WorldWideScience

Sample records for weak lensing shear

  1. Spurious Shear in Weak Lensing with LSST

    CERN Document Server

    Chang, C; 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

    2012-01-01

    The Large Synoptic Survey Telescope (LSST) is one of the most powerful ground-based weak lensing survey telescopes in the upcoming decade. The complete 10-year survey will image $\\sim$ 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to $r\\sim27.5$, 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 \\textit{additive} systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing ana...

  2. Spurious Shear in Weak Lensing with LSST

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-09-19

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

  3. Shear calibration biases in weak lensing surveys

    CERN Document Server

    Hirata, C M; Hirata, Christopher M.; Seljak, Uros

    2003-01-01

    We investigate biases induced by the conversion between the observed image shape to shear distortion in current weak lensing analysis methods. Such overall calibration biases cannot be detected by the standard tests such as E/B decomposition or calibration with stars. We find that the non-Gaussianity of point spread function has a significant effect and can lead to up to 15 per cent error on the linear amplitude of fluctuations sigma_8 depending on the method of analysis. This could explain some of the discrepancies seen in recent amplitude determinations from weak lensing. Using an elliptical Laguerre expansion method we develop a re-Gaussianization method which reduces the error to calibration error of order 1 per cent even for poorly resolved galaxies. We also discuss a new type of shear selection bias which results in up to roughly 8 percent underestimation of the signal. It is expected to scale with redshift, inducing errors in the growth factor extraction if not properly corrected for. Understanding and...

  4. Probabilistic Cosmological Mass Mapping from Weak Lensing Shear

    CERN Document Server

    Schneider, Michael D; Dawson, William A; Marshall, Philip J; Meyers, Joshua; Bard, Deborah J

    2016-01-01

    We infer gravitational lensing shear and convergence fields from galaxy ellipticity catalogs under a spatial process prior for the lensing potential. We demonstrate the performance of our algorithm with simulated Gaussian-distributed cosmological lensing shear maps and a reconstruction of the mass distribution of the merging galaxy cluster Abell 781 using galaxy ellipticities measured with the Deep Lens Survey. Given interim posterior samples of lensing shear or convergence fields on the sky, we describe an algorithm to infer cosmological parameters via lens field marginalization. In the most general formulation of our algorithm we make no assumptions about weak shear or Gaussian distributed shape noise or shears. Because we require solutions and matrix determinants of a linear system of dimension that scales with the number of galaxies, we expect our algorithm to require parallel high-performance computing resources for application to ongoing wide field lensing surveys.

  5. The DES Science Verification Weak Lensing Shear Catalogs

    CERN Document Server

    Jarvis, M; Zuntz, J; Kacprzak, T; Bridle, S L; Amara, A; Armstrong, R; Becker, M R; Bernstein, G M; Bonnett, C; Chang, C; Das, R; Dietrich, J P; Drlica-Wagner, A; Eifler, T F; Gangkofner, C; Gruen, D; Hirsch, M; Huff, E M; Jain, B; Kent, S; MacCrann, N; Melchior, P; Plazas, A A; Refregier, A; Rowe, B; Rykoff, E S; Samuroff, S; Sánchez, C; Suchyta, E; Troxel, M A; Vikram, V; Abbott, T; Abdalla, F B; Allam, S; Annis, J; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Doel, P; Neto, A Fausti; Flaugher, B; Fosalba, P; Frieman, J; Gaztanaga, E; Gerdes, D W; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; March, M; Martini, P; Miquel, R; Mohr, J J; Neilsen, E; Nord, B; Ogando, R; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Walker, A R; Wechsler, R H

    2015-01-01

    We present weak lensing shear catalogs for 139 square degrees of data taken during the Science Verification (SV) time for the new Dark Energy Camera (DECam) being used for the Dark Energy Survey (DES). We describe our object selection, point spread function estimation and shear measurement procedures using two independent shear pipelines, IM3SHAPE and NGMIX, which produce catalogs of 2.12 million and 3.44 million galaxies respectively. We detail a set of null tests for the shear measurements and find that they pass the requirements for systematic errors at the level necessary for weak lensing science applications using the SV data. We also discuss some of the planned algorithmic improvements that will be necessary to produce sufficiently accurate shear catalogs for the full 5-year DES, which is expected to cover 5000 square degrees.

  6. Direct Shear Mapping - a new weak lensing tool

    CERN Document Server

    de Burgh-Day, Catherine O; Webster, Rachel L; Hopkins, Andrew M

    2015-01-01

    We have developed a new technique called Direct Shear Mapping (DSM) to measure gravitational lensing shear directly from observations of a single background source. The technique assumes the velocity map of an un-lensed, stably-rotating galaxy will be rotationally symmetric. Lensing distorts the velocity map making it asymmetric. The degree of lensing can be inferred by determining the transformation required to restore axisymmetry. This technique is in contrast to traditional weak lensing methods, which require averaging an ensemble of background galaxy ellipticity measurements, to obtain a single shear measurement. We have tested the efficacy of our fitting algorithm with a suite of systematic tests on simulated data. We demonstrate that we are in principle able to measure shears as small as 0.01. In practice, we have fitted for the shear in very low redshift (and hence un-lensed) velocity maps, and have obtained null result with an error of $\\pm 0.01$. This high sensitivity results from analysing spatially...

  7. Weak lensing power spectra for precision cosmology: Multiple-deflection, reduced shear and lensing bias corrections

    CERN Document Server

    Krause, Elisabeth

    2009-01-01

    It is usually assumed that the ellipticity power spectrum measured in weak lensing observations can be expressed as an integral over the underlying matter power spectrum. This is true at second order in the gravitational potential. We extend the standard calculation, constructing all corrections to fourth order in the gravitational potential. There are four types of corrections: corrections to the lensing shear due to multiple-deflections; corrections due to the fact that shape distortions probe the reduced shear $\\gamma/(1-\\kappa)$ rather than the shear itself; corrections associated with the non-linear conversion of reduced shear to mean ellipticity; and corrections due to the fact that observational galaxy selection and shear measurement is based on galaxy brightnesses and sizes which have been (de)magnified by lensing. We show how the previously considered corrections to the shear power spectrum correspond to terms in our analysis, and highlight new terms that were not previously identified. All correctio...

  8. High resolution weak lensing mass mapping combining shear and flexion

    Science.gov (United States)

    Lanusse, F.; Starck, J.-L.; Leonard, A.; Pires, S.

    2016-06-01

    Aims: We propose a new mass mapping algorithm, specifically designed to recover small-scale information from a combination of gravitational shear and flexion. Including flexion allows us to supplement the shear on small scales in order to increase the sensitivity to substructures and the overall resolution of the convergence map without relying on strong lensing constraints. Methods: To preserve all available small scale information, we avoid any binning of the irregularly sampled input shear and flexion fields and treat the mass mapping problem as a general ill-posed inverse problem, which is regularised using a robust multi-scale wavelet sparsity prior. The resulting algorithm incorporates redshift, reduced shear, and reduced flexion measurements for individual galaxies and is made highly efficient by the use of fast Fourier estimators. Results: We tested our reconstruction method on a set of realistic weak lensing simulations corresponding to typical HST/ACS cluster observations and demonstrate our ability to recover substructures with the inclusion of flexion, which are otherwise lost if only shear information is used. In particular, we can detect substructures on the 15'' scale well outside of the critical region of the clusters. In addition, flexion also helps to constrain the shape of the central regions of the main dark matter halos. Our mass mapping software, called Glimpse2D, is made freely available at http://www.cosmostat.org/software/glimpse

  9. Direct Shear Mapping: Prospects for weak lensing studies of individual galaxy-galaxy lensing systems

    CERN Document Server

    de Burgh-Day, Catherine O; Webster, Rachel L; Hopkins, Andrew M

    2015-01-01

    We have investigated, using both a theoretical and an empirical approach, the frequency of low redshift galaxy-galaxy lensing systems in which the signature of weak lensing might be directly detectable. We find good agreement between these two approaches. In order to make a theoretical estimate of the weak lensing shear, $\\gamma$, for each galaxy in a catalogue, we have made an estimate of the asymptotic circular velocity from the stellar mass using three different approaches: from a simulation based relation, from an empirically-derived relation, and using the baryonic Tully-Fisher relation. Using data from the Galaxy and Mass Assembly redshift survey we estimate the frequency of detectable weak lensing at low redshift. We find that to a redshift of $z\\sim 0.6$, the probability of a galaxy being weakly lensed by at least $\\gamma = 0.02$ is $\\sim 0.01$. A scatter in the $M_*-M_h$ relation results in a shift towards higher measured shears for a given population of galaxies. Given this, and the good probability...

  10. Extreme value statistics of weak lensing shear peak counts

    CERN Document Server

    Reischke, Robert; Bartelmann, Matthias

    2015-01-01

    The statistics of peaks in weak gravitational lensing maps is a promising technique to constrain cosmological parameters in present and future surveys. Here we investigate its power when using general extreme value statistics which is very sensitive to the exponential tail of the halo mass function. To this end, we use an analytic method to quantify the number of weak lensing peaks caused by galaxy clusters, large-scale structures and observational noise. Doing so, we further improve the method in the regime of high signal-to-noise ratios dominated by non-linear structures by accounting for the embedding of those counts into the surrounding shear caused by large scale structures. We derive the extreme value and order statistics for both over-densities (positive peaks) and under-densities (negative peaks) and provide an optimized criterion to split a wide field survey into sub-fields in order to sample the distribution of extreme values such that the expected objects causing the largest signals are mostly due ...

  11. Shear Nulling after PSF Gaussianisation: moment-based weak lensing measurements with subpercent noise bias

    CERN Document Server

    Herbonnet, Ricardo; Kuijken, Konrad

    2016-01-01

    Current optical imaging surveys for cosmology are covering large areas of sky. To exploit the statistical power of these surveys for weak lensing measurements requires shape measurement methods with subpercent systematic errors. We introduce a new weak lensing shear measurement algorithm, Shear Nulling after PSF Gaussianisation (SNAPG), designed to avoid the noise biases that affect most other methods. SNAPG operates on images that have been convolved with a kernel that renders the Point Spread Function (PSF) a circular Gaussian, and uses weighted second moments of the sources. The response of such second moments to a shear of the pre-seeing galaxy image can be predicted analytically, allowing us to construct a shear nulling scheme that finds the shear parameters for which the observed galaxies are consistent with an unsheared, isotropically oriented population of sources. The inverse of this nulling shear is then an estimate of the gravitational lensing shear. We identify the uncertainty of the estimated cen...

  12. Shear nulling after PSF Gaussianisation: Moment-based weak lensing measurements with subpercent noise bias

    Science.gov (United States)

    Herbonnet, Ricardo; Buddendiek, Axel; Kuijken, Konrad

    2017-03-01

    Context. Current optical imaging surveys for cosmology cover large areas of sky. Exploiting the statistical power of these surveys for weak lensing measurements requires shape measurement methods with subpercent systematic errors. Aims: We introduce a new weak lensing shear measurement algorithm, shear nulling after PSF Gaussianisation (SNAPG), designed to avoid the noise biases that affect most other methods. Methods: SNAPG operates on images that have been convolved with a kernel that renders the point spread function (PSF) a circular Gaussian, and uses weighted second moments of the sources. The response of such second moments to a shear of the pre-seeing galaxy image can be predicted analytically, allowing us to construct a shear nulling scheme that finds the shear parameters for which the observed galaxies are consistent with an unsheared, isotropically oriented population of sources. The inverse of this nulling shear is then an estimate of the gravitational lensing shear. Results: We identify the uncertainty of the estimated centre of each galaxy as the source of noise bias, and incorporate an approximate estimate of the centroid covariance into the scheme. We test the method on extensive suites of simulated galaxies of increasing complexity, and find that it is capable of shear measurements with multiplicative bias below 0.5 percent.

  13. The Shear TEsting Programme 2: Factors affecting high precision weak lensing analyses

    CERN Document Server

    Massey, R; Berge, J; Bernstein, G; Bridle, S; Clowe, D; Dahle, H; Ellis, R; Erben, T; Hetterscheidt, M; High, F W; Hirata, C; Hoekstra, H; Hudelot, P; Jarvis, M; Johnston, D; Kuijken, K; Margoniner, V; Mandelbaum, R; Mellier, Y; Nakajima, R; Paulin-Henriksson, S; Peeples, M; Roat, C; Réfrégier, A; Rhodes, J; Schrabback, T; Schirmer, M; Seljak, U; Semboloni, E; Van Waerbeke, L; Massey, Richard; Heymans, Catherine; Berge, Joel; Bernstein, Gary; Bridle, Sarah; Clowe, Douglas; Dahle, Hakon; Ellis, Richard; Erben, Thomas; Hetterscheidt, Marco; Hirata, Christopher; Hoekstra, Henk; Hudelot, Patrick; Jarvis, Mike; Johnston, David; Kuijken, Konrad; Margoniner, Vera; Mandelbaum, Rachel; Mellier, Yannick; Nakajima, Reiko; Paulin-Henriksson, Stephane; Peeples, Molly; Roat, Chris; Refregier, Alexandre; Rhodes, Jason; Schrabback, Tim; Schirmer, Mischa; Seljak, Uros; Semboloni, Elisabetta; Waerbeke, Ludovic Van

    2006-01-01

    The Shear TEsting Programme (STEP) is a collaborative project to improve the accuracy and reliability of weak lensing measurement, in preparation for the next generation of wide-field surveys. We review sixteen current and emerging shear measurement methods in a common language, and assess their performance by running them (blindly) on simulated images that contain a known shear signal. We determine the common features of algorithms that most successfully recover the input parameters. We achieve previously unattained discriminatory precision in our analysis, via a combination of more extensive simulations, and pairs of galaxy images that have been rotated with respect to each other, thus removing noise from their intrinsic ellipticities. The robustness of our simulation approach is also confirmed by testing the relative calibration of methods on real data. Weak lensing measurement has improved since the first STEP paper. Several methods now consistently achieve better than 2% precision, and are still being de...

  14. Radio Weak Lensing Shear Measurement in the Visibility Domain - I. Methodology

    CERN Document Server

    Rivi, Marzia; Makhathini, Sphesihle; Abdalla, Filipe Batoni

    2016-01-01

    The high sensitivity of the new generation of radio telescopes such as the Square Kilometre Array (SKA) will allow cosmological weak lensing measurements at radio wavelengths that are competitive with optical surveys. We present an adaptation to radio data of "lensfit", a method for galaxy shape measurement originally developed and used for optical weak lensing surveys. This likelihood method uses an analytical galaxy model and makes a Bayesian marginalisation of the likelihood over uninteresting parameters. It has the feature of working directly in the visibility domain, which is the natural approach to adopt with radio interferometer data, avoiding systematics introduced by the imaging process. As a proof of concept, we provide results for visibility simulations of individual galaxies with flux density S >= 10muJy at the phase centre of the proposed SKA1-MID baseline configuration, adopting 12 frequency channels in the band 950-1190 MHz. Weak lensing shear measurements from a population of galaxies with rea...

  15. High Resolution Weak Lensing Mass-Mapping Combining Shear and Flexion

    CERN Document Server

    Lanusse, Francois; Leonard, Adrienne; Pires, Sandrine

    2016-01-01

    We propose a new mass-mapping algorithm, specifically designed to recover small-scale information from a combination of gravitational shear and flexion. Including flexion allows us to supplement the shear on small scales in order to increase the sensitivity to substructures and the overall resolution of the convergence map without relying on strong lensing constraints. In order to preserve all available small scale information, we avoid any binning of the irregularly sampled input shear and flexion fields and treat the mass-mapping problem as a general ill-posed inverse problem, regularised using a robust multi-scale wavelet sparsity prior. The resulting algorithm incorporates redshift, reduced shear, and reduced flexion measurements for individual galaxies and is made highly efficient by the use of fast Fourier estimators. We test our reconstruction method on a set of realistic weak lensing simulations corresponding to typical HST/ACS cluster observations and demonstrate our ability to recover substructures ...

  16. Constraining primordial non-Gaussianity with cosmological weak lensing: shear and flexion

    CERN Document Server

    Fedeli, C; Moscardini, L

    2012-01-01

    We examine the cosmological constraining power of future large-scale weak lensing surveys on the model of \\emph{Euclid}, with particular reference to primordial non-Gaussianity. Our analysis considers several different estimators of the projected matter power spectrum, based on both shear and flexion, for which we review the covariances and Fisher matrices. The bounds provided by cosmic shear alone for the local bispectrum shape, marginalized over $\\sigma_8$, are at the level of $\\Delta f_\\mathrm{NL} \\sim 100$. We consider three additional bispectrum shapes, for which the cosmic shear constraints range from $\\Delta f_\\mathrm{NL}\\sim 340$ (equilateral shape) up to $\\Delta f_\\mathrm{NL}\\sim 500$ (orthogonal shape). The competitiveness of cosmic flexion constraints against cosmic shear ones depends on the galaxy intrinsic flexion noise, that is still virtually unconstrained. Adopting the very high value that has been occasionally used in the literature results in the flexion contribution being basically negligib...

  17. Radio Weak Lensing Shear Measurement in the Visibility Domain - I. Methodology

    Science.gov (United States)

    Rivi, M.; Miller, L.; Makhathini, S.; Abdalla, F. B.

    2016-08-01

    The high sensitivity of the new generation of radio telescopes such as the Square Kilometre Array (SKA) will allow cosmological weak lensing measurements at radio wavelengths that are competitive with optical surveys. We present an adaptation to radio data of lensfit, a method for galaxy shape measurement originally developed and used for optical weak lensing surveys. This likelihood method uses an analytical galaxy model and makes a Bayesian marginalisation of the likelihood over uninteresting parameters. It has the feature of working directly in the visibility domain, which is the natural approach to adopt with radio interferometer data, avoiding systematics introduced by the imaging process. As a proof of concept, we provide results for visibility simulations of individual galaxies with flux density S ≥ 10μJy at the phase centre of the proposed SKA1-MID baseline configuration, adopting 12 frequency channels in the band 950 - 1190 MHz. Weak lensing shear measurements from a population of galaxies with realistic flux and scalelength distributions are obtained after natural gridding of the raw visibilities. Shear measurements are expected to be affected by `noise bias': we estimate the bias in the method as a function of signal-to-noise ratio (SNR). We obtain additive and multiplicative bias values that are comparable to SKA1 requirements for SNR > 18 and SNR > 30, respectively. The multiplicative bias for SNR >10 is comparable to that found in ground-based optical surveys such as CFHTLenS, and we anticipate that similar shear measurement calibration strategies to those used for optical surveys may be used to good effect in the analysis of SKA radio interferometer data.

  18. Radio weak lensing shear measurement in the visibility domain - I. Methodology

    Science.gov (United States)

    Rivi, M.; Miller, L.; Makhathini, S.; Abdalla, F. B.

    2016-12-01

    The high sensitivity of the new generation of radio telescopes such as the Square Kilometre Array (SKA) will allow cosmological weak lensing measurements at radio wavelengths that are competitive with optical surveys. We present an adaptation to radio data of lensfit, a method for galaxy shape measurement originally developed and used for optical weak lensing surveys. This likelihood method uses an analytical galaxy model and makes a Bayesian marginalization of the likelihood over uninteresting parameters. It has the feature of working directly in the visibility domain, which is the natural approach to adopt with radio interferometer data, avoiding systematics introduced by the imaging process. As a proof of concept, we provide results for visibility simulations of individual galaxies with flux density S ≥ 10 μJy at the phase centre of the proposed SKA1-MID baseline configuration, adopting 12 frequency channels in the band 950-1190 MHz. Weak lensing shear measurements from a population of galaxies with realistic flux and scalelength distributions are obtained after natural gridding of the raw visibilities. Shear measurements are expected to be affected by `noise bias': we estimate the bias in the method as a function of signal-to-noise ratio (SNR). We obtain additive and multiplicative bias values that are comparable to SKA1 requirements for SNR > 18 and SNR > 30, respectively. The multiplicative bias for SNR >10 is comparable to that found in ground-based optical surveys such as CFHTLenS, and we anticipate that similar shear measurement calibration strategies to those used for optical surveys may be used to good effect in the analysis of SKA radio interferometer data.

