproduce actual observations with the William Herschel Telescope. By applying an artificial shear to the simulated images, we test the shear measurement method proposed by Kaiser, Squires & Broadhurst (1995, KSB). Overall, we find the KSB method to be reliable with several provisos. To guide future weak lensing surveys, we study how seeing size, exposure time and pixelisation affect the sensitivity to shear. In addition, we study the impact of overlapping isophotes of neighboring galaxies, and find that this effect can produce spurious lensing signals on small scales. We discuss the prospects of using the KSB method for future, more sensitive, surveys. Numerical simulations of this kind are a required component of present and future analyses of weak lensing surveys.
Pixelation Effects in Weak Lensing
F. William High; Jason Rhodes; Richard Massey; Richard Ellis
2007-03-17
Weak gravitational lensing is a promising probe of dark matter and dark energy requiring accurate measurement of the shapes of faint, distant galaxies. Such measures are hindered by the finite resolution and pixel scale of typical cameras. On the other hand, as imaging telescopes are practically limited to a fixed number of pixels and operational life-span, so the survey area increases with pixel size. We investigate the optimum choice of pixel scale in this trade-off for a space-based mission, using the full engineering model and survey strategy of the proposed SuperNova/Acceleration Probe as an example. Our methodology is to simulate realistic astronomical images of known shear and to evaluate the surface density of sources where the shear is accurately recovered using the Rhodes, Refregier, & Groth algorithm in the context of the derived dark matter power spectrum. In addition to considering single exposures, we also examine the benefits of sub-pixel dithering. Although some of our results depend upon the adopted shape measurement method, the relative trends, particularly those involving the surface density of resolved galaxies, are robust. Our approach provides a practical counterpart to studies which consider the effects of pixelation from analytic principles, which necessarily assume an idealized shape measurement method. We find that the statistical error on the mass power spectrum is minimized with a pixel scale equal to 75-80% of the FWHM of the point-spread function, and that dithering is marginally beneficial at larger pixel scales.
Gravitational Lensing by NFW Halos
Candace Oaxaca Wright; Tereasa G. Brainerd
1999-08-19
We investigate the gravitational lensing properties of dark matter halos with Navarro, Frenk & White (NFW) density profiles and derive an analytic expression for the radial dependence of the shear, $\\gamma(x)$, due to these objects. In addition, we derive an expression for the mean shear interior to a given radius, $\\bar{\\gamma}(x)$, and use this to quantify systematic errors that will arise in weak lensing mass estimates of astronomical objects in the case that the mass estimate is based on an a priori assumption that the underlying potential is that of a singular isothermal sphere when, in fact, the potential is that of an NFW-type object. On mass scales between $10^{11} \\Msun \\ls M_{200} \\ls 10^{15} \\Msun$, the assumption of an isothermal sphere potential results in an overestimate of the halo mass, and the amount by which the mass is overestimated increases linearly with the value of the NFW concentration parameter. Considerable overestimates of the mass ($\\sim 60%$) can occur for galaxy-sized halos, but for rich clusters the mass overestimate is small. The degree to which the mass is systematically in error is dependent upon the cosmology adopted, with a COBE-normalized standard CDM model yielding the largest systematic errors for a given true value of the halo mass.
CONSTRAINING SOURCE REDSHIFT DISTRIBUTIONS WITH GRAVITATIONAL LENSING
Wittman, D.; Dawson, W. A., E-mail: dwittman@physics.ucdavis.edu [Physics Department, University of California, Davis, CA 95616 (United States)
2012-09-10
We introduce a new method for constraining the redshift distribution of a set of galaxies, using weak gravitational lensing shear. Instead of using observed shears and redshifts to constrain cosmological parameters, we ask how well the shears around clusters can constrain the redshifts, assuming fixed cosmological parameters. This provides a check on photometric redshifts, independent of source spectral energy distribution properties and therefore free of confounding factors such as misidentification of spectral breaks. We find that {approx}40 massive ({sigma}{sub v} = 1200 km s{sup -1}) cluster lenses are sufficient to determine the fraction of sources in each of six coarse redshift bins to {approx}11%, given weak (20%) priors on the masses of the highest-redshift lenses, tight (5%) priors on the masses of the lowest-redshift lenses, and only modest (20%-50%) priors on calibration and evolution effects. Additional massive lenses drive down uncertainties as N{sub lens}{sup -1/2}, but the improvement slows as one is forced to use lenses further down the mass function. Future large surveys contain enough clusters to reach 1% precision in the bin fractions if the tight lens-mass priors can be maintained for large samples of lenses. In practice this will be difficult to achieve, but the method may be valuable as a complement to other more precise methods because it is based on different physics and therefore has different systematic errors.
NASA Astrophysics Data System (ADS)
Leauthaud, Alexie; J. Benson, Andrew; Civano, Francesca; L. Coil, Alison; Bundy, Kevin; Massey, Richard; Schramm, Malte; Schulze, Andreas; Capak, Peter; Elvis, Martin; Kulier, Andrea; Rhodes, Jason
2015-01-01
Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter haloes in which they reside is key to constraining how black hole fuelling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modelling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to the fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies, irrespective of nuclear activity. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z < 1 from the COSMOS field, we report the first measurements of weak gravitational lensing from an X-ray-selected sample. Comparing this signal to predictions from the global SHMR, we find that, contrary to previous results, most X-ray AGN do not live in medium size groups - nearly half reside in relatively low mass haloes with M200b ˜ 1012.5 M?. The AGN occupation function is well described by the same form derived for all galaxies but with a lower normalization - the fraction of haloes with AGN in our sample is a few per cent. The number of AGN satellite galaxies scales as a power law with host halo mass with a power-law index ? = 1. By highlighting the relatively `normal' way in which moderate luminosity X-ray AGN hosts occupy haloes, our results suggest that the environmental signature of distinct fuelling modes for luminous quasars compared to moderate luminosity X-ray AGN is less obvious than previously claimed.
Weak Lensing from Space III: Cosmological Parameters
Alexandre Refregier; Richard Massey; Jason Rhodes; Richard Ellis; Justin Albert; David Bacon; Gary Bernstein; Tim McKay; Saul Perlmutter
2004-03-12
Weak gravitational lensing provides a unique method to directly map the dark matter in the universe and measure cosmological parameters. Current weak lensing surveys are limited by the atmospheric seeing from the ground and by the small field of view of existing space telescopes. We study how a future wide-field space telescope can measure the lensing power spectrum and skewness, and set constraints on cosmological parameters. The lensing sensitivity was calculated using detailed image simulations and instrumental specifications studied in earlier papers in this series. For instance, the planned SuperNova/Acceleration Probe (SNAP) mission will be able to measure the matter density parameter Omega_m and the dark energy equation of state parameter w with precisions comparable and nearly orthogonal to those derived with SNAP from supernovae. The constraints degrade by a factor of about 2 if redshift tomography is not used, but are little affected if the skewness only is dropped. We also study how the constraints on these parameters depend upon the survey geometry and define an optimal observing strategy.
WEAK LENSING MASS RECONSTRUCTION: FLEXION VERSUS SHEAR
Pires, S. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/SEDI-SAP, Service d'Astrophysique, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette (France); Amara, A. [Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland)
2010-11-10
Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone should not be used to do convergence map reconstruction, even on small scales.
Computational Methods for Gravitational Lensing
Charles R. Keeton
2001-02-20
Modern applications of strong gravitational lensing require the ability to use precise and varied observational data to constrain complex lens models. I discuss two sets of computational methods for lensing calculations. The first is a new algorithm for solving the lens equation for general mass distributions. This algorithm makes it possible to apply arbitrarily complicated models to observed lenses. The second is an evaluation of techniques for using observational data including positions, fluxes, and time delays of point-like images, as well as maps of extended images, to constrain models of strong lenses. The techniques presented here are implemented in a flexible and user-friendly software package called gravlens, which is made available to the community.
Weak lensing of the Sunyaev-Zel'dovich sky
Xiang-Ping Wu
2003-12-18
We address the question of whether the angular power spectrum of the thermal Sunyaev-Zel'dovich (SZ) sky is further distorted by weak gravitational lensing of foreground large-scale structures. Using an analytic approach to both gaseous and dark halo models, we show that the contamination of weak lensing in the measurement of SZ power power is negligibly small, and relatively corrections |\\Delta C_l|/C_l are less than 3% up to l=10^5. This arises from both the weaker gravitational potentials of low-redshift matter inhomogeneities that can act as lenses for SZ sources (clusters) and the shallower shape of intrinsic SZ power spectrum at large l, in contrast to the cosmic microwave background which can be significantly affected by weak lensing because of the distant location and significant damping of its intrinsic power spectrum at small angular scales.
Weak Lensing Results of the Merging Cluster A1758
NASA Technical Reports Server (NTRS)
Markevitch, M.; Gonzalez, A. H.; Bradac, M.
2011-01-01
Here we present the weak lensing results of A1758, which is known to have four cluster members undergoing two separate mergers, A1758N and A1758S. Weak lensing results of A1758N agree with previous weak lensing results of clusters lE0657-558 (Bullet cluster) and MACS J0025.4-1222, whose X-ray gas components were found to be largely separated from their clusters' gravitational potentials. A1758N has a geometry that is different from previously published mergers in that one of its X-ray peaks overlays the corresponding gravitational potential and the other X-ray peak is well separated from its cluster's gravitational potential.
Influence of Gravitational Lensing on Sources of Gravitational Radiation
NASA Astrophysics Data System (ADS)
Zakharov, A. F.
In a recent paper by Wang, Turner and Stebbins (1996) an influence of gravitational lensing on increasing an estimated rate of gravitational radiation sources was considered. We show that the authors used the incorrect model for this case and thus they gave overestimated rate of possible events for possible sources of gravitational radiation for the advanced LIGO detector. We show also that if we would use a more correct model of gravitational lensing, one could conclude that more strong influence on increasing rate of estimated events of gravitational radiation for advanced LIGO detector could give gravitational lenses of galactic masses but not gravitational lenses of stellar masses as Wang et al. concluded. Moreover, binary gravitational lenses could give essential distortion of gravitational wave form template, especially gravitational wave template of periodic sources and the effect could be significant for templates of quasi-periodic sources which could be detected by a future gravitational wave space detector like LISA.
Gravitational Lensing Analyzed by Graded Refractive Index of Vacuum
Xing-Hao Ye; Qiang Lin
2008-02-13
We found strong similarities between the gravitational lensing and the conventional optical lensing. The similarities imply a graded refractive index description of the light deflection in gravitational field. We got a general approach to this refractive index in a static spherically symmetric gravitational field and obtained its exterior and interior solutions exactly through the general relativity. In weak field case, the two solutions come to a simple unified exponential function of the gravitational potential. With these results, the gravitational lensing can be analyzed in a convenient optical way. Especially, the long puzzling problem of the central image missing can be solved easily. We also pointed out that the graded refraction property of the gravitational spacetime is related to the vacuum influenced by the gravitational matter.
Towards noiseless gravitational lensing simulations
NASA Astrophysics Data System (ADS)
Angulo, Raul E.; Chen, Ruizhu; Hilbert, Stefan; Abel, Tom
2014-11-01
The microphysical properties of the dark matter (DM) particle can, in principle, be constrained by the properties and abundance of substructures in galaxy clusters, as measured through strong gravitational lensing. Unfortunately, there is a lack of accurate theoretical predictions for the lensing signal of these substructures, mainly because of the discreteness noise inherent to N-body simulations. Here, we present a method, dubbed as Recursive-TCM, that is able to provide lensing predictions with an arbitrarily low discreteness noise. This solution is based on a novel way of interpreting the results of N-body simulations, where particles simply trace the evolution and distortion of Lagrangian phase-space volume elements. We discuss the advantages and limitations of this method compared to the widely used density estimators based on cloud-in-cells and adaptive-kernel smoothing. Applying the new method to a cluster-sized DM halo simulated in warm and cold DM scenarios, we show how the expected differences in their substructure population translate into differences in convergence and magnification maps. We anticipate that our method will provide the high-precision theoretical predictions required to interpret and fully exploit strong gravitational lensing observations.
Weak Lensing Constraints on Cluster Structural Parameters
Jeffrey A. Willick; Nikhil Padmanabhan
2000-12-12
We study the reliability of dark matter (DM) profile determinations for rich clusters of galaxies based on weak gravitational lensing measurements. We consider three functional forms for the mass distribution: a softened isothermal sphere (SIS), the Navarro, Frenk, & White model (NFW) and the Klypin, Kravstov, Bullock, & Primack model (KKBP). A maximum likelihood parametric method is developed and applied to simulated images of background galaxies (z=2.0) lensed by clusters at z=0.2, 0.5, and 0.8. The images have field size (~10 arcmin) and angular resolution (~0.5 arcsec) characteristic of the new generation of 8-10 meter-class ground-based telescopes. The method recovers the correct virial mass of the DM halo, M_{200}, to within ~10% at all redshifts. The recovered values of \\delta_c and r_s are only accurate to ~25%; however, their correlated errors are such that greater accuracy is obtained for the mass. Clusters with an SIS density profile are recognized by the method, while NFW and KKBP clusters are recognized as not being SIS. The method does not discriminate between NFW and KKBP profiles for clusters of a given mass, because they are too similar in their outer regions. Strongly lensed arcs near the cluster centers would be needed to distinguish NFW from KKBP.
Weak Lensing Detection in CMB Maps
F. Bernardeau
1997-03-05
The weak lensing effects are known to change only weakly the shape of the power spectrum of the Cosmic Microwave Background (CMB) temperature fluctuations. I show here that they nonetheless induce specific non-Gaussian effects that can be detectable with the four-point correlation function of the CMB anisotropies. The magnitude and geometrical dependences of this correlation function are investigated in detail. It is thus found to scale as the square of the derivative of the two-point correlation function and as the angular correlation function of the gravitational displacement field. It also contains specific dependences on the shape of the quadrangle formed by the four directions. When averaged at a given scale, the four-point function, that identifies with the connected part of the fourth moment of the probability distribution function of the local filtered temperature, scales as the square of logarithmic slope of its second moment, and as the variance of the gravitational magnification at the same angular scale. All these effects have been computed for specific cosmological models. It is worth noting that, as the amplitude of the gravitational lens effects has a specific dependence on the cosmological parameters, the detection of the four-point correlation function could provide precious complementary constraints to those brought by the temperature power spectrum.
Lossy compression of weak lensing data
Vanderveld, R Ali; Bernstein, Gary M; Stoughton, Chris; Rhodes, Jason; Massey, Richard; Dobke, Benjamin M
2011-06-01
Future orbiting observatories will survey large areas of sky in order to constrain the physics of dark matter and dark energy using weak gravitational lensing and other methods. Lossy compression of the resultant data will improve the cost and feasibility of transmitting the images through the space communication network. We evaluate the consequences of the lossy compression algorithm of Bernstein et al. (2010) for the high-precision measurement of weak-lensing galaxy ellipticities. This square-root algorithm compresses each pixel independently, and the information discarded is by construction less than the Poisson error from photon shot noise. For simulated space-based images (without cosmicmore »rays) digitized to the typical 16 bits per pixel, application of the lossy compression followed by image-wise lossless compression yields images with only 2.4 bits per pixel, a factor of 6.7 compression. We demonstrate that this compression introduces no bias in the sky background. The compression introduces a small amount of additional digitization noise to the images, and we demonstrate a corresponding small increase in ellipticity measurement noise. The ellipticity measurement method is biased by the addition of noise, so the additional digitization noise is expected to induce a multiplicative bias on the galaxies measured ellipticities. After correcting for this known noise-induced bias, we find a residual multiplicative ellipticity bias of m {approx} -4 x 10{sup -4}. This bias is small when compared to the many other issues that precision weak lensing surveys must confront, and furthermore we expect it to be reduced further with better calibration of ellipticity measurement methods.« less
Lossy compression of weak lensing data
Vanderveld, R Ali [Chicago U., EFI; Caltech /Caltech, JPL; Bernstein, Gary M [Pennsylvania U.; Stoughton, Chris [Fermilab; Rhodes, Jason [Caltech; Caltech, JPL; Massey, Richard [Royal Observ., Edinburgh; Dobke, Benjamin M [Caltech; Caltech, JPL
2011-06-01
Future orbiting observatories will survey large areas of sky in order to constrain the physics of dark matter and dark energy using weak gravitational lensing and other methods. Lossy compression of the resultant data will improve the cost and feasibility of transmitting the images through the space communication network. We evaluate the consequences of the lossy compression algorithm of Bernstein et al. (2010) for the high-precision measurement of weak-lensing galaxy ellipticities. This square-root algorithm compresses each pixel independently, and the information discarded is by construction less than the Poisson error from photon shot noise. For simulated space-based images (without cosmic rays) digitized to the typical 16 bits per pixel, application of the lossy compression followed by image-wise lossless compression yields images with only 2.4 bits per pixel, a factor of 6.7 compression. We demonstrate that this compression introduces no bias in the sky background. The compression introduces a small amount of additional digitization noise to the images, and we demonstrate a corresponding small increase in ellipticity measurement noise. The ellipticity measurement method is biased by the addition of noise, so the additional digitization noise is expected to induce a multiplicative bias on the galaxies measured ellipticities. After correcting for this known noise-induced bias, we find a residual multiplicative ellipticity bias of m {approx} -4 x 10{sup -4}. This bias is small when compared to the many other issues that precision weak lensing surveys must confront, and furthermore we expect it to be reduced further with better calibration of ellipticity measurement methods.
Weak Lensing from Space I: Instrumentation and Survey Strategy
Jason Rhodes; Alexandre Refregier; Richard Massey; Justin Albert; David Bacon; Gary Bernstein; Richard Ellis; Bhuvnesh Jain; Alex Kim; Mike Lampton; Tim McKay; C. Akerlof; G. Aldering; R. Amanullah; P. Astier; E. Barrelet; C. Bebek; L. Bergstrom; J. Bercovitz; M. Bester; A. Bonissent; C. Bower; W. Carithers; E. Commins; C. Day; S. Deustua; R. DiGennaro; A. Ealet; M. Eriksson; A. Fruchter; J.-F. Genat; G. Goldhaber; A. Goobar; D. Groom; S. Harris; P. Harvey; H. Heetderks; S. Holland; D. Huterer; A. Karcher; W. Kolbe; B. Kreiger; R. Lafever; J. Lamoureux; M. Levi; D. Devin; E. Linder; S. Loken; R. Malina; S. McKee; R. Miquel; E. Mortsell; N. Mostek; S. Mufson; J. Musser; P. Nugent; H. Oluseyi; R. Pain; N. Palaio; D. Pankow; S. Perlmutter; R. Pratt; E. Prieto; K. Robinson; N. Roe; M. Sholl; M. Schubnell; G. Smadja; G. Smoot; A. Spadafora; G. Tarle; A. Tomasch; H. von der Lippe; D. Vincent; J.-P. Walder; G. Wang
2003-01-01
A wide field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova\\/Acceleration Probe (SNAP). Using SNAP engineering models, we
Weak Lensing Studies of Mass Substructure in Clusters of Galaxies
NASA Astrophysics Data System (ADS)
Huwe, Paul M.
2012-01-01
Cluster mass substructure is an important test of the hierarchical model of CDM. We use weak gravitational lensing shear measurements, combined with variable aperture filter methods and PSF correction, to extract information about mass subclumping in HST observations of clusters of galaxies. This work is funded by NASA Rhode Island Space Grant.
Thirty Meter Telescopes and Gravitational Lensing
R. G. Carlberg
2004-09-09
Diffraction limited 30m class telescopes will play an important role in gravitational lensing studies, coming online in approximately 2015. As imaging telescopes they will complement the ~6m JWST, probing to smaller angular scales in greatly magnified objects near critical lines and for measuring shear of objects below the JWST angular scale, such as luminous super-star clusters at high redshift. The high source density will allow more detailed mass mapping in the weak lensing regime and will be useful in breaking the cosmology-lens potential degeneracy in strong lensing. As multi-object spectrographs 30m telescopes should provide spectra over the entire optical and near infrared spectrum region. The statistical distribution of redshifts needed to invert projected shear measurements and calibration of photometric redshifts for ``tomography'' will be available to flux levels around 5-10 nano-Jansky (approx 29.5 m_AB). However, a one nJy object is expected to require ~500 hours to acquire a redshift, which is most of the dark time in an observing season. Accordingly ``gravitational telescopes'' will be an important tool for probing the very faint high redshift universe, magnifying a few square arc-seconds at a time by factors of 10-1000.
Gravitational Lensing Extends SETI Range
NASA Astrophysics Data System (ADS)
Factor, Richard
Microwave SETI (The Search for Extraterrestrial Intelligence) focuses on two primary strategies, the "Targeted Search" and the "All-Sky Survey." Although the goal of both strategies is the unequivocal discovery of a signal transmitted by intelligent species outside our solar system, they pursue the strategies in very different manners and have vastly different requirements. This chapter introduces Gravitational Lensing SETI (GL-SETI), a third strategy. Its goal is the unequivocal discovery of an extraterrestrial signal, with equipment and data processing requirements that are substantially different from the commonly-used strategies. This strategy is particularly suitable for use with smaller radio telescopes and has budgetary requirements suitable for individual researchers.
Defining a weak lensing experiment in space
NASA Astrophysics Data System (ADS)
Cropper, Mark; Hoekstra, Henk; Kitching, Thomas; Massey, Richard; Amiaux, Jérôme; Miller, Lance; Mellier, Yannick; Rhodes, Jason; Rowe, Barnaby; Pires, Sandrine; Saxton, Curtis; Scaramella, Roberto
2013-06-01
This paper describes the definition of a typical next-generation space-based weak gravitational lensing experiment. We first adopt a set of top-level science requirements from the literature, based on the scale and depth of the galaxy sample, and the avoidance of systematic effects in the measurements which would bias the derived shear values. We then identify and categorize the contributing factors to the systematic effects, combining them with the correct weighting, in such a way as to fit within the top-level requirements. We present techniques which permit the performance to be evaluated and explore the limits at which the contributing factors can be managed. Besides the modelling biases resulting from the use of weighted moments, the main contributing factors are the reconstruction of the instrument point spread function, which is derived from the stellar images on the image, and the correction of the charge transfer inefficiency in the CCD detectors caused by radiation damage.
A Computer Program to Visualize Gravitational Lenses
Francisco Frutos-Alfaro
2014-06-12
Gravitational lenses are presently playing an important role in astrophysics. By means of these lenses the parameters of the deflector such as its mass, ellipticity, etc. and Hubble's constant can be determined. Using C, Xforms, Mesa and Imlib a computer program to visualize this lens effect has been developed. This program has been applied to generate sequences of images of a source object and its corresponding images. It has also been used to visually test different models of gravitational lenses.
On the role of Lambda in gravitational lensing
Mauro Sereno
2010-01-01
The cosmological constant Lambda affects gravitational lensing phenomena. Related effect can be studied in the framework of the Schwarzschild-de Sitter space-time in the weak deflection limit. The main contribution of Lambda can be accounted for by a proper use of angular diameter distances. For near lenses and static observers, unresolved images are slightly de-magnified, the radius of the Einstein ring
Separating weak lensing and intrinsic alignments using radio observations
Whittaker, Lee; Battye, Richard A
2015-01-01
We discuss methods for performing weak lensing using radio observations to recover information about the intrinsic structural properties of the source galaxies. Radio surveys provide unique information that can benefit weak lensing studies, such as HI emission, which may be used to construct galaxy velocity maps, and polarized synchrotron radiation; both of which provide information about the unlensed galaxy and can be used to reduce galaxy shape noise and the contribution of intrinsic alignments. Using a proxy for the intrinsic position angle of an observed galaxy, we develop techniques for cleanly separating weak gravitational lensing signals from intrinsic alignment contamination in forthcoming radio surveys. Random errors on the intrinsic orientation estimates introduce biases into the shear and intrinsic alignment estimates. However, we show that these biases can be corrected for if the error distribution is accurately known. We demonstrate our methods using simulations, where we reconstruct the shear an...
A Simple Optical Analysis of Gravitational Lensing
Xing-Hao Ye; Qiang Lin
2007-04-26
We analyzed the influence of static gravitational field on the vacuum and proposed the concept of inhomogeneous vacuum. According to the corresponding Fermat's principle in the general relativity, we derived a graded refractive index of vacuum in a static gravitational field. We found that the light deflection in a gravitational field can be calculated correctly with the use of this refractive index and therefore the gravitational lensing can be treated conveniently with the optical method. For illustration, we simulated the imaging of gravitational lensing, figured out the time delay between the two images and calculated the lens mass in a conventional optical way.
Strong Gravitational Lensing with SKA
L. V. E. Koopmans; I. W. A. Browne; N. J. Jackson
2004-09-04
The advent of new observational facilities in the last two decades has allowed the rapid discovery and high-resolution optical imaging of many strong lens systems from galaxy to cluster scales, as well as their spectroscopic follow-up. Radio telescopes have played the dominant role in the systematic detection of dozens of new arcsec-scale lens systems. For the future, we expect nothing less! The next major ground- and space-based facilities, especially the Square Kilometer Array can discover tens of thousands of new lens systems in large sky surveys. For optical imaging and spectroscopic follow-up a strong synergy with planned optical facilities is needed. Here, we discuss the field where strong gravitational lensing is expected to play the dominant role and where SKA can have a major impact: The study of the internal mass structure and evolution of galaxies and clusters to z~1. In addition, studies of more exotic phenomena are contemplated. For example, milli- and microlensing can provide a way to measure the mass-functions of stars and CDM substructure at cosmological distances. All-sky radio monitoring will also rapidly develop the field of time-domain lensing.
Magnified Weak Lensing Cross Correlation Tomography
Ulmer, Melville P., Clowe, Douglas I.
2010-11-30
This project carried out a weak lensing tomography (WLT) measurement around rich clusters of galaxies. This project used ground based photometric redshift data combined with HST archived cluster images that provide the WLT and cluster mass modeling. The technique has already produced interesting results (Guennou et al, 2010,Astronomy & Astrophysics Vol 523, page 21, and Clowe et al, 2011 to be submitted). Guennou et al have validated that the necessary accuracy can be achieved with photometric redshifts for our purposes. Clowe et al titled "The DAFT/FADA survey. II. Tomographic weak lensing signal from 10 high redshift clusters," have shown that for the **first time** via this purely geometrical technique, which does not assume a standard rod or candle, that a cosmological constant is **required** for flat cosmologies. The intent of this project is not to produce the best constraint on the value of the dark energy equation of state, w. Rather, this project is to carry out a sustained effort of weak lensing tomography that will naturally feed into the near term Dark Energy Survey (DES) and to provide invaluable mass calibration for that project. These results will greatly advance a key cosmological method which will be applied to the top-rated ground-based project in the Astro2020 decadal survey, LSST. Weak lensing tomography is one of the key science drivers behind LSST. CO-I Clowe is on the weak lensing LSST committee, and senior scientist on this project, at FNAL James Annis, plays a leading role in the DES. This project has built on successful proposals to obtain ground-based imaging for the cluster sample. By 1 Jan, it is anticipated the project will have accumulated complete 5-color photometry on 30 (or about 1/3) of the targeted cluster sample (public webpage for the survey is available at http://cencos.oamp.fr/DAFT/ and has a current summary of the observational status of various clusters). In all, the project has now been awarded the equivalent of over 60 nights on 4-m class telescopes, which gives concrete evidence of strong community support for this project. The WLT technique is based on the dependence of the gravitational shear signal on the angular diameter distances between the observer, the lens, and the lensed galaxy to measure cosmological parameters. By taking the ratio of measured shears of galaxies with different redshifts around the same lens, one obtains a measurement of the ratios of the angular diameter distances involved. Making these observations over a large range of lenses and background galaxy redshifts will measure the history of the expansion rate of the universe. Because this is a purely geometric measurement, it is insensitive to any form of evolution of objects or the necessity to understand the physics in the early universe. Thus, WLT was identified by the Dark Energy Task Force as perhaps the best method to measure the evolution of DE. To date, however, the conjecture of the DETF has not been experimentally verified, but will be by the proposed project. The primary reason for the lack of tomography measurements is that one must have an exceptional data-set to attempt the measurement. One needs both extremely good seeing (or space observations) in order to minimize the point spread function smearing corrections on weak lensing shear measurements and deep, multi-color data, from B to z, to measure reliable photometric redshifts of the background galaxies being lensed (which are typically too faint to obtain spectroscopic redshifts). Because the entire process from multi-drizzling the HST images, and then creating shear maps, to gathering the necessary ground based observations, to generating photo-zs and then carrying out the tomography is a complicated task, until the creation of our team, nobody has taken the time to connect all the levels of expertise necessary to carry out this project based on HST archival data. Our data are being used in 2 Ph.D. theses. Kellen Murphy, at Ohio University, is using the tomography data along with simulations in a thesis expected to be completed in Jun
Weak Lensing: Dark Matter, Dark Energy
Jain, Bhuvnesh (University of Pennsylvania) [University of Pennsylvania
2006-02-27
The light rays from distant galaxies are deflected by massive structures along the line of sight, causing the galaxy images to be distorted. Measurements of these distortions, known as weak lensing, provide a way of measuring the distribution of dark matter as well as the spatial geometry of the universe. I will describe the ideas underlying this approach to cosmology. With planned large imaging surveys, weak lensing is a powerful probe of dark energy. I will discuss the observational challenges ahead and recent progress in developing multiple, complementary approaches to lensing measurements.
Gravitational lensing of gravitational waves from merging neutron star binaries
Wang, Yun; Stebbins, Albert; Turner, Edwin L.
1996-05-01
We discuss the gravitational lensing of gravitational waves from merging neutron star binaries, in the context of advanced LIGO type gravitational wave detectors. We consider properties of the expected observational data with cut on the signal-to-noise ratio \\rho, i.e., \\rho>\\rho_0. An advanced LIGO should see unlensed inspiral events with a redshift distribution with cut-off at a redshift z_{\\rm max} < 1 for h \\leq 0.8. Any inspiral events detected at z>z_{\\rm max} should be lensed. We compute the expected total number of events which are present due to gravitational lensing and their redshift distribution for an advanced LIGO in a flat Universe. If the matter fraction in compact lenses is close to 10\\%, an advanced LIGO should see a few strongly lensed events per year with \\rho >5.
Gravitational Lensing of Gravitational Waves from Merging Neutron Star Binaries
Wang, Y.; Stebbins, A.; Turner, E.L. [NASA/Fermilab Astrophysics Center, FNAL, Batavia, Illinois 60510 (United States)] [NASA/Fermilab Astrophysics Center, FNAL, Batavia, Illinois 60510 (United States); [Princeton University Observatory, Peyton Hall, Princeton, New Jersey 08544 (United States)
1996-09-01
We discuss the gravitational lensing of gravitational waves from merging neutron star binaries, in the context of advanced LIGO type gravitational wave detectors. An advanced LIGO should see unlensed inspiral events with a redshift distribution with cutoff at a redshift {ital z}{sub max}{lt}1 for {ital h}{le}0.8. Any inspiral events detected at {ital z}{approx_gt}{ital z}{sub max} should be lensed. We compute the expected total number of events which are present due to gravitational lensing and their redshift distribution for an advanced LIGO in a flat universe. If the matter fraction in compact lenses is close to 10{percent}, an advanced LIGO should see a few strongly lensed events per year with {rho}{approx_gt}5. {copyright} {ital 1996 The American Physical Society.}
Influence of gravitational lensing on sources of gravitational radiation
NASA Astrophysics Data System (ADS)
Zakharov, Alexander F.; Baryshev, Yuri V.
2002-04-01
In a recent paper by Wang et al (Wang Y, Stebbins A, and Turner E L 1996 Phys. Rev. Lett. 77 2875) the influence of gravitational lensing on increasing the estimated rate of gravitational radiation sources was considered. We show that the authors used the incorrect model for this case and thus they gave an overestimated rate of possible events for possible sources of gravitational radiation for the advanced LIGO detector. We also show that if we use a more correct model of gravitational lensing, one could conclude that stronger influence on increasing rate of estimated events of gravitational radiation for the advanced LIGO detector could give gravitational lenses of galactic masses but not gravitational lenses of stellar masses as Wang et al concluded. Moreover, binary gravitational lenses could give essential distortion of gravitational wave form templates, especially the gravitational wave template of periodic sources, and the effect could be significant for templates of quasi-periodic sources which could be detected by a future gravitational wave space detector such as LISA.
Gravitational lensing of the CMB with SPTpol
NASA Astrophysics Data System (ADS)
Story, Kyle Tyler; SPTpol Collaboration
2015-01-01
Measurements of gravitational lensing of the cosmic microwave background (CMB) directly probe the projected mass in the universe out to high redshifts. Gravitational lensing encodes a wealth of information in the CMB about the growth and geometry of large-scale structure, which is sensitive to cosmic acceleration (dark energy), the expansion history of the universe and the properties of neutrinos. Additionally, gravitational lensing can be used to improve inflationary gravitational wave searches in the CMB, and constrain the relationship between dark and luminous matter at high redshifts. I will present recent lensing results from the first two years of data from the South Pole Telescope polarimeter (SPTpol) and discuss future opportunities for this powerful technique.
Gravitational lenses and large scale structure
NASA Technical Reports Server (NTRS)
Turner, Edwin L.
1987-01-01
Four possible statistical tests of the large scale distribution of cosmic material are described. Each is based on gravitational lensing effects. The current observational status of these tests is also summarized.
Weak lensing goes bananas: What flexion really measures
Schneider, Peter
2007-01-01
In weak gravitational lensing, the image distortion caused by shear measures the projected tidal gravitational field of the deflecting mass distribution. To lowest order, the shear is proportional to the mean image ellipticity. If the image sizes are not small compared to the scale over which the shear varies, higher-order distortions occur, called flexion. For ordinary weak lensing, the observable quantity is not the shear, but the reduced shear, owing to the mass-sheet degeneracy. Likewise, the flexion itself is unobservable. Rather, higher-order image distortions measure the reduced flexion, i.e., derivatives of the reduced shear. We derive the corresponding lens equation in terms of the reduced flexion and calculate the resulting relation between brightness moments of source and image. Assuming an isotropic distribution of source orientations, estimates for the reduced shear and flexion are obtained; these are then tested with simulations. In particular, the presence of flexion affects the determination o...
The conceptual origins of gravitational lensing
Valls-Gabaud, David
2012-01-01
We critically examine the evidence available of the early ideas on the bending of light due to a gravitational attraction, which led to the concept of gravitational lenses, and attempt to present an undistorted historical perspective. Contrary to a widespread but baseless claim, Newton was not the precursor to the idea, and the first Query in his {\\sl Opticks} is totally unrelated to this phenomenon. We briefly review the roles of Voltaire, Marat, Cavendish, Soldner and Einstein in their attempts to quantify the gravitational deflection of light. The first, but unpublished, calculations of the lensing effect produced by this deflection are found in Einstein's 1912 notebooks, where he derived the lensing equation and the formation of images in a gravitational lens. The brief 1924 paper by Chwolson which presents, without calculations, the formation of double images and rings by a gravitational lens passed mostly unnoticed. The unjustly forgotten and true pioneer of the subject is F. Link, who not only publishe...
Weak lensing from space I: instrumentation and survey strategy
Jason Rhodes; Alexandre Refregier; Richard Massey; Justin Albert; David Bacon; Gary Bernstein; Richard Ellis; Bhuvnesh Jain; Alex Kim; Mike Lampton; Tim McKay; C. Akerlof; G. Aldering; R. Amanullah; P. Astier; C. Baltay; E. Barrelet; C. Bebek; L. Bergström; J. Bercovitz; M. Bester; B. Bigelow; R. Bohlin; A. Bonissent; C. Bower; M. Brown; M. Campbell; W. Carithers; E. Commins; C. Day; S. Deustua; R. Digennaro; A. Ealet; W. Emmet; M. Eriksson; D. Fouchez; A. Fruchter; J. F. Genat; D. Gerdes; L. Gladney; G. Goldhaber; A. Goobar; D. Groom; S. Harris; P. Harvey; H. Heetderks; S. Holland; D. Huterer; W. Johnston; A. Karcher; W. Kolbe; B. Krieger; G. Kushner; N. Kuznetsova; R. Lafever; J. Lamoureux; M. Levi; E. Linder; S. Loken; W. Lorenzon; R. Malina; A. Mazure; S. McKee; R. Miquel; N. Morgan; E. Mörtsell; N. Mostek; S. Mufson; J. Musser; P. Nugent; H. Oluseyi; R. Pain; N. Palaio; D. Pankow; S. Perlmutter; R. Pratt; E. Prieto; D. Rabinowitz; K. Robinson; N. Roe; D. Rusin; M. Schubnell; M. Sholl; G. Smadja; R. Smith; G. Smoot; J. Snyder; A. Spadafora; A. Szymkowiak; G. Tarlé; K. Taylor; A. Tilquin; A. Tomasch; H. von der Lippe; D. Vincent; J.-P. Walder; G. Wang
2004-01-01
A wide-field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova\\/Acceleration Probe (SNAP). Using SNAP engineering models, we quantify
Weak Lensing of Galaxy Clusters in MOND
Ryuichi Takahashi; Takeshi Chiba
2007-10-31
We study weak gravitational lensing of galaxy clusters in terms of the MOND (MOdified Newtonian Dynamics) theory. We calculate shears and convergences of background galaxies for three clusters (A1689, CL0024+1654, CL1358+6245) and the mean profile of 42 SDSS (Sloan Digital Sky Survey) clusters and compare them with observational data. The mass profile is modeled as a sum of X-ray gas, galaxies and dark halo. For the shear as a function of the angular radius, MOND predicts a shallower slope than the data irrespective of the critical acceleration parameter $g_0$. The dark halo is necessary to explain the data for any $g_0$ and for three interpolation functions. If the dark halo is composed of massive neutrinos, its mass should be heavier than 2 eV. However the constraint still depends on the dark halo model and there are systematic uncertainties, and hence the more careful study is necessary to put a stringent constraint.
Gravitational lenses and dark matter - Theory
NASA Technical Reports Server (NTRS)
Gott, J. Richard, III
1987-01-01
Theoretical models are presented for guiding the application of gravitational lenses to probe the characteristics of dark matter in the universe. Analytical techniques are defined for quantifying the mass associated with lensing galaxies (in terms of the image separation), determining the quantity of dark mass of the lensing bodies, and estimating the mass density of the lenses. The possibility that heavy halos are made of low mass stars is considered, along with the swallowing of central images of black holes or cusps in galactic nuclei and the effects produced on a lensed quasar image by nonbaryonic halos. The observable effects of dense groups and clusters and the characteristics of dark matter strings are discussed, and various types of images which are possible due to lensing phenomena and position are described.
Probing cosmology with weak lensing peak counts
Jan M. Kratochvil; Zoltan Haiman; Morgan May
2010-01-01
We propose counting peaks in weak lensing (WL) maps, as a function of their height, to probe models of dark energy and to constrain cosmological parameters. Because peaks can be identified in two-dimensional WL maps directly, they can provide constraints that are free from potential selection effects and biases involved in identifying and determining the masses of galaxy clusters. As
Constraining the QSO luminosity function using gravitational lensing statistics
Fakhouri, Onsi Joe, 1983-
2004-01-01
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 ...
Time delay in Swiss cheese gravitational lensing
Chen, B.; Kantowski, R.; Dai, X. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Room 100, Norman, Oklahoma 73019 (United States)
2010-08-15
We compute time delays for gravitational lensing in a flat {Lambda} dominated cold dark matter Swiss cheese universe. We assume a primary and secondary pair of light rays are deflected by a single point mass condensation described by a Kottler metric (Schwarzschild with {Lambda}) embedded in an otherwise homogeneous cosmology. We find that the cosmological constant's effect on the difference in arrival times is nonlinear and at most around 0.002% for a large cluster lens; however, we find differences from time delays predicted by conventional linear lensing theory that can reach {approx}4% for these large lenses. The differences in predicted delay times are due to the failure of conventional lensing to incorporate the lensing mass into the mean mass density of the universe.
Separating weak lensing and intrinsic alignments using radio observations
NASA Astrophysics Data System (ADS)
Whittaker, Lee; Brown, Michael L.; Battye, Richard A.
2015-07-01
We discuss methods for performing weak lensing using radio observations to recover information about the intrinsic structural properties of the source galaxies. Radio surveys provide unique information that can benefit weak lensing studies, such as H I emission, which may be used to construct galaxy velocity maps, and polarized synchrotron radiation; both of which provide information about the unlensed galaxy and can be used to reduce galaxy shape noise and the contribution of intrinsic alignments. Using a proxy for the intrinsic position angle of an observed galaxy, we develop techniques for cleanly separating weak gravitational lensing signals from intrinsic alignment contamination in forthcoming radio surveys. Random errors on the intrinsic orientation estimates introduce biases into the shear and intrinsic alignment estimates. However, we show that these biases can be corrected for if the error distribution is accurately known. We demonstrate our methods using simulations, where we reconstruct the shear and intrinsic alignment auto- and cross-power spectra in three overlapping redshift bins. We find that the intrinsic position angle information can be used to successfully reconstruct both the lensing and intrinsic alignment power spectra with negligible residual bias.
Weak Lensing from Space I: Instrumentation and Survey Strategy
Rhodes, Jason; Refregier, Alexandre; Massey, Richard; Albert, Justin; Bacon, David; Bernstein, Gary; Ellis, Richard; Jain, Bhuvnesh; Kim, Alex; Lampton, Mike; McKay, Tim; Akerlof, C.; Aldering, G.; Amanullah, R.; Astier, P.; Barrelet, E.; Bebek, C.; Bergstrom, L.; Bercovitz, J.; Bester, M.; Bonissent, A.; Bower, C.; Carithers, W.; Commins, E.; Day, C.; Deustua, S.; DiGennaro, R.; Ealet, A.; Eriksson, M.; Fruchter, A.; Genat, J.-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Harris, S.; Harvey, P.; Heetderks, H.; Holland, S.; Huterer, D.; Karcher, A.; Kolbe, W.; Kreiger, B.; Lafever, R.; Lamoureux, J.; Levi, M.; Devin, D.; Linder, E.; Loken, S.; Malina, R.; McKee, S.; Miquel, R.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Pratt, R.; Prieto, E.; Robinson, K.; Roe, N.; Sholl, M.; Schubnell, M.; Smadja, G.; Smoot, G.; Spadafora, A.; Tarle, G.; Tomasch, A.; von der Lippe, H.; Vincent, D.; Walder, J.-P.; Wang, G.
2003-04-23
A wide field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using SNAP engineering models, we quantify the major contributions to this telescope's Point Spread Function (PSF). These PSF contributions are relevant to any similar wide field space telescope. We further show that the PSF of SNAP or a similar telescope will be smaller than current ground-based PSFs, and more isotropic and stable over time than the PSF of the Hubble Space Telescope. We outline survey strategies for two different regimes - a ''wide'' 300 square degree survey and a ''deep'' 15 square degree survey that will accomplish various weak lensing goals including statistical studies and dark matter mapping.
Weak Lensing Observables in the Halo Model
Kimmo Kainulainen; Valerio Marra
2011-08-19
The halo model (HM) describes the inhomogeneous universe as a collection of halos. The full nonlinear power spectrum of the universe is well approximated by the HM, whose prediction can be easily computed without lengthy numerical simulations. This makes the HM a useful tool in cosmology. Here we explore the lensing properties of the HM by use of the stochastic gravitational lensing (sGL) method. We obtain for the case of point sources exact and simple integral expressions for the expected value and variance of the lensing convergence, which encode detailed information about the internal halo properties. In particular a wide array of observational biases can be easily incorporated and the dependence of lensing on cosmology is properly taken into account. This simple setup should be useful for a quick calculation of the power spectrum and the related lensing observables, which can play an important role in the extraction of cosmological parameters from, e.g., SNe observations. Finally, we discuss the probability distribution function of the HM which encodes more information than the first two moments and can more strongly constrain the large-scale structures of the universe. To check the accuracy of our modelling we compare our predictions to the results from the Millennium Simulation.
The conceptual origins of gravitational lensing
David Valls-Gabaud
2012-06-06
We critically examine the evidence available of the early ideas on the bending of light due to a gravitational attraction, which led to the concept of gravitational lenses, and attempt to present an undistorted historical perspective. Contrary to a widespread but baseless claim, Newton was not the precursor to the idea, and the first Query in his {\\sl Opticks} is totally unrelated to this phenomenon. We briefly review the roles of Voltaire, Marat, Cavendish, Soldner and Einstein in their attempts to quantify the gravitational deflection of light. The first, but unpublished, calculations of the lensing effect produced by this deflection are found in Einstein's 1912 notebooks, where he derived the lensing equation and the formation of images in a gravitational lens. The brief 1924 paper by Chwolson which presents, without calculations, the formation of double images and rings by a gravitational lens passed mostly unnoticed. The unjustly forgotten and true pioneer of the subject is F. Link, who not only published the first detailed lensing calculations in 1936, nine months prior to Einstein's famous paper in {\\sl Science}, but also extended the theory to include the effects of finite-size sources and lenses, binary sources, and limb darkening that same year. Link correctly predicted that the microlensing effect would be easier to observe in crowded fields or in galaxies, as observations confirmed five decades later. The calculations made by Link are far more detailed than those by Tikhov and Bogorodsky. We discuss briefly some papers of the early 1960s which marked the renaissance of this theoretical subject prior to the first detection of a gravitational lens in 1979, and we conclude with the unpublished chapter of Petrou's 1981 PhD thesis addressing the microlensing of stars in the Magellanic clouds by dark objects in the Galactic halo.
The conceptual origins of gravitational lensing
NASA Astrophysics Data System (ADS)
Valls-Gabaud, David
2006-11-01
We critically examine the evidence available of the early ideas on the bending of light due to a gravitational attraction, which led to the concept of gravitational lenses, and attempt to present an undistorted historical perspective. Contrary to a widespread but baseless claim, Newton was not the precursor to the idea, and the first Query in his Opticks is totally unrelated to this phenomenon. We briefly review the roles of Voltaire, Marat, Cavendish, Soldner and Einstein in their attempts to quantify the gravitational deflection of light. The first, but unpublished, calculations of the lensing effect produced by this deflection are found in Einstein's 1912 notebooks, where he derived the lensing equation and the formation of images in a gravitational lens. The brief 1924 paper by Chwolson which presents, without calculations, the formation of double images and rings by a gravitational lens passed mostly unnoticed. The unjustly forgotten and true pioneer of the subject is F. Link, who not only published the first detailed lensing calculations in 1936, nine months prior to Einstein's famous paper in Science, but also extended the theory to include the effects of finite-size sources and lenses, binary sources, and limb darkening that same year. Link correctly predicted that the microlensing effect would be easier to observe in crowded fields or in galaxies, as observations confirmed five decades later. The calculations made by Link are far more detailed than those by Tikhov and Bogorodsky. We discuss briefly some papers of the early 1960s which marked the renaissance of this theoretical subject prior to the first detection of a gravitational lens in 1979, and we conclude with the unpublished chapter of Petrou's 1981 PhD thesis addressing the microlensing of stars in the Magellanic clouds by dark objects in the Galactic halo.
Cosmological test using strong gravitational lensing systems
Yuan, C C
2015-01-01
As one of the probes of universe, strong gravitational lensing systems allow us to compare different cosmological models and constrain vital cosmological parameters. This purpose can be reached from the dynamic and geometry properties of strong gravitational lensing systems, for instance, time-delay $\\Delta\\tau$ of images, the velocity dispersion $\\sigma$ of the lensing galaxies and the combination of these two effects, $\\Delta\\tau/\\sigma^2$. In this paper, in order to carry out one-on-one comparisons between $\\Lambda$CDM universe and $R_h=ct$ universe, we use a sample containing 36 strong lensing systems with the measurement of velocity dispersion from the SLACS and LSD survey. Concerning the time-delay effect, 12 two-image lensing systems with $\\Delta\\tau$ are also used. In addition, Monte Carlo (MC) simulations are used to compare the efficiency of the three methods as mentioned above. From simulations, we estimate the number of lenses required to rule out one model at the $99.7\\%$ confidence level. Compar...
Statistics of gravitational lenses - The uncertainties
NASA Technical Reports Server (NTRS)
Mao, Shude
1991-01-01
The assumptions in the analysis of gravitational lensing statistics are examined. Special emphasis is given to the uncertainties in the theoretical predictions. It is shown that a simple redshift cutoff model, which may result from galaxy evolution, can significantly reduce the lensing probability and explain the large mean separation of images in observed gravitational lenses. This effect may affect the constraint on the contribution of the cosmological constant to producing a flat universe from the number counts of the observed lenses. For the Omega(0) = 1 (filled beam) model, the lensing probability of early-type galaxies with finite core radii is reduced roughly by a factor of 2 for high-redshift quasars as compared with the corresponding singular isothermal sphere model. The finite core radius effect is about 20 percent for a lambda-dominated flat universe. It is also shown that the most recent galaxy luminosity function gives lensing probabilities that are smaller than previously estimated roughly by a factor of 3.
Gravitational Lensing and the Variability of G
Lawrence Krauss; Martin White
1992-04-26
The four observables associated with gravitational lensing of distant quasars by intervening galaxies: image splittings, relative amplifications, time delays, and optical depths, provide separate measures of the strength of the gravitational constant $G$ at cosmological distances. These allow one, in principle, to factor out unknown lensing parameters to directly to probe the variation of $G$ over cosmological time. We estimate constraints on $\\dot{G}$ which may be derivable by this method both now and in the future. The limits one may obtain can compete or exceed other direct limits on $\\dot{G}$ today, but unfortunately extracting this information, is not independent of the effort to fix other cosmological parameters such as $H_0$ and $\\Omega_0$ from lensing observations.
Gravitational lensing of STU black holes
Hassan Saadat
2013-06-03
In this paper we study gravitational lensing by STU black holes. We considered extremal limit of two special cases of zero-charged and one-charged black holes, and obtain the deflection angle. We find that the black hole charge increases the deflection angle.
Perturbative analysis in planetary gravitational lensing
V. Bozza
1999-04-22
The traditional perturbative method is applied to the case of gravitational lensing of planetary systems. A complete and detailed description of the structure of caustics for a system with an arbitrary number of planets can be obtained. I have also found precise analytical expressions for microlensing light curves perturbed by the presence of planets.
Weak Lensing as a Calibrator of the Cluster Mass-Temperature Relation
Dragan Huterer; Martin White
2002-09-09
The abundance of clusters at the present epoch and weak gravitational lensing shear both constrain roughly the same combination of the power spectrum normalization sigma_8 and matter energy density Omega_M. The cluster constraint further depends on the normalization of the mass-temperature relation. Therefore, combining the weak lensing and cluster abundance data can be used to accurately calibrate the mass-temperature relation. We discuss this approach and illustrate it using data from recent surveys.
Gravitational Lensing of Supernova Neutrinos
Mena, Olga; /Fermilab /Rome U.; Mocioiu, Irina; /Penn State U.; Quigg, Chris; /Fermilab
2006-10-01
The black hole at the center of the galaxy is a powerful lens for supernova neutrinos. In the very special circumstance of a supernova near the extended line of sight from Earth to the galactic center, lensing could dramatically enhance the neutrino flux at Earth and stretch the neutrino pulse.
Noise bias in weak lensing shape measurements
NASA Astrophysics Data System (ADS)
Refregier, Alexandre; Kacprzak, Tomasz; Amara, Adam; Bridle, Sarah; Rowe, Barnaby
2012-09-01
Weak lensing experiments are a powerful probe into cosmology through their measurement of the mass distribution of the universe. A challenge for this technique is to control systematic errors that occur when measuring the shapes of distant galaxies. In this paper, we investigate noise bias, a systematic error that arises from second-order noise terms in the shape measurement process. We first derive analytical expressions for the bias of general maximum-likelihood estimators in the presence of additive noise. We then find analytical expressions for a simplified toy model in which galaxies are modelled and fitted with a Gaussian with its size as a single free parameter. Even for this very simple case we find a significant effect. We also extend our analysis to a more realistic six-parameter elliptical Gaussian model. We find that the noise bias is generically of the order of the inverse-squared signal-to-noise ratio (SNR) of the galaxies and is thus of the order of a percent for galaxies of SNR 10, i.e. comparable to the weak lensing shear signal. This is nearly two orders of magnitude greater than the systematic requirements for future all-sky weak lensing surveys. We discuss possible ways to circumvent this effect, including a calibration method using simulations discussed in an associated paper.
Correlated gravitational lensing of the CMB
Eric V. Linder
1996-06-21
Cosmological inhomogeneities gravitationally deflect radiation propagating from distant sources, transforming the spatial and angular correlation functions of intrinsic source properties. For a gaussian distribution of deflections (e.g. from a primordial gaussian density perturbation spectrum or from the central limit theorem) we calculate the probability distributions for geodesic deviations. If the intrinsic variable is also gaussian, e.g. the large scale velocity flow field or cosmic microwave background temperature anisotropies, then distributions and correlation functions of the observed image sky properties can be obtained. Specialising to CMB temperature fluctuations we rederive simply the influence of independent gravitational lensing on the anisotropy angular correlation function and calculate the new effect of lensing correlated with the anisotropies, e.g. arising from the same primordial gravitational perturbation field. Characteristic magnitudes and scales are given in terms of the density power spectrum. The correlated deflection-temperature effect is shown to be negligible.
Shapelets: II. A Method for Weak Lensing Measurements
Alexandre Refregier; David Bacon
2001-05-10
Weak gravitational lensing provides a unique method to directly measure the distribution of mass in the universe. Because the distortions induced by lensing in the shape of background galaxies are small, the measurement of weak lensing requires high precision. Here, we present a new method for obtaining reliable weak shear measurements. It is based on the Shapelet basis function formalism of Refregier (2001), in which galaxy images are decomposed into several shape components, each providing independent estimates of the local shear. The formalism affords an efficient modelling and deconvolution of the Point Spread Function. Using the remarkable properties of Shapelets under distortions, we construct a simple, minimum variance estimator for the shear. We describe how we implement the method in practice, and test the method using realistic simulated images. We find our method to be stable and reliable for conditions analogous to ground-based surveys. Compared to earlier methods, our method has the advantages of being accurate, linear, mathematically well-defined, and optimally sensitive, since it uses the full shape information available for each galaxy.
A Method for Weak Lensing Observations
Nick Kaiser; Gordon Squires; Tom Broadhurst
1994-11-01
We develop and test a method for measuring the gravitational lensing induced distortion of faint background galaxies. We first describe how we locate the galaxies and measure a 2-component `polarisation' or ellipticity statistic $e_\\alpha$ whose expectation value should be proportional to the gravitational shear $\\gamma_\\alpha$. We then show that an anisotropic instrumental psf perturbs the polarisation by $\\delta e_\\alpha = P^s_{\\alpha\\beta} p_\\beta$, where $p_\\alpha$ is a measure of the psf anisotropy and $P^s_{\\alpha\\beta}$ is the `linearised smear polarisability tensor'. By estimating $P^s_{\\alpha\\beta}$ for each object we can determine $p_\\alpha$ from the foreground stars and apply a correction $-P^s_{\\alpha\\beta}p_\\beta$ to the galaxies. We test this procedure using deep high-resolution images from HST which are smeared with an anisotropic psf and then have noise added to simulate ground-based observations. We find that the procedure works very well. A similar analysis yields a linear shear polarisability tensor $P^\\gamma_{\\alpha\\beta}$ which describes the response to a gravitational shear. This calibrates the polarisation-shear relation, but only for galaxies which are well resolved. To empirically calibrate the effect of seeing on the smaller galaxies we artificially stretch HST images to simulate lensing and then degrade them as before. These experiments provide a rigorous and exacting test of the method under realistic conditions. They show that it is possible to remove the effect of instrumental psf anisotropy, and that the method provides an efficient and quantitative measurement of the gravitational shear.
Discovering Nearby Compact Objects with Gravitational Lensing
NASA Astrophysics Data System (ADS)
Di Stefano, Rosanne; Primini, F.
2013-04-01
Within a kiloparsec of Earth there are more than 10 million black holes, and ten times as many neutron stars. These compact objects have proved difficult to discover, and only a handful have been identified. Black holes and neutron stars regularly serve as gravitational lenses, however. We report on our efforts to use existing and new data to use their action as lenses to discover them. For example, several percent of the 2000 lensing events found by the OGLE and MOA teams each year are generated by nearby compact objects. We describe how this optical data, combined with x-ray data, including some to be collected by new Chandra programs, can be used to identify those events caused by compact objects. If this approach is successful, direct mass measurements will be carried out on a regular basis.
New optical surveys for gravitationally lensed quasars
NASA Astrophysics Data System (ADS)
Morgan, Nicholas D.
This thesis describes four new optical surveys for gravitationally lensed quasars. Three of these surveys take the form of traditional “targeted” searches. These include: (1)a ground-based survey targeting 173 radio-loud quasars using the 2.4 m telescope at Michigan-Dartmouth-
Iterative approach to gravitational lensing theory
Thomas P. Kling; Ezra T. Newman; Alejandro Perez
2000-01-01
We develop an iterative approach to gravitational lensing theory based on\\u000aapproximate solutions of the null geodesic equations. The approach can be\\u000aemployed in any space-time which is ``close'' to a space-time in which the null\\u000ageodesic equations can be completely integrated, such as Minkowski space-time,\\u000aRobertson-Walker cosmologies, or Schwarzschild-Kerr geometries. To illustrate\\u000athe method, we construct the iterative gravitational
Wave optics and image formation in gravitational lensing
Yasusada Nambu
2012-07-30
We discuss image formation in gravitational lensing systems using wave optics. Applying the Fresnel-Kirchhoff diffraction formula to waves scattered by a gravitational potential of a lens object, we demonstrate how images of source objects are obtained directly from wave functions without using a lens equation for gravitational lensing.
The Third Gravitational Lensing Accuracy Testing (GREAT3) Challenge Handbook
NASA Astrophysics Data System (ADS)
Mandelbaum, Rachel; Rowe, Barnaby; Bosch, James; Chang, Chihway; Courbin, Frederic; Gill, Mandeep; Jarvis, Mike; Kannawadi, Arun; Kacprzak, Tomasz; Lackner, Claire; Leauthaud, Alexie; Miyatake, Hironao; Nakajima, Reiko; Rhodes, Jason; Simet, Melanie; Zuntz, Joe; Armstrong, Bob; Bridle, Sarah; Coupon, Jean; Dietrich, Jörg P.; Gentile, Marc; Heymans, Catherine; Jurling, Alden S.; Kent, Stephen M.; Kirkby, David; Margala, Daniel; Massey, Richard; Melchior, Peter; Peterson, John; Roodman, Aaron; Schrabback, Tim
2014-05-01
The GRavitational lEnsing Accuracy Testing 3 (GREAT3) challenge is the third in a series of image analysis challenges, with a goal of testing and facilitating the development of methods for analyzing astronomical images that will be used to measure weak gravitational lensing. This measurement requires extremely precise estimation of very small galaxy shape distortions, in the presence of far larger intrinsic galaxy shapes and distortions due to the blurring kernel caused by the atmosphere, telescope optics, and instrumental effects. The GREAT3 challenge is posed to the astronomy, machine learning, and statistics communities, and includes tests of three specific effects that are of immediate relevance to upcoming weak lensing surveys, two of which have never been tested in a community challenge before. These effects include many novel aspects including realistically complex galaxy models based on high-resolution imaging from space; a spatially varying, physically motivated blurring kernel; and a combination of multiple different exposures. To facilitate entry by people new to the field, and for use as a diagnostic tool, the simulation software for the challenge is publicly available, though the exact parameters used for the challenge are blinded. Sample scripts to analyze the challenge data using existing methods will also be provided. See http://great3challenge.info and http://great3.projects.phys.ucl.ac.uk/leaderboard/ for more information.
