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.
Weak gravitational lensing with SKA
Peter Schneider
1999-07-12
I shall outline the basic principles and some observational aspects of weak gravitational lensing, and discuss several applications of this powerful tool in observational cosmology. It will be explained why the applications have been restricted to optical observations up to now, and why SKA is going to change this. I conclude with a few general remarks on a comparison between SKA and the NGST, both being facilities which will provide a tremendous step forward in radio and near-IR astronomy, respectively, into completely unknown territory.
Weak gravitational lensing with DEIMOS
NASA Astrophysics Data System (ADS)
Melchior, P.; Viola, M.; Schäfer, B. M.; Bartelmann, M.
2011-04-01
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 point spread function (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 accuracy and capabilities of this new method in the context of weak gravitational lensing measurements with a set of specialized tests and show its competitive performance on the GREAT08 Challenge data. A complete C++ implementation of the method can be requested from the authors.
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.
Instrumental systematics and weak gravitational lensing
Mandelbaum, Rachel
2015-01-01
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.
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...
Precision cosmology with weak gravitational lensing
NASA Astrophysics Data System (ADS)
Hearin, Andrew P.
In recent years, cosmological science has developed a highly predictive model for the universe on large scales that is in quantitative agreement with a wide range of astronomical observations. While the number and diversity of successes of this model provide great confidence that our general picture of cosmology is correct, numerous puzzles remain. In this dissertation, I analyze the potential of planned and near future galaxy surveys to provide new understanding of several unanswered questions in cosmology, and address some of the leading challenges to this observational program. In particular, I study an emerging technique called cosmic shear, the weak gravitational lensing produced by large scale structure. I focus on developing strategies to optimally use the cosmic shear signal observed in galaxy imaging surveys to uncover the physics of dark energy and the early universe. In chapter 1 I give an overview of a few unsolved mysteries in cosmology and I motivate weak lensing as a cosmological probe. I discuss the use of weak lensing as a test of general relativity in chapter 2 and assess the threat to such tests presented by our uncertainty in the physics of galaxy formation. Interpreting the cosmic shear signal requires knowledge of the redshift distribution of the lensed galaxies. This redshift distribution will be significantly uncertain since it must be determined photometrically. In chapter 3 I investigate the influence of photometric redshift errors on our ability to constrain dark energy models with weak lensing. The ability to study dark energy with cosmic shear is also limited by the imprecision in our understanding of the physics of gravitational collapse. In chapter 4 I present the stringent calibration requirements on this source of uncertainty. I study the potential of weak lensing to resolve a debate over a long-standing anomaly in CMB measurements in chapter 5. Finally, in chapter 6 I summarize my findings and conclude with a brief discussion of my outlook on the future of weak lensing studies of cosmology.
Simulating weak gravitational lensing for cosmology
Kiessling, Alina Anne
2011-11-23
This thesis will present a new cosmic shear analysis pipeline SUNGLASS (Simulated UNiverses for Gravitational Lensing Analysis and Shear Surveys). SUNGLASS is a pipeline that rapidly generates simulated universes for ...
Weak gravitational lensing with the Square Kilometre Array
Brown, M L; Camera, S; Harrison, I; Joachimi, B; Metcalf, R B; Pourtsidou, A; Takahashi, K; Zuntz, J A; Abdalla, F B; Bridle, S; Jarvis, M; Kitching, T D; Miller, L; Patel, P
2015-01-01
We investigate the capabilities of various stages of the SKA to perform world-leading weak gravitational lensing surveys. We outline a way forward to develop the tools needed for pursuing weak lensing in the radio band. We identify the key analysis challenges and the key pathfinder experiments that will allow us to address them in the run up to the SKA. We identify and summarize the unique and potentially very powerful aspects of radio weak lensing surveys, facilitated by the SKA, that can solve major challenges in the field of weak lensing. These include the use of polarization and rotational velocity information to control intrinsic alignments, and the new area of weak lensing using intensity mapping experiments. We show how the SKA lensing surveys will both complement and enhance corresponding efforts in the optical wavebands through cross-correlation techniques and by way of extending the reach of weak lensing to high redshift.
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.
Karhunen-Loeve Analysis for Weak Gravitational Lensing
Vanderplas, Jacob T
2013-01-01
In the past decade, weak gravitational lensing has become an important tool in the study of the universe at the largest scale, giving insights into the distribution of dark matter, the expansion of the universe, and the nature of dark energy. This thesis research explores several applications of Karhunen-Loeve (KL) analysis to speed and improve the comparison of weak lensing shear catalogs to theory in order to constrain cosmological parameters in current and future lensing surveys. After providing a brief introduction to cosmology and to KL analysis, this work addresses three related aspects of weak lensing analysis: (1) Three-dimensional tomographic mapping (based on work published in Vanderplas et al. 2011); (2) Shear peak statistics with incomplete/gappy data (based on work published in Vanderplas et al. 2012); and (3) two-point parameter estimation from gappy data using KL modes (previously unpublished)... [this abstract has been abbreviated; please see the thesis for the full abstract].
Gravitational Potential Reconstruction from Peculiar Velocity and Weak Lensing Measurements
Olivier Doré; Lloyd Knox; Alan Peel
2002-07-18
We present an analytic method for rapidly forecasting the accuracy of gravitational potential reconstruction possible from measurement of radial peculiar velocities of every galaxy cluster with M > M_th in solid angle \\theta^2 and over redshift range z_min gravitational potential (on length scales > 60 Mpc) can be reconstructed for every ~8 cluster velocity determinations. Deeper surveys require measurement of more clusters per S/N > 1 mode. Accuracy is limited by the ``undersampling noise'' due to our non-observation of the large fraction of mass that is not in galaxy clusters. Determining the gravitational potential will allow for detailed study of the relationship between galaxies and their surrounding large-scale density fields over a wide range of redshifts, and test the gravitational instability paradigm on very large scales. Observation of weak lensing by large-scale structure provides complementary information since lensing is sensitive to the tangential modes that do not affect the velocity.
Digging into Dark Matter with Weak Gravitational Lensing
NASA Astrophysics Data System (ADS)
Massey, R.
2010-07-01
Ordinary baryonic particles (such as protons and neutrons) account for only one-sixth of the total matter in the Universe. The remainder is a mysterious “dark matter” component, which does not interact via the electromagnetic force and thus neither emits nor reflects light. However, evidence is mounting for its gravitational influence. The past few years have seen particular progress in observations of weak gravitational lensing, the slight deflection of light from distant galaxies due to the curvature of space around foreground mass. Recent surveys from the Hubble Space Telescope have provided direct proof for dark matter, and the first measurements of its properties. We review recent results, then prospects and challenges for future gravitational lensing surveys.
The general theory of secondary weak gravitational lensing
NASA Astrophysics Data System (ADS)
Clarkson, Chris
2015-09-01
Weak gravitational lensing is normally assumed to have only two principle effects: a magnification of a source and a distortion of the sources shape in the form of a shear. However, further distortions are actually present owing to changes in the gravitational field across the scale of the ray bundle of light propagating to us, resulting in the familiar arcs in lensed images. This is normally called the flexion, and is approximated by Taylor expanding the shear and magnification across the image plane. However, the physical origin of this effect arises from higher-order corrections in the geodesic deviation equation governing the gravitational force between neighbouring geodesics— so involves derivatives of the Riemann tensor. We show that integrating the second-order geodesic deviation equation results in a `Hessian map' for gravitational lensing, which is a higher-order addition to the Jacobi map. We derive the general form of the Hessian map in an arbitrary spacetime paying particular attention to the separate effects of local Ricci versus non-local Weyl curvature. We then specialise to the case of a perturbed FLRW model, and give the general form of the Hessian for the first time. This has a host of new contributions which could in principle be used as tests for modified gravity.
The general theory of secondary weak gravitational lensing
Clarkson, Chris
2015-01-01
Weak gravitational lensing is normally assumed to have only two principle effects: a magnification of a source and a distortion of the sources shape in the form of a shear. However, further distortions are actually present owing to changes in the gravitational field across the scale of the ray bundle of light propagating to us, resulting in the familiar arcs in lensed images. This is normally called the flexion, and is approximated by Taylor expanding the shear and magnification across the image plane. However, the physical origin of this effect arises from higher-order corrections in the geodesic deviation equation governing the gravitational force between neighbouring geodesics - so involves derivatives of the Riemann tensor. We show that integrating the second-order geodesic deviation equation results in a 'Hessian map' for gravitational lensing, which is a higher-order addition to the Jacobi map. We derive the general form of the Hessian map in an arbitrary spacetime paying particular attention to the sep...
The general theory of secondary weak gravitational lensing
Chris Clarkson
2015-03-30
Weak gravitational lensing is normally assumed to have only two principle effects: a magnification of a source and a distortion of the sources shape in the form of a shear. However, further distortions are actually present owing to changes in the gravitational field across the scale of the ray bundle of light propagating to us, resulting in the familiar arcs in lensed images. This is normally called the flexion, and is approximated by Taylor expanding the shear and magnification across the image plane. However, the physical origin of this effect arises from higher-order corrections in the geodesic deviation equation governing the gravitational force between neighbouring geodesics - so involves derivatives of the Riemann tensor. We show that integrating the second-order geodesic deviation equation results in a 'Hessian map' for gravitational lensing, which is a higher-order addition to the Jacobi map. We derive the general form of the Hessian map in an arbitrary spacetime paying particular attention to the separate effects of local Ricci versus non-local Weyl curvature. We then specialise to the case of a perturbed FLRW model, and give the general form of the Hessian for the first time. This has a host of new contributions which could in principle be used as tests for modified gravity.
Weak Gravitational Lensing from Regular Bardeen Black Holes
NASA Astrophysics Data System (ADS)
Ghaffarnejad, Hossein; niad, Hassan
2015-09-01
In this article we study weak gravitational lensing of regular Bardeen black hole which has scalar charge g and mass m. We investigate the angular position and magnification of non-relativistic images in two cases depending on the presence or absence of photon sphere. Defining dimensionless charge parameter q=g/2m we seek to disappear photon sphere in the case of |q|>{24?5}/{125} for which the space time metric encounters strongly with naked singularities. We specify the basic parameters of lensing in terms of scalar charge by using the perturbative method and found that the parity of images is different in two cases: (a) The strongly naked singularities is present in the space time. (b) singularity of space time is weak or is eliminated (the black hole lens).
Resource Letter: Gravitational Lensing
Treu, T; Clowe, D
2012-01-01
This Resource Letter provides a guide to a selection of the literature on gravitational lensing and its applications. Journal articles, books, popular articles, and websites are cited for the following topics: foundations of gravitational lensing, foundations of cosmology, history of gravitational lensing, strong lensing, weak lensing, and microlensing.
Karhunen-Loeve Analysis for Weak Gravitational Lensing
NASA Astrophysics Data System (ADS)
Vanderplas, Jacob T.
In the past decade, weak gravitational lensing has become an important tool in the study of the universe at the largest scale, giving insights into the distribution of dark matter, the expansion of the universe, and the nature of dark energy. This thesis research explores several applications of Karhunen-Loève (KL) analysis to speed and improve the comparison of weak lensing shear catalogs to theory in order to constrain cosmological parameters in current and future lensing surveys. This work addresses three related aspects of weak lensing analysis: Three-dimensional Tomographic Mapping: (Based on work published in Vanderplas et al 2011) We explore a new fast approach to three-dimensional mass mapping in weak lensing surveys. The KL approach uses a KL-based filtering of the shear signal to reconstruct mass structures on the line-of-sight, and provides a unified framework to evaluate the efficacy of linear reconstruction techniques. We find that the KL-based filtering leads to near-optimal angular resolution, and computation times which are faster than previous approaches. We also use the KL formalism to show that linear non-parametric reconstruction methods are fundamentally limited in their ability to resolve lens redshifts. Shear Peak Statistics with Incomplete Data: (Based on work published in Vanderplas et al 2012) We explore the use of KL eigenmodes for interpolation across masked regions in observed shear maps. Mass mapping is an inherently non-local calculation, meaning gaps in the data can have a significant effect on the properties of the derived mass map. Our KL mapping procedure leads to improvements in the recovery of detailed statistics of peaks in the mass map, which holds promise of improved cosmological constraints based on such studies. Two-point parameter estimation with KL modes: The power spectrum of the observed shear can yield powerful cosmological constraints. Incomplete survey sky coverage, however, can lead to mixing of power between Fourier modes, and obfuscate the cosmologically sensitive signal. We show that KL can be used to derive an alternate orthonormal basis for the problem which avoids mode-mixing and allows a convenient formalism for cosmological likelihood computations. Cosmological constraints derived using this method are shown to be competitive with those from the more conventional correlation function approach. We also discuss several aspects of the KL approach which will allow improved handling of correlated errors and redshift information in future surveys.
Quantum Lukewarm Black Holes and Weak Gravitational Lensing
Ghaffarnejad, H
2015-01-01
Aim of the paper is study gravitational lensing of quantum Lukewarm black hole (QLBL) and compare with results of gravitational lensing from classical Lukewarm black hole lens (CLBL). Applying numerical method, we evaluate deflection angle, image positions and magnifications in weak deflection limits. In CLBL case, bending light ray moves from both side of the lens but in QLBL case it moves from one side of the lens. Increasing amount of dimensionless cosmological parameter (quantum matter interaction parameter), rake of bending light ray is decreased in case of QLBL with respect to CLBL. Number and size of radius of Einstein rings rises in case of QLBL with respect to CLBL. Maximum number of rings is 3 in case of QLBL namely one more with respect to case of CLBL which is physically related to effects of quantum matter. There is two images (elementary and secondary) with maximum magnification which their locations are changed in case of QLBL with respect to case of CLBL. Also their locations changed by increa...
Radio Weak Gravitational Lensing with VLA and MERLIN
Patel, P; Beswick, R J; Muxlow, T W B; Hoyle, B
2009-01-01
We carry out an exploratory weak gravitational lensing analysis on a combined VLA and MERLIN radio data set: a deep (3.3 micro-Jy beam^-1 rms noise) 1.4 GHz image of the Hubble Deep Field North. We measure the shear estimator distribution at this radio sensitivity for the first time, finding a similar distribution to that of optical shear estimators for HST ACS data in this field. We examine the residual systematics in shear estimation for the radio data, and give cosmological constraints from radio-optical shear cross-correlation functions. We emphasize the utility of cross-correlating shear estimators from radio and optical data in order to reduce the impact of systematics. Unexpectedly we find no evidence of correlation between optical and radio intrinsic ellipticities of matched objects; this result improves the properties of optical-radio lensing cross-correlations. We explore the ellipticity distribution of the radio counterparts to optical sources statistically, confirming the lack of correlation; as a...
LIGHT ON DARK MATTER WITH WEAK GRAVITATIONAL LENSING 1 Light on Dark Matter
Starck, Jean-Luc
LIGHT ON DARK MATTER WITH WEAK GRAVITATIONAL LENSING 1 Light on Dark Matter with Weak Gravitational reviews statistical methods re- cently developed to reconstruct and analyze dark matter mass maps from decades showing that the visible matter represents only about 4-5% of the Universe, the rest being dark
Detection of (dark) matter concentrations via weak gravitational lensing
Peter Schneider
1996-01-16
The distortion of images of faint background galaxies by (weak) gravitational lensing can be used to measure the mass distribution of the deflector. The image distortions can be used to define a weighted mean of the mass inside a circular aperture, as was first suggested by Kaiser. The aperture mass can be used to {\\it detect} dark matter concentrations. Keeping in mind that wide-field cameras will become increasingly available, this method can be used to search for mass concentrations on wide-field images. To do this, the aperture mass measure is generalized to account for different weighting functions. For each such weighting function, a signal-to-noise ratio can be calculated. For an assumed mass profile of the density concentrations, the weighting function can be chosen such as to maximize the resulting signal-to-noise ratio. Numerical simulations which adopt parameters characteristic of 4-m class telescopes are then used to show that dark halos with a velocity dispersion in excess of $\\sim 600$\\ts km/s can be reliably detected as significant peaks in the signal-to-noise map. The effects of seeing and an anisotropic PSF are then investigated and shown to be less important than might be feared. It is thus suggested that the method of aperture mass measures developed here can be used to obtain a mass-selected sample of dark halos, in contrast to flux-selected samples. Shear fields around high-redshift bright QSOs as detected by Fort et al. provide a first successful application of this strategy. The simplicity of the method allows its routine application to wide-field images of sufficient depth and image quality.
Constraining modified gravitational theories by weak lensing with Euclid
Martinelli, Matteo; Calabrese, Erminia; De Bernardis, Francesco; Melchiorri, Alessandro; Pagano, Luca; Scaramella, Roberto
2011-01-15
Future proposed satellite missions such as Euclid can offer the opportunity to test general relativity on cosmic scales through mapping of the galaxy weak-lensing signal. In this paper we forecast the ability of these experiments to constrain modified gravity scenarios such as those predicted by scalar-tensor and f(R) theories. We find that Euclid will improve constraints expected from the Planck satellite on these modified theories of gravity by 2 orders of magnitude. We discuss parameter degeneracies and the possible biases introduced by modifications to gravity.
Gravitational lensing beyond the weak-field approximation
NASA Astrophysics Data System (ADS)
Perlick, Volker
2014-01-01
Gravitational lensing is considered in the full spacetime formalism of general relativity, assuming that the light rays are lightlike geodesics in a Lorentzian manifold. The review consists of three parts. The first part is devoted to spherically symmetric and static spacetimes. In particular, an exact lens map for this situation is discussed. The second part is on axisymmetric and stationary spacetimes. It concentrates on the investigation of the photon region, i.e., the region filled by spherical lightlike geodesics, in the Kerr spacetime. The photon region is of crucial relevance for the formation of a shadow. Finally, the third part briefly addresses two topics that apply to spacetimes without symmetry, namely Fermat's principle and the exact lens map of Frittelli and Newman.
Gravitational lensing beyond the weak-field approximation
Perlick, Volker
2014-01-14
Gravitational lensing is considered in the full spacetime formalism of general relativity, assuming that the light rays are lightlike geodesics in a Lorentzian manifold. The review consists of three parts. The first part is devoted to spherically symmetric and static spacetimes. In particular, an exact lens map for this situation is discussed. The second part is on axisymmetric and stationary spacetimes. It concentrates on the investigation of the photon region, i.e., the region filled by spherical lightlike geodesics, in the Kerr spacetime. The photon region is of crucial relevance for the formation of a shadow. Finally, the third part briefly addresses two topics that apply to spacetimes without symmetry, namely Fermat’s principle and the exact lens map of Frittelli and Newman.
The Effect of Weak Gravitational Lensing on the Angular Distribution of Gamma-Ray Bursts
L. L. R. Williams
1996-06-10
If Gamma-Ray Bursts (GRBs) are cosmologically distributed standard candles and are associated with the luminous galaxies, then the observed angular distribution of all GRBs is altered due to weak gravitational lensing of bursts by density inhomogeneities. The amplitude of the effect is generally small. For example, if the current catalogs extend to $z_{max}\\sim 1$ and we live in a flat $\\Omega=1$ Universe, the angular auto-correlation function of GRBs will be enhanced by $\\sim 8\\%$ due to lensing, on all angular scales. For an extreme case of $z_{max}= 1.5$ and ($\\Omega$, $\\Lambda$)=(0.2, 0.8), an enhancement of $\\sim 33\\%$ is predicted. If the observed distribution of GRBs is used in the future to derive power spectra of mass density fluctuations on large angular scales, the effect of weak lensing should probably be taken into account.
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.
Rotation of the cosmic microwave background polarization from weak gravitational lensing.
Dai, Liang
2014-01-31
When a cosmic microwave background (CMB) photon travels from the surface of last scatter through spacetime metric perturbations, the polarization vector may rotate about its direction of propagation. This gravitational rotation is distinct from, and occurs in addition to, the lensing deflection of the photon trajectory. This rotation can be sourced by linear vector or tensor metric perturbations and is fully coherent with the curl deflection field. Therefore, lensing corrections to the CMB polarization power spectra as well as the temperature-polarization cross correlations due to nonscalar perturbations are modified. The rotation does not affect lensing by linear scalar perturbations, but needs to be included when calculations go to higher orders. We present complete results for weak lensing of the full-sky CMB power spectra by general linear metric perturbations, taking into account both deflection of the photon trajectory and rotation of the polarization. For the case of lensing by gravitational waves, we show that the B modes induced by the rotation largely cancel those induced by the curl component of deflection. PMID:24580435
An accurate and practical method for inference of weak gravitational lensing from galaxy images
Bernstein, Gary M; Krawiec, Christina; March, Marisa C
2015-01-01
We demonstrate recovery of weak gravitational lensing shear at parts-per-thousand accuracy using an implementation of the Bayesian Fourier Domain (BFD) method proposed by Bernstein \\& Armstrong (2014, BA14). The BFD formalism is rigorously correct for Nyquist-sampled, background-limited, uncrowded image of background galaxies. BFD does not assign shapes to galaxies, instead compressing the pixel data D into a vector of moments M, such that we have an analytic expression for the probability P(M|g) of obtaining the observations with gravitational lensing distortion g along the line of sight. We extend the BA14 formalism to include detection and selection of galaxies without inducing biases on the inferred g. We describe a practical algorithm for conducting BFD's integrations over the population of unlensed source galaxies. Our BFD implementation measures ~10 galaxies per second per core on current hardware, a speed that will be largely independent of the number of images taken of each target. Initial tests ...
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.
Hirata, Christopher M.; Cutler, Curt
2010-06-15
Gravitational wave sources are a promising cosmological standard candle because their intrinsic luminosities are determined by fundamental physics (and are insensitive to dust extinction). They are, however, affected by weak lensing magnification due to the gravitational lensing from structures along the line of sight. This lensing is a source of uncertainty in the distance determination, even in the limit of perfect standard candle measurements. It is commonly believed that the uncertainty in the distance to an ensemble of gravitational wave sources is limited by the standard deviation of the lensing magnification distribution divided by the square root of the number of sources. Here we show that by exploiting the non-Gaussian nature of the lensing magnification distribution, we can improve this distance determination, typically by a factor of 2-3; we provide a fitting formula for the effective distance accuracy as a function of redshift for sources where the lensing noise dominates.
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)
Cosmological Applications of Gravitational Lensing
Peter Schneider
1995-12-08
The last decade has seen an enormous increase of activity in the field of gravitational lensing, mainly driven by improvements of observational capabilities. I will review the basics of gravitational lens theory, just enough to understand the rest of this contribution, and will then concentrate on several of the main applications in cosmology. Cluster lensing, and weak lensing, will constitute the main part of this review.
Andrew J. Barber; Peter A. Thomas; H. M. P. Couchman; C. J. Fluke
2000-02-23
We present the results of weak gravitational lensing statistics in four different cosmological $N$-body simulations. The data has been generated using an algorithm for the three-dimensional shear, which makes use of a variable softening facility for the $N$-body particle masses, and enables a physical interpretation for the large-scale structure to be made. Working in three-dimensions also allows the correct use of the appropriate angular diameter distances. Our results are presented on the basis of the filled beam approximation in view of the variable particle softening scheme in our algorithm. The importance of the smoothness of matter in the universe for the weak lensing results is discussed in some detail. The low density cosmology with a cosmological constant appears to give the broadest distributions for all the statistics computed for sources at high redshifts. In particular, the range in magnification values for this cosmology has implications for the determination of the cosmological parameters from high-redshift Type Ia Supernov\\ae. The possibility of determining the density parameter from the non-Gaussianity in the probability distribution for the convergence is discussed.
Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit
Gyulchev, G. N.; Yazadjiev, S. S.
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.
Enrique Martinez-Gonzalez; Jose L. Sanz; Laura Cayon
1997-02-26
We have studied the effect of gravitational lensing on the Cosmic Microwave Background (CMB) anisotropy in flat and open universes. We develop a formalism to calculate the changes on the radiation power spectrum induced by lensing in the Newtonian and synchronous-comoving gauges. The previously considered negligible contribution to the CMB radiation power spectrum of the anisotropic term of the lensing correlation is shown to be appreciable. However, considering the nonlinear evolution of the matter power spectrum produces only slight differences on the results based on linear evolution. The general conclusion for flat as well as open universes is that lensing slightly smoothes the radiation power spectrum. For a given range of multipoles the effect of lensing increases with Omega but for the same acoustic peak it decreases with $\\Omega$. The maximum contribution of lensing to the radiation power spectrum for $l\\leq 2000$ is $\\sim$ 5% for $\\Omega$ values in the range 0.1-1.
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.
Wittman; Tyson; Kirkman; Dell'Antonio; Bernstein
2000-05-11
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 matter in the foreground. The patterns of the induced distortions reflect the density of mass along the line of sight and its distribution, and the resulting 'cosmic shear' can be used to distinguish between alternative cosmologies. But previous attempts to measure this effect have been inconclusive. Here we report the detection of cosmic shear on angular scales of up to half a degree using 145,000 galaxies and along three separate lines of sight. We find that the dark matter is distributed in a manner consistent with either an open universe, or a flat universe that is dominated by a cosmological constant. Our results are inconsistent with the standard cold-dark-matter model. PMID:10821262
M. Bradac; M. Lombardi; P. Schneider
2004-07-01
Weak gravitational lensing is considered to be one of the most powerful tools to study the mass and the mass distribution of galaxy clusters. However, weak lensing mass reconstructions are plagued by the so-called mass-sheet degeneracy--the surface mass density \\kappa of the cluster can be determined only up to a degeneracy transformation \\kappa \\to \\kappa' = \\lambda \\kappa + (1 -\\lambda), where \\lambda is an arbitrary constant. This transformation fundamentally limits the accuracy of cluster mass determinations if no further assumptions are made. We discuss here a possibility to break the mass-sheet degeneracy in weak lensing mass maps using distortion and redshift information of background galaxies. Compared to other techniques proposed in the past, it does not rely on any assumptions on cluster potential and does not make use of weakly constrained information (such as the source number counts, used in the magnification effect).Our simulations show that we are effectively able to break the mass-sheet degeneracy for supercritical lenses and that for undercritical lenses the mass-sheet degeneracy is very difficult to be broken, even under idealised conditions.
NASA Technical Reports Server (NTRS)
Turner, Edwin L.
1989-01-01
Recent observational and theoretical investigations of gravitational-lens phenomena are reviewed, and sample numerical data are presented in tables. Particular attention is given to luminous arcs, radio rings, galaxy-quasar associations, the problem of deriving actually or practically unique models of individual lens systems, and time delays and the Hubble constant.
Zhang Pengjie, E-mail: pjzhang@shao.ac.c [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China)
2010-09-10
The galaxy intrinsic alignment is a severe challenge to precision cosmic shear measurement. We propose self-calibrating the induced gravitational shear-galaxy intrinsic ellipticity correlation (the GI correlation) in weak lensing surveys with photometric redshift measurements. (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 necessary GI correlation. We perform a concept study under simplified conditions and demonstrate its capability to significantly reduce GI contamination. We discuss the impact of various complexities on the two key ingredients of the self-calibration technique, namely the method for extracting the I-g correlation and the scaling relation between the I-g and the GI correlation. We expect that none of them will likely be able to completely invalidate the proposed self-calibration technique.
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
Mass and concentration estimates from weak and strong gravitational lensing: a systematic study
NASA Astrophysics Data System (ADS)
Giocoli, Carlo; Meneghetti, Massimo; Metcalf, R. Benton; Ettori, Stefano; Moscardini, Lauro
2014-05-01
We study how well halo properties of galaxy clusters, such as mass and concentration, are recovered using lensing data. In order to generate a large sample of systems at different redshifts, we use the code MOKA. We measure halo mass and concentration using weak lensing data alone (WL), fitting to a Navarro, Frenk & White (NFW) profile the reduced tangential shear profile, or by combining weak and strong lensing data, by adding information about the size of the Einstein radius (WL+SL). For different redshifts, we measure the mass and the concentration biases and find that these are mainly caused by the random orientation of the halo ellipsoid with respect to the line of sight. Since our simulations account for the presence of a bright central galaxy, we perform mass and concentration measurements using a generalized NFW profile which allows for a free inner slope. This reduces both the mass and the concentration biases. We discuss how the mass function and the concentration-mass relation change when using WL and WL+SL estimates. We investigate how selection effects impact the measured concentration-mass relation showing that strong lens clusters may have a concentration 20-30 per cent higher than the average, at fixed mass, considering also the particular case of strong lensing selected samples of relaxed clusters. Finally, we notice that selecting a sample of relaxed galaxy clusters, as is done in some cluster surveys, explains the concentration-mass relation biases.
Bradac, M; Schneider, P
2004-01-01
Weak gravitational lensing is considered to be one of the most powerful tools to study the mass and the mass distribution of galaxy clusters. However, weak lensing mass reconstructions are plagued by the so-called mass-sheet degeneracy--the surface mass density \\kappa of the cluster can be determined only up to a degeneracy transformation \\kappa \\to \\kappa' = \\lambda \\kappa + (1 -\\lambda), where \\lambda is an arbitrary constant. This transformation fundamentally limits the accuracy of cluster mass determinations if no further assumptions are made. We discuss here a possibility to break the mass-sheet degeneracy in weak lensing mass maps using distortion and redshift information of background galaxies. Compared to other techniques proposed in the past, it does not rely on any assumptions on cluster potential and does not make use of weakly constrained information (such as the source number counts, used in the magnification effect).Our simulations show that we are effectively able to break the mass-sheet degene...
Weak gravitational lensing due to large-scale structure of the universe
NASA Technical Reports Server (NTRS)
Jaroszynski, Michal; Park, Changbom; Paczynski, Bohdan; Gott, J. Richard, III
1990-01-01
The effect of the large-scale structure of the universe on the propagation of light rays is studied. The development of the large-scale density fluctuations in the omega = 1 universe is calculated within the cold dark matter scenario using a smooth particle approximation. The propagation of about 10 to the 6th random light rays between the redshift z = 5 and the observer was followed. It is found that the effect of shear is negligible, and the amplification of single images is dominated by the matter in the beam. The spread of amplifications is very small. Therefore, the filled-beam approximation is very good for studies of strong lensing by galaxies or clusters of galaxies. In the simulation, the column density was averaged over a comoving area of approximately (1/h Mpc)-squared. No case of a strong gravitational lensing was found, i.e., no 'over-focused' image that would suggest that a few images might be present. Therefore, the large-scale structure of the universe as it is presently known does not produce multiple images with gravitational lensing on a scale larger than clusters of galaxies.
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 ...
Dragan Huterer
2002-01-01
We study the power of upcoming weak lensing surveys to probe dark energy. Dark energy modifies the distance-redshift relation as well as the matter power spectrum, both of which affect the weak lensing convergence power spectrum. Some dark-energy models predict additional clustering on very large scales, but this probably cannot be detected by weak lensing alone due to cosmic variance.
NASA Astrophysics Data System (ADS)
Rhodes, J. D.; Bennett, D. P.; Kaiser, N.
2001-12-01
Weak lensing by large-scale structure (cosmic shear) provides an opportunity to directly observe the dark matter in the universe. Current ground-based and space-based surveys have demonstrated the efficacy of this technique in determining the mass distribution and thus placing constraints on cosmological parameters such as ? m, ? 8, and the bias parameter b. Current surveys have been hampered by the comparatively low resolution of ground-based telescopes and the small field of view of HST. To make significant progress in this field, wide field space-based surveys are needed. The Galactic Exoplanet Survey Telescope (GEST) will be able to provide 500- 1000 sqare degrees with a resolution of better than 0.2 arcseconds in multiple filters. This will make it an ideal instrument for a weak lensing survey.
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.
Wang, Wenting; Mandelbaum, Rachel; Henriques, Bruno; Anderson, Michael E; Han, Jiaxin
2015-01-01
We use weak gravitational lensing to measure mean mass profiles around Locally Brightest Galaxies (LBGs). These are selected from the SDSS/DR7 spectroscopic and photometric catalogues to be brighter than any neighbour projected within 1.0 Mpc and differing in redshift by $ 83\\%$) are expected to be the central galaxies of their dark matter halos. Previous stacking analyses have used this LBG sample to measure mean Sunyaev-Zeldovich flux and mean X-ray luminosity as a function of LBG stellar mass. In both cases, a simulation of the formation of the galaxy population was used to estimate effective halo mass for LBGs of given stellar mass, allowing the derivation of scaling relations between the gas properties of halos and their mass. By comparing results from a variety of simulations to our lensing data, we show that this procedure has significant model dependence reflecting: (i) the failure of any given simulation to reproduce observed galaxy abundances exactly; (ii) a dependence on the cosmology underlying th...
Gravitational lensing as a probe of structure
Peter Schneider
2003-06-23
Gravitational lensing has become one of the most interesting tools to study the mass distribution in the Universe. Since gravitational light deflection is independent of the nature and state of the matter, it is ideally suited to investigate the distribution of all (and thus also of dark) matter in the Universe. Lensing results have now become available over a wide range of scales, from the search for MACHOs in the Galactic halo, to the mass distribution in galaxies and clusters of galaxies, and the statistical properties of the large-scale matter distribution in the Universe. Here, after introducing the concepts of strong and weak lensing, several applications are outlined, from strong lensing by galaxies, to strong and weak lensing by clusters and the lensing properties of the large-scale structure.
Gravitational lensing in plasmic medium
NASA Astrophysics Data System (ADS)
Bisnovatyi-Kogan, G. S.; Tsupko, O. Yu.
2015-07-01
The influence of plasma on different effects of gravitational lensing is reviewed. Using the Hamiltonian approach for geometrical optics in a medium in the presence of gravity, an exact formula for the photon deflection angle by a black hole (or another body with a Schwarzschild metric) embedded in plasma with a spherically symmetric density distribution is derived. The deflection angle in this case is determined by the mutual combination of different factors: gravity, dispersion, and refraction. While the effects of deflection by the gravity in vacuum and the refractive deflection in a nonhomogeneous medium are well known, the new effect is that, in the case of a homogeneous plasma, in the absence of refractive deflection, the gravitational deflection differs from the vacuum deflection and depends on the photon frequency. In the presence of a plasma nonhomogeneity, the chromatic refractive deflection also occurs, so the presence of plasma always makes gravitational lensing chromatic. In particular, the presence of plasma leads to different angular positions of the same image if it is observed at different wavelengths. It is discussed in detail how to apply the presented formulas for the calculation of the deflection angle in different situations. Gravitational lensing in plasma beyond the weak deflection approximation is also considered.
Gravitational Lensing in Plasmic Medium
G. S. Bisnovatyi-Kogan; O. Yu. Tsupko
2015-07-24
The influence of plasma on different effects of gravitational lensing is reviewed. Using the Hamiltonian approach for geometrical optics in a medium in the presence of gravity, an exact formula for the photon deflection angle by a black hole (or another body with a Schwarzschild metric) embedded in plasma with a spherically symmetric density distribution is derived. The deflection angle in this case is determined by the mutual combination of different factors: gravity, dispersion, and refraction. While the effects of deflection by the gravity in vacuum and the refractive deflection in a nonhomogeneous medium are well known, the new effect is that, in the case of a homogeneous plasma, in the absence of refractive deflection, the gravitational deflection differs from the vacuum deflection and depends on the photon frequency. In the presence of a plasma nonhomogeneity, the chromatic refractive deflection also occurs, so the presence of plasma always makes gravitational lensing chromatic. In particular, the presence of plasma leads to different angular positions of the same image if it is observed at different wavelengths. It is discussed in detail how to apply the presented formulas for the calculation of the deflection angle in different situations. Gravitational lensing in plasma beyond the weak deflection approximation is also considered.
Visualization of Gravitational Lenses
NASA Astrophysics Data System (ADS)
Frutos-Alfaro, Francisco
In scientific research the visualization of the natural phenomena is becoming important. Gravitational lenses are presently a topic of intense research, therefore a program to visualize them is very useful, not only for research, but also for teaching. The visualization program that we are presenting, was written in C and runs under Unix and Linux platforms with previously installed libraries (XForms, Mesa or Open GL and Imlib). These libraries can be found freely on the Internet.
Statistical challenges in weak lensing cosmology
NASA Astrophysics Data System (ADS)
Takada, Masahiro
2014-05-01
Cosmological weak lensing is the powerful probe of cosmology. Here we address one of the most fundamental, statistical questions inherent in weak lensing cosmology: whether or not we can recover the initial Gaussian information content of large-scale structure by combining the weak lensing observables, here focused on the weak lensing power spectrum and bispectrum. To address this question we fully take into account correlations between the power spectra of different multipoles and the bispectra of different triangle configurations, measured from a finite area survey. In particular we show that super-survey modes whose length scale is larger than or comparable with the survey size cause significant sample variance in the weak lensing correlations via the mode-coupling with sub-survey modes due to nonlinear gravitational clustering - the so-called super-sample variance. In this paper we discuss the origin of the super-sample variance and then study the information content inherent in the weak lensing correlation functions up to three-point level.
Nbody Simulations and Weak Gravitational Lensing using new HPC-Grid resources: the PI2S2 project
NASA Astrophysics Data System (ADS)
Becciani, U.; Antonuccio-Delogu, V.; Costa, A.; Comparato, M.
2008-08-01
We present the main project of the new grid infrastructure and the researches, that have been already started in Sicily and will be completed by next year. The PI2S2 project of the COMETA consortium is funded by the Italian Ministry of University and Research and will be completed in 2009. Funds are from the European Union Structural Funds for Objective 1 regions. The project, together with a similar project called Trinacria GRID Virtual Laboratory (Trigrid VL), aims to create in Sicily a computational grid for e-science and e-commerce applications with the main goal of increasing the technological innovation of local enterprises and their competition on the global market. PI2S2 project aims to build and develop an e-Infrastructure in Sicily, based on the grid paradigm, mainly for research activity using the grid environment and High Performance Computer systems. As an example we present the first results of a new grid version of FLY a tree Nbody code developed by INAF Astrophysical Observatory of Catania, already published in the CPC program Library, that will be used in the Weak Gravitational Lensing field.
Cosmological model discrimination with weak lensing
NASA Astrophysics Data System (ADS)
Pires, S.; Starck, J.-L.; Amara, A.; Réfrégier, A.; Teyssier, R.
2009-10-01
Weak gravitational lensing provides a unique way of mapping directly the dark matter in the Universe. The majority of lensing analyses use the two-point statistics of the cosmic shear field to constrain the cosmological model, a method that is affected by degeneracies, such as that between ?8 and ?m which are respectively the rms of the mass fluctuations on a scale of 8 Mpc/h and the matter density parameter, both at z = 0. However, the two-point statistics only measure the Gaussian properties of the field, and the weak lensing field is non-Gaussian. It has been shown that the estimation of non-Gaussian statistics for weak lensing data can improve the constraints on cosmological parameters. In this paper, we systematically compare a wide range of non-Gaussian estimators to determine which one provides tighter constraints on the cosmological parameters. These statistical methods include skewness, kurtosis, and the higher criticism test, in several sparse representations such as wavelet and curvelet; as well as the bispectrum, peak counting, and a newly introduced statistic called wavelet peak counting (WPC). Comparisons based on sparse representations indicate that the wavelet transform is the most sensitive to non-Gaussian cosmological structures. It also appears that the most helpful statistic for non-Gaussian characterization in weak lensing mass maps is the WPC. Finally, we show that the ?8 - ?m degeneracy could be even better broken if the WPC estimation is performed on weak lensing mass maps filtered by the wavelet method, MRLens.
Cosmological model discrimination from weak lensing data
NASA Astrophysics Data System (ADS)
Pires, S.; Starck, J.-L.; Amara, A.; Réfrégier, A.; Teyssier, R.
2010-06-01
Weak gravitational lensing provides a unique way of mapping directly the dark matter in the Universe. The majority of lensing analyses use the two-point statistics of the cosmic shear field to constrain the cosmological model, a method that is affected by degeneracies, such as that between ?8 and ?m which are respectively the rms of the mass fluctuations on a scale of 8 Mpc/h and the matter density parameter, both at z = 0. However, the two-point statistics only measure the Gaussian properties of the field, and the weak lensing field is non-Gaussian. It has been shown that the estimation of non-Gaussian statistics for weak lensing data can improve the constraints on cosmological parameters. In this paper, we systematically compare a wide range of non-Gaussian estimators to determine which one provides tighter constraints on the cosmological parameters. These statistical methods include skewness, kurtosis, and the higher criticism test, in several sparse representations such as wavelet and curvelet; as well as the bispectrum, peak counting, and a newly introduced statistic called wavelet peak counting (WPC). Comparisons based on sparse representations indicate that the wavelet transform is the most sensitive to non-Gaussian cosmological structures. It also appears that the most helpful statistic for non-Gaussian characterization in weak lensing mass maps is the WPC. Finally, we show that the ?8-?m degeneracy could be even better broken if the WPC estimation is performed on weak lensing mass maps filtered by the wavelet method, MRLens.
The application of weak lensing
NASA Astrophysics Data System (ADS)
Song, Yong-Seon
2004-12-01
Gravitational lensing distorts cosmic shear maps and Cosmic Microwave Background (CMB) anisotropies maps. We derive the correlation functions of the lensing-induced shear and the reconstructed deflection angle. We investigate the applications of those correlations in determining cosmological parameters: (1) The reconstructed lensing potential enhances the detectability of CMB tensor B-mode anisotropy which completes all required initial conditions to explain the primordial universe. (2) The cross-correlation between the lensed CMB maps and Far Infrared Radiation Background (FIRB) anisotropy maps is studied to understand the nature of FIRB sources and their relation to the distribution of dark matter. (3) CMB lensing and cosmic shear can be used to probe massive neutrinos collapsing into the gravitational wells when they become non-relativistic. (4) The cosmological parameters related to cosmic acceleration can be precisely determined by cosmic shear maps. We study how to generalise those parameters and how to discriminate different models.
NASA Astrophysics Data System (ADS)
Liesenborgs, J.; de Rijcke, S.; Dejonghe, H.; Bekaert, P.
2011-03-01
Gravitational lenses are a spectacular astrophysical phenomenon, a cosmic mirage caused by the gravitational deflection of light in which multiple images of a same background object can be seen. Their beauty is only exceeded by their usefulness, as the gravitational lens effect is a direct probe of the total mass of the deflecting object. Furthermore, since the image configuration arising from the gravitational lens effect depends on the exact gravitational potential of the deflector, it even holds the promise of learning about the distribution of the mass. In this presentation, a method for extracting the information encoded in the images and reconstructing the mass distribution is presented. Being a non-parametric method, it avoids making a priori assumptions about the shape of the mass distribution. At the core of the procedure lies a genetic algorithm, an optimization strategy inspired by Darwin's principle of ``survival of the fittest''. One only needs to specify a criterion to decide if one particular trial solution is deemed better than another, and the genetic algorithm will ``breed'' appropriate solutions to the problem. In a similar way, one can create a multi-objective genetic algorithm, capable of optimizing several fitness criteria at the same time. This provides a very flexible way to incorporate all the available information in the gravitational lens system: not only the positions and shapes of the multiple images are used, but also the so-called ``null space'', i.e. the area in which no such images can be seen. The effectiveness of this approach is illustrated using simulated data, which allows one to compare the reconstruction to the true mass distribution.
Blake, Chris; Heymans, Catherine; Choi, Ami; Erben, Thomas; Harnois-Deraps, Joachim; Hildebrandt, Hendrik; Joachimi, Benjamin; Nakajima, Reiko; van Waerbeke, Ludovic; Viola, Massimo
2015-01-01
The unknown nature of dark energy motivates continued cosmological tests of large-scale gravitational physics. We present a new consistency check based on the relative amplitude of non-relativistic galaxy peculiar motions, measured via redshift-space distortion, and the relativistic deflection of light by those same galaxies traced by galaxy-galaxy lensing. We take advantage of the latest generation of deep, overlapping imaging and spectroscopic datasets, combining the Red Cluster Sequence Lensing Survey (RCSLenS), the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the WiggleZ Dark Energy Survey and the Baryon Oscillation Spectroscopic Survey (BOSS). We quantify the results using the "gravitational slip" statistic E_G, which we estimate as 0.48 +/- 0.10 at z=0.32 and 0.30 +/- 0.07 at z=0.57, the latter constituting the highest redshift at which this quantity has been determined. These measurements are consistent with the predictions of General Relativity, for a perturbed Friedmann-Robertson-Walker ...
Gravitational lensing and Catastrophe theory
Y. Kakigi; T. Okamura; T. Fukuyama
1995-07-20
Singularities of caustics appeared in gravitational lensing effect are discussed analytically. Multipole expansion model of lensing object is mainly studied since it is tractable and universal. Our analyses are confirmed by numerical calculations and applied to multiple quasar system of PG1115+080. Consistencies with elliptical lens models are also discussed.
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.
EDITORIAL: Focus on Gravitational Lensing
NASA Astrophysics Data System (ADS)
Jain, Bhuvnesh
2007-11-01
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 of advances has continued into the new century. Lensing is currently one of best techniques for finding and mapping dark matter over a wide range of scales, and also addresses broader cosmological questions such as understanding the nature of dark energy. This focus issue of New Journal of Physics presents a snapshot of current research in some of the exciting areas of lensing. It provides an occasion to look back at the advances of the last decade and ahead to the potential of the coming years. Just about a decade ago, microlensing was discovered through the magnification of stars in our galaxy by invisible objects with masses between that of Jupiter and a tenth the mass of the Sun. Thus a new component of the mass of our galaxy, dubbed MACHOs, was established (though a diffuse, cold dark matter-like component is still needed to make up most of the galaxy mass). More recently, microlensing led to another exciting discovery—of extra-solar planets with masses ranging from about five times that of Earth to that of Neptune. We can expect many more planets to be discovered through ongoing surveys. Microlensing is the best technique for finding Earth mass planets, though it is not as productive overall as other methods and does not allow for follow up observations. Beyond planet hunting, microlensing has enabled us to observe previously inaccessible systems, ranging from the surfaces of other stars to the accretion disks around the black holes powering distant quasars. Galaxies and galaxy clusters at cosmological distances can produce dramatic lensing effects: multiple images of background galaxies or quasars which are strongly magnified and sheared. In the last decade, double and quadruply imaged systems due to galactic lenses have been studied with optical and radio observations. An interesting result obtained from the flux ratio 'anomalies' of quadruply imaged systems is the statistical detection of dark sub-clumps in galaxy halos. More broadly, while we have learned a lot about the mass distribution in lens galaxies and improved time delay constraints on the Hubble constant, the limitations of cosmological studies with strong lensing due to uncertainties in lens mass models have also come to be appreciated. That said, progress will no doubt continue with qualitative advances in observations such as astrometric counterparts to the flux anomalies, clever ideas such as the use of spectroscopic signatures to assemble the SLACS lens sample, and combining optical imaging, spectroscopy and radio data to continue the quest for a set of golden lenses to measure the Hubble constant. Galaxy clusters are a fascinating arena for studying the distribution of dark and baryonic matter. Weak and strong lensing information can be combined with dynamical information from the spectroscopic measurements of member galaxies and x-ray/Sunyaev Zeldovich measurements of the hot ionized gas. Hubble Space Telescope observations have yielded spectacular images of clusters, such as Abell 1689, which has over a hundred multiply imaged arcs. Mass measurements have progressed to the level of 10 percent accuracy for several clusters. Unfortunately, it is unclear if one can do much better for individual clusters given inherent limitations such as unknown projection effects. The statistical study of clusters is likely to remain a promising way to study dark matter, gravity theories, and cosmology. Techniques to combine weak and strong lensing information to obtain the mass distribution of clusters have also advanced, and work continues on parameter-free techniques that are agnostic to the relation of cluster light and mass. An interesting twist in cluster lensing was provided by the pos
Cosmological models discrimination with Weak Lensing
Pires, S; Amara, A; Réfrégier, A; Teyssier, R
2009-01-01
Weak gravitational lensing provides a unique method to map directly the dark matter in the Universe. The majority of lensing analyses uses the two-point statistics of the cosmic shear field to constrain the cosmological model yielding degeneracies, such as that between sigma_8 and Omega_M respectively the r.m.s. of the mass fluctuations at a scale of 8 Mpc/h and the matter density parameter both at z = 0. However, the two-point statistics only measure the Gaussian properties of the field and the weak lensing field is non-Gaussian. It has been shown that the estimation of non-Gaussian statistics on weak lensing data can improve the constraints on cosmological parameters. In this paper, we systematically compare a wide range of non-Gaussian estimators in order to determine which one provides tighter constraints on the cosmological parameters. These statistical methods include skewness, kurtosis and the Higher Criticism test in several sparse representations such as wavelet and curvelet; as well as the bispectru...
