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1

We review theory and applications of weak gravitational lensing. After summarising Friedmann–Lema??tre cosmological models, we present the formalism of gravitational lensing and light propagation in arbitrary space–times. We discuss how weak-lensing effects can be measured. The formalism is then applied to reconstructions of galaxy-cluster mass distributions, gravitational lensing by large-scale matter distributions, QSO–galaxy correlations induced by weak lensing, lensing of

Matthias Bartelmann; Peter Schneider

2001-01-01

2

Weak gravitational lensing with DEIMOS

NASA Astrophysics Data System (ADS)

We introduce a novel method for weak-lensing measurements, which is based on a mathematically exact deconvolution of the moments of the apparent brightness distribution of galaxies from the telescope's point spread function (PSF). No assumptions on the shape of the galaxy or the PSF are made. The (de)convolution equations are exact for unweighted moments only, while in practice a compact weight function needs to be applied to the noisy images to ensure that the moment measurement yields significant results. We employ a Gaussian weight function, whose centroid and ellipticity are iteratively adjusted to match the corresponding quantities of the source. The change of the moments caused by the application of the weight function can then be corrected by considering higher order weighted moments of the same source. Because of the form of the deconvolution equations, even an incomplete weighting correction leads to an excellent shear estimation if galaxies and PSF are measured with a weight function of identical size. We demonstrate the accuracy and capabilities of this new method in the context of weak gravitational lensing measurements with a set of specialized tests and show its competitive performance on the GREAT08 Challenge data. A complete C++ implementation of the method can be requested from the authors.

Melchior, P.; Viola, M.; Schäfer, B. M.; Bartelmann, M.

2011-04-01

3

Constraining dark energy from the abundance of weak gravitational lenses

We examine the prospect of using the observed abundance of weak gravitational lenses to constrain the equation-of-state parameter w=p\\/rho of dark energy. Dark energy modifies the distance-redshift relation, the amplitude of the matter power spectrum, and the rate of structure growth. As a result, it affects the efficiency with which dark-matter concentrations produce detectable weak-lensing signals. Here we solve the

Nevin N. Weinberg; Marc Kamionkowski

2002-01-01

4

Weak gravitational lensing by compact objects in fourth order gravity

NASA Astrophysics Data System (ADS)

We discuss weak lensing characteristics in the gravitational field of a compact object in the low-energy approximation of fourth order f(R)-gravity theory. The particular solution is characterized by a gravitational strength parameter ? and a distance scale rc much larger than the Schwarzschild radius. Above rc gravity is strengthened and as a consequence weak lensing features are modified compared to the Schwarzschild case. We find a critical impact parameter (depending upon rc) for which the behavior of the deflection angle changes. Using the Virbhadra-Ellis lens equation we improve the computation of the image positions, Einstein ring radii, magnification factors and the magnification ratio. We demonstrate that the magnification ratio as function of image separation obeys a power law depending on the parameter ?, with a double degeneracy. No ??0 value gives the same power as the one characterizing Schwarzschild black holes. As the magnification ratio and the image separation are the lensing quantities most conveniently determined by direct measurements, future lensing surveys will be able to constrain the parameter ? based on this prediction.

Horváth, Zsolt; Gergely, László Á.; Hobill, David; Capozziello, Salvatore; De Laurentis, Mariafelicia

2013-09-01

5

NASA Astrophysics Data System (ADS)

Weak gravitational lensing can be used to constrain cosmological parameters to high precision using the 2- and 3-point weak lensing shear correlations. The intrinsic alignment (IA) of galaxies has been shown to be a significant barrier to precision weak lensing measurements. We review a proposed self-calibration technique to calculate the induced gravitational lensing-galaxy intrinsic alignment correlation (GI) for the power spectrum in weak gravitational lensing surveys with photometric redshift measurements, which is expected to reduce the IA contamination by at least a factor of 10 for currently proposed surveys. We confirm this using an independent analysis and propose an expansion to the self-calibration technique for the weak lensing bispectrum in order to calculate the dominant lensing-lensing-intrinsic alignment correlation (GGI). We explore the performance of the GGI self-calibration technique and show that it can potentially reduce the IA contamination by up to a factor of 5-10 for most redshift bin choices. The self-calibration thus promises to be an efficient technique to remove both the 2-point and 3-point intrinsic alignment contamination from weak gravitational lensing measurements.

Troxel, Michael; Ishak, Mustapha

2011-10-01

6

\\u000a Gravitational lenses are becoming a precious mean of probing the matter distribution in the Universe. From the search of matter\\u000a in the Galactic halo to the study of the large-scale structures of the Universe, the gravitational lens effects offer a unique\\u000a alternative to light surveys and are now widely used. This evolution is due in particular to the use of

Francis Bernardeau; C. E. de Saclay

1999-01-01

7

Constraining Horava-Lifshitz gravity by weak and strong gravitational lensing

We discuss gravitational lensing in the Kehagias-Sfetsos space-time emerging in the framework of Horava-Lifshitz gravity. In weak lensing, we show that there are three regimes, depending on the value of {lambda}=1/{omega}d{sup 2}, where {omega} is the Horava-Lifshitz parameter and d characterizes the lensing geometry. When {lambda} is close to zero, light deflection typically produces two images, as in Schwarzschild lensing. For very large {lambda}, the space-time approaches flatness, therefore there is only one undeflected image. In the intermediate range of {lambda}, only the upper focused image is produced due to the existence of a maximal deflection angle {delta}{sub max}, a feature inexistent in the Schwarzschild weak lensing. We also discuss the location of Einstein rings, and determine the range of the Horava-Lifshitz parameter compatible with present-day lensing observations. Finally, we analyze in the strong lensing regime the first two relativistic Einstein rings and determine the constraints on the parameter range to be imposed by forthcoming experiments.

Horvath, Zsolt; Gergely, Laszlo A.; Keresztes, Zoltan; Harko, Tiberiu; Lobo, Francisco S. N. [Departments of Theoretical and Experimental Physics, University of Szeged, Dom ter 9, Szeged 6720 (Hungary); Department of Physics and Center for Theoretical and Computational Physics, University of Hong Kong, Pok Fu Lam Road (Hong Kong); Centro de Astronomia e Astrofisica da Universidade de Lisboa, Campo Grande, Edificio C8 1749-016 Lisboa (Portugal)

2011-10-15

8

Testing dark energy paradigms with weak gravitational lensing

NASA Astrophysics Data System (ADS)

Any theory invoked to explain cosmic acceleration predicts consistency relations between the expansion history, structure growth, and all related observables. Currently there exist high-quality measurements of the expansion history from type Ia supernovae, the cosmic microwave background temperature and polarization spectra, and baryon acoustic oscillations. We can use constraints from these data sets to predict what future probes of structure growth should observe. We apply this method to predict what range of cosmic shear power spectra would be expected if we lived in a ?CDM universe, with or without spatial curvature, and what results would be inconsistent and therefore falsify the model. Though predictions are relaxed if one allows for an arbitrary quintessence equation of state -1?w(z)?1, we find that any observation that rules out ?CDM due to excess lensing will also rule out all quintessence models, with or without early dark energy. We further explore how uncertainties in the nonlinear matter power spectrum, e.g. from approximate fitting formulas such as Halofit, warm dark matter, or baryons, impact these limits.

Vanderveld, R. Ali; Mortonson, Michael J.; Hu, Wayne; Eifler, Tim

2012-05-01

9

Initial Results from a Laboratory Emulation of Weak Gravitational Lensing Measurements

NASA Astrophysics Data System (ADS)

Weak gravitational lensing observations are a key science driver for the NASA Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of the WFIRST infrared detectors, we have performed a laboratory emulation of weak gravitational lensing measurements. Our experiments used a custom precision projector system to image a target mask composed of a grid of pinholes, emulating stellar point sources, onto a 1.7 ?m cut-off Teledyne HgCdTe/H2RG detector. We used a 0.88 ?m LED illumination source and f/22 pupil stop to produce undersampled point spread functions similar to those expected from WFIRST. We also emulated the WFIRST image reconstruction strategy, using the image combination (IMCOM) algorithm to derive oversampled images from dithered, undersampled input images. We created shear maps for this data and computed shear correlation functions to mimic a real weak lensing analysis. After removing only second-order polynomial fits to the shear maps, we found that the correlation functions could be reduced to O(10-6). This places a conservative upper limit on the detector-induced bias to the correlation function (under our test conditions). This bias is two orders of magnitude lower than the expected weak lensing signal. Restricted to scales relevant to dark energy analyses (sky separations >0.5'), the bias is O(10-7) - comparable to the requirement for future weak lensing missions to avoid biasing cosmological parameter estimates. Our experiment will need to be upgraded and repeated under different configurations to fully characterize the shape measurement performance of WFIRST IR detectors.

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

2013-09-01

10

Resource Letter GL-1: Gravitational Lensing

NASA Astrophysics Data System (ADS)

This Resource Letter provides a guide to a selection of the literature on gravitational lensing and its applications. Journal articles, books, popular articles, and websites are cited for the following topics: foundations of gravitational lensing, foundations of cosmology, history of gravitational lensing, strong lensing, weak lensing, and microlensing.

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

2012-09-01

11

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

NASA Astrophysics Data System (ADS)

We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r?/b, where M is the black hole mass, a is the angular momentum, r? = Q2/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

Gyulchev, G. N.; Yazadjiev, S. S.

2010-11-01

12

TOPICAL REVIEW Gravitational lensing

NASA Astrophysics Data System (ADS)

Gravitational lensing has developed into one of the most powerful tools for the analysis of the dark universe. This review summarizes the theory of gravitational lensing, its main current applications and representative results achieved so far. It has two parts. In the first, starting from the equation of geodesic deviation, the equations of thin and extended gravitational lensing are derived. In the second, gravitational lensing by stars and planets, galaxies, galaxy clusters and large-scale structures is discussed and summarized.

Bartelmann, Matthias

2010-12-01

13

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

We investigate analytically gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black hole in the weak deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b and r{sub {alpha}}/b, where M is the black hole mass, a is the angular momentum, r{sub {alpha}}= Q{sup 2}/M,Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images up to post-Newtonian order. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The lensing observables are compared to these characteristics for particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

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

2010-11-25

14

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

15

We present the first direct maps of the large-scale distribution of mass in the Universe. Measurements of weak gravitational lensing from the Hubble Space Telescope COSMOS survey directly trace the 3D distribution of mass, regardless of its nature or state. They reveal a filamentary network of structures that encompass large voids and meet in massive clusters of galaxies. By comparing

Richard Massey; J. Rhodes; A. Leauthaud; R. Ellis; N. Scoville; A. Finoguenov

2006-01-01

16

CFHTLenS: combined probe cosmological model comparison using 2D weak gravitational lensing

NASA Astrophysics Data System (ADS)

We present cosmological constraints from 2D weak gravitational lensing by the large-scale structure in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) which spans 154 deg2 in five optical bands. Using accurate photometric redshifts and measured shapes for 4.2 million galaxies between redshifts of 0.2 and 1.3, we compute the 2D cosmic shear correlation function over angular scales ranging between 0.8 and 350 arcmin. Using non-linear models of the dark-matter power spectrum, we constrain cosmological parameters by exploring the parameter space with Population Monte Carlo sampling. The best constraints from lensing alone are obtained for the small-scale density-fluctuations amplitude ?8 scaled with the total matter density ?m. For a flat ?cold dark matter (?CDM) model we obtain ?8(?m/0.27)0.6 = 0.79 ± 0.03. We combine the CFHTLenS data with 7-year Wilkinson Microwave Anisotropy Probe (WMAP7), baryonic acoustic oscillations (BAO): SDSS-III (BOSS) and a Hubble Space Telescope distance-ladder prior on the Hubble constant to get joint constraints. For a flat ?CDM model, we find ?m = 0.283 ± 0.010 and ?8 = 0.813 ± 0.014. In the case of a curved wCDM universe, we obtain ?m = 0.27 ± 0.03, ?8 = 0.83 ± 0.04, w0 = -1.10 ± 0.15 and ?K = 0.006+ 0.006- 0.004. We calculate the Bayesian evidence to compare flat and curved ?CDM and dark-energy CDM models. From the combination of all four probes, we find models with curvature to be at moderately disfavoured with respect to the flat case. A simple dark-energy model is indistinguishable from ?CDM. Our results therefore do not necessitate any deviations from the standard cosmological model.

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

2013-04-01

17

Most of the matter in the Universe is not luminous, and can be observed only through its gravitational influence on the appearance of luminous matter. Weak gravitational lensing is a technique that uses the distortions of the images of distant galaxies as a tracer of dark matter: such distortions are induced as the light passes through large-scale distributions of dark matter in the foreground. The patterns of the induced distortions reflect the density of mass along the line of sight and its distribution, and the resulting 'cosmic shear' can be used to distinguish between alternative cosmologies. But previous attempts to measure this effect have been inconclusive. Here we report the detection of cosmic shear on angular scales of up to half a degree using 145,000 galaxies and along three separate lines of sight. We find that the dark matter is distributed in a manner consistent with either an open universe, or a flat universe that is dominated by a cosmological constant. Our results are inconsistent with the standard cold-dark-matter model. PMID:10821262

Wittman; Tyson; Kirkman; Dell'Antonio; Bernstein

2000-05-11

18

Rigorous approach to gravitational lensing

We revisit a weak gravitational lensing problem by constructing a setup which describes the actual system as accurately as possible and solving the null geodesic equations. Details are given for the case of a universe driven only by a cosmological constant, {lambda}, which confirm the conventional results: The conventional lensing analysis is correct as it is, without any need for correction of O({lambda}). We also treat the cases of the lensing in generic Friedmann-Robertson-Walker backgrounds.

Park, Minjoon [Department of Physics, University of California, Davis, California 95616 (United States)

2008-07-15

19

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 /Marseille, CPPM /Marseille, Lab. Astrophys. /Yale U. /Pennsylvania U. /UC, Berkeley /Michigan U. /Baltimore, Space Telescope Sci. /Indiana U. /Caltech, JPL /Australian Natl. U., Canberra /American Astron. Society /Chicago U. /Cambridge U. /Saclay /Lyon, IPN

2005-08-08

20

NASA Astrophysics Data System (ADS)

The galaxy intrinsic alignment is a severe challenge to precision cosmic shear measurement. We propose self-calibrating the induced gravitational shear-galaxy intrinsic ellipticity correlation (the GI correlation) in weak lensing surveys with photometric redshift measurements. (1) We propose a method to extract the intrinsic ellipticity-galaxy density cross-correlation (I-g) from the galaxy ellipticity-density measurement in the same redshift bin. (2) We also find a generic scaling relation to convert the extracted I-g correlation to the necessary GI correlation. We perform a concept study under simplified conditions and demonstrate its capability to significantly reduce GI contamination. We discuss the impact of various complexities on the two key ingredients of the self-calibration technique, namely the method for extracting the I-g correlation and the scaling relation between the I-g and the GI correlation. We expect that none of them will likely be able to completely invalidate the proposed self-calibration technique.

Zhang, Pengjie

2010-09-01

21

Gravitational lenses in astrophysics

NASA Astrophysics Data System (ADS)

After describing the expected characteristics of observable gravitational lensing effects, attention is given to the observation and interpretation of the lensed objects Q0957+561 and Q1115+080. It is shown that, in addition to permitting the determination of the distance scale for quasars, the large mean amplification of the two observed lenses, which is in the 10-13 factor range, suggests that the brightest large-redshift QSOs may nearly all be lensed objects that appear to be bright because of the lensing. In addition, it has been suggested by Gott (1981) that lenses may allow the investigation of the missing mass problem.

Gunn, J. E.

1981-12-01

22

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.

23

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

24

NASA Astrophysics Data System (ADS)

We compute statistical properties of weak gravitational lensing by large-scale structure in three cold dark matter (CDM) models: two flat models with (?0,?0)=(1, 0) and (0.3, 0.7) and one open model with (?0,?0)=(0.3, 0), where ?0 and ?0 are the density parameter and cosmological constant, respectively. We use a particle-particle/particle-mesh (P3M) N-body code to simulate the formation and evolution of large-scale structure in the universe. We perform 1.1x107 ray-tracing experiments for each model, by computing the Jacobian matrix along random lines of sight, using the multiple lens-plane algorithm. From the results of these experiments, we calculate the probability distribution functions of the convergences, shears, and magnifications, and their rms values. We find that the rms values of the convergence and shear agree with the predictions of a nonlinear analytical model. We also find that the probability distribution functions of the magnifications ? have a peak at values slightly smaller than ?=1 and are strongly skewed toward large magnifications. In particular, for the high-density (?0=1) model, a power-law tail appears in the distribution function at large magnifications for sources at redshifts zs>2. The rms values of the magnifications essentially agree with the nonlinear analytical predictions for sources at low redshift but exceed these predictions for high redshift sources, once the power-law tail appears. We study the effect of magnification bias on the luminosity functions of high-redshift quasars, using the calculated probability distribution functions of the magnifications. We show that the magnification bias is moderate in the absence of the power-law tail in the magnification distribution but depends strongly on the value of the density parameter ?0. In presence of the power-law tail, the bias becomes considerable, especially at the bright end of the luminosity functions where its logarithmic slope steepens. We present a specific example that demonstrates that the bias flattens the bright-side logarithmic slope of a double power-law luminosity function.

Hamana, Takashi; Martel, Hugo; Futamase, Toshifumi

2000-01-01

25

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

26

NASA Astrophysics Data System (ADS)

The weak lensing signal (cosmic shear) has been shown to be contaminated by correlations between the intrinsic alignment (IA) of galaxies, which poses a barrier to precision weak lensing measurements in planned surveys. We review recent work to extend the self-calibration approach to the cosmic shear bispectrum. The self-calibration techniques use the redshift separation dependencies of the IA bispectra and the non-linear galaxy bias in order to isolate and remove the impact of the IA correlations on the cosmic shear signal. We outline the proposed self-calibration techniques for the 3-point cosmic shear auto- and cross-correlations and summarize their performance. Using conservative estimates of photo-z accuracy, we find that planned surveys will be able to measure the IA redshift separation dependence over ranges of |?z^P|<=0.2 in the 3-point ellipticity auto-correlation. For the 3-point cross-correlations, we find that the self-calibration technique allows for reductions in the IA contamination by a factor of 10 or more over most scales and redshift bin choices and in all cases by a factor of 3-5 or more. The 3-point self-calibration techniques thus provide a means to greatly reduce the impact of IA on the cosmic shear signal.

Troxel, Michael; Ishak, Mustapha

2012-10-01

27

Unfolding the matter distribution using three-dimensional weak gravitational lensing

NASA Astrophysics Data System (ADS)

Combining redshift and galaxy shape information offers new exciting ways of exploiting the gravitational lensing effect for studying the large scales of the cosmos. One application is the three-dimensional (3D) reconstruction of the matter density distribution which is explored in this paper. We give a generalization of an already known minimum-variance estimator of the 3D matter density distribution that facilitates the combination of thin redshift slices of sources with samples of broad redshift distributions for an optimal reconstruction; sources can be given individual statistical weights. We show how, in principle, intrinsic alignments of source ellipticities or shear/intrinsic alignment correlations can be accommodated, albeit these effects are not the focus of this paper. We describe an efficient and fast way to implement the estimator on a contemporary desktop computer. Analytic estimates for the noise and biases in the reconstruction are given. Some regularization (Wiener filtering) of the estimator, adjustable by a tuning parameter, is necessary to increase the signal-to-noise ratio (S/N) to a sensible level and to suppress oscillations in radial direction. This, however, introduces as side effect a systematic shift and stretch of structures in radial direction. This bias can be expressed in terms of a radial point-spread function (PSF) comprising the limitations of the reconstruction due to given source shot noise and a lack of knowledge of the exact source redshifts. We conclude that a 3D mass-density reconstruction on galaxy cluster scales (~1Mpc) is feasible but, for foreseeable surveys, a map with a S/N >~ 3 threshold is limited to structures with M200 >~ 1 × 1014 or 7 × 1014Msolarh-1, at low to moderate redshifts (z = 0.1 or 0.6). However, we find that a heavily smoothed full-sky map of the very large-scale density field may also be possible as the S/N of reconstructed modes increases towards larger scales. Future improvements of the method may be obtained by including higher order lensing information (flexion) which could also be implemented into our algorithm.

Simon, P.; Taylor, A. N.; Hartlap, J.

2009-10-01

28

NASA Astrophysics Data System (ADS)

Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component ? X at greater than 99% confidence for an equation-of-state parameter -2.5 <= w <= -0.1. For the case w = -1, we find a value for the cosmological constant density parameter ?? = 0.85+0.044 -0.19 (68% CL) and detect cosmic acceleration (q 0 < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA Inc. under the NASA contract NAS 5-26555; the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the European Southern Observatory under the Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

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

2012-04-01

29

NASA Astrophysics Data System (ADS)

In this dissertation, we describe the results of applying weak gravitational lensing techniques to probe the connection between luminous galaxies and the dark matter halos in which they live. Specifically, we study galaxy-shear correlations in the Deep Lens Survey, and we investigate how this function changes with observable galaxy properties such as stellar mass, luminosity, color, and redshift. In Chapter 3, we examine the galaxy-shear correlation function on a large range of scales from small radii where the dominant contribution is from halos associated with individual galaxies to large radii where the dominant contribution is from neighboring galaxies and large-scale structure. We study the lensing signal for galaxies binned by luminosity and find that more luminous galaxies are more massive. More interestingly, the galaxy-shear correlation function shows features consistent with satellite and 2-halo terms from the halo model and cannot be fit with a single power law out to 15 Mpc. We also find more correlated large scale structure mass at lower redshift, consistent with the paradigm of bottom-up hierarchical structure formation. In Chapter 4, we focus on a subset of the survey with ancillary infrared data that allow estimates of stellar mass. We study the lensing signal for galaxies binned by stellar mass and infer the nature and evolution of the relationship between virial mass and stellar mass. We show that stellar mass and virial mass scale such that galaxies with smaller stellar masses also have smaller virial masses. This work has implications for the idea of downsizing, but does not yet have the S/N to provide competitive constraints. In the process of making lensing measurements on the Deep Lens Survey, we have also investigated errors related to the two most important variables: shapes and photometric redshifts. we discuss our findings in the context of the survey characteristics in Chapter 2 and in the simulations section of Chapter 3. While neither the shapes nor the photometric redshifts are perfect, their associated errors can be reasonably controlled such that the results of the scientific analysis discussed above are meaningful. We conclude and comment on future work in Chapter 5. The Appendix contains a useful reference for equations related to lensing formalism and the halo model.

Choi, Ami

30

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

31

Gravitational lensing from compact bodies: Analytical results for strong and weak deflection limits

We develop a nonperturbative method that yields analytical expressions for the deflection angle of light in a general static and spherically symmetric metric. The method works by introducing into the problem an artificial parameter, called {delta}, and by performing an expansion in this parameter to a given order. The results obtained are analytical and nonperturbative because they do not correspond to a polynomial expression in the physical parameters. Already to first order in {delta} the analytical formulas obtained using our method provide at the same time accurate approximations both at large distances (weak deflection limit) and at distances close to the photon sphere (strong deflection limit). We have applied our technique to different metrics and verified that the error is at most 0.5% for all regimes. We have also proposed an alternative approach which provides simpler formulas, although with larger errors.

Amore, Paolo; Cervantes, Mayra; De Pace, Arturo; Fernandez, Francisco M. [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima, Colima (Mexico) and Istituto Nazionale di Fisica Nucleare, Sezione di Torino, via P.Giuria 1, I-10125 Turin (Italy); INIFTA (Conicet, UNLP), Division Quimica Teorica, Diag. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)

2007-04-15

32

Measuring neutrino masses with weak lensing

Weak gravitational lensing of distant galaxies by large scale structure (LSS) provides an unbiased way to map the matter distribution in the low redshift universe. This technique, based on the measurement of small distortions in the images of the source galaxies induced by the intervening LSS, is expected to become a key cosmological probe in the future. We discuss how future lensing surveys can probe the sum of the neutrino masses at the 0 05 eV level.

Wong, Yvonne Y. Y. [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Munich (Germany)

2006-11-17

33

Weighing Neutrinos: Weak Lensing Approach

We study the possibility for a measurement of neutrino mass using weak\\u000agravitational lensing. The presence of non-zero mass neutrinos leads to a\\u000asuppression of power at small scales and reduces the expected weak lensing\\u000asignal. The measurement of such a suppression in the weak lensing power\\u000aspectrum allows a direct measurement of the neutrino mass, in contrast to\\u000avarious

Asantha R. Cooray

1999-01-01

34

EDITORIAL: Focus on Gravitational Lensing

NASA Astrophysics Data System (ADS)

Gravitational lensing emerged as an observational field following the 1979 discovery of a doubly imaged quasar lensed by a foreground galaxy. In the 1980s and '90s dozens of other multiply imaged systems were observed, as well as time delay measurements, weak and strong lensing by galaxies and galaxy clusters, and the discovery of microlensing in our galaxy. The rapid pace of advances has continued into the new century. Lensing is currently one of best techniques for finding and mapping dark matter over a wide range of scales, and also addresses broader cosmological questions such as understanding the nature of dark energy. This focus issue of New Journal of Physics presents a snapshot of current research in some of the exciting areas of lensing. It provides an occasion to look back at the advances of the last decade and ahead to the potential of the coming years. Just about a decade ago, microlensing was discovered through the magnification of stars in our galaxy by invisible objects with masses between that of Jupiter and a tenth the mass of the Sun. Thus a new component of the mass of our galaxy, dubbed MACHOs, was established (though a diffuse, cold dark matter-like component is still needed to make up most of the galaxy mass). More recently, microlensing led to another exciting discovery—of extra-solar planets with masses ranging from about five times that of Earth to that of Neptune. We can expect many more planets to be discovered through ongoing surveys. Microlensing is the best technique for finding Earth mass planets, though it is not as productive overall as other methods and does not allow for follow up observations. Beyond planet hunting, microlensing has enabled us to observe previously inaccessible systems, ranging from the surfaces of other stars to the accretion disks around the black holes powering distant quasars. Galaxies and galaxy clusters at cosmological distances can produce dramatic lensing effects: multiple images of background galaxies or quasars which are strongly magnified and sheared. In the last decade, double and quadruply imaged systems due to galactic lenses have been studied with optical and radio observations. An interesting result obtained from the flux ratio 'anomalies' of quadruply imaged systems is the statistical detection of dark sub-clumps in galaxy halos. More broadly, while we have learned a lot about the mass distribution in lens galaxies and improved time delay constraints on the Hubble constant, the limitations of cosmological studies with strong lensing due to uncertainties in lens mass models have also come to be appreciated. That said, progress will no doubt continue with qualitative advances in observations such as astrometric counterparts to the flux anomalies, clever ideas such as the use of spectroscopic signatures to assemble the SLACS lens sample, and combining optical imaging, spectroscopy and radio data to continue the quest for a set of golden lenses to measure the Hubble constant. Galaxy clusters are a fascinating arena for studying the distribution of dark and baryonic matter. Weak and strong lensing information can be combined with dynamical information from the spectroscopic measurements of member galaxies and x-ray/Sunyaev Zeldovich measurements of the hot ionized gas. Hubble Space Telescope observations have yielded spectacular images of clusters, such as Abell 1689, which has over a hundred multiply imaged arcs. Mass measurements have progressed to the level of 10 percent accuracy for several clusters. Unfortunately, it is unclear if one can do much better for individual clusters given inherent limitations such as unknown projection effects. The statistical study of clusters is likely to remain a promising way to study dark matter, gravity theories, and cosmology. Techniques to combine weak and strong lensing information to obtain the mass distribution of clusters have also advanced, and work continues on parameter-free techniques that are agnostic to the relation of cluster light and mass. An interesting twist in cluster lensing was provided by the pos

Jain, Bhuvnesh

2007-11-01

35

Weak-Lensing Ellipticities in a Strong-Lensing Regime

NASA Astrophysics Data System (ADS)

It is now routine to measure the weak gravitational lensing shear signal from the mean ellipticity of distant galaxies. However, conversion between ellipticity and shear assumes local linearity of the lensing potential (i.e., that the spatial derivatives of the shear are small), and this condition is not satisfied in some of the most interesting regions of the sky. We extend a derivation of lensing equations to include higher order terms, and assess the level of biases introduced by assuming that first-order weak-lensing theory holds in a relatively strong shear regime. We find that even in a worst-case scenario, a fully linear analysis is accurate to within 1% outside ~1.07 times the Einstein radius of a lens, by deriving an analytic function that can be used to estimate the applicability of any first-order analysis. The effect is too small to explain the discrepancy between weak- and strong-lensing estimates of the mass of the Bullet Cluster, and should not impact cluster surveys for the foreseeable future. In fact, it means that arclets can be used to measure shears closer to a cluster core than has been generally appreciated. However, the bias is significant for galaxy group or galaxy-galaxy lensing applications. At the level of accuracy demanded by dedicated future surveys, it also needs to be considered for measurements of the inner slope of cluster mass distributions and the small-scale end of the mass power spectrum.

Massey, Richard; Goldberg, David M.

2008-02-01

36

Constraining Source Redshift Distributions with Gravitational Lensing

NASA Astrophysics Data System (ADS)

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 ~40 massive (? v = 1200 km s-1) cluster lenses are sufficient to determine the fraction of sources in each of six coarse redshift bins to ~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_lens^{-{1\\over 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.

2012-09-01

37

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

38

Properties of Galaxy Dark Matter Halos using galaxy-galaxy weak lensing in the CFHTLS-Deep

Gravitational lensing can be used as a direct probe of the distribution of dark matter around galaxies , groups, and clusters, making it a powerful tool in astrophysics. In this thesis, we introduce the basics of gravitational lensing and weak gravitational lensing. Using weak lensing to study the ensemble-averaged properties of a population of objects, we present a study of

Jennifer Golding

2009-01-01

39

SUNGLASS: A Weak-lensing Simulation Pipeline

NASA Astrophysics Data System (ADS)

Weak gravitational lensing analysis is a powerful tool to investigate the dark Universe. Next generation weak-lensing telescope surveys (e.g. Euclid and WFIRST) promise to determine the equation of state of dark energy to 1% as well as probing the possibilities of extra dimensional gravity models and alternative cosmologies. To realize the potential of these new telescope surveys and to test new weak-lensing analysis techniques, challenges must be met. To achieve the small statistical errors required, experiments require full end-to-end simulations of huge volumes, which also probe the non-linear regime to assist in understanding the limitations of the analysis techniques. We have developed a new cosmic shear analysis pipeline SUNGLASS (Simulated UNiverses for Gravitational Lensing Analysis and Shear Surveys) that rapidly generates cosmic shear and convergence catalogues using N-body simulations. In this poster, I introduce the SUNGLASS pipeline and show how the SUNGLASS mock shear catalogues can be used in preparation for upcoming telescope missions and for analysis of existing observational data sets.

Kiessling, Alina; Taylor, A.; Heavens, A.; Rhodes, J.; Bartlett, J.

2013-01-01

40

Gravitational lenses - Observational status

NASA Astrophysics Data System (ADS)

Four reported examples of the gravitational-lens effect are characterized from an astrophysical perspective. The criteria based on the Einstein equivalence principle are reviwed, and the objects are discussed: the twin quasar 0957+561, the 'triple' quasar 1115+080, the double quasar 2345+0007, and the triple source 2016+112. All four objects are found to meet the criteria, and the importance of apparent discrepancies among them is demonstrated.

Burke, B. F.

1984-02-01

41

Galaxies as gravitational lenses.

The probability that a galaxy gathers light from another remote galaxy, and deflects and focuses it toward an observer on Earth, is calculated according to various cosmologic models. I pose the question of whether an object called a quasar is a single, intrinsically luminous entity or the result of accidental alignment, along the line of sight, of two normal galaxies, the more distant of which has its light amplified by the gravitational-lens effect of the nearer galaxy. If galaxies are distributed at random in the universe, the former alternative is true. But, if we assume that most galaxies exist in pairs, we can find about 30 galaxies occurring exactly one behind the other in such a way as to enable amplification of the order of 50. This model explains also the variations in intensity in quasars, but fails to explain others of their observed properties. PMID:17734305

Sadeh, D

1967-12-01

42

Weak lensing probes of modified gravity

We study the effect of modifications to general relativity on large-scale weak lensing observables. In particular, we consider three modified gravity scenarios: f(R) gravity, the Dvali-Gabadadze-Porrati model, and tensor-vector-scalar theory. Weak lensing is sensitive to the growth of structure and the relation between matter and gravitational potentials, both of which will in general be affected by modified gravity. Restricting ourselves to linear scales, we compare the predictions for galaxy-shear and shear-shear correlations of each modified gravity cosmology to those of an effective dark energy cosmology with the same expansion history. In this way, the effects of modified gravity on the growth of perturbations are separated from the expansion history. We also propose a test which isolates the matter-potential relation from the growth factor and matter power spectrum. For all three modified gravity models, the predictions for galaxy and shear correlations will be discernible from those of dark energy with very high significance in future weak lensing surveys. Furthermore, each model predicts a measurably distinct scale dependence and redshift evolution of galaxy and shear correlations, which can be traced back to the physical foundations of each model. We show that the signal-to-noise for detecting signatures of modified gravity is much higher for weak lensing observables as compared to the integrated Sachs-Wolfe effect, measured via the galaxy-cosmic microwave background cross-correlation.

Schmidt, Fabian [Department of Astronomy and Astrophysics, University of Chicago, Chicago, Illinois 60637-1433 (United States) and Kavli Institute for Cosmological Physics, Chicago, Illinois 60637-1433 (United States)

2008-08-15

43

WEAK LENSING MASS RECONSTRUCTION: FLEXION VERSUS SHEAR

Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone should not be used to do convergence map reconstruction, even on small scales.

Pires, S. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/SEDI-SAP, Service d'Astrophysique, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette (France); Amara, A. [Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland)

2010-11-10

44

Natural wormholes as gravitational lenses

Once quantum mechanical effects are included, the hypotheses underlying the positive mass theorem of classical general relativity fail. As an example of the peculiarities attendant upon this observation, a wormhole mouth embedded in a region of high mass density might accrete mass, giving the other mouth a net [ital negative] mass of unusual gravitational properties. The lensing of such a gravitationally negative anomalous compact halo object (GNACHO) will enhance background stars with a time profile that is observable and qualitatively different from that recently observed for massive compact halo objects (MACHO's) of positive mass. While the analysis is discussed in terms of wormholes, the observational test proposed is more generally a search for compact negative mass objects of any origin. We recommend that MACHO search data be analyzed for GNACHO's.

Cramer, J.G.; Forward, R.L.; Morris, M.S.; Visser, M.; Benford, G.; Landis, G.A. (Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States) Forward Unlimited, P.O. Box 2783, Malibu, California 90265 (United States) Department of Physics and Astronomy, Butler University, Indianapolis, Indiana 46208 (United States) Physics Department, Washington University, St. Louis, Missouri 63130-4899 (United States) Physics Department, University of California at Irvine, Irvine, California 92717-4575 (United States) NASA Lewis Research Center, Mail Code 302-1, Cleveland, Ohio 44135-3191 (United States))

1995-03-15

45

Computer Modeling of Gravitational Lensing Systems

The purpose of this research project is to determine the properties of gravitational lensing systems through the use of computer simulations. Modeling the lens galaxy as a Singular Isothermal Ellipsoid (SIE), we solved the gravitational lens equation for many different source and lens configurations in order to determine the properties of the system which reproduce the observed lensed images. Although

Philip Naudus; J. Wallin; P. Marshall

2010-01-01

46

Multi-wavelength applications of gravitational lensing

NASA Astrophysics Data System (ADS)

Using an array of multi-wavelength data, we examine a variety of astrophysical problems with gravitational lensing. First, we seek to understand the mass distribution of an early-type galaxy with an analysis of the lens Q0957+561. We dissect the lens galaxy into luminous and dark components, and model the environment using results from weak lensing. Combining constraints from newly-discovered lensed images and stellar population models, we find the lens has a density profile which is shallower than isothermal, unlike those of typical early-type galaxies. Finally, using the measured time delay between the quasar images we find the Hubble constant to be H 0 = 79.3+6.7-8.5 km s-1 Mpc-1 . One intriguing application of lensing is to exploit the lens magnification boost to study high-redshift objects in greater detail than otherwise possible. Here, we analyze the mid-infrared properties of two lensed z ˜ 2 star-forming galaxies, SDSS J120602.09+514229.5 and SDSS J090122.37+181432.3, using Spitzer /IRS spectra to study their rest-frame ˜ 5-12 ?m emission. Both systems exhibit strong polycyclic aromatic hydrocarbon (PAH) features in the spectra, indicating strong star formation and the absence of significant AGN activity. For SDSS J090122.37+181432.3, this detection belies that inferred from optical measurements, indicating mid-IR spectroscopy provides key information needed to understand the properties of high-redshift star-forming galaxies. While lensing provides measurements of the macroscopic properties of lens systems, it can also shed light on small-scale structure of galaxies. To identify and understand lens substructure, we examine the multi-wavelength properties of flux ratios for six lenses. Variations of the flux ratios with wavelength can be used to study the lensed quasars and the small-scale mass distribution of lens galaxies. We detect strong multi-wavelength variations in the lenses HE 0435-1223 and SDSS 0806+2006. For HE 0435-1223, we study its substructure with a series of lens models which add clumps of mass near the lensed images. We detect the presence of a clump near image A, with a mass of log (MA

Fadely, Ross

2010-12-01

47

Gravitational lensing in fourth order gravity

Gravitational lensing is investigated in the weak field limit of fourth order gravity in which the Lagrangian of the gravitational field is modified by replacing the Ricci scalar curvature R with an analytical expression f(R). Considering the case of a pointlike lens, we study the behavior of the deflection angle in the case of power-law Lagrangians, i.e. with f(R){proportional_to}R{sup n}. In order to investigate possible detectable signatures, the position of the Einstein ring and the solutions of the lens equation are evaluated considering the change with respect to the standard case. Effects on the amplification of the images and the Paczynski curve in microlensing experiments are also estimated.

Capozziello, S.; Troisi, A. [Dipartimento di Scienze Fisiche, Universita di Napoli 'Federico II', and INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Edificio N, via Cinthia, 80121-Naples (Italy); Cardone, V.F. [Dipartimento di Fisica 'E. R. Caianiello', Universita di Salerno, and INFN, Sezione di Napoli, Gruppo Collegato di Salerno, via S. Allende, 84081-Baronissi (Salerno) (Italy)

2006-05-15

48

Gravitational lensing: Models and astrophysical applications

NASA Astrophysics Data System (ADS)

This dissertation is an investigation of gravitational lens models and detailed analyses of the lensing properties of three astrophysically interesting multiply- imaged quasi-stellar objects (QSOs) Q2237+0305, Q0957+561, and H1413+1143. A general-form power-law elliptical mass distribution is considered as a model for a lensing object, and a Fourier series expansion technique is applied to obtain semi-analytical expressions for the deflection and magnification due to the general power-law mass model. Investigating more sophisticated lens models permitted by most recent and comprehensive sets of data, the following astrophysical/cosmological results are derived. For Q2237+0305, lensing properties of the elliptical mass model with varying radial index are calculated, and similarities and quantitative differences between the elliptical lens model and a pseudo-elliptical lens model (a power-law sphere plus shear) are highlighted. For Q0957+561, the elliptical mass model and a power-law sphere are used to model the lensing galaxy and cluster respectively, as motivated by recent Hubble Space Telescope (HST) imaging of the galaxy and weak lensing observations of the cluster. The lens model for Q0957+561 gives a best-fit to present observational constraints and yields a Hubble constant of H0=57+19- 16 (95% confidence) km s-1 Mpc-1. For H1413+1143, recent data from HST WFPC1,2, NICMOS, and FOS are used to explore possible lens models. Analyses of two-component lens models (namely, two-galaxy and galaxy+cluster) indicate that at least the continuum source region is microlensed. The broad emission line region could also be microlensed. However, information from present observations are not sufficient to draw any conclusions on the lensing nature of the broad emission line region or its size scale.

Chae, Kyu-Hyun

1999-11-01

49

Gravitational lensing by rotating naked singularities

We model massive compact objects in galactic nuclei as stationary, axially symmetric naked singularities in the Einstein-massless scalar field theory and study the resulting gravitational lensing. In the weak deflection limit we study analytically the position of the two weak field images, the corresponding signed and absolute magnifications as well as the centroid up to post-Newtonian order. We show that there are static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are functions of the scalar charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly for the weakly naked and vastly for the strongly naked singularities with the increase of the scalar charge. The pointlike caustics drift away from the optical axis and do not depend on the scalar charge. In the strong deflection limit approximation, we compute numerically the position of the relativistic images and their separability for weakly naked singularities. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as Janis-Newman-Winicour naked singularities.

