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1

NASA Astrophysics Data System (ADS)

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.

Pires, Sandrine; Starck, Jean-Luc; Leonard, Adrienne; Réfrégier, Alexandre

2012-03-01

2

Weak gravitational lensing with SKA

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.

Peter Schneider

1999-07-12

3

Galaxy Halo Masses from Weak Gravitational Lensing

NASA Astrophysics Data System (ADS)

In this review, I discuss the use of galaxy-galaxy weak lensing measurements to study the masses of dark matter halos in which galaxies reside. After summarizing how weak gravitational lensing measurements can be interpreted in terms of halo mass, I review measurements that were used to derive the relationship between optical galaxy mass tracers, such as stellar mass or luminosity, and dark matter halo mass. Measurements of galaxy-galaxy lensing from the past decade have led to increasingly tight constraints on the connection between dark matter halo mass and optical mass tracers, including both the mean relationships between these quantities and the intrinsic scatter between them. I also review some of the factors that can complicate analysis, such as the choice of modeling procedure, and choices made when dividing up samples of lens galaxies.

Mandelbaum, Rachel

2015-04-01

4

Weak gravitational lensing of intrinsically aligned galaxies

NASA Astrophysics Data System (ADS)

Subject of this paper is the weak lensing effect on galaxies that show intrinsically correlated ellipticities. In our model, we investigate the distortion of the ellipticity field if the galaxies experience an apparent shift in their position by weak lensing deflection and compare this effect to the shearing effect induced by tidal fields. Starting with a derivation of intrinsic ellipticity spectra by employing a tidal torquing model generating galactic angular momenta, we model the galaxy ellipticity by assuming that the galactic disc forms perpendicularly to the host halo angular momentum direction and derives intrinsic ellipticity E-mode and B-mode spectra from the angular momentum statistics. The lensing effect on the ellipticity field is modelled by employing the methodology developed in the framework of lensing of the cosmic microwave background polarization. For Euclid, ellipticity correlations are altered by lensing deflection on multipoles ? ? 1000 by ˜5 per cent for the ellipticity E modes and ˜30 per cent for the B modes, while a shallower survey would exhibit larger changes on larger angular scales. In addition to the convolving effect of lensing on the ellipticity spectra, we investigate the E/B-mode conversion and discuss the possibility of measuring correlations between different multipoles, which is evoked by the homogeneity breaking effect of the lensing displacement. Our conclusion is that although shape correlations generated by weak gravitational shear is dominant, the shifting effect due to lensing is shaping the ellipticity spectra on small angular scales and causing a number of interesting phenomena, which might be observable by future surveys.

Giahi-Saravani, Aram; Schäfer, Björn Malte

2014-01-01

5

Poisson equation for weak gravitational lensing

Using the Newman and Penrose [E. T. Newman and R. Penrose, J. Math. Phys. (N.Y.) 3, 566 (1962).] spin-coefficient formalism, we examine the full Bianchi identities of general relativity in the context of gravitational lensing, where the matter and space-time curvature are projected into a lens plane perpendicular to the line of sight. From one component of the Bianchi identity, we provide a rigorous, new derivation of a Poisson equation for the projected matter density where the source term involves second derivatives of the observed weak gravitational lensing shear. We also show that the other components of the Bianchi identity reveal no new results. Numerical integration of the Poisson equation in test cases shows an accurate mass map can be constructed from the combination of a ground-based, wide-field image and a Hubble Space Telescope image of the same system.

Kling, Thomas P.; Campbell, Bryan [Department of Physics, Bridgewater State College, Bridgewater, Massachusetts 02325 (United States)

2008-06-15

6

Weak Gravitational Lensing by Large-Scale Structure

Weak gravitational lensing provides a unique method to map directly the distribution of dark matter in the universe and to measure cosmological parameters. This cosmic-shear technique is based on the measurement of the weak distortions that lensing induces in the shape of background galaxies as photons travel through large-scale structures. This technique is now widely used to measure the mass

Alexandre Refregier

2003-01-01

7

Atomic Inference from Weak Gravitational Lensing Data

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.

Marshall, Phil; /KIPAC, Menlo Park

2005-12-14

8

Weak Gravitational Lensing in Fourth Order Gravity

For a general class of analytic $f(R,R_{\\alpha\\beta}R^{\\alpha\\beta},R_{\\alpha\\beta\\gamma\\delta}R^{\\alpha\\beta\\gamma\\delta})$ we discuss the gravitational lensing in the Newtonian Limit of theory. From the properties of Gauss Bonnet invariant it is successful to consider only two curvature invariants between the Ricci and Riemann tensor. Then we analyze the dynamics of photon embedded in a gravitational field of a generic $f(R,R_{\\alpha\\beta}R^{\\alpha\\beta})$-Gravity. The metric is time independent and spherically symmetric. The metric potentials are Schwarzschild-like, but there are two additional Yukawa terms linked to derivatives of $f$ with respect to two curvature invariants. Considering the case of a point-like lens, and after of a generic matter distribution of lens, we study the deflection angle and the images angular position. Though the additional Yukawa terms in the gravitational potential modifies dynamics with respect to General Relativity, the geodesic trajectory of photon is unaffected by the modification in the action by only $f(R)$. While we find different results (deflection angle smaller than one of General Relativity) only thank to introduction of a generic function of Ricci tensor square. Finally we can affirm the lensing phenomena for all $f(R)$-Gravities are equal to the ones known from General Relativity. We conclude the paper showing and comparing the deflection angle and image positions for $f(R,R_{\\alpha\\beta}R^{\\alpha\\beta})$-Gravity with respect to ones of General Relativity.

A. Stabile; An. Stabile

2011-12-21

9

Clustering of Faint Galaxies: $\\\\w $, Induced by Weak Gravitational Lensing

Weak gravitational lensing by large scale structure affects the number counts of faint galaxies through the ``magnification bias'' and thus affects the measurement of the angular two-point correlation function $\\\\w $. At faint magnitudes the clustering amplitude will decrease differently with limiting magnitude than expected from Limber's equation. The amplitude will hit a minimum and then rise with limiting magnitude.

Jens Verner Villumsen; Max Planck; Karl Schwarzschild-Str

1995-01-01

10

Studying the LSS through weak gravitational lensing maps

Weak gravitational lensing is a promising tool for the study of the mass distribution in the Universe. Here we report some partial results that show how lensing maps can be used to differentiate between cosmological models. We pay special attention to the role of noise and smoothing. As an application, we use mock convergence fields constructed from N-body simulations of the large-scale structure for three historically important cosmological models. Various map analyses are used, including Minkowski functionals, and their ability to differentiate the models is calculated and discussed.

Antonio C. C. Guimarães

2001-12-10

11

The Intrinsic Alignment of Galaxies and Weak Gravitational Lensing

NASA Astrophysics Data System (ADS)

Galaxy intrinsic alignments (IA) are correlations between intrinsic galaxy shapes and the surrounding density field. These correlations can bias weak gravitational lensing measurements and are the most significant source of astrophysical uncertainty for the next generation of lensing experiments. Despite its importance, IA is poorly understood. The work presented here aims to improve our understanding through both modeling and measuring IA. First, we examine the most frequently employed IA model, the tidal (linear) alignment model, in which galaxy shapes are closely correlated with the surrounding gravitational tidal field. The tidal alignment model provides an accurate description of IA on large scales (r > 10 Mpc/h), as measured for luminous red galaxies in the Sloan Digital Sky Survey (SDSS). The IA amplitude for these objects, as determined in this analysis, will allow predictions for possible contamination in current and future lensing studies. We explore several ways in which the model could be improved and expanded, including how the relationship between galaxies and their host halos can modulate the strength of IA, as well as relevant effects on smaller scales (r < 10 Mpc/h). Second, we develop a method to separate IA from galaxy-galaxy lensing measurements using photometric redshift information. This technique allows the removal of contamination from the desired lensing signal while also providing a probe of IA in different galaxy populations. We employ this method to constrain fractional IA contamination in the SDSS lensing sample to 1-2%, finding that it is a subdominant source of uncertainty at the current level of statistical precision. These developments in both modeling and measurement techniques can be applied in future lensing analyses to mitigate potential contamination from IA. Such considerations will become more important as statistical precision continues to improve.

Blazek, Jonathan

2014-01-01

12

LIGHT ON DARK MATTER WITH WEAK GRAVITATIONAL LENSING 1 Light on Dark Matter

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 higher energy theories- called "dark matter" (20-21%) and by an even more mysterious term, described

Starck, Jean-Luc

13

Detection of (dark) matter concentrations via weak gravitational lensing

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.

Peter Schneider

1996-01-16

14

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

J. Anthony Tyson; David Kirkman; Ian Dell'Antonio; Gary Bernstein; David M. Wittman

2000-01-01

15

Gravitational lensing beyond the weak-field approximation

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.

Perlick, Volker, E-mail: perlick@zarm.uni-bremen.de [ZARM, University of Bremen, 28359 Bremen (Germany)

2014-01-14

16

Gravitational lensing beyond the weak-field approximation

NASA Astrophysics Data System (ADS)

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.

Perlick, Volker

2014-01-01

17

Testing dark energy paradigms with weak gravitational lensing R. Ali Vanderveld,1

Testing dark energy paradigms with weak gravitational lensing R. Ali Vanderveld,1 Michael J all quintessence models, with or without early dark energy. We further explore how uncertainties a given dark energy paradigm, such as the standard CDM model of cold dark matter and a cosmological

Hu, Wayne

18

Weak gravitational lensing as a method to constrain unstable dark matter

The nature of the dark matter remains a mystery. The possibility of an unstable dark matter particle decaying to invisible daughter particles has been explored many times in the past few decades. Meanwhile, weak gravitational lensing shear has gained a lot of attention as a probe of dark energy, though it was previously considered a dark matter probe. Weak lensing is a useful tool for constraining the stability of the dark matter. In the coming decade a number of large galaxy imaging surveys will be undertaken and will measure the statistics of cosmological weak lensing with unprecedented precision. Weak lensing statistics are sensitive to unstable dark matter in at least two ways. Dark matter decays alter the matter power spectrum and change the angular diameter distance-redshift relation. We show how measurements of weak lensing shear correlations may provide the most restrictive, model-independent constraints on the lifetime of unstable dark matter. Our results rely on assumptions regarding nonlinear evolution of density fluctuations in scenarios of unstable dark matter and one of our aims is to stimulate interest in theoretical work on nonlinear structure growth in unstable dark matter models.

Wang Meiyu; Zentner, Andrew R. [Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)

2010-12-15

19

Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements

NASA Astrophysics Data System (ADS)

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.

Seshadri, S.; Shapiro, C.; Goodsall, T.; Fucik, J.; Hirata, C.; Rhodes, J. D.; Rowe, B. T. P.; Smith, R. M.

2013-09-01

20

Weak gravitational lensing can be used to directly measure the mass along a line-of-sight without any dependence on the dynamical state of the mass, and thus can be used to measure the masses of clusters even if they are not relaxed. One common technique used to measure cluster masses is fitting azimuthally-averaged gravitational shear profiles with a spherical mass model. In this paper we quantify how asphericity and projected substructure in clusters can affect the virial mass and concentration measured with this technique by simulating weak lensing observations on 30 independent lines-of-sights through each of four high-resolution N-body cluster simulations. We find that the variations in the measured virial mass and concentration are of a size similar to the error expected in ideal weak lensing observations and are correlated, but that the virial mass and concentration of the mean shear profile agree well with that measured in three dimensional models of the clusters. The dominant effect causing the variations is the proximity of the line-of-sight to the major axis of the 3-D cluster mass distribution, with projected substructure only causing minor perturbations in the measured concentration. Finally we find that the best-fit "universal" CDM models used to fit the shear profiles over-predict the surface density of the clusters due to the cluster mass density falling off faster than the r^{-3} model assumption.

D. Clowe; G. De Lucia; L. King

2004-02-12

21

Weak Gravitational Lensing as a Probe of Physical Properties of Substructures in Dark Matter Halos

NASA Astrophysics Data System (ADS)

We propose a novel method to select satellite galaxies in outer regions of galaxy groups or clusters using weak gravitational lensing. The method is based on the theoretical expectation that the tangential shear pattern around satellite galaxies would appear with negative values at an offset distance from the center of the main halo. We can thus locate the satellite galaxies statistically with an offset distance of several lensing smoothing scales by using the standard reconstruction of surface mass density maps from weak lensing observation. We test the idea using high-resolution cosmological simulations. We show that subhalos separated from the center of the host halo are successfully located even without assuming the position of the center. For a number of such subhalos, the characteristic mass and offset length can be also estimated on a statistical basis. We perform a Fisher analysis to show how well upcoming weak lensing surveys can constrain the mass density profile of satellite galaxies. In the case of the Large Synoptic Survey Telescope with a sky coverage of 20,000 deg2, the mass of the member galaxies in the outer region of galaxy clusters can be constrained with an accuracy of ~0.1 dex for galaxy clusters with mass 1014 h –1 M ? at z = 0.15. Finally we explore the detectability of tidal stripping features for subhalos having a wide range of masses of 1011-1013 h –1 M ?.

Shirasaki, Masato

2015-02-01

22

Resource Letter GL-1: Gravitational Lensing

NASA Astrophysics Data System (ADS)

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.

Treu, Tommaso; Marshall, Philip J.; Clowe, Douglas

2012-09-01

23

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.

Hirata, Christopher M. [Caltech M/C 350-17, Pasadena, California 91125 (United States); Holz, Daniel E. [Theoretical Division, MS-B227, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Cutler, Curt [Jet Propulsion Laboratory, M/S 169-327, 4800 Oak Grove Drive, Pasadena, California 91109 (United States)

2010-06-15

24

Weyl fluid dark matter model tested on the galactic scale by weak gravitational lensing

NASA Astrophysics Data System (ADS)

The higher-dimensional Weyl curvature induces on the brane a new source of gravity. This Weyl fluid of geometrical origin (reducing in the spherically symmetric, static configuration to a dark radiation and dark pressure) modifies spacetime geometry around galaxies and has been shown to explain the flatness of galactic rotation curves. Independent observations for discerning between the Weyl fluid and other dark matter models are necessary. Gravitational lensing could provide such a test. Therefore we study null geodesics and weak gravitational lensing in the dark radiation dominated region of galaxies in a class of spherically symmetric braneworld metrics. We find that the lensing profile in the braneworld scenario is distinguishable from dark matter lensing, despite both the braneworld scenario and dark matter models fitting the rotation curve data. In particular, in the asymptotic regions, light deflection is 18% enhanced as compared to dark matter halo predictions. For a linear equation of state of the Weyl fluid, we further find a critical radius below which braneworld effects reduce, while above it they amplify light deflection. This is in contrast to any dark matter model, the addition of which always increases the deflection angle.

Wong, K. C.; Harko, T.; Cheng, K. S.; Gergely, L. Á.

2012-08-01

25

Statistical properties of the convergence due to weak gravitational lensing by non-linear structures

Density fluctuations in the matter distribution lead to distortions of the images of distant galaxies through weak gravitational lensing effects. This provides an efficient probe of the cosmological parameters and of the density field. In this article, we investigate the statistical properties of the convergence due to weak gravitational lensing by non-linear structures (i.e. we consider small angular windows $\\theta \\la 1'$). Previous studies have shown how to relate the second and third order moments of the convergence to those of the density contrast while models based on the Press-Schechter prescription provide an estimate of the tail of $P(\\kappa)$. Here we present a method to obtain an estimate of the full p.d.f. of the convergence $P(\\kappa)$. It is based on a realistic description of the density field which applies to overdense as well as underdense regions. We show that our predictions agree very well with the results of N-body simulations for the convergence. This could allow one to derive the cosmological parameters $(\\Omega_m,\\Omega_{\\Lambda})$ as well as the full p.d.f. $P(\\delta_R)$ of the density contrast itself in the non-linear regime from observations. Hence this gives a very powerfull tool to constrain scenarios of structure formation.

P. Valageas

2000-05-12

26

Improving three-dimensional mass mapping with weak gravitational lensing using galaxy clustering

NASA Astrophysics Data System (ADS)

Context. The weak gravitational lensing distortion of distant galaxy images (defined as sources) probes the projected large-scale matter distribution in the Universe. The availability of redshift information in galaxy surveys also allows us to recover the radial matter distribution to a certain degree. Aims: To improve quality in the mass mapping, we combine the lensing information with the spatial clustering of a population of galaxies (defined as tracers) that trace the matter density with a known galaxy bias. Methods: We construct a minimum-variance estimator for the 3D matter density that incorporates the angular distribution of galaxy tracers, which are coarsely binned in redshift. Merely the second-order bias of the tracers has to be known, which can in principle be self-consistently constrained in the data by lensing techniques. This synergy introduces a new noise component because of the stochasticity in the matter-tracer density relation. We give a description of the stochasticity noise in the Gaussian regime, and we investigate the estimator characteristics analytically. We apply the estimator to a mock survey based on the Millennium Simulation. Results: The estimator linearly mixes the individual lensing mass and tracer number density maps into a combined smoothed mass map. The weighting in the mix depends on the signal-to-noise ratio (S/N) of the individual maps and the correlation, R, between the matter and galaxy density. The weight of the tracers can be reduced by hand. For moderate mixing, the S/N in the mass map improves by a factor ~2-3 for R ? 0.4. Importantly, the systematic offset between a true and apparent mass peak distance (defined as z-shift bias) in a lensing-only map is eliminated, even for weak correlations of R ~ 0.4. Conclusions: If the second-order bias of tracer galaxies can be determined, the synergy technique potentially provides an option to improve redshift accuracy and completeness of the lensing 3D mass map. Herein, the aim is to visualise the spatial distribution of cluster-sized mass peaks. Our noise description of the estimator is accurate in the linear, Gaussian regime. However, its performance on sub-degree scales depends on the details in the galaxy bias mechanism and, hence, on the choice of the tracer population. Nonetheless, we expect that the mapping technique yields qualitatively reasonable results even for arcmin smoothing scales, as observed when this technique is applied to the mock survey with two different tracer populations.

Simon, Patrick

2013-12-01

27

Cosmological Applications of Gravitational Lensing

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.

Peter Schneider

1995-12-08

28

Gravitational Lensing by Kerr-Sen Dilaton-Axion Black Hole in the Weak Deflection Limit

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.

Gyulchev, G. N. [Department of Physics, Biophysics and Roentgenology, Faculty of Medicine, St. Kliment Ohridski, University of Sofia, 1 Kozyak str., 1407 Sofia (Bulgaria); Yazadjiev, S. S. [Department of Theoretical Physics, Faculty of Physics, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia (Bulgaria)

2010-11-25

29

Probing Dark Energy via Weak Gravitational Lensing with the SuperNova Acceleration Probe (SNAP)

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 companion 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.

SNAP Collaboration

2005-07-19

30

Constraints on the shapes of galaxy dark matter haloes from weak gravitational lensing

NASA Astrophysics Data System (ADS)

We study the shapes of galaxy dark matter haloes by measuring the anisotropy of the weak gravitational lensing signal around galaxies in the second Red-sequence Cluster Survey (RCS2). We determine the average shear anisotropy within the virial radius for three lens samples: the "all" sample, which contains all galaxies with 19 < mr' < 21.5, and the "red" and "blue" samples, whose lensing signals are dominated by massive low-redshift early-type and late-type galaxies, respectively. To study the environmental dependence of the lensing signal, we separate each lens sample into an isolated and clustered part and analyse them separately. We address the impact of several complications on the halo ellipticity measurement, including PSF residual systematics in the shape catalogues, multiple deflections, and the clustering of lenses. We estimate that the impact of these is small for our lens selections. Furthermore, we measure the azimuthal dependence of the distribution of physically associated galaxies around the lens samples. We find that these satellites preferentially reside near the major axis of the lenses, and constrain the angle between the major axis of the lens and the average location of the satellites to ??? = 43.7° ± 0.3° for the "all" lenses, ??? = 41.7° ± 0.5° for the "red" lenses and ??? = 42.0° ± 1.4° for the "blue" lenses. We do not detect a significant shear anisotropy for the average "red" and "blue" lenses, although for the most elliptical "red" and "blue" galaxies it is marginally positive and negative, respectively. For the "all" sample, we find that the anisotropy of the galaxy-mass cross-correlation function ?f - f45? = 0.23 ± 0.12, providing weak support for the view that the average galaxy is embedded in, and preferentially aligned with, a triaxial dark matter halo. Assuming an elliptical Navarro-Frenk-White profile, we find that the ratio of the dark matter halo ellipticity and the galaxy ellipticity fh = eh/eg = 1.50-1.01+1.03, which for a mean lens ellipticity of 0.25 corresponds to a projected halo ellipticity of eh = 0.38-0.25+0.26 if the halo and the lens are perfectly aligned. For isolated galaxies of the "all" sample, the average shear anisotropy increases to ?f-f45? = 0.51-0.25+0.26 and fh = 4.73-2.05+2.17, whilst for clustered galaxies the signal is consistent with zero. These constraints provide lower limits on the average dark matter halo ellipticity, as scatter in the relative position angle between the galaxies and the dark matter haloes is expected to reduce the shear anisotropy by a factor ~2.

van Uitert, E.; Hoekstra, H.; Schrabback, T.; Gilbank, D. G.; Gladders, M. D.; Yee, H. K. C.

2012-09-01

31

Probing Dark Energy via Weak Gravitational Lensing with the Supernova Acceleration Probe (SNAP)

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.

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

32

NASA Technical Reports Server (NTRS)

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.

Turner, Edwin L.

1989-01-01

33

Dynamic velocity dispersion and mass estimates are given for a sample of five X-ray luminous rich clusters of galaxies at intermediate redshifts (z~0.3) drawn from a sample of 39 clusters for which we have obtained gravitational lens mass estimates. The velocity dispersions are determined from between 9 and 20 redshifts measured with the LDSS spectrograph of the William Herschel Telescope, and virial radii are determined from imaging using the UH8K mosaic CCD camera on the University of Hawaii 2.24m telescope. Including clusters with velocity dispersions taken from the literature, we have velocity dispersion estimates for 12 clusters in our gravitational lensing sample. For this sample we compare the dynamical velocity dispersion estimates with our estimates of the velocity dispersions made from gravitational lensing by fitting a singular isothermal sphere profile to the observed tangential weak lensing distortion as a function of radius. In all but two clusters, we find a good agreement between the velocity dispersion estimates based on spectroscopy and on weak lensing.

Ragnvald J. Irgens; Per B. Lilje; Haakon Dahle; S. J. Maddox

2002-08-01

34

Cosmology with weak lensing surveys.

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

Munshi, Dipak; Valageas, Patrick

2005-12-15

35

CFHTLenS: the relation between galaxy dark matter haloes and baryons from weak gravitational lensing

NASA Astrophysics Data System (ADS)

We present a study of the relation between dark matter halo mass and the baryonic content of their host galaxies, quantified through galaxy luminosity and stellar mass. Our investigation uses 154 deg2 of Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) lensing and photometric data, obtained from the CFHT Legacy Survey. To interpret the weak lensing signal around our galaxies, we employ a galaxy-galaxy lensing halo model which allows us to constrain the halo mass and the satellite fraction. Our analysis is limited to lenses at redshifts between 0.2 and 0.4, split into a red and a blue sample. We express the relationship between dark matter halo mass and baryonic observable as a power law with pivot points of 10^{11} h_{70}^{-2} L_{{?}} and 2× 10^{11} h_{70}^{-2} M_{{?}} for luminosity and stellar mass, respectively. For the luminosity-halo mass relation, we find a slope of 1.32 ± 0.06 and a normalization of 1.19^{+0.06}_{-0.07}× 10^{13} h_{70}^{-1} M_{{?}} for red galaxies, while for blue galaxies the best-fitting slope is 1.09^{+0.20}_{-0.13} and the normalization is 0.18^{+0.04}_{-0.05}× 10^{13} h_{70}^{-1} M_{{?}}. Similarly, we find a best-fitting slope of 1.36^{+0.06}_{-0.07} and a normalization of 1.43^{+0.11}_{-0.08}× 10^{13} h_{70}^{-1} M_{{?}} for the stellar mass-halo mass relation of red galaxies, while for blue galaxies the corresponding values are 0.98^{+0.08}_{-0.07} and 0.84^{+0.20}_{-0.16}× 10^{13} h_{70}^{-1} M_{{? }}. All numbers convey the 68 per cent confidence limit. For red lenses, the fraction which are satellites inside a larger halo tends to decrease with luminosity and stellar mass, with the sample being nearly all satellites for a stellar mass of 2× 109 h_{70}^{-2} M_{{?}}. The satellite fractions are generally close to zero for blue lenses, irrespective of luminosity or stellar mass. This, together with the shallower relation between halo mass and baryonic tracer, is a direct confirmation from galaxy-galaxy lensing that blue galaxies reside in less clustered environments than red galaxies. We also find that the halo model, while matching the lensing signal around red lenses well, is prone to overpredicting the large-scale signal for faint and less massive blue lenses. This could be a further indication that these galaxies tend to be more isolated than assumed.

Velander, Malin; van Uitert, Edo; Hoekstra, Henk; Coupon, Jean; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bonnett, Christopher; Fu, Liping; Giodini, Stefania; Hudson, Michael J.; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta

2014-01-01

36

NASA Astrophysics Data System (ADS)

Euclid is the ESA mission to map the geometry of the dark universe. It uses weak gravitational lensing, which requires the accurate measurement of galaxy shapes over a large area in the sky. Radiation damage in the 36 Charge-Coupled Devices (CCDs) composing the Euclid visible imager focal plane has already been identified as a major contributor to the weak-lensing error budget; radiation-induced charge transfer inefficiency (CTI) distorts the galaxy images and introduces a bias in the galaxy shape measurement. We designed a laboratory experiment to project Euclid-like sky images onto an irradiated Euclid CCD. In this way - and for the first time - we are able to directly assess the effect of CTI on the Euclid weak-lensing measurement free of modelling uncertainties. We present here the experiment concept, setup, and first results. The results of such an experiment provide test data critical to refine models, design and test the Euclid data processing CTI mitigation scheme, and further optimize the Euclid CCD operation.

Prod'homme, T.; Verhoeve, P.; Oosterbroek, T.; Boudin, N.; Short, A.; Kohley, R.

2014-07-01

37

Aberration in gravitational lensing

It is known that a relative translational motion between the deflector and the observer affects gravitational lensing. In this paper, a lens equation is obtained to describe such effects on actual lensing observables. Results can be easily interpreted in terms of aberration of light rays. Both radial and transverse motions with relativistic velocities are considered. The lens equation is derived by first considering geodesic motion of photons in the rest-frame Schwarzschild space-time of the lens, and, then, light-ray detection in the moving observer's frame. Because of the transverse motion images are displaced and distorted in the observer's celestial sphere, whereas the radial velocity along the line of sight causes an effective rescaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still pointlike. Either for null transverse motion or up to linear order in velocities, the critical curve is still a circle with its radius corrected by a factor (1+z{sub d}) with respect to the static case, z{sub d} being the relativistic Doppler shift of the deflector. From the observational point of view, the orbital motion of the Earth can cause potentially observable corrections of the order of the {mu}arcsec in lensing towards the supermassive black hole at the Galactic center. On a cosmological scale, tangential peculiar velocities of a cluster of galaxies bring about a typical flexion in images of background galaxies in the weak lensing regime but future measurements seem to be too challenging.

Sereno, M. [Institut fuer Theoretische Physik, Universitaet Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland)

2008-10-15

38

We report the first confirmation of colour-selected galaxy cluster candidates by means of weak gravitational lensing. Significant lensing signals were identified in the course of the shear-selection programme of dark matter haloes in the Garching-Bonn Deep Survey, which currently covers 20 square degrees of deep, high-quality imaging data on the southern sky. The detection was made in a field that was previously covered by the ESO Imaging Survey (EIS) in 1997. A highly significant shear-selected mass-concentration perfectly coincides with the richest EIS cluster candidate at z~0.2, thus confirming its cluster nature. Several other shear patterns in the field can also be identified with cluster candidates, one of which could possibly be part of a filament at z~0.45.

Mischa Schirmer; Thomas Erben; Peter Schneider; Christian Wolf; Klaus Meisenheimer

2004-01-12

39

What is Gravitational Lensing?

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.

Alexie Leauthaud and Reiko Nakajima

2010-01-08

40

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component {Omega}{sub X} at greater than 99% confidence for an equation-of-state parameter -2.5 {<=} w {<=} -0.1. For the case w = -1, we find a value for the cosmological constant density parameter {Omega}{sub {Lambda}} = 0.85{sup +0.044}{sub -}0{sub .19} (68% CL) and detect cosmic acceleration (q{sub 0} < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys.

Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Massey, Richard J. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Rhodes, Jason; Ellis, Richard; Scoville, Nick [California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kitching, Thomas D. [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Ilbert, Olivier; Kneib, Jean-Paul [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Jullo, Eric [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Koekemoer, Anton M., E-mail: taylor@uwaterloo.ca [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2012-04-20

41

Cosmology with Weak Lensing Surveys

Weak gravitational lensing surveys measure the distortion of the image of distant sources due to the deflections of light rays by the fluctuations of the gravitational potential along the line of sight. Since they probe the non-linear matter power spectrum itself at medium redshift such surveys are complimentary to both galaxy surveys (which follow stellar light) and cosmic microwave background observations (which probe the linear regime at high redshift). Ongoing CMB experiments such as WMAP and the future Planck satellite mission will measure the standard cosmological parameters with unprecedented accuracy. The focus of attention will then shift to understanding the nature of dark matter and vacuum energy: several recent studies suggest that lensing is the best method for constraining the dark energy equation of state. During the next 5 year period ongoing and future weak lensing surveys such as the Joint Dark Energy Mission (JDEM, e.g. SNAP) or the Large-aperture Synoptic Survey Telescope (LSST) will play a major role in advancing our understanding of the universe in this direction. In this review article we describe various aspects of weak lensing surveys and how they can help us in understanding our universe.

Dipak Munshi; Patrick Valageas

2005-09-27

42

Arcs from gravitational lensing

NASA Technical Reports Server (NTRS)

The proposal made by Paczynski (1987) that the arcs of blue light found recently in two cluster cores are gravitationally lensed elongated images of background galaxies is investigated. It is shown that lenses that are circularly symmetric in projection produce pairs of arcs, in conflict with the observations. However, more realistic asymmetric lenses produce single arcs, which can become as elongated as the observed ones whenever the background galaxy is located on or close to a cusp caustic. Detailed computer simulations of lensing by clusters using a reasonable model of the mass distribution are presented. Elongated and curved lensed images longer than 10 arcsec occur in 12 percent of the simulated clusters. It is concluded that the lensing hypothesis must be taken seriously.

Grossman, Scott A.; Narayan, Ramesh

1988-01-01

43

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.

Dragan Huterer

2002-01-01

44

NASA Astrophysics Data System (ADS)

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component ? X at greater than 99% confidence for an equation-of-state parameter -2.5 <= w <= -0.1. For the case w = -1, we find a value for the cosmological constant density parameter ?? = 0.85+0.044 -0.19 (68% CL) and detect cosmic acceleration (q 0 < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA Inc. under the NASA contract NAS 5-26555; the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the European Southern Observatory under the 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.

Taylor, James E.; Massey, Richard J.; Leauthaud, Alexie; George, Matthew R.; Rhodes, Jason; Kitching, Thomas D.; Capak, Peter; Ellis, Richard; Finoguenov, Alexis; Ilbert, Olivier; Jullo, Eric; Kneib, Jean-Paul; Koekemoer, Anton M.; Scoville, Nick; Tanaka, Masayuki

2012-04-01

45

Gravitational lensing as a probe of structure

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.

Peter Schneider

2003-06-23

46

Gravitational lenses and particle properties

NASA Technical Reports Server (NTRS)

The potential of observations of gravitational lens systems for the determination of cosmological constants and for tests of the nature and distribution of dark matter is illustrated. The advantages and disadvantages of gravitational lenses as cosmological probes are evaluated.

Turner, Edwin L.

1986-01-01

47

Weak lensing cosmology beyond ?CDM

Weak gravitational lensing is one of the key probes of the cosmological model, dark energy, and dark matter, providing insight into both the cosmic expansion history and large scale structure growth history. Taking into account a broad spectrum of physics affecting growth — dynamical dark energy, extended gravity, neutrino masses, and spatial curvature — we analyze the cosmological constraints. Similarly we consider the effects of a range of systematic uncertainties, in shear measurement, photometric redshifts, intrinsic alignments, and the nonlinear power spectrum, on cosmological parameter extraction. We also investigate, and provide fitting formulas for, the influence of survey parameters such as redshift depth, galaxy number densities, and sky area on the cosmological constraints in the beyond-?CDM parameter space. Finally, we examine the robustness of results for different fiducial cosmologies.

Das, Sudeep; Linder, Eric V.; Nakajima, Reiko [Berkeley Center for Cosmological Physics, University of California, Berkeley, CA (United States); Putter, Roland de, E-mail: sdas@hep.anl.gov, E-mail: rdeputter@icc.ub.edu, E-mail: evlinder@lbl.gov, E-mail: reiko@astro.uni-bonn.de [IFIC, Universidad de Valencia-CSIC, Valencia (Spain)

2012-11-01

48

NASA Astrophysics Data System (ADS)

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.

Liesenborgs, J.; de Rijcke, S.; Dejonghe, H.; Bekaert, P.

2011-03-01

49

Cosmological model discrimination from weak lensing data

NASA Astrophysics Data System (ADS)

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.

Pires, S.; Starck, J.-L.; Amara, A.; Réfrégier, A.; Teyssier, R.

2010-06-01

50

Cosmological model discrimination with weak lensing

NASA Astrophysics Data System (ADS)

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.

Pires, S.; Starck, J.-L.; Amara, A.; Réfrégier, A.; Teyssier, R.

2009-10-01

51

Dynamics of Fermat potentials in non-perturbative gravitational lensing

We present a framework, based on the null-surface formulation of general relativity, for discussing the dynamics of Fermat potentials for gravitational lensing in a generic situation without approximations of any kind. Additionally, we derive two lens equations: one for the case of thick compact lenses and the other one for lensing by gravitational waves. These equations in principle generalize the astrophysical scheme for lensing by removing the thin-lens approximation while retaining the weak fields.

Simonetta Frittelli; Ezra T. Newman

2002-05-03

52

Gravitational Lensing in Modified Gravity and the Lensing of Merging Clusters without Dark Matter

Gravitational lensing in a modified gravity (MOG) is derived and shown to describe lensing without postulating dark matter. The recent data for merging clusters identified with the interacting cluster 1E0657-56 is shown to be consistent with a weak lensing construction based on MOG without exotic dark matter.

J. W. Moffat

2006-08-30

53

Gravitational Lensing by NFW Halos

We investigate the gravitational lensing properties of dark matter halos with Navarro, Frenk & White (NFW) density profiles and derive an analytic expression for the radial dependence of the shear, $\\gamma(x)$, due to these objects. In addition, we derive an expression for the mean shear interior to a given radius, $\\bar{\\gamma}(x)$, and use this to quantify systematic errors that will arise in weak lensing mass estimates of astronomical objects in the case that the mass estimate is based on an a priori assumption that the underlying potential is that of a singular isothermal sphere when, in fact, the potential is that of an NFW-type object. On mass scales between $10^{11} \\Msun \\ls M_{200} \\ls 10^{15} \\Msun$, the assumption of an isothermal sphere potential results in an overestimate of the halo mass, and the amount by which the mass is overestimated increases linearly with the value of the NFW concentration parameter. Considerable overestimates of the mass ($\\sim 60%$) can occur for galaxy-sized halos, but for rich clusters the mass overestimate is small. The degree to which the mass is systematically in error is dependent upon the cosmology adopted, with a COBE-normalized standard CDM model yielding the largest systematic errors for a given true value of the halo mass.