  19. The Shear Testing Programme 2: Factors affecting high-precision weak-lensing analyses

    Science.gov (United States)

    Massey, Richard; Heymans, Catherine; Bergé, Joel; Bernstein, Gary; Bridle, Sarah; Clowe, Douglas; Dahle, Håkon; Ellis, Richard; Erben, Thomas; Hetterscheidt, Marco; High, F. William; Hirata, Christopher; Hoekstra, Henk; Hudelot, Patrick; Jarvis, Mike; Johnston, David; Kuijken, Konrad; Margoniner, Vera; Mandelbaum, Rachel; Mellier, Yannick; Nakajima, Reiko; Paulin-Henriksson, Stephane; Peeples, Molly; Roat, Chris; Refregier, Alexandre; Rhodes, Jason; Schrabback, Tim; Schirmer, Mischa; Seljak, Uroš; Semboloni, Elisabetta; van Waerbeke, Ludovic

    2007-03-01

    The Shear Testing Programme (STEP) is a collaborative project to improve the accuracy and reliability of weak-lensing measurement, in preparation for the next generation of wide-field surveys. We review 16 current and emerging shear-measurement methods in a common language, and assess their performance by running them (blindly) on simulated images that contain a known shear signal. We determine the common features of algorithms that most successfully recover the input parameters. A desirable goal would be the combination of their best elements into one ultimate shear-measurement method. In this analysis, we achieve previously unattained discriminatory precision via a combination of more extensive simulations and pairs of galaxy images that have been rotated with respect to each other. That removes the otherwise overwhelming noise from their intrinsic ellipticities. Finally, the robustness of our simulation approach is confirmed by testing the relative calibration of methods on real data. Weak-lensing measurements have improved since the first STEP paper. Several methods now consistently achieve better than 2 per cent precision, and are still being developed. However, we can now distinguish all methods from perfect performance. Our main concern continues to be the potential for a multiplicative shear calibration bias: not least because this cannot be internally calibrated with real data. We determine which galaxy populations are responsible for bias and, by adjusting the simulated observing conditions, we also investigate the effects of instrumental and atmospheric parameters. The simulated point spread functions are not allowed to vary spatially, to avoid additional confusion from interpolation errors. We have isolated several previously unrecognized aspects of galaxy shape measurement, in which focused development could provide further progress towards the sub-per cent level of precision desired for future surveys. These areas include the suitable treatment of

  20. CLASH: Weak-lensing shear-and-magnification analysis of 20 galaxy clusters

    Energy Technology Data Exchange (ETDEWEB)

    Umetsu, Keiichi; Czakon, Nicole [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Medezinski, Elinor; Lemze, Doron; Ford, Holland [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Nonino, Mario; Balestra, Italo; Biviano, Andrea [INAF-Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, I-34143 Trieste (Italy); Merten, Julian [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Postman, Marc; Koekemoer, Anton [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Meneghetti, Massimo [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Donahue, Megan [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Molino, Alberto; Benítez, Narciso [Instituto de Astrofísica de Andalucía (CSIC), E-18008 Granada (Spain); Seitz, Stella; Gruen, Daniel [Universitäts-Sternwarte, München, Scheinerstrasse 1, D-81679 Munich Germany (Germany); Broadhurst, Tom [Ikerbasque, Basque Foundation for Science, Alameda Urquijo, 36-5 Plaza Bizkaia, E-48011 Bilbao (Spain); Grillo, Claudio [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Melchior, Peter, E-mail: keiichi@asiaa.sinica.edu.tw [Center for Cosmology and Astro-Particle Physics and Department of Physics, The Ohio State University, Columbus, OH 43210 (United States); and others

    2014-11-10

    We present a joint shear-and-magnification weak-lensing analysis of a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19 ≲ z ≲ 0.69 selected from the Cluster Lensing And Supernova survey with Hubble (CLASH). Our analysis uses wide-field multi-color imaging, taken primarily with Suprime-Cam on the Subaru Telescope. From a stacked-shear-only analysis of the X-ray-selected subsample, we detect the ensemble-averaged lensing signal with a total signal-to-noise ratio of ≅ 25 in the radial range of 200-3500 kpc h {sup –1}, providing integrated constraints on the halo profile shape and concentration-mass relation. The stacked tangential-shear signal is well described by a family of standard density profiles predicted for dark-matter-dominated halos in gravitational equilibrium, namely, the Navarro-Frenk-White (NFW), truncated variants of NFW, and Einasto models. For the NFW model, we measure a mean concentration of c{sub 200c}=4.01{sub −0.32}{sup +0.35} at an effective halo mass of M{sub 200c}=1.34{sub −0.09}{sup +0.10}×10{sup 15} M{sub ⊙}. We show that this is in excellent agreement with Λ cold dark matter (ΛCDM) predictions when the CLASH X-ray selection function and projection effects are taken into account. The best-fit Einasto shape parameter is α{sub E}=0.191{sub −0.068}{sup +0.071}, which is consistent with the NFW-equivalent Einasto parameter of ∼0.18. We reconstruct projected mass density profiles of all CLASH clusters from a joint likelihood analysis of shear-and-magnification data and measure cluster masses at several characteristic radii assuming an NFW density profile. We also derive an ensemble-averaged total projected mass profile of the X-ray-selected subsample by stacking their individual mass profiles. The stacked total mass profile, constrained by the shear+magnification data, is shown to be consistent with our shear-based halo-model predictions, including the effects of surrounding large-scale structure as

  1. Redshift Distributions of Galaxies in the DES Science Verification Shear Catalogue and Implications for Weak Lensing

    Energy Technology Data Exchange (ETDEWEB)

    Bonnett, C. [Universitat Autonoma de Barcelona (Spain). et al.

    2015-07-21

    We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods { annz2, bpz calibrated against BCC-U fig simulations, skynet, and tpz { are analysed. For training, calibration, and testing of these methods, we also construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evalu-ated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-zs. From the galaxies in the DES SV shear catalogue, which have mean redshift 0.72 ±0.01 over the range 0:3 < z < 1:3, we construct three tomographic bins with means of z = {0.45; 0.67,1.00g}. These bins each have systematic uncertainties δz ≲ 0.05 in the mean of the fiducial skynet photo-z n(z). We propagate the errors in the redshift distributions through to their impact on cosmological parameters estimated with cosmic shear, and find that they cause shifts in the value of σ8 of approx. 3%. This shift is within the one sigma statistical errors on σ8 for the DES SV shear catalog. We also found that further study of the potential impact of systematic differences on the critical surface density, Σcrit, contained levels of bias safely less than the statistical power of DES SV data. We recommend a final Gaussian prior for the photo-z bias in the mean of n(z) of width 0:05 for each of the three tomographic bins, and show that this is a sufficient bias model for the corresponding cosmology analysis.

  2. Calibration of weak-lensing shear in the Kilo-Degree Survey

    CERN Document Server

    Conti, Ian Fenech; Hoekstra, Henk; Merten, Julian; Miller, Lance; Viola, Massimo

    2016-01-01

    We describe and test the pipeline used to measure the weak lensing shear signal from the Kilo Degree Survey (KiDS). It includes a novel method of `self-calibration' that partially corrects for the effect of noise bias. We also discuss the `weight bias' that may arise in optimally-weighted measurements, and present a scheme to mitigate that bias. To study the residual biases arising from both galaxy selection and shear measurement, and to derive an empirical correction to reduce the shear biases to $\\lesssim 1\\%$, we create a suite of simulated images whose properties are close to those of the KiDS survey observations. We find that the use of `self-calibration' reduces the additive and multiplicative shear biases significantly, although further correction via a calibration scheme is required, which also corrects for a dependence of the bias on galaxy properties. We find that the calibration relation itself is biased by the use of noisy, measured galaxy properties, which may limit the final accuracy that can be...

  3. Redshift distributions of galaxies in the DES Science Verification shear catalogue and implications for weak lensing

    CERN Document Server

    Bonnett, C; Amara, A; Leistedt, B; Becker, M R; Bernstein, G M; Bridle, S; Bruderer, C; Busha, M T; Kind, M Carrasco; Childress, M J; Castander, F J; Chang, C; Crocce, M; Davis, T M; Eifler, T F; Frieman, J; Gangkofner, C; Gaztanaga, E; Glazebrook, K; Gruen, D; Kacprzak, T; King, A; Kwan, J; Lahav, O; Lewis, G; Lidman, C; Lin, H; MacCrann, N; Miquel, R; O'Neill, C R; Palmese, A; Peiris, H V; Refregier, A; Rozo, E; Rykoff, E S; Sadeh, I; Sánchez, C; Sheldon, E; Uddin, S; Wechsler, R H; Zuntz, J; Abbott, T; Abdalla, F B; Allam, S; Armstrong, R; Banerji, M; Bauer, A H; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Carretero, J; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Neto, A Fausti; Fernandez, E; Flaugher, B; Fosalba, P; Gerdes, D W; Gruendl, R A; Honscheid, K; Jain, B; James, D J; Jarvis, M; Kim, A G; Kuehn, K; Kuropatkin, N; Li, T S; Lima, M; Maia, M A G; March, M; Marshall, J L; Martini, P; Melchior, P; Miller, C J; Neilsen, E; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Santiago, B; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Vikram, V; Walker, A R

    2015-01-01

    We present photometric redshift estimates for galaxies used in the weak lensing analysis of the Dark Energy Survey Science Verification (DES SV) data. Four model- or machine learning-based photometric redshift methods -- ANNZ2, BPZ calibrated against BCC-Ufig simulations, SkyNet, and TPZ -- are analysed. For training, calibration, and testing of these methods, we construct a catalogue of spectroscopically confirmed galaxies matched against DES SV data. The performance of the methods is evaluated against the matched spectroscopic catalogue, focusing on metrics relevant for weak lensing analyses, with additional validation against COSMOS photo-zs. From the galaxies in the DES SV shear catalogue, which have mean redshift $0.72\\pm0.01$ over the range $0.3

  4. CLASH: Joint Analysis of Strong-lensing, Weak-lensing Shear, and Magnification Data for 20 Galaxy Clusters

    Science.gov (United States)

    Umetsu, Keiichi; Zitrin, Adi; Gruen, Daniel; Merten, Julian; Donahue, Megan; Postman, Marc

    2016-04-01

    We present a comprehensive analysis of strong-lensing, weak-lensing shear and magnification data for a sample of 16 X-ray-regular and 4 high-magnification galaxy clusters at 0.19≲ z≲ 0.69 selected from Cluster Lensing And Supernova survey with Hubble (CLASH). Our analysis combines constraints from 16-band Hubble Space Telescope observations and wide-field multi-color imaging taken primarily with Suprime-Cam on the Subaru Telescope, spanning a wide range of cluster radii (10″-16‧). We reconstruct surface mass density profiles of individual clusters from a joint analysis of the full lensing constraints, and determine masses and concentrations for all of the clusters. We find the internal consistency of the ensemble mass calibration to be ≤5% ± 6% in the one-halo regime (200-2000 kpc h-1) compared to the CLASH weak-lensing-only measurements of Umetsu et al. For the X-ray-selected subsample of 16 clusters, we examine the concentration-mass (c-M) relation and its intrinsic scatter using a Bayesian regression approach. Our model yields a mean concentration of c{| }z=0.34=3.95+/- 0.35 at M200c ≃ 14 × 1014 M⊙ and an intrinsic scatter of σ ({ln}{c}200{{c}})=0.13+/- 0.06, which is in excellent agreement with Λ cold dark matter predictions when the CLASH selection function based on X-ray morphological regularity and the projection effects are taken into account. We also derive an ensemble-averaged surface mass density profile for the X-ray-selected subsample by stacking their individual profiles. The stacked lensing signal is detected at 33σ significance over the entire radial range ≤4000 kpc h-1, accounting for the effects of intrinsic profile variations and uncorrelated large-scale structure along the line of sight. The stacked mass profile is well described by a family of density profiles predicted for cuspy dark-matter-dominated halos in gravitational equilibrium, namely, the Navarro-Frenk-White (NFW), Einasto, and DARKexp models, whereas the single

  5. Very weak lensing in the CFHTLS Wide: Cosmology from cosmic shear in the linear regime

    CERN Document Server

    Fu, L; Hoekstra, H; Kilbinger, M; Van Waerbeke, L; Tereno, I; Mellier, Y; Heymans, C; Coupon, J; Benabed, K; Benjamin, J; Bertin, E; Doré, O; Hudson, M J; Ilbert, O; Maoli, R; Marmo, C; McCracken, H J; Ménard, B

    2007-01-01

    We present an exploration of weak lensing by large-scale structure in the linear regime, using the third-year (T0003) CFHTLS Wide data release. Our results place tight constraints on the scaling of the amplitude of the matter power spectrum sigma_8 with the matter density Omega_m. Spanning 57 square degrees to i'_AB = 24.5 over three independent fields, the unprecedented contiguous area of this survey permits high signal-to-noise measurements of two-point shear statistics from 1 arcmin to 4 degrees. Understanding systematic errors in our analysis is vital in interpreting the results. We therefore demonstrate the percent-level accuracy of our method using STEP simulations, an E/B-mode decomposition of the data, and the star-galaxy cross correlation function. We also present a thorough analysis of the galaxy redshift distribution using redshift data from the CFHTLS T0003 Deep fields that probe the same spatial regions as the Wide fields. We find sigma_8(Omega_m/0.25)^0.64 = 0.785+-0.043 using the aperture-mass ...

  6. Elliptical Weighted HOLICs for Weak Lensing Shear Measurement. part1:Definitions and isotropic PSF correction

    CERN Document Server

    Okura, Yuki

    2010-01-01

    We develop a new method to estimate gravitational shear by adopting an elliptical weight function to measure background galaxy images. In doing so, we introduce a new concept of "zero plane" which is an imaginal source plane where shapes of all sources are perfect circles, and regard the intrinsic shear as the result of an imaginal lensing distortion. This makes the relation between the observed shear, the intrinsic shear and lensing distortion more simple and thus higher-order calculation more easy. The elliptical weight function allows us to measure the mutiplemoment of shape of background galaxies more precisely by weighting highly to brighter parts of image and moreover to reduce systematic error due to insufficient expansion of the weight function in the original approach of KSB. Point Spread Function(PSF) correction in E-HOLICs methods becomes more complicated than those in KSB methods. In this paper we studied isotropic PSF correction in detail. By adopting the lensing distortion as the ellipticity of ...

  7. CALCLENS: weak lensing simulations for large-area sky surveys and second-order effects in cosmic shear power spectra

    Science.gov (United States)

    Becker, Matthew R.

    2013-10-01

    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.

  8. CFHTLenS: A Weak Lensing Shear Analysis of the 3D-Matched-Filter Galaxy Clusters

    CERN Document Server

    Ford, Jes; Milkeraitis, Martha; Laigle, Clotilde; Hildebrandt, Hendrik; Erben, Thomas; Heymans, Catherine; Hoekstra, Henk; Kitching, Thomas; Mellier, Yannick; Miller, Lance; Choi, Ami; Coupon, Jean; Fu, Liping; Hudson, Michael J; Kuijken, Konrad; Robertson, Naomi; Rowe, Barnaby; Schrabback, Tim; Velander, Malin

    2014-01-01

    We present the cluster mass-richness scaling relation calibrated by a weak lensing analysis of >18,000 galaxy cluster candidates in the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). Detected using the 3D-Matched-Filter cluster-finder of Milkeraitis et al., these cluster candidates span a wide range of masses, from the small group scale up to $\\sim10^{15} M_{\\odot}$, and redshifts 0.2 $\\lesssim z\\lesssim$ 0.9. The total significance of the shear measurement amounts to 54$\\sigma$. We compare cluster masses determined using weak lensing shear and magnification, finding the measurements in individual richness bins to yield 1$\\sigma$ compatibility, but with magnification estimates biased low. This first direct mass comparison yields important insights for improving the systematics handling of future lensing magnification work. In addition, we confirm analyses that suggest cluster miscentring has an important effect on the observed 3D-Matched-Filter halo profiles, and we quantify this by fitting for pro...

  9. Galaxy-galaxy weak lensing in SDSS: intrinsic alignments and shear calibration errors

    CERN Document Server

    Hirata, C M; Seljak, U; Guzik, J; Padmanabhan, N; Blake, C; Brinkmann, J; Budavari, T; Connolly, A; Csabai, I; Scranton, R; Szalay, A S; Hirata, Christopher M.; Mandelbaum, Rachel; Seljak, Uros; Guzik, Jacek; Padmanabhan, Nikhil; Blake, Cullen; Brinkmann, Jonathan; Budavari, Tamas; Connolly, Andrew; Csabai, Istvan; Scranton, Ryan; Szalay, Alexander S.

    2004-01-01

    Galaxy-galaxy lensing has emerged as a powerful probe of the dark matter haloes of galaxies, but is subject to contamination if intrinsically aligned satellites of the lens galaxy are used as part of the source sample. We present a measurement of this intrinsic shear using 200,747 lens galaxies from the Sloan Digital Sky Survey (SDSS) spectroscopic sample and a sample of satellites selected using photometric redshifts. The mean intrinsic shear at transverse separations of 30--446$h^{-1}$ kpc is constrained to be $-0.0062<\\Delta\\gamma<+0.0066$ (99.9 per cent confidence, including identified systematics), which limits contamination of the galaxy-galaxy lensing signal to at most $\\sim 15$ per cent on these scales. We present these limits as a function of transverse separation and lens luminosity. We furthermore investigate shear calibration biases in the SDSS and conclude that the shear amplitude is calibrated to better than 18 per cent. This includes noise-induced calibration biases in the ellipticity, wh...

  10. Shapes and Shears, Stars and Smears Optimal Measurements for Weak Lensing

    CERN Document Server

    Bernstein, G M

    2001-01-01

    We present the theoretical and analytical bases of optimal techniques to measure weak gravitational shear from images of galaxies. We first characterize the geometric space of shears and ellipticity, then use this geometric interpretation to analyse images. The steps of this analysis include: measurement of object shapes on images, combining measurements of a given galaxy on different images, estimating the underlying shear from an ensemble of galaxy shapes, and compensating for the systematic effects of image distortion, bias from PSF asymmetries, and `"dilution" of the signal by the seeing. These methods minimize the ellipticity measurement noise, provide calculable shear uncertainty estimates, and allow removal of systematic contamination by PSF effects to arbitrary precision. Galaxy images and PSFs are decomposed into a family of orthogonal 2d Gaussian-based functions, making the PSF correction and shape measurement relatively straightforward and computationally efficient. We also discuss sources of noise...

  11. Weak-lensing shear estimates with general adaptive moments, and studies of bias by pixellation, PSF distortions, and noise

    CERN Document Server

    Simon, Patrick

    2016-01-01

    In weak gravitational lensing, weighted quadrupole moments of the brightness profile in galaxy images are a common way to estimate gravitational shear. We employ general adaptive moments (GLAM) to study causes of shear bias on a fundamental level and for a practical definition of an image ellipticity. For GLAM, the ellipticity is identical to that of isophotes of elliptical images, and this ellipticity is always an unbiased estimator of reduced shear. Our theoretical framework reiterates that moment-based techniques are similar to a model-based approach in the sense that they fit an elliptical profile to the image to obtain weighted moments. As a result, moment-based estimates of ellipticities are prone to underfitting bias. The estimation is fundamentally limited mainly by pixellation which destroys information on the original, pre-seeing image. We give an optimized estimator for the pre-seeing GLAM ellipticity and its bias for noise-free images. To deal with images where pixel noise is prominent, we conside...

  12. Elliptically Weighted HOLICs for Weak-lensing Shear Measurement. I. Definitions and Isotropic Point-spread Function Correction

    Science.gov (United States)

    Okura, Yuki; Futamase, Toshifumi

    2011-03-01

    We develop a new method of estimating gravitational shear by adopting an elliptical weight function to measure background galaxy images. In doing so, we introduce the new concept of "zero plane," which is an imaginary source plane where shapes of all sources are perfect circles, and regard the intrinsic shear as the result of an imaginary lensing distortion. This makes the relation between the observed shear, intrinsic shear, and lensing distortion much simpler, and thus higher-order calculations are easier. The elliptical weight function allows us to measure the multipole moments of the shapes of background galaxies more precisely by weighting brighter parts of the image highly, and to reduce systematic error due to insufficient expansion of the weight function in the original approach of Kaiser et al. (KSB). Point-spread function (PSF) correction in the elliptically weighted higher-order lensing image characteristics (E-HOLICs) method becomes more complicated than in the KSB method. In this paper, we study isotropic PSF correction in detail. By adopting the lensing distortion as the ellipticity of the weight function, we are able to show that the shear estimation in the E-HOLICs method reduces to solve a polynomial in the absolute magnitude of the distortion. We compare the systematic errors between our approach and that of KSB using the Shear Testing Programme 2 simulation. It is confirmed that the KSB method overestimates the input shear for images with large ellipticities, and E-HOLICs correctly estimates the input shear even for such images. Anisotropic PSF correction and analysis of real data will be presented in a forthcoming paper.

  13. Roulettes: a weak lensing formalism for strong lensing: I. Overview

    Science.gov (United States)

    Clarkson, Chris

    2016-08-01

    We present a new perspective on gravitational lensing. We describe a new extension of the weak lensing formalism capable of describing strongly lensed images. By integrating the nonlinear geodesic deviation equation, the amplification matrix of weak lensing is generalised to a sum over independent amplification tensors of increasing rank. We show how an image distorted by a generic lens may be constructed as a sum over ‘roulettes’, which are the natural curves associated with the independent spin modes of the amplification tensors. Highly distorted images can be constructed even for large sources observed near or within the Einstein radius of a lens where the shear and convergence are large. The amplitude of each roulette is formed from a sum over appropriate derivatives of the lensing potential. Consequently, measuring these individual roulettes for images around a lens gives a new way to reconstruct a strong lens mass distribution without requiring a lens model. This formalism generalises the convergence, shear and flexion of weak lensing to arbitrary order, and provides a unified bridge between the strong and weak lensing regimes. This overview paper is accompanied by a much more detailed paper II, arXiv:1603.04652.

  14. A demonstration of position angle-only weak lensing shear estimators on the GREAT3 simulations

    CERN Document Server

    Whittaker, Lee; Battye, Richard A

    2015-01-01

    We develop and apply the position angle-only shear estimator of Whittaker et al. (2014) to realistic galaxy images. This is done by demonstrating the method on the simulations of the GREAT3 challenge (Mandelbaum et al. 2014b), which include contributions from anisotropic PSFs. We measure the position angles of the galaxies using three distinct methods - the integrated light method, quadrupole moments of surface brightness, and using model-based ellipticity measurements provided by IM3SHAPE. A weighting scheme is adopted to address biases in the position angle measurements which arise in the presence of an anisotropic PSF. Biases on the shear estimates, due to measurement errors on the position angles and correlations between the measurement errors and the true position angles, are corrected for using simulated galaxy images and an iterative procedure. The properties of the simulations are estimated using the deep field images provided as part of the challenge. A method is developed to match the distributions ...

  15. Roulettes: A weak lensing formalism for strong lensing - I. Overview

    CERN Document Server

    Clarkson, Chris

    2016-01-01

    We present a new perspective on gravitational lensing. We describe a new extension of the weak lensing formalism capable of describing strongly lensed images. By integrating the non-linear geodesic deviation equation, the amplification matrix of weak lensing is generalised to a sum over independent amplification tensors of increasing rank. We show how an image distorted by a generic lens may be constructed as a sum over `roulettes', which are the natural curves associated with the independent spin modes of the amplification tensors. Highly distorted images can be constructed even for large sources observed near or within the Einstein radius of a lens where the shear and convergence are large. The amplitude of each roulette is formed from a sum over appropriate derivatives of the lensing potential. Consequently, measuring these individual roulettes for images around a lens gives a new way to reconstruct a strong lens mass distribution without requiring a lens model. This formalism generalises the convergence, ...

