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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

Continuous image distortion in weak gravitational lensing

NASA Astrophysics Data System (ADS)

We examine the shearing and magnification of images distorted by the weak gravitational lensing of a thick gravitational lens using a perturbation theory approach based on the optical scalar and geodesic deviation equations with no reference to lens planes. We compare the image distortion from optical scalars with the typical thin-lens image distortion for realistic, axially symmetric astrophysical lens, finding that the thin-lens approach often overestimates the ellipticity by up to 2 sigma near the lens. Application to non-symmetric lenses is discussed. )

Kling, Thomas

2010-02-01

3

Galaxy Halo Masses from Weak Gravitational Lensing

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

2014-01-01

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

Probing Satellite Halos with Weak Gravitational Lensing

We demonstrate the possibility of detecting tidal stripping of dark matter subhalos within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups, using various models with different distributions of mass between galaxy and group halos to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 10^12--10^15 Msun.

Gillis, Bryan R; Hilbert, Stefan; Hartlap, Jan

2012-01-01

6

Probing satellite haloes with weak gravitational lensing

NASA Astrophysics Data System (ADS)

We demonstrate the possibility of detecting tidal stripping of dark matter subhaloes within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups using various models with different distributions of mass between galaxy and group haloes to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 1012-1015 M?.

Gillis, Bryan R.; Hudson, Michael J.; Hilbert, Stefan; Hartlap, Jan

2013-02-01

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

NASA Astrophysics Data System (ADS)

The gravitational lensing effects in the weak gravitational field by exotic lenses have been investigated intensively to find nonluminous exotic objects. Gravitational lensing based on 1/rn fall-off metric, as a one-parameter model that can treat by hand both the Schwarzschild lens (n =1) and the Ellis wormhole (n =2) in the weak field, has been recently studied. Only for n=1 case, however, it has been explicitly shown that effects of relativistic lens images by the strong field on the light curve can be neglected. We discuss whether relativistic images by the strong field can be neglected for n>1 in the Tangherlini spacetime which is one of the simplest models for our purpose. We calculate the divergent part of the deflection angle for arbitrary n and the regular part for n=1, 2 and 4 in the strong field limit, the deflection angle for arbitrary n under the weak gravitational approximation. We also compare the radius of the Einstein ring with the radii of the relativistic Einstein rings for arbitrary n. We conclude that the images in the strong gravitational field have little effect on the total light curve and that the time-symmetric demagnification parts in the light curve will appear even after taking account of the images in the strong gravitational field for n>1.

Tsukamoto, Naoki; Kitamura, Takao; Nakajima, Koki; Asada, Hideki

2014-09-01

9

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

10

The Cluster Mass Function from Weak Gravitational Lensing

We present the first measurement of the mass function of galaxy clusters based directly on cluster masses derived from observations of weak gravitational lensing. To investigate the degree of sample incompleteness resulting from the X-ray based selection of the target clusters, we use a sample of 50 clusters with weak lensing mass measurements to empirically determine the relation between lensing mass and X-ray luminosity and the scatter about this relation. We use a complete, volume-limited sub-sample of 35 X-ray luminous clusters of galaxies at 0.15~ 10^15/h M_sun) clusters. From this, we constrain sigma_8(Omega_m/0.3)^{0.37} = 0.67^{+0.04}_{-0.05} (68% confidence limits), agreeing well with constraints from the 3-year WMAP CMB measurements and estimates of cluster abundances based on X-ray observations, but somewhat lower than constraints from ``cosmic shear'' weak lensing measurements in random fields.

H. Dahle

2006-08-23

11

Combining Strong and Weak Gravitational Lensing in Abell 1689

We present a reconstruction of the mass distribution of galaxy cluster Abell 1689 at z = 0.18 using detected strong lensing features from deep HST/ACS observations and extensive ground based spectroscopy. Earlier analyses have reported up to 32 multiply imaged systems in this cluster, of which only 3 were spectroscopically confirmed. In this work, we present a parametric strong lensing mass reconstruction using 24 multiply imaged systems with newly determined spectroscopic redshifts, which is a major step forward in building a robust mass model. In turn, the new spectroscopic data allows a more secure identification of multiply imaged systems. The resultant mass model enables us to reliably predict the redshifts of additional multiply imaged systems for which no spectra are currently available, and to use the location of these systems to further constrain the mass model. In particular, we have detected 5 strong galaxy-galaxy lensing systems just outside the Einstein ring region, further constraining the mass profile. Our strong lensing mass model is consistent with that inferred from our large scale weak lensing analysis derived using CFH12k wide field images. Thanks to a new method for reliably selecting a well defined background lensed galaxy population, we resolve the discrepancy found between the strong and weak lensing mass models reported in earlier work. [ABRIDGED

M. Limousin; J. Richard; E. Jullo; J. -P. Kneib; B. Fort; G. Soucail; A. Elíasdóttir; P. Natarajan; R. S. Ellis; I. Smail; O. Czoske; G. P. Smith; P. Hudelot; S. Bardeau; H. Ebeling; E. Egami; K. K. Knudsen

2006-12-06

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 decades showing that the visible matter represents only about 4-5% of the Universe, the rest being dark

Starck, Jean-Luc

13

NSDL National Science Digital Library

This description of current research experiments on gravitational lensing contains several color pictures of multiply-imaged quasars along with a list of articles on the subject. It also includes a bibliographical database of gravitational lensing literature for the user to search.

2009-06-12

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

Constraining modified gravitational theories by weak lensing with Euclid

Future proposed satellite missions such as Euclid can offer the opportunity to test general relativity on cosmic scales through mapping of the galaxy weak-lensing signal. In this paper we forecast the ability of these experiments to constrain modified gravity scenarios such as those predicted by scalar-tensor and f(R) theories. We find that Euclid will improve constraints expected from the Planck satellite on these modified theories of gravity by 2 orders of magnitude. We discuss parameter degeneracies and the possible biases introduced by modifications to gravity.

Martinelli, Matteo; Calabrese, Erminia; De Bernardis, Francesco; Melchiorri, Alessandro; Pagano, Luca [Physics Department and INFN, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Scaramella, Roberto [INAF, Osservatorio Astronomico di Roma, via Frascati 33, 0040 Monte Porzio Catone (Italy)

2011-01-15

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A compilation of weak gravitational lensing studies of clusters of galaxies

We present a list of clusters that have had their dark matter content measured using weak gravitational lensing. The list consists of 139 clusters, with weak lensing measurements reported in 64 different publications. Details are provided about the selection criteria and some basic properties of the sample, such as the redshift distribution. An electronic, sortable version of this list with links to public database information on the clusters and publications is provided at http://folk.uio.no/hdahle/WLclusters.html

H. Dahle

2007-01-21

17

Significant adjustments to the values of the cosmological parameters estimated from high-redshift Type Ia supernovae data are reported, almost an order of magnitude greater than previously found. They arise from the effects of weak gravitational lensing on observations of high-redshift sources. The lensing statistics used have been obtained from computations of the three-dimensional shear in a range of cosmological N-body

Andrew J. Barber

2000-01-01

18

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

19

Weak Gravitational lensing from regular Bardeen black holes

In this article we consider regular charged Bardeen black hole as a gravitational lens. Weak deflection limit is studied for deflection angle by regarding perturbation approach presented by Keeton et al. From which we obtain the positions and magnifications of the non-relativistic images. In this article we assume that the quotient between the charge $|q|$ and twice the mass $2m$ of the Bardeen black hole is $|g|/2m>2\\sqrt{3}/9$ in which apparent horizon and photon sphere disappear. Results of this work predicts for a fixed $|g|/2m$ (impact parameter), the deflection angle decreases with respect to impact parameter ($|g|/2m$). Fixing position of the source and increasing ($|g|/2m$), positions of the non-relativistic images are closer and primary images locations transmit to corresponding secondary image positions. Magnification of the images reduces to an infinite value for Einstein rings for different values of the charge parameter ($|g|/2m$) and its absolute value increases in terms of positions of the sour...

Ghaffarnejad, Hossein

2014-01-01

20

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

21

Weak gravitational lensing as a probe of physical properties of substructures in dark matter halos

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 the offset distance from the center of the main halo. We can thus locate the satellite galaxies statistically with a 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 the off-set 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 c...

Shirasaki, Masato

2014-01-01

22

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

23

Significant adjustments to the values of the cosmological parameters estimated from high-redshift Type Ia Supernov\\ae data are reported, almost an order of magnitude greater than previously found. They arise from the effects of weak gravitational lensing on observations of high-redshift sources. The lensing statistics used have been obtained from computations of the three-dimensional shear in a range of cosmological N-body simulations, from which it is estimated that cosmologies with an underlying deceleration parameter q_0 = -0.51 +0.03/-0.24 may be interpreted as having q_0 = -0.55 (appropriate to the currently popular cosmology with density parameter $\\Omega_M = 0.3$ and vacuum energy density parameter $\\Omega_{\\Lambda} = 0.7$). In addition, the standard deviation expected from weak lensing for the peak magnitudes of Type Ia Supernov\\ae at redshifts of 1 is expected to be approximately 0.078 magnitudes, and 0.185 magnitudes at redshift 2. This latter value is greater than the accepted intrinsic dispersion ...

Barber, A J

2000-01-01

24

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

1999-11-17

25

Measuring the Galaxy-Galaxy-Mass Three-point Correlation Function with Weak Gravitational Lensing

We discuss the galaxy-galaxy-mass three-point correlation function and show how to measure it with weak gravitational lensing. The method entails choosing a large of pairs of foreground lens galaxies and constructing a mean shear map with respect to their axis, by averaging the ellipticities of background source galaxies. An average mass map can be reconstructed from this shear map and this will represent the average mass distribution around pairs of galaxies. We show how this mass map is related to the projected galaxy-galaxy-mass three-point correlation function. Using a large N-body dark matter simulation populated with galaxies using the Halo Occupation Distribution (HOD) bias prescription, we compute these correlation functions, mass maps, and shear maps. The resultant mass maps are distinctly bimodal, tracing the galaxy centers and remaining anisotropic up to scales much larger than the galaxy separation. At larger scales, the shear is approximately tangential about the center of the pair but with small azimuthal variation in amplitude. We estimate the signal-to-noise ratio of the reconstructed mass maps for a survey of similar depth to the Sloan Digital Sky Survey (SDSS) and conclude that the galaxy-galaxy-mass three-point function should be measurable with the current SDSS weak lensing data. Measurements of this three-point function, along with galaxy-galaxy lensing and galaxy auto-correlation functions, will provide new constraints on galaxy bias models. The anisotropic shear profile around close pairs of galaxies is a prediction of cold dark matter models and may be difficult to reconcile with alternative theories of gravity without dark matter.

David E. Johnston

2005-03-13

26

Weighing 40 X-ray Luminous Clusters of Galaxies with Weak Gravitational Lensing

Deep two-color imaging of 40 clusters of galaxies with the NOT and the University of Hawaii 2.24-m telescope is used to measure the weak gravitational shear acting on faint background galaxies. From this, maps of the projected cluster mass distribution are constructed, and the cluster masses are measured within circular apertures of up to ~3 Mpc/h. The results are used to derive the cluster mass function at z~0.2. The average mass-to-light ratio of the clusters indicate a low-density Universe with Omega_0 around 0.25. Additional mass concentrations are found along the lines of sight to the clusters, some of which are most likely associated with clusters at z > 0.5. In addition, the data are used to measure weak gravitational lensing due to large-scale structures along the line of sight. The future prospects for this kind of research with the NOT are briefly discussed.

H. Dahle

2000-09-25

27

Lensing Basics I Light deflection of a point mass : Deflection by a mass distribution (linear: Observational Cosmology II (Â§ 8) SS 2010 6 Weak Lensing Basics V Deflection: Deformation: ~ 2 i j to through an operation in Fourier space: minus x ellipticity structure created by a ,,point mass

Boehringer, Hans

28

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

29

NASA Astrophysics Data System (ADS)

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 nine and 20 redshifts measured with the low-dispersion survey spectrograph (LDSS) of the William Herschel Telescope, and virial radii are determined from imaging using the UH8K mosaic CCD camera on the University of Hawaii 2.24 m 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 dynamic 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 those based on weak lensing. Based on observations made with the William Herschel Telescope, operated on the island of La Palma by the Isaac Newton Group in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, and with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

Irgens, Ragnvald J.; Lilje, Per B.; Dahle, Håkon; Maddox, S. J.

2002-11-01

30

Cosmology with weak lensing surveys

NASA Astrophysics Data System (ADS)

Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening matter. The distortions are due to fluctuations in the gravitational potential, and are directly related to the distribution of matter and to the geometry and dynamics of the Universe. As a consequence, weak gravitational lensing offers unique possibilities for probing the Dark Matter and Dark Energy in the Universe. In this review, we summarise the theoretical and observational state of the subject, focussing on the statistical aspects of weak lensing, and consider the prospects for weak lensing surveys in the future. Weak gravitational lensing surveys are complementary to both galaxy surveys and cosmic microwave background (CMB) observations as they probe the unbiased non-linear matter power spectrum at modest redshifts. Most of the cosmological parameters are accurately estimated from CMB and large-scale galaxy surveys, so the focus of attention is shifting to understanding the nature of Dark Matter and Dark Energy. On the theoretical side, recent advances in the use of 3D information of the sources from photometric redshifts promise greater statistical power, and these are further enhanced by the use of statistics beyond two-point quantities such as the power spectrum. The use of 3D information also alleviates difficulties arising from physical effects such as the intrinsic alignment of galaxies, which can mimic weak lensing to some extent. On the observational side, in the next few years weak lensing surveys such as CFHTLS, VST-KIDS and Pan-STARRS, and the planned Dark Energy Survey, will provide the first weak lensing surveys covering very large sky areas and depth. In the long run even more ambitious programmes such as DUNE, the Supernova Anisotropy Probe (SNAP) and Large-aperture Synoptic Survey Telescope (LSST) are planned. Weak lensing of diffuse components such as the CMB and 21 cm emission can also provide valuable cosmological information. Finally, we consider the prospects for joint analysis with other probes, such as (1) the CMB to probe background cosmology (2) galaxy surveys to probe large-scale bias and (3) Sunyaev Zeldovich surveys to study small-scale baryonic physics, and consider the lensing effect on cosmological supernova observations.

Munshi, Dipak; Valageas, Patrick; van Waerbeke, Ludovic; Heavens, Alan

2008-06-01

31

Weak gravitational lensing due to large-scale structure of the universe

NASA Technical Reports Server (NTRS)

The effect of the large-scale structure of the universe on the propagation of light rays is studied. The development of the large-scale density fluctuations in the omega = 1 universe is calculated within the cold dark matter scenario using a smooth particle approximation. The propagation of about 10 to the 6th random light rays between the redshift z = 5 and the observer was followed. It is found that the effect of shear is negligible, and the amplification of single images is dominated by the matter in the beam. The spread of amplifications is very small. Therefore, the filled-beam approximation is very good for studies of strong lensing by galaxies or clusters of galaxies. In the simulation, the column density was averaged over a comoving area of approximately (1/h Mpc)-squared. No case of a strong gravitational lensing was found, i.e., no 'over-focused' image that would suggest that a few images might be present. Therefore, the large-scale structure of the universe as it is presently known does not produce multiple images with gravitational lensing on a scale larger than clusters of galaxies.

Jaroszynski, Michal; Park, Changbom; Paczynski, Bohdan; Gott, J. Richard, III

1990-01-01

32

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

2009-07-31

33

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

34

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

M. Sereno

2008-01-01

35

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

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.

2013-07-01

37

Means of confusion: how pixel noise affects shear estimates for weak gravitational lensing

NASA Astrophysics Data System (ADS)

Weak-lensing shear estimates show a troublesome dependence on the apparent brightness of the galaxies used to measure the ellipticity: in several studies, the amplitude of the inferred shear falls sharply with decreasing source significance. This dependence limits the overall ability of upcoming large weak-lensing surveys to constrain cosmological parameters. We seek to provide a concise overview of the impact of pixel noise on weak-lensing measurements, covering the entire path from noisy images to shear estimates. We show that there are at least three distinct layers, where pixel noise not only obscures but also biases the outcome of the measurements: (1) the propagation of pixel noise to the non-linear observable ellipticity; (2) the response of the shape-measurement methods to limited amount of information extractable from noisy images and (3) the reaction of shear estimation statistics to the presence of noise and outliers in the measured ellipticities. We identify and discuss several fundamental problems and show that each of them is able to introduce biases in the range of a few tens to a few per cent for galaxies with typical significance levels. Furthermore, all of these biases do not only depend on the brightness of galaxies but also depend on their ellipticity, with more elliptical galaxies often being harder to measure correctly. We also discuss existing possibilities to mitigate and novel ideas to avoid the biases induced by pixel noise. We present a new shear estimator that shows a more robust performance for noisy ellipticity samples. Finally, we release the open-source PYTHON code to predict and efficiently sample from the noisy ellipticity distribution and the shear estimators used in this work at https://github.com/pmelchior/epsnoise.

Melchior, P.; Viola, M.

2012-08-01

38

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

39

Weak lensing and cosmological investigation

NASA Astrophysics Data System (ADS)

In the last few years the scientific community has been dealing with the challenging issue of identifying the dark energy component. We regard weak gravitational lensing as a brand new, and extremely important, tool for cosmological investigation in this field. In fact, the features imprinted on the Cosmic Microwave Background radiation by the lensing from the intervening distribution of matter represent a pretty unbiased estimator, and can thus be used for putting constraints on different dark energy models. This is true in particular for the magnetic-type B-modes of CMB polarization, whose unlensed spectrum at large multipoles (l ~= 1000) is very small even in presence of an amount of gravitational waves as large as currently allowed by the experiments: therefore, on these scales the lensing phenomenon is the only responsible for the observed power, and this signal turns out to be a faithful tracer of the dark energy dynamics. We first recall the formal apparatus of the weak lensing in extended theories of gravity, introducing the physical observables suitable to cast the bridge between lensing and cosmology, and then evaluate the amplitude of the expected effect in the particular case of a Non-Minimally-Coupled model, featuring a quadratic coupling between quintessence and Ricci scalar.

Acquaviva, Viviana

2005-03-01

40

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

41

SUNGLASS: A new weak lensing simulation pipeline

A new cosmic shear analysis pipeline SUNGLASS (Simulated UNiverses for\\u000aGravitational Lensing Analysis and Shear Surveys) is introduced. SUNGLASS is a\\u000apipeline that rapidly generates simulated universes for weak lensing and cosmic\\u000ashear analysis. The pipeline forms suites of cosmological N-body simulations\\u000aand performs tomographic cosmic shear analysis using line-of-sight integration\\u000athrough these simulations while saving the particle lightcone information.

A. Kiessling; A. F. Heavens; A. N. Taylor

2010-01-01

42

On 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 spacetime of the lens, and, then, light-ray detection in the moving observer's frame. Due to 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 re-scaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still point-like. 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_d) with respect to the static case, z_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 microarcsec in lensing towards the super-massive black hole at the Galactic center. On a cosmological scale, tangential peculiar velocities of 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 much challenging.

M. Sereno

2008-09-23

43

Cosmological applications of gravitational lensing

NASA Astrophysics Data System (ADS)

In this thesis we use the gravitational lensing effect as a tool to tackle two rather different cosmological topics: the nature of the dark matter in galaxy halos, and the rotation of the universe. Firstly, we study the microlensing effect in the gravitational lens systems Q0957+561 and Q2237+0305. In these systems the light from the quasar shines directly through the lensing galaxy. Due to the relative motion of the quasar, the lensing galaxy, and the observer compact objects in the galaxy or galaxy halo cause brightness fluctuations of the light from the background quasar. We compare light curve data from a monitoring program of the double quasar Q0957+561 at the 3.5m telescope at Apache Point Observatory from 1995 to 1998 (Colley, Kundic & Turner 2000) with numerical simulations to test whether the halo of the lensing galaxy consists of massive compact objects (MACHOs). This test was first proposed by Gott (1981). We can exclude MACHO masses from 10^-6 M_sun up to 10^-2 M_sun for quasar sizes of less than 3x10^14 h_60^-0.5 cm if the MACHOs make up at least 50% of the dark halo. Secondly, we present new light curve data for the gravitationally lensed quadruple quasar Q2237+0305 taken at the 3.5m telescope at Apache Point Observatory from June 1995 to January 1998. Although the images were taken under variable, often poor seeing conditions and with coarse pixel sampling, photometry is possible for the two brighter quasar images A and B with the help from HST observations. We find independent evidence for a brightness peak in image A of 0.4 to 0.5 mag with a duration of at least 100 days, which indicates that microlensing has taken place in the lensing galaxy. Finally, we use the weak gravitational lensing effect to put limits on a class of Goedel-type rotating cosmologies described by Korotky & Obukhov (1996). In weak lensing studies the shapes of thousands of background galaxies are measured and averaged to reveal coherent gravitational distortions of the galaxy shapes by foreground matter distributions, or by the large-scale structure of space-time itself. We calculate the predicted shear as a function of redshift in Goedel-type rotating cosmologies and compare this to the upper limit on cosmic shear gamma_limit of approximately 0.04 from weak lensing studies. We find that Goedel-type models cannot have larger rotations omega than H_0=6.1x10^-11 h_60/year if this shear limit is valid for the whole sky. In dieser Arbeit benutze ich den Gravitationslinseneffekt als ein Werkzeug, um zwei recht unterschiedliche kosmologische Fragestellungen zu bearbeiten: die Natur der dunklen Materie in Galaxienhalos und die Rotation des Universums. Zuerst untersuche ich den Mikrolinseneffekt in den Gravitationlinsensystemen Q0957+561 und Q2237+0305. In diesen Systemen scheint das Licht eines Quasars durch die Linsengalaxie hindurch. Aufgrund der Relativbewegung zwischen Quasar, Linsengalaxie und Beobachter verursachen kompakte Objekte innerhalb der Galaxie oder dem Galaxienhalo Helligkeitsfluktuationen des Hintergrundquasars. Ich vergleiche die am 3.5m Teleskop des Apache Point Observatory zwischen 1995 und 1998 gewonnene Lichtkurve des Doppelquasars Q0957+561 (Colley, Kundic & Turner 2000) mit numerischen Simulationen, um zu untersuchen, ob der Halo der Linsengalaxie aus massiven kompakten Objekten (MACHOs) besteht. Dieser Test wurde zuerst von Gott (1981) vorgeschlagen. Ich kann MACHO-Massen von 10^-6 M_sun bis zu 10^-2 M_sun ausschliessen, sofern der Quasar kleiner ist als 3x10^14 h_60^-0.5 cm und MACHOs mehr als 50% des dunklen Halos ausmachen. Im zweiten Teil der Arbeit stelle ich neue Beobachtungsdaten fuer den Vierfachquasar Q2237+0305 vor, die am 3.5m Teleskop des Apache Point Observatory zwischen Juni 1995 und Januar 1998 gewonnen wurden. Obwohl die Daten bei veraenderlichen, oft schlechten Seeing Bedingungen und grober Pixelaufloesung aufgenommen wurden, ist die Photometrie der beiden helleren Quasarbilder A und B mit Hilfe von HST-Beobachtungen moeglich. Ich finde ein Helligkeitsmaximum in Bild A mit einer Amplitu

Schmidt, Robert W.

2000-06-01

44

Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modeling. 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 a fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies. 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 fro...

Leauthaud, A; Civano, F; Coil, A L; Bundy, K; Massey, R; Schramm, M; Schulze, A; Capak, P; Elvis, M; Kulier, A; Rhodes, J

2014-01-01

45

Can weak lensing surveys confirm BICEP2?

NASA Astrophysics Data System (ADS)

The detection of B-modes in the cosmic microwave background (CMB) polarization by the BICEP2 experiment, if interpreted as evidence for a primordial gravitational wave background, has enormous ramifications for cosmology and physics. It is crucial to test this hypothesis with independent measurements. A gravitational wave background leads to B-modes in galaxy shape correlations (shear) both through lensing and tidal alignment effects. Since the systematics and foregrounds of galaxy shapes and CMB polarization are entirely different, a detection of a cross correlation between the two observables would provide conclusive proof for the existence of a primordial gravitational wave background. We find that upcoming weak lensing surveys will be able to detect the cross correlation between B-modes of the CMB and galaxy shapes. However, this detection is not sufficient to confirm or falsify the hypothesis of a primordial origin for CMB B-mode polarization.

Chisari, Nora Elisa; Dvorkin, Cora; Schmidt, Fabian

2014-08-01

46

SUNGLASS: A new weak lensing simulation pipeline

A new cosmic shear analysis pipeline SUNGLASS (Simulated UNiverses for Gravitational Lensing Analysis and Shear Surveys) is introduced. SUNGLASS is a pipeline that rapidly generates simulated universes for weak lensing and cosmic shear analysis. The pipeline forms suites of cosmological N-body simulations and performs tomographic cosmic shear analysis using line-of-sight integration through these simulations while saving the particle lightcone information. Galaxy shear and convergence catalogues with realistic 3D galaxy redshift distributions are produced for the purposes of testing weak lensing analysis techniques and generating covariance matrices for data analysis and cosmological parameter estimation. We present a suite of fast medium resolution simulations with shear and convergence maps for a generic 100 square degree survey out to a redshift of z = 1.5, with angular power spectra agreeing with the theory to better than a few percent accuracy up to l = 10^3 for all source redshifts up to z = 1.5 and wav...

Kiessling, A; Taylor, A N

2010-01-01

47

CONSTRAINING SOURCE REDSHIFT DISTRIBUTIONS WITH GRAVITATIONAL LENSING

We introduce a new method for constraining the redshift distribution of a set of galaxies, using weak gravitational lensing shear. Instead of using observed shears and redshifts to constrain cosmological parameters, we ask how well the shears around clusters can constrain the redshifts, assuming fixed cosmological parameters. This provides a check on photometric redshifts, independent of source spectral energy distribution properties and therefore free of confounding factors such as misidentification of spectral breaks. We find that {approx}40 massive ({sigma}{sub v} = 1200 km s{sup -1}) cluster lenses are sufficient to determine the fraction of sources in each of six coarse redshift bins to {approx}11%, given weak (20%) priors on the masses of the highest-redshift lenses, tight (5%) priors on the masses of the lowest-redshift lenses, and only modest (20%-50%) priors on calibration and evolution effects. Additional massive lenses drive down uncertainties as N{sub lens}{sup -1/2}, but the improvement slows as one is forced to use lenses further down the mass function. Future large surveys contain enough clusters to reach 1% precision in the bin fractions if the tight lens-mass priors can be maintained for large samples of lenses. In practice this will be difficult to achieve, but the method may be valuable as a complement to other more precise methods because it is based on different physics and therefore has different systematic errors.

Wittman, D.; Dawson, W. A., E-mail: dwittman@physics.ucdavis.edu [Physics Department, University of California, Davis, CA 95616 (United States)

2012-09-10

48

Recent Developments in Weak Lensing

Measurement of the gravitational distortion of images of distant galaxies is rapidly becoming established as a powerful probe of the dark mass distribution in clusters of galaxies. With the advent of large mosaics of CCD's these methods should provide a composite total mass profile for galaxy haloes and also measure the power spectrum of mass fluctuations on supercluster scales. We describe how HST observations have been used to place the observational measurement of the shear on a quantitative footing. By artifically stretching and then degrading WFPC2 images to simulate ground based observing it is now possible to directly calibrate the effect of atmospheric seeing. Similar experiments show that one can remove the effect of artificial image anisotropy arising in the atmosphere or telescope. There have also been important advances in the interpretation of the shear: reconstruction techniques have been extended to encompass the strong distortion regime of giant arcs etc., progress has been made in removing a bias present in earlier reconstruction techniques, and we describe new techniques for `aperture densitometry'. We present some new results on clusters of galaxies, and discuss the intimate connections between weak lensing and deep spectroscopy.

Nick Kaiser; Gordon Squires; Greg Fahlman; David Woods; Tom Broadhurst

1994-11-07

49

NASA Astrophysics Data System (ADS)

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. With reasonable prior information on other cosmological parameters, we find that a survey covering 1000 sq. deg. down to a limiting magnitude of R = 27 can impose constraints comparable to those expected from upcoming type Ia supernova and number-count surveys. This result, however, is contingent on the control of both observational and theoretical systematics. Concentrating on the latter, we find that the nonlinear power spectrum of matter perturbations and the redshift distribution of source galaxies both need to be determined accurately in order for weak lensing to achieve its full potential. Finally, we discuss the sensitivity of the three-point statistics to dark energy.

Huterer, Dragan

50

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

51

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

52

Gravitational Lensing by Boson Stars

NASA Astrophysics Data System (ADS)

Boson stars can be gravitational lenses in a similar way as other astrophysical objects (Dabrowski & Schunck 2000). They can be transparent which allows the light to pass through them and to be gravitationally deflected. We discuss the lens equation for these stars as well as the details of magnification assuming they are on non-cosmological distance from the observer and that their mass is M = 1010M?. We find that there are typically three images of a star. There is one tangential critical curve (Einstein ring) and one radial critical curve for tangential and radial magnification, respectively. The deflection angles for the light moving in the gravitational field of boson stars can be very large (even of the order of degrees) which means that they are very strong relativistic objects. We derive an analytic formula for the lens equation applied for such large deflection angles. Although the large deflection angle images are highly demagnified, their existence in the area of the tangential critical curve may help in observational detection of suitable lenses possessing characteristic features of boson stars which could serve as a direct evidence for scalar fields in the universe...

Schunck, Franz E.; Dabrowski, Mariusz P.

2002-12-01

53

Weak Lensing Results of the Merging Cluster A1758

NASA Technical Reports Server (NTRS)

Here we present the weak lensing results of A1758, which is known to have four cluster members undergoing two separate mergers, A1758N and A1758S. Weak lensing results of A1758N agree with previous weak lensing results of clusters lE0657-558 (Bullet cluster) and MACS J0025.4-1222, whose X-ray gas components were found to be largely separated from their clusters' gravitational potentials. A1758N has a geometry that is different from previously published mergers in that one of its X-ray peaks overlays the corresponding gravitational potential and the other X-ray peak is well separated from its cluster's gravitational potential.

Markevitch, M.; Gonzalez, A. H.; Bradac, M.

2011-01-01

54

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

55

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

2002-04-30

56

Host Galaxies of Gravitationally Lensed Quasars

We present 15 Einstein Rings and arcs in the CfA--Arizona--Space Telescope Gravitational Lensing survey (CASTLES), the majority of which are candidate quasar host galaxies. All of the objects are at z>=1.3, thus lensing provides one of the largest quasar hosts samples beyond z>1. Gravitational lensing stretches out quasar hosts into Einstein rings and arcs, enhancing host detections and enabling measurements

C. Y. Peng; C. D. Impey; E. E. Falco; C. R. Keeton; C. S. Kochanek; J. Lehar; B. A. McLeod; J. A. Munoz; H. W. Rix

2001-01-01

57

SUNGLASS: a new weak-lensing simulation pipeline

A new cosmic shear analysis pipeline SUNGLASS (Simulated UNiverses for Gravitational Lensing Analysis and Shear Surveys) is introduced. SUNGLASS is a pipeline that rapidly generates simulated universes for weak-lensing and cosmic shear analysis. The pipeline forms suites of cosmological N-body simulations and performs tomographic cosmic shear analysis using line-of-sight integration through these simulations while saving the particle lightcone information. Galaxy

A. Kiessling; A. F. Heavens; A. N. Taylor; B. Joachimi

2011-01-01

58

On 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 spacetime of the lens, and, then, light-ray detection in the moving observer's frame. Due to 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 re-scaling of the lens mass. The Einstein ring is distorted to an ellipse whereas the caustics in the source plane are still point-like. 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...

Sereno, M

2008-01-01

59

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

60

Gravitational lenses and dark matter - Observations

NASA Technical Reports Server (NTRS)

Following a few general comments on gravitational lenses from an observer's perspective, the currently available observations of the six known gravitational lenses are summarized. Attention is called to some regularities and peculiarities of the properties of the known lenses and to how they might be interpreted. The most important conclusions, relevant to the dark matter problem, which can be obtained from current observations are that the distributions of mass and light appear to be quite different in at least some of the lensing objects and that objects with projected mass/brightness values about 10 times larger than those ordinarily associated with galaxies exist and are not too rare.

Turner, Edwin L.