Gyulchev, Galin N. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria); Yazadjiev, Stoytcho S. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria); Institut fuer Theoretische Physik, Universitaet Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany)

2008-10-15

50

WEAK-LENSING RESULTS FOR THE MERGING CLUSTER A1758

Here we present the weak-lensing results for A1758, which is known to consist of four subclusters undergoing two separate mergers, A1758N and A1758S. Weak-lensing results for A1758N agree with previous weak-lensing results for clusters 1E0657-558 (Bullet cluster) and MACS J0025.4-1222, whose X-ray gas components were found to be largely separated from their clusters' gravitational potentials. A1758N has a geometry that is different from previously published mergers in that one of its X-ray peaks overlays the corresponding gravitational potential and the other X-ray peak is well separated from its cluster's gravitational potential. The weak-lensing mass peaks of the two northern clusters are separated at the 2.5{sigma} level. We estimate the combined mass of the clusters in A1758N to be (2.2 {+-} 0.5) Multiplication-Sign 10{sup 15} M{sub Sun} and r{sub 200} = 2300{sup +100}{sub -130} kpc. We also detect seven strong-lensing candidates, two of which may provide information that would improve the mass measurements of A1758N.

Ragozzine, B.; Clowe, D. [Department of Physics and Astronomy, Astrophysical Institute, Ohio University, Athens, OH 45701 (United States); Markevitch, M. [NASA GSFC, Code 662, Greenbelt, MD 20771 (United States); Gonzalez, A. H. [Department of Astronomy, University of Florida, Gainesville, FL 32611-2055 (United States); Bradac, M., E-mail: ragoz@phy.ohiou.edu [Department of Physics, University of California Davis, Davis, CA 95616 (United States)

2012-01-10

51

Gravitational lensing of active galactic nuclei.

Most of the known cases of strong gravitational lensing involve multiple imaging of an active galactic nucleus. The properties of lensed active galactic nuclei make them promising systems for astrophysical applications of gravitational lensing; in particular, they show structure on scales of milliseconds of arc to tens of seconds of arc, they are variable, and they are polarized. More than 20 cases of strong gravitational lenses are now known, and about half of them are radio sources. High-resolution radio imaging is making possible the development of well-constrained lens models. Variability studies at radio and optical wavelengths are beginning to yield results of astrophysical interest, such as an independent measure of the distance scale and limits on source sizes.

Hewitt, J N

1995-01-01

52

Weak Lensing Studies of Mass Substructure in Clusters of Galaxies

NASA Astrophysics Data System (ADS)

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

Huwe, Paul M.

2012-01-01

53

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

54

Evidence for Dust in Gravitational Lenses

NASA Astrophysics Data System (ADS)

In a near-infrared survey of known lensed systems 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 extincted and reddened 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 in the lensing galaxy. Extinction by dust in lenses could hide the large number of lensed systems predicted for universe with a large value of the cosmological constant Lambda. These results substantially weaken the strongest constraint on models with a large cosmological constant. They also raise the prospect of using gravitational lenses to study the interstellar medium in high redshift galaxies. (A more complete discussion of this work has been published by Malhotra, Rhoads, & Turner [1997] in the Monthly Notices of the Royal Astronomical Society, vol. 288, p. 138.)

Rhoads, J. E.; Malhotra, S.; Turner, E. L.

55

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

56

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

57

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

58

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.

Jain, Bhuvnesh (University of Pennsylvania)

2006-02-27

59

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.

60

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.

61

Effect of Masked Regions on Weak-lensing Statistics

NASA Astrophysics Data System (ADS)

Sky masking is unavoidable in wide-field weak-lensing observations. We study how masks affect the measurement of statistics of matter distribution probed by weak gravitational lensing. We first use 1000 cosmological ray-tracing simulations to examine in detail the impact of masked regions on the weak-lensing Minkowski Functionals (MFs). We consider actual sky masks used for a Subaru Suprime-Cam imaging survey. The masks increase the variance of the convergence field and the expected values of the MFs are biased. The bias then compromises the non-Gaussian signals induced by the gravitational growth of structure. We then explore how masks affect cosmological parameter estimation. We calculate the cumulative signal-to-noise ratio (S/N) for masked maps to study the information content of lensing MFs. We show that the degradation of S/N for masked maps is mainly determined by the effective survey area. We also perform simple ?2 analysis to show the impact of lensing MF bias due to masked regions. Finally, we compare ray-tracing simulations with data from a Subaru 2 deg2 survey in order to address if the observed lensing MFs are consistent with those of the standard cosmology. The resulting ?2/n dof = 29.6/30 for three combined MFs, obtained with the mask effects taken into account, suggests that the observational data are indeed consistent with the standard ?CDM model. We conclude that the lensing MFs are a powerful probe of cosmology only if mask effects are correctly taken into account.

Shirasaki, Masato; Yoshida, Naoki; Hamana, Takashi

2013-09-01

62

Gravitational lensing effects on submillimetre galaxy counts

NASA Astrophysics Data System (ADS)

We study the effects on the number counts of submillimetre galaxies due to gravitational lensing. We explore the effects on the magnification cross-section due to halo density profiles, ellipticity and cosmological parameter (the power-spectrum normalization ?8). We show that the ellipticity does not strongly affect the magnification cross-section in gravitational lensing while the halo radial profiles do. Since the baryonic cooling effect is stronger in galaxies than clusters, galactic haloes are more concentrated. In light of this, a new scenario of two-halo-population model is explored where galaxies are modelled as a singular isothermal sphere profile and clusters as a Navarro, Frenk and White profile. We find that the transition mass between the two has modest effects on the lensing probability. The cosmological parameter ?8 alters the abundance of haloes and therefore affects our results. Compared with other methods, our model is simpler and more realistic. The conclusions of previous works confirm that gravitational lensing is a natural explanation for the number count excess at the bright end.

Er, Xinzhong; Li, Guoliang; Mao, Shude; Cao, Liang

2013-04-01

63

Strong gravitational lensing of gravitational waves in Einstein Telescope

NASA Astrophysics Data System (ADS)

Gravitational wave experiments have entered a new stage which gets us closer to the opening a new observational window on the Universe. In particular, the Einstein Telescope (ET) is designed to have a fantastic sensitivity that will provide with tens or hundreds of thousand NS-NS inspiral events per year up to the redshift z = 2. Some of such events should be gravitationally lensed by intervening galaxies. We explore the prospects of observing gravitationally lensed inspiral NS-NS events in the Einstein telescope. Being conservative we consider the lens population of elliptical galaxies. It turns out that depending on the local insipral rate ET should detect from one per decade detection in the pessimistic case to a tens of detections per year for the most optimistic case. The detection of gravitationally lensed source in gravitational wave detectors would be an invaluable source of information concerning cosmography, complementary to standard ones (like supernovae or BAO) independent of the local cosmic distance ladder calibrations.

Piórkowska, Aleksandra; Biesiada, Marek; Zhu, Zong-Hong

2013-10-01

64

NASA Astrophysics Data System (ADS)

In this paper, we obtain a relation between the high-energy absorption cross section and the strong gravitational lensing for a static and spherically symmetric black hole. It provides us a possible way to measure the high-energy absorption cross section for a black hole from strong gravitational lensing through astronomical observation. More importantly, it allows us to compute the total energy emission rate for high-energy particles emitted from the black hole acting as a gravitational lens. It could tell us the range of the frequency, among which the black hole emits the most of its energy and the gravitational waves are most likely to be observed. We also apply it to the Janis-Newman-Winicour solution. The results suggest that we can test the cosmic censorship hypothesis through the observation of gravitational lensing by the weakly naked singularities acting as gravitational lenses.

Wei, Shao-Wen; Liu, Yu-Xiao; Guo, Heng

2011-08-01

65

Computer Modeling of Gravitational Lensing Systems

NASA Astrophysics Data System (ADS)

The purpose of this research project is to determine the properties of gravitational lensing systems through the use of computer simulations. Modeling the lens galaxy as a Singular Isothermal Ellipsoid (SIE), we solved the gravitational lens equation for many different source and lens configurations in order to determine the properties of the system which reproduce the observed lensed images. Although exploring the entire parameter space is a computationally intense process, we have shown that solutions can be found relatively quickly by incorporating interaction between a user and the computer (solutions were found within a few minutes in our test cases). For this reason, we are collaborating with Galaxy Zoo to create and deploy an interactive Java applet which will allow non-experts to contribute to the modeling process. This project promises to determine properties of source galaxies in addition to finding the dark matter distributions of lens galaxies.

Naudus, Philip; Wallin, J.; Marshall, P.

2010-01-01

66

Gravitational lensing and the Hubble Deep Field

NASA Astrophysics Data System (ADS)

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

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

1999-04-01

67

Investigating the Dark Universe through Gravitational Lensing

NASA Astrophysics Data System (ADS)

A variety of precision observations suggest that the present universe is dominated by some unknown components, the so-called dark matter and dark energy. The distribution and properties of these components are the focus of modern cosmology and we are only beginning to understand them. Gravitational lensing, the bending of light in the gravitational field of a massive object, is one of the predictions of the general theory of relativity. It has become an ever more important tool for investigating the dark universe, especially with recent and coming advances in observational data. This thesis studies gravitational lensing effects on scales ranging over ten orders of magnitude to probe very different aspects of the dark universe. Implementing a matter distribution following the predictions of recent simulations, we show that microlensing by a large population of massive compact halo objects (MACHOs) is unlikely to be the source of the observed long-term variability in quasars. We study the feasibility of detecting the so far elusive galactic dark matter substructures, the so-called "missing satellites", via millilensing in galaxies close to the line-of-sight to distant light sources. Finally, we utilise massive galaxy clusters, some of the largest structures known in the universe, as gravitational telescopes in order to detect distant supernovae, thereby gaining insight into the expansion history of the universe. We also show, how such observations can be used to put constraints on the dark matter component of these galaxy clusters.

Riehm, Teresa

68

Measuring the dark side (with weak lensing)

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

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

2008-04-15

69

Gravitational lensing by a structure in a cosmological background

NASA Astrophysics Data System (ADS)

We use an exact general relativistic model structure within a Friedmann-Robertson-Walker cosmological background based on a Lemaître, Tolman, and Bondi metric to study the gravitational lensing by a cosmological and dynamical structure. Using different density profiles for the model structure, the deviation angle and the time delay through the gravitational lensing has been studied by solving the geodesic equations. The results of these exact calculations have been compared to the thin lens approximation. We have shown that the result for the thin lens approximation based on a modified Navarro-Frenk-White density profile with a void before going over to the Friedmann-Robertson-Walker background matches very well with the exact general relativistic calculations. However, the thin lens approximation based on a normal Navarro-Frenk-White profile does differ from the exact relativistic calculation. The difference is more the less compact the structure is. We have also looked at the impact of our calculation on the observational interpretation of arcs in the case of strong lensing and also the reduced shear in the case of weak lensing. No significant difference has been seen in the data available.

Mood, M. Parsi; Firouzjaee, Javad T.; Mansouri, Reza

2013-10-01

70

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

71

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

72

Non-Perturbative Gravitational Lensing by Three Dimensional Mass Models

Gravitational lensing is the bending and distortion of light rays by the gravitational pull of massive objects in the universe. Lensing studies are significant to the current revolution in modern astrophysics through which the ultimate questions of the universe – how did the universe begin and what conditions permit life to develop – are being answered. Although the distortion of

Thomas Kling

2005-01-01

73

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

74

Cannon Prize: Weak lensing - Revealing the Dark Side of the Universe

NASA Astrophysics Data System (ADS)

Weak gravitational lensing, the deflection of light from distant galaxies due to all intervening mass along the line of sight, is one of the most direct ways to observe dark matter. As a result, in the past decade, weak lensing has become a very important tool both for constraining cosmological parameters and for revealing the connection between galaxies and dark matter. I will begin by reviewing some of the most significant recent observational advances that were made possible by weak lensing. Next, I will outline some of the challenges and opportunities facing the lensing community in existing and upcoming imaging surveys. I will conclude with some perspective on how these challenges will be addressed to do ground-breaking work in the fields of cosmology, galaxy formation, and galaxy cluster formation and evolution with weak lensing observations in the next decade.

Mandelbaum, Rachel

2012-01-01

75

Can strong gravitational lensing constrain dark energy?

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

Lee, Seokcheon [Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (China); Ng, K.-W. [Institute of Physics, Academia Sinica, Taipei, Taiwan 11529 (China); Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan 11529 (China)

2007-08-15

76

Extreme gravitational lensing near rotating black holes

NASA Astrophysics Data System (ADS)

We describe a new approach to calculating photon trajectories and gravitational lensing effects in the strong gravitational field of the Kerr black hole. These techniques are applied to explore both the imaging and spectral properties of photons emitted from an accretion disc, which perform multiple orbits of the central mass before escaping to infinity. Viewed at large inclinations, these higher-order photons contribute ~20 per cent of the total luminosity of the system for a Schwarzschild hole, while for an extreme Kerr black hole this fraction rises to ~60 per cent. In more realistic models, these photons will be reabsorbed by the disc at large distances from the hole, but this returning radiation could provide a physical mechanism to resolve the discrepancy between the predicted and observed optical/ultraviolet colours in active galactic nuclei. Conversely, at low inclinations, higher-order images reintercept the disc plane close to the black hole, so need not be absorbed by the disc if this is within the plunging region. These photons form a bright ring carrying approximately 10 per cent of the total disc luminosity for a Schwarzschild black hole. The spatial separation between the inner edge of the disc and the ring is similar to the size of the event horizon. This is resolvable for supermassive black holes with proposed X-ray interferometery missions such as the Microarcsecond X-ray Imaging Mission (MAXIM), and so has the potential to provide an observational test of strong field gravity.

Beckwith, Kris; Done, Chris

2005-06-01

77

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

78

The weak-lensing science of the Large Synoptic Survey Telescope (LSST) project drives the need to carefully model and separate the instrumental artifacts from the intrinsic shear signal caused by gravitational lensing. The dominant source of the systematics for all ground-based telescopes is the spatial correlation of the point-spread function (PSF) modulated by both atmospheric turbulence and optical aberrations in the

M. James Jee; J. Anthony Tyson

2011-01-01

79

Combining weak-lensing tomography and spectroscopic redshift surveys

NASA Astrophysics Data System (ADS)

Redshift space distortion (RSD) is a powerful way of measuring the growth of structure and testing General Relativity, but it is limited by cosmic variance and the degeneracy between the galaxy bias b and the growth rate factor f. The cross-correlation of lensing shear with the galaxy density field can in principle measure b in a manner free from cosmic variance limits, breaking the f - b degeneracy and allowing inference of the matter power spectrum from the galaxy survey. We analyse the growth constraints from a realistic tomographic weak-lensing photo-z survey combined with a spectroscopic galaxy redshift survey over the same sky area. For sky coverage fsky= 0.5, analysis of the transverse modes measures b to 2-3 per cent accuracy per ?z= 0.1 bin at z < 1 when ˜10 galaxies arcmin-2 are measured in the lensing survey and all haloes with M > Mmin= 1013 h-1 M? have spectra. For the gravitational growth parameter parameter ? (?, combining the lensing information with RSD analysis of non-transverse modes yields accuracy ?(?) ? 0.01. Adding lensing information to the RSD survey improves ?(?) by an amount equivalent to a 3 × (10 ×) increase in the RSD survey area when the spectroscopic survey extends down to halo mass 1013.5 (1014) h-1 M?. We also find that the ?(?) of overlapping surveys is equivalent to that of surveys 1.5-2× larger if they are separated on the sky. This gain is greatest when the spectroscopic mass threshold is 1013-1014 h-1 M?, similar to Luminous Red Galaxy surveys. The gain of overlapping surveys is reduced for very deep or very shallow spectroscopic surveys, but any practical surveys are more powerful when overlapped than when separated. The gain of overlapped surveys is larger in the case when the primordial power spectrum normalization is uncertain by >0.5 per cent.

Cai, Yan-Chuan; Bernstein, Gary

2012-05-01

80

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)

2009-07-28

81

Gravitational lensing, time delay, and gamma-ray bursts

The probability distributions of time delay in gravitational lensing by point masses and isolated galaxies (modeled as singular isothermal spheres) are studied. For point lenses (all with the same mass) the probability distribution is broad, and with a peak at delta(t) of about 50 S; for singular isothermal spheres, the probability distribution is a rapidly decreasing function with increasing time

Shude Mao

1992-01-01

82

Gravitational Lenses and the Sloan Digital Sky Survey

The imaging data from the Sloan Digital Sky Survey (SDSS) provides the basis for a powerful gravitational lens survey as it allows the photometric selection of a large number of quasars. It is expected that the photometric sample will contain of order 1000 gravitationally lensed QSOs. On the order of 100 of these will be brighter than the SDSS spectroscopic

G. T. Richards; J. A. Annis; A. R. Cooray; S. Dodelson; J. A. Frieman; D. Johnston; T. A. McKay; S. Monk; H. J. Newberg; B. Pindor; R. Scranton; E. S. Sheldon; E. L. Turner

1999-01-01

83

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

84

COSMOS: Three-dimensional Weak Lensing and the Growth of Structure

We present a three-dimensional cosmic shear analysis of the Hubble Space Telescope COSMOS survey, the largest ever optical imaging program performed in space. We have measured the shapes of galaxies for the telltale distortions caused by weak gravitational lensing and traced the growth of that signal as a function of redshift. Using both 2D and 3D analyses, we measure cosmological

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

2007-01-01

85

Various Approaches to Cosmological Gravitational Lensing in Inhomogeneous Models

NASA Astrophysics Data System (ADS)

Gravitational lensing of distant objects caused by gravitational tidal forces from inhomogeneities in the universe is weak in most cases, but it is noticed that it gives a great deal of information about the universe, especially regarding the distribution of dark matter. The statistical values of optical quantities such as convergence, amplification and shear have been derived by many people using various approaches, which include the linear perturbational treatment in the weak limit and the nonlinear treatment considering small-scale matter distribution. In this review paper we compare the following three main approaches: (a) the approach in the multi-lens-plane theory; (b) the approach due to the direct integration method; and (c) the perturbational approach. In the former two approaches inhomogeneous matter distributions are produced in the CDM model using N-body simulations (the P3M code and the tree-code, respectively). In (c) the power spectrum corresponding to the CDM model is used for the large-scale matter distribution.

Tomita, K.; Premadi, P.; Nakamura, T. T.

86

BIASED DARK ENERGY CONSTRAINTS FROM NEGLECTING REDUCED SHEAR IN WEAK-LENSING SURVEYS

The weak gravitational lensing of distant galaxies by a large-scale structure is expected to become a powerful probe of dark energy. By measuring the ellipticities of large number of background galaxies, the subtle gravitational distortion called 'cosmic shear' can be measured and used to constrain dark energy parameters. The observed galaxy ellipticities, however, are induced not by shear but by reduced shear, which also accounts for slight magnifications of the images. This distinction is negligible for present weak-lensing surveys, but it will become more important as we improve our ability to measure and understand small-angle cosmic shear modes. I calculate the discrepancy between shear and reduced shear in the context of power spectra and cross spectra, finding the difference could be as high as 10% on the smallest accessible angular scales. I estimate how this difference will bias dark energy parameters obtained from two weak-lensing methods: weak-lensing tomography and the shear ratio method known as offset-linear scaling. For weak-lensing tomography, ignoring the effects of reduced shear will cause future surveys considered by the Dark Energy Task Force to measure dark energy parameters that are biased by amounts comparable to their error bars. I advocate that reduced shear be properly accounted for in such surveys, and I provide a semi-analytic formula for doing so. Since reduced shear cross spectra do not follow an offset-linear scaling relation, the shear ratio method is similarly biased but with smaller significance.

Shapiro, Charles [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 2EG (United Kingdom)], E-mail: charles.shapiro@port.ac.uk

2009-05-01

87

Particle motion in weak relativistic gravitational fields

NASA Astrophysics Data System (ADS)

We derive the geodesic equation of motion in the presence of weak gravitational fields produced by relativistic sources such as cosmic strings, decomposed into scalar, vector and tensor parts. To test the result, we perform the first N-body simulations with relativistic weak gravitational external fields. Our test case is a moving straight string, for which we recover the well-known result for the impulse on nonrelativistic particles. We find that the vector (gravito-magnetic) force is an essential contributor. Our results mean that it is now possible to incorporate straightforwardly into N-body simulations all weak relativistic sources, including networks of cosmic defects.

Obradovic, Miki; Kunz, Martin; Hindmarsh, Mark; Iliev, Ilian T.

2012-09-01

88

Dixon's extended bodies and weak gravitational waves

NASA Astrophysics Data System (ADS)

General relativity considers Dixon’s theory as the standard theory to deal with the motion of extended bodies in a given gravitational background. We discuss here the features of the “reaction” of an extended body to the passage of a weak gravitational wave. We find that the body acquires a dipolar moment induced by its quadrupole structure. Furthermore, we derive the “world function” for the weak field limit of a gravitational wave background and use it to estimate the deviation between geodesics and the world lines of structured bodies. Measuring such deviations, due to the existence of cumulative effects, should be favorite with respect to measuring the amplitude of the gravitational wave itself.

Bini, Donato; Cherubini, Christian; Geralico, Andrea; Ortolan, Antonello

2009-01-01

89

When light goes astray: gravitational lensing in astrophysics

NASA Astrophysics Data System (ADS)

Light propagating in an inhomogeneous medium does not travel in straight lines. Light rays wander; they are focused, magnified and dispersed as they travel through an inhomogeneous medium. Such deflections are familiar to physicists. They are the stuff of optics. On cosmic scales light is 'deflected' in a more profound way, tracing inhomogeneities in the underlying space-time. The meandering of light rays as they propagate through the Universe encodes unique information about variations in the space-time metric. General relativity tells us these variations are impressed on the metric by inhomogeneities in the matter distribution. As a result, this 'gravitational lensing' provides information about the distribution of mass in the Universe. In this work we review briefly the main features of gravitational lensing, with an emphasis on observable effects. Remarkable progress has been made in lensing observations since 1990. We discuss some aspects of this rapid development, commenting especially on astrophysical topics where lensing studies have had a major impact. We suggest that gravitational lensing is now a standard part of the astrophysical toolkit, akin in some ways to photometry. We conclude with a discussion of areas in which lensing studies will have a strong impact in years to come, and comment on technical requirements for these future studies.

McKay, Timothy A.

2002-06-01

90

Constraints on neutrino masses from weak lensing

Weak lensing (WL) distortions of distant galaxy images are sensitive to neutrino masses by probing the suppression effect on clustering strengths of total matter in large-scale structure. We use the latest measurements of WL correlations, the Canada-France-Hawaii Telescope Legacy Survey data, to explore constraints on neutrino masses. We find that, while the WL data alone cannot place a stringent limit on neutrino masses due to parameter degeneracies, the constraint can be significantly improved when combined with other cosmological probes, such as the WMAP 5-year data (WMAP5) and the distance measurements of type-Ia supernovae (SNe) and baryon acoustic oscillations (BAO). The upper bounds on the sum of neutrino masses are , 0.76, and 0.54 eV (95% CL) for WL+WMAP5, WMAP5+SNe+BAO, and WL+WMAP5+SNe+BAO, respectively, assuming a flat {lambda}CDM model with finite-mass neutrinos. In deriving these constraints, our analysis includes the non-Gaussian covariances of the WL correlation functions to properly take into account significant correlations between different angles.

Ichiki, Kiyotomo [Department of Physics and Astrophysics, Nagoya University, Nagoya 464-8602 (Japan); Research Center for the Early Universe, University of Tokyo, Tokyo 113-0033 (Japan); Takada, Masahiro [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Chiba 277-8582 (Japan); Takahashi, Tomo [Department of Physics, Saga University, Saga 840-8502 (Japan)

2009-01-15

91

GREAT3: The Third Gravitational Lensing Accuracy Testing Challenge

NASA Astrophysics Data System (ADS)

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

Mandelbaum, Rachel; Rowe, B.; GREAT3 Collaboration

2013-01-01

92

Weak Lensing Measurements with the Hubble Space Telescope Advanced Camera for Surveys

NASA Astrophysics Data System (ADS)

We present the weak lensing analysis of imagery from 10 high-redshift clusters using the Hubble Advanced Camera for Surveys, from the ESO Distant Cluster Survey (EDisCS). Weak Gravitational Lensing is the miniscule bending of light from distant background galaxies by the presence of large foreground masses. Particularly, we examine images of galaxy clusters at reshifts z < 1.0 (corresponding to a physical distance on the megaparsec scale) and look for distant elliptical galaxies (i.e. redshifts z >> 1.0). These galaxies are expected to have an isotropic distribution in space, and their semi-major axes should subtend the entire possible space of orientation angles (i.e. when statistically measuring the mean ellipticity, we should find it averages to zero across a well-defined sample). These ten clusters, in particular, provide unprecedented depth and allow a perfect test bed on which to study the application of weak lensing tomography.

Murphy, Kellen

2010-10-01

93

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 {Lambda}CDM model of structure formation. Gravitational lensing is a technique for measuring the total mass distribution which is independent of the nature of the gravitating matter, making it a vital tool for studying these dark-matter-dominated objects. We present a new method for measuring weak gravitational lensing flexion fields, the gradients of the lensing shear field, to measure mass distributions on small angular scales. While previously published methods for measuring flexion focus on measuring derived properties of the lensed images, such as shapelet coefficients or surface brightness moments, our method instead fits a mass-sheet transformation invariant Analytic Image Model (AIM) to each galaxy image. This simple parametric model traces the distortion of lensed image isophotes and constrains the flexion fields. We test the AIM method using simulated data images with realistic noise and a variety of unlensed image properties, and show that it successfully reproduces the input flexion fields. We also apply the AIM method for flexion measurement to Hubble Space Telescope observations of A1689 and detect mass structure in the cluster using flexion measured with this method. We also estimate the scatter in the measured flexion fields due to the unlensed shape of the background galaxies and find values consistent with previous estimates.

Cain, Benjamin [MIT Kavli Institue for Astrophysics and Space Research/University of California Davis, Department of Physics, One Shields Avenue, Davis, CA 95616 (United States); Schechter, Paul L.; Bautz, M.W., E-mail: bmcain@ucdavis.edu, E-mail: schech@mit.edu, E-mail: mwb@space.mit.edu [MIT Kavli Institue for Astrophysics and Space Research, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States)

2011-07-20

94

Measuring Gravitational Lensing Flexion in A1689 Using an Analytic Image Model

NASA Astrophysics Data System (ADS)

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 independent of the nature of the gravitating matter, making it a vital tool for studying these dark-matter-dominated objects. We present a new method for measuring weak gravitational lensing flexion fields, the gradients of the lensing shear field, to measure mass distributions on small angular scales. While previously published methods for measuring flexion focus on measuring derived properties of the lensed images, such as shapelet coefficients or surface brightness moments, our method instead fits a mass-sheet transformation invariant Analytic Image Model (AIM) to each galaxy image. This simple parametric model traces the distortion of lensed image isophotes and constrains the flexion fields. We test the AIM method using simulated data images with realistic noise and a variety of unlensed image properties, and show that it successfully reproduces the input flexion fields. We also apply the AIM method for flexion measurement to Hubble Space Telescope observations of A1689 and detect mass structure in the cluster using flexion measured with this method. We also estimate the scatter in the measured flexion fields due to the unlensed shape of the background galaxies and find values consistent with previous estimates.

Cain, Benjamin; Schechter, Paul L.; Bautz, M. W.

2011-07-01

95

To the horizon and beyond: Weak lensing of the CMB and binary inspirals into horizonless objects

NASA Astrophysics Data System (ADS)

This thesis examines two predictions of general relativity: weak lensing and gravitational waves. The cosmic microwave background (CMB) is gravitationally lensed by the large-scale structure between the observer and the last- scattering surface. This weak lensing induces non-Gaussian correlations that can be used to construct estimators for the deflection field. The error and bias of these estimators are derived and used to analyze the viability of lensing reconstruction for future CMB experiments. Weak lensing also affects the one-point probability distribution function of the CMB. The skewness and kurtosis induced by lensing and the Sunayev- Zel'dovich (SZ) effect are calculated as functions of the angular smoothing scale of the map. While these functions offer the advantage of easy computability, only the skewness from lensing-SZ correlations can potentially be detected, even in the limit of the largest amplitude fluctuations allowed by observation. Lensing estimators are also essential to constrain inflation, the favored explanation for large-scale isotropy and the origin of primordial perturbations. B-mode polarization is considered to be a "smoking-gun" signature of inflation, and lensing estimators can be used to recover primordial B-modes from lensing-induced contamination. The ability of future CMB experiments to constrain inflation is assessed as functions of survey size and instrumental sensitivity. A final application of lensing estimators is to constrain a possible cutoff in primordial density perturbations on near-horizon scales. The paucity of independent modes on such scales limits the statistical certainty of such a constraint. Measurements of the deflection field can be used to constrain at the 3s level the existence of a cutoff large enough to account for current CMB observations. A final chapter of this thesis considers an independent topic: the gravitational-wave (GW) signature of a binary inspiral into a horizonless object. If the supermassive objects at galactic centers lack the horizons of traditional black holes, inspiraling objects could emit GWs after passing within their surfaces. The GWs produced by such an inspiral are calculated, revealing distinctive features potentially observable by future GW observatories.

Kesden, Michael

96

Strong biases in infrared-selected gravitational lenses

NASA Astrophysics Data System (ADS)

Bright submillimetre-selected galaxies have been found to be a rich source of strong gravitational lenses. However, strong gravitational lensing of extended sources leads inevitably to differential magnification. In this paper I quantify the effect of differential magnification on simulated far-infrared and submillimetre surveys of strong gravitational lenses, using a foreground population of Navarro-Frenk-White plus de Vaucouleurs' density profiles, with a model source resembling the Cosmic Eyelash and quasi-stellar object J1148+5251. Some emission-line diagnostics are surprisingly unaffected by differential magnification effects: for example, the bolometric fractions of [CII] 158 ?m and CO(J = 1 - 0), often used to infer densities and ionization parameters, have typical differential magnification effects that are smaller than the measurement errors. However, the CO ladder itself is significantly affected. Far-infrared lensed galaxy surveys (e.g. at 60 ?m) strongly select for high-redshift galaxies with caustics close to active galactic nuclei (AGNs), boosting the apparent bolometric contribution of AGN. The lens configuration of IRAS F10214+4724 is naturally explained in this context. Conversely, submillimetre/millimetre-wave surveys (e.g. 500-1400 ?m) strongly select for caustics close to knots of star formation boosting the latter's bolometric fraction. In general, estimates of bolometric fractions from spectral energy distributions of strongly lensed infrared galaxies are so unreliable as to be useless, unless a lens mass model is available to correct for differential magnification.

Serjeant, Stephen

2012-08-01

97

The Unreasonable Effectiveness of Strong Gravitational Lensing in Cosmology

This Chapter presents a brief overview of the main concepts required to understand phenomena associated with strong gravitational lensing, from the formation of multiple images of distant quasars to the microlensing of stars within the Galaxy, and from the arcs in clusters of galaxies to the determination of Hubble's parameter. After a brief history of the subject, the general relativistic

D. Valls-Gabaud

1997-01-01

98

Gravitational Lensing of Stars Surrounding Supermassive Black Holes

Many indications suggest that both the Milky Way and M31 host a supermassive black holes in their central regions. General Relativity tells us that these black holes, acting as gravitational lenses, are able in principle to bend the light rays of the source stars moving in their neighborhood. As a consequence of this fact, a secondary image and two infinite

V. Bozza; L. Mancini

2008-01-01

99

SHELS: TESTING WEAK-LENSING MAPS WITH REDSHIFT SURVEYS

Weak-lensing surveys are emerging as an important tool for the construction of 'mass-selected' clusters of galaxies. We evaluate both the efficiency and completeness of a weak-lensing selection by combining a dense, complete redshift survey, the Smithsonian Hectospec Lensing Survey (SHELS), with a weak-lensing map from the Deep Lens Survey (DLS). SHELS includes 11,692 redshifts for galaxies with R <= 20.6 in the 4 deg{sup 2} DLS field; the survey is a solid basis for identifying massive clusters of galaxies with redshift z approx< 0.55. The range of sensitivity of the redshift survey is similar to the range for the DLS convergence map. Only four of the 12 convergence peaks with signal to noise >=3.5 correspond to clusters of galaxies with M approx> 1.7 x 10{sup 14} M{sub sun}. Four of the eight massive clusters in SHELS are detected in the weak-lensing map yielding a completeness of approx50%. We examine the seven known extended cluster X-ray sources in the DLS field: three can be detected in the weak-lensing map, three should not be detected without boosting from superposed large-scale structure, and one is mysteriously undetected even though its optical properties suggest that it should produce a detectable lensing signal. Taken together, these results underscore the need for more extensive comparisons among different methods of massive cluster identification.

Geller, Margaret J.; Kurtz, Michael J.; Fabricant, Daniel G. [Smithsonian Astrophysical Observatory, 60 Garden St., Cambridge, MA 02138 (United States); Dell'Antonio, Ian P. [Department of Physics, Brown University, Box 1843, Providence, RI 02912 (United States); Ramella, Massimo, E-mail: mgeller@cfa.harvard.ed, E-mail: mkurtz@cfa.harvard.ed, E-mail: dfabricant@cfa.harvard.ed, E-mail: ian@het.brown.ed, E-mail: ramella@oats.inaf.i [INAF, Osservatorio Astronomico di Trieste, via C. B. Tiepolo 11, I-34131 Trieste (Italy)

2010-02-01

100

The impact of camera optical alignments on weak lensing measures for the Dark Energy Survey

NASA Astrophysics Data System (ADS)

Telescope point spread function (PSF) quality is critical for realizing the potential of cosmic weak lensing observations to constrain dark energy and test general relativity. In this paper, we use quantitative weak gravitational lensing measures to inform the precision of lens optical alignment, with specific reference to the Dark Energy Survey (DES). We compute optics spot diagrams and calculate the shear and flexion of the PSF as a function of position on the focal plane. For perfect optical alignment, we verify the high quality of the DES optical design, finding a maximum PSF contribution to the weak lensing shear of 0.04 near the edge of the focal plane. However, this can be increased by a factor of approximately 3 if the lenses are only just aligned within their maximum specified tolerances. We calculate the E- and B-mode shear and flexion variance as a function of the decentre or tilt of each lens in turn. We find tilt accuracy to be a few times more important than decentre, depending on the lens considered. Finally, we consider the compound effect of decentre and tilt of multiple lenses simultaneously, by sampling from a plausible range of values of each parameter. We find that the compound effect can be around twice as detrimental as when considering any one lens alone. Furthermore, this combined effect changes the conclusions about which lens is most important to align accurately. For DES, the tilt of the first two lenses is the most important.

Antonik, Michelle L.; Bacon, David J.; Bridle, Sarah; Doel, Peter; Brooks, David; Worswick, Sue; Bernstein, Gary; Bernstein, Rebecca; DePoy, Darren; Flaugher, Brenna; Frieman, Joshua A.; Gladders, Michael; Gutierrez, Gaston; Jain, Bhuvnesh; Jarvis, Michael; Kent, Stephen M.; Lahav, Ofer; Parker, S.-J.; Roodman, Aaron; Walker, Alistair R.

2013-06-01

101

The Missing Weak Lensing Mass in A781

NASA Astrophysics Data System (ADS)

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? limit on the mass of <5 × 1013 M ?. 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.

2012-05-01

102

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

103

Quasar structure from microlensing in gravitationally lensed quasars

NASA Astrophysics Data System (ADS)

I analyze microlensing in gravitationally lensed quasars to yield measurements of the structure of their continuum emission regions. I first describe our lensed quasar monitoring program and RETROCAM, the auxiliary port camera I built for the 2.4m Hiltner telescope to monitor lensed quasars. I describe the application of our Monte Carlo microlensing analysis technique to SDSS 0924+0219, a system with a highly anomalous optical flux ratio. For an inclination angle i, I find an optical scale radius log[( r s /cm)[Special characters omitted.] ] = [Special characters omitted.] . I extrapolate the best-fitting light curves into the future to find a roughly 45% probability that the anomalous image (D) will brighten by at least an order of magnitude during the next decade. I expand our method to make simultaneous estimates of the time delays and structure of HE1104-1805 and QJ0158-4325, two doubly-imaged quasars with microlensing and intrinsic variability on comparable time scales. For HE1104- 1805 I find a time delay of D t AB = t A - t B = [Special characters omitted.] days and estimate a scale radius of log[( r s /cm)[Special characters omitted.] ] = [Special characters omitted.] at 0.2mm in the rest frame. I am unable to measure a time delay for QJ0158-4325, but the scale radius is log[( r s /cm) [Special characters omitted.] ] = 14.9 ±1 0.3 at 0.3mm in the rest frame. I then apply our Monte Carlo microlensing analysis technique to the optical light curves of 11 lensed quasar systems to show that quasar accretion disk sizes at 2500Å are related to black hole mass ( M BH ) by log( R 2500 /cm) = (15.7 ± 0.16) + (0.64± 0.18) log( M BH /10 9 [Special characters omitted.] ). This scaling is consistent with the expectation from thin disk theory (R 0( [Special characters omitted.] ), but it implies that black holes radiate with relatively low efficiency, log(e) = -1.54 ± 0.36 + log( L/L E ) where e=3D L / ( M c 2 ). These sizes are also larger, by a factor of ~ 3, than the size needed to produce the observed 0.8mm quasar flux by thermal radiation from a thin disk with the same T 0( R -3/4 temperature profile. Finally, I analyze the microlensing of the X-ray and optical emission of the lensed quasar PG 1115+080. I find that the effective radius of the X-ray emission is [Special characters omitted.] dex smaller than that of the optical emission. I find a weak trend supporting models with low stellar mass fractions near the lensed images in mild contradiction to inferences from the stellar velocity dispersion and the time delays.

Morgan, Christopher Warren

2008-02-01

104

Strong gravitational lensing in a noncommutative black-hole spacetime

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

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

2011-04-15

105

CFHTLenS tomographic weak lensing: quantifying accurate redshift distributions

NASA Astrophysics Data System (ADS)

The Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) comprises deep multicolour (u*g'r'i'z') photometry spanning 154 deg2, with accurate photometric redshifts and shape measurements. We demonstrate that the redshift probability distribution function summed over galaxies provides an accurate representation of the galaxy redshift distribution accounting for random and catastrophic errors for galaxies with best-fitting photometric redshifts zp < 1.3. We present cosmological constraints using tomographic weak gravitational lensing by large-scale structure. We use two broad redshift bins 0.5 < zp ? 0.85 and 0.85 < zp ? 1.3 free of intrinsic alignment contamination, and measure the shear correlation function on angular scales in the range ˜1-40 arcmin. We show that the problematic redshift scaling of the shear signal, found in previous Canada-France-Hawaii Telescope Legacy Survey data analyses, does not affect the CFHTLenS data. For a flat ? cold dark matter model and a fixed matter density ?m = 0.27, we find the normalization of the matter power spectrum ?8 = 0.771 ± 0.041. When combined with cosmic microwave background data (Wilkinson Microwave Anisotropy Probe 7-year results), baryon acoustic oscillation data (BOSS) and a prior on the Hubble constant from the Hubble Space Telescope distance ladder, we find that CFHTLenS improves the precision of the fully marginalized parameter estimates by an average factor of 1.5-2. Combining our results with the above cosmological probes, we find ?m = 0.2762 ± 0.0074 and ?8 = 0.802 ± 0.013.

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

2013-05-01

106

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

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

Cevallos, Marissa; /Caltech /SLAC

2006-01-04

107

Polarization as an indicator of intrinsic alignment in radio weak lensing

NASA Astrophysics Data System (ADS)

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

Brown, Michael L.; Battye, Richard A.