  16. Weak lensing in the Dark Energy Survey

    Science.gov (United States)

    Troxel, Michael

    2016-03-01

    I will present the current status of weak lensing results from the Dark Energy Survey (DES). DES will survey 5000 square degrees in five photometric bands (grizY), and has already provided a competitive weak lensing catalog from Science Verification data covering just 3% of the final survey footprint. I will summarize the status of shear catalog production using observations from the first year of the survey and discuss recent weak lensing science results from DES. Finally, I will report on the outlook for future cosmological analyses in DES including the two-point cosmic shear correlation function and discuss challenges that DES and future surveys will face in achieving a control of systematics that allows us to take full advantage of the available statistical power of our shear catalogs.

  17. Atmospheric dispersion effects in weak lensing measurements

    CERN Document Server

    Plazas, Andrés A

    2012-01-01

    The wavelength dependence of atmospheric refraction causes elongation of finite-bandwidth images along the elevation vector, which produces spurious signals in weak gravitational lensing shear measurements unless this atmospheric dispersion is calibrated and removed to high precision. Because astrometric solutions and point spread function (PSF) characteristics are typically calibrated from stellar images, differences between the reference stars' spectra and the galaxies' spectra will leave residual errors in both the astrometric positions ($\\Delta{\\bar{R}}$) and in the second moment (width) of the wavelength-averaged PSF ($\\Delta{v}$) for galaxies. We estimate the level of $\\Delta{V}$ that will induce spurious weak lensing signals in PSF-corrected galaxy shapes that exceed the statistical errors of the {\\em Dark Energy Survey (DES)} and the {\\em Large Synoptic Survey Telescope (LSST)} cosmic-shear experiments. We also estimate the $\\Delta{\\bar{R}}$ signals that will produce unacceptable spurious distortions ...

  18. Subaru Weak Lensing Measurements of Four Strong Lensing Clusters: Are Lensing Clusters Over-Concentrated?

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-01-29

    We derive radial mass profiles of four strong lensing selected clusters which show prominent giant arcs (Abell 1703, SDSS J1446+3032, SDSS J1531+3414, and SDSS J2111-0115), by combining detailed strong lens modeling with weak lensing shear measured from deep Subaru Suprime-cam images. Weak lensing signals are detected at high significance for all four clusters, whose redshifts range from z = 0.28 to 0.64. We demonstrate that adding strong lensing information with known arc redshifts significantly improves constraints on the mass density profile, compared to those obtained from weak lensing alone. While the mass profiles are well fitted by the universal form predicted in N-body simulations of the {Lambda}-dominated cold dark matter model, all four clusters appear to be slightly more centrally concentrated (the concentration parameters c{sub vir} {approx} 8) than theoretical predictions, even after accounting for the bias toward higher concentrations inherent in lensing selected samples. Our results are consistent with previous studies which similarly detected a concentration excess, and increases the total number of clusters studied with the combined strong and weak lensing technique to ten. Combining our sample with previous work, we find that clusters with larger Einstein radii are more anomalously concentrated. We also present a detailed model of the lensing cluster Abell 1703 with constraints from multiple image families, and find the dark matter inner density profile to be cuspy with the slope consistent with -1, in agreement with expectations.

  19. The imprint of $f(R)$ gravity on weak gravitational lensing II : Information content in cosmic shear statistics

    CERN Document Server

    Shirasaki, Masato; Li, Baojiu; Higuchi, Yuichi

    2016-01-01

    We investigate the information content of various cosmic shear statistics on the theory of gravity. Focusing on the Hu-Sawicki type $f(R)$ model, we perform a set of ray-tracing simulations and measure the convergence bispectrum, peak counts and Minkowski functionals, paying a special attention to their complementarity to the standard power spectrum analysis. We first show that while the convergence power spectrum does have sensitivity to the current value of extra scalar degree of freedom $|f_{\\rm R0}|$, it is largely compensated by a change in the present density amplitude parameter $\\sigma_{8}$ and the matter density parameter $\\Omega_{\\rm m0}$. With accurate covariance matrices obtained from 1000 lensing simulations, we then examine the constraining power of the three additional statistics. We find that these probes are indeed helpful to break the parameter degeneracy, which can not be resolved from the power spectrum alone. We show that especially the peak counts and Minkowski functionals have the potent...

  20. The imprint of f(R) gravity on weak gravitational lensing - II. Information content in cosmic shear statistics

    Science.gov (United States)

    Shirasaki, Masato; Nishimichi, Takahiro; Li, Baojiu; Higuchi, Yuichi

    2017-04-01

    We investigate the information content of various cosmic shear statistics on the theory of gravity. Focusing on the Hu-Sawicki-type f(R) model, we perform a set of ray-tracing simulations and measure the convergence bispectrum, peak counts and Minkowski functionals. We first show that while the convergence power spectrum does have sensitivity to the current value of extra scalar degree of freedom |fR0|, it is largely compensated by a change in the present density amplitude parameter σ8 and the matter density parameter Ωm0. With accurate covariance matrices obtained from 1000 lensing simulations, we then examine the constraining power of the three additional statistics. We find that these probes are indeed helpful to break the parameter degeneracy, which cannot be resolved from the power spectrum alone. We show that especially the peak counts and Minkowski functionals have the potential to rigorously (marginally) detect the signature of modified gravity with the parameter |fR0| as small as 10-5 (10-6) if we can properly model them on small (∼1 arcmin) scale in a future survey with a sky coverage of 1500 deg2. We also show that the signal level is similar among the additional three statistics and all of them provide complementary information to the power spectrum. These findings indicate the importance of combining multiple probes beyond the standard power spectrum analysis to detect possible modifications to general relativity.

  1. Weak lensing and cosmological investigation

    CERN Document Server

    Acquaviva, V

    2005-01-01

    In the last few years the scientific community has been dealing with the challenging issue of identifying the dark energy component. We regard weak gravitational lensing as a brand new, and extremely important, tool for cosmological investigation in this field. In fact, the features imprinted on the cosmic microwave background radiation by the lensing from the intervening distribution of matter represent a pretty unbiased estimator, and can thus be used for putting constraints on different dark energy models. This is true in particular for the magnetic-type B-modes of CMB polarization, whose unlensed spectrum at large multipoles (l approximately=1000) is very small even in presence of an amount of gravitational waves as large as currently allowed by the experiments: therefore, on these scales the lensing phenomenon is the only responsible for the observed power, and this signal turns out to be a faithful tracer of the dark energy dynamics. We first recall the formal apparatus of the weak lensing in extended t...

  2. Weak lensing using only galaxy position angles

    CERN Document Server

    Whittaker, Lee; Battye, Richard

    2013-01-01

    We develop a method for performing a weak lensing analysis using only measurements of galaxy position angles. By analyzing the statistical properties of the galaxy orientations given a known intrinsic ellipticity distribution, we show that it is possible to obtain estimates of the shear by minimizing a $\\chi^2$ statistic. The method is demonstrated using simulations where the components of the intrinsic ellipticity are taken to be Gaussian distributed. Uncertainties on the position angle measurements introduce a bias into the shear estimates which can be reduced to negligible levels by introducing a correction term into the formalism. We generalize our approach by developing an algorithm to obtain direct shear estimators given any azimuthally symmetric intrinsic ellipticity distribution. We demonstrate this technique by applying it to simulations where the ellipticities are taken to follow a log-normal distribution. We compare the performance of the position angle only method with the standard method based on...

  3. Can weak lensing surveys confirm BICEP2 ?

    CERN Document Server

    Chisari, Nora Elisa; Schmidt, Fabian

    2014-01-01

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

  4. Weak lensing goes bananas: What flexion really measures

    CERN Document Server

    Schneider, Peter

    2007-01-01

    In weak gravitational lensing, the image distortion caused by shear measures the projected tidal gravitational field of the deflecting mass distribution. To lowest order, the shear is proportional to the mean image ellipticity. If the image sizes are not small compared to the scale over which the shear varies, higher-order distortions occur, called flexion. For ordinary weak lensing, the observable quantity is not the shear, but the reduced shear, owing to the mass-sheet degeneracy. Likewise, the flexion itself is unobservable. Rather, higher-order image distortions measure the reduced flexion, i.e., derivatives of the reduced shear. We derive the corresponding lens equation in terms of the reduced flexion and calculate the resulting relation between brightness moments of source and image. Assuming an isotropic distribution of source orientations, estimates for the reduced shear and flexion are obtained; these are then tested with simulations. In particular, the presence of flexion affects the determination o...

  5. Weak gravitational lensing with the Hyper Suprime-Cam survey

    Science.gov (United States)

    Mandelbaum, Rachel; Hyper Suprime-Cam (HSC) Collaboration

    2017-01-01

    Data from the Hyper Suprime-Cam (HSC) survey on the Subaru telescope show great promise for weak gravitational lensing science. The unprecedented combination of area, depth, and imaging quality of this survey (with median i-band seeing of 0.6 arcsec) will enable a wide array of weak lensing measurements, with significant contributions from lenses up to redshift z~1. Applications include cosmological weak lensing measurements from shear-shear and galaxy-shear correlations, which will be especially powerful when combined with the overlapping SDSS-III spectroscopic datasets; and studies of the dark matter halos of galaxies and galaxy clusters. In this talk, I will demonstrate the imaging quality and the tests used to validate the weak lensing measurements. These include null tests internal to the data, comparisons with external datasets, and image simulation-based tests. I will also show the lensing mass profiles of spectroscopic galaxies from the SDSS-III, illustrating the current signal-to-noise ratio on small and large scales and demonstrating the potential for innovative galaxy and cosmological science with the complete survey area.

  6. Optimal Weak Lensing Skewness Measurements

    CERN Document Server

    Zhang, T J; Zhang, P; Dubinski, J; Zhang, Tong-Jie; Pen, Ue-Li; Zhang, Pengjie; Dubinski, John

    2003-01-01

    Weak lensing measurements are entering a precision era to statistically map the distribution of matter in the universe. The most common measurement has been of the variance of the projected surface density of matter, which corresponds to the induced correlation in alignments of background galaxies. This measurement of the fluctuations is insensitive to the total mass content, like using waves on the ocean to measure its depths. But when the depth is shallow as happens near a beach, waves become skewed. Similarly, a measurement of skewness in the projected matter distribution directly measures the total matter content of the universe. While skewness has already been convincingly detected, its constraint on cosmology is still weak. We address optimal analyses for the CFHT Legacy Survey in the presence of noise. We show that a compensated Gaussian filter with a width of 2.5 arc minutes optimizes the cosmological constraint, yielding $\\Delta \\Omega_m/\\Omega_m\\sim 10%$. This is significantly better than other filt...

  7. Baryons, Neutrinos, Feedback and Weak Gravitational Lensing

    CERN Document Server

    Harnois-Déraps, Joachim; Viola, Massimo; Heymans, Catherine

    2014-01-01

    (Abridged) The effect of baryonic feedback on the dark matter mass distribution is generally considered to be a nuisance to weak gravitational lensing. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arcminutes. Recent progress on the numerical modelling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current weak lensing surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform our analysis, we construct an analytic fitting formula that describes the effect of the baryons on the mass power spectrum. This fitting formula is based on three scenarios of the OWL hydrodynamical simulations. It is specifically calibrated for $z<1.5$, where it models the simulations to an accuracy that is better than $2\\%$ for scales $k<10 h\\mbox{Mpc}^{-1}$ and better than ...

  8. Magnified Weak Lensing Cross Correlation Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, Melville P., Clowe, Douglas I.

    2010-11-30

    nights on 4-m class telescopes, which gives concrete evidence of strong community support for this project. The WLT technique is based on the dependence of the gravitational shear signal on the angular diameter distances between the observer, the lens, and the lensed galaxy to measure cosmological parameters. By taking the ratio of measured shears of galaxies with different redshifts around the same lens, one obtains a measurement of the ratios of the angular diameter distances involved. Making these observations over a large range of lenses and background galaxy redshifts will measure the history of the expansion rate of the universe. Because this is a purely geometric measurement, it is insensitive to any form of evolution of objects or the necessity to understand the physics in the early universe. Thus, WLT was identified by the Dark Energy Task Force as perhaps the best method to measure the evolution of DE. To date, however, the conjecture of the DETF has not been experimentally verified, but will be by the proposed project. The primary reason for the lack of tomography measurements is that one must have an exceptional data-set to attempt the measurement. One needs both extremely good seeing (or space observations) in order to minimize the point spread function smearing corrections on weak lensing shear measurements and deep, multi-color data, from B to z, to measure reliable photometric redshifts of the background galaxies being lensed (which are typically too faint to obtain spectroscopic redshifts). Because the entire process from multi-drizzling the HST images, and then creating shear maps, to gathering the necessary ground based observations, to generating photo-zs and then carrying out the tomography is a complicated task, until the creation of our team, nobody has taken the time to connect all the levels of expertise necessary to carry out this project based on HST archival data. Our data are being used in 2 Ph.D. theses. Kellen Murphy, at Ohio University, is

  9. Magnified Weak Lensing Cross Correlation Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, Melville P., Clowe, Douglas I.

    2010-11-30

    nights on 4-m class telescopes, which gives concrete evidence of strong community support for this project. The WLT technique is based on the dependence of the gravitational shear signal on the angular diameter distances between the observer, the lens, and the lensed galaxy to measure cosmological parameters. By taking the ratio of measured shears of galaxies with different redshifts around the same lens, one obtains a measurement of the ratios of the angular diameter distances involved. Making these observations over a large range of lenses and background galaxy redshifts will measure the history of the expansion rate of the universe. Because this is a purely geometric measurement, it is insensitive to any form of evolution of objects or the necessity to understand the physics in the early universe. Thus, WLT was identified by the Dark Energy Task Force as perhaps the best method to measure the evolution of DE. To date, however, the conjecture of the DETF has not been experimentally verified, but will be by the proposed project. The primary reason for the lack of tomography measurements is that one must have an exceptional data-set to attempt the measurement. One needs both extremely good seeing (or space observations) in order to minimize the point spread function smearing corrections on weak lensing shear measurements and deep, multi-color data, from B to z, to measure reliable photometric redshifts of the background galaxies being lensed (which are typically too faint to obtain spectroscopic redshifts). Because the entire process from multi-drizzling the HST images, and then creating shear maps, to gathering the necessary ground based observations, to generating photo-zs and then carrying out the tomography is a complicated task, until the creation of our team, nobody has taken the time to connect all the levels of expertise necessary to carry out this project based on HST archival data. Our data are being used in 2 Ph.D. theses. Kellen Murphy, at Ohio University, is

  10. Separating weak lensing and intrinsic alignments using radio observations

    CERN Document Server

    Whittaker, Lee; Battye, Richard A

    2015-01-01

    We discuss methods for performing weak lensing using radio observations to recover information about the intrinsic structural properties of the source galaxies. Radio surveys provide unique information that can benefit weak lensing studies, such as HI emission, which may be used to construct galaxy velocity maps, and polarized synchrotron radiation; both of which provide information about the unlensed galaxy and can be used to reduce galaxy shape noise and the contribution of intrinsic alignments. Using a proxy for the intrinsic position angle of an observed galaxy, we develop techniques for cleanly separating weak gravitational lensing signals from intrinsic alignment contamination in forthcoming radio surveys. Random errors on the intrinsic orientation estimates introduce biases into the shear and intrinsic alignment estimates. However, we show that these biases can be corrected for if the error distribution is accurately known. We demonstrate our methods using simulations, where we reconstruct the shear an...

  11. Weak Lensing Galaxy Cluster Field Reconstruction

    CERN Document Server

    Jullo, Eric; Jauzac, Mathilde; Kneib, Jean-Paul

    2013-01-01

    In this paper, we compare three methods to reconstruct galaxy cluster density fields with weak lensing data. The first method called FLens integrates an inpainting concept to invert the shear field with possible gaps, and a multi-scale entropy denoising procedure to remove the noise contained in the final reconstruction, that arises mostly from the random intrinsic shape of the galaxies. The second and third methods are based on a model of the density field made of a multi-scale grid of radial basis functions. In one case, the model parameters are computed with a linear inversion involving a singular value decomposition. In the other case, the model parameters are estimated using a Bayesian MCMC optimization implemented in the lensing software Lenstool. Methods are compared on simulated data with varying galaxy density fields. We pay particular attention to the errors estimated with resampling. We find the multi-scale grid model optimized with MCMC to provide the best results, but at high computational cost, ...

  12. Weak Lensing Simulations for the SKA

    CERN Document Server

    Patel, Prina; Makhathini, Sphesihle; Abdalla, Filipe; Bacon, David; Brown, Michael L; Heywood, Ian; Jarvis, Matt; Smirnov, Oleg

    2015-01-01

    Weak gravitational lensing measurements are traditionally made at optical wavelengths where many highly resolved galaxy images are readily available. However, the Square Kilometre Array (SKA) holds great promise for this type of measurement at radio wavelengths owing to its greatly increased sensitivity and resolution over typical radio surveys. The key to successful weak lensing experiments is in measuring the shapes of detected sources to high accuracy. In this document we describe a simulation pipeline designed to simulate radio images of the quality required for weak lensing, and will be typical of SKA observations. We provide as input, images with realistic galaxy shapes which are then simulated to produce images as they would have been observed with a given radio interferometer. We exploit this pipeline to investigate various stages of a weak lensing experiment in order to better understand the effects that may impact shape measurement. We first show how the proposed SKA1-Mid array configurations perfor...

  13. The Sloan Nearby Cluster Weak Lensing Survey

    CERN Document Server

    Kubo, Jeffrey M; Hardin, Frances Mei; Kubik, Donna; Lawhorn, Kelsey; Lin, Huan; Nicklaus, Liana; Nelson, Dylan; Reis, Ribamar R R; Seo, Hee-Jong; Soares-Santos, Marcelle; Stebbins, Albert; Yunker, Tony

    2009-01-01

    We describe and present initial results of a weak lensing survey of nearby ($\\rm{z}\\lesssim0.1$) 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 \\citet{miller05} and \\citet{berlind06}. We report a total of seven individual low redshift cluster weak lensing measurements which 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 $\\sim 200$ clusters, making it the largest weak lensing survey of individual galaxy clusters to date.

  14. Fast weak-lensing simulations with halo model

    Science.gov (United States)

    Giocoli, Carlo; Di Meo, Sandra; Meneghetti, Massimo; Jullo, Eric; de la Torre, Sylvain; Moscardini, Lauro; Baldi, Marco; Mazzotta, Pasquale; Metcalf, R. Benton

    2017-09-01

    Full ray-tracing maps of gravitational lensing, constructed from N-body simulations, represent a fundamental tool to interpret present and future weak-lensing data. However, the limitation of computational resources and storage capabilities severely restricts the number of realizations that can be performed in order to accurately sample both the cosmic shear models and covariance matrices. In this paper, we present a halo model formalism for weak gravitational lensing that alleviates these issues by producing weak-lensing mocks at a reduced computational cost. Our model takes as input the halo population within a desired light cone and the linear power spectrum of the underlined cosmological model. We examine the contribution given by the presence of substructures within haloes to the cosmic shear power spectrum and quantify it to the percent level. Our method allows us to reconstruct high-resolution convergence maps, for any desired source redshifts, of light cones that realistically trace the matter density distribution in the universe, account for masked area and sample selections. We compare our analysis on the same large-scale structures constructed using ray-tracing techniques and find very good agreements in both the linear and non-linear regimes up to few percent levels. The accuracy and speed of our method demonstrate the potential of our halo model for weak-lensing statistics and the possibility to generate a large sample of convergence maps for different cosmological models as needed for the analysis of large galaxy redshift surveys.

  15. Geometry of weak lensing of CMB polarization

    CERN Document Server

    Challinor, A D; Challinor, Anthony; Chon, Gayoung

    2002-01-01

    Hu has presented a harmonic-space method for calculating the effects of weak gravitational lensing on the cosmic microwave background (CMB) over the full sky. Computing the lensed power spectra to first order in the deflection power requires one to formulate the lensing displacement beyond the tangent-space approximation. We point out that for CMB polarization this displacement must undergo geometric corrections on the spherical sky to maintain statistical isotropy of the lensed fields. Although not discussed by Hu, these geometric effects are implicit in his analysis. However, there they are hidden by an overly-compact notation that is both unconventional and rather confusing. Here we aim to ameliorate this deficiency by providing a rigorous derivation of the lensed spherical power spectra.

  16. Weak lensing galaxy cluster field reconstruction

    Science.gov (United States)

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

    2014-02-01

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

  17. Hopfield Neural Network deconvolution for weak lensing measurement

    CERN Document Server

    Nurbaeva, Guldariya; Courbin, Frederic; Meylan, Georges

    2014-01-01

    Weak gravitational lensing has the potential to place tight constraints on the equation of the state of dark energy. However, this will only be possible if shear measurement methods can reach the required level of accuracy. We present a new method to measure the ellipticity of galaxies used in weak lensing surveys. The method makes use of direct deconvolution of the data by the total Point Spread Function (PSF). We adopt a linear algebra formalism that represents the PSF as a Toeplitz matrix. This allows us to solve the convolution equation by applying the Hopfield Neural Network iterative scheme. The ellipticity of galaxies in the deconvolved images are then measured using second order moments of the autocorrelation function of the images. To our knowledge, it is the first time full image deconvolution is used to measure weak lensing shear. We apply our method to the simulated weak lensing data proposed in the GREAT10 challenge and obtain a quality factor of Q=87. This result is obtained after applying image...