1987-01-01

61

Testing gravity on cosmological scales with weak lensing

via refraction #12;Two kinds of lenses (1) Lensing via refraction Light rays move at a different speed in the lens medium #12;Two kinds of lenses (1) Lensing via refraction (2) Lensing via gravitation Light rays move at a different speed in the lens medium #12;Two kinds of lenses (1) Lensing via refraction (2

62

Gravitational Lensing of Cosmological 21cm Emission

We investigate the feasibility of measuring weak gravitational lensing using 21cm 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 HI 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 signal-to-noise's dependence on the area and diameter of the telescope 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 r...

Pourtsidou, A

2014-01-01

63

New stochastic approach to cumulative weak lensing

We study the weak gravitational lensing effects caused by a stochastic distribution of dark matter halos. We develop a simple approach to calculate the magnification probability distribution function which allows us to easily compute the magnitude bias and dispersion for an arbitrary data sample and a given universe model. As an application we consider the effects of single-mass large-scale cosmic inhomogeneities (M{approx}10{sup 15}h{sup -1}M{sub {center_dot}}) to the SNe magnitude-redshift relation, and conclude that such structures could bias the PDF enough to affect the extraction of cosmological parameters from the limited size of present-day SNe data samples. We also release turboGL[turboGL is available at: http://www.turbogl.org.], a simple and very fast (< or approx. 1 s) Mathematica code based on the method here presented.

Kainulainen, Kimmo; Marra, Valerio [Department of Physics, University of Jyvaeskylae, PL 35 (YFL), FIN-40014 Jyvaeskylae, Finland and Helsinki Institute of Physics, University of Helsinki, PL 64, FIN-00014 Helsinki (Finland)

2009-12-15

64

New stochastic approach to cumulative weak lensing

NASA Astrophysics Data System (ADS)

We study the weak gravitational lensing effects caused by a stochastic distribution of dark matter halos. We develop a simple approach to calculate the magnification probability distribution function which allows us to easily compute the magnitude bias and dispersion for an arbitrary data sample and a given universe model. As an application we consider the effects of single-mass large-scale cosmic inhomogeneities (M˜1015h-1M?) to the SNe magnitude-redshift relation, and conclude that such structures could bias the PDF enough to affect the extraction of cosmological parameters from the limited size of present-day SNe data samples. We also release turboGL [turboGL is available at: http://www.turbogl.org.], a simple and very fast (?1s) Mathematica code based on the method here presented.

Kainulainen, Kimmo; Marra, Valerio

2009-12-01

65

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

66

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

67

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

68

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

69

Magnified Weak Lensing Cross Correlation Tomography

This project carried out a weak lensing tomography (WLT) measurement around rich clusters of galaxies. This project used ground based photometric redshift data combined with HST archived cluster images that provide the WLT and cluster mass modeling. The technique has already produced interesting results (Guennou et al, 2010,Astronomy & Astrophysics Vol 523, page 21, and Clowe et al, 2011 to be submitted). Guennou et al have validated that the necessary accuracy can be achieved with photometric redshifts for our purposes. Clowe et al titled "The DAFT/FADA survey. II. Tomographic weak lensing signal from 10 high redshift clusters," have shown that for the **first time** via this purely geometrical technique, which does not assume a standard rod or candle, that a cosmological constant is **required** for flat cosmologies. The intent of this project is not to produce the best constraint on the value of the dark energy equation of state, w. Rather, this project is to carry out a sustained effort of weak lensing tomography that will naturally feed into the near term Dark Energy Survey (DES) and to provide invaluable mass calibration for that project. These results will greatly advance a key cosmological method which will be applied to the top-rated ground-based project in the Astro2020 decadal survey, LSST. Weak lensing tomography is one of the key science drivers behind LSST. CO-I Clowe is on the weak lensing LSST committee, and senior scientist on this project, at FNAL James Annis, plays a leading role in the DES. This project has built on successful proposals to obtain ground-based imaging for the cluster sample. By 1 Jan, it is anticipated the project will have accumulated complete 5-color photometry on 30 (or about 1/3) of the targeted cluster sample (public webpage for the survey is available at http://cencos.oamp.fr/DAFT/ and has a current summary of the observational status of various clusters). In all, the project has now been awarded the equivalent of over 60 nights on 4-m class telescopes, which gives concrete evidence of strong community support for this project. The WLT technique is based on the dependence of the gravitational shear signal on the angular diameter distances between the observer, the lens, and the lensed galaxy to measure cosmological parameters. By taking the ratio of measured shears of galaxies with different redshifts around the same lens, one obtains a measurement of the ratios of the angular diameter distances involved. Making these observations over a large range of lenses and background galaxy redshifts will measure the history of the expansion rate of the universe. Because this is a purely geometric measurement, it is insensitive to any form of evolution of objects or the necessity to understand the physics in the early universe. Thus, WLT was identified by the Dark Energy Task Force as perhaps the best method to measure the evolution of DE. To date, however, the conjecture of the DETF has not been experimentally verified, but will be by the proposed project. The primary reason for the lack of tomography measurements is that one must have an exceptional data-set to attempt the measurement. One needs both extremely good seeing (or space observations) in order to minimize the point spread function smearing corrections on weak lensing shear measurements and deep, multi-color data, from B to z, to measure reliable photometric redshifts of the background galaxies being lensed (which are typically too faint to obtain spectroscopic redshifts). Because the entire process from multi-drizzling the HST images, and then creating shear maps, to gathering the necessary ground based observations, to generating photo-zs and then carrying out the tomography is a complicated task, until the creation of our team, nobody has taken the time to connect all the levels of expertise necessary to carry out this project based on HST archival data. Our data are being used in 2 Ph.D. theses. Kellen Murphy, at Ohio University, is using the tomography data along with simulations in a thesis expected to be completed in Jun

Ulmer, Melville P., Clowe, Douglas I.

2010-11-30

70

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

71

Time delay in Swiss cheese gravitational lensing

NASA Astrophysics Data System (ADS)

We compute time delays for gravitational lensing in a flat ? dominated cold dark matter Swiss cheese universe. We assume a primary and secondary pair of light rays are deflected by a single point mass condensation described by a Kottler metric (Schwarzschild with ?) embedded in an otherwise homogeneous cosmology. We find that the cosmological constant’s effect on the difference in arrival times is nonlinear and at most around 0.002% for a large cluster lens; however, we find differences from time delays predicted by conventional linear lensing theory that can reach ˜4% for these large lenses. The differences in predicted delay times are due to the failure of conventional lensing to incorporate the lensing mass into the mean mass density of the universe.

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

2010-08-01

72

Kinematic Weak Lensing: Forecasts for a Next-Generation Lensing Measurement

NASA Astrophysics Data System (ADS)

Weak gravitational lensing by cosmic structure is a major science driver for several large ongoing and planned imaging surveys, such as the Dark Energy Survey and the Euclid space mission. Traditionally, lensing in this regime is measured via statistical distortions to the shapes of galaxies. While the cosmological constraining power for a large imaging survey employing this technique is great, the signal itself is noisy, and susceptible to a number of systematic biases. Here we propose a new lensing technique that makes use of the kinematics of disk galaxies and the Tully-Fisher relation. Our method controls for that part of the shape noise which arises from the random orientation of galaxy disks, and promises an increase in signal-to-noise sufficient to bring weak lensing measurements within the reach of the next generation of spectroscopic surveys. We define such a survey here, discuss the advantages and disadvantages, and show that the cosmological constraining power of this kinematic weak lensing method is competitive with the most powerful planned lensing measurements.

Huff, Eric M.; George, M. R.; Krause, E.; Eifler, T.; Schlegel, D. J.

2014-01-01

73

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

74

Cluster Cores, Gravitational Lensing, and Cosmology

Many multiply--imaged quasars have been found over the years, but none so far with image separation in excess of $8\\arcsec$. The absence of such large splittings has been used as a test of cosmological models: the standard Cold Dark Matter model has been excluded on the basis that it predicts far too many large--separation double images. These studies assume that the lensing structure has the mass profile of a singular isothermal sphere. However, such large splittings would be produced by very massive systems such as clusters of galaxies, for which other gravitational lensing data suggest less singular mass profiles. Here we analyze two cases of mass profiles for lenses: an isothermal sphere with a finite core radius (density $\\rho \\propto (r^2+r_{core}^2)^{-1})$, and a Hernquist profile ($\\rho \\propto r^{-1}(r+a)^{-3}$). We find that small core radii $r_{core} \\sim 30 h^{-1}$ kpc, as suggested by the cluster data, or large $a \\gsim 300 h^{-1}$ kpc, as needed for compatibility with gravitational distortion data, would reduce the number of large--angle splittings by an order of magnitude or more. Thus, it appears that these tests are sensitive both to the cosmological model (number density of lenses) and to the inner lens structure, which is unlikely to depend sensitively on the cosmology, making it difficult to test the cosmological models by large--separation quasar lensing until we reliably know the structure of the lenses themselves.

Ricardo A. Flores; Joel R. Primack

1995-12-11

75

A toolbox for general elliptical gravitational lenses

We introduce a formalism to describe 2D-Potentials for 2D-matter (or charge) distributions with arbitrary elliptical symmetry including varying eccentricity and twisting of the iso-density curves. We use this approach to describe elliptical matter distributions such as elliptical galaxies or clusters as gravitational lenses. Figures are available upon request: tschramm@hs.uni-hamburg.de

T. Schramm

1993-11-09

76

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

77

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

78

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

79

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 with 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 increase the total number of clusters studied with the combined strong and weak lensing technique to 10. 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 [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Hennawi, Joseph F. [Department of Astronomy, University of California Berkeley, Berkeley, CA 94720 (United States); Gladders, Michael D.; Koester, Benjamin P.; Sharon, Keren; Bayliss, Matthew [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Dahle, Haakon [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029, Blindern, N-0315 Oslo (Norway); Natarajan, Priyamvada [Department of Astronomy, Yale University, P. O. Box 208101, New Haven CT 06511-208101 (United States); Dalal, Neal [Canadian Institute for Theoretical Astrophysics, 60 St. George Street, University of Toronto, Toronto, ON M5S3H8 (Canada)

2009-07-10

80

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

81

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

82

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

83

Statistics of Dark Matter Halos from Gravitational Lensing.

We present a new approach to measure the mass function of dark matter halos and to discriminate models with differing values of Omega through weak gravitational lensing. We measure the distribution of peaks from simulated lensing surveys and show that the lensing signal due to dark matter halos can be detected for a wide range of peak heights. Even when the signal-to-noise ratio is well below the limit for detection of individual halos, projected halo statistics can be constrained for halo masses spanning galactic to cluster halos. The use of peak statistics relies on an analytical model of the noise due to the intrinsic ellipticities of source galaxies. The noise model has been shown to accurately describe simulated data for a variety of input ellipticity distributions. We show that the measured peak distribution has distinct signatures of gravitational lensing, and its non-Gaussian shape can be used to distinguish models with different values of Omega. The use of peak statistics is complementary to the measurement of field statistics, such as the ellipticity correlation function, and is possibly not susceptible to the same systematic errors. PMID:10642191

Jain; Van Waerbeke L

2000-02-10

84

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

85

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

86

Weak Lensing Analysis of CL 1358+62 Using Hubble Space Telescope Observations

We report on the detection of weak gravitational lensing of faint, distant background objects by Cl 1358+62, a rich cluster of galaxies at a redshift of z = 0.33. The observations consist of a large, multicolor mosaic of Hubble Space Telescope WFPC2 images. The number density of approximately 50 background objects arcmin-2 allows us to do a detailed weak lensing

Henk Hoekstra; Marijn Franx; Konrad Kuijken; Gordon Squires

1998-01-01

87

Strong gravitational lensing and dark energy complementarity

In the search for the nature of dark energy most cosmological probes measure simple functions of the expansion rate. While powerful, these all involve roughly the same dependence on the dark energy equation of state parameters, with anticorrelation between its present value w{sub 0} and time variation w{sub a}. Quantities that have instead positive correlation and so a sensitivity direction largely orthogonal to, e.g., distance probes offer the hope of achieving tight constraints through complementarity. Such quantities are found in strong gravitational lensing observations of image separations and time delays. While degeneracy between cosmological parameters prevents full complementarity, strong lensing measurements to 1 percent accuracy can improve equation of state characterization by 15-50 percent. Next generation surveys should provide data on roughly 105 lens systems, though systematic errors will remain challenging.

Linder, Eric V.

2004-01-21

88

Applications of the Gauss-Bonnet theorem to gravitational lensing

In this geometrical approach to gravitational lensing theory, we apply the Gauss-Bonnet theorem to the optical metric of a lens, modelled as a static, spherically symmetric, perfect non-relativistic fluid, in the weak deflection limit. We find that the focusing of the light rays emerges here as a topological effect, and we introduce a new method to calculate the deflection angle from the Gaussian curvature of the optical metric. As examples, the Schwarzschild lens, the Plummer sphere and the singular isothermal sphere are discussed within this framework.

G W Gibbons; M C Werner

2008-07-05

89

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

90

Weak Lensing with Sizes, Magnitudes and Shapes

Weak lensing can be observed through a number of effects on the images of distant galaxies; their shapes are sheared, their sizes and fluxes (magnitudes) are magnified and their positions on the sky are modified by the lensing field. Galaxy shapes probe the shear field whilst size, magnitude and number density probe the convergence field. Both contain cosmological information. In this paper we are concerned with the magnification of the size and magnitude of individual galaxies as a probe of cosmic convergence. We develop a Bayesian approach for inferring the convergence field from a measured size, magnitude and redshift and demonstrate that the inference on convergence requires detailed knowledge of the joint distribution of intrinsic sizes and magnitudes. We build a simple parameterised model for the size-magnitude distribution and estimate this distribution for CFHTLenS galaxies. In light of the measured distribution, we show that the typical dispersion on convergence estimation is ~0.8, compared to ~0.38 ...

Alsing, Justin; Heavens, Alan; Jaffe, Andrew

2014-01-01

91

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

92

Gravitational Lensing by Nearby Clusters of Galaxies

We present an estimation of the expected number of arcs and arclets in a sample of nearby (z<0.1) clusters of galaxies, that takes into account the magnitude limit of the objects as well as seeing effects. We show that strong lensing effects are not common, but also they are not as rare as usually stated. Indeed, for a given cluster, they present a strong dependence with the magnitude limit adopted in the analysis and the seeing of the observations. We also describe the procedures and results of a search for lensing effects in a sample of 33 clusters spanning the redshift range of 0.014 to 0.076, representative of the local cluster distribution. This search produced two arc candidates. The first one is in A3408 (z=0.042), the same arc previously discovered by Campusano & Hardy (1996), with z=0.073 and associated to the brightest cluster galaxy. The second candidate is in the cluster A3266 (z=0.059) and is near a bright elliptical outside the cluster center, requiring the presence of a very massive sub-structure around this galaxy to be produced by gravitational lensing.

Eduardo S. Cypriano; Laerte Sodre' Jr.; Luis E. Campusano; Jean-Paul Kneib; Riccardo Giovanelli; Martha P. Haynes; Daniel A. Dale; Eduardo Hardy

2000-05-09

93

MULTIPOLE FORMULAE FOR GRAVITATIONAL LENSING SHEAR AND FLEXION

The gravitational lensing equations for convergence, potential, shear, and flexion are simple in polar coordinates and separate under a multipole expansion once the shear and flexion spinors are rotated into a 'tangential' basis. We use this to investigate whether the useful monopole aperture-mass shear formulae generalize to all multipoles and to flexions. We re-derive the result of Schneider and Bartelmann that the shear multipole m at radius R is completely determined by the mass multipole at R, plus specific moments Q '('m') {sub in} and Q '('m') {sub out} of the mass multipoles internal and external, respectively, to R. The m {>=} 0 multipoles are independent of Q {sub out}. But in contrast to the monopole, the m < 0 multipoles are independent of Q {sub in}. These internal and external mass moments can be determined by shear (and/or flexion) data on the complementary portion of the plane, which has practical implications for lens modeling. We find that the ease of E/B separation in the monopole aperture moments does not generalize to m {ne} 0: the internal monopole moment is the only nonlocal E/B discriminant available from lensing observations. We have also not found practical local E/B discriminants beyond the monopole, though they could exist. We show also that the use of weak-lensing data to constrain a constant shear term near a strong-lensing system is impractical without strong prior constraints on the neighboring mass distribution.

Bernstein, Gary M.; Nakajima, Reiko [Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19104 (United States)], E-mail: garyb@physics.upenn.edu, E-mail: rnakajima@berkeley.edu

2009-03-10

94

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

95

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

96

Galaxy-cluster associations from gravitational lensing

We investigate the associations between background galaxies and foreground clusters of galaxies due to the effect of gravitational lensing by clusters of galaxies. Similar to the well-known quasar-galaxy ones, these associations depend sensitively on the shape of galaxy number-magnitude or number-flux relation, and both positive and ``negative" associations are found to be possible, depending on the limiting magnitude and/or the flux threshold in the surveys. We calculate the enhancement factors assuming a singular isothermal sphere model for clusters of galaxies and a pointlike model for background sources selected in three different wavelengths, $B$, $K$ and radio. Our results show that $K-$ selected galaxies might constitute the best sample to test the ``negative" associations while it is unlikely that one can actually observe any association for blue galaxies. We also point out that bright radio sources ($S>1$ Jy) can provide strong positive associations, which may have been already detected in 3CR sample.

Xiang-Ping Wu; Francois Hammer

1993-12-24

97

Data Mining for Gravitationally Lensed Quasars

Gravitationally lensed (GL) 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 catalog-level information ($griz$+WISE magnitudes, second moments) to preselect 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 cand...

Agnello, Adriano; Treu, Tommaso; Marshall, Philip J

2014-01-01

98

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

99

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

100

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

101

Gravitational lensing in eclipsing binary stars

I consider the effect of the gravitational deflection of light upon the light curves of eclipsing binary stars, focussing mainly upon systems containing at least one white dwarf component. In absolute terms the effects are small, however they are strongest at the time of secondary eclipse when the white dwarf transits its companion, and act to reduce the depth of this feature. If not accounted for, this may lead to under-estimation of the radius of the white dwarf compared to that of its companion. I show that the effect is significant for plausible binary parameters, and that it leads to ~25% reduction in the transit depth in the system KPD 1930+2752. The reduction of eclipse depth is degenerate with the stellar radius ratio, and therefore cannot be used to establish the existence of lensing. A second order effect of the light bending is to steepen the ingress and egress features of the secondary eclipse relative to the primary eclipse, although it will be difficult to see this in practice. I consider also binaries containing neutron stars and black-holes. I conclude that, although relatively large effects are possible in such systems, a combination of rarity, faintness and intrinsic variability make it unlikely that lensing will be detectable in them.

T. R. Marsh

2000-12-18

102

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

103

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

104

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

105

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 $r < 0.1$, even if the consistency relation is difficult to confirm with a high significance, the gravitational-wave induced lensing would be detected at more than ...

Namikawa, Toshiya; Taruya, Atsushi

2014-01-01

106

NASA Astrophysics Data System (ADS)

The gravitational lensing effect is important to the detection of electromagnetic signals in astrophysics. The gravitational wave lensing effect has also been found significant to gravitational wave detection in the past decade. Recent analysis shows that the lensing events for advanced detectors could be quite plausible. The black holes in our Milky Way Galaxy may play the role of lens objects. These facts motivate us to study the lensing effects on gravitational wave signals for advanced detectors. Taking advanced LIGO and Einstein Telescope for examples, we investigate the lensing effects on the parameter extraction of gravitational wave signals. Using the Markov chain Monte Carlo simulation together with matched filtering methods, we find that the lensing effect for a lens object with small mass is negligible. But when the mass of the lens object increases to larger than 1000M? the lensing effect becomes important. Using the template without lensing corrections would result in loss of signal detections. In contrast if we consider templates with lensing effects, the lensed signal may provide much information about the lens black hole. These facts may give us a new way to determine the parameters of the lensing object. For example, this kind of signal may also help us estimate the mass and the distance of the supermassive black hole hosted at the center of our Galaxy.

Cao, Zhoujian; Li, Li-Fang; Wang, Yan

2014-09-01

107

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

108

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 $r sensitivity experiments will be also powerful to constrain the gravitational waves generated after the recombination epoch. Compared to the B-mode polarization, the curl mode is particularly sensitive to gravitational waves generated at low redshifts ($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

2014-11-27

109

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

2008-04-25

110

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

111

Setting limits on q0 from gravitational lensing

NASA Technical Reports Server (NTRS)

Gravitational lensing by galaxies in a wide variety of cosmological models is considered. For closed models, the lensing depends on the parameter beta(crit). If beta(crit) is greater than zero, a normal lensing case can be obtained with two bright images separated by an angle twice beta(crit) and a third, arbitrarily dim image between them coincident with the position of the lensing galaxy nucleus. As the QSO approaches the antipodal redshift, which can occur in models with large values of the cosmological constant, the cross sections for lensing blow up. An overfocused case where beta(crit) is less than zero can be obtained for a QSO beyond the antipodal redshift. In this case, when a lensing event occurs, only one arbitrarily dim image coincident with the position of the lensing galaxy nucleus is seen. If galaxy rotation curves are always flat or slowly rising, the overfocused case always produces one image.

Gott, J. Richard, III; Park, Myeong-Gu; Lee, Hyung Mok

1989-01-01

112

Strong lensing, plane gravitational waves and transient flashes

Plane-symmetric gravitational waves are considered as gravitational lenses. Numbers of images, frequency shifts, mutual angles, and image distortion parameters are computed exactly in essentially all non-singular plane wave spacetimes. For a fixed observation event in a particular plane wave spacetime, the number of images is found to be the same for almost every source. This number can be any positive integer, including infinity. Wavepackets of finite width are discussed in detail as well as waves which maintain a constant amplitude for all time. Short wavepackets are found to generically produce up to two images of each source which appear (separately) only some time after the wave has passed. They are initially infinitely bright, infinitely blueshifted images of the infinitely distant past. Later, these images become dim and acquire a rapidly-increasing redshift. For sufficiently weak wavepackets, one such "flash" almost always exists. The appearance of a second flash requires that the Ricci tensor inside the wave exceed a certain threshold. This might occur if a gravitational plane wave is sourced by, e.g., a sufficiently strong electromagnetic plane wave.

Abraham I. Harte

2012-10-04

113

Part 1: Introduction to gravitational lensing and cosmology

NASA Astrophysics Data System (ADS)

In this introductory first part we shall provide an outline of the basics of gravitational lensing, covering aspects that are at the base of it and which will be used extensively in the three main lectures. We start with a brief historical account; the study of the influence of a gravitational field on the propagation of light started long before the proper theory of gravity - Einstein's General Relativity - was formulated. Illustrations of the most common phenomena of gravitational lensing will be given next, before we will introduce the basic equations of gravitational lensing theory. A few simple lens models will be considered in particular the point-mass lens and the singular isothermal sphere model. Since the sources and deflectors in gravitational lensing are often located at distances comparable to the radius of the observable Universe, the large-scale geometry of spacetime needs to be accounted for. Thus, we give a brief introduction to the standard model of cosmology. We then proceed with some basic considerations about lensing statistics, i.e., the question of how probable it is that observations of a source at large distance are significantly affected by a lensing effect, and conclude with a description of the large-scale matter distribution in the Universe.

Schneider, P.

114

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

115

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

116

CDM Substructure in Gravitational Lenses: Tests and Results

We use a simple statistical test to show that the anomalous flux ratios observed in gravitational lenses are created by gravitational perturbations from substructure rather than propagation effects in the interstellar medium or incomplete models for the gravitational potential of the lens galaxy. We review current estimates that the substructure represents between 0.6% and 7% (90% confidence) of the lens galaxy mass, and outline future observational programs which can improve the results.

C. S. Kochanek; N. Dalal

2002-12-11

117

2016+112: A Gravitationally Lensed Type-II Quasar

A single-screen model of the gravitational lens system 2016+112 is proposed, that explains recent Hubble Space Telescope} (HST) infrared (NICMOS-F160W) observations and new high-resolution European VLBI Network (EVN) 5-GHz radio observations, presented in this paper. In particular, we find that a massive `dark' structure at the lens position, previously suggested by X-ray, optical and spectroscopic observations of the field around 2016+112, is not necessarily required to accommodate the strong lensing constraints. A massive structure to the north-west of the lens system, suggested from a weak-lensing analysis of the field, is included in the model. The lensed source is an X-ray bright active galaxy at z=3.273 with a central bright optical continuum core and strong narrow emission lines, suggestive of a type-II quasar. The EVN 5-GHz radio maps show a radio-jet structure with at least two compact subcomponents. We propose that the diamond caustic crosses the counter-jet of the radio source, so that part of the counter-jet, host galaxy and narrow-line emission regions are quadruply imaged. The remainder of the radio source, including the core, is doubly imaged. Our lens model predicts a very high magnification (mu~300) at the bightness peaks of the inner two radio components of complex C. If the jet exhibits relativistic velocities on micro-arsecond scales, it might result in apparent hyperluminal motion. However, the lack of strong radio variability and the peaked radio spectrum imply that these motions need not be present in the source. Our model furthermore implies that the optical spectrum of C' can only show features of the AGN and its host galaxy.

L. V. E. Koopmans; M. A. Garrett; R. D. Blandford; C. R. Lawrence; A. R. Patnaik; R. W. Porcas

2001-06-29

118

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

119

Gravitational Lensing of the Microwave Background by Galaxy Clusters

Galaxy clusters will distort the pattern of temperature anisotropies in the microwave background via gravitational lensing. We create lensed microwave background maps using clusters drawn from numerical cosmological simulations. A distinctive dipole-like temperature fluctuation pattern is formed aligned with the underlying microwave temperature gradient. For a massive cluster, the characteristic angular size of the temperature distortion is a few arcminutes and the characteristic amplitude a few micro-Kelvin. We demonstrate a simple technique for estimating the lensing deflection induced by the cluster; microwave background lensing measurements have the potential to determine the mass distribution for some clusters with good accuracy on angular scales up to a few arcminutes. Future high-resolution and high-sensitivity microwave background maps will have the capability to detect lensing by clusters; we discuss various systematic limitations on probing cluster masses using this technique.

Gilbert P. Holder; Arthur Kosowsky

2004-01-23

120

Gravitational lensing and structural stability of dark matter caustic rings

NASA Astrophysics Data System (ADS)

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-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.

2006-12-01

121

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

2013-04-29

122

Through a Lens Darkly: Evidence for Dusty Gravitational Lenses

Foreground galaxies that amplify the light from background quasars may also dim that light if the galaxies contain enough dust. Extinction by dust in lenses could hide the large number of lensed systems predicted for a flat universe with a large value of the cosmological constant $\\Lambda$. We look for one signature of dust, namely reddening, by examining optical-infrared colors of gravitationally lensed images of quasars. We find that the lensed systems identified in radio and infrared searches have redder optical-IR colors than optically selected ones. This could be due to a bias against selecting reddened (hence extincted) quasars in the optical surveys, or due to the differences in the intrinsic colors of optical and radio quasars. Comparison of the radio-selected lensed and unlensed quasars shows that the lensed ones have redder colors. We therefore conclude that at least part of the color difference between the two lens samples is due to dust. From the color difference between lensed and unlensed radio quasars (and assuming Galactic extinction law) we can reconcile a large cosmological constant ($\\Lambda=0.9$) with the number of lensed systems observed in flux limited optical surveys. These results substantially weaken the strongest constraint on cosmological scenarios that invoke a non-zero cosmological constant to explain age discrepancy problems, satisfy predictions of inflationary models of the early universe and play a role in large scale structure formation models. They also raise the prospect of using gravitational lenses to study the interstellar medium in high redshift galaxies.

Sangeeta Malhotra; James E. Rhoads; Edwin L. Turner

1996-10-29

123

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

124

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

2007-11-29

125

Gravitational Lensing in the metric theory proposed by Sobouti

NASA Astrophysics Data System (ADS)

Recently, Y. Sobouti (2007) has provided a metric theory f(R) that can account for certain dynamical anomalies observed in spiral galaxies. Mendoza & Rosas-Guevara (2007) have shown that in this theory there is an extra-bending as compared to standard general relativity. In the present work we have developed in more specific detail this additional lensing effect and we have made evaluations of the ? parameter used in the model adjusting the theory to observations in X-rays of 13 clusters of galaxies with gravitational lensing ([6]).

Bernal, Tula; Mendoza, Sergio

2008-12-01

126

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

127

SNAP Spectrograph For Super Nova, Weak Lensing And Calibration Science

We present the current design and status of the integral field spectrograph for the SNAP proposal for JDEM. The spectrograph is designed to provide needed spectroscopy for the SNAP Supernova Program ( Type Ia SN ID and spectrophotometry), for the SNAP Weak Lensing Program (photo-z calibration) and for the SNAP fundamental Calibration Program ( 1-2 % on calibrated stars).The design

Roger F. Malina; A. Ealet; E. Prieto; M. Aumeunier; A. Bonissent; C. Cerna; P. Karst; C. Rossin; G. Smadja; S. Vives

2007-01-01

128

A compressed sensing approach to 3D weak lensing

NASA Astrophysics Data System (ADS)

Context. Weak gravitational lensing is an ideal probe of the dark universe. In recent years, several linear methods have been developed to reconstruct the density distribution in the Universe in three dimensions, making use of photometric redshift information to determine the radial distribution of lensed sources. Aims: We aim to address three key problems seen in these methods; namely, the bias in the redshifts of detected objects, the line-of-sight smearing seen in reconstructions, and the damping of the amplitude of the reconstruction relative to the underlying density. We also aim to detect structures at higher redshifts than have previously been achieved, and to improve the line-of-sight resolution of our reconstructions. Methods: We considered the problem under the framework of compressed sensing (CS). Under the assumption that the data are sparse or compressible in an appropriate dictionary, we constructed a robust estimator and employ state-of-the-art convex optimisation methods to reconstruct the density contrast. For simplicity in implementation, and as a proof of concept of our method, we reduced the problem to one dimension, considering the reconstruction along each line of sight independently. We also assumed an idealised survey in which the redshifts of sources are known. Results: Despite the loss of information inherent in our one-dimensional implementation, we demonstrate that our method is able to accurately reproduce cluster haloes up to a redshift of zcl = 1.0, deeper than state-of-the-art linear methods. We directly compare our method with these linear methods, and demonstrate minimal radial smearing and redshift bias in our reconstructions, as well as a reduced damping of the reconstruction amplitude as compared to the linear methods. In addition, the CS framework allows us to consider an underdetermined inverse problem, thereby allowing us to reconstruct the density contrast at finer resolution than the input data. Conclusions: The CS approach allows us to recover the density distribution more accurately than current state-of-the-art linear methods. Specifically, it addresses three key problem areas inherent in linear methods. Moreover, we are able to achieve super-resolution and increased high-redshift sensitivity in our reconstructions.

Leonard, A.; Dupé, F.-X.; Starck, J.-L.

2012-03-01

129

Reducing Systematic Error in Weak Lensing Cluster Surveys

NASA Astrophysics Data System (ADS)

Weak lensing provides an important route toward collecting samples of clusters of galaxies selected by mass. Subtle systematic errors in image reduction can compromise the power of this technique. We use the B-mode signal to quantify this systematic error and to test methods for reducing this error. We show that two procedures are efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10'. Application of these procedures reduces the systematic error to 20% of its original amplitude. We provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the weak-lensing ?-signal-to-noise ratio (S/N) maps as a function of the detection threshold. Based on this analysis, we select a threshold S/N = 4.56 for identifying an uncontaminated set of weak-lensing peaks in two test fields covering a total area of ~3 deg2. Taken together these fields contain seven peaks above the threshold. Among these, six are probable systems of galaxies and one is a superposition. We confirm the reliability of these peaks with dense redshift surveys, X-ray, and imaging observations. The systematic error reduction procedures we apply are general and can be applied to future large-area weak-lensing surveys. Our high-peak analysis suggests that with an S/N threshold of 4.5, there should be only 2.7 spurious weak-lensing peaks even in an area of 1000 deg2, where we expect ~2000 peaks based on our Subaru fields. Based in part on data collected at Subaru Telescope and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan.

Utsumi, Yousuke; Miyazaki, Satoshi; Geller, Margaret J.; Dell'Antonio, Ian P.; Oguri, Masamune; Kurtz, Michael J.; Hamana, Takashi; Fabricant, Daniel G.