2011-01-01

108

Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS

NASA Astrophysics Data System (ADS)

We present a comprehensive analysis of weak gravitational lensing by large-scale structure in the Hubble Space Telescope Cosmic Evolution Survey (COSMOS), in which we combine space-based galaxy shape measurements with ground-based photometric redshifts to study the redshift dependence of the lensing signal and constrain cosmological parameters. After applying our weak lensing-optimized data reduction, principal-component interpolation for the spatially, and temporally varying ACS point-spread function, and improved modelling of charge-transfer inefficiency, we measured a lensing signal that is consistent with pure gravitational modes and no significant shape systematics. We carefully estimated the statistical uncertainty from simulated COSMOS-like fields obtained from ray-tracing through the Millennium Simulation, including the full non-Gaussian sampling variance. We tested our lensing pipeline on simulated space-based data, recalibrated non-linear power spectrum corrections using the ray-tracing analysis, employed photometric redshift information to reduce potential contamination by intrinsic galaxy alignments, and marginalized over systematic uncertainties. We find that the weak lensing signal scales with redshift as expected from general relativity for a concordance ?CDM cosmology, including the full cross-correlations between different redshift bins. Assuming a flat ?CDM cosmology, we measure ?_8(?_m/0.3)0.51 = 0.75±0.08 from lensing, in perfect agreement with WMAP-5, yielding joint constraints ?_m = 0.266+0.025-0.023, ?_8 = 0.802+0.028-0.029 (all 68.3% conf.). Dropping the assumption of flatness and using priors from the HST Key Project and Big-Bang nucleosynthesis only, we find a negative deceleration parameter q0 at 94.3% confidence from the tomographic lensing analysis, providing independent evidence of the accelerated expansion of the Universe. For a flat wCDM cosmology and prior w ? [-2,0], we obtain w <-0.41 (90% conf.). Our dark energy constraints are still relatively weak solely due to the limited area of COSMOS. However, they provide an important demonstration of the usefulness of tomographic weak lensing measurements from space. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archives at the Space Telescope European Coordinating Facility and the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Schrabback, T.; Hartlap, J.; Joachimi, B.; Kilbinger, M.; Simon, P.; Benabed, K.; Brada?, M.; Eifler, T.; Erben, T.; Fassnacht, C. D.; High, F. William; Hilbert, S.; Hildebrandt, H.; Hoekstra, H.; Kuijken, K.; Marshall, P. J.; Mellier, Y.; Morganson, E.; Schneider, P.; Semboloni, E.; van Waerbeke, L.; Velander, M.

2010-06-01

109

Two new large-separation gravitational lenses from SDSS

NASA Astrophysics Data System (ADS)

We present discovery images, together with follow-up imaging and spectroscopy, of two large-separation gravitational lenses found by our survey for wide arcs [the CAmbridge Sloan Survey Of Wide ARcs in the skY (CASSOWARY)]. The survey exploits the multicolour photometry of the Sloan Digital Sky Survey to find multiple blue components around red galaxies. CASSOWARY 2 (or `the Cheshire Cat') is composed of two massive early-type galaxies at z = 0.426 and 0.432, respectively, lensing two background sources, the first a star-forming galaxy at z = 0.97 and the second a high -redshift galaxy (z > 1.4). There are at least three images of the former source and probably four or more of the latter, arranged in two giant arcs. The mass enclosed within the larger arc of radius ~11 arcsec is ~33 × 1012Msolar. CASSOWARY 3 comprises an arc of three bright images of a z = 0.725 source, lensed by a foreground elliptical at z = 0.274. The radius of the arc is ~4 arcsec and the enclosed mass is ~2.5 × 1012Msolar. Together with earlier discoveries like the Cosmic Horseshoe and the 8 o'clock Arc, these new systems, with separations intermediate between the arcsecond-separation lenses of typical strong galaxy lensing and arcminute-separation cluster lenses, probe the very high end of the galaxy mass function.

Belokurov, V.; Evans, N. W.; Hewett, P. C.; Moiseev, A.; McMahon, R. G.; Sanchez, S. F.; King, L. J.

2009-01-01

110

Gravitational force in weakly correlated particle distributions

We study the statistics of the gravitational (Newtonian) force in a\\u000aparticular kind of weakly correlated distribution of point-like and unitary\\u000amass particles generated by the so-called Gauss-Poisson point process. In\\u000aparticular we extend to these distributions the analysis a' la Chandrasekhar\\u000aintroduced for purely Poisson processes. In this way we can find the asymptotic\\u000abehavior of the probability density

Andrea Gabrielli; Adolfo Paolo Masucci; Francesco Sylos Labini

2003-01-01

111

Wave effect in gravitational lensing by the Ellis wormhole

NASA Astrophysics Data System (ADS)

We propose the use of modulated spectra of astronomical sources due to gravitational lensing to probe Ellis wormholes. The modulation factor due to gravitational lensing by the Ellis wormhole is calculated. Within the geometrical optics approximation, the normal point-mass lens and the Ellis wormhole are indistinguishable unless we know the source’s unlensed luminosity. This degeneracy is resolved with the significant wave effect in the low-frequency domain if we take the deviation from the geometrical optics into account. We can roughly estimate the upper bound for the number density of Ellis wormholes as n?4×10-10AU-3 with throat radius a˜1cm from the existing femtolensing analysis for compact objects.

Yoo, Chul-Moon; Harada, Tomohiro; Tsukamoto, Naoki

2013-04-01

112

Gravitational lensing in the Kerr-Randers optical geometry

NASA Astrophysics Data System (ADS)

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?m, it is shown explicitly how the two leading terms of the asymptotic deflection angle of gravitational lensing can be found in this way.

Werner, M. C.

2012-12-01

113

B2(II): Cosmology (ii). Late Universe and Gravitational Lenses

NASA Astrophysics Data System (ADS)

The "Late Universe and Gravitational Lenses" session featured a broad spectrum of talks, with topics ranging from the cosmic microwave background to the density profiles of dark matter halos, and from perturbation theory to cosmic topology. The common thread through all of the talks was the way general relativity impacts our current understanding of cosmology. As GR forms the underpinning of our cosmological standard model, seemingly abstract and abstruse relativity questions can often yield important cosmological insights.

Holz, Daniel E.

2005-11-01

114

Optical Gravitational Lensing Experiment - Database of 1992 results

NASA Astrophysics Data System (ADS)

Description and technical details of the data bases constructed for handling a huge amount of data from the Optical Gravitational Lensing Experiment (OGLE) are presented. The described software allows easy and fast retrieving photometric data of any from about 10 exp 6 stars observed during the 1992 OGLE observing season (6.5 GBytes of raw data, about 1.3 x 10 exp 8 photometric measurements).

Szymanski, M.; Udalski, A.

1993-04-01

115

Measuring the mass distribution of voids with stacked weak lensing

NASA Astrophysics Data System (ADS)

We study the prospects for measuring the dark matter distribution of voids with stacked weak lensing. We select voids from a large set of N-body simulations and explore their lensing signals with the full ray-tracing simulations including the effect of the large-scale structure along the line of sight. The lensing signals are compared with simple void model predictions to infer the three-dimensional mass distribution of voids. We show that the stacked weak lensing signals are detected at a significant level (S/N ? 5) for a 5000 degree2 survey area, for a wide range of void radii up to ˜50 Mpc. The error from the galaxy shape noise little affects lensing signals at large scale. It is also found that dense ridges around voids have a great impact on the weak lensing signals, suggesting that proper modelling of the void density profile including surrounding ridges is essential for extracting the average total underdense mass of voids.

Higuchi, Yuichi; Oguri, Masamune; Hamana, Takashi

2013-06-01

116

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

NASA Astrophysics Data System (ADS)

We examine a gravitational lens model inspired by modified gravity theories and exotic matter and energy. We study an asymptotically flat, static, and spherically symmetric spacetime that is modified in such a way that the spacetime metric depends on the inverse distance to the power of positive n in the weak-field approximation. It is shown analytically and numerically that there is a lower limit on the source angular displacement from the lens object to get demagnification. Demagnifying gravitational lenses could appear, provided the source position ? and the power n satisfy ?>2/(n+1) in the units of the Einstein ring radius under a large-n approximation. Unusually, the total amplification of the lensed images, though they are caused by the gravitational pull, could be less than unity. Therefore, time-symmetric demagnification parts in numerical light curves by gravitational microlensing [F. Abe, Astrophys. J. 725, 787 (2010)] may be evidence of an Ellis wormhole (being an example of traversable wormholes), but they do not always prove it. Such a gravitational demagnification of the light might be used for hunting a clue of exotic matter and energy that are described by an equation of state more general than the Ellis wormhole case. Numerical calculations for the n=3 and 10 cases show maximally ˜10 and ˜60 percent depletion of the light, when the source position is ?˜1.1 and ?˜0.7, respectively.

Kitamura, Takao; Nakajima, Koki; Asada, Hideki

2013-01-01

117

QUANTIFYING THE BIASES OF SPECTROSCOPICALLY SELECTED GRAVITATIONAL LENSES

Spectroscopic selection has been the most productive technique for the selection of galaxy-scale strong gravitational lens systems with known redshifts. Statistically significant samples of strong lenses provide a powerful method for measuring the mass-density parameters of the lensing population, but results can only be generalized to the parent population if the lensing selection biases are sufficiently understood. We perform controlled Monte Carlo simulations of spectroscopic lens surveys in order to quantify the bias of lenses relative to parent galaxies in velocity dispersion, mass axis ratio, and mass-density profile. For parameters typical of the SLACS and BELLS surveys, we find (1) no significant mass axis ratio detection bias of lenses relative to parent galaxies; (2) a very small detection bias toward shallow mass-density profiles, which is likely negligible compared to other sources of uncertainty in this parameter; (3) a detection bias toward smaller Einstein radius for systems drawn from parent populations with group- and cluster-scale lensing masses; and (4) a lens-modeling bias toward larger velocity dispersions for systems drawn from parent samples with sub-arcsecond mean Einstein radii. This last finding indicates that the incorporation of velocity-dispersion upper limits of non-lenses is an important ingredient for unbiased analyses of spectroscopically selected lens samples. In general, we find that the completeness of spectroscopic lens surveys in the plane of Einstein radius and mass-density profile power-law index is quite uniform, up to a sharp drop in the region of large Einstein radius and steep mass-density profile, and hence that such surveys are ideally suited to the study of massive field galaxies.

Arneson, Ryan A.; Brownstein, Joel R.; Bolton, Adam S., E-mail: arnesonr@uci.edu, E-mail: joelbrownstein@astro.utah.edu, E-mail: bolton@astro.utah.edu [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States)

2012-07-01

118

Gravitational lensing in plasma: Relativistic images at homogeneous plasma

NASA Astrophysics Data System (ADS)

We investigate the influence of plasma presence on relativistic images formed by Schwarzschild black hole lensing. When a gravitating body is surrounded by a plasma, the lensing angle depends on a frequency of the electromagnetic wave due to refraction properties, and the dispersion properties of the light propagation in gravitational field in plasma. The last effect leads to a difference, even in uniform plasma, of the gravitational deflection angle in plasma from the vacuum case. This angle depends on the photon frequency, which resembles the properties of the refractive prism spectrometer. Here we consider the case of a strong deflection angle for the light, traveling near the Schwarzschild black hole, surrounded by a uniform plasma. Asymptotic formulas are obtained for the case of a very large deflection angle, exceeding 2?. We apply these formulas for calculation of position and magnification of relativistic images in a homogeneous plasma, which are formed by the photons performing one or several revolutions around the central object. We conclude that the presence of the uniform plasma increases the angular size of relativistic rings or the angular separation of point images from the gravitating center. The presence of the uniform plasma increases also a magnification of relativistic images. The angular separation and the magnification become significantly larger than in the vacuum case, when the photon frequency goes to a plasma frequency.

Tsupko, Oleg Yu.; Bisnovatyi-Kogan, Gennady S.

2013-06-01

119

Testing the Dark Energy with Gravitational Lensing Statistics

NASA Astrophysics Data System (ADS)

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 ?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 ?? = 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 ?? = 0.81 ± 0.05 when limiting to gravitational lenses with image separation ?? > 2'' and no-evolution. In both cases, results accounting for galaxy evolution are consistent within 1?. The present test supports the accelerated expansion, by excluding the null hypothesis (i.e., ?? = 0) at more than 4?, 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; Covone, Giovanni; Zhu, Zong-Hong

2012-08-01

120

Scatter and bias in weak lensing selected clusters

NASA Astrophysics Data System (ADS)

We examine scatter and bias in weak lensing selected clusters, employing both an analytic model of dark matter haloes and numerical mock data of weak lensing cluster surveys. We pay special attention to effects of the diversity of dark matter distributions within clusters. We find that peak heights of the lensing convergence map correlate rather poorly with the virial mass of haloes. The correlation is tighter for the spherical overdensity mass with a higher mean interior density (e.g. M1000). We examine the dependence of the halo shape on the peak heights, and find that the root mean square scatter caused by the halo diversity scales linearly with the peak heights with the proportionality factor of 0.1-0.2. The noise originated from the halo shape is found to be comparable to the source galaxy shape noise and the cosmic shear noise. We find the significant halo orientation bias, i.e. weak lensing selected clusters on average have their major axes aligned with the line-of-sight direction, and that the orientation bias is stronger for higher signal-to-noise ratio (S/N) peaks. We compute the orientation bias using an analytic triaxial halo model and obtain results quite consistent with the ray-tracing results. We develop a prescription to analytically compute the number count of weak lensing peaks taking into account all the main sources of scatters in the peak heights. We find that the improved analytic predictions agree well with the simulation results for high-S/N peaks of ??5. We also compare the expected number count with our weak lensing analysis results for 4 deg2 of Subaru/Suprime-Cam observations and find a good agreement.

Hamana, Takashi; Oguri, Masamune; Shirasaki, Masato; Sato, Masanori

2012-09-01

121

Gravitationally Lensed X-Ray Sources at the Galactic Center

NASA Astrophysics Data System (ADS)

More than two thousand x-ray sources located within 20 pc of the Galactic Center (GC) have been identified by Muno et al. (2003). If an x-ray source is located behind the Galactic Center and offset by a small angle from the GC projected on the sky, then that x-ray source could be gravitationally lensed. The consequences of finding gravitationally lensed sources at the Galactic Center include the ability to independently measure the mass of the GC as well as provide a new probe of the density distribution of the GC (e.g. Wardle & Yusef-Zadeh 1992). Inspecting x-ray images of the GC we were immediately drawn to a set of four x-ray objects. The identified objects are cataloged as CXOJ 174541.0-290014, 174540.1-290005, 174540.0-290031, and 174538.1-290022. These are the brightest and most obvious variable x-ray objects whose positions suggest patterns of images that may either be an inclined quad or two sets of dual gravitational lens patterns. Based on the image patterns, and image brightnesses and relative variations, we modeled possible lens systems using two algorithms. Both of the algorithms describing gravitational lenses are based on the Fermat potential and its time derivatives. For a lens radius of R = 0.01 pc, the total enclosed mass is 2.6 x 107 M? and for R = 0.001 pc, the total enclosed mass is 2.6 x 105 M?. These masses are consistent with other measurements of the mass of the GC, such as 4.5 x 106 M? (Ghez et al. 2008). We will present these results and our plans to further study the nature of these x-ray objects.

Castelaz, Michael W.; Rottler, L.

2012-01-01

122

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

123

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

124

Probing Primordial Non-Gaussianity with Weak-lensing Minkowski Functionals

NASA Astrophysics Data System (ADS)

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 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 deg2 field of view for f 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 ?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 deg2, the primordial non-Gaussianity can be constrained with a level of f NL ~ 80 and w ~ 0.036 by weak-lensing MFs. If simply scaled by the effective survey area, a 20,000 deg2 lensing survey using the Large Synoptic Survey Telescope will yield constraints of f NL ~ 25 and w ~ 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; Hamana, Takashi; Nishimichi, Takahiro

2012-11-01

125

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

126

SPITZER IMAGING OF HERSCHEL-ATLAS GRAVITATIONALLY LENSED SUBMILLIMETER SOURCES

We present physical properties of two submillimeter selected gravitationally lensed sources, identified in the Herschel Astrophysical Terahertz Large Area Survey. These submillimeter galaxies (SMGs) have flux densities >100 mJy at 500 {mu}m, but are not visible in existing optical imaging. We fit light profiles to each component of the lensing systems in Spitzer IRAC 3.6 and 4.5 {mu}m data and successfully disentangle the foreground lens from the background source in each case, providing important constraints on the spectral energy distributions (SEDs) of the background SMG at rest-frame optical-near-infrared wavelengths. The SED fits show that these two SMGs have high dust obscuration with A{sub V} {approx} 4-5 and star formation rates of {approx}100 M{sub sun} yr{sup -1}. They have low gas fractions and low dynamical masses compared with 850 {mu}m selected galaxies.

Hopwood, R.; Negrello, M. [Department of Physics and Astronomy, Open University, Milton Keynes, MK7 6AA (United Kingdom); Wardlow, J.; Cooray, A.; Khostovan, A. A.; Kim, S.; Barton, E. [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Da Cunha, E.; Cooke, J. [Department of Physics, University of Crete, Heraklion (Greece); Burgarella, D. [Laboratoire d'Astrophysique de Marseille, OAMP, CNRS, Aix-Marseille Universite (France); Aretxaga, I. [Instituto Nacional de Astrofisica, Optica y Electronica, Aptdo. Postal 51 y 216, 72000 Puebla (Mexico); Auld, R. [School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA (United Kingdom); Baes, M. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Bertoldi, F. [Argenlander Institute for Astronomy, University of Bonn, Auf dem Hugel 71, 53121 Bonn (Germany); Bonfield, D. G. [Centre for Astrophysics Research, Science and Technology Research Centre, University of Hertfordshire, Herts AL10 9AB (United Kingdom); Blundell, R. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Buttiglione, S. [INAF, Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, I-35122 Padova (Italy); Cava, A. [Instituto de Astrofisica de Canarias, C/Va Lactea s/n, E-38200 La Laguna (Spain); Clements, D. L. [Astrophysics Group, Physics Department, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom); Dannerbauer, H. [Laboratoire AIM Paris Saclay, CEA-CNRS-Universite, Irfu/Service d'Astrophysique, CEA Saclay, Orme de Merisiers, 91191 Gif-sur-Yvette Cedex (France)

2011-02-10

127

The impact of AGN feedback and baryonic cooling on galaxy clusters as gravitational lenses

NASA Astrophysics Data System (ADS)

We investigate the impact of active galactic nucleus (AGN) feedback on the gravitational lensing properties of a sample of galaxy clusters with masses in the range 1014-1015 Msolar, using state-of-the-art simulations. Adopting a ray-tracing algorithm, we compute the cross-section of giant arcs from clusters simulated with dark matter (DM) only physics, DM plus gas with cooling and star formation (CSF) and DM plus gas with cooling, star formation and AGN feedback (CSFBH). Once AGN feedback is included, baryonic physics boosts the strong-lensing cross-section by much less than previously estimated using clusters simulated with only CSF. For a cluster with a virial mass of 7.4 × 1014 Msolar, inclusion of baryonic physics without feedback can boost the cross-section by as much as a factor of 3, in agreement with previous studies, whereas once AGN feedback is included this maximal figure falls to a factor of 2 at most. Typically, clusters simulated with DM and CSFBH physics have similar cross-sections for the production of giant arcs. We also investigate how baryonic physics affects the weak-lensing properties of the simulated clusters by fitting NFW profiles to synthetic weak-lensing data sets using a Markov Chain Monte Carlo approach, and by performing non-parametric mass reconstructions. Without the inclusion of AGN feedback, measured concentration parameters can be much larger than those obtained with AGN feedback, which are similar to the DM-only case.

Mead, James M. G.; King, Lindsay J.; Sijacki, Debora; Leonard, Adrienne; Puchwein, Ewald; McCarthy, Ian G.

2010-07-01

128

Effects of supermassive binary black holes on gravitational lenses

NASA Astrophysics Data System (ADS)

Recent observations indicate that many, if not all, galaxies host massive central black holes (BHs). In this paper, we explore the influence of supermassive binary black holes (SMBBHs) on their actions as gravitational lenses. When lenses are modelled as singular isothermal ellipsoids, binary BHs change the critical curves and caustics differently as a function of distance. Each BH can in principle create at least one additional image, which, if observed, provides evidence of BHs. By studying how SMBBHs affect the cumulative distribution of magnification for images created by BHs, we find that the cross-section for at least one such additional image to have a magnification larger than 10-5 is comparable to the cross-section for producing multiple images in singular isothermal lenses. Such additional images may be detectable with high-resolution and large dynamic range maps of multiply imaged systems from future facilities, such as the Square Kilometre Array. The probability of detecting at least one image (two images) with magnification above 10-3 is ˜0.2fBH (˜0.05fBH) in a multiply imaged lens system, where fBH is the fraction of galaxies housing binary BHs. We also study the effects of SMBBHs on the core images when galaxies have shallower central density profiles (modelled as non-singular isothermal ellipsoids). We find that the cross-section of the usually faint core images is further suppressed by SMBBHs. Thus, their presence should also be taken into account when one constrains the core radius from the lack of central images in gravitational lenses.

Li, Nan; Mao, Shude; Gao, Liang; Loeb, Abraham; di Stefano, R.

2012-01-01

129

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

130

Precision photometric redshift calibration for galaxy-galaxy weak lensing

NASA Astrophysics Data System (ADS)

Accurate photometric redshifts are among the key requirements for precision weak lensing measurements. Both the large size of the Sloan Digital Sky Survey (SDSS) and the existence of large spectroscopic redshift samples that are flux-limited beyond its depth have made it the optimal data source for developing methods to properly calibrate photometric redshifts for lensing. Here, we focus on galaxy-galaxy lensing in a survey with spectroscopic lens redshifts, as in the SDSS. We develop statistics that quantify the effect of source redshift errors on the lensing calibration and on the weighting scheme, and show how they can be used in the presence of redshift failure and sampling variance. We then demonstrate their use with 2838 source galaxies with spectroscopy from DEEP2 and zCOSMOS, evaluating several public photometric redshift algorithms, in two cases including a full p(z) for each object, and find lensing calibration biases as low as <1 per cent (due to fortuitous cancellation of two types of bias) or as high as 20 per cent for methods in active use (despite the small mean photoz bias of these algorithms). Our work demonstrates that lensing-specific statistics must be used to reliably calibrate the lensing signal, due to asymmetric effects of (frequently non-Gaussian) photoz errors. We also demonstrate that large-scale structure (LSS) can strongly impact the photoz calibration and its error estimation, due to a correlation between the LSS and the photoz errors, and argue that at least two independent degree-scale spectroscopic samples are needed to suppress its effects. Given the size of our spectroscopic sample, we can reduce the galaxy-galaxy lensing calibration error well below current SDSS statistical errors. Based in part on observations undertaken at the European Southern Observatory (ESO) Very Large Telescope (VLT) under Large Programme 175.A-0839. E-mail: rmandelb@ias.edu (RM); seljak@itp.uzh.ch (US) ‡ Hubble Fellow.

Mandelbaum, R.; Seljak, U.; Hirata, C. M.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Carollo, M.; Contini, T.; Cunha, C. E.; Garilli, B.; Iovino, A.; Kampczyk, P.; Kneib, J.-P.; Knobel, C.; Koo, D. C.; Lamareille, F.; Le Fèvre, O.; Le Borgne, J.-F.; Lilly, S. J.; Maier, C.; Mainieri, V.; Mignoli, M.; Newman, J. A.; Oesch, P. A.; Perez-Montero, E.; Ricciardelli, E.; Scodeggio, M.; Silverman, J.; Tasca, L.

2008-05-01

131

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

132

Cold Dark Matter and Strong Gravitational Lensing: Concord or Conflict?

NASA Astrophysics Data System (ADS)

Using the number and sizes of observed gravitational lenses, I derive upper limits on the dark matter content of elliptical galaxies. On average, dark matter can account for no more than 33% of the total mass within one effective radius (Re) of elliptical galaxies or 40% of the mass within 2Re (95% confidence upper limits). I show that galaxies built from cold dark matter (CDM) mass distributions are too concentrated to comfortably satisfy these limits; a high-density (?M=1) CDM cosmology is ruled out at better than 95% confidence, while a low-density, flat cosmology is only marginally consistent with the lens data. Thus, lensing adds to the evidence from spiral galaxy dynamics that CDM mass distributions are too concentrated on kiloparsec scales to agree with real galaxies and extends the argument to elliptical galaxies. Lensing also provides a unique probe of the very inner regions of galaxies, because images are predicted to form near the centers of lens galaxies but are not observed. The lack of central images in deep maps of radio lenses places strong lower limits on the central densities of galaxies. The central densities of CDM galaxies are too low on ~10 pc scales. Supermassive black holes can help suppress central images, but they must lie well off the observed black hole-bulge mass correlation in order to satisfy current limits on central images. Self-interacting dark matter, or any other modification to regular cold dark matter, must simultaneously reduce the densities on kiloparsec scales and increase the densities on parsec scales in order to satisfy the unique constraints from lensing.

Keeton, Charles R.

2001-11-01

133

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

134

Application of a New, Relativistic Gravitational Lensing Technique to RXJ1347-1145

Gravitational lensing is the bending and distortion of light rays by the gravitational pull of massive objects in the universe. Lensing studies are significant to the current revolution in modern astrophysics through which the ultimate questions of the universe – how did the universe begin and what conditions permit life to develop – are being answered. Although the distortion of

Thomas P. Kling

2004-01-01

135

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

136

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

137

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

138

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

139

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

140

Wide-field weak lensing by RXJ1347-1145

NASA Astrophysics Data System (ADS)

We present an analysis of weak lensing observations for RXJ1347--1145 over a 43 ' × 43 ' field taken in B and R filters on the Blanco 4m telescope at CTIO. RXJ1347--1145 is a massive cluster at redshift z=0.45. Using a population of galaxies with 20

Kling, Thomas P.; dell'Antonio, Ian; Wittman, David; Tyson, J. Anthony

2004-05-01

141

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

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

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

2010-06-15

142

NASA Astrophysics Data System (ADS)

The first half of this paper explores the origin of systematic biases in the measurement of weak gravitational lensing. Compared to previous work, we expand the investigation of point spread function instability and fold in for the first time the effects of non-idealities in electronic imaging detectors and imperfect galaxy shape measurement algorithms. Together, these now explain the additive {A}(?) and multiplicative {M}(?) systematics typically reported in current lensing measurements. We find that overall performance is driven by a product of a telescope/camera's absolute performance, and our knowledge about its performance. The second half of this paper propagates any residual shear measurement biases through to their effect on cosmological parameter constraints. Fully exploiting the statistical power of Stage IV weak lensing surveys will require additive biases overline{{A}}? 1.8× 10^{-12} and multiplicative biases overline{{M}}? 4.0× 10^{-3}. These can be allocated between individual budgets in hardware, calibration data and software, using results from the first half of the paper. If instrumentation is stable and well calibrated, we find extant shear measurement software from Gravitational Lensing Accuracy Testing 2010 (GREAT10) already meet requirements on galaxies detected at signal-to-noise ratio = 40. Averaging over a population of galaxies with a realistic distribution of sizes, it also meets requirements for a 2D cosmic shear analysis from space. If used on fainter galaxies or for 3D cosmic shear tomography, existing algorithms would need calibration on simulations to avoid introducing bias at a level similar to the statistical error. Requirements on hardware and calibration data are discussed in more detail in a companion paper. Our analysis is intentionally general, but is specifically being used to drive the hardware and ground segment performance budget for the design of the European Space Agency's recently selected Euclid mission.

Massey, Richard; Hoekstra, Henk; Kitching, Thomas; Rhodes, Jason; Cropper, Mark; Amiaux, Jérôme; Harvey, David; Mellier, Yannick; Meneghetti, Massimo; Miller, Lance; Paulin-Henriksson, Stéphane; Pires, Sandrine; Scaramella, Roberto; Schrabback, Tim

2013-02-01

143

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 /Kapteyn Astron. Inst., Groningen /UC, Santa Barbara /KIPAC, Menlo Park /Carnegie Inst. Observ.

2006-04-03

144

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 Park

2006-01-25

145

Seeing the Invisible Universe with Gravitational Lensing and SNAP

Recent high-precision cosmological measurements provide solid evidence that normal matter comprises only 4% of the content of the Universe. The dominant substances are completely invisible and have never been detected in a laboratory: 23% in some 'dark matter' particles, and 73% in a form of 'dark energy' that is currently accelerating the expansion of the Universe. The dark matter and dark energy do, however, distort our view of the Universe behind them through gravitational lensing, just as the 'obscure glass' on the doors of a shower stall is designed to be transparent but produces a distorted view of its occupant. I will describe how present and future experiments such as the SNAP spacecraft can measure this very subtle distorting effect and use it to infer the properties of the dark matter and dark energy that dominate the Universe.

146

Gravitational Lensing by Damped Ly-Alpha Absorbers

NASA Astrophysics Data System (ADS)

Damped Ly-Alpha {DLAs} are thought to arise in the disk of the progenitors of present-day spiral galaxies. Recent surveys reveal that they contain a large fraction of the HI at high redshift, in quantities similar to the one needed to form the entire star population in the local Universe; thus the redshift evolution of the HI content of the Universe may provide clues to the evolution of the overall star formation rate. However, we recently found indications that existing surveys for z< 1 DLAs may be affected by the magnification bias due to gravitational lensing {Smette, Claeskens & Surdej 1997}. On the other hand, HST images of QSOs with 0.4 < z < 1 DLAs were studied by Le Brun et al. {1996}: several of them lie at impact parameter similar to the Einstein radius of the absorber, as derived from its luminosity. We thus expect that some of these QSOs be multiply imaged by their absorbers, but with a secondary image possibly severely absorbed by dust located in the galaxy. We suggest a search for possible secondary images due to gravitational lensing by the galaxy responsible of the absorption; we therefore propose to obtain IR images with NICMOS of 13 quasars in the spectrum of which DLAs, 21 cm or strong MgII absorption lines have been detected. As multiple images offer a direct mean of measuring the mass of the lens, HST would thus directly determine the mass associated with DLA absorbers and test the dark matter hypothesis for spiral galaxies in a way which do not rely on their dynamical properties.

Smette, Alain

1997-12-01

147

Intrinsic ellipticity correlations of galaxies: models, likelihoods and interplay with weak lensing

NASA Astrophysics Data System (ADS)

Subject of this paper is the statistical properties of ellipticity alignments between galaxies evoked by their coupled angular momenta. Starting from physical angular momentum models, we bridge the gap towards ellipticity correlations, ellipticity spectra and derived quantities such as aperture moments, comparing the intrinsic signals with those generated by gravitational lensing, with the projected galaxy sample of Euclid in mind. We investigate the dependence of intrinsic ellipticity correlations on cosmological parameters and show that intrinsic ellipticity correlations give rise to non-Gaussian likelihoods as a result of non-linear functional dependences. Comparing intrinsic ellipticity spectra to weak lensing spectra we quantify the magnitude of their contaminating effect on the estimation of cosmological parameters and find that biases on dark energy parameters are very small in an angular momentum-based model in contrast to the linear alignment model commonly used. Finally, we quantify whether intrinsic ellipticities can be measured in the presence of the much stronger weak lensing induced ellipticity correlations, if prior knowledge on a cosmological model is assumed.

Capranico, Federica; Merkel, Philipp M.; Schäfer, Björn Malte

2013-10-01

148

Three quasi-stellar objects acting as strong gravitational lenses

NASA Astrophysics Data System (ADS)

We report the discovery of three new cases of quasi-stellar objects (QSOs) acting as strong gravitational lenses on background emission line galaxies: SDSS J0827+5224 (zQSO = 0.293, zs = 0.412), SDSS J0919+2720 (zQSO = 0.209, zs = 0.558), SDSS J1005+4016 (zQSO = 0.230, zs = 0.441). The selection was carried out using a sample of 22,298 SDSS spectra displaying at least four emission lines at a redshift beyond that of the foreground QSO. The lensing nature is confirmed from Keck imaging and spectroscopy, as well as from HST/WFC3 imaging in the F475W and F814W filters. Two of the QSOs have face-on spiral host galaxies and the third is a QSO+galaxy pair. The velocity dispersion of the host galaxies, inferred from simple lens modeling, is between ? = 210 and 285 km s-1, making these host galaxies comparable in mass with the SLACS sample of early-type strong lenses. Based on data 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. Also based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #GO12233.

Courbin, F.; Faure, C.; Djorgovski, S. G.; Rérat, F.; Tewes, M.; Meylan, G.; Stern, D.; Mahabal, A.; Boroson, T.; Dheeraj, R.; Sluse, D.

2012-04-01

149

Gravitational lensing by a collection of objects with radial densities

NASA Astrophysics Data System (ADS)

In a recent paper by Bayer et al. (Gen Rel Grav 38:1379-1385, 2006), the authors considered a certain class of gravitational lenses consisting of n non-overlapping objects with radial densities. They concluded that there can be at most 6( n - 1) + 1 lensed images of a single light source. The only assumption made on the projected mass density of each object is that it is radial and does not diverge faster than 1/ r, where r is the distance to the center of the object. We show that this is too general a class of densities to consider while imposing a bound of 6( n - 1) + 1. We also provide an example to emphasize [together with the results in Bayer et al. (Gen Rel Grav 38:1379-1385, 2006)] that the general problem of finding the correct hypothesis to obtain sharp bounds for the maximal number of images inside the region occupied by masses with radial densities is wide open.

Khavinson, Dmitry; Lundberg, Erik

2011-09-01

150

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

151

EFFECTIVE MODELS FOR STATISTICAL STUDIES OF GALAXY-SCALE GRAVITATIONAL LENSING

We have worked out simple analytical formulae that accurately approximate the relationship between the position of the source with respect to the lens center and the amplification of the images, hence the lens cross section, for realistic lens profiles. We find that, for essentially the full range of parameters either observationally determined or yielded by numerical simulations, the combination of dark matter and star distribution can be very well described, for lens radii relevant to strong lensing, by a simple power law whose slope is very weakly dependent on the parameters characterizing the global matter surface density profile and close to isothermal in agreement with direct estimates for individual lens galaxies. Our simple treatment allows an easy insight into the role of the different ingredients that determine the lens cross section and the distribution of gravitational amplifications. They also ease the reconstruction of the lens mass distribution from the observed images and, vice versa, allow a fast application of ray-tracing techniques to model the effect of lensing on a variety of source structures. The maximum amplification depends primarily on the source size. Amplifications larger than Almost-Equal-To 20 are indicative of compact source sizes at high-z, in agreement with expectations if galaxies formed most of their stars during the dissipative collapse of cold gas. Our formalism has allowed us to reproduce the counts of strongly lensed galaxies found in the H-ATLAS Science Demonstration Phase field. While our analysis is focused on spherical lenses, we also discuss the effect of ellipticity and the case of late-type lenses (showing why they are much less common, even though late-type galaxies are more numerous). Furthermore, we discuss the effect of a cluster halo surrounding the early-type lens and of a supermassive black hole at its center.

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

2012-08-10

152

Gravitational Lensing by the Supermassive Black Hole in the Center of M31

NASA Astrophysics Data System (ADS)

We examine the possibility of observing gravitational lensing in the weak deflection regime by the supermassive black hole in the center of the galaxy M31. This black hole is significantly more massive than the black hole in the center of our Galaxy, qualifying itself as a more effective lens. However, it is also more distant, and the candidate stellar sources appear consequently fainter. We separately consider as potential sources stars belonging to the bulge, to the disk, and to the triple nucleus formed by P1 + P2 and by the recently discovered inner cluster P3. We calculate the number of simultaneously lensed stars at a given time as a function of the threshold magnitude required for the secondary image. For observations in the K band we find 1.4 expected stars having secondary images brighter than K=24 and 182 brighter than K=30. For observations in the V band we expect 1.3 secondary images brighter than V=27 and 271 brighter than V=33. The bulge stars have the highest chance of being lensed by the supermassive black hole, whereas the disk and the composite nucleus stars contribute 10% each. The typical angular separation of the secondary images from the black hole range from 1 mas to 0.1". For each population we also show the distribution of the lensed sources as a function of their distance and absolute magnitude, the expected angular positions and velocities of the generated secondary images, and the rate and the typical duration of the lensing events.

Bozza, V.; Calchi Novati, S.; Mancini, L.

2008-03-01

153

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

154

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

155

Constraining cosmological parameters with observational data including weak lensing effects

NASA Astrophysics Data System (ADS)

In this Letter, we study the cosmological implications of the 100 square degree Weak Lensing survey (the CFHTLS-Wide, RCS, VIRMOS-DESCART and GaBoDS surveys). We combine these weak lensing data with the cosmic microwave background (CMB) measurements from the WMAP5, BOOMERanG, CBI, VSA, ACBAR, the SDSS LRG matter power spectrum and the Type Ia Supernoave (SNIa) data with the “Union” compilation (307 sample), using the Markov Chain Monte Carlo method to determine the cosmological parameters, such as the equation-of-state (EoS) of dark energy w, the density fluctuation amplitude ?, the total neutrino mass ?m and the parameters associated with the power spectrum of the primordial fluctuations. Our results show that the ?CDM model remains a good fit to all of these data. In a flat universe, we obtain a tight limit on the constant EoS of dark energy, w=-0.97±0.041 (1?). For the dynamical dark energy model with time evolving EoS parameterized as w(a)=w+w(1-a), we find that the best-fit values are w=-1.064 and w=0.375, implying the mildly preference of Quintom model whose EoS gets across the cosmological constant boundary during evolution. Regarding the total neutrino mass limit, we obtain the upper limit, ?m<0.471 eV (95% C.L.) within the framework of the flat ?CDM model. Due to the obvious degeneracies between the neutrino mass and the EoS of dark energy model, this upper limit will be relaxed by a factor of 2 in the framework of dynamical dark energy models. Assuming that the primordial fluctuations are adiabatic with a power law spectrum, within the ?CDM model, we find that the upper limit on the ratio of the tensor to scalar is r<0.35 (95% C.L.) and the inflationary models with the slope n?1 are excluded at more than 2? confidence level. In this Letter we pay particular attention to the contribution from the weak lensing data and find that the current weak lensing data do improve the constraints on matter density ?, ?, ?m, and the EoS of dark energy.

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

2009-05-01

156

Structure and History of Dark Matter Halos Probed with Gravitational Lensing

NASA Astrophysics Data System (ADS)

We test with gravitational lensing (GL) data the dark matter (DM) halos embedding the luminous baryonic component of galaxy clusters; our benchmark is provided by their two-stage cosmogonical development that we compute with its variance, and by the related "?-profiles" we derive. The latter solve the Jeans equation for the self-gravitating, anisotropic DM equilibria, and yield the radial runs of the density ?(r) and the velocity dispersion ?2 r (r) in terms of the DM "entropy" K ? ?2 r /?2/3 vprop r ? highlighted by recent N-body simulations; the former constrains the slope to the narrow range ? ? 1.25-1.3. These physically based ?-profiles meet the overall requirements from GL observations, being intrinsically flatter at the center and steeper in the outskirts relative to the empirical Navarro, Frenk, & White formula. Specifically, we project them along the line of sight and compare with a recent extensive data set from strong and weak lensing observations in and around the cluster A1689. We find an optimal fit at both small and large scales in terms of a halo constituted by an early body with ? ? 1.25 and by recent extensive outskirts, that make up an overall mass 1015 M sun with a concentration parameter c ? 10 consistent with the variance we compute in the ?CDM cosmogony. The resulting structure corresponds to a potential well shallow in the outskirts as that inferred from the X rays radiated from the hot electrons and baryons constituting the intracluster plasma.

Lapi, A.; Cavaliere, A.

2009-04-01

157

Evidence for a massive, dark gravitational lensing object in Q2345 + 007

The pattern of Ly-alpha forest absorption lines noted by the present analysis of narrow absorption line spectra of a double quasar is taken as evidence for a quasar that is gravitationally lensed. If the lensing object's z value is of the order of 1.49, then a low-luminosity lensing mass of about 10 to the 13th solar masses is implied. If the quasar is not lensed, the Ly-alpha clouds are larger by a factor of about 6.5. Observational tests capable of verifying the presence of a massive, dark, lensing object are suggested. 29 refs.