  18. Probing dark matter caustics with weak lensing

    CERN Document Server

    Gavazzi, R; Fort, B; Gavazzi, Raphael; Mohayaee, Roya; Fort, Bernard

    2006-01-01

    Caustics are high-density structures that form frequently in collisionless media. Under self-gravity, cold dark matter flows focus onto caustics which are yet to be resolved in numerical simulations and or observed in the real world. If detected, caustics would provide a strong evidence for dark matter and would rule out alternative models such as those with modified dynamics. Here, we demonstrate how they might be observed in the weak lensing data. We evaluate the shear distortion and show that its radial profile is marked by a characteristic sawtooth pattern due to the caustics in dark matter haloes that form by selfsimilar accretion. We discuss the observational complications, mainly due to the poor knowledge of the virial radii of the haloes and demonstrate that a superposition of about 600 cluster-size haloes would give a signal-to-noise ratio which is sufficiently large for the detection of caustics with ground-based observations. This number is reduced to 200 for space-based observations. These bounds ...

  19. RCSLenS: Cosmic Distances from Weak Lensing

    CERN Document Server

    Kitching, T D; Hildebrandt, H; Choi, A; Erben, T; Gilbank, D G; Heymans, C; Miller, L; Nakajima, R; van Uitert, E

    2015-01-01

    In this paper we present results of applying the shear-ratio method to the RCSLenS data. The method takes the ratio of the mean of the weak lensing tangential shear signal about galaxy clusters, averaged over all clusters of the same redshift, in multiple background redshift bins. In taking a ratio the mass-dependency of the shear signal is cancelled-out leaving a statistic that is dependent on the geometric part of the lensing kernel only. We apply this method to 535 clusters and measure a cosmology-independent distance-redshift relation to redshifts z~1. In combination with Planck data the method lifts the degeneracies in the CMB measurements, resulting in cosmological parameter constraints of OmegaM=0.31 +/- 0.10 and w0 = -1.02 +/- 0.37, for a flat wCDM cosmology.

  20. Measuring the dark side (with weak lensing)

    CERN Document Server

    Amendola, Luca; Sapone, Domenico

    2007-01-01

    We introduce a convenient parametrization 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. We find that a large-scale weak-lensing tomographic survey is able to easily distinguish the Dvali-Gabadadze-Porrati model from LCDM and to determine the perturbation growth index to an absolute error of 0.02-0.03.

  1. Weak lensing goes bananas: what flexion really measures

    Science.gov (United States)

    Schneider, P.; Er, X.

    2008-07-01

    In weak gravitational lensing, the image distortion caused by shear measures the projected tidal gravitational field of the deflecting mass distribution. To lowest order, the shear is proportional to the mean image ellipticity. If the image sizes are not small compared to the scale over which the shear varies, higher-order distortions occur, called flexion. For ordinary weak lensing, the observable quantity is not the shear, but the reduced shear, owing to the mass-sheet degeneracy. Likewise, the flexion itself is unobservable. Instead, higher-order image distortions measure the reduced flexion, i.e., derivatives of the reduced shear. We derive the corresponding lens equation in terms of the reduced flexion and calculate the resulting relation between brightness moments of source and image. Assuming an isotropic distribution of source orientations, estimates for the reduced shear and flexion are obtained and then tested with simulations. In particular, the presence of flexion affects the determination of the reduced shear. The results of these simulations yield the amount of bias of the estimators as a function of the shear and flexion. We point out and quantify a fundamental limitation of the flexion formalism in terms of the product of reduced flexion and source size. If this product increases above the derived threshold, multiple images of the source are formed locally, and the formalism breaks down. Finally, we show how a general (reduced) flexion field can be decomposed into its four components. Two of them are due to a shear field, carrying an E- and B-mode in general. The other two components do not correspond to a shear field, and they can also be split up into corresponding E- and B-modes.

  2. Testing PSF Interpolation In Weak Lensing With Real Data

    CERN Document Server

    Lu, Tianhuan; Dong, Fuyu; Li, Yingke; Liu, Dezi; Fu, Liping; Li, Guoliang; Fan, Zuhui

    2016-01-01

    Reconstruction of the point spread function (PSF) is a critical process in weak lensing measurement. We develop a real-data based and galaxy-oriented pipeline to compare the performances of various PSF reconstruction schemes. Making use of a large amount of the CFHTLenS data, the performances of three classes of interpolating schemes - polynomial, Kriging, and Shepard - are evaluated. We find that polynomial interpolations with optimal orders and domains perform the best. We quantify the effect of the residual PSF reconstruction error on shear recovery in terms of the multiplicative and additive biases, and their spatial correlations using the shear measurement method of Zhang et al. (2015). We find that the impact of PSF reconstruction uncertainty on the shear-shear correlation can be significantly reduced by cross correlating the shear estimators from different exposures. It takes only 0.2 stars (SNR > 100) per square arcmin on each exposure to reach the best performance of PSF interpolation, a requirement ...

  3. Studying dark matter haloes with weak lensing

    NARCIS (Netherlands)

    Velander, Malin Barbro Margareta

    2012-01-01

    Our Universe is comprised not only of normal matter but also of unknown components: dark matter and dark energy. This Thesis recounts studies of dark matter haloes, using a technique known as weak gravitational lensing, in order to learn more about the nature of these dark components. The haloes

  4. Studying dark matter haloes with weak lensing

    NARCIS (Netherlands)

    Velander, Malin Barbro Margareta

    2012-01-01

    Our Universe is comprised not only of normal matter but also of unknown components: dark matter and dark energy. This Thesis recounts studies of dark matter haloes, using a technique known as weak gravitational lensing, in order to learn more about the nature of these dark components. The haloes ana

  5. Weak Lensing by Galaxy Troughs in DES Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Gruen, D. [Ludwig Maximilian Univ., Munich (Germany); Max Planck Inst. for Extraterrestrial Physics, Garching (Germany). et al.

    2015-09-29

    We measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Our detection of the shear signal is highly significant (10σ–15σ for the smallest angular scales) for troughs with the redshift range z ϵ [0.2, 0.5] of the projected galaxy field and angular diameters of 10 arcmin…1°. These measurements probe the connection between the galaxy, matter density, and convergence fields. By assuming galaxies are biased tracers of the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial Λ cold dark matter model. Furthermore, the prediction for the lensing signal on large trough scales is virtually independent of the details of the underlying model for the connection of galaxies and matter. Our comparison of the shear around troughs with that around cylinders with large galaxy counts is consistent with a symmetry between galaxy and matter over- and underdensities. In addition, we measure the two-point angular correlation of troughs with galaxies which, in contrast to the lensing signal, is sensitive to galaxy bias on all scales. Finally, the lensing signal of troughs and their clustering with galaxies is therefore a promising probe of the statistical properties of matter underdensities and their connection to the galaxy field.

  6. Weak Lensing On the Celestial Sphere

    OpenAIRE

    Stebbins, Albert

    1996-01-01

    This paper details a description of the pattern of galaxy image distortion over the entire sky caused by the gravitational lensing which is the result of large scale inhomogeneities in our universe. We present a tensor spherical harmonic formalism to describe this pattern, giving many useful formulae. This is applied to density inhomogeneities, where we compute the angular power spectrum of the shear pattern, as well as the noise properties due to finite galaxy sampling and cosmic variance. W...

  7. Cluster mass reconstruction from weak gravitational lensing

    CERN Document Server

    Wilson, G; Frenk, C S; Wilson, Gillian; Cole, Shaun; Frenk, Carlos S

    1996-01-01

    Kaiser & Squires have proposed a technique for mapping the dark matter in galaxy clusters using the coherent weak distortion of background galaxy images caused by gravitational lensing. We investigate the effectiveness of this technique under controlled conditions by creating simulated CCD frames containing galaxies lensed by a model cluster, measuring the resulting galaxy shapes, and comparing the reconstructed mass distribution with the original. Typically, the reconstructed surface density is diminished in magnitude when compared to the original. The main cause of this reduced signal is the blurring of galaxy images by atmospheric seeing, but the overall factor by which the reconstructed surface density is reduced depends also on the signal-to-noise ratio in the CCD frame and on both the sizes of galaxy images and the magnitude limit of the sample that is analysed. We propose a method for estimating a multiplicative compensation factor. We test our technique using a lensing cluster drawn from a cosmolo...

  8. Bayesian hierarchical modelling of weak lensing - the golden goal

    CERN Document Server

    Heavens, Alan; Jaffe, Andrew; Hoffmann, Till; Kiessling, Alina; Wandelt, Benjamin

    2016-01-01

    To accomplish correct Bayesian inference from weak lensing shear data requires a complete statistical description of the data. The natural framework to do this is a Bayesian Hierarchical Model, which divides the chain of reasoning into component steps. Starting with a catalogue of shear estimates in tomographic bins, we build a model that allows us to sample simultaneously from the the underlying tomographic shear fields and the relevant power spectra (E-mode, B-mode, and E-B, for auto- and cross-power spectra). The procedure deals easily with masked data and intrinsic alignments. Using Gibbs sampling and messenger fields, we show with simulated data that the large (over 67000-)dimensional parameter space can be efficiently sampled and the full joint posterior probability density function for the parameters can feasibly be obtained. The method correctly recovers the underlying shear fields and all of the power spectra, including at levels well below the shot noise.

  9. Quantifying the effect of baryon physics on weak lensing tomography

    CERN Document Server

    Semboloni, Elisabetta; Schaye, Joop; van Daalen, Marcel P; McCarthy, Ian J

    2011-01-01

    We use matter power spectra from cosmological hydrodynamic simulations to quantify the effect of baryon physics on the weak gravitational lensing shear signal. The simulations consider a number of processes, such as radiative cooling, star formation, supernovae and feedback from active galactic nuclei (AGN). Van Daalen et al. (2011) used the same simulations to show that baryon physics, in particular the strong feedback that is required to solve the overcooling problem, modifies the matter power spectrum on scales relevant for cosmological weak lensing studies. As a result, the use of power spectra from dark matter simulations can lead to significant biases in the inferred cosmological parameters. We show that the typical biases are much larger than the precision with which future missions aim to constrain the dark energy equation of state, w_0. For instance, the simulation with AGN feedback, which reproduces X-ray and optical properties of groups of galaxies, gives rise to a ~40% bias in w_0. We demonstrate ...

  10. Predicting weak lensing statistics from halo mass reconstructions - Final Paper

    Energy Technology Data Exchange (ETDEWEB)

    Everett, Spencer [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-20

    As dark matter does not absorb or emit light, its distribution in the universe must be inferred through indirect effects such as the gravitational lensing of distant galaxies. While most sources are only weakly lensed, the systematic alignment of background galaxies around a foreground lens can constrain the mass of the lens which is largely in the form of dark matter. In this paper, I have implemented a framework to reconstruct all of the mass along lines of sight using a best-case dark matter halo model in which the halo mass is known. This framework is then used to make predictions of the weak lensing of 3,240 generated source galaxies through a 324 arcmin² field of the Millennium Simulation. The lensed source ellipticities are characterized by the ellipticity-ellipticity and galaxy-mass correlation functions and compared to the same statistic for the intrinsic and ray-traced ellipticities. In the ellipticity-ellipticity correlation function, I and that the framework systematically under predicts the shear power by an average factor of 2.2 and fails to capture correlation from dark matter structure at scales larger than 1 arcminute. The model predicted galaxy-mass correlation function is in agreement with the ray-traced statistic from scales 0.2 to 0.7 arcminutes, but systematically underpredicts shear power at scales larger than 0.7 arcminutes by an average factor of 1.2. Optimization of the framework code has reduced the mean CPU time per lensing prediction by 70% to 24 ± 5 ms. Physical and computational shortcomings of the framework are discussed, as well as potential improvements for upcoming work.

  11. Gravitational Shear, Flexion and Strong Lensing in Abell 1689

    CERN Document Server

    Leonard, A; Haaga, J L; Massey, R; Leonard, Adrienne; Goldberg, David M.; Haaga, Jason L.; Massey, Richard

    2007-01-01

    We present a gravitational lensing analysis of the galaxy cluster Abell 1689, incorporating measurements of the weak shear, flexion, and strong lensing induced in background galaxies. This is the first time that a shapelet technique has been used to reconstruct the distribution of mass in this cluster, and the first time that a flexion signal has been measured using cluster members as lenses. From weak shear measurements alone, we generate a non-parametric mass reconstruction, which shows significant substructure corresponding to groups of galaxies within the cluster. Additionally, our galaxy-galaxy flexion signal demonstrates that the cluster galaxies can be well-fit by a singular isothermal sphere model with a characteristic velocity dispersion of $\\sigma = 295\\pm 40 km/s $. We identify a major, distinct dark matter clump, offset by 40$h^{-1}$kpc from the central cluster members, which was not apparent from shear measurements alone. This secondary clump is present in both a non-parametric mass reconstructio...

  12. Weak lensing from self-ordering scalar fields

    Science.gov (United States)

    Saga, Shohei; Horiguchi, Kouichirou; Ichiki, Kiyotomo

    2017-06-01

    Cosmological defects result from cosmological phase transitions in the early Universe and the dynamics reflects their symmetry-breaking mechanisms. These cosmological defects may be probed through weak lensing effects because they interact with ordinary matters only through the gravitational force. In this paper, we investigate global textures by using weak lensing curl and B modes. Nontopological textures are modeled by the nonlinear sigma model (NLSM) and induce not only the scalar perturbation but also vector and tensor perturbations in the primordial plasma due to the nonlinearity in the anisotropic stress of scalar fields. We show angular power spectra of curl and B modes from both vector and tensor modes based on the NLSM. Furthermore, we give the analytic estimations for curl and B-mode power spectra. The amplitude of weak lensing signals depends on a combined parameter ɛv2=N-1(v/mpl) 4 where N and v are the number of the scalar fields and the vacuum expectation value, respectively. We discuss the detectability of the curl and B modes with several observation specifications. In the case of the CMB lensing observation without including the instrumental noise, we can reach ɛv≈2.7 ×10-6 . This constraint is about 10 times stronger than the current one determined from the Planck. For the cosmic shear observation, we find that the signal-to-noise ratio depends on the mean redshift and the observing number of galaxies as ∝zm0.7 and ∝Ng0.2, respectively. In the study of textures using cosmic shear observations, the mean redshift would be one of the key design parameters.

  13. A Lens Mapping Algorithm for Weak Lensing

    CERN Document Server

    Saini, T D; Saini, Tarun Deep; Raychaudhury, Somak

    2001-01-01

    We develop an algorithm for the reconstruction of the two-dimensional massdistribution of a cluster of galaxies from the observable distortion ofbackground galaxies. From the measured reduced shear gamma_i/(1-kappa) the lensmapping is directly obtained, from which a mass distribution is derived. Thisis unlike other methods where the convergence (kappa) is first obtained. Weshow that this method works best for sub-critical lenses but can be applied toa critical lens away from the critical lines. For finite fields the usualmass-sheet degeneracy is shown to exist in this method as well. We suggest aniterative scheme to remove the mass-sheet degeneracy for the case of asub-critical lens, in the absence of a substantial external shear. The sametechnique can be used with additional information for the case of a criticallens as well. A scheme to reduce the effects of noise is also suggested.

  14. Precision cluster mass determination from weak lensing

    CERN Document Server

    Mandelbaum, Rachel; Baldauf, Tobias; Smith, Robert E

    2009-01-01

    Weak gravitational lensing has been used extensively in the past decade to constrain the masses of galaxy clusters, and is the most promising observational technique for providing the mass calibration necessary for precision cosmology with clusters. There are several challenges in estimating cluster masses, particularly (a) the sensitivity to astrophysical effects and observational systematics that modify the signal relative to the theoretical expectations, and (b) biases that can arise due to assumptions in the mass estimation method, such as the assumed radial profile of the cluster. All of these challenges are more problematic in the inner regions of the cluster, suggesting that their influence would ideally be suppressed for the purpose of mass estimation. However, at any given radius the differential surface density measured by lensing is sensitive to all mass within that radius, and the corrupted signal from the inner parts is spread out to all scales. We develop a new statistic that is ideal for estima...

  15. Weak lensing mass reconstructions of the ESO Distant Cluster Survey

    CERN Document Server

    Clowe, D; Aragón-Salamanca, A; Bremer, M; De Lucia, G; Halliday, C; Jablonka, P; Milvang-Jensen, B; Pellò, R; Poggianti, B M; Rudnick, G; Saglia, R; Simard, L; White, S; Zaritsky, D

    2005-01-01

    We present weak lensing mass reconstructions for the 20 high-redshift clusters i n the ESO Distant Cluster Survey. The weak lensing analysis was performed on deep, 3-color optical images taken with VLT/FORS2, using a composite galaxy catalog with separate shape estimators measured in each passband. We find that the EDisCS sample is composed primarily of clusters that are less massive than t hose in current X-ray selected samples at similar redshifts, but that all of the fields are likely to contain massive clusters rather than superpositions of low mass groups. We find that 7 of the 20 fields have additional massive structures which are not associated with the clusters and which can affect the weak lensing mass determination. We compare the mass measurements of the remaining 13 clusters with luminosity measurements from cluster galaxies selected using photometric redshifts and find evidence of a dependence of the cluster mass-to-light ratio with redshift. Finally we determine the noise level in the shear meas...

  16. Simultaneous Constraints on Cosmology and Photometric Redshift Bias from Weak Lensing and Galaxy Clustering

    CERN Document Server

    Samuroff, S; Bridle, SL; Zuntz, J; MacCrann, N; Krause, E; Eifler, T; Kirk, D

    2016-01-01

    We investigate the expected cosmological constraints from a combination of weak lensing and large-scale galaxy clustering using realistic redshift distributions. Introducing a systematic bias in the weak lensing redshift distributions (of 0.05 in redshift) produces a $>2\\sigma$ bias in the recovered matter power spectrum amplitude and dark energy equation of state, for preliminary Stage III surveys. We demonstrate that these cosmological errors can be largely removed by marginalising over unknown biases in the assumed weak lensing redshift distributions, if we assume high quality redshift information for the galaxy clustering sample. Furthermore the cosmological constraining power is mostly retained despite removing much of the information on the weak lensing redshift distribution biases. We show that this comes from complementary degeneracy directions between cosmic shear and the combination of galaxy clustering with cross-correlation between shear and galaxy number density. Finally we examine how the self-c...

  17. Weak gravitational lensing with the Square Kilometre Array

    CERN Document Server

    Brown, M L; Camera, S; Harrison, I; Joachimi, B; Metcalf, R B; Pourtsidou, A; Takahashi, K; Zuntz, J A; Abdalla, F B; Bridle, S; Jarvis, M; Kitching, T D; Miller, L; Patel, P

    2015-01-01

    We investigate the capabilities of various stages of the SKA to perform world-leading weak gravitational lensing surveys. We outline a way forward to develop the tools needed for pursuing weak lensing in the radio band. We identify the key analysis challenges and the key pathfinder experiments that will allow us to address them in the run up to the SKA. We identify and summarize the unique and potentially very powerful aspects of radio weak lensing surveys, facilitated by the SKA, that can solve major challenges in the field of weak lensing. These include the use of polarization and rotational velocity information to control intrinsic alignments, and the new area of weak lensing using intensity mapping experiments. We show how the SKA lensing surveys will both complement and enhance corresponding efforts in the optical wavebands through cross-correlation techniques and by way of extending the reach of weak lensing to high redshift.

  18. LensTools: Weak Lensing computing tools

    Science.gov (United States)

    Petri, A.

    2016-02-01

    LensTools implements a wide range of routines frequently used in Weak Gravitational Lensing, including tools for image analysis, statistical processing and numerical theory predictions. The package offers many useful features, including complete flexibility and easy customization of input/output formats; efficient measurements of power spectrum, PDF, Minkowski functionals and peak counts of convergence maps; survey masks; artificial noise generation engines; easy to compute parameter statistical inferences; ray tracing simulations; and many others. It requires standard numpy and scipy, and depending on tools used, may require Astropy (ascl:1304.002), emcee (ascl:1303.002), matplotlib, and mpi4py.

  19. The Origin of Weak Lensing Convergence Peaks

    CERN Document Server

    Liu, Jia

    2016-01-01

    Weak lensing convergence peaks are a promising tool to probe nonlinear structure evolution at late times, providing additional cosmological information beyond second-order statistics. Previous theoretical and observational studies have shown that the cosmological constraints on $\\Omega_m$ and $\\sigma_8$ are improved by a factor of up to ~ 2 when peak counts and second-order statistics are combined, compared to using the latter alone. We study the origin of lensing peaks using observational data from the 154 deg$^2$ Canada-France-Hawaii Telescope Lensing Survey. We found that while high peaks (with height $\\kappa$ >3.5 $\\sigma_\\kappa$, where $\\sigma_\\kappa$ is the r.m.s. of the convergence $\\kappa$) are typically due to one single massive halo of ~$10^{15}M_\\odot$, low peaks ($\\kappa$ ~ their virial radii), compared with ~0.25 virial radii for halos linked with high peaks, hinting that low peaks are more immune to baryonic processes whose impact is confined to the inner regions of the dark matter halos. Our fi...

  20. Compact Groups analysis using weak gravitational lensing

    Science.gov (United States)

    Chalela, Martín; Johana Gonzalez, Elizabeth; Garcia Lambas, Diego; Foëx, Gael

    2017-01-01

    We present a weak lensing analysis of a sample of SDSS Compact Groups (CGs). Using the measured radial density contrast profile, we derive the average masses under the assumption of spherical symmetry, obtaining a velocity dispersion for the Singular Isothermal Spherical model, σV = 270 ± 40 km s-1, and for the NFW model, R_{200}=0.53± 0.10 h_{70}^{-1}Mpc. We test three different definitions of CGs centres to identify which best traces the true dark matter halo centre, concluding that a luminosity weighted centre is the most suitable choice. We also study the lensing signal dependence on CGs physical radius, group surface brightness, and morphological mixing. We find that groups with more concentrated galaxy members show steeper mass profiles and larger velocity dispersions. We argue that both, a possible lower fraction of interloper and a true steeper profile, could be playing a role in this effect. Straightforward velocity dispersion estimates from member spectroscopy yields σV ≈ 230 km s-1 in agreement with our lensing results.