Environments of strong gravitational lenses
NASA Astrophysics Data System (ADS)
Momcheva, Ivelina Gospodinova
2009-06-01
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 hindered their use. Here, we present a spectroscopic survey of the environments and lines of sight of 28 strong galaxy-mass lenses. We determine redshifts for 9698 galaxies in the fields of these lenses and identify 163 structures with at least five members in 26 fields. We find that 12 of 26 lenses are group members. Six of these groups are newly discovered. Overall, between 38-67% of lenses are in groups, and in 8-31% of the lenses the group makes a significant contribution to the lens potential. Line-of-sight structures are present in virtually every lens field, and in 19% of lenses the structures appear to be a significant perturbation to the lens potential. We consider the effect of the environment on H 0 derived from gravitational lenses. We find that, when the environment is ignored, lenses in groups predict a systematically higher value of H 0 , inconsistent at the 1? level with H 0 derived from isolated lenses. Correcting for the environment and line of sight structures brings the two values into agreement and lowers the combined value ( [Special characters omitted.] Without correction for the environment, the H0 values from strong lenses should be considered a strict upper limit. We explore the correlation between the observed lens properties and external perturbations from the observational perspective. We find that four-image lenses are statistically more likely to be in groups than two-image lenses. Furthermore, the distributions of convergences are statistically different for quads and doubles. This finding strongly supports the idea that the high quad-to-double ratios are at least partially due to the effect of the environment. We also examine the connections between flux anomalies and environment and the correlations between image separations and convergence. We find no significant links due to the limitations of our sample.
Mapping Dark Matter in Galaxy Clusters: Gravitational Lensing & Numerical Simulations
Marceau Limousin
2008-07-17
The different regimes of gravitational lensing constitutes an interesting tool in order to map the mass distribution in galaxy clusters on different scales. In this proceedings article, I review some work I have performed on this topic. More precisely, I will focus on : (i) galaxy scale substructures, using weak galaxy-galaxy lensing in order to study how does the environment shape their properties; (ii) the mass profile of Abell~1689 as probed combining strong and weak lensing; (iii) the slope of the inner dark matter distribution in Abell~1703 as measured by strong lensing. The lensing results will be compared to the expectations from numerical simulations, when available.
Tomography and weak lensing statistics
Munshi, Dipak; Coles, Peter; Kilbinger, Martin E-mail: peter.coles@astro.cf.ac.uk
2014-04-01
We provide generic predictions for the lower order cumulants of weak lensing maps, and their correlators for tomographic bins as well as in three dimensions (3D). Using small-angle approximation, we derive the corresponding one- and two-point probability distribution function for the tomographic maps from different bins and for 3D convergence maps. The modelling of weak lensing statistics is obtained by adopting a detailed prescription for the underlying density contrast that involves hierarchal ansatz and lognormal distribution. We study the dependence of our results on cosmological parameters and source distributions corresponding to the realistic surveys such as LSST and DES. We briefly outline how photometric redshift information can be incorporated in our results. We also show how topological properties of convergence maps can be quantified using our results.
WEAK LENSING MASS RECONSTRUCTION: FLEXION VERSUS SHEAR
Pires, S.
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.
Gravitational lensing and anomalous redshifts
NASA Astrophysics Data System (ADS)
Surdej, J.; Claeskens, J.-F.; Sluse, D.
2006-04-01
In this chapter, we should like to address the following question: can we invoke gravitational lensing as a possible explanation for anomalous redshifts? In the rest of the chapter, anomalous redshifts refer to redshifts observed for two distinct objects with an angular separation less than 5" and whose difference is larger than 0.1.
Weak lensing of baryon acoustic oscillations
Vallinotto, Alberto; Dodelson, Scott; Schimd, Carlo; Uzan, Jean-Philippe [Institut d'Astrophysique de Paris, CNRS-UMR 7095, Universite Paris VI Pierre et Marie Curie, 98 bis boulevard Arago, 75014 Paris (France); Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States) and Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637-1433 (United States); DAPNIA, CEA Saclay, 91191 Gif-sur-Yvette cedex (France); Institut d'Astrophysique de Paris, CNRS-UMR 7095, Universite Paris VI Pierre et Marie Curie, 98 bis boulevard Arago, 75014 Paris (France)
2007-05-15
Baryon acoustic oscillations (BAO) have recently been observed in the distribution of distant galaxies. The height and location of the BAO peak are strong discriminators of cosmological parameters. Here we consider the ways in which weak gravitational lensing distorts the BAO signal. We find two effects that can affect the height of the BAO peak in the correlation function at the percent level but that do not significantly impact the position of the peak and the measurement of the sound horizon. BAO turn out to be robust cosmological standard rulers.
Precision cluster mass determination from weak lensing
Mandelbaum, Rachel; Baldauf, Tobias; Smith, Robert E
2009-01-01
Weak gravitational lensing has been used extensively in the past decade to constrain the masses of galaxy clusters, and is the most promising observational technique for providing the mass calibration necessary for precision cosmology with clusters. There are several challenges in estimating cluster masses, particularly (a) the sensitivity to astrophysical effects and observational systematics that modify the signal relative to the theoretical expectations, and (b) biases that can arise due to assumptions in the mass estimation method, such as the assumed radial profile of the cluster. All of these challenges are more problematic in the inner regions of the cluster, suggesting that their influence would ideally be suppressed for the purpose of mass estimation. However, at any given radius the differential surface density measured by lensing is sensitive to all mass within that radius, and the corrupted signal from the inner parts is spread out to all scales. We develop a new statistic that is ideal for estima...
Weak Lensing Simulations for the SKA
NASA Astrophysics Data System (ADS)
Patel, P.; Harrison, I.; Makhathini, S.; Abdalla, F. B.; Bacon, D.; Brown, M.; Heywood, I.; Jarvis, M.; Smirnov, O.
Weak gravitational lensing measurements are traditionally made at optical wavelengths where many highly resolved galaxy images are readily available. However, the Square Kilometre Array (SKA) holds great promise for this type of measurement at radio wavelengths owing to its greatly increased sensitivity and resolution over typical radio surveys. The key to successful weak lensing experiments is in measuring the shapes of detected sources to high accuracy. In this document we describe a simulation pipeline designed to simulate radio images of the quality required for weak lensing, and will be typical of SKA observations. We provide as input, images with realistic galaxy shapes which are then simulated to produce images as they would have been observed with a given radio interferometer. We exploit this pipeline to investigate various stages of a weak lensing experiment in order to better understand the effects that may impact shape measurement. We first show how the proposed SKA1-Mid array configurations perform when we compare the (known) input and output ellipticities. We then investigate how making small changes to these array configurations impact on this input-outut ellipticity comparison. We also demonstrate how alternative configurations for SKA1-Mid that are smaller in extent, and with a faster survey speeds produce similar performance to those originally proposed. We then show how a notional SKA configuration performs in the same shape measurement challenge. Finally, we describe ongoing efforts to utilise our simulation pipeline to address questions relating to how applicable current (mostly originating from optical data) shape measurement techniques are to future radio surveys. As an alternative to such image plane techniques, we lastly discuss a shape measurement technique based on the shapelets formalism that reconstructs the source shapes directly from the visibility data.
HUBBLE'S TOP TEN GRAVITATIONAL LENSES
NASA Technical Reports Server (NTRS)
2002-01-01
The NASA Hubble Space Telescope serendipitous survey of the sky has uncovered exotic patterns, rings, arcs and crosses that are all optical mirages produced by a gravitational lens, nature's equivalent of having giant magnifying glass in space. Shown are the top 10 lens candidates uncovered in the deepest 100 Hubble fields. Hubble's sensitivity and high resolution allow it to see faint and distant lenses that cannot be detected with ground-based telescopes whose images are blurred by Earth's atmosphere. [Top Left] - HST 01248+0351 is a lensed pair on either side of the edge-on disk lensing galaxy. [Top Center] - HST 01247+0352 is another pair of bluer lensed source images around the red spherical elliptical lensing galaxy. Two much fainter images can be seen near the detection limit which might make this a quadruple system. [Top Right] - HST 15433+5352 is a very good lens candidate with a bluer lensed source in the form of an extended arc about the redder elliptical lensing galaxy. [Middle Far Left] - HST 16302+8230 could be an 'Einstein ring' and the most intriguing lens candidate. It has been nicknamed the 'the London Underground' since it resembles that logo. [Middle Near Left] - HST 14176+5226 is the first, and brightest lens system discovered in 1995 with the Hubble telescope. This lens candidate has now been confirmed spectroscopically using large ground-based telescopes. The elliptical lensing galaxy is located 7 billion light-years away, and the lensed quasar is about 11 billion light-years distant. [Middle Near Right] - HST 12531-2914 is the second quadruple lens candidate discovered with Hubble. It is similar to the first, but appears smaller and fainter. [Middle Far Right] - HST 14164+5215 is a pair of bluish lensed images symmetrically placed around a brighter, redder galaxy. [Bottom Left] - HST 16309+8230 is an edge-on disk-like galaxy (blue arc) which has been significantly distorted by the redder lensing elliptical galaxy. [Bottom Center] - HST 12368+6212 is a blue arc in the Hubble Deep Field (HDF). [Bottom Right] - HST 18078+4600 is a blue arc caused by the gravitational potential of a small group of 4 galaxies. Credit: Kavan Ratnatunga (Carnegie Mellon Univ.) and NASA
Cluster masses from CMB and galaxy weak lensing
Lewis, Antony; King, Lindsay [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA (United Kingdom)
2006-03-15
Gravitational lensing can be used to directly constrain the projected density profile of galaxy clusters. We discuss possible future constraints using lensing of the cosmic microwave background (CMB) temperature and polarization, and compare to results from using galaxy weak lensing. We model the moving lens and kinetic Sunyaev-Zel'dovich signals that confuse the temperature CMB lensing when cluster velocities and angular momenta are unknown, and show how they degrade parameter constraints. The CMB polarization cluster lensing signal is {approx}1 {mu}K for massive clusters and challenging to detect; however it should be significantly cleaner than the temperature signal and may provide the most robust constraints at low noise levels. Galaxy lensing is likely to be much better for constraining cluster masses at low redshift, but for clusters at redshift z > or approx. 1 future CMB lensing observations may be able to do better.
Attributes of Gravitational Lensing Parallax
Robert J. Nemiroff
1998-05-31
The density of stars and MACHOs in the universe could theoretically be determined or limited by simultaneous measurements of compact sources by well separated observers. A gravitational lens effect would be expected to create a slight differential amplification between the observers detectable with sufficiently sensitive relative photometry: "lensing parallax." When applied to expanding fireballs such as those from GRBs and supernovae, the mass of the lens can be indicated by the end of lensing parallax, when the angular size of the source becomes much greater than the angular size of the Einstein ring of the lens.
Weak lensing corrections to tSZ-lensing cross correlation
NASA Astrophysics Data System (ADS)
Tröster, Tilman; Van Waerbeke, Ludovic
2014-11-01
The cross correlation between the thermal Sunyaev-Zeldovich (tSZ) effect and gravitational lensing in wide field has recently been measured. It can be used to probe the distribution of the diffuse gas in large scale structure, as well as inform us about the missing baryons. As for any lensing-based quantity, higher order lensing effects can potentially affect the signal. Here, we extend previous higher order lensing calculations to the case of tSZ-lensing cross correlations. We derive terms analogous to corrections due to the Born approximation, lens-lens coupling, and reduced shear up to order l gtrsim 3000.
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.
Numerical simulation of gravitational lenses
NASA Astrophysics Data System (ADS)
Cherniak, Yakov
Gravitational lens is a massive body or system of bodies with gravitational field that bends directions of light rays propagating nearby. This may cause an observer to see multiple images of a light source, e.g. a star, if there is a gravitational lens between the star and the observer. Light rays that form each individual image may have different distances to travel, which creates time delays between them. In complex gravitational fields generated by the system of stars, analytical calculation of trajectories and light intensities is virtually impossible. Gravitational lens of two massive bodies, one behind another, are able to create four images of a light source. Furthermore, the interaction between the four light beams can form a complicated interference pattern. This article provides a brief theory of light behavior in a gravitational field and describes the algorithm for constructing the trajectories of light rays in a gravitational field, calculating wave fronts and interference pattern of light. If you set gravitational field by any number of transparent and non- transparent objects (stars) and set emitters of radio wave beams, it is possible to calculate the interference pattern in any region of space. The proposed method of calculation can be applied even in the case of the lack of continuity between the position of the emitting stars and position of the resulting image. In this paper we propose methods of optimization, as well as solutions for some problems arising in modeling of gravitational lenses. The simulation of light rays in the sun's gravitational field is taken as an example. Also caustic is constructed for objects with uniform mass distribution.
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
Combined reconstruction of weak and strong lensing data with WSLAP
NASA Astrophysics Data System (ADS)
Diego, J. M.; Tegmark, M.; Protopapas, P.; Sandvik, H. B.
2007-03-01
We describe a method to estimate the mass distribution of a gravitational lens and the position of the sources from combined strong and weak lensing data. The algorithm combines weak and strong lensing data in a unified way producing a solution which is valid in both the weak and the strong lensing regimes. The method is non-parametric, allowing the mass to be located anywhere in the field of view. We study how the solution depends on the choice of basis used to represent the mass distribution. We find that combining weak and strong lensing information has two major advantages: it alleviates the need for priors and/or regularization schemes for the intrinsic size of the background galaxies (this assumption was needed in previous strong lensing algorithms) and it reduces (although does not remove) biases in the recovered mass in the outer regions where the strong lensing data are less sensitive. The code is implemented into a software package called Weak & Strong Lensing Analysis Package (WSLAP) which is publicly available at http://darwin.cfa.harvard.edu/SLAP/.
Strong Gravitational Lensing by Kiselev Black Hole
Azka Younas; Saqib Hussain; Mubasher Jamil; Sebastian Bahamonde
2015-04-13
We investigate the gravitational lensing scenario due to Schwarzschild-like black hole surrounded by quintessence (Kiselev black hole). We discuss here three special cases of Kiselev black hole: non-extreme, extreme and naked singularity. We present the detailed derivation for the bending angles of light as it traverses in the equatorial plane of the black hole. We also calculate the approximate bending angle and compare it with exact bending angle expressions. In the weak field approximation, we calculate the position and total magnification of relativistic images.
WEAK-LENSING RESULTS FOR THE MERGING CLUSTER A1758
Ragozzine, B.; Clowe, D.; Markevitch, M.; Gonzalez, A. H.; Bradac, M.
2012-01-10
Here we present the weak-lensing results for A1758, which is known to consist of four subclusters undergoing two separate mergers, A1758N and A1758S. Weak-lensing results for A1758N agree with previous weak-lensing results for clusters 1E0657-558 (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. The weak-lensing mass peaks of the two northern clusters are separated at the 2.5{sigma} level. We estimate the combined mass of the clusters in A1758N to be (2.2 {+-} 0.5) Multiplication-Sign 10{sup 15} M{sub Sun} and r{sub 200} = 2300{sup +100}{sub -130} kpc. We also detect seven strong-lensing candidates, two of which may provide information that would improve the mass measurements of A1758N.
Gravitational lensing by rotating naked singularities
Gyulchev, Galin N. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria); Yazadjiev, Stoytcho S. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria); Institut fuer Theoretische Physik, Universitaet Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany)
2008-10-15
We model massive compact objects in galactic nuclei as stationary, axially symmetric naked singularities in the Einstein-massless scalar field theory and study the resulting gravitational lensing. In the weak deflection limit we study analytically the position of the two weak field images, the corresponding signed and absolute magnifications as well as the centroid up to post-Newtonian order. We show 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 scalar 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 for the weakly naked and vastly for the strongly naked singularities with the increase of the scalar charge. The pointlike caustics drift away from the optical axis and do not depend on the scalar charge. In the strong deflection limit approximation, we compute numerically the position of the relativistic images and their separability for weakly naked singularities. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as Janis-Newman-Winicour naked singularities.
Gravitational Lensing by Rotating Naked Singularities
Galin N. Gyulchev; Stoytcho S. Yazadjiev
2008-06-19
We model massive compact objects in galactic nuclei as stationary, axially-symmetric naked singularities in the Einstein-massless scalar field theory and study the resulting gravitational lensing. In the weak deflection limit we study analytically the position of the two weak field images, the corresponding signed and absolute magnifications as well as the centroid up to post-Newtonian order. We show that there are a static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are function of the scalar charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightingly for the weakly naked and vastly for the strongly naked singularities with the increase of the scalar charge. The point-like caustics drift away from the optical axis and do not depend on the scalar charge. In the strong deflection limit approximation we compute numerically the position of the relativistic images and their separability for weakly naked singularities. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as Janis--Newman--Winicour naked singularities.
Gravitational Lensing in Clusters of Galaxies
Hattori, M; Makino, N
1999-01-01
Gravitational lensing in clusters of galaxies is an efficient tool to probe the mass distribution of galaxies and clusters, high redshift objects thanks to the gravitational amplification, and the geometry of the universe. We review some important aspects of cluster lensing and related issues in observational cosmology.
Gravitational Lensing in Clusters of Galaxies
M. Hattori; J. -P. Kneib; N. Makino
1999-05-03
Gravitational lensing in clusters of galaxies is an efficient tool to probe the mass distribution of galaxies and clusters, high redshift objects thanks to the gravitational amplification, and the geometry of the universe. We review some important aspects of cluster lensing and related issues in observational cosmology.
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.
Exploring degeneracies in modified gravity with weak lensing
NASA Astrophysics Data System (ADS)
Leonard, C. Danielle; Baker, Tessa; Ferreira, Pedro G.
2015-04-01
By considering linear-order departures from general relativity, we compute a novel expression for the weak lensing convergence power spectrum under alternative theories of gravity. This comprises an integral over a "kernel" of general relativistic quantities multiplied by a theory-dependent "source" term. The clear separation between theory-independent and -dependent terms allows for an explicit understanding of each physical effect introduced by altering the theory of gravity. We take advantage of this to explore the degeneracies between gravitational parameters in weak lensing observations.
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...
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.
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.
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
Gravitational lenses, cosmology, and galaxy structure
NASA Astrophysics Data System (ADS)
Winn, J.
2002-05-01
Gravitational lenses can be used to study dark matter in galaxies and to measure the Hubble constant. The statistics of lensing can be used to measure the cosmological constant. I have been conducting a survey of the southern sky for new lenses at radio wavelengths, which has resulted in 4 confirmed lenses and 3 strong candidates that require further follow-up. I will describe the survey and the scientific results that have been obtained from the new lenses. I will also describe my other life as a science journalist.
Reconstruction of Cluster Masses using Particle Based Lensing I: Application to Weak Lensing
Sanghamitra Deb; David M. Goldberg; Vede J. Ramdass
2008-06-13
We present Particle-Based Lensing (PBL), a new technique for gravitational lensing mass reconstructions of galaxy clusters. Traditionally, most methods have employed either a finite inversion or gridding to turn observational lensed galaxy ellipticities into an estimate of the surface mass density of a galaxy cluster. We approach the problem from a different perspective, motivated by the success of multi-scale analysis in smoothed particle hydrodynamics. In PBL, we treat each of the lensed galaxies as a particle and then reconstruct the potential by smoothing over a local kernel with variable smoothing scale. In this way, we can tune a reconstruction to produce constant signal-noise throughout, and maximally exploit regions of high information density. PBL is designed to include all lensing observables, including multiple image positions and fluxes from strong lensing, as well as weak lensing signals including shear and flexion. In this paper, however, we describe a shear-only reconstruction, and apply the method to several test cases, including simulated lensing clusters, as well as the well-studied ``Bullet Cluster'' (1E0657-56). In the former cases, we show that PBL is better able to identify cusps and substructures than are grid-based reconstructions, and in the latter case, we show that PBL is able to identify substructure in the Bullet Cluster without even exploiting strong lensing measurements. We also make our codes publicly available.
Lensing of 21-cm fluctuations by primordial gravitational waves.
Book, Laura; Kamionkowski, Marc; Schmidt, Fabian
2012-05-25
Weak-gravitational-lensing distortions to the intensity pattern of 21-cm radiation from the dark ages can be decomposed geometrically into curl and curl-free components. Lensing by primordial gravitational waves induces a curl component, while the contribution from lensing by density fluctuations is strongly suppressed. Angular fluctuations in the 21-cm background extend to very small angular scales, and measurements at different frequencies probe different shells in redshift space. There is thus a huge trove of information with which to reconstruct the curl component of the lensing field, allowing tensor-to-scalar ratios conceivably as small as r~10(-9)-far smaller than those currently accessible-to be probed. PMID:23003237
New optical surveys for gravitationally lensed quasars
Morgan, Nicholas D., 1975-
2002-01-01
This thesis describes four new optical surveys for gravitationally lensed quasars. The goal of this work has been to (1) explore new strategies for conducting optical surveys, especially in the southern hemisphere, in the ...
EFFECT OF MASKED REGIONS ON WEAK-LENSING STATISTICS
Shirasaki, Masato; Yoshida, Naoki [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Hamana, Takashi, E-mail: masato.shirasaki@utap.phys.s.u-tokyo.ac.jp [National Astronomical Observatory of Japan, Tokyo 181-0015 (Japan)
2013-09-10
Sky masking is unavoidable in wide-field weak-lensing observations. We study how masks affect the measurement of statistics of matter distribution probed by weak gravitational lensing. We first use 1000 cosmological ray-tracing simulations to examine in detail the impact of masked regions on the weak-lensing Minkowski Functionals (MFs). We consider actual sky masks used for a Subaru Suprime-Cam imaging survey. The masks increase the variance of the convergence field and the expected values of the MFs are biased. The bias then compromises the non-Gaussian signals induced by the gravitational growth of structure. We then explore how masks affect cosmological parameter estimation. We calculate the cumulative signal-to-noise ratio (S/N) for masked maps to study the information content of lensing MFs. We show that the degradation of S/N for masked maps is mainly determined by the effective survey area. We also perform simple {chi}{sup 2} analysis to show the impact of lensing MF bias due to masked regions. Finally, we compare ray-tracing simulations with data from a Subaru 2 deg{sup 2} survey in order to address if the observed lensing MFs are consistent with those of the standard cosmology. The resulting {chi}{sup 2}/n{sub dof} = 29.6/30 for three combined MFs, obtained with the mask effects taken into account, suggests that the observational data are indeed consistent with the standard {Lambda}CDM model. We conclude that the lensing MFs are a powerful probe of cosmology only if mask effects are correctly taken into account.
Probing the accelerating Universe with radio weak lensing in the JVLA Sky Survey
Brown, M L; Amara, A; Bacon, D J; Battye, R A; Bell, M R; Beswick, R J; Birkinshaw, M; Böhm, V; Bridle, S; Browne, I W A; Casey, C M; Demetroullas, C; lin, T Enß; Ferreira, P G; Garrington, S T; Grainge, K J B; Gray, M E; Hales, C A; Harrison, I; Heavens, A F; Heymans, C; Hung, C L; Jackson, N J; Jarvis, M J; Joachimi, B; Kay, S T; Kitching, T D; Leahy, J P; Maartens, R; Miller, L; Muxlow, T W B; Myers, S T; Nichol, R C; Patel, P; Pritchard, J R; Raccanelli, A; Refregier, A; Richards, A M S; Riseley, C; Santos, M G; Scaife, A M M; Schäfer, B M; Schilizzi, R T; Smail, I; Starck, J -L; Szepietowski, R M; Taylor, A N; Whittaker, L; Wrigley, N; Zuntz, J
2013-01-01
We outline the prospects for performing pioneering radio weak gravitational lensing analyses using observations from a potential forthcoming JVLA Sky Survey program. A large-scale survey with the JVLA can offer interesting and unique opportunities for performing weak lensing studies in the radio band, a field which has until now been the preserve of optical telescopes. In particular, the JVLA has the capacity for large, deep radio surveys with relatively high angular resolution, which are the key characteristics required for a successful weak lensing study. We highlight the potential advantages and unique aspects of performing weak lensing in the radio band. In particular, the inclusion of continuum polarisation information can greatly reduce noise in weak lensing reconstructions and can also remove the effects of intrinsic galaxy alignments, the key astrophysical systematic effect that limits weak lensing at all wavelengths. We identify a VLASS "deep fields" program (total area ~10-20 square degs), to be con...
Neutrino mass and dark energy from weak lensing.
Abazajian, Kevork N; Dodelson, Scott
2003-07-25
Weak gravitational lensing of background galaxies by intervening matter directly probes the mass distribution in the Universe. This distribution is sensitive to both the dark energy and neutrino mass. We examine the potential of lensing experiments to measure features of both simultaneously. Focusing on the radial information contained in a future deep 4000 deg(2) survey, we find that the expected (1-sigma) error on a neutrino mass is 0.1 eV, if the dark-energy parameters are allowed to vary. The constraints on dark-energy parameters are similarly restrictive, with errors on w of 0.09. PMID:12906650
Kinematic Weak Lensing: Forecasts for a Next-Generation Lensing Measurement
NASA Astrophysics Data System (ADS)
Huff, Eric M.; George, M. R.; Krause, E.; Eifler, T.; Schlegel, D. J.
2014-01-01
Weak gravitational lensing by cosmic structure is a major science driver for several large ongoing and planned imaging surveys, such as the Dark Energy Survey and the Euclid space mission. Traditionally, lensing in this regime is measured via statistical distortions to the shapes of galaxies. While the cosmological constraining power for a large imaging survey employing this technique is great, the signal itself is noisy, and susceptible to a number of systematic biases. Here we propose a new lensing technique that makes use of the kinematics of disk galaxies and the Tully-Fisher relation. Our method controls for that part of the shape noise which arises from the random orientation of galaxy disks, and promises an increase in signal-to-noise sufficient to bring weak lensing measurements within the reach of the next generation of spectroscopic surveys. We define such a survey here, discuss the advantages and disadvantages, and show that the cosmological constraining power of this kinematic weak lensing method is competitive with the most powerful planned lensing measurements.
Strong gravitational lensing with the SKA
McKean, J P; Vegetti, S; Rybak, M; Serjeant, S; Koopmans, L V E; Metcalf, R B; Fassnacht, C D; Marshall, P J; Pandey-Pommier, M
2015-01-01
Strong gravitational lenses provide an important tool to measure masses in the distant Universe, thus testing models for galaxy formation and dark matter; to investigate structure at the Epoch of Reionization; and to measure the Hubble constant and possibly w as a function of redshift. However, the limiting factor in all of these studies has been the currently small samples of known gravitational lenses (~10^2). The era of the SKA will transform our understanding of the Universe with gravitational lensing, particularly at radio wavelengths where the number of known gravitational lenses will increase to ~10^5. Here we discuss the technical requirements, expected outcomes and main scientific goals of a survey for strong gravitational lensing with the SKA. We find that an all-sky (3pi sr) survey carried out with the SKA1-MID array at an angular resolution of 0.25-0.5 arcsec and to a depth of 3 microJy / beam is required for studies of galaxy formation and cosmology with gravitational lensing. In addition, the ca...
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...
Strong Gravitational Lensing: Relativity in Action
NASA Astrophysics Data System (ADS)
Wambsganss, Joachim
2009-05-01
Deflection of light by gravity was predicted by Einstein's Theory of General Relativity and observationally confirmed in 1919. In the following decades, various aspects of the gravitational lens effect were explored theoretically, among them measuring the Hubble constant from multiple images of a background source, making use of the magnifying effect as a gravitational telescope, or the possibility of a "relativistic eclipse" as a perfect test of GR. Only in 1979, gravitational lensing became an observational science when the first doubly imaged quasar was discovered. Today lensing is a booming part of astrophysics and cosmology. A whole suite of strong lensing phenomena have been investigated since: multiple quasars, giant luminous arcs, Einstein rings, quasar microlensing, and galactic microlensing. The most recent lensing application is the detection of extrasolar planets. Lensing has contributed significant new results in areas as different as the cosmological distance scale, mass determination of galaxy clusters, physics of quasars, searches for dark matter in galaxy halos, structure of the Milky Way, stellar atmospheres and exoplanets. A guided tour through some of these applications -- with both photometric and astrometric signatures of lensing being discussed -- will illustrate how gravitational lensing has established itself as a very useful universal astrophysical tool.
Strong gravitational lensing: relativity in action
NASA Astrophysics Data System (ADS)
Wambsganss, Joachim
2010-01-01
Deflection of light by gravity was predicted by Einstein's Theory of General Relativity and observationally confirmed in 1919. In the following decades, various aspects of the gravitational lens effect were explored theoretically, among them measuring the Hubble constant from multiple images of a background source, making use of the magnifying effect as a gravitational telescope, or the possibility of a “relativistic eclipse” as a perfect test of GR. Only in 1979, gravitational lensing became an observational science when the first doubly imaged quasar was discovered. Today lensing is a booming part of astrophysics and cosmology. A whole suite of strong lensing phenomena have been investigated: multiple quasars, giant luminous arcs, Einstein rings, quasar microlensing, and galactic microlensing. The most recent lensing application is the detection of extrasolar planets. Lensing has contributed significant new results in areas as different as the cosmological distance scale, mass determination of galaxy clusters, physics of quasars, searches for dark matter in galaxy halos, structure of the Milky Way, stellar atmospheres and exoplanets. A guided tour through some of these applications will illustrate how gravitational lensing has established itself as a very useful universal astrophysical tool.
Shirasaki, Masato
2013-01-01
Measurement of cosmic shear using weak gravitational lensing is a challenging task that involves a number of complicated procedures. We study in detail the systematic errors in measurement of weak lensing Minkowski Functionals (MFs). Specifically, we focus on systematics associated with galaxy shape measurement, photometric redshift errors, and shear calibration correction. We first generate mock weak lensing catalogues that directly incorporate the actual observational characteristics of the Canada-France-Hawaii Lensing Survey (CFHTLenS). We then perform the Fisher analysis using the large set of mock catalogues for various cosmological models. We find that the statistical error associated with the observational effects degrades the cosmological parameter constraints by a factor of a few. Subaru Hyper Suprime-Cam (HSC) survey with the sky coverage of ~1400 deg2 will constrain the dark energy equation of state parameter with an error of Delta w_0 ~ 0.25 by the lensing MFs alone, but biases induced by the syst...
Dark matter and galaxies: using gravitational lensing to map their relative distributions
Koens, Lars Arnout
2015-07-01
Cosmological constraints from galaxy surveys are as accurate as our understanding of the relative distributions of dark matter and galaxies, known as galaxy bias. Weak gravitational lensing is a powerful probe of galaxy ...
Okura, Yuki [National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan); Futamase, Toshifumi, E-mail: yuki.okura.2014@gmail.com, E-mail: tof@astr.tohoku.ac.jp [Astronomical Institute, Tohoku University, Sendai 980-8578 (Japan)
2014-09-10
Highly accurate weak lensing analysis is urgently required for planned cosmic shear observations. For this purpose we have eliminated various systematic noises in the measurement. The point-spread function (PSF) effect is one of them. A perturbative approach for correcting the PSF effect on the observed image ellipticities has been previously employed. Here we propose a new non-perturbative approach for PSF correction that avoids the systematic error associated with the perturbative approach. The new method uses an artificial image for measuring shear which has the same ellipticity as the lensed image. This is done by re-smearing the observed galaxy images and observed star images (PSF) with an additional smearing function to obtain the original lensed galaxy images. We tested the new method with simple simulated objects that have Gaussian or Sérsic profiles smeared by a Gaussian PSF with sufficiently large size to neglect pixelization. Under the condition of no pixel noise, it is confirmed that the new method has no systematic error even if the PSF is large and has a high ellipticity.
Bayesian Inference of CMB Gravitational Lensing
NASA Astrophysics Data System (ADS)
Anderes, Ethan; Wandelt, Benjamin D.; Lavaux, Guilhem
2015-08-01
The Planck satellite, along with several ground-based telescopes, has mapped the cosmic microwave background (CMB) at sufficient resolution and signal-to-noise so as to allow a detection of the subtle distortions due to the gravitational influence of the intervening matter distribution. A natural modeling approach is to write a Bayesian hierarchical model for the lensed CMB in terms of the unlensed CMB and the lensing potential. So far there has been no feasible algorithm for inferring the posterior distribution of the lensing potential from the lensed CMB map. We propose a solution that allows efficient Markov Chain Monte Carlo sampling from the joint posterior of the lensing potential and the unlensed CMB map using the Hamiltonian Monte Carlo technique. The main conceptual step in the solution is a re-parameterization of CMB lensing in terms of the lensed CMB and the “inverse lensing” potential. We demonstrate a fast implementation on simulated data, including noise and a sky cut, that uses a further acceleration based on a very mild approximation of the inverse lensing potential. We find that the resulting Markov Chain has short correlation lengths and excellent convergence properties, making it promising for applications to high-resolution CMB data sets in the future.
Comments on the gravitational lensing magnification
Takashi Hamana
1998-08-29
We rederive a relation between gravitational lensing magnification relative to the standard Friedmann distance and one relative to the Dyer-Roeder distance by investigating the null geodesic deviation equation. We show that the relation comes from a natural consequence of the definition of the lensing magnification matrices and is not based on the averaging of the magnifications, which has conventionally been used to derive it. We therefore conclude that the relation is true for each individual ray bundle.
Weak Lensing from Space II: Dark Matter Mapping
Richard Massey; Jason Rhodes; Alexandre Refregier; Justin Albert; David Bacon; Gary Bernstein; Richard Ellis; Bhuvnesh Jain; Tim McKay; Saul Perlmutter; Andy Taylor
2004-03-12
We study the accuracy with which weak lensing measurements could be made from a future space-based survey, predicting the subsequent precisions of 3-dimensional dark matter maps, projected 2-dimensional dark matter maps, and mass-selected cluster catalogues. As a baseline, we use the instrumental specifications of the Supernova/Acceleration Probe (SNAP) satellite. We first compute its sensitivity to weak lensing shear as a function of survey depth. Our predictions are based on detailed image simulations created using `shapelets', a complete and orthogonal parameterization of galaxy morphologies. We incorporate a realistic redshift distribution of source galaxies, and calculate the average precision of photometric redshift recovery using the SNAP filter set to be Delta z=0.034. The high density of background galaxies resolved in a wide space-based survey allows projected dark matter maps with a rms sensitivity of 3% shear in 1 square arcminute cells. This will be further improved using a proposed deep space-based survey, which will be able to detect isolated clusters using a 3D lensing inversion techniques with a 1 sigma mass sensitivity of approximately 10^13 solar masses at z~0.25. Weak lensing measurements from space will thus be able to capture non-Gaussian features arising from gravitational instability and map out dark matter in the universe with unprecedented resolution.
Time Delay in Swiss Cheese Gravitational Lensing
Chen, Bin; Dai, Xinyu
2010-01-01
We compute time delays for gravitational lensing in a flat LambdaCDM 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 non-linear 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 ~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.
Time Delay in Swiss Cheese Gravitational Lensing
Bin Chen; Ronald Kantowski; Xinyu Dai
2010-06-17
We compute time delays for gravitational lensing in a flat LambdaCDM 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 non-linear 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 ~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.
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 ...
Oguri, Masamune; Hennawi, Joseph F.; Gladders, Michael D.; Dahle, Haakon; Natarajan, Priyamvada; Dalal, Neal; Koester, Benjamin P.; Sharon, Keren; Bayliss, Matthew
2009-01-29
We derive radial mass profiles of four strong lensing selected clusters which show prominent giant arcs (Abell 1703, SDSS J1446+3032, SDSS J1531+3414, and SDSS J2111-0115), by combining detailed strong lens modeling with weak lensing shear measured from deep Subaru Suprime-cam images. Weak lensing signals are detected at high significance for all four clusters, whose redshifts range from z = 0.28 to 0.64. We demonstrate that adding strong lensing information with known arc redshifts significantly improves constraints on the mass density profile, compared to those obtained from weak lensing alone. While the mass profiles are well fitted by the universal form predicted in N-body simulations of the {Lambda}-dominated cold dark matter model, all four clusters appear to be slightly more centrally concentrated (the concentration parameters c{sub vir} {approx} 8) than theoretical predictions, even after accounting for the bias toward higher concentrations inherent in lensing selected samples. Our results are consistent with previous studies which similarly detected a concentration excess, and increases the total number of clusters studied with the combined strong and weak lensing technique to ten. Combining our sample with previous work, we find that clusters with larger Einstein radii are more anomalously concentrated. We also present a detailed model of the lensing cluster Abell 1703 with constraints from multiple image families, and find the dark matter inner density profile to be cuspy with the slope consistent with -1, in agreement with expectations.
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.
Quantifying the effect of baryon physics on weak lensing tomography
Semboloni, Elisabetta; Schaye, Joop; van Daalen, Marcel P; McCarthy, Ian J
2011-01-01
We use matter power spectra from cosmological hydrodynamic simulations to quantify the effect of baryon physics on the weak gravitational lensing shear signal. The simulations consider a number of processes, such as radiative cooling, star formation, supernovae and feedback from active galactic nuclei (AGN). Van Daalen et al. (2011) used the same simulations to show that baryon physics, in particular the strong feedback that is required to solve the overcooling problem, modifies the matter power spectrum on scales relevant for cosmological weak lensing studies. As a result, the use of power spectra from dark matter simulations can lead to significant biases in the inferred cosmological parameters. We show that the typical biases are much larger than the precision with which future missions aim to constrain the dark energy equation of state, w_0. For instance, the simulation with AGN feedback, which reproduces X-ray and optical properties of groups of galaxies, gives rise to a ~40% bias in w_0. We demonstrate ...
Galilean-invariant scalar fields can strengthen gravitational lensing.
Wyman, Mark
2011-05-20
The mystery of dark energy suggests that there is new gravitational physics on long length scales. Yet light degrees of freedom in gravity are strictly limited by Solar System observations. We can resolve this apparent contradiction by adding a Galilean-invariant scalar field to gravity. Called Galileons, these scalars have strong self-interactions near overdensities, like the Solar System, that suppress their dynamical effect. These nonlinearities are weak on cosmological scales, permitting new physics to operate. In this Letter, we point out that a massive-gravity-inspired coupling of Galileons to stress energy can enhance gravitational lensing. Because the enhancement appears at a fixed scaled location for dark matter halos of a wide range of masses, stacked cluster analysis of weak lensing data should be able to detect or constrain this effect. PMID:21668215
Testing Cosmogonic Models with Gravitational Lensing
Joachim Wambsganss; Renyue Cen; Jeremiah P. Ostriker; Edwin L. Turner
1994-09-16
Gravitational lensing provides a strict test of cosmogonic models. Detailed numerical propagation of light rays through a universe having a distribution of inhomogeneities derived from the standard CDM (cold dark matter) scenario with the aid of massive, fully nonlinear computer simulations is used to test the model. It predicts that we should have seen far more widely split quasar images than have been found. These and other inconsistencies rule out the COBE normalized CDM model with $\\Omega=1$ and $H_0=50$km/s/Mpc; but variants of this model might be constructed, which could pass the stringent tests provided by strong gravitational lensing.
Cosmological test using strong gravitational lensing systems
NASA Astrophysics Data System (ADS)
Yuan, C. C.; Wang, F. Y.
2015-09-01
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 ?? of images, the velocity dispersion ? of the lensing galaxies and the combination of these two effects, ??/?2. In this paper, in order to carry out one-on-one comparisons between ?CDM universe and Rh = ct universe, we use a sample containing 36 strong lensing systems with the measurement of velocity dispersion from the Sloan Lens Advanced Camera for Surveys (SLACS) and Lens Structure and Dynamic survey (LSD) survey. Concerning the time-delay effect, 12 two-image lensing systems with ?? are also used. In addition, Monte Carlo 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 per cent confidence level. Comparing with constraints from ?? and the velocity dispersion ?, we find that using ??/?2 can improve the discrimination between cosmological models. Despite the independence tests of these methods reveal a correlation between ??/?2 and ?, ??/?2 could be considered as an improved method of ? if more data samples are available.
Cluster Cores, Gravitational Lensing, and Cosmology
Ricardo A. Flores; Joel R. Primack
1995-12-11
Many multiply--imaged quasars have been found over the years, but none so far with image separation in excess of $8\\arcsec$. The absence of such large splittings has been used as a test of cosmological models: the standard Cold Dark Matter model has been excluded on the basis that it predicts far too many large--separation double images. These studies assume that the lensing structure has the mass profile of a singular isothermal sphere. However, such large splittings would be produced by very massive systems such as clusters of galaxies, for which other gravitational lensing data suggest less singular mass profiles. Here we analyze two cases of mass profiles for lenses: an isothermal sphere with a finite core radius (density $\\rho \\propto (r^2+r_{core}^2)^{-1})$, and a Hernquist profile ($\\rho \\propto r^{-1}(r+a)^{-3}$). We find that small core radii $r_{core} \\sim 30 h^{-1}$ kpc, as suggested by the cluster data, or large $a \\gsim 300 h^{-1}$ kpc, as needed for compatibility with gravitational distortion data, would reduce the number of large--angle splittings by an order of magnitude or more. Thus, it appears that these tests are sensitive both to the cosmological model (number density of lenses) and to the inner lens structure, which is unlikely to depend sensitively on the cosmology, making it difficult to test the cosmological models by large--separation quasar lensing until we reliably know the structure of the lenses themselves.
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 of large scale structure in the presence of screening
Tessore, Nicolas; Metcalf, R Benton; Ferreira, Pedro G
2015-01-01
A number of alternatives to general relativity exhibit gravitational screening in the non-linear regime of structure formation. We describe a set of algorithms that can produce weak lensing maps of large scale structure in such theories and can be used to generate mock surveys for cosmological analysis. By analysing a few basic statistics we indicate how these alternatives can be distinguished from general relativity with future weak lensing surveys.
Gravitational Lensing of Supernova Neutrinos
Mena, Olga; Mocioiu, Irina; 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.
Predicted Lens Redshifts and Magnitudes for Gravitational Lenses
Phillip Helbig
1995-07-31
For suitable gravitational lens systems with unknown lens redshifts, the redshifts and brightnesses (in different colours) of the lenses are predicted for a variety of cosmological models, for both elliptical and spiral galaxy lenses. Besides providing hints as to which systems should be observed with a realistic chance of measuring the lens redshifts, which are needed for detailed lensing statistics and for modelling the lenses, these calculations give a visual impression of the influence of the cosmological model in gravitational lensing.
Weak lensing induced by second-order vector mode
NASA Astrophysics Data System (ADS)
Saga, Shohei; Yamauchi, Daisuke; Ichiki, Kiyotomo
2015-09-01
The vector mode of cosmological perturbation theory imprints characteristic signals on the weak lensing signals such as curl and B modes which are never imprinted by the scalar mode. However, the vector mode is neglected in the standard first-order cosmological perturbation theory since it only has a decaying mode. This situation changes if the cosmological perturbation theory is expanded up to second order. The second-order vector and tensor modes are inevitably induced by the product of the first-order scalar modes. We study the effect of the second-order vector mode on the weak lensing curl and B modes. We find that the curl mode induced by the second-order vector mode is comparable to that induced by the primordial gravitational waves with the tensor-to-scalar ratio r =0.1 at ??200 . In this case, the curl mode induced by the second-order vector mode dominates at ?>200 . Furthermore, the B-mode cosmic shear induced by the second-order vector mode dominates on almost all scales. However, we find that the observational signatures of the second-order vector and tensor modes cannot exceed the expected noise of ongoing and upcoming weak lensing measurements. We conclude that the curl and B modes induced by the second-order vector and tensor modes are unlikely to be detected in future experiments.
Weak lensing induced by second-order vector mode
Shohei Saga; Daisuke Yamauchi; Kiyotomo Ichiki
2015-05-11
Vector mode of cosmological perturbation theory imprints characteristic signals on the weak lensing signals such as curl- and B-modes which are never imprinted by the scalar mode. However, the vector mode is neglected in the standard first-order cosmological perturbation theory since it only has a decaying mode. This situation changes if the cosmological perturbation theory is expanded up to second order. The second-order vector and tensor modes are inevitably induced by the product of the first-order scalar modes. We study the effect of the second-order vector mode on the weak lensing curl- and B-modes. The curl-mode induced by the second-order vector mode dominates instead of the primordial gravitational waves when the tensor-to-scalar ratio is $r = 0.1$ and the second-order tensor mode at $\\ell \\geq 200$. Furthermore, the B-mode cosmic shear induced by the second-order vector mode dominates on almost all scales. However, we find that the observational signatures of the second-order vector and tensor modes cannot exceed the expected noise of ongoing and upcoming weak lensing measurements. We conclude that the curl- and B-modes induced by the second-order vector and tensor modes are unlikely to be detected in future experiments.
First measurement of gravitational lensing by cosmic voids in SDSS
NASA Astrophysics Data System (ADS)
Melchior, Peter; Sutter, P. M.; Sheldon, Erin S.; Krause, Elisabeth; Wandelt, Benjamin D.
2014-06-01
We report the first measurement of the diminutive lensing signal arising from matter underdensities associated with cosmic voids. While undetectable individually, by stacking the weak gravitational shear estimates around 901 voids detected in Sloan Digital Sky Survey DR7 by Sutter et al., we find substantial evidence for a depression of the lensing signal compared to the cosmic mean. This depression is most pronounced at the void radius, in agreement with analytical models of void matter profiles. Even with the largest void sample and imaging survey available today, we cannot put useful constraints on the radial dark matter void profile. We invite independent investigations of our findings by releasing data and analysis code to the public at https://github.com/pmelchior/void-lensing.
Strong gravitational lenses in the 2020s
NASA Astrophysics Data System (ADS)
Oguri, Masamune
2014-07-01
Strong gravitational lenses are a useful cosmological probe, and will continue to be so until 2020s. TMT will play a crucial role in strong lens studies as it allows us to take very high spatial resolution images with help of adaptive optics. In the talk I will discuss prospects for future strong lens searches in wide-field surveys, and show what kind of studies will be enabled in the TMT era. I also discuss our ongoing adaptive optics observations of strongly lensed quasars that highlight the difficulty and importance of an accurate characterization of the point spread function in adaptive optics observations.
Disentangling dark sector models using weak lensing statistics
NASA Astrophysics Data System (ADS)
Giocoli, Carlo; Metcalf, R. Benton; Baldi, Marco; Meneghetti, Massimo; Moscardini, Lauro; Petkova, Margarita
2015-09-01
We perform multiplane 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 (CDM). We show that the presence of the coupling is evident not only in the redshift evolution of the normalization of the convergence power spectrum, but also in differences in non-linear structure formation with respect to ?CDM. Using a tomographic approach under the assumption of a ?CDM cosmology, we demonstrate that weak lensing measurements would result in a ?8 value that changes with the source redshift if the true underlying cosmology is a coupled dark energy (cDE) one. This provides a generic null test for these types of models. We also find that different models of cDE can show either an enhanced or a suppressed correlation between convergence maps with differing source redshifts as compared to ?CDM. This would provide a direct way to discriminate between different possible realizations of the cDE scenario. Finally, we discuss the impact of the coupling on several lensing observables for different source redshifts and angular scales with realistic source redshift distributions for current ground-based and future space-based lensing surveys.
Direct shear mapping - a new weak lensing tool
NASA Astrophysics Data System (ADS)
de Burgh-Day, C. O.; Taylor, E. N.; Webster, R. L.; Hopkins, A. M.
2015-08-01
We have developed a new technique called direct shear mapping (DSM) to measure gravitational lensing shear directly from observations of a single background source. The technique assumes the velocity map of an unlensed, stably rotating galaxy will be rotationally symmetric. Lensing distorts the velocity map making it asymmetric. The degree of lensing can be inferred by determining the transformation required to restore axisymmetry. This technique is in contrast to traditional weak lensing methods, which require averaging an ensemble of background galaxy ellipticity measurements, to obtain a single shear measurement. We have tested the efficacy of our fitting algorithm with a suite of systematic tests on simulated data. We demonstrate that we are in principle able to measure shears as small as 0.01. In practice, we have fitted for the shear in very low redshift (and hence unlensed) velocity maps, and have obtained null result with an error of ±0.01. This high-sensitivity results from analysing spatially resolved spectroscopic images (i.e. 3D data cubes), including not just shape information (as in traditional weak lensing measurements) but velocity information as well. Spirals and rotating ellipticals are ideal targets for this new technique. Data from any large Integral Field Unit (IFU) or radio telescope is suitable, or indeed any instrument with spatially resolved spectroscopy such as the Sydney-Australian-Astronomical Observatory Multi-Object Integral Field Spectrograph (SAMI), the Atacama Large Millimeter/submillimeter Array (ALMA), the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) and the Square Kilometer Array (SKA).
Gravitational lensing statistics of amplified supernovae
NASA Technical Reports Server (NTRS)
Linder, Eric V.; Wagoner, Robert V.; Schneider, P.
1988-01-01
Amplification statistics of gravitationally lensed supernovae can provide a valuable probe of the lensing matter in the universe. A general probability distribution for amplification by compact objects is derived which allows calculation of the lensed fraction of supernovae at or greater than an amplification A and at or less than an apparent magnitude. Comparison of the computed fractions with future results from ongoing supernova searches can lead to determination of the mass density of compact dark matter components with masses greater than about 0.001 solar mass, while the time-dependent amplification (and polarization) of the expanding supernovae constrain the individual masses. Type II supernovae are found to give the largest fraction for deep surveys, and the optimum flux-limited search is found to be at approximately 23d magnitude, if evolution of the supernova rate is neglected.
Spurious Shear in Weak Lensing with LSST
Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.
2012-09-19
The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
The geometry of gravitational lensing magnification
Amir Babak Aazami; Marcus C. Werner
2015-07-10
We present a definition of unsigned magnification in gravitational lensing valid on arbitrary convex normal neighborhoods of time oriented Lorentzian manifolds. This definition is a function defined at any two points along a null geodesic that lie in a convex normal neighborhood, and foregoes the usual notions of lens and source planes in gravitational lensing. Rather, it makes essential use of the van Vleck determinant, which we present via the exponential map, and Etherington's definition of luminosity distance for arbitrary spacetimes. We then specialize our definition to spacetimes, like Schwarzschild's, in which the lens is compact and isolated, and show that our magnification function is monotonically increasing along any geodesic contained within a convex normal neighborhood.