Duncan, R.C. (McDonald Observatory (USA) Texas, University, Austin (USA))

1991-07-01

158

WEAK LENSING MEASUREMENT OF GALAXY CLUSTERS IN THE CFHTLS-WIDE SURVEY

We present the first weak gravitational lensing analysis of the completed Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We study the 64 deg{sup 2} W1 field, the largest of the CFHTLS-Wide survey fields, and present the largest contiguous weak lensing convergence 'mass map' yet made. 2.66 million galaxy shapes are measured, using the Kaiser Squires and Broadhurst Method (KSB) pipeline verified against high-resolution Hubble Space Telescope imaging that covers part of the CFHTLS. Our i'-band measurements are also consistent with an analysis of independent r'-band imaging. The reconstructed lensing convergence map contains 301 peaks with signal-to-noise ratio {nu} > 3.5, consistent with predictions of a {Lambda}CDM model. Of these peaks, 126 lie within 3.'0 of a brightest central galaxy identified from multicolor optical imaging in an independent, red sequence survey. We also identify seven counterparts for massive clusters previously seen in X-ray emission within 6 deg{sup 2} XMM-LSS survey. With photometric redshift estimates for the source galaxies, we use a tomographic lensing method to fit the redshift and mass of each convergence peak. Matching these to the optical observations, we confirm 85 groups/clusters with {chi}{sup 2}{sub reduced} < 3.0, at a mean redshift (z{sub c} ) = 0.36 and velocity dispersion ({sigma}{sub c}) = 658.8 km s{sup -1}. Future surveys, such as DES, LSST, KDUST, and EUCLID, will be able to apply these techniques to map clusters in much larger volumes and thus tightly constrain cosmological models.

Shan Huanyuan; Tao Charling [Department of Physics and Tsinghua Center for Astrophysics, Tsinghua University, Beijing, 100084 (China); Kneib, Jean-Paul; Jauzac, Mathilde; Limousin, Marceau [Laboratoire d'Astrophysique de Marseille, CNRS-Universite de Provence, 38 rue Frederic Joliot-Curie, F-13388 Marseille Cedex 13 (France); Fan Zuhui [Department of Astronomy, Peking University, Beijing, 100871 (China); Massey, Richard [Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Rhodes, Jason [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Thanjavur, Karun [Canada France Hawaii Telescope, 65-1238 Mamalahoa Hwy, Kamuela, HI 96743 (United States); McCracken, Henry J., E-mail: shanhuany@gmail.com [Institude d'Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, F-75014 Paris (France)

2012-03-20

159

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

NASA Astrophysics Data System (ADS)

The intrinsic alignment (IA) of galaxies has been shown to be a significant barrier to precision cosmic shear measurements. Zhang [P. Zhang, Astrophys. J. 720, 1090 (2010)] proposed a self-calibration technique for the power spectrum to calculate the induced gravitational shear-galaxy intrinsic ellipticity correlation (GI) in weak lensing surveys with photo-z measurements which is expected to reduce the IA contamination by at least a factor of 10 for currently proposed surveys. We confirm this using an independent analysis and propose an expansion to the self-calibration technique for the bispectrum in order to calculate the dominant IA gravitational shear-gravitational shear-intrinsic ellipticity correlation (GGI) contamination. We first establish an estimator to extract the galaxy density-density-intrinsic ellipticity (ggI) correlation from the galaxy ellipticity-density-density measurement for a photo-z galaxy sample. We then develop a relation between the GGI and ggI bispectra, which allows for the estimation and removal of the GGI correlation from the cosmic shear signal. We explore the performance of these two methods, compare to other possible sources of error, and show that the GGI self-calibration technique can potentially reduce the IA contamination by up to a factor of 5-10 for all but a few bin choices, thus reducing the contamination to the percent level. The self-calibration is less accurate for adjacent bins, but still allows for a factor of three reduction in the IA contamination. The self-calibration thus promises to be an efficient technique to isolate both the 2-point and 3-point intrinsic alignment signals from weak lensing measurements. This work was supported in part by grants from NSF and NASA.

Troxel, Michael A.; Ishak, M.

2012-01-01

160

Self-calibration technique for three-point intrinsic alignment correlations in weak lensing surveys

NASA Astrophysics Data System (ADS)

The intrinsic alignment (IA) of galaxies has been shown to be a significant barrier to precision cosmic shear measurements. Recently, Zhang proposed a self-calibration technique for the power spectrum to calculate the induced gravitational shear-galaxy intrinsic ellipticity correlation (GI) in weak lensing surveys with photo-z measurements, which is expected to reduce the IA contamination by at least a factor of 10 for currently proposed surveys. We confirm this using an independent analysis and propose an expansion to the self-calibration technique for the bispectrum in order to calculate the dominant IA gravitational shear-gravitational shear-intrinsic ellipticity correlation (GGI) contamination. We first establish an estimator to extract the galaxy density-density-intrinsic ellipticity (ggI) correlation from the galaxy ellipticity-density-density measurement for a photo-z galaxy sample. We then develop a relation between the GGI and ggI bispectra, which allows for the estimation and removal of the GGI correlation from the cosmic shear signal. We explore the performance of these two methods, compare to other possible sources of error, and show that the GGI self-calibration technique can potentially reduce the IA contamination by up to a factor of 5-10 for all but a few bin choices, thus reducing the contamination to the per cent level. The self-calibration is less accurate for adjacent bins, but still allows for a factor of 3 reduction in the IA contamination. The self-calibration thus promises to be an efficient technique to isolate both the two-point and three-point intrinsic alignment signals from weak lensing measurements.

Troxel, M. A.; Ishak, M.

2012-01-01

161

Detecting dark matter substructure spectroscopically in strong gravitational lenses

NASA Astrophysics Data System (ADS)

The cold dark matter (CDM) model for galaxy formation predicts that a significant fraction of mass in the dark matter haloes that surround L~L* galaxies is bound in substructures of mass 104-107 Msolar. The number of observable baryonic substructures (such as dwarf galaxies and globular clusters) falls short of these predictions by at least an order of magnitude. We present a method for searching for substructure in the haloes of gravitational lenses that produce multiple images of quasi-stellar objects (QSOs), such as four-image Einstein Cross lenses. Current methods based on broad-band flux ratios cannot cleanly distinguish between substructure, differential extinction, scattering in the radio by ionized regions in the lens galaxy, microlensing by stars and, most importantly, ambiguities in the host lens model. These difficulties may be overcome by utilizing the prediction that, when substructure is present, the magnification will be a function of source size. QSO broad-line and narrow-line emission regions are ~1 pc and >100 pc in size, respectively. The radio emission region is typically intermediate to these and the continuum emission region is much smaller. When narrow-line region (NLR) features are used as a normalization, the relative intensity and equivalent width of broad-line region (BLR) features will respectively reflect substructure-lensing and microlensing effects. Spectroscopic observations of just a few image pairs would probably be able to extract the desired substructure signature cleanly and distinguish it from microlensing - depending on the actual level of projected mass in substructure. In the rest-optical, the H?/[OIII] region is ideal, since the narrow wavelength range also largely eliminates differential reddening problems. In the rest-ultraviolet, the region longward of and including Ly? may also work. Simulations of Q2237+0305 are done as an example, to determine the level of substructure that is detectable in this way. Possible systematic difficulties are also discussed. This is an ideal experiment to be carried out with near-infrared integral field unit spectrographs on 8-m class telescopes, and will provide a fundamentally new probe of the internal structure of dark matter haloes.

Moustakas, Leonidas A.; Metcalf, R. Benton

2003-03-01

162

NASA Astrophysics Data System (ADS)

We present a method of estimating the lensing potential from massive galaxy clusters for given observational X-ray data. The concepts developed and applied in this work can be easily combined with other techniques to infer the lensing potential, e.g. weak gravitational lensing or galaxy kinematics, to obtain an overall best-fit model for the lensing potential. After elaborating on the physical details and assumptions the method is based on, we explain how the numerical algorithm itself is implemented with a Richardson-Lucy algorithm as a central part. Our reconstruction method is tested on simulated galaxy clusters with a spherically symmetric NFW density profile filled with gas in hydrostatic equilibrium. We describe in detail how these simulated observational data sets are created and how they need to be fed into our algorithm. We tested the robustness of the algorithm against small parameter changes and estimate the quality of the reconstructed lensing potentials. As it turns out, we achieve a very high degree of accuracy in reconstructing the lensing potential. The statistical errors remain below 2.0%, whereas the systematical error does not exceed 1.0%.

Konrad, S.; Majer, C. L.; Meyer, S.; Sarli, E.; Bartelmann, M.

2013-05-01

163

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

164

NASA Astrophysics Data System (ADS)

Many astrophysicists consider the mystery of accelerated expansion of the universe by a field called dark energy as the greatest challenge to solve in cosmology. Gravitational weak lensing has been identfied as one of the best methods to provide constraints on dark energy model parameters. Weak lensing introduces image shear which can be measured statistically from a large sample of galaxies by determining the ellipticity parameters. Several papers have suggested that a goal in the ability to measure shape biases should be <0.1% - this goal will be reviewed in terms of the observatory "transfer function" with comments interspersed regarding allocation inconsistencies. Time-varying effects introduced by thermoelastic deformations and vibration add bias and noise to the galaxy shape measurements. This is compounded by the wide field-of-view required for the weak lensing science which leads to a spatially varying point spead function (PSF). To fully understand these effects, a detailed integrated model (IM) was constructed which includes a coupled scene/ structure/ optics/ disturbance model. This IM was applied to the Joint Dark Energy Mission (JDEM) Omega design concept. Results indicate that previous models of vibration disturbance effects have been too simplified and the allocation for vibration needs to be re-evaluated. Furthermore, because of the complicated processing required to accurately extract shape parameters, it is argued that an IM is needed for maximizing science return by iterating the telescope/ instrument design against mission cost constraints, and processing eÂ¤ectiveness of shape extraction algorithms, instrument calibration techniques and measurement desensitization of observatory effects.

Lieber, Michael; Kaplan, Michael; Sholl, Michael; Bernstein, Gary

2010-07-01

165

Weak-Lensing Surveys and the Intrinsic Correlation of Galaxy Ellipticities

NASA Astrophysics Data System (ADS)

We explore the possibility that an intrinsic correlation between galaxy ellipticities arising during the galaxy formation process may account for part of the shear signal recently reported by several groups engaged in weak gravitational lensing surveys. Using high-resolution N-body simulations, we measure the projected ellipticities of dark matter halos and their correlations as a function of pair separation. With this simplifying, but not necessarily realistic, assumption (halo shapes as a proxy for galaxy shapes), we find a positive detection of correlations up to scales of at least 20 h-1 Mpc (limited by the box size). The signal is not strongly affected by variations in the halo-finding technique, or by the resolution of the simulations (over the range tested). We translate our three-dimensional results into angular measurements of ellipticity correlation functions and shear variance, which can be directly compared to observational results. We also make simulated angular surveys by projecting our simulation boxes onto the plane of the sky and applying a radial selection function. Measurements from these catalogs are consistent with the analytic projection of the statistics. Interestingly, the shear variance we measure is a small, but not entirely negligible, fraction (from ~10%-20%, depending on the angular scale) of that seen by the observational groups, and the ellipticity correlation functions approximately mimic the functional form expected to be caused by weak lensing. The amplitude of these projected quantities depends strongly on the width in redshift of the galaxy distribution. If in the future photometric redshifts are used to pick out a screen of background galaxies with a small redshift width, then the intrinsic correlation may become comparable to the weak-lensing signal. Although we are dealing with simulated dark matter halos, we might expect there to be a similar sort of signal when real galaxies are used. This could be checked fruitfully using a nearby sample with known redshifts.

Croft, Rupert A. C.; Metzler, Christopher A.

2000-12-01

166

The Origin of Gravitational Lensing: A Postscript to Einstein's 1936 Science Paper

Gravitational lensing, now taken as an important astrophysical consequence of the general theory of relativity, was found even before this theory was formulated but was discarded as a speculative idea without any chance of empirical confirmation. Reconstruction of some of Einstein's research notes dating back to 1912 reveals that he explored the possibility of gravitational lensing 3 years before completing his general theory of relativity. On the basis of preliminary insights into this theory, Einstein had already derived the basic features of the lensing effect. When he finally published the very same results 24 years later, it was only in response to prodding by an amateur scientist. PMID:8985006

Renn; Sauer; Stachel

1997-01-10

167

Finslerian MOND versus the strong gravitational lensing of the early-type galaxies

NASA Astrophysics Data System (ADS)

The gravitational lensing of Bullet Clusters and early-type galaxies pose serious challenges on the validity of MOND. Recently, Finslerian MOND, a generalization of MOND in the framework of Finsler gravity, has been proposed to explain the mass discrepancy problem of Bullet Cluster 1E0657-558. In this paper, we check the validity of the Finslerian MOND in describing the strong gravitational lensing of early-type galaxies. The investigation on ten strong lenses of the CASTLES samples shows that there is no strong evidence for the existence of dark matter.

Chang, Zhe; Li, Ming-Hua; Li, Xin; Lin, Hai-Nan; Wang, Sai

2013-08-01

168

Cosmic superstring gravitational lensing phenomena: Predictions for networks of (p,q) strings

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

Shlaer, Benjamin [Laboratory for Elementary Particle Physics, Cornell University, Ithaca, New York 14853 (United States); Wyman, Mark [Laboratory for Elementary Particle Physics, Cornell University, Ithaca, New York 14853 (United States); Center for Radiophysics and Space Research, Cornell University, Ithaca, New York 14853 (United States)

2005-12-15

169

Magnification of light from many distant quasars by gravitational lenses.

Exceptionally bright quasars with redshifts up to z = 6.28 have recently been discovered. Quasars are thought to be powered by the accretion of gas onto supermassive black holes at the centres of galaxies. Their maximum (Eddington) luminosity depends on the mass of the black hole, and the brighter quasars are inferred to have black holes with masses of more than a few billion solar masses. The existence of such massive black holes poses a challenge to models for the formation of structures in the early Universe, as it requires their formation within one billion years of the Big Bang. Here we show that up to one-third of known quasars with z approximately equal to 6 will have had their observed flux magnified by a factor of ten or more, as a consequence of gravitational lensing by galaxies along the line of sight. The inferred abundance of quasar host galaxies, as well as the luminosity density provided by the quasars, has therefore been substantially overestimated. PMID:12087397

Wyithe, J Stuart B; Loeb, Abraham

2002-06-27

170

Gravitational Lensing of Stars Surrounding Supermassive Black Holes

NASA Astrophysics Data System (ADS)

Many indications suggest that both the Milky Way and M31 host a supermassive black holes in their central regions. General Relativity tells us that these black holes, acting as gravitational lenses, are able in principle to bend the light rays of the source stars moving in their neighborhood. As a consequence of this fact, a secondary image and two infinite series of relativistic images will be generated. In the case of our Galaxy, the central supermassive black hole corresponds to the radio source Sgr A* and, thanks to the observations in the near infrared band, it has been possible to determine the orbits of several stars moving in the neighborhood of the Galactic center. In the framework of Schwarzschild black hole, it is now possible to calculate the expected light curves for the secondary and for the main relativistic images for these stars. In this way, it is easy to predict the best times to observe the secondary images, which occur when the stars approach the minimum distance from the black hole. Concerning M31, we draw some perspectives for observations.

Bozza, V.; Mancini, L.

2008-09-01

171

Direct measurement of the magnification produced by galaxy clusters as gravitational lenses

Context. Weak lensing is one of the most readily available diagnostic tools to measure the total density profiles of distant clusters of galaxies. Unfortunately, it suffers from the well-known mass-sheet degeneracy, so that weak lensing analyses cannot lead to fully reliable determinations of the total mass of the clusters. One possible way to set the relevant scale of the density

A. Sonnenfeld; G. Bertin; M. Lombardi

2011-01-01

172

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

NASA Astrophysics Data System (ADS)

We investigate analytical gravitational lensing by charged, stationary, axially symmetric Kerr-Sen dilaton-axion black holes in the weak-deflection limit. Approximate solutions to the lightlike equations of motion are present up to and including third-order terms in M/b, a/b, and r?/b, where M is the black hole mass, a is the angular momentum, r?=Q2/M, Q being the charge and b is the impact parameter of the light ray. We compute the positions of the two weak field images, the corresponding signed and absolute magnifications up to post-Newtonian order. It is shown that there are static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are functions of the charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly with the increase of the charge. The pointlike caustics drift away from the optical axis and do not depend on the charge. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as the Gibbons-Maeda-Garfinkle-Horowitz-Strominger black hole.

Gyulchev, Galin N.; Yazadjiev, Stoytcho S.

2010-01-01

173

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

174

Weak Galaxy-Galaxy Lensing in HST DATA

NASA Astrophysics Data System (ADS)

We present an in depth study of galaxy - galaxy weak lensing as visable in archival data from HST. We expand on the work of Griffiths et al. (1996) using a larger data set including many redshifts for individual galaxies. We analyse the ellipticity distribution in our images as a function of varous parameters (magnitude, size, concentration and asymmetry) and find that a clear change in the distribution is seen as one goes deeper in the data. Using simulations, we show that this change can be attributed mainly to detection effects. We use a direct method to show that the lensing signal signal is clearly detectable and is sensitive to the choice of background - foreground pairs. However, this signal is stable to noise purturbations above about 10 thousand galaxy pairs. We investigate the dependance of the signal on both galaxy colour and type and projected distance from the lens galaxy. Building upon the direct method, we develope a maximum likelyhood method which allows us to take acount of multiple lens planes and also the effect of non-spherical mass distributions. This is applied to our large data set and constraints on the mass-to-light ration and radial extent of field galaxy halos are presented.

Ebbels, T.; Kneib, J. P.; Ellis, R.

175

Breaking degeneracies with the fundamental plane and weak lensing

NASA Astrophysics Data System (ADS)

Constraining dark matter profiles in the inner regions of halos is important to understanding both the properties of dark matter and of galaxies. The ability to separate the contributions of dark matter and stars on galactic scales has long been hindered by model degeneracies between effects like IMF uncertainties and baryonic contraction. Recent work has shown that measurements of stellar and dynamical masses, together with reasonable models for the halo contribution, can break some of these degeneracies. I will present work building on these developments, using the fundamental plane for early type galaxies in SDSS to constrain IMF variation and halo contraction as a function of stellar mass and galaxy size. I will also show how potential new weak lensing measurements for this sample, using both shear and magnification of background sources, can help constrain the mass on small scales, reducing the need for model assumptions when estimating the halo contribution.

George, Matthew

2013-07-01

176

SNAP Spectrograph For Super Nova, Weak Lensing And Calibration Science

NASA Astrophysics Data System (ADS)

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 provides for a large field of view ( 10 arc sec) and moderate spectral resolution ( lambda/delta lambda >100) from .4 to 1.7 microns allowing spectroscopy of both stellar and extended sources. It is based on the use of an image slicer Integral Field Unit. A demonstrator unit has been built and tested and meets performance, control of scattered light and calibration accuracy. Funding for the spectrograph which is being developed in Marseille, France has been provided by CNES, CNRS (IN2P3 and INSU).

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

2007-12-01

177

The effect of satellite galaxies on gravitational lensing flux ratios

NASA Astrophysics Data System (ADS)

Gravitational lenses with anomalous flux ratios are often cited as possible evidence for dark matter satellites predicted by simulations of hierarchical merging in cold dark matter cosmogonies. We show that the fraction of quads with anomalous flux ratios depends primarily on the total mass and spatial extent of the satellites, and the characteristic length-scale d1/2 of their distribution. If d1/2 ~ 100kpc, then for a moderately elliptical galaxy with a line-of-sight velocity dispersion of ~ 250kms-1, a mass of ~3 × 109Msolar in highly concentrated (Plummer model) satellites is needed for 20 per cent of quadruplets to show anomalous flux ratios, rising to ~1.25 × 1010Msolar for 50 per cent. Several times these masses are required if the satellites have more extended Hernquist profiles. Compared to a typical elliptical, the flux ratios of quads formed by typical edge-on disc galaxies with maximum discs are significantly less susceptible to changes through substructure - three times the mass in satellite galaxies is needed to affect 50 per cent of the systems. In many of the lens systems with anomalous flux ratios, there is evidence for visible satellites (e.g. B2045+265 or MG0414+0534). We show that if the anomaly is produced by substructure with properties similar to the simulations, then optically identified substructure should not be preponderant among lens systems with anomalies. There seem to be two possible resolutions of this difficulty. First, in some cases, visible substructure may be projected within or close to the Einstein radius and wrongly ascribed as the culprit, whereas dark matter substructure is causing the flux anomaly. Secondly, bright satellites, in which baryon cooling and condensation have taken place, may have higher central densities than dark satellites, rendering them more efficient at causing flux anomalies.

Shin, E. M.; Evans, N. W.

2008-04-01

178

Gravitational anomaly and Hawking radiation near a weakly isolated horizon

NASA Astrophysics Data System (ADS)

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

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

2008-06-01

179

On the Contribution of Large-Scale Structure to Strong Gravitational Lensing

We study the correlation between the locations of galaxy-galaxy strong-lensing candidates and tracers of large-scale structure from both weak lensing (WL) or X-ray emission. The Cosmological Evolution Survey (COSMOS) is a unique data set, combining deep, high resolution and contiguous imaging in which strong lenses have been discovered, plus unparalleled multiwavelength coverage. To help interpret the COSMOS data, we have

C. Faure; J.-P. Kneib; S. Hilbert; R. Massey; G. Covone; A. Finoguenov; A. Leauthaud; J. E. Taylor; S. Pires; N. Scoville; Anton M. Koekemoer

2009-01-01

180

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

181

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

182

Discovery of Four Gravitationally Lensed Quasars from the Sloan Digital Sky Survey

We present the discovery of four gravitationally lensed quasars selected from the spectroscopic quasar catalog of the Sloan Digital Sky Survey (SDSS). We describe imaging and spectroscopic follow-up observations that support the lensing interpretation of the following four quasars: SDSS J0832+0404 (image separation theta = 198, source redshift zs = 1.115, lens redshift zl = 0.659); SDSS J1216+3529 (theta =

Masamune Oguri; Naohisa Inada; Alejandro Clocchiatti; Issha Kayo; Min-Su Shin; Joseph F. Hennawi; Tomoki Morokuma; Donald P. Schneider; Donald G. York

2008-01-01

183

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

184

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

185

Gravitational force in weakly correlated particle spatial distributions

We study the statistics of the gravitational (Newtonian) force in a particular class of weakly correlated spatial distributions of pointlike and unitary mass particles generated by the so-called Gauss-Poisson point processes. In particular we extend to these distributions the analysis that Chandrasekhar introduced for purely Poisson processes. In this way we can find the explicit asymptotic behavior of the probability

Andrea Gabrielli; Adolfo Paolo Masucci; Francesco Sylos Labini

2004-01-01

186

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

187

We estimate the impact of weak lensing by strongly nonlinear cosmological structures on the cosmic microwave background. Accurate calculation of large l multipoles requires N-body simulations and ray-tracing schemes with both high spatial and temporal resolution. To this end, we have developed a new code that combines a gravitational Adaptive Particle-Particle, Particle-Mesh solver with a weak-lensing evaluation routine. The lensing deviations are evaluated while structure evolves during the simulation so that all evolution steps-rather than just a few outputs-are used in the lensing computations. The new code also includes a ray-tracing procedure that avoids periodicity effects in a universe that is modeled as a three-dimensional torus in the standard way. Results from our new simulations are compared with previous ones based on Particle-Mesh simulations. We also systematically investigate the impact of box volume, resolution, and ray-tracing directions on the variance of the computed power spectra. We find that a box size of 512 h {sup -1} Mpc is sufficient to provide a robust estimate of the weak-lensing angular power spectrum in the l-interval (2000-7000). For a reaslistic cosmological model, the power [l(l + 1)C{sub l}/2pi]{sup 1/2} takes on values of a few muK in this interval, which suggests that a future detection is feasible and may explain the excess power at high l in the Berkeley-Illinois-Maryland Association and Cosmic Background Imager observations.

Fullana, M. J. [Institut de Matematica Multidisciplinaria, Universitat Politecnica de Valencia, 46022 Valencia (Spain); Arnau, J. V. [Departamento de Matematica Aplicada, Universidad de Valencia, 46100 Burjassot, Valencia (Spain); Thacker, R. J. [Department of Astronomy and Physics, Saint Mary's University, Halifax, Nova Scotia, B3H 3C3 (Canada); Couchman, H. M. P. [Department of Physics and Astronomy, McMaster University, 1280 Main St. West, Hamilton, Ontario, L8S 4M1 (Canada); Saez, D., E-mail: diego.saez@uv.e [Departamento de AstronomIa y Astrofisica, Universidad de Valencia, 46100 Burjassot, Valencia (Spain)

2010-03-20

188

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

189

Republication of: Quantum theory of weak gravitational fields

NASA Astrophysics Data System (ADS)

This is an English translation of a paper by Matvei Bronstein, first published in German in 1936 in a long-extinct Soviet journal, in which he presented the first attempt at quantizing a weak (linearized) gravitational field, rather modern in its approach. The paper has been selected by the Editors of General Relativity and Gravitation for re-publication in the Golden Oldies series of the journal. This republication is accompanied by an editorial note written by Stanley Deser and Alexei Starobinsky, and Bronstein's brief biography written by Stanley Deser.

Bronstein, Matvei

2012-01-01

190

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

191

THE IMPACT OF CORRELATED PROJECTIONS ON WEAK LENSING CLUSTER COUNTS

Large-scale structure projections are an obstacle in converting the shear signal of clusters detected in weak-lensing maps into virial masses. However, this step is not necessary for constraining cosmology with the shear-peak abundance, if we are able to predict its amplitude. We generate a large ensemble of N-body simulations spanning four cosmological models, with total volume V{sub tot} approx 1(h {sup -1} Gpc){sup 3} per model. Variations to the matter density parameter and amplitude of fluctuations are considered. We measure the abundance of peaks in the mass density projected in approx100 h {sup -1} Mpc slabs to determine the impact of structures spatially correlated with the simulation clusters, identified by the three-dimensional (3D) friends-of-friends (FoF) algorithm. The halo model shows that the choice of the smoothing filter for the density field is important in reducing the contribution of correlated projections to individual halo masses. Such contributions are less than 2% in the case of the optimal, compensated filter used throughout this analysis. We measure the change in the mass of peaks when projected in slabs of various thicknesses. Peaks in slabs of 26 h {sup -1} Mpc and 102 h {sup -1} Mpc suffer an average mass change of less than 2% compared to their mass in slabs of 51 h {sup -1} Mpc. We then explore the cosmology dependence of the projected-peak mass function, and find that, for a wide range of slab thicknesses (< 500 h {sup -1} Mpc), it scales with cosmology in exactly the same way as the 3D FoF mass function and the Sheth-Tormen (ST) formula. This extends the earlier result of Marian et al. Finally, we show that for all cosmological models considered, the low and intermediate mass bins of the peak abundance can be described using a modified ST functional form to within 10%-20% accuracy.

Marian, Laura [Argelander-Institut fuer Astronomie, Universitaet Bonn, Bonn, D-53121 (Germany); Smith, Robert E. [Institute for Theoretical Physics, University of Zuerich, Zuerich, CH 8037 (Switzerland); Bernstein, Gary M., E-mail: lmarian@astro.uni-bonn.d [Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104 (United States)

2010-01-20

192

CALCLENS: Curved-sky grAvitational Lensing for Cosmological Light conE simulatioNS

NASA Astrophysics Data System (ADS)

CALCLENS, written in C and employing widely available software libraries, efficiently computes weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. The algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift-dependent shear signals including corrections to the Born approximation by using multiple-plane ray tracing, and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multgrid methods. As a result, large areas of sky (~10,000 square degrees) can be ray traced efficiently at high-resolution using only a few hundred cores on widely available machines. Coupled with realistic galaxy populations placed in large N-body light cone simulations, CALCLENS is ideally suited for the construction of synthetic weak lensing shear catalogs to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys.

Becker, Matthew R.

2012-10-01

193

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

The MOND paradigm of modified dynamics predicts that the asymptotic gravitational potential of an isolated, bounded (baryonic) mass, M, is ?(r)=(MGa0)1/2ln(r). Relativistic MOND theories predict that the lensing effects of M are dictated by ?(r) as general-relativity lensing is dictated by the Newtonian potential. Thus MOND predicts that the asymptotic Newtonian potential deduced from galaxy-galaxy gravitational lensing will have (1) a logarithmic r dependence, and (2) a normalization (parametrized standardly as 2?2) that depends only on M: ?=(MGa0/4)1/4. I compare these predictions with recent results of galaxy-galaxy lensing, and find agreement on all counts. For the “blue”-lenses subsample (“spiral” galaxies) MOND reproduces the observations well with an r?-band M/Lr??(1–3)(M/L)?, and for “red” lenses (“elliptical” galaxies) with M/Lr??(3–6)(M/L)?, both consistent with baryons only. In contradistinction, Newtonian analysis requires, typically, M/Lr??130(M/L)?, bespeaking a mass discrepancy of a factor ?40. Compared with the staple, rotation-curve tests, MOND is here tested in a wider population of galaxies, through a different phenomenon, using relativistic test objects, and is probed to several-times-lower accelerations–as low as a few percent of a0. PMID:23931350

Milgrom, Mordehai

2013-07-25

194

Nonsingular Density Profiles of Dark Matter Halos and Strong Gravitational Lensing

NASA Astrophysics Data System (ADS)

We use the statistics of strong gravitational lenses to investigate whether mass profiles with a flat density core are supported. The probability for lensing by halos modeled by a nonsingular truncated isothermal sphere (NTIS) with image separations greater than a certain value (ranging from 0" to 10") is calculated. NTIS is an analytical model for the postcollapse equilibrium structure of virialized objects derived by Shapiro, Iliev, & Raga. This profile has a soft core and matches quite well with the mass profiles of dark matter-dominated dwarf galaxies deduced from their observed rotation curves. It also agrees well with the NFW (Navarro-Frenk-White) profile at all radii outside of a few NTIS core radii. Unfortunately, comparing the results with those for singular lensing halos (NFW and SIS + NFW) and strong lensing observations, the probabilities for lensing by NTIS halos are far too low. As this result is valid for any other nonsingular density profile (with a large core radius), we conclude that nonsingular density profiles (with a large core radius) for CDM halos are ruled out by statistics of strong gravitational lenses.

Chen, Da-Ming

2005-08-01

195

Strong deflection limit of black hole gravitational lensing with arbitrary source distances

The gravitational field of supermassive black holes is able to strongly bend light rays emitted by nearby sources. When the deflection angle exceeds {pi}, gravitational lensing can be analytically approximated by the so-called strong deflection limit. In this paper we remove the conventional assumption of sources very far from the black hole, considering the distance of the source as an additional parameter in the lensing problem to be treated exactly. We find expressions for critical curves, caustics, and all lensing observables valid for any position of the source up to the horizon. After analyzing the spherically symmetric case we focus on the Kerr black hole, for which we present an analytical 3-dimensional description of the higher order caustic tubes.

Bozza, V. [Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno, via Allende, I-84081 Baronissi (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy); Scarpetta, G. [Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno, via Allende, I-84081 Baronissi (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Napoli (Italy); International Institute for Advanced Scientific Studies, Vietri sul Mare (Italy)

2007-10-15

196

Observations of Cluster Substructure Using Weakly Lensed Sextupole Moments.

National Technical Information Service (NTIS)

Since dark matter clusters and groups may have substructure, we have examined the sextupole content of Hubble images looking for a curvature signature in background galaxies that would arise from galaxy-galaxy lensing. We describe techniques for extractin...

J. Irwin M. Shmakova

2003-01-01

197

NASA Astrophysics Data System (ADS)

Gravitational lensing induces significant errors in the measured distances to high-redshift standard candles and standard sirens such as Type Ia supernovae, gamma-ray bursts and merging supermassive black hole binaries. There will therefore be a significant benefit from correcting for the lensing error by using independent and accurate estimates of the lensing magnification. Here, we investigate how accurately the magnification can be inferred from convergence maps reconstructed from galaxy shear and flexion data. We employ ray-tracing through the Millennium Simulation (MS) to simulate lensing observations in large fields, and perform a weak-lensing reconstruction on the simulated fields. We identify optimal ways to filter the reconstructed convergence maps and to convert them to magnification maps, and analyse the resulting relation between the estimated and true magnification for sources at redshifts zS= 1 to 5. We find that a deep shear survey with 100 galaxies arcmin-2 can help to reduce the lensing-induced distance errors for standard candles/sirens at redshifts zS? 1.5 (zS? 5) on average by 20 per cent (10 per cent), whereas a futuristic survey with shear and flexion estimates from 500 galaxies arcmin-2 yields much larger reductions of 50 per cent (35 per cent). For redshifts zS? 3, a further improvement by ˜5 per cent can be achieved, if the individual redshifts of the galaxies are used in the reconstruction. Moreover, the reconstruction allows one to identify regions for which the convergence is low, and in which an error reduction by up to 75 per cent can be achieved. Such strongly reduced magnification uncertainties will greatly improve the value of high-redshift standard candles/sirens as cosmological probes.

Hilbert, Stefan; Gair, Jonathan R.; King, Lindsay J.

2011-04-01

198

Rotation of Galaxies as a Signature of Cosmic Strings in Weak Lensing Surveys

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

199

Mapping the dark matter with weak gravitational lensing

NASA Astrophysics Data System (ADS)

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 ellipticities. This can be removed by filtering. Our method is very similar in form to that of Tyson et al. (1990), and the latter is given a rigorous interpretation as a particular implementation of filtering. We present simulations to illustrate the application of the method.

Kaiser, Nick; Squires, Gordon

1993-02-01

200

Gravitational diffusion of solar system WIMPs. [Weakly interacting massive particles

It is shown here that, because of purely gravitational diffusion, the most important solar-bound weakly interacting massive particles (WIMPs) are populated at the same phase-space density as low-velocity unbound orbits. This diffusion occurs on time scales short compared both to the lifetime of the earth and to weak-interaction depletion. The effect is that direct capture from bound and unbound orbits together is very nearly equal to direct capture by the earth considered as a body in free space. The same gravitational diffusion virtually eliminates indirect capture. The net result is that free-space formulas for capture reported in a previous paper may be used without modification despite the fact that the earth is bound in the potential well of the sun. 10 refs.

Gould, A. (Institute for Advanced Study, Princeton, NJ (USA))

1991-02-01

201

A weak-lensing analysis of the Abell 383 cluster

NASA Astrophysics Data System (ADS)

Aims: We use deep CFHT and SUBARU uBVRIz archival images of the Abell 383 cluster (z = 0.187) to estimate its mass by weak-lensing. Methods: To this end, we first use simulated images to check the accuracy provided by our Kaiser-Squires-Broadhurst (KSB) pipeline. These simulations include shear testing programme (STEP) 1 and 2 simulations, as well as more realistic simulations of the distortion of galaxy shapes by a cluster with a Navarro-Frenk-White (NFW) profile. From these simulations we estimate the effect of noise on shear measurement and derive the correction terms. The R-band image is used to derive the mass by fitting the observed tangential shear profile with an NFW mass profile. Photometric redshifts are computed from the uBVRIz catalogs. Different methods for the foreground/background galaxy selection are implemented, namely selection by magnitude, color, and photometric redshifts, and the results are compared. In particular, we developed a semi-automatic algorithm to select the foreground galaxies in the color-color diagram, based on the observed colors. Results: Using color selection or photometric redshifts improves the correction of dilution from foreground galaxies: this leads to higher signals in the inner parts of the cluster. We obtain a cluster mass Mvir = 7.5+2.7_{-1.9 × 1014} M?: this value is 20% higher than previous estimates and is more consistent the mass expected from X-ray data. The R-band luminosity function of the cluster is computed and gives a total luminosity Ltot = (2.14 ± 0.5) × 1012 L? and a mass-to-luminosity ratio M/L 300 M?/L?. Based on: data collected with the Subaru Telescope (University of Tokyo) and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan; 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 Institute National des Sciences de l'Univers of the Centre National de la Recherche Scientifique 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.

Huang, Z.; Radovich, M.; Grado, A.; Puddu, E.; Romano, A.; Limatola, L.; Fu, L.

2011-05-01

202

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

203

WFPC2 Follow Up of Strong Gravitational Lenses

NASA Astrophysics Data System (ADS)

We present new lens reconstruction models based on HST WFPC2 for a sample of strong lenses that probe the group mass environment. Our sample is based almost entirely upon data from the SDSS data set which we have confirmed with follow-up spectroscopy and imaging using the 3.5 m telescope at the Apache Point Observatory. The Sample cover mass from 1012-1013 Msun, and have Einstein radii between 4 and 15 arcsec.

Allam, Sahar S.; Tucker, D.; Lin, H.; Annis, J.; Buckley-Geer, E.; Buckley-Geer, E.; Diehl, H. T.

2010-01-01

204

SDSSJ102111.02+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, B; Eisenstein, D J; Gregg, M D; Becker, R H; Inada, N; Oguri, M; Hall, P B; Johnston, D E; Richards, G T; Schneider, D P; Turner, E L; Brasi, G; Hinz, P M; Kenworthy, M A; Miller, D; Barentine, J C; Brewington, H J; Brinkmann, J; Harvanek, M; Kleinman, S J; Krzesinski, J; Long, D; Neilsen Jr., E H; Newman, P R; Nitta, A; Snedden, S A; York, D G

2005-11-10

205

A Measurement of Gravitational Lensing of the Microwave Background Using South Pole Telescope Data

NASA Astrophysics Data System (ADS)

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 ?CDM cosmological model to be 0.86 ± 0.16, with no lensing disfavored at 6.3?. Marginalizing over ?CDM cosmological models allowed by the Wilkinson Microwave Anisotropy Probe (WMAP7) results in a measurement of A lens = 0.90 ± 0.19, indicating that the amplitude of matter fluctuations over the redshift range 0.5 <~ z <~ 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 ?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, ? k = -0.0014 ± 0.0172; a 10% improvement in the amplitude of matter fluctuations within ?CDM, ?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.; Keisler, R.; Zahn, O.; Aird, K. A.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Dudley, J.; George, E. M.; Halverson, N. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hou, Z.; Hrubes, J. D.; Joy, M.; Knox, L.; Lee, A. T.; Leitch, E. M.; Lueker, M.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Millea, M.; Mohr, J. J.; Montroy, T. E.; Natoli, T.; Padin, S.; Plagge, T.; Pryke, C.; Reichardt, C. L.; Ruhl, J. E.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Spieler, H. G.; Staniszewski, Z.; Stark, A. A.; Story, K.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.

2012-09-01

206

Gravitational force in weakly correlated particle spatial distributions.

We study the statistics of the gravitational (Newtonian) force in a particular class of weakly correlated spatial distributions of pointlike and unitary mass particles generated by the so-called Gauss-Poisson point processes. In particular we extend to these distributions the analysis that Chandrasekhar introduced for purely Poisson processes. In this way we can find the explicit asymptotic behavior of the probability density function of the force for both large and small values of the field as a generalization of the Holtzmark statistics. In particular, we show how the modifications at large fields depend on the density correlations introduced at small scales. The validity of the introduced approximations is positively tested through a direct comparison with the analysis of the statistics of the gravitational force in numerical simulations of Gauss-Poisson processes. PMID:15089268

Gabrielli, Andrea; Masucci, Adolfo Paolo; Labini, Francesco Sylos

2004-03-30

207

Gravitational force in weakly correlated particle spatial distributions

NASA Astrophysics Data System (ADS)

We study the statistics of the gravitational (Newtonian) force in a particular class of weakly correlated spatial distributions of pointlike and unitary mass particles generated by the so-called Gauss-Poisson point processes. In particular we extend to these distributions the analysis that Chandrasekhar introduced for purely Poisson processes. In this way we can find the explicit asymptotic behavior of the probability density function of the force for both large and small values of the field as a generalization of the Holtzmark statistics. In particular, we show how the modifications at large fields depend on the density correlations introduced at small scales. The validity of the introduced approximations is positively tested through a direct comparison with the analysis of the statistics of the gravitational force in numerical simulations of Gauss-Poisson processes.

Gabrielli, Andrea; Masucci, Adolfo Paolo; Sylos Labini, Francesco

2004-03-01

208

NASA Astrophysics Data System (ADS)

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 ?2% precision (statistical only), which can improve the figure of merit of the DES cluster abundance experiment by a factor of ~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; Wu, Hao-Yi; Schmidt, Fabian

2011-07-01

209

Weak- and strong-lensing analyses of the triaxial matter distribution of Abell 1689

NASA Astrophysics Data System (ADS)

Haloes formed in the standard ? cold dark matter framework should follow a universal mass density profile and fit a well-defined mass-concentration relation. Lensing analyses of clusters with a large Einstein radius seem to contradict this scenario, with the massive cluster Abell 1689 being often claimed as a notable example of a highly over-concentrated halo. Shape and orientation biases in lensing studies might be on the basis of this disagreement between theory and observations. We developed a method for a full three-dimensional analysis of strong- and weak-lensing data. Surface density maps estimated from lensing are deprojected to infer the actual triaxial structure of the cluster, whose mass distribution is approximated as an ellipsoidal Navarro-Frenk-White halo with arbitrary orientation. Inversion is performed under competing a priori assumptions, integrated in the method, thanks to Bayesian statistics. We applied the method to Abell 1689. Whatever the considered priors on shape and orientation, both weak- and strong-lensing analyses found the halo to be slightly over-concentrated but still consistent with theoretical predictions. We found some evidence for a mildly-triaxial lens (minor-to-major-axis ratio ˜ 0.5 ± 0.2) with the major-axis orientated along the line of sight. Exploiting priors from N-body simulations, we found mass M200= (1.3 ± 0.4) × 1015 M? and concentration c200= 10 ± 3 for the weak-lensing analysis of Subaru data, M200= (1.7 ± 0.3) × 1015 M? and c200= 6.1 ± 0.9 for the strong-lensing analysis of multiple-image systems, and M200= (1.3 ± 0.2) × 1015 M? and c200= 7.3 ± 0.8 for the combined weak- plus strong-lensing analysis. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.