Candace Oaxaca Wright; Tereasa G. Brainerd

1999-08-19

54

Numerical Simulations of Weak Lensing Measurements

(Abridged) Weak gravitational lensing induces distortions on the images of background galaxies, and thus provides a direct measure of mass fluctuations in the universe. Since the distortions induced by lensing on the images of background galaxies are only of a few percent, a reliable measurement demands very accurate galaxy shape estimation and a careful treatment of systematic effects. Here, we present a study of a shear measurement method using detailed simulations of artificial images. The images are produced using realisations of a galaxy ensemble drawn from the HST Groth strip. We consider realistic observational effects including atmospheric seeing, PSF anisotropy and pixelisation, incorporated in a manner to reproduce actual observations with the William Herschel Telescope. By applying an artificial shear to the simulated images, we test the shear measurement method proposed by Kaiser, Squires & Broadhurst (1995, KSB). Overall, we find the KSB method to be reliable with several provisos. To guide future weak lensing surveys, we study how seeing size, exposure time and pixelisation affect the sensitivity to shear. In addition, we study the impact of overlapping isophotes of neighboring galaxies, and find that this effect can produce spurious lensing signals on small scales. We discuss the prospects of using the KSB method for future, more sensitive, surveys. Numerical simulations of this kind are a required component of present and future analyses of weak lensing surveys.

David Bacon; Alexandre Refregier; Douglas Clowe; Richard Ellis

2000-07-03

55

Pixelation Effects in Weak Lensing

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.

F. William High; Jason Rhodes; Richard Massey; Richard Ellis

2007-03-17

56

EDITORIAL: Focus on Gravitational Lensing

NASA Astrophysics Data System (ADS)

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

Jain, Bhuvnesh

2007-11-01

57

NASA Astrophysics Data System (ADS)

Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter haloes in which they reside is key to constraining how black hole fuelling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modelling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to the fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies, irrespective of nuclear activity. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z < 1 from the COSMOS field, we report the first measurements of weak gravitational lensing from an X-ray-selected sample. Comparing this signal to predictions from the global SHMR, we find that, contrary to previous results, most X-ray AGN do not live in medium size groups - nearly half reside in relatively low mass haloes with M200b ˜ 1012.5 M?. The AGN occupation function is well described by the same form derived for all galaxies but with a lower normalization - the fraction of haloes with AGN in our sample is a few per cent. The number of AGN satellite galaxies scales as a power law with host halo mass with a power-law index ? = 1. By highlighting the relatively `normal' way in which moderate luminosity X-ray AGN hosts occupy haloes, our results suggest that the environmental signature of distinct fuelling modes for luminous quasars compared to moderate luminosity X-ray AGN is less obvious than previously claimed.

Leauthaud, Alexie; J. Benson, Andrew; Civano, Francesca; L. Coil, Alison; Bundy, Kevin; Massey, Richard; Schramm, Malte; Schulze, Andreas; Capak, Peter; Elvis, Martin; Kulier, Andrea; Rhodes, Jason

2015-01-01

58

Pixelation Effects in Weak Lensing

NASA Technical Reports Server (NTRS)

Weak gravitational lensing can be used to investigate both dark matter and dark energy but requires accurate measurements of the shapes of faint, distant galaxies. Such measurements are hindered by the finite resolution and pixel scale of digital cameras. We investigate the optimum choice of pixel scale for a space-based mission, using the engineering model and survey strategy of the proposed Supernova Acceleration Probe as a baseline. We do this by simulating realistic astronomical images containing a known input shear signal and then attempting to recover the signal using the Rhodes, Refregier, and Groth algorithm. We find that the quality of shear measurement is always improved by smaller pixels. However, in practice, telescopes are usually limited to a finite number of pixels and operational life span, so the total area of a survey increases with pixel size. We therefore fix the survey lifetime and the number of pixels in the focal plane while varying the pixel scale, thereby effectively varying the survey size. In a pure trade-off for image resolution versus survey area, we find that measurements of the matter power spectrum would have minimum statistical error with a pixel scale of 0.09' for a 0.14' FWHM point-spread function (PSF). The pixel scale could be increased to 0.16' if images dithered by exactly half-pixel offsets were always available. Some of our results do depend on our adopted shape measurement method and should be regarded as an upper limit: future pipelines may require smaller pixels to overcome systematic floors not yet accessible, and, in certain circumstances, measuring the shape of the PSF might be more difficult than those of galaxies. However, the relative trends in our analysis are robust, especially those of the surface density of resolved galaxies. Our approach thus provides a snapshot of potential in available technology, and a practical counterpart to analytic studies of pixelation, which necessarily assume an idealized shape measurement method.

High, F. William; Rhodes, Jason; Massey, Richard; Ellis, Richard

2007-01-01

59

Gravitational lenses with angular momentum

NASA Astrophysics Data System (ADS)

The Einstein (1936), Liebes (1964), Refsdal (1965), and Bourassa et al. (1973, 1975) theories of the effects of gravitational lenses have considered the bending of light as due to the mass distribution of the deflector. The effect of deflector dynamical properties has not been taken into account. The influence of angular momentum in a gravitational lens is presently demonstrated by the bending angle of a photon passing near a rotating body. The expressions used are evaluated for spherical and spheroidal deflectors.

Ibanez, J.

1983-08-01

60

Second-order weak lensing from modified gravity

We explore the sensitivity of weak gravitational lensing to second-order corrections to the spacetime metric within a cosmological adaptation of the parameterized post-Newtonian framework. Whereas one might expect nonlinearities of the gravitational field to introduce non-Gaussianity into the statistics of the lensing convergence field, we show that such corrections are actually always small within a broad class of scalar-tensor theories of gravity. We show this by first computing the weak lensing convergence within our parameterized framework to second order in the gravitational potential, and then computing the relevant post-Newtonian parameters for scalar-tensor gravity theories. In doing so we show that this potential systematic factor is generically negligible, thus clearing the way for weak lensing to provide a direct tracer of mass on cosmological scales for a wide class of gravity theories despite uncertainties in the precise nature of the departures from general relativity.

R. Ali Vanderveld; Robert R. Caldwell; Jason Rhodes

2011-11-07

61

Gravitational Lenses in the Classroom

ERIC Educational Resources Information Center

It is not common to introduce current astronomy in school lessons. This article presents a set of experiments about gravitational lenses. It is normal to simulate them by means of computers, but it is very simple to simulate similar effects using a drinking glass full of liquid or using only the glass base. These are, of course, cheap and easy…

Ros, Rosa M.

2008-01-01

62

Attributes of Gravitational Lensing Parallax

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.

Robert J. Nemiroff

1998-05-31

63

Gravitational Lensing Analyzed by Graded Refractive Index of Vacuum

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.

Xing-Hao Ye; Qiang Lin

2008-02-13

64

Towards noiseless gravitational lensing simulations

NASA Astrophysics Data System (ADS)

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.

Angulo, Raul E.; Chen, Ruizhu; Hilbert, Stefan; Abel, Tom

2014-11-01

65

Wavefronts, Caustic Sheets, and Caustic Surfing in Gravitational Lensing

Very little attention has been paid to the properties of optical wavefronts and caustic surfaces due to gravitational lensing. Yet the wavefront-based point of view is natural and provides insights into the nature of the caustic surfaces on a gravitationally lensed lightcone. We derive analytically the basic equations governing the wavefronts, lightcones, caustics on wavefronts, and caustic surfaces on lightcones in the context of weak-field, thin-screen gravitational lensing. These equations are all related to the potential of the lens. In the process, we also show that the standard single-plane gravitational lensing map extends to a new mapping, which we call a wavefront lensing map. Unlike the standard lensing map, the Jacobian matrix of a wavefront lensing map is not symmetric. Our formulas are then applied to caustic ``surfing.'' By surfing a caustic surface, a space-borne telescope can be fixed on a gravitationally lensed source to obtain an observation of the source at very high magnification over an extended time period, revealing structure about the source that could not otherwise be resolved. Using our analytical expressions for caustic sheets, we present a scheme for surfing a caustic sheet of a lensed source in rectilinear motion. Detailed illustrations are also presented of the possible types of wavefronts and caustic sheets due to nonsingular and singular elliptical potentials, and singular isothermal spheres, including an example of caustic surfing for a singular elliptical potential lens.

S. Frittelli; A. O. Petters

2002-08-06

66

Spheroidal gravitational lenses

NASA Astrophysics Data System (ADS)

The author presents a minor correction to the internal solution of Bourassa & Kantowski. This leads to a simple proof of the fact that if the projected density has elliptical symmetry, then there is no contribution to the bending angle due to mass lying outside the ellipse formed by the impact parameter. Diagrams are also presented which show the multi-imaging aspect of the gravitational lens effect as a function of the position of the source with respect to the lens.

Bray, I.

1984-06-01

67

Weak lensing corrections to tSZ-lensing cross correlation

NASA Astrophysics Data System (ADS)

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.

Tröster, Tilman; Van Waerbeke, Ludovic

2014-11-01

68

Weak lensing studies with GOODS/ACS fields

NASA Astrophysics Data System (ADS)

The main goal of this thesis is to improve current understanding of structure formation in the universe at z ~ 1--2 through weak lensing studies with the Hubble Space Telescope ( HST ) Advanced Camera for Surveys (ACS) data, obtained as part of the Great Observatories Origin Deep Survey (GOODS) project. In this thesis, we present a uniform approach to describes light propagation in both isotropic universe and weakly perturbed universe to discuss the effects of gravitational lensing, apply it to two prime applications of gravitational lensing to cosmology; lensing by dark matter halos and lensing by the large- scale structure, investigate the expected weak lensing effects from the applications and discuss how the effects can be measured through galaxy shape. We describe how galaxy shapes are measured from the GOODS data. We present preliminary measurements of galaxy-galaxy lensing and detection of cosmic shear. We detect a clear galaxy-galaxy lensing signal for lens galaxies at z ~ 0.5 at projected separations ranging from 10" to 200". The detected shear is compatible with ground-based measurements obtained for low-redshift galaxies. We also detect a clear cosmic shear signal using source galaxies at z ~ 1.0. The detected shear is generally consistent with other observations that measured s 8 ~= 0.7.

Park, Yousin

2006-06-01

69

Numerical simulation of gravitational lenses

NASA Astrophysics Data System (ADS)

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.

Cherniak, Yakov

70

Resolving Galaxy Cluster Substructure with Gravitational Lensing Flexion

NASA Astrophysics Data System (ADS)

While it is well established that clusters of galaxies reside in dark matter haloes, simulations lead us to believe that there is substantial residual dark matter substructure in those halos. Weak gravitational lensing is well suited to to studying the large scale properties of these halos but less so for studying substructure. Gravitational lensing flexion, the next-higher order lensing effect after shear, is extremely well-suited to measuring substructure, both because it acts at shorter range and because fewer background objects are needed to get a significant signal. We propose to apply a gravitational lensing analysis and mass reconstruction particularly suited to detecting substructure to a sample of 20 massive galaxy clusters, complementing strong lensing and weak lensing measurements with flexion in the mass reconstructions. Because flexion is a sensitive probe of mass gradients, we will detect structure on smaller spatial scales than are accessible to shear analyses, and will do so over a larger area than is possible with strong lensing analyses alone. Our strong+weak+flexion lensing approach will make a census of substructures down to M 3x10^12 solar masses over an entire HST/ACS field of view. Using our detailed mapping of the cluster mass distributions we will measure the normalization of the subhalo mass function {which is equivalent to the substructure mass fraction} to 10% error, and place an empirical constraint on its slope as well.

Cain, Benjamin

2013-10-01

71

Covariance of Weak Lensing Observables

Analytical expressions for covariances of weak lensing statistics related to the aperture mass $\\Map$ are derived for realistic survey geometries such as SNAP for a range of smoothing angles and redshift bins. We incorporate the contributions to the noise due to the intrinsic ellipticity distribution and the effects of finite size of the catalogue. Extending previous results to the most general case where the overlap of source populations is included in a complete analysis of error estimates, we study how various angular scales in various redshifts are correlated and how the estimation scatter changes with survey parameters. Dependence on cosmological parameters and source redshift distributions are studied in detail. Numerical simulations are used to test the validity of various ingredients to our calculations. Correlation coefficients are defined in a way that makes them practically independent of cosmology. They can provide important tools to cross-correlate one or more different surveys, as well as various redshift bins within the same survey or various angular scales from same or different surveys. Dependence of these coefficients on various models of underlying mass correlation hierarchy is also studied. Generalisations of these coefficients at the level of three-point statistics have the potential to probe the complete shape dependence of the underlying bi-spectrum of the matter distribution. A complete error analysis incorporating all sources of errors suggest encouraging results for studies using future space based weak lensing surveys such as SNAP.

Dipak Munshi; Patrick Valageas

2004-09-20

72

Gravitational Lensing Extends SETI Range

NASA Astrophysics Data System (ADS)

Microwave SETI (The Search for Extraterrestrial Intelligence) focuses on two primary strategies, the "Targeted Search" and the "All-Sky Survey." Although the goal of both strategies is the unequivocal discovery of a signal transmitted by intelligent species outside our solar system, they pursue the strategies in very different manners and have vastly different requirements. This chapter introduces Gravitational Lensing SETI (GL-SETI), a third strategy. Its goal is the unequivocal discovery of an extraterrestrial signal, with equipment and data processing requirements that are substantially different from the commonly-used strategies. This strategy is particularly suitable for use with smaller radio telescopes and has budgetary requirements suitable for individual researchers.

Factor, Richard

73

Lossy compression of weak lensing data

Future orbiting observatories will survey large areas of sky in order to constrain the physics of dark matter and dark energy using weak gravitational lensing and other methods. Lossy compression of the resultant data will improve the cost and feasibility of transmitting the images through the space communication network. We evaluate the consequences of the lossy compression algorithm of Bernstein et al. (2010) for the high-precision measurement of weak-lensing galaxy ellipticities. This square-root algorithm compresses each pixel independently, and the information discarded is by construction less than the Poisson error from photon shot noise. For simulated space-based images (without cosmic rays) digitized to the typical 16 bits per pixel, application of the lossy compression followed by image-wise lossless compression yields images with only 2.4 bits per pixel, a factor of 6.7 compression. We demonstrate that this compression introduces no bias in the sky background. The compression introduces a small amount of additional digitization noise to the images, and we demonstrate a corresponding small increase in ellipticity measurement noise. The ellipticity measurement method is biased by the addition of noise, so the additional digitization noise is expected to induce a multiplicative bias on the galaxies measured ellipticities. After correcting for this known noise-induced bias, we find a residual multiplicative ellipticity bias of m {approx} -4 x 10{sup -4}. This bias is small when compared to the many other issues that precision weak lensing surveys must confront, and furthermore we expect it to be reduced further with better calibration of ellipticity measurement methods.

Vanderveld, R Ali [Chicago U., EFI; Caltech /Caltech, JPL; Bernstein, Gary M [Pennsylvania U.; Stoughton, Chris [Fermilab; Rhodes, Jason [Caltech; Caltech, JPL; Massey, Richard [Royal Observ., Edinburgh; Dobke, Benjamin M [Caltech; Caltech, JPL

2011-06-01

74

Gravitational lensing of cosmological 21 cm emission

NASA Astrophysics Data System (ADS)

We investigate the feasibility of measuring weak gravitational lensing using 21-cm intensity mapping with special emphasis on the performance of the planned Square Kilometre Array (SKA). We find that the current design for SKA_Mid should be able to measure the evolution of the lensing power spectrum at z ˜ 2-3 using this technique. This will be a probe of the expansion history of the Universe and gravity at a unique range in redshift. The signal to noise is found to be highly dependent on evolution of the neutral hydrogen fraction in the Universe with a higher H I density resulting in stronger signal. With realistic models for this, SKA Phase 1 should be capable of measuring the lensing power spectrum and its evolution. The dependence of signal to noise on the area and diameter of the array is quantified. We further demonstrate the applications of this technique by applying it to two specific coupled dark energy models that would be difficult to observationally distinguish without information from this range of redshift. We also investigate measuring the lensing signal with 21 cm emission from the Epoch of Reionization (EoR) using SKA and find that it is unlikely to constrain cosmological parameters because of the small survey size, but could provide a map of the dark matter within a small region of the sky.

Pourtsidou, A.; Metcalf, R. Benton

2015-04-01

75

A Computer Program to Visualize Gravitational Lenses

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.

Francisco Frutos-Alfaro

2014-06-12

76

Weak Lensing Studies of Mass Substructure in Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Cluster mass substructure is an important test of the hierarchical model of CDM. We use weak gravitational lensing shear measurements, combined with variable aperture filter methods and PSF correction, to extract information about mass subclumping in HST observations of clusters of galaxies. This work is funded by NASA Rhode Island Space Grant.

Huwe, Paul M.

2012-01-01

77

Exploring degeneracies in modified gravity with weak lensing

NASA Astrophysics Data System (ADS)

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.

Leonard, C. Danielle; Baker, Tessa; Ferreira, Pedro G.

2015-04-01

78

Caustic and Weak Lensing Estimators of Galaxy Cluster Masses

There are only two methods for estimating the mass distribution in the outer regions of galaxy clusters, where virial equilibrium does not hold: weak gravitational lensing and identification of caustics in redshift space. For the first time, we apply both methods to three clusters: A2390, MS1358 and Cl 0024. The two measures are in remarkably good agreement out to ~2 Mpc/h from the cluster centers. This result demonstrates that the caustic technique is a valuable complement to weak lensing. With a few tens of redshifts per (Mpc/h)^2 within the cluster, the caustic method is applicable for any z<~0.5.

Antonaldo Diaferio; Margaret J. Geller; Kenneth J. Rines

2005-06-23

79

Exploring degeneracies in modified gravity with weak lensing

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.

C. Danielle Leonard; Tessa Baker; Pedro G. Ferreira

2015-04-21

80

Exploring degeneracies in modified gravity with weak lensing

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.

Leonard, C Danielle; Ferreira, Pedro G

2015-01-01

81

Weak lensing statistics from the Coyote Universe

Analyzing future weak lensing data sets from KIDS, DES, LSST, Euclid, WFIRST\\u000arequires precise predictions for the weak lensing measures. In this paper we\\u000apresent a weak lensing prediction code based on the Coyote Universe emulator.\\u000aThe Coyote Universe emulator predicts the (non-linear) power spectrum of\\u000adensity fluctuations (P_delta) to high accuracy for k \\\\in [0.002;3.4] h\\/Mpc\\u000awithin the redshift

Tim Eifler

2010-01-01

82

A Simple Optical Analysis of Gravitational Lensing

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.

Xing-Hao Ye; Qiang Lin

2007-04-26

83

Nonstationary Gravitational Lenses and the Fermat Principle

We apply Perlick's (1990a) rigorous formulation of the Fermat principle in arbitrary spacetimes to prove the correctness of the description of gravitational lensing by gravitational waves, given in the literature using the scalar and vector formalisms. We obtain an expression for the time delay due to such nonstationary lenses; the advantage over previous papers is that Perlick's formulation of the Fermat principle is very rigorous and more suitable for practical calculations in some cases. It is also shown that ordinary moving gravitational lenses must be considered as a stationary case.

Valerio Faraoni

1992-05-01

84

Separating weak lensing and intrinsic alignments using radio observations

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...

Whittaker, Lee; Battye, Richard A

2015-01-01

85

The Sloan Nearby Cluster Weak Lensing Survey

We describe and present initial results of a weak lensing survey of nearby (z {approx}< 0.1) galaxy clusters in the Sloan Digital Sky Survey (SDSS). In this first study, galaxy clusters are selected from the SDSS spectroscopic galaxy cluster catalogs of Miller et al. and Berlind et al. We report a total of seven individual low-redshift cluster weak lensing measurements that include A2048, A1767, A2244, A1066, A2199, and two clusters specifically identified with the C4 algorithm. Our program of weak lensing of nearby galaxy clusters in the SDSS will eventually reach {approx}200 clusters, making it the largest weak lensing survey of individual galaxy clusters to date.

Kubo, Jeffrey M.; /Fermilab; Annis, James T.; /Fermilab; Hardin, Frances Mei; /Illinois Math. Sci. Acad.; Kubik, Donna; /Fermilab; Lawhorn, Kelsey; /Illinois Math. Sci. Acad.; Lin, Huan; /Fermilab; Nicklaus, Liana; /Illinois Math. Sci. Acad.; Nelson, Dylan; /UC, Berkeley; Reis, Ribamar Rondon de Rezende; /Fermilab; Seo, Hee-Jong; /Fermilab; Soares-Santos, Marcelle; /Fermilab /Inst. Geo. Astron., Havana /Sao Paulo U. /Fermilab

2009-08-01

86

Gravitational lensing of gravitational waves from merging neutron star binaries

We discuss the gravitational lensing of gravitational waves from merging neutron star binaries, in the context of advanced LIGO type gravitational wave detectors. We consider properties of the expected observational data with cut on the signal-to-noise ratio \\rho, i.e., \\rho>\\rho_0. An advanced LIGO should see unlensed inspiral events with a redshift distribution with cut-off at a redshift z_{\\rm max} < 1 for h \\leq 0.8. Any inspiral events detected at z>z_{\\rm max} should be lensed. We compute the expected total number of events which are present due to gravitational lensing and their redshift distribution for an advanced LIGO in a flat Universe. If the matter fraction in compact lenses is close to 10\\%, an advanced LIGO should see a few strongly lensed events per year with \\rho >5.

Wang, Yun; Stebbins, Albert; Turner, Edwin L.

1996-05-01

87

Gravitational lensing of the CMB with SPTpol

NASA Astrophysics Data System (ADS)

Measurements of gravitational lensing of the cosmic microwave background (CMB) directly probe the projected mass in the universe out to high redshifts. Gravitational lensing encodes a wealth of information in the CMB about the growth and geometry of large-scale structure, which is sensitive to cosmic acceleration (dark energy), the expansion history of the universe and the properties of neutrinos. Additionally, gravitational lensing can be used to improve inflationary gravitational wave searches in the CMB, and constrain the relationship between dark and luminous matter at high redshifts. I will present recent lensing results from the first two years of data from the South Pole Telescope polarimeter (SPTpol) and discuss future opportunities for this powerful technique.

Story, Kyle Tyler; SPTpol Collaboration

2015-01-01

88

Investigations of Galaxy Clusters Using Gravitational Lensing

NASA Astrophysics Data System (ADS)

In this dissertation talk I describe my studies of galaxy clustering and gravitational lensing; both are important phenomena which can be used to study the structure and evolution of the universe. First I describe a sample of ten strong-lensing galaxy clusters of mass between 1-30x1014 h-1M?. These clusters were found in the Sloan Digital Sky Survey and were further observed using the WIYN 3.5-m telescope at Kitt Peak National Observatory and the Astrophysical Research Consortium 3.5-m telescope at Apache Point Observatory. Analyses of these clusters showed that the four lowest mass clusters in this sample exhibit overconcentration, that is, the concentration of mass in the centers of the clusters was higher than theory would predict. Second, I describe lens models of three of the strong lenses in this sample using a Bayesian algorithm for lens modeling. Finally I describe measurements of a mass-richness relation for galaxy clusters found at higher median redshift (z?0.6) than has been typical of previous sky surveys. This relation empirically describes how the mass of galaxy clusters is related to the number of galaxies in the cluster. Mass-richness calibration is a key component of cosmology analyses using galaxy clusters; thus this work will be important to studies of cosmology done with this decade's large sky surveys. Galaxy clusters were found using a Voronoi Tessellation cluster finder and masses were measured using stacked weak lensing shear measurements in bins of similar richness. The mass-richness relation was derived using data from the Blanco Cosmology Survey and from the Sloan Digital Sky Survey Stripe 82 coadd, leading to a sample of clusters covering a total sky area of about 400 square degrees.

Wiesner, Matthew P.; Lin, H.; Soares-Santos, M.

2014-01-01

89

Weak Lensing: Dark Matter, Dark Energy

The light rays from distant galaxies are deflected by massive structures along the line of sight, causing the galaxy images to be distorted.Measurements of these distortions, known as weak lensing, provide a way of measuring the distribution of dark matter as well as the spatial geometry of the universe. I will describe the ideas underlying this approach to cosmology. With planned large imaging surveys, weak lensing is a powerful probe of dark energy. I will discuss the observational challenges ahead and recent progress in developing multiple, complementary approaches to lensing measurements.

Bhuvnesh Jain

2006-02-27

90

Strong gravitational lensing with the SKA

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...

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

91

EFFECT OF MASKED REGIONS ON WEAK-LENSING STATISTICS

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.

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

92

Gravitational lenses and dark matter - Theory

NASA Technical Reports Server (NTRS)

Theoretical models are presented for guiding the application of gravitational lenses to probe the characteristics of dark matter in the universe. Analytical techniques are defined for quantifying the mass associated with lensing galaxies (in terms of the image separation), determining the quantity of dark mass of the lensing bodies, and estimating the mass density of the lenses. The possibility that heavy halos are made of low mass stars is considered, along with the swallowing of central images of black holes or cusps in galactic nuclei and the effects produced on a lensed quasar image by nonbaryonic halos. The observable effects of dense groups and clusters and the characteristics of dark matter strings are discussed, and various types of images which are possible due to lensing phenomena and position are described.

Gott, J. Richard, III

1987-01-01

93

Measuring the dark side (with weak lensing)

We introduce a convenient parameterization of dark energy models that is general enough to include several modified gravity models and generalized forms of dark energy. In particular we take into account the linear perturbation growth factor, the anisotropic stress and the modified Poisson equation. We discuss the sensitivity of large-scale weak lensing surveys like the proposed DUNE satellite to these parameters (assuming systematic errors can be controlled). We find that a large-scale weak lensing tomographic survey is able to easily distinguish the Dvali-Gabadadze-Porrati model from {Lambda}CDM and to determine the perturbation growth index to an absolute error of 0.02-0.04.

Amendola, Luca [INAF/Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monteporzio Catone, Roma (Italy); Kunz, Martin; Sapone, Domenico, E-mail: amendola@mporzio.astro.it, E-mail: martin.kunz@physics.unige.ch, E-mail: domenico.sapone@physics.unige.ch [Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, CH-1211 Geneve 4 (Switzerland)

2008-04-15

94

Atmospheric Dispersion Effects in Weak Lensing Measurements

NASA Astrophysics Data System (ADS)

The wavelength dependence of atmospheric refraction causes elongation of finite-bandwidth images along the elevation vector, which produces spurious signals in weak gravitational lensing shear measurements unless this atmospheric dispersion is calibrated and removed to high precision. Because astrometric solutions and point spread function (PSF) characteristics are typically calibrated from stellar images, differences between the reference stars'' spectra and the galaxies'' spectra will leave residual errors in both the astrometric positions (?R\\OverBar ¯) and in the second moment (width) of the wavelength-averaged PSF (?V) for galaxies. We estimate the level of ?V that will induce spurious weak lensing signals in PSF-corrected galaxy shapes that exceed the statistical errors of the Dark Energy Survey (DES) and the Large Synoptic Survey Telescope (LSST) cosmic-shear experiments. We also estimate the ?R\\OverBar ¯ signals that will produce unacceptable spurious distortions after stacking of exposures taken at different air masses and hour angles. Using standard galaxy and stellar spectral templates we calculate the resultant errors in the griz bands and find that atmospheric dispersion shear systematics, left uncorrected, are up to 6 and 2 times larger in g and r bands, respectively, than the thresholds at which they become significant contributors to the DES error budget, but can be safely ignored in i and z bands. For the stricter LSST requirements, the factors are about 30, 10, and 3 in g, r, and i bands, respectively. These shear systematic errors scale with observed zenith angle z as < tan2z>, for which we take a nominal value of unity - simulations of DES and LSST suggest 0.6--1.0. We find that a simple correction linear in galaxy color is accurate enough to reduce dispersion shear systematics to insignificant levels in the r band for DES and i band for LSST, but still as much 5× above the threshold of significance for LSST r band observations. More complex approaches to correction of the atmospheric dispersion signal will likely be able to reduce the systematic cosmic shear errors below statistical errors for LSST r band. But g-band dispersion effects remain large enough that it seems likely that induced systematics will dominate the statistical errors of both surveys, and cosmic-shear measurements should rely on the redder bands.

Alejandro Plazas, Andrés; Bernstein, Gary

2012-10-01

95

Detection of Gravitational Waves from Gravitationally Lensed Systems

It is accepted that quasars are powered by supermassive black holes (SMBH) with masses in the range 10^6 - 10^9 solar masses in their cores. Occasionally, compact stars can plunge into SMBH. In addition, there may be a number of such compact objects circling the central SMBH in any given quasar. Both of these processes are known to emit gravitational waves. LISA has the right sensitivity to detect these waves. We show that gravitational lenses amplify the amplitudes of these gravitational waves just as they amplify the observed light of quasars. Given the geometry of the lensing configuration, this amplification can be as large as a factor of 2 to 10, allowing the waves to be above the detection threshold of LISA. We also show that waves from lensed quasars arrive with time delays which are much larger than the coherence time of the gravitational waves, making interference effects negligible. Thus, a simple geometrical optics application leads to the lensing theory of gravitational waves. In this context, we analyze and show in this preliminary analysis that there is an enhancement of the amplitudes of gravitational radiation coming from observed lensed quasars.

T. Wickramasinghe; M. Benacquista

2001-06-05

96

Constraining the QSO luminosity function using gravitational lensing statistics

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 ...

Fakhouri, Onsi Joe, 1983-

2004-01-01

97

Gravitational Lensing, Dark Matter and the Optical Gravitational Lens Experiment

NASA Astrophysics Data System (ADS)

After briefly reviewing the history of gravitational lensing, we recall the basic principles of the theory. We then describe and use a simple optical gravitational lens experiment which has the virtue of accounting for all types of image configurations observed so far among the presently known gravitational lens systems. Finally, we briefly present the 4m International Liquid Mirror Telescope project in the context of a photometric monitoring of multiply imaged quasars.

Surdej, J.; Claeskens, J.-F.; Delacroix, C.; Sadibekova, T.; Bartczak, P.; Coleman, P. H. I.; Magette, A.; Poels, J.; Ricci, D.; Sluse, D.

2008-08-01

98

Galilean-invariant scalar fields can strengthen gravitational lensing.

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

Wyman, Mark

2011-05-20

99

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.

Oguri, Masamune; Hennawi, Joseph F.; Gladders, Michael D.; Dahle, Haakon; Natarajan, Priyamvada; Dalal, Neal; Koester, Benjamin P.; Sharon, Keren; Bayliss, Matthew

2009-01-29

100

Statistics of gravitational lenses - The uncertainties

NASA Technical Reports Server (NTRS)

The assumptions in the analysis of gravitational lensing statistics are examined. Special emphasis is given to the uncertainties in the theoretical predictions. It is shown that a simple redshift cutoff model, which may result from galaxy evolution, can significantly reduce the lensing probability and explain the large mean separation of images in observed gravitational lenses. This effect may affect the constraint on the contribution of the cosmological constant to producing a flat universe from the number counts of the observed lenses. For the Omega(0) = 1 (filled beam) model, the lensing probability of early-type galaxies with finite core radii is reduced roughly by a factor of 2 for high-redshift quasars as compared with the corresponding singular isothermal sphere model. The finite core radius effect is about 20 percent for a lambda-dominated flat universe. It is also shown that the most recent galaxy luminosity function gives lensing probabilities that are smaller than previously estimated roughly by a factor of 3.

Mao, Shude

1991-01-01

101

Weak Lensing from Space I: Instrumentation and Survey Strategy

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.

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

102

Weak Lensing from Space I: Instrumentation and Survey Strategy

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.

Jason Rhodes; Alexandre Refregier; Richard Massey; the SNAP Collaboration

2004-03-11

103

Measuring neutrino masses and dark energy with weak lensing tomography

Surveys of weak gravitational lensing of distant galaxies will be one of the key cosmological probes in the future. We study the ability of such surveys to constrain neutrino masses and the equation of state parameter of the dark energy, focussing on how tomographic information can improve the sensitivity to these parameters. We also provide a detailed discussion of systematic effects pertinent to weak lensing surveys, and the possible degradation of sensitivity to cosmological parameters due to these effects. For future probes such as the Large Synoptic Survey Telescope survey, we find that, when combined with cosmic microwave background data from the Planck satellite, a sensitivity to neutrino masses of sigma(sum m_nu) the running of the scalar spectral index, the time-dependence of dark energy equation of state, and/or the number of relativistic degrees of freedom.

Steen Hannestad; Huitzu Tu; Yvonne Y. Y. Wong

2006-06-28

104

Constraints on warm dark matter from weak lensing in anomalous quadruple lenses

NASA Astrophysics Data System (ADS)

We investigate the weak lensing effect by line-of-sight structures with a surface mass density of ? 108 M? arcsec-2 in QSO-galaxy quadruple lens systems. Using high-resolution N-body simulations in warm dark matter (WDM) models and observed four quadruple lenses that show anomalies in the flux ratios, we obtain constraints on the mass of thermal WDM, mWDM ? 1.3 keV (95 per cent CL) assuming that the density of the primary lens is described by a singular isothermal ellipsoid (SIE). The obtained constraint is consistent with those from Lyman ? forests and the number counts of high-redshift galaxies at z > 4. Our results show that WDM with a free-streaming comoving wavenumber kfs ? 27 h Mpc-1 is disfavoured as the major component of cosmological density at redshifts 0.5 ? z ? 4 provided that the SIE models describe the gravitational potentials of the primary lenses correctly.

Inoue, Kaiki Taro; Takahashi, Ryuichi; Takahashi, Tomo; Ishiyama, Tomoaki

2015-04-01

105

Perturbative analysis in planetary gravitational lensing

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.

V. Bozza

1999-04-22

106

Gravitational Lensing of Supernova Neutrinos

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.

Mena, Olga; /Fermilab /Rome U.; Mocioiu, Irina; /Penn State U.; Quigg, Chris; /Fermilab

2006-10-01

107

Correlated gravitational lensing of the CMB

Cosmological inhomogeneities gravitationally deflect radiation propagating from distant sources, transforming the spatial and angular correlation functions of intrinsic source properties. For a gaussian distribution of deflections (e.g. from a primordial gaussian density perturbation spectrum or from the central limit theorem) we calculate the probability distributions for geodesic deviations. If the intrinsic variable is also gaussian, e.g. the large scale velocity flow field or cosmic microwave background temperature anisotropies, then distributions and correlation functions of the observed image sky properties can be obtained. Specialising to CMB temperature fluctuations we rederive simply the influence of independent gravitational lensing on the anisotropy angular correlation function and calculate the new effect of lensing correlated with the anisotropies, e.g. arising from the same primordial gravitational perturbation field. Characteristic magnitudes and scales are given in terms of the density power spectrum. The correlated deflection-temperature effect is shown to be negligible.

Eric V. Linder

1996-06-21

108

First measurement of gravitational lensing by cosmic voids in SDSS

NASA Astrophysics Data System (ADS)

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.

Melchior, Peter; Sutter, P. M.; Sheldon, Erin S.; Krause, Elisabeth; Wandelt, Benjamin D.