Strong gravitational lensing of gravitational waves in Einstein Telescope
Piórkowska, Aleksandra; Biesiada, Marek [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Zhu, Zong-Hong, E-mail: aleksandra.piorkowska@us.edu.pl, E-mail: marek.biesiada@us.edu.pl, E-mail: zhuzh@bnu.edu.cn [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)
2013-10-01
Gravitational wave experiments have entered a new stage which gets us closer to the opening a new observational window on the Universe. In particular, the Einstein Telescope (ET) is designed to have a fantastic sensitivity that will provide with tens or hundreds of thousand NS-NS inspiral events per year up to the redshift z = 2. Some of such events should be gravitationally lensed by intervening galaxies. We explore the prospects of observing gravitationally lensed inspiral NS-NS events in the Einstein telescope. Being conservative we consider the lens population of elliptical galaxies. It turns out that depending on the local insipral rate ET should detect from one per decade detection in the pessimistic case to a tens of detections per year for the most optimistic case. The detection of gravitationally lensed source in gravitational wave detectors would be an invaluable source of information concerning cosmography, complementary to standard ones (like supernovae or BAO) independent of the local cosmic distance ladder calibrations.
Strong Gravitational Lensing and Dynamical Dark Energy
Andrea V. Maccio'
2005-06-06
We study the strong gravitational lensing properties of galaxy clusters obtained from N-body simulations with different kind of Dark Energy (DE). We consider both dynamical DE, due to a scalar field self--interacting through Ratra-Peebles (RP) or SUGRA potentials, and DE with constant negative w=p/rho= -1 (LCDM). We have 12 high resolution lensing systems for each cosmological model with a mass greater than 5x10^{14} solar masses. Using a Ray Shooting technique we make a detailed analysis of the lensing properties of these clusters with particular attention to the number of arcs and their properties (magnification, length and width). We found that the number of giant arcs produced by galaxy clusters changes in a considerable way from LCDM models to Dynamical Dark Energy models with a RP or SUGRA potentials. These differences originate from the different epochs of cluster formation and from the non-linearity of the strong lensing effect. We suggest the Strong lensing is one of the best tool to discriminate among different kind of Dark Energy.
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.
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.
Gravitational Lensing: Recent Progress & Future Goals
NASA Technical Reports Server (NTRS)
Brainerd, Tereasa
2001-01-01
This award was intended to provide financial support for an international astrophysics conference on gravitational lensing which was held at Boston University from July 25 to July 30, 1999. Because of the nature of the award, no specific research was proposed, nor was any carried out. The participants at the conference presented results of their on-going research efforts, and written summaries of their presentations have been published by the Astronomical Society of the Pacific as part of their conference series. The reference to the conference proceedings book is Gravitational Lensing: Recent Progress and Future Goals, ASP Conference Series volume 237, eds. T. G. Brainerd and C. S. Kochanek (2001). The ISBN number of this book is 1-58381-074-9. The goal of the conference was to bring together both senior and junior investigators who were actively involved in all aspects of gravitational lensing research. This was the first conference in four years to address gravitational lensing from such a broad perspective (the previous such conference being IAU Symposium 173 held in Melbourne, Australia in July 1995). The conference was attended by 190 participants, who represented of order 70 different institutions and of order 15 different countries. The Scientific Organizing Committee members were Matthias Bartelmann (co-chair), Tereasa Brainerd (co-chair), Ian Browne, Richard Ellis, Nick Kaiser, Yannick Mellier, Sjur Refsdal, HansWalter Rix, Joachim Wambsganss, and Rachel Webster. The Local Organizing Committee members were Tereasa Brainerd (chair), Emilio Falco, Jacqueline Hewitt, Christopher Kochanek, and Irwin Shapiro. The oral sessions were organized around specific applications of gravitational lensing and included invited reviews, invited 'targeted talks', and contributed talks. The review speakers were Roger Blandford, Tereasa Brainerd, Gus Evrard, Nick Kaiser, Guinevere Kaufmann, Chris Kochanek, Charley Lineweaver, Gerry Luppino, Shude Mao, Paul Schechter, Peter Snhneider, amd Ed Turner. The 'targeted talk' speakers were Andy Boden, Ian Browne, Emilio Falco, Harry Ferguson, Bhuvnesh Jain, Christine Jones, Arlie Petters, Hans-Walter Rix, Penny Sackett, Prasenjit Saha, Virginia Trimble, and Joachim Wambsganss. Due to limited time, only 25% of the abstracts which were submitted for consideration as contributed talks could actually be accepted for the final program; those which were not selected as talks were presented as posters, and a special poster viewing session was held to allow participants to present their work. A copy of the complete Final Program of the conference is included in the following pages.
Virbhadra, K. S.; Keeton, C. R. [Department of Mathematics, Physics and Statistics, University of the Sciences in Philadelphia, Philadelphia, PA 19104 (United States); Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)
2008-06-15
We model the massive dark object at the center of the Galaxy as a Schwarzschild black hole as well as Janis-Newman-Winicour naked singularities, characterized by the mass and scalar charge parameters, and study gravitational lensing (particularly time delay, magnification centroid, and total magnification) by them. We find that the lensing features are qualitatively similar (though quantitatively different) for Schwarzschild black holes, weakly naked, and marginally strongly naked singularities. However, the lensing characteristics of strongly naked singularities are qualitatively very different from those due to Schwarzschild black holes. The images produced by Schwarzschild black hole lenses and weakly naked and marginally strongly naked singularity lenses always have positive time delays. On the other hand, strongly naked singularity lenses can give rise to images with positive, zero, or negative time delays. In particular, for a large angular source position the direct image (the outermost image on the same side as the source) due to strongly naked singularity lensing always has a negative time delay. We also found that the scalar field decreases the time delay and increases the total magnification of images; this result could have important implications for cosmology. As the Janis-Newman-Winicour metric also describes the exterior gravitational field of a scalar star, naked singularities as well as scalar star lenses, if these exist in nature, will serve as more efficient cosmic telescopes than regular gravitational lenses.
Strong Gravitational Lensing in the Einstein-Proca Theory
Guoping Li; Yan Zhang; Li Zhang; Zhongwen Feng; Xiaotao Zu
2015-06-29
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.
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.
Applications of the Gauss-Bonnet theorem to gravitational lensing
G W Gibbons; M C Werner
2008-07-05
In this geometrical approach to gravitational lensing theory, we apply the Gauss-Bonnet theorem to the optical metric of a lens, modelled as a static, spherically symmetric, perfect non-relativistic fluid, in the weak deflection limit. We find that the focusing of the light rays emerges here as a topological effect, and we introduce a new method to calculate the deflection angle from the Gaussian curvature of the optical metric. As examples, the Schwarzschild lens, the Plummer sphere and the singular isothermal sphere are discussed within this framework.
Gravitational lensing by a rotating massive object in a plasma
NASA Astrophysics Data System (ADS)
Morozova, V. S.; Ahmedov, B. J.; Tursunov, A. A.
2013-08-01
We study gravitational lensing in the vicinity of a slowly rotating massive object surrounded by a plasma. We have studied two effects: (i) the influence of the frame dragging on the deflection angle of the light ray in the presence of plasma (ii) Faraday rotation of the polarization plane of the light. We derive the expression for the lensing angle in a non-diagonal space-time in the weak field regime in the presence of plasma and discuss it for the spacetime metric of the slowly rotating object. The obtained deflection angle depends on (i) the frequency of the electromagnetic wave, due to the dispersion properties of the plasma; (ii) the gravitational mass M; and (iii) the angular momentum J of the gravitational lens. We studied the influence of rotation of the gravitational lens on the magnification of brightness of the source star in the case of microlensing and have shown that it is negligibly small. For the completeness of our study the effect of the Faraday rotation of the polarization plane is considered.
Gravitational Aharonov-Bohm effect and gravitational lensing
A. Tartaglia
2000-03-08
Considering the spacetime around a rotating massif body it is seen that the time of flight of a light ray is different whether it travels on one side of the source or on the other. The difference is proportional to the angular momentum of the body. In the case that a compact rapidly rotating object is the source of a gravitational lensing effect, the contribution coming from the above mentioned gravitational Aharonov-Bohm effect should be added to the other causes of phase difference between light rays coming from different images of the same object.
Weak lensing using only galaxy position angles
NASA Astrophysics Data System (ADS)
Whittaker, Lee; Brown, Michael L.; Battye, Richard A.
2014-12-01
We develop a method for performing a weak lensing analysis using only measurements of galaxy position angles. By analysing the statistical properties of the galaxy orientations given a known intrinsic ellipticity distribution, we show that it is possible to obtain estimates of the shear by minimizing a ?2 statistic. The method is demonstrated using simulations where the components of the intrinsic ellipticity are taken to be Gaussian distributed. Uncertainties in the position angle measurements introduce a bias into the shear estimates which can be reduced to negligible levels by introducing a correction term into the formalism. We generalize our approach by developing an algorithm to obtain direct shear estimators given any azimuthally symmetric intrinsic ellipticity distribution. We introduce a method of measuring the position angles of the galaxies from noisy pixelized images, and propose a method to correct for biases which arise due to pixelization and correlations between measurement errors and galaxy ellipticities. We also develop a method to constrain the sample of galaxies used to obtain an estimate of the intrinsic ellipticity distribution such that fractional biases in the resulting shear estimates are below a given threshold value. We demonstrate the angle-only method by applying it to simulations where the ellipticities are taken to follow a lognormal distribution. We compare the performance of the position-angle-only method with the standard method based on full ellipticity measurements by reconstructing lensing convergence maps from both numerical simulations and from the Canada-France-Hawaii Lensing Survey data. We find that the difference between the convergence maps reconstructed using the two methods is consistent with noise.
Strong gravitational lensing and dark energy complementarity
Linder, Eric V.
2004-01-21
In the search for the nature of dark energy most cosmological probes measure simple functions of the expansion rate. While powerful, these all involve roughly the same dependence on the dark energy equation of state parameters, with anticorrelation between its present value w{sub 0} and time variation w{sub a}. Quantities that have instead positive correlation and so a sensitivity direction largely orthogonal to, e.g., distance probes offer the hope of achieving tight constraints through complementarity. Such quantities are found in strong gravitational lensing observations of image separations and time delays. While degeneracy between cosmological parameters prevents full complementarity, strong lensing measurements to 1 percent accuracy can improve equation of state characterization by 15-50 percent. Next generation surveys should provide data on roughly 105 lens systems, though systematic errors will remain challenging.
Weak lensing by voids in modified lensing potentials
NASA Astrophysics Data System (ADS)
Barreira, Alexandre; Cautun, Marius; Li, Baojiu; Baugh, Carlton M.; Pascoli, Silvia
2015-08-01
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 ? 10%, compared with that of GR. Overall, our results suggest that lensing by voids is a promising tool to test models of gravity that modify lensing.
Lognormal Property of Weak-Lensing Fields
NASA Astrophysics Data System (ADS)
Taruya, Atsushi; Takada, Masahiro; Hamana, Takashi; Kayo, Issha; Futamase, Toshifumi
2002-06-01
The statistical properties of weak-lensing fields are studied quantitatively using ray-tracing simulations. Motivated by an empirical lognormal model that excellently characterizes the probability distribution function of a three-dimensional mass distribution, we critically investigate the validity of the lognormal model in weak-lensing statistics. Assuming that the convergence field ? is approximately described by the lognormal distribution, we present analytic formulae of convergence for the one-point probability distribution function (PDF) and the Minkowski functionals. The validity of the lognormal models is checked in detail by comparing those predictions with ray-tracing simulations in various cold dark matter models. We find that the one-point lognormal PDF can accurately describe the non-Gaussian tails of convergence fields up to ?~10, where ? is the level threshold given by ???/1/2, although the systematic deviation from the lognormal prediction becomes manifest at higher source redshift and larger smoothing scales. The lognormal formulae for Minkowski functionals also fit the simulation results when the source redshift is low, zs=1. Accuracy of the lognormal fit remains good even at small angular scales 2'<~?<~4', where the perturbation formulae by the Edgeworth expansion break down. On the other hand, the lognormal model enables us to predict higher order moments, i.e., skewness S3,? and kurtosis S4,?, and we thus discuss the consistency by comparing the predictions with the simulation results. Since these statistics are very sensitive to the high- and low-convergence tails, the lognormal prediction does not provide a successful quantitative fit. We therefore conclude that the empirical lognormal model of the convergence field is safely applicable as a useful cosmological tool, as long as we are concerned with the non-Gaussianity of ?<~5 for low-zs samples.
Time Delay in Swiss Cheese Gravitational Lensing B. Chen,1,
Kantowski, Ron
Time Delay in Swiss Cheese Gravitational Lensing B. Chen,1, R. Kantowski,1, and X. Dai1, 1 Homer lensing in a flat CDM Swiss cheese universe. We assume a primary and secondary pair of light rays cheese cosmology [35]. Estimations of these time delays using a similar lensing model have recently
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.
COSMOLOGICAL PARAMETERS AND GRAVITATIONAL LENSING STATISTICS
Phillip Helbig
1995-02-07
The general idea of determining cosmological parameters with gravitational lensing statistics is outlined, and then recent work---with an emphasis on applicability to all cosmological models, observational bias, better statistics and robustness testing through numerical simulations---is discussed with relevance to a scheme originally introduced by Kochanek to avoid some of the uncertainties which plague other methods. The main result is that the observations at present---and probably in the future as well---are more indicative of intrinsic scatter than a hint of the correct cosmological model.
Statistics of dark matter haloes expected from weak lensing surveys
Guido Kruse; Peter Schneider
1998-06-04
The distortion of the images of faint high-redshift galaxies can be used to probe the intervening mass distribution. This weak gravitational lensing effect has been used recently to study the (projected) mass distribution of several clusters at intermediate and high redshifts. In addition, the weak lensing effect can be employed to detect (dark) matter concentrations in the Universe, based on their mass properties alone. Thus it is feasible to obtain a mass-selected sample of `clusters', and thereby probe the full range of their mass-to-light ratios. We study the expected number density of such haloes which can be detected in ongoing and future deep wide-field imaging surveys, using the number density of haloes as predicted by the Press-Schechter theory, and modeling their mass profile by the `universal' density profile found by Navarro, Frenk & White. We find that in all cosmological models considered, the number density of haloes with a signal-to-noise ratio larger than 5 exceeds 10 per square degree. With the planned MEGACAM imaging survey of $\\sim 25 deg^2$, it will be easily possible to distinguish between the most commonly discussed cosmological parameter sets.
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.
The CASTLES Imaging Survey of Gravitational Lenses
NASA Astrophysics Data System (ADS)
Peng, C. Y.; Falco, E. E.; Lehar, J.; Impey, C. D.; Kochanek, C. S.; McLeod, B. A.; Rix, H.-W.
1997-12-01
The CASTLES survey (Cfa-Arizona-(H)ST-Lens-Survey) is imaging most known small-separation gravitational lenses (or lens candidates), using the NICMOS camera (mostly H-band) and the WFPC2 (V and I band) on HST. To date nearly half of the IR imaging survey has been completed. The main goals are: (1) to search for lens galaxies where none have been directly detected so far; (2) obtain photometric redshift estimates (VIH) for the lenses where no spectroscopic redshifts exist; (3) study and model the lens galaxies in detail, in part to study the mass distribution within them, in part to identify ``simple" systems that may permit accurate time delay estimates for H_0; (3) measure the M/L evolution of the sample of lens galaxies with look-back time (to z ~ 1); (4) determine directly which fraction of sources are lensed by ellipticals vs. spirals. We will present the survey specifications and the images obtained so far.
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 ...
Interpolating Masked Weak Lensing Signal with Karhunen-Loeve Analysis
Vanderplas, Jake; Jain, Bhuvnesh; Jarvis, Mike
2011-01-01
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 ~ 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.
3D weak lensing with spin wavelets on the ball
Leistedt, Boris; Kitching, Thomas D; Peiris, Hiranya V
2015-01-01
We construct the spin flaglet transform, a wavelet transform to analyse spin signals in three dimensions. Spin flaglets can probe signal content localised simultaneously in space and frequency and, moreover, are separable so that their angular and radial properties can be controlled independently. They are particularly suited to analysing of cosmological observations such as the weak gravitational lensing of galaxies. Such observations have a unique 3D geometrical setting since they are natively made on the sky, have spin angular symmetries, and are extended in the radial direction by additional distance or redshift information. Flaglets are constructed in the harmonic space defined by the Fourier-Laguerre transform, previously defined for scalar functions and extended here to signals with spin symmetries. Thanks to various sampling theorems, both the Fourier-Laguerre and flaglet transforms are theoretically exact when applied to band-limited signals. In other words, in numerical computations the only loss of...
Weak lensing with sizes, magnitudes and shapes
NASA Astrophysics Data System (ADS)
Alsing, Justin; Kirk, Donnacha; Heavens, Alan; Jaffe, Andrew H.
2015-09-01
Weak lensing can be observed through a number of effects on the images of distant galaxies; their shapes are sheared, sizes and fluxes (magnitudes) are magnified and positions on the sky are modified by the lensing field. Galaxy shapes probe the shear field whilst size, magnitude and number density probe the convergence field. Both contain cosmological information. In this paper, we are concerned with the magnification of sizes and magnitudes of individual galaxies as a probe of cosmic convergence. We develop a Bayesian approach for inferring the convergence field from measured sizes, magnitudes and redshifts and demonstrate that this inference requires detailed knowledge of the joint distribution of intrinsic sizes and magnitudes. We build a simple parametrized model for the size-magnitude distribution and estimate this distribution for CFHTLenS galaxies. In light of the measured distribution, we show that the typical dispersion on convergence estimation is ˜0.8, compared to ˜0.38 for shear. We discuss the possibility of physical systematics for magnification (similar to intrinsic alignments for shear) and compute the expected gains in the dark energy figure-of-merit (FoM) from combining magnification with shear for different scenarios regarding systematics: accounting for intrinsic alignments but no systematics for magnification, including magnification could improve the FoM by up to a factor of ˜2.5, whilst when accounting for physical systematics in both shear and magnification we anticipate a gain between ˜25 and ˜65 per cent. The fact that shear and magnification are subject to different systematics makes magnification an attractive complement to any cosmic shear analysis.
Luminous satellite galaxies in gravitational lenses
S. E. Bryan; S. Mao; S. T. Kay
2008-09-18
Substructures, expected in cold dark matter haloes, have been proposed to explain the anomalous flux ratios in gravitational lenses. About 25% of lenses in the Cosmic Lens All-Sky Survey (CLASS) appear to have luminous satellites within ~ 5 kpc/h of the main lensing galaxies, which are usually at redshift z ~ 0.2-1. In this work we use the Millennium Simulation combined with galaxy catalogues from semi-analytical techniques to study the predicted frequency of such satellites in simulated haloes. The fraction of haloes that host bright satellites within the (projected) central regions is similar for red and blue hosts and is found to increase as a function of host halo mass and redshift. Specifically, at z = 1, about 11% of galaxy-sized haloes (with masses between 10^{12} M_sun/h and 10^{13} M_sun/h) host bright satellite galaxies within a projected radius of 5 kpc/h. This fraction increases to about 17% (25%) if we consider bright (all) satellites of only group-sized haloes (with masses between 10^{13} M_sun/h and 10^{14} M_sun/h). These results are roughly consistent with the fraction (~ 25%) of CLASS lensing galaxies observed to host luminous satellites. At z = 0, only ~ 3% of galaxy-sized haloes host bright satellite galaxies. The fraction rises to ~ 6%, (10%) if we consider bright (all) satellites of only group-sized haloes at z = 0. However, most of the satellites found in the inner regions are `orphan' galaxies where the dark matter haloes have been completely stripped. Thus the agreement crucially depends on the true survival rate of these `orphan' galaxies. We also discuss the effects of numerical resolution and cosmologies on our results.
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
Patel, Brandon; McCully, Curtis; Jha, Saurabh W.; Holoien, Thomas W.-S.; Rodney, Steven A.; Jones, David O.; Graur, Or; Riess, Adam G.; Merten, Julian; Zitrin, Adi; Matheson, Thomas; Sako, Masao; Postman, Marc; Coe, Dan; Bradley, Larry; Bartelmann, Matthias; Balestra, Italo; Benítez, Narciso; Bouwens, Rychard; Broadhurst, Tom; and others
2014-05-01
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 ?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 ?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 log{sub 10}?): 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.
Three Gravitationally Lensed Supernovae behind CLASH Galaxy Clusters
NASA Astrophysics Data System (ADS)
Patel, Brandon; McCully, Curtis; Jha, Saurabh 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; Benítez, Narciso; Bouwens, Rychard; Bradley, Larry; Broadhurst, Tom; Cenko, S. Bradley; Donahue, Megan; Filippenko, Alexei V.; Ford, Holland; Garnavich, Peter; Grillo, Claudio; Infante, Leopoldo; Jouvel, Stéphanie; 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
2014-05-01
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 ~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 ~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?): 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.
Future detectability of gravitational-wave induced lensing from high-sensitivity CMB experiments
Toshiya Namikawa; Daisuke Yamauchi; Atsushi Taruya
2015-03-03
We discuss the future detectability of gravitational-wave induced lensing from high-sensitivity cosmic microwave background (CMB) experiments. Gravitational waves can induce a rotational component of the weak-lensing deflection angle, usually referred to as the curl mode, which would be imprinted on the CMB maps. Using the technique of reconstructing lensing signals involved in CMB maps, this curl mode can be measured in an unbiased manner, offering an independent confirmation of the gravitational waves complementary to the B-mode polarization experiments. Based on the Fisher matrix analysis, we first show that with the noise levels necessary to confirm the consistency relation for the primordial gravitational waves, the future CMB experiments will be able to detect the gravitational-wave induced lensing signals. For a tensor-to-scalar ratio of $r wave induced lensing would be detected at more than $3\\,\\sigma$ significance level. Further, we point out that high-sensitivity experiments will be also powerful to constrain the gravitational waves generated after the recombination epoch. Compared to the B-mode polarization, the curl mode is particularly sensitive to gravitational waves generated at low redshifts ($z < 10$) with a low frequency ($k < 10^{-3}$ Mpc$^{-1}$), and it could give a much tighter constraint on their energy density $\\Omega_{\\rm GW}$ by more than three orders of magnitude.
Constraints on neutrino masses from weak lensing
Ichiki, Kiyotomo; Takada, Masahiro; Takahashi, Tomo
2009-01-15
Weak lensing (WL) distortions of distant galaxy images are sensitive to neutrino masses by probing the suppression effect on clustering strengths of total matter in large-scale structure. We use the latest measurements of WL correlations, the Canada-France-Hawaii Telescope Legacy Survey data, to explore constraints on neutrino masses. We find that, while the WL data alone cannot place a stringent limit on neutrino masses due to parameter degeneracies, the constraint can be significantly improved when combined with other cosmological probes, such as the WMAP 5-year data (WMAP5) and the distance measurements of type-Ia supernovae (SNe) and baryon acoustic oscillations (BAO). The upper bounds on the sum of neutrino masses are , 0.76, and 0.54 eV (95% CL) for WL+WMAP5, WMAP5+SNe+BAO, and WL+WMAP5+SNe+BAO, respectively, assuming a flat {lambda}CDM model with finite-mass neutrinos. In deriving these constraints, our analysis includes the non-Gaussian covariances of the WL correlation functions to properly take into account significant correlations between different angles.
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...
NASA Astrophysics Data System (ADS)
Eigenbrod, A.; Courbin, F.; Meylan, G.; Vuissoz, C.; Magain, P.
2006-06-01
Aims.We measure the redshift of the lensing galaxy in eight gravitationally lensed quasars in view of determining the Hubble parameter H0 from the time delay method. Methods.Deep VLT/FORS1 spectra of lensed quasars are spatially deconvolved in order to separate the spectrum of the lensing galaxies from the glare of the much brighter quasar images. A new observing strategy is devised. It involves observations in Multi-Object-Spectroscopy (MOS) which allows the simultaneous observation of the target and of several PSF and flux calibration stars. The advantage of this method over traditional long-slit observations is a much more reliable extraction and flux calibration of the spectra. Results.For the first time we measure the redshift of the lensing galaxy in three multiply-imaged quasars: SDSS J1138+0314 (z_lens = 0.445), SDSS J1226-0006 (z_lens = 0.517), SDSS J1335+0118 (z_lens = 0.440), and we give a tentative estimate of the redshift of the lensing galaxy in Q 1355-2257 (z_lens = 0.701). We confirm four previously measured redshifts: HE 0047-1756 (z_lens = 0.407), HE 0230-2130 (z_lens = 0.523), HE 0435-1223 (z_lens = 0.454) and WFI J2033-4723 (z_lens = 0.661). In addition, we determine the redshift of the second lensing galaxy in HE 0230-2130 (z_lens = 0.526). The spectra of all lens galaxies are typical for early-type galaxies, except for the second lensing galaxy in HE 0230-2130 which displays prominent [OII] emission.
S. W. Allen
1997-10-21
We present a detailed comparison of mass measurements for clusters of galaxies using ASCA and ROSAT X-ray data and constraints from strong and weak gravitational lensing. Our results for a sample of 13 clusters provide a consistent description of the distribution of gravitating matter in these systems. For the 6 cooling-flow clusters in the sample, which are the more dynamically-relaxed systems, the X-ray and strong gravitational lensing mass measurements show excellent agreement. The core radii for the mass distributions are small, with a mean value of ~ 50 $h_{50}^{-1}$ kpc. For the non-cooling flow clusters, the masses determined from the strong lensing data exceed the X-ray values by factors of $2-4$. However, significant offsets between the X-ray and lensing centres are observed, indicating that the X-ray and strong-lensing data are probing different lines of sight through the clusters. These offsets, and the generally complex dynamical states of the clusters inferred from their X-ray morphologies, lensing data and galaxy distributions, suggest that the gravitational potentials in the central regions of the non-cooling flow systems are evolving rapidly, and that the assumption of hydrostatic equilibrium involved in the X-ray mass measurements is likely to have broken down. The discrepancies between the X-ray and strong lensing mass measurements may be reconciled if the dynamical activity has caused the X-ray analyses to overestimate the core radii of the dominant mass clumps in these clusters. On larger spatial scales, comparisons of the X-ray mass results with measurements from weak gravitational lensing show excellent agreement for both cooling-flow and non-cooling flow clusters. (ABRIDGED)
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.
SHELS: TESTING WEAK-LENSING MAPS WITH REDSHIFT SURVEYS
Geller, Margaret J.; Kurtz, Michael J.; Fabricant, Daniel G.; Dell'Antonio, Ian P.; Ramella, Massimo E-mail: mkurtz@cfa.harvard.ed E-mail: ian@het.brown.ed
2010-02-01
Weak-lensing surveys are emerging as an important tool for the construction of 'mass-selected' clusters of galaxies. We evaluate both the efficiency and completeness of a weak-lensing selection by combining a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), with a weak-lensing map from the Deep Lens Survey (DLS). SHELS includes 11,692 redshifts for galaxies with R <= 20.6 in the 4 deg{sup 2} DLS field; the survey is a solid basis for identifying massive clusters of galaxies with redshift z approx< 0.55. The range of sensitivity of the redshift survey is similar to the range for the DLS convergence map. Only four of the 12 convergence peaks with signal to noise >=3.5 correspond to clusters of galaxies with M approx> 1.7 x 10{sup 14} M{sub sun}. Four of the eight massive clusters in SHELS are detected in the weak-lensing map yielding a completeness of approx50%. We examine the seven known extended cluster X-ray sources in the DLS field: three can be detected in the weak-lensing map, three should not be detected without boosting from superposed large-scale structure, and one is mysteriously undetected even though its optical properties suggest that it should produce a detectable lensing signal. Taken together, these results underscore the need for more extensive comparisons among different methods of massive cluster identification.
SALT Redshift Determinations of Herschel Discovered Strong Gravitational Lenses
NASA Astrophysics Data System (ADS)
Leeuw, Lerothodi; Crawford, S.; Herschel-ATLAS Team
2014-01-01
We present early results of the Southern African Large Telescope (SALT) observations of strong gravitational lenses. The lens systems were discovered by Herschel Space Observatory in large area maps conducted by the Herschel-ATLAS team and typically comprise a foreground optically-bright lensing galaxy and a background submm bright lensed galaxy. The SALT observations are aimed at determining the redshifts of the lensing galaxies and exploiting them to characterize the individual lensing systems and the sample, in conjunction with observations at other international telescope
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
NASA Astrophysics Data System (ADS)
Eigenbrod, A.; Courbin, F.; Meylan, G.
2007-04-01
Aims:The knowledge of the redshift of a lensing galaxy that produces multiple images of a background quasar is essential to any subsequent modeling, whether related to the determination of the Hubble constant H0 or to the mass profile of the lensing galaxy. We present the results of our ongoing spectroscopic observations of gravitationally lensed quasars in order to measure the redshift of their lensing galaxies. We report on the determination of the lens redshift in seven gravitationally lensed systems. Methods: Our deep VLT/FORS1 spectra are spatially deconvolved in order to separate the spectrum of the lensing galaxies from the glare of the much brighter quasar images. Our observing strategy involves observations in Multi-Object-Spectroscopy (MOS) mode which allows the simultaneous observation of the target and of several crucial PSF and flux calibration stars. The advantage of this method over traditional long-slit observations is that it allows a much more reliable extraction and flux calibration of the spectra. Results: We obtain the first reliable spectra of the lensing galaxies in six lensed quasars: FBQ 0951+2635 (z_lens~=0.260), BRI 0952-0115 (z_lens~=0.632), HE 2149-2745 (z_lens~=0.603), Q 0142-100 (z_lens~=0.491), SDSS J0246-0825 (z_lens~=0.723), and SDSS J0806+2006 (z_lens~=0.573). The last three redshifts also correspond to the Mg II doublet seen in absorption in the quasar spectra at the lens redshift. Our spectroscopic redshifts of HE 2149-2745 and FBQ 0951+2635 are higher than previously reported, which means that H0 estimates from these two systems must be revised to higher values. Finally, we reanalyse the blue side of our previously published spectra of Q 1355-2257 and find Mg II in absorption at z =0.702, confirming our previous redshift estimate. The spectra of all lenses are typical of early-type galaxies. Based on observations made with the ESO-VLT Unit Telescope 2 Kueyen (Cerro Paranal, Chile; Programs 077.A-0155, PI: G. Meylan).
Detection of Weak Lensing in the Fields of Luminous Radiosources
B. Fort; Y. Mellier; M. Dantel-Fort; H. Bonnet; J. -P. Kneib
1995-07-20
We present a first attempt to reveal the possible existence of large foreground mass condensations directly responsible for the gravitational magnification of four distant luminous radiosources and one optical QSO. The technique uses a weak lensing analysis of the distant galaxies in the field of each source. We find a coherent shear map with a large magnification bias on the line of sight to Q1622+0328. The local shear in the field of the bright radiosources is also often correlated with nearby groups or poor clusters of galaxies. For three of them, the groups are identified as gravitational deflectors that magnify the radiosources. This suggests that a substantial amount of invisible mass is condensed in groups and poor clusters It may explain the origin of a large angular correlation between the distribution of distant radiosources and the distribution of low redshift galaxies. We discuss the feasability and consequences of a future systematic survey to investigate the problem of magnification bias in the fields of luminous distant objects and to probe the mass distributions of galaxy groups at intermediate redshifts.
Gravitational lensing by a charged black hole of string theory
A. Bhadra
2003-06-04
We study gravitational lensing by the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole of heterotic string theory and obtain the angular position and magnification of the relativistic images. Modeling the supermassive central object of the galaxy as a GMGHS black hole, we estimate the numerical values of different strong-lensing parameters. We find that there is no significant string effect present in the lensing observables in the strong-gravity scenario.
Strong field limit analysis of gravitational retro-lensing
Ernesto F. Eiroa; Diego F. Torres
2003-12-12
We present a complete treatment in the strong field limit of gravitational retro-lensing by a static spherically symmetric compact object having a photon sphere. The results are compared with those corresponding to ordinary lensing in similar strong field situations. As examples of application of the formalism, a supermassive black hole at the galactic center and a stellar mass black hole in the galactic halo are studied as retro-lenses, in both cases using the Schwarzschild and Reissner-Nordstrom geometries.
Strong field limit analysis of gravitational retro-lensing
Eiroa, E F; Eiroa, Ernesto F.; Torres, Diego F.
2004-01-01
We present a complete treatment in the strong field limit of gravitational retro-lensing by a static spherically symmetric compact object having a photon sphere. The results are compared with those corresponding to ordinary lensing in similar strong field situations. As examples of application of the formalism, a supermassive black hole at the galactic center and a stellar mass black hole in the galactic halo are studied as retro-lenses, in both cases using the Schwarzschild and Reissner-Nordstrom geometries.
Gravitational lensing in the supernova legacy survey (SNLS)
T. Kronborg; D. Hardin; J. Guy; P. Astier; C. Balland; S. Basa; R. G. Carlberg; A. Conley; D. Fouchez; I. M. Hook; D. A. Howell; J. Jönsson; R. Pain; K. Pedersen; K. Perrett; C. J. Pritchet; N. Regnault; J. Rich; M. Sullivan; N. Palanque-Delabrouille; V. Ruhlmann-Kleider
2010-01-01
Aims: The observed brightness of type Ia supernovae is affected by gravitational lensing caused by the mass distribution along the line of sight, which introduces an additional dispersion into the Hubble diagram. We look for evidence of lensing in the SuperNova Legacy Survey 3-year data set. Methods: We investigate the correlation between the residuals from the Hubble diagram and the
Gravitational lensing and f ( R) theories in the Palatini approach
Matteo Luca Ruggiero
2009-01-01
We investigate gravitational lensing in the Palatini approach to the f ( R) extended theories of gravity. Starting from an exact solution of the f ( R) field equations, which corresponds to the Schwarzschild-de Sitter metric and, on the basis of recent studies on this metric, we focus on some lensing observables, in order to evaluate the effects of the
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
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.
What is Gravitational Lensing?(LBNL Summer Lecture Series)
Alexie, Leauthaud; Reiko, Nakajima [Berkeley Center for Cosmological Physics, Berkely, California, United States
2010-01-08
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.
Probing the dark matter issue in f( R)-gravity via gravitational lensing
NASA Astrophysics Data System (ADS)
Lubini, M.; Tortora, C.; Näf, J.; Jetzer, Ph.; Capozziello, S.
2011-12-01
For a general class of analytic f( R)-gravity theories, we discuss the weak field limit in view of gravitational lensing. Though an additional Yukawa term in the gravitational potential modifies dynamics with respect to the standard Newtonian limit of General Relativity, the motion of massless particles results unaffected thanks to suitable cancellations in the post-Newtonian limit. Thus, all the lensing observables are equal to the ones known from General Relativity. Since f( R)-gravity is claimed, among other things, to be a possible solution to overcome for the need of dark matter in virialized systems, we discuss the impact of our results on the dynamical and gravitational lensing analyses. In this framework, dynamics could, in principle, be able to reproduce the astrophysical observations without recurring to dark matter, but in the case of gravitational lensing we find that dark matter is an unavoidable ingredient. Another important implication is that gravitational lensing, in the post-Newtonian limit, is not able to constrain these extended theories, since their predictions do not differ from General Relativity.
Large-Scale QSO-Galaxy Correlations and Weak Lensing
Liliya L. R. Williams
1999-12-22
Several recent studies show that bright, intermediate and high redshift optically and radio selected QSOs are positively correlated with nearby galaxies on a range of angular scales up to a degree. Obscuration by unevenly distributed Galactic dust can be ruled out as the cause, leaving weak statistical lensing as the physical process responsible. However the amplitude of correlations on < 1 degree scales is at least a factor of a few larger than lensing model predictions. A possible way to reconcile the observations and theory is to revise the weak lensing formalism. We extend the standard lensing formulation to include the next higher order term (second order) in the geodesic equation of motion for photons. We derive relevant equations applicable in the weak lensing regime, and discuss qualitative properties of the updated formulation. We then perform numerical integrations of the revised equation and study the effect of the extra term using two different types of cosmic mass density fluctuations. We find that nearby large-scale coherent structures increase the amplitude of the predicted lensing-induced correlations between QSOs and foreground galaxies by ~ 10% (not a factor of several required by observations), while the redshift of the optimal, i.e. `most correlated' structures is moved closer to the observer compared to what is predicted using the standard lensing equation.
Transient weak lensing by cosmological dark matter microhaloes
NASA Astrophysics Data System (ADS)
Rahvar, Sohrab; Baghram, Shant; Afshordi, Niayesh
2014-03-01
We study the time variation of the apparent flux of cosmological point sources due to the transient weak lensing by dark matter microhaloes. Assuming a transverse motion of microhaloes with respect to our line of sight, we derive the correspondence between the temporal power spectrum of the weak lensing magnification and the spatial power spectrum of density on small scales. Considering different approximations for the small-scale structure of dark matter, we predict the apparent magnitude of cosmological point sources to vary by as much as 10-4-10-3, due to this effect, within a period of a few months. This red photometric noise has an almost perfect Gaussian statistics, to one part in ˜104. We also compare the transient weak lensing power spectrum with the background effects such as the stellar microlensing on cosmological scales. A quasar lensed by a galaxy or cluster like a SDSSJ1004+4112 strong lensing system, with multiple images, is a suitable system for this study because (i) using the time-delay method between different images, we can remove the intrinsic variations of the quasar, and (ii) strong lensing enhances signals from the transient weak lensing. We also require the images to form at large angular separations from the center of the lensing structure, in order to minimize contamination by the stellar microlensing. With long-term monitoring of quasar strong lensing systems with a 10-meter class telescope, we can examine the existence of dark microhaloes as the building blocks of dark matter structures. Failure to detect this signal may either be caused by a breakdown of cold dark matter (CDM) hierarchy on small scales, or rather interpreted as evidence against a CDM paradigm, e.g., in favor of modified gravity models.
Probing cosmology with weak lensing peak counts
Kratochvil, Jan M.; Haiman, Zoltan; May, Morgan
2010-02-15
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 a pilot study, we have run cosmological N-body simulations to produce WL convergence maps in three models with different constant values of the dark energy equation-of-state parameter, w=-0.8, -1, and -1.2, with a fixed normalization of the primordial power spectrum (corresponding to present-day normalizations of {sigma}{sub 8}=0.742, 0.798, and 0.839, respectively). By comparing the number of WL peaks in eight convergence bins in the range of -0.1<{kappa}<0.4, in multiple realizations of a single simulated 3x3 degree field, we show that the first (last) pair of models differ at the 95% (85%) confidence level. A survey with depth and area comparable to those expected from the Large Synoptic Survey Telescope should have a factor of {approx_equal}50 better parameter sensitivity. These results warrant further investigation, in order to assess the constraints available when marginalization over other uncertain parameters is included, and with the specifications of a realistic survey folded into the analysis. Here we find that relatively low-amplitude peaks ({kappa}{approx}0.03), which typically do not correspond to a single collapsed halo along the line of sight, account for most of the parameter sensitivity. We study a range of smoothing scales and source galaxy redshifts (z{sub s}). With a fixed source galaxy density of 15 arcmin{sup -2}, the best results are provided by the smallest scale we can reliably simulate, 1 arcmin, and z{sub s}=2 provides substantially better sensitivity than z{sub s{<=}}1.5.
Substructure in the Hubble Frontier Fields clusters from weak lensing flexion measurements
NASA Astrophysics Data System (ADS)
Rexroth, Markus
2015-08-01
Flexion is the second order weak gravitational lensing effect which is responsible for the arclike appearance of lensed sources. Its strong signal in the intermediate regime and the orthogonality to the shear field make flexion an ideal complement to today's strong and weak lensing measurements. Furthermore, its high sensitivity to local density peaks makes it a great tool for detecting substructure and increasing the resolution of mass maps. The strength of the Hubble Frontier Fields clusters and the high quality of the data make these objects a prime target for flexion measurements. We present an automated measurement pipeline and substructure constraints from its application to the clusters MACSJ0416.1-2403 and Abell 2744.
Constraining the mass-concentration relation through weak lensing peak function
Mainini, R. [Physics Department, University of Milano-Bicocca, Piazza della Scienza 3, I20126, Milano (Italy); Romano, A., E-mail: roberto.mainini@mib.infn.it, E-mail: anna.romano@oar.inaf.it [INAF — Astronomical Observatory of Rome, via Frascati 33, I00044, Monte Porzio Catone (RM) (Italy)
2014-08-01
Halo masses and concentrations have been studied extensively, by means of N-body simulations as well as observationally, during the last decade. Nevertheless, the exact form of the mass-concentration relation is still widely debated. One of the most promising method to estimate masses and concentrations relies on gravitational lensing from massive halos. Here we investigate the impact of the mass-concentration relation on halo peak abundance in weak lensing shear maps relying on the aperture mass method for peak detections. After providing a prescription to take into account the concentration dispersion (always neglected in previous works) in peak number counts predictions, we assess their power to constrain the mass-concentration relation by means of Fisher matrix technique. We find that, when combined with different cosmological probes, peak statistics information from near-future weak lensing surveys provides an interesting and complementary alternative method to lessen the long standing controversy about the mass-concentration relation.
A dearth of dark matter in strong gravitational lenses
NASA Astrophysics Data System (ADS)
Sanders, R. H.
2014-04-01
I show that the lensing masses of the Sloan Lens Advanced Camera Surveys sample of strong gravitational lenses are consistent with the stellar masses determined from population synthesis models using the Salpeter initial mass function. This is true in the context of both General Relativity and modified Newtonian dynamics (MOND), and is in agreement with the expectation of MOND that there should be little classical discrepancy within the high surface brightness regions probed by strong gravitational lensing. There is also dynamical evidence from this sample supporting the claim that the mass-to-light ratio of the stellar component increases with the velocity dispersion.
Accurate weak lensing of standard candles. I. Flexible cosmological fits
Valerio Marra; Miguel Quartin; Luca Amendola
2013-09-02
With the availability of thousands of type Ia supernovae in the near future the magnitude scatter induced by lensing will become a major issue as it affects parameter estimation. Current N-body simulations are too time consuming to be integrated in the likelihood analyses used for estimating the cosmological parameters. In this paper we show that in the weak lensing regime a statistical numerical approximation produces accurate results orders of magnitude faster. We write down simple fits to the second, third and fourth central moments of the lensing magnification probability distribution as a function of redshift, of the power spectrum normalization and of the present-day matter density. We also improve upon existing models of lensing variance and show that a shifted lognormal distribution fits well the numerical one. These fits can be easily employed in cosmological likelihood analyses. Moreover, our theoretical predictions make it possible to invert the problem and begin using supernovae lensing to constrain the cosmological parameters.
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.
An HST Snapshot Survey for Gravitationally Lensed z=6 Quasars
NASA Astrophysics Data System (ADS)
McGreer, Ian D.; Fan, X.; Richards, G. T.; Haiman, Z.; Strauss, M. A.; Jiang, L.; Schneider, D. P.
2013-01-01
Gravitational lensing magnification bias, boosted by the observed steep luminosity function of high redshift quasars, strongly suggests that lenses should be common amongst the highest redshift quasars. Currently over 60 quasars at z>5.7 have been discovered in wide-area ground-based imaging surveys; however, only a handful have been imaged with sufficient resolution to identify subarcsecond scale lenses. I will present results from an ongoing HST SNAP survey of all known 6 quasars, including some promising candidates for gravitational lenses. The observed sample is large enough to place strong constraints on the quasar luminosity function at 6, particularly on the contribution of faint quasars to the reionizing photon budget. Constraining the lensing rate among this unique sample is also needed to correctly derive physical parameters related to black hole growth from the observational data and to interpret quasar / host galaxy correlations at high redshift.
Wardlow, Julie L.; Cooray, Asantha; De Bernardis, Francesco; Calanog, J. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)] [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Amblard, A. [NASA, Ames Research Center, Moffett Field, CA 94035 (United States)] [NASA, Ames Research Center, Moffett Field, CA 94035 (United States); Arumugam, V. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)] [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Aussel, H.; Bethermin, M. [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu-CNRS-Universite Paris Diderot, CE-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France)] [Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu-CNRS-Universite Paris Diderot, CE-Saclay, pt courrier 131, F-91191 Gif-sur-Yvette (France); Baker, A. J. [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Rd, Piscataway, NJ 08854 (United States)] [Department of Physics and Astronomy, Rutgers, The State University of New Jersey, 136 Frelinghuysen Rd, Piscataway, NJ 08854 (United States); Blundell, R.; Bussmann, R. S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bock, J.; Bridge, C.; Carpenter, J. M. [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States)] [California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 (United States); Boselli, A.; Buat, V.; Burgarella, D. [Laboratoire d'Astrophysique de Marseille-LAM, Universite Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France)] [Laboratoire d'Astrophysique de Marseille-LAM, Universite Aix-Marseille and CNRS, UMR7326, 38 rue F. Joliot-Curie, F-13388 Marseille Cedex 13 (France); Cabrera-Lavers, A.; Castro-Rodriguez, N. [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain)] [Instituto de Astrofisica de Canarias (IAC), E-38200 La Laguna, Tenerife (Spain); Casey, C. M. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)] [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); and others
2013-01-01
We present a list of 13 candidate gravitationally lensed submillimeter galaxies (SMGs) from 95 deg{sup 2} of the Herschel Multi-tiered Extragalactic Survey, a surface density of 0.14 {+-} 0.04 deg{sup -2}. The selected sources have 500 {mu}m flux densities (S {sub 500}) greater than 100 mJy. Gravitational lensing is confirmed by follow-up observations in 9 of the 13 systems (70%), and the lensing status of the four remaining sources is undetermined. We also present a supplementary sample of 29 (0.31 {+-} 0.06 deg{sup -2}) gravitationally lensed SMG candidates with S {sub 500} = 80-100 mJy, which are expected to contain a higher fraction of interlopers than the primary candidates. The number counts of the candidate lensed galaxies are consistent with a simple statistical model of the lensing rate, which uses a foreground matter distribution, the intrinsic SMG number counts, and an assumed SMG redshift distribution. The model predicts that 32%-74% of our S {sub 500} {>=} 100 mJy candidates are strongly gravitationally lensed ({mu} {>=} 2), with the brightest sources being the most robust; this is consistent with the observational data. Our statistical model also predicts that, on average, lensed galaxies with S {sub 500} = 100 mJy are magnified by factors of {approx}9, with apparently brighter galaxies having progressively higher average magnification, due to the shape of the intrinsic number counts. 65% of the sources are expected to have intrinsic 500 {mu}m flux densities less than 30 mJy. Thus, samples of strongly gravitationally lensed SMGs, such as those presented here, probe below the nominal Herschel detection limit at 500 {mu}m. They are good targets for the detailed study of the physical conditions in distant dusty, star-forming galaxies, due to the lensing magnification, which can lead to spatial resolutions of {approx}0.''01 in the source plane.
Moving Gravitational Lenses: imprints on the CMB
N. Aghanim; S. Prunet; 0. Forni; F. R. Bouchet
1998-03-04
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.
Gravitational lensing, time delay, and gamma-ray bursts
NASA Technical Reports Server (NTRS)
Mao, Shude
1992-01-01
The probability distributions of time delay in gravitational lensing by point masses and isolated galaxies (modeled as singular isothermal spheres) are studied. For point lenses (all with the same mass) the probability distribution is broad, and with a peak at delta(t) of about 50 S; for singular isothermal spheres, the probability distribution is a rapidly decreasing function with increasing time delay, with a median delta(t) equals about 1/h month, and its behavior depends sensitively on the luminosity function of galaxies. The present simplified calculation is particularly relevant to the gamma-ray bursts if they are of cosmological origin. The frequency of 'recurrent' bursts due to gravitational lensing by galaxies is probably between 0.05 and 0.4 percent. Gravitational lensing can be used as a test of the cosmological origin of gamma-ray bursts.
Weak Lensing PSF Correction of Wide-field CCD Mosaic Images (SULI Paper)
Cevallos, Marissa; /Caltech /SLAC
2006-01-04
Gravitational lensing provides some of the most compelling evidence for the existence of dark matter. Dark matter on galaxy cluster scales can be mapped due to its weak gravitational lensing effect: a cluster mass distribution can be inferred from the net distortion of many thousands of faint background galaxies that it induces. Because atmospheric aberration and defects in the detector distort the apparent shape of celestial objects, it is of great importance to characterize accurately the point spread function (PSF) across an image. In this research, the PSF is studied in images from the Canada-France-Hawaii Telescope (CFHT), whose camera is divided into 12 CCD chips. Traditional weak lensing methodology involves averaging the PSF across the entire image: in this work we investigate the effects of measuring the PSF in each chip independently. This chip-by-chip analysis was found to reduce the strength of the correlation between star and galaxy shapes, and predicted more strongly the presence of known galaxy clusters in mass maps. These results suggest correcting the CFHT PSF on an individual chip basis significantly improves the accuracy of detecting weak lensing.
Strong Gravitational Lensing in a Brane-World Black Hole
GuoPing Li; Biao Cao; Zhongwen Feng; Xiaotao Zu
2015-06-28
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} exerted on the main observable quantities of this gravitational field is discussed.