  1. The general theory of secondary weak gravitational lensing

    CERN Document Server

    Clarkson, Chris

    2015-01-01

    Weak gravitational lensing is normally assumed to have only two principle effects: a magnification of a source and a distortion of the sources shape in the form of a shear. However, further distortions are actually present owing to changes in the gravitational field across the scale of the ray bundle of light propagating to us, resulting in the familiar arcs in lensed images. This is normally called the flexion, and is approximated by Taylor expanding the shear and magnification across the image plane. However, the physical origin of this effect arises from higher-order corrections in the geodesic deviation equation governing the gravitational force between neighbouring geodesics - so involves derivatives of the Riemann tensor. We show that integrating the second-order geodesic deviation equation results in a 'Hessian map' for gravitational lensing, which is a higher-order addition to the Jacobi map. We derive the general form of the Hessian map in an arbitrary spacetime paying particular attention to the sep...

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

    CERN Document Server

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

    2005-01-01

    Weak lensing is emerging as a powerful observational tool to constrain cosmological models, but is at present limited by an incomplete understanding of many sources of systematic error. Many of these errors are multiplicative and depend on the population of background galaxies. We show how the commonly cited geometric test, which is rather insensitive to cosmology, can be used as a ratio test of systematics in the lensing signal at the 1 per cent level. We apply this test to the galaxy-galaxy lensing analysis of the Sloan Digital Sky Survey (SDSS), which at present is the sample with the highest weak lensing signal to noise and has the additional advantage of spectroscopic redshifts for lenses. This allows one to perform meaningful geometric tests of systematics for different subsamples of galaxies at different mean redshifts, such as brighter galaxies, fainter galaxies and high-redshift luminous red galaxies, both with and without photometric redshift estimates. We use overlapping objects between SDSS and th...

  3. The Effective Number Density of Galaxies for Weak Lensing Measurements in the LSST Project

    CERN Document Server

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

    2013-01-01

    Future weak lensing surveys potentially hold the highest statistical power for constraining cosmological parameters compared to other cosmological probes. The statistical power of a weak lensing survey is determined by the sky coverage, the inverse of the noise in shear measurements, and the galaxy number density. The combination of the latter two factors is often expressed in terms of $n_{\\rm eff}$ -- the "effective number density of galaxies used for weak lensing measurements". In this work, we estimate $n_{\\rm eff}$ for the Large Synoptic Survey Telescope (LSST) project, the most powerful ground-based lensing survey planned for the next two decades. We investigate how the following factors affect the resulting $n_{\\rm eff}$ of the survey with detailed simulations: (1) survey time, (2) shear measurement algorithm, (3) algorithm for combining multiple exposures, (4) inclusion of data from multiple filter bands, (5) redshift distribution of the galaxies, and (6) masking and blending. For the first time, we qu...

  4. Weak lensing by galaxy troughs in DES Science Verification data

    CERN Document Server

    Gruen, D; Amara, A; Bacon, D; Bonnett, C; Hartley, W; Jain, B; Jarvis, M; Kacprzak, T; Krause, E; Mana, A; Rozo, E; Rykoff, E S; Seitz, S; Sheldon, E; Troxel, M A; Vikram, V; Abbott, T; Abdalla, F B; Allam, S; Armstrong, R; Banerji, M; Bauer, A H; Becker, M R; Benoit-Levy, A; Bernstein, G M; Bernstein, R A; Bertin, E; Bridle, S L; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Eifler, T F; Neto, A Fausti; Fernandez, E; Flaugher, B; Fosalba, P; Frieman, J; Gerdes, D W; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; Maia, M A G; March, M; Martini, P; Melchior, P; Miller, C J; Miquel, R; Mohr, J J; Nord, B; Ogando, R; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Walker, A R; Wechsler, R H; Weller, J; Zhang, Y; Zuntz, J

    2015-01-01

    We measure the weak lensing shear around galaxy troughs, i.e. the radial alignment of background galaxies relative to underdensities in projections of the foreground galaxy field over a wide range of redshift in Science Verification data from the Dark Energy Survey. Our detection of the shear signal is highly significant (10 to 15sigma for the smallest angular scales) for troughs with the redshift range z in [0.2,0.5] of the projected galaxy field and angular diameters of 10'...1{\\deg}. These measurements probe the connection between the galaxy, matter density, and convergence fields. By assuming galaxies are biased tracers of the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial LambdaCDM model. The prediction for the lensing signal on large trough scales is virtually independent of the details of the underlying model for the connection of galaxies and matter. Our comparison of the shear around troughs with that around cylinders with large galaxy count...

  5. Roulettes: A weak lensing formalism for strong lensing - II. Derivation and analysis

    CERN Document Server

    Clarkson, Chris

    2016-01-01

    We present a new extension of the weak lensing formalism capable of describing strongly lensed images. This paper accompanies Paper I, where we provided a condensed overview of the approach and illustrated how it works. Here we give all the necessary details, together with some more explicit examples. We solve the non-linear geodesic deviation equation order-by-order, keeping the leading derivatives of the optical tidal matrix, giving rise to a series of maps from which a complete strongly lensed image is formed. The family of maps are decomposed by separating the trace and trace-free parts of each map. Each trace-free tensor represents an independent spin mode, which distort circles into a variety of roulettes in the screen-space. It is shown how summing this series expansion allows us to create large strongly lensed images in regions where convergence, shear and flexion are not sufficient. This paper is a detailed exposition of Paper I which presents the key elements of the subject matter in a wider context...

  6. Roulettes: a weak lensing formalism for strong lensing: II. Derivation and analysis

    Science.gov (United States)

    Clarkson, Chris

    2016-12-01

    We present a new extension of the weak lensing formalism capable of describing strongly lensed images. This paper accompanies Paper I (Clarkson C 2016 Class. Quantum Grav. 33 16LT01), where we provide a condensed overview of the approach and illustrated how it works. Here we give all the necessary details, together with some more explicit examples. We solve the nonlinear geodesic deviation equation order-by-order, keeping the leading derivatives of the optical tidal matrix, giving rise to a series of maps from which a complete strongly lensed image is formed. The family of maps are decomposed by separating the trace and trace-free parts of each map. Each trace-free tensor represents an independent spin mode, which distorts circles into a variety of roulettes in the screen-space. It is shown how summing this series expansion allows us to create large strongly lensed images in regions where convergence, shear and flexion are not sufficient. This paper is a detailed exposition of Paper I [1], which presents the key elements of the subject matter in a wider context.

  7. Halo mass - concentration relation from weak lensing

    CERN Document Server

    Mandelbaum, Rachel; Hirata, Christopher M

    2008-01-01

    We perform a statistical weak lensing analysis of dark matter profiles around tracers of halo mass from galactic- to cluster-size halos. In this analysis we use 170,640 isolated ~L* galaxies split into ellipticals and spirals, 38,236 groups traced by isolated spectroscopic Luminous Red Galaxies (LRGs) and 13,823 MaxBCG clusters from the Sloan Digital Sky Survey (SDSS) covering a wide range of richness. Together these three samples allow a determination of the density profiles of dark matter halos over three orders of magnitude in mass, from 10^{12} M_{sun} to 10^{15} M_{sun}. The resulting lensing signal is consistent with an NFW or Einasto profile on scales outside the central region. We find that the NFW concentration parameter c_{200b} decreases with halo mass, from around 10 for galactic halos to 4 for cluster halos. Assuming its dependence on halo mass in the form of c_{200b} = c_0 [M/(10^{14}M_{sun}/h)]^{\\beta}, we find c_0=4.6 +/- 0.7 (at z=0.22) and \\beta=0.13 +/- 0.07, with very similar results for t...

  8. Approaching the Cramer-Rao Bound in Weak Lensing with PDF Symmetrization

    CERN Document Server

    Zhang, Jun

    2016-01-01

    Weak lensing statistics is typically measured as weighted sum of shear estimators or their products (shear-shear correlation). The weighting schemes are designed in the hope of minimizing the statistical error without introducing systematic errors. It would be ideal to approach the Cramer-Rao bound (the lower bound of the statistical uncertainty) in shear statistics, though it is generally difficult to do so in practice. The reasons may include: difficulties in galaxy shape measurement, inaccurate knowledge of the probability-distribution-function (PDF) of the shear estimator, misidentification of point sources as galaxies, etc.. Using the shear estimators defined in Zhang et al. (2015), we show that one can overcome all these problems, and allow shear measurement accuracy to approach the Cramer-Rao bound. This can be achieved by symmetrizing the PDF of the shear estimator, or the joint PDF of shear estimator pairs (for shear-shear correlation), without any prior knowledge of the PDF. Using simulated galaxy i...

  9. Weak lensing tomography with orthogonal polynomials

    CERN Document Server

    Schaefer, Bjoern Malte

    2011-01-01

    The topic of this article is weak cosmic shear tomography where the line of sight-weighting is carried out with a set of specifically constructed orthogonal polynomials, dubbed TaRDiS (Tomography with orthogonAl Radial Distance polynomIal Systems). We investigate the properties of these polynomials and employ weak convergence spectra, which have been obtained by weighting with these polynomials, for the estimation of cosmological parameters. We quantify their power in constraining parameters in a Fisher-matrix technique and demonstrate how each polynomial projects out statistically independent information, and how the combination of multiple polynomials lifts degeneracies. The assumption of a reference cosmology is needed for the construction of the polynomials, and as a last point we investigate how errors in the construction with a wrong cosmological model propagate to misestimates in cosmological parameters. TaRDiS performs on a similar level as traditional tomographic methods and some key features of tomo...

  10. Weak lensing tomography with orthogonal polynomials

    Science.gov (United States)

    Schäfer, Björn Malte; Heisenberg, Lavinia

    2012-07-01

    The topic of this paper is weak cosmic shear tomography where the line-of-sight weighting is carried out with a set of specifically constructed orthogonal polynomials, dubbed Tomography with Orthogonal Radial Distance Polynomial Systems (TaRDiS). We investigate the properties of these polynomials and employ weak convergence spectra, which have been obtained by weighting with these polynomials, for the estimation of cosmological parameters. We quantify their power in constraining parameters in a Fisher matrix technique and demonstrate how each polynomial projects out statistically independent information, and how the combination of multiple polynomials lifts degeneracies. The assumption of a reference cosmology is needed for the construction of the polynomials, and as a last point we investigate how errors in the construction with a wrong cosmological model propagate to misestimates in cosmological parameters. TaRDiS performs on a similar level as traditional tomographic methods and some key features of tomography are made easier to understand.

  11. Probing the mass distribution at the outskirts of galaxy clusters using weak lensing

    Science.gov (United States)

    Fong, Matthew; King, Lindsay J.

    2017-01-01

    Galaxy clusters are often described by NFW (Navarro, Frenk & White) profiles which are a good description of cluster scale halos formed in cosmological dark matter simulations. Here we discuss the lensing signals of high-resolution clusters extracted from cosmological dark matter and hydrodynamic simulations, and determine on what scales the clusters’ average weak lensing shear is best described by the shear of the Diemer-Kravtsov (DK) or NFW profile. In particular, we assess the number of clusters and the type of observations (e.g. number of galaxies available for the weak lensing analysis) that must be stacked in order to distinguish between these and other profiles, focusing on the larger scales where the best-fit shear profiles differ.

  12. SKA Weak Lensing II: Simulated Performance and Survey Design Considerations

    CERN Document Server

    Bonaldi, Anna; Camera, Stefano; Brown, Michael L

    2016-01-01

    We construct a pipeline for simulating weak lensing cosmology surveys with the Square Kilometre Array (SKA), taking as inputs telescope sensitivity curves; correlated source flux, size and redshift distributions; a simple ionospheric model; source redshift and ellipticity measurement errors. We then use this simulation pipeline to optimise a 2-year weak lensing survey performed with the first deployment of the SKA (SKA1). Our assessments are based on the total signal-to-noise of the recovered shear power spectra, a metric that we find to correlate very well with a standard dark energy figure of merit. We first consider the choice of frequency band, trading off increases in number counts at lower frequencies against poorer resolution; our analysis strongly prefers the higher frequency Band 2 (950-1760 MHz) channel of the SKA-MID telescope to the lower frequency Band 1 (350-1050 MHz). Best results would be obtained by allowing the centre of Band 2 to shift towards lower frequency, around 1.1 GHz. We then move o...

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

    Energy Technology Data Exchange (ETDEWEB)

    Antonik, M. L.; Bacon, D. J.; Bridle, S.; Doel, P.; Brooks, D.; Worswick, S.; Bernstein, G.; Bernstein, R.; DePoy, D.; Flaugher, B.; Frieman, J. A.; Gladders, M.; Gutierrez, G.; Jain, B.; Jarvis, M.; Kent, S. M.; Lahav, O.; Parker, S. -. J.; Roodman, A.; Walker, A. R.

    2013-04-10

    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.

  14. Cosmological constraints from Subaru weak lensing cluster counts

    CERN Document Server

    Hamana, Takashi; Koike, Michitaro; Miller, Lance

    2015-01-01

    We present results of weak lensing cluster counts obtained from 11 sq.deg SuprimeCam data. Although the area is much smaller than previous work dealing with weak lensing peak statistics, the number density of galaxies usable for weak lensing analysis is about twice as large as those. The higher galaxy number density reduces the noise in the weak lensing mass maps, and thus increases the signal-to-noise ratio of peaks of the lensing signal due to massive clusters. This enables us to construct a weak lensing selected cluster sample by adopting a high threshold S/N, such that the contamination rate due to false signals is small. We find 6 peaks with S/N>5. For all the peaks, previously identified clusters of galaxies are matched within a separation of 1 arcmin, demonstrating good correspondence between the peaks and clusters of galaxies. We evaluate the statistical error using mock weak lensing data, and find Npeak=6+/-3.1 in an effective area of 9.0 sq.deg. We compare the measured weak lensing cluster counts wi...

  15. The Mass Of The Coma Cluster From Weak Lensing In The Sloan Digital Sky Survey

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, Jeffrey M.; Stebbins, Albert; Annis, James; Dell' Antonio, Ian P.; Lin, Huan; Khiabanian, Hossein; Frieman, Joshua A.

    2007-09-01

    We present a weak lensing analysis of the Coma Cluster using the Sloan Digital Sky Survey (SDSS) Data Release Five. Complete imaging of a {approx} 200 square degree region is used to measure the tangential shear of this cluster. The shear is fit to an NFW model and we find a virial radius of r{sub 200} = 1.99{sup +0.21}{sub -0.22}h{sup -1}Mpc which corresponds to a virial mass of M{sub 200} = 1.88{sup +0.65}{sub -0.56} x 10{sup 15}h{sup -1}M{circle_dot}. We additionally compare our weak lensing measurement to the virial mass derived using dynamical techniques, and find they are in agreement. This is the lowest redshift, largest angle weak lensing measurement of an individual cluster to date.

  16. Stacked Weak Lensing Mass Calibration: Estimators, Systematics, and Impact on Cosmological Parameter Constraints

    CERN Document Server

    Rozo, Eduardo; Schmidt, Fabian

    2010-01-01

    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 systematics 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 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 systema...

  17. Combined reconstruction of weak and strong lensing data with WSLAP

    CERN Document Server

    Diego-Rodriguez, J M; Protopapas, P; Sandvik, H B

    2005-01-01

    We describe a method to estimate the mass distribution of a gravitational lens and the position of the sources from combined strong and weak lensing data. The algorithm combines weak and strong lensing data in a unified way producing a solution which is valid in both the weak and strong lensing regimes. We study how the result depends on the relative weighting of the weak and strong lensing data and on choice of basis to represent the mass distribution. We find that combining weak and strong lensing information has two major advantages: it eliminates the need for priors and/or regularization schemes for the intrinsic size of the background galaxies (this assumption was needed in previous strong lensing algorithms) and it corrects for biases in the recovered mass in the outer regions where the strong lensing data is less sensitive. The code is implemented into a software package called WSLAP (Weak & Strong Lensing Analysis Package) which is publicly available at http://darwin.cfa.harvard.edu/SLAP/

  18. SKA Weak Lensing III: Added Value of Multi-Wavelength Synergies for the Mitigation of Systematics

    CERN Document Server

    Camera, Stefano; Bonaldi, Anna; Brown, Michael L

    2016-01-01

    In this third paper of a series on radio weak lensing for cosmology with the Square Kilometre Array, we scrutinise the added value of synergies between cosmic shear measurements in the radio and optical/near-IR bands for the purpose of mitigating systematic effects. We focus on three main classes of systematics: (i) experimental systematic errors in the observed shear, (ii) signal contamination by intrinsic alignments, and (iii) systematic effects in the estimation of cosmological parameters due to an incorrect modelling of non-linear scales. First, we quantitatively illustrate how the cross-correlation between radio and optical/near-IR cosmic shear surveys will greatly help in mitigating the impact of the systematic effects in the shear measurement considered, opening also the possibility of using such a cross-correlation as a means to detect unknown experimental systematics. Secondly, we show that, thanks to polarisation information, radio weak lensing surveys will be able to mitigate contamination by intri...

  19. Stacked Weak Lensing Mass Calibration: Estimators, Systematics, and Impact on Cosmological Parameter Constraints

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-11-04

    When extracting the weak lensing shear signal, one may employ either locally normalized or globally normalized shear estimators. The former is the standard approach when estimating cluster masses, while the latter is the more common method among peak finding efforts. While both approaches have identical signal-to-noise in the weak lensing limit, it is possible that higher order corrections or systematic considerations make one estimator preferable over the other. In this paper, we consider the efficacy of both estimators within the context of stacked weak lensing mass estimation in the Dark Energy Survey (DES). We find that the two estimators have nearly identical statistical precision, even after including higher order corrections, but that these corrections must be incorporated into the analysis to avoid observationally relevant biases in the recovered masses. We also demonstrate that finite bin-width effects may be significant if not properly accounted for, and that the two estimators exhibit different systematics, particularly with respect to contamination of the source catalog by foreground galaxies. Thus, the two estimators may be employed as a systematic cross-check of each other. Stacked weak lensing in the DES should allow for the mean mass of galaxy clusters to be calibrated to {approx}2% precision (statistical only), which can improve the figure of merit of the DES cluster abundance experiment by a factor of {approx}3 relative to the self-calibration expectation. A companion paper investigates how the two types of estimators considered here impact weak lensing peak finding efforts.

  20. Weak lensing at the limit of the sky background noise

    CERN Document Server

    Mellier, Y

    1996-01-01

    Recent weak lensing observations have pushed the use of 4 meter-class telescopes to the limits of their capabilities with exposure times exceeding several hours. The leading idea is that the surface density of faint galaxies up to very faint magnitude ($B > 28-30$) raises continuously thus potentially offering a dense template of distant sources whose intensity contrast is at the sky noise level. In complement to the Peter Schneider's presentation on dark matter search from weak lensing (this conference), we review some of these recent advances in weak lensing analysis based on this extreme faint population of galaxies in order to explore: the dark matter distribution on large scales, the redshift ditribution of lensed sources at very large distance, and eventually the values of cosmological parameters. For each observational topic we will briefly discuss these new methods as compare to more classical lensing studies as well as the possible VLT scientific impact in the domain.

  1. Weak Lensing Analysis of Massive Galaxy Cluster IDCS J1426.5+3508 at z=1.75

    Science.gov (United States)

    Mo, Wenli; Gonzalez, Anthony H.; Jee, Myungkook J.; Massey, Richard; Rhodes, Jason; Brodwin, Mark; Eisenhardt, Peter R.; Marrone, Daniel P.; Stanford, S. Adam; Zeimann, Gregory

    2016-01-01

    We present a weak lensing study of the galaxy cluster IDCS J1426.5+3508 at z=1.75, which is the highest redshift strong lensing cluster known and the most distant cluster for which a weak lensing analysis has been undertaken. Using F160W, F814W, and F606W observations with the Hubble Space Telescope, we detect tangential shear at 2σ significance. Fitting a Navarro-Frenk-White mass profile to the shear with a theoretical median mass-concentration relation, we derive a mass consistent with previous mass estimates from the Sunyaev-Zel'dovich (SZ) effect, X-ray, and strong lensing. The cluster lies on the local SZ-weak lensing mass scaling relation observed at low redshift, indicative of minimal evolution in this relation.

  2. IDCS J1426.5+3508: Weak Lensing Analysis of a Massive Galaxy Cluster at z = 1.75

    Science.gov (United States)

    Mo, Wenli; Gonzalez, Anthony; Jee, M. James; Massey, Richard; Rhodes, Jason; Brodwin, Mark; Eisenhardt, Peter; Marrone, Daniel P.; Stanford, S. A.; Zeimann, Gregory R.

    2016-02-01

    We present a weak lensing study of the galaxy cluster IDCS J1426.5+3508 at z = 1.75, which is the highest-redshift strong lensing cluster known and the most distant cluster for which a weak lensing analysis has been undertaken. Using F160W, F814W, and F606W observations with the Hubble Space Telescope, we detect tangential shear at 2σ significance. Fitting a Navarro-Frenk-White mass profile to the shear with a theoretical median mass-concentration relation, we derive a mass {M}200,{crit}={2.3}-1.4+2.1× {10}14 M⊙. This mass is consistent with previous mass estimates from the Sunyaev-Zel’dovich (SZ) effect, X-ray, and strong lensing. The cluster lies on the local SZ-weak lensing mass scaling relation observed at low redshift, indicative of minimal evolution in this relation.

  3. IDCS J1426.5+3508: Weak Lensing Analysis of a Massive Galaxy Cluster at $z=1.75$

    CERN Document Server

    Mo, Wenli; Jee, M James; Massey, Richard; Rhodes, Jason; Brown, Mark; Eisenhardt, Peter; Marrone, Daniel P; Stanford, S A; Zeimann, Gregory R

    2016-01-01

    We present a weak lensing study of the galaxy cluster IDCS J1426.5+3508 at $z=1.75$, which is the highest redshift strong lensing cluster known and the most distant cluster for which a weak lensing analysis has been undertaken. Using F160W, F814W, and F606W observations with the Hubble Space Telescope, we detect tangential shear at $2\\sigma$ significance. Fitting a Navarro-Frenk-White mass profile to the shear with a theoretical median mass-concentration relation, we derive a mass $M_{200,\\mathrm{crit}}=2.3^{+2.1}_{-1.4}\\times10^{14}$ M$_{\\odot}$. This mass is consistent with previous mass estimates from the Sunyaev-Zel'dovich (SZ) effect, X-ray, and strong lensing. The cluster lies on the local SZ-weak lensing mass scaling relation observed at low redshift, indicative of minimal evolution in this relation.