Morphology of gravitationally lensed galaxies
NASA Astrophysics Data System (ADS)
Tyson, Tony; Kochanski, Greg; Dell'Antonio, Ian
1997-05-01
The compound optical system formed by the Hubble Space Telescope and a 200 kpc diameter gravitational objective lens provides an unprecedented view of a distant star forming galaxy in the UV. We describe a high resolution reconstruction of the UV image of the high redshift galaxy behind the z=0.4 cluster 0024+1654. Using a simultaneous parametric solution for the source morphology and the gravitational lens mass distribution, we have found a robust unique solution for the source galaxy: all five arcs map back through the lens to give the same source-plane image. The reconstructed image of this forming galaxy, has 7 milliarcsec pixels, or 200 pc resolution in two rest-frame bands: 1800+/-200 Å, and 3300+/-400 Å.
Twist and Turn: Weak Lensing Image Distortions to Second Order
David J. Bacon; Bjoern Malte Schaefer
2009-04-17
We account for all the image distortions relevant to weak gravitational lensing to second order. Besides the familiar shear, convergence, rotation and flexions, we find a new image distortion with two distinct descriptions, the twist and the turn. Like rotation, this distortion is not activated gravitationally to first order, but will be activated by systematic effects. We examine the rotational properties of twist and turn, and their effect on images in real and shapelet space. We construct estimators for the new distortion, taking into account the centroid shift which it generates. We then use these estimators to make first constraints on twist using the STAGES HST survey; we find that the mean twist estimator is consistent with zero. We measure correlation functions for our twist estimator on the survey, again finding no evidence of systematic effects.
Weak Lensing Tomography Using > 50 High Redshift, z > 0.4, Galaxy Clusters
NASA Astrophysics Data System (ADS)
Santana, Rebecca
2015-01-01
Weak gravitational lensing is a powerful and unique tool for studying galaxy clusters and cosmology. I will be presenting weak gravitational lensing shear results from a sample set of 57 high redshift galaxy clusters, z > 0.4, from the Hubble Space Telescope Advanced Camera for Surveys in several different optical bandpasses. I will discuss point spread function (psf) measurement adaptations in the principal component analysis made to improve the data. I will address the implications that increased sample size, psf changes, background galaxy cuts, mass profile choice and redshift have on the tomography signal and cosmological constraints.
Strong Gravitational Lensing in the Einstein-Proca Theory
NASA Astrophysics Data System (ADS)
Li, GuoPing; Zhang, Yan; Zhang, Li; Feng, Zhongwen; Zu, Xiaotao
2015-04-01
Adopting the strong field limit approach, we investigate the strong gravitational lensing of a spherically symmetric spacetime in the Einstein-Proca theory. With the strong field limit coefficient, three observable quantities are obtained, which are the innermost relativistic image, the deflection angle and the ratio of the flux. Comparing the observable value and the theoretical value of the strong gravitational lensing, we can verify the effectiveness of the strong gravitational lensing model.
Weak lensing mass reconstruction using wavelets
NASA Astrophysics Data System (ADS)
Starck, J.-L.; Pires, S.; Réfrégier, A.
2006-06-01
This paper presents a new method for the reconstruction of weak lensing mass maps. It uses the multiscale entropy concept, which is based on wavelets, and the False Discovery Rate (FDR) which allows us to derive robust detection levels in wavelet space. We show that this new restoration approach outperforms several standard techniques currently used for weak shear mass reconstruction. This method can also be used to separate E and B modes in the shear field, and thus test for the presence of residual systematic effects. We concentrate on large blind cosmic shear surveys, and illustrate our results using simulated shear maps derived from N-Body ?CDM simulations (Vale & White 2003) with added noise corresponding to both ground-based and space-based observations.
Theoretical Modeling of Weakly Lensed Polarized Radio Sources
Christopher R. Burns; Charles C. Dyer; Philipp P. Kronberg; Hermann-Josef Roser
2004-06-17
In this paper we present the theoretical basis for the modeling of weakly gravitationally lensed extended sources that are polarized. This technique has been used in the past to constrain the mass profiles of galaxies projected against the jet of the quasar 3C9. Since then, work has been done to improve both the measurement and theoretical modeling of the lensing signal, which manifests itself as an alignment breaking between the morphology and the polarization, parametrized as eta-g. To this end, we present the mathematical derivation of the theoretical value of eta-g as well as numerical simulations of expected signals in polarized radio jets. We use the radio jet sources 3C9 and 1253+104 as illustrative examples of the measurement and modeling of the eta-g signal. For 3C9, we present constraints on the parameters of the two intervening lenses and quantify their confidence intervals. One lens has no measured redshift and in this case, we show the dependence of mass and mass-to-light ratio on assumed redshift.
Weak gravitational shear and flexion with polar shapelets
NASA Astrophysics Data System (ADS)
Massey, Richard; Rowe, Barnaby; Refregier, Alexandre; Bacon, David J.; Bergé, Joel
2007-09-01
We derive expressions, in terms of `polar shapelets', for the image distortion operations associated with weak gravitational lensing. Shear causes galaxy shapes to become elongated, and is sensitive to the second derivative of the projected gravitational potential along their line of sight; flexion bends galaxy shapes into arcs, and is sensitive to the third derivative. Polar shapelets provide a natural representation, in which both shear and flexion transformations are compact. Through this tool, we understand progress in several weak lensing methods. We then exploit various symmetries of shapelets to construct a range of shear estimators with useful properties. Through an analogous investigation, we also explore several flexion estimators. In particular, some of the estimators can be measured simultaneously and independently for every galaxy, and will provide unique checks for systematics in future weak lensing analyses. Using simulated images from the Shear TEsting Programme, we show that we can recover input shears with no significant bias. A complete software package to parametrize astronomical images in terms of polar shapelets, and to perform a full weak lensing analysis, is available on the Internet.
Weak gravitational shear and flexion with polar shapelets
Richard Massey; Barnaby Rowe; Alexandre Refregier; David J. Bacon; Joel Berge
2007-09-01
We derive expressions, in terms of "polar shapelets", for the image distortion operations associated with weak gravitational lensing. Shear causes galaxy shapes to become elongated, and is sensitive to the second derivative of the projected gravitational potential along their line of sight; flexion bends galaxy shapes into arcs, and is sensitive to the third derivative. Polar shapelets provide a natural representation, in which both shear and flexion transformations are compact. Through this tool, we understand progress in several weak lensing methods. We then exploit various symmetries of shapelets to construct a range of shear estimators with useful properties. Through an analogous investigation, we also explore several flexion estimators. In particular, some of the estimators can be measured simultaneously and independently for every galaxy, and will provide unique checks for systematics in future weak lensing analyses. Using simulated images from the Shear TEsting Programme (STEP), we show that we can recover input shears with no significant bias. A complete software package to parametrize astronomical images in terms of polar shapelets, and to perform a full weak lensing analysis, is available at http://www.astro.caltech.edu/~rjm/shapelets/ .
Not only Gravitational Lensing, but in general Medium Lensing
NASA Astrophysics Data System (ADS)
Smarandache, Florentin
2013-05-01
According to the General Theory of Relativity the gravity curves the spacetime and everything over there follows a curved path. The space being curved near massive cosmic bodies is just a metaphor, not a fact. We dough that gravity is only geometry. The deflection of light (Gravitational Lensing) near massive cosmic bodies is not due because of a ``curved space'', but because of the medium composition (medium that could be formed by waves, particles, plasma, dust, gaseous, fluids, solids, etc.), to the medium density, medium heterogeneity, and to the electromagnetic and gravitational fields contained in that medium that light passes through. This medium deviates the light direction, because of the interactions of photons with other particles. The space is not empty; it has various nebulae and fields and corpuscles, etc. Light bends not only because of the gravity but also because of the medium gradient and refraction index, similarly as light bends when it leaves or enters a liquid, a plastic, a glass, or a quartz. The inhomogeneous medium may act as an optical lens such that its refractive index varies in a fashion, alike the Gradient-Index Lens. We talk about a Medium Lensing, which means that photons interact with other particles in the medium. For example, the interaction between a photon of electromagnetic radiation with a charged particle (let's say with a free electron), which is known as Compton Effect, produces an increase in the photon's wavelength. In the Inverse Compton Effect the low-energy photons gain energy because they were scattered by much-higher energy free electrons.
Observational signatures of the weak lensing magnification of supernovae
Yun Wang
2005-03-14
Due to the deflection of light by density fluctuations along the line of sight, weak lensing is an unavoidable systematic uncertainty in the use of type Ia supernovae (SNe Ia) as cosmological distance indicators. We derive the expected weak lensing signatures of SNe Ia by convolving the intrinsic distribution in SN Ia peak luminosity with magnification distributions of point sources. We analyze current SN Ia data, and find marginal evidence for weak lensing effects. The statistics is poor because of the small number of observed SNe Ia. Future observational data will allow unambiguous detection of the weak lensing effect of SNe Ia. The observational signatures of weak lensing of SNe Ia that we have derived provide useful templates with which future data can be compared.
COSMOS: 3D weak lensing and the growth of structure
Richard Massey; Jason Rhodes; Alexie Leauthaud; Peter Capak; Richard Ellis; Anton Koekemoer; Alexandre Refregier; Nick Scoville; James E. Taylor; Justin Albert; Joel Berge; Catherine Heymans; David Johnston; Jean-Paul Kneib; Yannick Mellier; Bahram Mobasher; Elisabetta Semboloni; Patrick Shopbell; Lidia Tasca; Ludovic Van Waerbeke
2007-02-01
We present a three dimensional cosmic shear analysis of the Hubble Space Telescope COSMOS survey, the largest ever optical imaging program performed in space. We have measured the shapes of galaxies for the tell-tale distortions caused by weak gravitational lensing, and traced the growth of that signal as a function of redshift. Using both 2D and 3D analyses, we measure cosmological parameters Omega_m, the density of matter in the universe, and sigma_8, the normalization of the matter power spectrum. The introduction of redshift information tightens the constraints by a factor of three, and also reduces the relative sampling (or "cosmic") variance compared to recent surveys that may be larger but are only two dimensional. From the 3D analysis, we find sigma_8*(Omega_m/0.3)^0.44=0.866+^0.085_-0.068 at 68% confidence limits, including both statistical and potential systematic sources of error in the total budget. Indeed, the absolute calibration of shear measurement methods is now the dominant source of uncertainty. Assuming instead a baseline cosmology to fix the geometry of the universe, we have measured the growth of structure on both linear and non-linear physical scales. Our results thus demonstrate a proof of concept for tomographic analysis techniques that have been proposed for future weak lensing surveys by a dedicated wide-field telescope in space.
The probability distribution of ellipticity: implications for weak lensing measurement
NASA Astrophysics Data System (ADS)
Viola, Massimo
2014-05-01
The weak lensing effect generates spin-2 distortions, referred to as shear, on the observable shape of distant galaxies, induced by intervening gravitational tidal fields. Traditionally, the spin-2 distortion in the light distribution of distant galaxies is measured in terms of a galaxy ellipticity. This is a very good unbiased estimator of the shear field in the limit that a galaxy is measured at infinite signal-to-noise. However, the ellipticity is always defined as a ratio between two quantities (for example, between the polarisation and measurement of the galaxy size, or between the semi-major and semi-minor axis of the galaxy) and therefore requires some non-linear combination of the image pixels. This means, in any realistic case, this would lead to biases in the measurement of the shear (and hence in the cosmological parameters) whenever noise is present in the image. This type of bias can be understood from the particular shape of the 2D probability distribution of the ellipticity of an object measured from data. Moreover this probability distribution can be used to explore strategies for calibration of noise biases in present and future weak lensing surveys (e.g. KiDS, DES, HSC,Euclid, LSST...)
Extreme value statistics of weak lensing shear peak counts
Reischke, Robert; Bartelmann, Matthias
2015-01-01
The statistics of peaks in weak gravitational lensing maps is a promising technique to constrain cosmological parameters in present and future surveys. Here we investigate its power when using general extreme value statistics which is very sensitive to the exponential tail of the halo mass function. To this end, we use an analytic method to quantify the number of weak lensing peaks caused by galaxy clusters, large-scale structures and observational noise. Doing so, we further improve the method in the regime of high signal-to-noise ratios dominated by non-linear structures by accounting for the embedding of those counts into the surrounding shear caused by large scale structures. We derive the extreme value and order statistics for both over-densities (positive peaks) and under-densities (negative peaks) and provide an optimized criterion to split a wide field survey into sub-fields in order to sample the distribution of extreme values such that the expected objects causing the largest signals are mostly due ...
COSMOS: Three-dimensional Weak Lensing and the Growth of Structure
Richard Massey; Jason Rhodes; Alexie Leauthaud; Peter Capak; Richard Ellis; Anton Koekemoer; Alexandre Réfrégier; Nick Scoville; James E. Taylor; Justin Albert; Joel Bergé; Catherine Heymans; David Johnston; Jean-Paul Kneib; Yannick Mellier; Bahram Mobasher; Elisabetta Semboloni; Patrick Shopbell; Lidia Tasca; Ludovic Van Waerbeke
2007-01-01
We present a three-dimensional cosmic shear analysis of the Hubble Space Telescope COSMOS survey, the largest ever optical imaging program performed in space. We have measured the shapes of galaxies for the telltale distortions caused by weak gravitational lensing and traced the growth of that signal as a function of redshift. Using both 2D and 3D analyses, we measure cosmological
Non-Perturbative Gravitational Lensing by Three Dimensional Mass Models
Thomas Kling
2005-01-01
Gravitational lensing is the bending and distortion of light rays by the gravitational pull of massive objects in the universe. Lensing studies are significant to the current revolution in modern astrophysics through which the ultimate questions of the universe – how did the universe begin and what conditions permit life to develop – are being answered. Although the distortion of
Point mass deflectors in gravitational lenses
NASA Technical Reports Server (NTRS)
Dolan, Joseph F.
1988-01-01
The observed properties of the six systems generally accepted as gravitational lenses are compared with the properties predicted for the images of point-mass and distributed mass deflectors. Taken as a statistical distribution, the characteristics of the six known systems strongly suggest the existence of a super-massive black hole as the effective deflecting mass in one or more of these systems. If the deflecting mass in a gravitational lens is a black hole, the distance to the deflecting mass can be determined directly from the difference in light travel time along the separate image paths. (No direct solution for the distance to the deflecting mass exists when the deflecting mass is a galaxy or a cluster of galaxies). Geometric parallaxes of objects at 1000 Mpc distance are of obvious importance in a wide variety of cosmological studies.
GLIMPSE: accurate 3D weak lensing reconstructions using sparsity
NASA Astrophysics Data System (ADS)
Leonard, Adrienne; Lanusse, François; Starck, Jean-Luc
2014-05-01
We present GLIMPSE - Gravitational Lensing Inversion and MaPping with Sparse Estimators - a new algorithm to generate density reconstructions in three dimensions from photometric weak lensing measurements. This is an extension of earlier work in one dimension aimed at applying compressive sensing theory to the inversion of gravitational lensing measurements to recover 3D density maps. Using the assumption that the density can be represented sparsely in our chosen basis - 2D transverse wavelets and 1D line-of-sight Dirac functions - we show that clusters of galaxies can be identified and accurately localized and characterized using this method. Throughout, we use simulated data consistent with the quality currently attainable in large surveys. We present a thorough statistical analysis of the errors and biases in both the redshifts of detected structures and their amplitudes. The GLIMPSE method is able to produce reconstructions at significantly higher resolution than the input data; in this paper, we show reconstructions with 6 times finer redshift resolution than the shear data. Considering cluster simulations with 0.05 ? zcl ? 0.75 and 3 × 1013 ? Mvir ? 1015 h-1 M?, we show that the redshift extent of detected peaks is typically 1-2 pixel, or ?z ? 0.07, and that we are able to recover an unbiased estimator of the redshift of a detected cluster by considering many realizations of the noise. We also recover an accurate estimator of the mass, which is largely unbiased when the redshift is known and whose bias is constrained to ?5 per cent in the majority of our simulations when the estimated redshift is taken to be the true redshift. This shows a substantial improvement over earlier 3D inversion methods, which showed redshift smearing with a typical standard deviation of ? ˜ 0.2-0.3, a significant damping of the amplitude of the peaks detected, and a bias in the detected redshift.
Biased Dark Energy Constraints from Neglecting Reduced Shear in Weak Lensing Surveys
Charles Shapiro
2008-12-03
The weak gravitational lensing of distant galaxies by large-scale structure is expected to become a powerful probe of dark energy. By measuring the ellipticities of large numbers of background galaxies, the subtle gravitational distortion called "cosmic shear" can be measured and used to constrain dark energy parameters. The observed galaxy ellipticities, however, are induced not by shear but by reduced shear, which also accounts for slight magnifications of the images. This distinction is negligible for present weak lensing surveys, but it will become more important as we improve our ability to measure and understand small-angle cosmic shear modes. I calculate the discrepancy between shear and reduced shear in the context of power spectra and cross spectra, finding the difference could be as high as 10% on the smallest accessible angular scales. I estimate how this difference will bias dark energy parameters obtained from two weak lensing methods: weak lensing tomography and the shear ratio method known as offset-linear scaling. For weak lensing tomography, ignoring the effects of reduced shear will cause future surveys considered by the Dark Energy Task Force to measure dark energy parameters that are biased by amounts comparable to their error bars. I advocate that reduced shear be properly accounted for in such surveys, and I provide a semi-analytic formula for doing so. Since reduced shear cross spectra do not follow an offset-linear scaling relation, the shear ratio method is similarly biased but with smaller significance.
BIASED DARK ENERGY CONSTRAINTS FROM NEGLECTING REDUCED SHEAR IN WEAK-LENSING SURVEYS
Shapiro, Charles [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 2EG (United Kingdom)], E-mail: charles.shapiro@port.ac.uk
2009-05-01
The weak gravitational lensing of distant galaxies by a large-scale structure is expected to become a powerful probe of dark energy. By measuring the ellipticities of large number of background galaxies, the subtle gravitational distortion called 'cosmic shear' can be measured and used to constrain dark energy parameters. The observed galaxy ellipticities, however, are induced not by shear but by reduced shear, which also accounts for slight magnifications of the images. This distinction is negligible for present weak-lensing surveys, but it will become more important as we improve our ability to measure and understand small-angle cosmic shear modes. I calculate the discrepancy between shear and reduced shear in the context of power spectra and cross spectra, finding the difference could be as high as 10% on the smallest accessible angular scales. I estimate how this difference will bias dark energy parameters obtained from two weak-lensing methods: weak-lensing tomography and the shear ratio method known as offset-linear scaling. For weak-lensing tomography, ignoring the effects of reduced shear will cause future surveys considered by the Dark Energy Task Force to measure dark energy parameters that are biased by amounts comparable to their error bars. I advocate that reduced shear be properly accounted for in such surveys, and I provide a semi-analytic formula for doing so. Since reduced shear cross spectra do not follow an offset-linear scaling relation, the shear ratio method is similarly biased but with smaller significance.
Cosmological constraints from Subaru weak lensing cluster counts
NASA Astrophysics Data System (ADS)
Hamana, Takashi; Sakurai, Junya; Koike, Michitaro; Miller, Lance
2015-06-01
We present results of weak lensing cluster counts obtained from 11-degree2 Subaru/SuprimeCam data. Although the area is much smaller than previous work dealing with weak lensing peak statistics, the number density of galaxies usable for weak lensing analysis is about twice as large. The higher galaxy number density reduces the noise in the weak lensing mass maps, and thus increases the signal-to-noise ratio (S/N) of peaks of the lensing signal due to massive clusters. This enables us to construct a weak lensing selected cluster sample by adopting a high threshold S/N, such that the contamination rate due to false signals is small. We find six peaks with S/N > 5. For all the peaks, previously identified clusters of galaxies are matched within a separation of 1', demonstrating good correspondence between the peaks and clusters of galaxies. We evaluate the statistical error in the weak lensing cluster counts using mock weak lensing data generated from full-sky ray-tracing simulations, and find Npeak = 6 ± 3.1 in an effective area of 9.0 degree2. We compare the measured weak lensing cluster counts with the theoretical model prediction based on halo models and place the constraint on the ?m-?8 plane which is found to be consistent with currently standard ?CDM models. It is demonstrated that the weak lensing cluster counts can place a unique constraint on the ?8-c0 plane, where c0 is the normalization of the dark matter halo mass-concentration relationship. Finally we discuss prospects for ongoing/future wide field optical galaxy surveys.
Analytical Kerr black hole lensing in the weak deflection limit
Sereno, Mauro [Institut fuer Theoretische Physik, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland); De Luca, Fabiana [Institut fuer Theoretische Physik, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zurich (Switzerland) and Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno, via Allende, I-84081 Baronissi (SA) (Italy)
2006-12-15
We present an analytical treatment of gravitational lensing by a Kerr black hole in the weak deflection limit. Lightlike geodesics are expanded as a Taylor series up to and including third-order terms in m/b and a/b, where m is the black hole mass, a the angular momentum, and b the impact parameter of the light ray. Positions and magnifications of individual images are computed with a perturbative analysis. At this order, the degeneracy with the translated Schwarzschild lens is broken. The critical curve is still a circle displaced from the black hole position in the equatorial direction and the corresponding caustic is pointlike. The degeneracy between the black hole spin and its inclination relative to the observer is broken through the angular coordinates of the perturbed images.
Weak lensing by voids in modified lensing potentials
Barreira, Alexandre; Li, Baojiu; Baugh, Carlton; Pascoli, Silvia
2015-01-01
We study lensing by voids in Cubic Galileon and Nonlocal gravity cosmologies, which are examples of theories of gravity that modify the lensing potential. We find voids in the dark matter and halo density fields of N-body simulations and compute their lensing signal analytically from the void density profiles, which we show are well fit by a simple analytical formula. In the Cubic Galileon model, the modifications to gravity inside voids are not screened and they approximately double the size of the lensing effects compared to GR. The difference is largely determined by the direct effects of the fifth force on lensing and less so by the modified density profiles. For this model, we also discuss the subtle impact on the force and lensing calculations caused by the screening effects of haloes that exist in and around voids. In the Nonlocal model, the impact of the modified density profiles and the direct modifications to lensing are comparable, but they boost the lensing signal by only $\\approx 10\\%$, compared ...
Weak lensing goes bananas: What flexion really measures
Peter Schneider; Xinzhong Er
2007-09-07
In weak gravitational lensing, the image distortion caused by shear measures the projected tidal gravitational field of the deflecting mass distribution. To lowest order, the shear is proportional to the mean image ellipticity. If the image sizes are not small compared to the scale over which the shear varies, higher-order distortions occur, called flexion. For ordinary weak lensing, the observable quantity is not the shear, but the reduced shear, owing to the mass-sheet degeneracy. Likewise, the flexion itself is unobservable. Rather, higher-order image distortions measure the reduced flexion, i.e., derivatives of the reduced shear. We derive the corresponding lens equation in terms of the reduced flexion and calculate the resulting relation between brightness moments of source and image. Assuming an isotropic distribution of source orientations, estimates for the reduced shear and flexion are obtained; these are then tested with simulations. In particular, the presence of flexion affects the determination of the reduced shear. The results of these simulations yield the amount of bias of the estimators, as a function of the shear and flexion. We point out and quantify a fundamental limitation of the flexion formalism, in terms of the product of reduced flexion and source size. If this product increases above the derived threshold, multiple images of the source are formed locally, and the formalism breaks down. Finally, we show how a general (reduced) flexion field can be decomposed into its four components: two of them are due to a shear field, carrying an E- and B-mode in general. The other two components do not correspond to a shear field; they can also be split up into corresponding E- and B-modes.
Three Gravitationally Lensed Supernovae Behind Clash Galaxy Clusters
NASA Technical Reports Server (NTRS)
Patel, Brandon; McCully, Curtis; Jha, Saurbh W.; Rodney, Steven A.; Jones, David O.; Graur, Or; Merten, Julian; Zitrin, Adi; Riess, Adam G.; Matheson, Thomas; Sako, Masao; Holoien, Thomas W. -S.; Postman, Marc; Coe, Dan; Bartelmann, Matthias; Balestra, Italo; Benitez, Narciso; Bouwens, Rychard; Bradley, Larry; Broadhurst, Tom; Cenko, Stephen Bradley; Donahue, Megan; Filippenko, Alexei V.; Ford, Holland; Garnavich, Peter; Grillo, Claudio; Infante, Leopoldo; Jouvel, Stephanie; Kelson, Daniel; Koekemoer, Anton; Lahav, Ofer; Lemze, Doron; Maoz, Dan; Medezinski, Elinor; Melchior, Peter; Meneghetti, Massimo; Molino, Alberto; Moustakas, John; Moustakas, Leonidas A.; Nonino, Mario; Rosati, Piero; Seitz, Stella; Strolger, Louis G.; Umetsu, Keiichi; Zheng, Wei
2014-01-01
We report observations of three gravitationally lensed supernovae (SNe) in the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program. These objects, SN CLO12Car (z = 1.28), SN CLN12Did (z = 0.85), and SN CLA11Tib (z = 1.14), are located behind three different clusters, MACSJ1720.2+3536 (z = 0.391), RXJ1532.9+3021 (z = 0.345), and A383 (z = 0.187), respectively. Each SN was detected in Hubble Space Telescope optical and infrared images. Based on photometric classification, we find that SNe CLO12Car and CLN12Did are likely to be Type Ia supernovae (SNe Ia), while the classification of SN CLA11Tib is inconclusive. Using multi-color light-curve fits to determine a standardized SN Ia luminosity distance, we infer that SN CLO12Car was approx. 1.0 +/- 0.2 mag brighter than field SNe Ia at a similar redshift and ascribe this to gravitational lens magnification. Similarly, SN CLN12Did is approx. 0.2 +/- 0.2 mag brighter than field SNe Ia. We derive independent estimates of the predicted magnification from CLASH strong+weak-lensing maps of the clusters (in magnitude units, 2.5 log10 µ): 0.83 +/- 0.16 mag for SN CLO12Car, 0.28 +/- 0.08 mag for SN CLN12Did, and 0.43 +/- 0.11 mag for SN CLA11Tib. The two SNe Ia provide a new test of the cluster lens model predictions: we find that the magnifications based on the SN Ia brightness and those predicted by the lens maps are consistent. Our results herald the promise of future observations of samples of cluster-lensed SNe Ia (from the ground or space) to help illuminate the dark-matter distribution in clusters of galaxies, through the direct determination of absolute magnifications.
FASTLens (FAst STatistics for weak Lensing) : Fast method for Weak Lensing Statistics and map making
S. Pires; J. -L. Starck; A. Amara; R. Teyssier; A. Refregier; J. Fadili
2009-02-19
With increasingly large data sets, weak lensing measurements are able to measure cosmological parameters with ever greater precision. However this increased accuracy also places greater demands on the statistical tools used to extract the available information. To date, the majority of lensing analyses use the two point-statistics of the cosmic shear field. These can either be studied directly using the two-point correlation function, or in Fourier space, using the power spectrum. But analyzing weak lensing data inevitably involves the masking out of regions or example to remove bright stars from the field. Masking out the stars is common practice but the gaps in the data need proper handling. In this paper, we show how an inpainting technique allows us to properly fill in these gaps with only $N \\log N$ operations, leading to a new image from which we can compute straight forwardly and with a very good accuracy both the pow er spectrum and the bispectrum. We propose then a new method to compute the bispectrum with a polar FFT algorithm, which has the main advantage of avoiding any interpolation in the Fourier domain. Finally we propose a new method for dark matter mass map reconstruction from shear observations which integrates this new inpainting concept. A range of examples based on 3D N-body simulations illustrates the results.
Gravitational lensing in a non-uniform plasma
G. S. Bisnovatyi-Kogan; O. Yu. Tsupko
2010-06-11
We develop a model of gravitational lensing in a non-uniform plasma. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and of a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. We take into account both effects, and derive the expression for the lensing angle in the case of a strongly nonuniform plasma in presence of the gravitation. Dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, which strongest action is for very long radiowaves. We discuss the observational appearances of this effect for the gravitational lens with a Schwarzschild metric, surrounded by a uniform plasma. We obtain formulae for the lensing angle and the magnification factors in this case and discuss a possibility of observation of this effect by the planned VLBI space project Radioastron. We also consider models with a nonuniform plasma distribution. For different gravitational lens models we compare the corrections to the vacuum lensing due to the gravitational effect in plasma, and due to the plasma inhomogeneity. We have shown that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.
Disentangling dark sector models using weak lensing statistics
Giocoli, Carlo; Baldi, Marco; Meneghetti, Massimo; Moscardini, Lauro; Petkova, Margarita; -,; Astronomia, Dipartimento di Fisica e; di Bologna, Alma Mater Studiorum Università; di Bologna, INAF - Osservatorio Astronomico; di Bologna, INFN - Sezione; Université, Aix Marseille; CNRS,; LAM,; France,; Laboratory, Jet Propulsion; Physics, Department of; Ludwig-Maximilians-Universitaet),
2015-01-01
We perform multi-plane ray-tracing using the GLAMER gravitational lensing code within high-resolution light-cones extracted from the CoDECS simulations: a suite of cosmological runs featuring a coupling between Dark Energy and Cold Dark Matter. We show that the presence of the coupling is evident not only in the redshift evolution of the normalisation of the convergence power spectrum, but also in differences in non-linear structure formation with respect to {\\Lambda}CDM. Using a tomographic approach under the assumption of a {\\Lambda}CDM cosmology, we demonstrate that weak lensing measurements would result in a {\\sigma}8 value that changes with the source redshift if the true underlying cosmology is a coupled Dark Energy one. This provides a generic null test for these types of models. We also find that different models of coupled Dark Energy can show either an enhanced or a suppressed correlation between convergence maps with differing source redshifts as compared to {\\Lambda}CDM. This would provide a direc...
Aberration by gravitational lenses in motion
Simonetta Frittelli
2003-01-01
It is known that a fully relativistic integration of the null geodesics of a weak perturbation of flat space-time leads to a correction of order v\\/c to the bending angle and time delay due to a gravitational lens in slow motion with small acceleration. The existence of the v\\/c correction was verified by the very long baseline interferometry experiment of
Power Spectra Estimation for Weak Lensing
Wayne Hu; Martin White
2000-10-18
We develop a method for estimating the shear power spectra from weak lensing observations and test it on simulated data. Our method describes the shear field in terms of angular power spectra and cross correlation of the two shear modes which differ under parity transformations. Two of the three power spectra can be used to monitor unknown sources of noise in the data. The power spectra are decomposed in a model independent manner in terms of ``band-powers'' which are then extracted from the data using a quadratic estimator to find the maximum of the likelihood and its local curvature (for error estimates). We test the method against simulated data from Gaussian realizations and cosmological N-body simulations. In the Gaussian case, the mean bandpowers and their covariance are well recovered even for irregular (or sparsely) sampled fields. The mild non-Gaussianity of the N-body realizations causes a slight underestimation of the errors that becomes negligible for scales much larger than several arcminutes and does not bias the recovered band powers.
Weak lensing calibration of mass bias in the RBC X-ray galaxy cluster catalog
Simet, Melanie; Mandelbaum, Rachel; Seljak, Uroš
2015-01-01
The use of large, X-ray selected galaxy cluster catalogs for cosmological analyses requires a thorough understanding of the X-ray mass estimates, including the possibility of biases due to the assumption of hydrostatic equilibrium. Weak gravitational lensing is an ideal method to shed light on such issues, due to its insensitivity to the cluster dynamical state. We perform a weak lensing calibration of 166 galaxy clusters from the RBC cluster catalog and compare our results to the hydrostatic X-ray masses from that catalog. To interpret the weak lensing signal in terms of cluster masses, we compare the lensing signal to simple theoretical Navarro-Frenk-White models and to simulated cluster lensing profiles, including complications such as cluster substructure, projected large-scale structure, and Malmquist bias. We find evidence of underestimation in the X-ray masses, as expected, with $= 0.66_{-0.12}^{+0.07}$ for our best-fit model, a more than $4\\sigma$ detection of a bias between X-ray and weak lensing mas...
Detection of dark galaxies by gravitational lensing
NASA Astrophysics Data System (ADS)
Kochanski, G. P.; dell'Antonio, I. P.; Tyson, J. A.
1997-12-01
Gravitational lensing gives one the opportunity to measure a mass distribution, independent of the presence of luminous matter. We have made an detailed reconstruction of the mass in the galaxy cluster CL0024+1654, to search for and detect ``dark galaxies" directly. Because we have multiple, well-resolved images of a very complex background source, we are able to reconstruct the mass distribution in exquisite detail. In addition to a smooth dark matter distribution and to the mass associated with visible galaxies, we find several statistically significant Mtot ~ 10(10) Msun clumps with little or no associated light. We will present the analysis of the mass and the limits on the luminosity of these objects. We also discuss the implications of the existence of these objects for theories of structure formation and cluster dynamics.
Gravitational lenses in the dark Universe
R. C. Freitas; S. V. B. Gonçalves; A. M. Oliveira
2013-08-30
We discuss how different cosmological models of the Universe affect the probability that a background source has multiple images related by an angular distance $\\theta_E$ of the line of sight, \\textit{i. e.}, the optical depth of gravitational lensing. We examine some cosmological models for different values of the density parameter $\\Omega_i$: i) the cold dark matter model, ii) the $\\Lambda$CDM model, iii) the Bose-Einstein condensate dark matter model, iv) the Chaplygin gas model, v) the viscous fluid cosmological model and vi) the holographic dark energy model. We note that the dependence of the energy-matter content of the universe profoundly alters the frequency of multiple quasar image.
Higher-order Catastrophes in Gravitational Lenses
NASA Astrophysics Data System (ADS)
Baltz, E. A.; Blandford, R. D.; Marshall, P. J.
2005-12-01
Future wide field sky surveys such as have been proposed by the SNAP and LSST teams will contain large numbers of gravitational lens systems. Such large samples afford the possibility of observing rare, exotic lens configurations in the form of higher order catastrophes. The fold (critical curve) and cusp catastrophes are well known; pairs of images are created for sources at these positions. Less well known are the swallowtail, butterfly and the umbilics. We have constructed a raytracing code that evaluates quantities which locally characterize these higher-order catastrophes. This necessarily goes beyond the usual deflection angle and magnification. Globally, catastrophes represent a change in the number of images or a change in the topology of the critical curves. We present a preliminary study of the detectability of lens systems exhibiting these features in large samples of lenses. Such systems depend sensitively on the source--lens configuration. It may be possible to find ``golden lenses'' which can be modeled much more accurately than is usually possible, giving insight into the shapes and density profiles of dark matter halos. This work was supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
GLAMER - II. Multiple-plane gravitational lensing
NASA Astrophysics Data System (ADS)
Petkova, Margarita; Metcalf, R. Benton; Giocoli, Carlo
2014-12-01
We present an extension to multiple planes of the gravitational lensing code GLAMER. The method entails projecting the mass in the observed light-cone on to a discrete number of lens planes and inverse ray-shooting from the image to the source plane. The mass on each plane can be represented as haloes, simulation particles, a projected mass map extracted form a numerical simulation or any combination of these. The image finding is done in a source-oriented fashion, where only regions of interest are iteratively refined on an initially coarse image plane grid. The calculations are performed in parallel on shared memory machines. The code is able to handle different types of analytic haloes (NFW, NSIE, power law, etc.), haloes extracted from numerical simulations and clusters constructed from semi-analytic models (MOKA). Likewise, there are several different options for modelling the source(s) which can be distributed throughout the light-cone. The distribution of matter in the light-cone can be either taken from a pre-existing N-body numerical simulations, from halo catalogues, or are generated from an analytic mass function. We present several tests of the code and demonstrate some of its applications such as generating mock images of galaxy and galaxy cluster lenses.
Can strong gravitational lensing constrain dark energy?
Lee, Seokcheon [Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (China); Ng, K.-W. [Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (China); Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan 11529 (China)
2007-08-15
We discuss the ratio of the angular diameter distances from the source to the lens, D{sub ds}, and to the observer at present, D{sub s}, for various dark energy models. It is well known that the difference of D{sub s}s between the models is apparent and this quantity is used for the analysis of Type Ia supernovae. However we investigate the difference between the ratio of the angular diameter distances for a cosmological constant, (D{sub ds}/D{sub s}){sup {lambda}}, and that for other dark energy models, (D{sub ds}/D{sub s}){sup other}, in this paper. It has been known that there is lens model degeneracy in using strong gravitational lensing. Thus, we investigate the model independent observable quantity, Einstein radius ({theta}{sub E}), which is proportional to both D{sub ds}/D{sub s} and velocity dispersion squared, {sigma}{sub v}{sup 2}. D{sub ds}/D{sub s} values depend on the parameters of each dark energy model individually. However, (D{sub ds}/D{sub s}){sup {lambda}}-(D{sub ds}/D{sub s}){sup other} for the various dark energy models, is well within the error of {sigma}{sub v} for most of the parameter spaces of the dark energy models. Thus, a single strong gravitational lensing by use of the Einstein radius may not be a proper method to investigate the property of dark energy. However, better understanding to the mass profile of clusters in the future or other methods related to arc statistics rather than the distances may be used for constraints on dark energy.
Probing the cosmic web: intercluster filament detection using gravitational lensing
James M. G. Mead; Lindsay J. King; Ian G. McCarthy
2010-01-01
The problem of detecting dark matter filaments in the cosmic web is considered. Weak lensing is an ideal probe of dark matter, and therefore forms the basis of particularly promising detection methods. We consider and develop a number of weak lensing techniques that could be used to detect filaments in individual or stacked cluster fields, and apply them to synthetic
Cosmography with strong lensing of LISA gravitational wave sources
NASA Astrophysics Data System (ADS)
Sereno, M.; Jetzer, Ph.; Sesana, A.; Volonteri, M.
2011-08-01
Laser Interferometer Space Antenna (LISA) might detect gravitational waves from mergers of massive black hole binaries strongly lensed by intervening galaxies. The detection of multiple gravitational lensing events would provide a new tool for cosmography. Constraints on cosmological parameters could be placed by exploiting either lensing statistics of strongly lensed sources or time-delay measurements of lensed gravitational wave signals. These lensing methods do not need the measurement of the redshifts of the sources and the identification of their electromagnetic counterparts. They would extend cosmological probes to redshift z? 10 and are then complementary to other lower or higher redshift tests, such as Type Ia supernovae or cosmic microwave background. The accuracy of lensing tests strongly depends on the formation history of the merging binaries, and the related number of total detectable multiple images. Lensing amplification might also help to find the host galaxies. Any measurement of the source redshifts would allow us to exploit the distance-redshift test in combination with lensing methods. Time-delay analyses might measure the Hubble parameter H0 with an accuracy of ?10 km s-1 Mpc-1. With prior knowledge of H0, lensing statistics and time delays might constrain the dark matter density (??M? 0.08, due to parameter degeneracy). Inclusion of our methods with other available orthogonal techniques might significantly reduce the uncertainty contours for ?M and the dark energy equation of state.
THE MISSING WEAK LENSING MASS IN A781
Cook, Richard I.; Dell'Antonio, I. P. [Department of Physics, Brown University, Providence, RI 02912 (United States)
2012-05-10
Measuring cluster masses accurately is important for testing the cosmological paradigm. Weak lensing is one of the most promising methods for detecting, measuring, and calibrating cluster mass estimates made using other mass proxies (e.g., X-ray, Sunyaev-Zel'dovich effect, spectroscopy). However, it is still essential to characterize and understand the causes of systematic error and bias in weak lensing measurements. A781D is a cluster of galaxies with a mass and redshift that places it well within the theoretical detection limits of weak lensing analyses from the ground yet has evaded detection in previous weak lensing studies. Previous weak lensing measurements in the region surrounding this cluster from the Deep Lens Survey were unable to detect it and placed a 1{sigma} limit on the mass of <5 Multiplication-Sign 10{sup 13} M{sub Sun }. Given independent estimates of the cluster mass by X-ray and spectroscopic measurements and its spectroscopically confirmed redshift of 0.43, it is difficult to explain its absence from the weak lensing mass reconstructions. We re-analyzed this cluster using imaging from the Orthogonal Parallel Transfer Imaging Camera and archival Suprime-Cam data. We successfully detect A781A in both analyses, but A781D remains undetected. We use these two new independent analyses to rule out systematic effects from the telescope, instrument, and point-spread function correction as the cause of the null detection. We also demonstrate the first use of an orthogonal transfer camera for weak lensing analysis and demonstrate its suitability for weak lensing studies.
Optimal surveys for weak-lensing tomography
NASA Astrophysics Data System (ADS)
Amara, Adam; Réfrégier, Alexandre
2007-11-01
Weak-lensing surveys provide a powerful probe of dark energy through the measurement of the mass distribution of the local Universe. A number of ground-based and space-based surveys are being planned for this purpose. Here, we study the optimal strategy for these future surveys using the joint constraints on the equation-of-state parameter wn and its evolution wa as a figure of merit by considering power spectrum tomography. For this purpose, we first consider an `ideal' survey which is both wide and deep and exempt from systematics. We find that such a survey has great potential for dark energy studies, reaching 1? precisions of 1 and 10 per cent on the two parameters, respectively. We then study the relative impact of various limitations by degrading this ideal survey. In particular, we consider the effect of sky coverage, survey depth, shape measurement systematics, photometric redshift systematics and uncertainties in the non-linear power spectrum predictions. We find that, for a given observing time, it is always advantageous to choose a wide rather than a deep survey geometry. We also find that the dark energy constraints from power spectrum tomography are robust to photometric redshift errors and catastrophic failures, if a spectroscopic calibration sample of 104-105 galaxies are available. The impact of these systematics is small compared to the limitations that come from potential uncertainties in the power spectrum, due to shear measurement and theoretical errors. To help the planning of future surveys, we summarize our results with comprehensive scaling relations which avoid the need for full Fisher matrix calculations.
Optimal Surveys for Weak Lensing Tomography
Adam Amara; Alexandre Refregier
2007-08-15
Weak lensing surveys provide a powerful probe of dark energy through the measurement of the mass distribution of the local Universe. A number of ground-based and space-based surveys are being planned for this purpose. Here, we study the optimal strategy for these future surveys using the joint constraints on the equation of state parameter wn and its evolution wa as a figure of merit by considering power spectrum tomography. For this purpose, we first consider an `ideal' survey which is both wide and deep and exempt from systematics. We find that such a survey has great potential for dark energy studies, reaching one sigma precisions of 1% and 10% on the two parameters respectively. We then study the relative impact of various limitations by degrading this ideal survey. In particular, we consider the effect of sky coverage, survey depth, shape measurements systematics, photometric redshifts systematics and uncertainties in the non-linear power spectrum predictions. We find that, for a given observing time, it is always advantageous to choose a wide rather than a deep survey geometry. We also find that the dark energy constraints from power spectrum tomography are robust to photometric redshift errors and catastrophic failures, if a spectroscopic calibration sample of 10^4-10^5 galaxies is available. The impact of these systematics is small compared to the limitations that come from potential uncertainties in the power spectrum, due to shear measurement and theoretical errors. To help the planning of future surveys, we summarize our results with comprehensive scaling relations which avoid the need for full Fisher matrix calculations.
A Catalog of Mass Models for Gravitational Lensing
Charles R. Keeton
2002-06-04
Many different families of mass models are used in modern applications of strong gravitational lensing. I review a wide range of popular models, with two points of emphasis: (1) a discussion of strategies for building models suited to a particular lensing problem; and (2) a summary of technical results for a canonical set of models. All of the models reviewed here are included in publicly-available lensing software called gravlens.
Gravitational Lenses and the Structure and Evolution of Galaxies
NASA Technical Reports Server (NTRS)
Kockanek, Christopher; Oliversen, Ronald J. (Technical Monitor)
2002-01-01
This grant has supported papers which present a new direction in the theory and interpretation of gravitational lenses. During the second year we have focused more closely on the relationship of baryons and dark matter.
What is Gravitational Lensing? (LBNL Summer Lecture Series)
Leauthaud, Alexie; Nakajima, Reiko [Berkeley Center for Cosmological Physics
2011-04-28
Summer Lecture Series 2009: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
What is Gravitational Lensing? (LBNL Summer Lecture Series)
Leauthaud, Alexie; Nakajima, Reiko (Berkeley Center for Cosmological Physics) [Berkeley Center for Cosmological Physics
2009-07-28
Summer Lecture Series 2009: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
An atlas of predicted exotic gravitational lenses
NASA Astrophysics Data System (ADS)
Orban de Xivry, Gilles; Marshall, Phil
2009-10-01
Wide-field optical imaging surveys will contain tens of thousands of new strong gravitational lenses. Some of these will have new and unusual image configurations, and so will enable new applications: for example, systems with high image multiplicity will allow more detailed study of galaxy and group mass distributions, while high magnification is needed to super-resolve the faintest objects in the high-redshift universe. Inspired by a set of six unusual lens systems [including five selected from the Sloan Lens ACS survey (SLACS) and Strong Lens Legacy Survey (SL2S), plus the cluster Abell 1703], we consider several types of multi-component, physically motivated lens potentials, and use the ray-tracing code GLAMROC to predict exotic image configurations. We also investigate the effects of galaxy source profile and size, and use realistic sources to predict observable magnifications and estimate very approximate relative cross-sections. We find that lens galaxies with misaligned discs and bulges produce swallowtail and butterfly catastrophes, observable as `broken' Einstein rings. Binary or merging galaxies show elliptic umbilic catastrophes, leading to an unusual Y-shaped configuration of four merging images. While not the maximum magnification configuration possible, it offers the possibility of mapping the local small-scale mass distribution. We estimate the approximate abundance of each of these exotic galaxy-scale lenses to be ~1 per all-sky survey. In higher mass systems, a wide range of caustic structures are expected, as already seen in many cluster lens systems. We interpret the central ring and its counter-image in Abell 1703 as a `hyperbolic umbilic' configuration, with total magnification ~100 (depending on source size). The abundance of such configurations is also estimated to be ~1 per all-sky survey.
Weak lensing generated by vector perturbations and detectability of cosmic strings
Yamauchi, Daisuke [Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Namikawa, Toshiya [Department of Physics, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-033 (Japan); Taruya, Atsushi, E-mail: yamauchi@icrr.u-tokyo.ac.jp, E-mail: namikawa@utap.phys.s.u-tokyo.ac.jp, E-mail: ataruya@utap.phys.s.u-tokyo.ac.jp [Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-033 (Japan)
2012-10-01
We study the observational signature of vector metric perturbations through the effect of weak gravitational lensing. In the presence of vector perturbations, the non-vanishing signals for B-mode cosmic shear and curl-mode deflection angle, which have never appeared in the case of scalar metric perturbations, naturally arise. Solving the geodesic and geodesic deviation equations, we drive the full-sky formulas for angular power spectra of weak lensing signals, and give the explicit expressions for E-/B-mode cosmic shear and gradient-/curl-mode deflection angle. As a possible source for seeding vector perturbations, we then consider a cosmic string network, and discuss its detectability from upcoming weak lensing and CMB measurements. Based on the formulas and a simple model for cosmic string network, we calculate the angular power spectra and expected signal-to-noise ratios for the B-mode cosmic shear and curl-mode deflection angle. We find that the weak lensing signals are enhanced for a smaller intercommuting probability of the string network, P, and they are potentially detectable from the upcoming cosmic shear and CMB lensing observations. For P ? 10{sup ?1}, the minimum detectable tension of the cosmic string will be down to G? ? 5 × 10{sup ?8}. With a theoretically inferred smallest value P ? 10{sup ?3}, we could even detect the string with G? ? 5 × 10{sup ?10}.
Gravitational lensing by globular clusters and Arp objects
A. Yushchenko; Chulhee Kim; A. Sergeev; P. Niarchos; V. Manimanis
2003-08-20
We try to explain quasar-galaxy associations by gravitational lensing by globular clusters, located in the halos of foreground galaxies. We propose observational test for verification of this hypothesis. We processed SUPERCOSMOS sky survey and found overdensities of star-like sources with zero proper motions in the vicinities of foreground galaxies from CfA3 catalog. We show mean effect for galaxies with different redshifts. Two effects can explain observational data - these are lensing by globular clusters and lensing by dwarf galaxies. We made CCD 3-color photometry with 2.0-1.2 meter telescopes to select extremely lensed objects around several galaxies for spectroscopic observations.
Gravitational Lenses and the Structure and Evolution of Galaxies
NASA Technical Reports Server (NTRS)
Kochanek, Christopher
2003-01-01
The grant has supported the completion of 16 papers and 4 conference proceedings to date. During the first year of the project we completed five papers, each of which represents a new direction in the theory and interpretation of gravitational lenses. In the first paper, "The Importance of Einstein Rings", we developed the first theory for the formation and structure of the Einstein rings formed by lensing extended sources like the host galaxies of quasar and radio sources. We applied the theory to three lenses with lensed host galaxies. For the time delay lens PG 1115+080 we found that the structure of the Einstein ring ruled out models of the gravitational potential which permitted a large Hubble constant (70 km/s Mpc). In the second paper, :Cusped Mass Models Of Gravitational Lenses", we introduced a new class of lens models where the central density is characterized by a cusp ( rho proportional to tau(sup -gamma), 1 less than gamma less than 2) as in most modern models and theories of galaxies rather than a finite core radius. In the third paper, "Global Probes of the Impact of Baryons on Dark Matter Halos", we made the first globally consistent models for the separation distribution of gravitational lenses including both galaxy and cluster lenses. We show that the key physics for the origin of the sharp separation cutoff in the separation distribution near 3 arc sec is the effect of the cooling baryons in galaxies on the density structure of the system.
Constraints on cosmological models from strong gravitational lensing systems
NASA Astrophysics Data System (ADS)
Cao, Shuo; Pan, Yu; Biesiada, Marek; Godlowski, Wlodzimierz; Zhu, Zong-Hong
2012-03-01
Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances Dds/Ds from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (?CDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.
Constraints on cosmological models from strong gravitational lensing systems
Cao, Shuo; Pan, Yu; Zhu, Zong-Hong [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Biesiada, Marek [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Godlowski, Wlodzimierz, E-mail: baodingcaoshuo@163.com, E-mail: panyu@cqupt.edu.cn, E-mail: biesiada@us.edu.pl, E-mail: godlowski@uni.opole.pl, E-mail: zhuzh@bnu.edu.cn [Institute of Physics, Opole University, Oleska 48, 45-052 Opole (Poland)
2012-03-01
Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances D{sub ds}/D{sub s} from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (?CDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.
How Sensitive Are Weak Lensing Statistics to Dark Energy Content?
Dipak Munshi; Yun Wang
2002-10-04
Future weak lensing surveys will directly probe the clustering of dark matter, in addition to providing a test for various cosmological models. Recent studies have provided us with the tools which can be used to construct the complete probability distribution function for convergence fields. It is also possible to construct the bias associated with the hot-spots in convergence maps. These techniques can be used in both the quasi-linear and the highly nonlinear regimes using various well developed numerical methods. We use these results here to study the weak lensing statistics of cosmological models with dark energy. We study how well various classes of dark energy models can be distinguished from models with a cosmological constant. We find that the ratio of the square root of the variance of convergence is complementary to the convergence skewness $S_3$ in probing dark energy equation of state; it can be used to predict the expected difference in weak lensing statistics between various dark energy models, and for choosing optimized smoothing angles to constrain a given class of dark energy models. Our results should be useful for probing dark energy using future weak lensing data with high statistics from galaxy weak lensing surveys and supernova pencil beam surveys.
Scaling the universe: Gravitational lenses and the Hubble constant
Myers, Steven T.
1999-01-01
Gravitational lenses, besides being interesting in their own right, have been demonstrated to be suitable as “gravitational standard rulers” for the measurement of the rate of expansion of the Universe (Ho), as well as to constrain the values of the cosmological parameters such as ?o and ?o that control the evolution of the volume of the Universe with cosmic time. PMID:10200245
Strong Gravitational Lensing in a Brane-World Black Hole
NASA Astrophysics Data System (ADS)
Li, GuoPing; Cao, Biao; Feng, Zhongwen; Zu, Xiaotao
2015-03-01
Adopting the strong field limit approach, we investigated the strong gravitational lensing in a Brane-World black hole, which means that the strong field limit coefficients and the deflection angle in this gravitational field are obtained. With this result, it can be said with certainly that the strong gravitational lensing is related to the metric of gravitational fields closely, the cosmology parameter ? and the dark matter parameter ? come from the Brane-World black hole exerts a great influence on it. Comparing with the Schwarzschild-AdS spacetime and the Schwarzschild-XCMD spacetime, the parameters ?, ? of black holes have the similar effects on the gravitational lensing. In some way, we infer that the real gravitational fields in our universe can be described by this metric, so the results of the strong gravitational lensing in this spacetime will be more reasonable for us to observe. Finally, it has to be noticed that the influence which the parameters ?, ? exerted on the main observable quantities of this gravitational field is discussed.
Is There a Quad Problem among Optical Gravitational Lenses?
Masamune Oguri
2007-05-29
Most of optical gravitational lenses recently discovered in the Sloan Digital Sky Survey Quasar Lens Search (SQLS) have two-images rather than four-images, in marked contrast to radio lenses for which the fraction of four-image lenses (quad fraction) is quite high. We revisit the quad fraction among optical lenses by taking the selection function of the SQLS into account. We find that the current observed quad fraction in the SQLS is indeed lower than, but consistent with, the prediction of our theoretical model. The low quad fraction among optical lenses, together with the high quad fraction among radio lenses, implies that the quasar optical luminosity function has a relatively shallow faint end slope.
Is There a Quad Problem Among Pptical Gravitational Lenses?
Oguri, Masamune
2007-06-06
Most of optical gravitational lenses recently discovered in the Sloan Digital Sky Survey Quasar Lens Search (SQLS) have two-images rather than four images, in marked contrast to radio lenses for which the fraction of four-image lenses (quad fraction) is quite high. We revisit the quad fraction among optical lenses by taking the selection function of the SQLS into account. We find that the current observed quad fraction in the SQLS is indeed lower than, but consistent with, the prediction of our theoretical model. The low quad fraction among optical lenses, together with the high quad fraction among radio lenses, implies that the quasar optical luminosity function has a relatively shallow faint end slope.
Gravitational lensing by black holes: The case of Sgr A*
Bozza, V. [Dipartimento di Fisica E.R. Caianiello, Università di Salerno, Italy. Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy)
2014-01-14
The strong gravitational fields created by black holes dramatically affect the propagation of photons by bending their trajectories. Gravitational lensing thus stands as the main source of information on the space-time structure in such extreme regimes. We will review the theory and phenomenology of gravitational lensing by black holes, with the generation of higher order images and giant caustics by rotating black holes. We will then focus on Sgr A*, the black hole at the center of the Milky Way, for which next-to-come technology will be able to reach resolutions of the order of the Schwarzschild radius and ultimately test the existence of an event horizon.
Isolating Geometry in Weak-Lensing Measurements
Jun Zhang; Lam Hui; Albert Stebbins
2005-01-01
Given a foreground galaxy-density field or shear field, its cross-correlation with the shear field from a background population of source galaxies scales with the source redshift in a way that is specific to lensing. Such a source scaling can be exploited to effectively measure geometrical distances as a function of redshift and thereby constrain dark energy properties, free of any
GREAT3: The Third Gravitational Lensing Accuracy Testing Challenge
NASA Astrophysics Data System (ADS)
Simet, Melanie; Mandelbaum, R.; Rowe, B.; Great3 Collaboration
2014-01-01
We describe the ongoing weak lensing community data challenge, GREAT3, and the associated open-source image simulation software, GalSim. The GREAT3 challenge tests the impact on weak lensing measurements of (a) realistic galaxy morphologies, (b) realistic uncertainty in the point-spread function estimation, and (c) the need to combine multiple exposures when estimating the galaxy shape. It includes simulated ground- and space-based data. The tests of realistic galaxy morphologies rely on a training set of galaxies from the Hubble Space Telescope, a subset of which has been publicly released for community use, with the remainder to be released at the end of the challenge. We describe some technical considerations for generating the challenge data and for testing weak lensing measurements with the next generation of weak lensing surveys, such as DES, HSC, KIDS, and Pan-STARRS.
Galaxy-Galaxy Flexion: Weak Lensing to Second Order
David M. Goldberg; David J. Bacon
2004-10-15
In this paper, we develop a new gravitational lensing inversion technique. While traditional approaches assume that the lensing field varies little across a galaxy image, we note that this variation in the field can give rise to a ``Flexion'' or bending of a galaxy image, which may then be used to detect a lensing signal with increased signal to noise. Since the significance of the Flexion signal increases on small scales, this is ideally suited to galaxy-galaxy lensing. We develop an inversion technique based on the ``Shapelets'' formalism of Refregier (2003). We then demonstrate the proof of this concept by measuring a Flexion signal in the Deep Lens Survey. Assuming an intrinsically isothermal distribution, we find from the Flexion signal alone a velocity width of v_c=221\\pm 12 km/s for lens galaxies of r < 21.5, subject to uncertainties in the intrinsic Flexion distribution.
Deep field weak lensing: testing (Lambda)CDM
NASA Astrophysics Data System (ADS)
Tyson, J. Anthony; Dell'Antonio, Ian; Wittman, David; Bernstein, Gary; Guhathakurta, Raja; Kochanski, Greg
1999-02-01
We propose to observe weak gravitational lensing shear correlations as a function of source redshift. A deep 50 arcmin BTC mosaic forms a ``thick" pencil-beam probe, covering an adequate area at both low and high redshift. Different cosmologies predict significantly different dependences of shear on source redshift. This observation will test the competing flat universe models (Lambda)CDM, Hot-Cold DM, and SCDM. In the first case (suggested by recent SNIa observations) the universe is older and larger, giving rise to larger deflections and shear. Such a deep mass probe will pass through many large-scale filaments/walls/lumps of the kind expected from n-body CDM simulations. In addition to measuring the shear correlations induced by the large scale structure, mass maps made from inverting the 100,000 arclets will reveal some of these projected stuctures directly. Three color photometric redshifts enable a reliable low/high source redshift selection. Because these two fields will go fainter than any other planned observations, we propose to release the data to the community 12 months after acquisition.
Strong Gravitational Lensing in a Brane-World Black Hole
Li, GuoPing; Feng, Zhongwen; Zu, Xiaotao
2015-01-01
Adopting the strong field limit approach, we investigated the strong gravitational lensing in a Brane-World black hole, which means that the strong field limit coefficients and the deflection angle in this gravitational field are obtained. With this result, it can be said with certainly that the strong gravitational lensing is related to the metric of gravitational fields closely, the cosmology parameter {\\alpha} and the dark matter parameter \\b{eta} come from the Brane-World black hole exerts a great influence on it. Comparing with the Schwarzschild-AdS spacetime and the Schwarzschild-XCMD spacetime, the parameters {\\alpha}, \\b{eta} of black holes have the similar effects on the gravitational lensing. In some way, we infer that the real gravitational fields in our universe can be described by this metric, so the results of the strong gravitational lensing in this spacetime will be more reasonable for us to observe. Finally, it has to be noticed that the influence which the parameters {\\alpha}, \\b{eta} exerte...
Gravitational lensing of the cosmic microwave background by non-linear structures
NASA Astrophysics Data System (ADS)
Merkel, Philipp M.; Schäfer, Björn Malte
2011-02-01
Weak gravitational lensing changes the angular power spectra of the cosmic microwave background (CMB) temperature and polarization in a characteristic way containing valuable information for cosmological parameter estimation. So far, analytical expressions for the lensed CMB power spectra assume the probability density function (PDF) of the lensing excursion angle to be Gaussian. However, coherent light deflection by non-linear structures at low redshifts causes deviations from a pure Gaussian PDF. Working in the flat-sky limit, we develop a method for computing the lensed CMB power spectra which takes these non-Gaussian features into account. Our method does not assume any specific PDF but uses instead an expansion of the characteristic function of the lensing excursion angle into its moments. Measuring these in the CMB lensing deflection field obtained from the Millennium Simulation we show that the change in the lensed power spectra is only at the 0.1-0.4 per cent level on very small scales (??? 4 arcmin, l? 2500) and demonstrate that the assumption of a Gaussian lensing excursion angle PDF is well applicable.