2014-06-01

109

Gravitational Lensing and Dark Structures

We examine whether a cosmologically significant distribution of dark galaxy group or cluster-sized objects can have an optical depth for multiple imaging of distant background sources, which is comparable with that from known galaxies while at the same time producing angular splittings of the same order of magnitude. Our purpose is to explore whether such objects could realistically account for some of the observed lenses. Modeling such systems as isothermal spheres with core radii and assuming a Schechter-type distribution function, we find that independent of the cosmology (open, flat matter{endash}dominated, or flat cosmological constant{endash}dominated) an allowed, albeit narrow, parameter range exists that is comparable in velocity dispersion with that for known compact groups of galaxies, although the preferred core radii are somewhat smaller than that normally assumed for compact groups. Dark cluster-sized objects, on the other hand, cannot reproduce the observed lensing characteristics. If the one known dark cluster were a good representative of such a distribution, most such objects would not produce multiple images. We also present a result for the angular splitting from an isothermal sphere lens with nonzero core radius, extending earlier work of Hinshaw & Krauss. Our results are expressed as contour plots for fixed lensing probabilities and angular splittings. {copyright} {ital {copyright} 1999.} {ital The American Astronomical Society}

Cheng, Y.N. [not known ()] [not known (); Krauss, L.M. [Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7079 (United States)] [Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7079 (United States)

1999-03-01

110

Weak Lensing: Prospects for Measuring Cosmological Parameters

Weak lensing of galaxies by large scale structure can potentially measure cosmological quantities as accurately as the cosmic microwave background (CMB). However, the relation between observables and fundamental parameters is more complex and degenerate, especially in the full space of adiabatic cold dark matter models considered here. We introduce a Fisher matrix analysis of the information contained in weak lensing surveys to address these issues and provide a simple means of estimating how survey properties and source redshift uncertainties affect parameter measurement. We find that surveys on degree scales and above can improve the accuracy on parameters that affect the growth rate of structure by up to an order of magnitude compared to using the CMB alone even if the characteristic redshift of the sources must be determined from the data itself. Surprisingly, both sparse sampling and increasing the source redshift can weaken the cosmological constraints.

Wayne Hu; Max Tegmark

1998-11-11

111

Lognormal Property of Weak Lensing Fields

The statistical property of the weak lensing fields is studied quantitatively using the ray-tracing simulations. Motivated by the empirical lognormal model that characterizes the probability distribution function(PDF) of the three-dimensional mass distribution excellently, we critically investigate the validity of lognormal model in the weak lensing statistics. Assuming that the convergence field, $\\kappa$, is approximately described by the lognormal distribution, we present analytic formulae of convergence for the one-point PDF and the Minkowski functionals. Comparing those predictions with ray-tracing simulations in various cold dark matter models, we find that the one-point lognormal PDF can describe the non-Gaussian tails of convergence fields accurately up to $\

A. Taruya; M. Takada; T. Hamana; I. Kayo; T. Futamase

2002-02-05

112

Strong gravitational lenses in the 2020s

NASA Astrophysics Data System (ADS)

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.

Oguri, Masamune

2014-07-01

113

On Cross-correlating Weak Lensing Surveys

The present generation of weak lensing surveys will be superseded by surveys run from space with much better sky coverage and high level of signal to noise ratio, such as SNAP. However, removal of any systematics or noise will remain a major cause of concern for any weak lensing survey. One of the best ways of spotting any undetected source of systematic noise is to compare surveys which probe the same part of the sky. In this paper we study various measures which are useful in cross correlating weak lensing surveys with diverse survey strategies. Using two different statistics - the shear components and the aperture mass - we construct a class of estimators which encode such cross-correlations. These techniques will also be useful in studies where the entire source population from a specific survey can be divided into various redshift bins to study cross correlations among them. We perform a detailed study of the angular size dependence and redshift dependence of these observables and of their sensitivity to the background cosmology. We find that one-point and two-point statistics provide complementary tools which allow one to constrain cosmological parameters and to obtain a simple estimate of the noise of the survey.

Dipak Munshi; Patrick Valageas

2004-06-03

114

Gravitational Lensing Limits on Early-Type Galaxies

Gravitational lenses are a unique new constraint on the structure of galaxies. We review the evidence that most lenses are early-type galaxies, the optical properties of the lens galaxies, the evidence against constant M/L models, recent work on the axis ratios of the mass distribution, and the role stellar dynamics plays in gravitational lensing.

C. S. Kochanek; C. R. Keeton

1996-11-26

115

Gravitational lensing statistics of amplified supernovae

NASA Technical Reports Server (NTRS)

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.

Linder, Eric V.; Wagoner, Robert V.; Schneider, P.

1988-01-01

116

Testing cosmogonic models with gravitational lensing.

Gravitational lensing provides a strict test of cosmogonic models because it is directly sensitive to mass inhomogeneities. Detailed numerical propagation of light rays through a universe that has a distribution of inhomogeneities derived from the standard CDM (cold dark matter) scenario, with the aid of massive, fully nonlinear computer simulations, was used to test the model. It predicts that more widely split quasar images should have been seen than were actually found. These and other inconsistencies rule out the Cosmic Background Explorer (COBE)-normalized CDM model with density parameter Omega = 1 and the Hubble constant (H(o)) = 50 kilometers second(-1) megaparsec(-1); but variants of this model might be constructed, which could pass the stringent tests provided by strong gravitational lensing. PMID:17814792

Wambsganss, J; Cen, R; Ostriker, J P; Turner, E L

1995-04-14

117

Gravitational lensing of wormholes in noncommutative geometry

It has been shown that a noncommutative-geometry background may be able to support traversable wormholes. This paper discusses the possible detection of such wormholes in the outer regions of galactic halos by means of gravitational lensing. The procedure allows a comparison to other models such as the NFW model and f(R) modified gravity and is likely to favor a model based on noncommutative geometry.

Peter K. F. Kuhfittig

2015-03-04

118

Gravitational Lensing and the Hubble Deep Field

We calculate the expected number of multiply-imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with m_I < 27 that were detected in all four HDF passbands. A comparison of these expectations with the observed number of strongly lensed galaxies constrains the current value of Omega_m-Omega_Lambda, where Omega_m is the mean mass density of the universe and Omega_Lambda is the normalized cosmological constant. Based on current estimates of the HDF luminosity function and associated uncertainties in individual parameters, our 95% confidence lower limit on Omega_m-Omega_Lambda ranges between -0.44, if there are no strongly lensed galaxies in the HDF, and -0.73, if there are two strongly lensed galaxies in the HDF. If the only lensed galaxy in the HDF is the one presently viable candidate, then, in a flat universe (Omega_m+Omega_Lambda=1), Omega_Lambda < 0.79 (95% C.L.). These limits are compatible with estimates based on high-redshift supernovae and with previous limits based on gravitational lensing.

Asantha R. Cooray; Jean M. Quashnock; M. Coleman Miller

1998-11-07

119

Wave optics and image formation in gravitational lensing

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.

Yasusada Nambu

2012-07-30

120

The Third Gravitational Lensing Accuracy Testing (GREAT3) Challenge Handbook

NASA Astrophysics Data System (ADS)

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.

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

121

MEASURING GALAXY MASSES USING GALAXY-GALAXY GRAVITATIONAL LENSING

We report a significant detection of weak, tangential distortion of the images of cosmologically distant, faint galaxies due to gravitational lensing by foreground galaxies. A mean image polarisation of $=0.011\\pm 0.006$ is measured for 3202 pairs of source galaxies with magnitudes $23< r \\le 24$ and lens galaxies with magnitudes $20\\le r\\le 23$. The signal remains strong for lens-source separations $\\lo 90''$, consistent with quasi-isothermal galaxy halos extending to large radii ($\\go 100h^{-1}$ kpc). Our observations thus provide the first evidence from weak gravitational lensing of large scale dark halos associated with individual galaxies. The observed polarisation is also consistent with the signal expected on the basis of simulations incorporating measured properties of local galaxies and modest extrapolations of the observed redshift distribution of faint galaxies. From the simulations we derive a best-fit halo circular velocity of $V\\sim 220$ km/s and characteristic radial extent of $s \\go 100h^{-1}$ kpc. Our best-fit halo parameters imply typical masses for the lens galaxies within a radius of $100h^{-1}$ kpc on the order of $1.0^{+1.1}_{-0.7}\\times 10^{12}h^{-1} M_\\odot$, in good agreement with recent dynamical estimates of the masses of local spiral galaxies. This is particularly encouraging as the lensing and dynamical mass estimators rely on different sets of assumptions. Contamination of the gravitational lensing signal by a population of tidally distorted satellite galaxies can be ruled out with reasonable confidence. The prospects for corroborating and improving this measurement seem good, especially using deep HST archival data.

Tereasa Brainerd; Roger Blandford; Ian Smail

1995-03-17

122

Gravitational Lensing: Recent Progress & Future Goals

NASA Technical Reports Server (NTRS)

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.

Brainerd, Tereasa

2001-01-01

123

Weak Lensing Galaxy Shear Extraction Testing for LSST

NASA Astrophysics Data System (ADS)

The accuracy and reliability of weak-lensing measurement for LSST depend on the level of the atmospheric turbulence of the site, the integrity of the design and fabrication of the optical system, the ability to describe and model both the atmospheric and instrumental characteristics, and the accuracy of the algorithm to remove these systematics and extract gravitational shears of galaxies. Of course, at the core of this removal of the systematics is the high-fidelity modeling and correction of the point spread function (PSF) on the delivered images. In this poster, we present the results of our on-going end-to-end shear extraction simulation efforts to investigate the impacts of the above factors on lensing signal measurement. First, we review our past accomplishments on the issue of accurate description and removal of the PSF effects using a principal component analysis method. Then, we present the results of our current shear extraction simulation using artificially sheared galaxy images. Finally, we discuss some key issues that need to be addressed in order to meet the requirement of the LSST weak-lensing science.

Jee, Myungkook J.; Tyson, J. A.; Wittman, D.; Connolly, A. J.; Jernigan, G.; Peterson, J. R.; Ivezic, Z.

2011-01-01

124

Strong Gravitational Lensing in the Einstein-Proca Theory

NASA Astrophysics Data System (ADS)

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.

Li, GuoPing; Zhang, Yan; Zhang, Li; Feng, Zhongwen; Zu, Xiaotao

2014-09-01

125

Spurious Shear in Weak Lensing with LSST

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.

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

126

Gravitational Aharonov-Bohm effect and gravitational lensing

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.

A. Tartaglia

2000-03-08

127

Systematic errors in weak lensing: application to SDSS galaxy-galaxy weak lensing

Weak lensing is emerging as a powerful observational tool to constrain cosmological models, but is at present limited by an incomplete understanding of many sources of systematic error. Many of these errors are multiplicative and depend on the population of background galaxies. We show how the commonly cited geometric test, which is rather insensitive to cosmology, can be used as

Rachel Mandelbaum; Christopher M. Hirata; Uros Seljak; Jacek Guzik; Nikhil Padmanabhan; Cullen Blake; Michael R. Blanton; Robert Lupton; Jonathan Brinkmann

2005-01-01

128

Weak-lensing statistics from the Coyote Universe

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 (Pdelta) to high accuracy for k?[0.002; 3.4] h Mpc-1 within the

Tim Eifler

2011-01-01

129

Weak lensing mass reconstruction using wavelets

NASA Astrophysics Data System (ADS)

This paper presents a new method for the reconstruction of weak lensing mass maps. It uses the multiscale entropy concept, which is based on wavelets, and the False Discovery Rate (FDR) which allows us to derive robust detection levels in wavelet space. We show that this new restoration approach outperforms several standard techniques currently used for weak shear mass reconstruction. This method can also be used to separate E and B modes in the shear field, and thus test for the presence of residual systematic effects. We concentrate on large blind cosmic shear surveys, and illustrate our results using simulated shear maps derived from N-Body ?CDM simulations (Vale & White 2003) with added noise corresponding to both ground-based and space-based observations.

Starck, J.-L.; Pires, S.; Réfrégier, A.

2006-06-01

130

Gravitational Lensing Corrections in Flat ?CDM Cosmology

NASA Astrophysics Data System (ADS)

We compute the deflection angle to order (m/r 0)2 and m/r 0 × ?r 2 0 for a light ray traveling in a flat ?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 ~2% for weakly lensed galaxies behind the rich cluster A1689 and that the reduction can be as large as ~5% for similar rich clusters at z ? 1. Weak-lensing deflection angles caused by galaxies can likewise be reduced by as much as ~4%. We show that the lowest order correction in which ? appears is proportional to m/r_0× ?{? r_0^2}}} and could cause as much as a ~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_0× ?{m/r_0} and can increase the deflection angle by ~0.005% for weak lensing by galaxies.

Kantowski, Ronald; Chen, Bin; Dai, Xinyu

2010-08-01

131

Weak Lensing Cosmology with Pan-STARRS

NASA Astrophysics Data System (ADS)

The Pan-STARRS wide-field imaging system will provide a dramatic leap in performance for cosmological studies using weak lensing of faint background galaxies. Pan-STARRS will use 1.8m diameter optical systems with revolutionary 1.4 giga-pixel CCD cameras, and has been designed from the outset with high precision photometry, astrometry and shape measurements as drivers. The project is proceeding in two phases: PS1 is a single aperture system that has been deployed on Haleakala on Maui and which will become fully operational this year. PS1 will operate for 3.5 years to perform a number of surveys, with the majority of the time assigned to a "3-pi" survey that will give powerful constraints on the large-scale matter power spectrum and its evolution. The full-scale four aperture system PS4 is planned to be deployed on Mauna Kea ca. 2010 with a nominal 10 year survey mission. In this talk I will describe the features of the hardware and survey design that support the challenge of high-precision cosmology from weak lensing and provide forecasts for the constraints that the Pan-STARRS surveys will provide on cosmology.

Kaiser, Nick

2007-05-01

132

Weak lensing using only galaxy position angles

NASA Astrophysics Data System (ADS)

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.

Whittaker, Lee; Brown, Michael L.; Battye, Richard A.

2014-12-01

133

Weighing the light gravitino mass with weak lensing surveys

NASA Astrophysics Data System (ADS)

We explore the discovery potential of light gravitino mass m 3/2 by combining future cosmology surveys and collider experiments. The former probe the imprint of light gravitinos in the cosmic matter density field, whereas the latter search signatures of a supersymmetry breaking mechanism. Free-streaming of light gravitinos suppresses the density fluctuations at galactic and sub-galactic length scales, where weak gravitational lensing can be used as a powerful probe. We perform numerical simulations of structure formation to quantify the effect. We then run realistic ray-tracing simulations of gravitational lensing to measure the cosmic shear in models with light gravitino. We forecast the possible reach of future wide-field surveys by Fisher analysis; the light gravitino mass can be determined with an accuracy of m 3/2 = 4 ± 1 eV by a combination of the Hyper Suprime Cam survey and cosmic microwave background anisotropy data obtained by Planck satellite. The corresponding accuracy to be obtained by the future Large Synoptic Survey Telescope is ?m 3/2 = 0 .6 eV. Data from experiments at Large Hadron Collider at 14 TeV will provide constraint at m 3/2 ? 5 eV in the minimal framework of gauge-mediated supersymmetry breaking (GMSB) model. We conclude that a large class of the GMSB model can be tested by combining the cosmological observations and the collider experiments.

Kamada, Ayuki; Shirasaki, Masato; Yoshida, Naoki

2014-06-01

134

Future detectability of gravitational-wave induced lensing from high-sensitivity CMB experiments

NASA Astrophysics Data System (ADS)

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 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 ?0.1 , even if the consistency relation is difficult to confirm with a high significance, the gravitational-wave induced lensing will be detected at more than 3 ? 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 ?1 0-3 Mpc-1 ), and it could give a much tighter constraint on their energy density ?GW by more than 3 orders of magnitude.

Namikawa, Toshiya; Yamauchi, Daisuke; Taruya, Atsushi

2015-02-01

135

Detecting gravitational lensing from the Cosmic Microwave Background

NASA Astrophysics Data System (ADS)

Gravitational lensing of the Cosmic Microwave Background (CMB) measures all the matter content in the Universe. It can be used to constrain neutrino masses, calibrate biased tracers for large scale structure, and remove contamination of primordial B-modes. The theoretical framework, which includes simulations and reconstruction of gravitational lensing effects from CMB observations, has been established and applied through this dissertation. From observations of the CMB's temperature anisotropy, WMAP datasets are used to probe gravitational lensing effects. It is found that the lensing signal can not be directly detected from WMAP alone but can be indirectly detected at >3sigma if WMAP's CMB observations are cross-correlated with galaxy surveys. Other than the CMB temperature, the CMB polarization is of great importance because the CMB's polarization is more sensitive than its temperature to probing lensing effects. From the ground-based small-scale polarization experiment, POLARBEAR, we (for the first time) measure polarization lensing and lensing B-modes from different types of correlation functions. The B-mode power spectrum is measured, showing the evidence for lensing B-modes at the 2sigma level. Lensing reconstruction with B-modes is also performed. From the auto-correlation of the lensing reconstruction with B-modes, the polarization lensing and lensing B-mode signal is measured at the 4.2sigma level, including systematics. This signal measures dark matter fluctuations with 27% uncertainty. The matter structure seen in the lensing reconstruction is further validated by the cross-correlation with cosmic infrared background, which shows evidence for polarization lensing at 4sigma. This state-of-the-art technique is capable of mapping all gravitating matter in the Universe, is sensitive to the sum of neutrino masses, and is essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves.

Feng, Chang

136

Weak Lensing and the Sloan Digital Sky Survey

While the strategy for the first applications of weak lensing has been to ``go deep'' it is equally interesting to use one's telescope time to instead ``go wide''. The Sloan Survey (SDSS) provides a natural framework for a very wide area weak lensing survey.

Albert Stebbins; Tim Mckay; Joshua A. Frieman

1995-10-04

137

Cosmological Constraints from Weak Lensing Surveys

Focusing on the well motivated aperture mass statistics $\\Map$, we study the possibility of constraining cosmological parameters using future space based SNAP class weak lensing missions. Using completely analytical results we construct the covariance matrix for estimators based on two-point and three-point statistics. Our approach incorporates an accurate modelling of higher-order statistics to describe cosmic variance as well as various sources of discrete noise at small angular scales. These results are then fed into a Fisher matrix based analysis to study cosmological parameter degeneracies. Joint and independent analysis, with or without redshift binning, for various parameter combinations are presented. An analytical modelling of the covariance matrix opens up the possibility of testing various approximations which are often used in derivations of semi-analytical results. These include how inclusion of full non-Gaussian terms in covariance matrix affects parameter estimation. Inclusion of three-point information and how such information can enhance the accuracy with which certain parameters can be estimated is also studied in detail. It is shown that broad correlation structure among various angular scales in such circumstances implies reduction in number of available angular scales which carry completely independent information. On the other hand, the effect of theoretical inaccuracies, in modelling either the power-spectrum or bi-spectrum evolution, onto the measure of cosmological parameters from weak lensing surveys is also considered. Several cosmological parameters, $\\Om$, $\\sigma_8$, spectral index $n_s$, running of spectral index $\\alpha_s$ and equation of state of the dark energy $\\wde$ are included in the analysis.

Dipak Munshi; Patrick Valageas

2005-10-10

138

COSMOS: 3D weak lensing and the growth of structure

We present a three dimensional cosmic shear analysis of the Hubble Space Telescope COSMOS survey, the largest ever optical imaging program performed in space. We have measured the shapes of galaxies for the tell-tale distortions caused by weak gravitational lensing, and traced the growth of that signal as a function of redshift. Using both 2D and 3D analyses, we measure cosmological parameters Omega_m, the density of matter in the universe, and sigma_8, the normalization of the matter power spectrum. The introduction of redshift information tightens the constraints by a factor of three, and also reduces the relative sampling (or "cosmic") variance compared to recent surveys that may be larger but are only two dimensional. From the 3D analysis, we find sigma_8*(Omega_m/0.3)^0.44=0.866+^0.085_-0.068 at 68% confidence limits, including both statistical and potential systematic sources of error in the total budget. Indeed, the absolute calibration of shear measurement methods is now the dominant source of uncertainty. Assuming instead a baseline cosmology to fix the geometry of the universe, we have measured the growth of structure on both linear and non-linear physical scales. Our results thus demonstrate a proof of concept for tomographic analysis techniques that have been proposed for future weak lensing surveys by a dedicated wide-field telescope in space.

Richard Massey; Jason Rhodes; Alexie Leauthaud; Peter Capak; Richard Ellis; Anton Koekemoer; Alexandre Refregier; Nick Scoville; James E. Taylor; Justin Albert; Joel Berge; Catherine Heymans; David Johnston; Jean-Paul Kneib; Yannick Mellier; Bahram Mobasher; Elisabetta Semboloni; Patrick Shopbell; Lidia Tasca; Ludovic Van Waerbeke

2007-02-01

139

Statistics of dark matter haloes expected from weak lensing surveys

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.

Guido Kruse; Peter Schneider

1998-06-04

140

GLIMPSE: accurate 3D weak lensing reconstructions using sparsity

NASA Astrophysics Data System (ADS)

We present GLIMPSE - Gravitational Lensing Inversion and MaPping with Sparse Estimators - a new algorithm to generate density reconstructions in three dimensions from photometric weak lensing measurements. This is an extension of earlier work in one dimension aimed at applying compressive sensing theory to the inversion of gravitational lensing measurements to recover 3D density maps. Using the assumption that the density can be represented sparsely in our chosen basis - 2D transverse wavelets and 1D line-of-sight Dirac functions - we show that clusters of galaxies can be identified and accurately localized and characterized using this method. Throughout, we use simulated data consistent with the quality currently attainable in large surveys. We present a thorough statistical analysis of the errors and biases in both the redshifts of detected structures and their amplitudes. The GLIMPSE method is able to produce reconstructions at significantly higher resolution than the input data; in this paper, we show reconstructions with 6 times finer redshift resolution than the shear data. Considering cluster simulations with 0.05 ? zcl ? 0.75 and 3 × 1013 ? Mvir ? 1015 h-1 M?, we show that the redshift extent of detected peaks is typically 1-2 pixel, or ?z ? 0.07, and that we are able to recover an unbiased estimator of the redshift of a detected cluster by considering many realizations of the noise. We also recover an accurate estimator of the mass, which is largely unbiased when the redshift is known and whose bias is constrained to ?5 per cent in the majority of our simulations when the estimated redshift is taken to be the true redshift. This shows a substantial improvement over earlier 3D inversion methods, which showed redshift smearing with a typical standard deviation of ? ˜ 0.2-0.3, a significant damping of the amplitude of the peaks detected, and a bias in the detected redshift.

Leonard, Adrienne; Lanusse, François; Starck, Jean-Luc

2014-05-01

141

Dark Energy Constraints from Weak-Lensing Cross-Correlation Cosmography

We present a method for implementing the idea of Jain & Taylor for constraining cosmological parameters with weak gravitational lensing. Photometric redshift information on foreground galaxies is used to produce templates of the mass structure at foreground slices zl, and the predicted distortion field is cross-correlated with the measured shapes of sources at redshift zs. The variation of the cross-correlation

G. M. Bernstein; B. Jain

2004-01-01

142

Constraints on warm dark matter from weak lensing in anomalous quadruple lenses

We investigate the weak lensing effect by line-of-sight structures with a surface mass density of solar mass/arcsec^2 in QSO-galaxy quadruple lens systems. Using high-resolution N-body simulations in warm dark matter (WDM) models and observed four quadruple lenses that show anomalies in the flux ratios, we obtain constraints on the mass of thermal WDM, m_WDM>= 1.3keV(95%CL) assuming that the density of the primary lens is described by a singular isothermal ellipsoid (SIE). The obtained constraint is consistent with those from Lyman-$\\alpha$ forests and the number counts of high-redshift galaxies at z>4. Our results show that WDM with a free-streaming comoving wavenumber k_{fs} <= 27 h/Mpc is disfavored as the major component of cosmological density at redshifts 0.5 <~ z <~ 4 provided that the SIE models describe the gravitational potentials of the primary lenses correctly.

Kaiki Taro Inoue; Ryuichi Takahashi; Tomo Takahashi; Tomoaki Ishiyama

2015-02-12

143

Gravitational Lensing and Structural Stability of Dark Matter Caustic Rings

Gravitational lensing by the dual cusp catastrophes of the cold dark matter (CDM) caustic rings at cosmological distances may provide the tantalizing opportunity to detect CDM indirectly, and discriminate between axions and weakly interacting massive particles (WIMPs). Caustics are places where the CDM particles are naturally focussed. Our focus is upon the caustic rings which are closed tubes whose cross-section is an elliptic umbilic catastrophe with three dual cusps. A caustic ring has a specific density profile, a specific geometry and, therefore, precisely calculable gravitational lensing signatures. The magnification monotonically increases as the line of sight approaches to the cusps where it diverges in the limit of zero velocity dispersion. In this limit, we find 37% magnification at a sample point near the outer cusps of the CDM caustic rings at cosmological distances. In the presence of finite velocity dispersion, the lower and upper bounds of the effective velocity dispersions of the axion and WIMP flows in galactic halos may be used to constrain the lensing effects at the cusps. For a cosmological axion caustic ring, we find that the magnification may range between 3% and 2800% at the outer cusp, and between 2% and 46% at the non-planer cusps. For a cosmological WIMP caustic ring, on the other hand, we constrain the magnification between 3% and 28% at the outer cusp, and between 2% and 5% at the non-planer cusps. The images of extended sources may also show distortions that can be unambiguously attributed to lensing by dark matter caustics. Finally, we derive the Catastrophe Function of the triaxial caustic rings. We obtain the flow equations as the equilibrium points of this Catastrophe Function. The analysis of the Stability (Hessian) Matrix show that the caustic rings are structurally stable.

V. K. Onemli

2005-10-28

144

Future detectability of gravitational-wave induced lensing from high-sensitivity CMB experiments

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 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.

Toshiya Namikawa; Daisuke Yamauchi; Atsushi Taruya

2015-03-03

145

Gravitational lensing in a non-uniform plasma

We develop a model of gravitational lensing in a non-uniform plasma. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and of a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. We take into account both effects, and derive the expression for the lensing angle in the case of a strongly nonuniform plasma in presence of the gravitation. Dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, which strongest action is for very long radiowaves. We discuss the observational appearances of this effect for the gravitational lens with a Schwarzschild metric, surrounded by a uniform plasma. We obtain formulae for the lensing angle and the magnification factors in this case and discuss a possibility of observation of this effect by the planned VLBI space project Radioastron. We also consider models with a nonuniform plasma distribution. For different gravitational lens models we compare the corrections to the vacuum lensing due to the gravitational effect in plasma, and due to the plasma inhomogeneity. We have shown that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.

G. S. Bisnovatyi-Kogan; O. Yu. Tsupko

2010-06-11

146

Weak lensing galaxy cluster field reconstruction

NASA Astrophysics Data System (ADS)

In this paper, we compare three methods to reconstruct galaxy cluster density fields with weak lensing data. The first method called FLens integrates an inpainting concept to invert the shear field with possible gaps, and a multi-scale entropy denoising procedure to remove the noise contained in the final reconstruction, that arises mostly from the random intrinsic shape of the galaxies. The second and third methods are based on a model of the density field made of a multi-scale grid of radial basis functions. In one case, the model parameters are computed with a linear inversion involving a singular value decomposition (SVD). In the other case, the model parameters are estimated using a Bayesian Monte Carlo Markov Chain optimization implemented in the lensing software LENSTOOL. Methods are compared on simulated data with varying galaxy density fields. We pay particular attention to the errors estimated with resampling. We find the multi-scale grid model optimized with Monte Carlo Markov Chain to provide the best results, but at high computational cost, especially when considering resampling. The SVD method is much faster but yields noisy maps, although this can be mitigated with resampling. The FLens method is a good compromise with fast computation, high signal-to-noise ratio reconstruction, but lower resolution maps. All three methods are applied to the MACS J0717+3745 galaxy cluster field, and reveal the filamentary structure discovered in Jauzac et al. We conclude that sensitive priors can help to get high signal-to-noise ratio, and unbiased reconstructions.

Jullo, E.; Pires, S.; Jauzac, M.; Kneib, J.-P.

2014-02-01

147

FASTLens (FAst STatistics for weak Lensing) : Fast method for Weak Lensing Statistics and map making

With increasingly large data sets, weak lensing measurements are able to measure cosmological parameters with ever greater precision. However this increased accuracy also places greater demands on the statistical tools used to extract the available information. To date, the majority of lensing analyses use the two point-statistics of the cosmic shear field. These can either be studied directly using the two-point correlation function, or in Fourier space, using the power spectrum. But analyzing weak lensing data inevitably involves the masking out of regions or example to remove bright stars from the field. Masking out the stars is common practice but the gaps in the data need proper handling. In this paper, we show how an inpainting technique allows us to properly fill in these gaps with only $N \\log N$ operations, leading to a new image from which we can compute straight forwardly and with a very good accuracy both the pow er spectrum and the bispectrum. We propose then a new method to compute the bispectrum with a polar FFT algorithm, which has the main advantage of avoiding any interpolation in the Fourier domain. Finally we propose a new method for dark matter mass map reconstruction from shear observations which integrates this new inpainting concept. A range of examples based on 3D N-body simulations illustrates the results.

S. Pires; J. -L. Starck; A. Amara; R. Teyssier; A. Refregier; J. Fadili

2009-02-19

148

Gravitational Lensing by Dark Matter Caustics

Dark matter caustics have specific density profiles and, therefore, precisely calculable gravitational lensing properties. We present a formalism which simplifies the relevant calculations, and apply it to four specific cases. In the first three, the line of sight is tangent to a smooth caustic surface. The curvature of the surface at the tangent point is positive, negative or zero. In the fourth case the line of sight passes near a cusp. For each we derive the map between the image and source planes. In some cases, a point source has multiple images and experiences infinite magnification when the images merge. Unfortunately, for the dark matter caustics expected in realistic galactic halo models, the angular resolution required to resolve the multiple images is not presently achievable. A more promising approach aims to observe the distortions caused by dark matter caustics in the images of extended sources such as radio jets. PACS numbers: 95.35.+d

C. Charmousis A; V. Onemli B; Z. Qiu B; P. Sikivie B

2008-01-01

149

Gravitational lenses in the dark Universe

NASA Astrophysics Data System (ADS)

We discuss how different cosmological models of the Universe affect the probability that a background source has multiple images related by an angular distance, i.e., the optical depth of gravitational lensing. We examine some cosmological models for different values of the density parameter ? i : (i) the cold dark matter model, (ii) the ?CDM model, (iii) the Bose-Einstein condensate dark matter model, (iv) the Chaplygin gas model, (v) the viscous fluid cosmological model and (vi) the holographic dark energy model by using the singular isothermal sphere (SIS) model for the halos of dark matter. We note that the dependence of the energy-matter content of the universe profoundly modifies the frequency of multiple quasar images.

Freitas, R. C.; Gonçalves, S. V. B.; Oliveira, A. M.

2014-01-01

150

GLAMER - II. Multiple-plane gravitational lensing

NASA Astrophysics Data System (ADS)

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.

Petkova, Margarita; Metcalf, R. Benton; Giocoli, Carlo

2014-12-01

151

Gravitational lensing with three-dimensional ray tracing

NASA Astrophysics Data System (ADS)

High-redshift sources suffer from magnification or demagnification due to weak gravitational lensing by large-scale structure. One consequence of this is that the distance-redshift relation, in wide use for cosmological tests, suffers lensing-induced scatter which can be quantified by the magnification probability distribution. Predicting this distribution generally requires a method for ray tracing through cosmological N-body simulations. However, standard methods tend to apply the multiple-thin-lens approximation. In an effort to quantify the accuracy of these methods, we develop an innovative code that performs ray tracing without the use of this approximation. The efficiency and accuracy of this computationally challenging approach can be improved by careful choices of numerical parameters; therefore, the results are analysed for the behaviour of the ray-tracing code in the vicinity of Schwarzschild and Navarro-Frenk-White lenses. Preliminary comparisons are drawn with the multiple-lens-plane ray-bundle method in the context of cosmological mass distributions for a source redshift of zs= 0.5. Research undertaken as part of the Commonwealth Cosmology Initiative (CCI: ), an international collaboration supported by the Australian Research Council (ARC).

Killedar, M.; Lasky, P. D.; Lewis, G. F.; Fluke, C. J.

2012-02-01

152

Can Strong Gravitational Lensing Constrain Dark Energy?

We discuss the ratio of the angular diameter distances from the source to the lens, $D_{ds}$, and to the observer at present, $D_{s}$, for various dark energy models. It is well known that the difference of $D_s$s between the models is apparent and this quantity is used for the analysis of Type Ia supernovae. However we investigate the difference between the ratio of the angular diameter distances for a cosmological constant, $(D_{ds}/D_{s})^{\\Lambda}$ and that for other dark energy models, $(D_{ds}/D_{s})^{\\rm{other}}$ in this paper. It has been known that there is lens model degeneracy in using strong gravitational lensing. Thus, we investigate the model independent observable quantity, Einstein radius ($\\theta_E$), which is proportional to both $D_{ds}/D_s$ and velocity dispersion squared, $\\sigma_v^2$. $D_{ds}/D_s$ values depend on the parameters of each dark energy model individually. However, $(D_{ds}/D_s)^{\\Lambda} - (D_{ds}/D_{s})^{\\rm{other}}$ for the various dark energy models, is well within the error of $\\sigma_v$ for most of the parameter spaces of the dark energy models. Thus, a single strong gravitational lensing by use of the Einstein radius may not be a proper method to investigate the property of dark energy. However, better understanding to the mass profile of clusters in the future or other methods related to arc statistics rather than the distances may be used for constraints on dark energy.

Seokcheon Lee; Kin-Wang Ng

2007-07-12

153

Probing the cosmic web: intercluster filament detection using gravitational lensing

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

James M. G. Mead; Lindsay J. King; Ian G. McCarthy

2010-01-01

154

Hubristic Data Analysis: Weak Lensing Measurements from SDSS

Hubristic Data Analysis: Weak Lensing Measurements from SDSS Eric Huff Tim Eifler, Chris Hirata is not easy to model. SDSS #12;Lensing is the distortion of background images by foreground mass: dL dS dLS d is the ellipticity of this galaxy? #12;We've built a catalog from SDSS data that addresses these problems We set out

Militzer, Burkhard

155

Gravitational lensing by a charged black hole of string theory

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.

A. Bhadra

2003-06-04

156

Weak gravitational lensing due to the inhomogeneous matter distribution in the universe is an important systematic uncertainty in the use of standard candles in cosmology. There are two different descriptions of weak lensing amplification, one uses a local smoothness parameter $\\tilde{\\alpha}$, the other uses reduced convergence $\\eta= 1+ \\kappa/|\\kappa_{min}|$ (where $\\kappa$ is convergence). The $\\tilde{\\alpha}$ description involves Dyer-Roeder distance $D_A(\\tilde{\\alpha}|z)$ ($\\tilde{\\alpha}=1$ corresponds to a smooth universe); it is simple and convenient, and has been used by the community to illustrate the effect of weak lensing on point sources such as type Ia supernovae. Wang (1999) has shown that the $\\tilde{\\alpha}$ description can be made realistic by allowing $\\tilde{\\alpha}$ to be a local variable, the local smoothness parameter. The $\\eta$ description has been used by Wang, Holz, & Munshi (2002) to derive a universal probability distribution (UPDF) for weak lensing amplification. In this paper, we bridge the two different descriptions of weak lensing amplification by relating the reduced convergence $\\eta$ and the local smoothness parameter $\\tilde{\\alpha}$. We give the variance of $\\tilde{\\alpha}$ in terms of the matter power spectrum, thus providing a quantitative guidance to the use of Dyer-Roeder distances in illustrating the effect of weak lensing. The by-products of this work include a corrected definition of the reduced convergence, and simple and accurate analytical expressions for $D_A(\\tilde{\\alpha}|z)$. Our results should be very useful in studying the weak lensing of standard candles.