Sereno, Mauro; Umetsu, Keiichi

2011-10-01

210

The weak-lensing science of the LSST project drives the need to carefully\\u000amodel and separate the instrumental artifacts from the intrinsic lensing\\u000asignal. The dominant source of the systematics for all ground based telescopes\\u000ais the spatial correlation of the PSF modulated by both atmospheric turbulence\\u000aand optical aberrations. In this paper, we present a full FOV simulation of the

M. James Jee; J. Anthony Tyson

2010-01-01

211

NASA Astrophysics Data System (ADS)

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 of the Sloan Lens ACS (SLACS) Survey. The sample of lensed galaxies span 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 Sersic indices of the lensed galaxies. The measured properties of the lensed galaxies show a primarily compact, "disk"-like population with the peaks of the size and Sersic index distributions corresponding to ?1.50 kpc and n?1 respectively. Comparison of the SLACS lensed galaxies to a non-lensing, broad-band imaging based survey shows that a lensing survey allows us to probe a galaxy population that is typically ? 2 magnitudes fainter. Our analysis allows us to compare the

Bandara, Kaushala; Crampton, D.; Peng, C. Y.; Simard, L.

2012-01-01

212

The impact of AGN feedback and baryonic cooling on galaxy clusters as gravitational lenses

We investigate the impact of active galactic nucleus (AGN) feedback on the gravitational lensing properties of a sample of galaxy clusters with masses in the range 1014-1015 Msolar, using state-of-the-art simulations. Adopting a ray-tracing algorithm, we compute the cross-section of giant arcs from clusters simulated with dark matter (DM) only physics, DM plus gas with cooling and star formation (CSF)

James M. G. Mead; Lindsay J. King; Debora Sijacki; Adrienne Leonard; Ewald Puchwein; Ian G. McCarthy

2010-01-01

213

Paschen-alpha Emission in the Gravitationally Lensed Galaxy SMM J163554.2+661225

We report the detection of the Paalpha emission line in the z = 2.515 galaxy SMM J163554.2+661225 using Spitzer spectroscopy. SMM J163554.2+661225 is a submillimeter-selected infrared-luminous galaxy maintaining a high star formation rate (SFR), with no evidence of an active galactic nucleus from optical or infrared spectroscopy, nor X-ray emission. This galaxy is lensed gravitationally by the cluster Abell 2218,

Casey Papovich; Gregory Rudnick; Jane R. Rigby; Christopher N. A. Willmer; J.-D. T. Smith; Steven L. Finkelstein; Eiichi Egami; Marcia Rieke

2009-01-01

214

A New Approach to Identifying the Most Powerful Gravitational Lensing Telescopes

NASA Astrophysics Data System (ADS)

The best gravitational lenses for detecting distant galaxies are those with the largest mass concentrations and the most advantageous configurations of that mass along the line of sight. Our new method for finding such gravitational telescopes uses optical data to identify projected concentrations of luminous red galaxies (LRGs). LRGs are biased tracers of the underlying mass distribution, so lines of sight with the highest total luminosity in LRGs are likely to contain the largest total mass. We apply this selection technique to the Sloan Digital Sky Survey and identify the 200 fields with the highest total LRG luminosities projected within a 3.'5 radius over the redshift range 0.1 <= z <= 0.7. The redshift and angular distributions of LRGs in these fields trace the concentrations of non-LRG galaxies. These fields are diverse; 22.5% contain one known galaxy cluster and 56.0% contain multiple known clusters previously identified in the literature. Thus, our results confirm that these LRGs trace massive structures and that our selection technique identifies fields with large total masses. These fields contain two to three times higher total LRG luminosities than most known strong-lensing clusters and will be among the best gravitational lensing fields for the purpose of detecting the highest redshift galaxies.

Wong, Kenneth C.; Zabludoff, Ann I.; Ammons, S. Mark; Keeton, Charles R.; Hogg, David W.; Gonzalez, Anthony H.

2013-05-01

215

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

216

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

217

NASA Astrophysics Data System (ADS)

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, "disk"-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 langzrang = 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 sstarf > 109 M ?) evolve more in size and low-mass disk galaxies (M sstarf <= 109 M ?) evolve more in luminosity.

Bandara, Kaushala; Crampton, David; Peng, Chien; Simard, Luc

2013-11-01

218

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, Dennis; /KIPAC, Menlo Park /Bonn, Inst. Astrophys. /Arizona U., Astron. Dept. - Steward Observ. /Florida U. /Harvard-Smithsonian Ctr. Astrophys.

2006-09-27

219

NASA Astrophysics Data System (ADS)

The South Pole Telescope (SPT) has detected clusters above a nearly uniform mass threshold over an extremely broad range in redshift by searching for the Sunyaev-Zel'dovich effect. The observed abundance of clusters from such a well selected sample is directly sensitive to the growth function of matter perturbations over the majority of the history of the universe, and provides powerful constraints on dark energy with systematics that are complementary to traditional distance-based measures. The dominant source of uncertainty on dark energy constraints from this technique is our estimate of total cluster mass. We have observed 19 SPT clusters at 0.3 < z < 0.6 with Megacam on the Magellan-Clay 6.5 m telescope, and 14 SPT clusters at 0.6 < z < 1.3 with HST-ACS, to estimate total mass for these ~ (3-10)x10^14 Msun systems with weak gravitational lensing. We present results on the scaling of Y_SZ and Y_X with total mass, as well as the improvement in cosmological constraints afforded by the weak lensing data.

High, F. W.; South Pole Telescope Team

2013-01-01

220

Probing the dark-matter halos of cluster galaxies with weak lensing

NASA Astrophysics Data System (ADS)

Context. Understanding the evolution of the dark matter halos of galaxies after they become part of a cluster is essential for understanding the evolution of these satellite galaxies. Aims: We investigate the potential of galaxy-galaxy lensing to map the halo density profiles of galaxies in clusters. Methods: We propose a method that separates the weak-lensing signal of the dark-matter halos of galaxies in clusters from the weak-lensing signal of the cluster's main halo. Using toy cluster models as well as ray-tracing through N-body simulations of structure formation along with semi-analytic galaxy formation models, we test the method and assess its performance. Results: We show that with the proposed method, one can recover the density profiles of the cluster galaxy halos in the range 30-300 kpc. Using the method, we find that the weak-lensing signal of cluster member galaxies in the Millennium Simulation is well described by a Navarro-Frenk-White (NFW) profile. In contrast, non-singular isothermal mass distribution (like PIEMD) models provide a poor fit. Furthermore, we do not find evidence for a sharp truncation of the galaxy halos in the range probed by our method. Instead, there is an observed overall decrease of the halo mass profile of cluster member galaxies with increasing time spent in the cluster. This trend, as well as the presence or absence of a truncation radius, should be detectable in future weak-lensing surveys like the Dark Energy Survey (DES) or the Large Synoptic Survey Telescope (LSST) survey. Such surveys should also allow one to infer the mass-luminosity relation of cluster galaxies with our method over two decades in mass. Conclusions: It is possible to recover in a non-parametric way the mass profile of satellite galaxies and their dark matter halos in future surveys, using our proposed weak lensing method.

Pastor Mira, E.; Hilbert, S.; Hartlap, J.; Schneider, P.

2011-07-01

221

Extreme gravitational lensing in vicinity of Schwarzschild-de Sitter black holes

NASA Astrophysics Data System (ADS)

We have developed a realistic, fully general relativistic computer code to simulate optical projection in a strong, spherically symmetric gravitational field. The standard theoretical analysis of optical projection for an observer in the vicinity of a Schwarzschild black hole is extended to black hole spacetimes with a repulsive cosmological constant, i.e, Schwarzschild-de Sitterspacetimes. Influence of the cosmological constant is investigated for static observers and observers radially free-falling from the static radius. Simulations include effects of the gravitational lensing, multiple images, Doppler and gravitational frequency shift, as well as the intensity amplification. The code generates images of the sky for the static observer and a movie simulations of the changing sky for the radially free-falling observer. Techniques of parallel programming are applied to get a high performance and a fast run of the BHC simulation code.

Bakala, Pavel; ?ermák, Petr; Hledík, Stanislav; Stuchlík, Zden?k; Truparová, Kamila

2007-12-01

222

Complementarity of weak lensing and peculiar velocity measurements in testing general relativity

We explore the complementarity of weak lensing and galaxy peculiar velocity measurements to better constrain modifications to General Relativity. We find no evidence for deviations from General Relativity on cosmological scales from a combination of peculiar velocity measurements (for Luminous Red Galaxies in the Sloan Digital Sky Survey) with weak lensing measurements (from the Canadian France Hawaii Telescope Legacy Survey). We provide a Fisher error forecast for a Euclid-like space-based survey including both lensing and peculiar velocity measurements and show that the expected constraints on modified gravity will be at least an order of magnitude better than with present data, i.e. we will obtain {approx_equal}5% errors on the modified gravity parametrization described here. We also present a model-independent method for constraining modified gravity parameters using tomographic peculiar velocity information, and apply this methodology to the present data set.

Song, Yong-Seon [Korea Institute for Advanced Study, Dongdaemun-gu, Seoul 130-722 (Korea, Republic of); Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Zhao Gongbo; Bacon, David; Koyama, Kazuya; Nichol, Robert C. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX (United Kingdom); Pogosian, Levon [Department of Physics, Simon Fraser University, Burnaby, BC, V5A 1S6 (Canada)

2011-10-15

223

A Weak-lensing and Near-infrared Study of A3192: Disassembling a Richness Class 3 Abell Cluster

NASA Astrophysics Data System (ADS)

We present a joint gravitational lensing and near-infrared study of the galaxy cluster Abell 3192 (A3192) that has been associated both with galaxies at z = 0.168 and with the X-ray luminous cluster RXC J0358.8-2955 (RXC J0358) at z = 0.425. Weak-lensing analysis of our Hubble Space Telescope snapshot observation with the Advanced Camera for Surveys detects two mass over-densities separated by ~2 arcmin, one adjacent to the optical position of A3192 (4.4? significance) and the other adjacent to the X-ray position of RXC J0358 (6.2? significance). These mass peaks coincide with peaks in the K-band luminosity density of galaxies with near-infrared colors consistent with the red sequence at z = 0.168 and z = 0.425, respectively. Moreover, the Bayesian evidence of parameterized mass models that include two cluster/group-scale halos centered on the respective mass peaks exceeds that of single-halo models by a factor of >=10. The total projected mass of each galaxy system within 250 kpc of the respective peaks is M WL(z = 0.168) ~= 3 × 1013 M ? and M WL(z = 0.425) ~= 1.2 × 1014 M ?, both with total mass-to-light ratios of M WL/LK ~= 20 M ?/L ?. The original Abell cluster therefore comprises two independent galaxy systems—a foreground group at z = 0.168 and RXC J0358 at z = 0.425. Our results demonstrate the power of combining X-ray, near-infrared, and weak-lensing observations to select massive clusters, place those clusters and interloper galaxy systems along the line of sight, and measure their masses. This combination will be invaluable to robust interpretation of future high-redshift cluster surveys, including eROSITA.

Hamilton-Morris, Victoria; Smith, Graham P.; Edge, A. C.; Egami, E.; Haines, C. P.; Marshall, P. J.; Sanderson, A. J. R.; Targett, T. A.

2012-04-01

224

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, E(G), that combines measures of large-scale gravitational lensing, galaxy clustering and structure growth rate. The combination is insensitive to 'galaxy bias' (the difference between the clustering of visible galaxies and invisible dark matter) and is thus robust to the uncertainty in this parameter. Modified theories of gravity generally predict values of E(G) different from the general relativistic prediction because, in these theories, the 'gravitational slip' (the difference between the two potentials that describe perturbations in the gravitational metric) is non-zero, which leads to changes in the growth of structure and the strength of the gravitational lensing effect. Here we report that E(G) = 0.39 +/- 0.06 on length scales of tens of megaparsecs, in agreement with the general relativistic prediction of E(G) approximately 0.4. The measured value excludes a model within the tensor-vector-scalar gravity theory, which modifies both Newtonian and Einstein gravity. However, the relatively large uncertainty still permits models within f(R) theory, which is an extension of general relativity. A fivefold decrease in uncertainty is needed to rule out these models. PMID:20220843

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

2010-03-11

225

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

226

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

227

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

228

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

229

Spin effects in gravitational radiation back reaction. I. The Lense-Thirring approximation

NASA Astrophysics Data System (ADS)

The gravitational radiation back reaction effects are considered in the Lense-Thirring approximation. New methods for parametrizing the orbit and for averaging the instantaneous radiative losses are developed. To first order in the spin S of the black hole, both in the absence and in the presence of gravitational radiation, a complete description of the test-particle orbit is given. This is achieved by two improvements over the existing descriptions: first, by introducing new angle variables with a straightforward geometrical meaning; second, by finding a new parametrization of a generic orbit, which assures that the integration over a radial period can be done in an especially simple way, by applying the residue theorem. The instantaneous gravitational radiation losses of the system are computed using the formulation of Blanchet, Damour and Iyer. All losses are given both in terms of the dynamical constants of motion and the properly defined orbital elements a, e, ? and ?0. The radiative losses of the constants characterizing the Lense-Thirring motion, when suitably converted, are in agreement with earlier results of Kidder, Will and Wiseman, Ryan and Shibata. In addition, the radiative losses of two slowly changing orbital elements ?0,?0 are given in order to complete the characterization of the orbit.

Gergely, László Á.; Perjés, Zoltán I.; Vasúth, Mátyás

1998-01-01

230

Gravitational lensing effects on the gamma-ray burst Hubble diagram

Gamma-ray bursts (GRBs) offer a potential way to extend the Hubble diagram to very high redshifts and to constrain the nature of dark energy in a way complementary to distant type Ia supernovae. However, gravitational lensing systematically brightens distant GRBs through the magnification bias, in addition to increasing the dispersions of distance measurements. We investigate how the magnification bias limits the cosmological usage of GRBs. We perform Monte-Carlo simulations of Swift GRBs assuming a cosmological constant dominated universe and then constrain the dark energy equation of state neglecting gravitational lens effects. The originally assumed model is recovered with 68% confidence limit even when the dispersion of inferred luminosities is comparable to that of type Ia supernovae. This implies that the bias is not so drastic for Swift GRBs as to change constraints on dark energy and its evolution. However, the precise degree of the bias in cosmological parameter determinations depends strongly on the shape of the luminosity function of GRBs. Therefore, an accurate determination of the shape of the luminosity function is required to remove the effect of gravitational lensing and to obtain an unbiased Hubble diagram.

Oguri, Masamune [Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Takahashi, Keitaro [Department of Physics, Princeton University, Princeton, New Jersey 08544 (United States)

2006-06-15

231

Probing small-scale structure in galaxies with strong gravitational lensing

NASA Astrophysics Data System (ADS)

We use gravitational lensing to study the small-scale distribution of matter in galaxies. First, we examine galaxies and their dark matter halos. Roughly half of all observed four-image quasar lenses have image flux ratios that differ from the values predicted by simple lens potentials. We show that smooth departures from elliptical symmetry fail to explain anomalous radio fluxes, strengthening the case for dark matter substructure. Our results have important implications for the "missing satellites'' problem. We then consider how time delays between lensed images can be used to identify lens galaxies containing small-scale structure. We derive an analytic relation for the time delay between the close pair of images in a "fold'' lens, and perform Monte Carlo simulations to investigate the utility of time delays for probing small- scale structure in realistic lens populations. We compare our numerical predictions with systems that have measured time delays and discover two anomalous lenses. Next, we consider microlensing, where stars in the lens galaxy perturb image magnifications. This is relevant at optical wavelengths, where the size of the lensed source is comparable to the Einstein radius of a typical star. Our simulations of negative-parity images show that raising the fraction of dark matter relative to stars increases image flux variability for small sources, and decreases it for large sources. This suggests that quasar accretion disks and broad-emission-line regions may respond differently to microlensing. We also consider extended sources with a range of ellipticities, which has relevance to a population of inclined accretion disks. Depending on their orientation, more elongated sources lead to more rapid variability, which may complicate the interpretation of microlensing light curves. Finally, we consider prospects for observing strong lensing by the supermassive black hole at the center of the Milky Way, Sgr A*. Assuming a black hole on the million- solar-mass scale, we predict that the probability of observing strong lensing of a background star is roughly 56%. We also consider how lensing by Sgr A* could be used to test general relativity against alternative theories, concluding that microarcsecond resolution would make this possible.

Congdon, Arthur Benjamin

232

The impact of AGN feedback and baryonic cooling on galaxy clusters as gravitational lenses

We investigate the impact of AGN feedback on the gravitational lensing\\u000aproperties of a sample of galaxy clusters with masses in the range 10^14 -\\u000a10^15 Msol, using state-of-the-art simulations. Adopting a ray-tracing\\u000aalgorithm, we compute the cross-section of giant arcs from clusters simulated\\u000awith dark-matter only physics (DM), dark matter plus gas with cooling and star\\u000aformation (CSF), and

J. M. G. Mead; L. J. King; D. Sijacki; A. Leonard; E. Puchwein; I. G. McCarthy

2010-01-01

233

Strong gravitational lensing across a dilaton anti-de Sitter black hole

In this work we investigate the gravitational lensing effect in the strong field region around dilaton black holes in an anti-de Sitter space. We also analyze the dependence of the radius of the photon sphere and deflection angle on dilaton coupling and the cosmological constant in this black hole spacetime. Finally the values of minimum impact parameter, the separation between the first and the other images, as well as the ratio between the flux of the first image and the flux coming from all the other images are determined to characterize some possible distinct signatures of such black holes.

Ghosh, Tanwi; SenGupta, Soumitra [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)

2010-02-15

234

The CASSOWARY spectroscopy survey: a new sample of gravitationally lensed galaxies in SDSS

NASA Astrophysics Data System (ADS)

Bright gravitationally lensed galaxies provide our most detailed view of galaxies at high redshift. The very brightest (r < 21) systems enable high spatial and spectral resolution measurements, offering unique constraints on the outflow energetics, metallicity gradients and stellar populations in high-redshift galaxies. Yet as a result of the small number of ultrabright z ? 2 lensed systems with confirmed redshifts, most detailed spectroscopic studies have been limited in their scope. With the goal of increasing the number of bright lensed galaxies available for detailed follow-up, we have undertaken a spectroscopic campaign targeting wide separation (?3 arcsec) galaxy-galaxy lens candidates within the Sloan Digital Sky Survey (SDSS). Building on the earlier efforts of our Cambridge and Sloan Survey Of Wide Arcs in Thesky survey, we target a large sample of candidate galaxy-galaxy lens systems in SDSS using a well-established search algorithm which identifies blue arc-like structures situated around luminous red galaxies. In this paper, we present a new redshift catalogue containing 29 lensed sources in SDSS confirmed through spectroscopic follow-up of candidate galaxy-galaxy lens systems. Included in this new sample are two of the brightest galaxies (r = 19.6 and 19.7) known at z ? 2, a low metallicity (12 + log (O/H) ? 8.0) extreme nebular line emitting galaxy at z = 1.43, and numerous systems for which detailed follow-up will be possible. The source redshifts span 0.9 < z < 2.5 (median redshift of 1.9), and their optical magnitudes are in the range 19.6 ? r ? 22.3. We present a brief source-by-source discussion of the spectroscopic properties extracted from our confirmatory spectra and discuss some initial science results. Preliminary lens modelling reveals average source magnifications of 5-10 times. With more than 50 gravitationally lensed z ? 1 galaxies now confirmed within SDSS, it will soon be possible for the first time to develop generalized conclusions from detailed spectroscopic studies of the brightest lensed systems at high redshift.

Stark, Daniel P.; Auger, Matthew; Belokurov, Vasily; Jones, Tucker; Robertson, Brant; Ellis, Richard S.; Sand, David J.; Moiseev, Alexei; Eagle, Will; Myers, Thomas

2013-10-01

235

SHEAR-SELECTED CLUSTERS FROM THE DEEP LENS SURVEY. III. MASSES FROM WEAK LENSING

We present weak lensing mass estimates of seven shear-selected galaxy cluster candidates from the deep lens survey. The clusters were previously identified as mass peaks in convergence maps of 8.6 deg{sup 2} of R-band imaging, and followed up with X-ray and spectroscopic confirmation, spanning a redshift range 0.19-0.68. Most clusters contained multiple X-ray peaks, yielding 17 total mass concentrations. In this paper, we constrain the masses of these X-ray sources with weak lensing, using photometric redshifts from the full set of BVRz' imaging to properly weight background galaxies according to their lensing distance ratios. We fit both NFW and singular isothermal sphere profiles, and find that the results are insensitive to the assumed profile. We also show that the results do not depend significantly on the assumed prior on the position of the mass peak, but that this may become an issue in future larger samples. The inferred velocity dispersions for the extended X-ray sources range from 250 to 800 km s{sup -1}, with the exception of one source for which no lensing signal was found. This work further establishes shear selection as a viable technique for finding clusters, but also highlights some unresolved issues such as determination of the mass profile center without biasing the mass estimate, and fully accounting for line-of-sight projections. A follow-up paper will examine the mass-X-ray scaling relations of these clusters.

Abate, Alexandra [Laboratoire de l'Accelerateur Lineaire, IN2P3-CNRS, Universite de Paris-Sud, BP 34, 91898 Orsay Cedex (France); Wittman, D.; Margoniner, V. E.; Gee, Perry; Tyson, J. Anthony [Physics Department, University of California, Davis, CA 95616 (United States); Bridle, S. L. [Department of Physics, University College London, Gower Street, London WC1E 6BT (United Kingdom); Dell'Antonio, Ian P. [Physics Department, Brown University, Providence, RI 02912 (United States)], E-mail: abate@lal.in2p3.fr, E-mail: dwittman@physics.ucdavis.edu

2009-09-01

236

NASA Astrophysics Data System (ADS)

We calculate the expected number of multiply-imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with m_I < 27 that were detected in all four HDF passbands. A comparison of these expectations with the observed number of lensed sources in the HDF places a 95% confidence lower limit on the current value of Omega_m - Omega_Lambda between -0.17, if there are no strongly lensed sources in the HDF, and -0.59, if there are three strongly lensed sources in the HDF. For a flat universe, Lambda < 0.58 to 0.79. If the only lensed source in the HDF is the one presently viable candidate, then Omega_m - Omega_Lambda > -0.39. These lower limits are compatible with estimates based on high redshift supernovae and with previous limits based on gravitational lensing.

Quashnock, J. M.; Cooray, A. R.; Miller, M. C.

1998-12-01

237

Design issues for a mission to exploit the gravitational lensing effect at 550 AU

NASA Astrophysics Data System (ADS)

Reported herein are the first results of a NASA-sponsored study at the Jet Propulsion Laboratory (JPL), California Institute of Technology, exploring the scientific promise and technological viability of a mission to exploit the gravitational lensing effect of the Sun to obtain huge antenna gains for electromagnetic waves grazing the Sun's disk. With regard to scientific promise, these results, reported at about the halfway point of the study, substantiate the huge antenna gains offered by, as it will be called here, a Solar Gravitational Telescope (SGT) and point to the instrument's potential promise as a "discovery machine" but suggest considerable limitations to the telescope's usefulness as a general purpose astrophysical research tool. These limitations are seen to arise, primarily, from the geometry and scale of the "virtual" telescope which must be achieved and maintained to utilize the lensing effect and the turbulence effects of the Sun's plasma on the observed target's signal. With regard to technological viability, the preliminary results suggest a very aggressive use of unproven, as-yet-unflown new technology will be required to enable the desired science observations and mission durations approaching the short (3-10 year) NASA-targeted mission duration goal. Key needed new technologies are advanced propulsion, lightweight telescopes, membrane mirrors, inflatable/rigidizeable structures, and novel coronagraphic techniques.

West, John L.

1999-05-01

238

GRAVITATIONAL LENSING OF STARS ORBITING THE MASSIVE BLACK HOLE IN THE GALACTIC CENTER

The existence of a massive black hole in the center of the Milky Way, coinciding with the radio source Sgr A*, is being established on more and more solid grounds. In principle, this black hole, acting as a gravitational lens, is able to bend the light emitted by stars moving within its neighborhood, eventually generating secondary images. Extending a previous analysis of the gravitational lensing phenomenology to a new set of 27 stars, whose orbits have been well determined by recent observations, we have calculated all the properties of their secondary images, including time and magnitude of their luminosity peaks and their angular distances from the central black hole. The best lensing candidate is represented by the star S6, since the magnitude of its secondary image at the peak reaches K = 20.8, with an angular separation of 0.3 mas from the central black hole, which is just at the borders of the resolution limit in the K band of incoming astronomical instruments.

Bozza, V.; Mancini, L. [Dipartimento di Fisica 'E.R. Caianiello', Universita di Salerno (Italy)], E-mail: valboz@physics.unisa.it, E-mail: lmancini@physics.unisa.it

2009-05-01

239

HI Emission From Gravitationally Lensed Galaxies at z 0.4-0.5

NASA Astrophysics Data System (ADS)

We present observations with the Green Bank Telescope (GBT) of neutral hydrogen (HI) 21 cm emission from two gravitationally lensed galaxies behind the cluster Abell 773. If detected, these galaxies would be twice as distant as the previously most distant detected HI emission at z 0.2. The unique alignment of the galaxies with the cluster provides magnification of the sources due to gravitational lensing and coupled with the sensitivity, frequency coverage, and location of GBT in the National Radio Quiet Zone makes these observations feasible. The target galaxies have redshifts of 0.398 and 0.487 with magnifications of 2.7 and 3.7, respectively. Our observations will have a 5-sigma HI mass sensitivity of 5x109 solar masses for a velocity width of 130 km/s. One of the challenges of this project was the RFI removal. The data has suffered mostly from bright narrowband interference and in some cases broadband interference. Several RFI removal algorithms were used to remove the interference. The results of this project, clipping and mean comparison algorithms will be discussed in detail. Combined with future observations of other systems at similar redshifts, we can begin to do SKA science today.

Edel, Stanislav; Pisano, D. J.

2010-01-01

240

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

241

Two New Gravitationally Lensed Double Quasars from theSloan Digital Sky Survey

We report the discoveries of the two-image gravitationally lensed quasars, SDSS J0746+4403 and SDSS J1406+6126, selected from the Sloan Digital Sky Survey (SDSS). SDSS J0746+4403, which will be included in our lens sample for statistics and cosmology, has a source redshift of z{sub s} = 2.00, an estimated lens redshift of z{sub l} {approx} 0.3, and an image separation of 1.08''. SDSS J1406+6126 has a source redshift of z{sub s} = 2.13, a spectroscopically measured lens redshift of z{sub l} = 0.27, and an image separation of 1.98''. We find that the two quasar images of SDSS J1406+6126 have different intervening Mg II absorption strengths, which are suggestive of large variations of absorbers on kpc scales. The positions and fluxes of both the lensed quasar systems are easily reproduced by simple mass models with reasonable parameter values. These objects bring to 18 the number of lensed quasars that have been discovered from the SDSS data.

Inada, Naohisa; Oguri, Masamune; Becker, Robert H.; White, Richard L.; Kayo, Issha; Kochanek, Christopher S.; Hall, Patrick B.; Schneider, Donald P.; York, Donald G.; Richards, Gordon T.; /Tokyo U., Inst. Astron. /KIPAC, Menlo Park /Princeton U. Observ. /LLNL, Livermore /UC, Davis /Baltimore, Space Telescope Sci. /Nagoya U. /Ohio State U., Dept. Astron. /York U., Canada /Penn State U., Astron. Astrophys. /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI /Johns Hopkins U. /Drexel U.

2006-09-28

242

Mapping Dark Matter and the PSF: Weak Lensing Studies of Galaxy Clusters with pODI

NASA Astrophysics Data System (ADS)

We present first results from a science verification program to use the excellent delivered image quality of pODI in both direct imaging and coherent guiding modes to measure the PSF pattern and its stability across the full pODI field of view. We apply the results to observations of galaxy clusters to underscore the excellent potential of ODI for weak lensing science.

Dell'Antonio, Ian P.; McCleary, J. E.

2013-06-01

243

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

244

Wide-Field Weak Lensing by RX J1347-1145

NASA Astrophysics Data System (ADS)

We present an analysis of weak-lensing observations for RX J1347-1145 over a 43'×43' field taken in B and R filters on the Blanco 4 m telescope at CTIO. RX J1347-1145 is a massive cluster at redshift z=0.45. Using a population of galaxies with 20

Kling, Thomas P.; Dell'Antonio, Ian; Wittman, David; Tyson, J. Anthony

2005-06-01

245

NASA Astrophysics Data System (ADS)

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

Kneib, Jean-Paul; Natarajan, Priyamvada

2011-11-01

246

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

NASA Astrophysics Data System (ADS)

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 analysis, and results on the radial density profile of the lens galaxies. The lens candidates are selected from within the spectroscopic database of the Sloan Digital Sky Survey (SDSS) based on the appearance of two significantly different redshifts along the same line of sight, and lenses are confirmed within the candidate sample by follow-up imaging and spectroscopy. The sample of [approximate]20 early-type lenses presented in this thesis represents the largest single strong-lens galaxy sample discovered and published to date. These lenses probe the mass of the lens galaxies on scales roughly equal to one-half effective radius. We find a dynamical normalization between isothermal lens-model velocity dispersions and aperture-corrected SDSS stellar velocity dispersions of f = s lens /s stars = 0.95 +/- 0.03. By combining lens-model Einstein radii and de Vaucouleurs effective radii with stellar velocity dispersions through the Jeans equation, we find that the logarithmic slope [Special characters omitted.] of the density profile in our lens galaxies (r 0 ( [Special characters omitted.] ) is on average slightly steeper than isothermal ([Special characters omitted.] = 2) with a modest intrinsic scatter. Parameterizing the intrinsic distribution in [Special characters omitted.] as Gaussian, we find a maximum-likelihood mean of [Special characters omitted. ] and standard deviation of s[Special characters omitted.] = [Special characters omitted.] (68% confidence, for isotropic velocity-dispersion models). Our results rule out a single universal logarithmic density slope at >99.995% confidence. The success of this spectroscopic lens survey suggests that similar projects should be considered as an explicit science goal of future redshift surveys. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

Bolton, Adam Stallard

2005-11-01

247

NASA Astrophysics Data System (ADS)

We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all of the events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For seven events, we measure the Einstein radii and the lens-source relative proper motions. Among them, five events are found to have Einstein radii of less than 0.2 mas, making the lenses very low mass star or brown dwarf candidates. For MOA-2011-BLG-274, especially, the small Einstein radius of ?E ~ 0.08 mas combined with the short timescale of t E ~ 2.7 days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of ~0.84 M ? is consistent with that of a star blended with the source, suggesting that the blend is likely to be the lens. Although we did not find planetary signals for any of the events, we provide exclusion diagrams showing the confidence levels excluding the existence of a planet as a function of the separation and mass ratio.

Choi, J.-Y.; Shin, I.-G.; Park, S.-Y.; Han, C.; Gould, A.; Sumi, T.; Udalski, A.; Beaulieu, J.-P.; Street, R.; Dominik, M.; Allen, W.; Almeida, L. A.; Bos, M.; Christie, G. W.; Depoy, D. L.; Dong, S.; Drummond, J.; Gal-Yam, A.; Gaudi, B. S.; Henderson, C. B.; Hung, L.-W.; Jablonski, F.; Janczak, J.; Lee, C.-U.; Mallia, F.; Maury, A.; McCormick, J.; McGregor, D.; Monard, L. A. G.; Moorhouse, D.; Muñoz, J. A.; Natusch, T.; Nelson, C.; Park, B.-G.; Pogge, R. W.; "TG" Tan, T.-G.; Thornley, G.; Yee, J. C.; ?FUN Collaboration; Abe, F.; Barnard, E.; Baudry, J.; Bennett, D. P.; Bond, I. A.; Botzler, C. S.; Freeman, M.; Fukui, A.; Furusawa, K.; Hayashi, F.; Hearnshaw, J. B.; Hosaka, S.; Itow, Y.; Kamiya, K.; Kilmartin, P. M.; Kobara, S.; Korpela, A.; Lin, W.; Ling, C. H.; Makita, S.; Masuda, K.; Matsubara, Y.; Miyake, N.; Muraki, Y.; Nagaya, M.; Nishimoto, K.; Ohnishi, K.; Okumura, T.; Omori, K.; Perrott, Y. C.; Rattenbury, N.; Saito, To.; Skuljan, L.; Sullivan, D. J.; Suzuki, D.; Suzuki, K.; Sweatman, W. L.; Takino, S.; Tristram, P. J.; Wada, K.; Yock, P. C. M.; MOA Collaboration; Szyma?ski, M. K.; Kubiak, M.; Pietrzy?ski, G.; Soszy?ski, I.; Poleski, R.; Ulaczyk, K.; Wyrzykowski, ?.; Koz?owski, S.; Pietrukowicz, P.; OGLE Collaboration; Albrow, M. D.; Bachelet, E.; Batista, V.; Bennett, C. S.; Bowens-Rubin, R.; Brillant, S.; Cassan, A.; Cole, A.; Corrales, E.; Coutures, Ch.; Dieters, S.; Dominis Prester, D.; Donatowicz, J.; Fouqué, P.; Greenhill, J.; Kane, S. R.; Menzies, J.; Sahu, K. C.; Wambsganss, J.; Williams, A.; Zub, M.; PLANET Collaboration; Allan, A.; Bramich, D. M.; Browne, P.; Clay, N.; Fraser, S.; Horne, K.; Kains, N.; Mottram, C.; Snodgrass, C.; Steele, I.; Tsapras, Y.; RoboNet Collaboration; Alsubai, K. A.; Bozza, V.; Burgdorf, M. J.; Calchi Novati, S.; Dodds, P.; Dreizler, S.; Finet, F.; Gerner, T.; Glitrup, M.; Grundahl, F.; Hardis, S.; Harpsøe, K.; Hinse, T. C.; Hundertmark, M.; Jørgensen, U. G.; Kerins, E.; Liebig, C.; Maier, G.; Mancini, L.; Mathiasen, M.; Penny, M. T.; Proft, S.; Rahvar, S.; Ricci, D.; Scarpetta, G.; Schäfer, S.; Schönebeck, F.; Skottfelt, J.; Surdej, J.; Southworth, J.; Zimmer, F.; MiNDSTEp Consortium

2012-05-01

248

We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all of the events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For seven events, we measure the Einstein radii and the lens-source relative proper motions. Among them, five events are found to have Einstein radii of less than 0.2 mas, making the lenses very low mass star or brown dwarf candidates. For MOA-2011-BLG-274, especially, the small Einstein radius of {theta}{sub E} {approx} 0.08 mas combined with the short timescale of t{sub E} {approx} 2.7 days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of {approx}0.84 M{sub Sun} is consistent with that of a star blended with the source, suggesting that the blend is likely to be the lens. Although we did not find planetary signals for any of the events, we provide exclusion diagrams showing the confidence levels excluding the existence of a planet as a function of the separation and mass ratio.

Choi, J.-Y.; Shin, I.-G.; Park, S.-Y.; Han, C. [Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Gould, A.; Gaudi, B. S.; Henderson, C. B. [Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210 (United States); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Beaulieu, J.-P. [Institut d'Astrophysique de Paris, UMR7095 CNRS-Universite Pierre and Marie Curie, 98 bis boulevard Arago, 75014 Paris (France); Street, R. [Las Cumbres Observatory Global Telescope Network, 6740B Cortona Dr, Suite 102, Goleta, CA 93117 (United States); Dominik, M. [School of Physics and Astronomy, SUPA, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Allen, W. [Vintage Lane Observatory, Blenheim (New Zealand); Almeida, L. A. [Instituto Nacional de Pesquisas Espaciais/MCTI, Sao Jose dos Campos, Sao Paulo (Brazil); Bos, M. [Molehill Astronomical Observatory, North Shore (New Zealand); Christie, G. W. [Auckland Observatory, P.O. Box 24-180, Auckland (New Zealand); Depoy, D. L. [Department of Physics, Texas A and M University, College Station, TX (United States); Dong, S. [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Drummond, J. [Possum Observatory, Patutahi (New Zealand); Gal-Yam, A. [Benoziyo Center for Astrophysics, Weizmann Institute (Israel); Collaboration: muFUN Collaboration; MOA Collaboration; OGLE Collaboration; PLANET Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; and others

2012-05-20

249

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

250

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

251

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

252

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

253

Paschen-? Emission in the Gravitationally Lensed Galaxy SMM J163554.2+661225

NASA Astrophysics Data System (ADS)

We report the detection of the Pa? emission line in the z = 2.515 galaxy SMM J163554.2+661225 using Spitzer spectroscopy. SMM J163554.2+661225 is a submillimeter-selected infrared-luminous galaxy maintaining a high star formation rate (SFR), with no evidence of an active galactic nucleus from optical or infrared spectroscopy, nor X-ray emission. This galaxy is lensed gravitationally by the cluster Abell 2218, making it accessible to Spitzer spectroscopy. We measure a line luminosity, L(Pa?) = (2.05 ± 0.33) × 1042 erg s-1, corrected for gravitational lensing. Comparing the H? and Pa? luminosities, we derive a nebular extinction, A(V) = 3.6 ± 0.4 mag. The dust-corrected luminosity, L(Pa?) = (2.57 ± 0.43) × 1042 erg s-1, corresponds to an ionization rate, Q 0 = (1.6 ± 0.3) × 1055 ? s-1. The instantaneous SFR is ? = 171 ± 28 M ? yr-1, assuming a Salpeter-like initial mass function from 0.1 to 100 M ? yr-1. The total IR luminosity derived using 70, 450, and 850 ?m data is LIR = (5-10) × 1011 L ?, corrected for gravitational lensing. This corresponds to ? = 90-180 M ? yr-1, where the upper range is consistent with that derived from the Pa? luminosity. While the L(8 ?m)/L(Pa?) ratio is consistent with the extrapolated relation observed in local galaxies and star-forming regions, the rest-frame 24 ?m luminosity is significantly lower with respect to local galaxies of comparable Pa? luminosity. Thus, SMM J163554.2+661225 arguably lacks a warmer dust component (TD ~ 70 K), which is associated with deeply embedded star formation, and which contrasts with local galaxies with comparable SFRs. Rather, the starburst in SMM J163554.2+661225 is consistent with star-forming local galaxies with intrinsic luminosities, LIR ? 1010 L ?, but "scaled up" by a factor of ~10-100. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under NASA contract 1407.

Papovich, Casey; Rudnick, Gregory; Rigby, Jane R.; Willmer, Christopher N. A.; Smith, J.-D. T.; Finkelstein, Steven L.; Egami, Eiichi; Rieke, Marcia

2009-10-01

254

A WEAK-LENSING AND NEAR-INFRARED STUDY OF A3192: DISASSEMBLING A RICHNESS CLASS 3 ABELL CLUSTER

We present a joint gravitational lensing and near-infrared study of the galaxy cluster Abell 3192 (A3192) that has been associated both with galaxies at z = 0.168 and with the X-ray luminous cluster RXC J0358.8-2955 (RXC J0358) at z = 0.425. Weak-lensing analysis of our Hubble Space Telescope snapshot observation with the Advanced Camera for Surveys detects two mass over-densities separated by {approx}2 arcmin, one adjacent to the optical position of A3192 (4.4{sigma} significance) and the other adjacent to the X-ray position of RXC J0358 (6.2{sigma} significance). These mass peaks coincide with peaks in the K-band luminosity density of galaxies with near-infrared colors consistent with the red sequence at z = 0.168 and z 0.425, respectively. Moreover, the Bayesian evidence of parameterized mass models that include two cluster/group-scale halos centered on the respective mass peaks exceeds that of single-halo models by a factor of {>=}10. The total projected mass of each galaxy system within 250 kpc of the respective peaks is M{sub WL}(z = 0.168) {approx_equal} 3 Multiplication-Sign 10{sup 13} M{sub Sun} and M{sub WL}(z = 0.425) {approx_equal} 1.2 Multiplication-Sign 10{sup 14} M{sub Sun }, both with total mass-to-light ratios of M{sub WL}/L{sub K} {approx_equal} 20 M{sub Sun }/L{sub Sun }. The original Abell cluster therefore comprises two independent galaxy systems-a foreground group at z = 0.168 and RXC J0358 at z = 0.425. Our results demonstrate the power of combining X-ray, near-infrared, and weak-lensing observations to select massive clusters, place those clusters and interloper galaxy systems along the line of sight, and measure their masses. This combination will be invaluable to robust interpretation of future high-redshift cluster surveys, including eROSITA.