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.
Strong Gravitational Lensing in a Brane-World Black Hole
NASA Astrophysics Data System (ADS)
Li, GuoPing; Cao, Biao; Feng, Zhongwen; Zu, Xiaotao
2015-09-01
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.
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.
Planck 2015 results. XV. Gravitational lensing
Ade, P A R; Arnaud, M; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartlett, J G; Bartolo, N; Battaner, E; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chiang, H C; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; 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; Delabrouille, J; Désert, F -X; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dunkley, J; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Fergusson, J; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Kneissl, R; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Lesgourgues, J; Levrier, F; Lewis, A; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; McGehee, P; Meinhold, P R; 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; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Reach, W T; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rowan-Robinson, M; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Seiffert, M D; Shellard, E P S; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; White, M; Yvon, D; Zacchei, A; Zonca, A
2015-01-01
We present the most significant measurement of the cosmic microwave background (CMB) lensing potential to date (at a level of 40 sigma), using temperature and polarization data from the Planck 2015 full-mission release. Using a polarization-only estimator we detect lensing at a significance of 5 sigma. We cross-check the accuracy of our measurement using the wide frequency coverage and complementarity of the temperature and polarization measurements. Public products based on this measurement include an estimate of the lensing potential over approximately 70% of the sky, an estimate of the lensing potential power spectrum in bandpowers for the multipole range 40
Black hole tidal charge constrained by strong gravitational lensing
Horváth, Zsolt
2012-01-01
Spherically symmetric brane black holes have tidal charge, which modifies both weak and strong lensing characteristics. Even if lensing measurements are in agreement with a Schwarzschild lens, the margin of error of the detecting instrument allows for a certain tidal charge. In this note we derive the respective constraint on the tidal charge of the supermassive black hole (SMBH) in the center of our galaxy, from the radius of the first relativistic Einstein ring, emerging in strong lensing. We find that even if general relativistic predictions are confirmed by high precision strong lensing measurements, SMBHs could have a much larger tidal charge, than the Sun or neutron stars.
Black hole tidal charge constrained by strong gravitational lensing
Zsolt Horváth; László Á. Gergely
2013-12-16
Spherically symmetric brane black holes have tidal charge, which modifies both weak and strong lensing characteristics. Even if lensing measurements are in agreement with a Schwarzschild lens, the margin of error of the detecting instrument allows for a certain tidal charge. In this paper we derive the respective constraint on the tidal charge of the supermassive black hole (SMBH) in the center of our galaxy, from the radius of the first relativistic Einstein ring, emerging in strong lensing. We find that even if general relativistic predictions are confirmed by high precision strong lensing measurements, SMBHs could have a much larger tidal charge, than the Sun or neutron stars.
Data mining for gravitationally lensed quasars
NASA Astrophysics Data System (ADS)
Agnello, Adriano; Kelly, Brandon C.; Treu, Tommaso; Marshall, Philip J.
2015-04-01
Gravitationally lensed quasars are brighter than their unlensed counterparts and produce images with distinctive morphological signatures. Past searches and target-selection algorithms, in particular the Sloan Quasar Lens Search (SQLS), have relied on basic morphological criteria, which were applied to samples of bright, spectroscopically confirmed quasars. The SQLS techniques are not sufficient for searching into new surveys (e.g. DES, PS1, LSST), because spectroscopic information is not readily available and the large data volume requires higher purity in target/candidate selection. We carry out a systematic exploration of machine-learning techniques and demonstrate that a two-step strategy can be highly effective. In the first step, we use catalogue-level information (griz+WISE magnitudes, second moments) to pre-select targets, using artificial neural networks. The accepted targets are then inspected with pixel-by-pixel pattern recognition algorithms (gradient-boosted trees), to form a final set of candidates. The results from this procedure can be used to further refine the simpler SQLS algorithms, with a twofold (or threefold) gain in purity and the same (or 80 per cent) completeness at target-selection stage, or a purity of 70 per cent and a completeness of 60 per cent after the candidate-selection step. Simpler photometric searches in griz+WISE based on colour cuts would provide samples with 7 per cent purity or less. Our technique is extremely fast, as a list of candidates can be obtained from a Stage III experiment (e.g. DES catalogue/data base) in a few CPU hours. The techniques are easily extendable to Stage IV experiments like LSST with the addition of time domain information.
General requirements on matter power spectrum predictions for cosmology with weak lensing tomography
Hearin, Andrew P.; Zentner, Andrew R.; Ma, Zhaoming E-mail: zentner@pitt.edu
2012-04-01
Forthcoming projects such as DES, LSST, WFIRST, and Euclid aim to measure weak lensing shear correlations with unprecedented precision, constraining the dark energy equation of state at the percent level. Reliance on photometrically-determined redshifts constitutes a major source of uncertainty for these surveys. Additionally, interpreting the weak lensing signal requires a detailed understanding of the nonlinear physics of gravitational collapse. We present a new analysis of the stringent calibration requirements for weak lensing analyses of future imaging surveys that addresses both photo-z uncertainty and errors in the calibration of the matter power spectrum. We find that when photo-z uncertainty is taken into account the requirements on the level of precision in the prediction for the matter power spectrum are more stringent than previously thought. Including degree-scale galaxy clustering statistics in a joint analysis with weak lensing not only strengthens the survey's constraining power by ? 20%, but can also have a profound impact on the calibration demands, decreasing the degradation in dark energy constraints with matter power spectrum uncertainty by a factor of 2-5. Similarly, using galaxy clustering information significantly relaxes the demands on photo-z calibration. We compare these calibration requirements to the contemporary state-of-the-art in photometric redshift estimation and predictions of the power spectrum and suggest strategies to utilize forthcoming data optimally.
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.
A SNAP Survey for Gravitational Lenses Among z~6 Quasars
NASA Astrophysics Data System (ADS)
Fan, Xiaohui
2010-09-01
We propose a SNAP imaging survey of a complete sample of 54 quasars at 5.7 < z < 6.4 using HST/WFC3-IR to quantify the prevalence of strongly lensed quasars at z~6. Gravitational lensing magnification bias, boosted by the observed steep luminosity function of high-redshift quasars, strongly suggest that lenses should be common amongst the highest-redshift quasars known. However, the highest redshift strongly lensed quasar known is only at z=4.8; but among the 59 quasars known at z>5.9, only five have been imaged with HST. Our HST images will be sensitive to the multiple images of lensed quasar, even at small separations and large flux ratios. Based on the current best estimate of the quasar luminosity function, we expect to discover 2-9 strongly lensed quasars in our entire sample, or 1-4 for the nominal SNAP completion rate of 40%. This program will likely discover the first quasar lenses at z~6, enabling detailed follow-up observations to constrain lensing models, to study quasar host galaxy properties and to probe the small-scale structure of the IGM. The measurement of or upper limit on the lensing fraction will strongly constrain the bright end of the quasar luminosity function, leading to important constraints on models of quasar evolution and allowing us to better quantify the quasar contribution to the reionization photon budget.
Gravitational lensing and f ( R ) theories in the Palatini approach
Matteo Luca Ruggiero
2009-01-01
We investigate gravitational lensing in the Palatini approach to the f (R) extended theories of gravity. Starting from an exact solution of the f (R) field equations, which corresponds to the Schwarzschild–de Sitter metric and, on the basis of recent studies on this metric,\\u000a we focus on some lensing observables, in order to evaluate the effects of the nonlinearity of
Galaxy cluster center detection methods with weak lensing
NASA Astrophysics Data System (ADS)
Simet, Melanie
The precise location of galaxy cluster centers is a persistent problem in weak lensing mass estimates and in interpretations of clusters in a cosmological context. In this work, we test methods of centroid determination from weak lensing data and examine the effects of such self-calibration on the measured masses. Drawing on lensing data from the Sloan Digital Sky Survey Stripe 82, a 275 square degree region of coadded data in the Southern Galactic Cap, together with a catalog of MaxBCG clusters, we show that halo substructure as well as shape noise and stochasticity in galaxy positions limit the precision of such a self-calibration (in the context of Stripe 82, to ˜ 500 h-1 kpc or larger) and bias the mass estimates around these points to a level that is likely unacceptable for the purposes of making cosmological measurements. We also project the usefulness of this technique in future surveys.
Direct Shear Mapping: Prospects for weak lensing studies of individual galaxy-galaxy lensing systems
de Burgh-Day, Catherine O; Webster, Rachel L; Hopkins, Andrew M
2015-01-01
We have investigated, using both a theoretical and an empirical approach, the frequency of low redshift galaxy-galaxy lensing systems in which the signature of weak lensing might be directly detectable. We find good agreement between these two approaches. In order to make a theoretical estimate of the weak lensing shear, $\\gamma$, for each galaxy in a catalogue, we have made an estimate of the asymptotic circular velocity from the stellar mass using three different approaches: from a simulation based relation, from an empirically-derived relation, and using the baryonic Tully-Fisher relation. Using data from the Galaxy and Mass Assembly redshift survey we estimate the frequency of detectable weak lensing at low redshift. We find that to a redshift of $z\\sim 0.6$, the probability of a galaxy being weakly lensed by at least $\\gamma = 0.02$ is $\\sim 0.01$. A scatter in the $M_*-M_h$ relation results in a shift towards higher measured shears for a given population of galaxies. Given this, and the good probability...
Constraints in the lambda_0-Omega_0 plane from gravitational lensing
Phillip Helbig
2000-11-01
I review simultaneous constraints on the cosmological parameters lambda_0 and Omega_0 from gravitational lensing. The emphasis is on systematic extragalactic surveys for strong gravitational lenses, mainly the largest and best-defined such survey, JVAS/CLASS.
Gravitational lensing and structural stability of dark matter caustic rings
Onemli, V. K.
2006-12-15
In a cold dark matter (CDM) paradigm, density perturbations enter the nonlinear regime of structure formation where shell crossings occur, and caustics form. A dark matter caustic is generically a surface in space where the CDM particles are naturally focussed, and hence, the density is very large. The caustic ring model of galactic halo formation predicts a minimal caustic structure classified as outer caustics and caustic rings at certain locations in the halos. It provides a well-defined density profile and geometry near the caustics. Using this model, I show that the gravitational lensing by the cusps (A{sub -3} catastrophes) of caustic rings at cosmological distances may offer the tantalizing opportunity to detect CDM indirectly, and discriminate between axions and weakly interacting massive particles (WIMPs). The lensing effects of the caustic rings increase as the line of sight approaches to the cusps where it diverges in the limit of zero velocity dispersion. In the presence of finite velocity dispersion, the caustics are smeared out in space, and hence, the divergence is cut off. Primordial smearing distance of caustics may be used to obtain an upper bound for the lensing effects. Evidences found for the caustic rings, on the other hand, were used to estimate an upper bound for the smearing distance, which may be used to obtain a lower bound for the lensing effects. In that range of smearing out, the magnification of a cosmological axion caustic ring is constrained between 3% and 2800% at the outer cusp, and between 2% and 46% at the nonplanar cusps. For a cosmological WIMP caustic ring, the magnification is constrained between 3% and 28% at the outer cusp, and between 2% and 5% at the nonplanar cusps. As pointlike background sources cross behind the axion (WIMP) folds, the time scale of brightness change is about an hour (a year). Thus, they may be used to probe the cusps and discriminate between axions and WIMPs by present instruments. Finally, I derive and analyze the catastrophe function of the triaxial caustic rings to prove rigorously that they are structurally stable.
Weak lensing mass reconstructions of the ESO Distant Cluster Survey
D. Clowe; P. Schneider; A. Aragon-Salamanca; M. Bremer; G. De Lucia; C. Halliday; P. Jablonka; B. Milvang-Jensen; R. Pello; B. Poggianti; G. Rudnick; R. Saglia; L. Simard; S. White; D. Zaritsky
2005-11-28
We present weak lensing mass reconstructions for the 20 high-redshift clusters i n the ESO Distant Cluster Survey. The weak lensing analysis was performed on deep, 3-color optical images taken with VLT/FORS2, using a composite galaxy catalog with separate shape estimators measured in each passband. We find that the EDisCS sample is composed primarily of clusters that are less massive than t hose in current X-ray selected samples at similar redshifts, but that all of the fields are likely to contain massive clusters rather than superpositions of low mass groups. We find that 7 of the 20 fields have additional massive structures which are not associated with the clusters and which can affect the weak lensing mass determination. We compare the mass measurements of the remaining 13 clusters with luminosity measurements from cluster galaxies selected using photometric redshifts and find evidence of a dependence of the cluster mass-to-light ratio with redshift. Finally we determine the noise level in the shear measurements for the fields as a function of exposure time and seeing and demonstrate that future ground-based surveys which plan to perform deep optical imaging for use in weak lensing measurements must achieve point-spread functions smaller than a median of 0.6" FWHM.
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 ...
PROBING PRIMORDIAL NON-GAUSSIANITY WITH WEAK-LENSING MINKOWSKI FUNCTIONALS
Shirasaki, Masato; Yoshida, Naoki; Nishimichi, Takahiro [Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Hamana, Takashi, E-mail: masato.shirasaki@ipmu.jp [National Astronomical Observatory of Japan, Tokyo 181-0015 (Japan)
2012-11-20
We study the cosmological information contained in the Minkowski functionals (MFs) of weak gravitational lensing convergence maps. We show that the MFs provide strong constraints on the local-type primordial non-Gaussianity parameter f {sub NL}. We run a set of cosmological N-body simulations and perform ray-tracing simulations of weak lensing to generate 100 independent convergence maps of a 25 deg{sup 2} field of view for f {sub NL} = -100, 0 and 100. We perform a Fisher analysis to study the degeneracy among other cosmological parameters such as the dark energy equation of state parameter w and the fluctuation amplitude {sigma}{sub 8}. We use fully nonlinear covariance matrices evaluated from 1000 ray-tracing simulations. For upcoming wide-field observations such as those from the Subaru Hyper Suprime-Cam survey with a proposed survey area of 1500 deg{sup 2}, the primordial non-Gaussianity can be constrained with a level of f {sub NL} {approx} 80 and w {approx} 0.036 by weak-lensing MFs. If simply scaled by the effective survey area, a 20,000 deg{sup 2} lensing survey using the Large Synoptic Survey Telescope will yield constraints of f {sub NL} {approx} 25 and w {approx} 0.013. We show that these constraints can be further improved by a tomographic method using source galaxies in multiple redshift bins.
NASA Astrophysics Data System (ADS)
Shirasaki, Masato; Yoshida, Naoki
2014-05-01
The measurement of cosmic shear using weak gravitational lensing is a challenging task that involves a number of complicated procedures. We study in detail the systematic errors in the measurement of weak-lensing Minkowski Functionals (MFs). Specifically, we focus on systematics associated with galaxy shape measurements, photometric redshift errors, and shear calibration correction. We first generate mock weak-lensing catalogs that directly incorporate the actual observational characteristics of the Canada-France-Hawaii Lensing Survey (CFHTLenS). We then perform a Fisher analysis using the large set of mock catalogs for various cosmological models. We find that the statistical error associated with the observational effects degrades the cosmological parameter constraints by a factor of a few. The Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of ~1400 deg2 will constrain the dark energy equation of the state parameter with an error of ?w 0 ~ 0.25 by the lensing MFs alone, but biases induced by the systematics can be comparable to the 1? error. We conclude that the lensing MFs are powerful statistics beyond the two-point statistics only if well-calibrated measurement of both the redshifts and the shapes of source galaxies is performed. Finally, we analyze the CFHTLenS data to explore the ability of the MFs to break degeneracies between a few cosmological parameters. Using a combined analysis of the MFs and the shear correlation function, we derive the matter density \\Omega _m0 = 0.256+/- ^{0.054}_{0.046}.
NASA Astrophysics Data System (ADS)
Chen, Bin; Kantowski, R.; Dai, X.
2014-01-01
We have developed an accurate gravitational lens theory for an inhomogeneity embedded in an otherwise homogeneous universe, which to the lowest order is applicable to any mass distribution. We derive the Fermat potential for a spherically symmetric lens embedded in a FLRW cosmology and use it to investigate the late-time integrated Sachs-Wolfe effect (ISW) caused by individual large scale inhomogeneities, in particular, cosmic voids. We present a simple analytical expression for the CMB temperature fluctuation across such a lens as the derivative of the lens Fermat potential. Our formalism is applicable to both linear and nonlinear density evolution scenarios, to arbitrarily large density contrasts, and to all open and closed background cosmologies. Our results are particularly useful for modeling ISW effects extracted through stacking large numbers of cosmic voids and clusters (that is, the aperture photometry method). For structures co-expanding with the background cosmology, i.e., for time-independent density contrasts, we find that the gravitational lensing time delay alone can produce fluctuations of the order of seen in recent observations by WMAP and Planck. We revisit the possibility of explaining the non-Gaussian cold spot on the south hemisphere via the Rees-Sciama effect of a large cosmic void using constraints obtained from the most recent void catalogs and our new void-lensing formalism, and compare it with other explanations such as a collapsing cosmic texture. We also study the remapping of primordial CMB anisotropies, the weak-lensing shear, and magnification caused by void lensing.
Weak lensing tomography with orthogonal polynomials
NASA Astrophysics Data System (ADS)
Schäfer, Björn Malte; Heisenberg, Lavinia
2012-07-01
The topic of this paper is weak cosmic shear tomography where the line-of-sight weighting is carried out with a set of specifically constructed orthogonal polynomials, dubbed Tomography with Orthogonal Radial Distance Polynomial Systems (TaRDiS). We investigate the properties of these polynomials and employ weak convergence spectra, which have been obtained by weighting with these polynomials, for the estimation of cosmological parameters. We quantify their power in constraining parameters in a Fisher matrix technique and demonstrate how each polynomial projects out statistically independent information, and how the combination of multiple polynomials lifts degeneracies. The assumption of a reference cosmology is needed for the construction of the polynomials, and as a last point we investigate how errors in the construction with a wrong cosmological model propagate to misestimates in cosmological parameters. TaRDiS performs on a similar level as traditional tomographic methods and some key features of tomography are made easier to understand.
Constraining Galaxy Mass Profiles with Strong Gravitational Lensing
D. Rusin
2000-04-18
Measured time delays between the images of a gravitationally lensed source can lead to a determination of the Hubble constant ($H_o$), but only if the lensing mass distribution is well understood. The inability to sufficiently constrain galaxy mass models results in large uncertainties on the derived $H_o$, and severely hampers the cosmological application of this otherwise elegant method. At the same time, lensing must compete with new techniques that have the potential to measure the Hubble constant to within a few percent by the middle of the decade. In this letter we re-evaluate the role of strong gravitational lensing in the age of precision cosmology, and present a series of Monte Carlo simulations that demonstrate the effect of the galaxy mass distribution on Hubble constant determination. Though most gravitational lens systems are unlikely to contribute significantly to precision studies of the cosmological distance scale, the strong dependence of predicted time delays on the galaxy mass profile suggests that the most useful and interesting results may be obtained by running the traditional lensing problem in reverse -- namely, combining measured time delays with a well-constrained value of $H_o$ to study galaxy mass distributions.
Strong lensing of gravitational waves as seen by LISA.
Sereno, M; Sesana, A; Bleuler, A; Jetzer, Ph; Volonteri, M; Begelman, M C
2010-12-17
We discuss strong gravitational lensing of gravitational waves from the merging of massive black hole binaries in the context of the LISA mission. Detection of multiple events would provide invaluable information on competing theories of gravity, evolution and formation of structures and, possibly, constraints on H0 and other cosmological parameters. Most of the optical depth for lensing is provided by intervening massive galactic halos, for which wave optics effects are negligible. Probabilities to observe multiple events are sizable for a broad range of formation histories. For the most optimistic models, up to ? 4 multiple events with a signal to noise ratio ? 8 are expected in a 5-year mission. Chances are significant even for conservative models with either light (? 60%) or heavy (? 40%) seeds. Because of lensing amplification, some intrinsically too faint signals are brought over threshold (? 2 per year). PMID:21231571
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.
Cosmic Equation of state from Strong Gravitational Lensing Systems
Biesiada, M; Malec, B
2011-01-01
Accelerating expansion of the Universe is a great challenge for both physics and cosmology. In light of lacking the convincing theoretical explanation, an effective description of this phenomenon in terms of cosmic equation of state turns out useful. The strength of modern cosmology lies in consistency across independent, often unrelated pieces of evidence. Therefore, every alternative method of restricting cosmic equation of state is important. Strongly gravitationally lensed quasar-galaxy systems create such new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination form position of images). In this paper we apply such method to a combined data sets from SLACS and LSD surveys of gravitational lenses. In result we obtain the cosmic equation of state parameters, which generally agree with results already known in the literature. This demonstrates that the method can be further used on larger samples obtained in the future. In...
Strong Gravitational Lensing as a Probe of Gravity, Dark-
Ciotti, Luca
Strong Gravitational Lensing as a Probe of Gravity, Dark- Matter and Super-Massive Black Holes L as function of cosmic time, currently photons, neutrinos, baryons, "dark matter" and "dark-energy". Whereas on scales far beyond the solar system. Dark matter and energy could simply be "fabrications", confusing
On an illusion of superluminal velocities produced by gravitational lenses
Ingel, L.Kh.
1981-01-01
It is noted that gravitational lenses, by focusing the radiation of an object, increase the angle which it subtends. This in turn produces the illusion of an increase in velocities at right angles to the line of sight. Preliminary estimates are made which indicate a rather high probability of strong distortion of the observed velocities.
Gravitational lensing of the CMB: A Feynman diagram approach
NASA Astrophysics Data System (ADS)
Jenkins, Elizabeth E.; Manohar, Aneesh V.; Waalewijn, Wouter J.; Yadav, Amit P. S.
2014-09-01
We develop a Feynman diagram approach to calculating correlations of the Cosmic Microwave Background (CMB) in the presence of distortions. As one application, we focus on CMB distortions due to gravitational lensing by Large Scale Structure (LSS). We study the Hu-Okamoto quadratic estimator for extracting lensing from the CMB and derive the noise of the estimator up to O(?4) in the lensing potential ?. By identifying the diagrams responsible for the previously noted large O(?4) term, we conclude that the lensing expansion does not break down. The convergence can be significantly improved by a reorganization of the ? expansion. Our approach makes it simple to obtain expressions for quadratic estimators based on any CMB channel, including many previously unexplored cases. We briefly discuss other applications to cosmology of this diagrammatic approach, such as distortions of the CMB due to patchy reionization, or due to Faraday rotation from primordial axion fields.
The kinematical structure of gravitationally lensed arcs
Ole Moeller; Edo Noordermeer
2005-11-07
In this paper the expected properties of the velocity fields of strongly lensed arcs behind galaxy clusters are investigated. The velocity profile along typical lensed arcs is determined by ray tracing light rays from a model source galaxy through parametric cluster toy-models consisting of individual galaxies embedded in a dark cluster halo. We find that strongly lensed arcs of high redshift galaxies show complex velocity structures that are sensitive to the details of the mass distribution within the cluster, in particular at small scales. From fits to the simulated imaging and kinematic data we demonstrate that reconstruction of the source velocity field is in principle feasible: two dimensional kinematic information obtained with Integral Field Units (IFU's) on large ground based telescopes in combination with adaptive optics will allow the reconstruction of rotation curves of lensed high redshift galaxies. This makes it possible to determine the mass-to-light ratios of galaxies at redshifts z>1 out to about 2-3 scale lengths with better than about 20% accuracy. We also discuss the possibilities of using two dimensional kinematic information along the arcs to give additional constraints on the cluster lens mass models.
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.
Non-linear relativistic contributions to the cosmological weak-lensing convergence
Andrianomena, Sambatra; Clarkson, Chris; Patel, Prina; Umeh, Obinna [Astrophysics, Cosmology and Gravity Centre, and, Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7701 South Africa (South Africa); Uzan, Jean-Philippe, E-mail: andrianomena@gmail.com, E-mail: chris.clarkson@gmail.com, E-mail: prina83@gmail.com, E-mail: umeobinna@gmail.com, E-mail: uzan@iap.fr [Institut d'Astrophysique de Paris, UMR-7095 du CNRS, Université Pierre et Marie Curie, and, Sorbonne Universités, Institut Lagrange de Paris, 98 bis bd Arago, Paris, 75014 France (France)
2014-06-01
Relativistic contributions to the dynamics of structure formation come in a variety of forms, and can potentially give corrections to the standard picture on typical scales of 100 Mpc. These corrections cannot be obtained by Newtonian numerical simulations, so it is important to accurately estimate the magnitude of these relativistic effects. Density fluctuations couple to produce a background of gravitational waves, which is larger than any primordial background. A similar interaction produces a much larger spectrum of vector modes which represent the frame-dragging rotation of spacetime. These can change the metric at the percent level in the concordance model at scales below the equality scale. Vector modes modify the lensing of background galaxies by large-scale structure. This gives in principle the exciting possibility of measuring relativistic frame dragging effects on cosmological scales. The effects of the non-linear tensor and vector modes on the cosmic convergence are computed and compared to first-order lensing contributions from density fluctuations, Doppler lensing, and smaller Sachs-Wolfe effects. The lensing from gravitational waves is negligible so we concentrate on the vector modes. We show the relative importance of this for future surveys such as Euclid and SKA. We find that these non-linear effects only marginally affect the overall weak lensing signal so they can safely be neglected in most analyses, though are still much larger than the linear Sachs-Wolfe terms. The second-order vector contribution can dominate the first-order Doppler lensing term at moderate redshifts and are actually more important for survey geometries like the SKA.
The impact of cosmic variance on simulating weak lensing surveys
Kannawadi, Arun; Lackner, Claire
2014-01-01
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 datasets 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...
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
Weak Lensing Mass of Nearby Clusters of Galaxies
M. Joffre; P. Fischer; J. Frieman; D. Johnston; T. McKay; J. Mohr; B. Nichol; E. Sheldon; C. Cantaloupo; G. Griffin; J. Peterson; A. K. Romer
1999-09-01
We describe first results of a project to create weak lensing mass maps for a complete, X-ray luminosity-limited sample of 19 nearby (z < 0.1) southern galaxy clusters scheduled for Sunyaev-Zel'dovich observations by the Viper Telescope at the South Pole. We have collected data on 1/3 of the sample and present motivation for the project as well as projected mass maps of two clusters.
Weak lensing mass of nearby clusters of galaxies
Joffre, Michael; et al.
1999-09-01
We describe first results of a project to create weak lensing mass maps for a complete, X-ray luminosity-limited sample of 19 nearby (z < 0.1) southern galaxy clusters scheduled for Sunyaev-Zel'dovich observations by the Viper Telescope at the South Pole. We have collected data on 1/3 of the sample and present motivation for the project as well as projected mass maps of two clusters.
Cosmic equation of state from strong gravitational lensing systems
NASA Astrophysics Data System (ADS)
Biesiada, Marek; Piórkowska, Aleksandra; Malec, Beata
2010-08-01
The accelerating expansion of the Universe is a great challenge for both physics and cosmology. In light of lacking the convincing theoretical explanation, an effective description of this phenomenon in terms of a cosmic equation of state turns out useful. The strength of modern cosmology lies in consistency across independent, often unrelated pieces of evidence. Therefore, every alternative method of restricting the cosmic equation of state is important. 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). In this paper we apply such a method to a combined data sets from Sloan Lens ACS and Lens Structure and Dynamics surveys of gravitational lenses. As a result we obtain the cosmic equation of state parameters, which generally agree with results already known in the literature. This demonstrates that the method can be further used on larger samples obtained in the future. Independently noticed systematic deviation between fits done on standard candles and standard rulers is revealed in our findings. We also identify an important selection effect crucial to our method associated with the geometric configuration of the lensing system along the line of sight, which may have consequences for sample construction from the future lensing surveys.
Testing gravity with halo density profiles observed through gravitational lensing
Narikawa, Tatsuya; Yamamoto, Kazuhiro E-mail: kazuhiro@hiroshima-u.ac.jp
2012-05-01
We present a new test of the modified gravity endowed with the Vainshtein mechanism with the density profile of a galaxy cluster halo observed through gravitational lensing. A scalar degree of freedom in the galileon modified gravity is screened by the Vainshtein mechanism to recover Newtonian gravity in high-density regions, however it might not be completely hidden on the outer side of a cluster of galaxies. Then the modified gravity might yield an observational signature in a surface mass density of a cluster of galaxies measured through gravitational lensing, since the scalar field could contribute to the lensing potential. We investigate how the transition in the Vainshtein mechanism affects the surface mass density observed through gravitational lensing, assuming that the density profile of a cluster of galaxies follows the original Navarro-Frenk-White (NFW) profile, the generalized NFW profile and the Einasto profile. We compare the theoretical predictions with observational results of the surface mass density reported recently by other researchers. We obtain constraints on the amplitude and the typical scale of the transition in the Vainshtein mechanism in a subclass of the generalized galileon model.
Strong Gravitational Lenses in a Cold Dark Matter Universe
NASA Astrophysics Data System (ADS)
Oguri, Masamune
2004-08-01
We present theoretical and observational studies of strong gravitational lenses produced by clusters of galaxies. Our purpose is to test the Cold Dark Matter (CDM) model at small and highly non-linear scales where it has been claimed that the CDM model may confront several difficulties. We concentrate our attention on the statistics of strong gravitational lenses. We use two complementary statistics, lensed arcs and quasars, to probe the mass distributions. First, we construct a triaxial lens model, and develop a new method to include triaxiality of dark halos in the lens statistics. We find that the effect of triaxiality is significant; it enhances lensing probabilities by a factors of a few to ten, assuming the degree of triaxiality predicted in the CDM model. In particular, we argue that both central concentration and large triaxiality of dark halos are required to reproduce the observed number of arcs in clusters; thus the result can be interpreted as a strong evidence for the cold and collisionless dark matter. One of the most notable advantages of the triaxial modeling is that the triaxial modeling allows us to predict image multiplicities. We find that the CDM halos predict significant fraction (more than 20%) of naked cusp lenses. In addition, we point out the image multiplicities depend strongly on the central concentration of dark halos. Therefore we propose image multiplicities as a new powerful test of the CDM model. Finally we searched for large-separation lensed quasars from the data of the Sloan Digital Sky Survey, and succeeded in discovering the first large-separation lensed quasar SDSS J1004+4112. We find that the discovery of the large-separation quadruple lens SDSS J1004+4112 is quite consistent with the theoretical predictions based on the CDM model. (Abridged)
Gravitational Lensing by Self-Dual Black Holes in Loop Quantum Gravity
Sahu, Satyabrata; Narasimha, D
2015-01-01
We study gravitational lensing by a recently proposed black hole solution in Loop Quantum Gravity. We highlight the fact that the quantum gravity corrections to the Schwarzschild metric in this model evade the `mass suppression' effects (that the usual quantum gravity corrections are susceptible to) by virtue of one of the parameters in the model being dimensionless, which is unlike any other quantum gravity motivated parameter. Gravitational lensing in the strong and weak deflection regimes is studied and a sample consistency relation is presented which could serve as a test of this model. We discuss that though the consistency relation for this model is qualitatively similar to what would have been in Brans-Dicke, in general it can be a good discriminator between many alternative theories. Although the observational prospects do not seem to be very optimistic even for a galactic supermassive black hole case, time delay between relativistic images for billion solar mass black holes in other galaxies might be...
Cross-correlation of Planck CMB lensing and CFHTLenS galaxy weak lensing maps
NASA Astrophysics Data System (ADS)
Liu, Jia; Hill, J. Colin
2015-09-01
We cross-correlate cosmic microwave background (CMB) lensing and galaxy weak lensing maps using the Planck 2013 and 2015 data and the 154 deg2 Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). This measurement probes large-scale structure at intermediate redshifts ?0.9 , between the high- and low-redshift peaks of the CMB and CFHTLenS lensing kernels, respectively. Using the noise properties of these data sets and standard Planck 2015 ? CDM cosmological parameters, we forecast a signal-to-noise ratio ?4.6 for the cross-correlation. We find that the noise level of our actual measurement agrees well with this estimate, but the amplitude of the signal lies well below the theoretical prediction. The best-fit amplitudes of our measured cross-correlations are A2013=0.48 ±0.26 and A2015=0.44 ±0.22 , using the 2013 and 2015 Planck CMB lensing maps, respectively, where A =1 corresponds to the fiducial Planck 2015 ? CDM prediction. Due to the low measured amplitude, the detection significance is moderate (?2 ? ) and the data are in tension with the theoretical prediction (?2 - 2.5 ? ) . The tension is reduced somewhat when compared to predictions using WMAP9 parameters, for which we find A2013=0.56 ±0.30 and A2015=0.52 ±0.26 . We consider various systematic effects, finding that photometric redshift uncertainties, contamination by intrinsic alignments, and effects due to the masking of galaxy clusters in the Planck 2015 CMB lensing reconstruction are able to help resolve the tension at a significant level (?10 % each). An overall multiplicative bias in the CFHTLenS shear data could also play a role, which can be tested with existing data. We close with forecasts for measurements of the CMB lensing—galaxy lensing cross-correlation using ongoing and future weak lensing surveys, which will definitively test the significance of the tension in our results with respect to ? CDM .
Gravitational lensing by Elliptical Galaxies, and the Schwarz Function
C. D. Fassnacht; C. R. Keeton; D. Khavinson
2007-08-20
We discuss gravitational lensing by elliptical galaxies with some particular mass distributions. Using simple techniques from the theory of quadrature domains and the Schwarz function (cf. \\cite{Sh}) we show that when the mass density is constant on confocal ellipses, the total number of lensed images of a point source cannot exceed 5 (4 bright images and 1 dim image). Also, using the Dive--Nikliborc converse of the celebrated Newton's theorem concerning the potentials of ellipsoids, we show that ``Einstein rings'' must always be either circles (in the absence of a tidal shear), or ellipses.
Gravitational lensing model degeneracies: Is steepness all-important?
P. Saha; L. L. R. Williams
2006-08-24
In gravitational lensing, steeper mass profiles generically produce longer time delays but smaller magnifications, without necessarily changing the image positions or magnification ratios between different images. This is well known. We find in this paper, however, that even if steepness is fixed, time delays can still have significant model dependence, which we attribute to shape modeling degeneracies. This conclusion follows from numerical experiments with models of 35 galaxy lenses. We suggest that varying and twisting ellipticities, features that are explored by pixelated lens models but not so far by parametric models, have an important effect on time delays.
Two new large-separation gravitational lenses from SDSS
NASA Astrophysics Data System (ADS)
Belokurov, V.; Evans, N. W.; Hewett, P. C.; Moiseev, A.; McMahon, R. G.; Sanchez, S. F.; King, L. J.
2009-01-01
We present discovery images, together with follow-up imaging and spectroscopy, of two large-separation gravitational lenses found by our survey for wide arcs [the CAmbridge Sloan Survey Of Wide ARcs in the skY (CASSOWARY)]. The survey exploits the multicolour photometry of the Sloan Digital Sky Survey to find multiple blue components around red galaxies. CASSOWARY 2 (or `the Cheshire Cat') is composed of two massive early-type galaxies at z = 0.426 and 0.432, respectively, lensing two background sources, the first a star-forming galaxy at z = 0.97 and the second a high -redshift galaxy (z > 1.4). There are at least three images of the former source and probably four or more of the latter, arranged in two giant arcs. The mass enclosed within the larger arc of radius ~11 arcsec is ~33 × 1012Msolar. CASSOWARY 3 comprises an arc of three bright images of a z = 0.725 source, lensed by a foreground elliptical at z = 0.274. The radius of the arc is ~4 arcsec and the enclosed mass is ~2.5 × 1012Msolar. Together with earlier discoveries like the Cosmic Horseshoe and the 8 o'clock Arc, these new systems, with separations intermediate between the arcsecond-separation lenses of typical strong galaxy lensing and arcminute-separation cluster lenses, probe the very high end of the galaxy mass function.
Is Gravitational Lensing by Intercluster Filaments Always Negligible?
Martin Feix; Dong Xu; HuanYuan Shan; Benoit Famaey; Marceau Limousin; HongSheng Zhao; Andy Taylor
2008-10-01
Intercluster filaments negligibly contribute to the weak lensing signal in general relativity (GR), $\\gamma_{N}\\sim 10^{-4}-10^{-3}$. In the context of relativistic modified Newtonian dynamics (MOND) introduced by Bekenstein, however, a single filament inclined by $\\approx 45^\\circ$ from the line of sight can cause substantial distortion of background sources pointing towards the filament's axis ($\\kappa=\\gamma=(1-A^{-1})/2\\sim 0.01$); this is rigorous for infinitely long uniform filaments, but also qualitatively true for short filaments ($\\sim 30$Mpc), and even in regions where the projected matter density of the filament is equal to zero. Since galaxies and galaxy clusters are generally embedded in filaments or are projected on such structures, this contribution complicates the interpretation of the weak lensing shear map in the context of MOND. While our analysis is of mainly theoretical interest providing order-of-magnitude estimates only, it seems safe to conclude that when modeling systems with anomalous weak lensing signals, e.g. the "bullet cluster" of Clowe et al., the "cosmic train wreck" of Abell 520 from Mahdavi et al., and the "dark clusters" of Erben et al., filamentary structures might contribute in a significant and likely complex fashion. On the other hand, our predictions of a (conceptual) difference in the weak lensing signal could, in principle, be used to falsify MOND/TeVeS and its variations.
Is Gravitational Lensing by Intercluster Filaments Always Negligible?
NASA Astrophysics Data System (ADS)
Feix, Martin; Xu, Dong; Shan, HuanYuan; Famaey, Benoit; Limousin, Marceau; Zhao, HongSheng; Taylor, Andy
2008-08-01
Intercluster filaments negligibly contribute to the weak lensing signal in general relativity (GR), ?N~10-4-10-3. In the context of relativistic modified Newtonian dynamics (MOND) introduced by Bekenstein, however, a single filament inclined by ~45° from the line of sight can cause substantial distortion of background sources pointing toward the filament's axis [?=?=(1-A-1)/2~0.01] this is rigorous for infinitely long uniform filaments, but also qualitatively true for short filaments (~30 Mpc), and even in regions where the projected matter density of the filament is equal to zero. Since galaxies and galaxy clusters are generally embedded in filaments or are projected on such structures, this contribution complicates the interpretation of the weak lensing shear map in the context of MOND. While our analysis is of mainly theoretical interest providing order-of-magnitude estimates only, it seems safe to conclude that when modeling systems with anomalous weak lensing signals, e.g., the ``bullet cluster'' of Clowe et al., the ``cosmic train wreck'' of A520 from Mahdavi et al., and the ``dark clusters'' of Erben et al., filamentary structures might contribute in a significant and likely complex fashion. On the other hand, our predictions of a (conceptual) difference in the weak lensing signal could, in principle, be used to falsify MOND/TeVeS and its variations.
Lensing by Distant Clusters: HST Observations of Weak Shear in the Field of 3C324
Ian Smail; Mark Dickinson
1995-10-08
We present the detection of weak gravitational lensing in the field of the radio galaxy 3C324 (z=1.206) using deep HST imaging. ~From an analysis of the shapes of faint R=24.5-27.5 galaxies in the field we measure a weak, coherent distortion centered close to the radio source. This shear field most likely arises from gravitational lensing of distant field galaxies by a foreground mass concentration. In the light of previous observations of this region, which indicate the presence of a rich cluster around the radio source, we suggest that the most likely candidate for the lens is the cluster associated with the radio galaxy at z=1.2. If so, this is the most distant cluster to have been detected by weak shear observations. Such a statement has two important consequences. Firstly, it shows that massive, collapsed structures exist in the high redshift Universe, and secondly that a significant fraction of the R=24.5-27.5 field galaxy population lies beyond z=1.2.
Model-independent characterisation of strong gravitational lenses
Wagner, Jenny
2015-01-01
We develop a new approach to extracting model-independent information from observations of strong gravitational lenses. The approach is based on the generic properties of images near the fold and cusp catastrophes in caustics and critical curves. Observables used are the relative image positions, the magnification ratios and ellipticities of extended images, and time delays between images with temporally varying intensity. We show how these observables constrain derivatives and ratios of derivatives of the lensing potential near a critical curve. Based on these measured properties of the lensing potential, classes of parametric lens models can then easily be restricted to such parameter values compatible with the measurements, thus allowing fast scans of large varieties of models. Applying our approach to a representative galaxy (JVAS B1422+231) and a galaxy-cluster lens (MACS J1149.5+2223), we show which model-independent information can be extracted in those cases and demonstrate that the parameters obtaine...
Higher-order gravitational lensing reconstruction using Feynman diagrams
NASA Astrophysics Data System (ADS)
Jenkins, Elizabeth E.; Manohar, Aneesh V.; Waalewijn, Wouter J.; Yadav, Amit P. S.
2014-09-01
We develop a method for calculating the correlation structure of the Cosmic Microwave Background (CMB) using Feynman diagrams, when the CMB has been modified by gravitational lensing, Faraday rotation, patchy reionization, or other distorting effects. This method is used to calculate the bias of the Hu-Okamoto quadratic estimator in reconstructing the lensing power spectrum up to Script O (phi4) in the lensing potential phi. We consider both the diagonal noise TT TT, EB EB, etc. and, for the first time, the off-diagonal noise TT TE, TB EB, etc. The previously noted large Script O (phi4) term in the second order noise is identified to come from a particular class of diagrams. It can be significantly reduced by a reorganization of the phi expansion. These improved estimators have almost no bias for the off-diagonal case involving only one B component of the CMB, such as EE EB.
Higher-order gravitational lensing reconstruction using Feynman diagrams
Jenkins, Elizabeth E.; Manohar, Aneesh V.; Yadav, Amit P.S.; Waalewijn, Wouter J. E-mail: amanohar@ucsd.edu E-mail: ayadav@physics.ucsd.edu
2014-09-01
We develop a method for calculating the correlation structure of the Cosmic Microwave Background (CMB) using Feynman diagrams, when the CMB has been modified by gravitational lensing, Faraday rotation, patchy reionization, or other distorting effects. This method is used to calculate the bias of the Hu-Okamoto quadratic estimator in reconstructing the lensing power spectrum up to O (?{sup 4}) in the lensing potential ?. We consider both the diagonal noise TT TT, EB EB, etc. and, for the first time, the off-diagonal noise TT TE, TB EB, etc. The previously noted large O (?{sup 4}) term in the second order noise is identified to come from a particular class of diagrams. It can be significantly reduced by a reorganization of the ? expansion. These improved estimators have almost no bias for the off-diagonal case involving only one B component of the CMB, such as EE EB.
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.
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.
Hubble Frontier Fields : ``A New Era for Gravitational Lensing''
NASA Astrophysics Data System (ADS)
Jauzac, Mathilde; Eckert, Dominique; Jullo, Eric; Richard, Johan; Ebeling, Harald; Kneib, Jean-Paul; Limousin, Marceau; Atek, Hakim; Natarajan, Priyamvada; Rexroth, Markus
2015-08-01
The Hubble Frontier Fields (HFF) initiative constitutes the largest commitment ever of HST time to the exploration of the distant Universe via gravitational lensing by massive galaxy clusters.I will present the new gravitational lensing pictures of the first HFF complex clusters. We have demonstrated that we are now able to `weight’ these clusters' cores down to the percent level precision (recently published works), serving our quest for the high-redshift Universe.However, while the depth of these dataset makes these clusters amazing Cosmic Telescopes, it also enables us to get an unprecedented understanding of the cluster physics.Therefore, presenting the case of MACSJ0416 and Abell 2744, I will demonstrate the importance of such high-quality data to analyse the merging/dynamical history of the cluster itself while comparing dark matter, light and gas distributions.
Effects of the complex mass distribution of dark matter halos on weak lensing cluster surveys
J. Y. Tang; Z. H. Fan
2005-08-24
Gravitational lensing effects arise from the light ray deflection by all of the mass distribution along the line of sight. It is then expected that weak lensing cluster surveys can provide us true mass-selected cluster samples. With numerical simulations, we analyze the correspondence between peaks in the lensing convergence $\\kappa$-map and dark matter halos. Particularly we emphasize the difference between the peak $\\kappa$ value expected from a dark matter halo modeled as an isolated and spherical one, which exhibits a one-to-one correspondence with the halo mass at a given redshift, and that of the associated $\\kappa$-peak from simulations. For halos with the same expected $\\kappa$, their corresponding peak signals in the $\\kappa$-map present a wide dispersion. At an angular smoothing scale of $\\theta_G=1\\hbox{arcmin}$, our study shows that for relatively large clusters, the complex mass distribution of individual clusters is the main reason for the dispersion. The projection effect of uncorrelated structures does not play significant roles. The triaxiality of dark matter halos accounts for a large part of the dispersion, especially for the tail at high $\\kappa$ side. Thus lensing-selected clusters are not really mass-selected. (abridged)
CFHTLenS: The Environmental Dependence of Galaxy Halo Masses from Weak Lensing
NASA Astrophysics Data System (ADS)
Gillis, Bryan; Hudson, M. J.; Erben, T.; Heymans, C.; Hildebrandt, H.; Hoekstra, H.; Kitching, T. D.; Mellier, Y.; Miller, L.; van Waerbeke, L.; Bonnett, C.; Coupon, J.; Fu, L.; Hilbert, S.; Rowe, B.; Schrabback, T.; Semboloni, E.; van Uitert, E.; Velander, M.; Cfhtlens Team
2013-07-01
We use weak gravitational lensing to analyse the dark matter halos around satellite galaxies in galaxy groups in the CFHTLenS dataset. This dataset is derived from the CFHTLS-Wide survey, and encompasses 154 sq. deg of high-quality shape data. Using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 10^9 Msun to 10^10.5 Msun into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily 61%) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly 87%) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, the lensing signal around HDE galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ~500--1000 kpc, the typical separation between satellites and group centres. More importantly, the subhalos of HDE galaxies are less massive than those around LDE galaxies by a factor 0.65 +/- 0.12, significant at the 2.9 sigma level. A natural explanation is that the halos of satellite galaxies are stripped through tidal effects in the group environment. Our results are consistent with a typical tidal truncation radius of ~40 kpc.
Strong gravitational lensing in non-commutative wormholes
NASA Astrophysics Data System (ADS)
Sharif, M.; Iftikhar, Sehrish
2015-05-01
This paper is devoted to study gravitational lensing of static spherically symmetric non-commutative wormholes in galactic halo region. We formulate the field equations with anisotropic matter using particlelike source of gravitation in the form of Lorentzian distribution. We explore energy conditions and equilibrium condition of the wormhole model using generalized Tolman-Oppenheimmer-Volkov equation. To investigate position of wormhole, we evaluate angle of deflection in the strong field limit through numerical approach. It is found that the angle of deflection diverges for the photon radius.
Strong gravitational lensing with Gauss-Bonnet correction
Sadeghi, J.; Vaez, H. E-mail: h.vaez@umz.ac.ir
2014-06-01
In this paper we investigate the strong gravitational lensing in a five dimensional background with Gauss-Bonnet gravity, so that in 4-dimensions the Gauss-Bonnet correction disappears. By considering the logarithmic term for deflection angle, we obtain the deflection angle ?-circumflex and corresponding parameters ? and b-bar . Finally, we estimate some properties of relativistic images such as ?{sub ?}, s and r{sub m}.
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 ...
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.
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.
Relativistic weak lensing from a fully non-linear cosmological density field
NASA Astrophysics Data System (ADS)
Thomas, D. B.; Bruni, M.; Wands, D.
2015-09-01
In this paper we examine cosmological weak lensing on non-linear scales and show that there are Newtonian and relativistic contributions and that the latter can also be extracted from standard Newtonian simulations. We use the post-Friedmann formalism, a post-Newtonian type framework for cosmology, to derive the full weak-lensing deflection angle valid on non-linear scales for any metric theory of gravity. We show that the only contributing term that is quadratic in the first order deflection is the expected Born correction and lens-lens coupling term. We use this deflection angle to analyse the vector and tensor contributions to the E- and B- mode cosmic shear power spectra. In our approach, once the gravitational theory has been specified, the metric components are related to the matter content in a well-defined manner. Specifying General Relativity, we write down a complete set of equations for a GR+?CDM universe for computing all of the possible lensing terms from Newtonian N-body simulations. We illustrate this with the vector potential and show that, in a GR+?CDM universe, its contribution to the E-mode is negligible with respect to that of the conventional Newtonian scalar potential, even on non-linear scales. Thus, under the standard assumption that Newtonian N-body simulations give a good approximation of the matter dynamics, we show that the standard ray tracing approach gives a good description for a ?CDM cosmology.
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.
Biesiada, Marek; Ding, Xuheng; Zhu, Zong-Hong [Department of Astronomy, Beijing Normal University, Xinjiekouwai 19, Beijing, 100875 China (China); Piórkowska, Aleksandra, E-mail: marek.biesiada@us.edu.pl, E-mail: dingxuheng@mail.bnu.edu.cn, E-mail: aleksandra.piorkowska@us.edu.pl, E-mail: zhuzh@bnu.edu.cn [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, Katowice, 40-007 Poland (Poland)
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.
Gravitationally Lensed X-Ray Sources at the Galactic Center
NASA Astrophysics Data System (ADS)
Castelaz, Michael W.; Rottler, L.