Yun Wang; Jason Tenbarge; Bobby Fleshman

2005-01-17

157

What is Gravitational Lensing? (LBNL Summer Lecture Series)

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.

Leauthaud, Alexie; Nakajima, Reiko (Berkeley Center for Cosmological Physics) [Berkeley Center for Cosmological Physics

2009-07-28

158

What is Gravitational Lensing? (LBNL Summer Lecture Series)

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.

Leauthaud, Alexie; Nakajima, Reiko [Berkeley Center for Cosmological Physics

2011-04-28

159

THE MISSING WEAK LENSING MASS IN A781

Measuring cluster masses accurately is important for testing the cosmological paradigm. Weak lensing is one of the most promising methods for detecting, measuring, and calibrating cluster mass estimates made using other mass proxies (e.g., X-ray, Sunyaev-Zel'dovich effect, spectroscopy). However, it is still essential to characterize and understand the causes of systematic error and bias in weak lensing measurements. A781D is a cluster of galaxies with a mass and redshift that places it well within the theoretical detection limits of weak lensing analyses from the ground yet has evaded detection in previous weak lensing studies. Previous weak lensing measurements in the region surrounding this cluster from the Deep Lens Survey were unable to detect it and placed a 1{sigma} limit on the mass of <5 Multiplication-Sign 10{sup 13} M{sub Sun }. Given independent estimates of the cluster mass by X-ray and spectroscopic measurements and its spectroscopically confirmed redshift of 0.43, it is difficult to explain its absence from the weak lensing mass reconstructions. We re-analyzed this cluster using imaging from the Orthogonal Parallel Transfer Imaging Camera and archival Suprime-Cam data. We successfully detect A781A in both analyses, but A781D remains undetected. We use these two new independent analyses to rule out systematic effects from the telescope, instrument, and point-spread function correction as the cause of the null detection. We also demonstrate the first use of an orthogonal transfer camera for weak lensing analysis and demonstrate its suitability for weak lensing studies.

Cook, Richard I.; Dell'Antonio, I. P. [Department of Physics, Brown University, Providence, RI 02912 (United States)

2012-05-10

160

Gravitational lensing by globular clusters and Arp objects

We try to explain quasar-galaxy associations by gravitational lensing by globular clusters, located in the halos of foreground galaxies. We propose observational test for verification of this hypothesis. We processed SUPERCOSMOS sky survey and found overdensities of star-like sources with zero proper motions in the vicinities of foreground galaxies from CfA3 catalog. We show mean effect for galaxies with different redshifts. Two effects can explain observational data - these are lensing by globular clusters and lensing by dwarf galaxies. We made CCD 3-color photometry with 2.0-1.2 meter telescopes to select extremely lensed objects around several galaxies for spectroscopic observations.

A. Yushchenko; Chulhee Kim; A. Sergeev; P. Niarchos; V. Manimanis

2003-08-20

161

Gravitational Lenses and the Structure and Evolution of Galaxies

NASA Technical Reports Server (NTRS)

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.

Kochanek, Christopher

2003-01-01

162

An HST Snapshot Survey for Gravitationally Lensed z=6 Quasars

NASA Astrophysics Data System (ADS)

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.

McGreer, Ian D.; Fan, X.; Richards, G. T.; Haiman, Z.; Strauss, M. A.; Jiang, L.; Schneider, D. P.

2013-01-01

163

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.

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

164

Constraints on cosmological models from strong gravitational lensing systems

NASA Astrophysics Data System (ADS)

Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances Dds/Ds from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (?CDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.

Cao, Shuo; Pan, Yu; Biesiada, Marek; Godlowski, Wlodzimierz; Zhu, Zong-Hong

2012-03-01

165

Constraints on cosmological models from strong gravitational lensing systems

Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances D{sub ds}/D{sub s} from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (?CDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.

Cao, Shuo; Pan, Yu; Zhu, Zong-Hong [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Biesiada, Marek [Department of Astrophysics and Cosmology, Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland); Godlowski, Wlodzimierz, E-mail: baodingcaoshuo@163.com, E-mail: panyu@cqupt.edu.cn, E-mail: biesiada@us.edu.pl, E-mail: godlowski@uni.opole.pl, E-mail: zhuzh@bnu.edu.cn [Institute of Physics, Opole University, Oleska 48, 45-052 Opole (Poland)

2012-03-01

166

Weak lensing generated by vector perturbations and detectability of cosmic strings

We study the observational signature of vector metric perturbations through the effect of weak gravitational lensing. In the presence of vector perturbations, the non-vanishing signals for B-mode cosmic shear and curl-mode deflection angle, which have never appeared in the case of scalar metric perturbations, naturally arise. Solving the geodesic and geodesic deviation equations, we drive the full-sky formulas for angular power spectra of weak lensing signals, and give the explicit expressions for E-/B-mode cosmic shear and gradient-/curl-mode deflection angle. As a possible source for seeding vector perturbations, we then consider a cosmic string network, and discuss its detectability from upcoming weak lensing and CMB measurements. Based on the formulas and a simple model for cosmic string network, we calculate the angular power spectra and expected signal-to-noise ratios for the B-mode cosmic shear and curl-mode deflection angle. We find that the weak lensing signals are enhanced for a smaller intercommuting probability of the string network, P, and they are potentially detectable from the upcoming cosmic shear and CMB lensing observations. For P ? 10{sup ?1}, the minimum detectable tension of the cosmic string will be down to G? ? 5 × 10{sup ?8}. With a theoretically inferred smallest value P ? 10{sup ?3}, we could even detect the string with G? ? 5 × 10{sup ?10}.

Yamauchi, Daisuke [Institute for Cosmic Ray Research, The University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Namikawa, Toshiya [Department of Physics, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-033 (Japan); Taruya, Atsushi, E-mail: yamauchi@icrr.u-tokyo.ac.jp, E-mail: namikawa@utap.phys.s.u-tokyo.ac.jp, E-mail: ataruya@utap.phys.s.u-tokyo.ac.jp [Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-033 (Japan)

2012-10-01

167

Scaling the universe: gravitational lenses and the Hubble constant.

Gravitational lenses, besides being interesting in their own right, have been demonstrated to be suitable as "gravitational standard rulers" for the measurement of the rate of expansion of the Universe (Ho), as well as to constrain the values of the cosmological parameters such as Omegao and Lambdao that control the evolution of the volume of the Universe with cosmic time. PMID:10200245

Myers, S T

1999-04-13

168

Wave effect in gravitational lensing by a cosmic string

The wave effect in the gravitational lensing phenomenon by a straight cosmic string is investigated. The interference pattern is expressed in terms of a simple formula. We demonstrate that modulations of the interfered wave amplitude can be a unique signature of the wave effect. We briefly mention a possible chance of detecting the wave effect in future gravitational wave observatories.

Kazuhiro Yamamoto; Keiji Tsunoda

2003-09-25

169

Scaling the universe: Gravitational lenses and the Hubble constant

Gravitational lenses, besides being interesting in their own right, have been demonstrated to be suitable as “gravitational standard rulers” for the measurement of the rate of expansion of the Universe (Ho), as well as to constrain the values of the cosmological parameters such as ?o and ?o that control the evolution of the volume of the Universe with cosmic time. PMID:10200245

Myers, Steven T.

1999-01-01

170

Transient weak lensing by cosmological dark matter microhaloes

NASA Astrophysics Data System (ADS)

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.

Rahvar, Sohrab; Baghram, Shant; Afshordi, Niayesh

2014-03-01

171

Gravitational lensing by black holes: The case of Sgr A*

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.

Bozza, V. [Dipartimento di Fisica E.R. Caianiello, Università di Salerno, Italy. Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy)

2014-01-14

172

Gravitational lensing by black holes: The case of Sgr A*

NASA Astrophysics Data System (ADS)

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.

Bozza, V.

2014-01-01

173

Polarization as an indicator of intrinsic alignment in radio weak lensing

NASA Astrophysics Data System (ADS)

We propose a new technique for weak gravitational lensing in the radio band making use of polarization information. Since the orientation of a galaxy’s polarized emission is both unaffected by lensing and is related to the galaxy’s intrinsic orientation, it effectively provides information on the unlensed galaxy position angle. We derive a new weak-lensing estimator, which exploits this effect and makes full use of both the observed galaxy shapes and the estimates of the intrinsic position angles as provided by polarization. Our method has the potential both to reduce the effects of shot noise and to reduce to negligible levels, in a model-independent way, all effects of intrinsic galaxy alignments. We test our technique on simulated weak-lensing skies, including an intrinsic alignment contaminant consistent with recent observations, in three overlapping redshift bins. Adopting a standard weak-lensing analysis and ignoring intrinsic alignments results in biases of 5-10 per cent in the recovered power spectra and cosmological parameters. Applying our new estimator to one-tenth the number of galaxies used for the standard case, we recover both power spectra and the input cosmology with similar precision and with negligible residual bias. This remains true even in the presence of a substantial (astrophysical) scatter in the relationship between the observed orientation of the polarized emission and the intrinsic orientation. Assuming a reasonable polarization fraction for star-forming galaxies, and no cosmological conspiracy in the relationship between polarization direction and intrinsic morphology, our estimator should prove a valuable tool for weak-lensing analyses of forthcoming radio surveys, in particular, deep wide-field surveys with e-MERLIN, MeerKAT and ASKAP, and ultimately, definitive radio lensing surveys with the SKA.

Brown, Michael L.; Battye, Richard A.

2011-01-01

174

Weak Lensing Mass Calibration of the RBC X-ray Galaxy Cluster Catalog

NASA Astrophysics Data System (ADS)

In order to fully realize the potential of galaxy clusters as a cosmological probe, we must understand the mass function of the galaxy clusters we observe. Weak gravitational lensing provides a valuable tool for measuring the cluster masses because it is a direct probe of the gravitational field of the cluster, without assumptions about cluster structure. Here we present a weak lensing measurement of the masses of clusters in the RBC catalog. Our clusters are drawn from the ROSAT All-Sky Survey, an X-ray selected catalog, with a well-understood selection function. We compare our results to simulation outputs to probe the impact of substructure and three-dimensional shape not captured by simple analytical models, and discuss the relationship between the galaxy cluster masses we measure and the masses inferred based on assumptions of hydrostatic equilibrium.

Simet, Melanie; Battaglia, Nicholas; Mandelbaum, Rachel; Seljak, Uros

2015-01-01

175

Accurate weak lensing of standard candles. I. Flexible cosmological fits

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.

Valerio Marra; Miguel Quartin; Luca Amendola

2013-09-02

176

Prospects and pitfalls of gravitational lensing in large supernova surveys

NASA Astrophysics Data System (ADS)

Aims: To investigate the effect of gravitational lensing of supernovae in large ongoing surveys. Methods: We simulate the effect of gravitational lensing magnification on individual supernovae using observational data input from two large supernova surveys. To estimate the magnification due to matter in the foreground, we simulate galaxy catalogs and compute the magnification along individual lines of sight using the multiple lens plane algorithm. The dark matter haloes of the galaxies are modelled as gravitational lenses using singular isothermal sphere or Navarro-Frenk-White profiles. Scaling laws between luminosity and mass, provided by Faber-Jackson and Tully-Fisher relations, are used to estimate the masses of the haloes. Results: While our simulations show that the SDSSII supernova survey is marginally affected by gravitational lensing, we find that the effect will be measurable in the SNLS survey that probes higher redshifts. Our simulations show that the probability to measure a significant (3?) correlation between the Hubble diagram residuals and the calculated lensing magnification is ?95% in the SNLS data. Moreover, with this data it should be possible to constrain the normalisation of the masses of the lensing galaxy haloes at the 1? and 2? confidence level with ˜ 30% and ~ 60% accuracy, respectively.

Jönsson, J.; Kronborg, T.; Mörtsell, E.; Sollerman, J.

2008-08-01

177

Weak Lensing PSF Correction of Wide-field CCD Mosaic Images (SULI Paper)

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.

Cevallos, Marissa; /Caltech /SLAC

2006-01-04

178

GREAT3: The Third Gravitational Lensing Accuracy Testing Challenge

NASA Astrophysics Data System (ADS)

We describe the upcoming weak lensing community data challenge, GREAT3, and the associated open-source image simulation software, GalSim. The GREAT3 challenge will test the impact on weak lensing measurements of (a) realistic galaxy morphologies, (b) realistic uncertainty in the point-spread function estimation, and (c) the need to combine multiple exposures when estimating the galaxy shape. It will include simulated ground- and space-based data, and the tests of realistic galaxy morphologies will rely on a training set of galaxies from the Hubble Space Telescope which will be publicly released at the start of the challenge. We describe some technical considerations for generating the challenge data and for testing weak lensing measurements with the next generation of weak lensing surveys, such as DES, HSC, KIDS, and Pan-STARRS.

Mandelbaum, Rachel; Rowe, B.; GREAT3 Collaboration

2013-01-01

179

GREAT3: The Third Gravitational Lensing Accuracy Testing Challenge

NASA Astrophysics Data System (ADS)

We describe the ongoing weak lensing community data challenge, GREAT3, and the associated open-source image simulation software, GalSim. The GREAT3 challenge tests the impact on weak lensing measurements of (a) realistic galaxy morphologies, (b) realistic uncertainty in the point-spread function estimation, and (c) the need to combine multiple exposures when estimating the galaxy shape. It includes simulated ground- and space-based data. The tests of realistic galaxy morphologies rely on a training set of galaxies from the Hubble Space Telescope, a subset of which has been publicly released for community use, with the remainder to be released at the end of the challenge. We describe some technical considerations for generating the challenge data and for testing weak lensing measurements with the next generation of weak lensing surveys, such as DES, HSC, KIDS, and Pan-STARRS.

Simet, Melanie; Mandelbaum, R.; Rowe, B.; Great3 Collaboration

2014-01-01

180

Dark galaxies, spin bias and gravitational lenses

NASA Astrophysics Data System (ADS)

Gravitational lensing studies suggest that the universe may contain a population of dark galaxies. We investigate this intriguing possibility and propose a mechanism to explain their nature. In this mechanism a dark galaxy is formed with a low-density disk in a dark halo of high spin parameter; such galaxies can have surface densities below the critical Toomre value for instabilities to develop, and following Kennicutt's work we expect these galaxies to have low star formation rates. The only stellar component of the galaxies is a halo system, formed during the collapse of the protogalactic cloud. We compute synthetic stellar population models and show that, at a redshift z = 0.5, such galaxies have apparent magnitudes B of about 28, R of about 26, and I of about 25, and could be unveiled by deep searches with the Hubble Space Telescope. Dark galaxies have an initial short blue phase and then become essentially invisible; therefore they may account for the blue population of galaxies at high redshift. We find a strong mass dependence in the fraction of dark galaxies, and predict that spiral galaxies will not be found in haloes with masses less than about 10 exp 9 solar masses if Omega0 = 1. Above about 10 exp 12 solar masses, all haloes can produce luminous disks. The mass dependence of the galaxy formation efficiency introduces the possibility of 'spin bias' - luminous galaxies being associated preferentially with strongly clustered high-mass haloes. A further prediction is that the slope of the faint-end luminosity function for galaxies will be flatter than the associated halo mass function.

Jimenez, R.; Heavens, A. F.; Hawkins, M. R. S.; Padoan, P.

1997-11-01

181

Data mining for gravitationally lensed quasars

NASA Astrophysics Data System (ADS)

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.

Agnello, Adriano; Kelly, Brandon C.; Treu, Tommaso; Marshall, Philip J.

2015-04-01

182

Planck 2015 results. XV. Gravitational lensing

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 40fitting LCDM model based on the Planck temperature and polarization power spectra. Using the lensing likelihood alone we obtain a percent-level measurement of ...

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

183

A SNAP Survey for Gravitational Lenses Among z~6 Quasars

NASA Astrophysics Data System (ADS)

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.

Fan, Xiaohui

2010-09-01

184

Gravitational lensing by a charged black hole of string theory

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

A. Bhadra

2003-01-01

185

Gravitational Lenses and the Structure and Evolution of Galaxies

NASA Technical Reports Server (NTRS)

During the first year of the project we completed five papers, each of which represents a new direction in the theory and interpretation of gravitational lenses. In the first paper, The Importance of Einstein Rings, we developed the first theory for the formation and structure of the Einstein rings formed by lensing extended sources like the host galaxies of quasar and radio sources. In the second paper, Cusped Mass Models Of Gravitational Lenses, we introduced a new class of lens models. In the third paper, Global Probes of the Impact of Baryons on Dark Matter Halos, we made the first globally consistent models for the separation distribution of gravitational lenses including both galaxy and cluster lenses. The last two papers explore the properties of two lenses in detail. During the second year we have focused more closely on the relationship of baryons and dark matter. In the third year we have been further examining the relationship between baryons and dark matter. In the present year we extended our statistical analysis of lens mass distributions using a self-similar model for the halo mass distribution as compared to the luminous galaxy.

Oliversen, Ronald J. (Technical Monitor); Kochanek, Christopher

2004-01-01

186

Gravitational lensing and structural stability of dark matter caustic rings

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.

Onemli, V. K. [Department of Physics, University of Crete, GR-71003 Heraklion (Greece) and Laboratoire de Physique Theorique, Universite Paris XI, Bat. 210, 91405 Orsay (France)

2006-12-15

187

Galaxy cluster center detection methods with weak lensing

NASA Astrophysics Data System (ADS)

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.

Simet, Melanie

188

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 ...

Bautz, Marshall W.

189

Strong gravitational lensing and galactic bulges

Lensing probabilities of quasars with image separations greater than \\Delta\\theta and flux density ratios less than q_{\\mathrm{r}} are calculated by foreground dark matter halos in a flat, cosmological constant dominated (\\LambdaCDM) universe . The mass density of the lenses is taken to be the Navarro-Frenk-White (NFW) profile on all mass scales, plus a central point mass for low-mass halos with M

Da-Ming Chen

2003-03-10

190

Reverberation Mapping of a Gravitationally-lensed Quasar

NASA Astrophysics Data System (ADS)

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.

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

191

Gravitational lensing by Einstein-Born-Infeld black holes

In this paper, charged black holes in general relativity coupled to Born-Infeld electrodynamics are studied as gravitational lenses. The positions and magnifications of the relativistic images are obtained using the strong deflection limit, and the results are compared with those corresponding to a Reissner-Nordström black hole with the same mass and charge. As numerical examples, the model is applied to

Ernesto F. Eiroa; F ´ õsica del Espacio

2006-01-01

192

Gravitational lensing of the SNLS supernovae Taia Kronborg

Gravitational lensing of the SNLS supernovae Taia Kronborg February 3, 2011 tel-00562370,version1 the supernova group at the LPNHE in Paris and the people at DARK in Copenhagen for having accepted me, it simply makes my day... 2 tel-00562370,version1-3Feb2011 #12;Abstract Type Ia supernovae have become

Paris-Sud XI, UniversitÃ© de

193

A new weak lensing shear analysis method using ellipticity defined by 0th order moments

NASA Astrophysics Data System (ADS)

We developed a new method that uses ellipticity defined by 0th order moments (0th-ellipticity) for weak gravitational lensing shear analysis. Although there is a strong correlation between the ellipticity calculated using this approach and the usual ellipticity defined by the 2nd order moment, the ellipticity calculated here has a higher signal-to-noise ratio because it is weighted to the central region of the image. These results were confirmed using data for Abell 1689 from the Subaru telescope. For shear analysis, we adopted the ellipticity of re-smeared artificial image method for point spread function correction, and we tested the precision of this 0th-ellipticity with simple simulation, then we obtained the same level of precision with the results of ellipticity defined by quadrupole moments. Thus, we can expect that weak lensing analysis using 0 shear will be improved in proportion to the statistical error.

Okura, Yuki; Futamase, Toshifumi

2015-04-01

194

Flux-limited strong gravitational lensing and dark energy

In the standard flat cosmological constant ($\\Lambda$) cold dark matter (CDM) cosmology, a model of two populations of lens halos for strong gravitational lensing can reproduce the results of the Jodrell-Bank VLA Astrometric Survey (JVAS) and the Cosmic Lens All-Sky Survey (CLASS) radio survey. In such a model, lensing probabilities are sensitive to three parameters: the concentration parameter $c_1$, the cooling mass scale $M_\\mathrm{c}$ and the value of the CDM power spectrum normalization parameter $\\sigma_8$. The value ranges of these parameters are constrained by various observations. However, we found that predicted lensing probabilities are also quite sensitive to the flux density (brightness) ratio $q_{\\mathrm{r}}$ of the multiple lensing images, which has been, in fact, a very important selection criterion of a sample in any lensing survey experiments. We re-examine the above mentioned model by considering the flux ratio and galactic central Super Massive Black Holes (SMBHs), in flat, low-density cosmological models with different cosmic equations of state $\\omega$, and find that the predicted lensing probabilities without considering $q_{\\mathrm{r}}$ are over-estimated. A low value of $q_\\mathrm{r}$ can be compensated by raising the cooling mass scale $M_\\mathrm{c}$ in fitting the predicted lensing probabilities to JVAS/CLASS observations. In order to determine the cosmic equation of state $\\omega$, the uncertainty in $M_\\mathrm{c}$ must be resolved. The effects of SMBHs cannot be detected by strong gravitational lensing method when $q_{\\mathrm{r}}\\leq 10$.

Da-Ming Chen

2004-04-16

195

NASA Astrophysics Data System (ADS)

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}.

Shirasaki, Masato; Yoshida, Naoki

2014-05-01

196

NASA Astrophysics Data System (ADS)

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.

Chen, Bin; Kantowski, R.; Dai, X.

2014-01-01

197

NASA Astrophysics Data System (ADS)

Context. Evolution in the mass function of galaxy clusters sensitively traces both the expansion history of the Universe and cosmological structure formation. Robust cluster mass determinations are a key ingredient for a reliable measurement of this evolution, especially at high redshift. Weak gravitational lensing is a promising tool for, on average, unbiased mass estimates. Aims: This weak lensing project aims at measuring reliable weak lensing masses for a complete X-ray selected sample of 36 high redshift (0.35 < z < 0.9) clusters. The goal of this paper is to demonstrate the robustness of the methodology against commonly encountered problems, including pure instrumental effects, the presence of bright (8-9 mag) stars close to the cluster centre, ground based measurements of high-z (z ~0.8) clusters, and the presence of massive unrelated structures along the line-sight. Methods: We select a subsample of seven clusters observed with MMT/MegaCam. Instrumental effects are checked in detail by cross-comparison with an archival CFHT/MegaCam observation. We derive mass estimates for seven clusters by modelling the tangential shear with an NFW profile, in two cases with multiple components to account for projected structures in the line-of-sight. Results: We firmly detect lensing signals from all seven clusters at more than 3.5? and determine their masses, ranging from 1014 M? to 1015 M?, despite the presence of nearby bright stars. We retrieve the lensing signal of more than one cluster in the CL 1701+6414 field, while apparently observing CL 1701+6414 through a massive foreground filament. We also find a multi-peaked shear signal in CL 1641+4001. Shear structures measured in the MMT and CFHT images of CL 1701+6414 are highly correlated. Conclusions: We confirm the capability of MMT/MegaCam to infer weak lensing masses from high-z clusters, demonstrated by the high level of consistency between MMT and CFHT results for CL 1701+6414. This shows that, when a sophisticated analysis is applied, instrumental effects are well under control. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.Appendices are available in electronic form at http://www.aanda.orgReduced and coadded MMT image files are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/546/A79

Israel, H.; Erben, T.; Reiprich, T. H.; Vikhlinin, A.; Sarazin, C. L.; Schneider, P.

2012-10-01

198

Gravitational lenses in generalized Einstein-aether theory: The bullet cluster

We study the lensing properties of an asymmetric mass distribution and vector field in generalized Einstein-aether (GEA) theory. As vector-field fluctuations are responsible in GEA for seeding baryonic structure formation, vector-field concentrations can exist independently of baryonic matter. Such concentrations would not be expected to be tied to baryonic matter except gravitationally, and so, like dark matter halos, would become separated from baryonic matter in interacting systems such as the bullet cluster. These vector-field concentrations cause metric deviations that affect weak lensing. Therefore, the distribution of weak lensing deviates from that which would be inferred from the luminous mass distribution, in a way that numerical calculations demonstrate can be consistent with observations. This suggests that MOND-inspired theories can reproduce weak lensing observations, but makes clear the price: the existence of a coherent large-scale fluctuation of a field(s) weakly tied to the baryonic matter, not completely dissimilar to a dark matter halo.

Dai, D.-C. [HEPCOS, Department of Physics, SUNY at Buffalo, Buffalo, New York 14260-1500 (United States); Matsuo, Reijiro; Starkman, Glenn [CERCA, Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106-7079 (United States)

2008-11-15

199

An X-ray Study of Gravitational Lenses: Probing AGNs and the Cosmos with the Aid of Lensing

Gravitational lensing of distant quasars by intervening galaxies, where multiple images are formed, is a spectacular phenomenon in the universe. With the advent of Chandra, it is possible to resolve for the first time in the X-ray band lensed quasar images with separations greater than about 0.3 arcsec. We use lensing as a tool to study AGN and Cosmology. The

X. Dai

2003-01-01

200

Strong gravitational lensing in a noncommutative black-hole spacetime

Noncommutative geometry may be a starting point to a quantum gravity. We study the influence of the spacetime noncommutative parameter on the strong field gravitational lensing in the noncommutative Schwarzschild black-hole spacetime and obtain the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy can be described by this metric, we estimate the numerical values of the coefficients and observables for strong gravitational lensing. In comparison to the Reissner-Norstroem black hole, we find that the influences of the spacetime noncommutative parameter is similar to those of the charge, but these influences are much smaller. This may offer a way to distinguish a noncommutative black hole from a Reissner-Norstroem black hole, and may permit us to probe the spacetime noncommutative constant {theta} by the astronomical instruments in the future.

Ding Chikun; Kang Shuai; Chen Changyong; Chen Songbai; Jing Jiliang [Department of Physics and Information Engineering, Hunan Institute of Humanities Science and Technology, Loudi, Hunan 417000 (China); Institute of Physics and Department of Physics, Hunan Normal University, Changsha, Hunan 410081 (China) and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University), Ministry of Education (China)

2011-04-15

201

Testing gravity with halo density profiles observed through gravitational lensing

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.

Narikawa, Tatsuya; Yamamoto, Kazuhiro, E-mail: narikawa@theo.phys.sci.hiroshima-u.ac.jp, E-mail: kazuhiro@hiroshima-u.ac.jp [Department of Physical Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan)

2012-05-01

202

Non-linear relativistic contributions to the cosmological weak-lensing convergence

NASA Astrophysics Data System (ADS)

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.

Andrianomena, Sambatra; Clarkson, Chris; Patel, Prina; Umeh, Obinna; Uzan, Jean-Philippe

2014-06-01

203

A likelihood-based method for measuring weak gravitational lensing shear in deep galaxy surveys is described and applied to the Canada-France-Hawaii Telescope (CFHT) Lensing Survey (CFHTLenS). CFHTLenS comprises 154 sq deg of multicolour optical data from the CFHT Legacy Survey, with lensing measurements being made in the i' band to a depth i'(AB)<24.7, for galaxies with signal-to-noise ratio greater than about 10. The method is based on the lensfit algorithm described in earlier papers, but here we describe a full analysis pipeline that takes into account the properties of real surveys. The method creates pixel-based models of the varying point spread function (PSF) in individual image exposures. It fits PSF-convolved two-component (disk plus bulge) models, to measure the ellipticity of each galaxy, with bayesian marginalisation over model nuisance parameters of galaxy position, size, brightness and bulge fraction. The method allows optimal joint measurement of multiple, dithered image exposures, taking i...

Miller, L; Kitching, T D; Van Waerbeke, L; Erben, T; Hildebrandt, H; Hoekstra, H; Mellier, Y; Rowe, B T P; Coupon, J; Dietrich, J P; Fu, L; Harnois-Deraps, J; Hudson, M J; Kilbinger, M; Kuijken, K; Schrabback, T; Semboloni, E; Vafaei, S; Velander, M

2013-01-01

204

NASA Astrophysics Data System (ADS)

A likelihood-based method for measuring weak gravitational lensing shear in deep galaxy surveys is described and applied to the Canada-France-Hawaii Telescope (CFHT) Lensing Survey (CFHTLenS). CFHTLenS comprises 154 deg2 of multi-colour optical data from the CFHT Legacy Survey, with lensing measurements being made in the i' band to a depth i'AB < 24.7, for galaxies with signal-to-noise ratio ?SN ? 10. The method is based on the lensfit algorithm described in earlier papers, but here we describe a full analysis pipeline that takes into account the properties of real surveys. The method creates pixel-based models of the varying point spread function (PSF) in individual image exposures. It fits PSF-convolved two-component (disc plus bulge) models to measure the ellipticity of each galaxy, with Bayesian marginalization over model nuisance parameters of galaxy position, size, brightness and bulge fraction. The method allows optimal joint measurement of multiple, dithered image exposures, taking into account imaging distortion and the alignment of the multiple measurements. We discuss the effects of noise bias on the likelihood distribution of galaxy ellipticity. Two sets of image simulations that mirror the observed properties of CFHTLenS have been created to establish the method's accuracy and to derive an empirical correction for the effects of noise bias.

Miller, L.; Heymans, C.; Kitching, T. D.; van Waerbeke, L.; Erben, T.; Hildebrandt, H.; Hoekstra, H.; Mellier, Y.; Rowe, B. T. P.; Coupon, J.; Dietrich, J. P.; Fu, L.; Harnois-Déraps, J.; Hudson, M. J.; Kilbinger, M.; Kuijken, K.; Schrabback, T.; Semboloni, E.; Vafaei, S.; Velander, M.

2013-03-01

205

Weak Lensing Mass Distributions of Nearby Clusters of Galaxies

NASA Astrophysics Data System (ADS)

We describe results from a weak lensing survey of a complete, X-ray luminosity-limited sample of 18 nearby (z<0.1) southern clusters scheduled for Sunyaev--Ze'dovich (SZ) observations by the Viper telescope at the South Pole. We have collected data and produced mass maps of 1/2 of the sample. Using multiple images, we have shown the reproducibility of weak lensing measurements of the mass distributions in such clusters. We are combining these mass distributions with X-ray data, optical redshifts, SZ observations, and other high-quality ancillary data to study the baryon fractions, morphologies, and form robust measurements of the mass of these clusters. These are first steps in determining the local cluster mass function, a fundamental goal of cosmology, used to constrain the cosmological model and ? 0.

Joffre, M.; Fischer, P.; Frieman, J.; Johnston, D.; McKay, T.; Mohr, J.; Nichol, B.; Sheldon, E.; Cantaloupo, C.; Griffin, G.; Peterson, J.; Romer, A. K.

1999-12-01

206

Weak Lensing Mass Maps of Very Nearby Clusters of Galaxies

NASA Astrophysics Data System (ADS)

We present results from a weak lensing survey of an X-ray luminosity-limited sample of 18 nearby (z<0.1) southern clusters scheduled for Sunyaev--Zel'dovich (SZ) observations by the Viper telescope at the South Pole. We have observed and produced mass maps of 1/2 of the sample. We have shown the reproducibility of weak lensing measurements of the mass distributions in such clusters with multiple observations. We have combined these mass distributions with X-ray data, optical redshifts, SZ observations, and other high-quality ancillary data to study the baryon fractions, morphologies, and form robust measurements of the mass of these clusters. These are first steps in determining the local cluster mass function, a fundamental goal of cosmology, used to constrain the cosmological model and ?_0.

Joffre, M.; Fischer, P.; Frieman, J.; McKay, T.; Mohr, J. J.; Nichol, R. C.; Johnston, D.; Sheldon, E.; Cantaloupo, C.; Griffin, G.; Peterson, J.; Romer, A. K.

2000-04-01

207

Bayesian model selection for dark energy using weak lensing forecasts

NASA Astrophysics Data System (ADS)

The next generation of weak lensing probes can place strong constraints on cosmological parameters by measuring the mass distribution and geometry of the low-redshift Universe. We show that a future all-sky tomographic cosmic shear survey with design properties similar to Euclid can provide the statistical accuracy required to distinguish between different dark energy models. Using a fiducial cosmological model which includes cold dark matter, baryons, massive neutrinos (hot dark matter), a running primordial spectral index and possible spatial curvature as well as dark energy perturbations, we calculate Fisher matrix forecasts for different dynamical dark energy models. Using a Bayesian evidence calculation, we show how well a future weak lensing survey could do in distinguishing between a cosmological constant and dynamical dark energy.

Debono, Ivan

2014-01-01

208

Reflection Symmetry of Cusps in Gravitational Lensing

Criticality in graviational microlensing is an everyday issue because that is what generates microlensing signals which may be of photon-challenged compact objects such as black holes or planetary systems ET calls home. The criticality of these quasi-analytic lenses is intrinsically quadratic, and the critical curve behaves as a mirror generating two mirror images along the image line (parallel +/- E_-) at the same distances from the critical curve in the opposite sides. At the (pre)cusps where the caustic curve "reflects" and develops cusps, however, "would-be" two pairs of quadratic images "superpose" to produce three mirror images because of the degenerate criticality. The critical curve behaves as a parabolic mirror, and the image inside the parabola is indeed a superposed image having the sum of the magnifications of the other two that are outside the parabola. All three images lie on a parabolic image curve shaped by a property (nabla J) of the (pre)cusp, and two distances of the system determine the position of the image curve and positions of the three images on the image curve. The triplet images satisfy sum J^{-1} = 0, and the function sum J^{-1} is discontinuous at a caustic crossing where a pair of quadratic images disappear into a critical point. The reflection symmetry of the image curve is a manifestation of the symmetry of the cusp which is also respected by a trio of parabolic curves that are tangnet at the (pre)cusp and define the image domains. The symmetry is guaranteed when J_{+-} vanishes or can be ignored, and the cusps on the lens axis of the binary lenses are strongly symmetric having J_{+-} = 0 because of the global reflection symmetry of the binary lenses. "E_{+/-}-algebra" is laid out for users' convenience.

Sun Hong Rhie

2002-07-29

209

Gravitational Lensing Characteristics of the Transparent Sun

The transparent Sun is modeled as a spherically symmetric and centrally condensed gravitational lens using recent Standard Solar Model (SSM) data. The Sun's minimum focal length is computed to a refined accuracy of 23.5 +/- 0.1 AU, just beyond the orbit of Uranus. The Sun creates a single image of a distant point source visible to observers inside this minimum focal length and to observers sufficiently removed from the line connecting the source through the Sun's center. Regions of space are mapped where three images of a distant point source are created, along with their associated magnifications. Solar caustics, critical curves, and Einstein rings are computed and discussed. Extremely high gravitational lens magnifications exist for observers situated so that an angularly small, unlensed source appears near a three-image caustic. Types of radiations that might undergo significant solar lens magnifications as they can traverse the core of the Sun, including neutrinos and gravitational radiation, are discussed.

Bijunath Patla; Robert J. Nemiroff

2011-12-12

210

The SuperCLASS Weak Lensing Deep Field Survey

NASA Astrophysics Data System (ADS)

SuperCLASS is a survey of 1.75 square degrees of the Northern sky using the e-MERLIN telescope array at a frequency of 1.4GHz, aiming to reach an image noise RMS level of 4 micro-Jy/beam. The primary goal is to use the expected source density of ~1 per square arcminute (giving a total of ~10,000), ~150 milli-arcsecond resolution and presence in the survey region of 5 massive Abell clusters to measure a significant weak lensing effect in the radio band for only the second time, proving the potential of radio weak lensing as a powerful tool for mapping dark matter and constraining cosmological models. In doing this we will also learn a significant amount about the source population (star forming galaxies and radio AGN) themselves and their polarisation properties. SuperCLASS will not only require development of a pipeline for making the highly accurate determination of shapes of a large number of sources for performing standard weak lensing measurements, but will also form a test bed for new methods, such as the use of polarisation information to mitigate the biasing effect of intrinsic alignments between galaxies, which will be a key systematic for future weak lensing surveys. Whilst the challenges of the necessary shape measurement in image plane optical data are relatively well-explored, there is little experience in meeting those involved in the use of data from radio interferometers. The knowledge gained about efficient and accurate techniques for large scale radio astronomy from SuperCLASS will be invaluable in the build up to the next generation of experiments.