Scatter and bias in weak lensing selected clusters
NASA Astrophysics Data System (ADS)
Hamana, Takashi; Oguri, Masamune; Shirasaki, Masato; Sato, Masanori
2012-09-01
We examine scatter and bias in weak lensing selected clusters, employing both an analytic model of dark matter haloes and numerical mock data of weak lensing cluster surveys. We pay special attention to effects of the diversity of dark matter distributions within clusters. We find that peak heights of the lensing convergence map correlate rather poorly with the virial mass of haloes. The correlation is tighter for the spherical overdensity mass with a higher mean interior density (e.g. M1000). We examine the dependence of the halo shape on the peak heights, and find that the root mean square scatter caused by the halo diversity scales linearly with the peak heights with the proportionality factor of 0.1-0.2. The noise originated from the halo shape is found to be comparable to the source galaxy shape noise and the cosmic shear noise. We find the significant halo orientation bias, i.e. weak lensing selected clusters on average have their major axes aligned with the line-of-sight direction, and that the orientation bias is stronger for higher signal-to-noise ratio (S/N) peaks. We compute the orientation bias using an analytic triaxial halo model and obtain results quite consistent with the ray-tracing results. We develop a prescription to analytically compute the number count of weak lensing peaks taking into account all the main sources of scatters in the peak heights. We find that the improved analytic predictions agree well with the simulation results for high-S/N peaks of ??5. We also compare the expected number count with our weak lensing analysis results for 4 deg2 of Subaru/Suprime-Cam observations and find a good agreement.
The effect of weak lensing on distance estimates from supernovae
Smith, Mathew; Maartens, Roy [Department of Physics, University of the Western Cape, Cape Town 7535 (South Africa); Bacon, David J.; Nichol, Robert C.; Campbell, Heather; D'Andrea, Chris B. [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Clarkson, Chris [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch 7701 (South Africa); Bassett, Bruce A. [South African Astronomical Observatory, P.O. Box 9, Observatory 7935 (South Africa); Cinabro, David [Wayne State University, Department of Physics and Astronomy, Detroit, MI 48202 (United States); Finley, David A.; Frieman, Joshua A. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Galbany, Lluis [CENTRA Centro Multidisciplinar de Astrofísica, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon (Portugal); Garnavich, Peter M. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Olmstead, Matthew D. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Shapiro, Charles [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, La Canada Flintridge, CA 91109 (United States); Sollerman, Jesper, E-mail: matsmith2@gmail.com [The Oskar Klein Centre, Department of Astronomy, AlbaNova, SE-106 91 Stockholm (Sweden)
2014-01-01
Using a sample of 608 Type Ia supernovae from the SDSS-II and BOSS surveys, combined with a sample of foreground galaxies from SDSS-II, we estimate the weak lensing convergence for each supernova line of sight. We find that the correlation between this measurement and the Hubble residuals is consistent with the prediction from lensing (at a significance of 1.7?). Strong correlations are also found between the residuals and supernova nuisance parameters after a linear correction is applied. When these other correlations are taken into account, the lensing signal is detected at 1.4?. We show, for the first time, that distance estimates from supernovae can be improved when lensing is incorporated, by including a new parameter in the SALT2 methodology for determining distance moduli. The recovered value of the new parameter is consistent with the lensing prediction. Using cosmic microwave background data from WMAP7, H {sub 0} data from Hubble Space Telescope and Sloan Digital Sky Survey (SDSS) Baryon acoustic oscillations measurements, we find the best-fit value of the new lensing parameter and show that the central values and uncertainties on ? {sub m} and w are unaffected. The lensing of supernovae, while only seen at marginal significance in this low-redshift sample, will be of vital importance for the next generation of surveys, such as DES and LSST, which will be systematics-dominated.
Gravitational Lenses and the Structure and Evolution of Galaxies
NASA Technical Reports Server (NTRS)
Oliversen, Ronald J. (Technical Monitor); Kochanek, Christopher
2004-01-01
During the first year of the project we completed five papers, each of which represents a new direction in the theory and interpretation of gravitational lenses. In the first paper, The Importance of Einstein Rings, we developed the first theory for the formation and structure of the Einstein rings formed by lensing extended sources like the host galaxies of quasar and radio sources. In the second paper, Cusped Mass Models Of Gravitational Lenses, we introduced a new class of lens models. In the third paper, Global Probes of the Impact of Baryons on Dark Matter Halos, we made the first globally consistent models for the separation distribution of gravitational lenses including both galaxy and cluster lenses. The last two papers explore the properties of two lenses in detail. During the second year we have focused more closely on the relationship of baryons and dark matter. In the third year we have been further examining the relationship between baryons and dark matter. In the present year we extended our statistical analysis of lens mass distributions using a self-similar model for the halo mass distribution as compared to the luminous galaxy.
Gravitational lensing shear by an exotic lens object with negative convergence or negative mass
NASA Astrophysics Data System (ADS)
Izumi, Koji; Hagiwara, Chisaki; Nakajima, Koki; Kitamura, Takao; Asada, Hideki
2013-07-01
Gravitational lens models with negative convergence (surface mass density projected onto the lens plane) inspired by modified gravity theories, exotic matter, and energy have been recently discussed in such a way that a static and spherically symmetric modified spacetime metric depends on the inverse distance to the power of positive n (n=1 for Schwarzschild metric, n=2 for Ellis wormhole) in the weak-field approximation [T. Kitamura, K. Nakajima, and H. Asada, Phys. Rev. D 87, 027501 (2013)], and it has been shown that demagnification of images could occur for n>1 lens models associated with exotic matter (and energy), though they cause the gravitational pull on light rays. The present paper considers gravitational lensing shear by the demagnifying lens models and other models such as negative-mass compact objects causing the gravitational repulsion on light rays like a concave lens. It is shown that images by the lens models for the gravitational pull are tangentially elongated, whereas those by the repulsive ones are radially distorted. This feature of lensed image shapes may be used for searching (or constraining) localized exotic matter or energy with gravitational lensing surveys. It is suggested also that an underdense region such as a cosmic void might produce radially elongated images of background galaxies rather than tangential ones.
Topics in gravitational lensing: Clusters, quasars, and the cosmic microwave background
NASA Astrophysics Data System (ADS)
Hennawi, Joseph F.
Several different cosmological applications of gravitational lensing, both weak and strong, are addressed from both a theoretical and observational perspective. First, we study the potential of weak lensing surveys to detect clusters of galaxies, using a fast Particle Mesh cosmological N-body simulation algorithm specifically tailored to investigate the statistics of these shear- selected clusters. We then consider how weak lensing might be used as a tool to isolate secondary anisotropies of the cosmic microwave background (CMB) through cross-correlation. It is shown that a cross-correlation of the small angular scale CMB with an overlapping weak-lensing survey should be detectable with high signal to noise ratio, and will isolate the elusive kinetic Sunyaev-Zel ' dovich (kSZ) effect from secondary anisotropies generated at higher redshifts. Next we discuss strong gravitational lensing, and study the expected properties and statistics of giant arcs and multiply imaged quasars, produced by galaxy clusters in a cold dark matter (CDM) universe with a cosmological constant (ACDM). This is done by carrying out a large ensemble of ray tracing simulations through clusters from a cosmological N-body simulation of the ACDM cosmology. Our results are compared to current surveys for giant arcs and multiply imaged quasars. Our large ensemble of simulations also allows us to statistically characterize the cluster lens population, and we explore how the properties of cluster lenses differ from the total population of galaxy clusters. Finally, the results of an observational effort to discover close pairs of quasars are presented. The goal of this quasar pair survey is to find quasars multiply imaged by clusters and to find binary quasars which can be used to study quasar clustering on small scales. A sample of 59 new quasar pairs discovered in this program which we use to demonstrate that quasars exhibit excess clustering on small scales 20 h -1 kpc-1 h -1 Mpc.
Probing Cosmology with Weak Lensing Peak Counts and Minkowski Functionals
Jan Michael Kratochvil; S. Wang; E. A. Lim; Z. Haiman; M. May
2010-01-01
The new method of counting peaks in weak lensing (WL) maps, as a function of their height, to probe models of dark energy and to constrain cosmological parameters offers advantages over similar, more traditional statistics like cluster counts: Because peaks can be identified in two-dimensional WL maps directly, they can provide constraints which are free from potential selection effects and
Cosmic variance of the galaxy cluster weak lensing signal
NASA Astrophysics Data System (ADS)
Gruen, D.; Seitz, S.; Becker, M. R.; Friedrich, O.; Mana, A.
2015-06-01
Intrinsic variations of the projected density profiles of clusters of galaxies at fixed mass are a source of uncertainty for cluster weak lensing. We present a semi-analytical model to account for this effect, based on a combination of variations in halo concentration, ellipticity and orientation, and the presence of correlated haloes. We calibrate the parameters of our model at the 10 per cent level to match the empirical cosmic variance of cluster profiles at M_{200m}? 10^{14}ldots 10^{15} h^{-1}{ M_{?}}, z = 0.25…0.5 in a cosmological simulation. We show that weak lensing measurements of clusters significantly underestimate mass uncertainties if intrinsic profile variations are ignored, and that our model can be used to provide correct mass likelihoods. Effects on the achievable accuracy of weak lensing cluster mass measurements are particularly strong for the most massive clusters and deep observations (with ?20 per cent uncertainty from cosmic variance alone at M_{200m}? 10^{15} h^{-1}{ M_{?}} and z = 0.25), but significant also under typical ground-based conditions. We show that neglecting intrinsic profile variations leads to biases in the mass-observable relation constrained with weak lensing, both for intrinsic scatter and overall scale (the latter at the 15 per cent level). These biases are in excess of the statistical errors of upcoming surveys and can be avoided if the cosmic variance of cluster profiles is accounted for.
Bautz, Marshall W.
We use weak gravitational lensing to measure the masses of five galaxy clusters selected from the South Pole Telescope (SPT) survey, with the primary goal of comparing these with the SPT Sunyaev-Zel'dovich (SZ) and X-ray-based ...
Reducing Systematic Error in Weak Lensing Cluster Surveys
NASA Astrophysics Data System (ADS)
Utsumi, Yousuke; Miyazaki, Satoshi; Geller, Margaret J.; Dell'Antonio, Ian P.; Oguri, Masamune; Kurtz, Michael J.; Hamana, Takashi; Fabricant, Daniel G.
2014-05-01
Weak lensing provides an important route toward collecting samples of clusters of galaxies selected by mass. Subtle systematic errors in image reduction can compromise the power of this technique. We use the B-mode signal to quantify this systematic error and to test methods for reducing this error. We show that two procedures are efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10'. Application of these procedures reduces the systematic error to 20% of its original amplitude. We provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the weak-lensing ?-signal-to-noise ratio (S/N) maps as a function of the detection threshold. Based on this analysis, we select a threshold S/N = 4.56 for identifying an uncontaminated set of weak-lensing peaks in two test fields covering a total area of ~3 deg2. Taken together these fields contain seven peaks above the threshold. Among these, six are probable systems of galaxies and one is a superposition. We confirm the reliability of these peaks with dense redshift surveys, X-ray, and imaging observations. The systematic error reduction procedures we apply are general and can be applied to future large-area weak-lensing surveys. Our high-peak analysis suggests that with an S/N threshold of 4.5, there should be only 2.7 spurious weak-lensing peaks even in an area of 1000 deg2, where we expect ~2000 peaks based on our Subaru fields. Based in part on data collected at Subaru Telescope and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan.
Gravitational lensing shear by an exotic lens object with negative convergence or negative mass
Izumi, Koji; Nakajima, Koki; Kitamura, Takao; Asada, Hideki
2013-01-01
Gravitational lens models with negative convergence (surface mass density projected onto the lens plane) inspired by modified gravity theories, exotic matter and energy have been recently discussed in such a way that a static and spherically-symmetric modified spacetime metric depends on the inverse distance to the power of positive $n$ (n=1 for Schwarzschild metric, n=2 for Ellis wormhole) in the weak-field approximation [Kitamura, Nakajima and Asada, PRD 87, 027501 (2013)], and it has been shown that demagnification of images could occur for $n>1$ lens models associated with exotic matter (and energy), though they cause the gravitational pull on light rays. The present paper considers gravitational lensing shear by the demagnifying lens models and other models such as negative-mass compact objects causing the gravitational repulsion on light rays. It is shown that images by the lens models for the gravitational pull are tangentially elongated, whereas those by the repulsive ones are radially distorted. This...
Mapping the Dark Universe with Weak Gravitational Rachel N McInnes
Tittley, Eric
Mapping the Dark Universe with Weak Gravitational Lensing Rachel N McInnes Institute for Astronomy.1.2 Deflection Angle of a Point Mass . . . . . . . . . . . . . . . . . . . . 5 2.1.3 The Lens Equation. The mass map (dark matter) is shown in blue, and the xray is shown in purple, both on top of the optical
Gravitational lenses and lens candidates identified from the COSMOS field
Neal Jackson
2008-06-23
A complete manual search has been carried out of the list of 285423 objects, nearly all of them galaxies, identified in the COSMOS field that are brighter than I=25. Two certain and one highly probable new gravitational lenses are found, in addition to the lenses and candidate lens systems previously found by Faure et al. (2008). A further list of 112 candidate lens systems is presented. Few of these are likely to be true gravitational lens systems, most being star-forming rings or pairs of companion galaxies. It is possible to examine of order 10^6 objects by eye in a reasonable time, although reliable detection of lenses by such methods is likely to be possible only with high-resolution data. The loss of completeness involved in a rapid search is estimated as up to a factor of 2, depending on the morphology of the lens candidate.
Reverberation Mapping of a Gravitationally-lensed Quasar
NASA Astrophysics Data System (ADS)
Denney, Kelly D.; Courbin, Frederic; Kochanek, Christopher S.; MacLeod, Chelsea L.; Meylan, Georges; Morgan, Christopher W.; Mosquera, Ana; Moustakas, Leonidas; Onken, Christopher A.; Peterson, Bradley M.; Sluse, Dominique
2014-02-01
We propose a continuation of the program we began in 2013B to perform reverberation mapping on a gravitationally lensed quasar. Gravitationally lensed quasars are already rich test beds for studying cosmology, black hole accretion physics, dark matter, and galaxy properties. Here, we will expand their use by spectroscopically monitoring the CIV quasar emission line with GMOS to measure the broad line region size and black hole mass of the z=1.7 lensed quasar HE0435-1223. The success of this program has significant implications for studies of quasar physics, galaxy evolution at high redshift, and further studies of cosmology, and it is possible with only a modest addition (<2.5 nights) of Gemini time in 2014A.
Master Thesis The Effects of Dark Matter on Gravitational Lensing
van Suijlekom, Walter
Master Thesis The Effects of Dark Matter on Gravitational Lensing Properties of Galaxy Clusters, Australia #12;#12;Summary Dark matter is one of the main components in the universe. The type of dark matter cosmological model with cold dark matter (CDM) will have less structure compared to an equivalent model
TRANSCENDENTAL HARMONIC MAPPINGS AND GRAVITATIONAL LENSING BY ISOTHERMAL
Khavinson, Dmitry
TRANSCENDENTAL HARMONIC MAPPINGS AND GRAVITATIONAL LENSING BY ISOTHERMAL GALAXIES DMITRY KHAVINSON harmonic mapping. We use complex dynamics to give an upper bound on the total number of such zeros. 1 passes near an isothermal, ellipsoidal galaxy. Indeed, using the complex formulation of the thin
The Weak Lensing Signal and the Clustering of BOSS Galaxies. I. Measurements
NASA Astrophysics Data System (ADS)
Miyatake, Hironao; More, Surhud; Mandelbaum, Rachel; Takada, Masahiro; Spergel, David N.; Kneib, Jean-Paul; Schneider, Donald P.; Brinkmann, J.; Brownstein, Joel R.
2015-06-01
A joint analysis of the clustering of galaxies and their weak gravitational lensing signal is well-suited to simultaneously constrain the galaxy–halo connection as well as the cosmological parameters by breaking the degeneracy between galaxy bias and the amplitude of clustering signal. In a series of two papers, we perform such an analysis at the highest redshift (z? 0.53) in the literature using CMASS galaxies in the Sloan Digital Sky Survey-III Baryon Oscillation Spectroscopic Survey Eleventh Data Release (BOSS DR11) catalog spanning 8300 deg2. In this paper, we present details of the clustering and weak lensing measurements of these galaxies. We define a subsample of 400,916 CMASS galaxies based on their redshifts and stellar-mass estimates so that the galaxies constitute an approximately volume-limited and similar population over the redshift range 0.47?slant z?slant 0.59. We obtain a signal-to-noise ratio (S/N) ? 56 for the galaxy clustering measurement. We also explore the redshift and stellar-mass dependence of the clustering signal. For the weak lensing measurement, we use existing deeper imaging data from the Canada–France–Hawaii Telescope Legacy Survey with publicly available shape and photometric redshift catalogs from CFHTLenS, but only in a 105 deg2 area that overlaps with BOSS. This restricts the lensing measurement to only 5084 CMASS galaxies. After careful systematic tests, we find a highly significant detection of the CMASS weak lensing signal, with total S/N ? 26. These measurements form the basis of the halo occupation distribution and cosmology analysis presented in More et al. (Paper II).
On the contribution of large scale structure to strong gravitational lensing
C. Faure; J. -P. Kneib; S. Hilbert; R. Massey; G. Covone; A. Finoguenov; A. Leauthaud; J. E. Taylor; S. Pires; N. Scoville; A. Koekemoer
2009-03-09
We study the correlation between the locations of galaxy-galaxy strong lensing candidates and tracers of large-scale structure from both weak lensing or X-ray emission. The COSMOS survey is a unique data set, combining deep, high resolution and contiguous imaging in which strong lenses have been discovered, plus unparalleled multiwavelength coverage. To help interpret the COSMOS data, we have also produced mock COSMOS strong and weak lensing observations, based on ray-tracing through the Millenium simulation. In agreement with the simulations, we find that strongly lensed images with the largest angular separations are found in the densest regions of the COSMOS field. This is explained by a prevalence among the lens population in dense environments of elliptical galaxies with high total-to-stellar mass ratios, which can deflect light through larger angles. However, we also find that the overall fraction of elliptical galaxies with strong gravitational lensing is independent of the local mass density; this observation is not true of the simulations, which predict an increasing fraction of strong lenses in dense environments. The discrepancy may be a real effect, but could also be explained by various limitations of our analysis. For example, our visual search of strong lens systems could be incomplete and suffer from selection bias; the luminosity function of elliptical galaxies may differ between our real and simulated data; or the simplifying assumptions and approximations used in our lensing simulations may be inadequate. Work is therefore ongoing. Automated searches for strong lens systems will be particularly important in better constraining the selection function.
A Submillimeter Survey of Gravitationally Lensed Quasars
Richard Barvainis; Rob Ivison
2002-01-25
Submillimeter (and in some cases millimeter) wavelength continuum measurements are presented for a sample of 40 active galactic nuclei (probably all quasars) lensed by foreground galaxies. The object of this study is to use the lensing boost, anywhere from ~3- 20 times, to detect dust emission from more typical AGNs than the extremely luminous ones currently accessible without lensing. The sources are a mix of radio loud and radio quiet quasars, and, after correction for synchrotron radation (in the few cases where necessary), 23 of the 40 (58%) are detected in dust emission at 850um; 11 are also detected at 450um. Dust luminosities and masses are derived after correction for lensing magnification, and luminosities are plotted against redshift from z = 1 to z = 4.4, the redshift range of the sample. The main conclusions are (1) Monochromatic submillimeter luminosities of quasars are, on average, only a few times greater than those of local IRAS galaxies; (2) Radio quiet and radio loud quasars do not differ significantly in their dust lumimosity; (3) Mean dust luminosities of quasars and radio galaxies over the same redshift range are comparable; (4) Quasars and radio galaxies alike show evidence for more luminous and massive dust sources toward higher redshift, consistent with an early epoch of formation and possibly indicating that the percentage of obscured AGNs increases with redshift.
Gravitationally Lensed Gamma-Ray Bursts as Probes of Dark Compact Objects
G. F. Marani; R. J. Nemiroff; J. P. Norris; K. Hurley; J. T. Bonnell
1998-12-29
If dark matter in the form of compact objects comprises a large fraction of the mass of the universe, then gravitational lensing effects on gamma-ray bursts are expected. We utilize BATSE and Ulysses data to search for lenses of different mass ranges, which cause lensing in the milli, pico, and femto regimes. Null results are used to set weak limits on the cosmological abundance of compact objects in mass ranges from 10$^{-16}$ to 10$^{-9}$ $M_{\\odot} $. A stronger limit is found for a much discussed $\\Omega = 0.15$ universe dominated by black holes of masses $\\sim 10^{6.5} M_{\\odot}$, which is ruled out at the $\\sim$ 90% confidence level.
Strong gravitational lensing in a noncommutative black-hole spacetime
Ding Chikun; Kang Shuai; Chen Changyong; Chen Songbai; Jing Jiliang [Department of Physics and Information Engineering, Hunan Institute of Humanities Science and Technology, Loudi, Hunan 417000 (China); Institute of Physics and Department of Physics, Hunan Normal University, Changsha, Hunan 410081 (China) and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University), Ministry of Education (China)
2011-04-15
Noncommutative geometry may be a starting point to a quantum gravity. We study the influence of the spacetime noncommutative parameter on the strong field gravitational lensing in the noncommutative Schwarzschild black-hole spacetime and obtain the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy can be described by this metric, we estimate the numerical values of the coefficients and observables for strong gravitational lensing. In comparison to the Reissner-Norstroem black hole, we find that the influences of the spacetime noncommutative parameter is similar to those of the charge, but these influences are much smaller. This may offer a way to distinguish a noncommutative black hole from a Reissner-Norstroem black hole, and may permit us to probe the spacetime noncommutative constant {theta} by the astronomical instruments in the future.
The Statistics of Nearly On-Axis Gravitational Lensing Events
Yun Wang
1995-09-07
A small volume of space, nearly on-axis behind a gravitational lens with respect to a given source, will receive a greatly increased radiation flux. In the idealized case of a point mass lens acting on a point source in complete isolation, the volume will approach zero only as the flux tends to infinity; in fact, the volume weighted rms flux is divergent. In realistic cases, finite source size and the effects of other gravitational deflections (i.e., non-zero shear) limit the maximum flux and considerably complicate the physics, but very large fluxes are still produced in small volumes. We consider the physics and statistics of these Extreme Gravitational Lensing Events (EGLE) and present an initial examination of their possible astrophysical effects for various known and putative populations of lensing objects and sources, with particular attention to the case in which finite source size is important but shear is not.
Gravitational lenses: The current sample, recent results, and continuing searches
NASA Technical Reports Server (NTRS)
Hewitt, Jacqueline N.
1991-01-01
Gravitational lensing is one of the topics in astrophysics that was quite extensively discussed over time before it was actually discovered. Ten years after the discovery of the first one, it is interesting to note how the field has developed. After an initial slow rate of discovery, the last few years have seen an explosion in the number of reported cases. Attention was drawn to the first few cases because quasars at the same red shift, with similar optical spectra, were observed with angular separations of only a few arc seconds. Most observational effort has been devoted to searching for new candidate lens systems and carefully measuring their properties, both to test whether they are indeed lensed and to provide constraints for modeling. A classification of the lenses is into rings, arcs, multiples, and doubles, where the progression is from sources close to the optical axis to far from the optical axis. The known candidate systems are listed. The searches for gravitational lenses are proving to be successful, and more lenses continue to be discovered serendipitously. Many searches are under way, along with instruments that will routinely increase the resolution of astronomical imaging.
Robust weak-lensing mass calibration of Planck galaxy clusters
NASA Astrophysics Data System (ADS)
von der Linden, Anja; Mantz, Adam; Allen, Steven W.; Applegate, Douglas E.; Kelly, Patrick L.; Morris, R. Glenn; Wright, Adam; Allen, Mark T.; Burchat, Patricia R.; Burke, David L.; Donovan, David; Ebeling, Harald
2014-09-01
In light of the tension in cosmological constraints reported by the Planck team between their Sunyaev-Zel'dovich-selected cluster counts and Cosmic Microwave Background (CMB) temperature anisotropies, we compare the Planck cluster mass estimates with robust, weak-lensing mass measurements from the Weighing the Giants (WtG) project. For the 22 clusters in common between the Planck cosmology sample and WtG, we find an overall mass ratio of
Gravitational Lensing in the metric theory proposed by Sobouti
Tula Bernal; Sergio Mendoza
2008-11-12
Recently, Y. Sobouti (2007) has provided a metric theory f(R) that can account for certain dynamical anomalies observed in spiral galaxies. Mendoza & Rosas-Guevara (2007) have shown that in this theory there is an extra-bending as compared to standard general relativity. In the present work we have developed in more specific detail this additional lensing effect and we have made evaluations of the alpha parameter used in the model adjusting the theory to observations in X-rays of 13 clusters of galaxies with gravitational lensing (Hoekstra (2007)).
Sources of contamination to weak lensing tomography: redshift-dependent shear measurement bias
NASA Astrophysics Data System (ADS)
Semboloni, Elisabetta; Tereno, Ismael; van Waerbeke, Ludovic; Heymans, Catherine
2009-08-01
The current methods available to estimate gravitational shear from astronomical images of galaxies introduce systematic errors which can affect the accuracy of weak lensing cosmological constraints. We study the impact of KSB shape measurement bias on the cosmological interpretation of tomographic two-point weak lensing shear statistics. We use a set of realistic image simulations produced by the Shear Testing Programme (STEP) collaboration to derive shape measurement bias as a function of redshift. We define biased two-point weak lensing statistics and perform a likelihood analysis for two fiducial surveys. We present a derivation of the covariance matrix for tomography in real space and a fitting formula to calibrate it for non-Gaussianity. We find the biased aperture mass dispersion is reduced by ~20per cent at redshift ~1, and has a shallower scaling with redshift. This effect, if ignored in data analyses, biases ?8 and w0 estimates by a few per cent. The power of tomography is significantly reduced when marginalizing over a range of realistic shape measurement biases. For a Canada-France-Hawaii Telescope Legacy Survey (CFHTLS)-Wide-like survey, [?m, ?8] confidence regions are degraded by a factor of 2, whereas for a Kilo-Degree Survey (KIDS)-like survey the factor is 3.5. Our results are strictly valid only for KSB methods, but they demonstrate the need to marginalize over a redshift-dependent shape measurement bias in all future cosmological analyses.
Hu, Wayne
- ing probes of dark energy is weak gravitational lens- ing. Forthcoming weak lensing surveys expect of Baryons to Constrain Dark Energy Andrew R. Zentner,1, 2, 3 Douglas H. Rudd,2 and Wayne Hu2, 3 1 Department such as the Dark Energy Survey (DES), the SuperNova/Acceleration Probe (SNAP), and the Large Synoptic Survey
Gravitational lensing in a cold dark matter universe
NASA Technical Reports Server (NTRS)
Narayan, Ramesh; White, Simon D. M.
1988-01-01
Gravitational lensing due to mass condensations in a biased cold dark matter (CDM) universe is investigated using the Press-Schechter (1974) theory with density fluctuation amplitudes taken from previous N-body work. Under the critical assumption that CDM haloes have small core radii, a distribution of image angular separations for high-z lensed quasars with a peak at about 1 arcsec and a half-width of a factor of about 10. Allowing for selection effects at small angular separations, this is in good agreement with the observed separations. The estimated frequency of lensing is somewhat lower than that observed, but the discrepancy can be removed by invoking amplification bias and by making a small upward adjustment to the density fluctuation amplitudes assumed in the CDM model.
NASA Astrophysics Data System (ADS)
Massey, Richard; Hoekstra, Henk; Kitching, Thomas; Rhodes, Jason; Cropper, Mark; Amiaux, Jérôme; Harvey, David; Mellier, Yannick; Meneghetti, Massimo; Miller, Lance; Paulin-Henriksson, Stéphane; Pires, Sandrine; Scaramella, Roberto; Schrabback, Tim
2013-02-01
The first half of this paper explores the origin of systematic biases in the measurement of weak gravitational lensing. Compared to previous work, we expand the investigation of point spread function instability and fold in for the first time the effects of non-idealities in electronic imaging detectors and imperfect galaxy shape measurement algorithms. Together, these now explain the additive {A}(?) and multiplicative {M}(?) systematics typically reported in current lensing measurements. We find that overall performance is driven by a product of a telescope/camera's absolute performance, and our knowledge about its performance. The second half of this paper propagates any residual shear measurement biases through to their effect on cosmological parameter constraints. Fully exploiting the statistical power of Stage IV weak lensing surveys will require additive biases overline{{A}}? 1.8× 10^{-12} and multiplicative biases overline{{M}}? 4.0× 10^{-3}. These can be allocated between individual budgets in hardware, calibration data and software, using results from the first half of the paper. If instrumentation is stable and well calibrated, we find extant shear measurement software from Gravitational Lensing Accuracy Testing 2010 (GREAT10) already meet requirements on galaxies detected at signal-to-noise ratio = 40. Averaging over a population of galaxies with a realistic distribution of sizes, it also meets requirements for a 2D cosmic shear analysis from space. If used on fainter galaxies or for 3D cosmic shear tomography, existing algorithms would need calibration on simulations to avoid introducing bias at a level similar to the statistical error. Requirements on hardware and calibration data are discussed in more detail in a companion paper. Our analysis is intentionally general, but is specifically being used to drive the hardware and ground segment performance budget for the design of the European Space Agency's recently selected Euclid mission.
Casimir effect in a weak gravitational field
NASA Astrophysics Data System (ADS)
Sorge, Francesco
2005-12-01
We study the Casimir vacuum energy density for a massless scalar field confined between two nearby parallel plates (a cavity) in a slightly curved, static spacetime background, employing the weak-field approximation. Following an order-by-order perturbative approach, we evaluate the gravity-induced correction to Casimir energy. We find evidence for a small shift in the (negative) vacuum energy. As a consequence, the (attractive) force between the cavity walls is expected to weaken. Although derived in the weak-field approximation, and too small to be detected with the current technology, such gravitationally induced shift in vacuum energy seems nevertheless interesting from a theoretical point of view, since it might play a role in a cosmological scenario (e.g., gravitational influence on the ?-term) as well as at a microscopic level (quark confinement) in strong gravitational fields. Finally, the analysis of the possible gravitational effects on Casimir cavities faces the open issue concerning the limits of validity of general relativity at small distances.
Strong field gravitational lensing in stringy black hole
NASA Astrophysics Data System (ADS)
Geng, Jin-Ling; Zhang, Yu; Li, En-Kun; Duan, Peng-Fei
2015-06-01
In this paper, we studied the strong gravitational lensing due to the stringy black hole using the strong field limit approach. Modeling the supermassive object at the galactic center as stringy black hole, the numerical values of the strong field limit coefficients and the observables were estimated. Moreover, by measuring the observables, one can get the strong field limit coefficients to reconstruct the full expansion of the deflection angle for the strong field gravitational lensing in stringy black hole. Comparing our results with that of Schwarzschild black hole, it is easy to find that all the values in stringy black hole diverge from those of Schwarzschild spacetime under the influence of the parameter ?, which gives us an alternative way to distinguish the stringy black hole from the Schwarzschild black hole. In our model, with the parameter ? increasing, the angular position ? ? increases and the relative magnitudes decreases.
Wave effect in gravitational lensing by the Ellis wormhole
NASA Astrophysics Data System (ADS)
Yoo, Chul-Moon; Harada, Tomohiro; Tsukamoto, Naoki
2013-04-01
We propose the use of modulated spectra of astronomical sources due to gravitational lensing to probe Ellis wormholes. The modulation factor due to gravitational lensing by the Ellis wormhole is calculated. Within the geometrical optics approximation, the normal point-mass lens and the Ellis wormhole are indistinguishable unless we know the source’s unlensed luminosity. This degeneracy is resolved with the significant wave effect in the low-frequency domain if we take the deviation from the geometrical optics into account. We can roughly estimate the upper bound for the number density of Ellis wormholes as n?4×10-10AU-3 with throat radius a˜1cm from the existing femtolensing analysis for compact objects.
Analytic Time Delays and H_0 Estimates for Gravitational Lenses
H. J. Witt; S. Mao; C. R. Keeton
2000-04-05
We study gravitational lens time delays for a general family of lensing potentials, which includes the popular singular isothermal elliptical potential and singular isothermal elliptical density distribution but allows general angular structure. Using a novel approach, we show that the time delay can be cast in a very simple form, depending only on the observed image positions. Including an external shear changes the time delay proportional to the shear strength, and varying the radial profile of the potential changes the time delay approximately linearly. These analytic results can be used to obtain simple estimates of the time delay and the Hubble constant in observed gravitational lenses. The naive estimates for four of five time delay lenses show surprising agreement with each other and with local measurements of H_0; the complicated Q 0957+561 system is the only outlier. The agreement suggests that it is reasonable to use simple isothermal lens models to infer H_0, although it is still important to check this conclusion by examining detailed models and by measuring more lensing time delays.
Theoretical Aspects of Gravitational Lensing in TeVeS
Mu-Chen Chiu; Chung-Ming Ko; Yong Tian
2005-10-14
Since Bekenstein's (2004) creation of his Tensor-Vector-Scalar theory (TeVeS), the Modified Newtonian dynamics (MOND) paradigm has been redeemed from the embarrassment of lacking a relativistic version. One primary success of TeVeS is that it provides an enhancement of gravitational lensing, which could not be achieved by other MONDian theories. Following Bekenstein's work, we investigate the phenomena of gravitational lensing including deflection angles, lens equations and time delay. We find that the deflection angle would maintain its value while the distance of closest approach vary in the MOND regime, this coincides with the conclusion of Mortlock and Turner's (2001) intuitional approach. Moreover, the scalar field, which is introduced to enhance the deflection angle in TeVeS, contributes a negative effect on the potential time delay. Unfortunately this phenomenon is unmeasurable in lensing systems where we can only observe the time delay between two images for a given source. However, this measurable time delay offers another constraint on the mass ratio of the DM and MOND scenarios, which in general differs from that given by the deflection angle. In other words, for a lensing system, if two masses, m_gN and m_gM, are mutually alternatives for the deflection angles in their own paradigm, regarding the time delay they are in general in an exclusive relation.
Corless, Virginia Leigh
2005-01-01
In this 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 ...
Gravitational lensing in the Kerr-Randers optical geometry
M. C. Werner
2012-11-15
A new geometric method to determine the deflection of light in the equatorial plane of the Kerr solution is presented, whose optical geometry is a surface with a Finsler metric of Randers type. Applying the Gauss-Bonnet theorem to a suitable osculating Riemannian manifold, adapted from a construction by Naz\\i m, it is shown explicitly how the two leading terms of the asymptotic deflection angle of gravitational lensing can be found in this way.
Gravitational lensing by Einstein-Born-Infeld black holes
Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio, C.C. 67, Suc. 28, 1428, Buenos Aires (Argentina)
2006-02-15
In this paper, charged black holes in general relativity coupled to Born-Infeld electrodynamics are studied as gravitational lenses. The positions and magnifications of the relativistic images are obtained using the strong deflection limit, and the results are compared with those corresponding to a Reissner-Nordstroem black hole with the same mass and charge. As numerical examples, the model is applied to the supermassive Galactic center black hole and to a small size black hole situated in the Galactic halo.
The effects of source clustering on weak lensing statistics
F. Bernardeau
1998-04-22
I investigate the effects of source clustering on the weak lensing statistics, more particularly on the statistical properties of the local convergence, kappa, at large angular scales. The Perturbation Theory approach shows that the variance is not affected by source clustering at leading order but higher order moments such as the third and fourth moments can be. I compute the magnitude of these effects in case of an Einstein-de Sitter Universe for the angular top-hat filtered convergence. In these calculations the so-called Broadhurst and multiple lens coupling effects are neglected. The source clustering effect is found to be particularly important when the redshift distribution is broad enough so that remote background sources can be significantly lensed by closer concentrations of galaxy sources. The source clustering effects are shown to remain negligible, for both the skewness and the kurtosis, when the dispersion of the redshift of the sources is less than about 0.15.
Strong and weak lensing analysis of cluster Abell 2219 based on optical and near infrared data
J. Bezecourt; H. Hoekstra; M. E. Gray; H. M. AbdelSalam; K. Kuijken; R. S. Ellis
2000-01-29
We present a gravitational lensing study of the massive galaxy cluster A2219 (redshift 0.22). This investigation is based on multicolour images from U through H, which allows photometric redshifts to be estimated for the background sources. The redshifts provide useful extra information for the lensing models: we show how they can be used to identify a new multiple-image system (and rule out an old one), how this information can be used to anchor the mass model for the cluster, and how the redshifts can be used to construct optimal samples of background galaxies for a weak lensing analysis. Combining all results, we obtain the mass distribution in this cluster from the inner, strong lensing region, out to a radius of 1.5 Mpc. The mass profile is consistent with a singular isothermal model over this radius range. Parametric and non-parametric reconstructions of the mass distribution in the cluster are compared. The main features (elongation, sub-clumps, radial mass profile) are in good agreement.
Strong and weak lensing analysis of cluster Abell 2219 based on optical and near infrared data
Bézecourt, J; Gray, M E; Abdel-Salam, H M; Kuijken, K; Ellis, Richard S
2000-01-01
We present a gravitational lensing study of the massive galaxy cluster A2219 (redshift 0.22). This investigation is based on multicolour images from U through H, which allows photometric redshifts to be estimated for the background sources. The redshifts provide useful extra information for the lensing models: we show how they can be used to identify a new multiple-image system (and rule out an old one), how this information can be used to anchor the mass model for the cluster, and how the redshifts can be used to construct optimal samples of background galaxies for a weak lensing analysis. Combining all results, we obtain the mass distribution in this cluster from the inner, strong lensing region, out to a radius of 1.5 Mpc. The mass profile is consistent with a singular isothermal model over this radius range. Parametric and non-parametric reconstructions of the mass distribution in the cluster are compared. The main features (elongation, sub-clumps, radial mass profile) are in good agreement.
Demagnifying gravitational lenses toward hunting a clue of exotic matter and energy
NASA Astrophysics Data System (ADS)
Kitamura, Takao; Nakajima, Koki; Asada, Hideki
2013-01-01
We examine a gravitational lens model inspired by modified gravity theories and exotic matter and energy. We study an asymptotically flat, static, and spherically symmetric spacetime that is modified in such a way that the spacetime metric depends on the inverse distance to the power of positive n in the weak-field approximation. It is shown analytically and numerically that there is a lower limit on the source angular displacement from the lens object to get demagnification. Demagnifying gravitational lenses could appear, provided the source position ? and the power n satisfy ?>2/(n+1) in the units of the Einstein ring radius under a large-n approximation. Unusually, the total amplification of the lensed images, though they are caused by the gravitational pull, could be less than unity. Therefore, time-symmetric demagnification parts in numerical light curves by gravitational microlensing [F. Abe, Astrophys. J. 725, 787 (2010)] may be evidence of an Ellis wormhole (being an example of traversable wormholes), but they do not always prove it. Such a gravitational demagnification of the light might be used for hunting a clue of exotic matter and energy that are described by an equation of state more general than the Ellis wormhole case. Numerical calculations for the n=3 and 10 cases show maximally ˜10 and ˜60 percent depletion of the light, when the source position is ?˜1.1 and ?˜0.7, respectively.
Demagnifying gravitational lenses toward hunting a clue of exotic matter and energy
Kitamura, Takao; Asada, Hideki
2012-01-01
We examine a gravitational lens model inspired by modified gravity theories, exotic matter and energy. We study an asymptotically flat, static and spherically symmetric spacetime that is modified in such a way that the spacetime metric depends on the inverse distance to the power of positive n in the weak field approximation. It is shown analytically and numerically that demagnifying gravitational lenses could appear, provided the impact parameter of light $\\beta$ and the power n satisfy $\\beta > 2/(n+1)$ in the units of the Einstein ring radius. Unusually, the total amplification of the lensed images, though they are caused by the gravitational pull, could be less than the unity. Therefore, time-symmetric extinction parts in numerical light curves by gravitational microlensing (Abe, Astrophys. J. 725, 787, 2010) may be an evidence of an Ellis wormhole (being an example of traversable wormholes) but they do not always prove it. Such a gravitational extinction of the light might be used for hunting a clue of e...
Demagnifying gravitational lenses toward hunting a clue of exotic matter and energy
Takao Kitamura; Koki Nakajima; Hideki Asada
2013-01-16
We examine a gravitational lens model inspired by modified gravity theories and exotic matter and energy. We study an asymptotically flat, static, and spherically symmetric spacetime that is modified in such a way that the spacetime metric depends on the inverse distance to the power of positive $n$ in the weak-field approximation. It is shown analytically and numerically that there is a lower limit on the source angular displacement from the lens object to get demagnification. Demagnifying gravitational lenses could appear, provided the source position $\\beta$ and the power $n$ satisfy $\\beta > 2/(n+1)$ in the units of the Einstein ring radius under a large-$n$ approximation. Unusually, the total amplification of the lensed images, though they are caused by the gravitational pull, could be less than unity. Therefore, time-symmetric demagnification parts in numerical light curves by gravitational microlensing (F.Abe, Astrophys. J. 725, 787, 2010) may be evidence of an Ellis wormhole (being an example of traversable wormholes), but they do not always prove it. Such a gravitational demagnification of the light might be used for hunting a clue of exotic matter and energy that are described by an equation of state more general than the Ellis wormhole case. Numerical calculations for the $n=3$ and 10 cases show maximally $\\sim 10$ and $\\sim 60$ percent depletion of the light, when the source position is $\\beta \\sim 1.1$ and $\\beta \\sim 0.7$, respectively.
The HST Frontier Fields: Gravitational Lensing Models Release
NASA Astrophysics Data System (ADS)
Coe, Dan A.; Lotz, J.; Natarajan, P.; Richard, J.; Zitrin, A.; Kneib, J.; Ebeling, H.; Sharon, K.; Johnson, T.; Limousin, M.; Bradac, M.; Hoag, A.; Cain, B.; Merten, J.; Williams, L. L.; Sebesta, K.; Meneghetti, M.; Koekemoer, A. M.; Barker, E. A.
2014-01-01
The Hubble Frontier Fields (HFF) is a Director's Discretionary Time (DDT) program to deeply observe up to six massive strong-lensing galaxy clusters and six "blank" fields in parallel. These complementary observations will yield magnified and direct images of some of the most distant galaxies yet observed. The strongly lensed images will be our deepest views of our universe to date. Interpretation of some (but not all) observed properties of the strongly lensed galaxies requires gravitational lens modeling. In order to maximize the value of this public dataset to the extragalactic community, STScI commissioned five teams funded by NASA to derive the best possible lens models from existing data. After coordinating to share observational constraints, including measured redshifts of strongly lensed galaxies, the teams independently derived lens models using robust, established methodologies. STScI released these models to the community in October before HFF observations of the first cluster, Abell 2744. Here we describe these models as well as a web tool which allows users to extract magnification estimates with uncertainties from all models for any galaxy strongly lensed by a HFF cluster. Inputs are the galaxy's coordinates (RA and Dec), redshift, and (optionally) observed radius. We also discuss ongoing work to study lens model uncertainties by modeling simulated clusters.
QUANTIFYING THE BIASES OF SPECTROSCOPICALLY SELECTED GRAVITATIONAL LENSES
Arneson, Ryan A.; Brownstein, Joel R.; Bolton, Adam S., E-mail: arnesonr@uci.edu, E-mail: joelbrownstein@astro.utah.edu, E-mail: bolton@astro.utah.edu [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States)
2012-07-01
Spectroscopic selection has been the most productive technique for the selection of galaxy-scale strong gravitational lens systems with known redshifts. Statistically significant samples of strong lenses provide a powerful method for measuring the mass-density parameters of the lensing population, but results can only be generalized to the parent population if the lensing selection biases are sufficiently understood. We perform controlled Monte Carlo simulations of spectroscopic lens surveys in order to quantify the bias of lenses relative to parent galaxies in velocity dispersion, mass axis ratio, and mass-density profile. For parameters typical of the SLACS and BELLS surveys, we find (1) no significant mass axis ratio detection bias of lenses relative to parent galaxies; (2) a very small detection bias toward shallow mass-density profiles, which is likely negligible compared to other sources of uncertainty in this parameter; (3) a detection bias toward smaller Einstein radius for systems drawn from parent populations with group- and cluster-scale lensing masses; and (4) a lens-modeling bias toward larger velocity dispersions for systems drawn from parent samples with sub-arcsecond mean Einstein radii. This last finding indicates that the incorporation of velocity-dispersion upper limits of non-lenses is an important ingredient for unbiased analyses of spectroscopically selected lens samples. In general, we find that the completeness of spectroscopic lens surveys in the plane of Einstein radius and mass-density profile power-law index is quite uniform, up to a sharp drop in the region of large Einstein radius and steep mass-density profile, and hence that such surveys are ideally suited to the study of massive field galaxies.
A simple analysis of halo density profiles using gravitational lensing time delays
Benjamin M. Dobke; Lindsay J. King
2006-09-11
Gravitational lensing time delays depend upon the Hubble constant and the density distribution of the lensing galaxies. This allows one to either model the lens and estimate the Hubble constant, or to use a prior on the Hubble constant from other studies and investigate what the preferred density distribution is. Some studies have required compact dark matter halos (constant M/L ratio) in order to reconcile gravitational lenses with the HST/WMAP value of the Hubble constant (72 +/- 8 km/s /Mpc and 72 +/- 5 km/s /Mpc, respectively). This is in direct contradiction with X-ray, stellar dynamical, and weak lensing studies, which all point towards extended halos and isothermal density profiles. In this work, we examine an up-to-date sample of 13 lensing galaxies resulting in a data set consisting of 21 time delays. We select systems in which there is a single primary lensing galaxy (e.g. excluding systems undergoing mergers). Analysis is performed using analytic models based upon a powerlaw density profile (rho \\propto r^-n) of which the isothermal profile is a special case (n = 2). This yields a value of n = 2.11+/-0.12 (3sigma) for the mean profile when modeling with a prior on the Hubble constant, which is only consistent with isothermality within 3 sigma. Note that this is a formal error from our calculations, and does not include the impact of sample selection or simplifications in the lens modeling. We conclude that time delays are a useful probe of density profiles, in particular as a function of the environment in which the lens resides, when combined with a prior on the Hubble constant.
Strong gravitational lensing statistics as a test of cosmogonic scenarios
NASA Technical Reports Server (NTRS)
Cen, Renyue; Gott, J. Richard, III; Ostriker, Jeremiah P.; Turner, Edwin L.
1994-01-01
Gravitational lensing statistics can provide a direct and powerful test of cosmic structure formation theories. Since lensing tests, directly, the magnitude of the nonlinear mass density fluctuations on lines of sight to distant objects, no issues of 'bias' (of mass fluctuations with respect to galaxy density fluctuations) exist here, although lensing observations provide their own ambiguities of interpretation. We develop numerical techniques for generating model density distributions with the very large spatial dynamic range required by lensing considerations and for identifying regions of the simulations capable of multiple image lensing in a conservative and computationally efficient way that should be accurate for splittings significantly larger than 3 seconds. Applying these techniques to existing standard Cold dark matter (CDM) (Omega = 1) and Primeval Baryon Isocurvature (PBI) (Omega = 0.2) simulations (normalized to the Cosmic Background Explorer Satellite (COBE) amplitude), we find that the CDM model predicts large splitting (greater than 8 seconds) lensing events roughly an order-of-magnitude more frequently than the PBI model. Under the reasonable but idealized assumption that lensing structrues can be modeled as singular isothermal spheres (SIS), the predictions can be directly compared to observations of lensing events in quasar samples. Several large splitting (Delta Theta is greater than 8 seconds) cases are predicted in the standard CDM model (the exact number being dependent on the treatment of amplification bias), whereas none is observed. In a formal sense, the comparison excludes the CDM model at high confidence (essentially for the same reason that CDM predicts excessive small-scale cosmic velocity dispersions.) A very rough assessment of low-density but flat CDM model (Omega = 0.3, Lambda/3H(sup 2 sub 0) = 0.7) indicates a far lower and probably acceptable level of lensing. The PBI model is consistent with, but not strongly tested by, the available lensing data, and other open models would presumably do as well as PBI. These preliminary conclusions and the assumptions on which they are based can be tested and the analysis can be applied to other cosmogonic models by straightforward extension of the work presented here.
Intrinsic ellipticity correlations of galaxies: models, likelihoods and interplay with weak lensing
NASA Astrophysics Data System (ADS)
Capranico, Federica; Merkel, Philipp M.; Schäfer, Björn Malte
2013-10-01
Subject of this paper is the statistical properties of ellipticity alignments between galaxies evoked by their coupled angular momenta. Starting from physical angular momentum models, we bridge the gap towards ellipticity correlations, ellipticity spectra and derived quantities such as aperture moments, comparing the intrinsic signals with those generated by gravitational lensing, with the projected galaxy sample of Euclid in mind. We investigate the dependence of intrinsic ellipticity correlations on cosmological parameters and show that intrinsic ellipticity correlations give rise to non-Gaussian likelihoods as a result of non-linear functional dependences. Comparing intrinsic ellipticity spectra to weak lensing spectra we quantify the magnitude of their contaminating effect on the estimation of cosmological parameters and find that biases on dark energy parameters are very small in an angular momentum-based model in contrast to the linear alignment model commonly used. Finally, we quantify whether intrinsic ellipticities can be measured in the presence of the much stronger weak lensing induced ellipticity correlations, if prior knowledge on a cosmological model is assumed.
Weak-lensing statistics from the Coyote Universe
NASA Astrophysics Data System (ADS)
Eifler, Tim
2011-11-01
Analysing future weak-lensing data sets from KIDS, Dark Energy Survey (DES), LSST, Euclid and WFIRST requires precise predictions for the weak-lensing measures. In this paper, we present a weak-lensing prediction code based on the Coyote Universe emulator. The Coyote Universe emulator predicts the (non-linear) power spectrum of density fluctuations (P?) to high accuracy for k?[0.002; 3.4] h Mpc-1 within the redshift interval z?[0; 1]; outside this regime, we extend P? using a modified HALOFIT code. This pipeline is used to calculate various second-order cosmic shear statistics, e.g., shear power spectrum, shear-shear correlation function, ring statistics and Complete Orthogonal Set of EB-mode Integrals (COSEBIs), and we examine how the upper limit in k (and z), to which P? is known, impacts on these statistics. For example, we find that kmax˜ 8 h Mpc-1 causes a bias in the shear power spectrum at ?˜ 4000 that is comparable to the statistical errors (intrinsic shape noise and cosmic variance) of a DES-like survey, whereas for LSST-like errors kmax˜ 15 h Mpc-1 is needed to limit the bias at ?˜ 4000. For the most recently developed second-order shear statistics, the COSEBIs, we find that nine modes can be calculated accurately knowing P? to kmax= 10 h Mpc-1. The COSEBIs allow for an EB-mode decomposition using a shear-shear correlation function measured over a finite range, thereby avoiding any EB-mode mixing due to finite survey size. We perform a detailed study in a five-dimensional parameter space in order to examine whether all cosmological information is captured by these nine modes with the result that already 7-8 modes are sufficient.
A universal probability distribution function for weak-lensing amplification
Yun Wang; Daniel E. Holz; Dipak Munshi
2002-05-06
We present an approximate form for the weak lensing magnification distribution of standard candles, valid for all cosmological models, with arbitrary matter distributions, over all redshifts. Our results are based on a universal probability distribution function (UPDF), $P(\\eta)$, for the reduced convergence, $\\eta$. For a given cosmological model, the magnification probability distribution, $P(\\mu)$, at redshift $z$ is related to the UPDF by $P(\\mu)=P(\\eta)/2|\\kappa_{min}|$, where $\\eta=1+(\\mu-1)/(2|\\kappa_{min}|)$, and $\\kappa_{min}$ (the minimum convergence) can be directly computed from the cosmological parameters ($\\Omega_m$ and $\\Omega_\\Lambda$). We show that the UPDF can be well approximated by a three-parameter stretched Gaussian distribution, where the values of the three parameters depend only on $\\xi_\\eta$, the variance of $\\eta$. In short, all possible weak lensing probability distributions can be well approximated by a one-parameter family. We establish this family, normalizing to the numerical ray-shooting results for a ${\\Lambda}$CDM model by Wambsganss et al. (1997). Each alternative cosmological model is then described by a single function $\\xi_\\eta(z)$. We find that this method gives $P(\\mu)$ in excellent agreement with numerical ray-tracing and three-dimensional shear matrix calculations, and provide numerical fits for three representative models (SCDM, $\\Lambda$CDM, and OCDM). Our results provide an easy, accurate, and efficient method to calculate the weak lensing magnification distribution of standard candles, and should be useful in the analysis of future high-redshift supernova data.
A Cosmological Test of Standard Gravity by Weak Lensing
Yong-Seon Song
2006-03-06
The large scale structure formation in the standard Einstein gravity at later time is uniquely determined by the expansion history H(z) measured by the geometrical factor. A possible departure from the expected standard structure formation is detectable by growth structure test. We design new deviation parameters to test standard gravity at large scales and estimate the expected errors by weak lensing experiment. The effective Newtonian constant G_N at the present time can be constrained around 10% accuracy by measuring the difference curvature perturbations (\\Phi-\\Psi)/2 within 2% accuracy.
Gravitational Lensing Size Scales for Quasars
NASA Astrophysics Data System (ADS)
Chartas, G.; Kochanek, C.; Dai, X.; Morgan, C.; Blackburne, J.; Chen, B.; Mosquera, A.; MacLeod, C.
2015-07-01
We review results from our monitoring observations of several lensed quasars performed in the optical, UV, and X-ray bands. Modeling of the multi-wavelength light curves provides constraints on the extent of the optical, UV and X-ray emission regions. One of the important results of our analysis is that the optical sizes as inferred from the microlesning analysis are significantly larger than those predicted by the theoretical-thin-disk estimate. In a few cases we also constrain the slope of the size-wavelength relation. Our size constraints of the soft and hard X-ray emission regions of quasars indicate that in some objects of our sample the hard emission region is more compact than the soft and in others the soft emission region is smaller. This difference may be the result of the relative strengths of the disk-reflected (harder and extended) versus corona-direct (softer and compact) components in the quasars of our sample. Finally, we present the analysis of several strong microlensing events where we detect an evolution of the relativistic Fe line profile as the magnification caustic traverses the accretion disk. These caustic crossings are used to provide independent estimates of the size of Fe K emission region.
Reflection Symmetry of Cusps in Gravitational Lensing
Rhie, S H
2002-01-01
Criticality in graviational microlensing is an everyday issue because that is what generates microlensing signals which may be of photon-challenged compact objects such as black holes or planetary systems ET calls home. The criticality of these quasi-analytic lenses is intrinsically quadratic, and the critical curve behaves as a mirror generating two mirror images along the image line (parallel +/- E_-) at the same distances from the critical curve in the opposite sides. At the (pre)cusps where the caustic curve "reflects" and develops cusps, however, "would-be" two pairs of quadratic images "superpose" to produce three mirror images because of the degenerate criticality. The critical curve behaves as a parabolic mirror, and the image inside the parabola is indeed a superposed image having the sum of the magnifications of the other two that are outside the parabola. All three images lie on a parabolic image curve shaped by a property (nabla J) of the (pre)cusp, and two distances of the system determine the po...
On the Contribution of Large-Scale Structure to Strong Gravitational Lensing
NASA Astrophysics Data System (ADS)
Faure, C.; Kneib, J.-P.; Hilbert, S.; Massey, R.; Covone, G.; Finoguenov, A.; Leauthaud, A.; Taylor, J. E.; Pires, S.; Scoville, N.; Koekemoer, Anton M.
2009-04-01
We study the correlation between the locations of galaxy-galaxy strong-lensing candidates and tracers of large-scale structure from both weak lensing (WL) or X-ray emission. The Cosmological Evolution Survey (COSMOS) is a unique data set, combining deep, high resolution and contiguous imaging in which strong lenses have been discovered, plus unparalleled multiwavelength coverage. To help interpret the COSMOS data, we have also produced mock COSMOS strong- and WL observations, based on ray-tracing through the Millennium Simulation. In agreement with the simulations, we find that strongly lensed images with the largest angular separations are found in the densest regions of the COSMOS field. This is explained by a prevalence among the lens population in dense environments of elliptical galaxies with high total-to-stellar mass ratios, which can deflect light through larger angles. However, we also find that the overall fraction of elliptical galaxies with strong gravitational lensing is independent of the local mass density; this observation is not true of the simulations, which predict an increasing fraction of strong lenses in dense environments. The discrepancy may be a real effect, but could also be explained by various limitations of our analysis. For example, our visual search of strong lens systems could be incomplete and suffer from selection bias; the luminosity function of elliptical galaxies may differ between our real and simulated data; or the simplifying assumptions and approximations used in our lensing simulations may be inadequate. Work is therefore ongoing. Automated searches for strong lens systems will be particularly important in better constraining the selection function.
A Comparison of Cosmological Models Using Strong Gravitational Lensing Galaxies
Fulvio Melia; Jun-Jie Wei; Xue-Feng Wu
2014-10-03
Strongly gravitationally lensed quasar-galaxy systems allow us to compare competing cosmologies as long as one can be reasonably sure of the mass distribution within the intervening lens. In this paper, we assemble a catalog of 69 such systems, and carry out a one-on-one comparison between the standard model, LCDM, and the R_h=ct Universe. We find that both models account for the lens observations quite well, though the precision of these measurements does not appear to be good enough to favor one model over the other. Part of the reason is the so-called bulge-halo conspiracy that, on average, results in a baryonic velocity dispersion within a fraction of the optical effective radius virtually identical to that expected for the whole luminous-dark matter distribution. Given the limitations of doing precision cosmological testing using the current sample, we also carry out Monte Carlo simulations based on the current lens measurements to estimate how large the source catalog would have to be in order to rule out either model at a ~99.7% confidence level. We find that if the real cosmology is LCDM, a sample of ~200 strong gravitational lenses would be sufficient to rule out R_h=ct at this level of accuracy, while ~300 strong gravitational lenses would be required to rule out LCDM if the real Universe were instead R_h=ct. The difference in required sample size reflects the greater number of free parameters available to fit the data with LCDM. We point out that, should the R_h=ct Universe eventually emerge as the correct cosmology, its lack of any free parameters for this kind of work will provide a remarkably powerful probe of the mass structure in lensing galaxies, and a means of better understanding the origin of the bulge-halo conspiracy.
Gravitational lensing in plasma: Relativistic images at homogeneous plasma
Oleg Yu. Tsupko; Gennady S. Bisnovatyi-Kogan
2013-05-30
We investigate the influence of plasma presence on relativistic images formed by Schwarzschild black hole lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on a frequency of the electromagnetic wave due to refraction properties, and the dispersion properties of the light propagation in gravitational field in plasma. The last effect leads to difference, even in uniform plasma, of gravitational deflection angle in plasma from vacuum case. This angle depends on the photon frequency, what resembles the properties of the refractive prism spectrometer. Here we consider the case of a strong deflection angle for the light, traveling near the Schwarzschild black hole, surrounded by a uniform plasma. Asymptotic formulae are obtained for the case of a very large deflection angle, exceeding $2\\pi$. We apply these formulae for calculation of position and magnification of relativistic images in a homogeneous plasma, which are formed by the photons performing one or several revolutions around the central object. We conclude that the presence of the uniform plasma increases the angular size of relativistic rings or the angular separation of point images from the gravitating center. The presence of the uniform plasma increases also a magnification of relativistic images. The angular separation and the magnification become significantly larger than in the vacuum case, when the photon frequency goes to a plasma frequency.