2014-05-01

130

PROBING PRIMORDIAL NON-GAUSSIANITY WITH WEAK-LENSING MINKOWSKI FUNCTIONALS

We study the cosmological information contained in the Minkowski functionals (MFs) of weak gravitational lensing convergence maps. We show that the MFs provide strong constraints on the local-type primordial non-Gaussianity parameter f {sub NL}. We run a set of cosmological N-body simulations and perform ray-tracing simulations of weak lensing to generate 100 independent convergence maps of a 25 deg{sup 2} field of view for f {sub NL} = -100, 0 and 100. We perform a Fisher analysis to study the degeneracy among other cosmological parameters such as the dark energy equation of state parameter w and the fluctuation amplitude {sigma}{sub 8}. We use fully nonlinear covariance matrices evaluated from 1000 ray-tracing simulations. For upcoming wide-field observations such as those from the Subaru Hyper Suprime-Cam survey with a proposed survey area of 1500 deg{sup 2}, the primordial non-Gaussianity can be constrained with a level of f {sub NL} {approx} 80 and w {approx} 0.036 by weak-lensing MFs. If simply scaled by the effective survey area, a 20,000 deg{sup 2} lensing survey using the Large Synoptic Survey Telescope will yield constraints of f {sub NL} {approx} 25 and w {approx} 0.013. We show that these constraints can be further improved by a tomographic method using source galaxies in multiple redshift bins.

Shirasaki, Masato; Yoshida, Naoki; Nishimichi, Takahiro [Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Hamana, Takashi, E-mail: masato.shirasaki@ipmu.jp [National Astronomical Observatory of Japan, Tokyo 181-0015 (Japan)

2012-11-20

131

Constraining fast radio burst progenitors with gravitational lensing

Fast Radio Bursts (FRBs) are new transient radio sources discovered recently. Because of the angular resolution restriction in radio surveys, no optical counter part has been identified yet so it is hard to determine the progenitor of FRBs. In this paper we propose to use radio lensing survey to constrain FRB progenitors. We show that, different types of progenitors lead to different probabilities for a FRB to be gravitationally lensed by dark matter halos in foreground galaxies, since different type progenitors result in different redshift distributions of FRBs. For example, the redshift distribution of FRBs arising from double stars shifts toward lower redshift than of the FRBs arising from single stars, because double stars and single stars have different evolution timescales. With detailed calculations, we predict that the FRB sample size for producing one lensing event varies significantly for different FRB progenitor models. We argue that this fact can be used to distinguish different FRB models and als...

Li, Chun-Yu

2014-01-01

132

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

National Technical Information Service (NTIS)

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 s...

L. Zuo, E. A. Beaver, E. M. Burbidge, R. D. Cohen, V. T. Junkkarinen, R. W. Lyons

1997-01-01

133

Gravitational lensing in the Kerr-Randers optical geometry

A new geometric method to determine the deflection of light in the equatorial plane of the Kerr solution is presented, whose optical geometry is a surface with a Finsler metric of Randers type. Applying the Gauss-Bonnet theorem to a suitable osculating Riemannian manifold, adapted from a construction by Naz\\i m, it is shown explicitly how the two leading terms of the asymptotic deflection angle of gravitational lensing can be found in this way.

M. C. Werner

2012-05-17

134

Automatic detection of arcs and arclets formed by gravitational lensing

We present an algorithm developed particularly to detect gravitationally lensed arcs in clusters of galaxies. This algorithm is suited for automated surveys as well as individual arc detections. New methods are used for image smoothing and source detection. The smoothing is performed by so-called anisotropic diffusion, which maintains the shape of the arcs and does not disperse them. The algorithm is much more efficient in detecting arcs than other source finding algorithms and the detection by eye.

Frank Lenzen; Sabine Schindler; Otmar Scherzer

2003-11-25

135

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

136

Spectroscopic confirmation of redshifts predicted by gravitational lensing

NASA Astrophysics Data System (ADS)

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. 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 reach new limits, R = 24; the lensing magnification implies true source magnitudes as faint as R = 25. Statistically, our measured redshifts are in excellent agreement with those predicted from Kneib et al.'s lensing analysis, and this gives considerable support to the redshift distribution derived by the lensing inversion method for the more numerous and fainter arclets extending to R = 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 = 25.5 (B = 26-27) is low, (z = 0.8-1). We discuss this result in the context of redshift distributions estimated from multicolor photometry.

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

1998-03-01

137

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

138

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-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.

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

2014-02-18

139

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

2012-11-02

140

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

141

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

NASA Astrophysics Data System (ADS)

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 log-normal 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.

Marra, Valerio; Quartin, Miguel; Amendola, Luca

2013-09-01

142

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

143

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

144

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

145

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

146

Weak Lensing Mass of Nearby Clusters of Galaxies

We describe first results of a project to create weak lensing mass maps for a complete, X-ray luminosity-limited sample of 19 nearby (z < 0.1) southern galaxy clusters scheduled for Sunyaev-Zel'dovich observations by the Viper Telescope at the South Pole. We have collected data on 1/3 of the sample and present motivation for the project as well as projected mass maps of two clusters.

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

1999-09-01

147

Galactic Internet made possible by star gravitational lensing

NASA Astrophysics Data System (ADS)

In this paper we study how to create a radio bridge between the Sun and any other star made up by both the gravitational lenses of the Sun and that star. The alignment for this radio bridge to work is very strict, but the power-saving is enormous, due to the huge contributions of the two stars' lenses to the overall antenna gain of the system. In particular, we study in detail: The Sun-Alpha Centauri A radio bridge. The Sun-Barnard's star radio bridge. The Sun-Sirius A radio bridge. The radio bridge between the Sun and any Sun-like star located in the Galactic Bulge. The radio bridge between the Sun and a similar Sun-like star located inside the Andromeda galaxy (M31). Finally, we find the information channel capacity for each of the above radio bridges, putting thus a physical constraint to the maximum information transfer that will be enabled even by exploiting the stars as gravitational lenses. The conclusion is that a Galactic Internet is indeed physically possible. May be the Galactic Internet already is in existence, and was created long ago by civilizations more advanced than ours. But the potential for creating such a system has only recently been realized by Humans.

Maccone, Claudio

2013-02-01

148

Testing a new analytic model for gravitational lensing probabilities

We study gravitational lensing with a multiple lens plane approach, proposing a simple analytical model for the probability distribution function (PDF) of the dark matter convergence, kappa, for the different lens planes in a given cosmology as a function of redshift and smoothing angle, theta. The model is fixed solely by the variance of kappa, which in turn is fixed by the amplitude of the power spectrum, sigma_8. We test the PDF against a high resolution Tree-Particle-Mesh simulation and find that it is far superior to the Gaussian or the lognormal, especially for small values of theta probabilities of strong lensing by a single plane or by multiple planes. We find that for theta ~ 10 arcsec, a single plane accounts for almost all (~ 98%) of the strong lensing cases for source redshift unity. However, for a more typical source redshift of 4, about 12% of the strong lensing cases will result from the contribution of a secondary clump of matter along the line of sight, introducing a systematic error in the determination of the surface density of clusters, typically overestimating it by about 2-5%. We also find that matter inhomogenieties introduce a dispersion in the value of the angular diameter distance about its cosmological mean. The probable error relative to the mean increases with redshift to a value of about 8% for z ~ 6 and theta ~ 10 arcsec.

Sudeep Das; Jeremiah P. Ostriker

2005-12-29

149

Constraining fast radio burst progenitors with gravitational lensing

NASA Astrophysics Data System (ADS)

Fast Radio Bursts (FRBs) are new transient radio sources discovered recently. Because of the angular resolution restriction in radio surveys, no optical counter part has been identified yet so it is hard to determine the progenitor of FRBs. In this paper we propose to use radio lensing survey to constrain FRB progenitors. We show that, different types of progenitors lead to different probabilities for a FRB to be gravitationally lensed by dark matter halos in foreground galaxies, since different type progenitors result in different redshift distributions of FRBs. For example, the redshift distribution of FRBs arising from double stars shifts toward lower redshift than of the FRBs arising from single stars, because double stars and single stars have different evolution timescales. With detailed calculations, we predict that the FRB sample size for producing one lensing event varies significantly for different FRB progenitor models. We argue that this fact can be used to distinguish different FRB models and also discuss the practical possibility of using lensing observation in radio surveys to constrain FRB progenitors.

Li, ChunYu; Li, LiXin

2014-05-01

150

How to Measure Dark Energy with LSST's Strong Gravitational Lenses

NASA Astrophysics Data System (ADS)

Strong gravitational lensing is sensitive to dark energy (DE) via the combinations of angular diameter distances that appear in model predictions of the lens strength. Lenses with variable sources offer the most promise: the corresponding time delay distance has recently been shown to be measurable to 5% precision. Large samples of lensed quasars and supernovae will allow internal degeneracy-breaking and so enable the most direct access to the DE parameters, while multiple source-plane, compound lens systems may provide an alternative, complementary, H0-free probe. Its wide field survey and high cadence will enable LSST to provide a sample of several thousand measured time delays, two orders of magnitude larger than the current sample, and allow an independent, competitive Stage IV DE parameter measurement to be made. However, practical problems to be solved include: lens detection (which may be very sensitive to image quality and deblender performance); image and lightcurve modelling (which could be both CPU and manual labor-intensive); obtaining and analyzing high resolution spectro-imaging follow-up data; and interpreting the whole sample of lenses in the context of the well-studied subset.

Marshall, Philip J.; Treu, T.; Brunner, R. J.; Strong Lensing, LSST; Dark Energy Science Collaborations

2013-01-01

151

Sources of contamination to weak lensing tomography: redshift-dependent shear measurement bias

NASA Astrophysics Data System (ADS)

The current methods available to estimate gravitational shear from astronomical images of galaxies introduce systematic errors which can affect the accuracy of weak lensing cosmological constraints. We study the impact of KSB shape measurement bias on the cosmological interpretation of tomographic two-point weak lensing shear statistics. We use a set of realistic image simulations produced by the Shear Testing Programme (STEP) collaboration to derive shape measurement bias as a function of redshift. We define biased two-point weak lensing statistics and perform a likelihood analysis for two fiducial surveys. We present a derivation of the covariance matrix for tomography in real space and a fitting formula to calibrate it for non-Gaussianity. We find the biased aperture mass dispersion is reduced by ~20per cent at redshift ~1, and has a shallower scaling with redshift. This effect, if ignored in data analyses, biases ?8 and w0 estimates by a few per cent. The power of tomography is significantly reduced when marginalizing over a range of realistic shape measurement biases. For a Canada-France-Hawaii Telescope Legacy Survey (CFHTLS)-Wide-like survey, [?m, ?8] confidence regions are degraded by a factor of 2, whereas for a Kilo-Degree Survey (KIDS)-like survey the factor is 3.5. Our results are strictly valid only for KSB methods, but they demonstrate the need to marginalize over a redshift-dependent shape measurement bias in all future cosmological analyses.

Semboloni, Elisabetta; Tereno, Ismael; van Waerbeke, Ludovic; Heymans, Catherine

2009-08-01

152

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

153

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

154

Gravitationally lensed image simulations for the study of the substructure in galaxy clusters

As gravitational lensing is susceptible to all gravitating matter-both baryonic and dark-it provides a potentially clean way to study the mass distribution of galaxy clusters. We are particularly interested in the substructure ...

Peeples, Molly S

2005-01-01

155

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

156

CFHTLenS: The Environmental Dependence of Galaxy Halo Masses from Weak Lensing

We use weak gravitational lensing to analyse the dark matter halos around satellite galaxies in galaxy groups in the CFHTLenS dataset. This dataset is derived from the CFHTLS-Wide survey, and encompasses 154 sq. deg of high-quality shape data. Using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 10^9 Msun to 10^10.5 Msun into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily (~61%) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly (~87%) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, the lensing signal around HDE galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ~5...

Gillis, Bryan R; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; van Waerbeke, Ludovic; Bonnett, Christopher; Coupon, Jean; Fu, Liping; Hilbert, Stefan; Rowe, Barnaby T P; Schrabback, Tim; Semboloni, Elisabetta; van Uitert, Edo; Velander, Malin

2013-01-01

157

CFHTLenS: The Environmental Dependence of Galaxy Halo Masses from Weak Lensing

NASA Astrophysics Data System (ADS)

We use weak gravitational lensing to analyse the dark matter halos around satellite galaxies in galaxy groups in the CFHTLenS dataset. This dataset is derived from the CFHTLS-Wide survey, and encompasses 154 sq. deg of high-quality shape data. Using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 10^9 Msun to 10^10.5 Msun into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily 61%) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly 87%) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, the lensing signal around HDE galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ~500--1000 kpc, the typical separation between satellites and group centres. More importantly, the subhalos of HDE galaxies are less massive than those around LDE galaxies by a factor 0.65 +/- 0.12, significant at the 2.9 sigma level. A natural explanation is that the halos of satellite galaxies are stripped through tidal effects in the group environment. Our results are consistent with a typical tidal truncation radius of ~40 kpc.

Gillis, Bryan; Hudson, M. J.; Erben, T.; Heymans, C.; Hildebrandt, H.; Hoekstra, H.; Kitching, T. D.; Mellier, Y.; Miller, L.; van Waerbeke, L.; Bonnett, C.; Coupon, J.; Fu, L.; Hilbert, S.; Rowe, B.; Schrabback, T.; Semboloni, E.; van Uitert, E.; Velander, M.; Cfhtlens Team

2013-07-01

158

Effects of the complex mass distribution of dark matter halos on weak lensing cluster surveys

Gravitational lensing effects arise from the light ray deflection by all of the mass distribution along the line of sight. It is then expected that weak lensing cluster surveys can provide us true mass-selected cluster samples. With numerical simulations, we analyze the correspondence between peaks in the lensing convergence $\\kappa$-map and dark matter halos. Particularly we emphasize the difference between the peak $\\kappa$ value expected from a dark matter halo modeled as an isolated and spherical one, which exhibits a one-to-one correspondence with the halo mass at a given redshift, and that of the associated $\\kappa$-peak from simulations. For halos with the same expected $\\kappa$, their corresponding peak signals in the $\\kappa$-map present a wide dispersion. At an angular smoothing scale of $\\theta_G=1\\hbox{arcmin}$, our study shows that for relatively large clusters, the complex mass distribution of individual clusters is the main reason for the dispersion. The projection effect of uncorrelated structures does not play significant roles. The triaxiality of dark matter halos accounts for a large part of the dispersion, especially for the tail at high $\\kappa$ side. Thus lensing-selected clusters are not really mass-selected. (abridged)

J. Y. Tang; Z. H. Fan

2005-08-24

159

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

160

Weak lensing analysis of Cl 1358+62 using Hubble Space Telescope observations

We report on the detection of weak gravitational lensing of faint, distant background galaxies by Cl 1358+62, a cluster of galaxies at a redshift of z=0.33. The observations were made using the HST. The measured shear is consistent with a velocity dispersion of 780+-50 km/s. The weak lensing mass is slightly lower than dynamical estimates and agrees well with X-ray mass estimates. The mass distribution is elongated similar to the light. The axis ratio of 0.30+-0.15 and position angle of -21+-8 degrees were measured directly from the observed shear and agree very well with a previous strong lensing analysis. We estimate the mass-to-light ratio to be 90+-13 h50 M_sun/L_Vsun. The HST point spread function is highly anisotropic at the edges of the individual chips. This systematically perturbs the shapes of objects and we present a method for applying the appropriate correction.

H. Hoekstra; M. Franx; K. Kuijken; G. Squires

1997-11-10

161

HST Observations of 10 Two-Image Gravitational Lenses

We report on a program to obtain HST observations of galaxy-mass gravitational lens systems at optical and infrared wavelengths. Here we discuss the properties of 10 two-image gravitational lens systems (Q0142-100=UM673, B0218+357, SBS0909+532, BRI0952-0115, LBQS1009-0252, Q1017-207=J03.13, B1030+074, HE1104-1805, Q1208+1011, and PKS1830-211). We grouped these 10 systems because they have limited lens model constraints and often show poor contrast between the images and the lens galaxy. Of the 10 lens galaxies, 7 are probably early-type galaxies, 2 are probably late-type galaxies (B0218+357 and PKS1830-211), and one was not detected (Q1208+1011). We detect the host galaxies of the z_s=4.50 lensed quasar in BRI0952-0115, the z_s=2.32 lensed quasar in HE1104-1805, and the unlensed z=1.63 quasar near LBQS1009-0252. We fit a set of four standard lens models to each lens that had sufficient constraints to compare isothermal dark matter and constant mass-to-light lens models, and to explore the effects of local tidal shears.

J. Lehar; E. Falco; C. Kochanek; B. McLeod; J. Munoz; C. Impey; H-W. Rix; C. Keeton; C. Peng

1999-09-03

162

A gravitationally lensed water maser in the early Universe.

Water masers are found in dense molecular clouds closely associated with supermassive black holes at the centres of active galaxies. On the basis of the understanding of the local water-maser luminosity function, it was expected that masers at intermediate and high redshifts would be extremely rare. However, galaxies at redshifts z > 2 might be quite different from those found locally, not least because of more frequent mergers and interaction events. Here we use gravitational lensing to search for masers at higher redshifts than would otherwise be possible, and find a water maser at redshift 2.64 in the dust- and gas-rich, gravitationally lensed type-1 quasar MG J0414+0534 (refs 6-13). The isotropic luminosity is 10,000 (, solar luminosity), which is twice that of the most powerful local water maser and half that of the most distant maser previously known. Using the locally determined luminosity function, the probability of finding a maser this luminous associated with any single active galaxy is 10(-6). The fact that we see such a maser in the first galaxy we observe must mean that the volume densities and luminosities of masers are higher at redshift 2.64. PMID:19092930

Impellizzeri, C M Violette; McKean, John P; Castangia, Paola; Roy, Alan L; Henkel, Christian; Brunthaler, Andreas; Wucknitz, Olaf

2008-12-18

163

Weak-lensing statistics from the Coyote Universe

NASA Astrophysics Data System (ADS)

Analysing future weak-lensing data sets from KIDS, Dark Energy Survey (DES), LSST, Euclid and WFIRST requires precise predictions for the weak-lensing measures. In this paper, we present a weak-lensing prediction code based on the Coyote Universe emulator. The Coyote Universe emulator predicts the (non-linear) power spectrum of density fluctuations (P?) to high accuracy for k?[0.002; 3.4] h Mpc-1 within the redshift interval z?[0; 1]; outside this regime, we extend P? using a modified HALOFIT code. This pipeline is used to calculate various second-order cosmic shear statistics, e.g., shear power spectrum, shear-shear correlation function, ring statistics and Complete Orthogonal Set of EB-mode Integrals (COSEBIs), and we examine how the upper limit in k (and z), to which P? is known, impacts on these statistics. For example, we find that kmax˜ 8 h Mpc-1 causes a bias in the shear power spectrum at ?˜ 4000 that is comparable to the statistical errors (intrinsic shape noise and cosmic variance) of a DES-like survey, whereas for LSST-like errors kmax˜ 15 h Mpc-1 is needed to limit the bias at ?˜ 4000. For the most recently developed second-order shear statistics, the COSEBIs, we find that nine modes can be calculated accurately knowing P? to kmax= 10 h Mpc-1. The COSEBIs allow for an EB-mode decomposition using a shear-shear correlation function measured over a finite range, thereby avoiding any EB-mode mixing due to finite survey size. We perform a detailed study in a five-dimensional parameter space in order to examine whether all cosmological information is captured by these nine modes with the result that already 7-8 modes are sufficient.

Eifler, Tim

2011-11-01

164

Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing Through Galaxy Clustering

We report the serendipitous discovery of two strong gravitational lens candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, each less than 40'' from the previously known gravitational lens system CLASS B1608+656. The redshifts of both lens galaxies have been measured with Keck and Gemini: one is a member of a small galaxy group at z {approx} 0.63, which also includes the lensing galaxy in the B1608+656 system, and the second is a member of a foreground group at z {approx} 0.43. By measuring the effective radii and surface brightnesses of the two lens galaxies, we infer their velocity dispersions based on the passively evolving Fundamental Plane (FP) relation. Elliptical isothermal lens mass models are able to explain their image configurations within the lens hypothesis, with a velocity dispersion compatible with that estimated from the FP for a reasonable source-redshift range. Based on the large number of massive early-type galaxies in the field and the number-density of faint blue galaxies, the presence of two additional lens systems around CLASS B1608+656 is not unlikely in hindsight. Gravitational lens galaxies are predominantly early-type galaxies, which are clustered, and the lensed quasar host galaxies are also clustered. Therefore, obtaining deep high-resolution images of the fields around known strong lens systems is an excellent method of enhancing the probability of finding additional strong gravitational lens systems.

Fassnacht, Chris D.; McKean, J.P.; Koopmans, L.V.E.; Treu, T.; Blandford, R.D.; Auger, M.W.; Jeltema, T.E.; Lubin, L.M.; Margoniner, V.E.; Wittman, D.; /UC, Davis

2006-04-03

165

Hubble Space Telescope Weak-Lensing Study of the z=0.83 Cluster MS 1054-03

We have measured the weak gravitational lensing of faint, distant background galaxies by MS 1054-03, a rich and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a two-color mosaic of deep WFPC2 images. The small corrections for the size of the point-spread function and the high number density of background galaxies obtained in these observations result in

H. Hoekstra; M. Franx; K. Kuijken

2000-01-01

166

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), which 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.

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

2014-09-04

167

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

168

The gravitationally lensed galaxy IRAS FSC10214+4724

NASA Astrophysics Data System (ADS)

We present a multi-wavelength analysis of IRAS FSC10214+4724 from radio to X-ray wavelengths. This is a gravitationally lensed galaxy at a redshift z=2.3 (3 Gyr after the Big Bang) which hosts prodigious star formation as well as an obscured active nucleus. We derive a new lens model for the system employing a Bayesian Markov Chain Monte Carlo algorithm with extended-source, forward ray-tracing. An array of spatially resolved maps (radio, millimetre, near-infrared, optical) trace different physical components which enables a high resolution, multi-wavelength view of a high-redshift galaxy beyond the capabilities of current telescopes. The spatially-resolved molecular gas total intensity and velocity maps reveal a reasonably ordered system, however there is evidence for minor merger activity. We show evidence for an extended, low-excitation gas reservoir that either contains roughly half the total gas mass or has a different CO-to-H_2 conversion ratio. Very Long Baseline Interferometry (VLBI) is used to detect what we argue to be the obscured active nucleus with an effective angular resolution of <50 pc at z=2.3. The source plane inversion places the VLBI detection to within milli-arcseconds of the modeled cusp caustic, resulting in a very large magnification (mu > 70) which is over an order of magnitude larger than the derived co magnification. This implies an equivalent magnification difference between the starburst and AGN components, yielding significant distortion to the global continuum spectral energy distribution (SED). A primary result of this work is therefore the demonstration that emission regions of differing size and position within a galaxy can experience significantly different magnification factors (> 1 dex) and therefore distort our view of high-redshift, gravitationally lensed sources. This not only raises caution against unsophisticated uses of IRAS FSC10214+4724 as an archetype high-redshift Ultra-Luminous Infra-Red Galaxy (ULIRG), but also against statistical deductions based on samples of strong lenses with poorly constrained lens models and spatially-unresolved detections. Analogous to the continuum SED distortion quantified in this thesis, we predict a distortion of the CO spectral line energy distribution of IRAS FSC10214+4724 where higher order J lines, that are increasingly excited by the AGN and shock heating from the central starburst, will be preferentially lensed owing to their smaller solid angles and closer proximity to the AGN, and therefore the cusp of the caustic.

Deane, Roger Paul

169

CFHTLenS: the environmental dependence of galaxy halo masses from weak lensing

NASA Astrophysics Data System (ADS)

We use weak gravitational lensing to analyse the dark matter haloes around satellite galaxies in galaxy groups in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) data set. This data set is derived from the Canada-France-Hawaii Telescope Legacy Survey Wide survey, and encompasses 154 deg2 of high-quality shape data. Using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 109-1010.5 M? into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily (˜61 per cent) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly (˜87 per cent) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, the lensing signal around HDE galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ˜500-1000 kpc, the typical separation between satellites and group centres. More importantly, the subhaloes of HDE galaxies are less massive than those around LDE galaxies by a factor of 0.65 ± 0.12, significant at the 2.9? level. A natural explanation is that the haloes of satellite galaxies are stripped through tidal effects in the group environment. Our results are consistent with a typical tidal truncation radius of ˜40 kpc.

Gillis, Bryan R.; Hudson, Michael J.; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; van Waerbeke, Ludovic; Bonnett, Christopher; Coupon, Jean; Fu, Liping; Hilbert, Stefan; Rowe, Barnaby T. P.; Schrabback, Tim; Semboloni, Elisabetta; van Uitert, Edo; Velander, Malin

2013-05-01

170

Gravitational waves propagate along null geodesics like light rays in the geometrical optics approximation, and they may have a chance to suffer from gravitational lensing by intervening objects, as is the case for electromagnetic waves. Long wavelengths of gravitational waves and compactness of possible sources may enable us to extract information in the interference among the lensed images. We point out that the interference term contains information of relative transverse velocity of the source-lens-observer system, which may be obtained by possible future space-borne gravitational wave detectors such as BBO/DECIGO.

Itoh, Yousuke; Futamase, Toshifumi; Hattori, Makoto [Astronomical Institute, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan)

2009-08-15

171

Gravitational lensing and the angular-diameter distance relation

We show that the usual relation between redshift and angular-diameter distance can be obtained by considering light from a source to be gravitationally lensed by material that lies in the telescope beam as it passes from source to observer through an otherwise empty universe. This derivation yields an equation for the dependence of angular diameter on redshift in an inhomogeneous universe. We use this equation to model the distribution of angular-diameter distance for redshift z=3 in a realistically clustered cosmology. The distribution is such that attempts to determine q_0 from angular-diameter distances will systematically underestimate q_0 by ~0.15, and large samples would be required to beat down the intrinsic dispersion in measured values of q_0.

Fedja Hadrovic; James Binney

1997-08-12

172

Why Quasar Pairs Are Binary Quasars And Not Gravitational Lenses

We use simple comparisons of the optical and radio properties of the wide separation (3'' to 10'') quasar pairs to demonstrate that they are binary quasars rather than gravitational lenses. The most likely model is that all the pairs are binary quasars, with a one-sided 2--sigma (1--sigma) upper limit of 22% (8%) on the lens fraction. Simple models for the expected enhancement of quasar activity during galaxy mergers that are consistent with the enhancement observed at low redshift can explain the incidence, separations, redshifts, velocity differences, and radio properties of the binary quasar population. Only a modest fraction (quasar activity need be associated with galaxy mergers to explain the binary quasars.

C. S. Kochanek; E. E. Falco; J. A. Munoz

1997-10-15

173

Deflection of light and particles by moving gravitational lenses

Various authors have investigated the problem of light deflection by radially moving gravitational lenses - with inconsistent results. In this paper we generalize the calculations for arbitrary lens velocities and show that, to first order in the lens velocity v, the deflection angles scales with 1-v. We discuss the seeming inconsistency of relativistic light deflection with the classical picture of moving test particles by generalizing the lens effect to test particles of arbitrary velocity, including light as a limiting case. We show that the effect of radial motion of the lens is very different for slowly moving test particles and light and that a critical test particle velocity exists for which the motion of the lens has no effect on the deflection angle to first order. An interesting and not immediately intuitive result is obtained in the limit of a highly relativistic motion of the lens towards the observer, where the deflection angle of light reduces to zero. This phenomenon is elucidated in terms of moving refractive media. Furthermore, we discuss the dragging of inertial frames in the field of a moving lens and the corresponding Lense-Thirring precession, in order to shed more light on the geometrical effects in the surroundings of a moving mass. In a second part we discuss the effect of transversal motion on the observed redshift of lensed sources. We demonstrate how a simple kinematic calculation explains the effects for arbitrary velocities of the lens and test particles. Additionally we include the transversal motion of the source and observer to show that all three velocities can be combined into an effective relative transversal velocity similar to the approach used in microlensing studies.

Olaf Wucknitz; Ulrich Sperhake

2004-01-19

174

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

175

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

176

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

177

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

178

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

179

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

180

The Density Profile of Massive Galaxy Clusters from Weak Lensing

We use measurements of weak gravitational shear around a sample of massive galaxy clusters at z = 0.3 to constrain their average radial density profile. Our results are consistent with the density profiles of CDM halos in numerical simulations and inconsistent with simple models of self-interacting dark matter. Unlike some other recent studies, we are not probing the scales where the baryonic mass component becomes dynamically important, and so our results should be directly comparable to CDM N-body simulations.

H. Dahle

2003-10-20

181

Modelling of the complex CASSOWARY/SLUGS gravitational lenses

NASA Astrophysics Data System (ADS)

We present the first high-resolution images of CSWA 31, a gravitational lens system observed as part of the Sloan Lenses Unravelled by Gemini Studies programme. These systems exhibit complex image structure with the potential to strongly constrain the mass distribution of the massive lens galaxies, as well as the complex morphology of the sources. In this paper, we describe the strategy used to reconstruct the unlensed source profile and the lens galaxy mass profiles. We introduce a prior distribution over multiwavelength sources that is realistic as a representation of our knowledge about the surface brightness profiles of galaxies and groups of galaxies. To carry out the inference computationally, we use diffusive nested sampling, an efficient variant of nested sampling that uses Markov Chain Monte Carlo to sample the complex posterior distributions and compute the normalizing constant. We demonstrate the efficacy of this approach with the reconstruction of the group-group gravitational lens system CSWA 31, finding the source to be composed of five merging spiral galaxies magnified by a factor of 13.

Brewer, Brendon J.; Lewis, Geraint F.; Belokurov, Vasily; Irwin, Michael J.; Bridges, Terry J.; Evans, N. Wyn

2011-04-01

182

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

183

Gravitational Lensing of High Redshift Type Ia Supernova A Probe of Medium Scale Structure

Gravitational lensing will magnify and demagnify high redshift type Ia supernovae. The dispersion in the peak magnitudes due to this effect approaches the size of the intrinsic dispersion at z >~ 1. I propose a statistical method for measuring this effect. It is shown that the added dispersion is related to a^{-2} k P(k) which makes it sensitive to halo scale density structure - smaller scale structure than is accessible to measurements of lensing by large scale structure through galaxy shear. Using cold dark matter models it is estimated that the amount and quality of data needed is attainable in the next few years. A parameterization of the signal is motivated by these models. The signal is found to be highly dependent on scales where structure is nonlinear and weakly dependent on the Hubble parameter. The lensing's redshift dependence is related to the evolution of medium scale structure between the present and z ~ 0.5-1.5. The skewness of the magnification distribution is discussed and interpreted in term...

Metcalf, R B

1999-01-01

184

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

185

Analytical Kerr-Sen dilaton-axion black hole lensing in the weak deflection limit

We investigate analytical gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black holes in the weak-deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b, and r{sub {alpha}/}b, where M is the black hole mass, a is the angular momentum, r{sub {alpha}=}Q{sup 2}/M, Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images, the corresponding signed and absolute magnifications up to post-Newtonian order. It is shown that there are static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are functions of the charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The pointlike caustics drift away from the optical axis and do not depend on the charge. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

Gyulchev, Galin N.; Yazadjiev, Stoytcho S. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria)

2010-01-15

186

Up to 100,000 reliable strong gravitational lenses in future dark energy experiments

The Euclid space telescope will observe ~10^5 strong galaxy-galaxy gravitational lens events in its wide field imaging survey over around half the sky, but identifying the gravitational lenses from their observed morphologies requires solving the difficult problem of reliably separating the lensed sources from contaminant populations, such as tidal tails, as well as presenting challenges for spectroscopic follow-up redshift campaigns. Here I present alternative selection techniques for strong gravitational lenses in both Euclid and the Square Kilometer Array, exploiting the strong magnification bias present in the steep end of the Halpha luminosity function and HI mass function. Around 10^3 strong lensing events are detectable with this method in the Euclid wide survey. While only ~1% of the total haul of Euclid lenses, this sample has ~100% reliability, known source redshifts, high signal-to-noise and a magnification-based selection independent of assumptions of lens morphology. With the proposed Square Kilo...