Harrison, Ian; Superclass Collaboration

2014-04-01

211

Observing cosmic string loops with gravitational lensing surveys

We show that the existence of cosmic strings can be strongly constrained by the next generation of gravitational lensing surveys at radio frequencies. We focus on cosmic string loops, which simulations suggest would be far more numerous than long (horizon-sized) strings. Using simple models of the loop population and minimal assumptions about the lensing cross section per loop, we estimate the optical depth to lensing and show that extant radio surveys such as CLASS have already ruled out a portion of the cosmic string model parameter space. Future radio interferometers, such as LOFAR and especially SKA, may constrain $G\\mu/c^2 < 10^{-9}$ in some regions of parameter space, outperforming current constraints from pulsar timing and the CMB by up to two orders of magnitude. This method relies on direct detections of cosmic strings, and so is less sensitive to the theoretical uncertainties in string network evolution that weaken other constraints.

Katherine J. Mack; Daniel H. Wesley; Lindsay J. King

2007-09-26

212

Resolving high energy emission of jets using strong gravitational lensing

NASA Astrophysics Data System (ADS)

Chandra observations of M87 in 2004 uncovered an outburst originating in distant knot along the jet hundreds of parsecs from the core. This discovery challenges our understanding of the origin of high energy flares. Current technology is inadequate to resolve jets at distances greater than M87, or observed at higher energies. We propose to use gravitationally lensed jets to investigate the structure of more distant sources. Photons emitted at different sites cross the lens plane at different distances, thus magnification ratios and time delays differ between the mirage images. Monitoring of flares from lensed jets reveals the origin of the emission. With detectors like Chandra, lensed systems are a tool for resolving the structure of the jets and for investigating their cosmic evolution.

Barnacka, Anna

2014-11-01

213

Strong gravitational lensing: why no central black holes?

We investigate how central black holes (BHs) inhabited in galactic dark halos could affect strong gravitational lensing. The distribution of integral lensing probability with image separations are calculated for quasars of redshift 1.5 by foreground dark matter halos. The mass density of dark halos is taken to be the Navarro-Frenk-White (NFW) profile such that, when the mass of a halo is less than $10^{14} M_{\\sun}$, its central black holes or a bulge is included as a point mass. The relationship between the masses $M_{\\bullet}$ of supermassive black holes and the total gravitational mass $M_{\\mathrm{DM}}$ of their host galaxy is adopted from the most recent literature. Only a flat $\\Lambda$CDM model is considered here. It is shown that, while a single black hole for each galaxy contributes considerable but not sufficient lensing probabilities at small image separations compared with those without black holes, the bulges (which are about 100--1000 times larger in mass than a typical black hole) would definitely contribute enough probabilities at small image separations, although it gives too high probabilities at large separation angles compared with lensing observations.

Da-Ming Chen

2002-09-09

214

Gravitational lensing by Einstein-Born-Infeld black holes

In this paper, charged black holes in general relativity coupled to Born-Infeld electrodynamics are studied as gravitational lenses. The positions and magnifications of the relativistic images are obtained using the strong deflection limit, and the results are compared with those corresponding to a Reissner-Nordstroem black hole with the same mass and charge. As numerical examples, the model is applied to the supermassive Galactic center black hole and to a small size black hole situated in the Galactic halo.

Eiroa, Ernesto F. [Instituto de Astronomia y Fisica del Espacio, C.C. 67, Suc. 28, 1428, Buenos Aires (Argentina)

2006-02-15

215

Gravitational lensing by Einstein-Born-Infeld black holes

In this paper, charged black holes in general relativity coupled to Born-Infeld electrodynamics are studied as gravitational lenses. The positions and magnifications of the relativistic images are obtained using the strong deflection limit, and the results are compared with those corresponding to a Reissner-Nordstrom black hole with the same mass and charge. As numerical examples, the model is applied to the supermassive Galactic center black hole and to a small size black hole situated in the Galactic halo.

Ernesto F. Eiroa

2006-01-23

216

Lensing by Distant Clusters: HST Observations of Weak Shear in the Field of 3C324

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.

Ian Smail; Mark Dickinson

1995-10-08

217

A search for closely spaced gravitational lenses

A new image-stabilizing camera was used to search for closely spaced images of a sample of 25 intrinsically luminous quasars with z greater than 1.6 and m smaller than 19. Observations of seven similarly selected quasars with the regular CCD camera in good seeing conditions are also reported. Of the 32 quasars, seven are gravitational lens candidates. Two of these have subarcsecond separations. Additional information on all these candidates is required. 22 refs.

Crampton, D.; Mcclure, R.D.; Fletcher, J.M.; Hutchings, J.B. (Dominion Astrophysical Observatory, Victoria (Australia) National Research Council of Canada, Herzberg Institute of Astrophysics, Ottawa (Canada))

1989-10-01

218

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 ...

Corless, Virginia Leigh

2005-01-01

219

The HST Frontier Fields: Gravitational Lensing Models Release

NASA Astrophysics Data System (ADS)

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.

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

220

Demagnifying gravitational lenses toward hunting a clue of exotic matter and energy

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.

Takao Kitamura; Koki Nakajima; Hideki Asada

2013-01-16

221

Galaxy Cluster Studies with Weak Lensing Magnification and Shear

NASA Astrophysics Data System (ADS)

The magnification component of weak lensing provides complementary information to the more commonly measured shear distortion. While low redshift halos are better constrained by shear, at increasingly high redshifts the magnification signal becomes quite competitive. We present recent measurements of halo masses from the stacked magnification signal of >18,000 galaxy clusters in the 154 deg^2 Canada-France-Hawaii-Telescope Lensing Survey (CFHTLenS). We perform the first direct cluster mass comparison between magnification and shear, finding global agreement between the independent methods, but with systematic effects influencing particular cluster redshift ranges. We measure the mass-richness scaling relation of the CFHTLenS 3D-MF cluster sample, and search for evidence of its evolution with redshift.

Ford, Jes

2015-01-01

222

Strong and weak lensing analysis of cluster Abell 2219 based on optical and near infrared data

We present a gravitational lensing study of the massive galaxy cluster A2219 (redshift 0.22). This investigation is based on multicolour images from U through H, which allows photometric redshifts to be estimated for the background sources. The redshifts provide useful extra information for the lensing models: we show how they can be used to identify a new multiple-image system (and rule out an old one), how this information can be used to anchor the mass model for the cluster, and how the redshifts can be used to construct optimal samples of background galaxies for a weak lensing analysis. Combining all results, we obtain the mass distribution in this cluster from the inner, strong lensing region, out to a radius of 1.5 Mpc. The mass profile is consistent with a singular isothermal model over this radius range. Parametric and non-parametric reconstructions of the mass distribution in the cluster are compared. The main features (elongation, sub-clumps, radial mass profile) are in good agreement.

J. Bezecourt; H. Hoekstra; M. E. Gray; H. M. AbdelSalam; K. Kuijken; R. S. Ellis

2000-01-29

223

A Comparison of Cosmological Models Using Strong Gravitational Lensing Galaxies

Strongly gravitationally lensed quasar-galaxy systems allow us to compare competing cosmologies as long as one can be reasonably sure of the mass distribution within the intervening lens. In this paper, we assemble a catalog of 69 such systems, and carry out a one-on-one comparison between the standard model, LCDM, and the R_h=ct Universe. We find that both models account for the lens observations quite well, though the precision of these measurements does not appear to be good enough to favor one model over the other. Part of the reason is the so-called bulge-halo conspiracy that, on average, results in a baryonic velocity dispersion within a fraction of the optical effective radius virtually identical to that expected for the whole luminous-dark matter distribution. Given the limitations of doing precision cosmological testing using the current sample, we also carry out Monte Carlo simulations based on the current lens measurements to estimate how large the source catalog would have to be in order to rule out either model at a ~99.7% confidence level. We find that if the real cosmology is LCDM, a sample of ~200 strong gravitational lenses would be sufficient to rule out R_h=ct at this level of accuracy, while ~300 strong gravitational lenses would be required to rule out LCDM if the real Universe were instead R_h=ct. The difference in required sample size reflects the greater number of free parameters available to fit the data with LCDM. We point out that, should the R_h=ct Universe eventually emerge as the correct cosmology, its lack of any free parameters for this kind of work will provide a remarkably powerful probe of the mass structure in lensing galaxies, and a means of better understanding the origin of the bulge-halo conspiracy.

Fulvio Melia; Jun-Jie Wei; Xue-Feng Wu

2014-10-03

224

TESTING THE DARK ENERGY WITH GRAVITATIONAL LENSING STATISTICS

We study the redshift distribution of two samples of early-type gravitational lenses, extracted from a larger collection of 122 systems, to constrain the cosmological constant in the {Lambda}CDM model and the parameters of a set of alternative dark energy models (XCDM, Dvali-Gabadadze-Porrati, and Ricci dark energy models), in a spatially flat universe. The likelihood is maximized for {Omega}{sub {Lambda}} = 0.70 {+-} 0.09 when considering the sample excluding the Sloan Lens ACS systems (known to be biased toward large image-separation lenses) and no-evolution, and {Omega}{sub {Lambda}} = 0.81 {+-} 0.05 when limiting to gravitational lenses with image separation {Delta}{theta} > 2'' and no-evolution. In both cases, results accounting for galaxy evolution are consistent within 1{sigma}. The present test supports the accelerated expansion, by excluding the null hypothesis (i.e., {Omega}{sub {Lambda}} = 0) at more than 4{sigma}, regardless of the chosen sample and assumptions on the galaxy evolution. A comparison between competitive world models is performed by means of the Bayesian information criterion. This shows that the simplest cosmological constant model-that has only one free parameter-is still preferred by the available data on the redshift distribution of gravitational lenses. We perform an analysis of the possible systematic effects, finding that the systematic errors due to sample incompleteness, galaxy evolution, and model uncertainties approximately equal the statistical errors, with present-day data. We find that the largest sources of systemic errors are the dynamical normalization and the high-velocity cutoff factor, followed by the faint-end slope of the velocity dispersion function.

Cao Shuo; Zhu Zonghong [Department of Astronomy, Beijing Normal University, 100875 Beijing (China); Covone, Giovanni [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', Via Cinthia, I-80126 Napoli (Italy)

2012-08-10

225

Gravitationally Lensed X-Ray Sources at the Galactic Center

NASA Astrophysics Data System (ADS)

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.

Castelaz, Michael W.; Rottler, L.

2012-01-01

226

A universal probability distribution function for weak-lensing amplification

We present an approximate form for the weak lensing magnification distribution of standard candles, valid for all cosmological models, with arbitrary matter distributions, over all redshifts. Our results are based on a universal probability distribution function (UPDF), $P(\\eta)$, for the reduced convergence, $\\eta$. For a given cosmological model, the magnification probability distribution, $P(\\mu)$, at redshift $z$ is related to the UPDF by $P(\\mu)=P(\\eta)/2|\\kappa_{min}|$, where $\\eta=1+(\\mu-1)/(2|\\kappa_{min}|)$, and $\\kappa_{min}$ (the minimum convergence) can be directly computed from the cosmological parameters ($\\Omega_m$ and $\\Omega_\\Lambda$). We show that the UPDF can be well approximated by a three-parameter stretched Gaussian distribution, where the values of the three parameters depend only on $\\xi_\\eta$, the variance of $\\eta$. In short, all possible weak lensing probability distributions can be well approximated by a one-parameter family. We establish this family, normalizing to the numerical ray-shooting results for a ${\\Lambda}$CDM model by Wambsganss et al. (1997). Each alternative cosmological model is then described by a single function $\\xi_\\eta(z)$. We find that this method gives $P(\\mu)$ in excellent agreement with numerical ray-tracing and three-dimensional shear matrix calculations, and provide numerical fits for three representative models (SCDM, $\\Lambda$CDM, and OCDM). Our results provide an easy, accurate, and efficient method to calculate the weak lensing magnification distribution of standard candles, and should be useful in the analysis of future high-redshift supernova data.

Yun Wang; Daniel E. Holz; Dipak Munshi

2002-05-06

227

Creating images by adding masses to gravitational point lenses

NASA Astrophysics Data System (ADS)

A well-studied maximal gravitational point lens construction of S. H. Rhie produces images of a light source using deflector masses. The construction arises from a circular, symmetric deflector configuration on masses (producing only images) by adding a tiny mass in the center of the other mass positions (and reducing all the other masses a little bit). In a recent paper we studied this "image creating effect" from a purely mathematical point of view (Sète, Luce & Liesen, Comput. Methods Funct. Theory 15(1), 2014). Here we discuss a few consequences of our findings for gravitational microlensing models. We present a complete characterization of the effect of adding small masses to these point lens models, with respect to the number of images. In particular, we give several examples of maximal lensing models that are different from Rhie's construction and that do not share its highly symmetric appearance. We give generally applicable conditions that allow the construction of maximal point lenses on masses from maximal lenses on masses.

Sète, Olivier; Luce, Robert; Liesen, Jörg

2015-04-01

228

Broad Iron Emission from Gravitationally Lensed Quasars Observed by Chandra

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 1.0emission from these sources. Although the X-ray signal-to-noise (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 AGN, 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-sigma level. This implies that iron emission...

Walton, D J; Miller, J M; Reis, R C; Stern, D; Harrison, F A

2015-01-01

229

An attempt to measure the time delays of three gravitational lenses

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, ...

Chistol, Gheorghe

2007-01-01

230

NASA Astrophysics Data System (ADS)

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.

McCully, Curtis

231

Infrared observations of gravitational lensing in Abell 2219 with CIRSI

We present the first detection of a gravitational depletion signal at near-infrared wavelengths, based on deep panoramic images of the cluster Abell 2219 (z=0.22) taken with the Cambridge Infrared Survey Instrument (CIRSI) at the prime focus of the 4.2m William Herschel Telescope. Infrared studies of gravitational depletion offer a number of advantages over similar techniques applied at optical wavelengths, and can provide reliable total masses for intermediate redshift clusters. Using the maximum likelihood technique developed by Schneider, King & Erben (1999), we detect the gravitational depletion at the 3 sigma confidence level. By modeling the mass distribution as a singular isothermal sphere and ignoring uncertainty in the unlensed number counts, we find an Einstein radius of 13.7 +3.9/-4.2 arcsec (66% confidence limit). This corresponds to a projected velocity dispersion of approximately 800 km/s, in agreement with constraints from strongly-lensed features. For a Navarro, Frenk and White mass model, the radial dependence observed indicates a best-fitting halo scale length of 125/h kpc}. We investigate the uncertainties arising from the observed fluctuations in the unlensed number counts, and show that clustering is the dominant source of error. We extend the maximum likelihood method to include the effect of incompleteness, and discuss the prospects of further systematic studies of lensing in the near-infrared band.

Meghan E. Gray; Richard S. Ellis; Alexandre Refregier; Jocelyn Bezecourt; Richard G. McMahon; Martin G. Beckett; Craig D. Mackay; Michael D. Hoenig

2000-06-21

232

Quasar Structure from Microlensing in Gravitationally Lensed Quasars

NASA Astrophysics Data System (ADS)

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.

Morgan, Christopher W.

2007-12-01

233

A Comparison of Cosmological Models Using Strong Gravitational Lensing Galaxies

NASA Astrophysics Data System (ADS)

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.

Melia, Fulvio; Wei, Jun-Jie; Wu, Xue-Feng

2015-01-01

234

Spectroscopic Confirmation of Redshifts Predicted by Gravitational Lensing

We present deep spectroscopic measurements of 18 distant field galaxies identified as gravitationally-lensed arcs in a Hubble Space Telescope image of the cluster Abell 2218. Redshifts of these objects were predicted by Kneib et al. (1996) using a lensing analysis constrained by the properties of two bright arcs of known redshift and other multiply-imaged sources. The new spectroscopic identifications were obtained using long exposures with the LDSS-2 spectrograph on the William Herschel Telescope and demonstrate the capability of that instrument to new limits, $R\\simeq$24; the lensing magnification implies true source magnitudes as faint as $R\\simeq$25. Statistically, our measured redshifts are in excellent agreement with those predicted from Kneib et al.'s lensing analysis which gives considerable support to the redshift distribution derived by the lensing inversion method for the more numerous and fainter arclets extending to $R\\simeq 25.5$. We explore the remaining uncertainties arising from both the mass distribution in the central regions of Abell 2218 and the inversion method itself, and conclude that the mean redshift of the faint field population at $R\\simeq$25.5 ($B\\sim 26$-27) is low, $$=0.8-1. We discuss this result in the context of redshift distributions estimated from multi-colour photometry. Although such comparisons are not straightforward, we suggest that photometric techniques may achieve a reasonable level of agreement particularly when they include near-infrared photometry with discriminatory capabilities in the $1

Tim Ebbels; Richard Ellis; Jean-Paul Kneib; Jean-Francois Le Borgne; Roser Pello; Ian Smail; Blai Sanahuja

1997-03-26

235

Constraining Cosmological Parameters with Observational Data Including Weak Lensing Effects

In this paper, we study the cosmological implications of the 100 square degree Weak Lensing survey (the CFHTLS-Wide, RCS, VIRMOS-DESCART and GaBoDS surveys). We combine these weak lensing data with the cosmic microwave background (CMB) measurements from the WMAP5, BOOMERanG, CBI, VSA, ACBAR, the SDSS LRG matter power spectrum and the Type Ia Supernoave (SNIa) data with the "Union" compilation (307 sample), using the Markov Chain Monte Carlo method to determine the cosmological parameters. Our results show that the \\Lambda CDM model remains a good fit to all of these data. For the dynamical dark energy model with time evolving EoS parameterized as w_{\\DE}(a) = w_0 + w_a (1-a), we find that the best-fit model implying the mildly preference of Quintom model whose EoS gets across the cosmological constant boundary during evolution. Regarding the total neutrino mass limit, we obtain the upper limit, \\sum m_{\

Hong Li; Jie Liu; Jun-Qing Xia; Lei Sun; Zu-Hui Fan; Charling Tao; Andre Tilquin; Xinmin Zhang

2008-12-09

236

Gravitational lensing by self-dual black holes in loop quantum gravity

NASA Astrophysics Data System (ADS)

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 a billion solar mass black holes in other galaxies might be within reach of future relativistic lensing observations.

Sahu, Satyabrata; Lochan, Kinjalk; Narasimha, D.

2015-03-01

237

Cross-Correlation Tomography: Measuring Dark Energy Evolution with Weak Lensing

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

Bhuvnesh Jain; Andy Taylor

2003-01-01

238

NASA Astrophysics Data System (ADS)

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.

Tagore, Amitpal Singh

239

The central image of a gravitationally lensed quasar.

A galaxy can act as a gravitational lens, producing multiple images of a background object. Theory predicts that there should be an odd number of images produced by the lens, but hitherto almost all lensed objects have two or four images. The missing 'central' images, which should be faint and appear near the centre of the lensing galaxy, have long been sought as probes of galactic cores too distant to resolve with ordinary observations. There are five candidates for central images, but in one case the third image is not necessarily the central one, and in the others the putative central images might be foreground sources. Here we report a secure identification of a central image, based on radio observations of one of the candidates. Lens models using the central image reveal that the massive black hole at the centre of the lensing galaxy has a mass of <2 x 10(8) solar masses (M(o)), and the galaxy's surface density at the location of the central image is > 20,000M(o) pc(-2), which is in agreement with expections based on observations of galaxies that are much closer to the Earth. PMID:14961114

Winn, Joshua N; Rusin, David; Kochanek, Christopher S

2004-02-12

240

A Candidate Gravitationally Lensed Quasar at z=6.09

NASA Astrophysics Data System (ADS)

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.

McGreer, Ian

2013-10-01

241

X-RAY MONITORING OF GRAVITATIONAL LENSES WITH CHANDRA

We present Chandra monitoring data for six gravitationally lensed quasars: QJ 0158-4325, HE 0435-1223, SDSS 0924+0219, SDSS 1004+4112, HE 1104-1805, and Q 2237+0305. X-ray microlensing variability is detected in all six lenses with high confidence. We furthermore detect energy-dependent microlensing in HE 0435-1223, SDSS 0924+0219, SDSS 1004+4112, and Q 2237+0305. Through a detailed spectral analysis for each lens we find that simple power-law models plus Gaussian emission lines give good fits to the spectra. We detect intrinsic spectral variability in two epochs of Q 2237+0305, and differential absorption between images in QJ 0158-4325 and Q2237+0305. We also detect the Fe K{alpha} emission line in all six lenses, and the Ni XXVII K{alpha} line in two images of Q 2237+0305. The rest-frame equivalent widths of the Fe K{alpha} lines are measured to be 0.4-1.2 keV, significantly higher than those measured in typical active galactic nuclei of similar X-ray luminosities. This suggests that the Fe K{alpha} emission region is more compact or centrally concentrated than the continuum emission region.

Chen Bin; Dai Xinyu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Kochanek, Christopher S.; Blackburne, Jeffrey A. [Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States); Chartas, George [Department of Physics and Astronomy, College of Charleston, SC 29424 (United States); Morgan, Christopher W., E-mail: bchen@ou.edu [Department of Physics, United States Naval Academy, 572C Holloway Road, Annapolis, MD 21402 (United States)

2012-08-10

242

Self-Calibration Technique for 3-point Intrinsic Alignment Correlations in Weak Lensing Surveys

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.

M. A. Troxel; Mustapha Ishak

2011-12-23

243

Quasar-galaxy associations from gravitational lensing: revisited

The theoretically expected amplitude of the associations of background quasars with foreground galaxies as a result of gravitational lensing has been updated in this paper. Since the galactic matter alone yields an amplitude of quasar overdensity smaller than that observed, a special attention has been paid to the examination or re-examination of the uncertainties in the estimate of the quasar enhancement factor arising from the cosmic evolution of galaxies, the core radius and velocity bias of galactic matter distributions, the clusters of galaxies, the obstruction effect by galactic disks, the non-zero cosmological constant, etc. Unfortunately, none of these factors has been shown to be able to significantly improve the situation, although a combination of some effects may provide a result that marginally agrees with observations. It is concluded that the quasar-galaxy association still remains to be an unsolved puzzle in today's astronomy, if the reported quasar-galaxy associations are not due to the statistical variations and/or the observed quasar number counts as a whole have not been seriously contaminated by gravitational lensing.

Zong-Hong Zhu; Xiang-Ping Wu; Li-Zhi Fang

1997-06-29

244

Puzzles in Time Delay and Fermat Principle in Gravitational Lensing

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.

Sun Hong Rhie

2011-03-16

245

Constraints on early dark energy from CMB lensing and weak lensing tomography

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.

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

246

Weak Lensing Measurements in Simulations of Radio Images

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...

Patel, Prina; Bacon, David J; Rowe, Barnaby; Smirnov, Oleg; Beswick, Rob J

2013-01-01

247

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...

Petri, Andrea; Haiman, Zoltan; May, Morgan; Hui, Lam; Kratochvil, Jan M

2015-01-01

248

Evolution of the Dark Matter Distribution with 3-D Weak Lensing

We present a direct detection of the growth of large-scale structure, using weak gravitational lensing and photometric redshift data from the COMBO-17 survey. We use deep R-band imaging of two 0.25 square degree fields, affording shear estimates for over 52000 galaxies; we combine these with photometric redshift estimates from our 17 band survey, in order to obtain a 3-D shear field. We find theoretical models for evolving matter power spectra and correlation functions, and fit the corresponding shear correlation functions to the data as a function of redshift. We detect the evolution of the power at the 7.7 sigma level given minimal priors, and measure the rate of evolution for 0

D. J. Bacon; A. N. Taylor; M. L. Brown; M. E. Gray; C. Wolf; K. Meisenheimer; S. Dye; L. Wisotzki; A. Borch; M. Kleinheinrich

2004-03-16

249

Strong gravitational lensing in a squashed Kaluza-Klein black hole spacetime

We investigate the strong gravitational lensing in a Kaluza-Klein black hole with squashed horizons. We find the size of the extra dimension imprints in the radius of the photon sphere, the deflection angle, the angular position, and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the Galaxy can be described by this metric, we estimated the numerical values of the coefficients and observables for gravitational lensing in the strong field limit.

Liu Yue; Chen Songbai; Jing Jiliang [Institute of Physics and Department of Physics, Hunan Normal University, Changsha, Hunan 410081 (China) and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University), Ministry of Education (China)

2010-06-15

250

EFFECTIVE MODELS FOR STATISTICAL STUDIES OF GALAXY-SCALE GRAVITATIONAL LENSING

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.

Lapi, A. [Dipartimento Fisica, Universita 'Tor Vergata', Via Ricerca Scientifica 1, 00133 Roma (Italy); Negrello, M. [INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova (Italy); Gonzalez-Nuevo, J.; Cai, Z.-Y.; De Zotti, G.; Danese, L. [Astrophysics Sector, SISSA, Via Bonomea 265, 34136 Trieste (Italy)

2012-08-10

251

Microlensing Planets: Multiple Planet Systems as Gravitational Triple Lenses

NASA Astrophysics Data System (ADS)

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.

Rhie, S.; Bennett, D.

2000-12-01

252

A Bayesian Analysis of Regularised Source Inversions in Gravitational Lensing

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.

Suyu, Sherry H.; /Caltech /KIPAC, Menlo Park; Marshall, P.J.; /KIPAC, Menlo Park; Hobson, M.P.; /Cambridge U., Inst. of Astron.; Blandford, R.D.; /Caltech /KIPAC, Menlo

2006-01-25

253

Adaptive optics observations of the gravitationally lensed quasar SDSS J1405+0959

We present the result of Subaru Telescope multi-band adaptive optics observations of the complex gravitationally lensed quasar SDSS J1405+0959, which is produced by two lensing galaxies. These observations reveal dramatically enhanced morphological detail, leading to the discovery of an additional object 0. 26'' from the secondary lensing galaxy, as well as three collinear clumps located in between the two lensing galaxies. The new object is likely to be the third quasar image, although the possibility that it is a galaxy cannot be entirely excluded. If confirmed via future observations, it would be the first three image lensed quasar produced by two galaxy lenses. In either case, we show based on gravitational lensing models and photometric redshift that the collinear clumps represent merging images of a portion of the quasar host galaxy, with a magnification factor of 15 - 20, depending on the model.

Rusu, Cristian E; Minowa, Yosuke; Iye, Masanori; More, Anupreeta; Inada, Naohisa; Oya, Shin

2014-01-01

254

Adaptive optics observations of the gravitationally lensed quasar SDSS J1405+0959

NASA Astrophysics Data System (ADS)

We present the result of Subaru Telescope multiband adaptive optics observations of the complex gravitationally lensed quasar SDSS J1405+0959, which is produced by two lensing galaxies. These observations reveal dramatically enhanced morphological detail, leading to the discovery of an additional object 0.26 arcsec from the secondary lensing galaxy, as well as three collinear clumps located in between the two lensing galaxies. The new object is likely to be the third quasar image, although the possibility that it is a galaxy cannot be entirely excluded. If confirmed via future observations, it would be the first three-image lensed quasar produced by two galaxy lenses. In either case, we show based on gravitational lensing models and photometric redshift that the collinear clumps represent merging images of a portion of the quasar host galaxy, with a magnification factor of ˜ 15-20, depending on the model.

Rusu, Cristian E.; Oguri, Masamune; Minowa, Yosuke; Iye, Masanori; More, Anupreeta; Inada, Naohisa; Oya, Shin

2014-11-01

255

The principles of measuring the shapes of galaxies by a model-fitting approach are discussed in the context of shape-measurement for surveys of weak gravitational lensing. It is argued that such an approach should be optimal, allowing measurement with maximal signal-to-noise, coupled with estimation of measurement errors. The distinction between likelihood-based and Bayesian methods is discussed. Systematic biases in the Bayesian method may be evaluated as part of the fitting process, and overall such an approach should yield unbiased shear estimation without requiring external calibration from simulations. The principal disadvantage of model-fitting for large surveys is the computational time required, but here an algorithm is presented that enables large surveys to be analysed in feasible computation times. The method and algorithm is tested on simulated galaxies from the Shear TEsting Program (STEP).

L. Miller; T. D. Kitching; C. Heymans; A. F. Heavens; L. Van Waerbeke

2007-08-17

256

Interpolation of PSF based on compressive sampling and its application in weak lensing survey

NASA Astrophysics Data System (ADS)

We propose a new point spread function (PSF) interpolation method based on compressive sampling (CS). Complex-Valued fractional Brownion motion (CV-fBm) field is used as a model of the PSF spatial distribution. The 1/f property of the fBm implies that it is a compressible field; therefore, CS will be able to fully reconstruct the field based on a small number of random samples. Performance evaluation shows the advantages of the proposed method over boxcar filtering, polynomial fitting, inverse distance weighting, and thin-plate methods. Potential applicability of the proposed method in weak gravitational lensing survey, particularly for interpolating fast varying PSF that represent distortion by turbulent field is also discussed.

Suksmono, Andriyan B.

2014-09-01

257

Weak Lensing by Large-Scale Structure: A Dark Matter Halo Approach.

Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters that govern them, but they are currently limited to small fields and subject to selection biases. We show how the expected signal from large-scale structure arises from the contributions from and correlations between individual halos. We determine the convergence power spectrum as a function of the maximum halo mass and so provide the means to interpret results from surveys that lack high-mass halos either through selection criteria or small fields. Since shot noise from rare massive halos is mainly responsible for the sample variance below 10&arcmin;, our method should aid our ability to extract cosmological information from small fields. PMID:10828996

Cooray; Hu; Miralda-Escudé

2000-05-20

258

Seeing the Invisible Universe with Gravitational Lensing and SNAP

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.

Bernstein, Gary (University of Pennsylvania) [University of Pennsylvania

2005-11-03

259

Detection of Gravitational Lensing in the Cosmic Microwave Background

Gravitational lensing of the cosmic microwave background (CMB), a long-standing prediction of the standard cosmolgical model, is ultimately expected to be an important source of cosmological information, but first detection has not been achieved to date. We report a 3.4 sigma detection, by applying quadratic estimator techniques to all sky maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and correlating the result with radio galaxy counts from the NRAO VLA Sky Survey (NVSS). We present our methodology including a detailed discussion of potential contaminants. Our error estimates include systematic uncertainties from density gradients in NVSS, beam effects in WMAP, Galactic microwave foregrounds, resolved and unresolved CMB point sources, and the thermal Sunyaev-Zeldovich effect.

Kendrick M. Smith; Oliver Zahn; Olivier Dore

2007-05-28

260

Fermat Potentials for Non-Perturbative Gravitational Lensing

The images of many distant galaxies are displaced, distorted and often multiplied by the presence of foreground massive galaxies near the line of sight; the foreground galaxies act as gravitational lenses. Commonly, the lens equation, which relates the placement and distortion of the images to the real source position in the thin-lens scenario, is obtained by extremizing the time of arrival among all the null paths from the source to the observer (Fermat's principle). We show that the construction of envelopes of certain families of null surfaces consitutes an alternative variational principle or version of Fermat's principle that leads naturally to a lens equation in a generic spacetime with any given metric. We illustrate the construction by deriving the lens equation for static asymptotically flat thin lens spacetimes. As an application of the approach, we find the bending angle for moving thin lenses in terms of the bending angle for the same deflector at rest. Finally we apply this construction to cosmological spacetimes (FRW) by using the fact they are all conformally related to Minkowski space.

Simonetta Frittelli; Thomas P. Kling; Ezra T. Newman

2002-05-03

261

On the use of measured time delays in gravitational lenses to determine the Hubble constant

NASA Technical Reports Server (NTRS)

Gravitational lenses are rare in the known samples of quasars, indicating that the conditions involved in their formation are unusual. In particular, the distribution of matter along the light rays from the observer through the deflector to the quasar may be very different from mean conditions. It is shown that reasonable deviations in the density of matter along the beams can significantly alter the relationship between time delays and the Hubble constant, and it is concluded that gravitational lenses are not promising estimators of this constant. However, should an independent, precise determination of the Hubble constant become available, gravitational lenses could be used to probe long-range density fluctuations.

Alcock, C.; Anderson, N.

1985-01-01

262

Gravitational lensing: a unique probe of dark matter and dark energy

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

Ellis, Richard S.

2010-01-01

263

Gravitational lensing: a unique probe of dark matter and dark energy.

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

Ellis, Richard S

2010-03-13

264

OBSERVING GRAVITATIONAL LENSING EFFECTS BY Sgr A* WITH GRAVITY

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.

Bozza, V. [Department of Physics 'E.R. Caianiello', University of Salerno, Via Ponte Don Melillo, Fisciano I-84084 (Italy); Mancini, L., E-mail: valboz@physics.unisa.it, E-mail: mancini@mpia-hd.mpg.de [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)

2012-07-01

265

Discovering Gravitational Lenses Through Measurements Of Their Time Delays

We consider the possibility that future wide-field time-domain optical imaging surveys may be able to discover gravitationally lensed quasar pairs through serendipitous measurements of their time delays. We discuss the merits such a discovery technique would have relative to conventional lens searches. Using simulated quasar lightcurves, we demonstrate that in a survey which observes objects several times each lunar cycle over the course of five years, it is possible to improve the efficiency of a gravitational lens search by 2-3 orders of magnitude through the use of time delay selection. In the most advantageous scenario considered, we are able to improve efficiency by a factor of 1000 with no loss of completeness. In the least advantageous scenario, we are able to improve efficiency by a factor of 110 while reducing completeness by a factor of 9. We show that window function effects associated with the length of the observing season are more important than the total number of datapoints in determining the effectiveness of this method. We also qualitatively discuss several complications which might be relevant to a real time delay search.

Bart Pindor

2005-01-24

266

NASA Astrophysics Data System (ADS)

Intrinsic galaxy alignments constitute the major astrophysical systematic of forthcoming weak gravitational lensing surveys but also yield unique insights into galaxy formation and evolution. We build analytic models for the distribution of galaxy shapes based on halo properties extracted from the Millennium Simulation, differentiating between early- and late-type galaxies as well as central galaxies and satellites. The resulting ellipticity correlations are investigated for their physical properties and compared to a suite of current observations. The best-faring model is then used to predict the intrinsic alignment contamination of planned weak lensing surveys. We find that late-type galaxy models generally have weak intrinsic ellipticity correlations, marginally increasing towards smaller galaxy separation and higher redshift. The signal for early-type models at fixed halo mass strongly increases by three orders of magnitude over two decades in galaxy separation, and by one order of magnitude from z = 0 to z = 2. The intrinsic alignment strength also depends strongly on halo mass, but not on galaxy luminosity at fixed mass, or galaxy number density in the environment. We identify models that are in good agreement with all observational data, except that all models overpredict alignments of faint early-type galaxies. The best model yields an intrinsic alignment contamination of a Euclid-like survey between 0.5 and 10 per cent at z > 0.6 and on angular scales larger than a few arcminutes. Cutting 20 per cent of red foreground galaxies using observer-frame colours can suppress this contamination by up to a factor of 2.

Joachimi, B.; Semboloni, E.; Hilbert, S.; Bett, P. E.; Hartlap, J.; Hoekstra, H.; Schneider, P.