Fast calculation of the weak lensing aperture mass statistic
NASA Astrophysics Data System (ADS)
Leonard, Adrienne; Pires, Sandrine; Starck, Jean-Luc
2012-07-01
The aperture mass statistic is a common tool used in weak lensing studies. By convolving lensing maps with a filter function of a specific scale, chosen to be larger than the scale on which the noise is dominant, the lensing signal may be boosted with respect to the noise. This allows for detection of structures at increased fidelity. Furthermore, higher order statistics of the aperture mass (such as its skewness or kurtosis), or counting of the peaks seen in the resulting aperture mass maps, provide a convenient and effective method to constrain the cosmological parameters. In this paper, we more fully explore the formalism underlying the aperture mass statistic. We demonstrate that the aperture mass statistic is formally identical to a wavelet transform at a specific scale. Further, we show that the filter functions most frequently used in aperture mass studies are not ideal, being non-local in both real and Fourier space. In contrast, the wavelet formalism offers a number of wavelet functions that are localized both in real and Fourier space, yet similar to the optimal aperture mass filters commonly adopted. Additionally, for a number of wavelet functions, such as the starlet wavelet, very fast algorithms exist to compute the wavelet transform. This offers significant advantages over the usual aperture mass algorithm when it comes to image processing time, demonstrating speed-up factors of ˜5-1200 for aperture radii in the range 2-64 pixels on an image of 1024 × 1024 pixels.
NASA Astrophysics Data System (ADS)
Biesiada, Marek; Ding, Xuheng; Piórkowska, Aleksandra; Zhu, Zong-Hong
2014-10-01
Gravitational wave (GW) experiments are entering their advanced stage which should soon open a new observational window on the Universe. Looking into this future, the Einstein Telescope (ET) was designed to have a fantastic sensitivity improving significantly over the advanced GW detectors. One of the most important astrophysical GW sources supposed to be detected by the ET in large numbers are double compact objects (DCO) and some of such events should be gravitationally lensed by intervening galaxies. We explore the prospects of observing gravitationally lensed inspiral DCO events in the ET. This analysis is a significant extension of our previous paper [1]. We are using the intrinsic merger rates of the whole class of DCO (NS-NS,BH-NS,BH-BH) located at different redshifts as calculated by [2] by using StarTrack population synthesis evolutionary code. We discuss in details predictions from each evolutionary scenario. Our general conclusion is that ET would register about 50-100 strongly lensed inspiral events per year. Only the scenario in which nascent BHs receive strong kick gives the predictions of a few events per year. Such lensed events would be dominated by the BH-BH merging binary systems. Our results suggest that during a few years of successful operation ET will provide a considerable catalog of strongly lensed events.
Gravitational Lensing of the SDSS High-Redshift Quasars
Stuart Wyithe; Abraham Loeb
2002-05-23
We predict the effects of gravitational lensing on the color-selected flux-limited samples of z~4.3 and z>5.8 quasars, recently published by the Sloan Digital Sky Survey (SDSS). Our main findings are: (i) The lensing probability should be 1-2 orders of magnitude higher than for conventional surveys. The expected fraction of multiply-imaged quasars is highly sensitive to redshift and the uncertain slope of the bright end of the luminosity function, beta_h. For beta_h=2.58 (3.43) we find that at z~4.3 and i*5.8 quasars acquire median magnifications of med(mu_obs)~1.1-1.3 and mean magnifications of ~5-50. Estimates of the quasar luminosity density at high redshift must therefore filter out gravitationally-lensed sources. (iii) The flux in the Gunn-Peterson trough of the highest redshift (z=6.28) quasar is known to be f_lambda5.8 catalog varying by more than 0.5 magnitudes over the next decade. The median equivalent width would be lowered by ~20% with respect to the intrinsic value due to differential magnification of the continuum and emission-line regions.
Creating images by adding masses to gravitational point lenses
NASA Astrophysics Data System (ADS)
Sète, Olivier; Luce, Robert; Liesen, Jörg
2015-04-01
A well-studied maximal gravitational point lens construction of S. H. Rhie produces images of a light source using deflector masses. The construction arises from a circular, symmetric deflector configuration on masses (producing only images) by adding a tiny mass in the center of the other mass positions (and reducing all the other masses a little bit). In a recent paper we studied this "image creating effect" from a purely mathematical point of view (Sète, Luce & Liesen, Comput. Methods Funct. Theory 15(1), 2014). Here we discuss a few consequences of our findings for gravitational microlensing models. We present a complete characterization of the effect of adding small masses to these point lens models, with respect to the number of images. In particular, we give several examples of maximal lensing models that are different from Rhie's construction and that do not share its highly symmetric appearance. We give generally applicable conditions that allow the construction of maximal point lenses on masses from maximal lenses on masses.
Subaru Weak Lensing Study of Merging Clusters of Galaxies
NASA Astrophysics Data System (ADS)
Umetsu, K.; Okabe, N.
2008-10-01
We present 2D maps of mass, galaxies, and the intracluster medium (ICM) for a sample of merging clusters of galaxies based on a joint weak-lensing, optical photometric, and X-ray analysis. Our target clusters, representing various merging stages and conditions, allow us to investigate in details the physical interplay between dark matter, ICM, and galaxies associated with cluster formation and evolution. In the binary clusters, the projected mass, optical light, and X-ray distributions are overall similar and regular without significant substructures. On-going and cold-front merging clusters, on the other hand, reveal highly irregular mass distributions. Overall the mass distribution appears to be similar to the galaxy luminosity distribution, whereas their distributions are quite different from the ICM distribution in a various ways. A comparison of the ICM and virial temperatures of merging clusters from X-ray and weak-lensing analyses, respectively, shows that the ICM temperature of on-going and cold-front clusters is systematically higher than the cluster virial temperature by a factor of ˜ 2. This temperature excess in the ICM could be explained by the effects of merger boosts.
The Multi-Band Magnification Bias for Gravitational Lenses
J. Stuart B. Wyithe; Joshua N. Winn; David Rusin
2002-08-29
We present a generalization of the concept of magnification bias for gravitationally-lensed quasars, in which the quasars are selected by flux in more than one wavelength band. To illustrate the principle, we consider the case of two-band selection, in which the fluxes in the two bands are uncorrelated, perfectly correlated, or correlated with scatter. For uncorrelated fluxes, we show that the previously-held result - that the bias is the product of the single-band biases - is generally false. We demonstrate some important properties of the multi-band magnification bias using model luminosity functions inspired by observed correlations among X-ray, optical, infrared and radio fluxes of quasars. In particular, the bias need not be an increasing function of each flux, and the bias can be extremely large for non-linear correlations. The latter fact may account for the high lensing rates found in some X-ray/optical and infrared/radio selected samples.
Light Bending and Gravitational Lensing as Tests of Lorentz Symmetry
NASA Astrophysics Data System (ADS)
Tso, Rhondale; Bailey, Quentin
2011-12-01
Einstein's famous prediction from General Relativity (GR) of the bending of distant starlight by the Sun was first verified in 1919 by Eddington and Dyson. With the onset of radio astronomy this deflection angle has been verified to better than 1% accuracy. Today, state of the art light-bending experiments and gravitational lensing observations are underway that can rigorously test this prediction. In light of recent and upcoming tests for deviations from GR we utilize the gravity sector of the Standard-Model Extension (SME) to derive a modified deflection angle that describes deviations from Lorentz symmetry. The model developed can be used as a framework for analysis in upcoming light-bending and lensing observations that are designed to detect deviations from General Relativity.
SPITZER IMAGING OF HERSCHEL-ATLAS GRAVITATIONALLY LENSED SUBMILLIMETER SOURCES
Hopwood, R.; Negrello, M. [Department of Physics and Astronomy, Open University, Milton Keynes, MK7 6AA (United Kingdom); Wardlow, J.; Cooray, A.; Khostovan, A. A.; Kim, S.; Barton, E. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Da Cunha, E.; Cooke, J. [Department of Physics, University of Crete, Heraklion (Greece); Burgarella, D. [Laboratoire d'Astrophysique de Marseille, OAMP, CNRS, Aix-Marseille Universite (France); Aretxaga, I. [Instituto Nacional de Astrofisica, Optica y Electronica, Aptdo. Postal 51 y 216, 72000 Puebla (Mexico); Auld, R. [School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA (United Kingdom); Baes, M. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Bertoldi, F. [Argenlander Institute for Astronomy, University of Bonn, Auf dem Hugel 71, 53121 Bonn (Germany); Bonfield, D. G. [Centre for Astrophysics Research, Science and Technology Research Centre, University of Hertfordshire, Herts AL10 9AB (United Kingdom); Blundell, R. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Buttiglione, S. [INAF, Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, I-35122 Padova (Italy); Cava, A. [Instituto de Astrofisica de Canarias, C/Va Lactea s/n, E-38200 La Laguna (Spain); Clements, D. L. [Astrophysics Group, Physics Department, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Dannerbauer, H. [Laboratoire AIM Paris Saclay, CEA-CNRS-Universite, Irfu/Service d'Astrophysique, CEA Saclay, Orme de Merisiers, 91191 Gif-sur-Yvette Cedex (France)
2011-02-10
We present physical properties of two submillimeter selected gravitationally lensed sources, identified in the Herschel Astrophysical Terahertz Large Area Survey. These submillimeter galaxies (SMGs) have flux densities >100 mJy at 500 {mu}m, but are not visible in existing optical imaging. We fit light profiles to each component of the lensing systems in Spitzer IRAC 3.6 and 4.5 {mu}m data and successfully disentangle the foreground lens from the background source in each case, providing important constraints on the spectral energy distributions (SEDs) of the background SMG at rest-frame optical-near-infrared wavelengths. The SED fits show that these two SMGs have high dust obscuration with A{sub V} {approx} 4-5 and star formation rates of {approx}100 M{sub sun} yr{sup -1}. They have low gas fractions and low dynamical masses compared with 850 {mu}m selected galaxies.
Gravitationally lensed QSOs in the ISSIS/WSO-UV era
Goicoechea, Luis J; Gil-Merino, Rodrigo; 10.1007/s10509-011-0625-x
2011-01-01
Gravitationally lensed QSOs (GLQs) at redshift z = 1-2 play a key role in understanding the cosmic evolution of the innermost parts of active galaxies (black holes, accretion disks, coronas and internal jets), as well as the structure of galaxies at intermediate redshifts. With respect to studies of normal QSOs, GLQ programmes have several advantages. For example, a monitoring of GLQs may lead to unambiguous detections of intrinsic and extrinsic variations. Both kinds of variations can be used to discuss central engines in distant QSOs, and mass distributions and compositions of lensing galaxies. In this context, UV data are of particular interest, since they correspond to emissions from the immediate surroundings of the supermassive black hole. We describe some observation strategies to analyse optically bright GLQs at z of about 1.5, using ISSIS (CfS) on board World Space Observatory-Ultraviolet.
Improving efficiency in radio surveys for gravitational lenses
N. Jackson; I. W. A. Browne
2006-09-29
Many lens surveys have hitherto used observations of large samples of background sources to select the small minority which are multiply imaged by lensing galaxies along the line of sight. Recently surveys such as SLACS and OLS have improved the efficiency of surveys by pre-selecting double-redshift systems from SDSS. We explore other ways to improve survey efficiency by optimum use of astrometric and morphological information in existing large-scale optical and radio surveys. The method exploits the small position differences between FIRST radio positions of lensed images and the SDSS lens galaxy positions, together with the marginal resolution of some larger gravitational lens systems by the FIRST beam. We present results of a small pilot study with the VLA and MERLIN, and discuss the desirable criteria for future surveys.
An attempt to measure the time delays of three gravitational lenses
Chistol, Gheorghe
2007-01-01
I present the results of reduction and analysis of two seasons of gravitational lens monitoring using the Very Large Array (VLA) at 8.5 GHz. The campaign monitored five gravitational lenses, GL1608, GL1830, GL1632, GL1838, ...
Infrared observations of gravitational lensing in Abell 2219 with CIRSI
NASA Astrophysics Data System (ADS)
Gray, Meghan E.; Ellis, Richard S.; Refregier, Alexandre; Bézecourt, Jocelyn; McMahon, Richard G.; Beckett, Martin G.; Mackay, Craig D.; Hoenig, Michael D.
2000-10-01
We present the first detection of a gravitational depletion signal at near-infrared wavelengths, based on deep panoramic images of the cluster Abell 2219 (z=0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at the prime focus of the 4.2-m William Herschel Telescope. Infrared studies of gravitational depletion offer a number of advantages over similar techniques applied at optical wavelengths, and can provide reliable total masses for intermediate-redshift clusters. Using the maximum-likelihood technique developed by Schneider, King & Erben, we detect the gravitational depletion at the 3? confidence level. By modelling the mass distribution as a singular isothermal sphere and ignoring the uncertainty in the unlensed number counts, we find an Einstein radius of ?E ~= 13.7+3.9-4.2 arcsec (66per cent confidence limit). This corresponds to a projected velocity dispersion of ?v~800kms-1, in agreement with constraints from strongly lensed features. For a Navarro, Frenk & White mass model, the radial dependence observed indicates a best-fitting halo scalelength of 125h-1kpc. We investigate the uncertainties arising from the observed fluctuations in the unlensed number counts, and show that clustering is the dominant source of error. We extend the maximum-likelihood method to include the effect of incompleteness, and discuss the prospects of further systematic studies of lensing in the near-infrared band.
Infrared observations of gravitational lensing in Abell 2219 with CIRSI
Meghan E. Gray; Richard S. Ellis; Alexandre Refregier; Jocelyn Bezecourt; Richard G. McMahon; Martin G. Beckett; Craig D. Mackay; Michael D. Hoenig
2000-06-21
We present the first detection of a gravitational depletion signal at near-infrared wavelengths, based on deep panoramic images of the cluster Abell 2219 (z=0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at the prime focus of the 4.2m William Herschel Telescope. Infrared studies of gravitational depletion offer a number of advantages over similar techniques applied at optical wavelengths, and can provide reliable total masses for intermediate redshift clusters. Using the maximum likelihood technique developed by Schneider, King & Erben (1999), we detect the gravitational depletion at the 3 sigma confidence level. By modeling the mass distribution as a singular isothermal sphere and ignoring uncertainty in the unlensed number counts, we find an Einstein radius of 13.7 +3.9/-4.2 arcsec (66% confidence limit). This corresponds to a projected velocity dispersion of approximately 800 km/s, in agreement with constraints from strongly-lensed features. For a Navarro, Frenk and White mass model, the radial dependence observed indicates a best-fitting halo scale length of 125/h kpc}. We investigate the uncertainties arising from the observed fluctuations in the unlensed number counts, and show that clustering is the dominant source of error. We extend the maximum likelihood method to include the effect of incompleteness, and discuss the prospects of further systematic studies of lensing in the near-infrared band.
Quasar Structure from Microlensing in Gravitationally Lensed Quasars
NASA Astrophysics Data System (ADS)
Morgan, Christopher W.
2007-12-01
I investigate microlensing in gravitationally lensed quasars and discuss the use of its signal to probe quasar structure on small angular scales. I describe our lensed quasar optical monitoring program and RETROCAM, the optical camera I built for the 2.4m Hiltner telescope to monitor lensed quasars. I use the microlensing variability observed in 11 gravitationally lensed quasars to show that the accretion disk size at 2500Å is related to the black hole mass by log(R2500/cm) = (15.70±0.16) + (0.64±0.18)log(MBH/109M?). This scaling is consistent with the expectation from thin disk theory (R ? MBH2/3), but it implies that black holes radiate with relatively low efficiency, log(?) = -1.54±0.36 + log(L/LE) where ?=L/(Mdotc2). With one exception, these sizes are larger by a factor of 4 than the size needed to produce the observed 0.8µm quasar flux by thermal radiation from a thin disk with the same T ? R-3/4 temperature profile. More sophisticated disk models are clearly required, particularly as our continuing observations improve the precision of the measurements and yield estimates of the scaling with wavelength and accretion rate. This research made extensive use of a Beowulf computer cluster obtained through the Cluster Ohio program of the Ohio Supercomputer Center. Support for program HST-GO-9744 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS-5-26666.
Effects of supermassive binary black holes on gravitational lenses
NASA Astrophysics Data System (ADS)
Li, Nan; Mao, Shude; Gao, Liang; Loeb, Abraham; di Stefano, R.
2012-01-01
Recent observations indicate that many, if not all, galaxies host massive central black holes (BHs). In this paper, we explore the influence of supermassive binary black holes (SMBBHs) on their actions as gravitational lenses. When lenses are modelled as singular isothermal ellipsoids, binary BHs change the critical curves and caustics differently as a function of distance. Each BH can in principle create at least one additional image, which, if observed, provides evidence of BHs. By studying how SMBBHs affect the cumulative distribution of magnification for images created by BHs, we find that the cross-section for at least one such additional image to have a magnification larger than 10-5 is comparable to the cross-section for producing multiple images in singular isothermal lenses. Such additional images may be detectable with high-resolution and large dynamic range maps of multiply imaged systems from future facilities, such as the Square Kilometre Array. The probability of detecting at least one image (two images) with magnification above 10-3 is ˜0.2fBH (˜0.05fBH) in a multiply imaged lens system, where fBH is the fraction of galaxies housing binary BHs. We also study the effects of SMBBHs on the core images when galaxies have shallower central density profiles (modelled as non-singular isothermal ellipsoids). We find that the cross-section of the usually faint core images is further suppressed by SMBBHs. Thus, their presence should also be taken into account when one constrains the core radius from the lack of central images in gravitational lenses.
A Comparison of Cosmological Models Using Strong Gravitational Lensing Galaxies
NASA Astrophysics Data System (ADS)
Melia, Fulvio; Wei, Jun-Jie; Wu, Xue-Feng
2015-01-01
Strongly gravitationally lensed quasar-galaxy systems allow us to compare competing cosmologies as long as one can be reasonably sure of the mass distribution within the intervening lens. In this paper, we assemble a catalog of 69 such systems from the Sloan Lens ACS and Lens Structure and Dynamics surveys suitable for this analysis, and carry out a one-on-one comparison between the standard model, ?CDM, and the {{R}h}=ct universe, which has thus far been favored by the application of model selection tools to other kinds of data. We find that both models account for the lens observations quite well, though the precision of these measurements does not appear to be good enough to favor one model over the other. Part of the reason is the so-called bulge-halo conspiracy that, on average, results in a baryonic velocity dispersion within a fraction of the optical effective radius virtually identical to that expected for the whole luminous-dark matter distribution modeled as a singular isothermal ellipsoid, though with some scatter among individual sources. Future work can greatly improve the precision of these measurements by focusing on lensing systems with galaxies as close as possible to the background sources. Given the limitations of doing precision cosmological testing using the current sample, we also carry out Monte Carlo simulations based on the current lens measurements to estimate how large the source catalog would have to be in order to rule out either model at a ˜ 99.7% confidence level. We find that if the real cosmology is ?CDM, a sample of ˜ 200 strong gravitational lenses would be sufficient to rule out {{R}h}=ct at this level of accuracy, while ˜ 300 strong gravitational lenses would be required to rule out ?CDM if the real universe were instead {{R}h}=ct. The difference in required sample size reflects the greater number of free parameters available to fit the data with ?CDM. We point out that, should the {{R}h}=ct universe eventually emerge as the correct cosmology, its lack of any free parameters for this kind of work will provide a remarkably powerful probe of the mass structure in lensing galaxies, and a means of better understanding the origin of the bulge-halo conspiracy.
A comparison of cosmological models using strong gravitational lensing galaxies
Melia, Fulvio; Wei, Jun-Jie; Wu, Xue-Feng, E-mail: fmelia@email.arizona.edu, E-mail: jjwei@pmo.ac.cn, E-mail: xfwu@pmo.ac.cn, E-mail: fmelia@email.arizona.edu, E-mail: jjwei@pmo.ac.cn, E-mail: xfwu@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
2015-01-01
Strongly gravitationally lensed quasar-galaxy systems allow us to compare competing cosmologies as long as one can be reasonably sure of the mass distribution within the intervening lens. In this paper, we assemble a catalog of 69 such systems from the Sloan Lens ACS and Lens Structure and Dynamics surveys suitable for this analysis, and carry out a one-on-one comparison between the standard model, ?CDM, and the R{sub h}=ct universe, which has thus far been favored by the application of model selection tools to other kinds of data. We find that both models account for the lens observations quite well, though the precision of these measurements does not appear to be good enough to favor one model over the other. Part of the reason is the so-called bulge-halo conspiracy that, on average, results in a baryonic velocity dispersion within a fraction of the optical effective radius virtually identical to that expected for the whole luminous-dark matter distribution modeled as a singular isothermal ellipsoid, though with some scatter among individual sources. Future work can greatly improve the precision of these measurements by focusing on lensing systems with galaxies as close as possible to the background sources. Given the limitations of doing precision cosmological testing using the current sample, we also carry out Monte Carlo simulations based on the current lens measurements to estimate how large the source catalog would have to be in order to rule out either model at a ?99.7% confidence level. We find that if the real cosmology is ?CDM, a sample of ?200 strong gravitational lenses would be sufficient to rule out R{sub h}=ct at this level of accuracy, while ?300 strong gravitational lenses would be required to rule out ?CDM if the real universe were instead R{sub h}=ct. The difference in required sample size reflects the greater number of free parameters available to fit the data with ?CDM. We point out that, should the R{sub h}=ct universe eventually emerge as the correct cosmology, its lack of any free parameters for this kind of work will provide a remarkably powerful probe of the mass structure in lensing galaxies, and a means of better understanding the origin of the bulge-halo conspiracy.
Gravitational lens equation for embedded lenses; magnification and ellipticity
Chen, B. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks, Norman, Oklahoma 73019 (United States); Mathematics Department, University of Oklahoma, 601 Elm Avenue, Norman, Oklahoma 73019 (United States); Kantowski, R.; Dai, X. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks, Norman, Oklahoma 73019 (United States)
2011-10-15
We give the lens equation for light deflections caused by point mass condensations in an otherwise spatially homogeneous and flat universe. We assume the signal from a distant source is deflected by a single condensation before it reaches the observer. We call this deflector an embedded lens because the deflecting mass is part of the mean density. The embedded lens equation differs from the conventional lens equation because the deflector mass is not simply an addition to the cosmic mean. We prescribe an iteration scheme to solve this new lens equation and use it to compare our results with standard linear lensing theory. We also compute analytic expressions for the lowest order corrections to image amplifications and distortions caused by incorporating the lensing mass into the mean. We use these results to estimate the effect of embedding on strong lensing magnifications and ellipticities and find only small effects, <1%, contrary to what we have found for time delays and for weak lensing, {approx}5%.
IMPROVED CONSTRAINTS ON THE GRAVITATIONAL LENS Q0957+561. II. STRONG LENSING
Fadely, R.; Keeton, C. R. [Department of Physics and Astronomy, Rutgers, State University of New Jersey, Piscataway, NJ 08854 (United States); Nakajima, R.; Bernstein, G. M., E-mail: fadely@physics.rutgers.ed, E-mail: keeton@physics.rutgers.ed, E-mail: garyb@physics.upenn.ed, E-mail: rnakajima@berkeley.ed [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)
2010-03-01
We present a detailed strong lensing analysis of a Hubble Space Telescope/Advanced Camera for Surveys legacy data set for the first gravitational lens, Q0957+561. With deep imaging we identify 24 new strongly lensed features, which we use to constrain mass models. We model the stellar component of the lens galaxy using the observed luminosity distribution and the dark matter halo using several different density profiles. We draw on the weak lensing analysis by Nakajima et al. to constrain the mass sheet and environmental terms in the lens potential. Adopting the well-measured time delay, we find H{sub 0} = 85{sup +14}{sub -13} km s{sup -1} Mpc{sup -1} (68% CL) using lensing constraints alone. The principal uncertainties in H{sub 0} are tied to the stellar mass-to-light ratio (a variant of the radial profile degeneracy in lens models). Adding constraints from stellar population synthesis models, we obtain H{sub 0} = 79.3{sup +6.7}{sub -8.5} km s{sup -1} Mpc{sup -1} (68% CL). We infer that the lens galaxy has a rising rotation curve and a dark matter distribution with an inner core. Intriguingly, we find the quasar flux ratios predicted by our models to be inconsistent with existing radio measurements, suggesting the presence of substructure in the lens.
Cusped Mass Density Profiles and Magnification Ratios of Double Image Gravitational Lenses
P. T. Mutka
2009-01-01
We have been able to connect the statistics of the observed double image gravitational lenses to the general properties of the internal structure of dark matter haloes. Our analytical theory for the GNFW lenses with parametrized cusp slope (alpha) gives us a relation connecting the cusp slope of the lensing profile to the observed magnification ratio of the produced images
Discriminating weak lensing from intrinsic spin correlations using the curl-gradient decomposition
Robert G. Crittenden; Priyamvada Natarajan; Ue-Li Pen; Tom Theuns
2000-12-15
The distortion field defined by the ellipticities of galaxy shapes projected on the sky can be uniquely decomposed into a gradient and a curl component. If the observed ellipticities are induced by weak gravitational lensing, then the distortion field is curl free. Here we show that, in contrast, the distortion field resulting from intrinsic spin alignments is not curl free. This provides a powerful discriminant between lensing and intrinsic contributions to observed ellipticity correlations. We also show how these contributions can be disentangled statistically from the ellipticity correlations or computed locally from circular integrals of the ellipticity field. This allows for an unambiguous detection of intrinsic galaxy alignments in the data. When the distortions are dominated by lensing, as occurs at high redshifts, the decomposition provides a valuable tool for understanding properties of the noise and systematic errors. These techniques can be applied equally well to the polarization of the microwave background, where it can be used to separate curl-free scalar perturbations from those produced by gravity waves or defects.
Bowens-Rubin, Rachel
We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/ ...
Self-Calibration Technique for 3-point Intrinsic Alignment Correlations in Weak Lensing Surveys
M. A. Troxel; Mustapha Ishak
2011-12-23
The intrinsic alignment (IA) of galaxies has been shown to be a significant barrier to precision cosmic shear measurements. (Zhang, 2010, ApJ, 720, 1090) proposed a self-calibration technique for the power spectrum to calculate the induced gravitational shear-galaxy intrinsic ellipticity correlation (GI) in weak lensing surveys with photo-z measurements which is expected to reduce the IA contamination by at least a factor of 10 for currently proposed surveys. We confirm this using an independent analysis and propose an expansion to the self-calibration technique for the bispectrum in order to calculate the dominant IA gravitational shear-gravitational shear-intrinsic ellipticity correlation (GGI) contamination. We first establish an estimator to extract the galaxy density-density-intrinsic ellipticity (ggI) correlation from the galaxy ellipticity-density-density measurement for a photo-z galaxy sample. We then develop a relation between the GGI and ggI bispectra, which allows for the estimation and removal of the GGI correlation from the cosmic shear signal. We explore the performance of these two methods, compare to other possible sources of error, and show that the GGI self-calibration technique can potentially reduce the IA contamination by up to a factor of 5-10 for all but a few bin choices, thus reducing the contamination to the percent level. The self-calibration is less accurate for adjacent bins, but still allows for a factor of three reduction in the IA contamination. The self-calibration thus promises to be an efficient technique to isolate both the 2-point and 3-point intrinsic alignment signals from weak lensing measurements.
Application of a New, Relativistic Gravitational Lensing Technique to RXJ1347-1145
Thomas P. Kling
2004-01-01
Gravitational lensing is the bending and distortion of light rays by the gravitational pull of massive objects in the universe. Lensing studies are significant to the current revolution in modern astrophysics through which the ultimate questions of the universe – how did the universe begin and what conditions permit life to develop – are being answered. Although the distortion of
Random walks in cosmology: Weak lensing, the halo model, and reionization
Jun Zhang
2006-01-01
This thesis discusses theoretical problems in three areas of cosmology: weak lensing, the halo model, and reionization. In weak lensing, we investigate the impact of the intrinsic alignment on the density-ellipticity correlations using the tidal torquing theory. Under the assumption of the Gaussianity of the tidal field, we find that the intrinsic alignment does not contaminate the density-ellipticity correlation even
Weak Lensing and Supernovae: Complementary Probes of Dark Energy
L. Knox; A. Albrecht; Y. S. Song
2004-08-07
Weak lensing observations and supernova observations, combined with CMB observations, can both provide powerful constraints on dark energy properties. Considering statistical errors only, we find luminosity distances inferred from 2000 supernovae and large-scale (l < 1000) angular power spectra inferred from redshift-binned cosmic shear maps place complementary constraints on w_0 and w_a where w(z) = w_0 + w_a(a-1). Further, each set of observations can constrain higher-dimensional parameterizations of w(z); we consider eigenmodes of the w(z) error covariance matrix and find such datasets can each constrain the amplitude of about 5 w(z) eigenmodes. We also consider another parameterization of the dark energy.
Broad Iron Emission from Gravitationally Lensed Quasars Observed by Chandra
NASA Astrophysics Data System (ADS)
Walton, D. J.; Reynolds, M. T.; Miller, J. M.; Reis, R. C.; Stern, D.; Harrison, F. A.
2015-06-01
Recent work has demonstrated the potential of gravitationally lensed quasars to extend measurements of black hole spin out to high redshift with the current generation of X-ray observatories. Here we present an analysis of a large sample of 27 lensed quasars in the redshift range 1.0? z? 4.5 observed with Chandra, utilizing over 1.6 Ms of total observing time, focusing on the rest-frame iron K emission from these sources. Although the X-ray signal-to-noise ratio (S/N) currently available does not permit the detection of iron emission from the inner accretion disk in individual cases in our sample, we find significant structure in the stacked residuals. In addition to the narrow core, seen almost ubiquitously in local active galactic nuclei (AGNs), we find evidence for an additional underlying broad component from the inner accretion disk, with a clear red wing to the emission profile. Based on simulations, we find the detection of this broader component to be significant at greater than the 3? level. This implies that iron emission from the inner disk is relatively common in the population of lensed quasars, and in turn further demonstrates that, with additional observations, this population represents an opportunity to significantly extend the sample of AGN spin measurements out to high redshift.
The impact of cosmic variance on simulating weak lensing surveys
NASA Astrophysics Data System (ADS)
Kannawadi, Arun; Mandelbaum, Rachel; Lackner, Claire
2015-06-01
Upcoming weak lensing surveys will survey large cosmological volumes to measure the growth of cosmological structure with time and thereby constrain dark energy. One major systematic uncertainty in this process is the calibration of the weak lensing shape distortions, or shears. Most upcoming surveys plan to test several aspects of their shear estimation algorithms using sophisticated image simulations that include realistic galaxy populations based on high-resolution data from the Hubble Space Telescope (HST). However, existing data sets from the HST cover very small cosmological volumes, so cosmic variance could cause the galaxy populations in them to be atypical. A narrow redshift slice from such surveys could be dominated by a single large overdensity or underdensity. In that case, the morphology-density relation could alter the local galaxy populations and yield an incorrect calibration of shear estimates as a function of redshift. We directly test this scenario using the COSMOS survey, the largest-area HST survey to date, and show how the statistical distributions of galaxy shapes and morphological parameters (e.g. Sérsic n) are influenced by redshift-dependent cosmic variance. The typical variation in rms ellipticity due to environmental effects is 5 per cent (absolute, not relative) for redshift bins of width ?z = 0.05, which could result in uncertain shear calibration at the 1 per cent level. We conclude that the cosmic variance effects are large enough to exceed the systematic error budget of future surveys, but can be mitigated with careful choice of training data set and sufficiently large redshift binning.
Analytical Kerr-Sen dilaton-axion black hole lensing in the weak deflection limit
Gyulchev, Galin N.; Yazadjiev, Stoytcho S. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria)
2010-01-15
We investigate analytical gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black holes in the weak-deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b, and r{sub {alpha}/}b, where M is the black hole mass, a is the angular momentum, r{sub {alpha}=}Q{sup 2}/M, Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images, the corresponding signed and absolute magnifications up to post-Newtonian order. It is shown that there are static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are functions of the charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The pointlike caustics drift away from the optical axis and do not depend on the charge. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.
NASA Astrophysics Data System (ADS)
Petri, Andrea; Liu, Jia; Haiman, Zoltán; May, Morgan; Hui, Lam; Kratochvil, Jan M.
2015-05-01
Weak gravitational lensing is a powerful cosmological probe, with non-Gaussian features potentially containing the majority of the information. We examine constraints on the parameter triplet (?m,w ,?8) from non-Gaussian features of the weak lensing convergence field, including a set of moments (up to fourth order) and Minkowski functionals, using publicly available data from the 154 deg2 CFHTLenS survey. We utilize a suite of ray-tracing N-body simulations spanning 91 points in (?m,w ,?8) parameter space, replicating the galaxy sky positions, redshifts and shape noise in the CFHTLenS catalogs. We then build an emulator that interpolates the simulated descriptors as a function of (?m,w ,?8), and use it to compute the likelihood function and parameter constraints. We employ a principal component analysis to reduce dimensionality and to help stabilize the constraints with respect to the number of bins used to construct each statistic. Using the full set of statistics, we find ?8??8(?m/0.27 )0.55=0.75 ±0.04 (68% C.L.), in agreement with previous values. We find that constraints on the (?m,?8) doublet from the Minkowski functionals suffer a strong bias. However, high-order moments break the (?m,?8) degeneracy and provide a tight constraint on these parameters with no apparent bias. The main contribution comes from quartic moments of derivatives.
Frequency-dependent effects of gravitational lensing within plasma
NASA Astrophysics Data System (ADS)
Rogers, Adam
2015-07-01
The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions N ? 1/rh with h ? 0 in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens into a mirror. We obtain the turning points, circular orbit radii and angular momentum for general h. Previous results have shown that light rays behave like massive particles with an effective mass given by the plasma frequency for a constant density h = 0. We study the behaviour for general h and show that when h = 2 the plasma term acts like an additional contribution to the angular momentum of the passing ray. When h = 3 the potential and radii of circular orbits are analogous to those found in studies of massless scalar fields on the Schwarzschild background. As a physically motivated example we study the pulse profiles of a compact object with antipodal hotspots sheathed in a dense plasma, which shows dramatic frequency-dependent shifts from the behaviour in vacuum. Finally, we consider the potential observability and applications of such frequency-dependent plasma effects in general relativity for several types of neutron star.
Are some BL Lacs artefacts of gravitational lensing?
Ostriker, J P; Vietri, M
1990-03-01
WE suggested in 1985 that a significant fraction of BL Lacertae objects, a kind of lineless quasar, seen in nearby galaxies are in fact images, gravitationally lensed and substantially amplified by stars in the nearby galaxy, of background objects, optically violent variable (OVV) quasars at redshifts z > 1 (ref. 1). This hypothesis was made on the basis of certain general similarities between BL Lacs and O Ws, but for two recently observed BL Lacs(2,3) a strong case can be made that the accompanying elliptical galaxy is a foreground object. In addition, we argue that the distribution of BL Lac redshifts is hard to understand without gravitational lensing, unless we happen to be at a very local maximum of the spatial cosmic distribution of BL Lacs. Our analysis also indicates that the galaxies whose stars are likely to act as microlenses will be found in two peaks, one nearby, with redshift 0.05-0.10, and the other near the distant quasar. PMID:18278021
Puzzles in Time Delay and Fermat Principle in Gravitational Lensing
Sun Hong Rhie
2011-03-16
The current standard time delay formula (CSTD) in gravitational lensing and its claimed relation to the lens equation through Fermat's principle (least time principle) have been puzzling to the author for some time. We find that the so-called geometric path difference term of the CSTD is an error, and it causes a double counting of the correct time delay. We examined the deflection angle and the time delay of a photon trajectory in the Schwarzschild metric that allows exact perturbative calculations in the gravitational parameter $GM$ in two coordinate systems -- the standard Schwarzschild coordinate system and the isotropic Schwarzschild coordinate system. We identify a coordinate dependent term in the time delay which becomes irrelevant for the arrival time difference of two images. It deems necessary to sort out unambiguously what is what we measure. We calculate the second order corrections for the deflection angle and time delay. The CSTD does generate correct lens equations including multiple scattering lens equations under the variations and may be best understood as a generating function. It is presently unclear what the significance is. We call to reanalyze the existing strong lensing data with time delays.
Gravitational lensing as a mechanism for effective cloaking
NASA Astrophysics Data System (ADS)
Tippett, Benjamin K.
2011-11-01
In light of the surge in popularity of electromagnetic cloaking devices, we consider whether it is possible to use general relativity to cloak a volume of spacetime through gravitational lensing. We explore the cloaking properties of a spacetime through a ray-tracing procedure, wherein we plot the spatial trajectories of a congruence of initially parallel null geodesics as they cross the geometry. In this context, a cloaking device would cause all of the null geodesics in an initially parallel congruence incident upon the cloaking geometry to circumnavigate an internal region, and as the geodesics emerge from the geometry, they regain their original configuration. Thus, if gravitational lensing were used as a mechanism for cloaking, the internal region would be causally isolated from the external spacetime. For this reason, we propose an effective cloaking geometry wherein (only) most of ingoing null geodesics will splay away from a central region, and then regain their initial configuration as they exit the geometry. Thus, a compact object sitting within the effective cloaking geometry will impede a smaller cross section of the null congruence, and therefore appear optically smaller from all sides. We build our effective cloaking geometry by connecting a Minkowski spacetime exterior to a spherically symmetric, curved spacetime along a timelike hypersurface of constant radius using the Israel junction conditions. The junction conditions require a shell of matter of infinitesimal width confined to the junction surface. The matter required to build such a spacetime must violate the null energy condition.
Frequency-dependent effects of gravitational lensing within plasma
Adam Rogers
2015-05-26
The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions $N \\propto 1/r^h$ with $h \\geq 0$ in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens into a mirror. We obtain the turning points, circular orbit radii, and angular momentum for general $h$. Previous results have shown that light rays behave like massive particles with an effective mass given by the plasma frequency for a constant density $h=0$. We study the behaviour for general $h$ and show that when $h=2$ the plasma term acts like an additional contribution to the angular momentum of the passing ray. When $h=3$ the potential and radii of circular orbits are analogous to those found in studies of massless scalar fields on the Schwarzschild background. As a physically motivated example we study the pulse profiles of a compact object with antipodal hotspots sheathed in a dense plasma, which shows dramatic frequency-dependent shifts from the behaviour in vacuum. Finally, we consider the potential observability and applications of such frequency-dependent plasma effects in general relativity for several types of neutron star.
Frequency-dependent effects of gravitational lensing within plasma
Rogers, Adam
2015-01-01
The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions $N \\propto 1/r^h$ with $h \\geq 0$ in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens into a mirror. We obtain the turning points, circular orbit radii, and angular momentum for general $h$. Previous results have shown that light rays behave like massive particles with an effective mass given by the plasma frequency for a constant density $h=0$. We study the behaviour for general $h$ and show that when $h=2$ the plasma term acts like an additional contribution to the angular momentum of the passing ray. W...
Gravitational lensing constraints on dynamical and coupled dark energy
La Vacca, G [Dipartimento di Fisica Teorica e Nucleare, Universita di Pavia, via A. Bassi, 6 I-27100 Pavia (Italy); Colombo, L P L, E-mail: Giuseppe.Lavacca@mib.infn.it, E-mail: lavacca@mib.infn.it, E-mail: colombo@usc.edu [INFN Sezione di Milano-Bicocca (Italy)
2008-04-15
Upcoming weak lensing (WL) surveys can be used to constrain dark energy (DE) properties, namely if tomographic techniques are used to improve their sensitivity. In this work, we use a Fisher matrix technique to compare the power of CMB anisotropy and polarization data with tomographic WL data, in constraining DE parameters. Adding WL data to available CMB data improves the detection of all cosmological parameters, but the impact is really strong when DE-DM coupling is considered, as WL tomography can then succeed to reduce the errors on some parameters by factors >10.
Gravitational Lensing Analysis of the Kilo Degree Survey
Kuijken, Konrad; Hildebrandt, Hendrik; Nakajima, Reiko; Erben, Thomas; de Jong, Jelte T A; Viola, Massimo; Choi, Ami; Hoekstra, Henk; Miller, Lance; van Uitert, Edo; Amon, Alexandra; Blake, Chris; Brouwer, Margot; Buddendiek, Axel; Conti, Ian Fenech; Eriksen, Martin; Grado, Aniello; Harnois-Déraps, Joachim; Helmich, Ewout; Herbonnet, Ricardo; Irisarri, Nancy; Kitching, Thomas; Klaes, Dominik; Labarbera, Francesco; Napolitano, Nicola; Radovich, Mario; Schneider, Peter; Sifón, Cristóbal; Sikkema, Gert; Simon, Patrick; Tudorica, Alexandru; Valentijn, Edwin; Kleijn, Gijs Verdoes; van Waerbeke, Ludovic
2015-01-01
The Kilo-Degree Survey (KiDS) is a multi-band imaging survey designed for cosmological studies from weak lensing and photometric redshifts. It uses the ESO VLT Survey Telescope with its wide-field camera OmegaCAM. KiDS images are taken in four filters similar to the SDSS ugri bands. The best-seeing time is reserved for deep r-band observations that reach a median 5-sigma limiting AB magnitude of 24.9 with a median seeing that is better than 0.7arcsec. Initial KiDS observations have concentrated on the GAMA regions near the celestial equator, where extensive, highly complete redshift catalogues are available. A total of 101 survey tiles, one square degree each, form the basis of the first set of lensing analyses, which focus on measurements of halo properties of GAMA galaxies. 9 galaxies per square arcminute enter the lensing analysis, for an effective inverse shear variance of 69 per square arcminute. Accounting for the shape measurement weight, the median redshift of the sources is 0.53. KiDS data processing...
The Statistics of Weak Lensing at Small Angular Scales: Probability Distribution Function
Dipak Munshi; Bhuvnesh Jain
1999-11-29
Weak gravitational lensing surveys have the potential to directly probe mass density fluctuation in the universe. Recent studies have shown that it is possible to model the statistics of the convergence field at small angular scales by modeling the statistics of the underlying density field in the highly nonlinear regime. We propose a new method to model the complete probability distribution function of the convergence field as a function of smoothing angle and source redshift. The model relies on a hierarchical ansatz for the behavior of higher order correlations of the density field. We compare our results with ray tracing simulations and find very good agreement over a range of smoothing angles. Whereas the density probability distribution function is not sensitive to the cosmological model, the probability distribution function for the convergence can be used to constrain both the power spectrum and cosmological parameters.
Effective Models for Statistical Studies of Galaxy-scale Gravitational Lensing
NASA Astrophysics Data System (ADS)
Lapi, A.; Negrello, M.; González-Nuevo, J.; Cai, Z.-Y.; De Zotti, G.; Danese, L.
2012-08-01
We have worked out simple analytical formulae that accurately approximate the relationship between the position of the source with respect to the lens center and the amplification of the images, hence the lens cross section, for realistic lens profiles. We find that, for essentially the full range of parameters either observationally determined or yielded by numerical simulations, the combination of dark matter and star distribution can be very well described, for lens radii relevant to strong lensing, by a simple power law whose slope is very weakly dependent on the parameters characterizing the global matter surface density profile and close to isothermal in agreement with direct estimates for individual lens galaxies. Our simple treatment allows an easy insight into the role of the different ingredients that determine the lens cross section and the distribution of gravitational amplifications. They also ease the reconstruction of the lens mass distribution from the observed images and, vice versa, allow a fast application of ray-tracing techniques to model the effect of lensing on a variety of source structures. The maximum amplification depends primarily on the source size. Amplifications larger than ?20 are indicative of compact source sizes at high-z, in agreement with expectations if galaxies formed most of their stars during the dissipative collapse of cold gas. Our formalism has allowed us to reproduce the counts of strongly lensed galaxies found in the H-ATLAS Science Demonstration Phase field. While our analysis is focused on spherical lenses, we also discuss the effect of ellipticity and the case of late-type lenses (showing why they are much less common, even though late-type galaxies are more numerous). Furthermore, we discuss the effect of a cluster halo surrounding the early-type lens and of a supermassive black hole at its center.
NASA Astrophysics Data System (ADS)
Foëx, G.; Soucail, G.; Pointecouteau, E.; Arnaud, M.; Limousin, M.; Pratt, G. W.
2012-10-01
The total mass of clusters of galaxies is a key parameter for studing massive halos. It relates to numerous gravitational and baryonic processes at play in the framework of large-scale structure formation, thus rendering its determination both important and challenging. From a sample of the 11 X-ray bright clusters selected from the EXCPRES sample, we investigate the optical and X-ray properties of clusters with respect to their total mass derived from weak gravitational lensing. From multicolor, wide-field imaging obtained with MegaCam at CFHT, we derive the shear profile of each individual cluster of galaxies. We carefully investigate all systematic sources related to the weak lensing mass determination. The weak lensing masses are then compared to the X-ray masses obtained from the analysis of XMM-Newton observations assuming hydrostatic equilibrium. We find good agreement between the two mass proxies although a few outliers with either perturbed morphology or poor quality data prevent deriving robust mass estimates. The weak lensing mass is also correlated with the optical richness and the total optical luminosity, as well as with the X-ray luminosity, to provide scaling relations within the redshift range 0.4 < z < 0.6. These relations are in good agreement with previous works at lower redshifts. For the LX - M relation we combine our sample with two other cluster and group samples from the literature, thus covering two decades in mass and X-ray luminosity, with a regular and coherent correlation between the two physical quantities. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Science de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii.
Infrared observations of gravitational lensing in Abell 2219 with CIRSI
Gray, M E; Réfrégier, A; Bézecourt, J; McMahon, R G; Beckett, M G; MacKay, C D; Hönig, M D; Gray, Meghan E.; Ellis, Richard S.; Refregier, Alexandre; Bezecourt, Jocelyn; Mahon, Richard G. Mc; Beckett, Martin G.; Mackay, Craig D.; Hoenig, Michael D.
2000-01-01
We present the first detection of a gravitational depletion signal at near-infrared wavelengths, based on deep panoramic images of the cluster Abell 2219 (z=0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at the prime focus of the 4.2m William Herschel Telescope. Infrared studies of gravitational depletion offer a number of advantages over similar techniques applied at optical wavelengths, and can provide reliable total masses for intermediate redshift clusters. Using the maximum likelihood technique developed by Schneider, King & Erben (1999), we detect the gravitational depletion at the 3 sigma confidence level. By modeling the mass distribution as a singular isothermal sphere and ignoring uncertainty in the unlensed number counts, we find an Einstein radius of 13.7 +3.9/-4.2 arcsec (66% confidence limit). This corresponds to a projected velocity dispersion of approximately 800 km/s, in agreement with constraints from strongly-lensed features. For a Navarro, Frenk and White mass model,...
A Bayesian Analysis of Regularised Source Inversions in Gravitational Lensing
Suyu, Sherry H.; /Caltech /KIPAC, Menlo Park; Marshall, P.J.; /KIPAC, Menlo Park; Hobson, M.P.; /Cambridge U., Inst. of Astron.; Blandford, R.D.; /Caltech /KIPAC, Menlo
2006-01-25
Strong gravitational lens systems with extended sources are of special interest because they provide additional constraints on the models of the lens systems. To use a gravitational lens system for measuring the Hubble constant, one would need to determine the lens potential and the source intensity distribution simultaneously. A linear inversion method to reconstruct a pixellated source distribution of a given lens potential model was introduced by Warren and Dye. In the inversion process, a regularization on the source intensity is often needed to ensure a successful inversion with a faithful resulting source. In this paper, we use Bayesian analysis to determine the optimal regularization constant (strength of regularization) of a given form of regularization and to objectively choose the optimal form of regularization given a selection of regularizations. We consider and compare quantitatively three different forms of regularization previously described in the literature for source inversions in gravitational lensing: zeroth-order, gradient and curvature. We use simulated data with the exact lens potential to demonstrate the method. We find that the preferred form of regularization depends on the nature of the source distribution.
Self-Calibration Technique for 3-point Intrinsic Alignment Correlations in Weak Lensing Surveys
Troxel, M A
2011-01-01
The intrinsic alignment (IA) of galaxies has been shown to be a significant barrier to precision cosmic shear measurements. Zhang [P. Zhang, Astrophys. J. 720, 1090 (2010)] proposed a self-calibration technique for the power spectrum to calculate the induced gravitational shear-galaxy intrinsic ellipticity correlation (GI) in weak lensing surveys with photo-z measurements which is expected to reduce the IA contamination by at least a factor of 10 for currently proposed surveys. We confirm this using an independent analysis and propose an expansion to the self-calibration technique for the bispectrum in order to calculate the dominant IA gravitational shear-gravitational shear-intrinsic ellipticity correlation (GGI) contamination. We first establish an estimator to extract the galaxy density-density-intrinsic ellipticity (ggI) correlation from the galaxy ellipticity-density-density measurement for a photo-z galaxy sample. We then develop a relation between the GGI and ggI bispectra, which allows for the estima...
Yousuke Itoh; Toshifumi Futamase; Makoto Hattori
2009-08-03
Gravitational waves propagate along null geodesics like light rays in the geometrical optics approximation, and they may have a chance to suffer from gravitational lensing by intervening objects, as is the case for electromagnetic waves. Long wavelength of gravitational waves and compactness of possible sources may enable us to extract information in the interference among the lensed images. We point out that the interference term contains information of relative transverse velocity of the source-lens-observer system, which may be obtained by possible future space-borne gravitational wave detectors such as BBO/DECIGO.
Gravitationally lensed extended sources: the case of QSO RXJ0911
NASA Astrophysics Data System (ADS)
Hoai, Do Thi; Nhung, Pham Tuyet; Anh, Pham Tuan; Boone, Frederic; Darriulat, Pierre; Diep, Pham Ngoc; Dong, Pham Ngoc; Van Hiep, Nguyen; Thao, Nguyen Thi
2013-07-01
After a brief reminder of the mechanism of gravitational lensing of extended sources, the particular case of the host galaxy of QSO RXJ0911, a high redshift (z ~ 2.8) quadruply imaged quasar, is explored. The non linearity of the problem, together with the proximity of the source to a cusp of the lens inner caustic, has important consequences on the dependence of the image appearance on the size and shape of the source. Their expected main features and their interpretation in terms of source extension and shape are investigated in a spirit of simplicity and in preparation for the analysis of high sensitivity and spatial resolution images that will soon be within reach with the completion of the Atacama Large Millimeter/submillimeter Array (ALMA). In particular, the information on source size carried by relative image brightness is discussed. Extension of the results to other types of quadruply imaged quasars is briefly considered.
Gravitational lensing: a unique probe of dark matter and dark energy
Ellis, Richard S.
2010-01-01
I review the development of gravitational lensing as a powerful tool of the observational cosmologist. After the historic eclipse expedition organized by Arthur Eddington and Frank Dyson, the subject lay observationally dormant for 60 years. However, subsequent progress has been astonishingly rapid, especially in the past decade, so that gravitational lensing now holds the key to unravelling the two most profound mysteries of our Universe—the nature and distribution of dark matter, and the origin of the puzzling cosmic acceleration first identified in the late 1990s. In this non-specialist review, I focus on the unusual history and achievements of gravitational lensing and its future observational prospects. PMID:20123743
Probing the neutrino mass hierarchy with CMB weak lensing
Hall, Alex C
2012-01-01
We forecast constraints on cosmological parameters with primary CMB anisotropy information and weak lensing reconstruction with a future post-Planck CMB experiment, the Cosmic Origins Explorer (COrE), using oscillation data on the neutrino mass splittings as prior information. Our MCMC simulations in flat models with a non-evolving equation-of-state of dark energy w give typical 68% upper bounds on the total neutrino mass of 0.136 eV and 0.098 eV for the inverted and normal hierarchies respectively, assuming the total summed mass is close to the minimum allowed by the oscillation data for the respective hierarchies (0.10 eV and 0.06 eV). Including information from future baryon acoustic oscillation measurements with the complete BOSS, Type 1a supernovae distance moduli from WFIRST, and a realistic prior on the Hubble constant, these upper limits shrink to 0.118 eV and 0.080 eV for the inverted and normal hierarchies, respectively. Addition of these distance priors also yields percent-level constraints on w. W...
OBSERVING GRAVITATIONAL LENSING EFFECTS BY Sgr A* WITH GRAVITY
Bozza, V. [Department of Physics 'E.R. Caianiello', University of Salerno, Via Ponte Don Melillo, Fisciano I-84084 (Italy); Mancini, L., E-mail: valboz@physics.unisa.it, E-mail: mancini@mpia-hd.mpg.de [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)
2012-07-01
The massive black hole Sgr A* at the Galactic center is surrounded by a cluster of stars orbiting around it. Light from these stars is bent by the gravitational field of the black hole, giving rise to several phenomena: astrometric displacement of the primary image, the creation of a secondary image that may shift the centroid of Sgr A*, and magnification effects on both images. The soon-to-be second-generation Very Large Telescope Interferometer instrument GRAVITY will perform observations in the near-infrared of the Galactic center at unprecedented resolution, opening the possibility of observing such effects. Here we investigate the observability limits for GRAVITY of gravitational lensing effects on the S-stars in the parameter space 1[D{sub LS}, {gamma}, K], where D{sub LS} is the distance between the lens and the source, {gamma} is the alignment angle of the source, and K is the source's apparent magnitude in the K band. The easiest effect to observe in future years is the astrometric displacement of primary images. In particular, the shift of the star S17 from its Keplerian orbit will be detected as soon as GRAVITY becomes operative. For exceptional configurations, it will be possible to detect effects related to the spin of the black hole or post-Newtonian orders in the deflection.
Correcting the z ? 8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias
NASA Astrophysics Data System (ADS)
Mason, Charlotte A.; Treu, Tommaso; Schmidt, Kasper B.; Collett, Thomas E.; Trenti, Michele; Marshall, Philip J.; Barone-Nugent, Robert; Bradley, Larry D.; Stiavelli, Massimo; Wyithe, Stuart
2015-05-01
We present a Bayesian framework to account for the magnification bias from both strong and weak gravitational lensing in estimates of high-redshift galaxy luminosity functions (LFs). We illustrate our method by estimating the z ? 8 UV LF using a sample of 97 Y-band dropouts (Lyman break galaxies) found in the Brightest of Reionizing Galaxies (BoRG) survey and from the literature. We find the LF is well described by a Schechter function with characteristic magnitude of {{M}\\star }=-19.85-0.35+0.30, faint-end slope of ? =-1.72-0.29+0.30, and number density of {{log }10}{{{\\Psi }}\\star }(Mp{{c}-3})=-3.00-0.31+0.23. These parameters are consistent within the uncertainties with those inferred from the same sample without accounting for the magnification bias, demonstrating that the effect is small for current surveys at z ? 8, and cannot account for the apparent overdensity of bright galaxies compared to a Schechter function found recently by Bowler et al. and Finkelstein et al. We estimate that the probability of finding a strongly lensed z ? 8 source in our sample is in the range ?3–15% depending on limiting magnitude. We identify one strongly lensed candidate and three cases of intermediate lensing in BoRG (estimated magnification ? > 1.4) in addition to the previously known candidate group-scale strong lens. Using a range of theoretical LFs we conclude that magnification bias will dominate wide field surveys—such as those planned for the Euclid and WFIRST missions—especially at z > 10. Magnification bias will need to be accounted for in order to derive accurate estimates of high-redshift LFs in these surveys and to distinguish between galaxy formation models.
S. Jouvel; J. P. Kneib; G. Bernstein; O. Ilbert; P. Jelinsky; B. Milliard; A. Ealet; C. Schimd; T. Dahlen; S. Arnouts
2010-01-01
Accurate weak-lensing analysis requires not only accurate measurement of\\u000agalaxy shapes but also precise and unbiased measurement of galaxy redshifts.\\u000aThe photometric redshift technique appears as the only possibility to determine\\u000athe redshift of the background galaxies used in the weak-lensing analysis.\\u000aUsing the photometric redshift quality, simple shape measurement requirements,\\u000aand a proper sky model, we explore what could
Optical Gravitational Lensing Experiment. OGLE-2 -- the Second Phase of the OGLE Project
A. Udalski; M. Kubiak; M. Szymanski
1997-10-09
We describe a new 1.3 m Warsaw telescope located at Las Campanas Observatory and new instruments of the second phase of the Optical Gravitational Lensing Experiment - OGLE-2. Results of first observations are also presented.
Numerical wave optics and the lensing of gravitational waves by globular clusters
Andrew J. Moylan; David E. McClelland; Susan M. Scott; Antony C. Searle; G. V. Bicknell
2007-10-16
We consider the possible effects of gravitational lensing by globular clusters on gravitational waves from asymmetric neutron stars in our galaxy. In the lensing of gravitational waves, the long wavelength, compared with the usual case of optical lensing, can lead to the geometrical optics approximation being invalid, in which case a wave optical solution is necessary. In general, wave optical solutions can only be obtained numerically. We describe a computational method that is particularly well suited to numerical wave optics. This method enables us to compare the properties of several lens models for globular clusters without ever calling upon the geometrical optics approximation, though that approximation would sometimes have been valid. Finally, we estimate the probability that lensing by a globular cluster will significantly affect the detection, by ground-based laser interferometer detectors such as LIGO, of gravitational waves from an asymmetric neutron star in our galaxy, finding that the probability is insignificantly small.
Constraints on early-type galaxy structure from spectroscopically selected gravitational lenses
Bolton, Adam Stallard
2005-01-01
This thesis describes all aspects of a unique spectroscopic survey for strong galaxy-galaxy gravitational lenses: motivation, candidate selection, ground-based spectroscopic follow-up, Hubble Space Telescope imaging, data ...
A weak lensing analysis of the PLCK G100.2-30.4 cluster
NASA Astrophysics Data System (ADS)
Radovich, M.; Formicola, I.; Meneghetti, M.; Bartalucci, I.; Bourdin, H.; Mazzotta, P.; Moscardini, L.; Ettori, S.; Arnaud, M.; Pratt, G. W.; Aghanim, N.; Dahle, H.; Douspis, M.; Pointecouteau, E.; Grado, A.
2015-07-01
We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4, derived from a weak lensing analysis of deep Subaru griz images. We perform a careful selection of the background galaxies using the multi-band imaging data, and undertake the weak lensing analysis on the deep (1 h) r -band image. The shape measurement is based on the Kaiser-Squires-Broadhurst algorithm; we adopt the PSFex software to model the point spread function (PSF) across the field and correct for this in the shape measurement. The weak lensing analysis is validated through extensive image simulations. We compare the resulting weak lensing mass profile and total mass estimate to those obtained from our re-analysis of XMM-Newton observations, derived under the hypothesis of hydrostatic equilibrium. The total integrated mass profiles agree remarkably well, within 1? across their common radial range. A mass M500 ~ 7 × 1014M? is derived for the cluster from our weak lensing analysis. Comparing this value to that obtained from our reanalysis of XMM-Newton data, we obtain a bias factor of (1-b) = 0.8 ± 0.1. This is compatible within 1? with the value of (1-b) obtained in Planck 2015 from the calibration of the bias factor using newly available weak lensing reconstructed masses. Based on data collected at Subaru Telescope (University of Tokyo).
Cosmological constraints from the capture of non-Gaussianity in weak lensing data
NASA Astrophysics Data System (ADS)
Pires, Sandrine; Leonard, Adrienne; Starck, Jean-Luc
2012-06-01
Weak gravitational lensing has become a common tool to constrain the cosmological model. The majority of the methods to derive constraints on cosmological parameters use second-order statistics of the cosmic shear. Despite their success, second-order statistics are not optimal and degeneracies between some parameters remain. Tighter constraints can be obtained if second-order statistics are combined with a statistic that is efficient to capture non-Gaussianity. In this paper, we search for such a statistical tool and we show that there is additional information to be extracted from statistical analysis of the convergence maps beyond what can be obtained from statistical analysis of the shear field. For this purpose, we have carried out a large number of cosmological simulations along the ?8-?m degeneracy, and we have considered three different statistics commonly used for characterization of non-Gaussian features: skewness, kurtosis and peak count. To be able to investigate non-Gaussianity directly in the shear field, we have used the aperture mass definition of these three statistics for different scales. Then, the results have been compared with the results obtained with the same statistics estimated in the convergence maps at the same scales. First, we show that shear statistics give similar constraints to those given by convergence statistics, if the same scale is considered. In addition, we find that the peak count statistic is the best to capture non-Gaussianities in the weak lensing field and to break the ?8-?m degeneracy. We show that this statistical analysis should be conducted in the convergence maps: first, because there exist fast algorithms to compute the convergence map for different scales and secondly because it offers the opportunity to denoise the reconstructed convergence map, which improves the extraction of non-Gaussian features.