Serjeant, Stephen

2014-01-01

187

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

188

Gravitational lensing in the supernova legacy survey (SNLS)

NASA Astrophysics Data System (ADS)

Aims: The observed brightness of type Ia supernovae is affected by gravitational lensing caused by the mass distribution along the line of sight, which introduces an additional dispersion into the Hubble diagram. We look for evidence of lensing in the SuperNova Legacy Survey 3-year data set. Methods: We investigate the correlation between the residuals from the Hubble diagram and the gravitational magnification based on a modeling of the mass distribution of foreground galaxies. A deep photometric catalog, photometric redshifts, and well established mass luminosity relations are used. Results: We find evidence of a lensing signal with a 2.3? significance. The current result is limited by the number of SNe, their redshift distribution, and the other sources of scatter in the Hubble diagram. Separating the galaxy population into a red and a blue sample has a positive impact on the significance of the signal detection. On the other hand, increasing the depth of the galaxy catalog, the precision of photometric redshifts or reducing the scatter in the mass luminosity relations have little effect. We show that for the full SuperNova Legacy Survey sample (~400 spectroscopically confirmed type Ia SNe and ~200 photometrically identified type Ia SNe), there is an 80% probability of detecting the lensing signal with a 3? significance. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. Based on observations obtained at the European Southern Observatory using the Very Large Telescope on the Cerro Paranal (ESO Large Program 171.A-0486 & 176.A-0589). Based on observations (programs GS-2003B-Q-8, GN-2003B-Q-9, GS-2004A-Q-11, GN-2004A-Q-19, GS-2004B-Q-31, GN-2004B-Q-16, GS-2005A-Q-11, GN-2005A-Q-11, GS-2005B-Q-6, GN-2005B-Q-7, GN-2006A-Q-7, GN-2006B-Q-10, GN-2007A-Q-8) obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil) and CONICET (Argentina). Based on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Kronborg, T.; Hardin, D.; Guy, J.; Astier, P.; Balland, C.; Basa, S.; Carlberg, R. G.; Conley, A.; Fouchez, D.; Hook, I. M.; Howell, D. A.; Jönsson, J.; Pain, R.; Pedersen, K.; Perrett, K.; Pritchet, C. J.; Regnault, N.; Rich, J.; Sullivan, M.; Palanque-Delabrouille, N.; Ruhlmann-Kleider, V.

2010-05-01

189

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

190

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

191

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

192

Optimized detection of shear peaks in weak lensing maps

NASA Astrophysics Data System (ADS)

We present a new method to extract cosmological constraints from weak lensing (WL) peak counts, which we denote as ‘the hierarchical algorithm’. The idea of this method is to combine information from WL maps sequentially smoothed with a series of filters of different size, from the largest down to the smallest, thus increasing the cosmological sensitivity of the resulting peak function. We compare the cosmological constraints resulting from the peak abundance measured in this way and the abundance obtained by using a filter of fixed size, which is the standard practice in WL peak studies. For this purpose, we employ a large set of WL maps generated by ray tracing through N-body simulations, and the Fisher matrix formalism. We find that if low signal-to-noise ratio (?) peaks are included in the analysis (?), the hierarchical method yields constraints significantly better than the single-sized filtering. For a large future survey such as Euclid or Large Synoptic Survey Telescope, combined with information from a cosmic microwave background experiment like Planck, the results for the hierarchical (single-sized) method are ?ns= 0.0039 (0.004), ??m= 0.002 (0.0045), ??8= 0.003 (0.006) and ?w= 0.019 (0.0525). This forecast is conservative, as we assume no knowledge of the redshifts of the lenses, and consider a single broad bin for the redshifts of the sources. If only peaks with ? are considered, then there is little difference between the results of the two methods. We also examine the statistical properties of the hierarchical peak function: Its covariance matrix has off-diagonal terms for bins with ? and aperture mass of M < 3 × 1014 h-1 M?, the higher bins being largely uncorrelated and therefore well described by a Poisson distribution.

Marian, Laura; Smith, Robert E.; Hilbert, Stefan; Schneider, Peter

2012-06-01

193

Weakly bound states of neutrons in gravitational fields

In this paper a quantum-mechanical behaviour of neutrons in gravitational fields is considered. A first estimation is made using the semiclassical approximation, neglecting General Relativity, magnetic and rotation effects, for neutrons in weakly bound states in the weak gravitational field of the Earth. This result was generalized for a case, in which the Randall - Sundrum correction to Newton's gravitational law on the small scales was applied. Application of the results to Neutron Star physics is considered and further possible perspectives are discussed.

Avas V. Khugaev; Renat A. Sultanov; Dennis Guster

2010-12-24

194

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 o...

Melia, Fulvio; Wu, Xue-Feng

2014-01-01

195

Strong and weak gravitational field in $R+?^4/R$ gravity

We introduce a new approach for investigating the weak field limit of vacuum field equations in $f(R)$ gravity and we find the weak field limit of $f(R)=R+\\mu ^4/R$ gravity. Furthermore, we study the strong gravity regime in $R+\\mu^{4}/R$ model of $f(R)$ gravity. We show the existence of strong gravitational field in vacuum for such model. We find out in the limit $\\mu\\rightarrow 0$, the weak field limit and the strong gravitational field can be regarded as a perturbed Schwarzschild metric.

Kh. Saaidi; A. Vajdi; S. W. Rabiei; A. Aghamohammadi; H. Sheikhahmadi

2010-01-25

196

Weak lensing measurements in simulations of radio images

NASA Astrophysics Data System (ADS)

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 shapelet 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 shapelet ellipticities. We model and deconvolve the effective point spread function, 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 per cent) multiplicative bias on the ellipticity measurements. Our simulation pipeline can be used to test shear measurement procedures and systematics for the next generation of radio telescopes.

Patel, Prina; Abdalla, Filipe B.; Bacon, David J.; Rowe, Barnaby; Smirnov, Oleg M.; Beswick, Rob J.

2014-11-01

197

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

198

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

199

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

200

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

201

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

202

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

203

Mock weak lensing analysis of simulated galaxy clusters: bias and scatter in mass and concentration

(Abridged) We quantify the bias and scatter in galaxy cluster masses M200 and concentrations c derived from a mock weak gravitational lensing (WL) survey, and their effect on the cluster mass-concentration relation. For this, we simulate WL distortions on a population of background galaxies due to a large (approx. 3000) sample of galaxy cluster haloes extracted from the Millennium Simulation at z=0.2. While the normalisation of the derived M200-c relation agrees with the underlying true relation the slope is marginally too steep, owing to a bias in WL-derived concentrations that decreases from +11% for M200 10^14.8 Msun. There is also a small bias in the derived mass (approx. -6%), whose magnitude depends only very weakly on true halo mass. Both the mass and concentration derived from WL show considerable scatter about their true values; this decreases slightly over the above mass range (from ~55% to ~30% for concentration and from ~35% to ~20% for mass). The scatter and bias in mass are shown to be largely ...

Bahé, Yannick M; King, Lindsay J

2011-01-01

204

We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (Omega0+lambda0=1). It is shown that some of the lens observables are strongly affected by the cosmological constant, especially in a low-density universe, and its existence might be inferred by a statistical study of the lenses. In particular, the optical depth of the

Deepak Jain; N. Panchapakesan; S. Mahajan; V. B. Bhatia

1998-01-01

205

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

206

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''.04) 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.

Inada, N; Burles, S; Gregg, M D; Becker, R H; Schechter, P L; Eisenstein, D J; Oguri, M; Castander, F J; Hall, P B; Johnston, D E; Pindor, B; Richards, G T; Schneider, D P; White, R L; Brinkmann, J; Szalay, A; York, D G

2005-11-10

207

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

208

Gravitational lensing in WDM cosmologies: The cross section for giant arcs

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 {\\Lambda}CDM and observations of gravitationally lensed galaxies. Previous studies showed that galaxy clusters in the {\\Lambda}CDM are not strong enough to reproduce the observed number of lensed arcs. This work aims to constrain the warm dark matter 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 ({\\Lambda}WDM) and cold dark matter ({\\Lambda}CDM) cosmologies have been studied. The results show that even though the CDM clusters are more centrally concentrated and contain more substructures, the WDM clusters have slightly higher lensing efficiency than their CDM counterparts. The key differenc...

Mahdi, Hareth; Elahi, Pascal; Lewis, Geraint; Power, Chris; Killedar, Madhura

2014-01-01

209

SDSS J094604.90+183541.8: A GRAVITATIONALLY LENSED QUASAR AT z = 4.8

We report the discovery of a gravitationally lensed quasar identified serendipitously in the Sloan Digital Sky Survey (SDSS). The object, SDSS J094604.90+183541.8, was initially targeted for spectroscopy as a luminous red galaxy, but the SDSS spectrum has the features of both a z = 0.388 galaxy and a z = 4.8 quasar. We have obtained additional imaging that resolves the system into two quasar images separated by 3.''06 and a bright galaxy that is strongly blended with one of the quasar images. We confirm spectroscopically that the two quasar images represent a single-lensed source at z = 4.8 with a total magnification of 3.2, and we derive a model for the lensing galaxy. This is the highest redshift lensed quasar currently known. We examine the issues surrounding the selection of such an unusual object from existing data and briefly discuss implications for lensed quasar surveys.

McGreer, Ian D.; Fan Xiaohui; Bian Fuyan; Farnsworth, Kara [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Hall, Patrick B. [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON, M3J 1P3 (Canada); Inada, Naohisa [Cosmic Radiation Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Oguri, Masamune [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Strauss, Michael A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)

2010-08-15

210

We report the detection of a significant (5.5 sigma) excess of correlations between galaxy ellipticities at scales ranging from 0.5 to 3.5 arc-minutes. This detection of a gravitational lensing signal by large-scale structure was made using a composite high quality imaging survey of 6300 arcmin^2 obtained at the Canada France Hawaii Telescope (CFHT) with the UH8K and CFH12K panoramic CCD cameras. The amplitude of the excess correlation is 2.2\\pm 0.2 % at 1 arcmin scale, in agreement with theoretical predictions of the lensing effect induced by large-scale structure.We provide a quantitative analysis of systematics which could contribute to the signal and show that the net effect is small and can be corrected for. We show that the measured ellipticity correlations behave as expected for a gravitational shear signal. The relatively small size of our survey precludes tight constraints on cosmological models. However the data are in favor of cluster normalized cosmological models, and marginally reject Cold Dark Matter models with (Omega=0.3, sigma_8<0.6) or (Omega=1, sigma_8=1). The detection of cosmic shear demonstrates the technical feasibility of using weak lensing surveys to measure dark matter clustering and the potential for cosmological parameter measurements, in particular with upcoming wide field CCD cameras.

L. Van Waerbeke; Y. Mellier; T. Erben; J. C. Cuillandre; F. Bernardeau; R. Maoli; E. Bertin; H. J. Mc Cracken; O. Le Fevre; B. Fort; M. Dantel-Fort; B. Jain; P. Schneider

2000-02-27

211

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

212

Discovery of a new component in the gravitationally lensed quasar 0957 + 561

NASA Technical Reports Server (NTRS)

X-ray observations of the gravitationally lensed quasar 0957 + 561 with the Einstein Observatory High Resolution Imager indicate the presence of a new component in the system. The significantly greater X-ray intensity of image A compared with image B and the extended X-ray emission can be interpreted as the gravitational lensing of a quasi-circular X-ray emitting region into a partial Einstein ring. It is suggested that the observed X-ray emission is produced by a strong cooling flow which could arise were 0957 + 561 embedded in a group of cluster galaxies.

Jones, C.; Stern, C.; Falco, E.; Forman, W.; David, L.; Shapiro, I.; Fabian, A. C.

1993-01-01

213

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

214

Resolved Spectroscopy of a Gravitationally Lensed L* Lyman-break Galaxy at z~5

By combining HST imaging with optical (VIMOS) and near-infrared (SINFONI)\\u000aintegral field spectroscopy we exploit the gravitational potential of a\\u000amassive, rich cluster at z=0.9 to study the internal properties of a\\u000agravitationally lensed galaxy at z=4.88. Using a detailed gravitational lens\\u000amodel of the cluster RCS0224-002 we reconstruct the source-frame morphology of\\u000athe lensed galaxy on 200pc scales and

A. M. Swinbank; R. G. Bower; Graham P. Smith; R. J. Wilman; Ian Smail; R. S. Ellis; S. L. Morris; J.-P. Kneib

2007-01-01

215

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

216

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

2008-07-30

217

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

218

3D Weak Gravitational Lensing of the CMB and Galaxies

In this paper we present a power spectrum formalism that combines the full three-dimensional information from the galaxy ellipticity field, with information from the cosmic microwave background (CMB). We include in this approach galaxy cosmic shear and galaxy intrinsic alignments, CMB deflection, CMB temperature and CMB polarisation data; including the inter-datum power spectra between all quantities. We apply this to forecasting cosmological parameter errors for CMB and imaging surveys and show that the additional covariance between the CMB and ellipticity measurements can improve galaxy intrinsic alignment measurements by a factor of two, and dark energy equation of state measurements by thirty percent. We present predictions for Euclid-like, KiDS, ACTPoL, and CoRE-like experiments and show that the combination of cosmic shear and the CMB, from Euclid-like and CoRE-like experiments, can measure the sum of neutrino masses with an error of 0.02 eV, and the dark energy equation of state with an error on w0 of ...

Kitching, T D; Das, S

2014-01-01

219

Testing gravity on kiloparsec scales with strong gravitational lenses

Modifications to GR generically predict time and scale-dependent effects which may be probed by observations of strong lensing by galaxies. Measurements of the stellar velocity dispersion determine the dynamical mass whereas measurements of the Einstein radius determine the lensing mass. In GR these two masses are equal; in alternative gravity theories they may not be. Using measurements of the stellar velocity dispersion and strong lensing around galaxies from the Sloan Lens ACS (SLACS) survey we place constraints on lensing in modified gravity theories and extend previous studies by applying this data to explore its dependence on various properties of the lens such as the lens redshift or mass and thereby constrain scalar-tensor, f(R) gravity theories, and generic parameterizations of deviations from GR. Besides applying the observations to these specific gravity theories, the data places a constraint on a generic dependence of modifications to GR on the lens mass and redshift. At the 68% confidence level we find that the ratio between the lensing and dynamical masses can only vary by less then 50% over a mass range for the lens galaxies of 1E12 < M/Msun < 1E14 and less than 40% over the redshift range 0.06 < z < 0.36.

Tristan L. Smith

2009-07-28

220

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

221

Reducing the gravitational lensing scatter of Type Ia supernovae without introducing any extra bias

Magnification and de-magnification due to gravitational lensing will contribute to the brightness scatter of Type Ia supernovae (SNe Ia). The purpose of this paper is to investigate the possibility to decrease this scatter by correcting individual SNe Ia using observations of galaxies in the foreground, without introducing any extra bias. We simulate a large number of SN Ia lines of sight populated by galaxies. For each line of sight the true magnification factor and an estimate thereof are calculated. The estimated magnification factor corresponds to what an observer would infer from a survey like SNLS. Using the simulated data we investigate the possibility to estimate the magnification of individual supernovae with enough precision to be able to correct their brightness for gravitational lensing with negligible bias. Our simulations show that the bias arising from gravitational lensing corrections of individual SNe Ia is negligible for current and next generation surveys and that the scatter from lensing can be reduced by approximately a factor 2. The total scatter in the SN Ia magnitudes could be reduced by 4% for an intrinsic dispersion of 0.13 mag. For an intrinsic dispersion of 0.09 mag, which might not be to unrealistic for future surveys, the total scatter could be reduced by 6%. This will reduce the errors on cosmological parameters derived from supernova data by 4-8%. The prospect of correcting for lensing is thus very good.

Jakob Jonsson; Edvard Mortsell; Jesper Sollerman

2008-10-23

222

Cross-correlating Sunyaev-Zel'dovich and weak lensing maps

NASA Astrophysics Data System (ADS)

We present novel statistical tools to cross-correlate frequency cleaned thermal Sunyaev-Zel'dovich (tSZ) maps and tomographic weak lensing (wl) convergence maps. Moving beyond the lowest order cross-correlation, we introduce a hierarchy of mixed higher order statistics, the cumulants and cumulant correlators, to analyse non-Gaussianity in real space, as well as corresponding polyspectra in the harmonic domain. Using these moments, we derive analytical expressions for the joint two-point probability distribution function for smoothed tSZ (y) and convergence (?) maps. The presence of tomographic information allows us to study the evolution of higher order mixed tSZ-wl statistics with redshift. We express the joint PDFs p?y(?, y) in terms of individual one-point PDFs [p?(?), py(y)] and the relevant bias functions [b?(?), by(y)]. Analytical results for two different regimes are presented that correspond to the small and large angular smoothing scales. Results are also obtained for corresponding hotspots in the tSZ and convergence maps. In addition to results based on hierarchical techniques and perturbative methods, we present results of calculations based on the lognormal approximation. The analytical expressions derived here are generic and applicable to cross-correlation studies of arbitrary tracers of large-scale structure including, e.g., that of tSZ and soft X-ray background. We provide detailed comparison of our analytical results against state of the art Millennium Gas Simulations with and without non-gravitational effects such as pre-heating and cooling. Comparison of these results with gravity only simulations, shows reasonable agreement and can be used to isolate effect of non-gravitational physics from observational data.

Munshi, Dipak; Joudaki, Shahab; Coles, Peter; Smidt, Joseph; Kay, Scott T.

2014-07-01

223

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

224

CLASH: Weak-lensing Shear-and-magnification Analysis of 20 Galaxy Clusters

NASA Astrophysics Data System (ADS)

We present a joint shear-and-magnification weak-lensing analysis of a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19 <~ z <~ 0.69 selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). Our analysis uses wide-field multi-color imaging, taken primarily with Suprime-Cam on the Subaru Telescope. From a stacked-shear-only analysis of the X-ray-selected subsample, we detect the ensemble-averaged lensing signal with a total signal-to-noise ratio of ~= 25 in the radial range of 200-3500 kpc h –1, providing integrated constraints on the halo profile shape and concentration-mass relation. The stacked tangential-shear signal is well described by a family of standard density profiles predicted for dark-matter-dominated halos in gravitational equilibrium, namely, the Navarro-Frenk-White (NFW), truncated variants of NFW, and Einasto models. For the NFW model, we measure a mean concentration of c200c=4.01+0.35-0.32 at an effective halo mass of M200c=1.34+0.10-0.09× 1015 M_?. We show that this is in excellent agreement with ? cold dark matter (?CDM) predictions when the CLASH X-ray selection function and projection effects are taken into account. The best-fit Einasto shape parameter is ? _E=0.191+0.071-0.068, which is consistent with the NFW-equivalent Einasto parameter of ~0.18. We reconstruct projected mass density profiles of all CLASH clusters from a joint likelihood analysis of shear-and-magnification data and measure cluster masses at several characteristic radii assuming an NFW density profile. We also derive an ensemble-averaged total projected mass profile of the X-ray-selected subsample by stacking their individual mass profiles. The stacked total mass profile, constrained by the shear+magnification data, is shown to be consistent with our shear-based halo-model predictions, including the effects of surrounding large-scale structure as a two-halo term, establishing further consistency in the context of the ?CDM model. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.

Umetsu, Keiichi; Medezinski, Elinor; Nonino, Mario; Merten, Julian; Postman, Marc; Meneghetti, Massimo; Donahue, Megan; Czakon, Nicole; Molino, Alberto; Seitz, Stella; Gruen, Daniel; Lemze, Doron; Balestra, Italo; Benítez, Narciso; Biviano, Andrea; Broadhurst, Tom; Ford, Holland; Grillo, Claudio; Koekemoer, Anton; Melchior, Peter; Mercurio, Amata; Moustakas, John; Rosati, Piero; Zitrin, Adi

2014-11-01

225

Reducing the gravitational lensing scatter of type Ia supernovae without introducing any extra bias

Aims: Magnification and de-magnification due to gravitational lensing will contribute to the brightness scatter of type Ia supernovae (SNe Ia). The purpose of this paper is to investigate the possibility of decreasing this scatter by correcting individual SNe Ia using observations of galaxies in the foreground, without introducing any extra bias. Methods: We simulate a large number of SN Ia

J. Jönsson; E. Mörtsell; J. Sollerman

2009-01-01

226

Gravitational lensing provides a unique and powerful probe of the mass distributions of distant galaxies. Four-image lens systems with fold and cusp configurations have two or three bright images near a critical point. Within the framework of singularity theory, we derive analytic relations that are satisfied for a light source that lies a small but finite distance from the astroid

Arthur B. Congdon; Charles R. Keeton; C. Erik Nordgren

2008-01-01

227

Hubble Space Telescope weak lensing study of the z=0.83 cluster MS 1054-03

We have measured the weak gravitational lensing signal of MS 1054-03, a rich and X-ray luminous cluster of galaxies at a redshift of z=0.83, using a two-colour mosaic of deep WFPC2 images. The small corrections for the size of the PSF and the high number density of background galaxies obtained in these observations result in an accurate and well calibrated measurement of the lensing induced distortion. The strength of the lensing signal depends on the redshift distribution of the background galaxies. We used photometric redshift distributions from the Northern and Southern Hubble Deep Fields to relate the lensing signal to the mass. The predicted variations of the signal as a function of apparent source magnitude and colour agrees well with the observed lensing signal. We determine a mass of (1.2+-0.2)x10^15 Msun within an aperture of radius 1 Mpc. Under the assumption of an isothermal mass distribution, the corresponding velocity dispersion is 1311^{+83}_{-89} km/s. For the mass-to-light ratio we find 269+-37 Msun/Lsun. The errors in the mass and mass-to-light ratio include the contribution from the random intrinsic ellipticities of the source galaxies, but not the (systematic) error due to the uncertainty in the redshift distribution. However, the estimates for the mass and mass-to-light ratio of MS 1054-03 agree well with other estimators, suggesting that the mass calibration works well. The reconstruction of the projected mass surface density shows a complex mass distribution, consistent with the light distribution. The results indicate that MS 1054-03 is a young system. The timescale for relaxation is estimated to be at least 1 Gyr. Averaging the tangential shear around the cluster galaxies, we find that the velocity dispersion of an Lstar galaxy is 203+-33 km/s.

H. Hoekstra; M. Franx; K. Kuijken

1999-10-27

228

The Effect of the Cosmic Web on Cluster Weak Lensing Mass Estimates

In modern hierarchical theories of structure formation, rich clusters of galaxies form at the vertices of a weblike distribution of matter, with filaments emanating from them to large distances and with smaller objects forming and draining in along these filaments. The amount of mass contained in structure near the cluster can be comparable to the collapsed mass of the cluster itself. As the lensing kernel is quite broad along the line of sight around cluster lenses with typical redshifts near z=0.5, structures many Mpc away from the cluster are essentially at the same location as the cluster itself, when considering their effect on the cluster's weak lensing signal. We use large-scale numerical simulations of structure formation in a Lambda-dominated cold dark matter model to quantify the effect that large-scale structure near clusters has upon the cluster masses deduced from weak lensing analysis. A correction for the scatter in possible observed lensing masses should be included when interpreting mass functions from weak lensing surveys.

Christopher A. Metzler; Martin White; Chris Loken

2000-05-23

229

Gravitational Lensing as Signal and Noise in Lyman-alpha Forest Measurements

In Lyman-alpha forest measurements it is generally assumed that quasars are mere background light sources which are uncorrelated with the forest. Gravitational lensing of the quasars violates this assumption. This effect leads to a measurement bias, but more interestingly it provides a valuable signal. The lensing signal can be extracted by correlating quasar magnitudes with the flux power spectrum and with the flux decrement. These correlations will be challenging to measure but their detection provides a direct measure of how features in the Lyman-alpha forest trace the underlying mass density field. Observing them will test the fundamental hypothesis that fluctuations in the forest are predominantly driven by fluctuations in mass, rather than in the ionizing background, helium reionization or winds. We discuss ways to disentangle the lensing signal from other sources of such correlations, including dust, continuum and background residuals. The lensing-induced measurement bias arises from sample selection: ...

LoVerde, Marilena; Hui, Lam; Menard, Brice; Lidz, Adam

2010-01-01

230

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

231

TESTING WEAK-LENSING MAPS WITH REDSHIFT SURVEYS: A SUBARU FIELD

We use a dense redshift survey in the foreground of the Subaru GTO2deg{sup 2} weak-lensing field (centered at {alpha}{sub 2000} = 16{sup h}04{sup m}44{sup s}; {delta}{sub 2000} = 43 Degree-Sign 11'24'') to assess the completeness and comment on the purity of massive halo identification in the weak-lensing map. The redshift survey (published here) includes 4541 galaxies; 4405 are new redshifts measured with the Hectospec on the MMT. Among the weak-lensing peaks with a signal-to-noise greater than 4.25, 2/3 correspond to individual massive systems; this result is essentially identical to the Geller et al. test of the Deep Lens Survey (DLS) field F2. The Subaru map, based on images in substantially better seeing than the DLS, enables detection of less massive halos at fixed redshift as expected. We demonstrate that the procedure adopted by Miyazaki et al. for removing some contaminated peaks from the weak-lensing map improves agreement between the lensing map and the redshift survey in the identification of candidate massive systems.

Kurtz, Michael J.; Geller, Margaret J.; Fabricant, Daniel G. [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States); Utsumi, Yousuke [Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo (Japan); Miyazaki, Satoshi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo (Japan); Dell'Antonio, Ian P., E-mail: mkurtz@cfa.harvard.edu, E-mail: mgeller@cfa.harvard.edu, E-mail: dfabricant@cfa.harvard.edu, E-mail: yousuke.utsumi@nao.ac.jp, E-mail: satoshi@subaru.naoj.org, E-mail: ian@het.brown.edu [Department of Physics, Brown University, Box 1843, Providence, RI 02912 (United States)

2012-05-10

232

IM3SHAPE: A maximum-likelihood galaxy shear measurement code for cosmic gravitational lensing

We present and describe im3shape, a new publicly available galaxy shape measurement code for weak gravitational lensing shear. im3shape performs a maximum likelihood fit of a bulge-plus-disc galaxy model to noisy images, incorporating an applied point spread function. We detail challenges faced and choices made in its design and implementation, and then discuss various limitations that affect this and other maximum likelihood methods. We assess the bias arising from fitting an incorrect galaxy model using simple noise-free images and find that it should not be a concern for current cosmic shear surveys. We test im3shape on the GREAT08 Challenge image simulations, and meet the requirements for upcoming cosmic shear surveys in the case that the simulations are encompassed by the fitted model, using a simple correction for image noise bias. For the fiducial branch of GREAT08 we obtain a negligible additive shear bias and sub-two percent level multiplicative bias, which is suitable for analysis of current surveys...

Zuntz, Joe; Voigt, Lisa; Hirsch, Michael; Rowe, Barnaby; Bridle, Sarah

2013-01-01

233

Testing metallicity indicators at z ˜ 1.4 with the gravitationally lensed galaxy CASSOWARY 20

NASA Astrophysics Data System (ADS)

We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR ˜ 6 M? yr-1) galaxy at z = 1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy at z = 0.741. We analysed the integrated physical properties of the H II regions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be ˜1/7 of solar, while carbon is ˜50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid time-scale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from H II regions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of ˜2 uncertainty of each method. The interstellar medium (ISM) of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the ISM with speeds of up 750 km s-1, similar to the values measured in other high-z galaxies sustaining much higher rates of star formation.

James, Bethan L.; Pettini, Max; Christensen, Lise; Auger, Matthew W.; Becker, George D.; King, Lindsay J.; Quider, Anna M.; Shapley, Alice E.; Steidel, Charles C.

2014-05-01

234

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

235

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

236

NASA Astrophysics Data System (ADS)

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 Sachs–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 paper II (Umeh, Clarkson and Maartens 2014 Class. Quantum Grav. 31 205001) , where a comprehensive derivation is given.

Umeh, Obinna; Clarkson, Chris; Maartens, Roy

2014-10-01

237

High-Resolution Radio Imaging of Gravitational Lensing Candidates in the 1 Jansky BL Lac Sample

While BL Lacertae objects are widely believed to be highly beamed, low-luminosity radio galaxies, many radio-selected BL Lacs have extended radio power levels and optical emission lines that are too luminous to be low-luminosity radio galaxies. Also, Stocke & Rector discovered an excess of MgII absorption systems along BL Lac sightlines compared to quasars, suggesting that gravitational lensing may be another means of creating the BL Lac phenomenon in some cases. We present a search for gravitationally-lensed BL Lacs with deep, high-resolution, two-frequency VLA radio maps of seven lensing candidates from the 1 Jansky BL Lac sample. We find that none of these objects are resolved into an Einstein ring like B 0218+357, nor do any show multiple images of the core. All of the lensing candidates that were resolved show a flat-spectrum core and very unusual, steep-spectrum extended morphology that is incompatible with a multiply lensed system. Thus, while these observations do not rule out microlensing, no macrolensing is observed.

T. A. Rector; J. T. Stocke

2003-02-19

238

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

239

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

240

We present the results of a survey for Extremely Red Objects (EROs) in the fields of ten galaxy cluster lenses at z~0.2, combining high-resolution Hubble Space Telescope imaging with deep K-band imaging from UKIRT. We detect 60 EROs with R-K>=5.3, of which 26 have R-K>=6.0 in a total image plane survey area of 49arcmin^2 down to K=20.6. We use detailed models of the cluster lenses to quantify the lens amplification and thus correct the observed number counts and survey area for the effects of gravitational lensing. After making these corrections, we estimate surface densities at K=5.3 and 6.0 respectively. These ERO number counts agree with previous shallower surveys at K1 (K>~19.5). We also compare our results with various model predictions, including a model that attempts to explain EROs in terms of a single population of elliptical galaxies formed at high redshift. We find that a formation epoch of z_f~2.5 for this population matches the observed surface density of R-K>=5.3 EROs quite well, and the R-K>=6....

Smith, G P; Ebeling, H; Edge, A; Ivison, R J; Kneib, J P; Le Borgne, J F; Packham, C; Pellò, R; Smail, I; Borgne, Jean-Francois Le; Czoske, Oliver; Ebeling, Harald; Edge, Alastair; Ivison, Rob; Kneib, Jean-Paul; Packham, Chris; Pello, Roser; Smail, Ian; Smith, Graham P.

2002-01-01

241

We present the results of a survey for Extremely Red Objects (EROs) in the fields of ten galaxy cluster lenses at z~0.2, combining high-resolution Hubble Space Telescope imaging with deep K-band imaging from UKIRT. We detect 60 EROs with R-K>=5.3, of which 26 have R-K>=6.0 in a total image plane survey area of 49arcmin^2 down to K=20.6. We use detailed models of the cluster lenses to quantify the lens amplification and thus correct the observed number counts and survey area for the effects of gravitational lensing. After making these corrections, we estimate surface densities at K=5.3 and 6.0 respectively. These ERO number counts agree with previous shallower surveys at K1 (K>~19.5). We also compare our results with various model predictions, including a model that attempts to explain EROs in terms of a single population of elliptical galaxies formed at high redshift. We find that a formation epoch of z_f~2.5 for this population matches the observed surface density of R-K>=5.3 EROs quite well, and the R-K>=6.0 sample less well. More sophisticated models, including semi-analytic prescriptions, under-predict the ERO surface density by approximately an order of magnitude, suggesting that these models produce insufficient stars and/or dust at high redshift.

Graham P. Smith; Ian Smail; Jean-Paul Kneib; Oliver Czoske; Harald Ebeling; Alastair Edge; Roser Pello; Rob Ivison; Chris Packham; Jean-Francois LeBorgne

2001-09-26

242

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

243

The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multi-color, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known redshift of one of the multiply imaged systems, we determine the remaining source redshifts using the predictive power of the strong lens model. Combining this information with shape measurements of ''weakly'' lensed sources, we derive a high-resolution, absolutely-calibrated mass map, using no assumptions regarding the physical properties of the underlying cluster potential. This map provides the best available quantification of the total mass of the central part of the cluster. We also confirm the result from Clowe et al. (2004, 2006a) that the total mass does not trace the baryonic mass.

Bradac, Marusa; Clowe, Douglas; Gonzalez, Anthony H.; Marshall, Phil; Forman, William; Jones, Christine; Markevitch, Maxim; Randall, Scott; Schrabback, Tim; Zaritsky,; /KIPAC, Menlo Park /Bonn, Inst. Astrophys. /Arizona U., Astron. Dept. - Steward Observ. /Florida U. /Harvard-Smithsonian Ctr. Astrophys.