2013-11-01

267

Effect of Photometric Redshift Uncertainties on Weak Lensing Tomography

We perform a systematic analysis of the effects of photometric redshift uncertainties on weak lensing tomography. We describe the photo-z distribution with a bias and Gaussian scatter that are allowed to vary arbitrarily between intervals of dz = 0.1 in redshift.While the mere presence of bias and scatter does not substantially degrade dark energy information, uncertainties in both parameters do. For a fiducial next-generation survey each would need to be known to better than about 0.003-0.01 in redshift for each interval in order to lead to less than a factor of 1.5 increase in the dark energy parameter errors. The more stringent requirement corresponds to a larger dark energy parameter space, when redshift variation in the equation of state of dark energy is allowed.Of order 10^4-10^5 galaxies with spectroscopic redshifts fairly sampled from the source galaxy distribution will be needed to achieve this level of calibration. If the sample is composed of multiple galaxy types, a fair sample would be required for each. These requirements increase in stringency for more ambitious surveys; we quantify such scalings with a convenient fitting formula. No single aspect of a photometrically binned selection of galaxies such as their mean or median suffices, indicating that dark energy parameter determinations are sensitive to the shape and nature of outliers in the photo-z redshift distribution.

Zhaoming Ma; Wayne Hu; Dragan Huterer

2005-08-12

268

Fingerprinting dark energy. II. Weak lensing and galaxy clustering tests

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.

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

269

The Hubble constant estimation using 18 gravitational lensing time delays

NASA Astrophysics Data System (ADS)

Gravitational lens time delay method has been used to estimate the rate of cosmological expansion, called the Hubble constant, H0, independently of the standard candle method. This gravitational lensing method requires a good knowledge of the lens mass distribution, reconstructed using the lens image properties. The observed positions of the images, and the redshifts of the lens and the images serve as strong constraints to the lens equations, which are then solved as a set of simultaneous linear equations. Here we made use of a non-parametric technique to reconstruct the lens mass distribution, which is manifested in a linear equations solver named PixeLens. Input for the calculation is chosen based on prior known parameters obtained from analyzed result of the lens case observations, including time-delay, position angles of the images and the lens, and their redshifts. In this project, 18 fairly well studied lens cases are further grouped according to a number of common properties to examine how each property affects the character of the data, and therefore affects the calculation of H0. The considered lens case properties are lens morphology, number of image, completeness of time delays, and symmetry of lens mass distribution. Analysis of simulation shows that paucity of constraints on mass distribution of a lens yields wide range value of H0, which reflects the uniqueness of each lens system. Nonetheless, gravitational lens method still yields H0 within an acceptable range of value when compared to those determined by many other methods. Grouping the cases in the above manner allowed us to assess the robustness of PixeLens and thereby use it selectively. In addition, we use glafic, a parametric mass reconstruction solver, to refine the mass distribution of one lens case, as a comparison.

Jaelani, Anton T.; Premadi, Premana W.

2014-03-01

270

Weak Lensing Mass of Nearby Clusters of Galaxies: Towards a Complete Sample of Clusters

NASA Astrophysics Data System (ADS)

The study of weak gravitational lensing has grown into a mature science as the image distortion present in several galactic clusters has been detected. This very weak distortion has been extracted to give two-dimensional mass-maps of the clusters and allow determination of their total masses. To detect this very weak tidal shearing of the light from background galaxies requires averaging over many such galaxies to reduce the noise introduced by the intrinsic ellipticity of these background galaxies. In the past, distant clusters with a small angular size on the sky were observed very deeply to gain the requisite number of galaxies. However, with the advent of mosaic CCD cameras, we have been able to observe very nearby clusters (z < 0.1) with large angular size for shorter durations, thus obtaining a large sample of galaxies by going very wide (44' x 44') rather than very deep. This method provides a unique opportunity to directly study the mass concentrations in nearby clusters. It is these same clusters on which there exists large amounts of ancillary data on the light emitted by the clusters, from which we gain most of our understanding of cluster properties and dynamics. We are part of a project to find the weak lensing maps and masses for a complete, X-ray luminosity-limited sample of 24 nearby southern clusters scheduled for Sunyaev--Zel'dovich (SZ) observations by the Viper telescope at the South Pole. We have collected data from 1/4 of the sample and have shown that the systematic errors can be reduced to a level where lensing signal can be seen, proving the feasibility of this study. Combined with the extensive X-ray data, optical red shifts and high quality SZ observations available on these clusters, we will be able form robust measurements of their total mass. This is a first step towards a robust determination of the local cluster mass function: a fundamental goal of cosmology, used to constrain the underlying cosmological model and Omega_0 .

Frieman, J.; Joffre, M.; Fischer, P.; Nichol, B.; Johnston, D.; McKay, T.

1999-05-01

271

Constraints on early-type galaxy structure from spectroscopically selected gravitational lenses

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 ...

Bolton, Adam Stallard

2005-01-01

272

Measuring Gravitational Lensing Flexion in A1689 Using an Analytic Image Model

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 ...

Cain, Benjamin

273

Gravitational lensing analysis of galaxy clusters in the Southern Cosmology Survey

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 ...

McInnes, Rachel Natalie

2010-01-01

274

Numerical wave optics and the lensing of gravitational waves by globular clusters

We consider the possible effects of gravitational lensing by globular clusters on gravitational waves from asymmetric neutron stars in our galaxy. In the lensing of gravitational waves, the long wavelength, compared with the usual case of optical lensing, can lead to the geometrical optics approximation being invalid, in which case a wave optical solution is necessary. In general, wave optical solutions can only be obtained numerically. We describe a computational method that is particularly well suited to numerical wave optics. This method enables us to compare the properties of several lens models for globular clusters without ever calling upon the geometrical optics approximation, though that approximation would sometimes have been valid. Finally, we estimate the probability that lensing by a globular cluster will significantly affect the detection, by ground-based laser interferometer detectors such as LIGO, of gravitational waves from an asymmetric neutron star in our galaxy, finding that the probability is insignificantly small.

Andrew J. Moylan; David E. McClelland; Susan M. Scott; Antony C. Searle; G. V. Bicknell

2007-10-16

275

We consider the solutions of the scattering of scalar, electromagnetic, and gravitational waves by the gravitational field of a single particle, for the case of small wave amplitudes and weak gravitational fields. Scatterings are considered for both incident plane waves and incident spherical waves. For plane waves incident on a thin sheet of matter composed of free particles, the superimposed

P. C. Peters

1974-01-01

276

Seeing in the Dark: Weak Lensing from the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Statistical weak lensing by large-scale structure { cosmic shear { is a promising cosmological tool, which has motivated the design of several large upcoming astronomical surveys. This Thesis presents a measurement of cosmic shear using coadded Sloan Digital Sky Survey (SDSS) imaging in 168 square degrees of the equatorial region, with r < 23:5 and i < 22:5, a source number density of 2.2 per arcmin2 and median redshift of zmed = 0.52. These coadds were generated using a new rounding kernel method that was intended to minimize systematic errors in the lensing measurement due to coherent PSF anisotropies that are otherwise prevalent in the SDSS imaging data. Measurements of cosmic shear out to angular separations of 2 degrees are presented, along with systematics tests of the catalog generation and shear measurement steps that demonstrate that these results are dominated by statistical rather than systematic errors. Assuming a cosmological model corresponding to WMAP7 (Komatsu et al., 2011) and allowing only the amplitude of matter fluctuations sigma8 to vary, the best-t value of the amplitude of matter fluctuations is sigma 8=0.636+0.109-0.154 (1sigma); without systematic errors this would be sigma8=0.636+0.099 -0.137 (1sigma). Assuming a flat ? CDM model, the combined constraints with WMAP7 are sigma8=0.784+0.028 -0.026 (1sigma). The 2sigma error range is 14 percent smaller than WMAP7 alone. Aside from the intrinsic value of such cosmological constraints from the growth of structure, some important lessons are identified for upcoming surveys that may face similar issues when combining multi-epoch data to measure cosmic shear. Motivated by the challenges faced in the cosmic shear measurement, two new lensing probes are suggested for increasing the available weak lensing signal. Both use galaxy scaling relations to control for scatter in lensing observables. The first employs a version of the well-known fundamental plane relation for early type galaxies. This modified "photometric fundamental plane" replaces velocity dispersions with photometric galaxy properties, thus obviating the need for spectroscopic data. We present the first detection of magnification using this method by applying it to photometric catalogs from the Sloan Digital Sky Survey. This analysis shows that the derived magnification signal is comparable to that available from conventional methods using gravitational shear. We suppress the dominant sources of systematic error and discuss modest improvements that may allow this method to equal or even surpass the signal-to-noise achievable with shear. Moreover, some of the dominant sources of systematic error are substantially different from those of shear-based techniques. The second outlines an idea for using the optical Tully-Fisher relation to dramatically improve the signal-to-noise and systematic error control for shear measurements. The expected error properties and potential advantages of such a measurement are proposed, and a pilot study is suggested in order to test the viability of Tully-Fisher weak lensing in the context of the forthcoming generation of large spectroscopic surveys.

Huff, Eric Michael

277

Weak lensing leads to the non-Gaussian magnification distribution of standard candles at a 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 alpha essentially represents the amount of matter that can cause magnification of a given source. Since matter

Yun Wang

1999-01-01

278

ON THE ACCURACY OF WEAK-LENSING CLUSTER MASS RECONSTRUCTIONS

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.

Becker, Matthew R. [Department of Physics, 5720 S. Ellis Avenue, University of Chicago, Chicago, IL 60637 (United States); Kravtsov, Andrey V. [Kavli Institute for Cosmological Physics, 5640 South Ellis Avenue, University of Chicago, Chicago, IL 60637 (United States)

2011-10-10

279

Cosmic Superstring Gravitational Lensing Phenomena: Predictions for Networks of (p,q) Strings

The unique, conical spacetime created by cosmic strings brings about distinctive gravitational lensing phenomena. The variety of these distinctive phenomena is increased when the strings have non-trivial mutual interactions. In particular, when strings bind and create junctions, rather than intercommute, the resulting configurations can lead to novel gravitational lensing patterns. In this brief note, we use exact solutions to characterize these phenomena, the detection of which would be strong evidence for the existence of complex cosmic string networks of the kind predicted by string theory-motivated cosmic string models. We also correct some common errors in the lensing phenomenology of straight cosmic strings.

Benjamin Shlaer; Mark Wyman

2005-09-22

280

Rotation of galaxies as a signature of cosmic strings in weak lensing surveys.

Vector perturbations sourced by topological defects can generate rotations in the lensing of background galaxies. This is a potential smoking gun for the existence of defects since rotation generates a curl-like component in the weak lensing signal which is not generated by standard density perturbations at linear order. This rotation signal is calculated as generated by cosmic strings. Future large scale weak lensing surveys should be able to detect this signal even for string tensions an order of magnitude lower than current constraints. PMID:19905797

Thomas, Daniel B; Contaldi, Carlo R; Magueijo, João

2009-10-30

281

Rotation of galaxies as a signature of cosmic strings in weak lensing surveys

Vector perturbations sourced by topological defects can generate rotations in the lensing of background galaxies. This is a potential smoking gun for the existence of defects since rotation generates a curl-like component in the weak lensing signal which is not generated by standard density perturbations at linear order. This rotation signal is calculated as generated by cosmic strings. Future large scale weak lensing surveys should be able to detect this signal even for string tensions an order of magnitude lower than current constraints.

Daniel B. Thomas; Carlo R. Contaldi; Joao Magueijo

2009-09-15

282

NASA Astrophysics Data System (ADS)

I present a new algorithm, Curved-sky grAvitational Lensing for Cosmological Light conE simulatioNS (CALCLENS), for efficiently computing weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. This new algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift-dependent shear signals including corrections to the Born approximation by using multiple-plane ray tracing and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multigrid methods. As a result, large areas of sky (˜10 000 square degrees) can be ray traced efficiently at high resolution using only a few hundred cores. Using this new algorithm and curved-sky calculations that only use a slower but more accurate spherical harmonic transform Poisson solver, I study the convergence, shear E-mode, shear B-mode and rotation mode power spectra. Employing full-sky E/B-mode decompositions, I confirm that the numerically computed shear B-mode and rotation mode power spectra are equal at high accuracy (?1 per cent) as expected from perturbation theory up to second order. Coupled with realistic galaxy populations placed in large N-body light cone simulations, this new algorithm is ideally suited for the construction of synthetic weak lensing shear catalogues to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys. The implementation presented in this work, written in C and employing widely available software libraries to maintain portability, is publicly available at http://code.google.com/p/calclens.

Becker, Matthew R.

2013-10-01

283

Effects of Multiple Weak Deflections on the Galaxy-Galaxy Lensing Signal

NASA Astrophysics Data System (ADS)

Galaxy-galaxy lensing is a powerful tool with which the dark mass distribution around galaxies can be constrained directly. One potential complication to the interpretation of an observed galaxy-galaxy lensing signal, however, is the effect of multiple weak deflections. A number of previous studies have shown that for a typical deep data set, background source galaxies will have been lensed at a comparable level by two or more foreground galaxies. Contrary to naive expectations, these multiple weak deflections that are undergone by the images of the source galaxies do not generally cancel out, nor can they usually be ignored. Previous work as shown that at large angular scales the net shear experienced by distant source galaxies due to all foreground lenses generally exceeds the shear due to the single lens with the smallest impact parameter (the "closest lens"). When multiple deflections that have occurred in the observational data are not included in the interpretation of the observed shear profile, systematic errors in the constraints on the lens masses can occur. Here we explore the effects of multiple deflections on the galaxy-galaxy lensing signal using various toy models. We show that the main cause for the difference between the shear profile resulting from all foreground weak lenses and the shear profile resulting from the single closest weak lens is the fact that galaxies have a broad distribution in redshift space. That is, it is not correct to consider realistic galaxy-galaxy lensing as being confined primarily to a single lens plane in redshift space. We also explore the effect of multiple weak deflections on the surface mass density inferred for foreground lenses when the net mean tangential shear (i.e., the shear that results when all multiple weak deflections are taken into account) is used.

Brainerd, Tereasa G.; Blumenthal, Kelly

2014-06-01

284

The effective number density of galaxies for weak lensing measurements in the LSST project

NASA Astrophysics Data System (ADS)

Future weak lensing surveys potentially hold the highest statistical power for constraining cosmological parameters compared to other cosmological probes. The statistical power of a weak lensing survey is determined by the sky coverage, the inverse of the noise in shear measurements and the galaxy number density. The combination of the latter two factors is often expressed in terms of neff - the `effective number density of galaxies used for weak lensing measurements'. In this work, we estimate neff for the Large Synoptic Survey Telescope (LSST) project, the most powerful ground-based lensing survey planned for the next two decades. We investigate how the following factors affect the resulting neff of the survey with detailed simulations: (1) survey time, (2) shear measurement algorithm, (3) algorithm for combining multiple exposures, (4) inclusion of data from multiple filter bands, (5) redshift distribution of the galaxies and (6) masking and blending. For the first time, we quantify in a general weak lensing analysis pipeline the sensitivity of neff to the above factors. We find that with current weak lensing algorithms, expected distributions of observing parameters, and all lensing data (r and i band, covering 18 000 degree2 of sky) for LSST, neff ? 37 arcmin-2 before considering blending and masking, neff ? 31 arcmin-2 when rejecting seriously blended galaxies and neff ? 26 arcmin-2 when considering an additional 15 per cent loss of galaxies due to masking. With future improvements in weak lensing algorithms, these values could be expected to increase by up to 20 per cent. Throughout the paper, we also stress the ways in which neff depends on our ability to understand and control systematic effects in the measurements.

Chang, C.; Jarvis, M.; Jain, B.; Kahn, S. M.; Kirkby, D.; Connolly, A.; Krughoff, S.; Peng, E.-H.; Peterson, J. R.

2013-09-01

285

NASA Astrophysics Data System (ADS)

The weak-lensing science of the Large Synoptic Survey Telescope (LSST) project drives the need to carefully model and separate the instrumental artifacts from the intrinsic shear signal caused by gravitational lensing. The dominant source of the systematics for all ground-based telescopes is the spatial correlation of the point-spread function (PSF) modulated by both atmospheric turbulence and optical aberrations in the telescope and camera system. In this article, we present a full field-of-view simulation of the LSST images by modeling both the atmosphere and the system optics with the most current data for the telescope and camera specifications and the environment. To simulate the effects of atmospheric turbulence, we generated six-layer Kolmogorov/von Kármán phase screens with the parameters estimated from the on-site measurements. LSST will continuously sample the wavefront, correcting the optics alignment and focus. For the optics, we combined the ray-tracing tool ZEMAX and our simulated focal-plane data to introduce realistic residual aberrations and focal-plane height variations. Although this expected focal-plane flatness deviation for LSST is small compared with that of other existing cameras, the fast focal ratio of the LSST optics cause this focal-plane flatness variation and the resulting PSF discontinuities across the CCD boundaries to be significant challenges in our removal of the PSF-induced systematics. We resolve this complication by performing principal component analysis (PCA) CCD by CCD and by interpolating the basis functions derived from the analysis using conventional polynomials. We demonstrate that this PSF correction scheme reduces the residual PSF ellipticity correlation below 10 over the cosmologically interesting (dark-matter-dominated) scale 10-3°. From a null test using the Hubble Space Telescope (HST) Ultra Deep Field (UDF) galaxy images without input shear, we verify that the amplitude of the galaxy ellipticity correlation function, after the PSF correction, is consistent with the shot noise set by the finite number of objects. We conclude that the current optical design and specification for the accuracy in the focal-plane assembly are sufficient to enable the control of the PSF systematics required for weak-lensing science with LSST.

Jee, M. James; Tyson, J. Anthony

2011-05-01

286

Up to 100,000 Reliable Strong Gravitational Lenses in Future Dark Energy Experiments

NASA Astrophysics Data System (ADS)

The Euclid space telescope will observe ~105 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 103 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 105.

Serjeant, S.

2014-09-01

287

Probing the cosmic web: inter-cluster filament detection using gravitational lensing

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

James M. G. Mead; Lindsay J. King; Ian G. McCarthy

2009-01-01

288

Accurate Weak Lensing of Standard Candles, Part 1: Flexible Cosmological Fits

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 constra...

Marra, Valerio; Amendola, Luca

2013-01-01

289

Gravitational lensing of quasars by edge-on spiral galaxies

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 ...

Wang, Emily P

2007-01-01

290

The origin of peak-offsets in weak-lensing maps

NASA Astrophysics Data System (ADS)

Centroid positions of peaks identified in weak-lensing mass maps often show offsets with respect to other means of identifying halo centres, such as position of the brightest cluster galaxy or X-ray emission centroid. Here we study the effect of projected large-scale structure (LSS), smoothing of mass maps, and shape noise on the weak-lensing peak positions. In addition, we compare the offsets in mass maps to those found in parametric model fits. Using ray-tracing simulations through the Millennium Run N-body simulation, we find that projected LSS does not alter the weak-lensing peak position within the limits of our simulations' spatial resolution, which exceeds the typical resolution of weak-lensing maps. We conclude that projected LSS, although a major contaminant for weak-lensing mass estimates, is not a source of confusion for identifying halo centres. The typically reported offsets in the literature are caused by a combination of shape noise and smoothing alone. This is true for centroid positions derived both from mass maps and model fits.

Dietrich, J. P.; Böhnert, A.; Lombardi, M.; Hilbert, S.; Hartlap, J.

2012-02-01

291

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.

Rozo, Eduardo; /U. Chicago /Chicago U., KICP; Wu, Hao-Yi; /KIPAC, Menlo Park; Schmidt, Fabian; /Caltech

2011-11-04

292

Probing Dark Matter and Dark Energy with Space-Based Weak Lensing

Weak lensing provides a direct measure of the distribution of mass in the universe, and is therefore a uniquely powerful probe of dark matter. Weak lensing can also be used to measure the twin phenomenon of dark energy, via its effect upon the cosmological growth rate of structures. Essential for this technique are well-resolved images of background galaxies out to large distances. As a concrete example of the surveys that will become available by the end of the decade, we consider the planned Supernova/Acceleration Probe (SNAP) space telescope. Detailed simulations of space-based images, manufactured using the shapelets formalism, enable us to quantitatively predict the future sensitivity to weak lensing shear. The high number density of galaxies resolved from space will enable maps of dark matter to be produced in two and three dimensions, with a resolution superior to that from the ground. Such observations will also afford reduced systematics for high-precision measurements of weak lensing statistics. These will be used to set tight constraints on cosmological parameters. In particular, the parameter for equation of state of dark energy, w, will be measured using weak lensing with a precision comparable to and somewhat orthogonal to constraints from other methods.

Richard Massey; Alexandre Refregier; Jason Rhodes

2004-03-10

293

Modeling Galaxy-Galaxy Weak Lensing with SDSS Groups

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.

Ran Li; H. J. Mo; Zuhui Fan; Marcello Cacciato; Frank C. van den Bosch; Xiaohu Yang; Surhud More

2009-01-15

294

NASA Astrophysics Data System (ADS)

This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazar populations. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed Flat-Spectrum Radio Quasars. The magnification factor is estimated for each system assuming a singular isothermal profile for the lens. Based on data collected from 2007 to 2012 by the ANTARES neutrino telescope, the strongest constraint is obtained from the lensed quasar B0218+357, providing a limit on the total neutrino luminosity of this source of 1.08× 1046 erg s-1. This limit is about one order of magnitude lower than those previously obtained in the ANTARES standard point source searches with non-lensed Flat-Spectrum Radio Quasars.

Adrián-Martínez, S.; Albert, A.; André, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Baret, B.; Barrios-Martí, J.; Basa, S.; Bertin, V.; Biagi, S.; Bogazzi, C.; Bormuth, R.; Bou-Cabo, M.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Chiarusi, T.; Circella, M.; Coniglione, R.; Core, L.; Costantini, H.; Coyle, P.; Creusot, A.; De Rosa, G.; Dekeyser, I.; Deschamps, A.; De Bonis, G.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Dumas, A.; Eberl, T.; Elsässer, D.; Enzenhöfer, A.; Escoffier, S.; Fehn, K.; Felis, I.; Fermani, P.; Folger, F.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Gómez-González, J. P.; Graf, K.; Guillard, G.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Herold, B.; Herrero, A.; Hößl, J.; Hofestädt, J.; Hugon, C.; James, C. W.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U.; Kießling, D.; Kooijman, P.; Kouchner, A.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lambard, E.; Lambard, G.; Lefèvre, D.; Leonora, E.; Loehner, H.; Loucatos, S.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martínez-Mora, J. A.; Martini, S.; Mathieu, A.; Michael, T.; Migliozzi, P.; Müller, C.; Neff, M.; Nezri, E.; Palioselitis, D.; P?v?laš, G. E.; Perrina, C.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Richter, R.; Roensch, K.; Rostovtsev, A.; Saldaña, M.; Samtleben, D. F. E.; Sánchez-Losa, A.; Sanguineti, M.; Schmid, J.; Schnabel, J.; Schulte, S.; Schüssler, F.; Seitz, T.; Sieger, C.; Spies, A.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, Th.; Taiuti, M.; Tamburini, C.; Tayalati, Y.; Trovato, A.; Tselengidou, M.; Tönnis, C.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Visser, E.; Vivolo, D.; Wagner, S.; Wilms, J.; de Wolf, E.; Yatkin, K.; Yepes, H.; Zornoza, J. D.; Zúñiga, J.; Falco, E. E.

2014-11-01

295

We present a newly developed code that allows simulations of optical observations of galaxy fields with a variety of instruments. The code incorporates gravitational lensing effects and is targetted at simulating lensing by galaxy clusters. Our goal is to create the tools required for comparing theoretical expectations with observations to obtain a better understanding of how observational noise affects lensing applications such as mass estimates, studies on the internal properties of galaxy clusters and arc statistics. Starting from a set of input parameters, characterizing both the instruments and the observational conditions, the simulator provides a virtual observation of a patch of the sky. It includes several sources of noise such as photon-noise, sky background, seeing, and instrumental noise. Ray-tracing through simulated mass distributions accounts for gravitational lensing. Source morphologies are realistically simulated based on shapelet decompositions of galaxy images retrieved from the GOODS-ACS ...

Meneghetti, Massimo; Grazian, Andrea; De Lucia, Gabriella; Dolag, Klaus; Bartelmann, Matthias; Heymans, Catherine; Moscardini, Lauro; Radovich, Mario

2007-01-01

296

SDSS J0246-0825: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey

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.

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

297

Multiple Weak Deflections and the Detection of Flattened Halos with Galaxy-Galaxy Lensing

We investigate the occurrence of multiple weak deflections in deep data sets which are used to detect galaxy-galaxy lensing. Using the galaxies in the HDF (North) for which both redshifts and rest-frame blue luminosities are known, we show that the probability for a given source galaxy to be lensed by two or more foreground galaxies exceeds 50% for z_s > 1, and for which the separate, individual deflections yield gamma > 0.005. Neglecting multiple deflections when obtaining best-fitting halo parameters for the lens galaxies can lead to an overestimate by a factor of order 2 for the halo mass interior to a radius of 100 kpc/h. We also show that multiple weak deflections create systematic effects which may hinder observational efforts to use weak lensing to constrain the projected shapes of the halos of field galaxies. For a data set in which the galaxies have magnitudes in the rage 19 < I < 23, multiple deflections result in strong correlations between the post-lensing image shapes of most foreground-background pairs of galaxies. Imposing a simple redshift cut during the data anaysis is sufficient to reduce the correlation between the final images of lenses and sources to the point that the expected anisotropy in the weak lensing signal can be detected via a straightforward average. We conclude that previous theoretical calculations of weak lensing due to flattened halos have considerably underestimated the sizes of the observational data sets which would be required to detect this effect. [Abridged

C. O. Wright; T. G. Brainerd

2002-05-17

298

Probabilities for gravitational lensing by point masses in a locally inhomogeneous universe

NASA Technical Reports Server (NTRS)

Probability functions for gravitational lensing by point masses that incorporate Poisson statistics and flux conservation are formulated in the Dyer-Roeder construction. Optical depths to lensing for distant sources are calculated using both the method of Press and Gunn (1973) which counts lenses in an otherwise empty cone, and the method of Ehlers and Schneider (1986) which projects lensing cross sections onto the source sphere. These are then used as parameters of the probability density for lensing in the case of a critical (q0 = 1/2) Friedmann universe. A comparison of the probability functions indicates that the effects of angle-averaging can be well approximated by adjusting the average magnification along a random line of sight so as to conserve flux.

Isaacson, Jeffrey A.; Canizares, Claude R.

1989-01-01

299

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...

Hoekstra, Henk; Muzzin, Adam; Babul, Arif; Mahdavi, Andisheh; Viola, Massimo; Cacciato, Marcello

2015-01-01

300

A DETECTION OF WEAK-LENSING MAGNIFICATION USING GALAXY SIZES AND MAGNITUDES

Weak lensing is commonly measured using shear through galaxy ellipticities or using the effect of magnification bias on galaxy number densities. Here, we report on the first detection of weak-lensing magnification with a new, independent technique using the distribution of galaxy sizes and magnitudes. These data come for free in galaxy surveys designed for measuring shear. We present the magnification estimator and apply it to an X-ray-selected sample of galaxy groups in the COSMOS Hubble Space Telescope survey. The measurement of the projected surface density {Sigma}(r) is consistent with the shear measurements within the uncertainties and has roughly 40% of the signal to noise of the latter. We discuss systematic issues and challenges to realizing the potential of this new probe of weak lensing.

Schmidt, Fabian; Rhodes, Jason [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 2778582 (Japan); Massey, Richard [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany)

2012-01-10

301

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.

Ermanno F. Borra

1997-04-09

302

New results from the gravitational lensing of galaxies

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 ...

Schwab, Josiah (Josiah W.)

2009-01-01

303

A Weak Lensing Survey in the Fields of z~1 Luminous Radio Sources

In this paper we present weak lensing observations of the fields around 8 z~1 luminous radio sources. These data are searched for the lensing signatures of clusters that are either physically associated with the radio objects, or are foreground systems projected along the line of sight. The radio sources were all imaged with WFPC-2/HST providing high quality shape information on large numbers of faint galaxies around them. Statistical analysis of the coherent shear field visible in the shapes of the faint galaxies indicates that we have detected a weak lensing signal close to one of the targets, 3C336 at z=0.927, with a high level of confidence. A second, independent WFPC-2 observation of this target reinforces this detection. Our results support the earlier suggestion of weak lensing in this field by Fort et al (1996) using ground-based data. We also combined the shear distributions in the remaining 7 field to improve our sensitivity to weak shear signals from any structure typically associated with these sources. We find no detectable signal and estimate an upper limit on the maximum shear allowed by our observations. Using an N(z) estimated from lensing analyses we convert our observed lensing signal and limits into estimates of the masses of the various structures. We suggest that further lensing observations of distant radio sources and their host environments may allow the cluster L_X-mass relationship to be mapped at high-z. This is crucial for interpreting the results of the next generation of deep X-ray surveys, and thus constraining the redshift evolution of the cluster mass function out to z=1.

Richard G. Bower; Ian Smail

1996-12-16

304

Self-Calibration for 3-point Intrinsic Alignment Auto-Correlations in Weak Lensing Surveys

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.

M. A. Troxel; Mustapha Ishak

2012-03-09

305

Interaction of Dirac and Majorana neutrinos with weak gravitational fields

In this paper the interaction of high energy neutrinos with weak gravitational fields is briefly explored. The form of the graviton-neutrino vertex is motivated from Lorentz and gauge invariance and the nonrelativistic interpretations of the neutrino-gravitational form factors are obtained. We comment on the renormalization conditions, the preservation of the weak equivalence principle and the definition of the neutrino mass radius. We associate the neutrino-gravitational form factors with specific angular momentum states. Based on Feynman diagrams, spin-statistics, CP invariance and symmetries of the angular momentum states in the graviton-neutrino vertex, we deduce differences between the Majorana and Dirac cases. It is then proved that in spite of the theoretical differences between the two cases, as far as experiments are considered, they would be virtually indistinguishable for any space-time geometry satisfying the weak-field condition. We then calculate the transition gravitational form factors for the neutrino by evaluating the relevant Feynman diagrams at 1-loop and estimate a neutrino transition mass radius. The form factor is seen to depend on the momentum transfer very weakly. It is also seen that the neutrino transition mass radius is smaller than the typical neutrino charge radius by a couple of orders of magnitude.

Menon, A.; Thalapillil, Arun M. [Michigan Center for Theoretical Physics and Department of Physics, University of Michigan, 500 East University Avenue, Michigan 48109-1120 (United States); Enrico Fermi Institute and Department of Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637 (United States)

2008-12-01

306

Combined analysis of weak lensing and X-ray blind surveys

We present a joint weak lensing and X-ray analysis of 4 deg$^2$ from the CFHTLS and XMM-LSS surveys. Our weak lensing analysis is the first analysis of a real survey using shapelets, a new generation weak lensing analysis method. We create projected mass maps of the images, and extract 6 weak-lensing-detected clusters of galaxies. We show that their counts can be used to constrain the power spectrum normalisation $\\sigma_8 =0.92_{-0.30}^{+0.26}$ for $\\Omega_m=0.24$. We show that despite the large scatter generally observed in the M-T relation derived from lensing masses, tight constraints on both its slope and normalisation $M_*$ can be obtained with a moderate number of sources provided that the covered mass range is large enough. Adding clusters from Bardeau et al. (2007) to our sample, we measure $M_* = 2.71_{-0.61}^{+0.79} 10^{14} h^{-1} M_\\odot$. Although they are dominated by shot noise and sample variance, our measurements are consistent with currently favoured values, and set the stage for future surveys. We thus investigate the dependence of those estimates on survey size, depth, and integration time, for joint weak lensing and X-ray surveys. We show that deep surveys should be dedicated to the study of the physics of clusters and groups of galaxies. For a given exposure time, wide surveys provide a larger number of detected clusters and are therefore preferred for the measurement of cosmological parameters such as $\\sigma_8$ and $M_*$. We show that a wide survey of a few hundred square degrees is needed to improve upon current measurements of these parameters. More ambitious surveys covering 7000 deg$^2$ will provide the 1% accuracy in the estimation of the power spectrum and the M-T relation normalisations.

Joel Bergé; Florian Pacaud; Alexandre Réfrégier; Richard Massey; Marguerite Pierre; Adam Amara; Mark Birkinshaw; Stéphane Paulin-Henriksson; Graham P. Smith; Jon Willis

2008-02-25

307

Mapping the dark matter with weak gravitational lensing

We consider the problem of reconstructing the projected mass distribution in clusters from coherent distortions of background galaxies. The ellipticity of a background galaxy provides an estimate of the trace-free components of the tidal field. We present a technique for inverting this problem. The resulting surface density contains a strong, but incoherent, random component arising from the random intrinsic galaxy

Nick Kaiser; Gordon Squires

1993-01-01

308

NASA Astrophysics Data System (ADS)

We conduct a joint X-ray and weak-lensing study of four relaxed galaxy clusters (Hydra A, A 478, A 1689, and A 1835) observed by both Suzaku and Subaru out to virial radii, with the aim of understanding recently discovered unexpected features of the intracluster medium (ICM) in cluster outskirts. We show that the average hydrostatic-to-lensing total mass ratio for the four clusters decreases from ˜ 70% to ˜ 40% as the overdensity contrast decreases from 500 to the virial value. The average gas mass fraction from lensing total mass estimates increases with cluster radius and agrees with the cosmic mean baryon fraction within the virial radius, whereas the X-ray-based gas fraction considerably exceeds the cosmic values due to underestimation of the hydrostatic mass. We also develop a new advanced method for determining normalized cluster radial profiles for multiple X-ray observables by simultaneously taking into account both their radial dependence and multivariate scaling relations with weak-lensing masses. Although the four clusters span a range of halo mass, concentration, X-ray luminosity, and redshift, we find that the gas entropy, pressure, temperature, and density profiles are all remarkably self-similar when scaled with the weak-lensing M200 mass and r200 radius. The entropy monotonically increases out to ˜ 0.5 r200 ˜ r1000 following the accretion shock heating model K(r) ? r1.1, and flattens at ? 0.5 r200. The universality of the scaled entropy profiles indicates that the thermalization mechanism over the entire cluster region (> 0.1 r200) is controlled by gravitation in a common way for all clusters, although the heating efficiency in the outskirts needs to be modified from the standard r1.1 law. The bivariate scaling functions of the gas density and temperature reveal that the flattening of the outskirts entropy profile is caused by the steepening of the temperature, rather than the flattening of the gas density.

Okabe, Nobuhiro; Umetsu, Keiichi; Tamura, Takayuki; Fujita, Yutaka; Takizawa, Motokazu; Zhang, Yu-Ying; Matsushita, Kyoko; Hamana, Takashi; Fukazawa, Yasushi; Futamase, Tasushi; Kawaharada, Madoka; Miyazaki, Satoshi; Mochizuki, Yukiko; Nakazawa, Kazuhiro; Ohashi, Takaya; Ota, Naomi; Sasaki, Toru; Sato, Kosuke; Tam, Sutieng

2014-10-01

309

Nonsingular density profiles of dark matter halos and Strong gravitational lensing

We use the statistics of strong gravitational lenses to investigate whether mass profiles with a flat density core are supported. The probability for lensing by halos modeled by a nonsingular truncated isothermal sphere (NTIS) with image separations greater than a certain value (ranging from zero to ten arcseconds) is calculated. NTIS is an analytical model for the postcollapse equilibrium structure of virialized objects derived by Shapiro, Iliev & Raga. This profile has a soft core and matches quite well with the mass profiles of dark matter-dominated dwarf galaxies deduced from their observed rotation curves. It also agrees well with the NFW (Navarro-Frenk-White) profile at all radii outside of a few NTIS core radii. Unfortunately, comparing the results with those for singular lensing halos (NFW and SIS+NFW) and strong lensing observations, the probabilities for lensing by NTIS halos are far too low. As this result is valid for any other nonsingular density profiles (with a large core radius), we conclude that nonsingular density profiles (with a large core radius) for CDM halos are ruled out by statistics of strong gravitational lenses.