Hamilton-Morris, Victoria; Smith, Graham P.; Haines, C. P.; Sanderson, A. J. R. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Edge, A. C. [Institute of Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Egami, E. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Marshall, P. J. [Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Targett, T. A., E-mail: vhh@star.sr.bham.ac.uk, E-mail: gps@star.sr.bham.ac.uk [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)

2012-04-01

255

Fermi LAT Observations of Gamma-ray Flaring in the Gravitationally Lensed Blazar B0218+357

NASA Astrophysics Data System (ADS)

Beginning mid-2012, increased gamma-ray activity from the radio double-imaged gravitationally lensed blazar B0218+357 was observed with the Fermi Large Area Telescope (LAT). The sustained flaring with daily fluxes greater than 10x the source's nominal level afforded an opportunity to uniquely measure the expected gravitational lens delay in gamma rays. Additionally, Fermi-LAT pointed observations of the anticipated delayed emission from the brightest flares with peaks ~60x its nominal flux at the end of September 2012 allowed us to constrain the magnification ratio between the images in gamma-rays. We will present the results from our timing and spectral analysis of B0218+357 and consider prospects for future LAT studies of gravitationally lensed systems.

Cheung, Chi (Teddy) C.; Scargle, J. D.; Corbet, R. H.; Fermi-LAT Collaboration

2013-04-01

256

[The use of a detector of the extremely weak radiation as a variometer of gravitation field].

It was shown that the detector of extremely weak radiation with selectively increased sensitivity to the nonelectromagnetic, including the gravitational component of the spectrum of active physical fields can be used as the basis for constructing a variometer of gravitational field of a new type. PMID:11605376

Gorshkov, E S; Bondarenko, E G; Shapovalov, S N; Sokolovski?, V V; Troshichev, O A

257

Gravitational lensing as a tool for determining the age of the Universe

NASA Astrophysics Data System (ADS)

The main objective of this project is to determine cosmological parameters (e.g., the Hubble parameter) and to measure the mass-to-light distribution in galaxies using gravitationally lensed quasars, which are among the most promising objects for measuring cosmological distances, hence the age of the Universe. We have been conducting long-term photometric monitoring programmes of multiply imaged quasars at The Nordic Optical Telescope (NOT, La Palma, Canary Islands) and at the 1.54m Danish telescope (La Silla, Chile). The data have been obtained on a weekly basis. Four time delays have been measured since the programme started in 1998, for the systems B1600+434, RXJ0911+0550, SBS1520+530 (observed at the NOT) and HE2149-2745 (observed at the 1.5m Danish). Microlensing effects have been detected in the lightcurves of three out of the four systems studied, indicating that such effects are common at optical wavelengths. We argue that spectrophotometric monitoring and multiband imaging are the best methods to distinguish microlensing effects from intrinsic variations in order (1) to improve the time delay measurement and hence the estimates of H0, and (2) to study the microlensing signal in order to constrain source size (quasar) and compact mass in the deflector (lensing galaxy). By combining the H0 values obtained in this project and the H0 estimates from other lensed systems in the literature a mean value H0=60+/-4 km/s/Mpc (95% confidence) is calculated, which is in agreement with estimates from other methods. The small uncertainty in this mean value confirms that this method may yield statistically accurate results in spite of the seemingly large systematic errors in the individual systems.

Burud, Ingunn

2001-07-01

258

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

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

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

2010-08-20

259

Spurious shear in weak lensing with the Large Synoptic Survey Telescope

NASA Astrophysics Data System (ADS)

The complete 10-yr survey from the Large Synoptic Survey Telescope (LSST) will image ˜20 000 deg2 of the sky in six filter bands every few nights, bringing the final survey depth to r ˜ 27.5, with over four billion well-measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high-fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterize the atmospheric point spread function due to its high-frequency spatial variation on angular scales smaller than ˜10 arcmin in the single short exposures, which propagates into a spurious shear correlation function at the 10-4-10-3 level on these scales. With the large multi-epoch data set that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.

Chang, C.; Kahn, S. M.; Jernigan, J. G.; Peterson, J. R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R. R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M. A.; Jee, M. J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P. J.; Marshall, S.; Meert, A.; Nagarajan, S.; Peng, E.; Rasmussen, A. P.; Shmakova, M.; Sylvestre, N.; Todd, N.; Young, M.

2013-01-01

260

Constraining dark energy evolution with gravitational lensing by large scale structures

NASA Astrophysics Data System (ADS)

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 dark energy parameter degeneracies with the mass power spectrum shape ?, normalization ?8, and with the matter mean density ?M. We find that degeneracies are such that weak lensing turns out to be a good probe of dark energy evolution, even with limited knowledge on ?, ?8, and ?M. This result is a strong motivation for performing large scale structure simulations beyond the simple constant dark energy models, in order to calibrate the nonlinear regime accurately. Such calibration could then be used for any large scale structure tests of dark energy evolution. Prospective for the Canada France Hawaii Telescope Legacy Survey and Super-Novae Acceleration Probe are given. These results complement nicely the cosmic microwave background and supernovae constraints.

Benabed, Karim; van Waerbeke, Ludovic

2004-12-01

261

Weak lensing B modes on all scales as a probe of local isotropy

NASA Astrophysics Data System (ADS)

This article introduces a new multipolar hierarchy for the propagation of the weak-lensing shear, convergence, and twist valid in a general spacetime. Our approach is fully covariant and relies on no perturbative expansion. We show that the origin of B modes, in particular on large angular scales, is related to deviations of isotropy of the spacetime. Known results assuming a Friedmann-Lemaître background spacetime are naturally recovered. The example of a Bianchi I spacetime illustrates our formalism and its implications for future observations are stressed.

Pitrou, Cyril; Uzan, Jean-Philippe; Pereira, Thiago S.

2013-02-01

262

NASA Astrophysics Data System (ADS)

The gravitational lens system CLASS B2108+213 has two radio-loud lensed images separated by 4.56 arcsec. The relatively large image separation implies that the lensing is caused by a group of galaxies. In this paper, new optical imaging and spectroscopic data for the lensing galaxies of B2108+213 and the surrounding field galaxies are presented. These data are used to investigate the mass and composition of the lensing structure. The redshift and stellar velocity dispersion of the main lensing galaxy (G1) are found to be z = 0.3648 +/- 0.0002 and ?v = 325 +/- 25 kms-1, respectively. The optical spectrum of the lensed quasar shows no obvious emission or absorption features, and is consistent with a BL Lac type radio source. However, the tentative detection of the G-band and Mg-b absorption lines, and a break in the spectrum of the host galaxy of the lensed quasar gives a likely source redshift of z = 0.67. Spectroscopy of the field around B2108+213 finds 51 galaxies at a similar redshift to G1, thus confirming that there is a much larger structure at z ~ 0.365 associated with this system. The width of the group velocity distribution is 694 +/- 93 kms-1, but is non-Gaussian, implying that the structure is not yet viralized. The main lensing galaxy is also the brightest group member and has a surface brightness profile consistent with a typical cD galaxy. A lensing and dynamics analysis of the mass distribution, which also includes the newly found group members, finds that the logarithmic slope of the mass density profile is on average isothermal inside the Einstein radius, but steeper at the location of the Einstein radius. This apparent change in slope can be accounted for if an external convergence gradient, representing the underlying parent halo of the galaxy group, is included in the mass model.

McKean, J. P.; Auger, M. W.; Koopmans, L. V. E.; Vegetti, S.; Czoske, O.; Fassnacht, C. D.; Treu, T.; More, A.; Kocevski, D. D.

2010-05-01

263

We report the discovery of the two-image gravitationally lensed quasar SDSS J133222.62+034739.9 (SDSS J1332+0347) with an image separation of {Delta}{theta} = 1.14''. This system consists of a source quasar at z{sub s} = 1.445 and a lens galaxy at z{sub l} = 0.191. The agreement of the luminosity, ellipticity and position angle of the lens galaxy with those expected from lens model confirms the lensing hypothesis.

Morokuma, Tomoki; Inada, Naohisa; Oguri, Masamune; Ichikawa, Shin-Ichi; Kawano, Yozo; Tokita, Kouichi; Kayo, Issha; Hall, Patrick B.; Kochanek, Christopher S.; Richards, Gordon T.; York, Donald G.; Schneider, Donald P.; /Tokyo U., Inst. Astron. /KIPAC, Menlo Park /Princeton U. /Tokyo, Astron. Observ. /Nagoya U. /York U., Canada /Ohio State U., Dept. Astron. /Johns Hopkins U. /Drexel U. /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI /Penn State U., Astron. Astrophys.

2006-09-28

264

Correlation of CMB with large-scale structure. II. Weak lensing

We investigate the correlation of gravitational lensing of the cosmic microwave background (CMB) with several tracers of large-scale structure, including luminous red galaxies (LRGs), quasars, and radio sources. The lensing field is reconstructed based on the CMB maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite; the LRGs and quasars are observed by the Sloan Digital Sky Survey (SDSS); and the radio sources are observed in the NRAO VLA Sky Survey (NVSS). Combining all three large-scale structure samples, we find evidence for a positive cross correlation at the 2.5{sigma} level (1.8{sigma} for the SDSS samples and 2.1{sigma} for NVSS); the cross correlation amplitude is 1.06{+-}0.42 times that expected for the WMAP cosmological parameters. Our analysis extends other recent analyses in that we carefully determine bias-weighted redshift distribution of the sources, which is needed for a meaningful cosmological interpretation of the detected signal. We investigate contamination of the signal by galactic emission, extragalactic radio and infrared sources, thermal and kinetic Sunyaev-Zel'dovich effects, and the Rees-Sciama effect, and find all of them to be negligible.

Hirata, Christopher M. [California Institute of Technology M/C 130-33, Pasadena, California 91125 (United States); Ho, Shirley; Bahcall, Neta A. [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, New Jersey 08544 (United States); Padmanabhan, Nikhil [Lawrence Berkeley National Labs, 1 Cyclotron Road Mississippi 50R-5032, Berkeley, California 94720 (United States); Seljak, Uros [Institute for Theoretical Physics, University of Zurich, 8057 Zurich (Switzerland); International Center for Theoretical Physics, 34014 Trieste (Italy); Department of Physics, University of California at Berkeley, Berkeley, California 94720 (United States)

2008-08-15

265

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

266

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

267

NASA Astrophysics Data System (ADS)

Gravitational lenses have the potential to be excellent tools for investigating the Universe. This thesis describes the Cosmic Lens All-Sky Survey (CLASS), a program to find new gravitational lenses, and presents data on two newly-discovered lenses, 1608+656 and 2045+265. One of the major goals of CLASS is to find ``golden lenses,'' which can be used to measure the Hubble Constant (H0). The 1608+656 system contains four images of the background source. The lensing galaxy is at a redshift of zl = 0.630, while the background source is at zs = 1.394. Ground-based optical and infrared images clearly show the lensing galaxy. Images taken with the Hubble Space Telescope further resolve the lensing galaxy into two distinct objects, which may be a merging pair of galaxies. Radio maps of the 2045+265 system also show four images of the background source. In addition, a fifth component appears in the maps. The radio spectrum of the fifth component is significantly different from the spectra of the other four components, and its location matches that of the lensing galaxy to within the positional errors. Therefore, it appears that the fifth component is the flat-spectrum core of the lensing galaxy. The redshift of the lensing galaxy is zl = 0.8673. The redshift of the background source is z s = 1.28, based on one broad emission line. I conducted a dedicated monitoring program on 1608+656 with the Very Large Array from October 1996 to May 1997. The observations took place, on average, every four days. The calibrated light curves for components A, B, C, and D show variations in flux density at the 3-5% level. The time delays between the light curves are DtBA=30+5-7 d,DtBC

Fassnacht, Christopher D.

1999-07-01

268

NASA Astrophysics Data System (ADS)

Gravitational lensing and stellar dynamics are two independent methods, based solely on gravity, to study the mass distributions of galaxies. Both methods suffer from degeneracies, however, that are difficult to break. In this paper we present a new framework that self-consistently unifies gravitational lensing and stellar dynamics, breaking some classical degeneracies that have limited their individual usage, particularly in the study of high-redshift galaxies. For any given galaxy potential, the mapping of both the unknown lensed source brightness distribution and the stellar phase-space distribution function onto the photometric and kinematic observables can be cast as a single set of coupled linear equations, which are solved by maximizing the likelihood penalty function. The Bayesian evidence penalty function subsequently allows one to find the best potential-model parameters and to quantitatively rank potential-model families or other model assumptions (e.g., PSF). We have implemented a fast algorithm that solves for the maximum-likelihood pixelized lensed source brightness distribution and the two-integral stellar phase-space distribution function f(E,Lz), assuming axisymmetric potentials. To make the method practical, we have devised a new Monte Carlo approach to Schwarzschild's orbital superposition method, based on the superposition of two-integral (E and Lz) toroidal components, to find the maximum-likelihood two-integral distribution function in a matter of seconds in any axisymmetric potential. The nonlinear parameters of the potential are subsequently found through a hybrid MCMC and Simplex optimization of the evidence. Illustrated by the power-law potential models of Evans, we show that the inclusion of stellar kinematic constraints allows the correct linear and nonlinear model parameters to be recovered, including the potential strength, oblateness, and inclination, which, in the case of gravitational-lensing constraints only, would otherwise be fully degenerate.

Barnabè, Matteo; Koopmans, Léon V. E.

2007-09-01

269

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

270

Sixty percent of gamma-ray bursts (GRBs) reveal strong Mg II absorbing systems, which is a factor of {approx}2 times the rate seen along lines of sight to quasars. Previous studies argue that the discrepancy in the strong Mg II covering factor is most likely to be the result of either quasars being obscured due to dust or the consequence of many GRBs being strongly gravitationally lensed. We analyze observations of quasars that show strong foreground Mg II absorption. We find that GRB lines of sight pass closer to bright galaxies than would be expected for random lines of sight within the impact parameter expected for strong Mg II absorption. While this cannot be explained by obscuration in the GRB sample, it is a natural consequence of gravitational lensing. Upon examining the particular configurations of galaxies near a sample of GRBs with strong Mg II absorption, we find several intriguing lensing candidates. Our results suggest that lensing provides a viable contribution to the observed enhancement of strong Mg II absorption along lines of sight to GRBs, and we outline the future observations required to test this hypothesis conclusively.

Rapoport, Sharon; Onken, Christopher A.; Schmidt, Brian P.; Tucker, Brad E. [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); Wyithe, J. Stuart B. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Levan, Andrew J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

2012-08-01

271

We compare the efficiency of weak-lensing-selected galaxy cluster counts and of the weak-lensing bispectrum at capturing non-Gaussian features in the dark matter distribution. We use the halo model to compute the weak-lensing power spectrum, the bispectrum, and the expected number of detected clusters, and derive constraints on cosmological parameters for a large, low systematic weak-lensing survey, by focusing on the OMEGA{sub m}-sigma{sub 8} plane and on the dark energy equation of state. We separate the power spectrum into the resolved and the unresolved parts of the data, the resolved part being defined as detected clusters, and the unresolved part as the rest of the field. We consider four kinds of clusters counts, taking into account different amount of information: signal-to-noise ratio peak counts, counts as a function of clusters' mass, counts as a function of clusters' redshift, and counts as a function of clusters' mass and redshift. We show that when combined with the power spectrum, those four kinds of counts provide similar constraints, thus allowing one to perform the most direct counts, signal-to-noise peak counts, and get percent level constraints on cosmological parameters. We show that the weak-lensing bispectrum gives constraints comparable to those given by the power spectrum and captures non-Gaussian features as well as cluster counts, its combination with the power spectrum giving errors on cosmological parameters that are similar to, if not marginally smaller than, those obtained when combining the power spectrum with cluster counts. We finally note that in order to reach its potential, the weak-lensing bispectrum must be computed using all triangle configurations, as equilateral triangles alone do not provide useful information. The appendices summarize the halo model, and the way the power spectrum and bispectrum are computed in this framework.

Berge, Joel [Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, MS 169-327, Pasadena, CA 91109 (United States); Amara, Adam [Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland); Refregier, Alexandre, E-mail: Joel.Berge@jpl.nasa.go [Laboratoire AIM, CEA/DSM, CNRS, Universite Paris Diderot, DAPNIA/SAp, 91191 Gif-sur-Yvette (France)

2010-04-01

272

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

273

NASA Astrophysics Data System (ADS)

We have selected 42 elliptical galaxies from the literature and estimated their velocity dispersions at the effective radius (?Re) and at 0.54 effective radii (?0.54Re). We find by a dynamical analysis that the normalized velocity dispersion of the dark halo of an elliptical galaxy ?DM is roughly ?Re multiplied by a constant, which is almost independent of the core radius or the anisotropy parameter of each galaxy. Our sample analysis suggests that ?DM* lies in the range 178-198 km s-1. The power law relation we find between the luminosity and the dark matter velocity dispersion measured in this way is (L/L*)=(?DM/?DM*)?, where /? is between 2 and 3. These results are of interest for strong gravitational lensing statistics studies. In order to determine the value of ?DM*, we calculate MBT* in the same BT band in which ?DM* has been estimated. We select 131 elliptical galaxies as a complete sample set with apparent magnitudes BT between 9.26 and 12.19. We find that the luminosity function is well fitted to the Schechter form, with parameters MBT*=-19.66+5.log10h+/-0.30, /?=0.15+/-0.55, and the normalization constant ?*=(1.34+/-0.30)×10-3h3 Mpc-3, with the Hubble constant Ho=100 /h km s-1 Mpc-1. This normalization implies that morphology type E galaxies make up (10.8 /+/- 1.2) per cent of all galaxies.

Cheng, Y.-C. N.; Krauss, L. M.

2001-06-01

274

Gravitationally lensed galaxies at 2 < z < 3.5: direct abundance measurements of Ly ? emitters

NASA Astrophysics Data System (ADS)

Strong gravitational lensing magnifies the flux from distant galaxies, allowing us to detect emission lines that would otherwise fall below the detection threshold for medium-resolution spectroscopy. Here we present the detection of temperature-sensitive oxygen emission lines from three galaxies at 2 ? z ? 3.5, which enables us to directly determine the oxygen abundances and thereby double the number of galaxies at z > 2 for which this has been possible. The three galaxies have ˜10 per cent solar oxygen abundances in agreement with strong emission-line diagnostics. Carbon and nitrogen ratios relative to oxygen are subsolar as expected for young metal-poor galaxies. Two of the galaxies are Lyman ? (Ly?) emitters with rest-frame equivalent widths of 20 and 40 Å, respectively, and their high magnification factors allow us for the first time to gain insight into the physical characteristics of high-redshift Ly? emitters. Using constraints from the physical properties of the galaxies, we accurately reproduce their line profiles with radiative transfer models. The models show a relatively small outflow in agreement with the observed small velocity offsets between nebular emission and interstellar absorption lines. Based on data from the X-shooter GTO observations collected at the European Southern Observatory VLT/Kuyuen telescope, Paranal, Chile, collected under programme IDs: 084.B-0351(D), 086.A-0674(A), 086.A-0674(B), 087.A-0432(A) and 087.A-0432(B).

Christensen, Lise; Laursen, Peter; Richard, Johan; Hjorth, Jens; Milvang-Jensen, Bo; Dessauges-Zavadsky, Miroslava; Limousin, Marceau; Grillo, Claudio; Ebeling, Harald

2012-12-01

275

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

276

Critical Lines in Gravitational Lenses and the Determination of Cosmological Parameters

NASA Astrophysics Data System (ADS)

We investigate the cosmological test recently done by Fort, Mellier, & Dantel-Fort (FMD), in which the observed location of the critical line in gravitational lensing is used to determine the cosmological parameters Omega and lambda . Applying this method to the cluster of galaxies Cl 0024+1654, FMD obtained a bound on the cosmological constant, lambda > 0.6, assuming the spatially flat universe. The fact that the angular diameter distance-redshift relation depends on the cosmological models through the cosmological parameters plays a crucial role in this method. Using the angular diameter distance in the Friedmann-Lemaitre-Robertson-Walker universe for a wide range of cosmological parameters, we show that it is difficult to determine Omega by this method without the assumption of the spatially flat universe. Moreover, the uncertainty of the lens model is also mentioned, which is regarded as one of the most serious problems in this test. As a result, this method cannot be taken as a clear cosmological test to determine lambda , although one may put a bound on lambda by the use of many clusters of galaxies.

Asada, Hideki

1997-08-01

277

A Lower Limit on Omega_m-Omega_Lambda Using Gravitational Lensing in the Hubble Deep Field

NASA Astrophysics Data System (ADS)

We calculate the expected number of multiply imaged galaxies in the Hubble Deep Field (HDF), using photometric redshift information for galaxies with m_I<27 that were detected in all four HDF passbands. A comparison of these expectations with the observed number of strongly lensed galaxies places a lower limit on the current value of Omega_m-Omega_Lambda, where Omega_m is the cosmological mass density of the universe and Omega_Lambda is the normalized cosmological constant. Based on current estimates of the HDF luminosity function and associated uncertainties in individual parameters, our 95% confidence lower limit on Omega_m-Omega_Lambda is between -0.44, if there are no strongly lensed galaxies in the HDF, and -0.73, if there are two strongly lensed galaxies in the HDF. For a flat universe (Omega_m+Omega_Lambda=1), Omega_Lambda<0.58-0.79 (95% confidence limit). If the only lensed galaxy in the HDF is the one presently viable candidate, then in a flat universe (Omega_m+Omega_Lambda=1), Omega_Lambda<0.79 (95% confidence limit). These lower limits are compatible with estimates based on high-redshift supernovae and with previous limits based on gravitational lensing.

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

1999-02-01

278

The Canadian Cluster Comparison Project: weak lensing masses and SZ scaling relations

NASA Astrophysics Data System (ADS)

The Canadian Cluster Comparison Project is a comprehensive multi-wavelength survey targeting 50 massive X-ray selected clusters of galaxies to examine baryonic tracers of cluster mass and to probe the cluster-to-cluster variation in the thermal properties of the hot intra-cluster medium. In this paper we present the weak lensing masses, based on the analysis of deep wide field imaging data obtained using the Canada-France-Hawaii Telescope. The final sample includes two additional clusters that were located in the field-of-view. We take these masses as our reference for the comparison of cluster properties at other wavelengths. In this paper we limit the comparison to published measurements of the Sunyaev-Zel'dovich effect. We find that this signal correlates well with the projected lensing mass, with an intrinsic scatter of 12 ± 5 per cent at ˜r2500, demonstrating it is an excellent proxy for cluster mass. Based on observations from the Canada-France-Hawaii Telescope, which is operated by the National Research Council of Canada, le Centre National de la Recherche Scientifique and the University of Hawaii.

Hoekstra, Henk; Mahdavi, Andisheh; Babul, Arif; Bildfell, Chris

2012-12-01

279

NASA Astrophysics Data System (ADS)

Quasar-galaxy associations can be explained as gravitational lensing by globular clusters, located in the halos of the foreground galaxies and dwarf galaxies in small groups of galaxies. We propose an observational test for checking this hypothesis. We used the SUPERCOSMOS sky survey to find the overdensities of star-like sources with zero proper motions in the vicinities of the~foreground galaxies from the CfA3 catalog. The results obtained for 19413 galaxies are presented. We show the results of calculations of number densities of star-like sources with zero proper motions in the vicinity of 19413 galaxies. Two different effects can explain the observational data: lensing by globular clusters and lensing by dwarf galaxies. We carried out the CCD 3-color photometry with the 2.0-m telescope of the~Terskol Observatory and the 1.8-m telescope of the Bohyunsan Observatory (South Korea) to select extremely lensed objects around several galaxies for future spectroscopic observations. From ads Wed Jan 12 06:25:17 2005 Return-Path:

Yushchenko, A.; Kim, C.; Sergeev, A.

2003-04-01

280

A fast empirical method for galaxy shape measurements in weak lensing surveys

NASA Astrophysics Data System (ADS)

We describe a simple and fast method to correct ellipticity measurements of galaxies from the distortion by the instrumental and atmospheric point spread function (PSF), in view of weak lensing shear measurements. The method performs a classification of galaxies and associated PSFs according to measured shape parameters, and corrects the measured galaxy ellipticites by querying a large lookup table (LUT), built by supervised learning. We have applied this new method to the GREAT10 image analysis challenge, and present in this paper a refined solution that obtains the competitive quality factor of Q = 104, without any shear power spectrum denoising or training. Of particular interest is the efficiency of the method, with a processing time below 3 ms per galaxy on an ordinary CPU.

Tewes, M.; Cantale, N.; Courbin, F.; Kitching, T.; Meylan, G.

2012-08-01

281

Shape Reconstruction and Weak Lensing Measurement with Interferometers: A Shapelet Approach

NASA Astrophysics Data System (ADS)

We present a new approach for image reconstruction and weak lensing measurements with interferometers. Based on the shapelet formalism presented by Refregier, object images are decomposed into orthonormal Hermite basis functions. The shapelet coefficients of a collection of sources are simultaneously fitted on the uv plane, the Fourier transform of the sky brightness distribution observed by interferometers. The resulting ?2-fit is linear in its parameters and can thus be performed efficiently by simple matrix multiplications. We show how the complex effects of bandwidth smearing, time averaging, and non-coplanarity of the array can be easily and fully corrected for in our method. Optimal image reconstruction, co-addition, astrometry, and photometry can all be achieved using weighted sums of the derived coefficients. As an example we consider the observing conditions of the FIRST radio survey. We find that our method accurately recovers the shapes of simulated images even for the sparse uv sampling of this snapshot survey. Using one of the FIRST pointings, we find our method compares well with CLEAN, the commonly used method for interferometric imaging. Our method has the advantage of being linear in the fit parameters, of fitting all sources simultaneously, and of providing the full covariance matrix of the coefficients, which allows us to quantify the errors and cross-talk in image shapes. It is therefore well suited for quantitative shape measurements which require high precision. In particular, we show how our method can be combined with the results of Refregier & Bacon to provide an accurate measurement of weak lensing from interferometric data.

Chang, Tzu-Ching; Refregier, Alexandre

2002-05-01

282

NASA Astrophysics Data System (ADS)

Understanding the distribution of mass on cosmic scales provides context for a number of astrophysical topics, including galaxy evolution, structure formation, and cosmology. In this dissertation, I present new research into the distribution of mass throughout the universe, ranging from small (sub-galactic) to large (Supercluster) scales. This work is spread over four separate studies, each focusing on slightly different cosmological distance scales. In the first study, I employ strong and weak gravitational lensing to measure the mass profiles of a sample of massive elliptical galaxies at moderate redshift (z ˜ 0.6). I find that the total mass profile is best described by an isothermal (r -2) distribution, which disagrees with predictions made by numerical simulations. This disagreement provides important clues about the poorly understood interactions between dark matter and baryons. Furthermore, I compare these results to those of a low-redshift (z ˜ 0.2) galaxy sample, and this allows me to constrain the evolution of galaxy-scale mass profiles over a timescale of ˜ 7 billion years. In the second and third studies, I combine strong lensing constraints and high-resolution adaptive optics imaging to develop new mass models for the lens systems B0128+437 and B1938+666. I use these models to search for the presence of small-scale substructures (satellite galaxies) in the vicinity of the host lens. While structure formation models predict a large number of substructure galaxies orbiting a host, this does not agree with observations of the local universe, where only a handful of satellites are seen. I compare the upper-limit substructure constraints from the two strong lenses to the properties of known Milky Way satellites, and lay the foundation for a comprehensive census of extragalactic substructure, using a large sample of lenses to better resolve the tension between theory and observation. Finally, in the fourth study, I focus on mass at super-galactic scales, utilizing weak lensing to probe the structure of the high-redshift ( z ˜ 0.9) supercluster Cl 1604. Using deep Hubble Space Telescope imaging, I create the first ever two-dimensional mass map of the full supercluster field, and measure the virial masses of the three largest individual clusters. With this measurement, I constrain the mass environments of bound systems at earlier cosmological epochs, and provide complementary information to an already rich data set.

Lagattuta, David James

283

The Optical Gravitational Lensing Experiment. Gaia South Ecliptic Pole Field as Seen by OGLE-IV

NASA Astrophysics Data System (ADS)

We present a comprehensive analysis of the Gaia South Ecliptic Pole (GSEP) field, 5.3 square degrees area around the South Ecliptic Pole on the outskirts of the LMC, based on the data collected during the fourth phase of the Optical Gravitational Lensing Experiment, OGLE-IV. The GSEP field will be observed during the commissioning phase of the ESA Gaia space mission for testing and calibrating the Gaia instruments. We provide the photometric maps of the GSEP region containing the mean VI photometry of all detected stellar objects and their equatorial coordinates. We show the quality and completeness of the OGLE-IV photometry and color-magnitude diagrams of this region. We conducted an extensive search for variable stars in the GSEP field leading to the discovery of 6789 variable stars. In this sample we found 132 classical Cepheids, 686 RR Lyr type stars, 2819 long-period, and 1377 eclipsing variables. Several objects deserving special attention were also selected, including a new classical Cepheid in a binary eclipsing system. To provide empirical data for the Gaia Science Alert system we also conducted a search for optical transients. We discovered two firm type Ia supernovae and nine additional supernova candidates. To facilitate future Gaia supernovae detections we prepared a list of more than 1900 galaxies to redshift about 0.1 located in the GSEP field. Finally, we present the results of astrometric study of the GSEP field. With the 26 months time base of the presented here OGLE-IV data, proper motions of stars could be detected with the accuracy reaching 2 mas/yr. Astrometry allowed to distinguish galactic foreground variable stars detected in the GSEP field from LMC objects and to discover about 50 high proper motion stars (proper motion ? 100 mas/yr). Among them three new nearby white dwarfs were found. All data presented in this paper are available to the astronomical community from the OGLE Internet archive.

Soszy?ski, I.; Udalski, A.; Poleski, R.; Koz?owski, S.; Wyrzykowski, ?.; Pietrukowicz, P.; Szyma?ski, M. K.; Kubiak, M.; Pietrzy?ski, G.; Ulaczyk, K.; Skowron, J.

2012-09-01

284

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

2007-10-04

285

NASA Astrophysics Data System (ADS)

The validity of modified Newtonian dynamics (MOND) and tensor vector scalar (TeVeS) models of modified gravity has been recently tested by using lensing techniques, with the conclusion that a nontrivial component in the form of dark matter is needed in order to match the observations. In this work, those analyses are extended by comparing lensing to stellar masses for a sample of nine strong gravitational lenses which probe galactic scales. The sample is extracted from a recent work which presents the mass profile out to a few effective radii, therefore reaching into regions which are dominated by dark matter in the standard (general relativity) scenario. A range of interpolating functions are explored to test the validity of MOND/TeVeS in these systems. Out of the nine systems, there are five robust candidates with a significant excess (higher than 50%) of lensing mass with respect to stellar mass, irrespective of the stellar initial mass function. One of these lenses (Q0957) is located at the center of a galactic cluster. This system might be accommodated in MOND/TeVeS via the addition of a hot component, like a 2 eV neutrino, which contributes over cluster scales. However, the other four robust candidates (LBQS1009, HE1104, B1600, HE2149) are located in field/group regions, so that a cold component (cold dark matter) would be required even within the MOND/TeVeS framework. Our results, therefore, do not support recent claims that these alternative scenarios to cold dark matter can survive astrophysical data.

Ferreras, Ignacio; Mavromatos, Nick E.; Sakellariadou, Mairi; Yusaf, Muhammad Furqaan

2012-10-01

286

Nebular and global properties of the gravitationally lensed galaxy "the 8 o'clock arc"

NASA Astrophysics Data System (ADS)

We present the analysis of new near-infrared, intermediate-resolution spectra of the gravitationally lensed galaxy "the 8 o'clock arc" at zsys = 2.7350 obtained with the X-shooter spectrograph on the Very Large Telescope. These rest-frame optical data, combined with Hubble and Spitzer Space Telescopes images, provide very valuable information, which nicely complement our previous detailed rest-frame UV spectral analysis, and make the 8 o'clock arc one of the better understood "normal" star-forming galaxies at this early epoch of the history of the Universe. From high-resolution HST images, we reconstruct the morphology of the arc in the source plane, and identify that the source is formed of two majors parts, the main galaxy component and a smaller blob separated by 1.2 kpc in projected distance. The blob, with a twice larger magnification factor, is resolved in the X-shooter spectra. The multi-Gaussian fitting of detected nebular emission lines and the spectral energy distribution modeling of the available multi-wavelength photometry provide the census of gaseous and stellar dust extinctions, gas-phase metallicities, star-formation rates (SFRs), and stellar, gas, and dynamical masses for both the main galaxy and the blob. As a result, the 8 o'clock arc shows a marginal trend for a more attenuated ionized gas than stars, and supports a dependence of the dust properties on the SFR. With a high specific star-formation rate, SSFR = 33 ± 19 Gyr-1, this lensed Lyman-break galaxy deviates from the mass-SFR relation, and is characterized by a young age of 40+25-20 Myr and a high gas fraction of about 72%. The 8 o'clock arc satisfies the fundamental mass, SFR, and metallicity relation, and favors that it holds up beyond z ? 2.5. We believe that the blob, with a gas mass Mgas = (2.2 ± 0.9) × 109 M? (one order of magnitude lower than the mass of the galaxy), a half-light radius r1/2 = 0.53 ± 0.05 kpc, a star-formation rate SFRH? = 33 ± 19 M? yr-1, and in rotation around the main core of the galaxy, is one of these star-forming clumps commonly observed in z > 1 star-forming galaxies, because it is characterized by very similar physical properties. The knowledge of detailed physical properties of these clumps is a very useful input to models that aim to predict the formation and evolution of these clumps within high-redshift objects. Based on X-shooter observations made with the European Southern Observatory VLT/Kueyen telescope, Paranal, Chile, collected under the programme ID No. 284.A-5006(A).Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute.

Dessauges-Zavadsky, M.; Christensen, L.; D'Odorico, S.; Schaerer, D.; Richard, J.

2011-09-01

287

Cross-correlation Weak Lensing of SDSS Galaxy Clusters I: Measurements

This is the first in a series of papers on the weak lensing effect caused by clusters of galaxies in Sloan Digital Sky Survey. The photometrically selected cluster sample, known as MaxBCG, includes {approx}130,000 objects between redshift 0.1 and 0.3, ranging in size from small groups to massive clusters. We split the clusters into bins of richness and luminosity and stack the surface density contrast to produce mean radial profiles. The mean profiles are detected over a range of scales, from the inner halo (25 kpc/h) well into the surrounding large scale structure (30 Mpc/h), with a significance of 15 to 20 in each bin. The signal over this large range of scales is best interpreted in terms of the cluster-mass cross-correlation function. We pay careful attention to sources of systematic error, correcting for them where possible and bounding them where not. We find that the profiles scale strongly with richness and luminosity. We find the signal within a given richness bin depends upon luminosity, suggesting that luminosity is more closely correlated with mass than galaxy counts. We split the samples by redshift but detect no significant evolution. The profiles are not well described by power laws. In a subsequent series of papers we invert the profiles to three-dimensional mass profiles, show that they are well fit by a halo model description, measure mass-to-light ratios and provide a cosmological interpretation.

Sheldon, Erin S.; Johnston, David E.; Scranton, Ryan; Koester, Ben P.; McKay, Timothy A.; Oyaizu, Hiroaki; Cunha, Carlos; Lima, Marcos; Lin, Huan; Frieman, Joshua A.; Wechsler, Risa H.; Annis, James; Mandelbaum, Rachel; Bahcall, Neta A.; Fukugita, Masataka

2007-09-28

288

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 J.; 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., Urbana, Astron. Dept. /UC, Davis /LLNL, Livermore /Barcelona, IEEC /York U., Canada /Heidelberg, Max Planck Inst. Astron. /Penn State U., Astron. Astrophys. /Apache Point Observ. /Chicago U., EFI

2004-11-01

289

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

290

Localized electromagnetic and weak gravitational fields in the source-free space

NASA Astrophysics Data System (ADS)

Localized electromagnetic and weak gravitational time-harmonic fields in the source-free space are treated using expansions in plane waves. The presented solutions describe fields having a very small (about several wavelengths) and clearly defined core region with maximum intensity of field oscillations. In a given Lorentz frame L, a set of the obtained exact time-harmonic solutions of the free-space homogeneous Maxwell equations consists of three subsets (storms, whirls, and tornados), for which time average energy flux is identically zero at all points, azimuthal and spiral, respectively. In any other Lorentz frame L', they will be observed as a kind of electromagnetic missile moving without dispersing at speed V

Borzdov, G. N.

2001-03-01

291

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

292

Tomographic weak-lensing shear spectra from large N-body and hydrodynamical simulations

NASA Astrophysics Data System (ADS)

Context. Forthcoming experiments will enable us to determine tomographic shear spectra at a high precision level. Most predictions about them have until now been based on algorithms yielding the expected linear and non-linear spectrum of density fluctuations. Even when simulations have been used, so-called Halofit predictions on fairly large scales have been needed. Aims: We wish to go beyond this limitation. Methods: We perform N-body and hydrodynamical simulations within a sufficiently large cosmological volume to allow a direct connection between simulations and linear spectra. While covering large length-scales, the simulation resolution is good enough to allow us to explore the high-? harmonics of the cosmic shear (up to ? ~ 50 000), well into the domain where baryon physics becomes important. We then compare shear spectra in the absence and in presence of various kinds of baryon physics, such as radiative cooling, star formation, and supernova feedback in the form of galactic winds. Results: We distinguish several typical properties of matter fluctuation spectra in the different simulations and test their impact on shear spectra. Conclusions: We compare our outputs with those obtainable using approximate expressions for non-linear spectra, and identify substantial discrepancies even between our results and those of purely N-body results. Our simulations and the treatment of their outputs however enable us, for the first time, to obtain shear results that are fully independent of any approximate expression, also in the high-? range, where we need to incorporate a non-linear power spectrum of density perturbations and the effects of baryon physics. This will allow us to fully exploit the cosmological information contained in future high-sensitivity cosmic shear surveys, exploring the physics of cosmic shears via weak lensing measurements.

Casarini, L.; Bonometto, S. A.; Borgani, S.; Dolag, K.; Murante, G.; Mezzetti, M.; Tornatore, L.; La Vacca, G.

2012-06-01

293

Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data

A main science goal for the Large Synoptic Survey Telescope (LSST) is to measure the cosmic shear signal from weak lensing to extreme accuracy. One difficulty, however, is that with the short exposure time ({approx_equal}15 seconds) proposed, the spatial variation of the Point Spread Function (PSF) shapes may be dominated by the atmosphere, in addition to optics errors. While optics errors mainly cause the PSF to vary on angular scales similar or larger than a single CCD sensor, the atmosphere generates stochastic structures on a wide range of angular scales. It thus becomes a challenge to infer the multi-scale, complex atmospheric PSF patterns by interpolating the sparsely sampled stars in the field. In this paper we present a new method, psfent, for interpolating the PSF shape parameters, based on reconstructing underlying shape parameter maps with a multi-scale maximum entropy algorithm. We demonstrate, using images from the LSST Photon Simulator, the performance of our approach relative to a 5th-order polynomial fit (representing the current standard) and a simple boxcar smoothing technique. Quantitatively, psfent predicts more accurate PSF models in all scenarios and the residual PSF errors are spatially less correlated. This improvement in PSF interpolation leads to a factor of 3.5 lower systematic errors in the shear power spectrum on scales smaller than {approx} 13, compared to polynomial fitting. We estimate that with psfent and for stellar densities greater than {approx_equal}1/arcmin{sup 2}, the spurious shear correlation from PSF interpolation, after combining a complete 10-year dataset from LSST, is lower than the corresponding statistical uncertainties on the cosmic shear power spectrum, even under a conservative scenario.