2012-01-01
More than two thousand x-ray sources located within 20 pc of the Galactic Center (GC) have been identified by Muno et al. (2003). If an x-ray source is located behind the Galactic Center and offset by a small angle from the GC projected on the sky, then that x-ray source could be gravitationally lensed. The consequences of finding gravitationally lensed sources at the Galactic Center include the ability to independently measure the mass of the GC as well as provide a new probe of the density distribution of the GC (e.g. Wardle & Yusef-Zadeh 1992). Inspecting x-ray images of the GC we were immediately drawn to a set of four x-ray objects. The identified objects are cataloged as CXOJ 174541.0-290014, 174540.1-290005, 174540.0-290031, and 174538.1-290022. These are the brightest and most obvious variable x-ray objects whose positions suggest patterns of images that may either be an inclined quad or two sets of dual gravitational lens patterns. Based on the image patterns, and image brightnesses and relative variations, we modeled possible lens systems using two algorithms. Both of the algorithms describing gravitational lenses are based on the Fermat potential and its time derivatives. For a lens radius of R = 0.01 pc, the total enclosed mass is 2.6 x 107 M? and for R = 0.001 pc, the total enclosed mass is 2.6 x 105 M?. These masses are consistent with other measurements of the mass of the GC, such as 4.5 x 106 M? (Ghez et al. 2008). We will present these results and our plans to further study the nature of these x-ray objects.
Shirasaki, Masato; Yoshida, Naoki
2014-05-01
The measurement of cosmic shear using weak gravitational lensing is a challenging task that involves a number of complicated procedures. We study in detail the systematic errors in the measurement of weak-lensing Minkowski Functionals (MFs). Specifically, we focus on systematics associated with galaxy shape measurements, photometric redshift errors, and shear calibration correction. We first generate mock weak-lensing catalogs that directly incorporate the actual observational characteristics of the Canada-France-Hawaii Lensing Survey (CFHTLenS). We then perform a Fisher analysis using the large set of mock catalogs for various cosmological models. We find that the statistical error associated with the observational effects degrades the cosmological parameter constraints by a factor of a few. The Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of ?1400 deg{sup 2} will constrain the dark energy equation of the state parameter with an error of ?w {sub 0} ? 0.25 by the lensing MFs alone, but biases induced by the systematics can be comparable to the 1? error. We conclude that the lensing MFs are powerful statistics beyond the two-point statistics only if well-calibrated measurement of both the redshifts and the shapes of source galaxies is performed. Finally, we analyze the CFHTLenS data to explore the ability of the MFs to break degeneracies between a few cosmological parameters. Using a combined analysis of the MFs and the shear correlation function, we derive the matter density ?{sub m0}=0.256±{sub 0.046}{sup 0.054}.
How gravitational lensing helps ?-ray photons avoid ? – ? absorption
Barnacka, Anna [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Böttcher, Markus; Sushch, Iurii, E-mail: abarnacka@cfa.harvard.edu, E-mail: Markus.Bottcher@nwu.ac.za [Centre for Space Research, North-West University, Potchefstroom, 2520 (South Africa)
2014-08-01
We investigate potential ? – ? absorption of ?-ray emission from blazars arising from inhomogeneities along the line of sight, beyond the diffuse Extragalactic Background Light (EBL). As plausible sources of excess ? – ? opacity, we consider (1) foreground galaxies, including cases in which this configuration leads to strong gravitational lensing, (2) individual stars within these foreground galaxies, and (3) individual stars within our own galaxy, which may act as lenses for microlensing events. We found that intervening galaxies close to the line of sight are unlikely to lead to significant excess ? – ? absorption. This opens up the prospect of detecting lensed gamma-ray blazars at energies above 10 GeV with their gamma-ray spectra effectively only affected by the EBL. The most luminous stars located either in intervening galaxies or in our galaxy provide an environment in which these gamma-rays could, in principle, be significantly absorbed. However, despite a large microlensing probability due to stars located in intervening galaxies, ?-rays avoid absorption by being deflected by the gravitational potentials of such intervening stars to projected distances ({sup i}mpact parameters{sup )} where the resulting ? – ? opacities are negligible. Thus, neither of the intervening excess photon fields considered here, provide a substantial source of excess ? – ? opacity beyond the EBL, even in the case of very close alignments between the background blazar and a foreground star or galaxy.
How to Measure Dark Energy with LSST's Strong Gravitational Lenses
NASA Astrophysics Data System (ADS)
Marshall, Philip J.; Treu, T.; Brunner, R. J.; Strong Lensing, LSST; Dark Energy Science Collaborations
2013-01-01
Strong gravitational lensing is sensitive to dark energy (DE) via the combinations of angular diameter distances that appear in model predictions of the lens strength. Lenses with variable sources offer the most promise: the corresponding time delay distance has recently been shown to be measurable to 5% precision. Large samples of lensed quasars and supernovae will allow internal degeneracy-breaking and so enable the most direct access to the DE parameters, while multiple source-plane, compound lens systems may provide an alternative, complementary, H0-free probe. Its wide field survey and high cadence will enable LSST to provide a sample of several thousand measured time delays, two orders of magnitude larger than the current sample, and allow an independent, competitive Stage IV DE parameter measurement to be made. However, practical problems to be solved include: lens detection (which may be very sensitive to image quality and deblender performance); image and lightcurve modelling (which could be both CPU and manual labor-intensive); obtaining and analyzing high resolution spectro-imaging follow-up data; and interpreting the whole sample of lenses in the context of the well-studied subset.
Cross-Correlation Tomography: Measuring Dark Energy Evolution with Weak Lensing
Bhuvnesh Jain; Andy Taylor
2003-01-01
A cross-correlation technique of lensing tomography is developed to probe dark energy in the Universe. The variation of weak shear with redshift around foreground galaxies depends only on the angular distances and is robust to the dominant systematic error in lensing. We estimate the marginalized accuracies that deep lensing surveys with photometric redshifts can provide on the dark energy density
GRAVITATIONAL LENSING CORRECTIONS IN FLAT {Lambda}CDM COSMOLOGY
Kantowski, Ronald; Chen Bin; Dai Xinyu E-mail: Bin.Chen-1@ou.ed
2010-08-01
We compute the deflection angle to order (m/r {sub 0}){sup 2} and m/r{sub 0} x {Lambda}r {sup 2}{sub 0} for a light ray traveling in a flat {Lambda}CDM cosmology that encounters a completely condensed mass region. We use a Swiss cheese model for the inhomogeneities and find that the most significant correction to the Einstein angle occurs not because of the nonlinear terms but instead occurs because the condensed mass is embedded in a background cosmology. The Swiss cheese model predicts a decrease in the deflection angle of {approx}2% for weakly lensed galaxies behind the rich cluster A1689 and that the reduction can be as large as {approx}5% for similar rich clusters at z {approx} 1. Weak-lensing deflection angles caused by galaxies can likewise be reduced by as much as {approx}4%. We show that the lowest order correction in which {Lambda} appears is proportional to m/r{sub 0} x {radical}({Lambda}r{sub 0}{sup 2}) and could cause as much as a {approx}0.02% increase in the deflection angle for light that passes through a rich cluster. The lowest order nonlinear correction in the mass is proportional to m/r{sub 0}x{radical}(m/r{sub 0}) and can increase the deflection angle by {approx}0.005% for weak lensing by galaxies.
CFHTLenS: the environmental dependence of galaxy halo masses from weak lensing
NASA Astrophysics Data System (ADS)
Gillis, Bryan R.; Hudson, Michael J.; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; van Waerbeke, Ludovic; Bonnett, Christopher; Coupon, Jean; Fu, Liping; Hilbert, Stefan; Rowe, Barnaby T. P.; Schrabback, Tim; Semboloni, Elisabetta; van Uitert, Edo; Velander, Malin
2013-05-01
We use weak gravitational lensing to analyse the dark matter haloes around satellite galaxies in galaxy groups in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) data set. This data set is derived from the Canada-France-Hawaii Telescope Legacy Survey Wide survey, and encompasses 154 deg2 of high-quality shape data. Using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 109-1010.5 M? into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily (˜61 per cent) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly (˜87 per cent) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, the lensing signal around HDE galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ˜500-1000 kpc, the typical separation between satellites and group centres. More importantly, the subhaloes of HDE galaxies are less massive than those around LDE galaxies by a factor of 0.65 ± 0.12, significant at the 2.9? level. A natural explanation is that the haloes of satellite galaxies are stripped through tidal effects in the group environment. Our results are consistent with a typical tidal truncation radius of ˜40 kpc.
WEAK LENSING MEASUREMENT OF GALAXY CLUSTERS IN THE CFHTLS-WIDE SURVEY
Shan Huanyuan; Tao Charling [Department of Physics and Tsinghua Center for Astrophysics, Tsinghua University, Beijing, 100084 (China); Kneib, Jean-Paul; Jauzac, Mathilde; Limousin, Marceau [Laboratoire d'Astrophysique de Marseille, CNRS-Universite de Provence, 38 rue Frederic Joliot-Curie, F-13388 Marseille Cedex 13 (France); Fan Zuhui [Department of Astronomy, Peking University, Beijing, 100871 (China); Massey, Richard [Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Rhodes, Jason [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Thanjavur, Karun [Canada France Hawaii Telescope, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States); McCracken, Henry J., E-mail: shanhuany@gmail.com [Institude d'Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, F-75014 Paris (France)
2012-03-20
We present the first weak gravitational lensing analysis of the completed Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We study the 64 deg{sup 2} W1 field, the largest of the CFHTLS-Wide survey fields, and present the largest contiguous weak lensing convergence 'mass map' yet made. 2.66 million galaxy shapes are measured, using the Kaiser Squires and Broadhurst Method (KSB) pipeline verified against high-resolution Hubble Space Telescope imaging that covers part of the CFHTLS. Our i'-band measurements are also consistent with an analysis of independent r'-band imaging. The reconstructed lensing convergence map contains 301 peaks with signal-to-noise ratio {nu} > 3.5, consistent with predictions of a {Lambda}CDM model. Of these peaks, 126 lie within 3.'0 of a brightest central galaxy identified from multicolor optical imaging in an independent, red sequence survey. We also identify seven counterparts for massive clusters previously seen in X-ray emission within 6 deg{sup 2} XMM-LSS survey. With photometric redshift estimates for the source galaxies, we use a tomographic lensing method to fit the redshift and mass of each convergence peak. Matching these to the optical observations, we confirm 85 groups/clusters with {chi}{sup 2}{sub reduced} < 3.0, at a mean redshift (z{sub c} ) = 0.36 and velocity dispersion ({sigma}{sub c}) = 658.8 km s{sup -1}. Future surveys, such as DES, LSST, KDUST, and EUCLID, will be able to apply these techniques to map clusters in much larger volumes and thus tightly constrain cosmological models.
NASA Astrophysics Data System (ADS)
McCully, Curtis
Type Ia supernovae (SNe Ia) and gravitational lensing are important cosmological probes, but both are limited by theoretical, systematic uncertainties. One key uncertainty in distances derived using SNe Ia is our lack of understanding of the explosion mechanism for normal SNe Ia. We have studied peculiar type Iax supernovae that appear to be related to normal SNe Ia with the goal of understanding white dwarf explosions as a whole. In Chapter 2, using late-time Hubble Space Telescope (HST) observations of SN 2008A and SN 2005hk, both prototypical SNe Iax, we argue that these objects are pure deflagration explosions that do not unbind the white dwarf. In Chapter 3, we present observations of the type Iax SN 2012Z, one of the nearest ever discovered. Fortunately for us, its host galaxy, NGC 1309, was observed extensively with HST/ACS (to measure a Cepheid distance), giving us incredibly deep pre-explosion images of the site of SN 2012Z. We find that there is a source coincident with the position of the SN. We argue that the source is likely a helium star companion to the white dwarf that exploded. In galaxy-scale gravitational lenses, one of the largest systematic uncertainties arises due to other mass in the environment of the lens or along the line of sight (LOS). In Chapter 4, we develop an analytic framework to account for LOS effects. Our framework employs a hybrid approach treating a few perturbing galaxies as strong lenses, making it accurate, while treating the rest in the weak lensing approximation, making it also computationally efficient. In Chapter 5, we test our framework using simulations of realistic mass models. We suggest a method to characterize the strength of the LOS effects allowing us to systematically test when the weak lensing approximation is valid. We show that LOS effects are not equivalent to a single shear, but these non-linear effects are correctly captured by our framework. Our new methodology can be used to constrain cosmological parameters, like the Hubble Constant, in the era of precision gravitational lensing measurements.
THE WEIGHT OF EMPTINESS: THE GRAVITATIONAL LENSING SIGNAL OF STACKED VOIDS
Krause, Elisabeth; Dore, Olivier; Chang, Tzu-Ching; Umetsu, Keiichi
2013-01-10
The upcoming new generation of spectroscopic galaxy redshift surveys will provide large samples of cosmic voids, large distinct, underdense structures in the universe. Combining these with future galaxy imaging surveys, we study the prospects of probing the underlying matter distribution in and around cosmic voids via the weak gravitational lensing effects of stacked voids, utilizing both shear and magnification information. The statistical precision is greatly improved by stacking a large number of voids along different lines of sight, even when taking into account the impact of inherent miscentering and projection effects. We show that Dark Energy Task Force Stage IV surveys, such as the Euclid satellite and the Large Synoptic Survey Telescope, should be able to detect the void lensing signal with sufficient precision from stacking abundant medium-sized voids, thus providing direct constraints on the matter density profile of voids independent of assumptions on galaxy bias.
SPITZER IMAGING OF HERSCHEL-ATLAS GRAVITATIONALLY LENSED SUBMILLIMETER SOURCES
Hopwood, R.; Negrello, M.; Wardlow, J.; Cooray, A.; Khostovan, A. A.; Kim, S.; Barton, E.; Da Cunha, E.; Cooke, J.; Burgarella, D.; Aretxaga, I.; Auld, R.; Baes, M.; Bertoldi, F.; Bonfield, D. G.; Blundell, R.; Buttiglione, S.; Cava, A.; Dannerbauer, H.
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 image simulations for the study of the substructure in galaxy clusters
Peeples, Molly S
2005-01-01
As gravitational lensing is susceptible to all gravitating matter-both baryonic and dark-it provides a potentially clean way to study the mass distribution of galaxy clusters. We are particularly interested in the substructure ...
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, ...
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.
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.
Gravitational Lensing by Self-Dual Black Holes in Loop Quantum Gravity
Satyabrata Sahu; Kinjalk Lochan; D. Narasimha
2015-03-13
We study gravitational lensing by a recently proposed black hole solution in Loop Quantum Gravity. We highlight the fact that the quantum gravity corrections to the Schwarzschild metric in this model evade the `mass suppression' effects (that the usual quantum gravity corrections are susceptible to) by virtue of one of the parameters in the model being dimensionless, which is unlike any other quantum gravity motivated parameter. Gravitational lensing in the strong and weak deflection regimes is studied and a sample consistency relation is presented which could serve as a test of this model. We discuss that though the consistency relation for this model is qualitatively similar to what would have been in Brans-Dicke, in general it can be a good discriminator between many alternative theories. Although the observational prospects do not seem to be very optimistic even for a galactic supermassive black hole case, time delay between relativistic images for billion solar mass black holes in other galaxies might be within reach of future relativistic lensing observations.
IMPROVED CONSTRAINTS ON THE GRAVITATIONAL LENS Q0957+561. II. STRONG LENSING
Fadely, R.; Keeton, C. R.; Nakajima, R.; Bernstein, G. M. E-mail: keeton@physics.rutgers.ed E-mail: rnakajima@berkeley.ed
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.
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.
NASA Astrophysics Data System (ADS)
Lieber, Michael; Kaplan, Michael; Sholl, Michael; Bernstein, Gary
2010-07-01
Many astrophysicists consider the mystery of accelerated expansion of the universe by a field called dark energy as the greatest challenge to solve in cosmology. Gravitational weak lensing has been identfied as one of the best methods to provide constraints on dark energy model parameters. Weak lensing introduces image shear which can be measured statistically from a large sample of galaxies by determining the ellipticity parameters. Several papers have suggested that a goal in the ability to measure shape biases should be <0.1% - this goal will be reviewed in terms of the observatory "transfer function" with comments interspersed regarding allocation inconsistencies. Time-varying effects introduced by thermoelastic deformations and vibration add bias and noise to the galaxy shape measurements. This is compounded by the wide field-of-view required for the weak lensing science which leads to a spatially varying point spead function (PSF). To fully understand these effects, a detailed integrated model (IM) was constructed which includes a coupled scene/ structure/ optics/ disturbance model. This IM was applied to the Joint Dark Energy Mission (JDEM) Omega design concept. Results indicate that previous models of vibration disturbance effects have been too simplified and the allocation for vibration needs to be re-evaluated. Furthermore, because of the complicated processing required to accurately extract shape parameters, it is argued that an IM is needed for maximizing science return by iterating the telescope/ instrument design against mission cost constraints, and processing e¤ectiveness of shape extraction algorithms, instrument calibration techniques and measurement desensitization of observatory effects.
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/ ...
Constraints on early dark energy from CMB lensing and weak lensing tomography
Hollenstein, Lukas; Crittenden, Robert [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom)] [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Sapone, Domenico [Departement de Physique Theorique, Universite de Geneve, 24 Quai Ernest-Ansermet, CH-1211 Geneve 4 (Switzerland)] [Departement de Physique Theorique, Universite de Geneve, 24 Quai Ernest-Ansermet, CH-1211 Geneve 4 (Switzerland); Schaefer, Bjoern Malte, E-mail: lukas.hollenstein@port.ac.uk, E-mail: domenico.sapone@unige.ch, E-mail: robert.crittenden@port.ac.uk, E-mail: spirou@ita.uni-heidelberg.de [Astronomisches Recheninstitut, Zentrum fuer Astronomie, Universitaet Heidelberg, Moenchhofstrasse 12, 69120 Heidelberg (Germany)
2009-04-15
Dark energy can be studied by its influence on the expansion of the Universe as well as on the growth history of the large-scale structure. In this paper, we follow the growth of the cosmic density field in early dark energy cosmologies by combining observations of the primary CMB temperature and polarisation power spectra at high redshift, of the CMB lensing deflection field at intermediate redshift and of weak cosmic shear at low redshifts for constraining the allowed amount of early dark energy. We present these forecasts using the Fisher matrix formalism and consider the combination of Planck data with the weak lensing survey of Euclid. We find that combining these data sets gives powerful constraints on early dark energy and is able to break degeneracies in the parameter set inherent to the various observational channels. The derived statistical 1{sigma}-bound on the early dark energy density parameter is {sigma}({Omega}{sup e}{sub d}) = 0.0022 which suggests that early dark energy models can be well examined in our approach. In addition, we derive the dark energy figure of merit for the considered dark energy parameterisation and comment on the applicability of the growth index to early dark energy cosmologies.
Gravitational lensing in an exact locally inhomogeneous cosmology
NASA Astrophysics Data System (ADS)
Attard, Allen
2005-11-01
A Recursive Swiss-Cheese (RSC) cosmological model is an exact solution to Einstein's general relativistic field equations allowing for dramatic local density inhomogeneities while maintaining global homogeneity and isotropy. It is constructed by replacing spherical regions of an FRW background with higher density cores placed at the centre of a Schwarzschild vacuum, with each core itself potentially being given the same treatment and the process repeated to generate a range of multifractal structures. Code was developed to tightly pack spheres into spaces of constant curvature in an efficient manner, and was used to develop libraries of packings with positive, negative, and zero curvature. Various projections are used to illustrate their structure, and means of measuring its dimensionality are discussed. A method by which these packings can be used as building blocks of an RSC model, along with a way of selecting parameters to define the model, is described, and a coordinate system allowing a relativistically consistent means of synchronizing its various components is developed. Formulations of the optical scalar equations for the expansion and shear rates of a beam are considered, and a set suitable for numerical integration selected. The forms of the null geodesic beam trajectories in each region of the model are computed, and a parallel propagated shadow plane basis that can be consistently followed between the various model sections is established. This allowed the development of code using a fourth order, variable step size Runge-Kutta integration routine to compute the gravitational lensing effect within an RSC model by tracking the amplification and distortion of a series of beams that are propagated through it. The output generated allows the redshift evolution of these quantities to be plotted for each beam, and enables maps to be made of the "observed sky". The amplification signature produced by a single lens in the model is examined, and the form shown to be generally consistent with that found using a thin lens approximation, particularly when the lens ing is weak. Distortion values are likewise shown to be reasonable, and results derived from propagating beams through a full RSC model are also presented.
WEAK-LENSING PEAK FINDING: ESTIMATORS, FILTERS, AND BIASES
Schmidt, Fabian [Theoretical Astrophysics, California Institute of Technology, M/C 350-17, Pasadena, CA 91125 (United States); Rozo, Eduardo [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States)
2011-07-10
Large catalogs of shear-selected peaks have recently become a reality. In order to properly interpret the abundance and properties of these peaks, it is necessary to take into account the effects of the clustering of source galaxies, among themselves and with the lens. In addition, the preferred selection of magnified galaxies in a flux- and size-limited sample leads to fluctuations in the apparent source density that correlate with the lensing field. In this paper, we investigate these issues for two different choices of shear estimators that are commonly in use today: globally normalized and locally normalized estimators. While in principle equivalent, in practice these estimators respond differently to systematic effects such as magnification and cluster member dilution. Furthermore, we find that the answer to the question of which estimator is statistically superior depends on the specific shape of the filter employed for peak finding; suboptimal choices of the estimator+filter combination can result in a suppression of the number of high peaks by orders of magnitude. Magnification and size bias generally act to increase the signal-to-noise {nu} of shear peaks; for high peaks the boost can be as large as {Delta}{nu} {approx} 1-2. Due to the steepness of the peak abundance function, these boosts can result in a significant increase in the observed abundance of shear peaks. A companion paper investigates these same issues within the context of stacked weak-lensing mass estimates.
Wave Effects in Gravitational Lensing of Gravitational Waves from Chirping Binaries
Ryuichi Takahashi; Takashi Nakamura
2003-06-11
In the gravitational lensing of gravitational waves, the wave optics should be used instead of the geometrical optics when the wavelength $\\lambda$ of the gravitational waves is longer than the Schwarzschild radius of the lens mass $M_L$. For the gravitational lensing of the chirp signals from the coalescence of the super massive black holes at the redshift $z_S\\sim 1$ relevant to LISA, the wave effects become important for the lens mass smaller than $\\sim 10^8 M_{\\odot}$. For such cases, we compute how accurately we can extract the mass of the lens and the source position from the lensed signal. We consider two simple lens models: the point mass lens and the SIS (Singular Isothermal Sphere). We find that the lens mass and the source position can be determined within $\\sim 0.1% [(S/N)/10^3]^{-1}$ for the lens mass larger than $10^8 M_{\\odot}$ and $\\gsim 10% [(S/N)/10^3]^{-1}$ for the lens mass smaller than $10^7 M_{\\odot}$ due to the diffraction effect, where $(S/N)$ is the signal to noise ratio of the unlensed chirp signals. For the SIS model, if the source position is outside the Einstein radius, only a single image exists in the geometrical optics approximation so that the lens parameters can not be determined. While in the wave optics cases we find that the lens mass can be determined even for $M_L < 10^8 M_{\\odot}$. For the point mass lens, one can extract the lens parameters even if the source position is far outside the Einstein radius. As a result, the lensing cross section is an order of magnitude larger than that for the usual strong lensing of light.
Weak Lensing Measurements in Simulations of Radio Images
Patel, Prina; Bacon, David J; Rowe, Barnaby; Smirnov, Oleg; Beswick, Rob J
2013-01-01
We present a study of weak lensing shear measurements for simulated galaxy images at radio wavelengths. We construct a simulation pipeline into which we can input galaxy images of known ellipticity, and with which we then simulate observations with eMERLIN and the international LOFAR array. The simulations include the effects of the CLEAN algorithm, uv sampling, observing angle, and visibility noise, and produce realistic restored images of the galaxies. We apply a shapelet-based shear measurement method to these images and test our ability to recover the true source ellipticities. We model and deconvolve the effective PSF, and find suitable parameters for CLEAN and shapelet decomposition of galaxies. We demonstrate that ellipticities can be measured faithfully in these radio simulations, with no evidence of an additive bias and a modest (10%) multiplicative bias on the ellipticity measurements. Our simulation pipeline can be used to test shear measurement procedures and systematics for the next generation of...
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.
NASA Astrophysics Data System (ADS)
Tagore, Amitpal Singh
Gravitational lens modeling of spatially resolved sources is a challenging inverse problem that can involve many observational constraints and model parameters. I present a new software package, pixsrc, that works in conjunction with the lensmodel software and builds on established pixel-based source reconstruction (PBSR) algorithms for de-lensing a source and constraining lens model parameters. Using test data, I explore statistical and systematic uncertainties associated with gridding, source regularization, interpolation errors, noise, and telescope pointing. I compare two gridding schemes in the source plane: a fully adaptive grid and an adaptive Cartesian grid. I also consider regularization schemes that minimize derivatives of the source and introduce a scheme that minimizes deviations from an analytic source profile. Careful choice of gridding and regularization can reduce "discreteness noise" in the chi2 surface that is inherent in the pixel-based methodology. With a gridded source, errors due to interpolation need to be taken into account (especially for high S/N data). Different realizations of noise and telescope pointing lead to slightly different values for lens model parameters, and the scatter between different "observations" can be comparable to or larger than the model uncertainties themselves. The same effects create scatter in the lensing magnification at the level of a few percent for a peak S/N of 10. I then apply pixsrc to observations of lensed, high-redshift galaxies. SDSS J0901+1814, is an ultraluminous infrared galaxy at z=2.26 that is also UV-bright, and it is lensed by a foreground group of galaxies at z=0.35. I constrain the lens model using maps of CO(3-2) rotational line emission and optical imaging and apply the lens model to observations of CO(1-0), H-alpha, and [NII] line emission as well. Using the de-lensed images, I calculate properties of the source, such as the gas mass fraction and dynamical mass. Finally, I examine a serendipitously discovered pair of gravitationally lensed objects with strikingly different colors. One appears red and compact, while the other appears blue and extended. I use pixsrc to constrain the lens model using observations of the red object and present a PBSR as a first step towards understanding its properties.
A weak-lensing analysis of the galaxy cluster WHL J163355.8+430528
NASA Astrophysics Data System (ADS)
Ko, Jongwan; Utsumi, Yousuke
2015-08-01
A weak-lensing analysis is a powerful tool to measure the projected mass distribution of galaxy clusters. Galaxy redshift surveys resolve the structures along the line of sight and provide a map of the three-dimensional galaxy distribution. Therefore, the comparison of structures identified in the weak-lensing maps and in the redshift surveys is an important test of the application of weak-lensing maps. We use deep CFHT/MegaCam gr images of the field centered on the galaxy cluster at z=0.27, WHL J163355.8+430528 (a new candidate of an X-ray cluster 1RXS J163355.5+430523), to construct weak-lensing maps, and present the preliminary results from weak-lensing analysis.
Larsen, Patricia
2015-01-01
Correlations of galaxy ellipticities with large-scale structure, due to galactic tidal interactions, provide a potentially significant contaminant to measurements of cosmic shear. However, these intrinsic alignments are still poorly understood for galaxies at the redshifts typically used in cosmic shear analyses. For spiral galaxies, it is thought that tidal torquing is significant in determining alignments resulting in zero correlation between the intrinsic ellipticity and the gravitational potential in linear theory. Here, we calculate the leading-order correction to this result in the tidal-torque model from non-linear evolution, using second-order perturbation theory, and relate this to the contamination from intrinsic alignments to the recently-measured cross-correlation between galaxy ellipticities and the CMB lensing potential. We find that the angular cross-correlation from tidal torquing has a very similar scale dependence as in the linear alignment model (believed to be appropriate for elliptical ga...
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.
A Candidate Gravitationally Lensed Quasar at z=6.09
NASA Astrophysics Data System (ADS)
McGreer, Ian
2013-10-01
We have obtained WFC3/IR images of nearly half of the known quasars at z 6 through a Cycle 18 SNAP program. During the latter part of the Cycle we identified a candidate gravitationally lensed quasar, SDSSJ1602+4228, at z=6.09. The short duration SNAP exposure shows that the central arcsecond is resolved into multiple emission features, which we interpret as two lensed images of the z=6 quasar and the lens galaxy. However, from the single band image the nature of the components is inconclusive. We propose a brief {two orbit} follow-up program that will include imaging in three bands: WFC3/IR Y and H, and ACS/WFC R-band. The combination of infrared and optical imaging will allow us to use color information to isolate the quasar images, lens galaxy, or any contaminating foreground objects. The confirmation of even one lensed quasar among the SNAP sample has strong implications for the shape of the quasar luminosity function at z=6, with further implications for expected source counts at higher redshift, as well as models for black hole growth in the early Universe.
Analytical Kerr-Sen dilaton-axion black hole lensing in the weak deflection limit
Gyulchev, Galin N.; Yazadjiev, Stoytcho S.
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.
Analytical Kerr-Sen dilaton-axion black hole lensing in the weak deflection limit
NASA Astrophysics Data System (ADS)
Gyulchev, Galin N.; Yazadjiev, Stoytcho S.
2010-01-01
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?/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, 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.
Petri, Andrea; Haiman, Zoltan; May, Morgan; Hui, Lam; Kratochvil, Jan M
2015-01-01
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 $(\\Omega_m,w,\\sigma_8)$ from non-Gaussian features of the weak lensing convergence field, including a set of moments (up to $4^{\\rm th}$ order) and Minkowski functionals, using publicly available data from the 154deg$^2$ CFHTLenS survey. We utilize a suite of ray--tracing N-body simulations spanning 91 points in $(\\Omega_m,w,\\sigma_8)$ 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 $(\\Omega_m,w,\\sigma_8)$, 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 statis...
Stacking weak lensing signals of SZ clusters to constrain cluster physics
Carolyn Sealfon; Licia Verde; Raul Jimenez
2006-01-12
We show how to place constraints on cluster physics by stacking the weak lensing signals from multiple clusters found through the Sunyaev-Zeldovich (SZ) effect. For a survey that covers about 200 sq. deg. both in SZ and weak lensing observations, the slope and amplitude of the mass vs. SZ luminosity relation can be measured with few percent error for clusters at z~0.5. This can be used to constrain cluster physics, such as the nature of feedback. For example, we can distinguish a pre-heated model from a model with a decreased accretion rate at more than 5sigma. The power to discriminate among different non-gravitational processes in the ICM becomes even stronger if we use the central Compton parameter y_0, which could allow one to distinguish between models with pre-heating, SN feedback and AGN feedback, for example, at more than 5sigma. Measurement of these scaling relations as a function of redshift makes it possible to directly observe e.g., the evolution of the hot gas in clusters. With this approach the mass-L_SZ relation can be calibrated and its uncertainties can be quantified, leading to a more robust determination of cosmological parameters from clusters surveys. The mass-L_SZ relation calibrated in this way from a small area of the sky can be used to determine masses of SZ clusters from very large SZ-only surveys and is nicely complementary to other techniques proposed in the literature.
A gravitationally lensed water maser in the early Universe.
Impellizzeri, C M Violette; McKean, John P; Castangia, Paola; Roy, Alan L; Henkel, Christian; Brunthaler, Andreas; Wucknitz, Olaf
2008-12-18
Water masers are found in dense molecular clouds closely associated with supermassive black holes at the centres of active galaxies. On the basis of the understanding of the local water-maser luminosity function, it was expected that masers at intermediate and high redshifts would be extremely rare. However, galaxies at redshifts z > 2 might be quite different from those found locally, not least because of more frequent mergers and interaction events. Here we use gravitational lensing to search for masers at higher redshifts than would otherwise be possible, and find a water maser at redshift 2.64 in the dust- and gas-rich, gravitationally lensed type-1 quasar MG J0414+0534 (refs 6-13). The isotropic luminosity is 10,000 (, solar luminosity), which is twice that of the most powerful local water maser and half that of the most distant maser previously known. Using the locally determined luminosity function, the probability of finding a maser this luminous associated with any single active galaxy is 10(-6). The fact that we see such a maser in the first galaxy we observe must mean that the volume densities and luminosities of masers are higher at redshift 2.64. PMID:19092930
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.
Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing Through Galaxy Clustering
Fassnacht, Chris D.; McKean, J.P.; Koopmans, L.V.E.; Treu, T.; Blandford, R.D.; Auger, M.W.; Jeltema, T.E.; Lubin, L.M.; Margoniner, V.E.; Wittman, D.; /UC, Davis /Kapteyn Astron. Inst., Groningen /UC, Santa Barbara /KIPAC, Menlo Park /Carnegie Inst. Observ.
2006-04-03
We report the serendipitous discovery of two strong gravitational lens candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, each less than 40'' from the previously known gravitational lens system CLASS B1608+656. The redshifts of both lens galaxies have been measured with Keck and Gemini: one is a member of a small galaxy group at z {approx} 0.63, which also includes the lensing galaxy in the B1608+656 system, and the second is a member of a foreground group at z {approx} 0.43. By measuring the effective radii and surface brightnesses of the two lens galaxies, we infer their velocity dispersions based on the passively evolving Fundamental Plane (FP) relation. Elliptical isothermal lens mass models are able to explain their image configurations within the lens hypothesis, with a velocity dispersion compatible with that estimated from the FP for a reasonable source-redshift range. Based on the large number of massive early-type galaxies in the field and the number-density of faint blue galaxies, the presence of two additional lens systems around CLASS B1608+656 is not unlikely in hindsight. Gravitational lens galaxies are predominantly early-type galaxies, which are clustered, and the lensed quasar host galaxies are also clustered. Therefore, obtaining deep high-resolution images of the fields around known strong lens systems is an excellent method of enhancing the probability of finding additional strong gravitational lens systems.
The impact of correlated noise on galaxy shape estimation for weak lensing
Gurvich, Alex
2015-01-01
The robust estimation of the tiny distortions (shears) of galaxy shapes caused by weak gravitational lensing in the presence of much larger shape distortions due to the point-spread function (PSF) has been widely investigated. One major problem is that most galaxy shape measurement methods are subject to bias due to pixel noise in the images ("noise bias"). Noise bias is usually characterized using uncorrelated noise fields; however, real images typically have low-level noise correlations due to galaxies below the detection threshold, and some types of image processing can induce further noise correlations. We investigate the effective detection significance and its impact on noise bias in the presence of correlated noise for one method of galaxy shape estimation. For a fixed noise variance, the biases in galaxy shape estimates can differ substantially for uncorrelated versus correlated noise. However, use of an estimate of detection significance that accounts for the noise correlations can almost entirely re...
Effects of large-scale structure on the accuracy of weak lensing mass measurements
Hoekstra, Henk; Hilbert, Stefan; van Uitert, Edo
2010-01-01
Weak gravitational lensing has become an important method to determine the masses of galaxy clusters. The intrinsic shapes of the galaxies are a dominant source of uncertainty, but there are other limitations to the precision that can be achieved. In this paper we revisit a typically ignored source of uncertainty: structure along the line-of sight. Using results from the Millennium Simulation we confirm the validity of analytical calculations that have shown that such random projections are particularly important for studies of the cluster density profile. In general the contribution of large-scale structure to the total error budget is comparable to the statistical errors. We find that the precision of the mass measurement can be improved only slightly by modelling the large-scale structure using readily available data.
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...
Marusa Bradac; Douglas Clowe; Anthony H. Gonzalez; Phil Marshall; William Forman; Christine Jones; Maxim Markevitch; Scott Randall; Tim Schrabback; Dennis Zaritsky
2006-08-18
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).
Bradac, M; González, A H; Marshall, P; Forman, W; Jones, C; Markevitch, M L; Randall, S; Schrabback, T; Zaritsky, D; Bradac, Marusa; Clowe, Douglas; Gonzalez, Anthony H.; Marshall, Phil; Forman, William; Jones, Christine; Markevitch, Maxim; Randall, Scott; Schrabback, Tim; Zaritsky, Dennis
2006-01-01
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).
EFFECTIVE MODELS FOR STATISTICAL STUDIES OF GALAXY-SCALE GRAVITATIONAL LENSING
Lapi, A.; Negrello, M.; Gonzalez-Nuevo, J.; Cai, Z.-Y.; De Zotti, G.; Danese, L.
2012-08-10
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 Almost-Equal-To 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.
Galactic metric, dark radiation, dark pressure and gravitational lensing in brane world models
T. Harko; K. S. Cheng
2005-09-20
In the braneworld scenario, the four dimensional effective Einstein equation has extra terms which arise from the embedding of the 3-brane in the bulk. These non-local effects, generated by the free gravitational field of the bulk, may provide an explanation for the dynamics of the neutral hydrogen clouds at large distances from the galactic center, which is usually explained by postulating the existence of the dark matter. We obtain the exact galactic metric, the dark radiation and the dark pressure in the flat rotation curves region in the brane world scenario. Due to the presence of the bulk effects, the flat rotation curves could extend several hundred kpc. The limiting radius for which bulk effects are important is estimated and compared with the numerical values of the truncation parameter of the dark matter halos, obtained from weak lensing observations. There is a relatively good agreement between the predictions of the model and observations. The deflection of photons is also considered and the bending angle of light is computed. The bending angle predicted by the brane world models is much larger than that predicted by standard general relativistic and dark matter models. The angular radii of the Einstein rings are obtained in the small angles approximation. The predictions of the brane world model for the tangential shear are compared with the observational data obtained in the weak lensing of galaxies in the Red-Sequence Cluster Survey. Therefore the study of the light deflection by galaxies and the gravitational lensing could discriminate between the different dynamical laws proposed to model the motion of particles at the galactic level and the standard dark matter models.
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...
Mapping gravitational lensing of the CMB using local likelihoods
Anderes, Ethan; Knox, Lloyd; Engelen, Alexander van
2011-02-15
We present a new estimation method for mapping the gravitational lensing potential from observed CMB intensity and polarization fields. Our method uses Bayesian techniques to estimate the average curvature of the potential over small local regions. These local curvatures are then used to construct an estimate of a low pass filter of the gravitational potential. By utilizing Bayesian/likelihood methods one can easily overcome problems with missing and/or nonuniform pixels and problems with partial sky observations (E- and B-mode mixing, for example). Moreover, our methods are local in nature, which allow us to easily model spatially varying beams, and are highly parallelizable. We note that our estimates do not rely on the typical Taylor approximation which is used to construct estimates of the gravitational potential by Fourier coupling. We present our methodology with a flat sky simulation under nearly ideal experimental conditions with a noise level of 1 {mu}K-arcmin for the temperature field, {radical}(2) {mu}K-arcmin for the polarization fields, with an instrumental beam full width at half maximum (FWHM) of 0.25 arcmin.
A Bayesian Analysis of Regularised Source Inversions in Gravitational Lensing
Suyu, Sherry H.; Marshall, P.J.; Hobson, M.P.; Blandford, R.D.; /Caltech /KIPAC, Menlo Park
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.
Microlensing Planets: Multiple Planet Systems as Gravitational Triple Lenses
NASA Astrophysics Data System (ADS)
Rhie, S.; Bennett, D.
2000-12-01
Gravitational microlensing is a superb exoplanet search technique. The merits include: mass sensitivity to all range of planets down to Mars; the detection window is partially inclusive of the habitable zones; massive moons of the exoplanets can be found; the duration of the events is typically less than two months, ~ 70 times shorter than the 12 year orbital period of Jupiter; it is largely free of selection bias because microlensing occurs by chance, and "oddities" such as circumbinary planets and multiple planets will be detected with a fair share of chance; it is the only method that can probe the Galactic and extragalactic families of planets that may orbit ordinary stars. Most of the microlensing planets will be discovered as gravitational (planetary) binary lenses. However, some of them will be discovered as higher multiple lens systems. Here, we discuss the gravitational triple lens systems which can produce up to 10 images. Discussion subjects include: classification of caustics, effect of three-body instabilities, numerical complications, and discovery perspective of multiple planet systems with GEST (Galactic Exoplanet Survey Telescope). This work has been supported in part by the NASA and the NSF.
Itoh, Yousuke; Futamase, Toshifumi; Hattori, Makoto
2009-08-15
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 wavelengths 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.
Itoh, Yousuke; Hattori, Makoto
2009-01-01
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.
Probing dark matter halos with strong gravitational lensing
NASA Astrophysics Data System (ADS)
Ferreras, Ignacio
2015-08-01
Strong gravitational lensing over galaxy scales allows us to explore dark matter halos and their connection with the luminous component. In this talk we present recent work on a sample extracted from the SLACS dataset, where the spectroscopic information from SDSS allows us to study the effect of a non-universal initial mass function on the stellar mass-to-light ratio. In addition, by studying galaxies where the background source probes the central part of the lens, we can derive significant constraints on the properties of the dark matter halo. This is one of the few observational methods that can be used to contrast with the standard concentration-virial mass relationships proposed by numerical simulations.
Seeing the Invisible Universe with Gravitational Lensing and SNAP
Bernstein, Gary (University of Pennsylvania) [University of Pennsylvania
2005-11-03
Recent high-precision cosmological measurements provide solid evidence that normal matter comprises only 4% of the content of the Universe. The dominant substances are completely invisible and have never been detected in a laboratory: 23% in some 'dark matter' particles, and 73% in a form of 'dark energy' that is currently accelerating the expansion of the Universe. The dark matter and dark energy do, however, distort our view of the Universe behind them through gravitational lensing, just as the 'obscure glass' on the doors of a shower stall is designed to be transparent but produces a distorted view of its occupant. I will describe how present and future experiments such as the SNAP spacecraft can measure this very subtle distorting effect and use it to infer the properties of the dark matter and dark energy that dominate the Universe.
Gravitational lensing potential reconstruction in quadruply imaged systems
V. F. Cardone; S. Capozziello; V. Re; E. Piedipalumbo
2001-11-04
We develop a semi - analytical method to reconstruct the lensing potential in quadruply imaged gravitational lens systems. Assuming that the potential belongs to a broad class of boxy non - elliptical models, we show how it is possible to write down a system of equations which can be numerically solved to recover the potential parameters directly from image positions and using physical constraints. We also describe a code developed to search for solutions of the system previously found and test it on simulated cases. Finally, we apply the method to the quadruple lens PG1115+080 which allows us to get also an estimate of the Hubble constant H_0 from the measured time delay as H_0 = 56_{-11}^{+17} km/s/Mpc.
Cosmological Parameter Survey Using the Gravitational Lensing Method
NASA Astrophysics Data System (ADS)
Premadi, Premana W.; Martel, Hugo; Matzner, Richard; Futamase, Toshifumi
Using a multiple-lens plane algorithm, we study light propagation in inhomogeneous universes for 43 different COBE-normalized Cold Dark Matter models, with various values of the density parameter ?0, cosmological constant ?0, Hubble constant H0, and rms density fluctuation ?8. We performed a total of 3798 experiments, each experiment consisting of propagating a square beam of angular size 21.9'' × 21.9'' composed of 116 281 light rays from the observer up to redshift z = 3. These experiments provide statis-tics of the magnification, shear, and multiple imaging of distant sources. The results of these experiments might be compared with observations, and eventually help constrain the possible values of the cosmological parameters. Additionally, they provide insight into the gravitational lensing process and its complex relationship with the various cosmological parameters.
Cosmological constraints from surveys of the weak lensing of galaxies
NASA Astrophysics Data System (ADS)
Schneider, Michael David
2008-08-01
In this dissertation we describe several technical developments for extracting cosmological information from and controlling systematic errors in weak lensing surveys. We propose a method to constrain photometric redshift error distributions using galaxy angular cross correlation functions. This is a form of "self-calibration" of galaxy clustering data that allows better knowledge of the mean redshift errors produced by a given photometric redshift estimation code. No spectroscopic training samples are required, which makes this method an important complement to existing calibration techniques. We forecast the photo- z error constraints possible using only our method with the LSST and find that additional constraints are required to meet the survey targets. We also describe a statistical framework for using a select number of cosmological simulations in performing parameter inference from tracers of the matter power spectrum. Computational barriers are often met when theoretical predictions of the data must be computed via simulations or when the distribution of errors on the data is unknown. Our framework addresses both of these issues to allow accurate parameter constraints with a computationally feasible number of simulations of the data. We demonstrate the performance of this algorithm using a two-parameter toy model for the matter power spectrum.
Fingerprinting dark energy. II. Weak lensing and galaxy clustering tests
Sapone, Domenico [Departamento de Fisica Teorica and Instituto de Fisica Teorica, Universidad Autonoma de Madrid IFT-UAM/CSIC, Cantoblanco, Madrid (Spain); Kunz, Martin [Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, CH-1211 Geneve 4 (Switzerland); Institut d'Astrophysique Spatiale, Universite Paris-Sud XI, Orsay 91405 (France); Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Amendola, Luca [University of Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); INAF/Rome (Italy)
2010-11-15
The characterization of dark energy is a central task of cosmology. To go beyond a cosmological constant, we need to introduce at least an equation of state and a sound speed and consider observational tests that involve perturbations. If dark energy is not completely homogeneous on observable scales, then the Poisson equation is modified and dark matter clustering is directly affected. One can then search for observational effects of dark energy clustering using dark matter as a probe. In this paper we exploit an analytical approximate solution of the perturbation equations in a general dark energy cosmology to analyze the performance of next-decade large-scale surveys in constraining equation of state and sound speed. We find that tomographic weak lensing and galaxy redshift surveys can constrain the sound speed of the dark energy only if the latter is small, of the order of c{sub s} < or approx. 0.01 (in units of c). For larger sound speeds the error grows to 100% and more. We conclude that large-scale structure observations contain very little information about the perturbations in canonical scalar field models with a sound speed of unity. Nevertheless, they are able to detect the presence of cold dark energy, i.e. a dark energy with nonrelativistic speed of sound.
Gravitational lensing: a unique probe of dark matter and dark energy.
Ellis, Richard S
2010-03-13
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
arXiv:astro-ph/01080906Aug2001 Dark Synergy: Gravitational Lensing and the CMB
Hu, Wayne
anisotropies: the dark energy, the end of the dark ages, and the inflationary gravitational wave amplitude function of the Newtonian gravitational potential. I. INTRODUCTION With the launch of the MAP satellitearXiv:astro-ph/01080906Aug2001 Dark Synergy: Gravitational Lensing and the CMB Wayne Hu 5640 S
OBSERVING GRAVITATIONAL LENSING EFFECTS BY Sgr A* WITH GRAVITY
Bozza, V.; Mancini, L. E-mail: mancini@mpia-hd.mpg.de
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.
Cosmological parameters and the redshift distribution of gravitational lenses
Phillip Helbig; Rainer Kayser
1995-09-01
For known gravitational lens systems the redshift distribution of the lenses is compared with theoretical expectations for $10^{4}$~Friedmann-Lema\\^\\i tre~cosmological models, which more than cover the range of possible cases. The comparison is used for assigning a relative probability to each of the models. The entire procedure is repeated for different values of the inhomogeneity parameter~$\\eta$ and the limiting spectroscopic magnitude~$m_{\\rm lim}$, which is important for selection effects. The dependence on these two parameters is examined in more detail for the special cases~$\\lambda_{0}=0$ and $k=0$. Previous results that this method is a better probe for~$\\lambda_{0}$ than $\\Omega_{0}$ are confirmed, but it appears that the low probability of models with large~$\\lambda_{0}$~values found using similar methods is due to a selection effect. The power of this method to discriminate between cosmological models can of course be improved if more gravitational lens systems are found. However, our numerical simulations indicate that a reasonable number of observed systems cannot deliver interesting constraints on the cosmological parameters.
Harrison, Ian
2015-01-01
This document was submitted as supporting material to an Engineering Change Proposal (ECP) for the Square Kilometre Array (SKA). This ECP requests gridded visibilities as an extra imaging data product from the SKA, in order to enable bespoke analysis techniques to measure source morphologies to the accuracy necessary for precision cosmology with radio weak lensing. We also discuss the properties of an SKA weak lensing data set and potential overlaps with other cosmology science goals.
Gravitational lensing analysis of galaxy clusters in the Southern Cosmology Survey
McInnes, Rachel Natalie
2010-01-01
In this thesis I present the first gravitational lensing results from the Southern Cosmology Survey (SCS). I provide a preliminary study of an automated pipeline analysis of a large survey, in preparation for larger ...
Optimal cosmology from gravitational lensing: utilising the magnification and shear signals
Duncan, Christopher Alexander James
2015-07-01
Gravitational lensing studies the distortions of a distant galaxy’s observed size, shape or flux due to the tidal bending of photons by matter between the source and observer. Such distortions can be used to infer knowledge ...
New caustic singularities in multiple lens plane gravitational lensing are not stable
NASA Astrophysics Data System (ADS)
Kayser, R.; Schramm, T.
1993-10-01
The occurrence of new types of caustic singularities for multiple lens plane gravitational lensing has recently been reported. In this letter we discuss these caustics and show that they are not stable against small perturbations.
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 ...
Measuring Gravitational Lensing Flexion in A1689 Using an Analytic Image Model
Cain, Benjamin
Measuring dark matter substructure within galaxy cluster halos is a fundamental probe of the ?CDM model of structure formation. Gravitational lensing is a technique for measuring the total mass distribution which is ...