Impact of Atmospheric Chromatic Effects on Weak Lensing Measurements
NASA Astrophysics Data System (ADS)
Meyers, Joshua E.; Burchat, Patricia R.
2015-07-01
Current and future imaging surveys will measure cosmic shear with statistical precision that demands a deeper understanding of potential systematic biases in galaxy shape measurements than has been achieved to date. We use analytic and computational techniques to study the impact on shape measurements of two atmospheric chromatic effects for ground-based surveys such as the Dark Energy Survey and the Large Synoptic Survey Telescope (LSST): (1) atmospheric differential chromatic refraction and (2) wavelength dependence of seeing. We investigate the effects of using the point-spread function (PSF) measured with stars to determine the shapes of galaxies that have different spectral energy distributions than the stars. We find that both chromatic effects lead to significant biases in galaxy shape measurements for current and future surveys, if not corrected. Using simulated galaxy images, we find a form of chromatic “model bias” that arises when fitting a galaxy image with a model that has been convolved with a stellar, instead of galactic, PSF. We show that both forms of atmospheric chromatic biases can be predicted (and corrected) with minimal model bias by applying an ordered set of perturbative PSF-level corrections based on machine-learning techniques applied to six-band photometry. Catalog-level corrections do not address the model bias. We conclude that achieving the ultimate precision for weak lensing from current and future ground-based imaging surveys requires a detailed understanding of the wavelength dependence of the PSF from the atmosphere, and from other sources such as optics and sensors. The source code for this analysis is available at https://github.com/DarkEnergyScienceCollaboration/chroma.
Weak lensing reconstruction through cosmic magnification - I. A minimal variance map reconstruction
NASA Astrophysics Data System (ADS)
Yang, Xinjuan; Zhang, Pengjie
2011-08-01
We present a concept study on weak lensing map reconstruction through the cosmic magnification effect in galaxy number density distribution. We propose a minimal variance linear estimator to minimize both the dominant systematic and statistical errors in the map reconstruction. It utilizes the distinctively different flux dependences to separate the cosmic magnification signal from the overwhelming galaxy intrinsic clustering noise. It also minimizes the shot noise error by an optimal weighting scheme on the galaxy number density in each flux bin. Our method is in principle applicable to all galaxy surveys with reasonable redshift information. We demonstrate its applicability against the planned Square Kilometer Array survey, under simplified conditions. Weak lensing maps reconstructed through our method are complementary to that from cosmic shear and cosmic microwave background (CMB) and 21-cm lensing. They are useful for cross-checking over systematic errors in weak lensing reconstruction and for improving cosmological constraints.
Strong and weak lensing analysis of cluster Abell 2219 based on optical and near infrared data
J. Bezecourt; H. Hoekstra; M. E. Gray; H. M. AbdelSalam; K. Kuijken; R. S. Ellis
2000-01-01
We present a gravitational lensing study of the massive galaxy cluster A2219 (redshift 0.22). This investigation is based on multicolour images from U through H, which allows photometric redshifts to be estimated for the background sources. The redshifts provide useful extra information for the lensing models: we show how they can be used to identify a new multiple-image system (and
NASA Astrophysics Data System (ADS)
Sereno, Mauro; Veropalumbo, Alfonso; Marulli, Federico; Covone, Giovanni; Moscardini, Lauro; Cimatti, Andrea
2015-06-01
The joint analysis of clustering and stacked gravitational lensing of galaxy clusters in large surveys can constrain the formation and evolution of structures and the cosmological parameters. On scales outside a few virial radii, the halo bias, b, is linear and the lensing signal is dominated by the correlated distribution of matter around galaxy clusters. We discuss a method to measure the power spectrum amplitude ?8 and b based on a minimal modelling. We considered a sample of ˜120 000 clusters photometrically selected from the Sloan Digital Sky Survey in the redshift range 0.1 < z < 0.6. The autocorrelation was studied through the two-point function of a subsample of ˜70 000 clusters; the matter-halo correlation was derived from the weak lensing signal of the subsample of ˜1200 clusters with Canada-France-Hawaii Telescope Lensing Survey data. We obtained a direct measurement of b, which increases with mass in agreement with predictions of the ? cold dark matter paradigm. Assuming ?M = 0.3, we found ?8 = 0.79 ± 0.16. We used the same clusters for measuring both lensing and clustering and the estimate of ?8 did require neither the mass-richness relation, nor the knowledge of the selection function, nor the modelling of b. With an additional theoretical prior on the bias, we obtained ?8 = 0.75 ± 0.08.
Moving gravitational lenses: imprints on the cosmic microwave background
NASA Astrophysics Data System (ADS)
Aghanim, N.; Prunet, S.; Forni, O.; Bouchet, F. R.
1998-06-01
With the new generation of instruments for Cosmic Microwave Background (CMB) observations aiming at an accuracy level of a few percent in the measurement of the angular power spectrum of the anisotropies, the study of the contributions due to secondary effects has gained impetus. Furthermore, a reinvestigation of the main secondary effects is crucial in order to predict and quantify their effects on the CMB and the errors that they induce in the measurements. In this paper, we investigate the contribution, to the CMB, of secondary anisotropies induced by the transverse motions of clusters of galaxies. This effect is similar to the Kaiser-Stebbins effect. In order to address this problem, we model the gravitational potential well of an individual structure using the Navarro, Frenk & White profile. We generalise the effect of one structure to a population of objects predicted using the Press-Schechter formalism. We simulate maps of these secondary fluctuations, compute the angular power spectrum and derive the average contributions for three cosmological models. We then investigate a simple method to separate this new contribution from the primary anisotropies and from the main secondary effect, the Sunyaev-Zel'dovich kinetic effect from the lensing clusters.
Strong and weak gravitational field in $R+?^4/R$ gravity
Kh. Saaidi; A. Vajdi; S. W. Rabiei; A. Aghamohammadi; H. Sheikhahmadi
2012-01-18
We introduce a new approach for investigating the weak field limit of vacuum field equations in $f(R)$ gravity and we find the weak field limit of $f(R)=R+\\mu ^4/R$ gravity. Furthermore, we study the strong gravity regime in $R+\\mu^{4}/R$ model of $f(R)$ gravity. We show the existence of strong gravitational field in vacuum for such model. We find out in the limit $\\mu\\rightarrow 0$, the weak field limit and the strong gravitational field can be regarded as a perturbed Schwarzschild metric.
Gravitational Lenses With More Than Four Images: I. Classification of Caustics
C. R. Keeton; S. Mao; H. J. Witt
2000-02-22
We study the problem of gravitational lensing by an isothermal elliptical density galaxy in the presence of a tidal perturbation. When the perturbation is fairly strong and oriented near the galaxy's minor axis, the lens can produce image configurations with six or even eight highly magnified images lying approximately on a circle. We classify the caustic structures in the model and identify the range of models that can produce such lenses. Sextuple and octuple lenses are likely to be rare because they require special lens configurations, but a full calculation of the likelihood will have to include both the existence of lenses with multiple lens galaxies and the strong magnification bias that affects sextuple and octuple lenses. At optical wavelengths these lenses would probably appear as partial or complete Einstein rings, but at radio wavelengths the individual images could probably be resolved.
Rozo, Eduardo; /U. Chicago /Chicago U., KICP; Wu, Hao-Yi; /KIPAC, Menlo Park; Schmidt, Fabian; /Caltech
2011-11-04
When extracting the weak lensing shear signal, one may employ either locally normalized or globally normalized shear estimators. The former is the standard approach when estimating cluster masses, while the latter is the more common method among peak finding efforts. While both approaches have identical signal-to-noise in the weak lensing limit, it is possible that higher order corrections or systematic considerations make one estimator preferable over the other. In this paper, we consider the efficacy of both estimators within the context of stacked weak lensing mass estimation in the Dark Energy Survey (DES). We find that the two estimators have nearly identical statistical precision, even after including higher order corrections, but that these corrections must be incorporated into the analysis to avoid observationally relevant biases in the recovered masses. We also demonstrate that finite bin-width effects may be significant if not properly accounted for, and that the two estimators exhibit different systematics, particularly with respect to contamination of the source catalog by foreground galaxies. Thus, the two estimators may be employed as a systematic cross-check of each other. Stacked weak lensing in the DES should allow for the mean mass of galaxy clusters to be calibrated to {approx}2% precision (statistical only), which can improve the figure of merit of the DES cluster abundance experiment by a factor of {approx}3 relative to the self-calibration expectation. A companion paper investigates how the two types of estimators considered here impact weak lensing peak finding efforts.
Distortion of the Luminosity Function of High-redshift Galaxies by Gravitational Lensing
NASA Astrophysics Data System (ADS)
Fialkov, Anastasia; Loeb, Abraham
2015-06-01
The observed properties of high-redshift galaxies depend on the underlying foreground distribution of large-scale structure, which distorts their intrinsic properties via gravitational lensing. We focus on the regime where the dominant contribution originates from a single lens and examine the statistics of gravitational lensing by a population of virialized and non-virialized structures using sub-millimeter galaxies at z? 2.6 and Lyman-break galaxies (LBGs) at redshifts z? 6-15 as the background sources. We quantify the effect of lensing on the luminosity function of the high-redshift sources, focusing on the intermediate and small magnifications, ? ? 2, which affect the majority of the background galaxies, and comparing to the case of strong lensing. We show that, depending on the intrinsic properties of the background galaxies, gravitational lensing can significantly affect the observed luminosity function even when no obvious strong lenses are present. Finally, we find that in the case of the LBGs it is important to account for the surface brightness profiles of both the foreground and the background galaxies when computing the lensing statistics, which introduces a selection criterion for the background galaxies that can actually be observed. Not taking this criterion into account leads to an overestimation of the number densities of very bright galaxies by nearly two orders of magnitude.
Probing the cosmic web: inter-cluster filament detection using gravitational lensing
James M. G. Mead; Lindsay J. King; Ian G. McCarthy
2009-01-01
The problem of detecting dark matter filaments in the cosmic web is\\u000aconsidered. Weak lensing is an ideal probe of dark matter, and therefore forms\\u000athe basis of particularly promising detection methods. We consider and develop\\u000aa number of weak lensing techniques that could be used to detect filaments in\\u000aindividual or stacked cluster fields, and apply them to synthetic
Multiple Weak Deflections and the Detection of Flattened Halos with Galaxy-Galaxy Lensing
C. O. Wright; T. G. Brainerd
2002-05-17
We investigate the occurrence of multiple weak deflections in deep data sets which are used to detect galaxy-galaxy lensing. Using the galaxies in the HDF (North) for which both redshifts and rest-frame blue luminosities are known, we show that the probability for a given source galaxy to be lensed by two or more foreground galaxies exceeds 50% for z_s > 1, and for which the separate, individual deflections yield gamma > 0.005. Neglecting multiple deflections when obtaining best-fitting halo parameters for the lens galaxies can lead to an overestimate by a factor of order 2 for the halo mass interior to a radius of 100 kpc/h. We also show that multiple weak deflections create systematic effects which may hinder observational efforts to use weak lensing to constrain the projected shapes of the halos of field galaxies. For a data set in which the galaxies have magnitudes in the rage 19 < I < 23, multiple deflections result in strong correlations between the post-lensing image shapes of most foreground-background pairs of galaxies. Imposing a simple redshift cut during the data anaysis is sufficient to reduce the correlation between the final images of lenses and sources to the point that the expected anisotropy in the weak lensing signal can be detected via a straightforward average. We conclude that previous theoretical calculations of weak lensing due to flattened halos have considerably underestimated the sizes of the observational data sets which would be required to detect this effect. [Abridged
The Effect of Environment on Shear in Strong Gravitational Lenses
NASA Astrophysics Data System (ADS)
Wong, Kenneth C.; Keeton, Charles R.; Williams, Kurtis A.; Momcheva, Ivelina G.; Zabludoff, Ann I.
2011-01-01
Using new photometric and spectroscopic data in the fields of nine strong gravitational lenses that lie in galaxy groups, we analyze the effects of both the local group environment and line-of-sight (LOS) galaxies on the lens potential. We use Monte Carlo simulations to derive the shear directly from measurements of the complex lens environment, providing the first detailed independent check of the shear obtained from lens modeling. We account for possible tidal stripping of the group galaxies by varying the fraction of total mass apportioned between the group dark matter halo and individual group galaxies. The environment produces an average shear of ? = 0.08 (ranging from 0.02 to 0.17), significant enough to affect quantities derived from lens observables. However, the direction and magnitude of the shears do not match those obtained from lens modeling in three of the six four-image systems in our sample (B1422, RXJ1131, and WFI2033). The source of this disagreement is not clear, implying that the assumptions inherent in both the environment and lens model approaches must be reconsidered. If only the local group environment of the lens is included, the average shear is ? = 0.05 (ranging from 0.01 to 0.14), indicating that LOS contributions to the lens potential are not negligible. We isolate the effects of various theoretical and observational uncertainties on our results. Of those uncertainties, the scatter in the Faber-Jackson relation and error in the group centroid position dominate. Future surveys of lens environments should prioritize spectroscopic sampling of both the local lens environment and objects along the LOS, particularly those bright (I< 21.5) galaxies projected within 5' of the lens. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
THE EFFECT OF ENVIRONMENT ON SHEAR IN STRONG GRAVITATIONAL LENSES
Wong, Kenneth C.; Zabludoff, Ann I. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Keeton, Charles R. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Williams, Kurtis A. [Department of Astronomy, University of Texas at Austin, 1 University Station, C1400, Austin, TX 78712 (United States); Momcheva, Ivelina G., E-mail: kwong@as.arizona.edu, E-mail: azabludoff@as.arizona.edu, E-mail: keeton@physics.rutgers.edu [The Observatories of the Carnegie Institute of Washington, 813 Santa Barbara St., Pasadena, CA 91101 (United States)
2011-01-10
Using new photometric and spectroscopic data in the fields of nine strong gravitational lenses that lie in galaxy groups, we analyze the effects of both the local group environment and line-of-sight (LOS) galaxies on the lens potential. We use Monte Carlo simulations to derive the shear directly from measurements of the complex lens environment, providing the first detailed independent check of the shear obtained from lens modeling. We account for possible tidal stripping of the group galaxies by varying the fraction of total mass apportioned between the group dark matter halo and individual group galaxies. The environment produces an average shear of {gamma} = 0.08 (ranging from 0.02 to 0.17), significant enough to affect quantities derived from lens observables. However, the direction and magnitude of the shears do not match those obtained from lens modeling in three of the six four-image systems in our sample (B1422, RXJ1131, and WFI2033). The source of this disagreement is not clear, implying that the assumptions inherent in both the environment and lens model approaches must be reconsidered. If only the local group environment of the lens is included, the average shear is {gamma} = 0.05 (ranging from 0.01 to 0.14), indicating that LOS contributions to the lens potential are not negligible. We isolate the effects of various theoretical and observational uncertainties on our results. Of those uncertainties, the scatter in the Faber-Jackson relation and error in the group centroid position dominate. Future surveys of lens environments should prioritize spectroscopic sampling of both the local lens environment and objects along the LOS, particularly those bright (I< 21.5) galaxies projected within 5' of the lens.
Neutrino physics from future weak lensing surveys R. Ali Vanderveld1
Hu, Wayne
gravitational lens- ing fits into this picture, in light of forthcoming lensing- optimized large-area surveys supernovae, baryon acoustic oscillations, and local measures of the Hubble constant H0, coupled or subtracting relativis- tic species changes the ratio of the acoustic and damp- ing angular scales
A DETECTION OF WEAK-LENSING MAGNIFICATION USING GALAXY SIZES AND MAGNITUDES
Schmidt, Fabian; Rhodes, Jason [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 2778582 (Japan); Massey, Richard [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany)
2012-01-10
Weak lensing is commonly measured using shear through galaxy ellipticities or using the effect of magnification bias on galaxy number densities. Here, we report on the first detection of weak-lensing magnification with a new, independent technique using the distribution of galaxy sizes and magnitudes. These data come for free in galaxy surveys designed for measuring shear. We present the magnification estimator and apply it to an X-ray-selected sample of galaxy groups in the COSMOS Hubble Space Telescope survey. The measurement of the projected surface density {Sigma}(r) is consistent with the shear measurements within the uncertainties and has roughly 40% of the signal to noise of the latter. We discuss systematic issues and challenges to realizing the potential of this new probe of weak lensing.
The Mass Of The Coma Cluster From Weak Lensing In The Sloan Digital Sky Survey
Kubo, Jeffrey M.; Stebbins, Albert; Annis, James; Dell'Antonio, Ian P.; Lin, Huan; Khiabanian, Hossein; Frieman, Joshua A.
2007-09-01
We present a weak lensing analysis of the Coma Cluster using the Sloan Digital Sky Survey (SDSS) Data Release Five. Complete imaging of a {approx} 200 square degree region is used to measure the tangential shear of this cluster. The shear is fit to an NFW model and we find a virial radius of r{sub 200} = 1.99{sup +0.21}{sub -0.22}h{sup -1}Mpc which corresponds to a virial mass of M{sub 200} = 1.88{sup +0.65}{sub -0.56} x 10{sup 15}h{sup -1}M{circle_dot}. We additionally compare our weak lensing measurement to the virial mass derived using dynamical techniques, and find they are in agreement. This is the lowest redshift, largest angle weak lensing measurement of an individual cluster to date.
INTERPOLATING MASKED WEAK-LENSING SIGNAL WITH KARHUNEN-LOEVE ANALYSIS
VanderPlas, J. T.; Connolly, A. J. [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Jain, B.; Jarvis, M. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6396 (United States)
2012-01-10
We explore the utility of Karhunen-Loeve (KL) analysis in solving practical problems in the analysis of gravitational shear surveys. Shear catalogs from large-field weak-lensing surveys will be subject to many systematic limitations, notably incomplete coverage and pixel-level masking due to foreground sources. We develop a method to use two-dimensional KL eigenmodes of shear to interpolate noisy shear measurements across masked regions. We explore the results of this method with simulated shear catalogs, using statistics of high-convergence regions in the resulting map. We find that the KL procedure not only minimizes the bias due to masked regions in the field, it also reduces spurious peak counts from shape noise by a factor of {approx}3 in the cosmologically sensitive regime. This indicates that KL reconstructions of masked shear are not only useful for creating robust convergence maps from masked shear catalogs, but also offer promise of improved parameter constraints within studies of shear peak statistics.
Weak Lensing from Space I: Prospects for The Supernova/Acceleration Probe
Rhodes, J; Aldering, G; Amanullah, R; Astier, Pierre; Barrelet, E; Bebek, C; Bergstr, L; Bercovitz, J; Bester, M; Bonissent, A; Bower, C; Carithers, W C; Commins, Eugene D; Day, C; Deustua, S; Di Gennaro, R S; Ealet, A; Eriksson, M; Fruchter, A S; Genat, J F; Goldhaber, G; Goobar, A; Groom, D; Harris, S; Harvey, P; Heetderks, H; Holland, S; Huterer, D; Karcher, A; Kolbe, W F; Krieger, B; Lafever, R; Lamoureux, J; Levi, M; Levin, D; Linder, E V; Loken, S; Malina, R; McKee, S; Miquel, R; Mostek, N; Mufson, S L; Musser, J; Nugent, P; Oluseyi, H; Pain, R; Palaio, N; Pankow, D; Perlmutter, S; Pratt, R; Prieto, E; Robinson, K; Roe, N; Sholl, M; Schubnell, M S; Smadja, G; Smoot, G F; Spadafora, A; Tarl, G; Tomasch, A; Von der Lippe, H; Vincent, D; Walder, J P; Wang, G; Rhodes, Jason; Refregier, Alexandre; Massey, Richard
2003-01-01
The proposed Supernova/Acceleration Probe (SNAP) satellite has been recognized as an ideal instrument to measure the accelerating expansion of the universe through the distance moduli to type Ia supernovae. We show that SNAP will also be excellent for surveys of weak gravitational lensing by large-scale structure. Many of the requirements for precise photometry are compatible with those to accurately measure the shapes of background galaxies. We describe two surveys to be performed by SNAP. A 15 square degree ``deep'' survey will find clusters/groups and allow two-and three-dimensional dark matter maps to be made. A 300 square degree ``wide'' survey will be used to provide global constraints on cosmological parameters including Omega_M and w, the dark energy equation of state parameter. Both surveys will be conducted in 9 wide-band optical and near-IR filters, enabling photometric redshifts to be calculated. This first paper in a three part series outlines the survey strategies and introduces the SNAP instrum...
A weak lensing comparability study of galaxy mergers that host AGNs
NASA Astrophysics Data System (ADS)
Harvey, D.; Courbin, F.
2015-07-01
We compared the total mass density profiles of three different types of galaxies using weak gravitational lensing: (i) 29 galaxies that host quasars at bar{z}˜ 0.32 that are in a post-starburst quasar (PSQ) phase with high star formation indicating recent merger activity, (ii) 22 large elliptical galaxies from the Sloan Lens ACS Survey (SLACS) sample that do not host a quasar at bar{z}˜ 0.23, and (iii) 17 galaxies that host moderately luminous quasars at bar{z}˜ 0.36 powered by disc instabilities, but with no intense star formation. In an initial test we found no evidence for a connection between the merger state of a galaxy and the profile of the halo, with the PSQ profile comparable to that of the other two samples and consistent with the Leauthaud et al. study of moderately luminous quasars in Cosmic Evolution Survey (COSMOS). Given the compatibility of the two quasar samples, we combined these and found no evidence for any connection between black hole activity and the dark matter halo. All three mass profiles remained compatible with isothermality given the present data.
NASA Astrophysics Data System (ADS)
Hoekstra, Henk; Herbonnet, Ricardo; Muzzin, Adam; Babul, Arif; Mahdavi, Andi; Viola, Massimo; Cacciato, Marcello
2015-05-01
Masses of clusters of galaxies from weak gravitational lensing analyses of ever larger samples are increasingly used as the reference to which baryonic scaling relations are compared. In this paper we revisit the analysis of a sample of 50 clusters studied as part of the Canadian Cluster Comparison Project. We examine the key sources of systematic error in cluster masses. We quantify the robustness of our shape measurements and calibrate our algorithm empirically using extensive image simulations. The source redshift distribution is revised using the latest state-of-the-art photometric redshift catalogues that include new deep near-infrared observations. None the less we find that the uncertainty in the determination of photometric redshifts is the largest source of systematic error for our mass estimates. We use our updated masses to determine b, the bias in the hydrostatic mass, for the clusters detected by Planck. Our results suggest 1 - b = 0.76 ± 0.05 (stat) ± 0.06 (syst), which does not resolve the tension with the measurements from the primary cosmic microwave background.
A New Method for Measuring Weak Lensing Magnification With Weighted Number Counts
Gillis, Bryan
2015-01-01
We present a new local method for optimally estimating the local effects of magnification from weak gravitational lensing, using a comparison of number counts in an arbitrary region of space to the expected unmagnified number counts. This method has equivalent statistical power to the optimally-weighted correlation function method previously employed to measure magnification, but has the potential to be used for purposes such as mass mapping, and is also significantly computationally faster. We present a proof-of-principle test of this method on data from the CFHTLenS, showing that its calculated magnification signals agree with predictions from model fits to shear data. Finally, we investigate how magnification data can be used to supplement shear data in determining the best-fit model mass profiles for galaxy dark matter haloes. We find that at redshifts greater than z~0.6, the inclusion of magnification can often significantly improve the constraints on the components of the mass profile which relate to ga...
Constraining (Omega ,lambda ) from weak lensing in clusters: the triplet statistics
NASA Astrophysics Data System (ADS)
Gautret, L.; Fort, B.; Mellier, Y.
2000-01-01
We present a new geometrical method, the triplet statistics, which uses weak gravitational lensing effects around clusters to constrain the cosmological parameters Omega and lambda . On each background galaxy, a cluster induces a magnification which depends on the local convergence and shear terms and on the cosmological parameters (Omega , lambda ) through the angular distance ratio DLS/DOS. To disentangle the effects of these three quantities, we compare the ellipticities of each triplet of galaxies located at about the same apparent position in the lens plane, but having different redshifts. The simultaneous knowledge of ellipticities and redshifts of each triplet enable to build a purely geometrical estimator (hereafter the G(Omega ,lambda )-estimator) independently of the lens potential. More precisely G has the simple form of the determinant of a 3-3 matrix built with the triplet values of DLS/DOS and observed ellipticities. When G is averaged on many triplets of galaxies, it provides a global function of (Omega , lambda ) which converges to zero for the true values of the cosmological parameters. The calculation and the comparison of each source of statistical noise is performed. The linear form of G regarding the measured ellipticity of each galaxy implies that the different noises on G decrease as 1/sqrt {N}, where N is the total number of observed distorted galaxies. The possible systematics are analyzed with a multi-screen lensing model in order to estimate the effect of perturbative potentials on galaxy triplets. Improvements are then proposed to minimize these systematics and to optimize the statistical signal to noise ratio. Finally, simulations are performed with realistic geometry and convergence for the lensing clusters and a redshift distribution for galaxies similar to the observed ones. They lead to the encouraging result that a significant constraint on (Omega , lambda ) can be reached: lambda -0.2+0.3 in the case Omega +lambda =1 or Omega -0.25+0.3 in the case lambda =0 (at a 1sigma confidence level). These constraints would be obtained from the observations of nearly 100 clusters, using multicolor imaging in order to get photometric redshifts of triplets. This corresponds to about 20 nights of VLT observations. The method looks even more promising with the NGST, in particular if it was used jointly with the supernovae search which provides orthogonal constraints.
Testing Weak-lensing Maps with Redshift Surveys: A Subaru Field
NASA Astrophysics Data System (ADS)
Kurtz, Michael J.; Geller, Margaret J.; Utsumi, Yousuke; Miyazaki, Satoshi; Dell'Antonio, Ian P.; Fabricant, Daniel G.
2012-05-01
We use a dense redshift survey in the foreground of the Subaru GTO2deg2 weak-lensing field (centered at ?2000 = 16h04m44s; ?2000 = 43°11'24'') to assess the completeness and comment on the purity of massive halo identification in the weak-lensing map. The redshift survey (published here) includes 4541 galaxies; 4405 are new redshifts measured with the Hectospec on the MMT. Among the weak-lensing peaks with a signal-to-noise greater than 4.25, 2/3 correspond to individual massive systems; this result is essentially identical to the Geller et al. test of the Deep Lens Survey (DLS) field F2. The Subaru map, based on images in substantially better seeing than the DLS, enables detection of less massive halos at fixed redshift as expected. We demonstrate that the procedure adopted by Miyazaki et al. for removing some contaminated peaks from the weak-lensing map improves agreement between the lensing map and the redshift survey in the identification of candidate massive systems.
J. Liesenborgs; S. De Rijcke; H. Dejonghe; P. Bekaert
2007-07-17
Galaxies acting as gravitational lenses are surrounded by, at most, a handful of images. This apparent paucity of information forces one to make the best possible use of what information is available to invert the lens system. In this paper, we explore the use of a genetic algorithm to invert in a non-parametric way strong lensing systems containing only a small number of images. Perhaps the most important conclusion of this paper is that it is possible to infer the mass distribution of such gravitational lens systems using a non-parametric technique. We show that including information about the null space (i.e. the region where no images are found) is prerequisite to avoid the prediction of a large number of spurious images, and to reliably reconstruct the lens mass density. While the total mass of the lens is usually constrained within a few percent, the fidelity of the reconstruction of the lens mass distribution depends on the number and position of the images. The technique employed to include null space information can be extended in a straightforward way to add additional constraints, such as weak lensing data or time delay information.
NASA Astrophysics Data System (ADS)
Adrián-Martínez, S.; Albert, A.; André, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; Bogazzi, C.; Bormuth, R.; Bou-Cabo, M.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Chiarusi, T.; Circella, M.; Coniglione, R.; Core, L.; Costantini, H.; Coyle, P.; Creusot, A.; De Rosa, G.; Dekeyser, I.; Deschamps, A.; De Bonis, G.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Dumas, A.; Eberl, T.; Elsässer, D.; Enzenhöfer, A.; Escoffier, S.; Fehn, K.; Felis, I.; Fermani, P.; Folger, F.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Gómez-González, J. P.; Graf, K.; Guillard, G.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Herold, B.; Herrero, A.; Hößl, J.; Hofestädt, J.; Hugon, C.; James, C. W.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kießling, D.; Kooijman, P.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lambard, E.; Lambard, G.; Lefèvre, D.; Leonora, E.; Loehner, H.; Loucatos, S.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martínez-Mora, J. A.; Martini, S.; Mathieu, A.; Michael, T.; Migliozzi, P.; Müller, C.; Neff, M.; Nezri, E.; Palioselitis, D.; P?v?laš, G. E.; Perrina, C.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Richter, R.; Roensch, K.; Rostovtsev, A.; Saldaña, M.; Samtleben, D. F. E.; Sánchez-Losa, A.; Sanguineti, M.; Schmid, J.; Schnabel, J.; Schulte, S.; Schüssler, F.; Seitz, T.; Sieger, C.; Spies, A.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, Th.; Taiuti, M.; Tamburini, C.; Tayalati, Y.; Trovato, A.; Tselengidou, M.; Tönnis, C.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Visser, E.; Vivolo, D.; Wagner, S.; Wilms, J.; de Wolf, E.; Yatkin, K.; Yepes, H.; Zornoza, J. D.; Zúñiga, J.; Falco, E. E.
2014-11-01
This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazar populations. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed Flat-Spectrum Radio Quasars. The magnification factor is estimated for each system assuming a singular isothermal profile for the lens. Based on data collected from 2007 to 2012 by the ANTARES neutrino telescope, the strongest constraint is obtained from the lensed quasar B0218+357, providing a limit on the total neutrino luminosity of this source of 1.08× 1046 erg s-1. This limit is about one order of magnitude lower than those previously obtained in the ANTARES standard point source searches with non-lensed Flat-Spectrum Radio Quasars.
NASA Technical Reports Server (NTRS)
Maoz, D.; Bahcall, J. N.; Doxsey, R.; Schneider, D. P.; Bahcall, N. A.; Lahav, O.; Yanny, B.
1993-01-01
We present new HST Snapshot Survey observations of 163 high-luminosity z greater than 1 quasars, bringing the total number observed to date in the survey to 347 quasars. Each exposure was searched for evidence on gravitational lensing. Among the newly observed quasars, six have additional point sources at separations of 2-6 arcsec, but in all six cases ground-based data indicate that gravitational lensing is not involved. No point sources were found at smaller separations. Counting the one new lens candidate the survey has uncovered and the known lenses excluded from the sample, the observed frequency of lensing of quasars by galaxies is 5/351. This frequency is in the range predicted by models with a vanishing cosmological constant, but an order of magnitude lower than expected in models strongly dominated by a cosmological constant.
Jerome Degallaix; Chunnong Zhao; L. Ju; David G Blair
2003-01-01
This paper presents finite-element modelling simulations of thermal lensing and thermal lens compensation in transmissive optics for gravitational wave detectors. We compare the current candidate test mass materials, fused silica and sapphire, in terms of sample geometry and time-dependent phenomena. For both materials, the thermal-lensing time constant is a few minutes, yet the core temperature needs several tens of minutes
CALCLENS: Curved-sky grAvitational Lensing for Cosmological Light conE simulatioNS
NASA Astrophysics Data System (ADS)
Becker, Matthew R.
2012-10-01
CALCLENS, written in C and employing widely available software libraries, efficiently computes weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. The algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift-dependent shear signals including corrections to the Born approximation by using multiple-plane ray tracing, and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multgrid methods. As a result, large areas of sky (~10,000 square degrees) can be ray traced efficiently at high-resolution using only a few hundred cores on widely available machines. Coupled with realistic galaxy populations placed in large N-body light cone simulations, CALCLENS is ideally suited for the construction of synthetic weak lensing shear catalogs to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys.
Discovery of a new component in the gravitationally lensed quasar 0957 + 561
NASA Technical Reports Server (NTRS)
Jones, C.; Stern, C.; Falco, E.; Forman, W.; David, L.; Shapiro, I.; Fabian, A. C.
1993-01-01
X-ray observations of the gravitationally lensed quasar 0957 + 561 with the Einstein Observatory High Resolution Imager indicate the presence of a new component in the system. The significantly greater X-ray intensity of image A compared with image B and the extended X-ray emission can be interpreted as the gravitational lensing of a quasi-circular X-ray emitting region into a partial Einstein ring. It is suggested that the observed X-ray emission is produced by a strong cooling flow which could arise were 0957 + 561 embedded in a group of cluster galaxies.
A measurement of weak lensing by large scale structure in RCS fields
Henk Hoekstra; Howard K. C. Yee; Michael D. Gladders; L. Felipe Barrientos; Patrick B. Hall; Leopoldo Infante
2002-02-14
We have analysed ~24 square degrees of R_C-band imaging data from the Red-Sequence Cluster Survey (RCS), and measured the excess correlations between galaxy ellipticities on scales ranging from 1 to 30 arcminutes. We have used data from two different telescopes: ~16.4 square degrees of CFHT data and ~7.6 square degrees of CTIO 4-meter data, distributed over 13 widely separated patches. For the first time, a direct comparison can be made of the lensing signal measured using different instruments, which provides an important test of the weak lensing analysis itself. The measurements obtained from the two telescopes agree well. For the lensing analysis we use galaxies down to a limiting magnitude of R_C=24, for which the redshift distribution is known relatively well. This allows us to constrain some cosmological parameters. For the currently favored $\\Lambda$CDM model $(\\Omega_m=0.3, \\Omega_\\Lambda=0.7, \\Gamma=0.21)$ we obtain $\\sigma_8=0.81^{+0.14}_{-0.19}$ (95% confidence), in agreement with the results from Van Waerbeke et al. (2001) which used fainter galaxies (and consequently higher redshift galaxies). The good agreement between these two very different weak lensing studies demonstrates that weak lensing is a useful tool in observational cosmology.
New results from the gravitational lensing of galaxies
Schwab, Josiah (Josiah W.)
2009-01-01
We 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 ...
Theoretical analysis of a reported weak gravitational shielding effect
G. Modanese
1996-06-15
Under special conditions (Meissner-effect levitation in a high frequency magnetic field and rapid rotation) a disk of high-$T_c$ superconducting material has recently been found to produce a weak shielding of the gravitational field. We show that this phenomenon has no explanation in the standard gravity theories, except possibly in the non-perturbative Euclidean quantum theory.
Gravitational lensing frequencies - Galaxy cross-sections and selection effects
NASA Technical Reports Server (NTRS)
Fukugita, Masataka; Turner, Edwin L.
1991-01-01
Four issues - (1) the best currently available data on the galaxy velocity-dispersion distribution, (2) the effects of finite core radii potential ellipticity on lensing cross sections, (3) the predicted distribution of lens image separations compared to observational angular resolutions, and (4) the preferential inclusion of lens systems in flux limited samples - are considered in order to facilitate more realistic predictions of multiple image galaxy-quasar lensing frequencies. It is found that (1) the SIS lensing parameter F equals 0.047 +/-0.019 with almost 90 percent contributed by E and S0 galaxies, (2) observed E and S0 core radii are remarkably small, yielding a factor of less than about 2 reduction in total lensing cross sections, (3) 50 percent of galaxy-quasar lenses have image separations greater than about 1.3 arcsec, and (4) amplification bias factors are large and must be carefully taken into account. It is concluded that flat universe models excessively dominated by the cosmological constant are not favored by the small observed galaxy-quasar lensing rate.
Bradac, Marusa; Clowe, Douglas; Gonzalez, Anthony H.; Marshall, Phil; Forman, William; Jones, Christine; Markevitch, Maxim; Randall, Scott; Schrabback, Tim; Zaritsky,; /KIPAC, Menlo Park /Bonn, Inst. Astrophys. /Arizona U., Astron. Dept. - Steward Observ. /Florida U. /Harvard-Smithsonian Ctr. Astrophys.
2006-09-27
The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multi-color, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known redshift of one of the multiply imaged systems, we determine the remaining source redshifts using the predictive power of the strong lens model. Combining this information with shape measurements of ''weakly'' lensed sources, we derive a high-resolution, absolutely-calibrated mass map, using no assumptions regarding the physical properties of the underlying cluster potential. This map provides the best available quantification of the total mass of the central part of the cluster. We also confirm the result from Clowe et al. (2004, 2006a) that the total mass does not trace the baryonic mass.
Jouvel, S; Bernstein, G; Ilbert, O; Jelinsky, P; Milliard, B; Ealet, A; Schimd, C; Dahlen, T; Arnouts, S
2010-01-01
Accurate weak-lensing analysis requires not only accurate measurement of galaxy shapes but also precise and unbiased measurement of galaxy redshifts. The photometric redshift technique appears as the only possibility to determine the redshift of the background galaxies used in the weak-lensing analysis. Using the photometric redshift quality, simple shape measurement requirements, and a proper sky model, we explore what could be an optimal weak-lensing dark energy mission based on FoM calculation. We found that photometric redshifts reach their best accurracy for the bulk of the faint galaxy population when filters have a resolution R~3.2. We show that an optimal mission would survey the sky through 8 filters using 2 cameras (visible and near infrared). Assuming a 5-year mission duration, a mirror size of 1.5m, a 0.5deg2 FOV with a visible pixel scale of 0.15", to maximize the Weak Lensing FoM, an optimal exposure time is found to be 4x200s per filter (at the Galactic poles) thus covering ~11000deg2 of the sk...
NASA Astrophysics Data System (ADS)
Liu, Xiangkun; Pan, Chuzhong; Li, Ran; Shan, Huanyuan; Wang, Qiao; Fu, Liping; Fan, Zuhui; Kneib, Jean-Paul; Leauthaud, Alexie; Van Waerbeke, Ludovic; Makler, Martin; Moraes, Bruno; Erben, Thomas; Charbonnier, Aldée
2015-07-01
We derived constraints on cosmological parameters using weak lensing peak statistics measured on the ˜ 130 deg2 of the Canada-France-Hawaii Telescope Stripe 82 Survey. This analysis demonstrates the feasibility of using peak statistics in cosmological studies. For our measurements, we considered peaks with signal-to-noise ratio in the range of ? = [3, 6]. For a flat ? cold dark matter model with only (?m, ?8) as free parameters, we constrained the parameters of the following relation ?8 = ?8(?m/0.27)? to be ?8 = 0.82 ± 0.03 and ? = 0.43 ± 0.02. The ? value found is considerably smaller than the one measured in two-point and three-point cosmic shear correlation analyses, showing a significant complement of peak statistics to standard weak lensing cosmological studies. The derived constraints on (?m, ?8) are fully consistent with the ones from either WMAP9 or Planck. From the weak lensing peak abundances alone, we obtained marginalized mean values of ? _m=0.38^{+0.27}_{-0.24} and ?8 = 0.81 ± 0.26. Finally, we also explored the potential of using weak lensing peak statistics to constrain the mass-concentration relation of dark matter haloes simultaneously with cosmological parameters.
Algorithms And Programs For Strong Gravitational Lensing In Kerr Space-time Including Polarization
Chen, Bin; Dai, Xinyu; Baron, Eddie; Maddumage, Prasad
2015-01-01
Active galactic nuclei (AGNs) and quasars are important astrophysical objects to understand. Recently, microlensing observations have constrained the size of the quasar X-ray emission region to be of the order of 10 gravitational radii of the central supermassive black hole. For distances within a few gravitational radii, light paths are strongly bent by the strong gravity field of the central black hole. If the central black hole has nonzero angular momentum (spin), a photon's polarization plane will be rotated by the gravitational Faraday effect. The observed X-ray flux and polarization will then be influenced significantly by the strong gravity field near the source. Consequently, linear gravitational lensing theory is inadequate for such extreme circumstances. We present simple algorithms computing strong lensing effects of Kerr black holes, including effects on polarization. Our algorithms are realized in a program "KERTAP" in two versions: MATLAB and Python. The key ingredients of KERTAP are: a graphic ...
Imprint of Gravitational Lensing by Population III Stars in Gamma Ray Burst Light Curves
Y. Hirose; M. Umemura; A. Yonehara; J. Sato
2006-10-24
We propose a novel method to extract the imprint of gravitational lensing by Pop III stars in the light curves of Gamma Ray Bursts (GRBs). Significant portions of GRBs can originate in hypernovae of Pop III stars and be gravitationally lensed by foreground Pop III stars or their remnants. If the lens mass is on the order of $10^2-10^3M_\\odot$ and the lens redshift is greater than 10, the time delay between two lensed images of a GRB is $\\approx 1$s and the image separation is $\\approx 10 \\mu$as. Although it is difficult to resolve the two lensed images spatially with current facilities, the light curves of two images are superimposed with a delay of $\\approx 1$ s. GRB light curves usually exhibit noticeable variability, where each spike is less than 1s. If a GRB is lensed, all spikes are superimposed with the same time delay. Hence, if the autocorrelation of light curve with changing time interval is calculated, it should show the resonance at the time delay of lensed images. Applying this autocorrelation method to GRB light curves which are archived as the {\\it BATSE} catalogue, we demonstrate that more than half light curves can show the recognizable resonance, if they are lensed. Furthermore, in 1821 GRBs we actually find one candidate of GRB lensed by a Pop III star, which may be located at redshift 20-200. The present method is quite straightforward and therefore provides an effective tool to search for Pop III stars at redshift greater than 10. Using this method, we may find more candidates of GRBs lensed by Pop III stars in the data by the {\\it Swift} satellite.
Mapping the dark matter with weak gravitational lensing
Nick Kaiser; Gordon Squires
1993-01-01
We consider the problem of reconstructing the projected mass distribution in clusters from coherent distortions of background galaxies. The ellipticity of a background galaxy provides an estimate of the trace-free components of the tidal field. We present a technique for inverting this problem. The resulting surface density contains a strong, but incoherent, random component arising from the random intrinsic galaxy
P. Saha; F. Courbin; D. Sluse; S. Dye; G. Meylan
2006-01-17
Aims: To predict time delays for a sample of gravitationally lensed quasars and to evaluate the accuracy that can be realistically achieved on the value of H_0. Methods: We consider 14 lensed quasars that are candidates for time-delay monitoring and model them in detail using pixelized lens models. For each system, we provide a mass map, arrival-time surface and the distribution of predicted time-delays in a concordance cosmology, assuming H_0^{-1}=14 Gyr (H_0=70 in local units). Based on the predicted time-delays and on the observational circumstances, we rate each lens as `excellent' or `good' or `unpromising' for time-delay monitoring. Finally, we analyze simulated time delays for the 11 lens rated excellent or good, and show that H_0 can be recovered to a precision of 5%. Results: In combination with COSMOGRAIL paper I on the temporal sampling of lensed quasar light curves, the present work will help design monitoring campaigns of lensed quasars.
NASA Astrophysics Data System (ADS)
Chantry, V.; Sluse, D.; Magain, P.
2010-11-01
Aims: We attempt to place very accurate positional constraints on seven gravitationally lensed quasars currently being monitored by the COSMOGRAIL collaboration, and shape parameters for the light distribution of the lensing galaxy. We attempt to determine simple mass models that reproduce the observed configuration and predict time delays. We finally test, for the quads, whether there is evidence of astrometric perturbations produced by substructures in the lensing galaxy, which may preclude a good fit with the simple models. Methods: We apply the iterative MCS deconvolution method to near-IR HST archival data of seven gravitationally lensed quasars. This deconvolution method allows us to differentiate the contributions of the point sources from those of extended structures such as Einstein rings. This method leads to an accuracy of 1-2 mas in the relative positions of the sources and lens. The limiting factor of the method is the uncertainty in the instrumental geometric distortions. We then compute mass models of the lensing galaxy using state-of-the-art modeling techniques. Results: We determine the relative positions of the lensed images and lens shape parameters of seven lensed quasars: HE 0047-1756, RX J1131-1231, SDSS J1138+0314, SDSS J1155+6346, SDSS J1226-0006, WFI J2026-4536, and HS 2209+1914. The lensed image positions are derived with 1-2 mas accuracy. Isothermal and de Vaucouleurs mass models are calculated for the whole sample. The effect of the lens environment on the lens mass models is taken into account with a shear term. Doubly imaged quasars are equally well fitted by each of these models. A large amount of shear is necessary to reproduce SDSS J1155+6346 and SDSS J1226-006. In the latter case, we identify a nearby galaxy as the dominant source of shear. The quadruply imaged quasar SDSS J1138+0314 is reproduced well by simple lens models, which is not the case for the two other quads, RX J1131-1231 and WFI J2026-4536. This might be the signature of astrometric perturbations caused by massive substructures in the galaxy, which are unaccounted for by the models. Other possible explanations are also presented. Based on observations made with the NASA/ESA HST Hubble Space Telescope, obtained from the data archive at the Space Science Institute, which is operated by AURA, the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS-5-26555.
Accurate Modeling of Weak Lensing with the sGL Method
Kimmo Kainulainen; Valerio Marra
2010-12-27
We revise and extend the stochastic approach to cumulative weak lensing (hereafter the sGL method) first introduced in Ref. [1]. Here we include a realistic halo mass function and density profiles to model the distribution of mass between and within galaxies, galaxy groups and galaxy clusters. We also introduce a modeling of the filamentary large-scale structures and a method to embed halos into these structures. We show that the sGL method naturally reproduces the weak lensing results for the Millennium Simulation. The strength of the sGL method is that a numerical code based on it can compute the lensing probability distribution function for a given inhomogeneous model universe in a few seconds. This makes it a useful tool to study how lensing depends on cosmological parameters and its impact on observations. The method can also be used to simulate the effect of a wide array of systematic biases on the observable PDF. As an example we show how simple selection effects may reduce the variance of observed PDF, which could possibly mask opposite effects from very large scale structures. We also show how a JDEM-like survey could constrain the lensing PDF relative to a given cosmological model. The updated turboGL code is available at turboGL.org.
Strong deflection limit of black hole gravitational lensing with arbitrary source distances
Bozza, V. [Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno, via Allende, I-84081 Baronissi (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy); Scarpetta, G. [Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno, via Allende, I-84081 Baronissi (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy); International Institute for Advanced Scientific Studies, Vietri sul Mare (Italy)
2007-10-15
The gravitational field of supermassive black holes is able to strongly bend light rays emitted by nearby sources. When the deflection angle exceeds {pi}, gravitational lensing can be analytically approximated by the so-called strong deflection limit. In this paper we remove the conventional assumption of sources very far from the black hole, considering the distance of the source as an additional parameter in the lensing problem to be treated exactly. We find expressions for critical curves, caustics, and all lensing observables valid for any position of the source up to the horizon. After analyzing the spherically symmetric case we focus on the Kerr black hole, for which we present an analytical 3-dimensional description of the higher order caustic tubes.
Correcting the z~8 Galaxy Luminosity Function for Gravitational Lensing Magnification Bias
Mason, Charlotte A; Schmidt, Kasper B; Collett, Thomas E; Trenti, Michele; Marshall, Philip J; Barone-Nugent, Robert; Bradley, Larry D; Stiavelli, Massimo; Wyithe, Stuart
2015-01-01
We present a Bayesian framework to account for the magnification bias from both strong and weak gravitational lensing in estimates of high-redshift galaxy luminosity functions. We illustrate our method by estimating the $z\\sim8$ UV luminosity function using a sample of 97 Y-band dropouts (Lyman break galaxies) found in the Brightest of Reionizing Galaxies (BoRG) survey and from the literature. We find the luminosity function is well described by a Schechter function with characteristic magnitude of $M^\\star = -19.85^{+0.30}_{-0.35}$, faint-end slope of $\\alpha = -1.72^{+0.30}_{-0.29}$, and number density of $\\log_{10} \\Psi^\\star [\\textrm{Mpc}^{-3}] = -3.00^{+0.23}_{-0.31}$. These parameters are consistent within the uncertainties with those inferred from the same sample without accounting for the magnification bias, demonstrating that the effect is small for current surveys at $z\\sim8$, and cannot account for the apparent overdensity of bright galaxies found recently by Bowler et al. (2014a,b) and Finkelstein...
Weak lensing calibrated M-T scaling relation of galaxy groups in the cosmos field
Kettula, K.; Finoguenov, A. [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, FI-00014 Helsinki (Finland); Massey, R. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Rhodes, J. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Hoekstra, H. [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333-CA Leiden (Netherlands); Taylor, J. E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Spinelli, P. F. [Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG), Rua do Matão, 1226 Cidade Universitária 05508-090, São Paulo, SP (Brazil); Tanaka, M. [National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Ilbert, O. [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, F-13013 Marseille (France); Capak, P. [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard Pasadena, CA 91125 (United States); McCracken, H. J. [Institut d'Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, F-75014 Paris (France); Koekemoer, A., E-mail: kimmo.kettula@iki.fi [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
2013-11-20
The scaling between X-ray observables and mass for galaxy clusters and groups is instrumental for cluster-based cosmology and an important probe for the thermodynamics of the intracluster gas. We calibrate a scaling relation between the weak lensing mass and X-ray spectroscopic temperature for 10 galaxy groups in the COSMOS field, combined with 55 higher-mass clusters from the literature. The COSMOS data includes Hubble Space Telescope imaging and redshift measurements of 46 source galaxies per arcminute{sup 2}, enabling us to perform unique weak lensing measurements of low-mass systems. Our sample extends the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study, resulting in a power-law slope of 1.48{sub ?0.09}{sup +0.13}. The slope is consistent with the self-similar model, predictions from simulations, and observations of clusters. However, X-ray observations relying on mass measurements derived under the assumption of hydrostatic equilibrium have indicated that masses at group scales are lower than expected. Both simulations and observations suggest that hydrostatic mass measurements can be biased low. Our external weak lensing masses provide the first observational support for hydrostatic mass bias at group level, showing an increasing bias with decreasing temperature and reaching a level of 30%-50% at 1 keV.
New Programs to Promote Mass Measurements and Planet Discovery via Gravitational Lensing Events
NASA Astrophysics Data System (ADS)
Di Stefano, Rosanne; Bryk, W.; Ginsburg, I.; Kunapuli, N.; Murphy, M.; Oprescu, A.; Primini, F.; Tunbridge, B.
2014-01-01
Gravitational lensing events are opportunities to discover dim astronomical masses. Furthermore, whether or not the presence of the lens was known before the event, the lensing light curve provides information about the mass of the lens and about whether the lens has stellar or planetary companions. Until now, however, we have been able to derive detailed information about the lens system in fewer than one percent of the more than 10,000 already-identified candidate lensing events. In this talk we will describe an ongoing program to learn more about past lensing events, and a new program that will enhance the monitoring of future events in order to learn even more about the lenses. The programs to study new events have two components. The first component starts with events discovered by lensing monitoring teams, such as the OGLE and MOA surveys. By identifying catalogued counterparts to the events and implementing model fits that include a variety of physical effects, we can identify possible nearby-lens events that will be productive targets for enhanced monitoring. The second component consists of predicted close passages between a foreground and background star. These provide opportunities to search for evidence of lensing by planets of the foreground star. We describe planned investigations of both types to take place in 2014, and invite community participation.
New limits on a cosmological constant from statistics of gravitational lensing
Masashi Chiba; Yuzuru Yoshii
1998-08-28
We present new limits on cosmological parameters from the statistics of gravitational lensing, based on the recently revised knowledge of the luminosity function and internal dynamics of E/S0 galaxies that are essential in lensing high-redshift QSOs. We find that the lens models using updated Schechter parameters for such galaxies, derived from the recent redshift surveys combined with morphological classification, are found to give smaller lensing probabilities than earlier calculated. Inconsistent adoption of these parameters from a mixture of various galaxy surveys gives rise to systematic biases in the results. We also show that less compact dwarf-type galaxies which largely dominate the faint part of the Schechter-form luminosity function contribute little to lensing probabilities, so that earlier lens models overestimate incidents of small separation lenses. Applications of the lens models to the existing lens surveys indicate that reproduction of both the lensing probability of optical sources and the image separations of optical and radio lenses is significantly improved in the revised lens models. The likelihood analyses allow us to conclude that a flat universe with Omega=0.3(+0.2-0.1) and Omega+Lambda=1 is most preferable, and a matter-dominated flat universe with Lambda=0 is ruled out at 98 % confidence level. These new limits are unaffected by inclusion of uncertainties in the lens properties.
De Putter, Roland; Doré, Olivier [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Das, Sudeep [High Energy Physics Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States)
2014-01-10
Cross correlations between the galaxy number density in a lensing source sample and that in an overlapping spectroscopic sample can in principle be used to calibrate the lensing source redshift distribution. In this paper, we study in detail to what extent this cross-correlation method can mitigate the loss of cosmological information in upcoming weak lensing surveys (combined with a cosmic microwave background prior) due to lack of knowledge of the source distribution. We consider a scenario where photometric redshifts are available and find that, unless the photometric redshift distribution p(z {sub ph}|z) is calibrated very accurately a priori (bias and scatter known to ?0.002 for, e.g., EUCLID), the additional constraint on p(z {sub ph}|z) from the cross-correlation technique to a large extent restores the cosmological information originally lost due to the uncertainty in dn/dz(z). Considering only the gain in photo-z accuracy and not the additional cosmological information, enhancements of the dark energy figure of merit of up to a factor of four (40) can be achieved for a SuMIRe-like (EUCLID-like) combination of lensing and redshift surveys, where SuMIRe stands for Subaru Measurement of Images and Redshifts). However, the success of the method is strongly sensitive to our knowledge of the galaxy bias evolution in the source sample and we find that a percent level bias prior is needed to optimize the gains from the cross-correlation method (i.e., to approach the cosmology constraints attainable if the bias was known exactly).
The Einstein Cross: Constraint on Dark Matter from Stellar Dynamics and Gravitational Lensing
NASA Astrophysics Data System (ADS)
van de Ven, Glenn; Falcón-Barroso, Jesús; McDermid, Richard M.; Cappellari, Michele; Miller, Bryan W.; de Zeeuw, P. Tim
2010-08-01
We present two-dimensional line-of-sight stellar kinematics of the lens galaxy in the Einstein Cross, obtained with the GEMINI 8 m telescope, using the GMOS integral-field spectrograph. The stellar kinematics extend to a radius of 4'' (with 0farcs2 spaxels), covering about two-thirds of the effective (or half-light) radius Re ~= 6'' of this early-type spiral galaxy at redshift zl ~= 0.04, of which the bulge is lensing a background quasar at redshift zs ~= 1.7. The velocity map shows regular rotation up to ~100 km s-1 around the minor axis of the bulge, consistent with axisymmetry. The velocity dispersion map shows a weak gradient increasing toward a central (R < 1'') value of ?0 = 170 ± 9 km s-1. We deproject the observed surface brightness from Hubble Space Telescope imaging to obtain a realistic luminosity density of the lens galaxy, which in turn is used to build axisymmetric dynamical models that fit the observed kinematic maps. We also construct a gravitational lens model that accurately fits the positions and relative fluxes of the four quasar images. We combine these independent constraints from stellar dynamics and gravitational lensing to study the total mass distribution in the inner parts of the lens galaxy. We find that the resulting luminous and total mass distribution are nearly identical around the Einstein radius RE = 0farcs89, with a slope that is close to isothermal, but which becomes shallower toward the center if indeed mass follows light. The dynamical model fits to the observed kinematic maps result in a total mass-to-light ratio Upsilondyn = 3.7 ± 0.5 Upsilonsun,I (in the I band). This is consistent with the Einstein mass ME = 1.54 × 1010 M sun divided by the (projected) luminosity within RE , which yields a total mass-to-light ratio of Upsilon E = 3.4 Upsilonsun,I , with an error of at most a few percent. We estimate from stellar population model fits to colors of the lens galaxy a stellar mass-to-light ratio Upsilonsstarf from 2.8 to 4.1 Upsilonsun,I . Although a constant dark matter fraction of 20% is not excluded, dark matter may play no significant role in the bulge of this ~L sstarf early-type spiral galaxy.
The Dust-to-Gas Ratio in the Damped Ly alpha Clouds Towards the Gravitationally Lensed QSO 0957+561
NASA Technical Reports Server (NTRS)
Zuo, Lin; Beaver, E. A.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Lyons, R. W.
1997-01-01
We present HST/FOS spectra of the two bright images (A and B) of the gravitationally lensed QSO 0957+561 in the wavelength range 2200-3300 A. We find that the absorption system (Z(sub abs)) = 1.3911) near z(sub em) is a weak, damped Ly alpha system with strong Ly alpha absorption lines seen in both images. However, the H(I) column densities are different, with the line of sight to image A intersecting a larger column density. The continuum shapes of the two spectra differ in the sense that the flux level of image A increases more slowly toward shorter wavelengths than that of image B. We explain this as the result of differential reddening by dust grains in the damped Ly alpha absorber. A direct outcome of this explanation is a determination of the dust-to-gas ratio, k, in the damped Ly alpha system. We derive k = 0.55 + 0.18 for a simple 1/lambda extinction law and k = 0.31 + 0.10 for the Galactic extinction curve. For gravitationally lensed systems with damped Ly alpha absorbers, our method is a powerful tool for determining the values and dispersion of k, and the shapes of extinction curves, especially in the FUV and EUV regions. We compare our results with previous work.
Theoretical analysis of a reported weak gravitational shielding effect
Modanese, G
1995-01-01
Under special conditions (Meissner-effect levitation and rapid rotation) a disk of high-T_c superconducting material has recently been found to produce a weak shielding of the gravitational field. We show that this phenomenon has no explanation in the standard gravity theories, except possibly in the non-perturbative quantum theory on the Regge lattice. More data, and independent repetitions of the experiment are however necessary.
A. Udalski; M. Szymanski; K. Z. Stanek; J. Kaluzny; M. Kubiak; M. Mateo; W. Krzeminski; B. Paczynski; R. Venkat
1994-01-01
We present the analysis of the first two years of the OGLE search for gravitational lenses towards the Galactic bulge. We detected 9 microlensing events in an algorithmic search of sim 10^8 measurements of sim 10^6 stars. The characteristic time scales are in the range 8.6
NASA Astrophysics Data System (ADS)
Lee, Adrian
2014-03-01
We report the direct detection of gravitational lensing of the Cosmic Microwave Background polarization. We present maps of 30 square degrees of the sky measured to a depth of 6 microK*arcminute at 150 GHz. To detect the non-Gaussian signature of gravitational lensing, we measure the 4-point correlation functions EEEB and EBEB where E and B describe E-mode and B-mode maps. We reject the null hypotheses at 4.2 sigma significance, including the contribution of systematic errors, using the combination of these two 4-point correlation functions. Further, we measure a lensing amplitude normalized to LCDM of 1.06 +/-0.47(stat) +0.32/-0.27(sys) consistent with the current standard cosmological model. This result gives a measurement of the amplitude of matter fluctuations in the Universe with 26% error. Measurements of gravitational lensing of the Cosmic Microwave Background have great potential as a probe of structure formation, the behavior of Dark Energy, and the sum of the masses of neutrinos through their role as hot Dark Matter. The POLARBEAR project is funded by the National Science Foundation under grant AST-0618398 and AST-1212230.
Mapping the Small-Scale Structure of Dark Matter Halos with Strong Gravitational Lensing
NASA Astrophysics Data System (ADS)
Hezaveh, Yashar D.
2015-01-01
The abundance of substructure within dark matter halos surrounding galaxies has been an area of intensive study for over a decade. The number of observed low-mass satellites of the Milky Way is about three orders of magnitude lower than what cold dark matter (CDM) simulations predict, an issue that is referred to as the "Missing Satellite Problem". Disagreement between the abundance of dark matter subhalos and the CDM predictions may lead to exciting insights into the micro-physics of dark matter particles. However, measuring the abundance of subhalos, which may be entirely composed of dark matter, requires a purely gravitational probe. I have simulated observations of gravitationally lensed sub-millimeter galaxies, showing that they can be used to detect dark matter subhalos in the lensing galaxies, using the gravitationally-induced distortions that they cause in the images of background sources. I have shown that by measuring the observed surface brightness correlations of lensed images we can detect the power spectrum of low-mass dark matter subhalos with high significance. In this talk, I will give an overview of an observational campaign that I'm leading to use ALMA and a newly discovered population of strongly lensed sub-millimeter galaxies to measure the mass function of dark matter subhalos with unprecedented accuracy.