Da-Ming Chen

2005-06-28

310

Testing the MOND paradigm of modified dynamics with galaxy-galaxy gravitational lensing.

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

Milgrom, Mordehai

2013-07-26

311

Testing the MOND Paradigm of Modified Dynamics with Galaxy-Galaxy Gravitational Lensing

NASA Astrophysics Data System (ADS)

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.

Milgrom, Mordehai

2013-07-01

312

X-ray and Weak Lensing Masses for a Sample of 50 Relaxed and Non-Relaxed Clusters of Galaxies

NASA Astrophysics Data System (ADS)

We present an updated, recalibrated, multiwavelength, X-ray + weak lensing measurement of the mass profiles for 50 rich systems of galaxies. We find that our weak gravitational lensing masses, calibrated with state-of-the-art shear testing simulations, are 18% +/- 4% higher than those found for the clusters in the Planck satellite sample. Using the Joint Analysis of Cluster Observations codebase, we simultaneously model the baryonic and nonbaryonic matter profiles in these systems, deriving joint constraints on the gas entropy, pressure, metallicity, and dark matter distributions. Simultaneous analysis of Chandra and XMM-Newton data where both are available allows us to constrain these profiles over nearly two decades in radius. We find clusters with low BCG-to-X-ray center offsets form a remarkably regular sample, with NFW dark matter profiles and gas fraction values that are consistent with the cosmological value. Clusters with low central gas entropy exhibit a similar trend, and do so with an intrinsic scatter that is consistent with zero. Non-relaxed clusters, on the other hand---those with offset BCGs and high central entropies---exhibit significant scatter and have mass profiles inconsistent with the NFW value (most likely due to strong violations of spherical symmetry).

Mahdavi, Andisheh; Hoekstra, Henk; Babul, Arif

2014-08-01

313

We present weak gravitational lensing analysis of 22 high-redshift (z {approx}> 1) clusters based on Hubble Space Telescope images. Most clusters in our sample provide significant lensing signals and are well detected in their reconstructed two-dimensional mass maps. Combining the current results and our previous weak-lensing studies of five other high-z clusters, we compare gravitational lensing masses of these clusters with other observables. We revisit the question whether the presence of the most massive clusters in our sample is in tension with the current {Lambda}CDM structure formation paradigm. We find that the lensing masses are tightly correlated with the gas temperatures and establish, for the first time, the lensing mass-temperature relation at z {approx}> 1. For the power-law slope of the M-T{sub X} relation (M{proportional_to}T{sup {alpha}}), we obtain {alpha} = 1.54 {+-} 0.23. This is consistent with the theoretical self-similar prediction {alpha} = 3/2 and with the results previously reported in the literature for much lower redshift samples. However, our normalization is lower than the previous results by 20%-30%, indicating that the normalization in the M-T{sub X} relation might evolve. After correcting for Eddington bias and updating the discovery area with a more conservative choice, we find that the existence of the most massive clusters in our sample still provides a tension with the current {Lambda}CDM model. The combined probability of finding the four most massive clusters in this sample after the marginalization over cosmological parameters is less than 1%.

Jee, M. J.; Lubin, L.; Stanford, S. A. [Department of Physics, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States); Dawson, K. S.; Harris, D. W. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Hoekstra, H. [Leiden Observatory, Leiden University, Leiden (Netherlands); Perlmutter, S.; Suzuki, N.; Meyers, J.; Barbary, K. [E.O. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA 94720 (United States); Rosati, P. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching (Germany); Brodwin, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Koester, B.; Gladders, M. D. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Postman, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Barrientos, F. [Department of Astronomy and Astrophysics, Universidad Catolica de Chile, Santiago (Chile); Eisenhardt, P. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Ford, H. C. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Gilbank, D. G. [Department of Physics and Astronomy, University Of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Gonzalez, A. [Department of Astronomy, University of Florida, Gainesville, FL 32611-2055 (United States)

2011-08-20

314

The influence of baryons on the clustering of matter and weak lensing surveys

Future weak lensing measurements of cosmic shear will reach such high accuracy that second order effects in weak lensing modeling, like the influence of baryons on structure formation, become important. We use a controlled set of state of the art cosmological simulations to quantify this effect by comparing pure N-body dark matter runs with corresponding hydrodynamical simulations, carried out both in non-radiative, and in dissipative form with cooling and star formation. In both hydrodynamical simulations, the clustering of the gas is suppressed while that of dark matter is boosted at scales k>1 h/Mpc. Despite this counterbalance between dark matter and gas, the clustering of the total matter is suppressed by up to 1 percent at 1it is boosted, up to 2 percent in the non-radiative run and 10 percent in the run with star formation. The stellar mass formed in the latter is highly biased relative to the dark matter in the pure N-body simulation. Using our power spectrum measurements to predict the effect of baryons on the weak lensing signal at 10010000, we find that baryons may change the lensing power spectrum by less than 0.5 percent at l1000, but by 1 to 10 percent at 100010000. The size of the effect exceeds the predicted accuracy of future lensing power spectrum measurements and will likely be detected. Precise determinations of cosmological parameters with weak lensing, and studies of small-scale fluctuations and clustering, therefore rely on properly including baryonic physics.

Y. P. Jing; Pengjie Zhang; W. P. Lin; L. Gao; V. Springel

2006-03-09

315

Weak lensing and dark energy: The impact of dark energy on nonlinear dark matter clustering

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.

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

316

On Gravitational anomaly and Hawking radiation near weakly isolated horizon

Based on the idea of the work by Wilczek and his collaborators, we consider the gravitational anomaly near weekly isolated horizon. We find that there exists a universal choice of tortoise coordinate for any weakly isolated horizon. Under this coordinate, the leading behavior of a quite arbitrary scalar field near horizon is a 2-dimensional chiral scalar field. This means we can extend the idea of Wilczek and his collaborators to more general cases and show the relation between gravitational anomaly and Hawking radiation is a universal property of black hole horizon.

Xiaoning Wu; Chao-Guang Huang; Jia-Rui Sun

2008-01-09

317

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 ($b_h\\equiv b/(2 G M)$). 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 ($\\sim 20\\, b_h$) 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 $O(\\alpha^2)$ in the weak coupling $\\alpha$, 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.

Claudio Coriano; Luigi Delle Rose; Matteo Maria Maglio; Mirko Serino

2015-01-16

318

NASA Astrophysics Data System (ADS)

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.

Corianò, Claudio; Rose, Luigi Delle; Maglio, Matteo Maria; Serino, Mirko

2015-01-01

319

Gravitational lensing in WDM cosmologies: the cross-section for giant arcs

NASA Astrophysics Data System (ADS)

The nature of the dark sector of the Universe remains one of the outstanding problems in modern cosmology, with the search for new observational probes guiding the development of the next generation of observational facilities. Clues come from tension between the predictions from ? cold dark matter (?CDM) and observations of gravitationally lensed galaxies. Previous studies showed that galaxy clusters in the ?CDM are not strong enough to reproduce the observed number of lensed arcs. This work aims to constrain the warm dark matter (WDM) cosmologies by means of the lensing efficiency of galaxy clusters drawn from these alternative models. The lensing characteristics of two samples of simulated clusters in the ? warm dark matter and ?CDM cosmologies have been studied. The results show that even though the cold dark matter (CDM) clusters are more centrally concentrated and contain more substructures, the WDM clusters have slightly higher lensing efficiency than their CDM counterparts. The key difference is that WDM clusters have more extended and more massive subhaloes than CDM analogues. These massive substructures significantly stretch the critical lines and caustics and hence they boost the lensing efficiency of the host halo. Despite the increase in the lensing efficiency due to the contribution of massive substructures in the WDM clusters, this is not enough to resolve the arc statistics problem.

Mahdi, Hareth S.; van Beek, Martijn; Elahi, Pascal J.; Lewis, Geraint F.; Power, Chris; Killedar, Madhura

2014-07-01

320

THE EINSTEIN CROSS: CONSTRAINT ON DARK MATTER FROM STELLAR DYNAMICS AND GRAVITATIONAL LENSING

We present two-dimensional line-of-sight stellar kinematics of the lens galaxy in the Einstein Cross, obtained with the GEMINI 8 m telescope, using the GMOS integral-field spectrograph. The stellar kinematics extend to a radius of 4'' (with 0.''2 spaxels), covering about two-thirds of the effective (or half-light) radius R{sub e} {approx_equal} 6'' of this early-type spiral galaxy at redshift z{sub l} {approx_equal} 0.04, of which the bulge is lensing a background quasar at redshift z{sub s} {approx_equal} 1.7. The velocity map shows regular rotation up to {approx}100 km s{sup -1} around the minor axis of the bulge, consistent with axisymmetry. The velocity dispersion map shows a weak gradient increasing toward a central (R < 1'') value of {sigma}{sub 0} = 170 {+-} 9 km s{sup -1}. We deproject the observed surface brightness from Hubble Space Telescope imaging to obtain a realistic luminosity density of the lens galaxy, which in turn is used to build axisymmetric dynamical models that fit the observed kinematic maps. We also construct a gravitational lens model that accurately fits the positions and relative fluxes of the four quasar images. We combine these independent constraints from stellar dynamics and gravitational lensing to study the total mass distribution in the inner parts of the lens galaxy. We find that the resulting luminous and total mass distribution are nearly identical around the Einstein radius R{sub E} = 0.''89, with a slope that is close to isothermal, but which becomes shallower toward the center if indeed mass follows light. The dynamical model fits to the observed kinematic maps result in a total mass-to-light ratio Y{sub dyn} = 3.7 {+-} 0.5 Y{sub sun,I} (in the I band). This is consistent with the Einstein mass M{sub E} = 1.54 x 10{sup 10} M {sub sun} divided by the (projected) luminosity within R{sub E} , which yields a total mass-to-light ratio of Y {sub E} = 3.4 Y{sub sun,I}, with an error of at most a few percent. We estimate from stellar population model fits to colors of the lens galaxy a stellar mass-to-light ratio Y{sub *} from 2.8 to 4.1 Y{sub sun,I}. Although a constant dark matter fraction of 20% is not excluded, dark matter may play no significant role in the bulge of this {approx}L {sub *} early-type spiral galaxy.

Van de Ven, Glenn [Max Planck Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg (Germany); Falcon-Barroso, Jesus [Instituto de Astrofisica de Canarias, Via Lactea s/n, La Laguna, Tenerife (Spain); McDermid, Richard M. [Gemini Observatory, 670 N. A'ohoku Place Hilo, Hawaii, HI 96720 (United States); Cappellari, Michele [Sub-Department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Miller, Bryan W. [Gemini Observatory, Casilla 603, La Serena (Chile); De Zeeuw, P. Tim, E-mail: glenn@mpia.d [European Southern Observatory, Karl-Schwarzschild Strasse 2, 85748 Garching (Germany)

2010-08-20

321

NASA Astrophysics Data System (ADS)

I present a new algorithm, CALCLENS, for efficiently computing weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. This new algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift- dependent shear signals including corrections to the Born approximation by using multiple- plane ray tracing, and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multigrid methods. As a result, large areas of sky (~10,000 square degrees) can be ray traced efficiently at high-resolution using only a few hundred cores. Using this new algorithm and curved-sky calculations that only use a slower but more accurate spherical harmonic transform Poisson solver, I study the convergence, shear E-mode, shear B-mode and rotation mode power spectra. Employing full-sky E/B-mode decompositions, I confirm that the numerically computed shear B-mode and rotation mode power spectra are equal at high accuracy ( ? 1%) as expected from perturbation theory up to second order. Coupled with realistic galaxy populations placed in large N-body light cone simulations, this new algorithm is ideally suited for the construction of synthetic weak lensing shear catalogs to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys. The implementation presented in this work, written in C and employing widely available software libraries to maintain portability, is publicly available at http://code.google.com/p/calclens.

Becker, Matthew Rand

322

Weak lensing analysis of SZ-selected clusters of galaxies from the SPT and Planck surveys

NASA Astrophysics Data System (ADS)

We present the weak lensing analysis of the Wide-Field Imager Sunyaev-Zel'dovich Cluster of Galaxy (WISCy) sample, a set of 12 clusters of galaxies selected for their Sunyaev-Zel'dovich (SZ) effect. After developing new and improved methods for background selection and determination of geometric lensing scaling factors from absolute multiband photometry in cluster fields, we compare the weak lensing mass estimate with public X-ray and SZ data. We find consistency with hydrostatic X-ray masses with no significant bias, no mass dependent bias and less than 20 per cent intrinsic scatter and constrain f_{{gas},500c}=0.128^{+0.029}_{-0.023}. We independently calibrate the South Pole Telescope significance-mass relation and find consistency with previous results. The comparison of weak lensing mass and Planck Compton parameters, whether extracted self-consistently with a mass-observable relation (MOR) or using X-ray prior information on cluster size, shows significant discrepancies. The deviations from the MOR strongly correlate with cluster mass and redshift. This could be explained either by a significantly shallower than expected slope of Compton decrement versus mass and a corresponding problem in the previous X-ray based mass calibration, or a size or redshift dependent bias in SZ signal extraction.

Gruen, D.; Seitz, S.; Brimioulle, F.; Kosyra, R.; Koppenhoefer, J.; Lee, C.-H.; Bender, R.; Riffeser, A.; Eichner, T.; Weidinger, T.; Bierschenk, M.

2014-08-01

323

NASA Astrophysics Data System (ADS)

After some historical remarks, we consider observational data on the gravitational lensing, different types of lensing: strong, weak, and microlensing, discovery of planets around distant stars by microlensing. We consider lensing with large deviation angles, when light passes close to the gravitational radius of the lens, and formation of weak relativistic rings. In the last part we consider an influence of plasma on the gravitational lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to dispersion properties of plasma, in presence of a plasma inhomogeneity, and due to a gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. Both effects are taken into account. Dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, which strongest action is for longest radiowaves. We have shown that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.

Bisnovatyi-Kogan, G. S.; Tsupko, O. Yu.

324

Joint cosmic microwave background and weak lensing analysis: constraints on cosmological parameters.

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

Contaldi, Carlo R; Hoekstra, Henk; Lewis, Antony

2003-06-01

325

Detectability of weak lensing modifications under Galileon theories

NASA Astrophysics Data System (ADS)

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.

Park, Youngsoo; Wyman, Mark

2015-03-01

326

The Dust-to-Gas Ratio in the Damped Ly alpha Clouds Towards the Gravitationally Lensed QSO 0957+561

NASA Technical Reports Server (NTRS)

We present HST/FOS spectra of the two bright images (A and B) of the gravitationally lensed QSO 0957+561 in the wavelength range 2200-3300 A. We find that the absorption system (Z(sub abs)) = 1.3911) near z(sub em) is a weak, damped Ly alpha system with strong Ly alpha absorption lines seen in both images. However, the H(I) column densities are different, with the line of sight to image A intersecting a larger column density. The continuum shapes of the two spectra differ in the sense that the flux level of image A increases more slowly toward shorter wavelengths than that of image B. We explain this as the result of differential reddening by dust grains in the damped Ly alpha absorber. A direct outcome of this explanation is a determination of the dust-to-gas ratio, k, in the damped Ly alpha system. We derive k = 0.55 + 0.18 for a simple 1/lambda extinction law and k = 0.31 + 0.10 for the Galactic extinction curve. For gravitationally lensed systems with damped Ly alpha absorbers, our method is a powerful tool for determining the values and dispersion of k, and the shapes of extinction curves, especially in the FUV and EUV regions. We compare our results with previous work.

Zuo, Lin; Beaver, E. A.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Lyons, R. W.

1997-01-01

327

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.

Obinna Umeh; Chris Clarkson; Roy Maartens

2014-09-22

328

Accurate Weak Lensing of Standard Candles, Part 2: Measuring sigma8 with Supernovae

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. This method is independent of and complementary to the standard methods based on CMB, cosmic shear or cluster abundance observables.

Quartin, Miguel; Amendola, Luca

2014-01-01

329

Source-position transformation: an approximate invariance in strong gravitational lensing

NASA Astrophysics Data System (ADS)

The main obstacle that gravitational lensing has in determining accurate masses of deflectors, or in determining precise estimates for the Hubble constant, is the degeneracy of lensing observables with respect to the mass-sheet transformation (MST). The MST is a global modification of the mass distribution which leaves all image positions, shapes, and flux ratios invariant, but which changes the time delay. Here we show that another global transformation of lensing mass distributions exists which leaves image positions and flux ratios almost invariant, and of which the MST is a special case. As is the case for the MST, this new transformation only applies if one considers only those source components that are at the same distance from us. Whereas for axi-symmetric lenses this source position transformation exactly reproduces all strong lensing observables, it does so only approximately for more general lens situations. We provide crude estimates for the accuracy with which the transformed mass distribution can reproduce the same image positions as the original lens model, and present an illustrative example of its performance. This new invariance transformation is most likely the reason why the same strong lensing information can be accounted for with rather different mass models.

Schneider, Peter; Sluse, Dominique

2014-04-01

330

SDSS J102111.02+491330.4: A Newly discovered gravitationally lensed quasar

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.

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

331

A 7 deg2 survey for galaxy-scale gravitational lenses with the HST imaging archive

NASA Astrophysics Data System (ADS)

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?).

Pawase, R. S.; Courbin, F.; Faure, C.; Kokotanekova, R.; Meylan, G.

2014-04-01

332

Planck 2013 results. XVII. Gravitational lensing by large-scale structure

NASA Astrophysics Data System (ADS)

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.

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

333

Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe. As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity. Clusters act as some of the most powerful gravitational lenses in the Universe. Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified. Lensing by clusters occurs in two regimes, each with unique observational signatures. The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets. The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically. Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy. In this review, we present the basics of cluster lensing and provide a current status report of the field.

Jean-Paul Kneib; Priyamvada Natarajan

2012-02-03

334

The generation of gravitational waves. I - Weak-field sources

NASA Technical Reports Server (NTRS)

This paper derives and summarizes a 'plug-in-and-grind' formalism for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, the formalism reduces to standard 'linearized theory'. Independent of the effects of gravity on the motions, the formalism reduces to the standard 'quadrupole-moment formalism' if the motions are slow and internal stresses are weak. In the general case, the formalism expresses the radiation in terms of a retarded Green's function for slightly curved spacetime and breaks the Green's function integral into five easily understood pieces: direct radiation, produced directly by the motions of the source; whump radiation, produced by the 'gravitational stresses' of the source; transition radiation, produced by a time-changing time delay ('Shapiro effect') in the propagation of the nonradiative 1/r field of the source; focusing radiation, produced when one portion of the source focuses, in a time-dependent way, the nonradiative field of another portion of the source; and tail radiation, produced by 'back-scatter' of the nonradiative field in regions of focusing.

Thorne, K. S.; Kovacs, S. J.

1975-01-01

335

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.

Graham P. Smith

2002-01-15

336

On the universality of microlensing in quadruple gravitational lenses

NASA Technical Reports Server (NTRS)

It is well known that multiply imaged quasars are likely to be affected by microlensing. Quadruply imaged systems are especially useful laboratories for studying microlensing because their macrolens models are relatively well constrained. We begin with analytical results for a simple family of galaxy models. These results can be used to estimate the magnifications and time delays for the quadruple systems. We compute expected brightness fluctuations due to microlensing in several such systems for a range of source sizes. Among these we treat for the first time the limiting case of a completely unresolved source. For the case of MG 0414+0534 we interpret the discrepant optical-to-radio flux ratios for the different components as the result of microlensing. On the assumption that the lensing galaxy is roughly isothermal this gives a 95% confidence upper limit on the optical source size of 10(exp 16) cm x (mean value of M)/0.1 solar mass(exp 1/2) where (M) is the average stellar mass of the lensing galaxy. For more centrally concentrated macromodels the upper limit is greater. Sufficiently long strings of photometric observations can in principle constrain the degree of concentration.

Witt, Hans J.; Mao, S.; Schechter, Paul L.

1995-01-01

337

Microlensing Planets: Multiple Planet Systems as Gravitational Triple Lenses

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

S. Rhie; D. Bennett

2000-01-01

338

Impact of Dark Matter Substructure on the Matter and Weak Lensing Power Spectra

We explore the effect of substructure in dark matter halos on the power spectrum and bispectrum of matter fluctuations and weak lensing shear. By experimenting with substructure in a cosmological N = 512^3 simulation, we find that when a larger fraction of the host halo mass is in subhalos, the resulting power spectrum has less power at 1 power at k > 100 h Mpc^{-1}. We explain this effect using an analytic halo model including subhalos, which shows that the 1 100 h Mpc^{-1}. The corresponding effect due to substructures on the weak lensing power spectrum is up to about 11% at angular scale l power spectrum to a few percent accuracy for future surveys would therefore require large cosmological simulations that also have exquisite numerical resolution to model accurately the survivals of dark matter subhalos in the tidal fields of their hosts.

Bradley Hagan; Chung-Pei Ma; Andrey V. Kravtsov

2005-07-25

339

Cosmic microwave weak lensing data as a test for the dark universe

Combined analyses of WMAP 3-year and ACBAR cosmic microwave anisotropies angular power spectra have presented evidence for gravitational lensing at >3{sigma} level. This signal could provide a relevant test for cosmology. After evaluating and confirming the statistical significance of the detection in light of the new WMAP 5-year data, we constrain a new parameter A{sub L} that scales the lensing potential such that A{sub L}=0 corresponds to unlensed while A{sub L}=1 is the expected lensed result in the standard {lambda}-CDM model. We find from WMAP5+ACBAR a 2.5{sigma} indication for a lensing contribution larger than expected, with A{sub L}=3.1{sub -1.5}{sup +1.8} at 95% C.L. The result is stable under the assumption of different templates for an additional Sunyaev-Zel'dovich foreground component or the inclusion of an extra background of cosmic strings. We find negligible correlation with other cosmological parameters as, for example, the energy density in massive neutrinos. While unknown systematics may be present, dark energy or modified gravity models could be responsible for the over-smoothness of the power spectrum. Near-future data, most notably from the Planck satellite mission, will scrutinize this interesting possibility.

Calabrese, Erminia; Slosar, Anze; Melchiorri, Alessandro; Smoot, George F.; Zahn, Oliver [Physics Department, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Berkeley Center for Cosmological Physics, Physics Department, University of California, Berkeley, CA 94720 (United States); Physics Department and INFN, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Lawrence Berkeley National Laboratory and Berkeley Center for Cosmological Physics, Physics Department, University of California, Berkeley, CA 94720 (United States)

2008-06-15

340

Cosmic Microwave Weak lensing data as a test for the dark universe

Combined analyses of WMAP 3-year and ACBAR Cosmic Microwave Anisotropies angular power spectra have presented evidence for gravitational lensing >3 sigma level. This signal could provide a relevant test for cosmology. After evaluating and confirming the statistical significance of the detection in light of the new WMAP 5-year data, we constrain a new parameter A_L that scales the lensing potential such that A_L=0 corresponds to unlensed while A_L=1 is the expected lensed result. We find from WMAP5+ACBAR a 2.5 sigma indication for a lensing contribution larger than expected, with A_L=3.1_{-1.5}^{+1.8} at 95% c.l.. The result is stable under the assumption of different templates for an additional Sunyaev-Zel'dovich foreground component or the inclusion of an extra background of cosmic strings. We find negligible correlation with other cosmological parameters as, for example, the energy density in massive neutrinos. While unknown systematics may be present, dark energy or modified gravity models could be responsible for the over-smoothness of the power spectrum. Near future data, most notably from the Planck satellite mission, will scrutinize this interesting possibility.

Erminia Calabrese; Anze Slosar; Alessandro Melchiorri; George F. Smoot; Oliver Zahn

2008-03-17

341

The Shear TEsting Programme 1: Weak lensing analysis of simulated ground-based observations

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.

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

342

Dissecting the 3D structure of elliptical galaxies with gravitational lensing and stellar kinematics

NASA Astrophysics Data System (ADS)

The combination of strong gravitational lensing and stellar kinematics provides a powerful and robust method to investigate the mass and dynamical structure of early-type galaxies. We demonstrate this approach by analysing two massive ellipticals from the XLENS Survey for which both high-resolution HST imaging and X-Shooter spectroscopic observations are available. We adopt a flexible axisymmetric two-component mass model for the lens galaxies, consisting of a generalised NFW dark halo and a realistic self-gravitating stellar mass distribution. For both systems, we put constraints on the dark halo inner structure and flattening, and we find that they are dominated by the luminous component within one effective radius. By comparing the tight inferences on the stellar mass from the combined lensing and dynamics analysis with the values obtained from stellar population studies, we conclude that both galaxies are characterised by a Salpeter-like stellar initial mass function.

Barnabè, Matteo; Spiniello, Chiara; Koopmans, Léon V. E.

2015-02-01

343

We present a newly developed code that allows simulations of optical observations of galaxy fields with a variety of instruments. The code incorporates gravitational lensing effects and is targetted at simulating lensing by galaxy clusters. Our goal is to create the tools required for comparing theoretical expectations with observations to obtain a better understanding of how observational noise affects lensing applications such as mass estimates, studies on the internal properties of galaxy clusters and arc statistics. Starting from a set of input parameters, characterizing both the instruments and the observational conditions, the simulator provides a virtual observation of a patch of the sky. It includes several sources of noise such as photon-noise, sky background, seeing, and instrumental noise. Ray-tracing through simulated mass distributions accounts for gravitational lensing. Source morphologies are realistically simulated based on shapelet decompositions of galaxy images retrieved from the GOODS-ACS archive. According to their morphological class, spectral-energy-distributions are assigned to the source galaxies in order to reproduce observations of each galaxy in arbitrary photometric bands. We illustrate our techniques showing virtual observations of a galaxy-cluster core as it would be observed with the space telescope DUNE, which was recently proposed to ESA within its "Cosmic vision" programme. (Abridged)

Massimo Meneghetti; Peter Melchior; Andrea Grazian; Gabriella De Lucia; Klaus Dolag; Matthias Bartelmann; Catherine Heymans; Lauro Moscardini; Mario Radovich

2007-11-21

344

The time delay in strong gravitational lensing with Gauss-Bonnet correction

The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We derive and calculate the expression of time delay due to the Gauss-Bonnet coupling. It is shown that the time delay for two images with larger space each other is longer. We also find that the ratio of Gauss-Bonnet coefficient and the mass of gravitational source changes in the region like $\\frac{\\alpha}{M}\\in[0,2)$. The time delay is divergent with $\\frac{\\alpha}{M}\\longrightarrow 2$.

Jingyun Man; Hongbo Cheng

2014-09-13

345

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.

Yun Wang

1999-06-25

346

NASA Astrophysics Data System (ADS)

Weak-lensing measurements of the averaged shear profiles of galaxy clusters binned by some proxy for cluster mass are commonly converted to cluster mass estimates under the assumption that these cluster stacks have spherical symmetry. In this paper, we test whether this assumption holds for optically selected clusters binned by estimated optical richness. Using mock catalogues created from N-body simulations populated realistically with galaxies, we ran a suite of optical cluster finders and estimated their optical richness. We binned galaxy clusters by true cluster mass and estimated optical richness and measure the ellipticity of these stacks. We find that the processes of optical cluster selection and richness estimation are biased, leading to stacked structures that are elongated along the line of sight. We show that weak-lensing alone cannot measure the size of this orientation bias. Weak-lensing masses of stacked optically selected clusters are overestimated by up to 3-6 per cent when clusters can be uniquely associated with haloes. This effect is large enough to lead to significant biases in the cosmological parameters derived from large surveys like the Dark Energy Survey, if not calibrated via simulations or fitted simultaneously. This bias probably also contributes to the observed discrepancy between the observed and predicted Sunyaev-Zel'dovich signal of optically selected clusters.

Dietrich, Jörg P.; Zhang, Yuanyuan; Song, Jeeseon; Davis, Christopher P.; McKay, Timothy A.; Baruah, Leon; Becker, Matthew; Benoist, Christophe; Busha, Michael; da Costa, Luiz A. N.; Hao, Jiangang; Maia, Marcio A. G.; Miller, Christopher J.; Ogando, Ricardo; Romer, A. Kathy; Rozo, Eduardo; Rykoff, Eli; Wechsler, Risa

2014-09-01

347

Time Delay in Gravitational Lensing by a Charged Black Hole of String Theory

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.

Alexis Larranaga

2007-07-16

348

Time Delay in Gravitational Lensing by a Charged Black Hole of String Theory

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

Eduard Alexis Larranaga Rubio

2003-01-01

349

Cosmological constraints from strong gravitational lensing in clusters of galaxies.

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

Jullo, Eric; Natarajan, Priyamvada; Kneib, Jean-Paul; D'Aloisio, Anson; Limousin, Marceau; Richard, Johan; Schimd, Carlo

2010-08-20

350

Mapping the 3-D dark matter with weak lensing in COMBO-17

We present a 3-dimensional lensing analysis of the z=0.16 supercluster A901/2, resulting in a 3-D map of the dark matter distribution within a 3 X 10^{5} [Mpc]^3 volume from the COMBO-17 survey. We perform a chi^2-fit of isothermal spheres to the tangential shear pattern around each cluster as a function of redshift to estimate the 3-D positions and masses of the main clusters in the supercluster from lensing alone. We then present the first 3-D map of the dark matter gravitational potential field, Phi, using the Kaiser-Squires (1993) and Taylor (2001) inversion methods. These maps clearly show the potential wells of the main supercluster components, including a new cluster behind A902, and demonstrates the applicability of 3-D dark matter mapping and projection free-mass-selected cluster finding to current data. Finally, we develop the halo model of dark matter and galaxy clustering and compare this with the auto-and cross-correlation functions of the 3-D gravitational potential, galaxy number densities and galaxy luminosity densities measured in the A901/2 field. We find significant anti-correlations between the gravitational potential field and the galaxy number density and luminosities, as expected due to baryonic infall into dark matter concentrations. We find good agreement with the halo model for the number densities and luminosity correlation functions.

A. N. Taylor; D. J. Bacon; M. E. Gray; C. Wolf; K. Meisenheimer; S. Dye; A. Borch; M. Kleinheinrich; Z. Kovacs; L. Wisotzki

2004-02-04

351

Shadows (Mirages) Around Black Holes and Retro Gravitational Lensing

NASA Astrophysics Data System (ADS)

Recently Holz & Wheeler [1] 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 (a detailed description of the problem is given in [2]). 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. Some time ago Falcke, Melia & Agol [3] 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.

Zakharov, A. F.; Nucita, A. A.; Depaolis, F.; Ingrosso, G.

352

We study the equation of motion of photons and the strong gravitational lensing in a Schwarzschild black hole spacetime when the photons couple to Weyl tensor. We find that the propagation of the coupled photons and the corresponding gravitational lensing depend sharply on the coupling constant $\\alpha$ and the photon polarization directions. The marginally stable circular radius $r_{ps}$ exists only in the regime $\\alpha\\geq\\alpha_{c1}=-M^2/2$ for the photon with the polarization along $l_{\\mu}$ and in the regime $\\alpha\\leq\\alpha_{c2}=M^2$ for the photon with the polarization along $m_{\\mu}$. When the value of $\\alpha$ is beyond the above regime, we find that the marginally stable circular radius vanishes and there exists a singularity outside the event horizon of black hole in the propagation of the coupled photons. The deflection angle of the light ray near the singularity is a negative finite value, which is different entirely from that of the usual photons without the coupling to Weyl tensor. Finally, we estimated three observables in the strong gravitational lensing for the coupled photons in the case with the marginally circular orbit by assuming the supermassive central object in our Galaxy as a Schwarzschild compact object.

Songbai Chen; Jiliang Jing

2015-02-04

353

SDSS J133401.39+331534.3: A NEW SUBARCSECOND GRAVITATIONALLY LENSED QUASAR

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.

Rusu, Cristian E.; Iye, Masanori [Optical and Infrared Astronomy Division, National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Oguri, Masamune [Institute for the Physics and Mathematics of the Universe, The University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa, Chiba 277-8568 (Japan); Inada, Naohisa [Department of Physics, Nara National College of Technology, Yamatokohriyama, Nara 639-1080 (Japan); Kayo, Issha [Department of Physics, Toho University, Funabashi, Chiba 274-8510 (Japan); Hayano, Yutaka; Oya, Shin; Hattori, Masayuki; Saito, Yoshihiko; Ito, Meguru; Minowa, Yosuke; Pyo, Tae-Soo; Terada, Hiroshi; Takami, Hideki [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place, Hilo, HI 96720 (United States); Watanabe, Makoto [Department of Cosmosciences, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810 (Japan)

2011-09-01

354

A Lower Limit on Omega-Lambda Using Gravitational Lensing in the Hubble Deep Field

We calculate the expected number of multiply-imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with $m_I < 27$ that were detected in all four HDF passbands. A comparison of these expectations with the observed number of strongly lensed galaxies places a lower limit on the current value of $\\Omega_m-\\Omega_{\\Lambda}$, where $\\Omega_m$ is the cosmological mass density of the universe and $\\Omega_\\Lambda$ is the normalized cosmological constant. Based on current estimates of the HDF luminosity function and associated uncertainties in individual parameters, our 95% confidence lower limit on $\\Omega_m-\\Omega_{\\Lambda}$ is between -0.44, if there are no strongly lensed galaxies in the HDF, and -0.73, if there are two strongly lensed galaxies in the HDF. If the only lensed galaxy in the HDF is the one presently viable candidate, then, in a flat universe ($\\Omega_m+\\Omega_\\Lambda=1$), $\\Omega_{\\Lambda} < 0.79$ (95% C.L.). These lower limits are compatible with estimates based on high-redshift supernovae and with previous limits based on gravitational lensing.

Asantha R. Cooray; Jean M. Quashnock; M. Coleman Miller

1998-12-05

355

We take advantage of the magnification in size and flux of a galaxy provided by gravitational lensing to analyze the properties of 62 strongly lensed galaxies from the Sloan Lens ACS (SLACS) Survey. The sample of lensed galaxies spans a redshift range of 0.20 ? z ? 1.20 with a median redshift of z = 0.61. We use the lens modeling code LENSFIT to derive the luminosities, sizes, and Sérsic indices of the lensed galaxies. The measured properties of the lensed galaxies show a primarily compact, {sup d}isk{sup -}like population with the peaks of the size and Sérsic index distributions corresponding to ?1.50 kpc and n ? 1, respectively. Comparison of the SLACS galaxies to a non-lensing, broadband imaging survey shows that a lensing survey allows us to probe a galaxy population that reaches ?2 mag fainter. Our analysis allows us to compare the (z) = 0.61 disk galaxy sample (n ? 2.5) to an unprecedented local galaxy sample of ?670, 000 SDSS galaxies at z ? 0.1; this analysis indicates that the evolution of the luminosity-size relation since z ? 1 may not be fully explained by a pure-size or pure-luminosity evolution but may instead require a combination of both. Our observations are also in agreement with recent numerical simulations of disk galaxies that show evidence of a mass-dependent evolution since z ? 1, where high-mass disk galaxies (M{sub *} > 10{sup 9} M{sub ?}) evolve more in size and low-mass disk galaxies (M{sub *} ? 10{sup 9} M{sub ?}) evolve more in luminosity.