THE IMPACT OF CORRELATED PROJECTIONS ON WEAK LENSING CLUSTER COUNTS
Marian, Laura [Argelander-Institut fuer Astronomie, Universitaet Bonn, Bonn, D-53121 (Germany); Smith, Robert E. [Institute for Theoretical Physics, University of Zuerich, Zuerich, CH 8037 (Switzerland); Bernstein, Gary M., E-mail: lmarian@astro.uni-bonn.d [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)
2010-01-20
Large-scale structure projections are an obstacle in converting the shear signal of clusters detected in weak-lensing maps into virial masses. However, this step is not necessary for constraining cosmology with the shear-peak abundance, if we are able to predict its amplitude. We generate a large ensemble of N-body simulations spanning four cosmological models, with total volume V{sub tot} approx 1(h {sup -1} Gpc){sup 3} per model. Variations to the matter density parameter and amplitude of fluctuations are considered. We measure the abundance of peaks in the mass density projected in approx100 h {sup -1} Mpc slabs to determine the impact of structures spatially correlated with the simulation clusters, identified by the three-dimensional (3D) friends-of-friends (FoF) algorithm. The halo model shows that the choice of the smoothing filter for the density field is important in reducing the contribution of correlated projections to individual halo masses. Such contributions are less than 2% in the case of the optimal, compensated filter used throughout this analysis. We measure the change in the mass of peaks when projected in slabs of various thicknesses. Peaks in slabs of 26 h {sup -1} Mpc and 102 h {sup -1} Mpc suffer an average mass change of less than 2% compared to their mass in slabs of 51 h {sup -1} Mpc. We then explore the cosmology dependence of the projected-peak mass function, and find that, for a wide range of slab thicknesses (< 500 h {sup -1} Mpc), it scales with cosmology in exactly the same way as the 3D FoF mass function and the Sheth-Tormen (ST) formula. This extends the earlier result of Marian et al. Finally, we show that for all cosmological models considered, the low and intermediate mass bins of the peak abundance can be described using a modified ST functional form to within 10%-20% accuracy.
ON THE ACCURACY OF WEAK-LENSING CLUSTER MASS RECONSTRUCTIONS
Becker, Matthew R.; Kravtsov, Andrey V.
2011-10-10
We study the bias and scatter in mass measurements of galaxy clusters resulting from fitting a spherically symmetric Navarro, Frenk, and White model to the reduced tangential shear profile measured in weak-lensing (WL) observations. The reduced shear profiles are generated for {approx}10{sup 4} cluster-sized halos formed in a {Lambda}CDM cosmological N-body simulation of a 1 h{sup -1} Gpc box. In agreement with previous studies, we find that the scatter in the WL masses derived using this fitting method has irreducible contributions from the triaxial shapes of cluster-sized halos and uncorrelated large-scale matter projections along the line of sight. Additionally, we find that correlated large-scale structure within several virial radii of clusters contributes a smaller, but nevertheless significant, amount to the scatter. The intrinsic scatter due to these physical sources is {approx}20% for massive clusters and can be as high as {approx}30% for group-sized systems. For current, ground-based observations, however, the total scatter should be dominated by shape noise from the background galaxies used to measure the shear. Importantly, we find that WL mass measurements can have a small, {approx}5%-10%, but non-negligible amount of bias. Given that WL measurements of cluster masses are a powerful way to calibrate cluster mass-observable relations for precision cosmological constraints, we strongly emphasize that a robust calibration of the bias requires detailed simulations that include more observational effects than we consider here. Such a calibration exercise needs to be carried out for each specific WL mass estimation method, as the details of the method determine in part the expected scatter and bias. We present an iterative method for estimating mass M{sub 500c} that can eliminate the bias for analyses of ground-based data.
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.
Gravitational lensing in the supernova legacy survey (SNLS)
NASA Astrophysics Data System (ADS)
Kronborg, T.; Hardin, D.; Guy, J.; Astier, P.; Balland, C.; Basa, S.; Carlberg, R. G.; Conley, A.; Fouchez, D.; Hook, I. M.; Howell, D. A.; Jönsson, J.; Pain, R.; Pedersen, K.; Perrett, K.; Pritchet, C. J.; Regnault, N.; Rich, J.; Sullivan, M.; Palanque-Delabrouille, N.; Ruhlmann-Kleider, V.
2010-05-01
Aims: The observed brightness of type Ia supernovae is affected by gravitational lensing caused by the mass distribution along the line of sight, which introduces an additional dispersion into the Hubble diagram. We look for evidence of lensing in the SuperNova Legacy Survey 3-year data set. Methods: We investigate the correlation between the residuals from the Hubble diagram and the gravitational magnification based on a modeling of the mass distribution of foreground galaxies. A deep photometric catalog, photometric redshifts, and well established mass luminosity relations are used. Results: We find evidence of a lensing signal with a 2.3? significance. The current result is limited by the number of SNe, their redshift distribution, and the other sources of scatter in the Hubble diagram. Separating the galaxy population into a red and a blue sample has a positive impact on the significance of the signal detection. On the other hand, increasing the depth of the galaxy catalog, the precision of photometric redshifts or reducing the scatter in the mass luminosity relations have little effect. We show that for the full SuperNova Legacy Survey sample (~400 spectroscopically confirmed type Ia SNe and ~200 photometrically identified type Ia SNe), there is an 80% probability of detecting the lensing signal with a 3? significance. 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 Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. Based on observations obtained at the European Southern Observatory using the Very Large Telescope on the Cerro Paranal (ESO Large Program 171.A-0486 & 176.A-0589). Based on observations (programs GS-2003B-Q-8, GN-2003B-Q-9, GS-2004A-Q-11, GN-2004A-Q-19, GS-2004B-Q-31, GN-2004B-Q-16, GS-2005A-Q-11, GN-2005A-Q-11, GS-2005B-Q-6, GN-2005B-Q-7, GN-2006A-Q-7, GN-2006B-Q-10, GN-2007A-Q-8) obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil) and CONICET (Argentina). Based on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
The Effect of Environment on Shear in Strong Gravitational Lenses
NASA Astrophysics Data System (ADS)
Wong, Kenneth C.; Keeton, C. R.; Williams, K. A.; Momcheva, I. G.; Zabludoff, A. I.
2010-05-01
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 structures on the lens potential. We derive the shear directly from measurements of the lens environment, independent of the shear obtained from lens modeling. We account for possible tidal stripping of the group galaxies by allowing the fraction of total mass apportioned to the group dark matter halo and the individual group galaxies to vary freely. The environment produces an average shear of ? = 0.14 ± 0.04, significant enough to affect quantities derived from lens observables. However, the direction and magnitude of the shears derived from the environment does not match those obtained via lens modeling in three of the six 4-image systems where we have calculated model shears. 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 ? = 0.08 ± 0.03, indicating that line-of-sight contributions to the lens potential are not negligible. We isolate the effects of various theoretical and observational uncertainties on our results. Of those uncertainties, scatter in the Faber-Jackson relation dominates, boosting the scatter in the shear components ?c and ?s by as much as 0.04. Error in the group centroid position has a large effect on lenses near the centers of their respective groups, resulting in an offset in ?c or ?s of as much as 0.06. Future surveys of lens environments should prioritize spectroscopic sampling of both the local lens environment and objects along the line of sight, particularly bright (I < 21.5) objects projected within 2' of the lens.
Finslerian MOND versus the strong gravitational lensing of the early-type galaxies
NASA Astrophysics Data System (ADS)
Chang, Zhe; Li, Ming-Hua; Li, Xin; Lin, Hai-Nan; Wang, Sai
2013-08-01
The gravitational lensing of Bullet Clusters and early-type galaxies pose serious challenges on the validity of MOND. Recently, Finslerian MOND, a generalization of MOND in the framework of Finsler gravity, has been proposed to explain the mass discrepancy problem of Bullet Cluster 1E0657-558. In this paper, we check the validity of the Finslerian MOND in describing the strong gravitational lensing of early-type galaxies. The investigation on ten strong lenses of the CASTLES samples shows that there is no strong evidence for the existence of dark matter.
The Origin of Gravitational Lensing: A Postscript to Einstein's 1936 Science Paper
Renn; Sauer; Stachel
1997-01-10
Gravitational lensing, now taken as an important astrophysical consequence of the general theory of relativity, was found even before this theory was formulated but was discarded as a speculative idea without any chance of empirical confirmation. Reconstruction of some of Einstein's research notes dating back to 1912 reveals that he explored the possibility of gravitational lensing 3 years before completing his general theory of relativity. On the basis of preliminary insights into this theory, Einstein had already derived the basic features of the lensing effect. When he finally published the very same results 24 years later, it was only in response to prodding by an amateur scientist. PMID:8985006
NASA Astrophysics Data System (ADS)
Hilbert, Stefan; Gair, Jonathan R.; King, Lindsay J.
2011-04-01
Gravitational lensing induces significant errors in the measured distances to high-redshift standard candles and standard sirens such as Type Ia supernovae, gamma-ray bursts and merging supermassive black hole binaries. There will therefore be a significant benefit from correcting for the lensing error by using independent and accurate estimates of the lensing magnification. Here, we investigate how accurately the magnification can be inferred from convergence maps reconstructed from galaxy shear and flexion data. We employ ray-tracing through the Millennium Simulation (MS) to simulate lensing observations in large fields, and perform a weak-lensing reconstruction on the simulated fields. We identify optimal ways to filter the reconstructed convergence maps and to convert them to magnification maps, and analyse the resulting relation between the estimated and true magnification for sources at redshifts zS= 1 to 5. We find that a deep shear survey with 100 galaxies arcmin-2 can help to reduce the lensing-induced distance errors for standard candles/sirens at redshifts zS? 1.5 (zS? 5) on average by 20 per cent (10 per cent), whereas a futuristic survey with shear and flexion estimates from 500 galaxies arcmin-2 yields much larger reductions of 50 per cent (35 per cent). For redshifts zS? 3, a further improvement by ˜5 per cent can be achieved, if the individual redshifts of the galaxies are used in the reconstruction. Moreover, the reconstruction allows one to identify regions for which the convergence is low, and in which an error reduction by up to 75 per cent can be achieved. Such strongly reduced magnification uncertainties will greatly improve the value of high-redshift standard candles/sirens as cosmological probes.
A Gravitationally Lensed Quasar with Quadruple Images Separated by 14.62 Arcseconds
N. Inada; M. Oguri; B. Pindor; J. F. Hennawi; K. Chiu; W. Zheng; S. -I. Ichikawa; M. D. Gregg; R. H. Becker; Y. Suto; M. A. Strauss; E. L. Turner; C. R. Keeton; J. Annis; F. J. Castander; D. J. Eisenstein; J. A. Frieman; M. Fukugita; J. E. Gunn; D. E. Johnston; S. M. Kent; R. C. Nichol; G. T. Richards; H. -W. Rix; E. S. Sheldon; N. A. Bahcall; J. Brinkmann; Z. Ivezic; D. Q. Lamb; T. A. McKay; D. P. Schneider; D. G. York
2003-12-19
Gravitational lensing is a powerful tool for the study of the distribution of dark matter in the Universe. The cold-dark-matter model of the formation of large-scale structures predicts the existence of quasars gravitationally lensed by concentrations of dark matter so massive that the quasar images would be split by over 7 arcsec. Numerous searches for large-separation lensed quasars have, however, been unsuccessful. All of the roughly 70 lensed quasars known, including the first lensed quasar discovered, have smaller separations that can be explained in terms of galaxy-scale concentrations of baryonic matter. Although gravitationally lensed galaxies with large separations are known, quasars are more useful cosmological probes because of the simplicity of the resulting lens systems. Here we report the discovery of a lensed quasar, SDSS J1004+4112, which has a maximum separation between the components of 14.62 arcsec. Such a large separation means that the lensing object must be dominated by dark matter. Our results are fully consistent with theoretical expectations based on the cold-dark-matter model.
COMPARING DENSE GALAXY CLUSTER REDSHIFT SURVEYS WITH WEAK-LENSING MAPS
Hwang, Ho Seong; Geller, Margaret J.; Zahid, H. Jabran; Diaferio, Antonaldo; Rines, Kenneth J. E-mail: mgeller@cfa.harvard.edu E-mail: diaferio@ph.unito.it
2014-12-20
We use dense redshift surveys of nine galaxy clusters at z ? 0.2 to compare the galaxy distribution in each system with the projected matter distribution from weak lensing. By combining 2087 new MMT/Hectospec redshifts and the data in the literature, we construct spectroscopic samples within the region of weak-lensing maps of high (70%-89%) and uniform completeness. With these dense redshift surveys, we construct galaxy number density maps using several galaxy subsamples. The shape of the main cluster concentration in the weak-lensing maps is similar to the global morphology of the number density maps based on cluster members alone, mainly dominated by red members. We cross-correlate the galaxy number density maps with the weak-lensing maps. The cross-correlation signal when we include foreground and background galaxies at 0.5z {sub cl} < z < 2z {sub cl} is 10%-23% larger than for cluster members alone at the cluster virial radius. The excess can be as high as 30% depending on the cluster. Cross-correlating the galaxy number density and weak-lensing maps suggests that superimposed structures close to the cluster in redshift space contribute more significantly to the excess cross-correlation signal than unrelated large-scale structure along the line of sight. Interestingly, the weak-lensing mass profiles are not well constrained for the clusters with the largest cross-correlation signal excesses (>20% for A383, A689, and A750). The fractional excess in the cross-correlation signal including foreground and background structures could be a useful proxy for assessing the reliability of weak-lensing cluster mass estimates.
Constraining Warm Dark Matter using QSO gravitational lensing
M. Miranda; A. V. Macciò
2007-09-11
Warm Dark Matter (WDM) has been invoked to resolve apparent conflicts of Cold Dark Matter (CDM) models with observations on subgalactic scales. In this work we provide a new and independent lower limit for the WDM particle mass (e.g. sterile neutrino) through the analysis of image fluxes in gravitationally lensed QSOs. Starting from a theoretical unperturbed cusp configuration we analyze the effects of intergalactic haloes in modifying the fluxes of QSO multiple images, giving rise to the so-called anomalous flux ratio. We found that the global effect of such haloes strongly depends on their mass/abundance ratio and it is maximized for haloes in the mass range $10^6-10^8 \\Msun$. This result opens up a new possibility to constrain CDM predictions on small scales and test different warm candidates, since free streaming of warm dark matter particles can considerably dampen the matter power spectrum in this mass range. As a consequence, while a ($\\Lambda$)CDM model is able to produce flux anomalies at a level similar to those observed, a WDM model, with an insufficiently massive particle, fails to reproduce the observational evidences. Our analysis suggests a lower limit of a few keV ($m_{\
A combined analysis of 3D Weak Lensing, Lyman-alpha forest and WMAP year three data
J. Lesgourgues; M. Viel; M. G. Haehnelt; R. Massey
2007-10-10
We present constraints on the amplitude and shape of the matter power spectrum and the density of dark matter within the framework of a standard LambdaCDM model. We use a Markov Chain Monte Carlo approach to combine independent measurements of the three dimensional weak gravitational lensing shear field by the COSMOS survey, of low and high resolution Ly-alpha forest flux power spectrum by SDSS and LUQAS, and of Cosmic Microwave Background temperature and polarization anisotropies by WMAP. We note good agreement between the amplitude of the matter power spectrum on intermediate and small scales as inferred from Ly-alpha forest and lensing data. The Ly-alpha forest data helps to break the sigma_8-Omega_m degeneracy characteristic of weak lensing results, yielding sigma_8 = 0.876 +- 0.048 for COSMOS plus Ly-alpha SDSS data. This is somewhat larger than the value preferred by the WMAP year three CMB data. Combining all three data sets significantly tightens the constraints on sigma_8, the spectral index of primordial density fluctuation n_s, a possible running of the spectral index n_run and the matter density Omega_m. Assuming no running, the joint constraints for COSMOS, SDSS and WMAP are sigma_8 = 0.800 +- 0.023, n_s = 0.971 +- 0.011, Omega_m = 0.247 +- 0.016 (1-sigma error bars).
Songbai Chen; Jiliang Jing
2015-08-31
We have investigated the strong gravitational lensing for the photons coupled to Weyl tensor in a Schwarzschild black hole spacetime. We find that in the four-dimensional black hole spacetime the equation of motion of the photons depends not only on the coupling between photon and Weyl tensor, but also on the polarization direction of the photons. It is quite different from that in the case of the usual photon without coupling to Weyl tensor in which the equation of motion is independent of the polarization of the photon. Moreover, we find that the coupling and the polarization direction modify the properties of the photon sphere, the deflection angle, the coefficients in strong field lensing, and the observational gravitational lensing variables. Combining with the supermassive central object in our Galaxy, we estimated three observables in the strong gravitational lensing for the photons coupled to Weyl tensor.
NASA Astrophysics Data System (ADS)
Chen, Songbai; Jing, Jiliang
2015-10-01
We have investigated the strong gravitational lensing for the photons coupled to Weyl tensor in a Schwarzschild black hole spacetime. We find that in the four-dimensional black hole spacetime the equation of motion of the photons depends not only on the coupling between photon and Weyl tensor, but also on the polarization direction of the photons. It is quite different from that in the case of the usual photon without coupling to Weyl tensor in which the equation of motion is independent of the polarization of the photon. Moreover, we find that the coupling and the polarization direction modify the properties of the photon sphere, the deflection angle, the coefficients in strong field lensing, and the observational gravitational lensing variables. Combining with the supermassive central object in our Galaxy, we estimated three observables in the strong gravitational lensing for the photons coupled to Weyl tensor.
Weak lensing measurements of dark matter halos of galaxies from COMBO-17
M. Kleinheinrich; P. Schneider; H. -W. Rix; T. Erben; C. Wolf; M. Schirmer; K. Meisenheimer; A. Borch; S. Dye; Z. Kovacs; L. Wisotzki
2004-12-23
We present a measurement of mass estimates for dark matter halos around galaxies from the COMBO-17 survey using weak gravitational lensing. COMBO-17 is particularly useful for this kind of investigation because it covers observations in 17 optical filters from which accurate photometric redshifts and spectral classification for objects with $R<24$ are derived. This allows us to select lens and source galaxies from their redshifts and to thus avoid any uncertainties from estimates of the source redshift distribution. We study galaxy lenses at redshifts $z_\\mathrm{d}=0.2-0.7$ by fitting the normalization of either singular isothermal spheres (SIS) or Navarro-Frenk-White (NFW) profiles to the whole lens sample; we then consider halos around blue and red subsamples separately. We also constrain the scaling of halo mass with light. For the NFW model, we find virial masses $M_\\mathrm{vir}^*=3.9^{+3.3}_{-2.4}\\times 10^{11}h^{-1}M_{\\sun}$ (1-$\\sigma$) for blue and $M_\\mathrm{vir}^*=7.1^{+7.1}_{-3.8}\\times 10^{11}h^{-1}M_{\\sun}$ for red galaxies of $L_\\star=10^{10}h^{-2}L_{\\sun}$, respectively. The derived mass-to-light scaling relations suggest that the mass-to-light ratio might decrease with increasing luminosity for blue galaxies but increase with increasing luminosity for red galaxies. However, these differences between blue and red galaxies are only marginally significant and both subsamples are consistent with having the same mass-to-light ratio at all luminosities. Finally, we compare our results to those obtained from the Red-Sequence Cluster Survey (RCS) and the Sloan Digital Sky Survey (SDSS). Taking differences in the actual modelling into account, we find very good agreement with these surveys.
Rozo, Eduardo; Wu, Hao-Yi; 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.
Modeling Galaxy-Galaxy Weak Lensing with SDSS Groups
Ran Li; H. J. Mo; Zuhui Fan; Marcello Cacciato; Frank C. van den Bosch; Xiaohu Yang; Surhud More
2009-01-15
We use galaxy groups selected from the Sloan Digital Sky Survey (SDSS) together with mass models for individual groups to study the galaxy-galaxy lensing signals expected from galaxies of different luminosities and morphological types. We compare our model predictions with the observational results obtained from the SDSS by Mandelbaum et al. (2006) for the same samples of galaxies. The observational results are well reproduced in a $\\Lambda$CDM model based on the WMAP 3-year data, but a $\\Lambda$CDM model with higher $\\sigma_8$, such as the one based on the WMAP 1-year data,significantly over-predicts the galaxy-galaxy lensing signal. We model, separately, the contributions to the galaxy-galaxy lensing signals from different galaxies: central versus satellite, early-type versus late-type, and galaxies in halos of different masses. We also examine how the predicted galaxy-galaxy lensing signal depends on the shape, density profile, and the location of the central galaxy with respect to its host halo.
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
UP TO 100,000 RELIABLE STRONG GRAVITATIONAL LENSES IN FUTURE DARK ENERGY EXPERIMENTS
Serjeant, S.
2014-09-20
The Euclid space telescope will observe ?10{sup 5} strong galaxy-galaxy gravitational lens events in its wide field imaging survey over around half the sky, but identifying the gravitational lenses from their observed morphologies requires solving the difficult problem of reliably separating the lensed sources from contaminant populations, such as tidal tails, as well as presenting challenges for spectroscopic follow-up redshift campaigns. Here I present alternative selection techniques for strong gravitational lenses in both Euclid and the Square Kilometre Array, exploiting the strong magnification bias present in the steep end of the H? luminosity function and the H I mass function. Around 10{sup 3} strong lensing events are detectable with this method in the Euclid wide survey. While only ?1% of the total haul of Euclid lenses, this sample has ?100% reliability, known source redshifts, high signal-to-noise, and a magnification-based selection independent of assumptions of lens morphology. With the proposed Square Kilometre Array dark energy survey, the numbers of reliable strong gravitational lenses with source redshifts can reach 10{sup 5}.
The Effect of Satellite Galaxies on Gravitational Lensing Flux Ratios
E. M. Shin; N. W. Evans
2008-01-16
Gravitational lenses with anomalous flux ratios are often cited as possible evidence for dark matter satellites predicted by simulations of hierarchical merging in cold dark matter cosmogonies. We show that the fraction of quads with anomalous flux ratios depends primarily on the total mass and spatial extent of the satellites, and the characteristic lengthscale R of their distribution. If R is 100 kpc, then for a moderately elliptical galaxy with a line-of-sight velocity dispersion of 250 km/s, a mass of 3 x 10^9 solar masses in highly-concentrated (Plummer model) satellites is needed for 20% of quadruplets to show anomalous flux ratios, rising to 1.25 x 10^10 solar masses for 50%. Several times these masses are required if the satellites have more extended Hernquist profiles. Compared to a typical elliptical, the flux ratios of quads formed by typical edge-on disc galaxies with maximum discs are significantly less susceptible to changes through substructure -- three times the mass in satellite galaxies is needed to affect 50% of the systems. In many of the lens systems with anomalous flux ratios, there is evidence for visible satellites (e.g., B2045+265 or MG0414+0534). We show that optically identified substructure should not be preponderant among lens systems with anomalies. There are two possible resolutions of this difficulty. First, in some cases, visible substructure may be projected within or close to the Einstein radius and wrongly ascribed as the culprit, whereas dark matter substructure is causing the flux anomaly. Second, bright satellites, in which baryon cooling and condensation has taken place, may have higher central densities than dark satellites, rendering them more efficient at causing flux anomalies.
Statistical uncertainties and systematic errors in weak lensing mass estimates of galaxy clusters
Köhlinger, F; Eriksen, M
2015-01-01
Upcoming and ongoing large area weak lensing surveys will also discover large samples of galaxy clusters. Accurate and precise masses of galaxy clusters are of major importance for cosmology, for example, in establishing well calibrated observational halo mass functions for comparison with cosmological predictions. We investigate the level of statistical uncertainties and sources of systematic errors expected for weak lensing mass estimates. Future surveys that will cover large areas on the sky, such as Euclid or LSST and to lesser extent DES, will provide the largest weak lensing cluster samples with the lowest level of statistical noise regarding ensembles of galaxy clusters. However, the expected low level of statistical uncertainties requires us to scrutinize various sources of systematic errors. In particular, we investigate the bias due to cluster member galaxies which are erroneously treated as background source galaxies due to wrongly assigned photometric redshifts. We find that this effect is signifi...
The Shear TEsting Programme 1: Weak lensing analysis of simulated ground-based observations
Heymans, C; Bacon, D; Berge, J; Bernstein, G; Bertin, E; Bridle, S; Brown, M L; Clowe, D; Dahle, H; Erben, T; Gray, M; Hetterscheidt, M; Hoekstra, H; Hudelot, P; Jarvis, M; Kuijken, K; Margoniner, V; Massey, R; Mellier, Y; Nakajima, R; Réfrégier, A; Rhodes, J; Schrabback, T; Wittman, D; Heymans, Catherine; Waerbeke, Ludovic Van; Bacon, David; Berge, Joel; Bernstein, Gary; Bertin, Emmanuel; Bridle, Sarah; Brown, Michael L.; Clowe, Douglas; Dahle, Haakon; Erben, Thomas; Gray, Meghan; Hetterscheidt, Marco; Hoekstra, Henk; Hudelot, Patrick; Jarvis, Mike; Kuijken, Konrad; Margoniner, Vera; Massey, Richard; Mellier, Yannick; Nakajima, Reiko; Refregier, Alexandre; Rhodes, Jason; Schrabback, Tim; Wittman, David
2006-01-01
The Shear TEsting Programme, STEP, is a collaborative project to improve the accuracy and reliability of all weak lensing measurements in preparation for the next generation of wide-field surveys. In this first STEP paper we present the results of a blind analysis of simulated ground-based observations of relatively simple galaxy morphologies. The most successful methods are shown to achieve percent level accuracy. From the cosmic shear pipelines that have been used to constrain cosmology, we find weak lensing shear measured to an accuracy that is within the statistical errors of current weak lensing analyses, with shear measurements accurate to better than 7%. The dominant source of measurement error is shown to arise from calibration uncertainties where the measured shear is over or under-estimated by a constant multiplicative factor. This is of concern as calibration errors cannot be detected through standard diagnostic tests. The measured calibration errors appear to result from stellar contamination, fal...
Hubble Space Telescope weak lensing study of the z=0.83 cluster MS 1054-03
H. Hoekstra; M. Franx; K. Kuijken
1999-10-27
We have measured the weak gravitational lensing signal of MS 1054-03, a rich and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a two-colour mosaic of deep WFPC2 images. The small corrections for the size of the PSF 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 colour agrees well with the observed lensing signal. We determine a mass of (1.2+-0.2)x10^15 Msun within an aperture of radius 1 Mpc. Under the assumption of an isothermal mass distribution, the corresponding velocity dispersion is 1311^{+83}_{-89} km/s. For the mass-to-light ratio we find 269+-37 Msun/Lsun. 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. Averaging the tangential shear around the cluster galaxies, we find that the velocity dispersion of an Lstar galaxy is 203+-33 km/s.
Interpolating Masked Weak-lensing Signal with Karhunen-Loève Analysis
NASA Astrophysics Data System (ADS)
VanderPlas, J. T.; Connolly, A. J.; Jain, B.; Jarvis, M.
2012-01-01
We explore the utility of Karhunen-Loève (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 ~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.
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.
Hoekstra, Henk; Muzzin, Adam; Babul, Arif; Mahdavi, Andisheh; Viola, Massimo; Cacciato, Marcello
2015-01-01
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 catalogs that include new deep near-infrared observations. Nonetheless 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 t...
CLASH: Weak-lensing shear-and-magnification analysis of 20 galaxy clusters
Umetsu, Keiichi; Czakon, Nicole; Medezinski, Elinor; Lemze, Doron; Ford, Holland; Nonino, Mario; Balestra, Italo; Biviano, Andrea; Merten, Julian; Postman, Marc; Koekemoer, Anton; Meneghetti, Massimo; Donahue, Megan; Molino, Alberto; Benítez, Narciso; Seitz, Stella; Gruen, Daniel; Broadhurst, Tom; Grillo, Claudio; Melchior, Peter; and others
2014-11-10
We present a joint shear-and-magnification weak-lensing analysis of a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19 ? z ? 0.69 selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). Our analysis uses wide-field multi-color imaging, taken primarily with Suprime-Cam on the Subaru Telescope. From a stacked-shear-only analysis of the X-ray-selected subsample, we detect the ensemble-averaged lensing signal with a total signal-to-noise ratio of ? 25 in the radial range of 200-3500 kpc h {sup –1}, providing integrated constraints on the halo profile shape and concentration-mass relation. The stacked tangential-shear signal is well described by a family of standard density profiles predicted for dark-matter-dominated halos in gravitational equilibrium, namely, the Navarro-Frenk-White (NFW), truncated variants of NFW, and Einasto models. For the NFW model, we measure a mean concentration of c{sub 200c}=4.01{sub ?0.32}{sup +0.35} at an effective halo mass of M{sub 200c}=1.34{sub ?0.09}{sup +0.10}×10{sup 15} M{sub ?}. We show that this is in excellent agreement with ? cold dark matter (?CDM) predictions when the CLASH X-ray selection function and projection effects are taken into account. The best-fit Einasto shape parameter is ?{sub E}=0.191{sub ?0.068}{sup +0.071}, which is consistent with the NFW-equivalent Einasto parameter of ?0.18. We reconstruct projected mass density profiles of all CLASH clusters from a joint likelihood analysis of shear-and-magnification data and measure cluster masses at several characteristic radii assuming an NFW density profile. We also derive an ensemble-averaged total projected mass profile of the X-ray-selected subsample by stacking their individual mass profiles. The stacked total mass profile, constrained by the shear+magnification data, is shown to be consistent with our shear-based halo-model predictions, including the effects of surrounding large-scale structure as a two-halo term, establishing further consistency in the context of the ?CDM model.
Probing cosmology with weak lensing selected clusters II: Dark energy and f(R) gravity models
Shirasaki, Masato; Yoshida, Naoki
2015-01-01
Ongoing and future wide-field galaxy surveys can be used to locate a number of clusters of galaxies with cosmic shear measurement alone. We study constraints on cosmological models using statistics of weak lensing selected galaxy clusters. We extend our previous theoretical framework to model the statistical properties of clusters in variants of cosmological models as well as in the standard LCDM model. Weak lensing selection of clusters does not rely on the conventional assumption such as the relation between luminosity and mass and/or hydrostatic equilibrium, but a number of observational effects compromise robust identification. We use a large set of realistic mock weak-lensing catalogs as well as analytic models to perform a Fisher analysis and make forecast for constraining two competing cosmological models, wCDM model and f(R) model proposed by Hu & Sawicki, with our lensing statistics. We show that weak lensing selected clusters are excellent probe of cosmology when combined with cosmic shear power...
Gravitational lensing of quasars by edge-on spiral galaxies
Wang, Emily P
2007-01-01
In this thesis, I studied the lensed quasar CX2201-3201, which is lensed by an edge-on spiral galaxy. The unusually high tilt of the spiral galaxy provides us with a rare opportunity for mass modeling. In addition, the ...
Adrián-Martínez, S.; Ardid, M.; Bou-Cabo, M. [Institut d'Investigació per a la Gestió Integrada de les Zones Costaneres (IGIC), Universitat Politècnica de València, C/ Paranimf 1, Gandia, 46730 Spain (Spain); Albert, A. [GRPHE - Institut universitaire de technologie de Colmar, 34 rue du Grillenbreit BP 50568, Colmar, 68008 France (France); André, M. [Technical University of Catalonia, Laboratory of Applied Bioacoustics, Rambla Exposició, Vilanova i la Geltrú, Barcelona, 08800 Spain (Spain); Anton, G. [Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics, Erwin-Rommel-Str. 1, Erlangen, 91058 Germany (Germany); Aubert, J.-J.; Bertin, V.; Brunner, J.; Busto, J. [Aix Marseille Université, CNRS/IN2P3, CPPM UMR 7346, Marseille, 13288 France (France); Baret, B. [APC, AstroParticule et Cosmologie, Université Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cité, 10, rue Alice Domon et Léonie Duquet, Paris Cedex 13, F-75205 France (France); Barrios-Martí, J. [IFIC - Instituto de Física Corpuscular, Edificios Investigación de Paterna, CSIC - Universitat de València, Apdo de Correos 22085, Valencia, 46071 Spain (Spain); Basa, S. [LAM - Laboratoire d'Astrophysique de Marseille, Pôle de l'Étoile Site de Château-Gombert, rue Frédéric Joliot-Curie 38, Marseille Cedex 13, 13388 France (France); Biagi, S. [INFN - Sezione di Bologna, Viale Berti-Pichat 6/2, Bologna, 40127 Italy (Italy); Bogazzi, C.; Bormuth, R.; Bouwhuis, M.C.; Bruijn, R. [Nikhef, Science Park 105, Amsterdam, 1098XG The Netherlands (Netherlands); Capone, A. [INFN -Sezione di Roma, P.le Aldo Moro 2, Roma, 00185 Italy (Italy); Caramete, L., E-mail: antares.spokesperson@in2p3.fr [Institute for Space Sciences, Bucharest, M?gurele, R-77125 Romania (Romania); and others
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× 10{sup 46} erg s{sup -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.
Cross-correlating Sunyaev-Zel'dovich and weak lensing maps
NASA Astrophysics Data System (ADS)
Munshi, Dipak; Joudaki, Shahab; Coles, Peter; Smidt, Joseph; Kay, Scott T.
2014-07-01
We present novel statistical tools to cross-correlate frequency cleaned thermal Sunyaev-Zel'dovich (tSZ) maps and tomographic weak lensing (wl) convergence maps. Moving beyond the lowest order cross-correlation, we introduce a hierarchy of mixed higher order statistics, the cumulants and cumulant correlators, to analyse non-Gaussianity in real space, as well as corresponding polyspectra in the harmonic domain. Using these moments, we derive analytical expressions for the joint two-point probability distribution function for smoothed tSZ (y) and convergence (?) maps. The presence of tomographic information allows us to study the evolution of higher order mixed tSZ-wl statistics with redshift. We express the joint PDFs p?y(?, y) in terms of individual one-point PDFs [p?(?), py(y)] and the relevant bias functions [b?(?), by(y)]. Analytical results for two different regimes are presented that correspond to the small and large angular smoothing scales. Results are also obtained for corresponding hotspots in the tSZ and convergence maps. In addition to results based on hierarchical techniques and perturbative methods, we present results of calculations based on the lognormal approximation. The analytical expressions derived here are generic and applicable to cross-correlation studies of arbitrary tracers of large-scale structure including, e.g., that of tSZ and soft X-ray background. We provide detailed comparison of our analytical results against state of the art Millennium Gas Simulations with and without non-gravitational effects such as pre-heating and cooling. Comparison of these results with gravity only simulations, shows reasonable agreement and can be used to isolate effect of non-gravitational physics from observational data.
MACSJ1423.8+2404: Gravitational Lensing by a Massive, Relaxed Cluster of Galaxies at z=0.54
Limousin, M; Ma, C -J; Swinbank, A M; Smith, G P; Richard, J; Edge, A C; Jauzac, M; Kneib, J -P; Marshall, P; Schrabback, T; Smail, I R
2009-01-01
We present results of a gravitational-lensing and optical study of MACS ,J1423.8+2404 (z=0.545, MACS, J1423). Our analysis uses high-resolution images taken with the Hubble Space Telescope in the F555W and F814W passbands, ground based imaging in eight optical and near-infrared filters obtained with Subaru and CFHT, as well as extensive spectroscopic data gathered with the Keck telescopes. At optical wavelengths the cluster exhibits no sign of substructure and is dominated by a cD galaxy that is 2.1 magnitudes (K-band) brighter than the second brightest cluster member, suggesting that MACS, J1423 is close to be fully virialized. Analysis of the redshift distribution of 140 cluster members reveals a Gaussian distribution, mildly disturbed by the presence of a loose galaxy group that may be falling into the cluster along the line of sight. Combining strong-lensing constraints from two spectroscopically confirmed multiple-image systems near the cluster core with a weak-lensing measurement of the gravitational sh...
Effect of Hot Baryons on the Weak-Lensing Shear Power Spectrum
Hu Zhan; Lloyd Knox
2004-11-19
We investigate the impact of the intracluster medium on the weak-lensing shear power spectrum (PS). Using a halo model we find that, compared to the dark matter only case, baryonic pressure leads to a suppression of the shear PS on the order of a few percent or more for $l \\gtrsim 1000$. Cooling/cooled baryons and the intergalactic medium can further alter the shear PS. Therefore, the interpretation of future precision weak lensing data at high multipoles must take into account the effects of baryons.
Self-Calibration for 3-point Intrinsic Alignment Auto-Correlations in Weak Lensing Surveys
M. A. Troxel; Mustapha Ishak
2012-03-09
The weak lensing signal (cosmic shear) has been shown to be strongly contaminated by the various types of galaxy intrinsic alignment (IA) correlations, which poses a barrier to precision weak lensing measurements. The redshift dependence of the IA signal has been used at the 2-point level to reduce this contamination by only measuring cross-correlations between large redshift bins, which significantly reduces the galaxy intrinsic ellipticity - intrinsic ellipticity (II) correlation. A self-calibration technique based on the redshift dependences of the IA correlations has also been proposed as a means to remove the 2-point IA contamination from the lensing signal. We explore here the redshift dependences of the IA and lensing bispectra in order to propose a self-calibration of the IA auto-correlations at the 3-point level (i.e. GGI, GII, and III), which can be well understood without the assumption of any particular IA model. We find that future weak lensing surveys will be able to measure the distinctive IA redshift dependence over ranges of $|\\Delta z^P|\\le 0.2$. Using conservative estimates of photo-z accuracy, we describe the 3-point self-calibration technique for the total IA signal, which can be accomplished through lensing tomography of photo-z bin size $\\sim 0.01$. We find that the 3-point self-calibration can function at the accuracy of the 2-point technique with modest constraints in redshift separation. This allows the 3-point IA auto-correlation self-calibration technique proposed here to significantly reduce the contamination of the IA contamination to the weak lensing bispectrum.
SDSS J0246-0825: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
Naohisa Inada; Scott Burles; Michael D. Gregg; Robert H. Becker; Paul L. Schechter; Daniel J. Eisenstein; Masamune Oguri; Francisco J. Castander; Patrick B. Hall; David E. Johnston; Bartosz Pindor; Gordon T. Richards; Donald P. Schneider; Richard L. White; J. Brinkmann; Alexander S. Szalay; Donald G. York
2005-06-27
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 the spectroscopic observations using the W. M. Keck Observatory's Keck II telescope confirm that SDSS J0246-0825 consists of two lensed images ($\\Delta{\\theta}=$1\\farcs04) of a source quasar at z=1.68. Imaging observations with the Keck 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 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.
Probing cluster potentials through gravitational lensing of background X-ray sources
NASA Technical Reports Server (NTRS)
Refregier, A.; Loeb, A.
1996-01-01
The gravitational lensing effect of a foreground galaxy cluster, on the number count statistics of background X-ray sources, was examined. The lensing produces a deficit in the number of resolved sources in a ring close to the critical radius of the cluster. The cluster lens can be used as a natural telescope to study the faint end of the (log N)-(log S) relation for the sources which account for the X-ray background.
Gravitational Lensing and f(R) theories in the Palatini approach
Matteo Luca Ruggiero
2007-01-01
We investigate gravitational lensing in the Palatini approach to the f(R)\\u000aextended theories of gravity. Starting from an exact solution of the f(R) field\\u000aequations, which corresponds to the Schwarzschild-de Sitter metric and, on the\\u000abasis of recent studies on this metric, we focus on some lensing observables,\\u000ain order to evaluate the effects of the non linearity of the
Gravitational Lensing and f(R) theories in the Palatini approach
Ruggiero, Matteo Luca
2007-01-01
We investigate gravitational lensing in Palatini approach to the f(R) extended theories of gravity. Starting from an exact solution of the f(R) field equations, which corresponds to the Schwarzschild-de Sitter metric and, on the basis of recent studies on this metric, we focus on some lensing observables, in order to evaluate the effects of the non linearity of the gravity Lagrangian. We give estimates for some astrophysical events, and show that these effects are tiny for galactic lenses, but become interesting for extragalactic ones.
Gravitational Lensing and f(R) theories in the Palatini approach
Matteo Luca Ruggiero
2008-11-03
We investigate gravitational lensing in the Palatini approach to the f(R) extended theories of gravity. Starting from an exact solution of the f(R) field equations, which corresponds to the Schwarzschild-de Sitter metric and, on the basis of recent studies on this metric, we focus on some lensing observables, in order to evaluate the effects of the non linearity of the gravity Lagrangian. We give estimates for some astrophysical events, and show that these effects are tiny for galactic lenses, but become interesting for extragalactic ones.
Virginia L. Corless; Lindsay J. King; Douglas Clowe
2008-12-03
Measuring the 3D distribution of mass on galaxy cluster scales is a crucial test of the LCDM model, providing constraints on the nature of dark matter. Recent work investigating mass distributions of individual galaxy clusters (e.g. Abell 1689) using weak and strong gravitational lensing has revealed potential inconsistencies between the predictions of structure formation models relating halo mass to concentration and those relationships as measured in massive clusters. However, such analyses employ simple spherical halo models while a growing body of work indicates that triaxial 3D halo structure is both common and important in parameter estimates. We recently introduced a Markov Chain Monte Carlo (MCMC) method to fit fully triaxial models to weak lensing data that gives parameter and error estimates that fully incorporate the true shape uncertainty present in nature. In this paper we apply that method to weak lensing data obtained with the ESO/MPG Wide-Field Imager for galaxy clusters A1689, A1835, and A2204, under a range of Bayesian priors derived from theory and from independent X-ray and strong lensing observations. For Abell 1689, using a simple strong lensing prior we find marginalized mean parameter values M_200 = (0.83 +- 0.16)x10^15 M_solar/h and C=12.2 +- 6.7, which are marginally consistent with the mass-concentration relation predicted in LCDM. The large error contours that accompany our triaxial parameter estimates more accurately represent the true extent of our limited knowledge of the structure of galaxy cluster lenses, and make clear the importance of combining many constraints from other theoretical, lensing (strong, flexion), or other observational (X-ray, SZ, dynamical) data to confidently measure cluster mass profiles. (Abridged)
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.
Ermanno F. Borra
1997-04-09
I suggest that measurements of intensity fluctuations caused by classical wave interactions can be used to find unresolved gravitational lenses and determine time delays of essentially arbitrary length among the images formed by a gravitational lens. No interferometry i s needed, the time delays can be measured by analyzing the intensity signal alone. The technique works with lensed sources that have constant luminosities and is capable of measuring very long time delays. I suggest interferometric techniques, capable of measuring time delays of arbitrary length, that can be used to refine the measurements.
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 ...
Complementarity of weak lensing and peculiar velocity measurements in testing general relativity
Song, Yong-Seon; Zhao Gongbo; Bacon, David; Koyama, Kazuya; Nichol, Robert C.; Pogosian, Levon
2011-10-15
We explore the complementarity of weak lensing and galaxy peculiar velocity measurements to better constrain modifications to General Relativity. We find no evidence for deviations from General Relativity on cosmological scales from a combination of peculiar velocity measurements (for Luminous Red Galaxies in the Sloan Digital Sky Survey) with weak lensing measurements (from the Canadian France Hawaii Telescope Legacy Survey). We provide a Fisher error forecast for a Euclid-like space-based survey including both lensing and peculiar velocity measurements and show that the expected constraints on modified gravity will be at least an order of magnitude better than with present data, i.e. we will obtain {approx_equal}5% errors on the modified gravity parametrization described here. We also present a model-independent method for constraining modified gravity parameters using tomographic peculiar velocity information, and apply this methodology to the present data set.
Weak lensing and dark energy: The impact of dark energy on nonlinear dark matter clustering
Joudaki, Shahab; Cooray, Asantha; Holz, Daniel E. [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2009-07-15
We examine the influence of percent-level dark energy corrections to the nonlinear matter power spectrum on constraints of the dark energy equation of state from future weak lensing probes. We explicitly show that a poor approximation (off by > or approx.10%) to the nonlinear corrections causes a > or approx. 1{sigma} bias on the determination of the dark energy equation of state. Future weak lensing surveys must therefore incorporate dark energy modifications to the nonlinear matter power spectrum accurate to the percent-level, to avoid introducing significant bias in their measurements. For the WMAP5 cosmology, the more accurate power spectrum is more sensitive to dark energy properties, resulting in a factor of 2 improvement in dark energy equation of state constraints. We explore the complementary constraints on dark energy from future weak lensing and supernova surveys. A space-based, Joint Dark Energy Mission-like survey measures the equation of state in five independent redshift bins to {approx}10%, while this improves to {approx}5% for a wide-field ground-based survey like the Large Synoptic Survey Telescope. These constraints are contingent upon our ability to control weak lensing systematic uncertainties to the sub-percent level.
Bradac, Marusa; Clowe, Douglas; Gonzalez, Anthony H.; Marshall, Phil; Forman, William; Jones, Christine; Markevitch, Maxim; Randall, Scott; Schrabback, Tim; Zaritsky, Dennis; /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.
NASA Astrophysics Data System (ADS)
Brada?, Maruša; Clowe, Douglas; Gonzalez, Anthony H.; Marshall, Phil; Forman, William; Jones, Christine; Markevitch, Maxim; Randall, Scott; Schrabback, Tim; Zaritsky, Dennis
2006-12-01
The galaxy cluster 1ES 0657-558 (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. Multicolor, 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 and colleagues that the total mass does not trace the baryonic mass. Based on observations made 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 NAS5-26555. These observations are associated with program 10200. This work is also based in part on observations made with the Spitzer Space Telescope and with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.
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 ...
THREE-DIMENSIONAL RECONSTRUCTION OF THE DENSITY FIELD: AN SVD APPROACH TO WEAK-LENSING TOMOGRAPHY
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)
2011-02-01
We present a new method for constructing three-dimensional mass maps from gravitational lensing shear data. We solve the lensing inversion problem using truncation of singular values (within the context of generalized least-squares estimation) without a priori assumptions about the statistical nature of the signal. This singular value framework allows a quantitative comparison between different filtering methods: we evaluate our method beside the previously explored Wiener-filter approaches. Our method yields near-optimal angular resolution of the lensing reconstruction and allows cluster sized halos to be de-blended robustly. It allows for mass reconstructions which are two to three orders of magnitude faster than the Wiener-filter approach; in particular, we estimate that an all-sky reconstruction with arcminute resolution could be performed on a timescale of hours. We find however that linear, non-parametric reconstructions have a fundamental limitation in the resolution achieved in the redshift direction.
Sneaky Gamma-Rays: Using Gravitational Lensing to Avoid Gamma-Gamma-Absorption
NASA Astrophysics Data System (ADS)
Boettcher, Markus; Barnacka, Anna
2014-08-01
It has recently been suggested that gravitational lensing studies of gamma-ray blazars might be a promising avenue to probe the location of the gamma-ray emitting region in blazars. Motivated by these prospects, we have investigated potential gamma-gamma absorption signatures of intervening lenses in the very-high-energy gamma-ray emission from lensedblazars. We considered intervening galaxies and individual stars within these galaxies. We find that the collective radiation field of galaxies acting as sources of macrolensing are not expected to lead to significant gamma-gamma absorption. Individual stars within intervening galaxies could, in principle, cause a significant opacity to gamma-gamma absorption for VHE gamma-rays if the impact parameter (the distance of closest approach of the gamma-ray to the center of the star) is small enough. However, we find that the curvature of the photon path due to gravitational lensing will cause gamma-ray photons to maintain a sufficiently large distance from such stars to avoid significant gamma-gamma absorption. This re-inforces the prospect of gravitational-lensing studies of gamma-ray blazars without interference due to gamma-gamma absorption due to the lensing objects.
Testing the MOND paradigm of modified dynamics with galaxy-galaxy gravitational lensing.
Milgrom, Mordehai
2013-07-26
The MOND paradigm of modified dynamics predicts that the asymptotic gravitational potential of an isolated, bounded (baryonic) mass, M, is ?(r)=(MGa0)1/2ln(r). Relativistic MOND theories predict that the lensing effects of M are dictated by ?(r) as general-relativity lensing is dictated by the Newtonian potential. Thus MOND predicts that the asymptotic Newtonian potential deduced from galaxy-galaxy gravitational lensing will have (1) a logarithmic r dependence, and (2) a normalization (parametrized standardly as 2?2) that depends only on M: ?=(MGa0/4)1/4. I compare these predictions with recent results of galaxy-galaxy lensing, and find agreement on all counts. For the “blue”-lenses subsample (“spiral” galaxies) MOND reproduces the observations well with an r?-band M/Lr??(1–3)(M/L)?, and for “red” lenses (“elliptical” galaxies) with M/Lr??(3–6)(M/L)?, both consistent with baryons only. In contradistinction, Newtonian analysis requires, typically, M/Lr??130(M/L)?, bespeaking a mass discrepancy of a factor ?40. Compared with the staple, rotation-curve tests, MOND is here tested in a wider population of galaxies, through a different phenomenon, using relativistic test objects, and is probed to several-times-lower accelerations–as low as a few percent of a0. PMID:23931350
Testing the MOND Paradigm of Modified Dynamics with Galaxy-Galaxy Gravitational Lensing
NASA Astrophysics Data System (ADS)
Milgrom, Mordehai
2013-07-01
The MOND paradigm of modified dynamics predicts that the asymptotic gravitational potential of an isolated, bounded (baryonic) mass, M, is ?(r)=(MGa0)1/2ln?(r). Relativistic MOND theories predict that the lensing effects of M are dictated by ?(r) as general-relativity lensing is dictated by the Newtonian potential. Thus MOND predicts that the asymptotic Newtonian potential deduced from galaxy-galaxy gravitational lensing will have (1) a logarithmic r dependence, and (2) a normalization (parametrized standardly as 2?2) that depends only on M: ?=(MGa0/4)1/4. I compare these predictions with recent results of galaxy-galaxy lensing, and find agreement on all counts. For the “blue”-lenses subsample (“spiral” galaxies) MOND reproduces the observations well with an r'-band M/Lr'˜(1-3)(M/L)?, and for “red” lenses (“elliptical” galaxies) with M/Lr'˜(3-6)(M/L)?, both consistent with baryons only. In contradistinction, Newtonian analysis requires, typically, M/Lr'˜130(M/L)?, bespeaking a mass discrepancy of a factor ˜40. Compared with the staple, rotation-curve tests, MOND is here tested in a wider population of galaxies, through a different phenomenon, using relativistic test objects, and is probed to several-times-lower accelerations-as low as a few percent of a0.