Cosmological Constraints from Strong Gravitational Lensing in Galaxy Clusters
Eric Jullo; Priyamvada Natarajan; Jean-Paul Kneib; Anson d'Aloisio; Marceau Limousin; Johan Richard; Carlo Schimd
2010-01-01
Current efforts in observational cosmology are focused on characterizing the\\u000amass-energy content of the Universe. We present results from a geometric test\\u000abased on strong lensing in galaxy clusters. Based on Hubble Space Telescope\\u000aimages and extensive ground-based spectroscopic follow-up of the massive galaxy\\u000acluster Abell 1689, we used a parametric model to simultaneously constrain the\\u000acluster mass distribution and
Cosmological Constraints from Strong Gravitational Lensing in Clusters of Galaxies
Eric Jullo; Priyamvada Natarajan; J.-P. Kneib; A. D'Aloisio; Marceau Limousin; Johan Richard; Carlo Schimd
2010-01-01
Current efforts in observational cosmology are focused on characterizing the mass-energy content of the Universe. We present results from a geometric test based on strong lensing in galaxy clusters. Based on Hubble Space Telescope images and extensive ground-based spectroscopic follow-up of the massive galaxy cluster Abell 1689, we used a parametric model to simultaneously constrain the cluster mass distribution and
Jean-Paul Kneib; Priyamvada Natarajan
2012-02-03
Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.
Infrared observations of gravitational lensing in Abell 2219 with CIRSI
Meghan E. Gray; Richard S. Ellis; Alexandre Refregier; Jocelyn Bézecourt; Richard G. McMahon; Martin G. Beckett; Craig D. Mackay; Michael D. Hoenig
2000-01-01
We present the first detection of a gravitational depletion signal at near-infrared wavelengths, based on deep panoramic images of the cluster Abell 2219 (z=0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at the prime focus of the 4.2-m William Herschel Telescope. Infrared studies of gravitational depletion offer a number of advantages over similar techniques applied at optical wavelengths, and
Wavelet Helmholtz decomposition for weak lensing mass map reconstruction
NASA Astrophysics Data System (ADS)
Deriaz, E.; Starck, J.-L.; Pires, S.
2012-04-01
To derive the convergence field from the gravitational shear ? of the background galaxy images, the classical methods require a convolution of the shear to be performed over the entire sky, usually expressed by the fast Fourier transform (FFT). However, it is not optimal for an imperfect geometry survey. Furthermore, FFT implicitly uses periodic conditions that introduce errors into the reconstruction. A method has been proposed that relies on computation of an intermediate field u that combines the derivatives of ? and on convolution with a Green kernel. In this paper, we study the wavelet Helmholtz decomposition as a new approach to reconstructing the dark matter mass map. We show that a link exists between the Helmholtz decomposition and the electric and magnetic component separation. We introduce a new wavelet construction that has a property that gives us more flexibility in handling the border problem, and we propose a new method of reconstructing the dark matter mass map in the wavelet space. A set of experiments based on noise-free images illustrates that this Wavelet Helmholtz decomposition reconstructs the borders better than all other existing methods.
A new model to predict weak-lensing peak counts II. Parameter constraint strategies
Lin, Chieh-An
2015-01-01
Peak counts have been shown to be an excellent tool to extract the non-Gaussian part of the weak lensing signal. Recently, we developped a fast stochastic forward model to predict weak-lensing peak counts. Our model is able to reconstruct the underlying distribution of observables for analyses. In this work, we explore and compare various strategies for constraining parameter using our model, focusing on the matter density $\\Omega_\\mathrm{m}$ and the density fluctuation amplitude $\\sigma_8$. First, we examine the impact from the cosmological dependency of covariances (CDC). Second, we perform the analysis with the copula likelihood, a technique which makes a weaker assumption compared to the Gaussian likelihood. Third, direct, non-analytic parameter estimations are applied using the full information of the distribution. Fourth, we obtain constraints with approximate Bayesian computation (ABC), an efficient, robust, and likelihood-free algorithm based on accept-reject sampling. We find that neglecting the CDC ...
SDSS J102111.02+491330.4: A Newly discovered gravitationally lensed quasar
Pindor, Bart; Eisenstein, Daniel J.; Gregg, Michael D.; Becker, Robert H.; Inada, Naohisa; Oguri, Masamune; Hall, Patrick B.; Johnston, David E.; Richards, Gordon T.; Schneider, Donald P.; Turner, Edwin L.; Brasi, Guido; Hinz, Philip M.; Kenworthy, Matthew A.; Miller, Doug; Barentine, J.C.; Brewington, Howard J.; Brinkmann, J.; Harvanek,; Kleinman, S.J.; Krzesinski, Jurek; /Toronto U., Astron. Dept. /Arizona U., Astron. Dept. - Steward Observ. /UC, Davis /LLNL, Livermore /Tokyo U., Inst. Astron. /Tokyo U.
2005-09-01
We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a z = 1.72 quasar, with an image separation of 1.14'' {+-} 0.04''. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of z = 1.49, with an angular separation of 1.49'' {+-} 0.02''. However, the two quasars have markedly different SEDs and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates which follow-up observations have confirmed are not gravitational lenses.
SDSSJ102111.02+491330.4: A Newly Discovered Gravitationally Lensed Quasar
Pindor, B; Eisenstein, D J; Gregg, M D; Becker, R H; Inada, N; Oguri, M; Hall, P B; Johnston, D E; Richards, G T; Schneider, D P; Turner, E L; Brasi, G; Hinz, P M; Kenworthy, M A; Miller, D; Barentine, J C; Brewington, H J; Brinkmann, J; Harvanek, M; Kleinman, S J; Krzesinski, J; Long, D; Neilsen Jr., E H; Newman, P R; Nitta, A; Snedden, S A; York, D G
2005-11-10
We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a z = 1.72 quasar, with an image separation of 1''.14 {+-} 0.04. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of z = 1.49, with an angular separation of 1''.49 {+-} 0.02. However, the two quasars have markedly different SEDs and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates which follow-up observations have confirmed are not gravitational lenses.
SDSSJ102111.02+491330.4: A Newly Discovered Gravitationally Lensed Quasar
Bart Pindor; Daniel J. Eisenstein; Michael D. Gregg; Robert H. Becker; Naohisa Inada; Masamune Oguri; Patrick B. Hall; David E. Johnston; Gordon T. Richards; Donald P. Schneider; Edwin L. Turner; Guido Brasi; Philip M. Hinz; Matthew A. Kenworthy; Doug Miller; J. C. Barentine; Howard J. Brewington; J. Brinkmann; Michael Harvanek; S. J. Kleinman; Jurek Krzesinski; Dan Long; Eric H. Neilsen, Jr.; Peter R. Newman; Atsuko Nitta; Stephanie A. Snedden; Donald G. York
2005-09-12
We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a $z = 1.72$ quasar, with an image separation of $1{\\farcs}14 \\pm 0.04$. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of $z = 1.49$, with an angular separation of $1{\\farcs}49 \\pm 0.02$. However, the two quasars have markedly different SEDs and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates which follow-up observations have confirmed are \\textit{not} gravitational lenses.
Hubble Space Telescope Weak-Lensing Study of the z=0.83 Cluster MS 1054-03
NASA Astrophysics Data System (ADS)
Hoekstra, H.; Franx, M.; Kuijken, K.
2000-03-01
We have measured the weak gravitational lensing of faint, distant background galaxies by MS 1054-03, a rich and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a two-color mosaic of deep WFPC2 images. The small corrections for the size of the point-spread function and the high number density of background galaxies obtained in these observations result in an accurate and well-calibrated measurement of the lensing induced distortion. The strength of the lensing signal depends on the redshift distribution of the background galaxies. We used photometric redshift distributions from the northern and southern Hubble Deep Fields to relate the lensing signal to the mass. The predicted variations of the signal as a function of apparent source magnitude and color agrees well with the observed lensing signal. The uncertainty in the redshift distribution results in a 10% systematic uncertainty in the mass measurement. We determine a mass of (1.2+/-0.2)x1015 h-150 Msolar within an aperture of radius 1 h-150 Mpc. Under the assumption of an isothermal mass distribution, the corresponding velocity dispersion is 1311+83-89 km s-1. For the mass-to-light ratio we find 269+/-37 h50 Msolar/LBsolar after correcting for passband and luminosity evolution. The errors in the mass and mass-to-light ratio include the contribution from the random intrinsic ellipticities of the source galaxies, but not the (systematic) error due to the uncertainty in the redshift distribution. However, the estimates for the mass and mass-to-light ratio of MS 1054-03 agree well with other estimators, suggesting that the mass calibration works well. The reconstruction of the projected mass surface density shows a complex mass distribution, consistent with the light distribution. The results indicate that MS 1054-03 is a young system. The timescale for relaxation is estimated to be at least 1 Gyr. We have also studied the masses of the cluster galaxies, by averaging the tangential shear around the cluster galaxies. Using the Faber-Jackson scaling relation, we find the velocity dispersion of an L* galaxy (LB=8x1010 h-250 LBsolar for MS 1054-03) is 203+/-33 km s-1. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Cosmic microwave weak lensing data as a test for the dark universe
Calabrese, Erminia; Slosar, Anze; Melchiorri, Alessandro; Smoot, George F.; Zahn, Oliver [Physics Department, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Berkeley Center for Cosmological Physics, Physics Department, University of California, Berkeley, CA 94720 (United States); Physics Department and INFN, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Lawrence Berkeley National Laboratory and Berkeley Center for Cosmological Physics, Physics Department, University of California, Berkeley, CA 94720 (United States)
2008-06-15
Combined analyses of WMAP 3-year and ACBAR cosmic microwave anisotropies angular power spectra have presented evidence for gravitational lensing at >3{sigma} level. This signal could provide a relevant test for cosmology. After evaluating and confirming the statistical significance of the detection in light of the new WMAP 5-year data, we constrain a new parameter A{sub L} that scales the lensing potential such that A{sub L}=0 corresponds to unlensed while A{sub L}=1 is the expected lensed result in the standard {lambda}-CDM model. We find from WMAP5+ACBAR a 2.5{sigma} indication for a lensing contribution larger than expected, with A{sub L}=3.1{sub -1.5}{sup +1.8} at 95% C.L. The result is stable under the assumption of different templates for an additional Sunyaev-Zel'dovich foreground component or the inclusion of an extra background of cosmic strings. We find negligible correlation with other cosmological parameters as, for example, the energy density in massive neutrinos. While unknown systematics may be present, dark energy or modified gravity models could be responsible for the over-smoothness of the power spectrum. Near-future data, most notably from the Planck satellite mission, will scrutinize this interesting possibility.
Planck 2013 results. XVII. Gravitational lensing by large-scale structure
NASA Astrophysics Data System (ADS)
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Basak, S.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bridges, M.; Bucher, M.; Burigana, C.; Butler, R. C.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Déchelette, T.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Ho, S.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lavabre, A.; Lawrence, C. R.; Leahy, J. P.; Leonardi, R.; León-Tavares, J.; Lesgourgues, J.; Lewis, A.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Partridge, B.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Pullen, A. R.; Rachen, J. P.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Smith, K.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; White, M.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.
2014-11-01
On the arcminute angular scales probed by Planck, the cosmic microwave background (CMB) anisotropies are gently perturbed by gravitational lensing. Here we present a detailed study of this effect, detecting lensing independently in the 100, 143, and 217 GHz frequency bands with an overall significance of greater than 25?. We use thetemperature-gradient correlations induced by lensing to reconstruct a (noisy) map of the CMB lensing potential, which provides an integrated measure of the mass distribution back to the CMB last-scattering surface. Our lensing potential map is significantly correlated with other tracers of mass, a fact which we demonstrate using several representative tracers of large-scale structure. We estimate the power spectrum of the lensing potential, finding generally good agreement with expectations from the best-fitting ?CDM model for the Planck temperature power spectrum, showing that this measurement at z = 1100 correctly predicts the properties of the lower-redshift, later-time structures which source the lensing potential. When combined with the temperature power spectrum, our measurement provides degeneracy-breaking power for parameter constraints; it improves CMB-alone constraints on curvature by a factor of two and also partly breaks the degeneracy between the amplitude of the primordial perturbation power spectrum and the optical depth to reionization, allowing a measurement of the optical depth to reionization which is independent of large-scale polarization data. Discarding scale information, our measurement corresponds to a 4% constraint on the amplitude of the lensing potential power spectrum, or a 2% constraint on the root-mean-squared amplitude of matter fluctuations at z ~ 2.
Yun Wang
1999-06-25
Weak lensing leads to the non-Gaussian magnification distribution of standard candles at given redshift $z$, $p(\\mu|z)$. In this paper, we give accurate and simple empirical fitting formulae of the weak lensing numerical simulation results with the generalized Dyer-Roeder prescription. The smoothness parameter $\\tilde{\\alpha}$ essentially represents the amount of matter that can cause magnification of a given source. Since matter distribution in our universe is inhomogeneous, we can think of our universe as a mosaic of cones centered on the observer, each with a different value of $\\tilde{\\alpha}$. We define the {\\it direction dependent} smoothness parameter $\\tilde{\\alpha}$ via the Dyer-Roeder equation; there is a unique mapping between $\\tilde{\\alpha}$ and the magnification of a source. We find that the distribution of $\\tilde{\\alpha}$ at given $z$, $p(\\tilde{\\alpha}|z)$, is well described by a modified Gaussian distribution. For the same matter distribution, i.e., the same $p(\\tilde{\\alpha}|z)$, different values of $\\Omega_m$ and $\\Omega_{\\Lambda}$ can lead to very different magnification distributions. Our formulae can be conveniently used to calculate the weak lensing effects for observed Type Ia supernovae at arbitrary redshifts.
Non-Gaussian forecasts of weak lensing with and without priors
Sellentin, Elena
2015-01-01
Assuming a Euclid-like weak lensing data set, we compare different methods of dealing with its inherent parameter degeneracies. Including priors into a data analysis can mask the information content of a given data set alone. However, since the information content of a data set is usually estimated with the Fisher matrix, priors are added in order to enforce an approximately Gaussian likelihood. Here, we compare priorless forecasts to more conventional forecasts that use priors. We find strongly non-Gaussian likelihoods for 2d-weak lensing if no priors are used, which we approximate with the DALI-expansion. Without priors, the Fisher matrix of the 2d-weak lensing likelihood includes unphysical values of $\\Omega_m$ and $h$, since it does not capture the shape of the likelihood well. The Cramer-Rao inequality then does not need to apply. We find that DALI and Monte Carlo Markov Chains predict the presence of a dark energy with high significance, whereas a Fisher forecast of the same data set also allows deceler...
Graham P. Smith
2002-01-15
We are conducting a systematic lensing survey of X-ray luminous galaxy clusters at z~0.2 using the Hubble Space Telescope and large ground-based telescopes. We summarize initial results from our survey, including a measurement of the inner slope of the mass profile of A383, and a search for gravitationally lensed Extremely Red Objects.
Lens Model Degeneracy and Cosmological Tests by Strong Gravitational Lensing
Takeshi Chiba; Ryuichi Takahashi
2002-09-22
We estimate the sensitivity of lensing observables to the parameters in the lens model (isothermal sphere/Navarro-Frenk-White profile) parameters and to cosmological parameters. We find that the observables are primarily dependent on the lens model parameters, while the dependence on cosmological parameters is minor (especially so for the dark energy parameters). We demonstrate the lens model degeneracy by deriving both the projected mass density profile and the circular velocity profile. We also identify a possible source of the problem of fitting the averaged mass profile of CL 0024+1654 with the Navarro-Frenk-White profile.
SDSS J115517.35+634622.0: A Newly Discovered Gravitationally Lensed Quasar
Bart Pindor; Daniel J. Eisenstein; Naohisa Inada; Michael D. Gregg; Robert H. Becker; Jon Brinkmann; Scott Burles; Joshua A. Frieman; David E. Johnston; Gordon T. Richards; Donald P. Schneider; Ryan Scraton; Maki Sekiguchi; Edwin L. Turner; Donald G. York
2003-12-05
We report the discovery of SDSSJ115517.35+634622.0, a previously unknown gravitationally lensed quasar. The lens system exhibits two images of a $z = 2.89$ quasar, with an image separation of $1{\\farcs}832 \\pm 0.007$ . Near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Based on absorption features seen in the Sloan Digital Sky Survey (SDSS) spectrum, we determine a lens galaxy redshift of $z = 0.1756$. The lens is rather unusual in that one of the quasar images is only $0{\\farcs}22\\pm0{\\farcs}07$ ($\\sim 0.1 R_{\\rm eff}$) from the center of the lens galaxy and photometric modeling indicates that this image is significantly brighter than predicted by a SIS model. This system was discovered in the course of an ongoing search for strongly lensed quasars in the dataset from the SDSS.
Mapping the 3-D dark matter with weak lensing in COMBO-17
A. N. Taylor; D. J. Bacon; M. E. Gray; C. Wolf; K. Meisenheimer; S. Dye; A. Borch; M. Kleinheinrich; Z. Kovacs; L. Wisotzki
2004-02-04
We present a 3-dimensional lensing analysis of the z=0.16 supercluster A901/2, resulting in a 3-D map of the dark matter distribution within a 3 X 10^{5} [Mpc]^3 volume from the COMBO-17 survey. We perform a chi^2-fit of isothermal spheres to the tangential shear pattern around each cluster as a function of redshift to estimate the 3-D positions and masses of the main clusters in the supercluster from lensing alone. We then present the first 3-D map of the dark matter gravitational potential field, Phi, using the Kaiser-Squires (1993) and Taylor (2001) inversion methods. These maps clearly show the potential wells of the main supercluster components, including a new cluster behind A902, and demonstrates the applicability of 3-D dark matter mapping and projection free-mass-selected cluster finding to current data. Finally, we develop the halo model of dark matter and galaxy clustering and compare this with the auto-and cross-correlation functions of the 3-D gravitational potential, galaxy number densities and galaxy luminosity densities measured in the A901/2 field. We find significant anti-correlations between the gravitational potential field and the galaxy number density and luminosities, as expected due to baryonic infall into dark matter concentrations. We find good agreement with the halo model for the number densities and luminosity correlation functions.
The snapshot survey - A search for gravitationally lensed quasars with the Hubble Space Telescope
NASA Technical Reports Server (NTRS)
Bahcall, J. N.; Maoz, D.; Doxsey, R.; Schneider, D. P.; Bahcall, N. A.; Lahav, O.; Yanny, B.
1992-01-01
The first results from the HST Non-Proprietary Snapshot Survey are presented in order to investigate new examples of multiply imaged quasars that are the result of gravitational lensing. None of the approximately 30 quasars observed at high spatial resolution show evidence of multiple imaging by gravitational lensing. These results are compared with lower resolution ground-based surveys and current theoretical predictions. Several engineering problems in the observatory's performance are addressed. It particular, the large telescope pointing errors and drift rates are found to be primarily the result of the lack of correction for stellar aberration when pointing and tracking are performed solely with gyroscopes. The implications for the possibly low intrinsic gyro drift rate on future observations are discussed.
NASA Technical Reports Server (NTRS)
Maoz, D.; Bahcall, J. N.; Schneider, D. P.; Bahcall, N. A.; Djorgovski, S.; Doxsey, R.; Gould, A.; Kirhakos, S.; Meylan, G.; Yanny, B.
1993-01-01
We report the concluding results of the HST Snapshot Survey for gravitationally lensed quasars. New observations of 153 high-luminosity z above 1 quasars are presented, bringing to 498 the total number of quasars observed in the survey. The new observations do not reveal new candidates for gravitational lensing. We present tables summarizing all of the snapshot observations, with measured V-magnitudes, accurate to 0.1 mag, for each of the quasars successfully observed. The observed frequency of lensing of quasars into multiple images is 3-6 out of 502, depending on whether one counts candidates that are not yet securely confirmed and cases in which clusters play a role. This frequency is in the range predicted by calculations with a vanishing cosmological constant, assuming galaxies can be modeled by unevolving isothermal spheres dominated in their centers by dark matter. The observed frequency is an order of magnitude lower than expected in such models when the universe is strongly dominated by a cosmological constant. This conclusion is, however, sensitive to the model assumptions and to the precise number of actual lensed quasars.
High, F. W.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Hoekstra, H. [Leiden Observatory, Leiden University, Leiden (Netherlands); Leethochawalit, N. [Department of Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); De Haan, T. [Department of Physics, McGill University, 3600 Rue University, Montreal, QC H3A 2T8 (Canada); Abramson, L. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Armstrong, R. [National Center for Supercomputing Applications, University of Illinois, 1205 West Clark Street, Urbana, IL 61801 (United States); Ashby, M. L. N.; Conroy, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bautz, M. [MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Bayliss, M. [Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138 (United States); Bazin, G. [Department of Physics, Ludwig-Maximilians-Universitaet, Scheinerstr. 1, D-81679 Muenchen (Germany); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Cho, H. M. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); Clocchiatti, A., E-mail: fwhigh@kicp.uchicago.edu [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica, Casilla 306, Santiago 22 (Chile); and others
2012-10-10
We use weak gravitational lensing to measure the masses of five galaxy clusters selected from the South Pole Telescope (SPT) survey, with the primary goal of comparing these with the SPT Sunyaev-Zel'dovich (SZ) and X-ray-based mass estimates. The clusters span redshifts 0.28 < z < 0.43 and have masses M{sub 500} > 2 Multiplication-Sign 10{sup 14} h {sup -1} M{sub Sun }, and three of the five clusters were discovered by the SPT survey. We observed the clusters in the g'r'i' passbands with the Megacam imager on the Magellan Clay 6.5 m telescope. We measure a mean ratio of weak-lensing (WL) aperture masses to inferred aperture masses from the SZ data, both within an aperture of R{sub 500,SZ} derived from the SZ mass, of 1.04 {+-} 0.18. We measure a mean ratio of spherical WL masses evaluated at R{sub 500,SZ} to spherical SZ masses of 1.07 {+-} 0.18, and a mean ratio of spherical WL masses evaluated at R{sub 500,WL} to spherical SZ masses of 1.10 {+-} 0.24. We explore potential sources of systematic error in the mass comparisons and conclude that all are subdominant to the statistical uncertainty, with dominant terms being cluster concentration uncertainty and N-body simulation calibration bias. Expanding the sample of SPT clusters with WL observations has the potential to significantly improve the SPT cluster mass calibration and the resulting cosmological constraints from the SPT cluster survey. These are the first WL detections using Megacam on the Magellan Clay telescope.
The time delay in strong gravitational lensing with Gauss-Bonnet correction
Jingyun Man; Hongbo Cheng
2014-09-13
The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We derive and calculate the expression of time delay due to the Gauss-Bonnet coupling. It is shown that the time delay for two images with larger space each other is longer. We also find that the ratio of Gauss-Bonnet coefficient and the mass of gravitational source changes in the region like $\\frac{\\alpha}{M}\\in[0,2)$. The time delay is divergent with $\\frac{\\alpha}{M}\\longrightarrow 2$.
The strong field gravitational lensing in the Schwarzschild black hole pierced by a cosmic string
Jingyun Man; Huawen Wang; Hongbo Cheng
2015-06-24
In this work the gravitational lensing in the strong field limit around the Schwarzschild black hole pierced by a cosmic string is studied. We find that the deflection angle and the time delay of the relativistic images depend on the tension of cosmic string. It is interesting that the deflection angle is greater when the tension of cosmic string is stronger. The time delay between two images is more obvious in the case of weaker tension.
Time Delay in Gravitational Lensing by a Charged Black Hole of String Theory
Alexis Larranaga
2007-07-16
We calculate the time delay between different relativistic images formed by the gravitational lensing produced by the Gibbons-Maeda-Garfinkle-Horowitz-Stromiger (GMGHS) charged black hole of heterotic string theory. Modeling the supermassive central objects of some galaxies as GMGHS black holes, numerical values of the time delays are estimated and compared with the correspondient Reissner-Nordstrom black holes . The time difference amounts to hours, thus being measurable and permiting to distinguish between General Relativity and String Theory charged black holes.
Bandara, Kaushala; Crampton, David; Peng, Chien; Simard, Luc [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)
2013-11-01
We take advantage of the magnification in size and flux of a galaxy provided by gravitational lensing to analyze the properties of 62 strongly lensed galaxies from the Sloan Lens ACS (SLACS) Survey. The sample of lensed galaxies spans a redshift range of 0.20 ? z ? 1.20 with a median redshift of z = 0.61. We use the lens modeling code LENSFIT to derive the luminosities, sizes, and Sérsic indices of the lensed galaxies. The measured properties of the lensed galaxies show a primarily compact, {sup d}isk{sup -}like population with the peaks of the size and Sérsic index distributions corresponding to ?1.50 kpc and n ? 1, respectively. Comparison of the SLACS galaxies to a non-lensing, broadband imaging survey shows that a lensing survey allows us to probe a galaxy population that reaches ?2 mag fainter. Our analysis allows us to compare the (z) = 0.61 disk galaxy sample (n ? 2.5) to an unprecedented local galaxy sample of ?670, 000 SDSS galaxies at z ? 0.1; this analysis indicates that the evolution of the luminosity-size relation since z ? 1 may not be fully explained by a pure-size or pure-luminosity evolution but may instead require a combination of both. Our observations are also in agreement with recent numerical simulations of disk galaxies that show evidence of a mass-dependent evolution since z ? 1, where high-mass disk galaxies (M{sub *} > 10{sup 9} M{sub ?}) evolve more in size and low-mass disk galaxies (M{sub *} ? 10{sup 9} M{sub ?}) evolve more in luminosity.
Songbai Chen; Jiliang Jing
2015-02-04
We study the equation of motion of photons and the strong gravitational lensing in a Schwarzschild black hole spacetime when the photons couple to Weyl tensor. We find that the propagation of the coupled photons and the corresponding gravitational lensing depend sharply on the coupling constant $\\alpha$ and the photon polarization directions. The marginally stable circular radius $r_{ps}$ exists only in the regime $\\alpha\\geq\\alpha_{c1}=-M^2/2$ for the photon with the polarization along $l_{\\mu}$ and in the regime $\\alpha\\leq\\alpha_{c2}=M^2$ for the photon with the polarization along $m_{\\mu}$. When the value of $\\alpha$ is beyond the above regime, we find that the marginally stable circular radius vanishes and there exists a singularity outside the event horizon of black hole in the propagation of the coupled photons. The deflection angle of the light ray near the singularity is a negative finite value, which is different entirely from that of the usual photons without the coupling to Weyl tensor. Finally, we estimated three observables in the strong gravitational lensing for the coupled photons in the case with the marginally circular orbit by assuming the supermassive central object in our Galaxy as a Schwarzschild compact object.
A NEW APPROACH TO IDENTIFYING THE MOST POWERFUL GRAVITATIONAL LENSING TELESCOPES
Wong, Kenneth C.; Zabludoff, Ann I. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Ammons, S. Mark [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Keeton, Charles R. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Hogg, David W. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States)
2013-05-20
The best gravitational lenses for detecting distant galaxies are those with the largest mass concentrations and the most advantageous configurations of that mass along the line of sight. Our new method for finding such gravitational telescopes uses optical data to identify projected concentrations of luminous red galaxies (LRGs). LRGs are biased tracers of the underlying mass distribution, so lines of sight with the highest total luminosity in LRGs are likely to contain the largest total mass. We apply this selection technique to the Sloan Digital Sky Survey and identify the 200 fields with the highest total LRG luminosities projected within a 3.'5 radius over the redshift range 0.1 {<=} z {<=} 0.7. The redshift and angular distributions of LRGs in these fields trace the concentrations of non-LRG galaxies. These fields are diverse; 22.5% contain one known galaxy cluster and 56.0% contain multiple known clusters previously identified in the literature. Thus, our results confirm that these LRGs trace massive structures and that our selection technique identifies fields with large total masses. These fields contain two to three times higher total LRG luminosities than most known strong-lensing clusters and will be among the best gravitational lensing fields for the purpose of detecting the highest redshift galaxies.
A further discussion on quasar-galaxy associations from gravitational lensing
Xiang-Ping Wu
1993-12-24
Quasar-galaxy associations, if they result from the effect of gravitational lensing by foreground galaxies, depend sensitively on the shape of the quasar number counts. Two kinds of quasar number-magnitude relations are predicted to produce quite different properties in quasar-galaxy associations: the counts of Boyle, Shanks and Peterson (1988; BSP) provide both positive and ``negative" associations between distant quasars and foreground galaxies, relating closely with the knee ($B\\approx19.15$) in these counts. However, Hawkins and V\\'eron (1993; HV) quasar data lead to only a positive magnitude-independent quasar-galaxy association. The current observational evidence on quasar-galaxy associations, either positive or null, is shown to be the natural result of gravitational lensing if quasars follow the BSP number-magnitude relation. On the other hand, the HV counts are unable to produce the reported associations by the mechanism of gravitational lensing. It is emphasized that special attention should be paid to the limiting magnitudes in the selected quasar samples when one works on quasar-galaxy associations.
On combining galaxy clustering and weak lensing to unveil galaxy biasing via the halo model
NASA Astrophysics Data System (ADS)
Cacciato, M.; Lahav, O.; van den Bosch, F. C.; Hoekstra, H.; Dekel, A.
2012-10-01
Galaxies are (biased) tracers of the dark matter in theUniverse. This mapping can be conveniently divided into two parts: the connection between galaxies and dark matter haloes (halo occupation statistics) and the relation between haloes and the underlying matter distribution. The former is the focus of this paper in which we formulate the concept of non-linear and stochastic galaxy biasing in the framework of halo occupation statistics. Using two-point statistics in projection, we define the galaxy bias function, bg(rp), and the galaxy-dark matter cross-correlation function, R gm (rp), where rp is the projected distance. We use the analytical halo model to predict how the scale dependence of bg and R gm , over the range 0.1 ? rp ? 30 h-1 Mpc, depends on the non-linearity and stochasticity in halo occupation models. In particular, we quantify the effect due to the presence of central galaxies, the assumption for the radial distribution of satellite galaxies, the richness of the halo and the Poisson character of the probability to have a certain number of satellite galaxies in the halo of a certain mass. Overall, brighter galaxies reveal a stronger scale dependence, and out to a larger radius. In real space, we find that galaxy bias becomes scale independent, with Rg=1, for radii r ? 1-5 h-1 Mpc, depending on luminosity. However, galaxy bias is scale dependent out to much larger radii when one uses the projected quantities defined in this paper. These projected bias functions have the advantage that they are more easily accessible observationally and that their scale dependence carries a wealth of information regarding the properties of galaxy biasing. To observationally constrain the parameters of the halo model and to unveil the origin of galaxy biasing, we propose the use of the bias function ? gm (rp)?bg(rp)/R gm (rp). This function is obtained via a combination of weak gravitational lensing and galaxy clustering, and it can be measured using existing and forthcoming imaging and spectroscopic galaxy surveys.
How many SNeIa do we need to detect the effect of weak lensing ?
Munshi, D; Munshi, Dipak; Valageas, Patrick
2006-01-01
We show that as many as 4000 SNeIa may be required to detect the effect of weak lensing on their flux distribution with a high level of significance. However, if the intrinsic SNeIa magnitude dispersion is unknown one needs an even higher number of SNeIa (an order of magnitude more) to reach a similar level of statistical significance. Moreover, the ability to separate the lensing contribution from the intrinsic scatter depends sensitively on the amplitude of the latter. Using a Kolmogorov - Smirnov (K-S) test we check how the required number of SNeIa changes with level of significance. Our model incorporates a completely analytical description of weak lensing which has been tested extensively against numerical simulations. Thus, future missions such as SNAP may be able to detect non-Gaussianity at a lower significance level of 10% (through the K-S test) only if the intrinsic scatter is known from external data (e.g. from low redshift observations) whereas ALPACA with 100,000 SNe will definitely detect non-Ga...
How many SNeIa do we need to detect the effect of weak lensing ?
Dipak Munshi; Patrick Valageas
2006-01-30
We show that as many as 4000 SNeIa may be required to detect the effect of weak lensing on their flux distribution with a high level of significance. However, if the intrinsic SNeIa magnitude dispersion is unknown one needs an even higher number of SNeIa (an order of magnitude more) to reach a similar level of statistical significance. Moreover, the ability to separate the lensing contribution from the intrinsic scatter depends sensitively on the amplitude of the latter. Using a Kolmogorov - Smirnov (K-S) test we check how the required number of SNeIa changes with level of significance. Our model incorporates a completely analytical description of weak lensing which has been tested extensively against numerical simulations. Thus, future missions such as SNAP may be able to detect non-Gaussianity at a lower significance level of 10% (through the K-S test) only if the intrinsic scatter is known from external data (e.g. from low redshift observations) whereas ALPACA with 100,000 SNe will definitely detect non-Gaussianity with a very high confidence even if the intrinsic magnitude dispersion is not known a priori.
Constraints on Omega_m and sigma_8 from weak lensing in RCS fields
Henk Hoekstra; Howard Yee; Mike Gladders
2002-06-03
We have analysed 53 square degrees of imaging data from the Red-Sequence Cluster Survey (RCS), and measured the excess correlations in the shapes of galaxies on scales out to ~1.5 degrees. We separate the signal into an ``E''- (lensing) and ``B''-mode (systematics), which allows us to study residual systematics. On scales larger than 10 arcminutes, we find no ``B''-mode. On smaller scales we find a small, but significant ``B''-mode. This signal is also present when we select a sample of bright galaxies. These galaxies are rather insensitive to observational distortions, and we therefore conclude that the oberved ``B''-mode is likely to be caused by intrinsic alignments. We therefore limit the cosmic shear analysis to galaxies with 220.1+0.16\\Omega_m$ (95% confidence). Comparison of the RCS results with three other recent cosmic shear measurements shows excellent agreement. The current weak lensing results are also in good agreement with CMB measurements, when we allow the reionization optical depth tau and the spectral index n_s to vary. We present a simple demonstration of how the weak lensing results can be used as a prior in the parameter estimation from CMB measurements to derive constraints on the reionization optical depth tau. (abridged)
Can we use Weak Lensing to Measure Total Mass Profiles of Galaxies on 20 kiloparsec Scales?
Kobayashi, Masato I N; More, Surhud; Okabe, Nobuhiro; Laigle, Clotilde; Rhodes, Jason; Takeuchi, Tsutomu T
2015-01-01
Current constraints on dark matter density profiles from weak lensing are typically limited to radial scales greater than 50-100 kpc. In this paper, we explore the possibility of probing the very inner regions of galaxy/halo density profiles by measuring stacked weak lensing on scales of only a few tens of kpc. Our forecasts focus on scales smaller than the equality radius (Req) where the stellar component and the dark matter component contribute equally to the lensing signal. We compute the evolution of Req as a function of lens stellar mass and redshift and show that Req=7-34 kpc for galaxies with the stellar mass of 10^{9.5}-10^{11.5} solar masses. Unbiased shear measurements will be challenging on these scales. We introduce a simple metric to quantify how many source galaxies overlap with their neighbours and for which shear measurements will be challenging. Rejecting source galaxies with close-by companions results in about a 20 per cent decrease in the overall source density. Despite this decrease, we s...
Algorithms and Programs for Strong Gravitational Lensing In Kerr Space-time Including Polarization
NASA Astrophysics Data System (ADS)
Chen, Bin; Kantowski, Ronald; Dai, Xinyu; Baron, Eddie; Maddumage, Prasad
2015-05-01
Active galactic nuclei (AGNs) and quasars are important astrophysical objects to understand. Recently, microlensing observations have constrained the size of the quasar X-ray emission region to be of the order of 10 gravitational radii of the central supermassive black hole. For distances within a few gravitational radii, light paths are strongly bent by the strong gravity field of the central black hole. If the central black hole has nonzero angular momentum (spin), then a photon’s polarization plane will be rotated by the gravitational Faraday effect. The observed X-ray flux and polarization will then be influenced significantly by the strong gravity field near the source. Consequently, linear gravitational lensing theory is inadequate for such extreme circumstances. We present simple algorithms computing the strong lensing effects of Kerr black holes, including the effects on polarization. Our algorithms are realized in a program “KERTAP” in two versions: MATLAB and Python. The key ingredients of KERTAP are a graphic user interface, a backward ray-tracing algorithm, a polarization propagator dealing with gravitational Faraday rotation, and algorithms computing observables such as flux magnification and polarization angles. Our algorithms can be easily realized in other programming languages such as FORTRAN, C, and C++. The MATLAB version of KERTAP is parallelized using the MATLAB Parallel Computing Toolbox and the Distributed Computing Server. The Python code was sped up using Cython and supports full implementation of MPI using the “mpi4py” package. As an example, we investigate the inclination angle dependence of the observed polarization and the strong lensing magnification of AGN X-ray emission. We conclude that it is possible to perform complex numerical-relativity related computations using interpreted languages such as MATLAB and Python.
Infrared observations of gravitational lensing in Abell 2219 with CIRSI
Meghan E. Gray; Richard S. Ellis; Alexandre Refregier; Jocelyn Bezecourt; Richard G. McMahon; Martin G. Beckett; Craig D. Mackay; Michael D. Hoenig
2000-01-01
We present the first detection of a gravitational depletion signal at\\u000anear-infrared wavelengths, based on deep panoramic images of the cluster Abell\\u000a2219 (z=0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at\\u000athe prime focus of the 4.2m William Herschel Telescope. Infrared studies of\\u000agravitational depletion offer a number of advantages over similar techniques\\u000aapplied at optical wavelengths, and
Gravitational lensing effects of vacuum strings - Exact solutions
NASA Technical Reports Server (NTRS)
Gott, J. R., III
1985-01-01
Exact interior and exterior solutions to Einstein's field equations are derived for vacuum strings. The exterior solution for a uniform density vacuum string corresponds to a conical space while the interior solution is that of a spherical cap. For Mu equals 0-1/4 the external metric is ds-squared = -dt-squared + dr-squared + (1-4 Mu)-squared r-squared dphi-squared + dz-squared, where Mu is the mass per unit length in the string in Planck masses per Planck length. A maximum mass per unit length for a string is 6.73 x 10 to the 27th g/cm. It is shown that strings cause temperature fluctuations in the cosmic microwave background and produce equal brightness double QSO images separated by up to several minutes of arc. Formulae for lensing probabilities, image splittings, and time delays are derived for strings in a realistic cosmological setting. String searches using ST, the VLA, and the COBE satellite are discussed.
A WEAK-LENSING AND NEAR-INFRARED STUDY OF A3192: DISASSEMBLING A RICHNESS CLASS 3 ABELL CLUSTER
Hamilton-Morris, Victoria; Smith, Graham P.; Haines, C. P.; Sanderson, A. J. R. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Edge, A. C. [Institute of Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Egami, E. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Marshall, P. J. [Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Targett, T. A., E-mail: vhh@star.sr.bham.ac.uk, E-mail: gps@star.sr.bham.ac.uk [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)
2012-04-01
We present a joint gravitational lensing and near-infrared study of the galaxy cluster Abell 3192 (A3192) that has been associated both with galaxies at z = 0.168 and with the X-ray luminous cluster RXC J0358.8-2955 (RXC J0358) at z = 0.425. Weak-lensing analysis of our Hubble Space Telescope snapshot observation with the Advanced Camera for Surveys detects two mass over-densities separated by {approx}2 arcmin, one adjacent to the optical position of A3192 (4.4{sigma} significance) and the other adjacent to the X-ray position of RXC J0358 (6.2{sigma} significance). These mass peaks coincide with peaks in the K-band luminosity density of galaxies with near-infrared colors consistent with the red sequence at z = 0.168 and z 0.425, respectively. Moreover, the Bayesian evidence of parameterized mass models that include two cluster/group-scale halos centered on the respective mass peaks exceeds that of single-halo models by a factor of {>=}10. The total projected mass of each galaxy system within 250 kpc of the respective peaks is M{sub WL}(z = 0.168) {approx_equal} 3 Multiplication-Sign 10{sup 13} M{sub Sun} and M{sub WL}(z = 0.425) {approx_equal} 1.2 Multiplication-Sign 10{sup 14} M{sub Sun }, both with total mass-to-light ratios of M{sub WL}/L{sub K} {approx_equal} 20 M{sub Sun }/L{sub Sun }. The original Abell cluster therefore comprises two independent galaxy systems-a foreground group at z = 0.168 and RXC J0358 at z = 0.425. Our results demonstrate the power of combining X-ray, near-infrared, and weak-lensing observations to select massive clusters, place those clusters and interloper galaxy systems along the line of sight, and measure their masses. This combination will be invaluable to robust interpretation of future high-redshift cluster surveys, including eROSITA.
NASA Astrophysics Data System (ADS)
Pitrou, Cyril; Pereira, Thiago S.; Uzan, Jean-Philippe
2015-07-01
This article details the computation of the two-point correlators of the convergence, E and B modes of the cosmic shear induced by the weak lensing by large scale structure assuming that the background spacetime is spatially homogeneous and anisotropic. After detailing the perturbation equations and the general theory of weak lensing in an anisotropic universe, it develops a weak shear approximation scheme in which one can compute analytically the evolution of the Jacobi matrix. It allows one to compute the angular power spectrum of the E and B modes. In the linear regime, the existence of B modes is a direct tracer of a late-time anisotropy and their angular power spectrum scales as the square of the shear. It is then demonstrated that there must also exist off-diagonal correlations between the E modes, B modes and convergence that are linear in the geometrical shear and allow one to reconstruct the eigendirections of expansion. These spectra can be measured in future large scale surveys, such as Euclid and Square Kilometre Array, and offer a new tool to test the isotropy of the expansion of the universe at low redshift.
Cyril Pitrou; Thiago S. Pereira; Jean-Philippe Uzan
2015-03-03
This article details the computation of the two-point correlators of the convergence, $E$- and $B$-modes of the cosmic shear induced by the weak-lensing by large scale structure assuming that the background spacetime is spatially homogeneous and anisotropic. After detailing the perturbation equations and the general theory of weak-lensing in an anisotropic universe, it develops a weak shear approximation scheme in which one can compute analytically the evolution of the Jacobi matrix. It allows one to compute the angular power spectrum of the $E$- and $B$-modes. In the linear regime, the existence of $B$-modes is a direct tracer of a late time anisotropy and their angular power spectrum scales as the square of the shear. It is then demonstrated that there must also exist off-diagonal correlations between the $E$-modes, $B$-modes and convergence that are linear in the geometrical shear and allow one to reconstruct the eigendirections of expansion. These spectra can be measured in future large scale surveys, such as Euclid and SKA, and offer a new tool to test the isotropy of the expansion of the universe at low redshift.
Lens Statistics with Gravitationally Lensed yet Morphologically Regular Images
NASA Astrophysics Data System (ADS)
Morioka, Masayo; Futamase, Toshifumi
2015-06-01
GRAMORs are GRAvitationally highly magnified yet MORphologically regular images. An example of this phenomenon was discovered in the cluster MACS J1149.5+2223 in 2009. We investigate the lens statistics of GRAMORs in detail. Assuming a NFW profile for a sample of clusters, we calculate the expected number and redshift distribution of GRAMORs using parameters from COSMOS data for the number density of the background galaxy. A model with a cluster placed at z = 0.544 based on WMAP5 cosmology predicts the redshift of a GRAMOR at z? 1.49 which is close to the observed z = 1.4906. These results show that the expected number of GRAMORs is about two per cluster in the most likely case, and thus a large number of GRAMORs would be observed in a systematic survey. The probability distribution function of source redshift for GRAMORs depends strongly on dark energy and may be useful for constraining the nature of dark energy.
Weak-lensing $B$-modes as a probe of the isotropy of the universe
Thiago S. Pereira; Cyril Pitrou; Jean-Philippe Uzan
2015-03-03
We compute the angular power spectrum of the $B$-modes of the weak-lensing shear in a spatially anisotropic spacetime. We find that there must also exist off-diagonal correlations between the $E$-modes, $B$-modes, and convergence that allow one to reconstruct the eigendirections of expansion. Focusing on future surveys such as Euclid and SKA, we show that observations can constrain the geometrical shear in units of the Hubble rate at the percent level, or even better, offering a new and powerful method to probe our cosmological model.
Pinpointing the massive black hole in the Galactic Center with gravitationally lensed stars
Tal Alexander
2001-02-03
A new statistical method for pinpointing the massive black hole (BH) in the Galactic Center on the IR grid is presented and applied to astrometric IR observations of stars close to the BH. This is of interest for measuring the IR emission from the BH, in order to constrain accretion models; for solving the orbits of stars near the BH, in order to measure the BH mass and to search for general relativistic effects; and for detecting the fluctuations of the BH away from the dynamical center of the stellar cluster, in order to study the stellar potential. The BH lies on the line connecting the two images of any background source it gravitationally lenses, and so the intersection of these lines fixes its position. A combined search for a lensing signal and for the BH shows that the most likely point of intersection coincides with the center of acceleration of stars orbiting the BH. This statistical detection of lensing by the BH has a random probability of ~0.01. It can be verified by deep IR stellar spectroscopy, which will determine whether the most likely lensed image pair candidates (listed here) have identical spectra.
Model-free analysis of quadruply imaged gravitationally lensed systems and substructured galaxies
Woldesenbet, Addishiwot Girma
2015-01-01
Multiple image gravitational lens systems, and especially quads are invaluable in determining the amount and distribution of mass in galaxies. This is usually done by mass modeling using parametric or free-form methods. An alternative way of extracting information about lens mass distribution is to use lensing degeneracies and invariants. Where applicable, they allow one to make conclusions about whole classes of lenses without model fitting. Here, we use approximate, but observationally useful invariants formed by the three relative polar angles of quad images around the lens center to show that many smooth elliptical+shear lenses can reproduce the same set of quad image angles within observational error. This result allows us to show in a model-free way what the general class of smooth elliptical+shear lenses looks like in the three dimensional (3D) space of image relative angles, and that this distribution does not match that of the observed quads. We conclude that, even though smooth elliptical+shear lens...
n-point Gravitational Lenses with 5(n-1) Images
Rhie, S H
2003-01-01
It has been conjectured (astro-ph/0103463) that a gravitational lens consisting of n point masses can not produce more than 5(n-1) images as is known to be the case for n = 2 and 3. The reasoning is based on the number of finite limit points 2(n-1) which we believe to set the maximum number of positive images and the fact that the number of negative images exceeds the number of positive images by (n-1). It has been known that an n-point lens system (n\\ge 3) can produce (3n+1) images and so has been an explicit lens configuration with (3n+1) images. We start with the well-known n-point lens configuration that produces (3n+1) images and produce (2n-1) extra images by adding a small (n+1)-th mass so that the resulting (n+1)-point lens configuration has (2n) discrete limit points and produces 5n images of a source. It still remains to confirm in abstraction that the maximum number of positive image domains of a caustic domain is bounded by the number of the limit points.
Strong field limit analysis of gravitational lensing in Kerr-Taub-NUT spacetime
Wei, Shao-Wen; Liu, Yu-Xiao; Fu, Chun-E; Yang, Ke, E-mail: weishw@lzu.edu.cn, E-mail: liuyx@lzu.edu.cn, E-mail: fuche08@lzu.edu.cn, E-mail: yangke09@lzu.edu.cn [Theoretical Physics, Lanzhou University, Lanzhou 730000 (China)
2012-10-01
In this paper, we study numerically the quasi-equatorial lensing by the stationary, axially-symmetric black hole in Kerr-Taub-NUT spacetime in the strong field limit. The deflection angle of light ray and other strong deflection limit coefficients are obtained numerically and they are found to be closely dependent on the NUT charge n and spin a. We also compute the magnification and the positions of the relativistic images. The caustics are studied and the results show that these caustics drift away from the optical axis, which is quite different from the Schwarzschild black hole case. Moreover, the intersections of the critical curves on the equatorial plane are obtained and it is shown that they increase with the NUT charge. These results show that there is a significant effect of the NUT charge on the strong gravitational lensing.
Weak Lensing Calibrated M-T Scaling Relation of Galaxy Groups in the COSMOS Fieldsstarf
NASA Astrophysics Data System (ADS)
Kettula, K.; Finoguenov, A.; Massey, R.; Rhodes, J.; Hoekstra, H.; Taylor, J. E.; Spinelli, P. F.; Tanaka, M.; Ilbert, O.; Capak, P.; McCracken, H. J.; Koekemoer, A.
2013-11-01
The scaling between X-ray observables and mass for galaxy clusters and groups is instrumental for cluster-based cosmology and an important probe for the thermodynamics of the intracluster gas. We calibrate a scaling relation between the weak lensing mass and X-ray spectroscopic temperature for 10 galaxy groups in the COSMOS field, combined with 55 higher-mass clusters from the literature. The COSMOS data includes Hubble Space Telescope imaging and redshift measurements of 46 source galaxies per arcminute2, enabling us to perform unique weak lensing measurements of low-mass systems. Our sample extends the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study, resulting in a power-law slope of 1.48^{+0.13}_{-0.09}. The slope is consistent with the self-similar model, predictions from simulations, and observations of clusters. However, X-ray observations relying on mass measurements derived under the assumption of hydrostatic equilibrium have indicated that masses at group scales are lower than expected. Both simulations and observations suggest that hydrostatic mass measurements can be biased low. Our external weak lensing masses provide the first observational support for hydrostatic mass bias at group level, showing an increasing bias with decreasing temperature and reaching a level of 30%-50% at 1 keV. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555. Also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation; the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.; and the Canada-France-Hawaii Telescope (CFHT) with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the National Research Council of Canada, the Canadian Astronomy Data Centre, the Centre National de la Recherche Scientifique de France, TERAPIX, and the University of Hawaii.
Gravitational lensing effects on the gamma-ray burst Hubble diagram
Oguri, Masamune [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Takahashi, Keitaro [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)
2006-06-15
Gamma-ray bursts (GRBs) offer a potential way to extend the Hubble diagram to very high redshifts and to constrain the nature of dark energy in a way complementary to distant type Ia supernovae. However, gravitational lensing systematically brightens distant GRBs through the magnification bias, in addition to increasing the dispersions of distance measurements. We investigate how the magnification bias limits the cosmological usage of GRBs. We perform Monte-Carlo simulations of Swift GRBs assuming a cosmological constant dominated universe and then constrain the dark energy equation of state neglecting gravitational lens effects. The originally assumed model is recovered with 68% confidence limit even when the dispersion of inferred luminosities is comparable to that of type Ia supernovae. This implies that the bias is not so drastic for Swift GRBs as to change constraints on dark energy and its evolution. However, the precise degree of the bias in cosmological parameter determinations depends strongly on the shape of the luminosity function of GRBs. Therefore, an accurate determination of the shape of the luminosity function is required to remove the effect of gravitational lensing and to obtain an unbiased Hubble diagram.
Gravitational failure of sea cliffs in weakly lithified sediment
Hampton, M.A.
2002-01-01
Gravitational failure of sea cliffs eroded into weakly lithified sediment at several sites in California involves episodic stress-release fracturing and cantilevered block falls. The principal variables that influence the gravitational stability are tensional stresses generated during the release of horizontal confining stress and weakening of the sediment with increased saturation levels. Individual failures typically comprise less than a cubic meter of sediment, but large areas of a cliff face can be affected by sustained instability over a period of several days. Typically, only the outer meter or so of sediment is removed during a failure episode. In-place sediment saturation levels vary over time and space, generally being higher during the rainy season but moderate to high year-round. Laboratory direct-shear tests show that sediment cohesion decreases abruptly with increasing saturation level; the decrease is similar for all tested sediment if the cohesion is normalized by the maximum, dry-sediment cohesion. Large failures that extend over most or all of the height of the sea cliff are uncommon, but a few large wedge-shaped failures sometimes occur, as does separation of large blocks at sea cliff-gully intersections.
GALAXIES IN X-RAY GROUPS. II. A WEAK LENSING STUDY OF HALO CENTERING
George, Matthew R.; Ma, Chung-Pei [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Leauthaud, Alexie; Bundy, Kevin [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8583 (Japan); Finoguenov, Alexis [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Rykoff, Eli S. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Tinker, Jeremy L. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Massey, Richard [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Mei, Simona, E-mail: mgeorge@astro.berkeley.edu [Bureau des Galaxies, Etoiles, Physique, Instrumentation (GEPI), University of Paris Denis Diderot, F-75205 Paris Cedex 13 (France)
2012-09-20
Locating the centers of dark matter halos is critical for understanding the mass profiles of halos, as well as the formation and evolution of the massive galaxies that they host. The task is observationally challenging because we cannot observe halos directly, and tracers such as bright galaxies or X-ray emission from hot plasma are imperfect. In this paper, we quantify the consequences of miscentering on the weak lensing signal from a sample of 129 X-ray-selected galaxy groups in the COSMOS field with redshifts 0 < z < 1 and halo masses in the range 10{sup 13}-10{sup 14} M{sub Sun }. By measuring the stacked lensing signal around eight different candidate centers (such as the brightest member galaxy, the mean position of all member galaxies, or the X-ray centroid), we determine which candidates best trace the center of mass in halos. In this sample of groups, we find that massive galaxies near the X-ray centroids trace the center of mass to {approx}< 75 kpc, while the X-ray position and centroids based on the mean position of member galaxies have larger offsets primarily due to the statistical uncertainties in their positions (typically {approx}50-150 kpc). Approximately 30% of groups in our sample have ambiguous centers with multiple bright or massive galaxies, and some of these groups show disturbed mass profiles that are not well fit by standard models, suggesting that they are merging systems. We find that halo mass estimates from stacked weak lensing can be biased low by 5%-30% if inaccurate centers are used and the issue of miscentering is not addressed.
Probing The Gravity Induced Bias with Weak Lensing: Test of Analytical results Against Simulations
Dipak Munshi
2000-01-13
Future weak lensing surveys will directly probe the density fluctuation in the universe. Recent studies have shown how the statistics of the weak lensing convergence field is related to the statistics of collapsed objects. Extending earlier analytical results on the probability distribution function of the convergence field we show that the bias associated with the convergence field can directly be related to the bias associated with the statistics of underlying over-dense objects. This will provide us a direct method to study the gravity induced bias in galaxy clustering. Based on our analytical results which use the hierarchical {\\em ansatz} for non-linear clustering, we study how such a bias depends on the smoothing angle and the source red-shift. We compare our analytical results against ray tracing experiments through N-body simulations of four different realistic cosmological scenarios and found a very good match. Our study shows that the bias in the convergence map strongly depends on the background geometry and hence can help us in distinguishing different cosmological models in addition to improving our understanding of the gravity induced bias in galaxy clustering.
Weak lensing effects in the measurement of the dark energy equation of state with LISA
Van Den Broeck, Chris [Nikhef, National Institute for Subatomic Physics, Science Park 105, 1098 XG Amsterdam (Netherlands); School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom); Trias, M.; Sintes, A. M. [Departament de Fisica, Universitat de les Illes Balears, Carretera Valldemossa Km. 7.5, E-07122 Palma de Mallorca (Spain); Sathyaprakash, B. S. [School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom)
2010-06-15
The Laser Interferometer Space Antenna's (LISA's) observation of supermassive binary black holes (SMBBH) could provide a new tool for precision cosmography. Inclusion of subdominant signal harmonics in the inspiral signal allows for high-accuracy sky localization, dramatically improving the chances of finding the host galaxy and obtaining its redshift. A SMBBH merger can potentially have component masses from a wide range (10{sup 5}-10{sup 8}M{sub {center_dot}}) over which parameter accuracies vary considerably. We perform an in-depth study in order to understand (i) what fraction of possible SMBBH mergers allow for sky localization, depending on the parameters of the source, and (ii) how accurately w can be measured when the host galaxy can be identified. We also investigate how accuracies on all parameters improve when a knowledge of the sky position can be folded into the estimation of errors. We find that w can be measured to within a few percent in most cases, if the only error in measuring the luminosity distance is due to LISA's instrumental noise and the confusion background from Galactic binaries. However, weak lensing-induced errors will severely degrade the accuracy with which w can be obtained, emphasizing that methods to mitigate weak lensing effects would be required to take advantage of LISA's full potential.
Using Weak-Lensing Dilution to Measure Light Properties of A1689
NASA Astrophysics Data System (ADS)
Medezinski, Elinor; Broadhurst, Tom; Umetsu, Keiichi; Coe, Dan
Weak-lensing induced by clusters of galaxies can probe the total mass distribution out to the virial radius of the cluster, regardless of the nature of the mass or its dynamical state. To make a robust analysis, the cluster and background galaxy populations need to be separated. The E/S0 sequence of a cluster defines a boundary redward of which a reliable weak-lensing signal can be obtained from background galaxies, uncontaminated by the cluster. Below this limit, the signal is diluted by the proportion of unlensed cluster members. Employing deep Subaru and HST/ACS images of the massive cluster A1689, we use this dilution effect to carefully separate between the cluster members and the background, and thus derive the cluster light profile and luminosity functions to large radius. The light profile of A1689 is found to decline steadily to the limit of the data, r < 2 h-1Mpc, with a constant slope, d log(L)/d log(r) = -1.12 ± 0.06. We derive a cluster luminosity function with a flat faint-end slope of ? = -1.05 ± 0.07, nearly independent of radius and with no faint upturn to Mi? < -12. The major advantage of this new approach is that no subtraction of far-field background counts is required.
Weak lensing effects in the measurement of the dark energy equation of state with LISA
NASA Astrophysics Data System (ADS)
van den Broeck, Chris; Trias, M.; Sathyaprakash, B. S.; Sintes, A. M.
2010-06-01
The Laser Interferometer Space Antenna’s (LISA’s) observation of supermassive binary black holes (SMBBH) could provide a new tool for precision cosmography. Inclusion of subdominant signal harmonics in the inspiral signal allows for high-accuracy sky localization, dramatically improving the chances of finding the host galaxy and obtaining its redshift. A SMBBH merger can potentially have component masses from a wide range (105-108M?) over which parameter accuracies vary considerably. We perform an in-depth study in order to understand (i) what fraction of possible SMBBH mergers allow for sky localization, depending on the parameters of the source, and (ii) how accurately w can be measured when the host galaxy can be identified. We also investigate how accuracies on all parameters improve when a knowledge of the sky position can be folded into the estimation of errors. We find that w can be measured to within a few percent in most cases, if the only error in measuring the luminosity distance is due to LISA’s instrumental noise and the confusion background from Galactic binaries. However, weak lensing-induced errors will severely degrade the accuracy with which w can be obtained, emphasizing that methods to mitigate weak lensing effects would be required to take advantage of LISA’s full potential.
Discovery of an Exceptionally Bright Gravitationally Lensed Submillimeter Galaxy at z=4.69
NASA Astrophysics Data System (ADS)
Egami, Eiichi; Herschel Lensing Survey (HLS) Team
2012-05-01
We report the discovery of an exceptionally bright gravitationally lensed submillimeter galaxy at z=4.69. Through our on-going Herschel survey of gravitationally lensed high-redshift galaxies in the fields of massive galaxy clusters ("The Herschel Lensing Survey (HLS)" - PI: Egami), we identified in the field of a z=0.3 cluster a bright Herschel/SPIRE source ( 100 mJy at 500 um) whose far-infrared/submillimeter spectral energy distribution is peaking toward 500 um, indicating that its redshift is likely above 4. The APEX/LABOCA 870 um image showed that this source is not only bright (60 mJy at 870 um) but also spatially extended even with the LABOCA resolution of 20'', although it is invisible in the HST/ACS F606W image. The spectroscopic redshift came from the IRAM30m/EMIR observations, which detected the CO(4-3) and CO(5-4) lines with the corresponding redshift of 4.69. The high-resolution (beam=0.8"x0.7") SMA 345 GHz map has subsequently resolved this source into four components, which are likely four lensed images of the same background galaxy. This lensing interpretation has been confirmed by the HST WFC3/IR observations, which not only revealed the same morphology for the multiple sources but also detected the 5th image at the predicted location. We therefore conclude that this lensed system exhibits a rare hyperbolic umbilic image configuration, which produces a large magnification factor of x100-200 when the four components are combined. What is even more remarkable is that the four HST sources are not spatially coincident with the four SMA sources. In other words, this z=4.69 galaxy appears to consist of two spatially distinct components, one of which (the one responsible for the bright IR/submm emission) is completely invisible in the HST near-infrared images. This suggests that there may exist a population of dust-obscured galaxies at z>4 that are hidden from our deep optical/near-infrared view.