2006-09-27

244

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

245

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

246

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

247

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

248

The redshift of the gravitationally lensed radio source PKS1830-211

We report on the spectroscopic identification and the long awaited redshift measurement of the heavily obscured, gravitationally lensed radio source PKS 1830-211, which was first observed as a radio Einstein ring. The NE component of the doubly imaged core is identified, in our infrared spectrum covering the wavelength range 1.5-2.5 microns, as an impressively reddened quasar at z=2.507. Our redshift measurement, together with the recently measured time delay (Lovell et al.), means that we are a step closer to determining the Hubble constant from this lens. Converting the time delay into the Hubble constant by using existing models leads to high values for the Hubble constant. Since the lensing galaxy lies very close to the center of the lensed ring, improving the error bars on the Hubble constant will require not only a more precise time delay measurement, but also very precise astrometry of the whole system.

C. Lidman; F. Courbin; G. Meylan; T. Broadhurst; B. Frye; W. J. W. Welch

1999-02-23

249

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

250

Context. The jets of radio-loud Active Galactic Nuclei are among the most powerful particle accelerators in the Universe, and a plausible production site for high-energy cosmic rays. The detection of high-energy neutrinos from these sources would provide unambiguous evidence of a hadronic component in such jets. High-luminosity blazars, such as the flat-spectrum radio quasars (FSRQs), are promising candidates to search for such emission. Because of the low fluxes due to large redshift, these sources are however challenging for the current generation of neutrino telescopes such as ANTARES and IceCube. Aims. This paper proposes to exploit gravitational lensing effects to improve the sensitivity of neutrino telescopes to the intrinsic neutrino emission of distant blazars. Methods. This strategy is illustrated with a search for cosmic neutrinos in the direction of four distant and gravitationally lensed blazars, using data collected from 2007 to 2012 by ANTARES. The magnification factor is estimated for each syst...

Adrián-Martínez, S; André, M; Anton, G; Ardid, M; Aubert, J -J; Baret, B; Barrios-Martì, 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; DeBonis, 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?la?, 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

2014-01-01

251

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

252

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

253

Reducing the gravitational lensing scatter of Type Ia supernovae without introducing any extra bias

Magnification and de-magnification due to gravitational lensing will\\u000acontribute to the brightness scatter of Type Ia supernovae (SNe Ia). The\\u000apurpose of this paper is to investigate the possibility to decrease this\\u000ascatter by correcting individual SNe Ia using observations of galaxies in the\\u000aforeground, without introducing any extra bias. We simulate a large number of\\u000aSN Ia lines of

Jakob Jonsson; Edvard Mortsell; Jesper Sollerman

2008-01-01

254

Gravitational lensing provides a unique and powerful probe of the mass\\u000adistributions of distant galaxies. Four-image lens systems with fold and cusp\\u000aconfigurations have two or three bright images near a critical point. Within\\u000athe framework of singularity theory, we derive analytic relations that are\\u000asatisfied for a light source that lies a small but finite distance from the\\u000aastroid

Arthur B. Congdon; Charles R. Keeton; C. Erik Nordgren

2008-01-01

255

NASA Astrophysics Data System (ADS)

We present a 4 deg2 weak gravitational lensing survey of subhalos in the very nearby Coma cluster using the Subaru/Suprime-Cam. The large apparent size of cluster subhalos allows us to measure the mass of 32 subhalos detected in a model-independent manner, down to the order of 10-3 of the virial mass of the cluster. Weak-lensing mass measurements of these shear-selected subhalos enable us to investigate subhalo properties and the correlation between subhalo masses and galaxy luminosities for the first time. The mean distortion profiles stacked over subhalos show a sharply truncated feature which is well-fitted by a Navarro-Frenk-White (NFW) mass model with the truncation radius, as expected due to tidal destruction by the main cluster. We also found that subhalo masses, truncation radii, and mass-to-light ratios decrease toward the cluster center. The subhalo mass function, dn/dln M sub, in the range of 2 orders of magnitude in mass, is well described by a single power law or a Schechter function. Best-fit power indices of 1.09^{+0.42}_{-0.32} for the former model and 0.99_{-0.23}^{+0.34} for the latter, are in remarkable agreement with slopes of ~0.9-1.0 predicted by the cold dark matter paradigm. The tangential distortion signals in the radial range of 0.02-2 h -1 Mpc from the cluster center show a complex structure which is well described by a composition of three mass components of subhalos, the NFW mass distribution as a smooth component of the main cluster, and a lensing model from a large scale structure behind the cluster. Although the lensing signals are 1 order of magnitude lower than those for clusters at z ~ 0.2, the total signal-to-noise ratio, S/N = 13.3, is comparable, or higher, because the enormous number of background source galaxies compensates for the low lensing efficiency of the nearby cluster. Based on data collected from the Subaru Telescope and obtained from SMOKA, operated by the Astronomy Data Center, National Astronomical Observatory of Japan.

Okabe, Nobuhiro; Futamase, Toshifumi; Kajisawa, Masaru; Kuroshima, Risa

2014-04-01

256

Confirmation of general relativity on large scales from weak lensing and galaxy velocities

Although general relativity underlies modern cosmology, its applicability on cosmological length scales has yet to be stringently tested. Such a test has recently been proposed, using a quantity, EG, that combines measures of large-scale gravitational lensing, galaxy clustering and structure growth rate. The combination is insensitive to 'galaxy bias' (the difference between the clustering of visible galaxies and invisible dark matter) and is thus robust to the uncertainty in this parameter. Modified theories of gravity generally predict values of EG different from the general relativistic prediction because, in these theories, the 'gravitational slip' (the difference between the two potentials that describe perturbations in the gravitational metric) is non-zero, which leads to changes in the growth of structure and the strength of the gravitational lensing effect3. Here we report that EG = 0.39 +/- 0.06 on length scales of tens of megaparsecs, in agreement with the general relativistic prediction of EG $\\approx$ 0.4. The measured value excludes a model within the tensor-vector-scalar gravity theory, which modifies both Newtonian and Einstein gravity. However, the relatively large uncertainty still permits models within f(R) theory, which is an extension of general relativity. A fivefold decrease in uncertainty is needed to rule out these models.

Reinabelle Reyes; Rachel Mandelbaum; Uros Seljak; Tobias Baldauf; James E. Gunn; Lucas Lombriser; Robert E. Smith

2010-03-10

257

First evidence for a gravitational lensing-induced echo in gamma rays with Fermi LAT

Aims. This article shows the first evidence for gravitational lensing phenomena in high energy gamma-rays. This evidence comes from the observation of a gravitational lens induced echo in the light curve of the distant blazar PKS 1830-211. Methods. Traditional methods for the estimation of time delays in gravitational lensing systems rely on the cross-correlation of the light curves of the individual images. In this paper, we use 300 MeV-30 GeV photons detected by the Fermi-LAT instrument. The Fermi-LAT instrument cannot separate the images of known lenses. The observed light curve is thus the superposition of individual image light curves. The Fermi-LAT instrument has the advantage of providing long, evenly spaced, time series. In addition, the photon noise level is very low. This allows to use directly Fourier transform methods. Results. A time delay between the two compact images of PKS 1830-211 has been searched for both by the autocorrelation method and the â??double power spectrumâ? method. The d...

Barnacka, A; Moudden, Y

2010-01-01

258

Constraining dark energy evolution with gravitational lensing by large scale structures

We study the sensitivity of weak lensing by large scale structures as a probe of the evolution of dark energy. We explore a two-parameters model of dark energy evolution, inspired by tracking quintessence models. To this end, we compute the likelihood of a few fiducial models with varying and nonvarying equation of states. For the different models, we investigate the

Karim Benabed; Ludovic van Waerbeke

2004-01-01

259

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

260

Subaru Weak-Lensing Survey II: Multi-Object Spectroscopy and Cluster Masses

NASA Astrophysics Data System (ADS)

We present the first results of a multi-object spectroscopic campaign to follow up cluster candidates located via weak lensing. Our main goals are to search for spatial concentrations of galaxies that are plausible optical counterparts of the weak-lensing signals, and to determine the cluster redshifts from those of member galaxies. Around each of 36 targeted cluster candidates, we obtained 15-32 galaxy redshifts. For 28 of these targets, we confirmed a secure cluster identification, with more than five spectroscopic galaxies within a velocity of ±3000km s-1. This includes three cases where two clusters at different redshifts are projected along the same line-of-sight. In 6 of the 8 unconfirmed targets, we found multiple small galaxy concentrations at different redshifts, each containing at least three spectroscopic galaxies. The weak-lensing signal around those systems was thus probably created by the projection of groups or small clusters along the same line-of-sight. In both of the remaining two targets, a single small galaxy concentration was found. In some candidate super-cluster systems, we found additional evidence of filaments connecting the main density peak to an additional nearby structure. For a subsample of our most cleanly measured clusters, we investigated the statistical relation between their weak-lensing mass (MNFW, ?SIS) and the velocity dispersion of their member galaxies (?v), comparing our sample with optically and X-ray selected samples from the literature. Our lensing-selected clusters are consistent with ?v = ?SIS, with a similar scatter to that of optically and X-ray selected clusters. We also derived an empirical relation between the cluster mass and the galaxy velocity dispersion, M200E(z) = 11.0 × 1014 × (?v/1000km s-1)3.0 h-1 Modot, which is in reasonable agreement with predictions of N-body simulations in the ? CDM cosmology.

Hamana, Takashi; Miyazaki, Satoshi; Kashikawa, Nobunari; Ellis, Richard S.; Massey, Richard J.; Refregier, Alexandre; Taylor, James E.

2009-08-01

261

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

262

Perturbative signature of substructures in strong gravitational lenses

In the perturbative approach, substructures in the lens can be reduced to their effect on the two perturbative fields $f_1$ and $\\frac{d f_0}{d\\theta}$. A simple generic model of elliptical lens with a substructure situated near the critical radius is investigated in details. Analytical expressions are derived for each perturbative field, and basic properties are analyzed. The power spectrum of the fields is well approximated by a power-law, resulting in significant tails at high frequencies. Another feature of the perturbation by a substructure is that the ratio of the power spectrum at order $n$ of the 2 fields $R_n$ is nearly 1. The ratio $R_n \\simeq 1$ is specific to substructures, for instance an higher order distortion ($n>2$) but with auto-similar isophotes will result in $R_n \\propto \\frac{1}{n^2}$. Finally, the problem of reconstructing the perturbative field is investigated. Local field model are implemented and fitted to maximize image similarity in the source plane. The non-linear optimization is greatly facilitated, since in the perturbative approach the circular source solution is always known. Examples of images distortions in the subcritical regime due to substructures are presented, and analyzed for different source shapes. Provided enough images and signal is available, the substructure field can be identified confidently. These results suggests that the perturbative method is an efficient tool to estimate the contribution of substructures to the mass distribution of lenses.

C. Alard

2008-03-15

263

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

264

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

265

CFHTLenS: testing the laws of gravity with tomographic weak lensing and redshift-space distortions

NASA Astrophysics Data System (ADS)

Dark energy may be the first sign of new fundamental physics in the Universe, taking either a physical form or revealing a correction to Einsteinian gravity. Weak gravitational lensing and galaxy peculiar velocities provide complementary probes of general relativity, and in combination allow us to test modified theories of gravity in a unique way. We perform such an analysis by combining measurements of cosmic shear tomography from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) with the growth of structure from the WiggleZ Dark Energy Survey and the Six-degree-Field Galaxy Survey, producing the strongest existing joint constraints on the metric potentials that describe general theories of gravity. For scale-independent modifications to the metric potentials which evolve linearly with the effective dark energy density, we find present-day cosmological deviations in the Newtonian potential and curvature potential from the prediction of general relativity to be ??/? = 0.05 ± 0.25 and ??/? = -0.05 ± 0.3, respectively (68 per cent confidence limits).

Simpson, Fergus; Heymans, Catherine; Parkinson, David; Blake, Chris; Kilbinger, Martin; Benjamin, Jonathan; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Coupon, Jean; Fu, Liping; Harnois-Déraps, Joachim; Hudson, Michael J.; Kuijken, Koenraad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta; Vafaei, Sanaz; Velander, Malin

2013-03-01

266

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

267

Universal Profiles of the Intracluster Medium from Suzaku X-Ray and Subaru Weak Lensing Obesrvations

We conduct a joint X-ray and weak-lensing study of four relaxed galaxy clusters (Hydra A, A478, A1689 and A1835) observed by both Suzaku and Subaru out to virial radii, with an aim to understand recently-discovered unexpected feature of the ICM in cluster outskirts. We show that the average hydrostatic-to-lensing total mass ratio for the four clusters decreases from \\sim 70% to \\sim 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 ...

Okabe, N; Tamura, T; Fujita, Y; Takizawa, M; Zhang, Y -Y; Matsushita, K; Hamana, T; Fukazawa, Y; Futamase, T; Kawaharada, M; Miyazaki, S; Mochizuki, Y; Nakazawa, K; Ohashi, T; Ota, N; Sasaki, T; Sato, K; Tam, S I

2014-01-01

268

Combined analysis of weak lensing and X-ray blind surveys

NASA Astrophysics Data System (ADS)

We present a joint weak lensing and X-ray analysis of 4 deg2 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 six weak-lensing-detected clusters of galaxies. We show that their counts can be used to constrain the power-spectrum normalization ?8 = 0.92+0.26-0.30 for ?m = 0.24. We show that despite the large scatter generally observed in the mass-temperature (M-T) relation derived from lensing masses, tight constraints on both its slope and normalization M* can be obtained with a moderate number of sources provided that the covered mass range is large enough. Adding clusters given by Bardeau et al. to our sample, we measure M* = 2.71+0.79-0.61 × 1014h-1Msolar. 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 ?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 deg2 will provide the 1 per cent accuracy in the estimation of the power-spectrum and the M-T relation normalizations. Based on observations obtained with MegaPrime/MegaCam, a joint project of Canada-France-Hawaii Telescope (CFHT) and CEA/DAPNIA, at the CFHT which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. It makes use of photometric redshifts produced jointly by TERAPIX and VVDS teams. E-mail: joel.berge@jpl.nasa.gov

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

2008-04-01

269

CoMaLit III. Literature Catalogs of weak Lensing Clusters of galaxies (LC^2)

The measurement of the mass of clusters of galaxies is crucial for their use in cosmology and astrophysics. Masses can be efficiently determined with weak lensing (WL) analyses. I compiled from Literature a Catalog of weak Lensing Clusters (LC^2). Cluster identifiers, coordinates, and redshifts have been standardised. WL masses were reported to over-densities of 2500, 500, 200, and to the virial one in the reference Lambda-CDM model. Duplicate entries were carefully handled. I produced three catalogs: LC^2-single, with 485 unique groups and clusters analysed with the single-halo model; LC^2-substructure, listing substructures in complex systems; LC^2-all, listing all the 822 WL masses found in literature. The catalogs are publicly available at https://www.dropbox.com/sh/hukhb24c3ahiun2/AADVuW7yUAA2XjyDrFwofejAa?dl=0

Sereno, Mauro

2014-01-01

270

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

271

Weak Lensing and the Measurement of q0 from Type Ia Supernovae

On-going projects to discover Type Ia supernovae at redshifts z = 0.3 - 1,\\u000acoupled with improved techniques to narrow the dispersion in SN Ia peak\\u000amagnitudes, have renewed the prospects for determining the cosmic deceleration\\u000aparameter q_0. We estimate the expected uncertainty in the Hubble diagram\\u000adetermination of q_0 due to weak lensing by structure in the universe, which

Joshua A. Frieman

1996-01-01

272

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

273

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 uni...

Dietrich, Jörg P; Song, Jeeseon; McKay, Christopher P Davis 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

2014-01-01

274

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

1999-01-15

275

Gravitational lensing as signal and noise in Lyman-{alpha} forest measurements

In Lyman-{alpha} forest measurements it is generally assumed that quasars are mere background light sources which are uncorrelated with the forest. Gravitational lensing of the quasars violates this assumption. This effect leads to a measurement bias, but more interestingly it provides a valuable signal. The lensing signal can be extracted by correlating quasar magnitudes with the flux-power spectrum and with the flux decrement. These correlations will be challenging to measure but their detection provides a direct measure of how features in the Lyman-{alpha} forest trace the underlying mass density field. Observing them will test the fundamental hypothesis that fluctuations in the forest are predominantly driven by fluctuations in mass, rather than in the ionizing background, helium reionization, or winds. We discuss ways to disentangle the lensing signal from other sources of such correlations, including dust, continuum, and background residuals. The lensing-induced measurement bias arises from sample selection: one preferentially collects spectra of magnified quasars which are behind overdense regions. This measurement bias is {approx}0.1-1% for the flux-power spectrum, optical depth, and the flux probability distribution. Since the effect is systematic, quantities such as the amplitude of the flux-power spectrum averaged across scales should be interpreted with care.

LoVerde, Marilena [Institute for Advanced Study, Princeton, New Jersey 08540 (United States); ISCAP and Department of Physics, Columbia University, New York, New York 10027 (United States); Marnerides, Stefanos [ISCAP and Department of Physics, Columbia University, New York, New York 10027 (United States); Hui, Lam [Institute for Advanced Study, Princeton, New Jersey 08540 (United States); ISCAP and Department of Physics, Columbia University, New York, New York 10027 (United States); CCPP and Department of Physics, New York University, New York 10003 (United States); Menard, Brice [Canadian Institute for Theoretical Astrophysics, Toronto, Ontario M5S 3H8 (Canada); Lidz, Adam [Center for Astrophysics, Harvard University, Cambridge, Massachusetts 02138 (United States); Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

2010-11-15

276

Gravitational lensing with f (?) = ?3/2 gravity in accordance with astrophysical observations

NASA Astrophysics Data System (ADS)

In this article, we perform a second order perturbation analysis of the gravitational metric theory of gravity f (?) = ?3/2 developed by Bernal et al. We show that the theory accounts in detail for two observational facts: (1) the phenomenology of flattened rotation curves associated with the Tully-Fisher relation observed in spiral galaxies, and (2) the details of observations of gravitational lensing in galaxies and groups of galaxies, without the need of any dark matter. We show how all dynamical observations on flat rotation curves and gravitational lensing can be synthesized in terms of the empirically required metric coefficients of any metric theory of gravity. We construct the corresponding metric components for the theory presented at second order in perturbation, which are shown to be perfectly compatible with the empirically derived ones. It is also shown that under the theory being presented, in order to obtain a complete full agreement with the observational results, a specific signature of Riemann's tensor has to be chosen. This signature corresponds to the one most widely used nowadays in relativity theory. Also, a computational program, the Metric EXtended-gravity Incorporated through a Computer Algebraic System (MEXICAS) code, developed for its usage in the Computer Algebraic System Maxima for working out perturbations on a metric theory of gravity, is presented and made publicly available.

Mendoza, S.; Bernal, T.; Hernandez, X.; Hidalgo, J. C.; Torres, L. A.

2013-08-01

277

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

278

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

279

Full-sky formulae for weak lensing power spectra from total angular momentum method

NASA Astrophysics Data System (ADS)

We systematically derive full-sky formulae for the weak lensing power spectra generated by scalar, vector and tensor perturbations from the total angular momentum (TAM) method. Based on both the geodesic and geodesic deviation equations, we first give the gauge-invariant expressions for the deflection angle and Jacobi map as observables of the CMB lensing and cosmic shear experiments. We then apply the TAM method, originally developed in the theoretical studies of CMB, to a systematic derivation of the angular power spectra. The TAM representation, which characterizes the total angular dependence of the spatial modes projected along a line-of-sight, can carry all the information of the lensing modes generated by scalar, vector, and tensor metric perturbations. This greatly simplifies the calculation, and we present a complete set of the full-sky formulae for angular power spectra in both the E-/B-mode cosmic shear and gradient-/curl-mode lensing potential of deflection angle. Based on the formulae, we give illustrative examples of non-vanishing B-mode cosmic shear and curl-mode of deflection angle in the presence of the vector and tensor perturbations, and explicitly compute the power spectra.

Yamauchi, Daisuke; Namikawa, Toshiya; Taruya, Atsushi

2013-08-01

280

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

281

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

282

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

283

Discovery of an Exceptionally Bright Gravitationally Lensed Submillimeter Galaxy at z=4.69

NASA Astrophysics Data System (ADS)

We report the discovery of an exceptionally bright gravitationally lensed submillimeter galaxy at z=4.69. Through our on-going Herschel survey of gravitationally lensed high-redshift galaxies in the fields of massive galaxy clusters ("The Herschel Lensing Survey (HLS)" - PI: Egami), we identified in the field of a z=0.3 cluster a bright Herschel/SPIRE source ( 100 mJy at 500 um) whose far-infrared/submillimeter spectral energy distribution is peaking toward 500 um, indicating that its redshift is likely above 4. The APEX/LABOCA 870 um image showed that this source is not only bright (60 mJy at 870 um) but also spatially extended even with the LABOCA resolution of 20'', although it is invisible in the HST/ACS F606W image. The spectroscopic redshift came from the IRAM30m/EMIR observations, which detected the CO(4-3) and CO(5-4) lines with the corresponding redshift of 4.69. The high-resolution (beam=0.8"x0.7") SMA 345 GHz map has subsequently resolved this source into four components, which are likely four lensed images of the same background galaxy. This lensing interpretation has been confirmed by the HST WFC3/IR observations, which not only revealed the same morphology for the multiple sources but also detected the 5th image at the predicted location. We therefore conclude that this lensed system exhibits a rare hyperbolic umbilic image configuration, which produces a large magnification factor of x100-200 when the four components are combined. What is even more remarkable is that the four HST sources are not spatially coincident with the four SMA sources. In other words, this z=4.69 galaxy appears to consist of two spatially distinct components, one of which (the one responsible for the bright IR/submm emission) is completely invisible in the HST near-infrared images. This suggests that there may exist a population of dust-obscured galaxies at z>4 that are hidden from our deep optical/near-infrared view.

Egami, Eiichi; Herschel Lensing Survey (HLS) Team

2012-05-01

284

{}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

285

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

286

A technique for using radio jets as extended gravitational lensing probes

NASA Technical Reports Server (NTRS)

A new and potentially powerful method of measuring the mass of a galaxy (or dark matter concentration) which lies close in position to a background polarized radio jet is proposed. Using the fact that the polarization angle is not changed by lensing, an 'alignment-breaking parameter' is defined which is a sensitive indicator of gravitational distortion. The method remains sensitive over a wide redshift range of the gravitational lens. This technique is applied to the analysis of polarimetric observations of the jet of 3C 9 at z = 2.012, combined with a newly discovered 20.3 mag foreground galaxy at z = 0.2538 to 'weigh' the galaxy and obtain an approximate upper limit to the mass-to-light ratio.

Kronberg, Philipp P.; Dyer, Charles C.; Burbidge, E. Margaret; Junkkarinen, Vesa T.

1991-01-01

287

SDSS J131339.98+515128.3: A new GravitationallyLensed Quasar Selected Based on Near-infrared Excess

We report the discovery of a new gravitationally lensed quasar, SDSS J131339.98+515128.3, at a redshift of 1:875 with an image separation of 1: 0024. The lensing galaxy is clearly detected in visible-light follow-up observations. We also identify three absorption-line doublets in the spectra of the lensed quasar images, from which we measure the lens redshift to be 0:194. Like several other known lenses, the lensed quasar images have different continuum slopes. This difference is probably the result of reddening and microlensing in the lensing galaxy. The lensed quasar was selected by correlating Sloan Digital Sky Survey (SDSS) spectroscopic quasars with Two Micron All Sky Survey (2MASS) sources and choosing quasars that show near-infrared (IR) excess. The near-IR excess can originate, for example, from the contribution of the lensing galaxy at near-IR wavelengths. We show that the near-IR excess technique is indeed an efficient method to identify lensed systems from a large sample of quasars.

Ofek, E.O.; Oguri, M.; Jackson, N.; Inada, N.; Kayo, I.

2007-09-28

288

Gravitational Lensing Signatures of Supermassive Black Holes in Future Radio Surveys

Observational measurements of the relationship between supermassive black holes (SMBHs) and the properties of their host galaxies are an important method for probing theoretical hierarchical growth models. Gravitational lensing is a unique mechanism for acquiring this information in systems at cosmologically significant redshifts. We review the calculations required to include SMBHs in two standard galactic lens models, a cored isothermal sphere and a broken power law. The presence of the SMBH produces two primary effects depending on the lens configuration, either blocking the ``core'' image that is usually predicted to form from a softened lens model, or adding an extra, highly demagnified, image to the predictions of the unaltered lens model. The magnitudes of these effects are very sensitive to galaxy core sizes and SMBH masses. Therefore, observations of these lenses would probe the properties of the inner regions of galaxies, including their SMBHs. Lensing cross-sections and optical depth calculations indicate that in order to fully observe these characteristic signatures, flux ratios of order 10^6 or more between the brightest and faintest images of the lens must be detectable, and thus the next generation of radio telescope technology offers the first opportunity for a serious observational campaign. Core images, however, are already detectable and with additional observations their statistics may be used to guide future SMBH searches.

Judd D. Bowman; Jacqueline N. Hewitt; James R. Kiger

2004-06-24

289

GLAMER - I. A code for gravitational lensing simulations with adaptive mesh refinement

NASA Astrophysics Data System (ADS)

A computer code is described for the simulation of gravitational lensing data. The code incorporates adaptive mesh refinement in choosing which rays to shoot based on the requirements of the source size, location and surface brightness distribution or to find critical curves/caustics. A variety of source surface brightness models are implemented to represent galaxies and quasar emission regions. The lensing mass can be represented by point masses (stars), smoothed simulation particles, analytic halo models, pixelized mass maps or any combination of these. The deflection and beam distortions (convergence and shear) are calculated by modified tree algorithm when haloes, point masses or particles are used and by fast Fourier transform when mass maps are used. The combination of these methods allow for a very large dynamical range to be represented in a single simulation. Individual images of galaxies can be represented in a simulation that covers many square degrees. For an individual strongly lensed quasar, source sizes from the size of the quasar's host galaxy (˜100 kpc) down to microlensing scales (˜10-4 pc) can be probed in a self-consistent simulation. Descriptions of various tests of the code's accuracy are given.

Metcalf, R. Benton; Petkova, Margarita

2014-12-01

290

A new hybrid framework to efficiently model lines of sight to gravitational lenses

NASA Astrophysics Data System (ADS)

In strong gravitational lens systems, the light bending is usually dominated by one main galaxy, but may be affected by other mass along the line of sight (LOS). Shear and convergence can be used to approximate the contributions from less significant perturbers (e.g. those that are projected far from the lens or have a small mass), but higher order effects need to be included for objects that are closer or more massive. We develop a framework for multiplane lensing that can handle an arbitrary combination of tidal planes treated with shear and convergence and planes treated exactly (i.e. including higher order terms). This framework addresses all of the traditional lensing observables including image positions, fluxes, and time delays to facilitate lens modelling that includes the non-linear effects due to mass along the LOS. It balances accuracy (accounting for higher order terms when necessary) with efficiency (compressing all other LOS effects into a set of matrices that can be calculated up front and cached for lens modelling). We identify a generalized multiplane mass sheet degeneracy, in which the effective shear and convergence are sums over the lensing planes with specific, redshift-dependent weighting factors.

McCully, Curtis; Keeton, Charles R.; Wong, Kenneth C.; Zabludoff, Ann I.

2014-10-01

291

A new pixel-based method for analyzing spatially resolved, gravitationally lensed images

NASA Astrophysics Data System (ADS)

Gravitational lens modeling of spatially resolved sources is a challenging inverse problem that requires careful handling of parameter degeneracies. I describe a new pixel-based source reconstruction method and analyze statistical and systematic effects, including pixelization, noise, telescope pointing, and resolution. I show applications of the method to observations of two lensed, high-redshift galaxies. For SDSS J120602.09+514229.5 (also known as the Clone), a z=2.001 star-forming galaxy lensed by a foreground galaxy at z=0.42, the errors on the model are appropriately accounted for, and the results are in agreement with previous analyses. For SDSS J0901+1814 (J0901), a z=2.26 ultraluminous infrared star-forming galaxy lensed by a foreground group of galaxies at z=0.35, I constrain the lens model using CO rotational line maps of multiple velocity channels, in addition to optical and infrared data. The reconstructed velocity fields in the source plane make it possible to infer J0901's intrinsic dynamical mass and gas mass fraction. Combining the CO maps with H-alpha observations allows us to test the applicability of the local Kennicutt-Schmidt relation at high redshift.

Tagore, Amitpal S.; Keeton, C. R.; Baker, A. J.

2014-01-01

292

Orbifolds, the A, D, E family of caustic singularities, and gravitational lensing

NASA Astrophysics Data System (ADS)

We provide a geometric explanation for the existence of magnification relations for the An(n>=2),Dn(n>=4),E6,E7,E8 family of caustic singularities, which were established in recent work. In particular, it was shown that for families of general mappings between planes exhibiting any of these caustic singularities, and for any noncaustic target point, the total signed magnification of the corresponding preimages vanishes. As an application to gravitational lensing, it was also shown that, independent of the choice of a lens model, the total signed magnification vanishes for a light source anywhere in the four-image region close to elliptic and hyperbolic umbilic caustics. This is a more global and higher order analog of the well-known fold and cusp magnification relations. We now extend each of these mappings to weighted projective space, which is a compact orbifold, and show that magnification relations translate into a statement about the behavior of these extended mappings at infinity. This generalizes multidimensional residue techniques developed in previous work, and introduces weighted projective space as a new tool in the theory of caustic singularities and gravitational lensing.

Aazami, A. B.; Petters, A. O.; Rabin, J. M.

2011-02-01

293

ERIC Educational Resources Information Center

Describes cosmic flukes which offer a unique window on new information about the universe. Discusses the historical background, theory, and detection of this effect. Proposes the importance of information found by the examination of these phenomena. (CW)

Turner, Edwin L.

1988-01-01

294

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

295

Weak Lensing and the Measurement of $q_0$ from Type Ia Supernovae

On-going projects to discover Type Ia supernovae at redshifts z = 0.3 - 1, coupled with improved techniques to narrow the dispersion in SN Ia peak magnitudes, have renewed the prospects for determining the cosmic deceleration parameter q_0. We estimate the expected uncertainty in the Hubble diagram determination of q_0 due to weak lensing by structure in the universe, which stochastically shifts the apparent brightness of distant standard candles. Although the results are sensitive to the density power spectrum on small scales, the induced flux dispersion sigma_m 1.

Frieman, Joshua A

1996-01-01

296

Probing inflation with CMB polarization : weak lensing effect on the covariance of CMB spectra

CMB anisotropies are modified by the weak lensing effect of intervening large scale structures on the photon path from the last scattering surface to the observer. This has to be accounted for when observational data of sensitive experiments are used to constrain cosmological models. A common approximation to analyze the CMB angular power spectra is to include only the Gaussian part of the lensing correction and to ignore the non-gaussian terms in the error covariance matrix of the spectra. In order to investigate the validity of this approximation, we computed these non-Gaussian terms by using a perturbative expansion method. We present a graphical method to write down any N-point correlation functions at any order in lensing. We use a pedagogical approach to demonstrate that neglecting non-gaussian terms is an accurate approximation for all polarizations but B, and it will remain so even for the analysis of very sensitive post-Planck experiments. For the B polarization, non-gaussian contributions up to order 4 must be taken into account.

Jonathan Rocher; Karim Benabed; Francois Bouchet

2006-12-21

297

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

2013-07-03

298

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

299

NASA Astrophysics Data System (ADS)

The outstanding problem in galaxy cluster count cosmology is to determine accurate scaling relations between survey observables and cluster mass. As indicated by the tension between Planck CMB and Sunya'ev-Zeldovich cluster count cosmology, the robustness of the cluster count results are dominated by the mass measurements used to calibrate the scaling relations. Here we present our work on the scaling of X-ray observables obtained with XMM-Newton to unbiased weak lensing masses in the COSMOS and CFHTLenS survey fields. Our recently published mass-temperature relation for low mass systems in the COSMOS field extended the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study. It showed that previous X-ray mass estimates can be biased low by up to 30-50%, which is the level required to bring Planck cosmology into consistency. We showed that the bias is not attributable to uncertainties in X-ray cross-calibration. Our recent inclusion of low mass clusters from CFHTLenS allows us to improve the constraint on the M-T relation and to study the effects of substucture. With the CFHTLenS extension, we also include the first lensing calibrated mass-luminosity relation for individual low mass systems.

Kettula, K.