NASA Astrophysics Data System (ADS)
Corianò, Claudio; Rose, Luigi Delle; Maglio, Matteo Maria; Serino, Mirko
2015-01-01
We investigate the semiclassical approach to the lensing of photons in a spherically symmetric gravitational background, starting from Born level and include in our analysis the radiative corrections obtained from the electroweak theory for the graviton/photon/photon vertex. In this approach, the cross section is related to the angular variation of the impact parameter ( b), which is then solved for b as a function of the angle of deflection, and measured in horizon units ( b h ? b/(2 GM)). Exact numerical solutions for the angular deflection are presented. The numerical analysis shows that perturbation theory in a weak background agrees with the classical Einstein formula for the deflection already at distances of the order of 20 horizon units (˜20 b h ) and it is optimal in the description both of very strong and weak lensings. We show that the electroweak corrections to the cross section are sizeable, becoming very significant for high energy gamma rays. Our analysis covers in energy most of the photon spectrum, from the cosmic microwave background up to very high energy gamma rays, and scatterings with any value of the photon impact parameter. We also study the helicity-flip photon amplitude, which is of O( ? 2) in the weak coupling ?, and its massless fermion limit, which involves the exchange of a conformal anomaly pole. The corresponding cross section is proportional to the Born level result and brings to a simple renormalization of Einsten's formula.
Gravitational Lensing Limits on Cold Dark Matter and Its Variants
Christopher S. Kochanek
1994-11-19
Standard $\\Omega_0=1$ cold dark matter (CDM) needs $0.27 < \\sigma_8 < 0.63$ ($2\\sigma$) to fit the observed number of large separation lenses, and the constraint is nearly independent of $H_0=100h^{-1}\\kms$ Mpc$^{-1}$. This range is strongly inconsistent with the COBE estimate of $\\sigma_8=(2.8\\pm0.2)h$. Tilting the primordial spectrum $\\propto k^n$ from $n=1$ to $0.3 \\ltorder n \\ltorder 0.7$, using an effective Hubble constant of $0.15 \\ltorder \\Gamma=h \\ltorder 0.30$, or reducing the matter density to $0.15 \\ltorder \\Omega_0 h \\ltorder 0.3$ either with no cosmological constant ($\\lambda_0=0$) or in a flat universe with a cosmological constant ($\\Omega_0+\\lambda_0=1$) can bring the lensing estimate of $\\sigma_8$ into agreement with the COBE estimates. The models and values for $\\sigma_8$ consistent with both lensing and COBE match the estimates from the local number density of clusters and correlation functions. The conclusions are insensitive to systematic errors except for the assumption that cluster core radii are singular. If clusters with $\\rho\\propto(r^2+s^2)^{-1}$ have core radii exceeding $s = 15h^{-1}\\sigma_3^2$ kpc for a cluster with velocity dispersion $\\sigma=10^3\\sigma_3 \\kms$ then the estimates are invalid. There is, however, a fine tuning problem in making the cluster core radii large enough to invalidate the estimates of $\\sigma_8$ while producing several lenses that do not have central or ``odd images.'' The estimated completeness of the current samples of lenses larger than $5\\parcs0$ is 20\\%, because neither quasar surveys nor lens surveys are optimized to this class of lenses.
NASA Astrophysics Data System (ADS)
de Putter, Roland; Doré, Olivier; Das, Sudeep
2014-01-01
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 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 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).
De Putter, Roland; Doré, Olivier; Das, Sudeep
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).
Kernel regression estimates of time delays between gravitationally lensed fluxes
Otaibi, Sultanah AL; Cuevas-Tello, Juan C; Mandel, Ilya; Raychaudhury, Somak
2015-01-01
Strongly lensed variable quasars can serve as precise cosmological probes, provided that time delays between the image fluxes can be accurately measured. A number of methods have been proposed to address this problem. In this paper, we explore in detail a new approach based on kernel regression estimates, which is able to estimate a single time delay given several datasets for the same quasar. We develop realistic artificial data sets in order to carry out controlled experiments to test of performance of this new approach. We also test our method on real data from strongly lensed quasar Q0957+561 and compare our estimates against existing results.
Ding, Xuheng; Zhu, Zong-Hong
2015-01-01
With a fantastic sensitivity improving significantly over the advanced GW detectors, Einstein Telescope (ET) will be able to observe hundreds of thousand inspiralling double compact objects per year. By virtue of gravitational lensing effect, intrinsically unobservable faint sources can be observed by ET due to the magnification by intervening galaxies. We explore the possibility of observing such faint sources amplified by strong gravitational lensing. Following our previous work, we use the merger rates of DCO (NS-NS,BH-NS,BH-BH systems) as calculated by Dominik et al.(2013). It turns out that tens to hundreds of such (lensed) extra events will be registered by ET. This will strongly broaden the ET's distance reach for signals from such coalescences to the redshift range z=2 - 8. However, with respect to the full inspiral event catalog this magnification bias is at the level of 0.001 and should not affect much cosmological inferences.
Joint cosmic microwave background and weak lensing analysis: constraints on cosmological parameters.
Contaldi, Carlo R; Hoekstra, Henk; Lewis, Antony
2003-06-01
We use cosmic microwave background (CMB) observations together with the red-sequence cluster survey weak lensing results to derive constraints on a range of cosmological parameters. This particular choice of observations is motivated by their robust physical interpretation and complementarity. Our combined analysis, including a weak nucleosynthesis constraint, yields accurate determinations of a number of parameters including the amplitude of fluctuations sigma(8)=0.89+/-0.05 and matter density Omega(m)=0.30+/-0.03. We also find a value for the Hubble parameter of H(0)=70+/-3 km s(-1) Mpc(-1), in good agreement with the Hubble Space Telescope key-project result. We conclude that the combination of CMB and weak lensing data provides some of the most powerful constraints available in cosmology today. PMID:12857304
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.
Okabe, Nobuhiro [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Futamase, Toshifumi; Kuroshima, Risa [Astronomical Institute, Tohoku University, Sendai 980-8578 (Japan); Kajisawa, Masaru, E-mail: nobuhiro.okabe@ipmu.jp [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan)
2014-04-01
We present a 4 deg{sup 2} weak gravitational lensing survey of subhalos in the very nearby Coma cluster using the Subaru/Suprime-Cam. The large apparent size of cluster subhalos allows us to measure the mass of 32 subhalos detected in a model-independent manner, down to the order of 10{sup –3} of the virial mass of the cluster. Weak-lensing mass measurements of these shear-selected subhalos enable us to investigate subhalo properties and the correlation between subhalo masses and galaxy luminosities for the first time. The mean distortion profiles stacked over subhalos show a sharply truncated feature which is well-fitted by a Navarro-Frenk-White (NFW) mass model with the truncation radius, as expected due to tidal destruction by the main cluster. We also found that subhalo masses, truncation radii, and mass-to-light ratios decrease toward the cluster center. The subhalo mass function, dn/dln M {sub sub}, in the range of 2 orders of magnitude in mass, is well described by a single power law or a Schechter function. Best-fit power indices of 1.09{sub ?0.32}{sup +0.42} for the former model and 0.99{sub ?0.23}{sup +0.34} for the latter, are in remarkable agreement with slopes of ?0.9-1.0 predicted by the cold dark matter paradigm. The tangential distortion signals in the radial range of 0.02-2 h {sup –1} Mpc from the cluster center show a complex structure which is well described by a composition of three mass components of subhalos, the NFW mass distribution as a smooth component of the main cluster, and a lensing model from a large scale structure behind the cluster. Although the lensing signals are 1 order of magnitude lower than those for clusters at z ? 0.2, the total signal-to-noise ratio, S/N = 13.3, is comparable, or higher, because the enormous number of background source galaxies compensates for the low lensing efficiency of the nearby cluster.
Resolving the High Energy Universe with Strong Gravitational Lensing: The Case of PKS 1830-211
Barnacka, Anna; Dell'Antonio, Ian P; Benbow, Wystan
2015-01-01
Gravitational lensing is a potentially powerful tool for elucidating the origin of gamma-ray emission from distant sources. Cosmic lenses magnify the emission from distance sources and produce time delays between mirage images. Gravitationally-induced time delays depend on the position of the emitting regions in the source plane. The Fermi/LAT satellite continuously monitors the entire sky and detects gamma-ray flares, including those from gravitationally-lensed blazars. Therefore, temporal resolution at gamma-ray energies can be used to measure these time delays, which, in turn, can be used to resolve the origin of the gamma-ray flares spatially. We provide a guide to the application and Monte Carlo simulation of three techniques for analyzing these unresolved light curves: the Autocorrelation Function, the Double Power Spectrum, and the Maximum Peak Method. We apply these methods to derive time delays from the gamma-ray light curve of the gravitationally-lensed blazar PKS 1830-211. The result of temporal an...
On the gravitational effects of rotating masses: The Thirring-Lense papers
Bahram Mashhoon; Friedrich W. Hehl; Dietmar S. Theiss
1984-01-01
The purpose of this work is to provide a critical analysis of the classical papers of H. Thirring [Phys. Z.,19, 33 (1918);Phys. Z.,22, 29 (1921)] and J. Lense and H. Thirring [Phys. Z.,19, 156 (1918)] on rotating masses in the relativistic theory of gravitation and to render them accessible to a wider circle of scholars. An English translation of these
Caustics, critical curves and cross-sections for gravitational lensing by disc galaxies
NASA Astrophysics Data System (ADS)
Wang, Yun; Turner, Edwin L.
1997-12-01
We study strong gravitational lensing by spiral galaxies, modeling them as infinitely thin uniform disks embedded in singular isothermal spheres. We derive general properties of the critical curves and caustics analytically. The multiple-image cross section is a sensitive function of the inclination angle of the disk relative to the observer. We compute the inclination-averaged cross section for several sets of lensing parameters. For realistic disk mass and size parameters, we find that the cross section for multiple imaging is increased by only a modest factor, and that no dramatic increase in the optical depth for strong lensing of QSOs would be expected. However, the cross section for high magnifications is significantly increased due to the inclusion of a disk, especially for nearly edge-on configurations; due to the strong observational selection effects favoring high magnifications, there might be significant consequences for lensing statistics.
Detectability of weak lensing modifications under Galileon theories
NASA Astrophysics Data System (ADS)
Park, Youngsoo; Wyman, Mark
2015-03-01
Theories of modified gravity attempt to reconcile physics at the largest and the smallest scales by explaining the accelerated expansion of our Universe without introducing the cosmological constant. One class of such theories, known as Galileon theories, predicts lensing potentials of spherically symmetric bodies, such as dark matter halos, to receive a featurelike modification at the 5% level. With the advent of next-generation photometric surveys, such modifications can serve as novel probes of modified gravity. Assuming an Large Synoptic Survey Telescope-like fiducial data set, we produce halo-shear power spectra for cold dark matter and Galileon scenarios and perform a Fisher analysis including cosmological, nuisance, and Galileon parameters to study the detectability of the aforementioned modifications. With the cold dark matter scenario as our null hypothesis, we conclude, with a number of idealized assumptions and approximations, that the detection of Galileon modifications could in principle reach up to 4 -? if present, or strongly excluded in a nondetection, with a tomography of four redshift bins and four mass bins, an Large Synoptic Survey Telescope-like set of survey parameters, and Planck priors on cosmological parameters.
Gravitationally-Lensed Extragalactic Sources Identified with Planck
NASA Astrophysics Data System (ADS)
Cooray, Asantha
2015-08-01
I will summarize results from a program to identify and follow-up extragalactic sources from the Planck all-sky compact pouit source catalog. Observations are from Herschel, Keck, Hubble, among others. I will present nature of these sources, their properties, lensing models, and the environments of these galaxies.
Yang, Xinjuan; Zhang, Jun; Yu, Yu
2013-01-01
The existence of galaxy intrinsic clustering severely hampers the weak lensing reconstruction from cosmic magnification. In paper I \\citep{Yang2011}, we proposed a minimal variance estimator to overcome this problem. By utilizing the different dependences of cosmic magnification and galaxy intrinsic clustering on galaxy flux, we demonstrated that the otherwise overwhelming galaxy intrinsic clustering can be significantly suppressed such that lensing maps can be reconstructed with promising accuracy. This procedure relies heavily on the accuracy of determining the galaxy bias from the same data. Paper I adopts an iterative approach, which degrades toward high redshift. The current paper presents an alternative method, improving over paper I. We prove that the measured galaxy clustering between flux bins allows for simultaneous determination of the lensing power spectrum and the flux dependence of galaxy bias, at this redshift bin. Comparing to paper I, the new approach is not only more straightforward, but als...
Strong field gravitational lensing in the deformed Ho?ava-Lifshitz black hole
NASA Astrophysics Data System (ADS)
Chen, Songbai; Jing, Jiliang
2009-07-01
Adopting the strong field limit approach, we studied the properties of strong field gravitational lensing in the deformed Ho?ava-Lifshitz black hole and obtained the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy described by this metric, we estimated the numerical values of the coefficients and observables for gravitational lensing in the strong field limit. Comparing with the Reissner-Nordström black hole, we find that with the increase of parameter ?, the angular position ?? decreases more slowly and rm more quickly, but angular separation s increases more rapidly. This may offer a way to distinguish a deformed Ho?ava-Lifshitz black hole from a Reissner-Nordström black hole by the astronomical instruments in the future.
Obinna Umeh; Chris Clarkson; Roy Maartens
2014-09-22
The next generation of telescopes will usher in an era of precision cosmology, capable of determining the cosmological model to beyond the percent level. For this to be effective, the theoretical model must be understood to at least the same level of precision. A range of subtle relativistic effects remain to be explored theoretically, and offer the potential for probing general relativity in this new regime. We present the distance-redshift relation to second order in cosmological perturbation theory for a general dark energy model. This relation determines the magnification of sources at high precision, as well as redshift space distortions in the mildly non-linear regime. We identify a range of new lensing effects, including: double-integrated and nonlinear integrated Sach-Wolfe contributions, transverse Doppler effects, lensing from the induced vector mode and gravitational wave backgrounds, in addition to lensing from the second-order potential. Modifications to Doppler lensing from redshift-space distortions are identified. Finally, we find a new double-coupling between the density fluctuations integrated along the line of sight, and gradients in the density fluctuations coupled to transverse velocities along the line of sight. These can be large and thus offer important new probes of gravitational lensing and general relativity. This paper accompanies arXiv:1402.1933, where a comprehensive derivation is given.
Confirmation of general relativity on large scales from weak lensing and galaxy velocities.
Reyes, Reinabelle; Mandelbaum, Rachel; Seljak, Uros; Baldauf, Tobias; Gunn, James E; Lombriser, Lucas; Smith, Robert E
2010-03-11
Although general relativity underlies modern cosmology, its applicability on cosmological length scales has yet to be stringently tested. Such a test has recently been proposed, using a quantity, E(G), that combines measures of large-scale gravitational lensing, galaxy clustering and structure growth rate. The combination is insensitive to 'galaxy bias' (the difference between the clustering of visible galaxies and invisible dark matter) and is thus robust to the uncertainty in this parameter. Modified theories of gravity generally predict values of E(G) different from the general relativistic prediction because, in these theories, the 'gravitational slip' (the difference between the two potentials that describe perturbations in the gravitational metric) is non-zero, which leads to changes in the growth of structure and the strength of the gravitational lensing effect. Here we report that E(G) = 0.39 +/- 0.06 on length scales of tens of megaparsecs, in agreement with the general relativistic prediction of E(G) approximately 0.4. The measured value excludes a model within the tensor-vector-scalar gravity theory, which modifies both Newtonian and Einstein gravity. However, the relatively large uncertainty still permits models within f(R) theory, which is an extension of general relativity. A fivefold decrease in uncertainty is needed to rule out these models. PMID:20220843
HST Observations of Gravitationally Lensed Features in the Rich Cluster Ac114
Ian Smail; Warrick J. Couch; Richard S. Ellis; Ray M. Sharples
1994-05-11
Deep Hubble Space Telescope images of superlative resolution obtained for the distant rich cluster AC114 (z=0.31) reveal a variety of gravitational lensing phenomena for which ground-based spectroscopy is available. We present a luminous arc which is clearly resolved by HST and appears to be a lensed z=0.64 sub-L star spiral galaxy with a detected rotation curve. Of greatest interest is a remarkably symmetrical pair of compact blue images separated by 10 arcsec and lying close to the cluster cD. We propose that these images arise from a single very faint background source gravitationally lensed by the cluster core. Deep ground-based spectroscopy confirms the lensing hypothesis and suggests the source is a compact star forming system at a redshift z=1.86. Taking advantage of the resolved structure around each image and their very blue colours, we have identified a candidate third image of the same source roughly 50 arcsec away. The angular separation of the three images is much larger than previous multiply-imaged systems and indicates a deep gravitational potential in the cluster centre. Resolved multiply-imaged systems, readily recognised with HST, promise to provide unique constraints on the mass distribution in the cores of intermediate redshift clusters.
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.
Constraining the minimum luminosity of high redshift galaxies through gravitational lensing
NASA Astrophysics Data System (ADS)
Mashian, Natalie; Loeb, Abraham
2013-12-01
We simulate the effects of gravitational lensing on the source count of high redshift galaxies as projected to be observed by the Hubble Frontier Fields program and the James Webb Space Telescope (JWST) in the near future. Taking the mass density profile of the lensing object to be the singular isothermal sphere (SIS) or the Navarro-Frenk-White (NFW) profile, we model a lens residing at a redshift of zL = 0.5 and explore the radial dependence of the resulting magnification bias and its variability with the velocity dispersion of the lens, the photometric sensitivity of the instrument, the redshift of the background source population, and the intrinsic maximum absolute magnitude (Mmax) of the sources. We find that gravitational lensing enhances the number of galaxies with redshifts zgtrsim 13 detected in the angular region ?E/2 <= ? <= 2?E (where ?E is the Einstein angle) by a factor of ~ 3 and 1.5 in the HUDF (df/d?0 ~ 9 nJy) and medium-deep JWST surveys (df/d?0 ~ 6 nJy). Furthermore, we find that even in cases where a negative magnification bias reduces the observed number count of background sources, the lensing effect improves the sensitivity of the count to the intrinsic faint-magnitude cut-off of the Schechter luminosity function. In a field centered on a strong lensing cluster, observations of zgtrsim 6 and zgtrsim 13 galaxies with JWST can be used to infer this cut-off magnitude for values as faint as Mmax ~ -14.4 and -16.1 mag (Lmin ? 2.5 × 1026 and 1.2 × 1027 erg s-1 Hz-1) respectively, within the range bracketed by existing theoretical models. Gravitational lensing may therefore offer an effective way of constraining the low-luminosity cut-off of high-redshift galaxies.
Wavelet Helmholtz decomposition for weak lensing mass map reconstruction
Deriaz, E; Pires, S
2012-01-01
To derive the convergence field from the gravitational shear (gamma) of the background galaxy images, the classical methods require a convolution of the shear to be performed over the entire sky, usually expressed thanks to the Fast Fourier transform (FFT). However, it is not optimal for an imperfect geometry survey. Furthermore, FFT implicitly uses periodic conditions that introduce errors to the reconstruction. A method has been proposed that relies on computation of an intermediate field u that combines the derivatives of gamma 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 E/B mode 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 experim...
The Shear TEsting Programme 2: Factors affecting high precision weak lensing analyses
Massey, R; Berge, J; Bernstein, G; Bridle, S; Clowe, D; Dahle, H; Ellis, R; Erben, T; Hetterscheidt, M; High, F W; Hirata, C; Hoekstra, H; Hudelot, P; Jarvis, M; Johnston, D; Kuijken, K; Margoniner, V; Mandelbaum, R; Mellier, Y; Nakajima, R; Paulin-Henriksson, S; Peeples, M; Roat, C; Réfrégier, A; Rhodes, J; Schrabback, T; Schirmer, M; Seljak, U; Semboloni, E; Van Waerbeke, L; Massey, Richard; Heymans, Catherine; Berge, Joel; Bernstein, Gary; Bridle, Sarah; Clowe, Douglas; Dahle, Hakon; Ellis, Richard; Erben, Thomas; Hetterscheidt, Marco; Hirata, Christopher; Hoekstra, Henk; Hudelot, Patrick; Jarvis, Mike; Johnston, David; Kuijken, Konrad; Margoniner, Vera; Mandelbaum, Rachel; Mellier, Yannick; Nakajima, Reiko; Paulin-Henriksson, Stephane; Peeples, Molly; Roat, Chris; Refregier, Alexandre; Rhodes, Jason; Schrabback, Tim; Schirmer, Mischa; Seljak, Uros; Semboloni, Elisabetta; Waerbeke, Ludovic Van
2006-01-01
The Shear TEsting Programme (STEP) is a collaborative project to improve the accuracy and reliability of weak lensing measurement, in preparation for the next generation of wide-field surveys. We review sixteen current and emerging shear measurement methods in a common language, and assess their performance by running them (blindly) on simulated images that contain a known shear signal. We determine the common features of algorithms that most successfully recover the input parameters. We achieve previously unattained discriminatory precision in our analysis, via a combination of more extensive simulations, and pairs of galaxy images that have been rotated with respect to each other, thus removing noise from their intrinsic ellipticities. The robustness of our simulation approach is also confirmed by testing the relative calibration of methods on real data. Weak lensing measurement has improved since the first STEP paper. Several methods now consistently achieve better than 2% precision, and are still being de...
A New Estimate of the Hubble Time with Improved Modeling of Gravitational Lenses
Jonathan Coles
2008-02-21
This paper examines free-form modeling of gravitational lenses using Bayesian ensembles of pixelated mass maps. The priors and algorithms from previous work are clarified and significant technical improvements are made. Lens reconstruction and Hubble Time recovery are tested using mock data from simple analytic models and recent galaxy-formation simulations. Finally, using published data, the Hubble Time is inferred through the simultaneous reconstruction of eleven time-delay lenses. The result is H_0^{-1}=13.7^{+1.8}_{-1.0} Gyr.
The Shear TEsting Programme 1: Weak lensing analysis of simulated ground-based observations
Catherine Heymans; Ludovic Van Waerbeke; David Bacon; Joel Berge; Gary Bernstein; Emmanuel Bertin; Sarah Bridle; Michael L. Brown; Douglas Clowe; Haakon Dahle; Thomas Erben; Meghan Gray; Marco Hetterscheidt; Henk Hoekstra; Patrick Hudelot; Mike Jarvis; Konrad Kuijken; Vera Margoniner; Richard Massey; Yannick Mellier; Reiko Nakajima; Alexandre Refregier; Jason Rhodes; Tim Schrabback; David Wittman
2006-02-10
The Shear TEsting Programme, STEP, is a collaborative project to improve the accuracy and reliability of all weak lensing measurements in preparation for the next generation of wide-field surveys. In this first STEP paper we present the results of a blind analysis of simulated ground-based observations of relatively simple galaxy morphologies. The most successful methods are shown to achieve percent level accuracy. From the cosmic shear pipelines that have been used to constrain cosmology, we find weak lensing shear measured to an accuracy that is within the statistical errors of current weak lensing analyses, with shear measurements accurate to better than 7%. The dominant source of measurement error is shown to arise from calibration uncertainties where the measured shear is over or under-estimated by a constant multiplicative factor. This is of concern as calibration errors cannot be detected through standard diagnostic tests. The measured calibration errors appear to result from stellar contamination, false object detection, the shear measurement method itself, selection bias and/or the use of biased weights. Additive systematics (false detections of shear) resulting from residual point-spread function anisotropy are, in most cases, reduced to below an equivalent shear of 0.001, an order of magnitude below cosmic shear distortions on the scales probed by current surveys. Our results provide a snapshot view of the accuracy of current ground-based weak lensing methods and a benchmark upon which we can improve. To this end we provide descriptions of each method tested and include details of the eight different implementations of the commonly used Kaiser, Squires and Broadhurst (1995) method (KSB+) to aid the improvement of future KSB+ analyses.
A 7 deg2 survey for galaxy-scale gravitational lenses with the HST imaging archive
NASA Astrophysics Data System (ADS)
Pawase, R. S.; Courbin, F.; Faure, C.; Kokotanekova, R.; Meylan, G.
2014-04-01
We present the results of a visual search for galaxy-scale gravitational lenses in ˜7 deg2 of Hubble Space Telescope (HST) images. The data set comprises the whole imaging data ever taken with the Advanced Camera for Surveys (ACS) in the filter F814W (I-band) up to 2011 August 31, i.e. 6.03 deg2 excluding the field of the Cosmic Evolution Survey which has been the subject of a separate visual search. In addition, we have searched for lenses in the whole Wide Field Camera 3 (WFC3) near-IR imaging data set in all filters (1.01 deg2) up to the same date. Our primary goal is to provide a sample of lenses with a broad range of different morphologies and lens-source brightness contrast in order to estimate a lower limit to the number of galaxy-scale strong lenses in the future Euclid survey in its VIS band. Our criteria to select lenses are purely morphological as we do not use any colour or redshift information. The final candidate selection is very conservative hence leading to a nearly pure but incomplete sample. We find 49 new lens candidates: 40 in the ACS images and 9 in the WFC3 images. Out of these, 16 candidates are secure lenses owing to their striking morphology, 21 more are very good candidates and 12 more have morphologies compatible with gravitational lensing but also compatible with other astrophysical objects such as ring and chain galaxies or mergers. Interestingly, some lens galaxies include low surface brightness galaxies, compact groups and mergers. The imaging data set is heterogeneous in depth and spans a broad range of galactic latitudes. It is therefore insensitive to cosmic variance and allows us to estimate the number of galaxy-scale strong lenses on the sky for a putative survey depth, which is the main result of this work. Because of the incompleteness of the sample, the estimated lensing rates should be taken as lower limits. Using these, we anticipate that a 15 000 deg2 space survey such as Euclid will find at least 60 000 galaxy-scale strong lenses down to a limiting AB magnitude of I = 24.5 (10?) or I = 25.8 (3?).
NASA Astrophysics Data System (ADS)
Wang, Yun
1999-11-01
Weak lensing leads to the non-Gaussian magnification distribution of standard candles at a given redshift z, p(?|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 ?˜ 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 ?˜. We define the direction-dependent smoothness parameter ?˜ via the Dyer-Roeder equation; there is a unique mapping between ?˜ and the magnification of a source. We find that the distribution of ?˜ at a given z, p(?˜|z), is well described by a modified Gaussian distribution. For the same matter distribution, i.e., the same p(?˜|z), different values of ?m and ?? 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.
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.
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.
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.
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.
CFHTLenS: weak lensing calibrated scaling relations for low-mass clusters of galaxies
NASA Astrophysics Data System (ADS)
Kettula, K.; Giodini, S.; van Uitert, E.; Hoekstra, H.; Finoguenov, A.; Lerchster, M.; Erben, T.; Heymans, C.; Hildebrandt, H.; Kitching, T. D.; Mahdavi, A.; Mellier, Y.; Miller, L.; Mirkazemi, M.; Van Waerbeke, L.; Coupon, J.; Egami, E.; Fu, L.; Hudson, M. J.; Kneib, J. P.; Kuijken, K.; McCracken, H. J.; Pereira, M. J.; Rowe, B.; Schrabback, T.; Tanaka, M.; Velander, M.
2015-08-01
We present weak lensing and X-ray analysis of 12 low-mass clusters from the Canada-France-Hawaii Telescope Lensing Survey and XMM-CFHTLS surveys. We combine these systems with high-mass systems from Canadian Cluster Comparison Project and low-mass systems from Cosmic Evolution Survey to obtain a sample of 70 systems, spanning over two orders of magnitude in mass. We measure core-excised LX-TX, M-LX and M-TX scaling relations and include corrections for observational biases. By providing fully bias-corrected relations, we give the current limitations for LX and TX as cluster mass proxies. We demonstrate that TX benefits from a significantly lower intrinsic scatter at fixed mass than LX. By studying the residuals of the bias-corrected relations, we show for the first time using weak lensing masses that galaxy groups seem more luminous and warmer for their mass than clusters. This implies a steepening of the M-LX and M-TX relations at low masses. We verify the inferred steepening using a different high-mass sample from the literature and show that variance between samples is the dominant effect leading to discrepant scaling relations. We divide our sample into subsamples of merging and relaxed systems, and find that mergers may have enhanced scatter in lensing measurements, most likely due to stronger triaxiality and more substructure. For the LX-TX relation, which is unaffected by lensing measurements, we find the opposite trend in scatter. We also explore the effects of X-ray cross-calibration and find that Chandra calibration leads to flatter LX-TX and M-TX relations than XMM-Newton.
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.
Corless, Virginia L; Clowe, Douglas
2008-01-01
Measuring the 3D distribution of mass on galaxy cluster scales is a crucial test of the LCDM model, providing constraints on the nature of dark matter. Recent work investigating mass distributions of individual galaxy clusters (e.g. Abell 1689) using weak and strong gravitational lensing has revealed potential inconsistencies between the predictions of structure formation models relating halo mass to concentration and those relationships as measured in massive clusters. However, such analyses employ simple spherical halo models while a growing body of work indicates that triaxial 3D halo structure is both common and important in parameter estimates. We recently introduced a Markov Chain Monte Carlo (MCMC) method to fit fully triaxial models to weak lensing data that gives parameter and error estimates that fully incorporate the true shape uncertainty present in nature. In this paper we apply that method to weak lensing data obtained with the ESO/MPG Wide-Field Imager for galaxy clusters A1689, A1835, and A220...
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.
The SDSS-III BOSS quasar lens survey: discovery of thirteen gravitationally lensed quasars
More, Anupreeta; Kayo, Issha; Zinn, Joel; Strauss, Michael A; Santiago, Basilio X; Mosquera, Ana M; Inada, Naohisa; Kochanek, Christopher S; Rusu, Cristian E; Brownstein, Joel R; da Costa, Luiz N; Kneib, Jean-Paul; Maia, Marcio A G; Quimby, Robert M; Schneider, Donald P; Streblyanska, Alina; York, Donald G
2015-01-01
We report the discovery of 13 confirmed two-image quasar lenses from a systematic search for gravitationally lensed quasars in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We adopted a methodology similar to that used in the SDSS Quasar Lens Search (SQLS). In addition to the confirmed lenses, we report 11 quasar pairs with small angular separations ($\\lesssim$2") confirmed from our spectroscopy, which are either projected pairs, physical binaries, or possibly quasar lens systems whose lens galaxies have not yet been detected. The newly discovered quasar lens system, SDSS J1452+4224 at zs$\\approx$4.8 is one of the highest redshift multiply imaged quasars found to date. Furthermore, we have over 50 good lens candidates yet to be followed up. Owing to the heterogeneous selection of BOSS quasars, the lens sample presented here does not have a well-defined selection function.
Safety in numbers: Gravitational Lensing Degradation of the Luminosity Distance-Redshift Relation
Holz, D E; Holz, Daniel E.; Linder, Eric V.
2004-01-01
Observation of the expansion history of the Universe allows exploration of the physical properties and energy density of the Universe's various constituents. Standardizable candles such as Type Ia supernovae remain one of the most promising and robust tools in this endeavor, by allowing for a direct measure of the luminosity distance-redshift curve, and thereby producing detailed studies of the dark energy responsible for the Universe's currently accelerating expansion. As such observations are pushed to higher redshifts, the observed flux is increasingly affected by gravitational lensing magnification due to intervening structure along the line-of-sight. We simulate and analyze the non-Gaussian probability distribution function of de/amplification due to lensing of standard candles, quantify the effect of a convolution over many independent sources (which acts to restore the intrinsic average (unlensed) luminosity due to flux conservation), and compute the additional uncertainty due to lensing on derived cos...
Gravitational lensing by a massive black hole at the Galactic center
NASA Technical Reports Server (NTRS)
Wardle, Mark; Yusef-Zadeh, Farhad
1992-01-01
The manifestations of gravitational lensing by a massive black hole at the Galactic center, with particular attention given to lensing of stars in the stellar cluster that lie behind Sgr A*, and of Sgr A east, a nonthermal extended radio source which is known with certainty to lie behind the Galactic center. Lensing of the stellar cluster produces a deficit of stellar images within 10 mas of the center, and a surplus between 30 and 300 mas. The results suggest that the proper motion of the stars will produce brightness variations of stellar images on a time scale of a few years or less. Both images of such a source should be visible, and will rise and fall in luminosity together.
Aspects of electrostatics in a weak gravitational field
Hamsa Padmanabhan; T. Padmanabhan
2009-10-06
Several features of electrostatics of point charged particles in a weak, homogeneous, gravitational field are discussed using the Rindler metric to model the gravitational field. Some previously known results are obtained by simpler and more transparent procedures and are interpreted in an intuitive manner. Specifically: (i) We show that the electrostatic potential of a charge at rest in the Rindler frame is expressible as A_0=(q/l) where l is the affine parameter distance along the null geodesic from the charge to the field point. (ii) We obtain the sum of the electrostatic forces exerted by one charge on another in the Rindler frame and discuss its interpretation. (iii) We show how a purely electrostatic term in the Rindler frame appears as a radiation term in the inertial frame. (In part, this arises because charges at rest in a weak gravitational field possess additional weight due to their electrostatic energy. This weight is proportional to the acceleration and falls inversely with distance -- which are the usual characteristics of a radiation field.) (iv) We also interpret the origin of the radiation reaction term by extending our approach to include a slowly varying acceleration. Many of these results might have possible extensions for the case of electrostatics in an arbitrary static geometry. [Abridged Abstract
Full-sky formulae for weak lensing power spectra from total angular momentum method
Yamauchi, Daisuke; Taruya, Atsushi; Namikawa, Toshiya E-mail: namikawa@yukawa.kyoto-u.ac.jp
2013-08-01
We systematically derive full-sky formulae for the weak lensing power spectra generated by scalar, vector and tensor perturbations from the total angular momentum (TAM) method. Based on both the geodesic and geodesic deviation equations, we first give the gauge-invariant expressions for the deflection angle and Jacobi map as observables of the CMB lensing and cosmic shear experiments. We then apply the TAM method, originally developed in the theoretical studies of CMB, to a systematic derivation of the angular power spectra. The TAM representation, which characterizes the total angular dependence of the spatial modes projected along a line-of-sight, can carry all the information of the lensing modes generated by scalar, vector, and tensor metric perturbations. This greatly simplifies the calculation, and we present a complete set of the full-sky formulae for angular power spectra in both the E-/B-mode cosmic shear and gradient-/curl-mode lensing potential of deflection angle. Based on the formulae, we give illustrative examples of non-vanishing B-mode cosmic shear and curl-mode of deflection angle in the presence of the vector and tensor perturbations, and explicitly compute the power spectra.
High, F. W.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Hoekstra, H.; Leethochawalit, N.; De Haan, T.; Abramson, L.; Aird, K. A.; Armstrong, R.; Ashby, M. L. N.; Conroy, M.; Bautz, M.; Bayliss, M.; Bazin, G.; Brodwin, M.; Cho, H. M.; Clocchiatti, A.; 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.
NASA Astrophysics Data System (ADS)
High, F. W.; Hoekstra, H.; Leethochawalit, N.; de Haan, T.; Abramson, L.; Aird, K. A.; Armstrong, R.; Ashby, M. L. N.; Bautz, M.; Bayliss, M.; Bazin, G.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Clocchiatti, A.; Conroy, M.; Crawford, T. M.; Crites, A. T.; Desai, S.; Dobbs, M. A.; Dudley, J. P.; Foley, R. J.; Forman, W. R.; George, E. M.; Gladders, M. D.; Gonzalez, A. H.; Halverson, N. W.; Harrington, N. L.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hrubes, J. D.; Jones, C.; Joy, M.; Keisler, R.; 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.; Mehl, J.; Meyer, S. S.; Mocanu, L.; Mohr, J. J.; Montroy, T. E.; Murray, S. S.; Natoli, T.; Nurgaliev, D.; Padin, S.; Plagge, T.; Pryke, C.; Reichardt, C. L.; Rest, A.; Ruel, J.; Ruhl, J. E.; Saliwanchik, B. R.; Saro, A.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Schrabback, T.; Shirokoff, E.; Song, J.; Spieler, H. G.; Stalder, B.; Staniszewski, Z.; Stark, A. A.; Story, K.; Stubbs, C. W.; Šuhada, R.; Tokarz, S.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Williamson, R.; Zahn, O.; Zenteno, A.
2012-10-01
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 500 > 2 × 1014 h -1 M ?, 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 500, SZ derived from the SZ mass, of 1.04 ± 0.18. We measure a mean ratio of spherical WL masses evaluated at R 500, SZ to spherical SZ masses of 1.07 ± 0.18, and a mean ratio of spherical WL masses evaluated at R 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.
Dark matter halo properties of GAMA galaxy groups from 100 square degrees of KiDS weak lensing data
NASA Astrophysics Data System (ADS)
Viola, M.; Cacciato, 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.; Verdoes Kleijn, G.
2015-10-01
The Kilo-Degree Survey 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 ˜1400 spectroscopically identified galaxy groups and clusters from the Galaxy And Mass Assembly survey. We detect a highly significant signal (signal-to-noise-ratio ˜120), allowing us to study the properties of dark matter haloes over one and a half order of magnitude in mass, from M ˜ 1013-1014.5 h-1 M?. 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. In addition, we constrain scaling relations between the mass and a number of observable group properties. We find that the mass scales with the total r-band luminosity as a power law with slope 1.16 ± 0.13 (1?) and with the group velocity dispersion as a power law with slope 1.89 ± 0.27 (1?). Finally, we demonstrate the potential of weak lensing studies of groups to discriminate between models of baryonic feedback at group scales by comparing our results with the predictions from the Cosmo-OverWhelmingly Large Simulations project, ruling out models without AGN feedback.
Spectroscopic identification of 25 disk galaxy candidate gravitational lenses in the SDSS
NASA Astrophysics Data System (ADS)
Focardi, P.; Rossetti, E.
2015-09-01
Context. Galaxy-scale gravitational lenses are powerful tools, which can be used to address major astrophysical questions that are still open. They can be identified either through imaging or through spectroscopy, which is less efficient than imaging but offers the major advantage of having both source and deflector red shift previously measured at discovery. Spectroscopic identification requires huge data sets of high spectral quality, such as the SDSS, and has so far focused on early-type galaxies, as the most massive galaxies are found among them. Aims: We aimed to perform spectroscopic identification of disk galaxies acting as gravitational lenses. Methods: We have selected about 300 000 galaxy spectra with EW(H?) ?-10 Å from the SDSS DR 8. On these spectra, we ran our original code RES, which is a fast, reliable tool able to provide a red-shift measure and to identify discordant red-shift systems if present. We have required RES to identify only systems based on a minimum number of four emission lines. We have inspected all the (54) SDSS images of the double z systems identified by RES and discarded systems for which z duplicity could be easily ascribed to the presence of two distinct objects. The remaining 25 systems, for which double z is very likely to be due to the gravitational lensing phenomenon, constitute our sample. Results: For each gravitational lens candidate system, we provide SDSS identification and image emission lines detected by RES and activity classification, when derivable. The disky nature of our candidate lenses is confirmed by their images, stellar mass estimates, g - r rest-frame colours and occurrence of star burst phenomena.
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.
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses
NASA Astrophysics Data System (ADS)
Courbin, F.; Eigenbrod, A.; Vuissoz, C.; Meylan, G.; Magain, P.
2005-06-01
We describe a new project aiming at measuring time delays for most known lensed quasars, from optical light curves obtained with five (almost) dedicated 1-2 m telescopes in the Northern and Southern hemispheres. The goal is to evaluate the Hubble constant H0 with a precision below 2%. We present here numerical simulations in order to define the optimal temporal sampling in our observations as a function of typical quasar variations, object visibility, and for a given accuracy on the individual photometric points. It is also emphasized that the ongoing effort to obtain deep imaging using both space and ground based facilities must be continued, as illustrated by the comparison of HST and VLT near-IR images of the `cloverleaf': H 1413+117.
Cosmological constraints from strong gravitational lensing in clusters of galaxies.
Jullo, Eric; Natarajan, Priyamvada; Kneib, Jean-Paul; D'Aloisio, Anson; Limousin, Marceau; Richard, Johan; Schimd, Carlo
2010-08-20
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 dark energy equation of state. Combining our cosmological constraints with those from x-ray clusters and the Wilkinson Microwave Anisotropy Probe 5-year data gives Omega(m) = 0.25 +/- 0.05 and w(x) = -0.97 +/- 0.07, which are consistent with results from other methods. Inclusion of our method with all other available techniques brings down the current 2sigma contours on the dark energy equation-of-state parameter w(x) by approximately 30%. PMID:20724628
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)
SDSS J133401.39+331534.3: A NEW SUBARCSECOND GRAVITATIONALLY LENSED QUASAR
Rusu, Cristian E.; Iye, Masanori; Oguri, Masamune; Inada, Naohisa; Kayo, Issha; Hayano, Yutaka; Oya, Shin; Hattori, Masayuki; Saito, Yoshihiko; Ito, Meguru; Minowa, Yosuke; Pyo, Tae-Soo; Terada, Hiroshi; Takami, Hideki; Watanabe, Makoto
2011-09-01
The quasar SDSS J133401.39+331534.3 at z = 2.426 is found to be a two-image gravitationally lensed quasar with an image separation of 0.''833. The object is first identified as a lensed quasar candidate in the Sloan Digital Sky Survey Quasar Lens Search, and then confirmed as a lensed system from follow-up observations at the Subaru and University of Hawaii 2.2 m telescopes. We estimate the redshift of the lensing galaxy to be 0.557 based on absorption lines in the quasar spectra as well as the color of the galaxy. In particular, we observe the system with the Subaru Telescope AO188 adaptive optics with a laser guide star, in order to derive accurate astrometry, which well demonstrates the usefulness of the laser guide star adaptive optics imaging for studying strong lens systems. Our mass modeling with improved astrometry implies that a nearby bright galaxy {approx}4'' apart from the lensing galaxy is likely to affect the lens potential.
Safety in numbers: Gravitational Lensing Degradation of the Luminosity Distance-Redshift Relation
NASA Astrophysics Data System (ADS)
Linder, E. V.; Holz, D. E.
2004-12-01
For exploring dark energy, the cosmic expansion history, and the distance scale, standardizable candles such as Type Ia supernovae remain one of the most promising and robust tools. As such observations are pushed to higher redshifts, the observed flux is increasingly affected by gravitational lensing magnification due to intervening structure along the line-of-sight. We simulate and analyze the non-Gaussian probability distribution function of de/amplification due to lensing of standard candles, quantify the effect of a convolution over many independent sources (which acts to restore the intrinsic average (unlensed) luminosity due to flux conservation), and compute the additional uncertainty due to lensing on derived cosmological parameters. For example, the ``degradation factor'' due to lensing is a one-third reduction in the effective number of usable supernovae at z=1.5 (for sources with intrinsic flux dispersion of 10%). We also present a useful expression for the effective increased dispersion in standard candles due to lensing, as a function of redshift.
Safety in numbers: Gravitational Lensing Degradation of the Luminosity Distance-Redshift Relation
Daniel E. Holz; Eric V. Linder
2004-12-08
Observation of the expansion history of the Universe allows exploration of the physical properties and energy density of the Universe's various constituents. Standardizable candles such as Type Ia supernovae remain one of the most promising and robust tools in this endeavor, by allowing for a direct measure of the luminosity distance-redshift curve, and thereby producing detailed studies of the dark energy responsible for the Universe's currently accelerating expansion. As such observations are pushed to higher redshifts, the observed flux is increasingly affected by gravitational lensing magnification due to intervening structure along the line-of-sight. We simulate and analyze the non-Gaussian probability distribution function of de/amplification due to lensing of standard candles, quantify the effect of a convolution over many independent sources (which acts to restore the intrinsic average (unlensed) luminosity due to flux conservation), and compute the additional uncertainty due to lensing on derived cosmological parameters. For example, the ``degradation factor'' due to lensing is a factor of three reduction in the effective number of usable supernovae at z=1.5 (for sources with intrinsic flux dispersion of 10%). We also derive a useful expression for the effective increased dispersion in standard candles due to lensing, as a function of redshift.
Safety in Numbers: Gravitational Lensing Degradation of the Luminosity Distance-Redshift Relation
NASA Astrophysics Data System (ADS)
Holz, Daniel E.; Linder, Eric V.
2005-10-01
Observation of the expansion history of the universe allows exploration of the physical properties and energy density of the universe's various constituents. Standardizable candles such as Type Ia supernovae remain one of the most promising and robust tools in this endeavor by allowing for a direct measure of the luminosity distance-redshift curve and thereby producing detailed studies of the dark energy responsible for the universe's currently accelerating expansion. As such observations are pushed to higher redshifts, the observed flux is increasingly affected by gravitational lensing magnification due to intervening structure along the line of sight. We simulate and analyze the non-Gaussian probability distribution function of deamplification and amplification due to lensing of standard candles, quantify the effect of a convolution over many independent sources (which acts to restore the intrinsic average [unlensed] luminosity due to flux conservation), and compute the additional uncertainty due to lensing on derived cosmological parameters. We find that, in the case of large numbers of sources, the lensing distribution along any particular line of sight can be approximated by a Gaussian with standard deviation given by ?eff=0.088z as a function of redshift z. The resulting ``degradation factor'' due to lensing is a factor of 3 reduction in the effective number of usable supernovae at z=1.5 (for sources with intrinsic flux dispersion of 10%).
Correcting High-Redshift Galaxy Luminosity Functions for Gravitational Lensing Magnification Bias
NASA Astrophysics Data System (ADS)
Mason, Charlotte; Treu, Tommaso; Borello Schmidt, Kasper; Collett, Thomas; Trenti, Michele; Marshall, Philip; Barone-Nugent, Robert; Bradley, Larry; Stiavelli, Massimo; Wyithe, Stuart
2015-08-01
We present a Bayesian framework to account for the magnification bias from strong, intermediate and weak gravitational lensing in estimates of high-redshift galaxy UV luminosity functions (LFs), which is expected to significantly modify the bright-end of the LF. 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 HUDF. We find the LF is well described by a Schechter function with parameters consistent within the uncertainties of those inferred from the same sample without accounting for the magnification bias (Schmidt et al. 2014), demonstrating that the effect is small for current surveys at z ~ 8. Hence we find that magnification bias alone cannot account for the apparent overdensity of z ~ 7 bright galaxies compared to a Schechter function found recently by Bowler et al. (2014a,b) and Finkelstein et al. (2014). 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. In order to derive accurate estimates of high-redshift LFs in these surveys and to distinguish between galaxy formation models it will be vital to account for the magnification bias. We show that magnification bias can be an additional tool to probe the high-redshift universe and demonstrate this via a physical model for the UV LF at z > 8.
Complex structures in galaxy cluster fields: implications for gravitational lensing mass models
NASA Astrophysics Data System (ADS)
King, Lindsay; Corless, Virginia
2007-01-01
The distribution of mass on galaxy cluster scales is an important test of structure formation scenarios, providing constraints on the nature of dark matter itself. Several techniques have been used to probe the mass distributions of clusters, sometimes yielding results which are discrepant, or at odds with clusters formed in simulations - for example giving Navarro-Frenk-White (NFW) concentration parameters much higher than expected in the standard cold dark matter (CDM) model. In addition, the velocity fields of some well-studied galaxy clusters reveal the presence of several structures close to the line of sight, often not dynamically bound to the cluster itself. We investigate what impact such neighbouring but unbound massive structures would have on the determination of cluster profiles using weak gravitational lensing. Depending on its concentration and mass ratio to the primary halo, one secondary halo close to the line-of-sight can cause the estimated NFW concentration parameter to be significantly higher than that of the primary halo, and also cause the estimated mass to be biased high. Although it is difficult to envisage how this mechanism alone could yield concentrations as high as reported for some clusters, multiple haloes close to the line-of-sight, such as in the case of Abell 1689, can substantially increase the concentration parameter estimate. Together with the fact that clusters are triaxial, and that including baryonic physics also leads to an increase in the concentration of a dark matter halo, the tension between observations and the standard CDM model is eased. Additionally, we note that if the alignment with the secondary structure is imprecise, then the estimated concentration parameter can also be even lower than that of the primary halo, reinforcing the importance of identifying structures in cluster fields.