Chang, C.; Marshall, P.J.; Jernigan, J.G.; Peterson, J.R.; Kahn, S.M.; Gull, S.F.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, S.; Meert, A.

2012-09-19

294

NASA Astrophysics Data System (ADS)

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 X) and halo mass (M 200) where M 200 is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 degrees2 of contiguous imaging with the Advanced Camera for Surveys to a limiting magnitude of I F814W = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 × 10-15 erg cm-2 s-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 200 vprop (L X)?, with a slope of ? = 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 X relation. The combination of our group data with previously published cluster data demonstrates that the M-L X relation is well described by a single power law, ? = 0.64 ± 0.03, over two decades in mass, M 200 ~ 1013.5-1015.5 h -1 72 M sun. These results are inconsistent at the 3.7? level with the self-similar prediction of ? = 0.75. We examine the redshift dependence of the M-L X relation and find little evidence for evolution beyond the rate predicted by self-similarity from z ~ 0.25 to z ~ 0.8. 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 with MegaPrime/MegaCam operated as a joint project by the Canada-France-Hawaii-Telescope 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.

Leauthaud, Alexie; Finoguenov, Alexis; Kneib, Jean-Paul; Taylor, James E.; Massey, Richard; Rhodes, Jason; Ilbert, Olivier; Bundy, Kevin; Tinker, Jeremy; George, Matthew R.; Capak, Peter; Koekemoer, Anton M.; Johnston, David E.; Zhang, Yu-Ying; Cappelluti, Nico; Ellis, Richard S.; Elvis, Martin; Giodini, Stefania; Heymans, Catherine; Le Fèvre, Oliver; Lilly, Simon; McCracken, Henry J.; Mellier, Yannick; Réfrégier, Alexandre; Salvato, Mara; Scoville, Nick; Smoot, George; Tanaka, Masayuki; Van Waerbeke, Ludovic; Wolk, Melody

2010-01-01

295

Constraints on f(R) cosmologies from strong gravitational lensing systems

NASA Astrophysics Data System (ADS)

f(R) gravity is thought to be an alternative to dark energy which can explain the acceleration of the universe. It has been tested by different observations including type Ia supernovae (SNIa), the cosmic microwave background (CMB), the baryon acoustic oscillations (BAO) and so on. In this Letter, we use the Hubble constant independent ratio between two angular diameter distances D=Dls/Ds to constrain f(R) model in Palatini approach f(R)=R-?H02(. These data are from various large systematic lensing surveys and lensing by galaxy clusters combined with X-ray observations. We also combine the lensing data with CMB and BAO, which gives a stringent constraint. The best-fit results are (?,?)=(-1.50,0.696) or (?m,?)=(0.0734,0.696) using lensing data only. When combined with CMB and BAO, the best-fit results are (?,?)=(-3.75,0.0651) or (?m,?)=(0.286,0.0651). If we further fix ?=0 (corresponding to ?CDM), the best-fit value for ? is ?=-4.84-0.68+0.91(1?)-0.98+1.63(2?) for the lensing analysis and ?=-4.35-0.16+0.18(1?)-0.25+0.3(2?) for the combined data, respectively. Our results show that ?CDM model is within 1? range.

Liao, Kai; Zhu, Zong-Hong

2012-07-01

296

NASA Astrophysics Data System (ADS)

Aims: Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay estimates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914. Methods: We monitored these doubly lensed quasars in the R-band using four telescopes: the Mercator, Maidanak, Himalayan Chandra, and Euler telescopes, together spanning a period of 7 to 8.5 observing seasons from mid-2004 to mid-2011. The photometry of the quasar images was obtained through simultaneous deconvolution of these data. The time delays were determined from these resulting light curves using four very different techniques: a dispersion method, a spline fit, a regression difference technique, and a numerical model fit. This minimizes the bias that might be introduced by the use of a single method. Results: The time delay for SDSS J1206+4332 is ?tAB = 111.3 ± 3 days with A leading B, confirming a previously published result within the error bars. For HS 2209+1914 we present a new time delay of ?tBA = 20.0 ± 5 days with B leading A. Conclusions: The combination of data from up to four telescopes have led to well-sampled and nearly 9-season-long light curves, which were necessary to obtain these results, especially for the compact doubly lensed quasar HS 2209+1914. Based on observations made with the 1.2-m Swiss Euler telescope (La Silla, Chile), the 1.5-m AZT-22 telescope (Maidanak Observatory, Uzbekistan), the 2.0-m HCT telescope (Hanle, India), and the 1.2-m Mercator Telescope. Mercator is operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Numerical values of light curves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/553/A121 and at http://www.cosmograil.org

Eulaers, E.; Tewes, M.; Magain, P.; Courbin, F.; Asfandiyarov, I.; Ehgamberdiev, Sh.; Rathna Kumar, S.; Stalin, C. S.; Prabhu, T. P.; Meylan, G.; Van Winckel, H.

2013-05-01

297

Gravitational lensing by clusters of galaxies in the millimetre/submillimetre waveband

NASA Astrophysics Data System (ADS)

Rich clusters of galaxies are observed to produce strongly magnified arcs and multiple images of background galaxies in the optical waveband. Here the properties of the equivalent images in the submillimetre waveband are discussed. Carefully designed submillimetre-wave surveys preferentially select galaxies at large redshifts, because the flux density-redshift relations for distant dusty star-forming galaxies are expected to be flat in this waveband, and so distant galaxies are much brighter as compared with observations in the optical waveband. For the same reason, submillimetre-wave observations are also ideally suited to detect the lensed images of very distant galaxies in clusters. Here we combine a model of a lensing cluster with predicted source counts of distant galaxies in the submillimetre waveband in order to investigate the form of the magnification bias introduced into the population of faint galaxies by lensing. A positive magnification bias corresponds to an increase in the surface density of galaxies. In the submillimetre waveband magnification biases can be large and positive, and depend strongly on the form of evolution of distant galaxies. New submillimetre-wave instruments and telescopes will allow galaxies at redshifts z~10 to be observed in as much detail as galaxies at z~=0.5, and we assess the practicality of detecting a useful sample of lensed images in the fields of clusters using both single-antenna telescopes and large interferometer arrays. The surface and flux densities of the lensed images in the submillimetre waveband are expected to exceed those of galaxies within the lensing cluster, and their values can be used to infer the form of evolution of star-forming galaxies since redshifts of about 10.

Blain, A. W.

1997-09-01

298

The statistical effects on the observed number counts of quasars due to amplification by gravitational light deflection are investigated. It is shown that the approximation of point sources, hitherto made in most studies of this effect, can cause misleading results: whereas for point sources any amplification-dominated source count necessarily has the canonical integral (logarithmic) slope of d log N/d log S = -2, this ceases to be true if a finite source extent is taken into account. It is demonstrated explicitly by considering a distribution of masses for the deflectors that lensing can account for slopes of source counts which lie between the canonical value of -2 and the intrinsic (unlensed) one, provided the latter is steeper than -2. The implications of this effect are briefly discussed. 21 references.

Schneider, P.

1987-05-01

299

NASA Astrophysics Data System (ADS)

According to f =d(mv)/dt=m(dv/dt)+ v(dm/dt), a same gravitational formula had been de-duced from the variance in physical mass of QFT and from the variance in mass of inductive energy-transfer of GR respectively: f QF T = f GR = -G (mM/r2 )((r/r)+(v/c)) when their interaction-constants are all taken the experimental values (H05-0029-08, E15-0039-08). f QF T is the quasi-Casimir pressure of net virtual neutrinos ? 0 flux (after counteract contrary direction ? 0 ). f GR is equivalent to Einstein's equation, then more easy to solve it. The hypothesis of the equivalent principle is not used in f QF T , but required by f GR . The predictions of f QF T and f GR are identical except that f QF T has quantum effects but f GR has not and f GR has Lense-Thirring effect but f QF T has not. The quantum effects of gravitation had been verified by Nesvizhevsky et al with the ultracold neutrons falling in the earth's gravitational field in 2002. Yet Lense-Thirring effect had not been measured by GP-B. It shows that f QF T is essential but f GR is phenomenological. The origin problem of the basis geo-electric and geomagnetic fields can be solved with the positive-negative charge center separation caused by f QF T , but cannot by f GR . The de Broglie wavelength of an electron is longer than that of a nucleon, and the section is larger, so is the net ? 0 flux pressure. The pressures difference between ? 0 flux on the electron and on the nucleon is as an extra pressure solely exerted on the electrons by ? 0 flux, which causes a gravitational polarization of the positive-negative charge center separation and increases the static electric force from the nucleus to the electrons along the opposite direction of ? 0 flux to offset the extra pressure on the electrons. At the same time, there must be a polarized static electric reaction force from the electrons to the nucleus along ? 0 flux direction, just like transferring the extra ? 0 flux pressure of the electrons to the nucleus. Therefore, the extra ? 0 flux pressure exerted on the whole atom is not actually offset by the static electric force from the positive-negative charge separation, i.e., the gravitation will be dependent of the com-position of matter. That is certainly true in the interaction between two isolated mass-points. But nothing can exist without environment. The masses tested in Cavendish's experiment, Eotvos's experiment and other precise gravitational experiments are not isolated mass-points. The electric polarization by ? 0 flux makes the testing mass and around (brackets, walls, houses) become the electric dipoles. In a way of relays the polarization of charge separation will be transported to the edge of the body, and make it become the electric dipole with the positive and negative charge on its two surfaces and the electric neutrality in the center. The interaction between the electric dipoles finally transfers the extra ? 0 flux pressure on the electrons from a body being tested onto the bodies around, i.e., the static electric force from the polarization of the bodies around offsets the extra ? 0 flux pressure on the electrons of testing mass. Because the electromagnetic force is 30 more orders of magnitude stronger than the ? 0 flux weak force, the slightly polarization of the bodies around can completely offset the extra ? 0 flux pressure on the electrons. The compensating action of the static forces between electric dipoles is equiv-alent to the equal section in unit mass of an electron and a nucleon. That is to say, the ? 0 flux pressure gives the same force and displacement to the electron and nucleon just like no positive-negative charge separation. Therefore, for gravitation, the mass of an electron can be converted to a proton, which makes the atom like a particle of absolutely electric neutrality comprising all neutrons, i.e., the macro-gravitation of non-isolated bodies is corresponding to the section only contributed by nucleons in atom. Then no matter how many electrons there are in the atom, the force is always in direct proportion to the

Chen, Shao-Guang

300

Probing the neutrino mass hierarchy with cosmic microwave background weak lensing

NASA Astrophysics Data System (ADS)

We forecast constraints on cosmological parameters with primary cosmic microwave background (CMB) anisotropy information and weak lensing reconstruction with a future post-Planck CMB experiment, the Cosmic Origins Explorer (COrE), using oscillation data on the neutrino mass splittings as prior information. Our Markov chain Monte Carlo (MCMC) simulations in flat models with a non-evolving equation of state of dark energy w give typical 68 per cent upper bounds on the total neutrino mass of 0.136 and 0.098 eV for the inverted and normal hierarchies, respectively, assuming the total summed mass is close to the minimum allowed by the oscillation data for the respective hierarchies (0.10 and 0.06 eV). Including geometric information from future baryon acoustic oscillation measurements with the complete Baryon Oscillation Spectroscopic Survey, Type Ia supernovae distance moduli from Wide-Field Infrared Survey Telescope (WFIRST) and a realistic prior on the Hubble constant, these upper limits shrink to 0.118 and 0.080 eV for the inverted and normal hierarchies, respectively. Addition of these distance priors also yields per cent-level constraints on w. We find tension between our MCMC results and the results of a Fisher matrix analysis, most likely due to a strong geometric degeneracy between the total neutrino mass, the Hubble constant and w in the unlensed CMB power spectra. If the minimal-mass, normal hierarchy were realized in nature, the inverted hierarchy should be disfavoured by the full data combination at typically greater than the 2? level. For the minimal-mass inverted hierarchy, we compute the Bayes factor between the two hierarchies for various combinations of our forecast data sets, and find that the future cosmological probes considered here should be able to provide 'strong' evidence (odds ratio 12:1) for the inverted hierarchy. Finally, we consider potential biases of the other cosmological parameters from assuming the wrong hierarchy and find that all biases on the parameters are below their 1? marginalized errors.

Hall, Alex C.; Challinor, Anthony

2012-09-01

301

COSMOS: STOCHASTIC BIAS FROM MEASUREMENTS OF WEAK LENSING AND GALAXY CLUSTERING

In the theory of structure formation, galaxies are biased tracers of the underlying matter density field. The statistical relation between galaxy and matter density field is commonly referred to as galaxy bias. In this paper, we test the linear bias model with weak-lensing and galaxy clustering measurements in the 2 deg{sup 2} COSMOS field. We estimate the bias of galaxies between redshifts z = 0.2 and z = 1 and over correlation scales between R = 0.2 h{sup -1} Mpc and R = 15 h{sup -1} Mpc. We focus on three galaxy samples, selected in flux (simultaneous cuts I{sub 814W} < 26.5 and K{sub s} < 24) and in stellar mass (10{sup 9} < M{sub *} < 10{sup 10} h{sup -2} M{sub Sun} and 10{sup 10} < M{sub *} < 10{sup 11} h{sup -2} M{sub Sun }). At scales R > 2 h{sup -1} Mpc, our measurements support a model of bias increasing with redshift. The Tinker et al. fitting function provides a good fit to the data. We find the best-fit mass of the galaxy halos to be log (M{sub 200}/h{sup -1} M{sub Sun }) = 11.7{sup +0.6}{sub -1.3} and log (M{sub 200}/h{sup -1} M{sub Sun }) = 12.4{sup +0.2}{sub -2.9}, respectively, for the low and high stellar-mass samples. In the halo model framework, bias is scale dependent with a change of slope at the transition scale between the one and the two halo terms. We detect a scale dependence of bias with a turndown at scale R = 2.3 {+-} 1.5 h{sup -1} Mpc, in agreement with previous galaxy clustering studies. We find no significant amount of stochasticity, suggesting that a linear bias model is sufficient to describe our data. We use N-body simulations to quantify both the amount of cosmic variance and systematic errors in the measurement.

Jullo, Eric; Rhodes, Jason [Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Kiessling, Alina; Massey, Richard [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Berge, Joel [Institute of Astronomy, Department of Physics, ETH Zurich CH-8093 (Switzerland); Schimd, Carlo; Kneib, Jean-Paul [Laboratoire d'Astrophysique de Marseille, Universite de Provence, CNRS, 13388 Marseille CEDEX 13 (France); Scoville, Nick, E-mail: eric.jullo@oamp.fr [Astronomy Department, California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)

2012-05-01

302

NASA Astrophysics Data System (ADS)

Bayesian model selection methods provide a self-consistent probabilistic framework to test the validity of competing scenarios given a set of data. We present a case study application to strong gravitational lens parametric models. Our goal is to select a homogeneous lens subsample suitable for cosmological parameter inference. To this end we apply a Bayes factor analysis to a synthetic catalogue of 500 lenses with power-law potential and external shear. For simplicity, we focus on double-image lenses (the largest fraction of lens in the simulated sample) and select a subsample for which astrometry and time-delays provide strong evidence for a simple power-law model description. Through a likelihood analysis we recover the input value of the Hubble constant to within 3? statistical uncertainty. We apply this methodology to a sample of double-image-lensed quasars. In the case of B1600+434, SBS 1520+530 and SDSS J1650+4251 the Bayes' factor analysis favours a simple power-law model description with high statistical significance. Assuming a flat ? cold dark matter cosmology, the combined likelihood data analysis of such systems gives the Hubble constant H0 = 76+ 15- 5 km s- 1 Mpc- 1 having marginalized over the lens model parameters, the cosmic matter density and consistently propagated the observational errors on the angular position of the images. The next generation of cosmic structure surveys will provide larger lens data sets and the method described here can be particularly useful to select homogeneous lens subsamples adapted to perform unbiased cosmological parameter inference.

Balmès, I.; Corasaniti, P. S.

2013-05-01

303

LoCuSS: The Sunyaev-Zel'dovich Effect and Weak-lensing Mass Scaling Relation

NASA Astrophysics Data System (ADS)

We present the first weak-lensing-based scaling relation between galaxy cluster mass, M WL, and integrated Compton parameter Y sph. Observations of 18 galaxy clusters at z ~= 0.2 were obtained with the Subaru 8.2 m telescope and the Sunyaev-Zel'dovich Array. The M WL-Y sph scaling relations, measured at ? = 500, 1000, and 2500 ? 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 WL at fixed Y sph of 20%, larger than both previous measurements of M HSE-Y sph scatter as well as the scatter in true mass at fixed Y sph found in simulations. Moreover, the scatter in our lensing-based scaling relations is morphology dependent, with 30%-40% larger M WL for undisturbed compared to disturbed clusters at the same Y sph at r 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.; Smith, Graham P.; Okabe, Nobuhiro; Bonamente, Massimiliano; Carlstrom, John E.; Culverhouse, Thomas L.; Gralla, Megan; Greer, Christopher H.; Hasler, Nicole; Hawkins, David; Hennessy, Ryan; Joy, Marshall; Lamb, James W.; Leitch, Erik M.; Martino, Rossella; Mazzotta, Pasquale; Miller, Amber; Mroczkowski, Tony; Muchovej, Stephen; Plagge, Thomas; Pryke, Clem; Sanderson, Alastair J. R.; Takada, Masahiro; Woody, David; Zhang, Yuying

2012-08-01

304

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

305

The clustering of matter on cosmological scales is an essential probe for studying the physical origin and composition of our Universe. To date, most of the direct studies have focused on shear-shear weak lensing correlations, but it is also possible to extract the dark matter clustering by combining galaxy-clustering and galaxy-galaxy-lensing measurements. In order to extract the required information, one must relate the observable galaxy distribution to the underlying dark matter distribution. In this study we develop in detail a method that can constrain the dark matter correlation function from galaxy clustering and galaxy-galaxy-lensing measurements, by focusing on the correlation coefficient between the galaxy and matter overdensity fields. Our goal is to develop an estimator that maximally correlates the two. To generate a mock galaxy catalogue for testing purposes, we use the halo occupation distribution approach applied to a large ensemble of N-body simulations to model preexisting SDSS luminous red galaxy sample observations. Using this mock catalogue, we show that a direct comparison between the excess surface mass density measured by lensing and its corresponding galaxy clustering quantity is not optimal. We develop a new statistic that suppresses the small-scale contributions to these observations and show that this new statistic leads to a cross-correlation coefficient that is within a few percent of unity down to 5h{sup -1} Mpc. Furthermore, the residual incoherence between the galaxy and matter fields can be explained using a theoretical model for scale-dependent galaxy bias, giving us a final estimator that is unbiased to within 1%, so that we can reconstruct the dark matter clustering power spectrum at this accuracy up to k{approx}1h Mpc{sup -1}. We also perform a comprehensive study of other physical effects that can affect the analysis, such as redshift space distortions and differences in radial windows between galaxy clustering and weak lensing observations. We apply the method to a range of cosmological models and explicitly show the viability of our new statistic to distinguish between cosmological models.

Baldauf, Tobias; Smith, Robert E. [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Seljak, Uros [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Physics Department, Astronomy Department and Lawrence Berkeley National Laboratory, University of California, Berkeley, California (United States); Ewha University, 11-1 Daehyun-Dong Seodaemun-Gu Seoul 120-750 (Korea, Republic of); Mandelbaum, Rachel [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, New Jersey (United States)

2010-03-15

306

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

307

Effect of weak gravitation on the plane Poiseuille flow of a highly rarefied gas

NASA Astrophysics Data System (ADS)

Plane Poiseuille flow of a highly rarefied gas that flows horizontally in the presence of weak gravitation is studied based on the Boltzmann equation for a hard sphere molecular gas and the diffuse reflection boundary condition. The behavior of the solution in the regime of large mean free path and small strength of gravity is studied numerically based on the one-dimensional Boltzmann equation derived by means of the asymptotic analysis for a slow variation in the flow direction. It is clarified that the effect of weak gravity on the flow is not negligible when the gas is so rarefied that the mean free path is comparable to the maximum range that the molecules travel along the parabolic path within the channel. When the mean free path is much larger than this range, the effect of gravity that makes the molecules fall plays the dominant role in determining the distribution function, and thus the over-concentration in the distribution function as well as the flow velocity does not increase further even if the mean free path is increased. The upper bound of the flow velocity and the mass flow rate of the gas are obtained as a function of the gravitational acceleration.

Doi, Toshiyuki

2012-12-01

308

NASA Astrophysics Data System (ADS)

We present the results from nine years of optically monitoring the gravitationally lensed zQSO = 0.658 quasar RX J1131-1231. The R-band light curves of the four individual images of the quasar were obtained using deconvolution photometry for a total of 707 epochs. Several sharp quasar variability features strongly constrain the time delays between the quasar images. Using three different numerical techniques, we measured these delays for all possible pairs of quasar images while always processing the four light curves simultaneously. For all three methods, the delays between the three close images A, B, and C are compatible with being 0, while we measured the delay of image D to be 91 days, with a fractional uncertainty of 1.5% (1?), including systematic errors. Our analysis of random and systematic errors accounts in a realistic way for the observed quasar variability, fluctuating microlensing magnification over a broad range of temporal scales, noise properties, and seasonal gaps. Finally, we find that our time-delay measurement methods yield compatible results when applied to subsets of the data. Based on observations made with the 1.2-m Swiss Euler telescope (La Silla, Chile), the 1.3-m SMARTS telescope (Las Campanas, Chile), and the 1.2-m Mercator Telescope. Mercator is operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.Light curves are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/556/A22

Tewes, M.; Courbin, F.; Meylan, G.; Kochanek, C. S.; Eulaers, E.; Cantale, N.; Mosquera, A. M.; Magain, P.; Van Winckel, H.; Sluse, D.; Cataldi, G.; Vörös, D.; Dye, S.

2013-08-01

309

Geometrical approach to strong gravitational lensing in f(R) gravity

We present a framework for the study of lensing in spherically symmetric spacetimes within the context of f(R) gravity. Equations for the propagation of null geodesics, together with an expression for the bending angle, are derived for any f(R) theory and then applied to an exact spherically symmetric solution of R{sup n} gravity. We find that for this case more bending is expected for R{sup n} gravity theories in comparison to general relativity and is dependent on the value of n and the value of the distance of closest approach of the incident null geodesic.

Nzioki, Anne Marie; Goswami, Rituparno [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7701 (South Africa); Dunsby, Peter K. S. [Department of Mathematics and Applied Mathematics, University of Cape Town, Rondebosch, 7701 (South Africa); South African Astronomical Observatory, Observatory, Cape Town (South Africa); Carloni, Sante [Institut d'Estudis Espacials de Catalunya (IEEC), Campus UAB, Facultat Ciencies, Torre C5-Par-2a pl, E-08193 Bellaterra (Barcelona) (Spain)

2011-01-15

310

Gravitationally Lensed Galaxy Number Counts in the Infrared II: Concrete Examples

NASA Astrophysics Data System (ADS)

following the concept presented by Takeuchi, Yoshikawa, & Yonehara (2000), we show some concrete examples of number count of lensed galaxies in the infrared. Adopting a simple lens model of cluster of galaxies, we are able to estimate the expected number counts of galaxies. The result tells us that the expected number counts of galaxies around a single cluster are not so large, but in principle, we can discriminate global history of galaxy evolution efficiently at longer waveband, i.e. FIR and/or sub-mm.

Yonehara, A.; Yoshikawa, K.; Takeuchi, T. T.

2000-12-01

311

NASA Astrophysics Data System (ADS)

Galaxy clusters are usually detected in blind optical surveys via suitable filtering methods. We present an optimal matched filter which maximizes their signal-to-noise ratio by taking advantage of the knowledge we have of their intrinsic physical properties and of the data noise properties. In this paper we restrict our application to galaxy magnitudes, positions and photometric redshifts if available, and we also apply the filter separately to weak lensing data. The method is suitable to be naturally extended to a multi-band approach which could include not only additional optical bands but also observables with different nature such as X-rays. For each detection, the filter provides its significance, an estimate for the richness and for the redshift even if photo-z are not given. The provided analytical error estimate is tested against numerical simulations. We finally apply our method to the COSMOS field and compare the results with previous cluster detections obtained with different methods. Our catalogue contains 27 galaxy clusters with minimal threshold at 3? level including both optical and weak-lensing information.

Bellagamba, F.; Maturi, M.; Hamana, T.; Meneghetti, M.; Miyazaki, S.; Moscardini, L.

2011-05-01

312

A proposal on the galaxy intrinsic alignment self-calibration in weak lensing surveys

NASA Astrophysics Data System (ADS)

The galaxy intrinsic alignment causes the galaxy ellipticity-ellipticity power spectrum between two photometric redshifts to decrease faster with respect to the redshift separation ?zP, for fixed mean redshift. This offers a valuable diagnosis on the intrinsic alignment. We show that the distinctive dependences of the GG, II and GI correlations on ?zP over the range |?zP| <~ 0.2 can be understood robustly without strong assumptions on the intrinsic alignment. This allows us to measure the intrinsic alignment within each conventional photo-z bin of typical size >~0.2, through lensing tomography of photo-z bin size ~0.01. Both the statistical and systematical errors in the lensing cosmology can be reduced by this self-calibration technique.

Zhang, Pengjie

2010-07-01

313

NASA Astrophysics Data System (ADS)

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 200), mass (M 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 200 <= 317 and mass values to be in the range of 1 × 1014 h -1 M ? <= M 200 <= 30 × 1014 h -1 M ?. We also present measurements of Einstein radius, mass, and velocity dispersion for the lensing systems. The Einstein radii (? E ) are all relatively small, with 5farcs4 <= ? E <= 13''. Finally, we consider if there is evidence that our clusters are more concentrated than ?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 200 is 11.6, while for the six higher-mass clusters the average value of c 200 is 4.4. ?CDM would place c 200 between 3.4 and 5.7.

Wiesner, Matthew P.; Lin, Huan; Allam, Sahar S.; Annis, James; Buckley-Geer, Elizabeth J.; Diehl, H. Thomas; Kubik, Donna; Kubo, Jeffrey M.; Tucker, Douglas

2012-12-01

314

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

315

NASA Astrophysics Data System (ADS)

We present a galaxy lensing study from 400 degrees2 of Sloan Digital Sky Survey (SDSS) data. The mean projected mass density contrast S (

Sheldon, Erin S.

2002-09-01

316

Gravitational lensing in the QSO pair Q 1548 + 114 A,B

NASA Astrophysics Data System (ADS)

Calculations of possible gravitational lens effects have been made in the context of the close QSO pair Q 1548+114A and B, separated on the sky by only 4arcsec.8. Together with current observational constraints, they impose an upper limit of 2×1012M_sun; for the mass of the foreground QSO and an upper limit of 0.3 gm cm-2 for the surface density of any associated cluster. Estimates are made for a range of possible conditions of the properties of any secondary image of the background QSO which may eventually be detected.

Iovino, A.; Shaver, P. A.

1986-09-01

317

A generalized lens equation for light deflection in weak gravitational fields

NASA Astrophysics Data System (ADS)

A generalized lens equation for weak gravitational fields of Schwarzschild metric and valid for finite distances of source and observer from the light deflecting body is suggested. The magnitude of neglected terms in the generalized lens equation is estimated to be smaller than or equal to \\frac{15\\,\\pi }{4}\\,\\frac{m^2}{{d^{\\;\\prime }}^2}, where m is the Schwarzschild radius of the massive body and d ' is Chandrasekhar's impact parameter. The main applications of this generalized lens equation are extreme astrometrical configurations, where the standard post-Newtonian approach as well as the classical lens equation cannot be applied. It is shown that in the appropriate limits, the proposed lens equation yields the known post-Newtonian terms, 'enhanced' post-post-Newtonian terms and the classical lens equation, thus providing a link between both these essential approaches for determining the light deflection.

Zschocke, Sven

2011-06-01

318

Energy-momentum tensor for a Casimir apparatus in a weak gravitational field

The influence of the gravity acceleration on the regularized energy-momentum tensor of the quantized electromagnetic field between two plane-parallel conducting plates is derived. We use Fermi coordinates and work to first order in the constant acceleration parameter. A perturbative expansion, to this order, of the Green functions involved and of the energy-momentum tensor is derived by means of the covariant geodesic point-splitting procedure. In correspondence to the Green functions satisfying mixed and gauge-invariant boundary conditions, and Ward identities, the energy-momentum tensor is covariantly conserved and satisfies the expected relation between gauge-breaking and ghost parts, while a new simple formula for the trace anomaly is obtained to first order in the constant acceleration. A more systematic derivation is therefore obtained of the theoretical prediction according to which the Casimir device in a weak gravitational field will experience a tiny push in the upwards direction.

Bimonte, Giuseppe; Calloni, Enrico; Esposito, Giampiero; Rosa, Luigi [Dipartimento di Scienze Fisiche, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio N', 80126 Naples (Italy); INFN, Sezione di Napoli, Complesso Universitario di Monte S. Angelo, Via Cintia, Edificio N', 80126 Naples (Italy)

2006-10-15

319

NASA Astrophysics Data System (ADS)

We have analyzed the data on 16,836 RR Lyrae (RR Lyr) variables observed toward the Galactic bulge during the third phase of the Optical Gravitational Lensing Experiment (OGLE-III), which took place in 2001-2009. Using these standard candles, we show that the ratio of total-to-selective extinction toward the bulge is given by RI = AI /E(V - I) = 1.080 ± 0.007 and is independent of color. We demonstrate that the bulge RR Lyr stars form a metal-uniform population, slightly elongated in its inner part. The photometrically derived metallicity distribution is sharply peaked at [Fe/H] = -1.02 ± 0.18, with a dispersion of 0.25 dex. In the inner regions (|l| < 3°, |b| < 4°) the RR Lyr tend to follow the barred distribution of the bulge red clump giants. The distance to the Milky Way center inferred from the bulge RR Lyr is R 0 = 8.54 ± 0.42 kpc. We report a break in the mean density distribution at a distance of ~0.5 kpc from the center indicating its likely flattening. Using the OGLE-III data, we assess that (4-7) × 104 type ab RR Lyr variables should be detected toward the bulge area of the ongoing near-IR VISTA Variables in the Via Lactea (VVV) survey, where the uncertainty partially results from the unknown RR Lyr spatial density distribution within 0.2 kpc from the Galactic center.

Pietrukowicz, P.; Udalski, A.; Soszy?ski, I.; Nataf, D. M.; Wyrzykowski, ?.; Poleski, R.; Koz?owski, S.; Szyma?ski, M. K.; Kubiak, M.; Pietrzy?ski, G.; Ulaczyk, K.

2012-05-01

320

The Lense Thirring effect one of the main predictions of Einstein's theory of gravitation in the limit of weak field and slow motion represents a tiny relativistic precession of the orbital plane of a satellite produced by the angular momentum of the primary. In the present work, we estimated an updated error budget for the Lense Thirring effect measurement through

D. M. Lucchesi

2007-01-01

321

Density profiles of galaxy groups and clusters from SDSS galaxy-galaxy weak lensing

NASA Astrophysics Data System (ADS)

We present results of a measurement of the shape of the density profile of galaxy groups and clusters traced by 43335 Luminous Red Galaxies (LRGs) with spectroscopic redshifts from the Sloan Digital Sky Survey (SDSS). The galaxies are selected such that they are the brightest within a cylindrical aperture, split into two luminosity samples and modelled as the sum of stellar and dark matter components. We present a detailed investigation of many possible systematic effects that could contaminate our signal and develop methods to remove them, including a detected intrinsic alignment for galaxies within 100h-1kpc of LRGs which we remove using photometric redshift information. The resulting lensing signal is consistent with NFW (Navarro, Frenk & White) profile dark matter haloes; the singular isothermal sphere (SIS) profile is ruled out at the 96 (conservatively) and 99.96 per cent confidence level (CL) for the fainter and brighter lens samples (respectively) when we fit using lensing data between 0.4 and 2h-1Mpc with total signal-to-noise ratio of 19 and 25 for the two lens samples. The lensing signal amplitude suggests that the faint and bright sample galaxies typically reside in haloes of mass (2.9 +/- 0.4) × 1013 and (6.7 +/- 0.8) × 1013h-1Msolar, respectively, in good agreement with predictions based on halo spatial density with normalization lower than the `concordance' ?8 = 0.9. When fitting for the concentration parameter in the NFW profile, we find c = 5.0 +/- 0.6 (stat) +/- 1 (sys), and c = 5.6 +/- 0.6 (stat) +/- 1 (sys) for the faint and bright samples, consistent with ? cold dark matter (CDM) simulations. We also split the bright sample further to determine masses and concentrations for cluster-mass haloes, finding mass (1.3 +/- 0.2) × 1014h-1Msolar for the sample of LRGs brighter than -22.6 in r. We establish that on average there is a correlation between the halo mass and central galaxy luminosity relation that scales as M ~ L2.

Mandelbaum, Rachel; Seljak, Uroš; Cool, Richard J.; Blanton, Michael; Hirata, Christopher M.; Brinkmann, Jonathan

2006-10-01

322

CMB lensing constraints on dark energy and modified gravity scenarios

Weak gravitational lensing leaves a characteristic imprint on the cosmic microwave background temperature and polarization angular power spectra. Here, we investigate the possible constraints on the integrated lensing potential from future cosmic microwave background angular spectra measurements expected from Planck and EPIC. We find that Planck and EPIC will constrain the amplitude of the integrated projected potential responsible for lensing at 6% and 1% level, respectively, with very little sensitivity to the shape of the lensing potential. We discuss the implications of such a measurement in constraining dark energy and modified gravity scalar-tensor theories. We then discuss the impact of a wrong assumption on the weak lensing potential amplitude on cosmological parameter inference.

Calabrese, Erminia [Physics Department and INFN, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Center for Cosmology, Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697 (United States); Cooray, Asantha [Center for Cosmology, Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697 (United States); Martinelli, Matteo [Physics Department and INFN, Universita di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544 (United States); Melchiorri, Alessandro [Physics Department and INFN, Universita' di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Pagano, Luca [Physics Department and INFN, Universita' di Roma 'La Sapienza', Ple Aldo Moro 2, 00185, Rome (Italy); Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109 (United States); Slosar, Anze [Berkeley Center for Cosmological Physics, Lawrence Berkeley National Laboratory and Physics Department, University of California, Berkeley, California 94720 (United States); Smoot, George F. [Berkeley Center for Cosmological Physics, Lawrence Berkeley National Laboratory and Physics Department, University of California, Berkeley, California 94720 (United States); Institute for the Early Universe, Ewha Womans University and Ewha Advanced Academy, Seoul (Korea, Republic of); Chaire Blaise Pascal, Universite Paris Diderot - 75205 PARIS cedex 13 (France)

2009-11-15

323

We have analyzed the data on 16,836 RR Lyrae (RR Lyr) variables observed toward the Galactic bulge during the third phase of the Optical Gravitational Lensing Experiment (OGLE-III), which took place in 2001-2009. Using these standard candles, we show that the ratio of total-to-selective extinction toward the bulge is given by R{sub I} = A{sub I} /E(V - I) = 1.080 {+-} 0.007 and is independent of color. We demonstrate that the bulge RR Lyr stars form a metal-uniform population, slightly elongated in its inner part. The photometrically derived metallicity distribution is sharply peaked at [Fe/H] = -1.02 {+-} 0.18, with a dispersion of 0.25 dex. In the inner regions (|l| < 3 Degree-Sign , |b| < 4 Degree-Sign ) the RR Lyr tend to follow the barred distribution of the bulge red clump giants. The distance to the Milky Way center inferred from the bulge RR Lyr is R{sub 0} = 8.54 {+-} 0.42 kpc. We report a break in the mean density distribution at a distance of {approx}0.5 kpc from the center indicating its likely flattening. Using the OGLE-III data, we assess that (4-7) Multiplication-Sign 10{sup 4} type ab RR Lyr variables should be detected toward the bulge area of the ongoing near-IR VISTA Variables in the Via Lactea (VVV) survey, where the uncertainty partially results from the unknown RR Lyr spatial density distribution within 0.2 kpc from the Galactic center.

Pietrukowicz, P.; Udalski, A.; Soszynski, I.; Wyrzykowski, L.; Poleski, R.; Kozlowski, S.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Ulaczyk, K. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Nataf, D. M. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

2012-05-10

324

NASA Astrophysics Data System (ADS)

We address the amount of information in the non-Gaussian regime of weak lensing surveys by modelling all relevant covariances of the power spectra and bispectra, using 1000 ray-tracing simulation realizations for a ?cold dark matter (?CDM) model and an analytical halo model. We develop a formalism to describe the covariance matrices of power spectra and bispectra of all triangle configurations. In addition to the known contributions which extend up to six-point correlation functions, we propose a new contribution `the halo sample variance (HSV)' arising from the coupling of the lensing Fourier modes with large-scale mass fluctuations on scales comparable with the survey region via halo bias theory. We show that the model predictions are in good agreement with the simulation once we take the HSV into account. The HSV gives a dominant contribution to the covariance matrices at multipoles l ? 103, which arises from massive haloes with a mass of ? 1014 M? and at relatively low redshifts z ? 0.4. Since such haloes are easily identified from a multi-colour imaging survey, the effect can be estimated from the data. By adding the bispectrum to the power spectrum, the total information content or the cumulative signal-to-noise ratio up to a certain maximum multipole lmax of a few 103, (S/N)lmax, is improved by 20-50 per cent, which is equivalent to a factor of 1.4-2.3 larger survey area for the power spectrum measurement alone. However, it is still smaller than the case of a Gaussian field by a factor of 3 mostly due to the HSV. Thus bispectrum measurements are useful for cosmology, but using information from upcoming surveys requires that non-Gaussian covariances are carefully estimated.

Kayo, Issha; Takada, Masahiro; Jain, Bhuvnesh

2013-02-01

325

SDSS J1029+2623: A Gravitationally Lensed Quasar with an Image Separation of 22.5 Arcseconds

The authors report the discovery of a cluster-scale lensed quasar, SDSS J1029+2623, selected from the Sloan Digital Sky Survey. The lens system exhibits two lensed images of a quasar at z{sub s} = 2.197. The image separation of 22.5 makes it the largest separation lensed quasar discovered to date. The similarity of the optical spectra and the radio loudnesses of the two components support the lensing hypothesis. Images of the field show a cluster of galaxies at z{sub l} {approx} 0.55 that is responsible for the large image separation. The lensed images and the cluster light center are not collinear, which implies that the lensing cluster has a complex structure.

Inada, Naohisa; Oguri, Masamune; Morokuma, Tomoki; Doi, Mamoru; Yasuda, Naoki; Becker, Robert H.; Richards, Gordon T.; Kochanek, Christopher S.; Kayo, Issha; Konishi, Kohki; Utsunomiya, Hiroyuki; Shin, Min-Su; Strauss, Michael A.; Sheldon, Erin S.; York, Donald G.; Hennawi, Joseph F.; Schneider, Donald P.; Dai, Xinyu; Fukugita, Masataka; /Tokyo U., Inst. Astron. /JSPS, Tokyo /KIPAC, Menlo Park /Princeton U. Observ. /Tokyo U., ICRR /LLNL, Livermore /UC, Davis /Drexel U. /Johns Hopkins U. /Ohio State U., Dept. Astron. /Nagoya U. /CCPP, New York /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI /UC, Berkeley, Astron. Dept. /Penn State U., Astron. Astrophys.