2014-07-01

300

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

301

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

302

GALAXIES IN X-RAY GROUPS. II. A WEAK LENSING STUDY OF HALO CENTERING

Locating the centers of dark matter halos is critical for understanding the mass profiles of halos, as well as the formation and evolution of the massive galaxies that they host. The task is observationally challenging because we cannot observe halos directly, and tracers such as bright galaxies or X-ray emission from hot plasma are imperfect. In this paper, we quantify the consequences of miscentering on the weak lensing signal from a sample of 129 X-ray-selected galaxy groups in the COSMOS field with redshifts 0 < z < 1 and halo masses in the range 10{sup 13}-10{sup 14} M{sub Sun }. By measuring the stacked lensing signal around eight different candidate centers (such as the brightest member galaxy, the mean position of all member galaxies, or the X-ray centroid), we determine which candidates best trace the center of mass in halos. In this sample of groups, we find that massive galaxies near the X-ray centroids trace the center of mass to {approx}< 75 kpc, while the X-ray position and centroids based on the mean position of member galaxies have larger offsets primarily due to the statistical uncertainties in their positions (typically {approx}50-150 kpc). Approximately 30% of groups in our sample have ambiguous centers with multiple bright or massive galaxies, and some of these groups show disturbed mass profiles that are not well fit by standard models, suggesting that they are merging systems. We find that halo mass estimates from stacked weak lensing can be biased low by 5%-30% if inaccurate centers are used and the issue of miscentering is not addressed.

George, Matthew R.; Ma, Chung-Pei [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Leauthaud, Alexie; Bundy, Kevin [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), Todai Institutes for Advanced Study, University of Tokyo, Kashiwa 277-8583 (Japan); Finoguenov, Alexis [Max-Planck-Institut fuer Extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Rykoff, Eli S. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Tinker, Jeremy L. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); Massey, Richard [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Mei, Simona, E-mail: mgeorge@astro.berkeley.edu [Bureau des Galaxies, Etoiles, Physique, Instrumentation (GEPI), University of Paris Denis Diderot, F-75205 Paris Cedex 13 (France)

2012-09-20

303

Weak Lensing and the Measurement of q0 from Type Ia Supernovae

On-going projects to discover Type Ia supernovae at redshifts z = 0.3 - 1, coupled with improved techniques to narrow the dispersion in SN Ia peak magnitudes, have renewed the prospects for determining the cosmic deceleration parameter q_0. We estimate the expected uncertainty in the Hubble diagram determination of q_0 due to weak lensing by structure in the universe, which stochastically shifts the apparent brightness of distant standard candles. Although the results are sensitive to the density power spectrum on small scales, the induced flux dispersion sigma_m magnitudes, sigma_M \\simeq 0.2 mag. Thus, density inhomogeneities do not significantly impact the current program to measure q_0, in contrast to a recent claim. If, however, light-curve shape and other calibrators can reduce the effective intrinsic spread to 0.1 mag at high z, then weak lensing could increase the observed spread by 30% in an Omega_{m,0}=1 universe for SNe at z > 1.

Joshua A. Frieman

1996-08-13

304

Weak lensing effects in the measurement of the dark energy equation of state with LISA

The Laser Interferometer Space Antenna's (LISA's) observation of supermassive binary black holes (SMBBH) could provide a new tool for precision cosmography. Inclusion of subdominant signal harmonics in the inspiral signal allows for high-accuracy sky localization, dramatically improving the chances of finding the host galaxy and obtaining its redshift. A SMBBH merger can potentially have component masses from a wide range (10{sup 5}-10{sup 8}M{sub {center_dot}}) over which parameter accuracies vary considerably. We perform an in-depth study in order to understand (i) what fraction of possible SMBBH mergers allow for sky localization, depending on the parameters of the source, and (ii) how accurately w can be measured when the host galaxy can be identified. We also investigate how accuracies on all parameters improve when a knowledge of the sky position can be folded into the estimation of errors. We find that w can be measured to within a few percent in most cases, if the only error in measuring the luminosity distance is due to LISA's instrumental noise and the confusion background from Galactic binaries. However, weak lensing-induced errors will severely degrade the accuracy with which w can be obtained, emphasizing that methods to mitigate weak lensing effects would be required to take advantage of LISA's full potential.

Van Den Broeck, Chris [Nikhef, National Institute for Subatomic Physics, Science Park 105, 1098 XG Amsterdam (Netherlands); School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom); Trias, M.; Sintes, A. M. [Departament de Fisica, Universitat de les Illes Balears, Carretera Valldemossa Km. 7.5, E-07122 Palma de Mallorca (Spain); Sathyaprakash, B. S. [School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom)

2010-06-15

305

NASA Astrophysics Data System (ADS)

We demonstrate that the intrinsic alignment of galaxies with large-scale tidal fields sources an extra contribution to the recently detected cross-correlation of galaxy shear and weak lensing of the microwave background. The extra term is the analogy of the `GI' term in standard cosmic shear studies, and results in a reduction in the amplitude of the cross-correlation. We compute the intrinsic alignment contribution in linear and non-linear theory, and show that it can be at roughly the 15 per cent level for the Canada-France-Hawaii Telescope Stripe 82 redshift distribution, if the canonical amplitude of intrinsic alignments is assumed. The new term can therefore potentially reconcile the apparently low value of the measured cross-correlation with standard ? cold dark matter. We discuss various small-scale effects in the signal and the dependence on the source redshift distribution. We discuss the exciting possibility of self-calibrating intrinsic alignments with a joint analysis of cosmic shear and weak lensing of the microwave background.

Hall, Alex; Taylor, Andy

2014-09-01

306

A search for gravitationally lensed water masers in dusty quasars and star-forming galaxies

NASA Astrophysics Data System (ADS)

Luminous extragalactic water masers are known to be associated with active galactic nuclei and have provided accurate estimates for the mass of the central supermassive black hole and the size and structure of the circumnuclear accretion disc in nearby galaxies. To find water maser systems at much higher redshifts, we have begun a survey of known gravitationally lensed quasars and star-forming galaxies. In this paper, we present a search for 22 GHz (rest-frame) water masers towards five dusty, gravitationally lensed quasars and star-forming galaxies at redshifts between 2.3 and 2.9 with the Effelsberg radio telescope and the Expanded Very Large Array (EVLA). Our observations do not find any new definite examples of high-redshift water maser galaxies, suggesting that large reservoirs of dust and gas are not a sufficient condition for powerful water maser emission. However, we do find the tentative detection of a water maser system in the active galaxy IRAS 10214+4724 at redshift 2.285. Our survey has now doubled the number of gravitationally lensed galaxies and quasars that have been searched for high-redshift water maser emission. We also present an updated analysis of the high-redshift water maser luminosity function that is based on the results presented here and from the only cosmologically distant (z > 1) water maser galaxy found thus far, MG J0414+0534 at redshift 2.64. By comparing with the water maser luminosity function locally and at moderate redshifts, we find that there must be some evolution in the luminosity function of water maser galaxies at high redshifts. By assuming a moderate evolution [(1 +z)4] in the water maser luminosity function, we find that blind surveys for water maser galaxies are only worthwhile with extremely high sensitivity like that of the planned Square Kilometre Array (Phase 2), which is scheduled to be completed by 2020. However, instruments like the EVLA and MeerKAT will be capable of detecting water maser systems similar to the one found from MG J0414+0534 through dedicated pointed observations, providing suitable high-redshift targets can be selected.

McKean, J. P.; Impellizzeri, C. M. V.; Roy, A. L.; Castangia, P.; Samuel, F.; Brunthaler, A.; Henkel, C.; Wucknitz, O.

2011-02-01

307

Gravitational lensing effects in a time-variable cosmological 'constant' cosmology

NASA Technical Reports Server (NTRS)

A scalar field phi with a potential V(phi) varies as phi exp -alpha(alpha is greater than 0) has an energy density, behaving like that of a time-variable cosmological 'constant', that redshifts less rapidly than the energy densities of radiation and matter, and so might contribute significantly to the present energy density. We compute, in this spatially flat cosmology, the gravitational lensing optical depth, and the expected lens redshift distribution for fixed source redshift. We find, for the values of alpha of about 4 and baryonic density parameter Omega of about 0.2 consistent with the classical cosmological tests, that the optical depth is significantly smaller than that in a constant-Lambda model with the same Omega. We also find that the redshift of the maximum of the lens distribution falls between that in the constant-Lambda model and that in the Einstein-de Sitter model.

Ratra, Bharat; Quillen, Alice

1992-01-01

308

To determine the magnification of an extended source caused by gravitational lensing one has to perform a two-dimensional integral over point-source magnifications in general. Since the point-source magnification jumps to an infinite value on caustics, special care is required. For a uniformly bright source, it has been shown earlier that the calculation simplifies if one determines the magnification from the area of the images of the extended source by applying Green's theorem so that one ends up with a one-dimensional integration over the image boundaries. This approach is discussed here in detail, and it is shown that it can be used to yield a robust and efficient method also for limb-darkened sources. It is also shown that the centroid shift can be calculated in a similar way.

M. Dominik

1998-04-06

309

Strong Gravitational Lensing as a Tool to Investigate the Structure of Jets at High Energies

NASA Astrophysics Data System (ADS)

The components of blazar jets that emit radiation span a factor of 1010 in scale. The spatial structure of these emitting regions depends on the observed energy. Photons emitted at different sites cross the lens plane at different distances from the mass-weighted center of the lens. Thus there are differences in magnification ratios and time delays between the images of lensed blazars observed at different energies. When the lens structure and redshift are known from optical observations, these constraints can elucidate the structure of the source at high energies. At these energies, current technology is inadequate to resolve these sources, and the observed light curve is thus the sum of the images. Durations of ?-ray flares are short compared with typical time delays; thus both the magnification ratio and the time delay can be measured for the delayed counterparts. These measurements are a basis for localizing the emitting region along the jet. To demonstrate the power of strong gravitational lensing, we build a toy model based on the best studied and the nearest relativistic jet M87.

Barnacka, Anna; Geller, Margaret J.; Dell'antonio, Ian P.; Benbow, Wystan

2014-06-01

310

Gravitational Lensing Effect on the Hawking Radiation of Dyonic Black Holes

In this paper, we analyze the Hawking radiation (HR) of a non-asymptotically flat (NAF) dyonic black hole (dBH) in four-dimensional (4D) Einstein-Maxwell-Dilaton (EMD) gravity by using one of the semiclassical approaches which is the so-called Hamilton-Jacobi (HJ) method. We particularly motivate on the isotropic coordinate system (ICS) of the dBH in order to highlight the ambiguity to be appeared in the derivation of the Hawking temperature (T_{H}) via the HJ method. Besides, it will be shown that the ICS allows us to write the metric of the dBH in form of the Fermat metric, which renders possible of identification of the refractive index (n) of the dBH. It is shown that the value of n and therefore the gravitational lensing effect is decisive on the the tunneling rate of the HR. We also uncloak how one can resolve the discrepancy about the T_{H} of the dBH in spite of that lensing effect.

Sakalli, I; Mirekhtiary, S F

2014-01-01

311

Gravitational Lensing Effect on the Hawking Radiation of Dyonic Black Holes

In this paper, we analyze the Hawking radiation (HR) of a non-asymptotically flat (NAF) dyonic black hole (dBH) in four-dimensional (4D) Einstein-Maxwell-Dilaton (EMD) gravity by using one of the semiclassical approaches which is the so-called Hamilton-Jacobi (HJ) method. We particularly motivate on the isotropic coordinate system (ICS) of the dBH in order to highlight the ambiguity to be appeared in the derivation of the Hawking temperature (T_{H}) via the HJ method. Besides, it will be shown that the ICS allows us to write the metric of the dBH in form of the Fermat metric, which renders possible of identification of the refractive index (n) of the dBH. It is unraveled that the value of n and therefore the gravitational lensing effect is decisive on the the tunneling rate of the HR. We also uncloak how one can resolve the discrepancy about the T_{H} of the dBH in spite of that lensing effect.

I. Sakalli; A. Ovgun; S. F. Mirekhtiary

2014-05-21

312

MULTIPOLE GRAVITATIONAL LENSING AND HIGH-ORDER PERTURBATIONS ON THE QUADRUPOLE LENS

An arbitrary surface mass density of the gravitational lens can be decomposed into multipole components. We simulate the ray tracing for the multipolar mass distribution of the generalized Singular Isothermal Sphere model based on deflection angles, which are analytically calculated. The magnification patterns in the source plane are then derived from an inverse shooting technique. As has been found, the caustics of odd mode lenses are composed of two overlapping layers for some lens models. When a point source traverses this kind of overlapping caustics, the image numbers change by {+-}4, rather than {+-}2. There are two kinds of caustic images. One is the critical curve and the other is the transition locus. It is found that the image number of the fold is exactly the average value of image numbers on two sides of the fold, while the image number of the cusp is equal to the smaller one. We also focus on the magnification patterns of the quadrupole (m = 2) lenses under the perturbations of m = 3, 4, and 5 mode components and found that one, two, and three butterfly or swallowtail singularities can be produced, respectively. With the increasing intensity of the high-order perturbations, the singularities grow up to bring sixfold image regions. If these perturbations are large enough to let two or three of the butterflies or swallowtails make contact, then eightfold or tenfold image regions can be produced as well. The possible astronomical applications are discussed.

Chu, Z.; Lin, W. P. [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Li, G. L. [Purple Mountain Observatory, 2 West Beijing Road, Nanjing 210008 (China); Kang, X., E-mail: chuzhe@shao.ac.cn, E-mail: linwp@shao.ac.cn [Partner Group of MPI for Astronomy, Purple Mountain Observatory, 2 West Beijing Road, Nanjing 210008 (China)

2013-03-10

313

NASA Astrophysics Data System (ADS)

Gravitational lens modelling of spatially resolved sources is a challenging inverse problem with many observational constraints and model parameters. We examine established pixel-based source reconstruction algorithms for de-lensing the source and constraining lens model parameters. Using test data for four canonical lens configurations, we explore statistical and systematic uncertainties associated with gridding, source regularization, interpolation errors, noise, and telescope pointing. Specifically, we compare two gridding schemes in the source plane: a fully adaptive grid that follows the lens mapping but is irregular, and an adaptive Cartesian grid. We also consider regularization schemes that minimize derivatives of the source (using two finite difference methods) and introduce a scheme that minimizes deviations from an analytic source profile. Careful choice of gridding and regularization can reduce `discreteness noise' in the ?2 surface that is inherent in the pixel-based methodology. With a gridded source, some degree of interpolation is unavoidable, and errors due to interpolation need to be taken into account (especially for high signal-to-noise data). Different realizations of the 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 per cent for a peak signal-to-noise ratio of 10, which decreases as the data quality improves.

Tagore, Amitpal S.; Keeton, Charles R.

2014-11-01

314

The Impact of Galaxies on their Environment from Observations of Gravitationally lensed QSOs

Observations of absorption systems in close, multiple lines of sight to gravitationally lensed QSOs can be used to infer the density fluctuations and motions of the gas clouds giving rise to the Lyman alpha forest phenomenon and to QSO metal absorption lines. We describe a survey of lensed QSOs with the Keck HIRES instrument and argue that one can derive limits on the frequency and importance of hydrodynamical disturbances inflicted by galaxies on the surrounding gas from such data. We discuss differences between the kinematic properties of low density unsaturated Lyman alpha forest absorption systems, high ionization CIV absorption systems, and low ionization gas visible in SiII and CII. The general intergalactic medium appears to show very little turbulence, but the presumable denser CIV systems exhibit evidence of having been stirred repeatedly (by winds ?) in the past on time scales similar to those governing stellar feedback and possibly galaxy mergers. The quiescence of the low density IGM can be used to put upper limits on the incidence and energetics of galactic winds on a cosmological time scale.

Michael Rauch

2001-11-01

315

We explore the weak lensing effects by ministructures in the line-of-sight in a quadruply lensed quasar MG0414+0534 that shows an anomaly in the flux-ratios. We find that the observed flux-ratio anomaly can be explained by a presence of either a minifilament or a minivoid in the line-of-sight with a surface mass density of the order of 10^(8-9) h^(-1) solar mass /arcsec^2 without taking into account any subhalos in the lensing galaxy. The astrometric perturbation by a possible minifilament/minivoid is ~100 pc. Observation at the submillimeter band using interferometers will enable us to determine the origin of anomalies in the flux ratios.

Inoue, Kaiki Taro

2014-01-01

316

We use numerical simulations to test a broad range of plausible observational strategies designed to measure the time delay between the images of gravitationally lensed quasars. Artificial quasar light curves are created along with Monte-Carlo simulations in order to determine the best temporal sampling to adopt when monitoring the photometric variations of systems with time delays between 5 and 120 days, i.e., always shorter than the visibility window across the year. Few and realistic assumptions are necessary on the quasar photometric variations (peak-to-peak amplitude and time-scale of the variations) and on the accuracy of the individual photometric points. The output of the simulations is the (statistical) relative error made on the time delay measurement, as a function of 1- the object visibility over the year, 2- the temporal sampling of the light curves and 3- the time delay. Also investigated is the effect of long term microlensing variations which must be below the 5 % level (either intrinsically or by subtraction) if the goal is to measure time delays with an accuracy of 1-2 %. However, while microlensing increases the random error on the time delay, it does not significantly increase the systematic error, which is always a factor 5 to 10 smaller than the random error. Finally, it is shown that, when the time delay is comparable to the visibility window of the object, a logarithmic sampling can significantly improve the time delay determination. All results are presented in the form of compact plots to be used to optimize the observational strategy of future monitoring programs.

A. Eigenbrod; F. Courbin; C. Vuissoz; G. Meylan; P. Saha; S. Dye

2005-03-01

317

Wave propagation in a weak gravitational field and the validity of the thin lens approximation

Wave effects can be important for the gravitational lensing of gravitational waves. In such a case, wave optics must be used in stead of geometric optics. We consider a plane wave entering a lens object and solve numerically the wave equation for three lens models: the uniform density sphere, the singular isothermal sphere, and the Hernquist model. By comparing our numerical solutions with the analytical solutions under the thin lens approximation, we evaluate the error of this approximation. The results show that the relative error of the thin lens approximation is small if the geometrical thickness of the lens is much smaller than the distance between the lens and the observer.

Teruaki Suyama; Ryuichi Takahashi; Shugo Michikoshi

2005-05-02

318

SUBARU WEAK-LENSING STUDY OF A2163: BIMODAL MASS STRUCTURE

We present a weak-lensing analysis of the merging cluster A2163 using Subaru/Suprime-Cam and CFHT/Mega-Cam data and discuss the dynamics of this cluster merger, based on complementary weak-lensing, X-ray, and optical spectroscopic data sets. From two-dimensional multi-component weak-lensing analysis, we reveal that the cluster mass distribution is well described by three main components including the two-component main cluster A2163-A with mass ratio 1:8, and its cluster satellite A2163-B. The bimodal mass distribution in A2163-A is similar to the galaxy density distribution, but appears as spatially segregated from the brightest X-ray emitting gas region. We discuss the possible origins of this gas-dark-matter offset and suggest the gas core of the A2163-A subcluster has been stripped away by ram pressure from its dark matter component. The survival of this gas core from the tidal forces exerted by the main cluster lets us infer a subcluster accretion with a non-zero impact parameter. Dominated by the most massive component of A2163-A, the mass distribution of A2163 is well described by a universal Navarro-Frenk-White profile as shown by a one-dimensional tangential shear analysis, while the singular-isothermal sphere profile is strongly ruled out. Comparing this cluster mass profile with profiles derived assuming intracluster medium hydrostatic equilibrium (H.E.) in two opposite regions of the cluster atmosphere has allowed us to confirm the prediction of a departure from H.E. in the eastern cluster side, presumably due to shock heating. Yielding a cluster mass estimate of M{sub 500} = 11.18{sup +1.64}{sub -1.46} Multiplication-Sign 10{sup 14} h {sup -1} M{sub Sun }, our mass profile confirms the exceptionally high mass of A2163, consistent with previous analyses relying on the cluster dynamical analysis and Y{sub X} mass proxy.

Okabe, N. [Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), P.O. Box 23-141, Taipei 10617, Taiwan (China); Bourdin, H.; Mazzotta, P. [Dipartimento di Fisica, Universita degli Studi di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133 Roma (Italy); Maurogordato, S., E-mail: okabe@asiaa.sinica.edu.tw [Universite de Nice Sophia-Antipolis, CNRS, Laboratoire Cassiopee, CNRS, UMR 6202, Observatoire de la Cote d' Azur, BP4229, 06304 Nice Cedex 4 (France)

2011-11-10

319

Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray-selected galaxy groups to investigate the scaling relation between X-ray luminosity (L{sub X}) and halo mass (M{sub 200}) where M{sub 200} is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 degrees{sup 2} of contiguous imaging with the Advanced Camera for Surveys to a limiting magnitude of I{sub F814W} = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 x 10{sup -15} erg cm{sup -2} s{sup -1} in the 0.5-2 keV band. The combined depth of these two data sets allows us to probe the lensing signals of X-ray-detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law, M{sub 200} propor to (L{sub X}){sup a}lpha, with a slope of alpha = 0.66 +- 0.14. These results significantly extend the dynamic range for which the halo masses of X-ray-selected structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-L{sub X} relation. The combination of our group data with previously published cluster data demonstrates that the M-L{sub X} relation is well described by a single power law, alpha = 0.64 +- 0.03, over two decades in mass, M{sub 200} approx 10{sup 13.5}-10{sup 15.5} h {sup -1}{sub 72} M{sub sun}. These results are inconsistent at the 3.7sigma level with the self-similar prediction of alpha = 0.75. We examine the redshift dependence of the M-L{sub X} relation and find little evidence for evolution beyond the rate predicted by self-similarity from z approx 0.25 to z approx 0.8.

Leauthaud, Alexie [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley CA 94720 (United States); Finoguenov, Alexis; Cappelluti, Nico; Giodini, Stefania [Max Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garchingbei Muenchen (Germany); Kneib, Jean-Paul; Ilbert, Olivier; Le Fevre, Oliver [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Massey, Richard; Heymans, Catherine [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Rhodes, Jason [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Bundy, Kevin; George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Tinker, Jeremy [Berkeley Center for Cosmological Physics, University of California, Berkeley, CA 94720 (United States); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 E. California Blvd. Pasadena, CA 91125 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Johnston, David E. [Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208-2900 (United States); Zhang, Yu-Ying [Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, 53121 Bonn (Germany); Ellis, Richard S. [California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Elvis, Martin, E-mail: asleauthaud@lbl.go [Harvard-Smithsonian Center for Astrophysics 60 Garden St., Cambridge, MA 02138 (United States)

2010-01-20

320

Weak-lensing detection of intracluster filaments with ground-based data

NASA Astrophysics Data System (ADS)

According to the current standard model of cosmology, matter in the Universe arranges itself along a network of filamentary structure. These filaments connect the main nodes of this so-called "cosmic web", which are clusters of galaxies. Although its large-scale distribution is clearly characterized by numerical simulations, constraining the dark-matter content of the cosmic web in reality turns out to be difficult. The natural method of choice is gravitational lensing. However, the direct detection and mapping of the elusive filament signal is challenging and in this work we present two methods that are specifically tailored to achieve this task. A linear matched filter aims at detecting the smooth mass-component of filaments and is optimized to perform a shear decomposition that follows the anisotropic component of the lensing signal. Filaments clearly inherit this property due to their morphology. At the same time, the contamination arising from the central massive cluster is controlled in a natural way. The filament 1? detection is of about ? ~ 0.01 - 0.005 according to the filter's template width and length, enabling the detection of structures beyond reach with other approaches. The second, complementary method seeks to detect the clumpy component of filaments. The detection is determined by the number density of subclump identifications in an area enclosing the potential filament, as was found within the observed field with the filter approach. We tested both methods against mocked observations based on realistic N-body simulations of filamentary structure and proved the feasibility of detecting filaments with ground-based data.

Maturi, Matteo; Merten, Julian

2013-11-01

321

Sérsic galaxy models in weak lensing shape measurement: model bias, noise bias and their interaction

NASA Astrophysics Data System (ADS)

Cosmic shear is a powerful probe of cosmological parameters, but its potential can be fully utilized only if galaxy shapes are measured with great accuracy. Two major effects have been identified which are likely to account for most of the bias seen for maximum likelihood methods in recent shear measurement challenges. Model bias occurs when the true galaxy shape is not well represented by the fitted model. Noise bias occurs due to the non-linear relationship between image pixels and galaxy shape. In this paper we investigate the potential interplay between these two effects when an imperfect model is used in the presence of high noise. We present analytical expressions for this bias, which depends on the residual difference between the model and real data. They can lead to biases not accounted for in previous calibration schemes. By measuring the model bias, noise bias and their interaction, we provide a complete statistical framework for measuring galaxy shapes with model fitting methods from GRavitational lEnsing Accuracy Testing (GREAT)-like images. We demonstrate the noise and model interaction bias using a simple toy model, which indicates that this effect can potentially be significant. Using real galaxy images from the Cosmological Evolution Survey (COSMOS) we quantify the strength of the model bias, noise bias and their interaction. We find that the interaction term is often of a similar size to the model bias term, and is smaller than the requirements of current and near future galaxy surveys.

Kacprzak, Tomasz; Bridle, Sarah; Rowe, Barnaby; Voigt, Lisa; Zuntz, Joe; Hirsch, Michael; MacCrann, Niall

2014-07-01

322

NASA Astrophysics Data System (ADS)

We propose WFC3 G102 and G141 grism spectral imaging of two gravitationally lensed dusty, starburst galaxies found with the 600 square degree Herschel-ATLAS survey. One galaxy is the brightest {both in far-IR at 250 micron and in near-IR in J/K-band}, while the second is the largest {11 arcsec on the sky} of the lensed sub-mm galaxies in a sample of 200 imaged with WFC3/F110W. The two galaxies are at redshifts that are optimal for grism observations with HST/WFC3. The lensing flux magnification and spatial enhancement makes them very unique for the study proposed hereand will increase the number of lensed galaxies imaged in spectral lines with WFC3 grisms to three from existing single serendipitous lens studied in HST-3D survey. With WFC3 grism spectra taken in a specific orientation to minimize foreground and lensing galaxy confusion we can map each of these galaxies in a variety of spatially-resolved spectral lines in the rest-frame optical, including impostant Balmer lines for studies on the interstellar medium. The grism spectra will allow us to determine the gas-phase metallicities of these two galaxies and to study the extinction of optically-thin regions compared to direct sub-mm emission seen in interferometric continuum images of optically thick dust in starbursting knots and clumps. With spatial resolution provided by gravitational lensing combined with HST/WFC3 resolution, we will be able to study the dependence of line ratios in high density/SFR regions to low dense diffuse environments.

Cooray, Asantha

2013-10-01

323

Strong Gravitational Lensing as a Probe of Gravity, Dark-Matter and Super-Massive Black Holes

Whereas considerable effort has been afforded in understanding the properties of galaxies, a full physical picture, connecting their baryonic and dark-matter content, super-massive black holes, and (metric) theories of gravity, is still ill-defined. Strong gravitational lensing furnishes a powerful method to probe gravity in the central regions of galaxies. It can (1) provide a unique detection-channel of dark-matter substructure beyond

L. V. E. Koopmans; M. Barnabe; A. Bolton; M. Bradac; L. Ciotti; A. Congdon; O. Czoske; S. Dye; A. Dutton; A. Elliasdottir; E. Evans; C. D. Fassnacht; N. Jackson; C. Keeton; J. Lasio; L. Moustakas; M. Meneghetti; S. Myers; C. Nipoti; S. Suyu; G. van de Ven; S. Vegetti; O. Wucknitz; H.-S. Zhao; J. Wambsganss; R. Webster

2009-01-01

324

We use a mock catalog of galaxies based on the COSMOS galaxy catalog, including information on photometric redshift (photo-z) and spectral energy distribution types of galaxies, in order to study how to define a galaxy subsample suitable for weak lensing tomography feasible with optical (and near-IR) multi-band data. Since most useful cosmological information arises from the sample variance limited regime for upcoming lensing surveys, a suitable subsample can be obtained by discarding a large fraction of galaxies that have less reliable photo-z estimations. We develop a method to efficiently identify photo-z outliers by monitoring the width of the posterior likelihood function of redshift estimation for each galaxy. This clipping method may allow us to obtain clean tomographic redshift bins (here three bins are considered) that have almost no overlap, by discarding more than {approx}70% of galaxies with ill-defined photo-zs corresponding to the number densities of remaining galaxies less than {approx}20 arcmin{sup -2} for a Subaru-type deep survey. Restricting the ranges of magnitudes and redshifts and/or adding near-IR data help us obtain a cleaner redshift binning. Using the Fisher information matrix formalism, we propagate photo-z errors into biases in the dark energy equation of state parameter w. We find that, by discarding most of the ill-defined photo-z galaxies, the bias in w can be reduced to a level comparable to the marginalized statistical error; however, the residual small systematic bias remains due to asymmetric scatters around the relation between photometric and true redshifts. We also use the mock catalog to estimate the cumulative signal-to-noise ratios (S/Ns) for measuring the angular cross-correlations of galaxies between finer photo-z bins, finding higher S/N values for the bins that include photo-z outliers.

Nishizawa, Atsushi J. [Astronomical Institute, Tohoku University, Aramaki Aobaku, Sendai 980-8578 (Japan); Takada, Masahiro [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582 (Japan); Hamana, Takashi; Furusawa, Hisanori, E-mail: nishizawa@astr.tohoku.ac.j [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka City, Tokyo 181-8588 (Japan)

2010-08-01

325

NASA Astrophysics Data System (ADS)

We present a finely binned tomographic weak lensing analysis of the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) mitigating contamination to the signal from the presence of intrinsic galaxy alignments via the simultaneous fit of a cosmological model and an intrinsic alignment model. CFHTLenS spans 154 square degrees in five optical bands, with accurate shear and photometric redshifts for a galaxy sample with a median redshift of zm = 0.70. We estimate the 21 sets of cosmic shear correlation functions associated with six redshift bins, each spanning the angular range of 1.5 < ? < 35 arcmin. We combine this CFHTLenS data with auxiliary cosmological probes: the cosmic microwave background with data from WMAP7, baryon acoustic oscillations with data from Baryon Oscillation Spectroscopic Survey and a prior on the Hubble constant from the Hubble Space Telescope distance ladder. This leads to constraints on the normalization of the matter power spectrum ?8 = 0.799 ± 0.015 and the matter density parameter ?m = 0.271 ± 0.010 for a flat ? cold dark matter (?CDM) cosmology. For a flat wCDM cosmology, we constrain the dark energy equation-of-state parameter w = -1.02 ± 0.09. We also provide constraints for curved ?CDM and wCDM cosmologies. We find the intrinsic alignment contamination to be galaxy-type dependent with a significant intrinsic alignment signal found for early-type galaxies, in contrast to the late-type galaxy sample for which the intrinsic alignment signal is found to be consistent with zero.