Bandara, Kaushala; Crampton, David; Peng, Chien; Simard, Luc [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)

2013-11-01

356

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.

High, F. W.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Hoekstra, H. [Leiden Observatory, Leiden University, Leiden (Netherlands); Leethochawalit, N. [Department of Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); De Haan, T. [Department of Physics, McGill University, 3600 Rue University, Montreal, QC H3A 2T8 (Canada); Abramson, L. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Armstrong, R. [National Center for Supercomputing Applications, University of Illinois, 1205 West Clark Street, Urbana, IL 61801 (United States); Ashby, M. L. N.; Conroy, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bautz, M. [MIT Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Bayliss, M. [Department of Physics, Harvard University, 17 Oxford Street, Cambridge, MA 02138 (United States); Bazin, G. [Department of Physics, Ludwig-Maximilians-Universitaet, Scheinerstr. 1, D-81679 Muenchen (Germany); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Cho, H. M. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); Clocchiatti, A., E-mail: fwhigh@kicp.uchicago.edu [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica, Casilla 306, Santiago 22 (Chile); and others

2012-10-10

357

NASA Astrophysics Data System (ADS)

Context. Studying cosmological structure formation provides insights into all of the universe's components: baryonic matter, dark matter, and, notably, dark energy. Measuring the mass function of galaxy clusters at high redshifts is particularly useful probe for both learning about the history of structure formation and constraining cosmological parameters. Aims: We attempt to derive reliable masses for a high-redshift, high-luminosity sample of galaxy clusters selected from the 400d X-ray selected cluster survey. Weak gravitational lensing allows us to determine masses that can be compared with those inferred from X-rays, forming an independent test. We focus on a particular object, CL0030+2618 at z = 0.50. Methods: Using deep imaging in three passbands acquired using the Megacam instrument at MMT, we show that Megacam is well-suited to measuring gravitational shear, i.e., the shapes of faint galaxies. A catalogue of background galaxies is constructed by analysing the photometric properties of galaxies in the g'r'i' bands. Results: Using the aperture mass technique, we detect the weak lensing signal of CL0030+2618 at 5.8? significance. We find significant tangential alignment of galaxies out to 10' or a distance of >2 r200 from the cluster centre. The weak lensing centre of CL0030+2618 agrees with several X-ray measurements and the position of the brightest cluster galaxy. Finally, we infer a weak lensing virial mass of M200 = 7.2+3.6+2.3-2.9-2.5 × 1014 {M}? for CL0030+2618. Conclusions: Despite complications caused by a tentative foreground galaxy group along the line of sight, the X-ray and weak lensing estimates for CL0030+2618 are in remarkable agreement. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona. Our MMT observations were supported in part by a donation from the F. H. Levinson Fund of the Silicon Valley Community Foundation to the University of Virginia. In addition, MMT observations used for this project were granted by the Smithsonian Astrophysical Observatory and by NOAO, through the Telescope System Instrumentation Program (TSIP). TSIP is funded by NSF.

Israel, H.; Erben, T.; Reiprich, T. H.; Vikhlinin, A.; Hildebrandt, H.; Hudson, D. S.; McLeod, B. A.; Sarazin, C. L.; Schneider, P.; Zhang, Y.-Y.

2010-09-01

358

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

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

359

NASA Astrophysics Data System (ADS)

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.; Polarbear Collaboration

2014-04-01

360

Weak Lensing Masses of Nearby Clusters of Galaxies: Towards a Complete Sample of Clusters

NASA Astrophysics Data System (ADS)

We propose to carry out deep, multicolor BTC observations of 4 z~eq0.05 clusters which will be used to measure the weak lensing shear towards these nearby clusters of galaxies. The color information will allow us to define photometric redshifts for all galaxies thus separating cluster galaxies from the background population. When combined with the relatively insensitivity of the lensing signal towards low redshift clusters to the background galaxy redshift distribution, we will eliminate a major source of uncertainty in present, higher redshift, lensing studies. We will combined these lensing data with the extensive X-ray data, optical redshifts, and high quality Sunyaev-Zel'dovich (SZ) observations available on these clusters to obtain a robust determination of the total masses of these systems. These 4 clusters - in addition to 2 clusters observed in semester 98B - are part of a complete, X-ray luminosity limited sample of 24 nearby southern clusters scheduled for SZ observations by the Viper telescope at the South Pole. These 6 clusters - 25% of the sample - will be the first step towards a robust determination of the local cluster mass function: a fundamental goal of cosmology which will be used to constrain the underlying cosmological model and ?_0.

Nichol, Bob; McKay, Tim; Frieman, Josh; Connolly, Andy; Stebbins, Albert; Romer, Kathy; Peterson, Jeff; Griffin, Greg

1999-02-01

361

Weak Lensing Masses of Nearby Clusters of Galaxies: Towards a Complete Sample

NASA Astrophysics Data System (ADS)

We propose to carry out deep, multicolor, MOSAIC II imaging of 5 nearby (z < 0.1) clusters which will be used to measure the weak lensing shear toward these galaxy clusters. We will use the color information to separate cluster and background galaxies. When combined with the relative insensitivity of the lensing signal towards low redshift clusters to the background galaxy redshift distribution, we will eliminate a major source of uncertainty present in previous lensing mass determinations. These 5 clusters - in addition to 9 already observed at CTIO - are part of a complete X-ray luminosity-limited sample of 18 nearby southern clusters scheduled for Sunyaev-Zel'dovich (SZ) observations by the Viper telescope. We will combine this lensing data with extensive X-ray and radio data, optical redshifts, and high- quality SZ observations now available of these clusters to perform detailed studies of their baryon fraction, morphologies, as well as, obtaining determinations of their total masses. These 14 clusters - more than 3/4 of the total sample - will be a major step towards a robust determination of the local cluster mass function, a fundamental goal of cosmology.

Nichol, Bob; McKay, Timothy; Frieman, Joshua; Joffre, Michael; Fischer, Phillippe; Mohr, Joseph

2000-02-01

362

Weak Lensing by Nearby Clusters of Galaxies: A Complete Sample of Clusters

NASA Astrophysics Data System (ADS)

We propose to carry out deep, multicolor, MOSAIC II imaging of 5 nearby (z< 0.1) clusters which will be used to measure the weak lensing shear toward these galaxy clusters. We will use the color information to separate cluster members from background galaxies. The lensing signal in low-redshift clusters is relatively insensitive to the background galaxy redshift distribution, eliminating one of the major uncertainties in the interpretation of previous, high redshift, cluster lensing measurements. These 5 clusters - in addition to the 13 already observed at CTIO - will finish a complete X-ray luminosity-limited sample of 18 nearby southern clusters scheduled for Sunyaev-Zel'dovich (SZ) observations by the Viper telescope. We will combine this lensing data with extensive X-ray and radio data, optical redshifts and high- quality SZ observations to perform detailed studies of their baryon fractions, morphologies and total masses. This wide variety of data is uniquely available for these low-z clusters. This entire completed survey will be a major tool in the determination of the local cluster mass function, a fundamental goal of cosmology. This proposal covers clusters for which we were granted observing time in 2000A, however they were not observed as the entire observing run was lost due to extreme weather.

Nichol, Bob; Fischer, Philippe; Frieman, Joshua; Joffre, Michael; McKay, Timothy; Mohr, Joseph

2001-02-01

363

Gravitational lensing effects of vacuum strings - Exact solutions

NASA Technical Reports Server (NTRS)

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.

Gott, J. R., III

1985-01-01

364

We show how the combination of observations related to strong gravitational lensing and stellar dynamics in ellipticals offers a new way to measure the cosmological matter and dark-energy density parameters. A gravitational lensing estimate of the mass enclosed inside the Einstein circle can be obtained by measuring the Einstein angle, once the critical density of the system is known. A model-dependent dynamical estimate of this mass can also be obtained by measuring the central velocity dispersion of the stellar component. By assuming the well-tested homologous 1/r^{2} profile for the total density distribution in the lens elliptical galaxies, these two mass measurements can be properly compared. Thus, a relation between the Einstein angle and the central stellar velocity dispersion is derived, and the cosmological matter and the dark-energy density parameters can be estimated from this. We determined the accuracy of the cosmological parameter estimates by means of simulations that include realistic measurement uncertainties on the relevant quantities. Interestingly, the expected constraints on the cosmological parameter plane are complementary to those coming from other observational techniques. Then, we applied the method to the data sets of the Sloan Lens ACS and the Lenses Structure and Dynamics Surveys, and showed that the concordance value between 0.7 and 0.8 for the dark-energy density parameter is included in our 99% confidence regions. The small number of lenses available to date prevents us from precisely determining the cosmological parameters, but it still proves the feasibility of the method. When applied to samples made of hundreds of lenses that are expected to become available from forthcoming surveys, this technique will be an important tool for measuring the geometry of the Universe.

C. Grillo; M. Lombardi; G. Bertin

2007-11-06

365

Can we use Weak Lensing to Measure Total Mass Profiles of Galaxies on 20 kiloparsec Scales?

Current constraints on dark matter density profiles from weak lensing are typically limited to radial scales greater than 50-100 kpc. In this paper, we explore the possibility of probing the very inner regions of galaxy/halo density profiles by measuring stacked weak lensing on scales of only a few tens of kpc. Our forecasts focus on scales smaller than the equality radius (Req) where the stellar component and the dark matter component contribute equally to the lensing signal. We compute the evolution of Req as a function of lens stellar mass and redshift and show that Req=7-34 kpc for galaxies with the stellar mass of 10^{9.5}-10^{11.5} solar masses. Unbiased shear measurements will be challenging on these scales. We introduce a simple metric to quantify how many source galaxies overlap with their neighbours and for which shear measurements will be challenging. Rejecting source galaxies with close-by companions results in about a 20 per cent decrease in the overall source density. Despite this decrease, we s...

Kobayashi, Masato I N; More, Surhud; Okabe, Nobuhiro; Laigle, Clotilde; Rhodes, Jason; Takeuchi, Tsutomu T

2015-01-01

366

How many SNeIa do we need to detect the effect of weak lensing ?

We show that as many as 4000 SNeIa may be required to detect the effect of weak lensing on their flux distribution with a high level of significance. However, if the intrinsic SNeIa magnitude dispersion is unknown one needs an even higher number of SNeIa (an order of magnitude more) to reach a similar level of statistical significance. Moreover, the ability to separate the lensing contribution from the intrinsic scatter depends sensitively on the amplitude of the latter. Using a Kolmogorov - Smirnov (K-S) test we check how the required number of SNeIa changes with level of significance. Our model incorporates a completely analytical description of weak lensing which has been tested extensively against numerical simulations. Thus, future missions such as SNAP may be able to detect non-Gaussianity at a lower significance level of 10% (through the K-S test) only if the intrinsic scatter is known from external data (e.g. from low redshift observations) whereas ALPACA with 100,000 SNe will definitely detect non-Gaussianity with a very high confidence even if the intrinsic magnitude dispersion is not known a priori.

Dipak Munshi; Patrick Valageas

2006-01-30

367

How many SNeIa do we need to detect the effect of weak lensing ?

We show that as many as 4000 SNeIa may be required to detect the effect of weak lensing on their flux distribution with a high level of significance. However, if the intrinsic SNeIa magnitude dispersion is unknown one needs an even higher number of SNeIa (an order of magnitude more) to reach a similar level of statistical significance. Moreover, the ability to separate the lensing contribution from the intrinsic scatter depends sensitively on the amplitude of the latter. Using a Kolmogorov - Smirnov (K-S) test we check how the required number of SNeIa changes with level of significance. Our model incorporates a completely analytical description of weak lensing which has been tested extensively against numerical simulations. Thus, future missions such as SNAP may be able to detect non-Gaussianity at a lower significance level of 10% (through the K-S test) only if the intrinsic scatter is known from external data (e.g. from low redshift observations) whereas ALPACA with 100,000 SNe will definitely detect non-Ga...

Munshi, D; Munshi, Dipak; Valageas, Patrick

2006-01-01

368

Cosmological constraints from the large-scale weak lensing of SDSS MaxBCG clusters

NASA Astrophysics Data System (ADS)

We derive constraints on the matter density ?m and the amplitude of matter clustering ?8 from measurements of large-scale weak lensing (projected separation R = 5-30 h-1 Mpc) by clusters in the Sloan Digital Sky Survey MaxBCG catalogue. The weak lensing signal is proportional to the product of ?m and the cluster-mass correlation function ?cm. With the relation between optical richness and cluster mass constrained by the observed cluster number counts, the predicted lensing signal increases with increasing ?m or ?8, with mild additional dependence on the assumed scatter between richness and mass. The dependence of the signal on scale and richness partly breaks the degeneracies among these parameters. We incorporate external priors on the richness-mass scatter from comparisons to X-ray data and on the shape of the matter power spectrum from galaxy clustering, and we test our adopted model for ?cm against N-body simulations. Using a Bayesian approach with minimal restrictive priors, we find ?8(?m/0.325)0.501 = 0.828 ± 0.049, with marginalized constraints of ? _m=0.325_{-0.067}^{+0.086} and ? _8=0.828_{-0.097}^{+0.111}, consistent with constraints from other MaxBCG studies that use weak lensing measurements on small scales (R ? 2 h-1 Mpc). The (?m, ?8) constraint is consistent with and orthogonal to the one inferred from Wilkinson Microwave Anisotropy Probe cosmic microwave background data, reflecting agreement with the structure growth predicted by General Relativity for a ? cold dark matter (?CDM) cosmological model. A joint constraint assuming ?CDM yields ? _m=0.298_{-0.020}^{+0.019} and ? _8=0.831_{-0.020}^{+0.020}. For these parameters and our best-fitting scatter, we obtain a tightly constrained mean richness-mass relation of MaxBCG clusters, N200 = 25.4(M/3.61 × 1014 h-1 M?)0.74, with a normalization uncertainty of 1.5 per cent. Our cosmological parameter errors are dominated by the statistical uncertainties of the large-scale weak lensing measurements, which should shrink sharply with current and future imaging surveys.

Zu, Ying; Weinberg, David H.; Rozo, Eduardo; Sheldon, Erin S.; Tinker, Jeremy L.; Becker, Matthew R.

2014-04-01

369

Low X-ray Luminosity Galaxy Clusters. III: Weak Lensing Mass Determination at 0.18 $<$ z $<$ 0.70

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, six 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 are suitably fitted by other observations of the $M-L_{X}$ relation and models.

Gonzalez, Elizabeth Johana; Castellón, José Luis Nilo; Romero, Mariano J Domínguez; Alonso, María Victoria; Lambas, Diego García; Moreschi, Osvaldo; Gallo, Emanuel

2015-01-01

370

A MEASUREMENT OF GRAVITATIONAL LENSING OF THE MICROWAVE BACKGROUND USING SOUTH POLE TELESCOPE DATA

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.

Van Engelen, A.; De Haan, T.; Dobbs, M. A.; Dudley, J.; Holder, G. P. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); Keisler, R.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Hoover, S. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Zahn, O. [Berkeley Center for Cosmological Physics, Department of Physics, University of California, and Lawrence Berkeley National Labs, Berkeley, CA 94720 (United States); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Cho, H. M. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); George, E. M.; Holzapfel, W. L. [Department of Physics, University of California, Berkeley, CA 94720 (United States); Halverson, N. W. [Department of Astrophysical and Planetary Sciences and Department of Physics, University of Colorado, Boulder, CO 80309 (United States); Hou, Z. [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); and others

2012-09-10

371

STRONG GRAVITATIONAL LENSING BY THE SUPER-MASSIVE cD GALAXY IN ABELL 3827

We have discovered strong gravitational lensing features in the core of the nearby cluster Abell 3827 by analyzing Gemini South GMOS images. The most prominent strong lensing feature is a highly magnified, ring-shaped configuration of four images around the central cD galaxy. GMOS spectroscopic analysis puts this source at z {approx} 0.2. Located {approx}20'' away from the central galaxy is a secondary tangential arc feature which has been identified as a background galaxy with z {approx} 0.4. We have modeled the gravitational potential of the cluster core, taking into account the mass from the cluster, the brightest cluster galaxy (BCG), and other galaxies. We derive a total mass of (2.7 {+-} 0.4) x 10{sup 13} M {sub sun} within 37 h {sup -1} kpc. This mass is an order of magnitude larger than that derived from X-ray observations. The total mass derived from lensing data suggests that the BCG in this cluster is perhaps the most massive galaxy in the nearby universe.

Carrasco, E. R.; Gomez, P. L.; Lee, H.; Diaz, R.; Bergmann, M.; Turner, J. E. H.; Miller, B. W.; West, M. J. [Gemini Observatory, Southern Operations Center, AURA, Casilla 603, La Serena (Chile); Verdugo, T. [Departamento de FIsica y Astronomia, Universidad de ValparaIso, Avenida Gran Bretana 1111, ValparaIso (Chile)

2010-06-01

372

Redshifts of the Gravitational Lenses B1422+231 and PG1115+080

B1422+231 and PG1115+080 are gravitational lens systems producing quadruple QSO images where there is real promise that time delays can constrain the Hubble constant. In addition, the lensing galaxies are both part of groups which can play an important role in modelling the lens potential. This article reports redshifts for the lensing galaxies and three neighboring galaxies in each of the two systems. B1422+231 consists of a group at z=0.339 with a dispersion of 733 km/s, and PG1115+080 is a group at z=0.311 with a dispersion of 326 km/s. One of the neighboring galaxies in the B1422+231 system turned out to be an emission line galaxy at z=0.536, suggesting that QSO light passing through B1422+231 may have been subjected to lensing by a cluster at this more distant redshift. The velocity dispersion of the lensing galaxy in PG1115+080 is determined to be 281+/-25 km/s (1" square aperture), which is surprisingly large given the image splittings of 1.2" in that system.

John L. Tonry

1997-06-23

373

n-point Gravitational Lenses with 5(n-1) Images

It has been conjectured (astro-ph/0103463) that a gravitational lens consisting of n point masses can not produce more than 5(n-1) images as is known to be the case for n = 2 and 3. The reasoning is based on the number of finite limit points 2(n-1) which we believe to set the maximum number of positive images and the fact that the number of negative images exceeds the number of positive images by (n-1). It has been known that an n-point lens system (n\\ge 3) can produce (3n+1) images and so has been an explicit lens configuration with (3n+1) images. We start with the well-known n-point lens configuration that produces (3n+1) images and produce (2n-1) extra images by adding a small (n+1)-th mass so that the resulting (n+1)-point lens configuration has (2n) discrete limit points and produces 5n images of a source. It still remains to confirm in abstraction that the maximum number of positive image domains of a caustic domain is bounded by the number of the limit points.

Sun Hong Rhie

2003-05-10

374

NOISY WEAK-LENSING CONVERGENCE PEAK STATISTICS NEAR CLUSTERS OF GALAXIES AND BEYOND

Taking into account noise from intrinsic ellipticities of source galaxies, in this paper, we study the peak statistics in weak-lensing convergence maps around clusters of galaxies and beyond. We emphasize how the noise peak statistics is affected by the density distribution of nearby clusters, and also how cluster-peak signals are changed by the existence of noise. These are the important aspects to be thoroughly understood in weak-lensing analyses for individual clusters as well as in cosmological applications of weak-lensing cluster statistics. We adopt Gaussian smoothing with the smoothing scale {theta} {sub G} = 0.5arcmin in our analyses. It is found that the noise peak distribution near a cluster of galaxies sensitively depends on the density profile of the cluster. For a cored isothermal cluster with the core radius R{sub c} , the inner region with R {<=} R{sub c} appears noisy containing on average {approx}2.4 peaks with {nu} {>=} 5 for R{sub c} = 1.7arcmin and the true peak height of the cluster {nu} = 5.6, where {nu} denotes the convergence signal-to-noise ratio. For a Navarro-Frenk-White (NFW) cluster of the same mass and the same central {nu}, the average number of peaks with {nu} {>=} 5 within R {<=} R{sub c} is {approx}1.6. Thus a high peak corresponding to the main cluster can be identified more cleanly in the NFW case. In the outer region with R{sub c} < R {<=} 5R{sub c} , the number of high noise peaks is considerably enhanced in comparison with that of the pure noise case without the nearby cluster. For {nu} {>=} 4, depending on the treatment of the mass-sheet degeneracy in weak-lensing analyses, the enhancement factor f is in the range of {approx}5 to {approx}55 for both clusters as their outer density profiles are similar. The properties of the main-cluster-peak identified in convergence maps are also significantly affected by the presence of noise. Scatters as well as a systematic shift for the peak height are present. The height distribution is peaked at {nu} {approx} 6.6, rather than at {nu} = 5.6, corresponding to a shift of {Delta}{nu} {approx} 1, for the isothermal cluster. For the NFW cluster, {Delta}{nu} {approx} 0.8. The existence of noise also causes a location offset for the weak-lensing identified main-cluster-peak with respect to the true center of the cluster. The offset distribution is very broad and extends to R {approx} R{sub c} for the isothermal case. For the NFW cluster, it is relatively narrow and peaked at R {approx} 0.2R{sub c} . We also analyze NFW clusters of different concentrations. It is found that the more centrally concentrated the mass distribution of a cluster is, the less its weak-lensing signal is affected by noise. Incorporating these important effects and the mass function of NFW dark matter halos, we further present a model calculating the statistical abundances of total convergence peaks, true and false ones, over a large field beyond individual clusters. The results are in good agreement with those from numerical simulations. The model then allows us to probe cosmologies with the convergence peaks directly without the need of expensive follow-up observations to differentiate true and false peaks.

Fan Zuhui; Shan Huanyuan; Liu Jiayi, E-mail: fan@bac.pku.edu.c [Department of Astronomy, Peking University, Beijing 100871 (China)

2010-08-20

375

Spurious shear in weak lensing with the Large Synoptic Survey Telescope

NASA Astrophysics Data System (ADS)

The complete 10-yr survey from the Large Synoptic Survey Telescope (LSST) will image ˜20 000 deg2 of the sky in six filter bands every few nights, bringing the final survey depth to r ˜ 27.5, with over four 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 characterize the atmospheric point spread function due to its high-frequency spatial variation on angular scales smaller than ˜10 arcmin in the single short exposures, which propagates into a spurious shear correlation function at the 10-4-10-3 level on these scales. With the large multi-epoch data set 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.

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.; Nagarajan, S.; Peng, E.; Rasmussen, A. P.; Shmakova, M.; Sylvestre, N.; Todd, N.; Young, M.

2013-01-01

376

An optimal survey geometry of weak lensing survey: minimizing supersample covariance

NASA Astrophysics Data System (ADS)

Upcoming wide-area weak lensing surveys are expensive both in time and cost and require an optimal survey design in order to attain maximum scientific returns from a fixed amount of available telescope time. The supersample covariance (SSC), which arises from unobservable modes that are larger than the survey size, significantly degrades the statistical precision of weak lensing power spectrum measurement even for a wide-area survey. Using the 1000 mock realizations of the lognormal model, which approximates the weak lensing field for a ?-dominated cold dark matter model, we study an optimal survey geometry to minimize the impact of SSC contamination. For a continuous survey geometry with a fixed survey area, a more elongated geometry such as a rectangular shape of 1:400 side length ratio reduces the SSC effect and allows for a factor of 2 improvement in the cumulative signal-to-noise ratio (S/N) of power spectrum measurement up to ?max ? a few 103, compared to compact geometries such as squares or circles. When we allow the survey geometry to be disconnected but with a fixed total area, assuming 1 × 1 deg2 patches as the fundamental building blocks of survey footprints, the best strategy is to locate the patches with ˜15 deg separation. This separation angle corresponds to the scale at which the two-point correlation function has a negative minimum. The best configuration allows for a factor of 100 gain in the effective area coverage as well as a factor of 2.5 improvement in the S/N at high multipoles, yielding a much wider coverage of multipoles than in the compact geometry.

Takahashi, Ryuichi; Soma, Shunji; Takada, Masahiro; Kayo, Issha

2014-11-01

377

Separating the Weak Lensing and Kinetic SZ Effects from CMB Temperature Maps

A new generation of CMB experiments will soon make sensitive high resolution maps of the microwave sky. At angular scales less than $\\sim$10 arcminutes, most CMB anisotropies are generated at z $_c$, and show that it is identically zero for weakly lensed primary anisotropies and, therefore, allows a direct measurement of the kSZ effect. Measuring this statistic can offer a new tool for studing the reionization epoch. Models with the same optical depth, but different reionization histories, can differ by more than a factor of 3 in the amplitude of the kSZ-generated non-Gaussian signal.

Mario A. Riquelme; David N. Spergel

2007-02-27

378

Automated detection of galaxy-scale gravitational lenses in high resolution imaging data

Lens modeling is the key to successful and meaningful automated strong galaxy-scale gravitational lens detection. We have implemented a lens-modeling "robot" that treats every bright red galaxy (BRG) in a large imaging survey as a potential gravitational lens system. Using a simple model optimized for "typical" galaxy-scale lenses, we generate four assessments of model quality that are used in an automated classification. The robot infers the lens classification parameter H that a human would have assigned; the inference is performed using a probability distribution generated from a human-classified training set, including realistic simulated lenses and known false positives drawn from the HST/EGS survey. We compute the expected purity, completeness and rejection rate, and find that these can be optimized for a particular application by changing the prior probability distribution for H, equivalent to defining the robot's "character." Adopting a realistic prior based on the known abundance of lenses, we find that a lens sample may be generated that is ~100% pure, but only ~20% complete. This shortfall is due primarily to the over-simplicity of the lens model. With a more optimistic robot, ~90% completeness can be achieved while rejecting ~90% of the candidate objects. The remaining candidates must be classified by human inspectors. We are able to classify lens candidates by eye at a rate of a few seconds per system, suggesting that a future 1000 square degree imaging survey containing 10^7 BRGs, and some 10^4 lenses, could be successfully, and reproducibly, searched in a modest amount of time. [Abridged

Philip J. Marshall; David W. Hogg; Leonidas A. Moustakas; Christopher D. Fassnacht; Marusa Bradac; Tim Schrabback; Roger D. Blandford

2008-05-10

379

Gravitational Lensing in Clusters of Galaxies: New Clues Regarding the Dynamics of Intracluster Gas

Long arcs in clusters of galaxies, produced by gravitational lensing, can be used to estimate the mass interior to the arcs and therefore, constrain the cluster mass distribution. The radial density distribution of the intracluster gas (ICM) can be extracted from the X-ray surface brightness observations. If the gas temperature is also known, it is then possible to probe the dynamical state of the gas and test whether the ICM is in hydro- static equilibrium within the gravitational potential of the cluster as a result of thermal pressure support. We analyze three clusters that exhibit large arcs, whose X-ray surface brightness profiles have been observed, and whose gas temperatures have been determined. In two of the clusters, A2218 and A1689, the central mass implied by lensing is a factor of $2$--$2.5$ too large for the gas at the observed temperature to be in hydrostatic equilibrium solely due to thermal pressure support. In other words, if we accept the mass estimate derived from the lensing analysis and demand that the X-ray surface brightness profile be consistent with the observations, the required gas temperature is a factor of $2$--$2.5$ higher than observed. The results for the third cluster, A2163 (the most luminous and the hottest cluster known), are more ambiguous. The discrepancy between the X-ray and the lensing mass estimates arise because the presence of arcs imply a highly concentrated cluster mass distribution whereas the observed X-ray profiles imply a more extended mass distribution. The large X-ray core radii are not the result of the limited resolution of the X-ray detectors. We consider various possibilities that could account for the discrepancy.

Jordi Miralda-Escude; Arif Babul

1994-05-26

380

Accurate Weak Lensing of Standard Candles. II. Measuring sigma8 with Supernovae

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.

Miguel Quartin; Valerio Marra; Luca Amendola

2014-01-10

381

Accurate weak lensing of standard candles. II. Measuring ?8 with supernovae

NASA Astrophysics Data System (ADS)

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 ?8 of the matter power spectrum. By exploiting this relation, we are able to predict constraints on ?8 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 and its redshift evolution are known a priori. The intrinsic dispersion has been assumed to be Gaussian; possible intrinsic non-Gaussianities in the data set (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 cosmic microwave background, cosmic shear, or cluster abundance observables.

Quartin, Miguel; Marra, Valerio; Amendola, Luca

2014-01-01

382

{}From deep optical images of three clusters selected by virtue of their X-ray luminosity and/or optical richness (1455+22; $z=0.26$, 0016+16; $z=0.55$ and 1603+43; $z=0.89$), we construct statistically-complete samples of faint field galaxies ($I \\leq 25$) suitable for probing the effects of gravitational lensing. By selecting clusters across a wide redshift range we separate the effects of the mean redshift distribution of the faint field population well beyond spectroscopic limits and the distribution of dark matter in the lensing clusters. A significant lensing signature is seen in the two lower redshift clusters whose X-ray properties are well-constrained. Based on these and dynamical data, it is straightforward to rule out field redshift distributions for $I \\leq 25$ which have a significant low redshift excess compared to the no evolution prediction, such as would be expected if the number counts at faint limits were dominated by low-$z$ dwarf systems. The degree to which we can constrain any high redshift tail to the no evolution redshift distribution depends on the distribution of dark matter in the most distant lensing cluster. In the second paper in this series, we use the lensing signal to reconstruct the full two-dimensional mass distribution in the clusters and, together with high resolution X-ray images, demonstrate that their structural properties are well-understood. The principal result is therefore the absence of a dominant low-$z$ dwarf population to $I \\leq25$.

Ian Smail; Richard S. Ellis; Michael J. Fitchett

1994-02-21

383

We present the OGLE-III Photometric Maps of the Large Magellanic Cloud. They cover about 40 square degrees of the LMC and contain mean, calibrated VI photometry and astrometry of about 35 million stars observed during seven observing seasons of the third phase of the Optical Gravitational Lensing Experiment - OGLE-III. We discuss the quality of data and present color-magnitude diagrams of selected fields. The OGLE-III Photometric Maps of the LMC are available to the astronomical community from the OGLE Internet archive.

A. Udalski; I. Soszynski; M. K. Szymanski; M. Kubiak; G. Pietrzynski; L. Wyrzykowski; O. Szewczyk; K. Ulaczyk; R. Poleski

2008-07-24

384

Einstein-Rosen Bridges and the Characteristic Properties of Gravitational Lensing by Them

NASA Astrophysics Data System (ADS)

It is shown that Einstein-Rosen bridges (wormholes)—hypothetical objects that topologically connect separate locations in the Universe—can be static solutions of the Einstein equations. The corresponding equations for bridges are reduced to a form convenient for their analysis and numerical solution. The matter forming the bridge must have a sufficiently hard and anisotropic equation of state. Our results are compared with a previously known analytic solution for a bridge, which is a special case of the general solution in the framework of general relativity. The deflection of photons by the bridge (gravitational lensing) is studied.

Shatskii, A. A.

2004-07-01

385

Weak Lensing Calibrated M-T Scaling Relation of Galaxy Groups in the COSMOS Fieldsstarf

NASA Astrophysics Data System (ADS)

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.

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

386

Analyzing Star Formation Properties in Dusty Early Universe Galaxies Using Gravitational Lensing

NASA Astrophysics Data System (ADS)

Strong gravitational lensing has recently become one of the most important tools for studying star formation properties in extremely high redshift galaxies. Dust-obscured star-forming galaxies found at far-infrared/sub-millimeter wavelengths are important in the assembly of stellar mass and the evolution of massive galaxies. We present Submillimeter Array (SMA) imaging of Lockman 102, a strongly lensed submillimeter galaxy at z=5.29, discovered by the Herschel Space Observatory. The system was observed at 250, 350, 500 and 1000 microns, corresponding to rest frame wavelengths of 40, 56, 80, and 159 microns respectively. The observations were targeted at the thermal dust emission and the [CII] interstellar medium cooling line. We report an estimated photometric redshift of ~1.9 for the lensing galaxy, making it possibly the most distant lens currently known. We use uvmcmcfit, a publicly available Markov Chain Monte Carlo software tool we have developed for interferometric data, to fit lens models to Lockman 102. The results obtained from uvmcmcfit suggest the lensed system is composed of a single lensing galaxy and two extended sources. We have strong constraints on an intrinsic flux density of Lockman 102 of 4.55 + 0.45 mJy magnified by a factor of 12.5 + 1.2. From a modified blackbody fit we compute an intrinsic far infrared luminosity of 5.5e12 L?.This implies a star formation rate of ~950 M? yr-1, making Lockman 102 an extremely active dusty galaxy. We also compare Lockman 102 to other dusty luminous starburst galaxies at similar redshift, HLS0918 (Rawle et al. 2014) and AzTEC-3 (Riechers et al. 2014a) and determine it is among the most luminous and active galaxies ~1 Gyr after the Big Bang. It is only with strong lensing that the SMA is able to undertake such a detailed study of a galaxy at this distance; the continued improvements from new facilities such as ALMA offer a promising future in observing even more distant lensed systems.

Bradli, Jaclyn C.; Bussmann, R. Shane; Riechers, Dominik A.; Clements, David; Perez-Fournon, Ismael

2015-01-01

387

Impact of magnification and size bias on the weak lensing power spectrum and peak statistics

NASA Astrophysics Data System (ADS)

The weak lensing power spectrum is a powerful tool to probe cosmological parameters. Additionally, lensing peak counts contain cosmological information beyond the power spectrum. Both of these statistics can be affected by the preferential selection of source galaxies in patches of the sky with high magnification, as well as by the dilution in the source galaxy surface density in such regions. If not accounted for, these biases introduce systematic errors for cosmological measurements. Here we quantify these systematic errors, using convergence maps from a suite of ray-tracing N-body simulations. At the cutoff magnitude m of ongoing and planned major weak lensing surveys, the logarithmic slope of the cumulative number counts s ?d log n(>m)/d log m is in the range 0.1?s?0.5. At s?0.2, expected in the I band for Large Synoptic Survey Telescope, the inferred values of ?m, w, and ?8 are biased by many ? (where ? denotes the marginalized error), and therefore the biases will need to be carefully modeled. We also find that the parameters are biased differently in the (?m, w , ?8) parameter space when the power spectrum and the peak counts are used. In particular, w derived from the power spectrum is less affected than w derived from peak counts, while the opposite is true for the best-constrained combination of ?8?m? (with ? =0.62 from the power spectrum and ?=0.48 from peak counts). This suggests that the combination of the power spectrum and peak counts can help mitigate the impact of magnification and size biases.

Liu, Jia; Haiman, Zoltán; Hui, Lam; Kratochvil, Jan M.; May, Morgan

2014-01-01

388

Cosmic Discordance: Are Planck CMB and CFHTLenS weak lensing measurements out of tune?

We examine the level of agreement between low redshift weak lensing data and the CMB using measurements from the CFHTLenS and Planck+WMAP polarization. We perform an independent analysis of the CFHTLenS six bin tomography results of Heymans et al. (2013). We extend their systematics treatment and find the cosmological constraints to be relatively robust to the choice of non-linear modeling, extension to the intrinsic alignment model and inclusion of baryons. We find that the 90% confidence contours of CFHTLenS and Planck+WP do not overlap even in the full 6-dimensional parameter space of $\\Lambda$CDM, so the two datasets are discrepant. Allowing a massive active neutrino or tensor modes does not significantly resolve the disagreement 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 $\\Lambda$CDM does bring the 8-dimensional...

MacCrann, Niall; Bridle, Sarah; Jain, Bhuvnesh; Becker, Matthew R

2014-01-01

389

Non-linear relativistic contributions to the cosmological weak-lensing convergence

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...

Andrianomena, Sambatra; Patel, Prina; Umeh, Obinna; Uzan, Jean-Philippe

2014-01-01

390

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.

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

391

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