  4. Probing cosmology with weak lensing selected clusters II: Dark energy and f(R) gravity models

    CERN Document Server

    Shirasaki, Masato; Yoshida, Naoki

    2015-01-01

    Ongoing and future wide-field galaxy surveys can be used to locate a number of clusters of galaxies with cosmic shear measurement alone. We study constraints on cosmological models using statistics of weak lensing selected galaxy clusters. We extend our previous theoretical framework to model the statistical properties of clusters in variants of cosmological models as well as in the standard LCDM model. Weak lensing selection of clusters does not rely on the conventional assumption such as the relation between luminosity and mass and/or hydrostatic equilibrium, but a number of observational effects compromise robust identification. We use a large set of realistic mock weak-lensing catalogs as well as analytic models to perform a Fisher analysis and make forecast for constraining two competing cosmological models, wCDM model and f(R) model proposed by Hu & Sawicki, with our lensing statistics. We show that weak lensing selected clusters are excellent probe of cosmology when combined with cosmic shear power...

  5. Weak Lensing Peak Finding: Estimators, Filters, and Biases

    CERN Document Server

    Schmidt, Fabian

    2010-01-01

    Large catalogs of shear-selected peaks have recently become a reality. In order to properly interpret the abundance and properties of these peaks, it is necessary to take into account the effects of the clustering of source galaxies, among themselves and with the lens. In addition, the preferred selection of lensed galaxies in a flux- and size-limited sample leads to fluctuations in the apparent source density which correlate with the lensing field (lensing bias). In this paper, we investigate these issues for two different choices of shear estimators which are commonly in use today: globally-normalized and locally-normalized estimators. While in principle equivalent, in practice these estimators respond differently to systematic effects such as lensing bias and cluster member dilution. Furthermore, we find that which estimator is statistically superior depends on the specific shape of the filter employed for peak finding; suboptimal choices of the estimator+filter combination can result in a suppression of t...

  6. Measuring primordial non-Gaussianity with weak-lensing surveys

    CERN Document Server

    Hilbert, Stefan; Smith, Robert E; Desjacques, Vincent

    2012-01-01

    We study the ability of future weak lensing (WL) surveys to constrain primordial non-Gaussianity of the local type. We use a large ensemble of simulated WL maps with survey specifications relevant to Euclid and LSST. The simulations assume Cold Dark Matter cosmologies that vary certain parameters around fiducial values: the non-Gaussianity parameter f_NL, the matter density parameter Omega_m, the amplitude of the matter power spectrum sigma_8, the spectral index of the primordial power spectrum n_s, and the dark-energy equation-of-state parameter w_0. We assess the sensitivity of the cosmic shear correlation functions, the third-order aperture mass statistics, and the abundance of shear peaks to these parameters. We find that each of the considered probes provides unmarginalized constraints of Delta f_NL ~ 20 on f_NL. Marginalized constraints from any individual WL probe are much weaker due to strong correlations between parameters. However, the parameter errors can be substantially reduced by combining infor...

  7. Dark Energy Survey Year 1 Results: Weak Lensing Shape Catalogues

    Energy Technology Data Exchange (ETDEWEB)

    Zuntz, J.; et al.

    2017-08-04

    We present two galaxy shape catalogues from the Dark Energy Survey Year 1 data set, covering 1500 square degrees with a median redshift of $0.59$. The catalogues cover two main fields: Stripe 82, and an area overlapping the South Pole Telescope survey region. We describe our data analysis process and in particular our shape measurement using two independent shear measurement pipelines, METACALIBRATION and IM3SHAPE. The METACALIBRATION catalogue uses a Gaussian model with an innovative internal calibration scheme, and was applied to $riz$-bands, yielding 34.8M objects. The IM3SHAPE catalogue uses a maximum-likelihood bulge/disc model calibrated using simulations, and was applied to $r$-band data, yielding 21.9M objects. Both catalogues pass a suite of null tests that demonstrate their fitness for use in weak lensing science. We estimate the 1$\\sigma$ uncertainties in multiplicative shear calibration to be $0.013$ and $0.025$ for the METACALIBRATION and IM3SHAPE catalogues, respectively.

  8. WMAP anomaly : Weak lensing in disguise

    CERN Document Server

    Rotti, Aditya; Souradeep, Tarun

    2011-01-01

    Statistical isotropy (SI) has been one of the simplifying assumptions in cosmological model building. Experiments like WMAP and PLANCK are attempting to test this assumption by searching for specific signals in the Cosmic Microwave Background (CMB) two point correlation function. Modifications to this correlation function due to gravitational lensing by the large scale structure (LSS) surrounding us have been ignored in this context. Gravitational lensing will induce signals which mimic isotropy violation even in an isotropic universe. The signal detected in the Bipolar Spherical Harmonic (BipoSH) coefficients $A^{20}_{ll}$ by the WMAP team may be explained by accounting for the lensing modifications to these coefficients. Further the difference in the amplitude of the signal detected in the V-band and W-band maps can be explained by accounting for the differences in the designed angular sensitivity of the instrumental beams. The arguments presented in this article have crucial implications for SI violation s...

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

    CERN Document Server

    Antonik, Michelle L; 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; Roodman, Aaron; Walker, Alistair R

    2012-01-01

    Telescope Point Spread Function (PSF) quality is critical for realising 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 three 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 de-centre or tilt of each lens in turn. We find tilt accuracy to be a few times more important than de-centre, depending on the lens conside...

  10. A halo mass-concentration relation from weak lensing

    Energy Technology Data Exchange (ETDEWEB)

    Mandelbaum, Rachel [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Seljak, Uros [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Hirata, Christopher M, E-mail: rmandelb@ias.edu, E-mail: seljak@physik.unizh.ch, E-mail: chirata@tapir.caltech.edu [Mail Code 130-33, Caltech, Pasadena, CA 91125 (United States)

    2008-08-15

    We perform a statistical weak lensing analysis of dark matter profiles around tracers of halo mass from galaxy-size to cluster-size halos. In this analysis we use 170 640 isolated {approx}L{sub *} galaxies split into ellipticals and spirals, 38 236 groups traced via isolated spectroscopic luminous red galaxies and 13 823 maxBCG clusters from the Sloan Digital Sky Survey covering a wide range of richness. Together these three samples allow a determination of the density profiles of dark matter halos over three orders of magnitude in mass, from 10{sup 12}M{sub sun} to 10{sup 15}M{sub sun}. The resulting lensing signal is consistent with a Navarro-Frenk-White (NFW) or Einasto profile on scales outside the central region. In the inner regions, uncertainty in modeling of the proper identification of the halo center and inclusion of baryonic effects from the central galaxy make the comparison less reliable. We find that the NFW concentration parameter c{sub 200b} decreases with halo mass, from around 10 for galactic halos to 4 for cluster halos. Assuming its dependence on halo mass in the form of c{sub 200b}=c{sub 0} (M/10{sup 14}h{sup -1} M{sub sun}){sup -{beta}} we find c{sub 0} = 4.6 {+-} 0.7 (at z = 0.22) and {beta} = 0.13 {+-} 0.07, with very similar results for the Einasto profile. The slope ({beta}) is in agreement with theoretical predictions, while the amplitude is about two standard deviations below the predictions for this mass and redshift, but we note that the published values in the literature differ at a level of 10-20% and that for a proper comparison our analysis should be repeated in simulations. We compare our results to other recent determinations, some of which find significantly higher concentrations. We discuss the implications of our results for the baryonic effects on the shear power spectrum: since these are expected to increase the halo concentration, the fact that we see no evidence of high concentrations on scales above 20% of the virial

  11. Weak gravitational lensing by fourth order gravity black holes

    CERN Document Server

    Horváth, Zsolt; Hobill, David; Capozziello, Salvatore; De Laurentis, Mariafelicia

    2012-01-01

    We discuss weak lensing characteristics for black holes in a fourth order f(R) gravity theory, characterized by a gravitational strength parameter $\\sigma $ and a distance scale $r_{c}$. Above $r_{c}$ 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 $r_{c}$) 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 has a different power-law dependence for each parameter $\\sigma $. As these are the lensing quantities most conveniently determined by direct measurements, future lensing surveys will be able to constrain the parameter $\\sigma $ based on this prediction.

  12. Cosmological constraints from weak lensing non-Gaussian statistics

    Science.gov (United States)

    Liu, Jia; Haiman, Zoltan; Petri, Andrea; Hill, James; Hui, Lam; Kratochvil, Jan Michael; May, Morgan

    2016-01-01

    Weak gravitational lensing is one of the most promising techniques to probe dark energy. Our work to date suggests that the information in the nonlinear regime exceeds that in the two-point functions. Using the publicly available data from the 154 deg^2 CFHTLenS survey and a large suite of ray-tracing N-body simulations on a grid of 91 cosmological models, we find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined.I will also introduce the utility of cross-correlating weak galaxy lensing maps with CMB lensing maps, a technique that will be useful to probe structures at an intermediate redshift of 0.9, as larger weak lensing surveys such as HSC, DES, KiDS, Euclid, and LSST come online. We cross-correlate the CFHTLenS galaxy lensing convergence maps with Planck CMB lensing maps. Our results show two sigma tension with the constraints obtained from the Planck temperature measurements. I will discuss possible sources of the tension, including intrinsic alignments, photo-z uncertainties, masking of tSZ in the CMB maps, and the multiplicative bias.

  13. CMBR Weak Lensing and HI 21-cm Cross-correlation Angular Power Spectrum

    CERN Document Server

    Sarkar, Tapomoy Guha

    2009-01-01

    Weak gravitational lensing of the CMBR manifests as a secondary anisotropy in the temperature maps. The effect, quantified through the shear and convergence fields imprint the underlying large scale structure (LSS), geometry and evolution history of the Universe. It is hence perceived to be an important observational probe of cosmology. De-lensing the CMBR temperature maps is also crucial for detecting the gravitational wave generated B-modes. Future observations of redshifted 21-cm radiation from the cosmological neutral hydrogen (HI) distribution hold the potential of probing the LSS over a large redshift range. We have investigated the correlation between post-reionization HI signal and weak lensing convergence field. Assuming that the HI follows the dark matter distribution, the cross-correlation angular power spectrum at a multipole \\ell is found to be proportional to the cold dark matter power spectrum evaluated at \\ell/r, where r denotes the comoving distance to the redshift where the HI is located. Th...

  14. Constrainig the mass-concentration relation through weak lensing peak function

    CERN Document Server

    Mainini, Roberto

    2014-01-01

    Halo masses and concentrations have been studied extensively, by means of N-body simulations as well as observationally, during the last decade. Nevertheless, the exact form of the mass-concentration relation is still widely debated. One of the most promising method to estimate masses and concentrations relies on gravitational lensing from massive halos. Here we investigate the impact of the mass-concentration relation on halo peak abundance in weak lensing shear maps relying on the aperture mass method for peak detections. After providing a prescription to take into account the concentration dispersion (always neglected in previous works) in peak number counts predictions, we assess their power to constrain the mass-concentration relation by means of Fisher matrix technique. We find that, when combined with different cosmological probes, peak statistics information from near-future weak lensing surveys provides an interesting and complementary alternative method to lessen the long standing controversy about ...

  15. Looking through the same lens: shear calibration for LSST, Euclid & WFIRST with stage 4 CMB lensing

    CERN Document Server

    Schaan, Emmanuel; Eifler, Tim; Doré, Olivier; Miyatake, Hironao; Rhodes, Jason; Spergel, David N

    2016-01-01

    The next generation weak lensing surveys (i.e., LSST, Euclid and WFIRST) will require exquisite control over systematic effects. In this paper, we address shear calibration and present the most realistic forecast to date for LSST/Euclid/WFIRST and CMB lensing from a stage 4 CMB experiment (CMB S4). We use the CosmoLike code to simulate a joint analysis of all the two-point functions of galaxy density, galaxy shear and CMB lensing convergence. We include the full Gaussian and non-Gaussian covariances and explore the resulting joint likelihood with Monte Carlo Markov Chains. We constrain shear calibration biases while simultaneously varying cosmological parameters, galaxy biases and photometric redshift uncertainties. We find that CMB lensing from CMB S4 enables the calibration of the shear biases down to 0.2% - 3% in 10 tomographic bins for LSST (below the ~0.5% requirements in most tomographic bins), down to 0.4% - 2.4% in 10 bins for Euclid and 0.6% - 3.2% in 10 bins for WFIRST. For a given lensing survey, t...

  16. Abell 611: I. weak lensing analysis with LBC

    CERN Document Server

    Romano, A; Giordano, F; Maoli, R; Martini, P; Radovich, M; Scaramella, R; Antonuccio-Delogu, V; Donnarumma, A; Ettori, S; Kuijken, K; Meneghetti, M; Moscardini, L; Paulin-Henriksson, S; Giallongo, E; Ragazzoni, R; Baruffolo, A; DiPaola, A; Diolaiti, E; Fontana, A; Grazian, A; Gallozzi, S; Pedichini, F; Farinato, J; Speziali, R; Smareglia, R; Testa, V

    2010-01-01

    Aims. The Large Binocular Cameras (LBC) are two twin wide field cameras (FOV ~ 23'x 25') mounted at the prime foci of the 8.4m Large Binocular Telescope (LBT). We performed a weak lensing analysis of the z=0.288 cluster Abell 611 on g-band data obtained by the blue-optimized Large Binocular Camera in order to estimate the cluster mass. Methods. Due to the complexity of the PSF of LBC, we decided to use two different approaches, KSB and Shapelets, to measure the shape of background galaxies and to derive the shear signal produced by the cluster. Then we estimated the cluster mass with both aperture densitometry and parametric model fits. Results. The combination of the large aperture of the telescope and the wide field of view allowed us to map a region well beyond the expected virial radius of the cluster and to get a high surface density of background galaxies (23 galaxies/arcmin^2). This made possible to estimate an accurate mass for Abell 611. We find that the mass within 1.5 Mpc is: $(8\\pm3)\\times 10^{14}...

  17. Sample variance in weak lensing: how many simulations are required?

    CERN Document Server

    Petri, Andrea; May, Morgan

    2016-01-01

    Constraining cosmology using weak gravitational lensing consists of comparing a measured feature vector of dimension $N_b$ with its simulated counterpart. An accurate estimate of the $N_b\\times N_b$ feature covariance matrix $\\mathbf{C}$ is essential to obtain accurate parameter confidence intervals. When $\\mathbf{C}$ is measured from a set of simulations, an important question is how large this set should be. To answer this question, we construct different ensembles of $N_r$ realizations of the shear field, using a common randomization procedure that recycles the outputs from a smaller number $N_s\\leq N_r$ of independent ray-tracing $N$--body simulations. We study parameter confidence intervals as a function of ($N_s,N_r$) in the range $1\\leq N_s\\leq 200$ and $1\\leq N_r\\lesssim 10^5$. Previous work has shown that Gaussian noise in the feature vectors (from which the covariance is estimated) lead, at quadratic order, to an $O(1/N_r)$ degradation of the parameter confidence intervals. Using a variety of lensin...

  18. An Instrumentation Systematic for Weak Lensing from WFIRST

    Science.gov (United States)

    Jayaraman, Arun; Shapiro, Charles; Mandelbaum, Rachel; Hirata, Christopher M.; Kruk, Jeffrey W.; Rhodes, Jason

    2016-06-01

    The Wide Field Infra-Red Space Telescope (WFIRST), which is planned to be launched in 2025, will image the Universe in the near-Infrared bands and help measure shapes of ~400M galaxies according to the current survey design. Given such a big dataset, in order to be able to make precise weak lensing measurements and thereby understand the dark sectors of the Universe, it is necessary to not be biased by systematic effects. An understanding of systematic effects that arise from both astrophysical situations and from the instrumentation becomes crucial. The detectors used in WFIRST are made of HgCdTe and have CMOS based readout electronics, thus suffering from systematic effects that are different from that of CCDs. In this talk, I will focus on one such effect called the 'Interpixel Capacitance' (IPC) effect, which is a form of electrical crosstalk between neighboring pixels. I will show some results on how the shape of observed PSF, which will include the effect of IPC, varies as a function of the IPC parameters. I will also show how the shear measurement bias is affected if the IPC in the individual exposures is not perfectly corrected for, due to the misestimation of the IPC parameters. The requirements on PSF shapes and measurement biases can be translated into requirements on the IPC parameters and thus be used to specify the desired level of detector performance.

  19. Initial results from a laboratory emulation of weak gravitational lensing measurements

    CERN Document Server

    Seshadri, Suresh; Goodsall, Timothy; Fucik, Jason; Hirata, Christopher M; Rhodes, Jason; Rowe, Barnaby; Smith, Roger

    2013-01-01

    Weak gravitational lensing observations are a key science driver for the NASA Wide Field Infrared Survey Telescope (WFIRST). To validate the performance of the WFIRST infrared detectors, we have performed a laboratory emulation of weak gravitational lensing measurements. Our experiments used a custom precision projector system to image a target mask composed of a grid of pinholes, emulating stellar point sources, onto a 1.7 micron cut-off Teledyne HgCdTe/H2RG detector. We used a 880nm 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 2nd order polynomial fits to the shear maps, we found that the correlation functions could b...

  20. Comparing Dense Galaxy Cluster Redshift Surveys with Weak Lensing Maps

    CERN Document Server

    Hwang, Ho Seong; Diaferio, Antonaldo; Rines, Kenneth J; Zahid, H Jabran

    2014-01-01

    We use dense redshift surveys of nine galaxy clusters at $z\\sim0.2$ to compare the galaxy distribution in each system with the projected matter distribution from weak lensing. By combining 2087 new MMT/Hectospec redshifts and the data in the literature, we construct spectroscopic samples within the region of weak-lensing maps of high (70--89%) and uniform completeness. With these dense redshift surveys, we construct galaxy number density maps using several galaxy subsamples. The shape of the main cluster concentration in the weak-lensing maps is similar to the global morphology of the number density maps based on cluster members alone, mainly dominated by red members. We cross correlate the galaxy number density maps with the weak-lensing maps. The cross correlation signal when we include foreground and background galaxies at 0.5$z_{\\rm cl}$20% for A383, A689 and A750). The fractional excess in the cross correlation signal including foreground and background structures could be a useful proxy for assessing th...

  1. Probing cosmology with weak lensing selected clusters I: Halo approach and all-sky simulations

    CERN Document Server

    Shirasaki, Masato; Yoshida, Naoki

    2015-01-01

    Weak gravitational lensing enables us to search clusters without the conventional assumption on the relation between visible and dark matter. We explore a variety of statistics of clusters selected with cosmic shear measurement by utilizing both analytic models and large numerical simulations. We first develop a halo model to predict the abundance and the clustering of weak lensing selected clusters. Observational effects such as galaxy shape noise are included in our model. We then generate realistic mock weak lensing catalogs to test the accuracy of our analytic model. To this end, we perform full-sky ray-tracing simulations that allow us to have multiple realizations of a large continuous area. We model the masked regions on the sky using the actual positions of bright stars, and generate 200 mock weak lensing catalogs with sky coverage of $\\sim$1000 squared degrees. We utilize the large set of mock catalogs to evaluate the covariance matrices between the local and non-local statistics. We show that our th...

  2. RadioLensfit: Bayesian weak lensing measurement in the visibility domain

    CERN Document Server

    Rivi, Marzia; Makhathini, Spheshile; Abdalla, Filipe Batoni

    2016-01-01

    Observationally, weak lensing has been served so far by optical surveys due to the much larger number densities of background galaxies achieved, which is typically by two to three orders of magnitude compared to radio. However, the high sensitivity of the new generation of radio telescopes such as the Square Kilometre Array (SKA) will provide a density of detected galaxies that is comparable to that found at optical wavelengths, and with significant source shape measurements to make large area radio surveys competitive for weak lensing studies. This will lead weak lensing to become one of the primary science drivers in radio surveys too, with the advantage that they will access the largest scales in the Universe going beyond optical surveys, like LSST and Euclid, in terms of redshifts that are probed. RadioLensfit is an adaptation to radio data of "lensfit", a model-fitting approach for galaxy shear measurement, originally developed for optical weak lensing surveys. Its key advantage is working directly in th...

  3. SKA Weak Lensing I: Cosmological Forecasts and the Power of Radio-Optical Cross-Correlations

    Science.gov (United States)

    Harrison, Ian; Camera, Stefano; Zuntz, Joe; Brown, L.

    2016-09-01

    We construct forecasts for cosmological parameter constraints from weak gravitational lensing surveys involving the Square Kilometre Array (SKA). Considering matter content, dark energy and modified gravity parameters, we show that the first phase of the SKA (SKA1) can be competitive with other Stage III experiments such as the Dark Energy Survey (DES) and that the full SKA (SKA2) can potentially form tighter constraints than Stage IV optical weak lensing experiments, such as those that will be conducted with LSST, WFIRST-AFTA or Euclid-like facilities. Using weak lensing alone, going from SKA1 to SKA2 represents improvements by factors of ˜10 in matter, ˜10 in dark energy and ˜5 in modified gravity parameters. We also show, for the first time, the powerful result that comparably tight constraints (within ˜5%) for both Stage III and Stage IV experiments, can be gained from cross-correlating shear maps between the optical and radio wavebands, a process which can also eliminate a number of potential sources of systematic errors which can otherwise limit the utility of weak lensing cosmology.

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

    Energy Technology Data Exchange (ETDEWEB)

    Yamauchi, Daisuke; Taruya, Atsushi [Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033 (Japan); Namikawa, Toshiya, E-mail: yamauchi@resceu.s.u-tokyo.ac.jp, E-mail: namikawa@yukawa.kyoto-u.ac.jp, E-mail: ataruya@utap.phys.s.u-tokyo.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

    2013-08-01

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

  5. An accurate and practical method for inference of weak gravitational lensing from galaxy images

    Science.gov (United States)

    Bernstein, Gary M.; Armstrong, Robert; Krawiec, Christina; March, Marisa C.