Heymans, Catherine; Grocutt, Emma; Heavens, Alan; Kilbinger, Martin; Kitching, Thomas D.; Simpson, Fergus; Benjamin, Jonathan; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Brown, Michael L.; Coupon, Jean; Fu, Liping; Harnois-Déraps, Joachim; Hudson, Michael J.; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta; Vafaei, Sanaz; Velander, Malin

2013-07-01

326

NASA Astrophysics Data System (ADS)

We study the geometry and the internal structure of the outflowing wind from the accretion disk of a quasar by observing multiple sightlines with the aid of strong gravitational lensing. Using Subaru/High Dispersion Spectrograph, we performed high-resolution (R ~ 36,000) spectroscopic observations of images A and B of the gravitationally lensed quasar SDSS J1029+2623 (at z em ~ 2.197) whose image separation angle, ? ~ 22.''5, is the largest among those discovered so far. We confirm that the difference in absorption profiles in images A and B discovered by Misawa et al. has remained unchanged since 2010, implying the difference is not due to time variability of the absorption profiles over the delay between the images, ?t ~ 744 days, but rather due to differences along the sightlines. We also discovered a time variation of C IV absorption strength in both images A and B due to a change in the ionization condition. If a typical absorber's size is smaller than its distance from the flux source by more than five orders of magnitude, it should be possible to detect sightline variations among images of other smaller separation, galaxy-scale gravitationally lensed quasars. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Misawa, Toru; Inada, Naohisa; Oguri, Masamune; Gandhi, Poshak; Horiuchi, Takashi; Koyamada, Suzuka; Okamoto, Rina

2014-10-01

327

LoCuSS: the near-infrared luminosity and weak-lensing mass scaling relation of galaxy clusters

NASA Astrophysics Data System (ADS)

We present the first scaling relation between weak-lensing galaxy cluster mass, MWL, and near-infrared luminosity, LK. Our results are based on 17 clusters observed with wide-field instruments on Subaru, the United Kingdom Infrared Telescope, the Mayall Telescope, and the MMT. We concentrate on the relation between projected 2D weak-lensing mass and spectroscopically confirmed luminosity within 1 Mpc, modelled as M_WL ? LK^b, obtaining a power-law slope of b=0.83^{+0.27}_{-0.24} and an intrinsic scatter of ? _{lnM_WL|LK}=10^{+8}_{-5} per cent. Intrinsic scatter of ˜10 per cent is a consistent feature of our results regardless of how we modify our approach to measuring the relationship between mass and light. For example, deprojecting the mass and measuring both quantities within r500, that is itself obtained from the lensing analysis, yields ? _{lnM_WL|LK}=10^{+7}_{-5} per cent and b=0.97^{+0.17}_{-0.17}. We also find that selecting members based on their (J - K) colours instead of spectroscopic redshifts neither increases the scatter nor modifies the slope. Overall our results indicate that near-infrared luminosity measured on scales comparable with r500 (typically 1 Mpc for our sample) is a low scatter and relatively inexpensive proxy for weak-lensing mass. Near-infrared luminosity may therefore be a useful mass proxy for cluster cosmology experiments.

Mulroy, Sarah L.; Smith, Graham P.; Haines, Chris P.; Marrone, Daniel P.; Okabe, Nobuhiro; Pereira, Maria J.; Egami, Eiichi; Babul, Arif; Finoguenov, Alexis; Martino, Rossella

2014-10-01

328

Helical Jet in the Gravitationally Lensed Blazar PKS1830-211

Recent radio VLBI observations of the complex gravitationally lensed system PKS1830-211 have thrown up some questions with regard to the processes occuring at the heart of the blazar source at a redshift of 2.51, which is viewed almost straight down the jet axis. This work links, by a model of a helical jet tracked by ballistically ejected plasmons from a precessing nozzle, observations on the scale of tens of microarcseconds to those on the scale of milliarcseconds. An observed jet precession period of 1.08 years is inferred from the model, translating to an intrinsic period of 30.8 years for a source at redshift 2.51 and an assumed jet bulk velocity of 0.99 c. This fits well with the picture of an active galactic nucleus hosting a binary black hole system at its centre, with the jet emitted by one member of the system, and the precession as being due to its orbital motion around its companion.

S. Nair; C. Jin; M. A. Garrett

2005-07-01

329

Strong gravitational lensing as a tool to investigate the structure of jets at high energies

The components of blazar jets that emit radiation span a factor of $10^{10}$ in scale. The spatial structure of these emitting regions depends on the observed energy. Photons emitted at different sites cross the lens plane at different distances from the mass-weighted center of the lens. Thus there are differences in magnification ratios and time delays between the images of lensed blazars observed at different energies. When the lens structure and redshift are known from optical observations, these constraints can elucidate the structure of the source at high energies. At these energies, current technology is inadequate to resolve these sources and the observed light curve is thus the sum of the images. Durations of $\\gamma$-ray flares are short compared with typical time delays; thus both the magnification ratio and the time delay can be measured for the delayed counterparts. These measurements are a basis for localizing the emitting region along the jet. To demonstrate the power of strong gravitational len...

Barnacka, Anna; Dell'antonio, Ian P; Benbow, Wystan

2014-01-01

330

THE REMARKABLE {gamma}-RAY ACTIVITY IN THE GRAVITATIONALLY LENSED BLAZAR PKS 1830-211

We report the extraordinary {gamma}-ray activity (E > 100 MeV) of the gravitationally lensed blazar PKS 1830-211 (z = 2.507) detected by AGILE between 2010 October and November. On October 14, the source experienced a factor of {approx}12 flux increase with respect to its average value and remained brightest at this flux level ({approx}500 x 10{sup -8} photons cm{sup -2} s{sup -1}) for about four days. The one-month {gamma}-ray light curve across the flare showed a mean flux F(E > 100 MeV) = 200 x 10{sup -8} photons cm{sup -2} s{sup -1}, which resulted in a factor of four enhancement with respect to the average value. Following the {gamma}-ray flare, the source was observed in near-IR (NIR)-optical energy bands at the Cerro Tololo Inter-American Observatory and in X-Rays by Swift/X-Ray Telescope and INTEGRAL/IBIS. The main result of these multifrequency observations is that the large variability observed in {gamma}-rays does not have a significant counterpart at lower frequencies: no variation greater than a factor of {approx}1.5 appeared in the NIR and X-Ray energy bands. PKS 1830-211 is then a good '{gamma}-ray only flaring' blazar showing substantial variability only above 10-100 MeV. We discuss the theoretical implications of our findings.

Donnarumma, I.; De Rosa, A.; Vittorini, V.; Tavani, M.; Striani, E.; Pacciani, L. [INAF/IASF-Roma, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Miller, H. R.; Eggen, J.; Maune, J. [Department of Physics and Astronomy Georgia State University, GA 30303-3083 (United States); Popovic, L. C. [Astronomical Observatory, Volgina 7, 11160, Belgrade 74 (Serbia); Simic, S. [Isaac Newton Institute of Chile, Yugoslavia Branch, Belgrade (Serbia); Kuulkers, E. [European Space Astronomy Centre, SRE-O, Villanueva de la Canada, Madrid (Spain); Vercellone, S. [INAF/IASF Palermo Via Ugo La Malfa 153, 90146 Palermo (Italy); Pucella, G. [ENEA-Frascati, Via E. Fermi 45, I-00044 Frascati, Roma (Italy); Verrecchia, F.; Pittori, C.; Giommi, P. [ASI-ASDC, Via G. Galilei, I-00044 Frascati, Roma (Italy); Barbiellini, G. [Dipartimento di Fisica and INFN Trieste, Via Valerio 2, I-34127 Trieste (Italy); Bulgarelli, A. [INAF/IASF-Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Cattaneo, P. W., E-mail: immacolata.donnarumma@iasf-roma.inaf.it [INFN-Pavia, Via Bassi 6, I-27100 Pavia (Italy)

2011-08-01

331

The remarkable gamma-ray activity in the gravitationally lensed blazar PKS 1830-211

We report the extraordinary gamma-ray activity (E>100 MeV) of the gravitationally lensed blazar PKS 1830-211 (z=2.507) detected by AGILE between October and November 2010. The source experienced on October 14 a flux increase of a factor of ~ 12 with respect to its average value and kept brightest at this flux level (~ 500 x 10^{-8} ph cm^-2 sec^-1) for about 4 days. The 1-month gamma-ray light curve across the flare showed a mean flux F(E>100 MeV)= 200 x 10^{-8} ph cm^-2 sec^-1, which resulted in an enhancement by a factor of 4 with respect to the average value. Following the gamma-ray flare, the source was observed in NIR-Optical energy bands at the Cerro Tololo Inter-American Observatory and in X-rays by Swift/XRT and INTEGRAL/IBIS. The main result of these multifrequency observations is that the large variability observed in gamma-rays has not a significant counterpart at lower frequencies: no variation greater than a factor of ~ 1.5 resulted in NIR and X-ray energy bands. PKS 1830-211 is then a good "gamm...

Donnarumma, I; Vittorini, V; Miller, H R; Popovic, L C; Simic, S; Tavani, M; Eggen, J; Maune, J; Kuulkers, E; Striani, E; Vercellone, S; Pucella, G; Verrecchia, F; Pittori, C; Giommi, P; Pacciani, L; Barbiellini, G; Bulgarelli, A; Cattaneo, P W; Chen, A W; Costa, E; Del Monte, E; Evangelista, Y; Feroci, M; Fuschino, F; Gianotti, F; Giuliani, A; Giusti, M; Lazzarotto, F; Longo, F; Lucarelli, F; Pellizzoni, A; Piano, G; Soffitta, P; Trifoglio, M; Trois, A

2011-01-01

332

We present the first VLT near-IR observations of a gravitationally lensed quasar, using adaptive optics and laser guide star. These observations can be considered as a test bench for future systematic observations of lensed quasars with adaptive optics, even when bright natural guide stars are not available in the nearby field. With only 14 minutes of observing time, we derived very accurate astrometry of the quasar images and of the lensing galaxy, with 0.05 \\arcsec spatial resolution, comparable to the Hubble Space Telescope (HST). In combination with deep VLT optical spectra of the quasar images, we use our adaptive optics images to constrain simple models for the mass distribution of the lensing galaxy. The latter is almost circular and does not need any strong external shear to fit the data. The time delay predicted for SDSS0806+2006, assuming a singular isothermal ellipsoid model and the concordance cosmology, is Delta t \\simeq 50 days. Our optical spectra indicate a flux ratio between the quasar images of A/B=1.3 in the continuum and A/B=2.2 in both the MgII and in the CIII] broad emission lines. This suggests that microlensing affects the continuum emission. However, the constant ratio between the two emission lines indicates that the broad emission line region is not microlensed. Finally, we see no evidence of reddening by dust in the lensing galaxy.

D. Sluse; F. Courbin; A. Eigenbrod; G. Meylan

2008-09-17

333

Weak Gravitational Field in Finsler-Randers Space and Raychaudhuri Equation

The linearized form of the metric of a Finsler - Randers space is studied in relation to the equations of motion, the deviation of geodesics and the generalized Raychaudhuri equation are given for a weak gravitational field. This equation is also derived in the framework of a tangent bundle. By using Cartan or Berwald-like connections we get some types "gravito - electromagnetic" curvature. In addition we investigate the conditions under which a definite Lagrangian in a Randers space leads to Einstein field equations under the presence of electromagnetic field. Finally, some applications of the weak field in a generalized Finsler spacetime for gravitational waves are given.

P. Stavrinos

2012-02-17

334

Shape Profiles and Orientation Bias for Weak and Strong Lensing Cluster Halos

NASA Astrophysics Data System (ADS)

We study the intrinsic shape and alignment of isodensities of galaxy cluster halos extracted from the MultiDark MDR1 cosmological simulation. We find that the simulated halos are extremely prolate on small scales and increasingly spherical on larger ones. Due to this trend, analytical projection along the line of sight produces an overestimation of the concentration index as a decreasing function of radius, which we quantify by using both the intrinsic distribution of three-dimensional concentrations (c 200) and isodensity shape on weak and strong lensing scales. We find this difference to be ~18% (~9%) for low- (medium-)mass cluster halos with intrinsically low concentrations (c 200 = 1-3), while we find virtually no difference for halos with intrinsically high concentrations. Isodensities are found to be fairly well aligned throughout the entirety of the radial scale of each halo population. However, major axes of individual halos have been found to deviate by as much as ~30°. We also present a value-added catalog of our analysis results, which we have made publicly available to download.

Groener, A. M.; Goldberg, D. M.

2014-11-01

335

Baryonic effects on weak-lensing two-point statistics and its cosmological implications

We develop an extension of \\textit{the Halo Model} that describes analytically the corrections to the matter power spectrum due to the physics of baryons. We extend these corrections to the weak-lensing shear angular power spectrum. Within each halo, our baryonic model accounts for: 1) a central galaxy, the major stellar component whose properties are derived from abundance matching techniques; 2) a hot plasma in hydrostatic equilibrium and 3) an adiabatically-contracted dark matter component. This analytic approach allows us to compare our model to the dark-matter-only case. Our basic assumptions are tested against the hydrodynamical simulations of Martizzi et. al. (2014), with which a remarkable agreement is found. Our baryonic model has only one free parameter, $M_{\\rm crit}$, the critical halo mass that marks the transition between feedback-dominated halos, mostly devoid of gas, and gas rich halos, in which AGN feedback effects become weaker. We explore the entire cosmological parameter space, using the a...

Mohammed, Irshad; Teyssier, Romain; Amara, Adam

2014-01-01

336

We present the results of a survey for extremely red objects (EROs) undertaken in the fields of 10 massive galaxy cluster lenses at , combining sensitive, high-resolution Hubble Space Telescope imaging with deep, half-arcsecond K -band imaging from UKIRT. We detect 60 EROs with , of which 26 have in a total image-plane survey area of 49arcmin2 down to ,

Graham P. Smith; Ian Smail; J.-P. Kneib; Oliver Czoske; Harald Ebeling; A. C. Edge; R. Pelló; R. J. Ivison; Chris Packham; J.-F. Le Borgne

2002-01-01

337

NASA Technical Reports Server (NTRS)

With a redshift of 2.3, the IRAS source FSC 10214+4724 is apparently one of the most luminous objects known in the universe. We present an image of FSC 10214+4724 at 0.8 pm obtained with the Hubble Space Telescope (HST) WFPC2 Planetary Camera. The source appears as an unresolved (less then 0.06) arc 0.7 long, with significant substructure along its length. The center of curvature of the arc is located near an elliptical galaxy 1.18 to the north. An unresolved component 100 times fainter than the arc is clearly detected on the opposite side of this galaxy. The most straightforward interpretation is that FSC 10214+4724 is gravitationally lensed by the foreground elliptical galaxy, with the faint component a counter-image of the IRAS source. The brightness of the arc in the HST image is then magnified by approx. 100, and the intrinsic source diameter is approx. 0.0l (80 pc) at 0.25 microns rest wavelength. The bolometric luminosity is probably amplified by a smaller factor (approx. 30) as a result of the larger extent expected for the source in the far-infrared. A detailed lensing model is presented that reproduces the observed morphology and relative flux of the arc and counterimage and correctly predicts the position angle of the lensing galaxy. The model also predicts reasonable values for the velocity dispersion, mass, and mass-to-light ratio of the lensing galaxy for a wide range of galaxy redshifts. A redshift for the lensing galaxy of -0.9 is consistent with the measured surface brightness profile from the image, as well as with the galaxy's spectral energy distribution. The background lensed source has an intrinsic luminosity approx. 2 x 10(exp 13) L(solar mass) and remains a highly luminous quasar with an extremely large ratio of infrared to optical/ultraviolet luminosity.

Eisenhardt, Peter R.; Armus, Lee; Hogg, David W.; Soifer, B. T.; Neugebauer, G.; Werner, Michael W.

1996-01-01

338

Probing Structure in Cold Gas at z <~ 1 with Gravitationally Lensed Quasar Sightlines

NASA Astrophysics Data System (ADS)

Absorption lines in quasar spectra offer a powerful tool to study distant galaxies and intergalactic matter (IGM). The strongest of these absorbers, the damped Lyman-alpha (DLA) and sub-DLA absorbers constitute a large fraction of the neutral gas in galaxies. Galaxies located in front of gravitationally lensed quasars (GLQs) are probed by multiple sightlines; so DLA/sub-DLAs in these sightlines can probe the internal structure of interstellar material (ISM) and/or the environment of these galaxies. From the lens galaxy images, impact parameters of the absorbing regions from the galaxy centers can be obtained accurately. Unfortunately, very little information exists on the neutral gas and metal content of DLA/sub-DLAs located in front of GLQs with confirmed lens galaxies. This is because at low redshift where lens galaxies are well-imaged, the H I and key metal lines lie in the UV. Here we propose to study 6 GLQs with known lens redshifts and a total of 14 closely separated double or quadruple images, that show candidate DLA/sub-DLAs along multiple sightlines. Our goal is to measure H I Lyman-alpha absorption in these sightlines. Many of these absorbers are at the lens redshift, with impact parameters 0.6-5.8 kpc. Our observations will therefore allow us to constrain gradients in H I column density and metallicity (combining H I with ground-based metal line measurements) within these galaxies. Our data will also help to constrain the sizes of DLA/sub-DLA absorbing regions by increasing the existing sample of DLA/sub-DLAs probed at < 10 kpc separations by a factor of ~3. HST is essential because of the need for both UV coverage and high spatial resolution.

Kulkarni, Varsha

2014-10-01

339

NASA Astrophysics Data System (ADS)

We present RINGFINDER, a tool for finding galaxy-scale strong gravitational lenses in multi-band imaging data. By construction, the method is sensitive to configurations involving a massive foreground ETG and a faint, background, blue source. RINGFINDER detects the presence of blue residuals embedded in an otherwise smooth red light distribution by difference imaging in two bands. The method is automated for efficient application to current and future surveys, having originally been designed for the 150 deg2 Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We describe each of the steps of RINGFINDER. We then carry out extensive simulations to assess completeness and purity. For sources with magnification ? > 4, RINGFINDER reaches 42% (25%) completeness and 29% (86%) purity before (after) visual inspection. The completeness of RINGFINDER is substantially improved in the particular range of Einstein radii 0.''8 <= R Ein <= 2.''0 and lensed images brighter than g = 22.5, where it can be as high as ~70%. RINGFINDER does not introduce any significant bias in the source or deflector population. We conclude by presenting the final catalog of RINGFINDER CFHTLS galaxy-scale strong lens candidates. Additional information obtained with Hubble Space Telescope and Keck adaptive optics high-resolution imaging, and with Keck and Very Large Telescope spectroscopy, is used to assess the validity of our classification and measure the redshift of the foreground and the background objects. From an initial sample of 640,000 ETGs, RINGFINDER returns 2500 candidates, which we further reduce by visual inspection to 330 candidates. We confirm 33 new gravitational lenses from the main sample of candidates, plus an additional 16 systems taken from earlier versions of RINGFINDER. First applications are presented in the Strong Lensing Legacy Survey galaxy-scale lens sample paper series.

Gavazzi, Raphaël; Marshall, Philip J.; Treu, Tommaso; Sonnenfeld, Alessandro

2014-04-01

340

We propose an effective harmonic oscillator model in order to treat the fluctuations of the gravitational, strong and weak nuclear fields. With respect to the gravitational field, first we use the model to estimate its fluctuating strength, necessary to decohere the wavefunction of a cubic centimeter of air at the standard temperature and pressure conditions. Second, the fluctuation of a point mass through a distance equal to the Planck length leads to the self-gravitational interaction of a particle, which can be related to its de Broglie frequency. Third, by making the equality of the fluctuating field strength with the gravitational field of a mass M at half of its Schwarzschild radius, we obtain an estimate of the mass of the Universe. We also consider the fluctuations of the strong nuclear field, as a means to estimate the separation in energy between the ground state and the centroid of the excitated states of the nucleon. Finally, taking into account the neutron-proton mass difference, we use the fluctuations of the weak nuclear field in order to evaluate the weak coupling constant.

P. R. Silva

2001-12-10

341

Galaxy-scale strong gravitational lenses with measured stellar velocity dispersions allow a test of the weak-field metric on kiloparsec scales and a geometric measurement of the cosmological distance-redshift relation, ...

Schwab, Josiah

342

The standard cosmology is based on general relativity (GR) and includes dark matter and dark energy and predicts a fixed relationship between the gravitational potentials responsible for gravitational lensing and the matter overdensity. Alternative theories of gravity often make different predictions. We propose a set of measurements which can test this relationship, thereby distinguishing between dark energy or matter models and models in which gravity differs from GR. Planned surveys will be able to measure E(G), an observational quantity whose expectation value is equal to the ratio of the Laplacian of the Newtonian potentials to the peculiar velocity divergence, to percent accuracy. This will easily separate alternatives such as the cold dark matter model with a cosmological constant, Dvali-Gabadadze-Porrati, TeVeS, and f(R) gravity. PMID:17930657

Zhang, Pengjie; Liguori, Michele; Bean, Rachel; Dodelson, Scott

2007-10-01

343

Cross-correlation Weak Lensing of SDSS Galaxy Clusters III: Mass-to-light Ratios

We present measurements of the excess mass-to-light ratio measured around MaxBCG galaxy clusters observed in the SDSS. This red sequence cluster sample includes objects from small groups with M{sub 200} {approx} 5 x 10{sup 12}h{sup -1}M{sub {circle_dot}} to clusters with M{sub 200} {approx} 5 x 10{sup 15}h{sup -1}M{sub {circle_dot}}. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean {Delta}{yields}(r) = {rho}(r) -- {bar {rho}} for clusters in bins of richness and optical luminosity. We also measure the excess {sup 0.25}i-band luminosity density {Delta}{ell}(r) = {ell}(r) -- {bar {ell}}. For both mass and light, we de-project the profiles to produce 3D mass and light profiles over scales from 25h{sup -1} kpc to 22h{sup -1} Mpc. From these profiles we calculate the cumulative excess mass {Delta}M(r) and excess light {Delta}L(r) as a function of separation from the BCG. On small scales, where {rho}(r) >> {bar {rho}}, the integrated mass-to-light profile ({Delta}M/{Delta}L)(r) may be interpreted as the cluster mass-to-light ratio. We find the ({Delta}M/{Delta}L){sub 200}, the mass-to-light ratio within r{sub 200}, scales with cluster mass as a power law with index 0.33{+-}0.02. On large scales, where {rho}(r) {approx} {bar {rho}}, the {Delta}M/{Delta}L approaches an asymptotic value independent of scale or cluster richness. For small groups, the mean ({Delta}M/{Delta}L){sub 200} is much smaller than the asymptotic value, while for large clusters ({Delta}M/{Delta}L)200 is consistent with the asymptotic value. This asymptotic value should be proportional to the mean mass-to-light ratio of the universe {l_angle}M/L{r_angle}. We find {l_angle}M/L{r_angle} b{sup -2}{sub M/L} = 362 {+-} 54h measured in the {sup 0.25}i-bandpass. The parameter b{sup 2}{sub M/L} is primarily a function of the bias of the L {approx}< L* galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find {Omega}{sub m}b{sup -2}{sub M/L}= 0.20 {+-} 0.03, independent of the Hubble parameter.

Sheldon, Erin S.; Johnston, David E.; Masjedi, Morad; McKay, Timothy A.; Blanton, Michael R.; Scranton, Ryan; Wechsler, Risa H.; Koester, Ben P.; Hansen, Sarah M.; Frieman, Joshua A.; Annis, James

2007-09-28

344

Cross-correlation Weak Lensing of SDSS Galaxy Clusters III: Mass-to-light Ratios

We present measurements of the excess mass-to-light ratio measured aroundMaxBCG galaxy clusters observed in the SDSS. This red sequence cluster sample includes objects from small groups with masses ranging from ~5x10^{12} to ~10^{15} M_{sun}/h. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean \\Delta \\rho(r) = \\rho(r) - \\bar{\\rho} for clusters in bins of richness and optical luminosity. We also measure the excess luminosity density \\Delta l(r) = l(r) - \\bar{l} measured in the z=0.25 i-band. For both mass and light, we de-project the profiles to produce 3D mass and light profiles over scales from 25 kpc/ to 22 Mpc/h. From these profiles we calculate the cumulative excess mass M(r) and excess light L(r) as a function of separation from the BCG. On small scales, where \\rho(r) >> \\bar{\\rho}, the integrated mass-to-light profile may be interpreted as the cluster mass-to-light ratio. We find the M/L_{200}, the mass-to-light ratio within r_{200}, scales with cluster mass as a power law with index 0.33+/-0.02. On large scales, where \\rho(r) ~ \\bar{\\rho}, the M/L approaches an asymptotic value independent of cluster richness. For small groups, the mean M/L_{200} is much smaller than the asymptotic value, while for large clusters it is consistent with the asymptotic value. This asymptotic value should be proportional to the mean mass-to-light ratio of the universe . We find /b^2_{ml} = 362+/-54 h (statistical). There is additional uncertainty in the overall calibration at the ~10% level. The parameter b_{ml} is primarily a function of the bias of the L <~ L_* galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find \\Omega_m/b^2_{ml} = 0.02+/-0.03, independent of the Hubble parameter.

Erin S. Sheldon; David E. Johnston; Morad Masjedi; Timothy A. McKay; Michael R. Blanton; Ryan Scranton; Risa H. Wechsler; Ben P. Koester; Sarah M. Hansen; Joshua A. Frieman; James Annis

2007-09-07

345

We report the discovery of two doubly-imaged quasars, SDSS J100128.61+502756.9 and SDSS J120629.65+433217.6, at redshifts of 1.838 and 1.789 and with image separations of 2.86'' and 2.90'', respectively. The objects were selected as lens candidates from the Sloan Digital Sky Survey (SDSS). Based on the identical nature of the spectra of the two quasars in each pair and the identification of the lens galaxies, we conclude that the objects are gravitational lenses. The lenses are complicated; in both systems there are several galaxies in the fields very close to the quasars, in addition to the lens galaxies themselves. The lens modeling implies that these nearby galaxies contribute significantly to the lens potentials. On larger scales, we have detected an enhancement in the galaxy density near SDSS J100128.61+502756.9. The number of lenses with image separation of {approx} 3'' in the SDSS already exceeds the prediction of simple theoretical models based on the standard Lambda-dominated cosmology and observed velocity function of galaxies.

Oguri, Masamune; Inada, Naohisa; Hennawi, Joseph F.; Richards, Gordon T.; Johnston, David E.; Frieman, Joshua A.; Pindor, Bartosz; Strauss, Michael A.; Brunner, Robert; Becker, Robert H.; Castander, Francisco J.; Gregg, Michael D.; Hall, Patrick B.; Rix, Hans-Walter; Schneider, Donald P.; Bahcall, Neta A.; Brinkmann, Jonathan; York, Donald G. /Princeton U. Observ. /Tokyo U. /Tokyo U., Inst. Astron. /UC, Berkeley, Astron. Dept. /Chicago U., Astron. Astrophys. Ctr. /Fermilab /Canadian Inst. Theor. Astrophys. /Illinois U.,

2004-11-01

346

NASA Astrophysics Data System (ADS)

Application of the most robust method of measuring black hole masses, spatially resolved kinematics of gas and stars, is presently limited to nearby galaxies. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and 30m class telescopes (the Thirty Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope) with milli-arcsecond resolution are expected to extend such measurements to larger distances. Here, we study the possibility of exploiting the angular magnification provided by strong gravitational lensing to measure black hole masses at high redshifts (z ~ 1-6), using resolved gas kinematics with these instruments. We show that in ~15% and ~20% of strongly lensed galaxies, the inner 25 and 50 pc could be resolved, allowing the mass of >~ 108 M ? black holes to be dynamically measured with ALMA, if moderately bright molecular gas is present at these small radii. Given the large number of strong lenses discovered in current millimeter surveys and future optical surveys, this fraction could constitute a statistically significant population for studying the evolution of the M-? relation at high redshifts.

Hezaveh, Yashar D.

2014-08-01

347

NASA Astrophysics Data System (ADS)

Measuring time delays between the multiple images of gravitationally lensed quasars is now recognized as a competitive way to constrain the cosmological parameters, and it is complementary with other cosmological probes. This requires long and well sampled optical light curves of numerous lensed quasars, such as those obtained by the COSMOGRAIL collaboration. High-quality data from our monitoring campaign call for novel numerical techniques to robustly measure the delays, as well as the associated random and systematic uncertainties, even in the presence of microlensing variations. We propose three different point estimators to measure time delays, which are explicitly designed to handle light curves with extrinsic variability. These methods share a common formalism, which enables them to process data from n-image lenses. Since the estimators rely on significantly contrasting ideas, we expect them to be sensitive to different bias sources. For each method and data set, we empirically estimate both the precision and accuracy (bias) of the time delay measurement using simulated light curves with known time delays that closely mimic the observations. Finally, we test the self-consistency of our approach, and we demonstrate that our bias estimation is serviceable. These new methods, including the empirical uncertainty estimator, will represent the standard benchmark for analyzing the COSMOGRAIL light curves.

Tewes, M.; Courbin, F.; Meylan, G.

2013-05-01

348

We study the geometry and the internal structure of the outflowing wind from the accretion disk of a quasar by observing multiple sightlines with the aid of strong gravitational lensing. Using Subaru/HDS, we performed high-resolution ($R$ $\\sim$ 36,000) spectroscopic observations of images A and B of the gravitationally lensed quasar SDSS J1029+2623 (at $z_{em}$ $\\sim$ 2.197) whose image separation angle, $\\theta$ $\\sim$ 22$^{\\prime\\prime}\\!\\!$.5, is the largest among those discovered so far. We confirm that the difference in absorption profiles in the images A and B discovered by Misawa et al. (2013) remains unchanged since 2010, implying the difference is not due to time variability of the absorption profiles over the delay between the images, $\\Delta t$ $\\sim$ 744 days, but rather due to differences along the sightlines. We also discovered time variation of C IV absorption strength in both images A and B, due to change of ionization condition. If a typical absorber's size is smaller than its distance from ...

Misawa, Toru; Oguri, Masamune; Gandhi, Poshak; Horiuchi, Takashi; Koyamada, Suzuka; Okamoto, Rina

2014-01-01

349

NASA Astrophysics Data System (ADS)

In this study, stability conditions of self-gravitating disc models are obtained. The self-gravitating disc models under study include known models such as the Maclaurin disc and the infinite, self-gravitating, rotating sheet. These models also include a new class of analytically solvable models denoted by 'generalized Maclaurin discs'. These self-gravitating, finite discs are differentially rotating with adiabatic index ? > 2 and have the property that the derivatives of densities go smoothly to zero at the boundary. Stability conditions of the various models are obtained through the 'weak energy principle' introduced by Katz, Inagaki & Yahalom. It is shown that necessary and sufficient conditions of stability are obtained when we have only pair coupling in the gyroscopic terms of the perturbed Lagrangian; otherwise, the 'weak energy principle' gives only sufficient conditions. All perturbations considered are in the same plane as the configurations. For differentially rotating discs, we consider only radial perturbations. The limits of stability are identical with those given by a dynamical analysis when available, and with the results of the strong energy principle analysis when given. Thus, although the 'weak energy' method is mathematically more simple than the 'strong energy' method of Katz et al., since it does not involve solving second-order partial differential equations, it is by no means less effective. Additional results also derived through the 'weak energy principle' include stability conditions for the 2D Rayleigh flows and Toomre's local criterion for the stability of rotating discs. Among the most interesting results is an exact extension of Toomre's criterion to the global stability of generalized Maclaurin discs, whereby a necessary condition for local stability becomes a sufficient condition for global stability.

Yahalom, Asher

2011-11-01

350

NASA Astrophysics Data System (ADS)

Quiescent massive galaxies at z ~ 2 are thought to be the progenitors of present-day massive ellipticals. Observations revealed them to be extraordinarily compact. Until now, the determination of stellar ages, star formation rates, and dust properties via spectroscopic measurements has been feasible only for the most luminous and massive specimens (~3 × Msstarf). Here we present a spectroscopic study of two near-infrared-selected galaxies that are close to the characteristic stellar mass Msstarf (~0.9 × Msstarf and ~1.3 × Msstarf) and whose observed brightness has been boosted by the gravitational lensing effect. We measure the redshifts of the two galaxies to be z = 1.71 ± 0.02 and z = 2.15 ± 0.01. By fitting stellar population synthesis models to their spectrophotometric spectral energy distributions we determine their ages to be 2.4^{+0.8}_{-0.6} Gyr and 1.7 ± 0.3 Gyr, respectively, which implies that the two galaxies have higher mass-to-light ratios than most quiescent z ~ 2 galaxies in other studies. We find no direct evidence for active star formation or active galactic nucleus activity in either of the two galaxies, based on the non-detection of emission lines. Based on the derived redshifts and stellar ages we estimate the formation redshifts to be z=4.3^{+3.4}_{-1.2} and z=4.3^{+1.0}_{-0.6}, respectively. We use the increased spatial resolution due to the gravitational lensing to derive constraints on the morphology. Fitting Sérsic profiles to the de-lensed images of the two galaxies confirms their compactness, with one of them being spheroid-like and the other providing the first confirmation of a passive lenticular galaxy at a spectroscopically derived redshift of z ~ 2. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, under programs 087.B-0812 (PI: Toft) and 073.A-0537 (PI: Kneib).

Geier, S.; Richard, J.; Man, A. W. S.; Krühler, T.; Toft, S.; Marchesini, D.; Fynbo, J. P. U.

2013-11-01

351

Massive structures, such as galaxies, act as strong gravitational lenses on background sources. When the background source is a quasar, several lensed images are seen, as magnified or de-magnified versions of the same object. The detailed study of the image configuration and the measurement of ``time-delays'' between the images yield estimates of the Hubble parameter H_0. We describe in a simple way the phenomenon of strong lensing and review recent progress made in the field, including microlensing by stars in the main lensing galaxy.