SDSS J131339.98+515128.3: A new GravitationallyLensed Quasar Selected Based on Near-infrared Excess
Ofek, E.O.; Oguri, M.; Jackson, N.; Inada, N.; Kayo, I.
2007-09-28
We report the discovery of a new gravitationally lensed quasar, SDSS J131339.98+515128.3, at a redshift of 1:875 with an image separation of 1: 0024. The lensing galaxy is clearly detected in visible-light follow-up observations. We also identify three absorption-line doublets in the spectra of the lensed quasar images, from which we measure the lens redshift to be 0:194. Like several other known lenses, the lensed quasar images have different continuum slopes. This difference is probably the result of reddening and microlensing in the lensing galaxy. The lensed quasar was selected by correlating Sloan Digital Sky Survey (SDSS) spectroscopic quasars with Two Micron All Sky Survey (2MASS) sources and choosing quasars that show near-infrared (IR) excess. The near-IR excess can originate, for example, from the contribution of the lensing galaxy at near-IR wavelengths. We show that the near-IR excess technique is indeed an efficient method to identify lensed systems from a large sample of quasars.
Jee, M J; Ford, H C; Holden, B; Illingworth, G D; Mei, S; White, R L
2006-01-01
(Abridged) We present a HST/ACS weak-lensing study of RX J0849+4452 and RX J0848+4453, the two most distant (at z=1.26 and z=1.27, respectively) clusters yet measured with weak-lensing. The two clusters are separated by ~4' from each other and appear to form a supercluster in the Lynx field. Using our deep ACS F775W and F850LP imaging, we detected weak-lensing signals around both clusters at ~4 sigma levels. The mass distribution indicated by the reconstruction map is in good spatial agreement with the cluster galaxies. From the SIS fitting, we determined that RX J0849+4452 and RX J0848+4453 have similar projected masses of ~2.0x10^14 solar mass and ~2.1x10^14 solar mass, respectively, within a 0.5 Mpc (~60") aperture radius.
M. J. Jee; R. L. White; H. C. Ford; G. D. Illingworth; J. P. Blakeslee; B. Holden; S. Mei
2006-01-16
(Abridged) We present a HST/ACS weak-lensing study of RX J0849+4452 and RX J0848+4453, the two most distant (at z=1.26 and z=1.27, respectively) clusters yet measured with weak-lensing. The two clusters are separated by ~4' from each other and appear to form a supercluster in the Lynx field. Using our deep ACS F775W and F850LP imaging, we detected weak-lensing signals around both clusters at ~4 sigma levels. The mass distribution indicated by the reconstruction map is in good spatial agreement with the cluster galaxies. From the SIS fitting, we determined that RX J0849+4452 and RX J0848+4453 have similar projected masses of ~2.0x10^14 solar mass and ~2.1x10^14 solar mass, respectively, within a 0.5 Mpc (~60") aperture radius.
Dark matter halo properties of GAMA galaxy groups from 100 square degrees of KiDS weak lensing data
Viola, M; Brouwer, M; Kuijken, K; Hoekstra, H; Norberg, P; Robotham, A S G; van Uitert, E; Alpaslan, M; Baldry, I K; Choi, A; de Jong, J T A; Driver, S P; Erben, T; Grado, A; Graham, Alister W; Heymans, C; Hildebrandt, H; Hopkins, A M; Irisarri, N; Joachimi, B; Loveday, J; Miller, L; Nakajima, R; Schneider, P; Sifón, C; Kleijn, G Verdoes
2015-01-01
The Kilo-Degree Survey (KiDS) is an optical wide-field survey designed to map the matter distribution in the Universe using weak gravitational lensing. In this paper, we use these data to measure the density profiles and masses of a sample of $\\sim \\mathrm{1400}$ spectroscopically identified galaxy groups and clusters from the Galaxy And Mass Assembly (GAMA) survey. We detect a highly significant signal (signal-to-noise-ratio $\\sim$ 120), allowing us to study the properties of dark matter haloes over one and a half order of magnitude in mass, from $M \\sim 10^{13}-10^{14.5} h^{-1}\\mathrm{M_{\\odot}}$. We interpret the results for various subsamples of groups using a halo model framework which accounts for the mis-centring of the Brightest Cluster Galaxy (used as the tracer of the group centre) with respect to the centre of the group's dark matter halo. We find that the density profiles of the haloes are well described by an NFW profile with concentrations that agree with predictions from numerical simulations. ...
The Optical Gravitational Lensing Experiment. Final Reductions of the OGLE-III Data
A. Udalski; M. K. Szymanski; I. Soszynski; R. Poleski
2008-07-24
We describe methods applied to the final photometric reductions and calibrations to the standard system of the images collected during the third phase of the Optical Gravitational Lensing Experiment survey - OGLE-III. Astrometric reduction methods are also presented. The OGLE-III data constitute a unique data set covering the Magellanic Clouds, Galactic bulge and Galactic disk fields monitored regularly every clear night since 2001 and being significant extension and continuation of the earlier OGLE observations. With the earlier OGLE-II and OGLE-I photometry some of the observed fields have now 16-year long photometric coverage.
A. Udalski; I. Soszynski; M. K. Szymanski; M. Kubiak; G. Pietrzynski; L. Wyrzykowski; O. Szewczyk; K. Ulaczyk; R. Poleski
2008-07-24
We present the OGLE-III Photometric Maps of the Large Magellanic Cloud. They cover about 40 square degrees of the LMC and contain mean, calibrated VI photometry and astrometry of about 35 million stars observed during seven observing seasons of the third phase of the Optical Gravitational Lensing Experiment - OGLE-III. We discuss the quality of data and present color-magnitude diagrams of selected fields. The OGLE-III Photometric Maps of the LMC are available to the astronomical community from the OGLE Internet archive.
Weak lensing study of dark matter filaments and application to the binary cluster A 222 and A 223
NASA Astrophysics Data System (ADS)
Dietrich, J. P.; Schneider, P.; Clowe, D.; Romano-Díaz, E.; Kerp, J.
2005-09-01
We present a weak lensing analysis of the double cluster system Abell 222 and Abell 223. The lensing reconstruction shows evidence for a possible dark matter filament connecting both clusters. The case for a filamentary connection between A 222/223 is supported by an analysis of the galaxy density and X-ray emission between the clusters. Using the results of N-body simulations, we try to develop a criterion that separates this system into cluster and filament regions. The aim is to find a technique that allows the quantification of the significance of (weak lensing) filament candidates in close pairs of clusters. While this mostly fails, the aperture quadrupole statistics (Schneider & Bartelmann 1997, MNRAS, 286, 696) shows some promise in this area. The cluster masses determined from weak lensing in this system are considerably lower than those previously determined from spectroscopic and X-ray observations (Dietrich et al. 2002, A&A, 394, 395; Proust et al. 2000, A&A, 355, 443; David et al. 1999 ApJ, 519, 533). Additionally, we report the serendipitous weak lensing detection of a previously unknown cluster in the field of this double cluster system.
Okura, Yuki [National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan); Futamase, Toshifumi, E-mail: yuki.okura@nao.ac.jp, E-mail: tof@astr.tohoku.ac.jp [Astronomical Institute, Tohoku University, Sendai 980-8578 (Japan)
2013-07-01
This is the third paper on the improvement of systematic errors in weak lensing analysis using an elliptical weight function, referred to as E-HOLICs. In previous papers, we succeeded in avoiding errors that depend on the ellipticity of the background image. In this paper, we investigate the systematic error that depends on the signal-to-noise ratio of the background image. We find that the origin of this error is the random count noise that comes from the Poisson noise of sky counts. The random count noise makes additional moments and centroid shift error, and those first-order effects are canceled in averaging, but the second-order effects are not canceled. We derive the formulae that correct this systematic error due to the random count noise in measuring the moments and ellipticity of the background image. The correction formulae obtained are expressed as combinations of complex moments of the image, and thus can correct the systematic errors caused by each object. We test their validity using a simulated image and find that the systematic error becomes less than 1% in the measured ellipticity for objects with an IMCAT significance threshold of {nu} {approx} 11.7.
Berge, Joel [Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, MS 169-327, Pasadena, CA 91109 (United States); Amara, Adam [Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland); Refregier, Alexandre, E-mail: Joel.Berge@jpl.nasa.go [Laboratoire AIM, CEA/DSM, CNRS, Universite Paris Diderot, DAPNIA/SAp, 91191 Gif-sur-Yvette (France)
2010-04-01
We compare the efficiency of weak-lensing-selected galaxy cluster counts and of the weak-lensing bispectrum at capturing non-Gaussian features in the dark matter distribution. We use the halo model to compute the weak-lensing power spectrum, the bispectrum, and the expected number of detected clusters, and derive constraints on cosmological parameters for a large, low systematic weak-lensing survey, by focusing on the OMEGA{sub m}-sigma{sub 8} plane and on the dark energy equation of state. We separate the power spectrum into the resolved and the unresolved parts of the data, the resolved part being defined as detected clusters, and the unresolved part as the rest of the field. We consider four kinds of clusters counts, taking into account different amount of information: signal-to-noise ratio peak counts, counts as a function of clusters' mass, counts as a function of clusters' redshift, and counts as a function of clusters' mass and redshift. We show that when combined with the power spectrum, those four kinds of counts provide similar constraints, thus allowing one to perform the most direct counts, signal-to-noise peak counts, and get percent level constraints on cosmological parameters. We show that the weak-lensing bispectrum gives constraints comparable to those given by the power spectrum and captures non-Gaussian features as well as cluster counts, its combination with the power spectrum giving errors on cosmological parameters that are similar to, if not marginally smaller than, those obtained when combining the power spectrum with cluster counts. We finally note that in order to reach its potential, the weak-lensing bispectrum must be computed using all triangle configurations, as equilateral triangles alone do not provide useful information. The appendices summarize the halo model, and the way the power spectrum and bispectrum are computed in this framework.
Analyzing Star Formation Properties in Dusty Early Universe Galaxies Using Gravitational Lensing
NASA Astrophysics Data System (ADS)
Bradli, Jaclyn C.; Bussmann, R. Shane; Riechers, Dominik A.; Clements, David; Perez-Fournon, Ismael
2015-01-01
Strong gravitational lensing has recently become one of the most important tools for studying star formation properties in extremely high redshift galaxies. Dust-obscured star-forming galaxies found at far-infrared/sub-millimeter wavelengths are important in the assembly of stellar mass and the evolution of massive galaxies. We present Submillimeter Array (SMA) imaging of Lockman 102, a strongly lensed submillimeter galaxy at z=5.29, discovered by the Herschel Space Observatory. The system was observed at 250, 350, 500 and 1000 microns, corresponding to rest frame wavelengths of 40, 56, 80, and 159 microns respectively. The observations were targeted at the thermal dust emission and the [CII] interstellar medium cooling line. We report an estimated photometric redshift of ~1.9 for the lensing galaxy, making it possibly the most distant lens currently known. We use uvmcmcfit, a publicly available Markov Chain Monte Carlo software tool we have developed for interferometric data, to fit lens models to Lockman 102. The results obtained from uvmcmcfit suggest the lensed system is composed of a single lensing galaxy and two extended sources. We have strong constraints on an intrinsic flux density of Lockman 102 of 4.55 + 0.45 mJy magnified by a factor of 12.5 + 1.2. From a modified blackbody fit we compute an intrinsic far infrared luminosity of 5.5e12 L?.This implies a star formation rate of ~950 M? yr-1, making Lockman 102 an extremely active dusty galaxy. We also compare Lockman 102 to other dusty luminous starburst galaxies at similar redshift, HLS0918 (Rawle et al. 2014) and AzTEC-3 (Riechers et al. 2014a) and determine it is among the most luminous and active galaxies ~1 Gyr after the Big Bang. It is only with strong lensing that the SMA is able to undertake such a detailed study of a galaxy at this distance; the continued improvements from new facilities such as ALMA offer a promising future in observing even more distant lensed systems.
High-precision simulations of the weak lensing effect on cosmic microwave background polarization
NASA Astrophysics Data System (ADS)
Fabbian, Giulio; Stompor, Radek
2013-08-01
We studied the accuracy, robustness, and self-consistency of pixel-domain simulations of the gravitational lensing effect on the primordial cosmic microwave background (CMB) anisotropies due to the large-scale structure of the Universe. In particular, we investigated the dependence of the precision of the results precision on some crucial parameters of these techniques and propose a semi-analytic framework to determine their values so that the required precision is a priori assured and the numerical workload simultaneously optimized. Our focus was on the B-mode signal, but we also discuss other CMB observables, such as the total intensity, T, and E-mode polarization, emphasizing differences and similarities between all these cases. Our semi-analytic considerations are backed up by extensive numerical results. Those are obtained using a code, nicknamed lenS2HAT - for lensing using scalable spherical harmonic transforms (S2HAT) - which we have developed in the course of this work. The code implements a version of the previously described pixel-domain approach and permits performing the simulations at very high resolutions and data volumes, thanks to its efficient parallelization provided by the S2HAT library - a parallel library for calculating of the spherical harmonic transforms. The code is made publicly available.
Schlaufman, K
2004-10-11
Atmospheric turbulence can mimic the effects of weak lensing in astronomical images, so it is necessary to understand to what degree turbulence affects weak lensing measurements. In particular, we studied the ellipticity induced upon the point-spread functions (PSFs) of a grid of simulated stars separated by distances (d {approx} 1{prime}) that will be characteristic of Large Synoptic Survey Telescope (LSST) images. We observe that atmospherically induced ellipticity changes on small scales (d < 0.5{prime}) and use linear interpolation between stars separated by d = 0.5{prime} to determine the induced ellipticity everywhere in the field-of-view.
A technique for using radio jets as extended gravitational lensing probes
NASA Technical Reports Server (NTRS)
Kronberg, Philipp P.; Dyer, Charles C.; Burbidge, E. Margaret; Junkkarinen, Vesa T.
1991-01-01
A new and potentially powerful method of measuring the mass of a galaxy (or dark matter concentration) which lies close in position to a background polarized radio jet is proposed. Using the fact that the polarization angle is not changed by lensing, an 'alignment-breaking parameter' is defined which is a sensitive indicator of gravitational distortion. The method remains sensitive over a wide redshift range of the gravitational lens. This technique is applied to the analysis of polarimetric observations of the jet of 3C 9 at z = 2.012, combined with a newly discovered 20.3 mag foreground galaxy at z = 0.2538 to 'weigh' the galaxy and obtain an approximate upper limit to the mass-to-light ratio.
A technique for using radio jets as extended gravitational lensing probes
Kronberg, P.P.; Dyer, C.C.; Burbidge, E.M.; Junkkarinen, V.T. (Toronto Univ. (Canada) California Univ., La Jolla (USA))
1991-01-01
A new and potentially powerful method of measuring the mass of a galaxy (or dark matter concentration) which lies close in position to a background polarized radio jet is proposed. Using the fact that the polarization angle is not changed by lensing, an alignment-breaking parameter is defined which is a sensitive indicator of gravitational distortion. The method remains sensitive over a wide redshift range of the gravitational lens. This technique is applied to the analysis of polarimetric observations of the jet of 3C 9 at z = 2.012, combined with a newly discovered 20.3 mag foreground galaxy at z = 0.2538 to weigh the galaxy and obtain an approximate upper limit to the mass-to-light ratio. 15 refs.
Choi, J.-Y.; Shin, I.-G.; Park, S.-Y.; Han, C. [Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Gould, A.; Gaudi, B. S.; Henderson, C. B. [Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210 (United States); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Beaulieu, J.-P. [Institut d'Astrophysique de Paris, UMR7095 CNRS-Universite Pierre and Marie Curie, 98 bis boulevard Arago, 75014 Paris (France); Street, R. [Las Cumbres Observatory Global Telescope Network, 6740B Cortona Dr, Suite 102, Goleta, CA 93117 (United States); Dominik, M. [School of Physics and Astronomy, SUPA, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Allen, W. [Vintage Lane Observatory, Blenheim (New Zealand); Almeida, L. A. [Instituto Nacional de Pesquisas Espaciais/MCTI, Sao Jose dos Campos, Sao Paulo (Brazil); Bos, M. [Molehill Astronomical Observatory, North Shore (New Zealand); Christie, G. W. [Auckland Observatory, P.O. Box 24-180, Auckland (New Zealand); Depoy, D. L. [Department of Physics, Texas A and M University, College Station, TX (United States); Dong, S. [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Drummond, J. [Possum Observatory, Patutahi (New Zealand); Gal-Yam, A. [Benoziyo Center for Astrophysics, Weizmann Institute (Israel); Collaboration: muFUN Collaboration; MOA Collaboration; OGLE Collaboration; PLANET Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; and others
2012-05-20
We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all of the events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For seven events, we measure the Einstein radii and the lens-source relative proper motions. Among them, five events are found to have Einstein radii of less than 0.2 mas, making the lenses very low mass star or brown dwarf candidates. For MOA-2011-BLG-274, especially, the small Einstein radius of {theta}{sub E} {approx} 0.08 mas combined with the short timescale of t{sub E} {approx} 2.7 days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of {approx}0.84 M{sub Sun} is consistent with that of a star blended with the source, suggesting that the blend is likely to be the lens. Although we did not find planetary signals for any of the events, we provide exclusion diagrams showing the confidence levels excluding the existence of a planet as a function of the separation and mass ratio.
Two New Gravitationally Lensed Double Quasars from the Sloan Digital Sky Survey
Naohisa Inada; Masamune Oguri; Robert H. Becker; Richard L. White; Issha Kayo; Christopher S. Kochanek; Patrick B. Hall; Donald P. Schneider; Donald G. York; Gordon T. Richards
2006-09-26
We report the discoveries of the two-image gravitationally lensed quasars, SDSS J0746+4403 and SDSS J1406+6126, selected from the Sloan Digital Sky Survey (SDSS). SDSS J0746+4403, which will be included in our lens sample for statistics and cosmology, has a source redshift of z_s=2.00, an estimated lens redshift of z_l~0.3, and an image separation of 1.08". SDSS J1406+6126 has a source redshift of z_s=2.13, a spectroscopically measured lens redshift of z_l=0.27, and an image separation of 1.98". We find that the two quasar images of SDSS J1406+6126 have different intervening MgII absorption strengths, which are suggestive of large variations of absorbers on kpc scales. The positions and fluxes of both the lensed quasar systems are easily reproduced by simple mass models with reasonable parameter values. These objects bring to 18 the number of lensed quasars that have been discovered from the SDSS data.
Smooth matter and source size in microlensing simulations of gravitationally lensed quasars
Nicholas F. Bate; Rachel L. Webster; Stuart Wyithe
2007-08-07
Several gravitationally lensed quasars are observed with anomalous magnifications in pairs of images that straddle a critical curve. Simple theoretical arguments suggest that the magnification of these images should be approximately equivalent, whereas one image is observed to be significantly demagnified. Microlensing provides a possible explanation for this discrepancy. There are two key parameters when modelling this effect. The first, the fraction of smooth matter in the lens at the image positions, has been explored by Schechter and Wambsganss (2002). They have shown that the anomalous flux ratio observed in the lensed quasar MG 0414+0534 is a priori a factor of 5 more likely if the assumed smooth matter content in the lens model is increased from 0% to 93%. The second parameter, the size of the emission region, is explored in this paper, and shown to be more significant. We find that the broadening of the magnification probability distributions due to smooth matter content is washed out for source sizes that are predicted by standard models for quasars. We apply our model to the anomalous lensed quasar MG 0414+0534, and find a 95% upper limit of 2.62 x 10^(16) h^(-1/2) (M/Msun)^(1/2) cm on the radius of the I-band emission region. The smooth matter percentage in the lens is unconstrained.
Two New Gravitationally Lensed Double Quasars from theSloan Digital Sky Survey
Inada, Naohisa; Oguri, Masamune; Becker, Robert H.; White, Richard L.; Kayo, Issha; Kochanek, Christopher S.; Hall, Patrick B.; Schneider, Donald P.; York, Donald G.; Richards, Gordon T.; /Tokyo U., Inst. Astron. /KIPAC, Menlo Park /Princeton U. Observ. /LLNL, Livermore /UC, Davis /Baltimore, Space Telescope Sci. /Nagoya U. /Ohio State U., Dept.
2006-09-28
We report the discoveries of the two-image gravitationally lensed quasars, SDSS J0746+4403 and SDSS J1406+6126, selected from the Sloan Digital Sky Survey (SDSS). SDSS J0746+4403, which will be included in our lens sample for statistics and cosmology, has a source redshift of z{sub s} = 2.00, an estimated lens redshift of z{sub l} {approx} 0.3, and an image separation of 1.08''. SDSS J1406+6126 has a source redshift of z{sub s} = 2.13, a spectroscopically measured lens redshift of z{sub l} = 0.27, and an image separation of 1.98''. We find that the two quasar images of SDSS J1406+6126 have different intervening Mg II absorption strengths, which are suggestive of large variations of absorbers on kpc scales. The positions and fluxes of both the lensed quasar systems are easily reproduced by simple mass models with reasonable parameter values. These objects bring to 18 the number of lensed quasars that have been discovered from the SDSS data.
Gravitational Lensing Effects on High Redshift Type II Supernova Studies with NGST
Marri, S; Pozzetti, L; Marri, Simone; Ferrara, Andrea; Pozzetti, Lucia
2000-01-01
We derive the expected Type II SN differential number counts, N(m), and Hubble diagram for SCDM and LCDM cosmological models, taking into account the effects of gravitational lensing (GL) produced by the intervening cosmological mass. The mass distribution of dark matter halos (ie the lenses) is obtained by means of a Monte Carlo method applied to the Press-Schechter mass function. The halos are assumed to have a NFW density profile, in agreement with recent simulations of hierarchical cosmological models. Up to z=15, the (SCDM, LCDM) models predict a total number of (857, 3656) SNII/yr in 100 surveyed 4' times 4' fields of the Next Generation Space Telescope. NGST will be able to reach the peak of the N(m) curve, located at AB approx 30(31) for SCDM(LCDM) in J and K wavelength bands and detect (75%, 51%) of the above SN events. This will allow a detailed study of the early cosmic star formation history, as traced by SNIIe. N(m) is only very mildly affected by the inclusion of lensing effects. In addition, GL...
A new pixel-based method for analyzing spatially resolved, gravitationally lensed images
NASA Astrophysics Data System (ADS)
Tagore, Amitpal S.; Keeton, C. R.; Baker, A. J.
2014-01-01
Gravitational lens modeling of spatially resolved sources is a challenging inverse problem that requires careful handling of parameter degeneracies. I describe a new pixel-based source reconstruction method and analyze statistical and systematic effects, including pixelization, noise, telescope pointing, and resolution. I show applications of the method to observations of two lensed, high-redshift galaxies. For SDSS J120602.09+514229.5 (also known as the Clone), a z=2.001 star-forming galaxy lensed by a foreground galaxy at z=0.42, the errors on the model are appropriately accounted for, and the results are in agreement with previous analyses. For SDSS J0901+1814 (J0901), a z=2.26 ultraluminous infrared star-forming galaxy lensed by a foreground group of galaxies at z=0.35, I constrain the lens model using CO rotational line maps of multiple velocity channels, in addition to optical and infrared data. The reconstructed velocity fields in the source plane make it possible to infer J0901's intrinsic dynamical mass and gas mass fraction. Combining the CO maps with H-alpha observations allows us to test the applicability of the local Kennicutt-Schmidt relation at high redshift.
NASA Astrophysics Data System (ADS)
Guimarães, Antonio C. C.; Sodré, Laerte, Jr.
2011-02-01
Data from 58 strong-lensing events surveyed by the Sloan Lens ACS Survey are used to estimate the projected galaxy mass inside their Einstein radii by two independent methods: stellar dynamics and strong gravitational lensing. We perform a joint analysis of these two estimates inside models with up to three degrees of freedom with respect to the lens density profile, stellar velocity anisotropy, and line-of-sight (LOS) external convergence, which incorporates the effect of the large-scale structure on strong lensing. A Bayesian analysis is employed to estimate the model parameters, evaluate their significance, and compare models. We find that the data favor Jaffe's light profile over Hernquist's, but that any particular choice between these two does not change the qualitative conclusions with respect to the features of the system that we investigate. The density profile is compatible with an isothermal, being sightly steeper and having an uncertainty in the logarithmic slope of the order of 5% in models that take into account a prior ignorance on anisotropy and external convergence. We identify a considerable degeneracy between the density profile slope and the anisotropy parameter, which largely increases the uncertainties in the estimates of these parameters, but we encounter no evidence in favor of an anisotropic velocity distribution on average for the whole sample. An LOS external convergence following a prior probability distribution given by cosmology has a small effect on the estimation of the lens density profile, but can increase the dispersion of its value by nearly 40%.
Density profile and line-of-sight mass contamination of SLACS gravitational lenses
NASA Astrophysics Data System (ADS)
Guimarães, C. C.; Sodré, Laerte
2010-11-01
We use data from 58 strong lensing events surveyed by the Sloan Lens ACS Survey to estimate the projected galaxy mass inside their Einstein radii by two independent methods: stellar dynamics and strong gravitational lensing. We perform a joint analysis of both estimates examining the galaxy-lens density profile (that we approximate by a power law), the anisotropy of the velocity distribution (represented by an effective constant parameter), and a possible line-of-sigh (l.o.s.) mass contamination (which is suggested by various independent works in the literature). For each model, a likelihood analysis is performed to find the parameters that produce the best agreement between the dynamical and lensing masses, and the parameter confidence levels. The Bayesian evidence is calculated to allow a comparison among the models. We find a degeneracy among the slope of the density profile, the anisotropy parameter and the l.o.s. mass contamination. For a density profile close to isothermal, a l.o.s. mass contamination of the order of a few percent is possible, being less probable with larger anisotropy.
A new hybrid framework to efficiently model lines of sight to gravitational lenses
NASA Astrophysics Data System (ADS)
McCully, Curtis; Keeton, Charles R.; Wong, Kenneth C.; Zabludoff, Ann I.
2014-10-01
In strong gravitational lens systems, the light bending is usually dominated by one main galaxy, but may be affected by other mass along the line of sight (LOS). Shear and convergence can be used to approximate the contributions from less significant perturbers (e.g. those that are projected far from the lens or have a small mass), but higher order effects need to be included for objects that are closer or more massive. We develop a framework for multiplane lensing that can handle an arbitrary combination of tidal planes treated with shear and convergence and planes treated exactly (i.e. including higher order terms). This framework addresses all of the traditional lensing observables including image positions, fluxes, and time delays to facilitate lens modelling that includes the non-linear effects due to mass along the LOS. It balances accuracy (accounting for higher order terms when necessary) with efficiency (compressing all other LOS effects into a set of matrices that can be calculated up front and cached for lens modelling). We identify a generalized multiplane mass sheet degeneracy, in which the effective shear and convergence are sums over the lensing planes with specific, redshift-dependent weighting factors.
Gravitationally Lensed QSOs: Optical Monitoring with the EOCA and the Liverpool Telescope (LT)
Goicoechea, L J; Ovaldsen, J E; Koptelova, E; Shalyapin, V N; Gil-Merino, R
2006-01-01
The aim of this contribution is to present the two first phases of the optical monitoring programme of the Gravitational Lenses group at the Universidad de Cantabria (GLUC, http://grupos.unican.es/glendama/). In an initial stage (2003 March-June), the Estacion de Observacion de Calar Alto (EOCA) was used to obtain VR frames of SBS 0909+532 and QSO 0957+561. These observations in 2003 led to accurate fluxes of the two components of both double QSOs, which are being compared and complemented with data from other 1-1.5 m telescopes located in the North Hemisphere: Fred Lawrence Whipple Observatory (USA), Maidanak Observatory (Uzbekistan) and Wise Observatory (Israel). On the other hand, the GLUC started the second phase of its monitoring programme in 2005 January. In this second phase, they are using the 2 m fully robotic Liverpool Telescope (LT). The key idea is the two-band photometric follow-up of four lensed QSOs with different main lensing galaxies: SBS 0909+532 (elliptical), QSO 0957+561 (giant cD), B1600+...
The impact of spurious shear on cosmological parameter estimates from weak lensing observables
Petri, Andrea; May, Morgan; Haiman, Zoltan; Kratochvil, Jan M.
2014-12-01
Residual errors in shear measurements, after corrections for instrument systematics and atmospheric effects, can impact cosmological parameters derived from weak lensing observations. Here we combine convergence maps from our suite of ray-tracing simulations with random realizations of spurious shear. This allows us to quantify the errors and biases of the triplet (?m,w,?8) derived from the power spectrum (PS), as well as from three different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MFs), low-order moments (LMs), and peak counts (PKs). Our main results are as follows: (i) We find an order of magnitude smaller biases from themore »PS than in previous work. (ii) The PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of ?sys2?10-7, biases from the PS and LM would be unimportant even for a survey with the statistical power of Large Synoptic Survey Telescope. However, we find that for surveys larger than ?100 deg2, non-Gaussianity in the noise (not included in our analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (?m,w,?8) parameter space, allowing self-calibration by combining multiple statistics. Our results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.« less
The impact of spurious shear on cosmological parameter estimates from weak lensing observables
Petri, Andrea [Brookhaven National Laboratory (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States); May, Morgan [Brookhaven National Laboratory (BNL), Upton, NY (United States); Haiman, Zoltan [Columbia Univ., New York, NY (United States); Kratochvil, Jan M. [Univ. of KwaZulu-Natal, Durban (South Africa)
2014-12-01
Residual errors in shear measurements, after corrections for instrument systematics and atmospheric effects, can impact cosmological parameters derived from weak lensing observations. Here we combine convergence maps from our suite of ray-tracing simulations with random realizations of spurious shear. This allows us to quantify the errors and biases of the triplet (?m,w,?8) derived from the power spectrum (PS), as well as from three different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MFs), low-order moments (LMs), and peak counts (PKs). Our main results are as follows: (i) We find an order of magnitude smaller biases from the PS than in previous work. (ii) The PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of ?sys2?10-7, biases from the PS and LM would be unimportant even for a survey with the statistical power of Large Synoptic Survey Telescope. However, we find that for surveys larger than ?100 deg2, non-Gaussianity in the noise (not included in our analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (?m,w,?8) parameter space, allowing self-calibration by combining multiple statistics. Our results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.
The impact of spurious shear on cosmological parameter estimates from weak lensing observables
Petri, Andrea [Brookhaven National Laboratory (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States); May, Morgan [Brookhaven National Laboratory (BNL), Upton, NY (United States); Haiman, Zoltan [Columbia Univ., New York, NY (United States); Kratochvil, Jan M. [Univ. of KwaZulu-Natal, Durban (South Africa)
2014-12-01
Residual errors in shear measurements, after corrections for instrument systematics and atmospheric effects, can impact cosmological parameters derived from weak lensing observations. Here we combine convergence maps from our suite of ray-tracing simulations with random realizations of spurious shear. This allows us to quantify the errors and biases of the triplet (?_{m},w,?_{8}) derived from the power spectrum (PS), as well as from three different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MFs), low-order moments (LMs), and peak counts (PKs). Our main results are as follows: (i) We find an order of magnitude smaller biases from the PS than in previous work. (ii) The PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of ?_{sys}^{2}?10^{-7}, biases from the PS and LM would be unimportant even for a survey with the statistical power of Large Synoptic Survey Telescope. However, we find that for surveys larger than ?100 deg^{2}, non-Gaussianity in the noise (not included in our analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF, PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (?m,w,?8) parameter space, allowing self-calibration by combining multiple statistics. Our results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.
Planck's Dusty GEMS: Gravitationally lensed high-redshift galaxies discovered with the Planck survey
Canameras, R; Guery, D; McKenzie, T; Koenig, S; Petitpas, G; Dole, H; Frye, B; Flores-Cacho, I; Montier, L; Negrello, M; Beelen, A; Boone, F; Dicken, D; Lagache, G; Floch, E Le; Altieri, B; Bethermin, M; Chary, R; De Zotti, G; Giard, M; Kneissl, R; Krips, M; Malhotra, S; Martinache, C; Omont, A; Pointecouteau, E; Puget, J -L; Scott, D; Soucail, G; Valtchanov, I; Welikala, N; Yan, L
2015-01-01
We present an analysis of 11 bright far-IR/submm sources discovered through a combination of the Planck survey and follow-up Herschel-SPIRE imaging. Each source has a redshift z=2.2-3.6 obtained through a blind redshift search with EMIR at the IRAM 30-m telescope. Interferometry obtained at IRAM and the SMA, and optical/near-infrared imaging obtained at the CFHT and the VLT reveal morphologies consistent with strongly gravitationally lensed sources. Additional photometry was obtained with JCMT/SCUBA-2 and IRAM/GISMO at 850 um and 2 mm, respectively. All objects are bright, isolated point sources in the 18 arcsec beam of SPIRE at 250 um, with spectral energy distributions peaking either near the 350 um or the 500 um bands of SPIRE, and with apparent far-infrared luminosities of up to 3x10^14 L_sun. Their morphologies and sizes, CO line widths and luminosities, dust temperatures, and far-infrared luminosities provide additional empirical evidence that these are strongly gravitationally lensed high-redshift gala...
Bernard Raffaelli
2014-12-23
We examine in a semiclassical framework the deflection function of strong gravitational lensing, for static and spherically symmetric black holes, endowed with a photon sphere. From a first-order WKB analysis near the maximum of the Regge-Wheeler potential, we extract the real phase shifts from the S-matrix elements and then we derive the associated semiclassical deflection function, characterized by a logarithmic divergent behavior. More precisely, using the complex angular momentum techniques, we show that the Regge poles and the associated greybody factor residues, for a massless scalar field theory, from which one can recover the black hole quasinormal complex frequencies as well as the fluctuations of the high energy absorption cross section, play naturally the role of critical parameters in the divergent behavior of the semiclassical deflection function. For very high frequencies, we finally recover the logarithmic part of the classical strong deflection limit, which clarifies analytically the fundamental link between quasinormal modes and strong gravitational lensing, suggested in recent works.
Chen, Songbai
2015-01-01
We study the equation of motion of photons and the strong gravitational lensing in a Schwarzschild black hole spacetime when the photons couple to Weyl tensor. We find that the propagation of the coupled photons and the corresponding gravitational lensing depend sharply on the coupling constant $\\alpha$ and the photon polarization directions. The marginally stable circular radius $r_{ps}$ exists only in the regime $\\alpha\\geq\\alpha_{c1}=-M^2/2$ for the photon with the polarization along $l_{\\mu}$ and in the regime $\\alpha\\leq\\alpha_{c2}=M^2$ for the photon with the polarization along $m_{\\mu}$. When the value of $\\alpha$ is beyond the above regime, we find that the marginally stable circular radius vanishes and there exists a singularity outside the event horizon of black hole in the propagation of the coupled photons. The deflection angle of the light ray near the singularity is a negative finite value, which is different entirely from that of the usual photons without the coupling to Weyl tensor. Finally, w...
Charles C. Dyer; Francine R. Marleau
1994-11-21
We find solutions of Einstein's field equation for topologically stable strings associated with the breaking of a U(1) symmetry. Strings form in many GUTs and are expected whenever the homotopy group $\\Pi_1(M_0)$ is non-trivial. The behavior of the fields making up the string is described by the Euler-Lagrange equations. These fields appear in the energy-momentum tensor so we must solve simultaneously for the coupled Einstein-scalar-gauge field equations. Numerical results are obtained using a Taylor-series method. We obtain a 5-parameter family of solutions and discuss their physical characteristics. Significant gravitational lensing can occur due to strings based on this model and are shown for different solutions. Finally, we prove that the assumption of regularity at the string axis is not necessary by looking at the physical properties of the string solutions.
The abundance of lensing protoclusters
Anson D'Aloisio; Steven R. Furlanetto; Priyamvada Natarajan
2009-01-01
Weak gravitational lensing provides a potentially powerful method for the detection of clusters. In addition to cluster candidates, a large number of objects with possibly no optical or X-ray component have been detected in shear-selected samples. Determining the nature of these so-called `dark' lenses is an important step towards understanding the reliability of shear-selection techniques. We develop an analytic model
A search for z= 7.3 Ly? emitters behind gravitationally lensing clusters
NASA Astrophysics Data System (ADS)
Ota, Kazuaki; Richard, Johan; Iye, Masanori; Shibuya, Takatoshi; Egami, Eiichi; Kashikawa, Nobunari
2012-07-01
We searched for z= 7.3 Ly? emitters (LAEs) behind two gravitationally lensing clusters, Abell 2390 and CL 0024, using the Subaru Telescope Suprime-Cam and a narrow-band filter NB1006 (?c˜ 1005 nm and full width at half-maximum of about 21 nm). The combination of the fully depleted CCDs of the Suprime-Cam, sensitive to z˜ 7 Ly? emission at ˜ 1 ?m, and the magnification by the lensing clusters can be potentially a powerful tool to detect faint distant LAEs. Using the NB1006 and deep optical to mid-infrared images of the clusters taken with the Hubble Space Telescope and Spitzer Space Telescope, we investigated if there exist objects consistent with the colour of z= 7.3 LAEs behind the clusters. We could not detect any LAEs to the unlensed Ly? line flux limit of FLy?? 6.9 × 10-18 erg s-1 cm-2. Using several z=7 Ly? luminosity functions (LFs) from the literature, we estimated and compared the expected detection numbers of z˜ 7$ LAEs in lensing and blank field surveys in the case of using an 8-m class ground-based telescope. Given the steep bright-end slope of the LFs, when the detector field of view (FOV) is comparable to the angular extent of a massive lensing cluster, imaging cluster(s) is (are) more efficient in detecting z˜ 7 LAEs than imaging a blank field. However, the gain is expected to be modest, a factor of 2 at most and likely much less depending on the adopted LFs. The main advantage of lensing survey, therefore, remains the gain in depth and not necessarily in detection efficiency. For much larger detectors, the lensing effect becomes negligible and the efficiency of LAE detection is proportional to the instrumental FOV. We also investigated the NB1006 images of the three z˜ 7 z-dropout galaxy candidates previously detected in Abell 2390 and found that none of them is detected in NB1006. Two of them are consistent with the predictions from previous studies that they would be at lower redshifts. The other one has a photometric redshift of z? 7.3, and if we assume that it is at z= 7.3, the unlensed Ly? line flux would be very faint: FLy? < 4.4 × 10-18 erg s-1 cm-2 (1? upper limit) or equivalent width of ? Å. Its Ly? emission might be attenuated by neutral hydrogen, as recent studies show that the fraction of Lyman break galaxies displaying strong Ly? emission is lower at z˜ 7 than at z? 6.
Cosmology Constraints from the Weak Lensing Peak Counts and the Power Spectrum in CFHTLenS
Liu, Jia; May, Morgan; Petri, Andrea; Haiman, Zoltan; Hui, Lam; Kratochvil, Jan M.
2015-03-01
Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters ?m, ?8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator thatmore »interpolates the power spectrum and the peak counts to an accuracy of ? 5%, and compute the likelihood in the three-dimensional parameter space (?m, ?8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (?m, ?8) plane reduces by a factor of ? two, compared to using the power spectrum alone. For a flat ? cold dark matter model, combining both statistics, we obtain the constraint ?8(?m/0.27)0.63 = 0.85+0.03-0.03.« less
Cosmology Constraints from the Weak Lensing Peak Counts and the Power Spectrum in CFHTLenS
Liu, Jia [Department of Astronomy and Astrophysics, Columbia University, New York, NY, (United States); May, Morgan [Physics Department, Brookhaven National Laboratory, Upton, NY, (United States); Petri, Andrea [Department of Physics, Columbia University, New York, NY, (United States); Haiman, Zoltan [Department of Astronomy and Astrophysics, Columbia University, New York, NY, (United States); Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP), Columbia University, New York, (United States); Hui, Lam [Department of Physics, Columbia University, New York, NY, (United States); Institute for Strings, Cosmology, and Astroparticle Physics (ISCAP), Columbia University, New York, (United States); Kratochvil, Jan M. [Astrophysics and Cosmology Research Unit, University of KwaZulu-Natal, Westville, Durban, (South Africa)
2015-03-01
Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters ?m, ?8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator that interpolates the power spectrum and the peak counts to an accuracy of ? 5%, and compute the likelihood in the three-dimensional parameter space (?m, ?8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (?m, ?8) plane reduces by a factor of ? two, compared to using the power spectrum alone. For a flat ? cold dark matter model, combining both statistics, we obtain the constraint ?8(?m/0.27)0.63 = 0.85+0.03-0.03.
Comparison of weak lensing by NFW and Einasto halos and systematic errors
Sereno, Mauro; Moscardini, Lauro
2015-01-01
Recent $N$-body simulations have shown that Einasto radial profiles provide the most accurate description of dark matter halos. Predictions based on the traditional NFW functional form may fail to describe the structural properties of cosmic objects at the percent level required by precision cosmology. We computed the systematic errors expected for weak lensing analyses of clusters of galaxies if one wrongly models the lens properties. Even though the NFW fits of observed tangential shear profiles can be excellent, viral masses and concentrations of very massive halos ($>\\sim10^{15}M_\\odot/h$) can be over- and underestimated by $\\sim 10$ per cent, respectively. Misfitting effects also steepen the observed mass-concentration relation, in a way similar to that seen in multiwavelength observations of galaxy groups and clusters. Einasto lenses can be distinguished from NFW halos either with deep observations of very massive structures ($>\\sim10^{15}M_\\odot/h$) or by stacking the shear profiles of thousands of gro...
CoMaLit - III. Literature catalogues of weak lensing clusters of galaxies (LC2)
NASA Astrophysics Data System (ADS)
Sereno, Mauro
2015-07-01
The measurement of the mass of clusters of galaxies is crucial for their use in cosmology and astrophysics. Masses can be efficiently determined with weak lensing (WL) analyses. I compiled literature catalogues of WL clusters (LC2). Cluster identifiers, coordinates, and redshifts have been standardized. WL masses were reported to over-densities of 2500, 500, 200, and to the virial one in the reference ?CDM model. Duplicate entries were carefully handled. I produced three catalogues: LC2-single, with 485 unique groups and clusters analysed with the single-halo model; LC2-substructure, listing substructures in complex systems; LC2-all, listing all the 822 WL masses found in the literature. The catalogues and future updates are publicly available at http://pico.bo.astro.it/˜sereno/CoMaLit/LC2/.
Real space estimator for the weak lensing convergence from the CMB
Carvalho, C. S.; Moodley, K. [Astrophysics and Cosmology Research Unit, School of Mathematical Sciences, University of KwaZulu-Natal, 4000 Durban (South Africa)
2010-06-15
We propose an estimator defined in real space for the reconstruction of the weak lensing potential due to the intervening large-scale structure from high resolution maps of the cosmic microwave background. This estimator was motivated as an alternative to the quadratic estimator in harmonic space to surpass the difficulties of the analysis of maps containing galactic cuts and point source excisions. Using maps synthesized by pixel remapping, we implement the estimator for two experiments, namely, one in the absence and one in the presence of detector noise, and compare the reconstruction of the convergence field with that obtained with the quadratic estimator defined in harmonic space. We find good agreement between the input and the reconstructed power spectra using the proposed real space estimator. We discuss interesting features of the real space estimator and future extensions of this work.
Weak Lensing in Scalar-Tensor Theories of Gravity: Preliminary Results
NASA Astrophysics Data System (ADS)
Schimd, Carlo
2005-06-01
Scalar-tensor (ST) theories of gravity are the best motivated alternative to general relativity (GR), arising in every high-energy theory attempting to unify all the fundamental interactions. Furthermore, accomodating an arbitrary number of scalar fields, ST theories yield to cosmological scenarios with a dynamical realization of the dark energy. Solar-System experiments and binary-pulsars observations are compatible with very small departures from GR on the local universe (z? 0); on cosmological scales, big-bang nucleosynthesis and cosmic microwave background (CMB) observables can admit larger deviations from the predictions of GR. Weak lensing could provide a test for ST theories of gravity on intermediate scales. Based on a code developed to study ST theories on CMB observables, we implemented a plug-in code to compute the convergence power spectrum and some 2-points statistics. Preliminary results using a simple model of ST theory are presented. This study is aimed to constraint classes of ST models.
Characterizing the Shapes of Galaxy Clusters Using Moments of the Gravitational Lensing Shear
A. E. Schulz; Joseph Hennawi; Martin White
2005-11-07
We explore the use of the tangential component of weak lensing shear to characterize the ellipticity of clusters of galaxies. We introduce an ellipticity estimator, and quantify its properties for isolated clusters from LCDM N-body simulations. We compare the N-body results to results from smooth analytic models. The expected distribution of the estimator for mock observations is presented, and we show how this distribution is impacted by contaminants such as noise, line of sight projections, and misalignment of the central galaxy used to determine the orientation of the triaxial halo. We examine the radial profile of the estimator and discuss tradeoffs in the observational strategy to determine cluster shape.
Subaru Weak Lensing Study of Seven Merging Clusters: Distributions of Mass and Baryons
NASA Astrophysics Data System (ADS)
Okabe, Nobuhiro; Umetsu, Keiichi
2008-04-01
We present and compare projected distributions of mass, galaxies, and the intracluster medium (ICM) for a sample of merging clusters of galaxies based on a joint weak-lensing, optical photometric, and X-ray analysis. Our sample comprised seven nearby Abell clusters, for which we had conducted systematic, deep imaging observations with Suprime-Cam on the Subaru Telescope. Our seven target clusters, representing various merging stages and conditions, allowed us to investigate in detail the physical interplay between dark matter, ICM, and galaxies associated with cluster formation and evolution. A1750 and A1758 are binary systems consisting of two cluster-sized components; A520, A754, A1758N, A1758S, and A1914 are on-going cluster mergers; and A2034 and A2142 are cold-front clusters. In the binary clusters, the projected mass, optical light, and X-ray distributions are overall similar and regular without significant substructures. On-going and cold-front merging clusters, on the other hand, reveal highly irregular mass distributions. Overall, the mass distribution appears to be similar to the galaxy luminosity distribution, whereas their distributions are quite different from the ICM distribution in a various ways. We also measured for individual targets global cluster parameters, such as the cluster mass, the mass-to-light ratio, and the ICM temperature. A comparison of the ICM and the virial temperatures of merging clusters from X-ray and weak-lensing analyses, respectively, shows that the ICM temperature of on-going and cold-front clusters is significantly higher than the cluster virial temperature by a factor of ˜2. This temperature excess in the ICM could be explained by the effects of merger boosts.
ERIC Educational Resources Information Center
Turner, Edwin L.
1988-01-01
Describes cosmic flukes which offer a unique window on new information about the universe. Discusses the historical background, theory, and detection of this effect. Proposes the importance of information found by the examination of these phenomena. (CW)
Weak-lensing detection of intracluster filaments with ground-based data
NASA Astrophysics Data System (ADS)
Maturi, Matteo; Merten, Julian
2013-11-01
According to the current standard model of cosmology, matter in the Universe arranges itself along a network of filamentary structure. These filaments connect the main nodes of this so-called "cosmic web", which are clusters of galaxies. Although its large-scale distribution is clearly characterized by numerical simulations, constraining the dark-matter content of the cosmic web in reality turns out to be difficult. The natural method of choice is gravitational lensing. However, the direct detection and mapping of the elusive filament signal is challenging and in this work we present two methods that are specifically tailored to achieve this task. A linear matched filter aims at detecting the smooth mass-component of filaments and is optimized to perform a shear decomposition that follows the anisotropic component of the lensing signal. Filaments clearly inherit this property due to their morphology. At the same time, the contamination arising from the central massive cluster is controlled in a natural way. The filament 1? detection is of about ? ~ 0.01 - 0.005 according to the filter's template width and length, enabling the detection of structures beyond reach with other approaches. The second, complementary method seeks to detect the clumpy component of filaments. The detection is determined by the number density of subclump identifications in an area enclosing the potential filament, as was found within the observed field with the filter approach. We tested both methods against mocked observations based on realistic N-body simulations of filamentary structure and proved the feasibility of detecting filaments with ground-based data.
arXiv:0901.1132v1 A gravitationally lensed water maser in the early Universe
Brunthaler, Andreas
black holes in the centres of active galaxies. Based upon the understanding of the local water maserarXiv:0901.1132v1 [astroph] 8 Jan 2009 A gravitationally lensed water maser in the early Universe Bonn, Germany Water masers 1 4 are found in dense molecular clouds closely associated with supermassive
Antonio C. C. Guimarães; Laerte Sodré Jr.
2007-06-21
We readdress the calculation of the mass of early-type galaxies using strong gravitational lensing and stellar dynamics. Our sample comprises 27 galaxies in the Sloan Lens ACS (SLACS) Survey. Comparing the mass estimates from these two independent methods in a Bayesian framework, we find evidence of significant line-of-sight mass contamination. Assuming a power-law mass distribution, the best fit density profile is given by $\\rho \\propto r^{-1.69\\pm0.05}$. We show that neglecting the line-of-sight mass contamination produces an overestimate of the mass attributed to the lens-galaxy by the lensing method, which introduces a bias in favor of a SIS profile when using the joint lensing and dynamic analysis to determine the slope of the density profile. We suggest that the line-of-sight contamination could also be important for other astrophysical and cosmological uses of joint lensing and dynamical measurements.
LoCuSS: the near-infrared luminosity and weak-lensing mass scaling relation of galaxy clusters
NASA Astrophysics Data System (ADS)
Mulroy, Sarah L.; Smith, Graham P.; Haines, Chris P.; Marrone, Daniel P.; Okabe, Nobuhiro; Pereira, Maria J.; Egami, Eiichi; Babul, Arif; Finoguenov, Alexis; Martino, Rossella
2014-10-01
We present the first scaling relation between weak-lensing galaxy cluster mass, MWL, and near-infrared luminosity, LK. Our results are based on 17 clusters observed with wide-field instruments on Subaru, the United Kingdom Infrared Telescope, the Mayall Telescope, and the MMT. We concentrate on the relation between projected 2D weak-lensing mass and spectroscopically confirmed luminosity within 1 Mpc, modelled as M_WL ? LK^b, obtaining a power-law slope of b=0.83^{+0.27}_{-0.24} and an intrinsic scatter of ? _{lnM_WL|LK}=10^{+8}_{-5} per cent. Intrinsic scatter of ˜10 per cent is a consistent feature of our results regardless of how we modify our approach to measuring the relationship between mass and light. For example, deprojecting the mass and measuring both quantities within r500, that is itself obtained from the lensing analysis, yields ? _{lnM_WL|LK}=10^{+7}_{-5} per cent and b=0.97^{+0.17}_{-0.17}. We also find that selecting members based on their (J - K) colours instead of spectroscopic redshifts neither increases the scatter nor modifies the slope. Overall our results indicate that near-infrared luminosity measured on scales comparable with r500 (typically 1 Mpc for our sample) is a low scatter and relatively inexpensive proxy for weak-lensing mass. Near-infrared luminosity may therefore be a useful mass proxy for cluster cosmology experiments.
Measurement of Gravitational Lens Time Delays with LSST (SULI Paper)
Lowry Anna Kirkby
2006-01-01
The proposed Large Synoptic Survey Telescope will be the first to explore multiple dark energy probes simultaneously, including baryon acoustic oscillations, weak lensing, and strong gravitational lensing. The large data sample, covering the entire visible sky every few nights, will allow an unprecedented survey of deep supernova sources and their lensed images. The latter have not yet been observed. Notably,
Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam’s 2.3 deg2 field
NASA Astrophysics Data System (ADS)
Miyazaki, Satoshi; Oguri, Masamune; Hamana, Takashi; Tanaka, Masayuki; Miller, Lance; Utsumi, Yousuke; Komiyama, Yutaka; Furusawa, Hisanori; Sakurai, Junya; Kawanomoto, Satoshi; Nakata, Fumiaki; Uraguchi, Fumihiro; Koike, Michitaro; Tomono, Daigo; Lupton, Robert; Gunn, James E.; Karoji, Hiroshi; Aihara, Hiroaki; Murayama, Hitoshi; Takada, Masahiro
2015-07-01
We present properties of moderately massive clusters of galaxies detected by the newly developed Hyper Suprime-Cam on the Subaru telescope using weak gravitational lensing. Eight peaks exceeding a signal-to-noise ratio (S/N) of 4.5 are identified on the convergence S/N map of a 2.3 deg2 field observed during the early commissioning phase of the camera. Multi-color photometric data are used to generate optically selected clusters using the Cluster finding algorithm based on the Multiband Identification of Red-sequence galaxies algorithm. The optical cluster positions were correlated with the peak positions from the convergence map. All eight significant peaks have optical counterparts. The velocity dispersion of clusters is evaluated by adopting the Singular Isothemal Sphere fit to the tangential shear profiles, yielding virial mass estimates, {M}{500c}, of the clusters which range from 2.7 × 1013 to 4.4 × 10 {}14 {M}? . The number of peaks is considerably larger than the average number expected from ?CDM cosmology but this is not extremely unlikely if one takes the large sample variance in the small field into account. We could, however, safely argue that the peak count strongly favors the recent Planck result suggesting a high {? }8 value of 0.83. The ratio of stellar mass to the dark matter halo mass shows a clear decline as the halo mass increases. If the gas mass fraction, fg, in halos is universal, as has been suggested in the literature, the observed baryon mass in stars and gas shows a possible deficit compared with the total baryon density estimated from the baryon oscillation peaks in anisotropy of the cosmic microwave background.
Nishizawa, Atsushi J. [Astronomical Institute, Tohoku University, Aramaki Aobaku, Sendai 980-8578 (Japan); Takada, Masahiro [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582 (Japan); Hamana, Takashi; Furusawa, Hisanori, E-mail: nishizawa@astr.tohoku.ac.j [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka City, Tokyo 181-8588 (Japan)
2010-08-01
We use a mock catalog of galaxies based on the COSMOS galaxy catalog, including information on photometric redshift (photo-z) and spectral energy distribution types of galaxies, in order to study how to define a galaxy subsample suitable for weak lensing tomography feasible with optical (and near-IR) multi-band data. Since most useful cosmological information arises from the sample variance limited regime for upcoming lensing surveys, a suitable subsample can be obtained by discarding a large fraction of galaxies that have less reliable photo-z estimations. We develop a method to efficiently identify photo-z outliers by monitoring the width of the posterior likelihood function of redshift estimation for each galaxy. This clipping method may allow us to obtain clean tomographic redshift bins (here three bins are considered) that have almost no overlap, by discarding more than {approx}70% of galaxies with ill-defined photo-zs corresponding to the number densities of remaining galaxies less than {approx}20 arcmin{sup -2} for a Subaru-type deep survey. Restricting the ranges of magnitudes and redshifts and/or adding near-IR data help us obtain a cleaner redshift binning. Using the Fisher information matrix formalism, we propagate photo-z errors into biases in the dark energy equation of state parameter w. We find that, by discarding most of the ill-defined photo-z galaxies, the bias in w can be reduced to a level comparable to the marginalized statistical error; however, the residual small systematic bias remains due to asymmetric scatters around the relation between photometric and true redshifts. We also use the mock catalog to estimate the cumulative signal-to-noise ratios (S/Ns) for measuring the angular cross-correlations of galaxies between finer photo-z bins, finding higher S/N values for the bins that include photo-z outliers.
Resolved CO imaging in bright gravitationally lensed galaxies at z=2-6
NASA Astrophysics Data System (ADS)
Aravena, Manuel; Weiss, Axel; de Breuck, Carlos; Stark, Antony A.; Crawford, Thomas; Marrone, Dan; Tothill, Nick; McIntyre, Vince; Vieira, Joaquin; Carlstrom, John; Greve, Thomas; Chapman, Scott; Fassnacht, Chris; Murphy, Eric; Malkan, Matthew; Aguirre, James; Bothwell, Matt; Spilker, Justin; Gullberg, Bitten; Hezaveh, Yashar; Bethermin, Matthieu; Gonzalez, Anthony; Ma, Jingzhe; Strandet, Maria; Seymour, Nick
2014-04-01
Our successful ATCA low-J CO follow-up program has provided key measurements of the gas masses, excitation and free-free emission for a sample of mm-selected SPT sources that have ALMA CO redshifts and high-resolution submm imaging. While our HST and ALMA imaging reveals the distribution of the stellar and star-forming components of the ISM, critical measurements of the distribution and kinematics of the bulk of molecular gas, as best traced by low-J CO, are still lacking. Here, we propose to perform high-resolution (~0.4''-0.5'') low-J CO observations of eight unique, gravitationally lensed SPT sources at 2.5
Rusu, Cristian E; Minowa, Yosuke; Iye, Masanori; Inada, Naohisa; Oya, Shin; Kayo, Issha; Hayano, Yutaka; Hattori, Masayuki; Saito, Yoshihiko; Ito, Meguru; Pyo, Tae-Soo; Terada, Hiroshi; Takami, Hideki; Watanabe, Makoto
2015-01-01
We present the results of an imaging observation campaign conducted with the Subaru Telescope adaptive optics system (IRCS+AO188) on 26 gravitationally lensed quasars (24 doubles, 1 quad, and 1 possible triple) from the SDSS Quasar Lens Search. We develop a novel modelling technique that fits analytical and hybrid point spread functions (PSFs), while simultaneously measuring the relative astrometry, photometry, as well as the lens galaxy morphology. We account for systematics by simulating the observed systems using separately observed PSF stars. The measured relative astrometry is comparable with that typically achieved with the Hubble Space Telescope, even after marginalizing over the PSF uncertainty. We model for the first time the quasar host galaxies in 5 systems, without a-priory knowledge of the PSF, and show that their luminosities follow the known correlation with the mass of the supermassive black hole. For each system, we obtain mass models far more accurate than those previously published from low...
A Spectroscopic Survey of the Fields of 28 Strong Gravitational Lenses: The Redshift Catalog
Momcheva, Ivelina; Cool, Richard J; Keeton, Charles R; Zabludoff, Ann I
2015-01-01
We present the spectroscopic redshift catalog from a wide-field survey of the fields of 28 galaxy-mass strong gravitational lenses. We discuss the acquisition and reduction of the survey data, collected over 40 nights of 6.5m MMT and Magellan time, employing four different multi-object spectrographs. We determine that no biases are introduced by combining datasets obtained with different instrument/spectrograph combinations. Special care is taken to determine redshift uncertainties using repeat observations. The redshift catalog consists of 9768 new and unique galaxy redshifts. 82.4% of the catalog redshifts are between z=0.1 and z=0.7, and the catalog median redshift is z=0.36. The data from this survey will be used to study the lens environments and line-of-sight structures to gain a better understanding of the effects of large scale structure on lens statistics and lens-derived parameters.
Gravitational lensing time delays as a tool for testing Lorentz Invariance Violation
Marek Biesiada; Aleksandra Piórkowska
2008-09-11
Despite the fact that quantum gravity theory still remains elusive, it is generally expected that it will bring the picture of a space-time foam at short distances leading to Lorenz Invariance Violation (LIV) manifested e.g. by energy dependent modification of standard relativistic dispersion relation. One direction of research, pursued intensively is to measure energy dependent time of arrival delays in photons emitted by astrophysical sources located at cosmological distances. This is tempered however by our ignorance of either intrinsic delay (at source frame) in different energy channels or as recently shown, the correct model of the background cosmology. In this paper we propose a new test based on gravitational lensing. Monitoring time delays between images performed in different energy channels (e.g. optical - low energy and TeV photons) may reveal extra delays due to distorted dispersion relation typical in LIV theories - a test which is free from the systematics inherent in other settings.