    2016-07-01

    We demonstrate highly accurate recovery of weak gravitational lensing shear using an implementation of the Bayesian Fourier Domain (BFD) method proposed by Bernstein & Armstrong, extended to correct for selection biases. The BFD formalism is rigorously correct for Nyquist-sampled, background-limited, uncrowded images of background galaxies. BFD does not assign shapes to galaxies, instead compressing the pixel data D into a vector of moments M, such that we have an analytic expression for the probability P(M|g) of obtaining the observations with gravitational lensing distortion g along the line of sight. We implement an algorithm for conducting BFD's integrations over the population of unlensed source galaxies which measures ≈10 galaxies s-1 core-1 with good scaling properties. Initial tests of this code on ≈109 simulated lensed galaxy images recover the simulated shear to a fractional accuracy of m = (2.1 ± 0.4) × 10-3, substantially more accurate than has been demonstrated previously for any generally applicable method. Deep sky exposures generate a sufficiently accurate approximation to the noiseless, unlensed galaxy population distribution assumed as input to BFD. Potential extensions of the method include simultaneous measurement of magnification and shear; multiple-exposure, multiband observations; and joint inference of photometric redshifts and lensing tomography.

  6. Weak lensing measurement of the mass-richness relation of SDSS redMaPPer clusters

    Science.gov (United States)

    Simet, Melanie; McClintock, Tom; Mandelbaum, Rachel; Rozo, Eduardo; Rykoff, Eli; Sheldon, Erin; Wechsler, Risa H.

    2017-04-01

    We perform a measurement of the mass-richness relation of the redMaPPer galaxy cluster catalogue using weak lensing data from the Sloan Digital Sky Survey (SDSS). We have carefully characterized a broad range of systematic uncertainties, including shear calibration errors, photo-z biases, dilution by member galaxies, source obscuration, magnification bias, incorrect assumptions about cluster mass profiles, cluster centring, halo triaxiality and projection effects. We also compare measurements of the lensing signal from two independently produced shear and photometric redshift catalogues to characterize systematic errors in the lensing signal itself. Using a sample of 5570 clusters from 0.1 ≤ z ≤ 0.33, the normalization of our power-law mass versus λ relation is log10[M200m/h-1 M⊙] = 14.344 ± 0.021 (statistical) ±0.023 (systematic) at a richness λ = 40, a 7 per cent calibration uncertainty, with a power-law index of 1.33^{+0.09}_{-0.10} (1σ). The detailed systematics characterization in this work renders it the definitive weak lensing mass calibration for SDSS redMaPPer clusters at this time.

  7. Effect of Mask Regions on Weak Lensing Statistics

    CERN Document Server

    Shirasaki, Masato; Hamana, Takashi

    2013-01-01

    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 Gaussian simulations in order to examine in detail the impact of mask 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 thus the expected values of the MFs are biased even for a Gaussian random field. The bias is caused by two effects. One is owing to the reduced number of sampling Fourier modes, which can be accounted for analytically by considering the survey geometry appropriately. The other is owing to variation of the variance of the convergence field for each field of view. Lensing MFs are biased systematically when the reconstructed convergence field is normalized by its variance. We then use a large number of cosmological ray-tracing simulations in order to addr...

  8. Weak Lensing and CMB: Parameter forecasts including a running spectral index

    CERN Document Server

    Ishak, M; McDonald, P; Seljak, U; Ishak, Mustapha; Hirata, Christopher M.; Donald, Patrick Mc; Seljak, Uros

    2004-01-01

    We use statistical inference theory to explore the constraints from future galaxy weak lensing (cosmic shear) surveys combined with the current CMB constraints on cosmological parameters, focusing particularly on the running of the spectral index of the primordial scalar power spectrum, $\\alpha_s$. Recent papers have drawn attention to the possibility of measuring $\\alpha_s$ by combining the CMB with galaxy clustering and/or the Lyman-$\\alpha$ forest. Weak lensing combined with the CMB provides an alternative probe of the primordial power spectrum. We run a series of simulations with variable runnings and compare them to semi-analytic non-linear mappings to test their validity for our calculations. We find that a ``Reference'' cosmic shear survey with $f_{sky}=0.01$ and $6.6\\times 10^8$ galaxies per steradian can reduce the uncertainty on $n_s$ and $\\alpha_s$ by roughly a factor of 2 relative to the CMB alone. We investigate the effect of shear calibration biases on lensing by including the calibration factor...

  9. GLIMPSE: Accurate 3D weak lensing reconstructions using sparsity

    CERN Document Server

    Leonard, Adrienne; Starck, Jean-Luc

    2013-01-01

    We present GLIMPSE - Gravitational Lensing Inversion and MaPping with Sparse Estimators - a new algorithm to generate density reconstructions in three dimensions from photometric weak lensing measurements. This is an extension of earlier work in one dimension aimed at applying compressive sensing theory to the inversion of gravitational lensing measurements to recover 3D density maps. Using the assumption that the density can be represented sparsely in our chosen basis - 2D transverse wavelets and 1D line of sight dirac functions - we show that clusters of galaxies can be identified and accurately localised and characterised using this method. Throughout, we use simulated data consistent with the quality currently attainable in large surveys. We present a thorough statistical analysis of the errors and biases in both the redshifts of detected structures and their amplitudes. The GLIMPSE method is able to produce reconstructions at significantly higher resolution than the input data; in this paper we show reco...

  10. Weak Lensing Analysis of IDCS J1426.5+3508: A Massive Galaxy Cluster at z=1.75

    Science.gov (United States)

    Mo, Wenli

    2015-08-01

    We present a weak lensing study of the galaxy cluster IDCS J1426.5+3508 which, at z=1.75, is the highest redshift strong lensing cluster known and the most distant cluster for which a weak lensing analysis has been undertaken. Using F160W, F814W, and F606W observations with the Hubble Space Telescope, we detect a tangential shear signal out to a radius of ~1 Mpc. Fitting the shear to a Navarro-Frenk-White mass profile, we derive a mass that agrees with previous masses calculated from the Sunyaev-Zel'dovich (SZ) effect, X-ray, and strong lensing observations. The combination of weak lensing and SZ measurements are consistent with the scaling relation observed at low redshift, indicative of minimal evolution in this relation. The cluster concentration is not well-constrained by the weak lensing data alone, but we derive a concentration using the SZ mass measurements as a prior. It has previously been noted that an exceptionally high concentration might afford a means to explain the unexpected existence of a giant arc in this cluster. Our data argue that the concentration is not unusually large, indicating that an alternate solution is required.

  11. Weak gravitational lensing analysis of Sloan Digital Sky Survey data

    Science.gov (United States)

    Mandelbaum, Rachel

    Weak gravitational lensing, the distortion of images of distant galaxies due to gravitational deflection of light by more nearby masses, is a powerful tool that can address a wide variety of problems in astrophysics and cosmology. Observation of weak lensing requires large amounts of data since it can only be measured as an average over millions of galaxy shapes. This thesis focuses on lensing-related science that can be addressed using data from the Sloan Digital Sky Survey (SDSS), an excellent source of high-quality data. First, we discuss technical issues related to observing lensing in the data, with a description of our Reglens pipeline and constraints on systematic errors in current data. This is followed by a comparison of an analytical model known as the halo model (which can be used to relate the observed lensing signal to properties of the lens galaxies) against the lensing signal in N-body simulations. After these preliminaries, we address several very different science questions using our reductions of the SDSS data. The first is the question of intrinsic alignments of galaxies (alignments of galaxies on the sky due to local structure), which may be a contaminant for future lensing surveys that seek to determine the cosmological model to high precision. Second, we use a halo model analysis of the lensing signal to determine the relationship between galaxy luminosity, stellar mass, and halo mass, and to measure satellite fractions, all of which can help distinguish between models of galaxy formation. The third application we consider is methodology for the detection of dark matter halo ellipticity, including a first attempt at detecting it with SDSS lensing data, these results may be used to distinguish between cosmological models and learn more about galaxy intrinsic alignments. Finally, we measure the matter distributions around Luminous Red Galaxies (LRGs), which not only teaches us about the properties of these galaxies, but also gives us information

  12. Multi Dark Lens Simulations: weak lensing light-cones and data base presentation

    Science.gov (United States)

    Giocoli, Carlo; Jullo, Eric; Metcalf, R. Benton; de la Torre, Sylvain; Yepes, Gustavo; Prada, Francisco; Comparat, Johan; Göttlober, Stefan; Kyplin, Anatoly; Kneib, Jean-Paul; Petkova, Margarita; Shan, Huan Yuan; Tessore, Nicolas

    2016-09-01

    In this paper we present a large data base of weak lensing light cones constructed using different snapshots from the Big MultiDark simulation (BigMDPL). The ray-tracing through different multiple plane has been performed with the GLAMER code accounting both for single source redshifts and for sources distributed along the cosmic time. This first paper presents weak lensing forecasts and results according to the geometry of the VIPERS-W1 and VIPERS-W4 field of view. Additional fields will be available on our data base and new ones can be run upon request. Our data base also contains some tools for lensing analysis. In this paper we present results for convergence power spectra, one point and high order weak lensing statistics useful for forecasts and for cosmological studies. Covariance matrices have also been computed for the different realizations of the W1 and W4 fields. In addition we compute also galaxy-shear and projected density contrasts for different halo masses at two lens redshift according to the CFHTLS source redshift distribution both using stacking and cross-correlation techniques, finding very good agreement.

  13. An algorithm for the direct reconstruction of the dark matter correlation function from weak lensing and galaxy clustering

    CERN Document Server

    Baldauf, Tobias; Seljak, Uros; Mandelbaum, Rachel

    2009-01-01

    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 this study we develop 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. 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 pre-existing 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 devel...

  14. Cosmic variance of the galaxy cluster weak lensing signal

    CERN Document Server

    Gruen, D; Becker, M R; Friedrich, O; Mana, A

    2015-01-01

    Intrinsic variations of the projected density profiles of clusters of galaxies at fixed mass are a source of uncertainty for cluster weak lensing. We present a semi-analytical model to account for this effect, based on a combination of variations in halo concentration, ellipticity and orientation, and the presence of correlated haloes. We calibrate the parameters of our model at the 10 per cent level to match the empirical cosmic variance of cluster profiles at M_200m=10^14...10^15 h^-1 M_sol, z=0.25...0.5 in a cosmological simulation. We show that weak lensing measurements of clusters significantly underestimate mass uncertainties if intrinsic profile variations are ignored, and that our model can be used to provide correct mass likelihoods. Effects on the achievable accuracy of weak lensing cluster mass measurements are particularly strong for the most massive clusters and deep observations (with ~20 per cent uncertainty from cosmic variance alone at M_200m=10^15 h^-1 M_sol and z=0.25), but significant also...

  15. Robust Weak-lensing Mass Calibration of Planck Galaxy Clusters

    CERN Document Server

    von der Linden, Anja; Allen, Steven W; Applegate, Douglas E; Kelly, Patrick L; Morris, R Glenn; Wright, Adam; Allen, Mark T; Burchat, Patricia R; Burke, David L; Donovan, David; Ebeling, Harald

    2014-01-01

    In light of the tension in cosmological constraints reported by the Planck team between their SZ-selected cluster counts and Cosmic Microwave Background (CMB) temperature anisotropies, we compare the Planck cluster mass estimates with robust, weak-lensing mass measurements from the Weighing the Giants (WtG) project. For the 22 clusters in common between the Planck cosmology sample and WtG, we find an overall mass ratio of $\\left = 0.688 \\pm 0.072$. Extending the sample to clusters not used in the Planck cosmology analysis yields a consistent value of $\\left = 0.698 \\pm 0.062$ from 38 clusters in common. Identifying the weak-lensing masses as proxies for the true cluster mass (on average), these ratios are $\\sim 1.6\\sigma$ lower than the default mass bias of 0.8 assumed in the Planck cluster analysis. Adopting the WtG weak-lensing-based mass calibration would substantially reduce the tension found between the Planck cluster count cosmology results and those from CMB temperature anisotropies. We also find modes...

  16. An Implementation of Bayesian Lensing Shear Measurement

    CERN Document Server

    Sheldon, Erin S

    2014-01-01

    The Bayesian gravitational shear estimation algorithm developed by Bernstein and Armstrong (2014) can potentially be used to overcome noise bias and recover shear using very low signal-to-noise ratio (S/N) galaxy images. In that work the authors confirmed the method is sufficiently unbiased for planned surveys (fractional error less than 2 x 10^{-3}) in a simplified demonstration, but no test was performed on images. Here I present a full implementation for fitting models to galaxy images, including the effects of a point spread function (PSF) and pixelization. I tested the implementation using simulated galaxy images modeled as Sersic profiles with n=1 (exponential) and n=4 (De Vaucouleurs'), convolved with a PSF and a flat pixel response function. I used a round Gaussian model for the PSF to avoid potential PSF-fitting errors. I simulated galaxies with mean observed, post-PSF full-width at half maximum equal to approximately 1.2 times that of the PSF, with log-normal scatter. I also drew fluxes from a log-n...

  17. Simultaneous constraints on cosmology and photometric redshift bias from weak lensing and galaxy clustering

    Science.gov (United States)

    Samuroff, S.; Troxel, M. A.; Bridle, S. L.; Zuntz, J.; MacCrann, N.; Krause, E.; Eifler, T.; Kirk, D.

    2017-02-01

    We investigate the expected cosmological constraints from a combination of cosmic shear and large-scale galaxy clustering using realistic photometric redshift distributions. Introducing a systematic bias in the lensing distributions (of 0.05 in redshift) produces a >2σ bias in the recovered matter power spectrum amplitude and dark energy equation of state for preliminary Stage III surveys. We demonstrate that cosmological error can be largely removed by marginalizing over biases in the assumed weak-lensing redshift distributions. Furthermore, the cosmological constraining power is retained despite removing much of the information on the lensing redshift biases. This finding relies upon high-quality redshift estimates for the clustering sample, but does not require spectroscopy. All galaxies in this analysis can thus be assumed to come from a single photometric survey. We show that this internal constraint on redshift biases arises from complementary degeneracy directions between cosmic shear and the combination of galaxy clustering and shear-density cross-correlations. Finally we examine a case where the assumed redshift distributions differ from the truth by more than a simple uniform bias. We find that the effectiveness of this self-calibration method will depend on the survey details and the nature of the uncertainties on the estimated redshift distributions.

  18. Intrinsic alignment contamination to CMB lensing-galaxy weak lensing correlations from tidal torquing

    Science.gov (United States)

    Larsen, Patricia; Challinor, Anthony

    2016-10-01

    Correlations of galaxy ellipticities with large-scale structure, due to galactic tidal interactions, provide a potentially significant contaminant to measurements of cosmic shear. However, these intrinsic alignments are still poorly understood for galaxies at the redshifts typically used in cosmic shear analyses. For spiral galaxies, it is thought that tidal torquing is significant in determining alignments resulting in zero correlation between the intrinsic ellipticity and the gravitational potential in linear theory. Here, we calculate the leading-order correction to this result in the tidal-torque model from non-linear evolution, using second-order perturbation theory, and relate this to the contamination from intrinsic alignments to the recently measured cross-correlation between galaxy ellipticities and the cosmic microwave background (CMB) lensing potential. On the scales relevant for CMB lensing observations, the squeezed limit of the gravitational bispectrum dominates the correlation. Physically, the large-scale mode that sources CMB lensing modulates the small-scale power and hence the intrinsic ellipticity, due to non-linear evolution. We find that the angular cross-correlation from tidal torquing has a very similar scale dependence as in the linear alignment model, believed to be appropriate for elliptical galaxies. The amplitude of the cross-correlation is predicted to depend strongly on the formation redshift, being smaller for galaxies that formed at higher redshift when the bispectrum of the gravitational potential was smaller. Finally, we make simple forecasts for constraints on intrinsic alignments from the correlation of forthcoming cosmic shear measurements with current CMB lensing measurements. We note that cosmic variance can be significantly reduced in measurements of the difference in the intrinsic alignments for elliptical and spiral galaxies if these types can be separated (e.g. using colour).

  19. Galaxy–Galaxy Weak-lensing Measurements from SDSS. I. Image Processing and Lensing Signals

    Science.gov (United States)

    Luo, Wentao; Yang, Xiaohu; Zhang, Jun; Tweed, Dylan; Fu, Liping; Mo, H. J.; van den Bosch, Frank C.; Shu, Chenggang; Li, Ran; Li, Nan; Liu, Xiangkun; Pan, Chuzhong; Wang, Yiran; Radovich, Mario

    2017-02-01

    We present our image processing pipeline that corrects the systematics introduced by the point-spread function (PSF). Using this pipeline, we processed Sloan Digital Sky Survey (SDSS) DR7 imaging data in r band and generated a galaxy catalog containing the shape information. Based on our shape measurements of the galaxy images from SDSS DR7, we extract the galaxy–galaxy (GG) lensing signals around foreground spectroscopic galaxies binned in different luminosities and stellar masses. We estimated the systematics, e.g., selection bias, PSF reconstruction bias, PSF dilution bias, shear responsivity bias, and noise rectification bias, which in total is between ‑9.1% and 20.8% at 2σ levels. The overall GG lensing signals we measured are in good agreement with Mandelbaum et al. The reduced χ 2 between the two measurements in different luminosity bins are from 0.43 to 0.83. Larger reduced χ 2 from 0.60 to 1.87 are seen for different stellar mass bins, which is mainly caused by the different stellar mass estimator. The results in this paper with higher signal-to-noise ratio are due to the larger survey area than SDSS DR4, confirming that more luminous/massive galaxies bear stronger GG lensing signals. We divide the foreground galaxies into red/blue and star-forming/quenched subsamples and measure their GG lensing signals. We find that, at a specific stellar mass/luminosity, the red/quenched galaxies have stronger GG lensing signals than their counterparts, especially at large radii. These GG lensing signals can be used to probe the galaxy–halo mass relations and their environmental dependences in the halo occupation or conditional luminosity function framework.

  20. A Compressed Sensing Approach to 3D Weak Lensing

    CERN Document Server

    Leonard, Adrienne; Starck, Jean-Luc

    2011-01-01

    (Abridged) Weak gravitational lensing is an ideal probe of the dark universe. In recent years, several linear methods have been developed to reconstruct the density distribution in the Universe in three dimensions, making use of photometric redshift information to determine the radial distribution of lensed sources. In this paper, we aim to address three key issues seen in these methods; namely, the bias in the redshifts of detected objects, the line of sight smearing seen in reconstructions, and the damping of the amplitude of the reconstruction relative to the underlying density. We consider the problem under the framework of compressed sensing (CS). Under the assumption that the data are sparse in an appropriate dictionary, we construct a robust estimator and employ state-of-the-art convex optimisation methods to reconstruct the density contrast. For simplicity in implementation, and as a proof of concept of our method, we reduce the problem to one-dimension, considering the reconstruction along each line ...

  1. SKA weak lensing - III. Added value of multiwavelength synergies for the mitigation of systematics

    Science.gov (United States)

    Camera, Stefano; Harrison, Ian; Bonaldi, Anna; Brown, Michael L.

    2017-02-01

    In this third paper of a series on radio weak lensing for cosmology with the Square Kilometre Array, we scrutinize synergies between cosmic shear measurements in the radio and optical/near-infrared (IR) bands for mitigating systematic effects. We focus on three main classes of systematics: (i) experimental systematic errors in the observed shear; (ii) signal contamination by intrinsic alignments and (iii) systematic effects due to an incorrect modelling of non-linear scales. First, we show that a comprehensive, multiwavelength analysis provides a self-calibration method for experimental systematic effects, only implying errors on cosmological parameters. We also illustrate how the cross-correlation between radio and optical/near-IR surveys alone is able to remove residual systematics with variance as large as 10-5, i.e. the same order of magnitude of the cosmological signal. This also opens the possibility of using such a cross-correlation as a means to detect unknown experimental systematics. Secondly, we demonstrate that, thanks to polarization information, radio weak lensing surveys will be able to mitigate contamination by intrinsic alignments, in a way similar but fully complementary to available self-calibration methods based on position-shear correlations. Lastly, we illustrate how radio weak lensing experiments, reaching higher redshifts than those accessible to optical surveys, will probe dark energy and the growth of cosmic structures in regimes less contaminated by non-linearities in the matter perturbations. For instance, the higher redshift bins of radio catalogues peak at z ≃ 0.8-1, whereas their optical/near-IR counterparts are limited to z ≲ 0.5-0.7. This translates into having a cosmological signal 2-5 times less contaminated by non-linear perturbations.

  2. Constraints on the decay of dark matter to dark energy from weak lensing bispectrum tomography

    CERN Document Server

    Schaefer, Bjoern Malte; Maartens, Roy

    2008-01-01

    We consider a phenomenological model for a coupling between the dark matter and dark energy fluids and investigate the sensitivity of a weak lensing measurement for constraining the size of this coupling term. Physically, the functional form of the coupling term in our model describes the decay of dark matter into dark energy. We present forecasts for tomographic measurements of the weak shear bispectrum for the DUNE experiment in a Fisher-matrix formalism, where we describe the nonlinearities in structure formation by hyper-extended perturbation theory. Physically, CDM decay tends to increase the growth rate of density perturbations due to higher values for the CDM density at early times, and amplifies the lensing signal because of stronger fluctuations in the gravitational potential. We focus on degeneracies between the dark energy equation of state properties and the CDM decay constant relevant for structure formation and weak lensing. A typical lower bound on the CDM decay time ~7.7/H_0 = 75.3 Gyr/h$ whic...