2006-11-15

326

NASA Astrophysics Data System (ADS)

We study the Sloan Lens ACS (SLACS) survey strong-lensing system SDSS J1430+4105 at zl = 0.285. The lensed source (zs = 0.575) of this system has a complex morphology with several subcomponents. Its subcomponents span a radial range from 4 to 10 kpc in the plane of the lens. Therefore, we can constrain the slope of the total projected mass profile around the Einstein radius from lensing alone. We measure a density profile that is slightly but not significantly shallower than isothermal at the Einstein radius. We decompose the mass of the lensing galaxy into a de Vaucouleurs component to trace the stars and an additional dark component. The spread of multiple-image components over a large radial range also allows us to determine the amplitude of the de Vaucouleurs and dark matter components separately. We get a mass-to-light ratio of

Eichner, Thomas; Seitz, Stella; Bauer, Anne

2012-12-01

327

NASA Astrophysics Data System (ADS)

Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant H0 based on the so-called time-delay technique, (ii) unveil substructures along the line-of-sight toward distant galaxies, and (iii) compare the shape and the slope of baryons and dark matter distributions in the inner regions of galaxies. To reach these goals, we need high-accuracy astrometry of the quasar images relative to the lensing galaxy and morphology measurements of the lens. In this work, we first present new astrometry for 11 lenses with measured time delays, namely, JVAS B0218+357, SBS 0909+532, RX J0911.4+0551, FBQS J0951+2635, HE 1104-1805, PG 1115+080, JVAS B1422+231, SBS 1520+530, CLASS B1600+434, CLASS B1608+656, and HE 2149-2745. These measurements proceed from the use of the Magain-Courbin-Sohy (MCS) deconvolution algorithm applied in an iterative way (ISMCS) to near-IR HST images. We obtain a typical astrometric accuracy of about 1-2.5 mas and an accurate shape measurement of the lens galaxy. Second, we combined these measurements with those of 14 other lensing systems, mostly from the COSMOGRAIL set of targets, to present new mass models of these lenses. The modeling of these 25 gravitational lenses led to the following results: 1) in four double-image quasars (HE0047-1746, J1226-006, SBS 1520+530, and HE 2149-2745), we show that the influence of the lens environment on the time delay can easily be quantified and modeled, hence putting these lenses with high priority for time-delay determination; 2) for quadruple-image quasars, the difficulty often encountered in reproducing the image positions to milli-arcsec accuracy (astrometric anomaly problem) is overcome by explicitly including the nearest visible galaxy/satellite in the lens model. However, one anomalous system (RXS J1131-1231) does not show any luminous perturber in its vicinity, and three others (WFI 2026-4536, WFI 2033-4723, and B2045+265) have problematic modeling. These four systems are the best candidates for a pertubation by a dark matter substructure along the line-of-sight; 3) we revisit the correlation between the position angle (PA) and ellipticity of the light and of the mass distribution in lensing galaxies. As in previous studies, we find a significant correlation between the PA of the light and of the mass distributions. However, in contrast with these same studies, we find that the ellipticity of the light and of the mass also correlate well, suggesting that the overall spatial distribution of matter is not very different from the baryon distribution in the inner ~5 kpc of lensing galaxies. This offers a new test for high-resolution hydrodynamical simulations. Based on observations made with the NASA/ESA HST Hubble Space Telescope by the CfA-Arizona Space Telescope Lens Survey (CASTLeS) collaboration, obtained from the data archive at the Space Science Institute, which is operated by AURA, the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS-5-26555.

Sluse, D.; Chantry, V.; Magain, P.; Courbin, F.; Meylan, G.

2012-02-01

328

NASA Astrophysics Data System (ADS)

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 cm2 g-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 ~5? larger than the upper limit of 0.7 cm2 g-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. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program 12253. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

Clowe, Douglas; Markevitch, Maxim; Brada?, Maruša; Gonzalez, Anthony H.; Chung, Sun Mi; Massey, Richard; Zaritsky, Dennis

2012-10-01

329

NASA Astrophysics Data System (ADS)

We present a joint weak-lensing/X-ray study of galaxy cluster mass-observable scaling relations motivated by the critical importance of accurate calibration of mass proxies for future X-ray missions, including eROSITA. We use a sample of 12 clusters at z ~= 0.2 that we have observed with Subaru and XMM-Newton to construct relationships between the weak-lensing mass (M) and three X-ray observables, gas temperature (T), gas mass (M gas), and quasi-integrated gas pressure (Y X), at overdensities of ? = 2500, 1000, and 500 with respect to the critical density. We find that M gas at ? <= 1000 appears to be the most promising mass proxy of the three because it has the lowest intrinsic scatter in mass at a fixed observable, ?ln M ~= 0.1, independent of the cluster dynamical state. The scatter in mass at fixed T and Y X is a factor of ~2-3 larger than at fixed M gas, which are indicative of the structural segregation that we find in the M-T and M-Y X relationships. Undisturbed clusters are found to be ~40% and ~20% more massive than disturbed clusters at fixed T and Y X, respectively, at ~2? significance. In particular, A 1914—a well-known merging cluster—significantly increases the scatter and lowers the normalization of the relation for disturbed clusters. We also investigated the covariance between the intrinsic scatter in M-M gas and M-T relations, finding that they are positively correlated. This contradicts the adaptive mesh refinement simulations that motivated the idea that Y X may be a low-scatter mass proxy, and agrees with more recent smoothed particle hydrodynamic simulations based on the Millennium Simulation. We also propose a method to identify a robust mass proxy based on principal component analysis. The statistical precision of our results is limited by the small sample size and the presence of the extreme merging cluster in our sample. We therefore look forward to studying a larger, more complete sample in the future. This work is based in part on data collected at the Subaru Telescope and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan. Based on observations made with the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA).

Okabe, N.; Zhang, Y.-Y.; Finoguenov, A.; Takada, M.; Smith, G. P.; Umetsu, K.; Futamase, T.

2010-09-01

330

We present a joint weak-lensing/X-ray study of galaxy cluster mass-observable scaling relations motivated by the critical importance of accurate calibration of mass proxies for future X-ray missions, including eROSITA. We use a sample of 12 clusters at z {approx_equal} 0.2 that we have observed with Subaru and XMM-Newton to construct relationships between the weak-lensing mass (M) and three X-ray observables, gas temperature (T), gas mass (M{sub gas}), and quasi-integrated gas pressure (Y{sub X}), at overdensities of {Delta} = 2500, 1000, and 500 with respect to the critical density. We find that M{sub gas} at {Delta} {<=} 1000 appears to be the most promising mass proxy of the three because it has the lowest intrinsic scatter in mass at a fixed observable, {sigma}{sub ln{sub M}} {approx_equal} 0.1, independent of the cluster dynamical state. The scatter in mass at fixed T and Y{sub X} is a factor of {approx}2-3 larger than at fixed M{sub gas}, which are indicative of the structural segregation that we find in the M-T and M-Y{sub X} relationships. Undisturbed clusters are found to be {approx}40% and {approx}20% more massive than disturbed clusters at fixed T and Y{sub X}, respectively, at {approx}2{sigma} significance. In particular, A 1914-a well-known merging cluster-significantly increases the scatter and lowers the normalization of the relation for disturbed clusters. We also investigated the covariance between the intrinsic scatter in M-M{sub gas} and M-T relations, finding that they are positively correlated. This contradicts the adaptive mesh refinement simulations that motivated the idea that Y{sub X} may be a low-scatter mass proxy, and agrees with more recent smoothed particle hydrodynamic simulations based on the Millennium Simulation. We also propose a method to identify a robust mass proxy based on principal component analysis. The statistical precision of our results is limited by the small sample size and the presence of the extreme merging cluster in our sample. We therefore look forward to studying a larger, more complete sample in the future.

Okabe, N.; Futamase, T. [Astronomical Institute, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan); Zhang, Y.-Y. [Argelander-Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, 53121 Bonn (Germany); Finoguenov, A. [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Takada, M. [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8568 (Japan); Smith, G. P. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT (United Kingdom); Umetsu, K., E-mail: okabe@asiaa.sinica.edu.t [Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), P.O. Box 23-141, Taipei 10617, Taiwan (China)

2010-09-20

331

The Lense–Thirring effect – one of the main predictions of Einstein’s theory of gravitation in the limit of weak field and slow motion – represents a tiny relativistic precession of the orbital plane of a satellite produced by the angular momentum of the primary. In the present work, we estimated an updated error budget for the Lense–Thirring effect measurement through

D. M. Lucchesi

2007-01-01

332

Nonlocal metric formulations of modified Newtonian dynamics with sufficient lensing

NASA Astrophysics Data System (ADS)

We demonstrate how to construct purely metric modifications of gravity which agree with general relativity in the weak field regime appropriate to the Solar System, but which possess an ultra-weak field regime when the gravitational acceleration becomes comparable to a0˜10-10m/s2. In this ultra-weak field regime, the models reproduce the MOND force without dark matter and also give enough gravitational lensing to be consistent with existing data. Our models are nonlocal and might conceivably derive from quantum corrections to the effective field equations.

Deffayet, Cédric; Esposito-Farèse, Gilles; Woodard, Richard P.

2011-12-01

333

The recent weak-lensing measurement of the dark matter mass of the high-redshift galaxy cluster XMMUJ2235.3-2557 of (8.5{+-}1.7)x10{sup 14}M{sub {center_dot}} at z=1.4, indicates that, if the cluster is assumed to be the result of the collapse of dark matter in a primordial Gaussian field in the standard lambda cold dark matter model, then its abundance should be <2x10{sup -3} clusters in the observed area. Here we investigate how to boost the probability of XMMUJ2235.3-2557, in particular, resorting to deviations from Gaussian initial conditions. We show that this abundance can be boosted by factors >3-10 if the non-Gaussianity parameter f{sub NL}{sup local} is in the range 150-200. This value is comparable to the limit for f{sub NL} obtained by current constraints from the cosmic microwave background. We conclude that mass determination of high-redshift, massive clusters can offer a complementary probe of primordial non-Gaussianity.

Jimenez, Raul; Verde, Licia [ICREA and Institute of Sciences of the Cosmos (ICC), University of Barcelona, Barcelona 08028 (Spain); Theory Group, Physics Department, CERN, CH-1211 Geneva 23 (Switzerland)

2009-12-15

334

We study the potential of a large future weak lensing survey to constrain dark-energy properties by using both the number counts of detected galaxy clusters (sensitive primarily to density fluctuations on small scales) and tomographic shear-shear correlations (restricted to intermediate and large scales). We use the Fisher matrix formalism, assume a flat universe, and parametrize the equation of state of dark energy by w(a)=w{sub 0}+w{sub a}(1-a), to forecast the expected statistical errors from either observable, and from their combination. We show that the covariance between these two observables is small, and argue that they can therefore be regarded as independent constraints. We find that, when the number counts and the shear-shear correlations (on angular scales l{<=}1000) are combined, a LSST (Large Synoptic Survey Telescope)-like survey can yield statistical errors on {omega}{sub DE}, w{sub 0}, w{sub a} as tight as 0.003, 0.03, 0.1. These values are a factor of 2-25 better than using either observable alone. The results are also about a factor of 2 better than those from combining number counts of galaxy clusters and their power spectrum.

Fang Wenjuan [Department of Physics, Columbia University, New York, New York 10027 (United States); Haiman, Zoltan [Department of Astronomy, Columbia University, New York, New York 10027 (United States)

2007-02-15

335

NASA Astrophysics Data System (ADS)

We formulate the equations of equilibrium of neutron stars taking into account strong, weak, electromagnetic, and gravitational interactions within the framework of general relativity. The nuclear interactions are described by the exchange of the ?, ?, and ? virtual mesons. The equilibrium conditions are given by our recently developed theoretical framework based on the Einstein-Maxwell-Thomas-Fermi equations along with the constancy of the general relativistic Fermi energies of particles, the "Klein potentials", throughout the configuration. The equations are solved numerically in the case of zero temperatures and for selected parameterizations of the nuclear models. The solutions lead to a new structure of the star: a positively charged core at supranuclear densities surrounded by an electronic distribution of thickness ˜?/(mec)˜102?/(m?c) of opposite charge, as well as a neutral crust at lower densities. Inside the core there is a Coulomb potential well of depth ˜m?c2/e. The constancy of the Klein potentials in the transition from the core to the crust, imposes the presence of an overcritical electric field ˜(Ec, the critical field being Ec=me2c3/(e?). The electron chemical potential and the density decrease, in the boundary interface, until values ?ecrust

Belvedere, Riccardo; Pugliese, Daniela; Rueda, Jorge A.; Ruffini, Remo; Xue, She-Sheng

2012-06-01

336

NASA Astrophysics Data System (ADS)

The sightline to the brighter member of the gravitationally lensed quasar pair UM673A,B intersects a damped Ly? system (DLA) at z = 1.62650 which, because of its low redshift, has not been recognized before. Our high-quality echelle spectra of the pair, obtained with HIRES on the Keck I telescope, show a drop in neutral hydrogen column density N(HI) by a factor of at least 400 between UM673A and UM673B, indicating that the DLA's extent in this direction is much less than the 2.7 h-170kpc separation between the two sightlines at z = 1.62650. By re-assessing this new case together with published data on other quasar pairs, we conclude that the typical size (radius) of DLAs at these redshifts is R ~= (5 +/- 3) h-170kpc, smaller than previously realized. Highly ionized gas associated with the DLA is more extended, as we find only small differences in the CIV absorption profiles between the two sightlines. Coincident with UM673B, we detect a weak and narrow Ly? emission line which we attribute to star formation activity at a rate SFR >~ 0.2Msolaryr-1. The DLA in UM673A is metal poor, with an overall metallicity ZDLA ~= 1/30Zsolar, and has a very low internal velocity dispersion. It exhibits some apparent peculiarities in its detailed chemical composition, with the elements Ti, Ni and Zn being deficient relative to Fe by factors of 2-3. The [Zn/Fe] ratio is lower than those measured in any other DLA or Galactic halo star, presumably reflecting somewhat unusual previous enrichment by stellar nucleosynthesis. We discuss the implications of these results for the nature of the galaxy hosting the DLA. Based on data 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 NASA, and was made possible by the generous financial support of the W. M. Keck Foundation. E-mail: rcooke@ast.cam.ac.uk

Cooke, Ryan; Pettini, Max; Steidel, Charles C.; King, Lindsay J.; Rudie, Gwen C.; Rakic, Olivera

2010-12-01

337

We report on the serendipitous discovery in the Blanco Cosmology Survey (BCS) imaging data of a z = 0.9057 galaxy that is being strongly lensed by a massive galaxy cluster at a redshift of z = 0.3838. The lens (BCS J2352-5452) was discovered while examining i- and z-band images being acquired in 2006 October during a BCS observing run. Follow-up spectroscopic observations with the Gemini Multi-Object Spectrograph instrument on the Gemini-South 8 m telescope confirmed the lensing nature of this system. Using weak-plus-strong lensing, velocity dispersion, cluster richness N{sub 200}, and fitting to a Navarro-Frenk-White (NFW) cluster mass density profile, we have made three independent estimates of the mass M{sub 200} which are all very consistent with each other. The combination of the results from the three methods gives M{sub 200} = (5.1 {+-} 1.3) Multiplication-Sign 10{sup 14} M{sub Sun }, which is fully consistent with the individual measurements. The final NFW concentration c{sub 200} from the combined fit is c{sub 200} = 5.4{sup +1.4}{sub -1.1}. We have compared our measurements of M{sub 200} and c{sub 200} with predictions for (1) clusters from {Lambda}CDM simulations, (2) lensing-selected clusters from simulations, and (3) a real sample of cluster lenses. We find that we are most compatible with the predictions for {Lambda}CDM simulations for lensing clusters, and we see no evidence based on this one system for an increased concentration compared to {Lambda}CDM. Finally, using the flux measured from the [O II]3727 line we have determined the star formation rate of the source galaxy and find it to be rather modest given the assumed lens magnification.

Buckley-Geer, E. J.; Lin, H.; Drabek, E. R.; Allam, S. S.; Tucker, D. L.; Frieman, J. A. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Armstrong, R. [National Center for Supercomputing Applications, University of Illinois, 1205 West Clark Street, Urbana, IL 61801 (United States); Barkhouse, W. A. [Department of Physics and Astrophysics, University of North Dakota, Grand Forks, ND 58202 (United States); Bertin, E. [Institut d'Astrophysique de Paris, UMR 7095 CNRS, Universite Pierre et Marie Curie, 98 bis boulevard Arago, F-75014 Paris (France); Brodwin, M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Desai, S.; Ngeow, C.-C. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Hansen, S. M. [University of California Observatories and Department of Astronomy, University of California, Santa Cruz, CA 95064 (United States); High, F. W. [Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Mohr, J. J.; Zenteno, A. [Department of Physics, Ludwig-Maximilians-Universitaet, Scheinerstr. 1, 81679 Muenchen (Germany); Lin, Y.-T. [Institute for Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwa-no-ha, Kashiwa-shi, Chiba 277- 8568 (Japan); Rest, A. [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Smith, R. C. [Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, La Serena (Chile); Song, J. [Department of Physics, University of Michigan, 450 Church St., Ann Arbor, MI 48109 (United States)

2011-11-20

338

NASA Astrophysics Data System (ADS)

We present the first detailed analysis of the rest-frame ultraviolet spectrum of the gravitationally lensed Lyman break galaxy (LBG), the “8 o'clock arc”, obtained with the intermediate-resolution X-shooter spectrograph recently commissioned on the ESO Very Large Telescope. Besides MS 1512-cB58, the Cosmic Horseshoe, and the Cosmic Eye, three other lensed LBGs at comparable redshifts, this is the fourth of such a study, usually unfeasible at high redshifts. The spectrum of the 8 o'clock arc is rich in stellar and interstellar features, and presents several similarities to the well-known MS 1512-cB58 LBG. The stellar photospheric absorption lines allowed us to constrain the systemic redshift, z_sys = 2.7350 ±0.0003, of the galaxy, and derive its stellar metallicity, Z=0.82~Z?, which is in excellent agreement with the metallicity determined from nebular emission lines. With a total stellar mass of ˜4.2 ×1011~M?, the 8 o'clock arc agrees with the mass-metallicity relation found for z>2 star-forming galaxies, although being located near the upper end of the distribution given its high mass and high metallicity. Broad He II ?1640 emission is found, indicative of the presence of Wolf-Rayet stars formed in an intense period of star formation. The 31 interstellar absorption lines detected led to the abundance measurements of 9 elements. The metallicity of the interstellar medium (ISM), Z=0.65~Z? (Si), is very comparable to the metallicity of stars and ionized gas, and suggests that the ISM of the 8 o'clock arc has been rapidly polluted and enriched by ejecta of OB stars. The ISM lines extend over a very large velocity range, ? ? ˜ 1000 km s-1, from about -800 to +300 km s-1 relative to the systemic redshift, and have their peak optical depth blueshifted relative to the stars, implying gas outflows of ?_ISM ? -120 km s-1. The zero residual intensity in the strongest lines indicates a nearly complete coverage of the UV continuum by the ISM. The Ly? line is dominated by a damped absorption profile on top of which is superposed a weak emission, redshifted relative to the ISM lines by about +690 km s-1 and resulting from multiply backscattered Ly? photons emitted in the H II region surrounded by the cold, expanding ISM shell. A homogeneous spherical shell model with a constant outflow velocity, determined by the observations, is able to reproduce the observed Ly? line profile. Furthermore, the required dust content, E(B-V) ? 0.3, is in good agreement with the attenuation measured from the Balmer decrement. These results obtained from the radiation transfer modeling of the Ly? line in the 8 o'clock arc fully support the scenario proposed earlier, where the diversity of Ly? line profiles in Lyman break galaxies and Ly? emitters, from absorption to emission, is mostly due to variations of HI column density and dust content. Based on X-shooter observations made with the European Southern Observatory VLT/Melipal telescope, Paranal, Chile, collected during the first X-shooter Commissioning run.

Dessauges-Zavadsky, M.; D'Odorico, S.; Schaerer, D.; Modigliani, A.; Tapken, C.; Vernet, J.

2010-02-01

339

Search for exotic matter from gravitational microlensing observations of stars

NASA Astrophysics Data System (ADS)

We consider small-scale spheroidal clusters of weakly interacting massive particles in our Galaxy as non-compact gravitational microlenses and predict the appearance of caustics in the plane of a lensed source. The crossing of these caustics by a lensed star can produce a large variety of light curves, including some observed in actual microlensing events that have been interpreted as manifestations of binary gravitational lenses. We consider also observable effects during the gravitational microlensing of stars of non-zero angular size with a given brightness distribution across their disks by such an exotic objects as natural wormholes and objects whose space-time environment is described with the NUT metric. We demonstrate that, under certain conditions, the microlensing light curves, chromatic and polarizational effects due to the properties of the lens and the star disk brightness distributions can differ considerably from those observed for a Schwarzschild gravitational lens, so that their analysis can facilitate the identification of such objects.

Bogdanov, M. B.; Cherepashchuk, A. M.

2008-10-01

340

OMEGACAM and Gravitational Lensing

NASA Astrophysics Data System (ADS)

Het proefschrift van Fabrice Christen gaat over de ontwikkeling van nieuwe methoden voor het corrigeren van (digitale) foto's van melkwegstelsels. Met deze methoden kunnen de beelden uit het heelal beter worden geanalyseerd. Het eerste gedeelte is gewijd aan het werk dat bij ESO is uitgevoerd aan de CCD's van de OmegaCAM camera, het enige instrument van de VST. OmegaCAM is een optische groothoekcamera met een beeldveld van een vierkante graad, opgebouwd uit een mozaiek van 8 bij 4 CCD's. Van elk onderdeel moeten alle kenmerken volledig bekend zijn voordat het in het CCD mozaiek geplaatst kan worden. In het tweede deel van dit proefschrift wordt de ontwikkeling van een nieuwe methode voor het corrigeren van de ``point-spread function'' (PSF) en schatten van de ellipticiteit van de melkwegstelsels besproken. De nieuwe techniek wordt getest en vergeleken met een door sterrenkundigen algemeen gebruikte methode in het veld van zwaartekrachtslenzen, de Kaiser, Squire en Broadhurst (KSB) methode. De nieuwe methode, gebaseerd op shapelet ontleding (vergelijkbaar met wavelet ontleding), gaat verder, en is sneller en theoretisch preciezer dan de KSB methode. Door gebruik te maken van de gecorrigeerde ellipticiteit, kunnen we een statistische analyse uitvoeren om er een kosmisch vervormingssignaal uit te halen. De licht vervormde beelden van de melkwegstelsels bewij zen dat de niet-homogene massaverdeling op megaparsec-schaal voornamelijk bestaat uit grote hoeveelheden donkere materie. Verder vergelijken we de schattingen van de ellipticiteit van de shapelet en KSB methode. Bovendien voeren we ook nog een melkwegstelsel-melkwegstelsel lens analyse uit op de 50 VLT Fors1 afbeeldingen en slagen we erin de belangrijkste eigenschappen van de halo's van de stelsels, die zich op een afstand van een- tot tweeduizend megaparsec (1 parsec = 3,26 lichtjaar = 3,085 x 10^16 meter) bevinden, te bepalen door gebruik te maken van twee modellen van melkwegstelselhalo's. Vergeleken met andere overzichtsmetingen vinden we vergelijkbare resultaten.

Christen, Fabrice Frédéric Thiébaut

2007-04-01

341

NASA Astrophysics Data System (ADS)

Correlations between intrinsic shear and the density field on large scales, a potentially important contaminant for cosmic shear surveys, have been robustly detected at low redshifts with bright galaxies in Sloan Digital Sky Survey (SDSS) data. Here we present a more detailed characterization of this effect, which can cause anticorrelations between gravitational lensing shear and intrinsic ellipticity (GI correlations). This measurement uses 36278 luminous red galaxies (LRGs) from the SDSS spectroscopic sample with 0.15 < z < 0.35, split by redshift and luminosity; 7758 LRGs from the 2dF-SDSS LRG and QSO (2SLAQ) survey at 0.4 < z < 0.8; and a variety of other SDSS samples from previous, related work. We find >3? detections of the effect on large scales (up to 60h-1Mpc) for all galaxy subsamples within the SDSS LRG sample; for the 2SLAQ sample, we find a 2? detection for a bright subsample, and no detection for a fainter subsample. Fitting formulae are provided for the scaling of the GI correlations with luminosity, transverse separation and redshift (for which the 2SLAQ sample, while small, provides crucial constraints due to its longer baseline in redshift). We estimate contamination in the measurement of ?8 for future cosmic shear surveys on the basis of the fitted dependence of GI correlations on galaxy properties. We find contamination to the power spectrum ranging from -1.5 per cent (optimistic) to -33 per cent (pessimistic) for a toy cosmic shear survey using all galaxies to a depth of R = 24 using scales l ~ 500, though the central value of predicted contamination is -6.5 per cent. This corresponds to a bias in ?8 of ??8 = -0.004 (optimistic), -0.02 (central) or -0.10 (pessimistic). We provide a prescription for inclusion of this error in cosmological parameter estimation codes. The principal uncertainty is in the treatment of the L <= L* blue galaxies, for which we have no detection of the GI signal, but which could dominate the GI contamination if their GI amplitude is near our upper limits. Characterization of the tidal alignments of these galaxies, especially at redshifts relevant for cosmic shear, should be a high priority for the cosmic shear community.

Hirata, Christopher M.; Mandelbaum, Rachel; Ishak, Mustapha; Seljak, Uroš; Nichol, Robert; Pimbblet, Kevin A.; Ross, Nicholas P.; Wake, David

2007-11-01

342

NASA Astrophysics Data System (ADS)

Peaks in two-dimensional weak lensing (WL) maps contain significant cosmological information, complementary to the WL power spectrum. This has recently been demonstrated using N-body simulations which neglect baryonic effects. Here we employ ray-tracing N-body simulations in which we manually steepen the density profile of each dark matter halo, mimicking the cooling and concentration of baryons into dark matter potential wells. We find, in agreement with previous works, that this causes a significant increase in the amplitude of the WL power spectrum on small scales (spherical harmonic index l>1,000). We then study the impact of the halo concentration increase on the peak counts, and find the following. (i) Low peaks (with convergence 0.02 < kappa_{peak} < 0.08), remain nearly unaffected. These peaks are created by a constellation of several halos with low masses 10^{12}-10^{13} solar masses) and large angular offsets from the peak center (> 0.5 R_{vir}); as a result, they are insensitive to the central halo density profiles. These peaks contain most of the cosmological information, and thus provide an unusually sensitive and unbiased probe. (ii) The number of high peaks (with convergence kappa_{peak} > 0.08) is increased. However, when the baryon effects are neglected in cosmological parameter estimation, then the high peaks lead to a modest bias, comparable to that from the power spectrum on relatively large-scales (l<2000), and much smaller than the bias from the power spectrum on smaller scales (l>2,000). (iii) In the 3D parameter space (sigma_8, Omega_m, w), the biases from the high peaks and the power spectra are in different directions. This suggests the possibility of "self-calibration": the combination of peak counts and power spectrum can simultaneously constrain baryonic physics and cosmological parameters.

Kratochvil, Jan M.; Yang, X.; Huffenberger, K.; Haiman, Z.; May, M.

2013-01-01

343

Lack of strength; Muscle weakness ... weak, but there is no real loss of strength. For example, you may feel weak if you ... flu . Objective means there is a loss of strength that can be noted during a physical exam.

344

NASA Astrophysics Data System (ADS)

We present a study of multiwavelength X-ray and weak lensing scaling relations for a sample of 50 clusters of galaxies. Our analysis combines Chandra and XMM-Newton data using an energy-dependent cross-calibration. After considering a number of scaling relations, we find that gas mass is the most robust estimator of weak lensing mass, yielding 15% ± 6% intrinsic scatter at r_{500}^{WL} (the pseudo-pressure YX yields a consistent scatter of 22% ± 5%). The scatter does not change when measured within a fixed physical radius of 1 Mpc. Clusters with small brightest cluster galaxy (BCG) to X-ray peak offsets constitute a very regular population whose members have the same gas mass fractions and whose even smaller (<10%) deviations from regularity can be ascribed to line of sight geometrical effects alone. Cool-core clusters, while a somewhat different population, also show the same (<10%) scatter in the gas mass-lensing mass relation. There is a good correlation and a hint of bimodality in the plane defined by BCG offset and central entropy (or central cooling time). The pseudo-pressure YX does not discriminate between the more relaxed and less relaxed populations, making it perhaps the more even-handed mass proxy for surveys. Overall, hydrostatic masses underestimate weak lensing masses by 10% on the average at r_{500}^{WL}; but cool-core clusters are consistent with no bias, while non-cool-core clusters have a large and constant 15%-20% bias between r_{2500}^{WL} and r_{500}^{WL}, in agreement with N-body simulations incorporating unthermalized gas. For non-cool-core clusters, the bias correlates well with BCG ellipticity. We also examine centroid shift variance and power ratios to quantify substructure; these quantities do not correlate with residuals in the scaling relations. Individual clusters have for the most part forgotten the source of their departures from self-similarity.

Mahdavi, Andisheh; Hoekstra, Henk; Babul, Arif; Bildfell, Chris; Jeltema, Tesla; Henry, J. Patrick

2013-04-01

345

NASA Astrophysics Data System (ADS)

The light travel time differences in strong gravitational lensing systems allows an independent determination of the Hubble constant. This method has been successfully applied to several lens systems. The formally most precise measurements are, however, in tension with the recent determination of H0 from the Planck satellite for a spatially flat six-parameters ?CDM cosmology. We reconsider the uncertainties of the method, concerning the mass profile of the lens galaxies, and show that the formal precision relies on the assumption that the mass profile is a perfect power law. Simple analytical arguments and numerical experiments reveal that mass-sheet like transformations yield significant freedom in choosing the mass profile, even when exquisite Einstein rings are observed. Furthermore, the characterization of the environment of the lens does not break that degeneracy which is not physically linked to extrinsic convergence. We present an illustrative example where the multiple imaging properties of a composite (baryons + dark matter) lens can be extremely well reproduced by a power-law model having the same velocity dispersion, but with predictions for the Hubble constant that deviate by ~20%. Hence we conclude that the impact of degeneracies between parametrized models have been underestimated in current H0 measurements from lensing, and need to be carefully reconsidered.

Schneider, Peter; Sluse, Dominique

2013-11-01

346

NASA Astrophysics Data System (ADS)

We present a gravitational lensing and photometric study of the exceptional strong lensing system SDSS J1538+5817, identified by the Sloan Lens Advanced Camera for Survey. The lens is a luminous elliptical galaxy at redshift zl = 0.143. Using Hubble Space Telescope public images obtained with two different filters, the presence of two background sources lensed, respectively, into an Einstein ring and a double system is ascertained. Our new spectroscopic observations, performed at the Nordic Optical Telescope, reveal unequivocally that the two sources are located at the same redshift zs = 0.531. We investigate the total (luminous and dark) mass distribution of the lens between 1 and 4 kpc from the galaxy center by means of parametric and non-parametric lensing codes that describe the multiple images as point-like objects. Bootstrapping and Bayesian analyses are performed to determine the uncertainties on the quantities relevant to the lens mass characterization. Several disparate lensing models provide results that are consistent, given the errors, with those obtained from the best-fit model of the lens mass distribution in terms of a singular power-law ellipsoid model. In particular, the lensing models agree on: (1) reproducing accurately the observed positions of the images; (2) predicting a nearly axisymmetric total mass distribution, centered and oriented as the light distribution; (3) measuring a value of 8.11+0.27 -0.59 × 1010 M sun for the total mass projected within the Einstein radius of 2.5 kpc; and (4) estimating a total mass density profile slightly steeper than an isothermal one (? (r) ? r^{-2.33^{+0.43}_{-0.20}}). A fit of the Sloan Digital Sky Survey multicolor photometry with composite stellar population models provides a value of 20+1 -4 × 1010 M sun for the total mass of the galaxy in the form of stars and of 0.9+0.1 -0.2 for the fraction of projected luminous over total mass enclosed inside the Einstein radius. By combining lensing (total) and photometric (luminous) mass measurements, we differentiate the lens mass content in terms of luminous and dark matter components. This two-component modeling, which is viable only in extraordinary systems like SDSS J1538+5817, leads to a description of the global properties of the galaxy dark matter halo. Extending these results to a larger number of lens galaxies would considerably improve our understanding of galaxy formation and evolution processes in the ?CDM scenario. Based on observations made with the 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. Based on observations made 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 Astrofisica de Canarias.

Grillo, C.; Eichner, T.; Seitz, S.; Bender, R.; Lombardi, M.; Gobat, R.; Bauer, A.

2010-02-01

347

We analyze the gravitational perturbations induced by particles falling into a three dimensional, asymptotically AdS black hole geometry. More specifically, we solve the linearized perturbation equations obtained from the geodesic motion of a ringlike distribution of test particles in the BTZ background. This setup ensures that the U(1) symmetry of the background is preserved. The nonasymptotic flatness of the background raises difficulties in attributing the significance of energy and angular momentum to the conserved quantities of the test particles. This issue is well known but, to the best of our knowledge, has never been addressed in the literature. We confirm that the naive expressions for energy and angular momentum are the correct definitions. Finally, we put an asymptotically AdS version of the weak cosmic censorship to a test: by attempting to overspin the BTZ black hole with test particles it is found that the black hole cannot be spun-up past its extremal limit.

Rocha, Jorge V. [CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049 Lisboa (Portugal); Cardoso, Vitor [CENTRA, Departamento de Fisica, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais 1, 1049 Lisboa (Portugal); Department of Physics and Astronomy, University of Mississippi, University, Mississippi 38677 (United States)

2011-05-15

348

Hard thermal loops, weak gravitational fields and the quark-gluon plasma energy-momentum tensor

We use an auxiliary field construction to discuss the hard thermal loop effective action associated with massless thermal SU(N) QCD interacting with a weak grav- itational field. It is demonstrated that the previous attempt to derive this effective action has only been partially successful and that it is presently only known to first order in the graviton coupling constant. This

Eamonn Gaffney

1995-01-01

349

NASA Astrophysics Data System (ADS)

Thermal transpiration of a slightly rarefied gas through a horizontal straight pipe in the presence of weak gravitation is studied on the basis of kinetic theory. We consider the situation in which the Knudsen number (the mean free path divided by the characteristic length of the cross section) is small and the dimensionless gravity (the characteristic length divided by the ascent height of the molecules against gravity) is of the order of the square of the Knudsen number. The behavior of the gas is studied analytically on the basis of the fluid-dynamic-type equation and the slip-type boundary condition derived from the Boltzmann equation for small Knudsen numbers. Extending the analysis of the two-dimensional channel problem, the solution for a pipe with an arbitrary cross section is obtained in a semianalytical form. When the temperature gradient is imposed along the pipe, the pressure gradient is produced not only in the vertical direction but also in the horizontal direction due to the effect of gravity. Although this pressure gradient is of the order of the square of the Knudsen number, it induces a flow of the order of the Knudsen number. As a result, the apparently higher order effect of gravity produces a relatively finite effect on thermal transpiration. This phenomenon, first observed in plane thermal transpiration, is clarified for a pipe with a general cross section. The explicit solution is obtained for the pipe with the cross section of an annulus between eccentric circular cylinders. Based on the solution, the effect of weak gravitation on the mass flow rate of the gas, as well as on the flow velocity, is clarified over a wide range of the radii ratio and the eccentricity of the cylinders.

Doi, Toshiyuki

2013-10-01

350

The contributions of the cosmological constant to the deflection angle and the time delays are derived from the integration of the gravitational potential as well as from Fermat's principle. The findings are in agreement with recent results using exact solutions to Einstein's equations and reproduce precisely the new {lambda} term in the bending angle and the lens equation. The consequences on time-delay expressions are explored. While it is known that {lambda} contributes to the gravitational time delay, it is shown here that a new {lambda} term appears in the geometrical time delay as well. Although these newly derived terms are perhaps small for current observations, they do not cancel out as previously claimed. Moreover, as shown before, at galaxy cluster scale, the {lambda} contribution can be larger than the second-order term in the Einstein deflection angle for several cluster lens systems.

Ishak, Mustapha [Department of Physics, University of Texas at Dallas, Richardson, Texas 75083 (United States)

2008-11-15

351

Using the Subaru 8.2 m Telescope with the IRCS Echelle spectrograph, we obtained high-resolution (R = 10,000) near-infrared (1.01-1.38 {mu}m) spectra of images A and B of the gravitationally lensed QSO B1422+231 (z = 3.628) consisting of four known lensed images. We detected Mg II absorption lines at z = 3.54, which show a large variance of column densities ({approx}0.3 dex) and velocities ({approx}10 km s{sup -1}) between sightlines A and B with a projected separation of only 8.4h{sup -1}{sub 70} pc at that redshift. This is the smallest spatial structure of the high-z gas clouds ever detected after Rauch et al. found a 20 pc scale structure for the same z = 3.54 absorption system using optical spectra of images A and C. The observed systematic variances imply that the system is an expanding shell as originally suggested by Rauch et al. By combining the data for three sightlines, we managed to constrain the radius and expansion velocity of the shell ({approx}50-100 pc, 130 km s{sup -1}), concluding that the shell is truly a supernova remnant (SNR) rather than other types of shell objects, such as a giant H II region. We also detected strong Fe II absorption lines for this system, but with much broader Doppler width than that of {alpha}-element lines. We suggest that this Fe II absorption line originates in a localized Fe II-rich gas cloud that is not completely mixed with plowed ambient interstellar gas clouds showing other {alpha}-element low-ion absorption lines. Along with the Fe richness, we conclude that the SNR is produced by an SN Ia explosion.

Hamano, Satoshi; Kobayashi, Naoto [Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Kondo, Sohei [Koyama Astronomical Observatory, Kyoto-Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555 (Japan); Tsujimoto, Takuji [National Astronomical Observatory of Japan and Department of Astronomical Science, Graduate University for Advanced Studies, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Okoshi, Katsuya [Faculty of Industrial Science and Technology, Tokyo University of Science, 102-1 Tomino, Oshamanbe, Hokkaido 049-3514 (Japan); Shigeyama, Toshikazu, E-mail: hamano@ioa.s.u-tokyo.ac.jp [Research Center for the Early Universe, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033 (Japan)

2012-08-01

352

NASA Astrophysics Data System (ADS)

A detailed study of a power-law lens model is presented for the gravitational lens system Q2237+0305, also known as the Einstein Cross. The adopted three-dimensional distribution for the mass of the lens is more realistic than in previous models and is described by rho (X, Y, Z) = rho 0[1 + (X/a)2 + (Y/b)2 + (Z/c)2]- nu /2. Hubble Space Telescope (HST) optical positions of the image components and the center of the galactic bulge (Crane et al.) along with radio flux density ratios of the image components (Falco et al.) are used to constrain the model [8 (four relative optical positions) + 3 (relative magnifications) = 11 constraints]. The goodness of fit chi 2 is defined using these constraints. The best model has chi 2 ~ 14, which is a better fit than all previous models. We investigate the characteristics of models within the 99% confidence region of parameter space around the best model. We find that the lensing properties (i.e., total image magnification, relative image magnifications, and time delays between image pairs) of models are well described by the ellipticity of the projected mass of the lens, and we calculate a grid of models that illustrates how the lensing properties depend on the ellipticity. We discuss how future observations, such as placing tighter constraints on the brightness of any fifth image, can be used to further constrain the grid of models presented here. The possibility of using the grid of models to place constraints on the Hubble constant is also discussed.

Chae, Kyu-Hyun; Turnshek, David A.; Khersonsky, Valery K.

1998-03-01

353

NASA Astrophysics Data System (ADS)

We present a multiwavelength analysis of a sample of four hot (TX > 8 keV) X-ray galaxy clusters (A1689, A2261, A2142, and A2390) using joint AMiBA Sunyaev-Zel'dovich effect (SZE) and Subaru weak-lensing observations, combined with published X-ray temperatures, to examine the distribution of mass and the intracluster medium (ICM) in massive cluster environments. Our observations show that A2261 is very similar to A1689 in terms of lensing properties. Many tangential arcs are visible around A2261, with an effective Einstein radius ~40'' (at z ~ 1.5), which when combined with our weak-lensing measurements implies a mass profile well fitted by a Navarro-Frenk-White model with a high concentration c vir ~ 10, similar to A1689 and to other massive clusters. The cluster A2142 shows complex mass substructure, and displays a shallower profile (c vir ~ 5), consistent with detailed X-ray observations which imply recent interaction. The AMiBA map of A2142 exhibits an SZE feature associated with mass substructure lying ahead of the sharp northwest edge of the X-ray core suggesting a pressure increase in the ICM. For A2390 we obtain highly elliptical mass and ICM distributions at all radii, consistent with other X-ray and strong-lensing work. Our cluster gas fraction measurements, free from the hydrostatic equilibrium assumption, are overall in good agreement with published X-ray and SZE observations, with the sample-averaged gas fraction of langf gas(

Umetsu, Keiichi; Birkinshaw, Mark; Liu, Guo-Chin; Wu, Jiun-Huei Proty; Medezinski, Elinor; Broadhurst, Tom; Lemze, Doron; Zitrin, Adi; Ho, Paul T. P.; Huang, Chih-Wei Locutus; Koch, Patrick M.; Liao, Yu-Wei; Lin, Kai-Yang; Molnar, Sandor M.; Nishioka, Hiroaki; Wang, Fu-Cheng; Altamirano, Pablo; Chang, Chia-Hao; Chang, Shu-Hao; Chang, Su-Wei; Chen, Ming-Tang; Han, Chih-Chiang; Huang, Yau-De; Hwang, Yuh-Jing; Jiang, Homin;