F. Courbin; P. Saha; P. L. Schechter

2002-08-01

352

Using galaxy-galaxy weak lensing measurements to correct the finger of God

NASA Astrophysics Data System (ADS)

For decades, cosmologists have been using galaxies to trace the large-scale distribution of matter. At present, the largest source of systematic uncertainty in this analysis is the challenge of modelling the complex relationship between galaxy redshift and the distribution of dark matter. If all galaxies sat in the centres of haloes, there would be minimal finger-of-God (FoG) effects and a simple relationship between the galaxy and matter distributions. However, many galaxies, even some of the luminous red galaxies (LRGs), do not lie in the centres of haloes. Because the galaxy-galaxy lensing is also sensitive to the off-centred galaxies, we show that we can use the lensing measurements to determine the amplitude of this effect and to determine the expected amplitude of FoG effects. We develop an approach for using the lensing data to model how the FoG suppresses the power spectrum amplitudes and show that the current data imply a 30 per cent suppression at wavenumber k = 0.2 h Mpc-1. Our analysis implies that it is important to complement a spectroscopic survey with an imaging survey with sufficient depth and wide field coverage. Joint imaging and spectroscopic surveys allow a robust, unbiased use of the power spectrum amplitude information: it improves the marginalized error of growth rate fg? d ln D/d ln a by up to a factor of 2 over a wide range of redshifts z < 1.4. We also find that the dark energy equation-of-state parameter, w0, and the neutrino mass, f?, can be unbiasedly constrained by combining the lensing information, with an improvement of 10-25 per cent compared to a spectroscopic survey without lensing calibration.

Hikage, Chiaki; Takada, Masahiro; Spergel, David N.

2012-02-01

353

NASA Astrophysics Data System (ADS)

Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S 500 > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r half) and far-infrared luminosities (L FIR) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z lens > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 ?m flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L FIR (median L FIR = 7.9 × 1012 L ?) and two decades in FIR luminosity surface density (median ?FIR = 6.0 × 1011 L ? kpc-2). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift. IMAGING OF HERSCHEL

Bussmann, R. S.; Pérez-Fournon, I.; Amber, S.; Calanog, J.; Gurwell, M. A.; Dannerbauer, H.; De Bernardis, F.; Fu, Hai; Harris, A. I.; Krips, M.; Lapi, A.; Maiolino, R.; Omont, A.; Riechers, D.; Wardlow, J.; Baker, A. J.; Birkinshaw, M.; Bock, J.; Bourne, N.; Clements, D. L.; Cooray, A.; De Zotti, G.; Dunne, L.; Dye, S.; Eales, S.; Farrah, D.; Gavazzi, R.; González Nuevo, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Laporte, N.; Maddox, S.; Martínez-Navajas, P.; Michalowski, M.; Negrello, M.; Oliver, S. J.; Roseboom, I. G.; Scott, Douglas; Serjeant, S.; Smith, A. J.; Smith, Matthew; Streblyanska, A.; Valiante, E.; van der Werf, P.; Verma, A.; Vieira, J. D.; Wang, L.; Wilner, D.

2013-12-01

354

Using galaxy-galaxy weak lensing measurements to correct the Finger-of-God

For decades, cosmologists have been using galaxies to trace the large-scale distribution of matter. At present, the largest source of systematic uncertainty in this analysis is the challenge of modeling the complex relationship between galaxy redshift and the distribution of dark matter. If all galaxies sat in the centers of halos, there would be minimal Finger-of-God (FoG) effects and a simple relationship between the galaxy and matter distributions. However, many galaxies, even some of the luminous red galaxies (LRGs), do not lie in the centers of halos. Because the galaxy-galaxy lensing is also sensitive to the off-centered galaxies, we show that we can use the lensing measurements to determine the amplitude of this effect and to determine the expected amplitude of FoG effects. We develop an approach for using the lensing data to model how the FoG suppresses the power spectrum amplitudes and show that the current data implies a 30% suppression at wavenumber k=0.2h/Mpc. Our analysis implies that it is impor...

Hikage, Chiaki; Spergel, David N

2011-01-01

355

Spatial and Temporal Variations of Light Curves in Gravitationally Lensed Sources

Effects of macro-and microlensing on the spatial and temporal characteristics of images of remote sources, observed through the inner regions of lensing galaxies are discussed. A particular attention was given to the case, when microlenses, - stars, star-like or planetary bodies, - are situated near the critical curves of macrolenses, - galaxies, stellar clusters, etc. The investigation is of interest

Anatolyi Minakov; V. G. Vakulik

2004-01-01

356

NASA Technical Reports Server (NTRS)

A simple method for deriving well-behaved temperature solutions to the equation of hydrostatic equilibrium for intracluster media with X-ray imaging observations is presented and applied to a series of generalized models as well as to observations of the Perseus cluster and Abell 2256. In these applications the allowed range in the ratio of nonbaryons to baryons as a function of radius is derived, taking into account the uncertainties and crude spatial resolution of the X-ray spectra and considering a range of physically reasonable mass models with various scale heights. Particular attention is paid to the central regions of the cluster, and it is found that the dark matter can be sufficiently concentrated to be consistent with the high central mass surface densities for moderate-redshift clusters from their gravitational lensing properties.

Loewenstein, M.

1994-01-01

357

Strong gravitational lensing provides a powerful means for studying faint galaxies in the distant universe. By magnifying the apparent brightness of background sources, massive clusters enable the detection of galaxies fainter than the usual sensitivity limit for blank fields. However, this gain in effective sensitivity comes at the cost of a reduced survey volume and, in this {\\it Letter}, we demonstrate there is an associated increase in the cosmic variance uncertainty. As an example, we show that the cosmic variance uncertainty of the high redshift population viewed through the Hubble Space Telescope Frontier Field cluster Abell 2744 increases from ~35% at redshift z~7 to >~65% at z~10. Previous studies of high redshift galaxies identified in the Frontier Fields have underestimated the cosmic variance uncertainty that will affect the ultimate constraints on both the faint end slope of the high-redshift luminosity function and the cosmic star formation rate density, key goals of the Frontier Field program.

Robertson, Brant E; Dunlop, James S; McLure, Ross J; Stark, Daniel P; McLeod, Derek

2014-01-01

358

3D-HST GRISM SPECTROSCOPY OF A GRAVITATIONALLY LENSED, LOW-METALLICITY STARBURST GALAXY AT z = 1.847

We present Hubble Space Telescope (HST) imaging and spectroscopy of the gravitational lens SL2SJ02176-0513, a cusp arc at z = 1.847. The UV continuum of the lensed galaxy is very blue, which is seemingly at odds with its redder optical colors. The 3D-HST WFC3/G141 near-infrared spectrum of the lens reveals the source of this discrepancy to be extremely strong [O III] {lambda}5007 and H{beta} emission lines with rest-frame equivalent widths of 2000 {+-} 100 and 520 {+-} 40 A, respectively. The source has a stellar mass {approx}10{sup 8} M{sub Sun }, sSFR {approx} 100 Gyr{sup -1}, and detection of [O III] {lambda}4363 yields a metallicity of 12 + log (O/H) = 7.5 {+-} 0.2. We identify local blue compact dwarf analogs to SL2SJ02176-0513, which are among the most metal-poor galaxies in the Sloan Digital Sky Survey. The local analogs resemble the lensed galaxy in many ways, including UV/optical spectral energy distribution, spatial morphology, and emission line equivalent widths and ratios. Common to SL2SJ02176-0513 and its local counterparts is an upturn at mid-IR wavelengths likely arising from hot dust heated by starbursts. The emission lines of SL2SJ02176-0513 are spatially resolved owing to the combination of the lens and the high spatial resolution of HST. The lensed galaxy is composed of two clumps with combined size r{sub e} {approx}300 pc, and we resolve significant differences in UV color and emission line equivalent width between them. Though it has characteristics occasionally attributed to active galactic nuclei, we conclude that SL2SJ02176-0513 is a low-metallicity star-bursting dwarf galaxy. Such galaxies will be found in significant numbers in the full 3D-HST grism survey.

Brammer, Gabriel B.; Sanchez-Janssen, Ruben [European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago (Chile); Labbe, Ivo; Franx, Marijn; Fumagalli, Mattia; Patel, Shannon [Leiden Observatory, Leiden University, 2300-RA Leiden (Netherlands); Da Cunha, Elisabete; Rix, Hans-Walter; Schmidt, Kasper B.; Van der Wel, Arjen [Max Planck Institute for Astronomy (MPIA), Koenigstuhl 17, D-69117 Heidelberg (Germany); Erb, Dawn K. [Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States); Lundgren, Britt; Momcheva, Ivelina; Nelson, Erica; Skelton, Rosalind E.; Van Dokkum, Pieter G.; Wake, David A.; Whitaker, Katherine E. [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); Marchesini, Danilo [Physics and Astronomy Department, Tufts University, Robinson Hall, Room 257, Medford, MA 02155 (United States); Quadri, Ryan, E-mail: gbrammer@eso.org [Carnegie Observatories, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

2012-10-10

359

We present 11.2 {mu}m observations of the gravitationally lensed, radio-loud z{sub s} = 2.64 quasar MG0414+0534, obtained using the Michelle camera on Gemini North. We find a flux ratio anomaly of A2/A1 = 0.93 {+-} 0.02 for the quasar images A1 and A2. When combined with the 11.7 {mu}m measurements from Minezaki et al., the A2/A1 flux ratio is nearly 5{sigma} from the expected ratio for a model based on the two visible lens galaxies. The mid-IR flux ratio anomaly can be explained by a satellite (substructure), 0.''3 northeast of image A2, as can the detailed very long baseline interferometry (VLBI) structures of the jet produced by the quasar. When we combine the mid-IR flux ratios with high-resolution VLBI measurements, we find a best-fit mass between 10{sup 6.2} and 10{sup 7.5} M{sub Sun} inside the Einstein radius for a satellite substructure modeled as a singular isothermal sphere at the redshift of the main lens (z{sub l} = 0.96). We are unable to set an interesting limit on the mass to light ratio due to its proximity to the quasar image A2. While the observations used here were technically difficult, surveys of flux anomalies in gravitational lenses with the James Webb Space Telescope will be simple, fast, and should well constrain the abundance of substructure in dark matter halos.

MacLeod, Chelsea L. [Physics Department, United States Naval Academy, Annapolis, MD 21403 (United States); Jones, Ramsey; Agol, Eric [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Kochanek, Christopher S., E-mail: macleod@usna.edu [Department of Astronomy and the Center for Cosmology and Astroparticle Physics, Ohio State University, Columbus, OH 43210 (United States)

2013-08-10

360

We present spatially-resolved dynamics for six strongly lensed star-forming galaxies at z=1.7-3.1, each enlarged by a linear magnification factor ~8. Using the Keck laser guide star AO system and the OSIRIS integral field unit spectrograph we resolve kinematic and morphological detail in our sample with an unprecedented fidelity, in some cases achieving spatial resolutions of ~100 pc. With one exception our sources have diameters ranging from 1-7 kpc, star formation rates of 2-40 Msun/yr (uncorrected for extinction) and dynamical masses of 10^(9.7-10.3) Msun. With this exquisite resolution we find that four of the six galaxies display coherent velocity fields consistent with a simple rotating disk model, which can only be recovered with the considerably improved spatial resolution and sampling from the combination of adaptive optics and strong gravitational lensing. Our model fits imply ratios for the systemic to random motion, V sin(i)/sigma, ranging from 0.5-1.3 and Toomre disk parameters Q<1. The large ...

Jones, Tucker; Ellis, Richard; Richard, Johan; Stark, Dan

2009-01-01

361

NASA Astrophysics Data System (ADS)

We present rest-frame optical spectra for a sample of nine low-mass star-forming galaxies in the redshift range 1.5 < z < 3 which are gravitationally lensed by foreground clusters. We used Triplespec, an echelle spectrograph at the Palomar 200 inch telescope that is very effective for this purpose as it samples the entire near-infrared spectrum simultaneously. By measuring the flux of nebular emission lines, we derive gas-phase metallicities and star formation rates, and by fitting the optical to infrared spectral energy distributions we obtain stellar masses. Taking advantage of the high magnification due to strong lensing, we are able to probe the physical properties of galaxies with stellar masses in the range 7.8 < log M/M ? < 9.4 whose star formation rates are similar to those of typical star-forming galaxies in the local universe. We compare our results with the locally determined relation between stellar mass, gas metallicity, and star formation rate. Our data are in excellent agreement with this relation, with an average offset lang?log (O/H)rang = 0.01 ± 0.08, suggesting a universal relationship. Remarkably, the scatter around the fundamental metallicity relation is only 0.24 dex, smaller than that observed locally at the same stellar masses, which may provide an important additional constraint for galaxy evolution models.

Belli, Sirio; Jones, Tucker; Ellis, Richard S.; Richard, Johan

2013-08-01

362

We present rest-frame optical spectra for a sample of nine low-mass star-forming galaxies in the redshift range 1.5 < z < 3 which are gravitationally lensed by foreground clusters. We used Triplespec, an echelle spectrograph at the Palomar 200 inch telescope that is very effective for this purpose as it samples the entire near-infrared spectrum simultaneously. By measuring the flux of nebular emission lines, we derive gas-phase metallicities and star formation rates, and by fitting the optical to infrared spectral energy distributions we obtain stellar masses. Taking advantage of the high magnification due to strong lensing, we are able to probe the physical properties of galaxies with stellar masses in the range 7.8 < log M/M{sub Sun} < 9.4 whose star formation rates are similar to those of typical star-forming galaxies in the local universe. We compare our results with the locally determined relation between stellar mass, gas metallicity, and star formation rate. Our data are in excellent agreement with this relation, with an average offset ({Delta}log (O/H)) = 0.01 {+-} 0.08, suggesting a universal relationship. Remarkably, the scatter around the fundamental metallicity relation is only 0.24 dex, smaller than that observed locally at the same stellar masses, which may provide an important additional constraint for galaxy evolution models.

Belli, Sirio; Ellis, Richard S. [Department of Astronomy, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Jones, Tucker [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Richard, Johan [Centre de Recherche Astrophysique de Lyon, Universite Lyon 1, 9 Avenue Charles Andre, F-69561 Saint Genis Laval Cedex (France)

2013-08-01

363

Identification of a gravitationally lensed z=2.515 star-forming galaxy

NASA Astrophysics Data System (ADS)

We discuss the optical spectrum of a multiply imaged arc resolved by the Hubble Space Telescope in the z=0.175 cluster A2218. The spectrum, obtained with LDSS-2 on the 4.2-m William Herschel Telescope, reveals the source to be a galaxy at a redshift z=2.515, in excellent agreement with the value predicted by Kneib et al. on the basis of their inversion of a highly constrained mass model for the lensing cluster. The source is extremely blue in its optical-infrared colours, consistent with active star formation, and the spectrum reveals absorption lines characteristic of a young stellar population. Of particular significance is the absence of Lyalpha emission but the presence of a broad Lyalpha absorption. The spectrum is similar to that of other, much fainter, galaxies found at high redshift by various techniques, and illustrates the important role that lensing can play in detailed studies of the properties of distant galaxies.

Ebbels, T. M. D.; Le Borgne, J.-F.; Pello, R.; Ellis, R. S.; Kneib, J.-P.; Smail, I.; Sanahuja, B.

1996-08-01

364

LoCuSS: THE SUNYAEV-ZEL'DOVICH EFFECT AND WEAK-LENSING MASS SCALING RELATION

We present the first weak-lensing-based scaling relation between galaxy cluster mass, M{sub WL}, and integrated Compton parameter Y{sub sph}. Observations of 18 galaxy clusters at z {approx_equal} 0.2 were obtained with the Subaru 8.2 m telescope and the Sunyaev-Zel'dovich Array. The M{sub WL}-Y{sub sph} scaling relations, measured at {Delta} = 500, 1000, and 2500 {rho}{sub c}, are consistent in slope and normalization with previous results derived under the assumption of hydrostatic equilibrium (HSE). We find an intrinsic scatter in M{sub WL} at fixed Y{sub sph} of 20%, larger than both previous measurements of M{sub HSE}-Y{sub sph} scatter as well as the scatter in true mass at fixed Y{sub sph} found in simulations. Moreover, the scatter in our lensing-based scaling relations is morphology dependent, with 30%-40% larger M{sub WL} for undisturbed compared to disturbed clusters at the same Y{sub sph} at r{sub 500}. Further examination suggests that the segregation may be explained by the inability of our spherical lens models to faithfully describe the three-dimensional structure of the clusters, in particular, the structure along the line of sight. We find that the ellipticity of the brightest cluster galaxy, a proxy for halo orientation, correlates well with the offset in mass from the mean scaling relation, which supports this picture. This provides empirical evidence that line-of-sight projection effects are an important systematic uncertainty in lensing-based scaling relations.

Marrone, Daniel P.; Carlstrom, John E.; Gralla, Megan; Greer, Christopher H.; Hennessy, Ryan; Leitch, Erik M.; Plagge, Thomas [Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637 (United States); Smith, Graham P. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Okabe, Nobuhiro [Astronomical Institute, Tohoku University, Aramaki, Aoba-ku, Sendai, 980-8578 (Japan); Bonamente, Massimiliano; Hasler, Nicole [Department of Physics, University of Alabama, Huntsville, AL 35899 (United States); Culverhouse, Thomas L. [Radio Astronomy Lab, 601 Campbell Hall, University of California, Berkeley, CA 94720 (United States); Hawkins, David; Lamb, James W.; Muchovej, Stephen [Owens Valley Radio Observatory, California Institute of Technology, Big Pine, CA 93513 (United States); Joy, Marshall [Space Science-VP62, NASA Marshall Space Flight Center, Huntsville, AL 35812 (United States); Martino, Rossella; Mazzotta, Pasquale [Dipartimento di Fisica, Universita degli Studi di Roma 'Tor Vergata', via della Ricerca Scientifica 1, 00133, Roma (Italy); Miller, Amber [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Mroczkowski, Tony, E-mail: dmarrone@email.arizona.edu [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States); and others

2012-08-01

365

COSMOS 5921+0638: characterization and analysis of a new strong gravitationally lensed AGN

NASA Astrophysics Data System (ADS)

Context: Strong lens candidates have been newly identified within the COSMOS field. We present VLT/FORS1 spectroscopic follow-up observations and HST/WFPC2 imaging of the system COSMOS 5921+0638, which exhibits quadruply lensed images and a perfect Einstein ring. Aims: We investigate the nature of COSMOS 5921+0638 by studying its photometric, spectroscopic and physical properties. Methods: By analyzing our VLT/FORS1 spectroscopy and Subaru/CFHT/HST imaging of COSMOS 5921+0638, we completed both an environmental analysis and detailed analytical and grid-based mass modeling to determine it properties. Results: We measured the redshifts of the lensing galaxy in COSMOS 5921+0638 (zl = 0.551 ± 0.001) and 9 additional galaxies in the field (5 of them at z ~ 0.35). The redshift of the lensed source was inferred by identifying a candidate Ly? line at zs = 3.14 ± 0.05. The mass modeling reveals the requirement of a small external shear (? = 0.038), which is slightly larger than the lensing contribution expected by galaxy groups along the line-of-sight obtained from the zCOSMOS optical group catalog (?_groups ~ 0.01 and ?_groups ~ 0.005). The estimated time-delays between the different images are of the order of hours to half a week and the total magnification of the background source is ? ? 150. The measured mass-to-light ratio of the lensing galaxy within the Einstein ring is M/LB ? 8.5 ± 1.6. Anomalies are observed between the measured and expected flux ratios of the images of the background AGN. Conclusions: Our analysis indicates that the ring and point-like structures in COSMOS 5921+0638 consist of a lensed high redshift galaxy hosting a low luminosity AGN (LLAGN). The observed flux ratio anomalies are probably due to microlensing by stars in the lensing galaxy and/or a combination of static phenomena. Multi-epoch, multi-band space-based observations would allow us to differentiate between the possible causes of these anomalies, since static and/or dynamic variations could be identified. Because of its short time-delays and the possibility of microlensing, COSMOS 5921+0638 is a promising laboratory for future studies of LLAGNs. Based on observations made with ESO Telescopes at Paranal Observatory programme IDs: 077.A-0473(A) and 175.A-0839(B,D) and with NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Institute. STScI is operated by the association of Universities for Research in Astronomy, Inc. under the 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 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; and the Canada-France-Hawaii Telescope operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France and the University of Hawaii.

Anguita, T.; Faure, C.; Kneib, J.-P.; Wambsganss, J.; Knobel, C.; Koekemoer, A. M.; Limousin, M.

2009-11-01

366

NASA Technical Reports Server (NTRS)

Merging clusters of galaxies are unique in their power to directly probe and place limits on the self-interaction cross-section of dark matter. Detailed observations of several merging clusters have shown the intracluster gas to be displaced from the centroids of dark matter and galaxy density by ram pressure, while the latter components are spatially coincident, consistent with collisionless dark matter. This has been used to place upper limits on the dark matter particle self-interaction cross-section of order 1 sq cm/g. The cluster A520 has been seen as a possible exception. We revisit A520 presenting new Hubble Space Telescope Advanced Camera for Surveys mosaic images and a Magellan image set. We perform a detailed weak-lensing analysis and show that the weak-lensing mass measurements and morphologies of the core galaxy-filled structures are mostly in good agreement with previous works. There is, however, one significant difference: We do not detect the previously claimed "dark core" that contains excess mass with no significant galaxy overdensity at the location of the X-ray plasma. This peak has been suggested to be indicative of a large self-interaction cross-section for dark matter (at least approx 5alpha larger than the upper limit of 0.7 sq cm/g determined by observations of the Bullet Cluster). We find no such indication and instead find that the mass distribution of A520, after subtraction of the X-ray plasma mass, is in good agreement with the luminosity distribution of the cluster galaxies.We conclude that A520 shows no evidence to contradict the collisionless dark matter scenario.

Clowe, Douglas; Markevitch, Maxim; Bradac, Marusa; Gonzalez, Anthony H.; Chung, Sun Mi

2012-01-01

367

Merging clusters of galaxies are unique in their power to directly probe and place limits on the self-interaction cross-section of dark matter. Detailed observations of several merging clusters have shown the intracluster gas to be displaced from the centroids of dark matter and galaxy density by ram pressure, while the latter components are spatially coincident, consistent with collisionless dark matter. This has been used to place upper limits on the dark matter particle self-interaction cross-section of order 1 cm{sup 2} g{sup -1}. The cluster A520 has been seen as a possible exception. We revisit A520 presenting new Hubble Space Telescope Advanced Camera for Surveys mosaic images and a Magellan image set. We perform a detailed weak-lensing analysis and show that the weak-lensing mass measurements and morphologies of the core galaxy-filled structures are mostly in good agreement with previous works. There is, however, one significant difference: We do not detect the previously claimed 'dark core' that contains excess mass with no significant galaxy overdensity at the location of the X-ray plasma. This peak has been suggested to be indicative of a large self-interaction cross-section for dark matter (at least {approx}5{sigma} larger than the upper limit of 0.7 cm{sup 2} g{sup -1} determined by observations of the Bullet Cluster). We find no such indication and instead find that the mass distribution of A520, after subtraction of the X-ray plasma mass, is in good agreement with the luminosity distribution of the cluster galaxies. We conclude that A520 shows no evidence to contradict the collisionless dark matter scenario.

Clowe, Douglas [Department of Physics and Astronomy, Ohio University, 251B Clippinger Labs, Athens, OH 45701 (United States); Markevitch, Maxim [NASA Goddard Space Flight Center, Code 662, 8800 Greenbelt Road, Greenbelt, MD 20706 (United States); Bradac, Marusa [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, Anthony H.; Chung, Sun Mi [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Massey, Richard [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Zaritsky, Dennis, E-mail: clowe@ohio.edu [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

2012-10-20

368

Planck 2013 results. XVIII. The gravitational lensing-infrared background correlation

NASA Astrophysics Data System (ADS)

The multi-frequency capability of the Planck satellite provides information both on the integrated history of star formation (via the cosmic infrared background, or CIB) and on the distribution of dark matter (via the lensing effect on the cosmic microwave background, or CMB). The conjunction of these two unique probes allows us to measure directly the connection between dark and luminous matter in the high redshift (1 ? z ? 3) Universe. We use a three-point statistic optimized to detect the correlation between these two tracers, using lens reconstructions at 100, 143, and 217 GHz, together with CIB measurements at 100-857 GHz. Following a thorough discussion of possible contaminants and a suite of consistency tests, we report the first detection of the correlation between the CIB and CMB lensing. The well matched redshift distribution of these two signals leads to a detection significance with a peak value of 42/19? (statistical/statistical + systematics) at 545 GHz and a correlation as high as 80% across these two tracers. Our full set of multi-frequency measurements (both CIB auto- and CIB-lensing cross-spectra) are consistent with a simple halo-based model, with a characteristic mass scale for the halos hosting CIB sources of log10(M/M?) = 10.5 ± 0.6. Leveraging the frequency dependence of our signal, we isolate the high redshift contribution to the CIB, and constrain the star formation rate (SFR) density at z ? 1. We measure directly the SFR density with around 2? significance for three redshift bins between z = 1 and 7, thus opening a new window into the study of the formation of stars at early times.

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.; Bethermin, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bonaldi, A.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; 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.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; 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.; 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.; Lacasa, F.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Leonardi, R.; León-Tavares, J.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; 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.; Munshi, D.; 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.; 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.; 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.; Rusholme, B.; Sandri, M.; Santos, D.; Savini, G.; Scott, D.; Seiffert, M. D.; Serra, P.; Shellard, E. P. S.; 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.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.

2014-11-01

369

In this brief note a clarification about the observable used in a recently published paper on the measurement of the general relativistic Lense-Thirring in the gravitational field of the Earth is presented.

Iorio, L

2004-01-01

370

We study gravitational interaction of Higgs boson through the unique dimension-4 operator $\\xi H^\\dag H R$, with $H$ the Higgs doublet and $R$ the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling $\\xi$ on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone boson equivalence theorem with nonzero $\\xi$ coupling in both frames, and analyze the unitarity constraints. We study the $\\xi$-induced weak boson scattering cross sections at O(1-30)TeV scales, and propose to probe the Higgs-gravity coupling via weak boson scattering experiments at the LHC(14TeV) and the next generation pp colliders (50-100TeV). We further extend our study to Higgs inflation, and quantitatively derive the perturbative unitarity bounds via coupled channel analysis, under large field background at the inflation scale. We analyze the unitarity constraints on the parameter space in both the conventional Higgs inflation and the improved models in light of the recent BICEP2 data.

Jing Ren; Zhong-Zhi Xianyu; Hong-Jian He

2014-04-17

371

We developed a new method (E-HOLICs) of estimating gravitational shear by adopting an elliptical weight function to measure background galaxy images in our previous paper. Following the previous paper, in which an isotropic point-spread function (PSF) correction is calculated, in this paper we consider an anisotropic PSF correction in order to apply E-HOLICs to real data. As an example, E-HOLICs is applied to Subaru data of the massive and compact galaxy cluster A370 and is able to detect double peaks in the central region of the cluster consistent with the analysis of strong lensing. We also study the systematic error in E-HOLICs using STEP2 simulation. In particular, we consider the dependences of the signal-to-noise ratio (S/N) of background galaxies in the shear estimation. Although E-HOLICs does improve the systematic error due to the ellipticity dependence as shown in Paper I, a systematic error due to the S/N dependence remains, namely, E-HOLICs underestimates shear when background galaxies with low S/N objects are used. We discuss a possible improvement of the S/N dependence.

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)

2012-04-01

372

NASA Astrophysics Data System (ADS)

We present a derivation of the cosmological distance–redshift relation up to second order in perturbation theory. In addition, we find the observed redshift and the lensing magnification to second order. We do not require that the density contrast is small, but only that the metric potentials and peculiar velocities are small. Thus our results apply into the nonlinear regime, and can be used for most dark energy models. We present the results in a form that can be readily computed in an N-body simulation. This paper accompanies paper I (Umeh, Clarkson and Maartens 2014 Class. Quantum Grav. 31 202001), where the key results are summarized in a physically transparent form and applications are discussed.

Umeh, Obinna; Clarkson, Chris; Maartens, Roy

2014-10-01

373

We describe 10 strong lensing galaxy clusters of redshift 0.26 {<=} z {<=} 0.56 that were found in the Sloan Digital Sky Survey. We present measurements of richness (N{sub 200}), mass (M{sub 200}), and velocity dispersion for the clusters. We find that in order to use the mass-richness relation from Johnston et al., which was established at mean redshift of 0.25, it is necessary to scale measured richness values up by 1.47. Using this scaling, we find richness values for these clusters to be in the range of 22 {<=} N{sub 200} {<=} 317 and mass values to be in the range of 1 Multiplication-Sign 10{sup 14} h {sup -1} M{sub Sun} {<=} M{sub 200} {<=} 30 Multiplication-Sign 10{sup 14} h {sup -1} M{sub Sun }. We also present measurements of Einstein radius, mass, and velocity dispersion for the lensing systems. The Einstein radii ({theta}{sub E}) are all relatively small, with 5.''4 {<=} {theta}{sub E} {<=} 13''. Finally, we consider if there is evidence that our clusters are more concentrated than {Lambda}CDM would predict. We find that six of our clusters do not show evidence of overconcentration, while four of our clusters do. We note a correlation between overconcentration and mass, as the four clusters showing evidence of overconcentration are all lower-mass clusters. For the four lowest mass clusters the average value of the concentration parameter c{sub 200} is 11.6, while for the six higher-mass clusters the average value of c{sub 200} is 4.4. {Lambda}CDM would place c{sub 200} between 3.4 and 5.7.

Wiesner, Matthew P. [Department of Physics, Northern Illinois University, DeKalb, IL 60115 (United States); Lin, Huan; Allam, Sahar S.; Annis, James; Buckley-Geer, Elizabeth J.; Diehl, H. Thomas; Kubik, Donna; Kubo, Jeffrey M.; Tucker, Douglas [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)

2012-12-10

374

Search and Analysis of Galaxy-Scale Strong Gravitational Lenses in Cosmological Surveys

NASA Astrophysics Data System (ADS)

This article focuses on the development of a novel detector of strong galaxy-galaxy lenses based on the massive modelling of candidates in wide-field ground-based imaging data. Indeed, not only are these events rare in the Universe, but they are at the same time very valuable to understand galaxy formation and evolution in a cosmological context. We use parametric models, which are optimized by MCMC in a bayesian framework, so that we know the distribution of errors. We first generate several training samples : a hundred lenses simulated in HST and CFHT conditions, along with 325 observed lens candidates resulting from a series of preselections on the CFHTLS-Wide galaxies, and that we classify according to their credibility. The whole challenge in designing this detector lies in a subtle balance between the quality of models and the execution time. We massively run the modelling on our samples, beginning with ideal application conditions that we make more complex by stages so as to get closer to the observation conditions and save time. We show that a 7-parameter model assuming a spherical source can recover the Einstein radius from the CFHT simulations with a precision of 7%. We apply a mask to the input data that noticeably enhances the robustness of the models facing environment problems, with a median convergence time of 4 minutes that could be easily reduced by a factor of 10 with more direct optimization techniques. From our results, we define selection contours in the parameter space, resulting in a completeness of 38% and a purity of 55% for the sample of 51 candidates accepted by our robot among the 325 preselected systems.

Brault, F.

2013-11-01

375

We consider a Casimir apparatus consisting of two perfectly conducting parallel plates, subject to the weak gravitational field of the Earth. The aim of this paper is the calculation of the energy-momentum tensor of this system for a free, real massless scalar field satisfying Neumann boundary conditions on the plates. The small gravity acceleration (considered here as not varying between the two plates) allows us to perform all calculations to first order in this parameter. Some interesting results are found: a correction, depending on the gravity acceleration, to the well-known Casimir energy and pressure on the plates. Moreover, this scheme predicts a tiny force in the upwards direction acting on the apparatus. These results are supported by two consistency checks: the covariant conservation of the energy-momentum tensor and the vanishing of its regularized trace, when the scalar field is conformally coupled to gravity.

Napolitano, George M. [Dipartimento di Scienze Fisiche, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); Esposito, Giampiero [Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); Rosa, Luigi [Dipartimento di Scienze Fisiche, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio 6, 80126 Napoli (Italy)

2008-11-15

376