First evidence of a gravitational lensing-induced echo in gamma rays with Fermi LAT
NASA Astrophysics Data System (ADS)
Barnacka, A.; Glicenstein, J.-F.; Moudden, Y.
2011-04-01
Aims: This article shows the first evidence ever of gravitational lensing phenomena in high energy gamma-rays. This evidence comes from the observation of an echo in the light curve of the distant blazar PKS 1830-211 induced by a gravitational lens system. Methods: Traditional methods for estimating time delays in gravitational lensing systems rely on the cross-correlation of the light curves from individual images. We used the 300 MeV-30 GeV photons detected by the Fermi-LAT instrument. It cannot separate the images of known lenses, so the observed light curve is the superposition of individual image light curves. The Fermi-LAT instrument has the advantage of providing long, evenly spaced, time series with very low photon noise. This allows us to use Fourier transform methods directly. Results: A time delay between the two compact images of PKS 1830-211 has been searched for by both the autocorrelation method and the "double power spectrum" method. The double power spectrum shows a 4.2? proof of a time delay of 27.1 ± 0.6 days, consistent with others' results.
Low X-ray luminosity galaxy clusters - III. Weak lensing mass determination at 0.18 < z < 0.70
NASA Astrophysics Data System (ADS)
Gonzalez, Elizabeth Johana; Foëx, Gael; Nilo Castellón, José Luis; Domínguez Romero, Mariano J.; Alonso, María Victoria; García Lambas, Diego; Moreschi, Osvaldo; Gallo, Emanuel
2015-09-01
This is the third of a series of papers of low X-ray luminosity galaxy clusters. In this work we present the weak lensing analysis of eight clusters, based on observations obtained with the Gemini Multi-Object Spectrograph in the g', r' and i' passbands. For this purpose, we have developed a pipeline for the lensing analysis of ground-based images and we have performed tests applied to simulated data. We have determined the masses of seven galaxy clusters, five of them measured for the first time. For the four clusters with availably spectroscopic data, we find a general agreement between the velocity dispersions obtained via weak lensing assuming a singular isothermal sphere profile, and those obtained from the redshift distribution of member galaxies. The correlation between our weak lensing mass determinations and the X-ray luminosities is suitably fitted by other observations of the M-LX relation and models.
Mirages around Kerr black holes and retro-gravitational lenses
A. F. Zakharov; A. A. Nucita; F. DePaolis; G. Ingrosso
2004-11-17
Recently Holz & Wheeler (2002) considered a very attracting possibility to detect retro-MACHOs, i.e. retro-images of the Sun by a Schwarzschild black hole. In this paper we discuss glories (mirages) formed near rapidly rotating Kerr black hole horizons and propose a procedure to measure masses and rotation parameters analyzing these forms of mirages. In some sense that is a manifestation of gravitational lens effect in the strong gravitational field near black hole horizon and a generalization of the retro-gravitational lens phenomenon. We analyze the case of a Kerr black hole rotating at arbitrary speed for some selected positions of a distant observer with respect to the equatorial plane of a Kerr black hole. We discuss glories (mirages) formed near rapidly rotating Kerr black hole horizons and propose a procedure to measure masses and rotation parameters analyzing these forms of mirages. Some time ago Falcke et al. (2000) suggested to search shadows at the Galactic Center. In this paper we present the boundaries for shadows calculated numerically. We also propose to use future radio interferometer RADIOASTRON facilities to measure shapes of mirages (glories) and to evaluate the black hole spin as a function of the position angle of a distant observer.
Mirages around Kerr black holes and retro-gravitational lenses
Zakharov, A F; De Paolis, F; Ingrosso, G
2004-01-01
Recently Holz & Wheeler (2002) considered a very attracting possibility to detect retro-MACHOs, i.e. retro-images of the Sun by a Schwarzschild black hole. In this paper we discuss glories (mirages) formed near rapidly rotating Kerr black hole horizons and propose a procedure to measure masses and rotation parameters analyzing these forms of mirages. In some sense that is a manifestation of gravitational lens effect in the strong gravitational field near black hole horizon and a generalization of the retro-gravitational lens phenomenon. We analyze the case of a Kerr black hole rotating at arbitrary speed for some selected positions of a distant observer with respect to the equatorial plane of a Kerr black hole. We discuss glories (mirages) formed near rapidly rotating Kerr black hole horizons and propose a procedure to measure masses and rotation parameters analyzing these forms of mirages. Some time ago Falcke et al. (2000) suggested to search shadows at the Galactic Center. In this paper we present the ...
NASA Astrophysics Data System (ADS)
Yang, Xinjuan; Zhang, Pengjie; Zhang, Jun; Yu, Yu
2015-02-01
The existence of galaxy intrinsic clustering severely hampers the weak lensing reconstruction from cosmic magnification. In Paper I, we proposed a minimal variance estimator to overcome this problem. By utilizing the different dependences of cosmic magnification and galaxy intrinsic clustering on galaxy flux, we demonstrated that the otherwise overwhelming galaxy intrinsic clustering can be significantly suppressed such that lensing maps can be reconstructed with promising accuracy. This procedure relies heavily on the accuracy of determining the galaxy bias from the same data. Paper I adopts an iterative approach, which degrades towards high redshift. The current paper presents an alternative method, improving over Paper I. We prove that the measured galaxy clustering between flux bins allows for simultaneous determination of the lensing power spectrum and the flux dependence of galaxy bias, at this redshift bin. Compared to Paper I, the new approach is not only more straightforward but also more robust. It identifies an ambiguity in determining the galaxy bias and further discovers a mathematically robust way to suppress this ambiguity to negligible level (˜0.1 per cent). The accurately determined galaxy bias can then be applied to the minimal variance estimator proposed in Paper I to improve the lensing map-making. The gain at high redshift is significant. These maps can be used to measure other statistics, such as cluster finding and peak statistics. Furthermore, by including galaxy clustering measurement between different redshift bins, we can also determine the lensing cross power spectrum between these bins, up to a small and correctable multiplicative factor (˜0.2-1 per cent for different redshift bin couples).
NASA Astrophysics Data System (ADS)
Ade, P. A. R.; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Borys, C.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Leitch, E. M.; Linder, E.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Paar, H.; Peloton, J.; Poletti, D.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Rotermund, K.; Schanning, I.; Schenck, D. E.; Sherwin, B. D.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tikhomirov, A.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.; Polarbear Collaboration
2014-04-01
We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0? and indication of the presence of a lensing B-mode signal at a significance of 2.3?. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.
Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Borys, C; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Leitch, E M; Linder, E; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Poletti, D; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Rotermund, K; Schanning, I; Schenck, D E; Sherwin, B D; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tikhomirov, A; Tomaru, T; Wilson, B; Yadav, A; Zahn, O
2014-04-01
We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0? and indication of the presence of a lensing B-mode signal at a significance of 2.3?. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics. PMID:24745402
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.
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.
Perturbative signature of substructures in strong gravitational lenses
C. Alard
2008-03-15
In the perturbative approach, substructures in the lens can be reduced to their effect on the two perturbative fields $f_1$ and $\\frac{d f_0}{d\\theta}$. A simple generic model of elliptical lens with a substructure situated near the critical radius is investigated in details. Analytical expressions are derived for each perturbative field, and basic properties are analyzed. The power spectrum of the fields is well approximated by a power-law, resulting in significant tails at high frequencies. Another feature of the perturbation by a substructure is that the ratio of the power spectrum at order $n$ of the 2 fields $R_n$ is nearly 1. The ratio $R_n \\simeq 1$ is specific to substructures, for instance an higher order distortion ($n>2$) but with auto-similar isophotes will result in $R_n \\propto \\frac{1}{n^2}$. Finally, the problem of reconstructing the perturbative field is investigated. Local field model are implemented and fitted to maximize image similarity in the source plane. The non-linear optimization is greatly facilitated, since in the perturbative approach the circular source solution is always known. Examples of images distortions in the subcritical regime due to substructures are presented, and analyzed for different source shapes. Provided enough images and signal is available, the substructure field can be identified confidently. These results suggests that the perturbative method is an efficient tool to estimate the contribution of substructures to the mass distribution of lenses.
Aspects of electrostatics in a weak gravitational field
NASA Astrophysics Data System (ADS)
Padmanabhan, Hamsa; Padmanabhan, T.
2010-05-01
Several features of electrostatics of point charged particles in a weak, homogeneous, gravitational field are discussed using the Rindler metric to model the gravitational field. Some previously known results are obtained by simpler and more transparent procedures and are interpreted in an intuitive manner. Specifically: (a) We discuss possible definitions of the electric field in curved spacetime (and noninertial frames), argue in favour of a specific definition for the electric field and discuss its properties. (b) We show that the electrostatic potential of a charge at rest in the Rindler frame (which is known and is usually expressed as a complicated function of the coordinates) is expressible as A 0 = q/ ? where ? is the affine parameter distance along the null geodesic from the charge to the field point. (c) This relates well with the result that the electric field lines of a charge coincide with the null geodesics; that is, both light and the electric field lines ‘bend’ in the same manner in a weak gravitational field. We provide a simple proof for this result as well as for the fact that the null geodesics (and field lines) are circles in space. (d) We obtain the sum of the electrostatic forces exerted by one charge on another in the Rindler frame and discuss its interpretation. In particular, we compare the results in the Rindler frame and in the inertial frame and discuss their consistency. (e) We show how a purely electrostatic term in the Rindler frame appears as a radiation term in the inertial frame. (In part, this arises because charges at rest in a weak gravitational field possess additional weight due to their electrostatic energy. This weight is proportional to the acceleration and falls inversely with distance—which are the usual characteristics of a radiation field.) (f) We also interpret the origin of the radiation reaction term by extending our approach to include a slowly varying acceleration. Many of these results might have possible extensions for the case of electrostatics in an arbitrary static geometry.
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.
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.
NASA Astrophysics Data System (ADS)
Ling, Chenxiaoji; Wang, Qiao; Li, Ran; Li, Baojiu; Wang, Jie; Gao, Liang
2015-09-01
We explore the Minkowski functionals (MFs) of weak lensing convergence map to distinguish between f (R ) gravity and the general relativity (GR). The mock weak lensing convergence maps are constructed with a set of high-resolution simulations assuming different gravity models. It is shown that the lensing MFs of f (R ) gravity can be considerably different from that of GR because of the environmentally dependent enhancement of structure formation. We also investigate the effect of lensing noise on our results, and find that it is likely to distinguish F5, F6, and GR gravity models with a galaxy survey of ˜3000 degree2 and with a background source number density of ng=30 arcmin-2 , comparable to an upcoming survey dark energy survey (DES).We also find that the f (R ) signal can be partially degenerate with the effect of changing cosmology, but combined use of other observations, such as the cosmic microwave background (CMB) data, can help break this degeneracy.
Weak Lensing Analysis of IDCS J1426.5+3508: A Massive Galaxy Cluster at z=1.75
NASA Astrophysics Data System (ADS)
Mo, Wenli
2015-08-01
We present a weak lensing study of the galaxy cluster IDCS J1426.5+3508 which, at z=1.75, is the highest redshift strong lensing cluster known and the most distant cluster for which a weak lensing analysis has been undertaken. Using F160W, F814W, and F606W observations with the Hubble Space Telescope, we detect a tangential shear signal out to a radius of ~1 Mpc. Fitting the shear to a Navarro-Frenk-White mass profile, we derive a mass that agrees with previous masses calculated from the Sunyaev-Zel'dovich (SZ) effect, X-ray, and strong lensing observations. The combination of weak lensing and SZ measurements are consistent with the scaling relation observed at low redshift, indicative of minimal evolution in this relation. The cluster concentration is not well-constrained by the weak lensing data alone, but we derive a concentration using the SZ mass measurements as a prior. It has previously been noted that an exceptionally high concentration might afford a means to explain the unexpected existence of a giant arc in this cluster. Our data argue that the concentration is not unusually large, indicating that an alternate solution is required.
NASA Astrophysics Data System (ADS)
Jauzac, Mathilde; Jullo, Eric; Kneib, Jean-Paul; Ebeling, Harald; Leauthaud, Alexie; Ma, Cheng-Jiun; Limousin, Marceau; Massey, Richard; Richard, Johan
2012-11-01
We report the first weak lensing detection of a large-scale filament funnelling matter on to the core of the massive galaxy cluster MACS J0717.5+3745. Our analysis is based on a mosaic of 18 multipassband images obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope, covering an area of ˜10 × 20 arcmin2. We use a weak lensing pipeline developed for the Cosmic Evolution Survey, modified for the analysis of galaxy clusters, to produce a weak lensing catalogue. A mass map is then computed by applying a weak gravitational lensing multiscale reconstruction technique designed to describe irregular mass distributions such as the one investigated here. We test the resulting mass map by comparing the mass distribution inferred for the cluster core with the one derived from strong lensing constraints and find excellent agreement. Our analysis detects the MACS J0717.5+3745 filament within the 3? detection contour of the lensing mass reconstruction, and underlines the importance of filaments for theoretical and numerical models of the mass distribution in the cosmic web. We measure the filament's projected length as ˜4.5 h74-1 Mpc, and its mean density as (2.92 ± 0.66) × 108 h74 M? kpc-2. Combined with the redshift distribution of galaxies obtained after an extensive spectroscopic follow-up in the area, we can rule out any projection effect resulting from the chance alignment on the sky of unrelated galaxy group-scale structures. Assuming plausible constraints concerning the structure's geometry based on its galaxy velocity field, we construct a three-dimensional (3D) model of the large-scale filament. Within this framework, we derive the 3D length of the filament to be 18 h74-1 Mpc. The filament's deprojected density in terms of the critical density of the Universe is measured as (206 ± 46) ?crit, a value that lies at the very high end of the range predicted by numerical simulations. Finally, we study the distribution of stellar mass in the field of MACS J0717.5+3749 and, adopting a mean mass-to-light ratio
A MEASUREMENT OF GRAVITATIONAL LENSING OF THE MICROWAVE BACKGROUND USING SOUTH POLE TELESCOPE DATA
Van Engelen, A.; De Haan, T.; Dobbs, M. A.; Dudley, J.; Holder, G. P.; Keisler, R.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Hoover, S.; Zahn, O.; Aird, K. A.; Cho, H. M.; George, E. M.; Holzapfel, W. L.; Halverson, N. W.; Hou, Z.; and others
2012-09-10
We use South Pole Telescope data from 2008 and 2009 to detect the non-Gaussian signature in the cosmic microwave background (CMB) produced by gravitational lensing and to measure the power spectrum of the projected gravitational potential. We constrain the ratio of the measured amplitude of the lensing signal to that expected in a fiducial {Lambda}CDM cosmological model to be 0.86 {+-} 0.16, with no lensing disfavored at 6.3{sigma}. Marginalizing over {Lambda}CDM cosmological models allowed by the Wilkinson Microwave Anisotropy Probe (WMAP7) results in a measurement of A{sub lens} 0.90 {+-} 0.19, indicating that the amplitude of matter fluctuations over the redshift range 0.5 {approx}< z {approx}< 5 probed by CMB lensing is in good agreement with predictions. We present the results of several consistency checks. These include a clear detection of the lensing signature in CMB maps filtered to have no overlap in Fourier space, as well as a 'curl' diagnostic that is consistent with the signal expected for {Lambda}CDM. We perform a detailed study of bias in the measurement due to noise, foregrounds, and other effects and determine that these contributions are relatively small compared to the statistical uncertainty in the measurement. We combine this lensing measurement with results from WMAP7 to improve constraints on cosmological parameters when compared to those from WMAP7 alone: we find a factor of 3.9 improvement in the measurement of the spatial curvature of the universe, {Omega}{sub k} = -0.0014 {+-} 0.0172; a 10% improvement in the amplitude of matter fluctuations within {Lambda}CDM, {sigma}{sub 8} = 0.810 {+-} 0.026; and a 5% improvement in the dark energy equation of state, w = -1.04 {+-} 0.40. When compared with the measurement of w provided by the combination of WMAP7 and external constraints on the Hubble parameter, the addition of the lensing data improves the measurement of w by 15% to give w -1.087 {+-} 0.096.
Accurate Weak Lensing of Standard Candles. II. Measuring sigma8 with Supernovae
Miguel Quartin; Valerio Marra; Luca Amendola
2014-01-10
Soon the number of type Ia supernova (SN) measurements should exceed 100,000. Understanding the effect of weak lensing by matter structures on the supernova brightness will then be more important than ever. Although SN lensing is usually seen as a source of systematic noise, we will show that it can be in fact turned into signal. More precisely, the non-Gaussianity introduced by lensing in the SN Hubble diagram dispersion depends rather sensitively on the amplitude sigma8 of the matter power spectrum. By exploiting this relation, we are able to predict constraints on sigma8 of 7% (3%) for a catalog of 100,000 (500,000) SNe of average magnitude error 0.12 without having to assume that such intrinsic dispersion is known a priori. The intrinsic dispersion has been assumed to be Gaussian; possible intrinsic non-Gaussianities in the dataset (due to the SN themselves and/or to other transients) could be potentially dealt with by means of additional nuisance parameters describing higher moments of the intrinsic dispersion distribution function. This method is independent of and complementary to the standard methods based on CMB, cosmic shear or cluster abundance observables.
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.
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.
Probing The Dust-To-Gas Ratio of z > 0 Galaxies Through Gravitational Lenses
Xinyu Dai; Christopher S. Kochanek; George Chartas; Smita Mathur
2006-10-12
We report the detection of differential gas column densities in three gravitational lenses, MG0414+0534, HE1104-1805, and PKS1830-211. Combined with the previous differential column density measurements in B1600+434 and Q2237+0305 and the differential extinction measurements of these lenses, we probe the dust-to-gas ratio of a small sample of cosmologically distant normal galaxies. We obtain an average dust-to-gas ratio of E(B-V)/NH =(1.4\\pm0.5) e-22 mag cm^2/atoms with an estimated intrinsic dispersion in the ratio of ~40%. This average dust-to-gas ratio is consistent with the average Galactic value of 1.7e-22 mag cm^2/atoms and the estimated intrinsic dispersion is also consistent with the 30% observed in the Galaxy.
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.
Cosmic discordance: are Planck CMB and CFHTLenS weak lensing measurements out of tune?
NASA Astrophysics Data System (ADS)
MacCrann, Niall; Zuntz, Joe; Bridle, Sarah; Jain, Bhuvnesh; Becker, Matthew R.
2015-08-01
We examine the level of agreement between low-redshift weak lensing data and the cosmic microwave background using measurements from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) and Planck+Wilkinson Microwave Anisotropy Probe (WMAP) polarization. We perform an independent analysis of the CFHTLenS six bin tomography results of Heymans et al. We extend their systematics treatment and find the cosmological constraints to be relatively robust to the choice of non-linear modelling, extension to the intrinsic alignment model and inclusion of baryons. We find that when marginalized in the ?m-?8 plane, the 95 per cent confidence contours of CFHTLenS and Planck+WMAP only just touch, but the discrepancy is less significant in the full six-dimensional parameter space of ? cold dark matter (?CDM). Allowing a massive active neutrino or tensor modes does not significantly resolve the tension in the full n-dimensional parameter space. Our results differ from some in the literature because we use the full tomographic information in the weak lensing data and marginalize over systematics. We note that adding a sterile neutrino to ?CDM brings the 2D marginalized contours into greater overlap, mainly due to the extra effective number of neutrino species, which we find to be 0.88 ± 0.43 (68 per cent) greater than standard on combining the data sets. We discuss why this is not a completely satisfactory resolution, leaving open the possibility of other new physics or observational systematics as contributing factors. We provide updated cosmology fitting functions for the CFHTLenS constraints and discuss the differences from ones used in the literature.
LoCuSS: Weak-lensing mass calibration of galaxy clusters
Okabe, Nobuhiro
2015-01-01
We present weak-lensing mass measurements of 50 X-ray luminous galaxy clusters at $0.15\\le z\\le0.3$, based on high quality observations with Suprime-Cam mounted on the 8.2-m Subaru telescope. We pay close attention to possible systematic biases, aiming to control them at the $\\lt4$ per cent level. The dominant source of systematic bias in weak-lensing measurements of the mass of individual galaxy clusters is contamination of background galaxy catalogues by faint cluster and foreground galaxies. We extend our conservative method for selecting background galaxies with $(V-i')$ colours redder than the red sequence of cluster members to use a colour-cut that depends on cluster-centric radius. This allows us to define background galaxy samples that suffer $\\le1$ per cent contamination, and comprise $13$ galaxies per square arcminute. Thanks to the purity of our background galaxy catalogue, the largest systematic in our measurement is a shape measurement bias of $3$ per cent, that we measure using custom-made simul...
Weak lensing reconstructions in 2D & 3D: implications for cluster studies
Leonard, Adrienne; Starck, Jean-Luc
2015-01-01
We compare the efficiency with which 2D and 3D weak lensing mass mapping techniques are able to detect clusters of galaxies using two state-of-the-art mass reconstruction techniques: MRLens in 2D and GLIMPSE in 3D. We simulate otherwise-empty cluster fields for 96 different virial mass-redshift combinations spanning the ranges $3\\times10^{13}h^{-1}M_\\odot \\le M_{vir}\\le 10^{15}h^{-1}M_\\odot$ and $0.05 \\le z_{\\rm cl} \\le 0.75$, and for each generate 1000 realisations of noisy shear data in 2D and 3D. For each field, we then compute the cluster (false) detection rate as the mean number of cluster (false) detections per reconstruction over the sample of 1000 reconstructions. We show that both MRLens and GLIMPSE are effective tools for the detection of clusters from weak lensing measurements, and provide comparable quality reconstructions at low redshift. At high redshift, GLIMPSE reconstructions offer increased sensitivity in the detection of clusters, yielding cluster detection rates up to a factor of $\\sim 10\\...
The Shear TEsting Programme 2: Factors affecting high precision weak lensing analyses
Richard Massey; Catherine Heymans; Joel Berge; Gary Bernstein; Sarah Bridle; Douglas Clowe; Hakon Dahle; Richard Ellis; Thomas Erben; Marco Hetterscheidt; F. William High; Christopher Hirata; Henk Hoekstra; Patrick Hudelot; Mike Jarvis; David Johnston; Konrad Kuijken; Vera Margoniner; Rachel Mandelbaum; Yannick Mellier; Reiko Nakajima; Stephane Paulin-Henriksson; Molly Peeples; Chris Roat; Alexandre Refregier; Jason Rhodes; Tim Schrabback; Mischa Schirmer; Uros Seljak; Elisabetta Semboloni; Ludovic Van Waerbeke
2006-09-13
The Shear TEsting Programme (STEP) is a collaborative project to improve the accuracy and reliability of weak lensing measurement, in preparation for the next generation of wide-field surveys. We review sixteen current and emerging shear measurement methods in a common language, and assess their performance by running them (blindly) on simulated images that contain a known shear signal. We determine the common features of algorithms that most successfully recover the input parameters. We achieve previously unattained discriminatory precision in our analysis, via a combination of more extensive simulations, and pairs of galaxy images that have been rotated with respect to each other, thus removing noise from their intrinsic ellipticities. The robustness of our simulation approach is also confirmed by testing the relative calibration of methods on real data. Weak lensing measurement has improved since the first STEP paper. Several methods now consistently achieve better than 2% precision, and are still being developed. However, the simulations can now distinguish all methods from perfect performance. Our main concern continues to be the potential for a multiplicative shear calibration bias: not least because this can not be internally calibrated with real data. We determine which galaxy populations are responsible and, by adjusting the simulated observing conditions, we also investigate the effects of instrumental and atmospheric parameters. We have isolated several previously unrecognised aspects of galaxy shape measurement, in which focussed development could provide further progress towards the sub-percent level of precision desired for future surveys. [ABRIDGED
Bonnett, C; Amara, A; Leistedt, B; Becker, M R; Bernstein, G M; Bridle, S; Bruderer, C; Busha, M T; Kind, M Carrasco; Childress, M J; Castander, F J; Chang, C; Crocce, M; Davis, T M; Eifler, T F; Frieman, J; Gangkofner, C; Gaztanaga, E; Glazebrook, K; Gruen, D; Kacprzak, T; King, A; Kwan, J; Lahav, O; Lewis, G; Lidman, C; Lin, H; MacCrann, N; Miquel, R; O'Neill, C R; Palmese, A; Peiris, H V; Refregier, A; Rozo, E; Rykoff, E S; Sadeh, I; Sánchez, C; Sheldon, E; Uddin, S; Wechsler, R H; Zuntz, J; Abbott, T; Abdalla, F B; Allam, S; Armstrong, R; Banerji, M; Bauer, A H; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Carretero, J; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Neto, A Fausti; Fernandez, E; Flaugher, B; Fosalba, P; Gerdes, D W; Gruendl, R A; Honscheid, K; Jain, B; James, D J; Jarvis, M; Kim, A G; Kuehn, K; Kuropatkin, N; Li, T S; Lima, M; Maia, M A G; March, M; Marshall, J L; Martini, P; Melchior, P; Miller, C J; Neilsen, E; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Santiago, B; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Vikram, V; Walker, A R
2015-01-01
We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods -- ANNZ2, BPZ calibrated against BCC-Ufig simulations, SkyNet, and TPZ -- are analysed. For training, calibration, and testing of these methods, we construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evaluated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-zs. From the galaxies in the DES SV shear catalogue, which have mean redshift $0.72\\pm0.01$ over the range $0.3
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.
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.
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.
Properties of Weak Lensing Clusters Detected on Hyper Suprime-Cam 2.3 Square Degree Field
Miyazaki, Satoshi; 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; Karoji, Hiroshi; Aihara, Hiroaki; Murayama, Hitoshi; Takada, Masahiro
2015-01-01
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 S/N ratio of 4.5 are identified on the convergence S/N map of a 2.3 square degree field observed during the early commissioning phase of the camera. Multi-color photometric data is used to generate optically selected clusters using the CAMIRA 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 are evaluated by adopting the Singular Isothemal Sphere (SIS) fit to the tangential shear profiles, yielding virial mass estimates, M500c, of the clusters which range from 2.7x10^13 to 4.4x10^14 solar mass. The number of peaks is considerably larger than the average number expected from LambdaCDM cosmology but this is not extremely unlikely if one takes the large sample variance in t...
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. ...
Cosmological constraints from the 100-deg2 weak-lensing survey
NASA Astrophysics Data System (ADS)
Benjamin, Jonathan; Heymans, Catherine; Semboloni, Elisabetta; van Waerbeke, Ludovic; Hoekstra, Henk; Erben, Thomas; Gladders, Michael D.; Hetterscheidt, Marco; Mellier, Yannick; Yee, H. K. C.
2007-10-01
We present a cosmic shear analysis of the 100-deg2 weak-lensing survey, combining data from the CFHTLS-Wide, RCS, VIRMOS-DESCART and GaBoDS surveys. Spanning ~100 deg2, with a median source redshift z ~ 0.78, this combined survey allows us to place tight joint constraints on the matter density parameter ?m, and the amplitude of the matter power spectrum ?8, finding ?8(?m/0.24)0.59 = 0.84 +/- 0.05. Tables of the measured shear correlation function and the calculated covariance matrix for each survey are included as supplementary material to the online version of this article. The accuracy of our results is a marked improvement on previous work owing to three important differences in our analysis; we correctly account for sample variance errors by including a non-Gaussian contribution estimated from numerical simulations; we correct the measured shear for a calibration bias as estimated from simulated data; we model the redshift distribution, n(z), of each survey from the largest deep photometric redshift catalogue currently available from the CFHTLS-Deep. This catalogue is randomly sampled to reproduce the magnitude distribution of each survey with the resulting survey-dependent n(z) parametrized using two different models. While our results are consistent for the n(z) models tested, we find that our cosmological parameter constraints depend weakly (at the 5 per cent level) on the inclusion or exclusion of galaxies with low-confidence photometric redshift estimates (z > 1.5). These high-redshift galaxies are relatively few in number but contribute a significant weak-lensing signal. It will therefore be important for future weak-lensing surveys to obtain near-infrared data to reliably determine the number of high-redshift galaxies in cosmic shear analyses. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada (NRCC), the Institut des Sciences de l'Univers (INSU) of the Centre National de la Recherche Scientifique (CNRS) and the University of Hawaii (UH). E-mail: jonben@phas.ubc.ca
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.
The time delay in strong gravitational lensing with Gauss-Bonnet correction
Man, Jingyun; Cheng, Hongbo E-mail: hbcheng@ecust.edu.cn
2014-11-01
The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We make a complete analytical derivation of the expression of time delay in presence of Gauss-Bonnet coupling. With respect to Schwarzschild, the time delay decreases as a consequence of the shrinking of the photon sphere. As the coupling increases, the second term in the time delay expansion becomes more relevant. Thus time delay in strong limit encodes some new information about geometry in five-dimensional spacetime with Gauss-Bonnet correction.
NASA Astrophysics Data System (ADS)
Moustakas, Leonidas; Cyr-Racine, Francis-Yan; Keeton, Charles; Benson, Andrew
2015-08-01
The assembly of galactic halos is a direct consequence of the history of accumulation of dark matter, over all mass scales. Through time-domain observations of strong gravitational lenses, in combination with high-resolution static multi-wavelength images from space and from the ground, the spatial and mass function distribution of these dark matter subhalos may be mapped. We present the Bayesian Inference techniques by which the properties of dark matter structure can be mapped over cosmic time, including the best constraints determined to date, and place these in the context of theoretical and numerical expectations of the assembly of galactic halos under Cold and Warm Dark Matter scenarios.
Strong Gravitational Lensing in a Charged Squashed Kaluza- Klein Gödel Black hole
J. Sadeghi; H. Vaez
2013-10-20
In this paper we investigate the strong gravitational lansing in a charged squashed Kaluza-Klein G\\"{o}del black hole. The deflection angle is considered by the logarithmic term proposed by Bozza et al. Then we study the variation of deflection angle and its parameters $\\bar{a}$ and $\\bar{b}$ . We suppose that the supermassive black hole in the galaxy center can be considered by a charged squashed Kaluza-Klein black hole in a G\\"{o}del background and by relation between lensing parameters and observables, we estimate the observables for different values of charge, extra dimension and G\\"{o}del parameters.
Gravitational, lensing, and stability properties of Bose-Einstein condensate dark matter halos
Harko, Tiberiu
2015-01-01
The possibility that dark matter, whose existence is inferred from the study of the galactic rotation curves and from the mass deficit in galaxy clusters, can be in a form of a Bose-Einstein condensate has recently been extensively investigated. In the present work, we consider a detailed analysis of the astrophysical properties of the Bose-Einstein condensate dark matter halos that could provide clear observational signatures and help discriminate between different dark matter models. In the Bose-Einstein condensation model dark matter can be described as a non-relativistic, gravitationally confined Newtonian gas, whose density and pressure are related by a polytropic equation of state with index $n=1$. The mass and the gravitational properties of the condensate halos are obtained in a systematic form, including the mean logarithmic slopes of the density and of the tangential velocity. Furthermore, the lensing properties of the condensate dark matter are also investigated in detail. In particular, a general ...
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.
Strong gravitational lensing in a black-hole spacetime dominated by dark energy
Ding, Chikun; Xiao, Yuanyuan; Jiang, Liqun
2013-01-01
We study the influence of phantom fields on the strong field gravitational lensing. Supposing that the gravitational field of the supermassive central object of the galaxy described by phantom black hole metric, we estimate the numerical values of the coefficients and observations and find that the influences of the phantom fields is a little similar to those of the electric charge in Reissner-Norstr\\"{om} black hole, i.e. deflect angle and angular separation increase with phantom constant $b$. However other observations are contrary to Reissner-Norstr\\"{om} case, which show the influence of dark energy: (i), compressing the usual black hole and more powerfully attracting photons; (ii), making the relativistic Einstein ring more larger than that of the usual black hole; (iii), not weakening the usual relative magnitudes which will facilitate the observation.
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.
SUBARU WEAK-LENSING STUDY OF A2163: BIMODAL MASS STRUCTURE
Okabe, N. [Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), P.O. Box 23-141, Taipei 10617, Taiwan (China); Bourdin, H.; Mazzotta, P. [Dipartimento di Fisica, Universita degli Studi di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Roma (Italy); Maurogordato, S., E-mail: okabe@asiaa.sinica.edu.tw [Universite de Nice Sophia-Antipolis, CNRS, Laboratoire Cassiopee, CNRS, UMR 6202, Observatoire de la Cote d' Azur, BP4229, 06304 Nice Cedex 4 (France)
2011-11-10
We present a weak-lensing analysis of the merging cluster A2163 using Subaru/Suprime-Cam and CFHT/Mega-Cam data and discuss the dynamics of this cluster merger, based on complementary weak-lensing, X-ray, and optical spectroscopic data sets. From two-dimensional multi-component weak-lensing analysis, we reveal that the cluster mass distribution is well described by three main components including the two-component main cluster A2163-A with mass ratio 1:8, and its cluster satellite A2163-B. The bimodal mass distribution in A2163-A is similar to the galaxy density distribution, but appears as spatially segregated from the brightest X-ray emitting gas region. We discuss the possible origins of this gas-dark-matter offset and suggest the gas core of the A2163-A subcluster has been stripped away by ram pressure from its dark matter component. The survival of this gas core from the tidal forces exerted by the main cluster lets us infer a subcluster accretion with a non-zero impact parameter. Dominated by the most massive component of A2163-A, the mass distribution of A2163 is well described by a universal Navarro-Frenk-White profile as shown by a one-dimensional tangential shear analysis, while the singular-isothermal sphere profile is strongly ruled out. Comparing this cluster mass profile with profiles derived assuming intracluster medium hydrostatic equilibrium (H.E.) in two opposite regions of the cluster atmosphere has allowed us to confirm the prediction of a departure from H.E. in the eastern cluster side, presumably due to shock heating. Yielding a cluster mass estimate of M{sub 500} = 11.18{sup +1.64}{sub -1.46} Multiplication-Sign 10{sup 14} h {sup -1} M{sub Sun }, our mass profile confirms the exceptionally high mass of A2163, consistent with previous analyses relying on the cluster dynamical analysis and Y{sub X} mass proxy.
Mask Effects on Cosmological Studies with Weak-lensing Peak Statistics
NASA Astrophysics Data System (ADS)
Liu, Xiangkun; Wang, Qiao; Pan, Chuzhong; Fan, Zuhui
2014-03-01
With numerical simulations, we analyze in detail how the bad data removal, i.e., the mask effect, can influence the peak statistics of the weak-lensing convergence field reconstructed from the shear measurement of background galaxies. It is found that high peak fractions are systematically enhanced because of the presence of masks; the larger the masked area is, the higher the enhancement is. In the case where the total masked area is about 13% of the survey area, the fraction of peaks with signal-to-noise ratio ? >= 3 is ~11% of the total number of peaks, compared with ~7% of the mask-free case in our considered cosmological model. This can have significant effects on cosmological studies with weak-lensing convergence peak statistics, inducing a large bias in the parameter constraints if the effects are not taken into account properly. Even for a survey area of 9 deg2, the bias in (? m , ?8) is already intolerably large and close to 3?. It is noted that most of the affected peaks are close to the masked regions. Therefore, excluding peaks in those regions in the peak statistics can reduce the bias effect but at the expense of losing usable survey areas. Further investigations find that the enhancement of the number of high peaks around the masked regions can be largely attributed to the smaller number of galaxies usable in the weak-lensing convergence reconstruction, leading to higher noise than that of the areas away from the masks. We thus develop a model in which we exclude only those very large masks with radius larger than 3' but keep all the other masked regions in peak counting statistics. For the remaining part, we treat the areas close to and away from the masked regions separately with different noise levels. It is shown that this two-noise-level model can account for the mask effect on peak statistics very well, and the bias in cosmological parameters is significantly reduced if this model is applied in the parameter fitting.
Mask effects on cosmological studies with weak-lensing peak statistics
Liu, Xiangkun; Pan, Chuzhong; Fan, Zuhui; Wang, Qiao
2014-03-20
With numerical simulations, we analyze in detail how the bad data removal, i.e., the mask effect, can influence the peak statistics of the weak-lensing convergence field reconstructed from the shear measurement of background galaxies. It is found that high peak fractions are systematically enhanced because of the presence of masks; the larger the masked area is, the higher the enhancement is. In the case where the total masked area is about 13% of the survey area, the fraction of peaks with signal-to-noise ratio ? ? 3 is ?11% of the total number of peaks, compared with ?7% of the mask-free case in our considered cosmological model. This can have significant effects on cosmological studies with weak-lensing convergence peak statistics, inducing a large bias in the parameter constraints if the effects are not taken into account properly. Even for a survey area of 9 deg{sup 2}, the bias in (? {sub m}, ?{sub 8}) is already intolerably large and close to 3?. It is noted that most of the affected peaks are close to the masked regions. Therefore, excluding peaks in those regions in the peak statistics can reduce the bias effect but at the expense of losing usable survey areas. Further investigations find that the enhancement of the number of high peaks around the masked regions can be largely attributed to the smaller number of galaxies usable in the weak-lensing convergence reconstruction, leading to higher noise than that of the areas away from the masks. We thus develop a model in which we exclude only those very large masks with radius larger than 3' but keep all the other masked regions in peak counting statistics. For the remaining part, we treat the areas close to and away from the masked regions separately with different noise levels. It is shown that this two-noise-level model can account for the mask effect on peak statistics very well, and the bias in cosmological parameters is significantly reduced if this model is applied in the parameter fitting.
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)
2014-12-30
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.
Space Warps: I. Crowd-sourcing the Discovery of Gravitational Lenses
Marshall, Phil; More, Anupreeta; Davis, Chris; More, Surhud; Kapadia, Amit; Parrish, Michael; Snyder, Chris; Wilcox, Julianne; Baeten, Elisabeth; Macmillan, Christine; Cornen, Claude; Baumer, Michael; Simpson, Edwin; Lintott, Chris; Miller, David; Paget, Edward; Simpson, Robert; Smith, Arfon; Kueng, Rafael; Saha, Prasenjit; Collett, Tom; Tecza, Matthias
2015-01-01
We describe Space Warps, a novel gravitational lens discovery service that yields samples of high purity and completeness through crowd-sourced visual inspection. Carefully produced colour composite images are displayed to volunteers via a classi- fication interface which records their estimates of the positions of candidate lensed features. Simulated lenses, and expert-classified images which lack lenses, are inserted into the image stream at random intervals; this training set is used to give the vol- unteers feedback on their performance, as well as to calibrate it in order to allow dynamical updates to the probability of any image they classify to contain a lens. Low probability systems are retired from the site periodically, concentrating the sample towards a set of candidates. Having divided 160 square degrees of Canada-France- Hawaii Telescope Legacy Survey (CFHTLS) imaging into some 430,000 overlapping 84 by 84 arcsecond tiles and displaying them on the site, we were joined by around 37,000 volunteers...
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%.
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.
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.
Gravitational lensing limits on the cosmological constant in a flat universe
NASA Technical Reports Server (NTRS)
Turner, Edwin L.
1990-01-01
Inflationary cosmological theories predict, and some more general aesthetic criteria suggest, that the large-scale spatial curvature of the universe k should be accurately zero (i.e., flat), a condition which is satisfied when the universe's present mean density and the value of the cosmological constant Lambda have certain pairs of values. Available data on the frequency of multiple image-lensing of high-redshift quasars by galaxies suggest that the cosmological constant cannot make a dominant contribution to producing a flat universe. In particular, if the mean density of the universe is as small as the baryon density inferred from standard cosmic nucleosynthesis calculations or as determined from typical dynamical studies of galaxies and galaxy clusters, then a value of Lambda large enough to produce a k = 0 universe would result in a substantially higher frequency of multiple-image lensing of quasars than has been observed so far. Shortcomings of the available lens data and uncertainties concerning galaxy properties allow some possibility of escaping this conclusion, but systematic searches for a gravitational lenses and continuing investigations of galaxy mass distributions should soon provide decisive information. It is also noted that nonzero-curvature cosmological models can account for the observed frequency of galaxy-quasar lens systems and for a variety of other constraints.
Arthur B. Congdon; Charles R. Keeton; C. Erik Nordgren
2008-12-02
Gravitational lensing provides a unique and powerful probe of the mass distributions of distant galaxies. Four-image lens systems with fold and cusp configurations have two or three bright images near a critical point. Within the framework of singularity theory, we derive analytic relations that are satisfied for a light source that lies a small but finite distance from the astroid caustic of a four-image lens. Using a perturbative expansion of the image positions, we show that the time delay between the close pair of images in a fold lens scales with the cube of the image separation, with a constant of proportionality that depends on a particular third derivative of the lens potential. We also apply our formalism to cusp lenses, where we develop perturbative expressions for the image positions, magnifications and time delays of the images in a cusp triplet. Some of these results were derived previously for a source asymptotically close to a cusp point, but using a simplified form of the lens equation whose validity may be in doubt for sources that lie at astrophysically relevant distances from the caustic. Along with the work of Keeton et al. (2005), this paper demonstrates that perturbation theory plays an important role in theoretical lensing studies.
Gravitational Lensing by Black Holes: a comprehensive treatment and the case of the star S2
V. Bozza; L. Mancini
2004-04-27
Light rays passing very close to a black hole may experience very strong deviations. Two geometries were separately considered in the recent literature: a source behind the black hole (standard gravitational lensing); a source in front of the black hole (retro-lensing). In this paper we start from the Strong Field Limit approach to recover both situations under the same formalism, describing not only the two geometries just mentioned but also any intermediate possible configurations of the system source-lens-observer, without any small-angle limitations. This is done for any spherically symmetric black holes and for the equatorial plane of Kerr black holes. In the light of this formalism we revisit the previous literature on retro-lensing, sensibly improving the observational estimates. In particular, for the case of the star S2, we give sharp predictions for the magnitude of the relativistic images and the time of their highest brightness, which should occur at the beginning of year 2018. The observation of such images would open fascinating perspectives on the measure of the physical parameters of the central black hole, including mass, spin and distance.
GLAMER - I. A code for gravitational lensing simulations with adaptive mesh refinement
NASA Astrophysics Data System (ADS)
Metcalf, R. Benton; Petkova, Margarita
2014-12-01
A computer code is described for the simulation of gravitational lensing data. The code incorporates adaptive mesh refinement in choosing which rays to shoot based on the requirements of the source size, location and surface brightness distribution or to find critical curves/caustics. A variety of source surface brightness models are implemented to represent galaxies and quasar emission regions. The lensing mass can be represented by point masses (stars), smoothed simulation particles, analytic halo models, pixelized mass maps or any combination of these. The deflection and beam distortions (convergence and shear) are calculated by modified tree algorithm when haloes, point masses or particles are used and by fast Fourier transform when mass maps are used. The combination of these methods allow for a very large dynamical range to be represented in a single simulation. Individual images of galaxies can be represented in a simulation that covers many square degrees. For an individual strongly lensed quasar, source sizes from the size of the quasar's host galaxy (˜100 kpc) down to microlensing scales (˜10-4 pc) can be probed in a self-consistent simulation. Descriptions of various tests of the code's accuracy are given.
Searching for a Long Cosmic String through the Gravitational Lensing Effect
NASA Astrophysics Data System (ADS)
Shirasaki, Y.; Matsuzaki, Ei-ichi; Mizumoto, Yoshihiko; Kakimoto, Fumio; Ogio, Syoichi; Yasuda, Naoki; Tanaka, Masahiro; Yahagi, Hideki; Nagashima, Masahiro; Kosugi, George
2003-07-01
It has been suggested that cosmic strings produced at a phase transition in the early universe can be the origin of the extremely high energy cosmic rays (EHCR) observed by AGASA above 1020 eV. superheavy cosmic strings with linear mass density of 1022 g/cm can be indirectly observed through the gravitational lensing effect the distant galaxies. The lensing effect by a long straight object can be characterized by a line of double galaxies or quasars with angular separation of about 5 arcsec. We have searched for aligned double objects from the archived data taken by the Subaru Prime Fo cus Camera (Suprime-Cam). The SuprimeCam has a great advantage in observing the wide field of view (30×30 arcmin2 ) with high sensitivity (R<26 400s exposure), so it is suitable for this research. In this paper, we describe the result of simulation study for developing the method of searching the objects lensed by cosmic strings, and present the observational result obtained by this method.
Leauthaud, Alexie [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA 94720 (United States); Finoguenov, Alexis; Cappelluti, Nico; Giodini, Stefania [Max Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garchingbei Muenchen (Germany); Kneib, Jean-Paul; Ilbert, Olivier; Le Fevre, Oliver [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Massey, Richard; Heymans, Catherine [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Rhodes, Jason [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Bundy, Kevin; George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Tinker, Jeremy [Berkeley Center for Cosmological Physics, University of California, Berkeley, CA 94720 (United States); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 E. California Blvd. Pasadena, CA 91125 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Johnston, David E. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208-2900 (United States); Zhang, Yu-Ying [Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, 53121 Bonn (Germany); Ellis, Richard S. [California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Elvis, Martin, E-mail: asleauthaud@lbl.go [Harvard-Smithsonian Center for Astrophysics 60 Garden St., Cambridge, MA 02138 (United States)
2010-01-20
Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray-selected galaxy groups to investigate the scaling relation between X-ray luminosity (L{sub X}) and halo mass (M{sub 200}) where M{sub 200} is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 degrees{sup 2} of contiguous imaging with the Advanced Camera for Surveys to a limiting magnitude of I{sub F814W} = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 x 10{sup -15} erg cm{sup -2} s{sup -1} in the 0.5-2 keV band. The combined depth of these two data sets allows us to probe the lensing signals of X-ray-detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law, M{sub 200} propor to (L{sub X}){sup a}lpha, with a slope of alpha = 0.66 +- 0.14. These results significantly extend the dynamic range for which the halo masses of X-ray-selected structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-L{sub X} relation. The combination of our group data with previously published cluster data demonstrates that the M-L{sub X} relation is well described by a single power law, alpha = 0.64 +- 0.03, over two decades in mass, M{sub 200} approx 10{sup 13.5}-10{sup 15.5} h {sup -1}{sub 72} M{sub sun}. These results are inconsistent at the 3.7sigma level with the self-similar prediction of alpha = 0.75. We examine the redshift dependence of the M-L{sub X} relation and find little evidence for evolution beyond the rate predicted by self-similarity from z approx 0.25 to z approx 0.8.
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.
2015-03-04
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
Weak lensing mass map and peak statistics in Canada-France-Hawaii Telescope Stripe 82 survey
NASA Astrophysics Data System (ADS)
Shan, Huan Yuan; Kneib, Jean-Paul; Comparat, Johan; Jullo, Eric; Charbonnier, Aldée; Erben, Thomas; Makler, Martin; Moraes, Bruno; Van Waerbeke, Ludovic; Courbin, Frédéric; Meylan, Georges; Tao, Charling; Taylor, James E.
2014-08-01
We present a weak lensing mass map covering ˜124 deg2 of the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82). We study the statistics of rare peaks in the map, including peak abundance, the peak-peak correlation functions and the tangential-shear profiles around peaks. We find that the abundance of peaks detected in CS82 is consistent with predictions from a ? cold dark matter cosmological model, once noise effects are properly included. The correlation functions of peaks with different signal-to-noise ratio (SNR) are well described by power laws, and there is a clear cross-correlation between the Sloan Digital Sky Survey III/Constant Mass galaxies and high SNR peaks. The tangential-shear profiles around peaks increase with peak SNR. We fit analytical models to the tangential-shear profiles, including a projected singular isothermal sphere (SIS) model and a projected Navarro, Frenk & White (NFW) model, plus a two-halo term. For the high SNR peaks, the SIS model is rejected at ˜3?. The NFW model plus a two-halo term gives more acceptable fits to the data. Some peaks match the positions of optically detected clusters, while others are relatively dark. Comparing dark and matched peaks, we find a difference in lensing signal of a factor of 2, suggesting that about half of the dark peaks are false detections.
SIMULATIONS OF WIDE-FIELD WEAK LENSING SURVEYS. I. BASIC STATISTICS AND NON-GAUSSIAN EFFECTS
Sato, Masanori; Takahashi, Ryuichi; Matsubara, Takahiko; Sugiyama, Naoshi; Hamana, Takashi; Takada, Masahiro; Yoshida, Naoki
2009-08-20
We study the lensing convergence power spectrum and its covariance for a standard {lambda}CDM cosmology. We run 400 cosmological N-body simulations and use the outputs to perform a total of 1000 independent ray-tracing simulations. We compare the simulation results with analytic model predictions. The semianalytic model based on Smith et al. fitting formula underestimates the convergence power by {approx} 30% at arcmin angular scales. For the convergence power spectrum covariance, the halo model reproduces the simulation results remarkably well over a wide range of angular scales and source redshifts. The dominant contribution at small angular scales comes from the sample variance due to the number fluctuations of halos in a finite survey volume. The signal-to-noise ratio for the convergence power spectrum is degraded by the non-Gaussian covariances by up to a factor of 5 for a weak lensing survey to z{sub s} {approx} 1. The probability distribution of the convergence power spectrum estimators, among the realizations, is well approximated by a {chi}{sup 2} distribution with broadened variance given by the non-Gaussian covariance, but has a larger positive tail. The skewness and kurtosis have non-negligible values especially for a shallow survey. We argue that a prior knowledge on the full distribution may be needed to obtain an unbiased estimate on the ensemble-averaged band power at each angular scale from a finite volume survey.