A maximum-entropy method for reconstructing the projected mass distribution of gravitational lenses
S. L. Bridle; M. P. Hobson; A. N. Lasenby; Richard Saunders
1998-06-29
The maximum-entropy method is applied to the problem of reconstructing the projected mass density of a galaxy cluster using its gravitational lensing effects on background galaxies. We demonstrate the method by reconstructing the mass distribution in a model cluster using simulated shear and magnification data to which Gaussian noise is added. The mass distribution is reconstructed directly and the inversion is regularised using the entropic prior for this positive additive distribution. For realistic noise levels, we find that the method faithfully reproduces the main features of the cluster mass distribution not only within the observed field but also slightly beyond it. We estimate the uncertainties on the reconstruction by calculating an analytic approximation to the covariance matrix of the reconstruction values of each pixel. This result is compared with error estimates derived from Monte-Carlo simulations for different noise realisations and found to be in good agreement.
Multipole Gravitational Lensing and High-order Perturbations on the Quadrupole Lens
NASA Astrophysics Data System (ADS)
Chu, Z.; Lin, W. P.; Li, G. L.; Kang, X.
2013-03-01
An arbitrary surface mass density of the gravitational lens can be decomposed into multipole components. We simulate the ray tracing for the multipolar mass distribution of the generalized Singular Isothermal Sphere model based on deflection angles, which are analytically calculated. The magnification patterns in the source plane are then derived from an inverse shooting technique. As has been found, the caustics of odd mode lenses are composed of two overlapping layers for some lens models. When a point source traverses this kind of overlapping caustics, the image numbers change by ±4, rather than ±2. There are two kinds of caustic images. One is the critical curve and the other is the transition locus. It is found that the image number of the fold is exactly the average value of image numbers on two sides of the fold, while the image number of the cusp is equal to the smaller one. We also focus on the magnification patterns of the quadrupole (m = 2) lenses under the perturbations of m = 3, 4, and 5 mode components and found that one, two, and three butterfly or swallowtail singularities can be produced, respectively. With the increasing intensity of the high-order perturbations, the singularities grow up to bring sixfold image regions. If these perturbations are large enough to let two or three of the butterflies or swallowtails make contact, then eightfold or tenfold image regions can be produced as well. The possible astronomical applications are discussed.
MULTIPOLE GRAVITATIONAL LENSING AND HIGH-ORDER PERTURBATIONS ON THE QUADRUPOLE LENS
Chu, Z.; Lin, W. P. [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Li, G. L. [Purple Mountain Observatory, 2 West Beijing Road, Nanjing 210008 (China); Kang, X., E-mail: chuzhe@shao.ac.cn, E-mail: linwp@shao.ac.cn [Partner Group of MPI for Astronomy, Purple Mountain Observatory, 2 West Beijing Road, Nanjing 210008 (China)
2013-03-10
An arbitrary surface mass density of the gravitational lens can be decomposed into multipole components. We simulate the ray tracing for the multipolar mass distribution of the generalized Singular Isothermal Sphere model based on deflection angles, which are analytically calculated. The magnification patterns in the source plane are then derived from an inverse shooting technique. As has been found, the caustics of odd mode lenses are composed of two overlapping layers for some lens models. When a point source traverses this kind of overlapping caustics, the image numbers change by {+-}4, rather than {+-}2. There are two kinds of caustic images. One is the critical curve and the other is the transition locus. It is found that the image number of the fold is exactly the average value of image numbers on two sides of the fold, while the image number of the cusp is equal to the smaller one. We also focus on the magnification patterns of the quadrupole (m = 2) lenses under the perturbations of m = 3, 4, and 5 mode components and found that one, two, and three butterfly or swallowtail singularities can be produced, respectively. With the increasing intensity of the high-order perturbations, the singularities grow up to bring sixfold image regions. If these perturbations are large enough to let two or three of the butterflies or swallowtails make contact, then eightfold or tenfold image regions can be produced as well. The possible astronomical applications are discussed.
The Impact of Galaxies on their Environment from Observations of Gravitationally lensed QSOs
Michael Rauch
2001-11-01
Observations of absorption systems in close, multiple lines of sight to gravitationally lensed QSOs can be used to infer the density fluctuations and motions of the gas clouds giving rise to the Lyman alpha forest phenomenon and to QSO metal absorption lines. We describe a survey of lensed QSOs with the Keck HIRES instrument and argue that one can derive limits on the frequency and importance of hydrodynamical disturbances inflicted by galaxies on the surrounding gas from such data. We discuss differences between the kinematic properties of low density unsaturated Lyman alpha forest absorption systems, high ionization CIV absorption systems, and low ionization gas visible in SiII and CII. The general intergalactic medium appears to show very little turbulence, but the presumable denser CIV systems exhibit evidence of having been stirred repeatedly (by winds ?) in the past on time scales similar to those governing stellar feedback and possibly galaxy mergers. The quiescence of the low density IGM can be used to put upper limits on the incidence and energetics of galactic winds on a cosmological time scale.
Maximum-entropy reconstruction of gravitational lenses using shear and/or magnification data
S. L. Bridle; M. P. Hobson; Richard Saunders; A. N. Lasenby
2000-10-19
We demonstrate that the maximum-entropy method for gravitational lens reconstruction presented in Bridle et al. (1998) may be applied even when only shear \\emph{or} magnification information is present. We also demonstrate that the method can easily handle irregularly shaped observing fields and, because shear is a non-local function of the lensing mass, reconstructions that use shear information can successfully bridge small gaps in observations. For our simulations we use a mass density distribution that is realistic for a z=0.4 cluster of total mass around 10^15 h^-1 M_solar. Using HST-quality shear data alone, covering the area of four WFPC2 observations, we detect 60 per cent of the mass of the cluster within the area observed, despite the mass sheet degeneracy. This is qualitatively because the shear provides information about the variations in the mass distribution, and our prior includes a positivity constraint. We investigate the effect of using various sizes of observing field and find that 50 to 100 per cent of the cluster mass is detected, depending on the observing strategy and cluster shape. Finally we demonstrate how this method can cope with strong lensing regions of a mass distribution.
SDSS J024634.11-082536.2: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
NASA Astrophysics Data System (ADS)
Inada, Naohisa; Burles, Scott; Gregg, Michael D.; Becker, Robert H.; Schechter, Paul L.; Eisenstein, Daniel J.; Oguri, Masamune; Castander, Francisco J.; Hall, Patrick B.; Johnston, David E.; Pindor, Bartosz; Richards, Gordon T.; Schneider, Donald P.; White, Richard L.; Brinkmann, J.; Szalay, Alexander S.; York, Donald G.
2005-11-01
We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan Consortium's Walter Baade 6.5 m telescope and spectroscopic observations using the W. M. Keck Observatory's Keck II telescope confirm that SDSS J0246-0825 consists of two lensed images (??=1.04") of a source quasar at z=1.68. Imaging observations with the Keck I telescope and the Hubble Space Telescope reveal an extended object between the two quasar components, which is likely to be a lensing galaxy of this system. From the absorption lines in the spectra of the quasar components and the apparent magnitude of the galaxy, combined with the expected absolute magnitude from the Faber-Jackson relation, we estimate the redshift of the lensing galaxy to be z=0.724. A highly distorted ring is visible in the Hubble Space Telescope images, which is likely to be the lensed host galaxy of the source quasar. Simple mass modeling predicts the possibility that there is a small (faint) lensing object near the primary lensing galaxy. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. These observations are associated with HST program 9744.
Random walks in cosmology: Weak lensing, the halo model, and reionization
NASA Astrophysics Data System (ADS)
Zhang, Jun
This thesis discusses theoretical problems in three areas of cosmology: weak lensing, the halo model, and reionization. In weak lensing, we investigate the impact of the intrinsic alignment on the density-ellipticity correlations using the tidal torquing theory. Under the assumption of the Gaussianity of the tidal field, we find that the intrinsic alignment does not contaminate the density-ellipticity correlation even if the source clustering correlations are taken into account. The non-Gaussian contributions to both the intrinsic density-ellipticity and ellipticity- ellipticity correlations are often non-negligible. In a separate work, we discuss a useful scaling relation in weak lensing measurements. Given a foreground galaxy-density field or shear field, its cross-correlation with the shear field from a background population of source galaxies scales with the source redshift in a way that allows us to effectively measure geometrical distances as a function of redshift and thereby constrain dark energy properties without assuming anything about the galaxy-mass/mass power spectrum. Such a geometrical method can yield a ~ 0.03--0.07 [Special characters omitted.] measurement on the dark energy abundance and equation of state, for a photometric redshift accuracy of [Delta] z ~ 0.01--0.05 and a survey with median redshift of ~1. The geometrical method also provides a consistency check of the standard cosmological model because it is completely independent of structure formation. In the excursion set theory of the halo model, we derive the first-crossing distribution of random walks with a moving barrier of a general shape. Such a distribution is shown to satisfy an integral equation that can be solved by a simple matrix inversion, without the need for Monte Carlo simulations, making it useful for exploring a large parameter space. We discuss examples in which common analytic approximations fail, a failure that can be remedied using our method. In reionization, we calculate the large scale properties of the HII/HI and radiation distributions using the linear perturbation theory. Given the distribution and the spectrum of the ionizing sources, our formalism can be used to calculate the large scale bias of the HII regions from first principles by solving the equations of ionization balance and radiative transfer in Fourier space. We also discuss an approximate but easy way of solving these equations for UV dominated source spectra. Using the extended Press-Schechter model, we find: (1) reionization always proceeds inside-out, at least on large scales; (2) on sufficiently large scales, HII, HI and radiation exhibit a scale independent bias relative to dark matter; (3) the bias is suppressed on scales comparable to or smaller than the mean free path of the ionizing photons; (4) if the ionizing source spectrum is sufficiently soft, the HII bias closely tracks the source bias for most of the reionization process but drops precipitously after percolation; (5) if the ionizing source spectrum is hard, the HII bias drops in a more steady fashion throughout the reionization process. The tools developed here will be useful for interpreting future 21cm, CMB and Lyman-alpha forest observations, both to learn about the reionization astrophysics and to possibly extract interesting cosmological information.
On the constraint equations in Einstein-aether theories and the weak gravitational field limit
David Garfinkle; James Isenberg; Jose M. Martin-Garcia
2012-07-27
We discuss the set of constraints for Einstein-aether theories, comparing the flat background case with what is expected when the gravitational fields are dynamic. We note potential pathologies occurring in the weak gravitational field limit for some of the Einstein-aether theories.
NASA Astrophysics Data System (ADS)
Osato, Ken; Shirasaki, Masato; Yoshida, Naoki
2015-06-01
We study the impact of baryonic physics on cosmological parameter estimation with weak-lensing surveys. We run a set of cosmological hydrodynamics simulations with different galaxy formation models. We then perform ray-tracing simulations through the total matter density field to generate 100 independent convergence maps with a field of view of 25 {{deg }2}, and we use them to examine the ability of the following three lensing statistics as cosmological probes: power spectrum (PS), peak counts, and Minkowski functionals (MFs). For the upcoming wide-field observations, such as the Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of 1400 {{deg }2}, these three statistics provide tight constraints on the matter density, density fluctuation amplitude, and dark energy equation of state, but parameter bias is induced by baryonic processes such as gas cooling and stellar feedback. When we use PS, peak counts, and MFs, the magnitude of relative bias in the dark energy equation of state parameter w is at a level of, respectively, ? w? 0.017, 0.061, and 0.0011. For the HSC survey, these values are smaller than the statistical errors estimated from Fisher analysis. The bias could be significant when the statistical errors become small in future observations with a much larger survey area. We find that the bias is induced in different directions in the parameter space depending on the statistics employed. While the two-point statistic, i.e., PS, yields robust results against baryonic effects, the overall constraining power is weak compared with peak counts and MFs. On the other hand, using one of peak counts or MFs, or combined analysis with multiple statistics, results in a biased parameter estimate. The bias can be as large as 1? for the HSC survey and will be more significant for upcoming wider-area surveys. We suggest to use an optimized combination so that the baryonic effects on parameter estimation are mitigated. Such a “calibrated” combination can place stringent and robust constraints on cosmological parameters.
Morokuma, Tomoki; Inada, Naohisa; Oguri, Masamune; Ichikawa, Shin-Ichi; Kawano, Yozo; Tokita, Kouichi; Kayo, Issha; Hall, Patrick B.; Kochanek, Christopher S.; Richards,; York, Donald G.; Schneider, Donald P.; /Tokyo U., Inst. Astron. /KIPAC, Menlo Park /Princeton U. /Tokyo, Astron. Observ. /Nagoya U. /York U., Canada /Ohio State U.,
2006-09-28
We report the discovery of the two-image gravitationally lensed quasar SDSS J133222.62+034739.9 (SDSS J1332+0347) with an image separation of {Delta}{theta} = 1.14''. This system consists of a source quasar at z{sub s} = 1.445 and a lens galaxy at z{sub l} = 0.191. The agreement of the luminosity, ellipticity and position angle of the lens galaxy with those expected from lens model confirms the lensing hypothesis.
Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar
James, Oliver; Franklin, Paul; Thorne, Kip S
2015-01-01
Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this we developed a code called DNGR (Double Negative Gravitational Renderer) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering. This paper has four purposes: (i) To describe DNGR for physicists and CGI practitioners . (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies. (iv) To describe how the images of the black hole Gargantua and its accretion disk,...
Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar
Oliver James; Eugenie von Tunzelmann; Paul Franklin; Kip S. Thorne
2015-02-16
Interstellar is the first Hollywood movie to attempt depicting a black hole as it would actually be seen by somebody nearby. For this we developed a code called DNGR (Double Negative Gravitational Renderer) to solve the equations for ray-bundle (light-beam) propagation through the curved spacetime of a spinning (Kerr) black hole, and to render IMAX-quality, rapidly changing images. Our ray-bundle techniques were crucial for achieving IMAX-quality smoothness without flickering. This paper has four purposes: (i) To describe DNGR for physicists and CGI practitioners . (ii) To present the equations we use, when the camera is in arbitrary motion at an arbitrary location near a Kerr black hole, for mapping light sources to camera images via elliptical ray bundles. (iii) To describe new insights, from DNGR, into gravitational lensing when the camera is near the spinning black hole, rather than far away as in almost all prior studies. (iv) To describe how the images of the black hole Gargantua and its accretion disk, in the movie \\emph{Interstellar}, were generated with DNGR. There are no new astrophysical insights in this accretion-disk section of the paper, but disk novices may find it pedagogically interesting, and movie buffs may find its discussions of Interstellar interesting.
Cross-correlation Weak Lensing of SDSS Galaxy Clusters I: Measurements
Sheldon, Erin S.; Johnston, David E.; Scranton, Ryan; Koester, Ben P.; McKay, Timothy A.; Oyaizu, Hiroaki; Cunha, Carlos; Lima, Marcos; Lin, Huan; Frieman, Joshua A.; Wechsler, Risa H.; Annis, James; Mandelbaum, Rachel; Bahcall, Neta A.; Fukugita, Masataka
2007-09-28
This is the first in a series of papers on the weak lensing effect caused by clusters of galaxies in Sloan Digital Sky Survey. The photometrically selected cluster sample, known as MaxBCG, includes {approx}130,000 objects between redshift 0.1 and 0.3, ranging in size from small groups to massive clusters. We split the clusters into bins of richness and luminosity and stack the surface density contrast to produce mean radial profiles. The mean profiles are detected over a range of scales, from the inner halo (25 kpc/h) well into the surrounding large scale structure (30 Mpc/h), with a significance of 15 to 20 in each bin. The signal over this large range of scales is best interpreted in terms of the cluster-mass cross-correlation function. We pay careful attention to sources of systematic error, correcting for them where possible and bounding them where not. We find that the profiles scale strongly with richness and luminosity. We find the signal within a given richness bin depends upon luminosity, suggesting that luminosity is more closely correlated with mass than galaxy counts. We split the samples by redshift but detect no significant evolution. The profiles are not well described by power laws. In a subsequent series of papers we invert the profiles to three-dimensional mass profiles, show that they are well fit by a halo model description, measure mass-to-light ratios and provide a cosmological interpretation.
Brunthaler, Andreas
2010-01-01
densities of 107 to 1011 cm-3 and gas temperatures >300 K. All interferometric studies of powerful water lensed water masers in dusty quasars and star-forming galaxies J. P. McKean,1 C. M. V. Impellizzeri,2 A of known gravitationally lensed quasars and star-forming galaxies. In this paper, we present a search
Nupur Mukherjee; A. S. Majumdar
2006-12-22
We consider the metric exterior to a charged dilaton black hole in a de Sitter universe. We study the motion of a test particle in this metric. Conserved quantities are identified and the Hamilton-Jacobi method is employed for the solutions of the equations of motion. At large distances from the black hole the Hubble expansion of the universe modifies the effective potential such that bound orbits could exist up to an upper limit of the angular momentum per mass for the orbiting test particle. We then study the phenomenon of strong field gravitational lensing by these black holes by extending the standard formalism of strong lensing to the non-asymptotically flat dilaton-de Sitter metric. Expressions for the various lensing quantities are obtained in terms of the metric coefficients.
NASA Technical Reports Server (NTRS)
Wagoner, Robert V.; Linder, Eric V.
1987-01-01
A review is presented concerning the gravitational lensing of supernovae by intervening condensed objects, including dark matter candidates such as dim stars and black holes. the expansion of the supernova beam within the lens produces characteristic time-dependent amplification and polarization which depend upon the mass of the lens. The effects of the shearing of the beam due to surrounding masses are considered, although the study of these effects is confined to isolated masses whose size is much less than that of the supernova (about 10 to the 15th cm). Equations for the effects of lensing and graphs comparing these effects in different classes of supernovae are compared. It is found that candidates for lensing would be those supernovae at least as bright as their parent galaxy, or above the range of luminosities expected for their spectral class.
Constraining Dark Energy From Splitting Angle Statistic of Strong Gravitational Lenses
Qing-Jun Zhang; Ling-Mei Cheng; Yue-Liang Wu
2008-12-18
Utilizing the CLASS statistical sample, we investigate the constraint of the splitting angle statistic of strong gravitational lenses(SGL) on the equation-of-state parameter $w=p/\\rho$ of the dark energy in the flat cold dark matter cosmology. Through the comoving number density of dark halos described by Press-Schechter theory, dark energy affects the efficiency with which dark-matter concentrations produce strong lensing signals. The constraints on both constant $w$ and time-varying $w(z)=w_0+w_az/(1+z)$ from the SGL splitting angle statistic are consistently obtained by adopting a two model combined mechanism of dark halo density profile matched at the mass scale $M_c$. Our main observations are: (a) the resulting model parameter $M_c$ is found to be $M_c \\sim 1.4$ for both constant $w$ and time-varying $w(z)$, which is larger than $M_c \\sim 1$ obtained in literatures; (b) the fitting results for the constant $w$ are found to be $w =-0.89^{+0.49}_{-0.26}$ and $w =-0.94^{+0.57}_{-0.16}$ for the source redshift distributions of the Gaussian models $g(z_s)$ and $g^c(z_s)$ respectively, which are consistent with the $\\Lambda \\rm CDM$ at 95% C.L; (c) the time-varying $w(z)$ is found to be for $\\sigma_8 = 0.74$: $(M_c; w_0, w_a)=(1.36; -0.92, -1.31)$ and $(M_c; w_0, w_a)=(1.38; -0.89, -1.21)$ for $g(z_s)$ and $g^c(z_s)$ respectively.
A Snapshot Survey for Gravitational Lenses Among z>=4.0 Quasars: I. The z>5.7 Sample
Gordon T. Richards; Michael A. Strauss; Bartosz Pindor; Zoltan Haiman; Xiaohui Fan; Daniel Eisenstein; Donald P. Schneider; Neta A. Bahcall; J. Brinkmann; Robert Brunner
2003-09-09
Over the last few years, the Sloan Digital Sky Survey (SDSS) has discovered several hundred quasars with redshift between 4.0 and 6.4. Including the effects of magnification bias, one expects a priori that an appreciable fraction of these objects are gravitationally lensed. We have used the Advanced Camera for Surveys on the Hubble Space Telescope to carry out a snapshot imaging survey of high-redshift SDSS quasars to search for gravitationally split lenses. This paper, the first in a series reporting the results of the survey, describes snapshot observations of four quasars at z = 5.74, 5.82, 5.99 and 6.30, respectively. We find that none of these objects has a lensed companion within 5 magnitudes with a separation larger than 0.3 arcseconds; within 2.5 magnitudes, we can rule out companions within 0.1 arcseconds. Based on the non-detection of strong lensing in these four systems, we constrain the z~6 luminosity function to a slope of beta>-4.63 (3 sigma), assuming a break in the quasar luminosity function at M_{1450}^*=-24.0. We discuss the implications of this constraint on the ionizing background due to quasars in the early universe. Given that these quasars are not highly magnified, estimates of the masses of their central engines by the Eddington argument must be taken seriously, possibly challenging models of black hole formation.
Rapoport, Sharon; Onken, Christopher A.; Schmidt, Brian P.; Tucker, Brad E. [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); Wyithe, J. Stuart B. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Levan, Andrew J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)
2012-08-01
Sixty percent of gamma-ray bursts (GRBs) reveal strong Mg II absorbing systems, which is a factor of {approx}2 times the rate seen along lines of sight to quasars. Previous studies argue that the discrepancy in the strong Mg II covering factor is most likely to be the result of either quasars being obscured due to dust or the consequence of many GRBs being strongly gravitationally lensed. We analyze observations of quasars that show strong foreground Mg II absorption. We find that GRB lines of sight pass closer to bright galaxies than would be expected for random lines of sight within the impact parameter expected for strong Mg II absorption. While this cannot be explained by obscuration in the GRB sample, it is a natural consequence of gravitational lensing. Upon examining the particular configurations of galaxies near a sample of GRBs with strong Mg II absorption, we find several intriguing lensing candidates. Our results suggest that lensing provides a viable contribution to the observed enhancement of strong Mg II absorption along lines of sight to GRBs, and we outline the future observations required to test this hypothesis conclusively.
Antonio C. C. Guimaraes; Laerte Sodre Jr
We readdress the calculation of the mass of early-type galaxies using strong gravitational lensing and stellar dynamics. Our sample comprises 27 galaxies in the Sloan Lens ACS (SLACS) Survey. Comparing the mass estimates from these two independent methods in a Bayesian framework, we find evidence of significant line-of-sight mass contamination. Assuming a power- law mass distribution, the best fit density
Antonio C. C. Guimarães; Laerte Sodré Jr.
2007-01-01
We readdress the calculation of the mass of early-type galaxies using strong gravitational lensing and stellar dynamics. Our sample comprises 27 galaxies in the Sloan Lens ACS (SLACS) Survey. Comparing the mass estimates from these two independent methods in a Bayesian framework, we find evidence of significant line-of-sight mass contamination. Assuming a power-law mass distribution, the best fit density profile
D. Sluse; F. Courbin; A. Eigenbrod; G. Meylan
2008-12-08
We present the first VLT near-IR observations of a gravitationally lensed quasar, using adaptive optics and laser guide star. These observations can be considered as a test bench for future systematic observations of lensed quasars with adaptive optics, even when bright natural guide stars are not available in the nearby field. With only 14 minutes of observing time, we derived very accurate astrometry of the quasar images and of the lensing galaxy, with 0.05 \\arcsec spatial resolution, comparable to the Hubble Space Telescope (HST). In combination with deep VLT optical spectra of the quasar images, we use our adaptive optics images to constrain simple models for the mass distribution of the lensing galaxy. The latter is almost circular and does not need any strong external shear to fit the data. The time delay predicted for SDSS0806+2006, assuming a singular isothermal ellipsoid model and the concordance cosmology, is Delta t \\simeq 50 days. Our optical spectra indicate a flux ratio between the quasar images of A/B=1.3 in the continuum and A/B=2.2 in both the MgII and in the CIII] broad emission lines. This suggests that microlensing affects the continuum emission. However, the constant ratio between the two emission lines indicates that the broad emission line region is not microlensed. Finally, we see no evidence of reddening by dust in the lensing galaxy.
NASA Astrophysics Data System (ADS)
Takada, Masahiro; Spergel, David N.
2014-07-01
A coherent over- or under-density contrast across a finite survey volume causes an upward- or downward fluctuation in the observed number of haloes. This fluctuation in halo number adds a significant co-variant scatter in the observed amplitudes of weak lensing power spectrum at non-linear, small scales - the so-called super-sample variance or the halo sample variance. In this paper, we show that by measuring both the number counts of clusters and the power spectrum in the same survey region, we can mitigate this loss of information and significantly enhance the scientific return from the upcoming surveys. First, using the halo model approach, we derive the cross-correlation between the halo number counts and the weak lensing power spectrum, taking into account the super-sample covariance effect, which well matches the distributions measured from 1000 realizations for a ?-dominated cold dark matter model. Then we show that adding the observed number counts of massive haloes with M ? 1014 M?/h can significantly improve the information content of weak lensing power spectrum, almost recovering the Gaussian information up to lmax ? 1000, if the average mass profiles of the massive haloes are known, which can be estimated from stacked lensing. When combined with the halo number counts for M > 3 or 1 × 1014 M? h-1, the improvement is up to a factor of 1.4 or 2 at lmax ? 1000-2000, equivalent to a factor of 2 or 4 times larger survey volume, compared to the power spectrum measurement alone.
Atmospheric point spread function interpolation for weak lensing in short exposure imaging data
NASA Astrophysics Data System (ADS)
Chang, C.; Marshall, P. J.; Jernigan, J. G.; Peterson, J. R.; Kahn, S. M.; Gull, S. F.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R. R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M. A.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, S.; Meert, A.; Nagarajan, S.; Peng, E.; Rasmussen, A. P.; Shmakova, M.; Sylvestre, N.; Todd, N.; Young, M.
2012-12-01
A main science goal for the Large Synoptic Survey Telescope (LSST) is to measure the cosmic shear signal from weak lensing to extreme accuracy. One difficulty, however, is that with the short exposure time (?15 s) proposed, the spatial variation of the point spread function (PSF) shapes may be dominated by the atmosphere, in addition to optics errors. While optics errors mainly cause the PSF to vary on angular scales similar or larger than a single CCD sensor, the atmosphere generates stochastic structures on a wide range of angular scales. It thus becomes a challenge to infer the multiscale, complex atmospheric PSF patterns by interpolating the sparsely sampled stars in the field. In this paper we present a new method, PSFENT, for interpolating the PSF shape parameters, based on reconstructing underlying shape parameter maps with a multiscale maximum entropy algorithm. We demonstrate, using images from the LSST Photon Simulator, the performance of our approach relative to a fifth-order polynomial fit (representing the current standard) and a simple boxcar smoothing technique. Quantitatively, PSFENT predicts more accurate PSF models in all scenarios and the residual PSF errors are spatially less correlated. This improvement in PSF interpolation leads to a factor of 3.5 lower systematic errors in the shear power spectrum on scales smaller than ˜13 arcmin, compared to polynomial fitting. We estimate that with PSFENT and for stellar densities greater than ?1 arcmin-2, the spurious shear correlation from PSF interpolation, after combining a complete 10-yr data set from LSST, is lower than the corresponding statistical uncertainties on the cosmic shear power spectrum, even under a conservative scenario.
Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data
Chang, C.; Marshall, P.J.; Jernigan, J.G.; Peterson, J.R.; Kahn, S.M.; Gull, S.F.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, S.; Meert, A.
2012-09-19
A main science goal for the Large Synoptic Survey Telescope (LSST) is to measure the cosmic shear signal from weak lensing to extreme accuracy. One difficulty, however, is that with the short exposure time ({approx_equal}15 seconds) proposed, the spatial variation of the Point Spread Function (PSF) shapes may be dominated by the atmosphere, in addition to optics errors. While optics errors mainly cause the PSF to vary on angular scales similar or larger than a single CCD sensor, the atmosphere generates stochastic structures on a wide range of angular scales. It thus becomes a challenge to infer the multi-scale, complex atmospheric PSF patterns by interpolating the sparsely sampled stars in the field. In this paper we present a new method, psfent, for interpolating the PSF shape parameters, based on reconstructing underlying shape parameter maps with a multi-scale maximum entropy algorithm. We demonstrate, using images from the LSST Photon Simulator, the performance of our approach relative to a 5th-order polynomial fit (representing the current standard) and a simple boxcar smoothing technique. Quantitatively, psfent predicts more accurate PSF models in all scenarios and the residual PSF errors are spatially less correlated. This improvement in PSF interpolation leads to a factor of 3.5 lower systematic errors in the shear power spectrum on scales smaller than {approx} 13, compared to polynomial fitting. We estimate that with psfent and for stellar densities greater than {approx_equal}1/arcmin{sup 2}, the spurious shear correlation from PSF interpolation, after combining a complete 10-year dataset from LSST, is lower than the corresponding statistical uncertainties on the cosmic shear power spectrum, even under a conservative scenario.
Gravitational lensing and ghost images in the regular Bardeen no-horizon spacetimes
NASA Astrophysics Data System (ADS)
Schee, Jan; Stuchlík, Zden?k
2015-06-01
We study deflection of light rays and gravitational lensing in the regular Bardeen no-horizon spacetimes. Flatness of these spacetimes in the central region implies existence of interesting optical effects related to photons crossing the gravitational field of the no-horizon spacetimes with low impact parameters. These effects occur due to existence of a critical impact parameter giving maximal deflection of light rays in the Bardeen no-horizon spacetimes. We give the critical impact parameter in dependence on the specific charge of the spacetimes, and discuss "ghost" direct and indirect images of Keplerian discs, generated by photons with low impact parameters. The ghost direct images can occur only for large inclination angles of distant observers, while ghost indirect images can occur also for small inclination angles. We determine the range of the frequency shift of photons generating the ghost images and determine distribution of the frequency shift across these images. We compare them to those of the standard direct images of the Keplerian discs. The difference of the ranges of the frequency shift on the ghost and direct images could serve as a quantitative measure of the Bardeen no-horizon spacetimes. The regions of the Keplerian discs giving the ghost images are determined in dependence on the specific charge of the no-horizon spacetimes. For comparison we construct direct and indirect (ordinary and ghost) images of Keplerian discs around Reissner-Nördström naked singularities demonstrating a clear qualitative difference to the ghost direct images in the regular Bardeen no-horizon spacetimes. The optical effects related to the low impact parameter photons thus give clear signature of the regular Bardeen no-horizon spacetimes, as no similar phenomena could occur in the black hole or naked singularity spacetimes. Similar direct ghost images have to occur in any regular no-horizon spacetimes having nearly flat central region.
Resolved CO imaging in bright gravitationally lensed galaxies at z=2-6
NASA Astrophysics Data System (ADS)
Aravena, Manuel; Weiss, Axel; de Breuck, Carlos; Stark, Antony A.; Crawford, Thomas; Marrone, Dan; Tothill, Nick; McIntyre, Vince; Vieira, Joaquin; Carlstrom, John; Greve, Thomas; Chapman, Scott; Fassnacht, Chris; Murphy, Eric; Malkan, Matthew; Aguirre, James; Bothwell, Matt; Spilker, Justin; Gullberg, Bitten; Hezaveh, Yashar; Bethermin, Matthieu; Gonzalez, Anthony; Ma, Jingzhe; Strandet, Maria; Seymour, Nick
2014-10-01
Our successful ATCA low-J CO follow-up program has provided key measurements of the gas masses, excitation and free-free emission for a sample of mm-selected SPT sources that have ALMA CO redshifts and high-resolution submm imaging. While our HST and ALMA imaging reveals the distribution of the stellar and star-forming components of the ISM, critical measurements of the distribution and kinematics of the bulk of molecular gas, as best traced by low-J CO, are still lacking. Here, we propose to continue our high-resolution (~0.4''-0.5'') low-J CO observations of eight unique, gravitationally lensed SPT sources at 2.5
Resolved CO imaging in two unique gravitationally lensed galaxies at z > 2
NASA Astrophysics Data System (ADS)
Aravena, Manuel; Weiss, Axel; de Breuck, Carlos; Marrone, Dan; McIntyre, Vince; Vieira, Joaquin; Murphy, Eric; Aguirre, James; Bothwell, Matt; Hezaveh, Yashar
2013-10-01
Our successful ATCA low-J CO follow-up program has provided key measurements of the gas masses, excitation and free-free emission for a sample of mm-selected SPT sources that have accurate CO-based spectroscopic redshifts and high-resolution submm imaging from ALMA. While our HST and ALMA imaging reveals the distribution of the stellar and star-forming components of the ISM, critical measurements of the distribution and kinematics of the bulk of molecular gas, as best traced by low-J CO, are still lacking. Here, we propose to perform high-resolution (~0.4''-0.5'') low-J CO observations of two unique, gravitationally lensed SPT sources at z=2.7 and 5.7. For SPT sources these observations are only possible with ATCA and they are key to provide dynamical modeling of these galaxies, estimate CO-to-H2 conversion factors, and to compare the gas and SFR surface density distributions down to ~kpc-scales.
OGLE-IV: Fourth Phase of the Optical Gravitational Lensing Experiment
Udalski, A; Szyma?ski, G
2015-01-01
We present both the technical overview and main science drivers of the fourth phase of the Optical Gravitational Lensing Experiment (hereafter OGLE-IV). OGLE-IV is currently one of the largest sky variability surveys worldwide, targeting the densest stellar regions of the sky. The survey covers over 3000 square degrees in the sky and monitors regularly over a billion sources. The main targets include the inner Galactic Bulge and the Magellanic System. Their photometry spans the range of $12
NASA Astrophysics Data System (ADS)
Das, Sudeep; Louis, Thibaut; Nolta, Michael R.; Addison, Graeme E.; Battistelli, Elia S.; Bond, J. Richard; Calabrese, Erminia; Crichton, Devin; Devlin, Mark J.; Dicker, Simon; Dunkley, Joanna; Dünner, Rolando; Fowler, Joseph W.; Gralla, Megan; Hajian, Amir; Halpern, Mark; Hasselfield, Matthew; Hilton, Matt; Hincks, Adam D.; Hlozek, Renée; Huffenberger, Kevin M.; Hughes, John P.; Irwin, Kent D.; Kosowsky, Arthur; Lupton, Robert H.; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael D.; Page, Lyman A.; Partridge, Bruce; Reese, Erik D.; Schmitt, Benjamin L.; Sehgal, Neelima; Sherwin, Blake D.; Sievers, Jonathan L.; Spergel, David N.; Staggs, Suzanne T.; Swetz, Daniel S.; Switzer, Eric R.; Thornton, Robert; Trac, Hy; Wollack, Ed
2014-04-01
We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and show they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ?CDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6? detection significance.
Dusty starburst galaxies in the early Universe as revealed by gravitational lensing.
Vieira, J D; Marrone, D P; Chapman, S C; De Breuck, C; Hezaveh, Y D; Wei?, A; Aguirre, J E; Aird, K A; Aravena, M; Ashby, M L N; Bayliss, M; Benson, B A; Biggs, A D; Bleem, L E; Bock, J J; Bothwell, M; Bradford, C M; Brodwin, M; Carlstrom, J E; Chang, C L; Crawford, T M; Crites, A T; de Haan, T; Dobbs, M A; Fomalont, E B; Fassnacht, C D; George, E M; Gladders, M D; Gonzalez, A H; Greve, T R; Gullberg, B; Halverson, N W; High, F W; Holder, G P; Holzapfel, W L; Hoover, S; Hrubes, J D; Hunter, T R; Keisler, R; Lee, A T; Leitch, E M; Lueker, M; Luong-Van, D; Malkan, M; McIntyre, V; McMahon, J J; Mehl, J; Menten, K M; Meyer, S S; Mocanu, L M; Murphy, E J; Natoli, T; Padin, S; Plagge, T; Reichardt, C L; Rest, A; Ruel, J; Ruhl, J E; Sharon, K; Schaffer, K K; Shaw, L; Shirokoff, E; Spilker, J S; Stalder, B; Staniszewski, Z; Stark, A A; Story, K; Vanderlinde, K; Welikala, N; Williamson, R
2013-03-21
In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at present. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (z?>?4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z?>?4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation. PMID:23485967
Gravitational lenses magnify up to one third of the most distant quasars
Stuart Wyithe; Abraham Loeb
2002-05-01
Exceptionally bright quasars with redshifts up to z=6.28 have recently been discovered. Quasars are thought to be powered by the accretion of gas onto supermassive black holes at the centres of galaxies. Their maximum (Eddington) luminosity is proportional to the mass of the black hole, and so these bright quasars are inferred to have black holes with masses of more than a few billion solar masses. The existence of such massive black holes poses a challenge to models for the formation of structures in the early Universe, as it requires that the black holes would grow so massive in less than a billion years after the Big Bang. Here we show that up to a third of known quasars with z~6 will have their observed flux magnified by a factor of 10 or more through gravitational lensing by galaxies along the line of sight. The inferred abundance of quasar host galaxies, as well as the luminosity density provided by the quasars, are therefore substantially overestimated.
A Time Delay for the Largest Gravitationally Lensed Quasar: SDSS J1004+4112
J. Fohlmeister; C. S. Kochanek; E. E. Falco; J. Wambsganss; N. Morgan; C. W. Morgan; E. O. Ofek; D. Maoz; C. R. Keeton; J. C. Barentine; G. Dalton; J. Dembicky; W. Ketzeback; R. McMillan; C. S. Peters
2006-07-21
We present 426 epochs of optical monitoring data spanning 1000 days from December 2003 to June 2006 for the gravitationally lensed quasar SDSS J1004+4112. The time delay between the A and B images is 38.4+/-2.0 days in the expected sense that B leads A and the overall time ordering is C-B-A-D-E. The measured delay invalidates all published models. The models failed because they neglected the perturbations from cluster member galaxies. Models including the galaxies can fit the data well, but strong conclusions about the cluster mass distribution should await the measurement of the longer, and less substructure sensitive, delays of the C and D images. For these images, a CB delay of 681+/-15 days is plausible but requires confirmation, while CB and AD delays of >560 days and > 800 days are required. We clearly detect microlensing of the A/B images, with the delay-corrected flux ratios changing from B-A=0.44+/-0.01 mag in the first season to 0.29+/-0.01 mag in the second season and 0.32+/-0.01 mag in the third season.
Neronov, A
2015-01-01
We show that observation of the time-dependent effect of microlensing of relativistically broadened emission lines (such as e.g. the Fe Kalpha line in X-rays) in strongly lensed quasars could provide data on celestial mechanics of circular orbits in the direct vicinity of the horizon of supermassive black holes. This information can be extracted from the observation of evolution of red / blue edge of the magnified line just before and just after the period of crossing of the innermost stable circular orbit by the microlensing caustic. The functional form of this evolution is insensitive to numerous astrophysical parameters of the accreting black hole and of the microlensing caustics network system (as opposed to the evolution the full line spectrum). Measurement of the temporal evolution of the red / blue edge could provide a precision measurement of the radial dependence of the gravitational redshift and of velocity of the circular orbits, down to the innermost stable circular orbit. These measurements could...
Black hole solution and strong gravitational lensing in Eddington-inspired Born-Infeld gravity
NASA Astrophysics Data System (ADS)
Wei, Shao-Wen; Yang, Ke; Liu, Yu-Xiao
2015-06-01
A new theory of gravity called Eddington-inspired Born-Infeld (EiBI) gravity was recently proposed by Bañados and Ferreira. This theory leads to some exciting new features, such as free of cosmological singularities. In this paper, we first obtain a charged EiBI black hole solution with a nonvanishing cosmological constant when the electromagnetic field is included in. Then based on it, we study the strong gravitational lensing by the asymptotic flat charged EiBI black hole. The strong deflection limit coefficients and observables are shown to closely depend on the additional coupling parameter in the EiBI gravity. It is found that, compared with the corresponding charged black hole in general relativity, the positive coupling parameter will shrink the black hole horizon and photon sphere. Moreover, the coupling parameter will decrease the angular position and relative magnitudes of the relativistic images, while increase the angular separation, which may shine new light on testing such gravity theory in near future by the astronomical instruments.
The Remarkable ?-Ray Activity in the Gravitationally Lensed Blazar PKS 1830-211
NASA Astrophysics Data System (ADS)
Donnarumma, I.; De Rosa, A.; Vittorini, V.; Miller, H. R.; Popovi?, L. ?.; Simi?, S.; Tavani, M.; Eggen, J.; Maune, J.; Kuulkers, E.; Striani, E.; Vercellone, S.; Pucella, G.; Verrecchia, F.; Pittori, C.; Giommi, P.; Pacciani, L.; Barbiellini, G.; Bulgarelli, A.; Cattaneo, P. W.; Chen, A. W.; Costa, E.; Del Monte, E.; Evangelista, Y.; Feroci, M.; Fuschino, F.; Gianotti, F.; Giuliani, A.; Giusti, M.; Lazzarotto, F.; Longo, F.; Lucarelli, F.; Pellizzoni, A.; Piano, G.; Soffitta, P.; Trifoglio, M.; Trois, A.
2011-08-01
We report the extraordinary ?-ray activity (E > 100 MeV) of the gravitationally lensed blazar PKS 1830-211 (z = 2.507) detected by AGILE between 2010 October and November. On October 14, the source experienced a factor of ~12 flux increase with respect to its average value and remained brightest at this flux level (~500 × 10-8 photons cm-2 s-1) for about four days. The one-month ?-ray light curve across the flare showed a mean flux F(E > 100 MeV) = 200 × 10-8 photons cm-2 s-1, which resulted in a factor of four enhancement with respect to the average value. Following the ?-ray flare, the source was observed in near-IR (NIR)-optical energy bands at the Cerro Tololo Inter-American Observatory and in X-Rays by Swift/X-Ray Telescope and INTEGRAL/IBIS. The main result of these multifrequency observations is that the large variability observed in ?-rays does not have a significant counterpart at lower frequencies: no variation greater than a factor of ~1.5 appeared in the NIR and X-Ray energy bands. PKS 1830-211 is then a good "?-ray only flaring" blazar showing substantial variability only above 10-100 MeV. We discuss the theoretical implications of our findings.
The abundance of lensing protoclusters
Anson D'Aloisio; Steven R. Furlanetto; Priyamvada Natarajan
2008-12-22
Weak gravitational lensing provides a potentially powerful method for the detection of clusters. In addition to cluster candidates, a large number of objects with possibly no optical or X-ray component have been detected in shear-selected samples. We develop an analytic model to investigate the claim of Weinberg & Kamionkowski (2002) that unvirialised protoclusters account for a significant number of these so-called "dark" lenses. In our model, a protocluster consists of a small virialised region surrounded by in-falling matter. We find that, in order for a protocluster to simultaneously escape X-ray detection and create a detectable weak lensing signal, it must have a small virial mass (~10^{13} \\Msun) and large total mass (~ 10^{15} \\Msun), with a relatively flat density profile outside of the virial radius. Such objects would be characterized by rising tangential shear profiles well beyond the virial radius. We use a semi-analytic approach based on the excursion set formalism to estimate the abundance of lensing protoclusters with a low probability of X-ray detection. We find that they are extremely rare, accounting for less than 0.4 per cent of the total lenses in a survey with background galaxy density n = 30 arcmin^{-2} and an intrinsic ellipticity dispersion of 0.3. We conclude that lensing protoclusters with undetectable X-Ray luminosities are too rare to account for a significant number of dark lenses.
Cross-correlation Weak Lensing of SDSS Galaxy Clusters III: Mass-to-light Ratios
Erin S. Sheldon; David E. Johnston; Morad Masjedi; Timothy A. McKay; Michael R. Blanton; Ryan Scranton; Risa H. Wechsler; Ben P. Koester; Sarah M. Hansen; Joshua A. Frieman; James Annis
2008-02-27
We present measurements of the excess mass-to-light ratio measured aroundMaxBCG galaxy clusters observed in the SDSS. This red sequence cluster sample includes objects from small groups with masses ranging from ~5x10^{12} to ~10^{15} M_{sun}/h. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean \\Delta \\rho(r) = \\rho(r) - \\bar{\\rho} for clusters in bins of richness and optical luminosity. We also measure the excess luminosity density \\Delta l(r) = l(r) - \\bar{l} measured in the z=0.25 i-band. For both mass and light, we de-project the profiles to produce 3D mass and light profiles over scales from 25 kpc/ to 22 Mpc/h. From these profiles we calculate the cumulative excess mass M(r) and excess light L(r) as a function of separation from the BCG. On small scales, where \\rho(r) >> \\bar{\\rho}, the integrated mass-to-light profile may be interpreted as the cluster mass-to-light ratio. We find the M/L_{200}, the mass-to-light ratio within r_{200}, scales with cluster mass as a power law with index 0.33+/-0.02. On large scales, where \\rho(r) ~ \\bar{\\rho}, the M/L approaches an asymptotic value independent of cluster richness. For small groups, the mean M/L_{200} is much smaller than the asymptotic value, while for large clusters it is consistent with the asymptotic value. This asymptotic value should be proportional to the mean mass-to-light ratio of the universe . We find /b^2_{ml} = 362+/-54 h (statistical). There is additional uncertainty in the overall calibration at the ~10% level. The parameter b_{ml} is primarily a function of the bias of the L <~ L_* galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find \\Omega_m/b^2_{ml} = 0.02+/-0.03, independent of the Hubble parameter.
NASA Astrophysics Data System (ADS)
Baxter, E. J.; Keisler, R.; Dodelson, S.; Aird, K. A.; Allen, S. W.; Ashby, M. L. N.; Bautz, M.; Bayliss, M.; Benson, B. A.; Bleem, L. E.; Bocquet, S.; Brodwin, M.; Carlstrom, J. E.; Chang, C. L.; Chiu, I.; Cho, H.-M.; Clocchiatti, A.; Crawford, T. M.; Crites, A. T.; Desai, S.; Dietrich, J. P.; de Haan, T.; Dobbs, M. A.; Foley, R. J.; Forman, W. R.; George, E. M.; Gladders, M. D.; Gonzalez, A. H.; Halverson, N. W.; Harrington, N. L.; Hennig, C.; Hoekstra, H.; Holder, G. P.; Holzapfel, W. L.; Hou, Z.; Hrubes, J. D.; Jones, C.; Knox, L.; Lee, A. T.; Leitch, E. M.; Liu, J.; Lueker, M.; Luong-Van, D.; Mantz, A.; Marrone, D. P.; McDonald, M.; McMahon, J. J.; Meyer, S. S.; Millea, M.; Mocanu, L. M.; Murray, S. S.; Padin, S.; Pryke, C.; Reichardt, C. L.; Rest, A.; Ruhl, J. E.; Saliwanchik, B. R.; Saro, A.; Sayre, J. T.; Schaffer, K. K.; Shirokoff, E.; Song, J.; Spieler, H. G.; Stalder, B.; Stanford, S. A.; Staniszewski, Z.; Stark, A. A.; Story, K. T.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Williamson, R.; Zahn, O.; Zenteno, A.
2015-06-01
Clusters of galaxies are expected to gravitationally lens the cosmic microwave background (CMB) and thereby generate a distinct signal in the CMB on arcminute scales. Measurements of this effect can be used to constrain the masses of galaxy clusters with CMB data alone. Here we present a measurement of lensing of the CMB by galaxy clusters using data from the South Pole Telescope (SPT). We develop a maximum likelihood approach to extract the CMB cluster lensing signal and validate the method on mock data. We quantify the effects on our analysis of several potential sources of systematic error and find that they generally act to reduce the best-fit cluster mass. It is estimated that this bias to lower cluster mass is roughly 0.85? in units of the statistical error bar, although this estimate should be viewed as an upper limit. We apply our maximum likelihood technique to 513 clusters selected via their Sunyaev–Zeldovich (SZ) signatures in SPT data, and rule out the null hypothesis of no lensing at 3.1?. The lensing-derived mass estimate for the full cluster sample is consistent with that inferred from the SZ flux: {M}200,{lens}={0.83}-0.37+0.38 {M}200,{SZ} (68% C.L., statistical error only).
Cusped Mass Density Profiles and Magnification Ratios of Double Image Gravitational Lenses
P. T. Mutka
2009-01-01
We have been able to connect the statistics of the observed double image\\u000agravitational lenses to the general properties of the internal structure of\\u000adark matter haloes. Our analytical theory for the GNFW lenses with parametrized\\u000acusp slope (alpha) gives us a relation connecting the cusp slope of the lensing\\u000aprofile to the observed magnification ratio of the produced images
Probing Structure in Cold Gas at z <~ 1 with Gravitationally Lensed Quasar Sightlines
NASA Astrophysics Data System (ADS)
Kulkarni, Varsha
2014-10-01
Absorption lines in quasar spectra offer a powerful tool to study distant galaxies and intergalactic matter (IGM). The strongest of these absorbers, the damped Lyman-alpha (DLA) and sub-DLA absorbers constitute a large fraction of the neutral gas in galaxies. Galaxies located in front of gravitationally lensed quasars (GLQs) are probed by multiple sightlines; so DLA/sub-DLAs in these sightlines can probe the internal structure of interstellar material (ISM) and/or the environment of these galaxies. From the lens galaxy images, impact parameters of the absorbing regions from the galaxy centers can be obtained accurately. Unfortunately, very little information exists on the neutral gas and metal content of DLA/sub-DLAs located in front of GLQs with confirmed lens galaxies. This is because at low redshift where lens galaxies are well-imaged, the H I and key metal lines lie in the UV. Here we propose to study 6 GLQs with known lens redshifts and a total of 14 closely separated double or quadruple images, that show candidate DLA/sub-DLAs along multiple sightlines. Our goal is to measure H I Lyman-alpha absorption in these sightlines. Many of these absorbers are at the lens redshift, with impact parameters 0.6-5.8 kpc. Our observations will therefore allow us to constrain gradients in H I column density and metallicity (combining H I with ground-based metal line measurements) within these galaxies. Our data will also help to constrain the sizes of DLA/sub-DLA absorbing regions by increasing the existing sample of DLA/sub-DLAs probed at < 10 kpc separations by a factor of ~3. HST is essential because of the need for both UV coverage and high spatial resolution.
Chandra Observations of the Gravitational Lenses B1600+434 and B1608+656
NASA Astrophysics Data System (ADS)
Dai, Xinyu; Kochanek, Christopher S.
2005-06-01
We observed B1600+434 and B1608+656 with Chandra ACIS, detecting both quasar images in B1600+434 and three of four images in B1608+656. We did not detect significant X-ray emission from nearby galaxy groups or clusters associated with each lens galaxy. The upper limits on the X-ray luminosity of any cluster within 4' of each lens and at each lens redshift are ~2×1042 and ~6×1042 ergs s-1 for B1600+434 and B1608+656, respectively. The radio-loud source quasars have power-law photon indices of ?=1.9+/-0.2 and ?=1.4+/-0.3 and X-ray luminosities of 1.4+0.2-0.1×1045 and 2.9+0.7-0.4×1044 ergs s-1 for B1600+434 and B1608+656, respectively, before correcting for the magnification. We detected a differential absorption column density of ?NH~3×1021cm-2 between the two images of B1600+434, roughly consistent with expectations from differential extinction estimates of ?E(B-V)=0.1 mag and a standard dust-to-gas ratio. The differential absorption observed in gravitational lenses may serve as an important probe to study the gas content in high-redshift galaxies, since it can separate the absorbing column originating from the lens galaxy and those intrinsic to quasars. We also detected 157 serendipitous X-ray sources in the two Chandra fields and identified the brighter optical counterparts using the Sloan Digital Sky Survey and Palomar Digital Sky Survey.
Chandra Observations of Gravitational Lenses B1600+434 and B1608+656
Xinyu Dai; Christopher S. Kochanek
2005-02-01
We observed B1600+434 and B1608+656 with CXO/ACIS, detecting both quasar images in B1600+434 and three of four images in B1608+656. We did not detect significant X-ray emission from nearby galaxy groups or clusters associated with each lens galaxy. The upper limits on the X-ray luminosity of any cluster within 4 arcmin of each lens and at each lens redshift are of ~2\\times10^{42} and ~6\\times10^{42} erg/s for B1600+434 and B1608+656, respectively. The radio-loud source quasars have power-law photon indices of \\Gamma=1.9\\pm0.2 and \\Gamma=1.4\\pm0.3 and X-ray luminosities of 1.4^{+0.2}_{-0.1}\\times10^{45} and 2.9^{+0.7}_{-0.4}\\times10^{44} erg/s for B1600+434 and B1608+656, respectively before correcting for the magnification. We detected a differential absorption column density of \\Delta N_H ~ 3\\times10^{21} cm^{-2} between the two images of B1600+434, roughly consistent with expectations from differential extinction estimates of \\Delta E(B-V)=0.1 mag and a standard dust-to-gas ratio. The differential absorption observed in gravitational lenses may serve as an important probe to study the gas content in high redshift galaxies since it can separate the absorbing column originating from the lens galaxy and those intrinsic to quasars. We also detected 157 serendipitous X-ray sources in the two Chandra fields and identified the brighter optical counterparts using the SDSS and DPOSS surveys.
NASA Astrophysics Data System (ADS)
Gaztañaga, Enrique
2003-05-01
We report a detection of a galaxy-QSO cross-correlation wGQ in the Sloan Digital Sky Survey early data release over 0.2?-30' scales. We cross-correlate galaxy samples of different mean depths r'=19-22 (zG=0.15-0.35) with the main QSO population (i'Q<19.1) at zQ~=1.6. We find significant positive correlation in all cases except for the faintest QSOs, as expected if the signal were due to weak-lensing magnification. The amplitude of the signal on arcminute scales is about 20% at zG=0.15, decreasing to 10% at zG=0.35. This is a few times larger than currently expected from weak lensing in the ?CDM models but confirms, at a higher significance, previous measurements by several groups. When compared to the galaxy-galaxy correlation wGG, a weak-lensing interpretation indicates a strong and steep nonlinear amplitude for the underlying matter fluctuations: ?~=400 on scales of 0.2 Mpc h-1, in contradiction with nonlinear modeling of ?CDM fluctuations. We also detect a normalized skewness (galaxy-galaxy-QSO correlation) of S3~=21+/-6 at z~=0.15 (S3~=14+/-4 at z~=0.35), which is several standard deviations low compared to standard ?CDM expectations. These observational trends can be reconciled with lensing in a flat ? universe with ?8~=1, provided that the linear spectrum is steeper (n~=1) than in the ?CDM model on small (cluster) scales. Under this interpretation, the galaxy distribution traces the matter variance with an amplitude that is 100 times smaller; i.e., galaxies are antibiased with b~=0.1 on small scales, increasing to b~=1 at ~=10 Mpc h-1.
Background sky obscuration by cluster galaxies as a source of systematic error for weak lensing
NASA Astrophysics Data System (ADS)
Simet, Melanie; Mandelbaum, Rachel
2015-05-01
Lensing magnification and stacked shear measurements of galaxy clusters rely on measuring the density of background galaxies behind the clusters. The most common ways of measuring this quantity ignore the fact that some fraction of the sky is obscured by the cluster galaxies themselves, reducing the area in which background galaxies can be observed. We discuss the size of this effect in the Sloan Digital Sky Survey (SDSS) and the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), finding a minimum 1 per cent effect at 0.1 h-1 Mpc from the centres of clusters in SDSS; the effect is an order of magnitude higher in CFHTLenS. The resulting biases on cluster mass and concentration measurements are of the same order as the size of the obscuration effect, which is below the statistical errors for cluster lensing in SDSS but likely exceeds them for CFHTLenS. We also forecast the impact of this systematic error on cluster mass and magnification measurements in several upcoming surveys, and find that it typically exceeds the statistical errors. We conclude that future surveys must account for this effect in stacked lensing and magnification measurements in order to avoid being dominated by systematic error.
Nebular and global properties of the gravitationally lensed galaxy "the 8 o'clock arc"
NASA Astrophysics Data System (ADS)
Dessauges-Zavadsky, M.; Christensen, L.; D'Odorico, S.; Schaerer, D.; Richard, J.
2011-09-01
We present the analysis of new near-infrared, intermediate-resolution spectra of the gravitationally lensed galaxy "the 8 o'clock arc" at zsys = 2.7350 obtained with the X-shooter spectrograph on the Very Large Telescope. These rest-frame optical data, combined with Hubble and Spitzer Space Telescopes images, provide very valuable information, which nicely complement our previous detailed rest-frame UV spectral analysis, and make the 8 o'clock arc one of the better understood "normal" star-forming galaxies at this early epoch of the history of the Universe. From high-resolution HST images, we reconstruct the morphology of the arc in the source plane, and identify that the source is formed of two majors parts, the main galaxy component and a smaller blob separated by 1.2 kpc in projected distance. The blob, with a twice larger magnification factor, is resolved in the X-shooter spectra. The multi-Gaussian fitting of detected nebular emission lines and the spectral energy distribution modeling of the available multi-wavelength photometry provide the census of gaseous and stellar dust extinctions, gas-phase metallicities, star-formation rates (SFRs), and stellar, gas, and dynamical masses for both the main galaxy and the blob. As a result, the 8 o'clock arc shows a marginal trend for a more attenuated ionized gas than stars, and supports a dependence of the dust properties on the SFR. With a high specific star-formation rate, SSFR = 33 ± 19 Gyr-1, this lensed Lyman-break galaxy deviates from the mass-SFR relation, and is characterized by a young age of 40+25-20 Myr and a high gas fraction of about 72%. The 8 o'clock arc satisfies the fundamental mass, SFR, and metallicity relation, and favors that it holds up beyond z ? 2.5. We believe that the blob, with a gas mass Mgas = (2.2 ± 0.9) × 109 M? (one order of magnitude lower than the mass of the galaxy), a half-light radius r1/2 = 0.53 ± 0.05 kpc, a star-formation rate SFRH? = 33 ± 19 M? yr-1, and in rotation around the main core of the galaxy, is one of these star-forming clumps commonly observed in z > 1 star-forming galaxies, because it is characterized by very similar physical properties. The knowledge of detailed physical properties of these clumps is a very useful input to models that aim to predict the formation and evolution of these clumps within high-redshift objects. Based on X-shooter observations made with the European Southern Observatory VLT/Kueyen telescope, Paranal, Chile, collected under the programme ID No. 284.A-5006(A).Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute.
LoCuSS: Exploring the selection of faint blue background galaxies for cluster weak-lensing
Ziparo, Felicia; Okabe, Nobuhiro; Haines, Chris P; Pereira, Maria J; Egami, Eiichi
2015-01-01
Cosmological constraints from galaxy clusters rely on accurate measurements of the mass and internal structure of clusters. An important source of systematic uncertainty in cluster mass and structure measurements is the secure selection of background galaxies that are gravitationally lensed by clusters. This issue has been shown to be particular severe for faint blue galaxies. We therefore explore the selection of faint blue background galaxies, by reference to photometric redshift catalogs derived from the COSMOS survey and our own observations of massive galaxy clusters at z~0.2. We show that methods relying on photometric redshifts of galaxies in/behind clusters based on observations through five filters, and on deep 30-band COSMOS photometric redshifts are both inadequate to identify safely faint blue background galaxies. This is due to the small number of filters used by the former, and absence of massive galaxy clusters at redshifts of interest in the latter. We therefore develop a pragmatic method to c...
Wiesner, Matthew P; Soares-Santos, Marcelle
2015-01-01
We present mass-richness relations found in the Sloan Digital Sky Survey Stripe 82 co-add. These relations were found using stacked weak lensing shear observed in a large sample of galaxy clusters. These mass-richness relations are presented for four redshift bins, $0.1 bias weak lensing measurements, including photometric redshift bias, the effect of the central BCG, halo miscentering, photometric redshift uncertainty and foreground galaxy contamination. We present mass-richness relations using richness measure $N_{VT}$ with each of these effects considered separately as well as considered altogether. We present values fo...
Mapping the 3D dark matter with weak lensing in COMBO17
A. N. Taylor; D. J. Bacon; M. E. Gray; C. Wolf; K. Meisenheimer; S. Dye; A. Borch; M. Kleinheinrich; Z. Kovacs; L. Wisotzki
2004-01-01
We present a three-dimensional (3D) lensing analysis of the z= 0.16 supercluster A901\\/2, resulting in a 3D map of the dark matter distribution within a 3 × 105[h-1 Mpc]3 volume. This map is generated from a combined catalogue of 3D galaxy coordinates together with shear estimates, using R-band imaging and photometric redshifts from the COMBO-17 survey. We perform a chi2