  3. Orientation Bias of Optically Selected Galaxy Clusters and Its Impact on Stacked Weak Lensing Analyses

    CERN Document Server

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

    2014-01-01

    Weak-lensing measurements of the averaged shear profiles of galaxy clusters binned by some proxy for cluster mass are commonly converted to cluster mass estimates under the assumption that these cluster stacks have spherical symmetry. In this paper we test whether this assumption holds for optically selected clusters binned by estimated optical richness. Using mock catalogues created from N-body simulations populated realistically with galaxies, we ran a suite of optical cluster finders and estimated their optical richness. We binned galaxy clusters by true cluster mass and estimated optical richness and measure the ellipticity of these stacks. We find that the processes of optical cluster selection and richness estimation are biased, leading to stacked structures that are elongated along the line-of-sight. We show that weak-lensing alone cannot measure the size of this orientation bias. Weak lensing masses of stacked optically selected clusters are overestimated by up to 3-6 per cent when clusters can be uni...

  4. Searching in GaBoDS deep survey for clusters of galaxies by weak gravitational lensing

    Directory of Open Access Journals (Sweden)

    M Rahimi

    2011-06-01

    Full Text Available The aim of the present work is detection of galaxy clusters based on weak gravitational lensing method. We apply mass aperture statistics method to 0.32 square degrees data obtained with the WFI@MPG/ESO 2.2 m telescope and detect mass peaks based on their mass not the luminosity. So by the application of proper filter function, shear profile and mass map are produced. Finally mass peaks with higher detection significance are extracted. In future works, redshift of these mass concentrations and so their mass can be obtained.‎

  5. An accurate and practical method for inference of weak gravitational lensing from galaxy images

    CERN Document Server

    Bernstein, Gary M; Krawiec, Christina; March, Marisa C

    2015-01-01

    We demonstrate recovery of weak gravitational lensing shear at parts-per-thousand accuracy using an implementation of the Bayesian Fourier Domain (BFD) method proposed by Bernstein \\& Armstrong (2014, BA14). The BFD formalism is rigorously correct for Nyquist-sampled, background-limited, uncrowded image of background galaxies. BFD does not assign shapes to galaxies, instead compressing the pixel data D into a vector of moments M, such that we have an analytic expression for the probability P(M|g) of obtaining the observations with gravitational lensing distortion g along the line of sight. We extend the BA14 formalism to include detection and selection of galaxies without inducing biases on the inferred g. We describe a practical algorithm for conducting BFD's integrations over the population of unlensed source galaxies. Our BFD implementation measures ~10 galaxies per second per core on current hardware, a speed that will be largely independent of the number of images taken of each target. Initial tests ...

  6. Fast Calculation of the Weak Lensing Aperture Mass Statistic

    CERN Document Server

    Leonard, Adrienne; Starck, Jean-Luc

    2012-01-01

    The aperture mass statistic is a common tool used in weak lensing studies. By convolving lensing maps with a filter function of a specific scale, chosen to be larger than the scale on which the noise is dominant, the lensing signal may be boosted with respect to the noise. This allows for detection of structures at increased fidelity. Furthermore, higher-order statistics of the aperture mass (such as its skewness or kurtosis), or counting of the peaks seen in the resulting aperture mass maps, provide a convenient and effective method to constrain the cosmological parameters. In this paper, we more fully explore the formalism underlying the aperture mass statistic. We demonstrate that the aperture mass statistic is formally identical to a wavelet transform at a specific scale. Further, we show that the filter functions most frequently used in aperture mass studies are not ideal, being non-local in both real and Fourier space. In contrast, the wavelet formalism offers a number of wavelet functions that are loca...

  7. Weak Lensing Measurement of the Mass--Richness Relation of SDSS redMaPPer Clusters

    CERN Document Server

    Simet, Melanie; Mandelbaum, Rachel; Rozo, Eduardo; Rykoff, Eli; Sheldon, Erin; Wechsler, Risa H

    2016-01-01

    We perform a measurement of the mass--richness relation of the redMaPPer galaxy cluster catalogue using weak lensing data from the Sloan Digital Sky Survey. We have carefully characterized a broad range of systematic uncertainties, including shear calibration errors, photo-$z$ biases, dilution by member galaxies, source obscuration, magnification bias, incorrect assumptions about cluster mass profiles, cluster centering, halo triaxiality, and projection effects. We also compare measurements of the lensing signal from two independently-produced shear and photometric redshift catalogues to characterize systematic errors in the lensing signal itself. Using a sample of 5,570 clusters from $0.1\\le z\\le 0.33$, the normalization of our power-law mass vs.\\ $\\lambda$ relation is $\\log_{10}[M_{200m}/h^{-1}\\ M_{\\odot}]$ = $14.344 \\pm 0.021$ (statistical) $\\pm 0.023$ (systematic) at a richness $\\lambda=40$, a 7 per cent calibration uncertainty, with a power-law index of $1.33^{+0.09}_{-0.10}$ ($1\\sigma$). The detailed sy...

  8. A weak lensing view on primordial non-Gaussianities

    CERN Document Server

    Schaefer, Bjoern Malte; Gerstenlauer, Mischa; Byrnes, Christian T

    2011-01-01

    We investigate the signature of primordial non-Gaussianities in the weak lensing bispectrum, in particular the signals generated by local, orthogonal and equilateral non-Gaussianities. The questions we address include the signal-to-noise ratio generated in the Euclid weak lensing survey (we find the 1sigma-errors for fNL are 200, 575 and 1628 for local, orthogonal and equilateral non-Gaussianities, respectively), misestimations of fNL if one chooses the wrong non-Gaussianity model (misestimations by up to a factor of +/-3 in fNL are possible, depending on the choice of the model), the probability of noticing such a mistake (improbably large values for the chi^2-functional occur from fNL 200 on), degeneracies of the primordial bispectrum with other cosmological parameters (only the matter density Omega_m plays a significant role), and the subtraction of the much larger, structure-formation generated bispectrum. If a prior on a standard wCDM-parameter set is available from Euclid and Planck, the structure forma...

  9. Weak Lensing from Space I: Instrumentation and Survey Strategy

    Energy Technology Data Exchange (ETDEWEB)

    Rhodes, Jason; Refregier, Alexandre; Massey, Richard; Albert, Justin; Bacon, David; Bernstein, Gary; Ellis, Richard; Jain, Bhuvnesh; Kim, Alex; Lampton, Mike; McKay, Tim; Akerlof, C.; Aldering, G.; Amanullah, R.; Astier, P.; Barrelet, E.; Bebek, C.; Bergstrom, L.; Bercovitz, J.; Bester, M.; Bonissent, A.; Bower, C.; Carithers, W.; Commins, E.; Day, C.; Deustua, S.; DiGennaro, R.; Ealet, A.; Eriksson, M.; Fruchter, A.; Genat, J.-F.; Goldhaber, G.; Goobar, A.; Groom, D.; Harris, S.; Harvey, P.; Heetderks, H.; Holland, S.; Huterer, D.; Karcher, A.; Kolbe, W.; Kreiger, B.; Lafever, R.; Lamoureux, J.; Levi, M.; Devin, D.; Linder, E.; Loken, S.; Malina, R.; McKee, S.; Miquel, R.; Mortsell, E.; Mostek, N.; Mufson, S.; Musser, J.; Nugent, P.; Oluseyi, H.; Pain, R.; Palaio, N.; Pankow, D.; Perlmutter, S.; Pratt, R.; Prieto, E.; Robinson, K.; Roe, N.; Sholl, M.; Schubnell, M.; Smadja, G.; Smoot, G.; Spadafora, A.; Tarle, G.; Tomasch, A.; von der Lippe, H.; Vincent, D.; Walder, J.-P.; Wang, G.

    2003-04-23

    A wide field space-based imaging telescope is necessary to fully exploit the technique of observing dark matter via weak gravitational lensing. This first paper in a three part series outlines the survey strategies and relevant instrumental parameters for such a mission. As a concrete example of hardware design, we consider the proposed Supernova/Acceleration Probe (SNAP). Using SNAP engineering models, we quantify the major contributions to this telescope's Point Spread Function (PSF). These PSF contributions are relevant to any similar wide field space telescope. We further show that the PSF of SNAP or a similar telescope will be smaller than current ground-based PSFs, and more isotropic and stable over time than the PSF of the Hubble Space Telescope. We outline survey strategies for two different regimes - a ''wide'' 300 square degree survey and a ''deep'' 15 square degree survey that will accomplish various weak lensing goals including statistical studies and dark matter mapping.

  10. LoCuSS: weak-lensing mass calibration of galaxy clusters

    Science.gov (United States)

    Okabe, Nobuhiro; Smith, Graham P.

    2016-10-01

    We present weak-lensing mass measurements of 50 X-ray luminous galaxy clusters at 0.15 ≤ z ≤ 0.3, based on uniform high-quality observations with Suprime-Cam mounted on the 8.2-m Subaru telescope. We pay close attention to possible systematic biases, aiming to control them at the ≲4 per cent level. The dominant source of systematic bias in weak-lensing measurements of the mass of individual galaxy clusters is contamination of background galaxy catalogues by faint cluster and foreground galaxies. We extend our conservative method for selecting background galaxies with (V - i') colours redder than the red sequence of cluster members to use a colour-cut that depends on cluster-centric radius. This allows us to define background galaxy samples that suffer ≤1 per cent contamination, and comprise 13 galaxies per square arcminute. Thanks to the purity of our background galaxy catalogue, the largest systematic that we identify in our analysis is a shape measurement bias of 3 per cent, that we measure using simulations that probe weak shears up to g = 0.3. Our individual cluster mass and concentration measurements are in excellent agreement with predictions of the mass-concentration relation. Equally, our stacked shear profile is in excellent agreement with the Navarro Frenk and White profile. Our new Local Cluster Substructure Survey mass measurements are consistent with the Canadian Cluster Cosmology Project and Cluster Lensing And Supernova Survey with Hubble surveys, and in tension with the Weighing the Giants at ˜1σ-2σ significance. Overall, the consensus at z ≤ 0.3 that is emerging from these complementary surveys represents important progress for cluster mass calibration, and augurs well for cluster cosmology.

  11. Probing the accelerating Universe with radio weak lensing in the JVLA Sky Survey

    CERN Document Server

    Brown, M L; Amara, A; Bacon, D J; Battye, R A; Bell, M R; Beswick, R J; Birkinshaw, M; Böhm, V; Bridle, S; Browne, I W A; Casey, C M; Demetroullas, C; lin, T Enß; Ferreira, P G; Garrington, S T; Grainge, K J B; Gray, M E; Hales, C A; Harrison, I; Heavens, A F; Heymans, C; Hung, C L; Jackson, N J; Jarvis, M J; Joachimi, B; Kay, S T; Kitching, T D; Leahy, J P; Maartens, R; Miller, L; Muxlow, T W B; Myers, S T; Nichol, R C; Patel, P; Pritchard, J R; Raccanelli, A; Refregier, A; Richards, A M S; Riseley, C; Santos, M G; Scaife, A M M; Schäfer, B M; Schilizzi, R T; Smail, I; Starck, J -L; Szepietowski, R M; Taylor, A N; Whittaker, L; Wrigley, N; Zuntz, J

    2013-01-01

    We outline the prospects for performing pioneering radio weak gravitational lensing analyses using observations from a potential forthcoming JVLA Sky Survey program. A large-scale survey with the JVLA can offer interesting and unique opportunities for performing weak lensing studies in the radio band, a field which has until now been the preserve of optical telescopes. In particular, the JVLA has the capacity for large, deep radio surveys with relatively high angular resolution, which are the key characteristics required for a successful weak lensing study. We highlight the potential advantages and unique aspects of performing weak lensing in the radio band. In particular, the inclusion of continuum polarisation information can greatly reduce noise in weak lensing reconstructions and can also remove the effects of intrinsic galaxy alignments, the key astrophysical systematic effect that limits weak lensing at all wavelengths. We identify a VLASS "deep fields" program (total area ~10-20 square degs), to be con...

  12. Cosmological constraints from the capture of non-Gaussianity in Weak Lensing data

    CERN Document Server

    Pires, Sandrine; Starck, Jean-Luc

    2012-01-01

    Weak gravitational lensing has become a common tool to constrain the cosmological model. The majority of the methods to derive constraints on cosmological parameters use second-order statistics of the cosmic shear. Despite their success, second-order statistics are not optimal and degeneracies between some parameters remain. Tighter constraints can be obtained if second-order statistics are combined with a statistic that is efficient to capture non-Gaussianity. In this paper, we search for such a statistical tool and we show that there is additional information to be extracted from statistical analysis of the convergence maps beyond what can be obtained from statistical analysis of the shear field. For this purpose, we have carried out a large number of cosmological simulations along the {\\sigma}8-{\\Omega}m degeneracy, and we have considered three different statistics commonly used for non-Gaussian features characterization: skewness, kurtosis and peak count. To be able to investigate non-Gaussianity directly...

  13. Disentangling dark sector models using weak lensing statistics

    CERN Document Server

    Giocoli, Carlo; Baldi, Marco; Meneghetti, Massimo; Moscardini, Lauro; Petkova, Margarita; -,; Astronomia, Dipartimento di Fisica e; di Bologna, Alma Mater Studiorum Università; di Bologna, INAF - Osservatorio Astronomico; di Bologna, INFN - Sezione; Université, Aix Marseille; CNRS,; LAM,; France,; Laboratory, Jet Propulsion; Physics, Department of; Ludwig-Maximilians-Universitaet),

    2015-01-01

    We perform multi-plane ray-tracing using the GLAMER gravitational lensing code within high-resolution light-cones extracted from the CoDECS simulations: a suite of cosmological runs featuring a coupling between Dark Energy and Cold Dark Matter. We show that the presence of the coupling is evident not only in the redshift evolution of the normalisation of the convergence power spectrum, but also in differences in non-linear structure formation with respect to {\\Lambda}CDM. Using a tomographic approach under the assumption of a {\\Lambda}CDM cosmology, we demonstrate that weak lensing measurements would result in a {\\sigma}8 value that changes with the source redshift if the true underlying cosmology is a coupled Dark Energy one. This provides a generic null test for these types of models. We also find that different models of coupled Dark Energy can show either an enhanced or a suppressed correlation between convergence maps with differing source redshifts as compared to {\\Lambda}CDM. This would provide a direc...

  14. Quantum Lukewarm Black Holes and Weak Gravitational Lensing

    CERN Document Server

    Ghaffarnejad, H

    2015-01-01

    Aim of the paper is study gravitational lensing of quantum Lukewarm black hole (QLBL) and compare with results of gravitational lensing from classical Lukewarm black hole lens (CLBL). Applying numerical method, we evaluate deflection angle, image positions and magnifications in weak deflection limits. In CLBL case, bending light ray moves from both side of the lens but in QLBL case it moves from one side of the lens. Increasing amount of dimensionless cosmological parameter (quantum matter interaction parameter), rake of bending light ray is decreased in case of QLBL with respect to CLBL. Number and size of radius of Einstein rings rises in case of QLBL with respect to CLBL. Maximum number of rings is 3 in case of QLBL namely one more with respect to case of CLBL which is physically related to effects of quantum matter. There is two images (elementary and secondary) with maximum magnification which their locations are changed in case of QLBL with respect to case of CLBL. Also their locations changed by increa...

  15. Neutrino Mass and Dark Energy from Weak Lensing

    CERN Document Server

    Abazajian, Kevork N; Abazajian, Kevork; Dodelson, Scott

    2003-01-01

    Weak gravitational lensing directly probes the mass distribution in the universe. This distribution, and its evolution at late times, is sensitive to both the dark energy and neutrino mass. We examine the potential of lensing experiments to measure features of both simultaneously. Focusing on the radial information contained in a future deep 4000 square degree survey, we find that if the dark energy is fixed to be a cosmological constant (equation of state w=-1) and its density is known, then the expected (1-sigma) error on a neutrino mass is 0.02 eV. If the dark energy parameters are allowed to vary, then the expected error is 0.12 eV. The constraints on dark energy parameters are similarly restrictive, with errors on w of 0.01 if the two other parameters (neutrino mass and dark energy density) are held fixed, and 0.094 if the other parameters are allowed to vary. Much of the restrictive power on the dark energy comes not from the evolution of the gravitational potential but rather from how distances vary as...

  16. 3D weak lensing with spin wavelets on the ball

    CERN Document Server

    Leistedt, Boris; Kitching, Thomas D; Peiris, Hiranya V

    2015-01-01

    We construct the spin flaglet transform, a wavelet transform to analyse spin signals in three dimensions. Spin flaglets can probe signal content localised simultaneously in space and frequency and, moreover, are separable so that their angular and radial properties can be controlled independently. They are particularly suited to analysing of cosmological observations such as the weak gravitational lensing of galaxies. Such observations have a unique 3D geometrical setting since they are natively made on the sky, have spin angular symmetries, and are extended in the radial direction by additional distance or redshift information. Flaglets are constructed in the harmonic space defined by the Fourier-Laguerre transform, previously defined for scalar functions and extended here to signals with spin symmetries. Thanks to various sampling theorems, both the Fourier-Laguerre and flaglet transforms are theoretically exact when applied to band-limited signals. In other words, in numerical computations the only loss of...

  17. Weak Lensing by Galaxy Clusters: from Pixels to Cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Gruen, Daniel [Ludwig Maximilian Univ., Munich (Germany)

    2015-03-11

    The story of the origin and evolution of our Universe is told, equivalently, by space-time itself and by the structures that grow inside of it. Clusters of galaxies are the frontier of bottom-up structure formation. They are the most massive objects to have collapsed at the present epoch. By that virtue, their abundance and structural parameters are highly sensitive to the composition and evolution of the Universe. The most common probe of cluster cosmology, abundance, uses samples of clusters selected by some observable. Applying a mass-observable relation (MOR), cosmological parameters can be constrained by comparing the sample to predicted cluster abundances as a function of observable and redshift. Arguably, however, cluster probes have not yet entered the era of per cent level precision cosmology. The primary reason for this is our imperfect understanding of the MORs. The overall normalization, the slope of mass vs. observable, the redshift evolution, and the degree and correlation of intrinsic scatters of observables at fixed mass have to be constrained for interpreting abundances correctly. Mass measurement of clusters by means of the differential deflection of light from background sources in their gravitational field, i.e. weak lensing, is a powerful approach for achieving this. This thesis presents new methods for and scientific results of weak lensing measurements of clusters of galaxies. The former include, on the data reduction side, (i) the correction of CCD images for non-linear effects due to the electric fields of accumulated charges and (ii) a method for masking artifact features in sets of overlapping images of the sky by comparison to the median image. Also, (iii) I develop a method for the selection of background galaxy samples based on their color and apparent magnitude that includes a new correction for contamination with cluster member galaxies. The main scientific results are the following. (i) For the Hubble Frontier Field cluster RXC J

  18. CFHTLenS: Combined probe cosmological model comparison using 2D weak gravitational lensing

    CERN Document Server

    Kilbinger, Martin; Heymans, Catherine; Simpson, Fergus; Benjamin, Jonathan; Erben, Thomas; Harnois-Deraps, 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

    2012-01-01

    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 square degrees 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 sigma_8 scaled with the total matter density Omega_m. For a flat LambdaCDM model we obtain sigma_8(Omega_m/0.27)^0.6 = 0.79+-0.03. We combine the CFHTLenS data with WMAP7, BOSS and an HST distance-ladder prior on the Hubble constant to get joint constraints. For a flat LambdaCDM model, we find Omega_m = 0.283+...

  19. Weak lensing observation of potentially X-ray underluminous galaxy clusters

    CERN Document Server

    Dietrich, J P; Popesso, P; Zhang, Y -Y; Lombardi, M; Böhringer, H

    2009-01-01

    Optically selected clusters of galaxies display a relation between their optical mass estimates and their X-ray luminosities Lx with a large scatter. A substantial fraction of optically selected clusters have Lx estimates or upper limits significantly below the values expected from the Lx-mass relation established for X-ray selected clusters, i.e., these clusters are X-ray underluminous for their mass. Here we aim to confirm or falsify the X-ray underluminous nature of two clusters, Abell 315 and Abell 1456, with weak gravitational lensing as a third and independent measure of the clusters' masses. We obtained optical wide-field imaging data and selected background galaxies using their colors and measured the shear exerted by the tidal field of the foreground galaxy clusters. We then fitted parametrized models to our shear catalogs. After accounting for projections of large-scale structure and halo triaxiality we find that A~315 is significantly X-ray underluminous for its mass, while no significant lensing s...

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

    OpenAIRE

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

    2009-01-01

    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 or...

  1. Weak lensing mass estimates of galaxy groups and the line-of-sight contamination

    CERN Document Server

    Spinelli, P F; Lerchster, M; Brimioulle, F; Finoguenov, A

    2011-01-01

    Weak lensing is an important technique to determine the masses of galaxy groups. However, the distortion imprint on the shape of the background galaxies is affected by all the mass content along the line-of-sight. Using COSMOS shear mock data we study the shear profile of 165 groups and investigate the level at which the neighbouring groups can enhance or suppress the shear signal from the main halo. Our mock data are based on CFHT and Subaru observations and the information on the galaxy groups is taken from the COSMOS X-ray catalogue of extended sources. The expected gravitational shear field of these groups is calculated assuming that the haloes follow NFW density profiles. We conclude that, on average, the signal-to-noise for a detection of the main halo is affected by ~15%x\\sqrt{ngal/30} with respect to the signal-to-noise the same halo would have if it was isolated in the sky. Groups with neighbours that are close in projected distance (<1') are the most affected, but haloes located at larger angular...

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

    CERN Document Server

    Johnston, D E

    2006-01-01

    We discuss the galaxy-galaxy-mass three-point correlation function and show how to measure it with weak gravitational lensing. The method entails choosing a large of pairs of foreground lens galaxies and constructing a mean shear map with respect to their axis, by averaging the ellipticities of background source galaxies. An average mass map can be reconstructed from this shear map and this will represent the average mass distribution around pairs of galaxies. We show how this mass map is related to the projected galaxy-galaxy-mass three-point correlation function. Using a large N-body dark matter simulation populated with galaxies using the Halo Occupation Distribution (HOD) bias prescription, we compute these correlation functions, mass maps, and shear maps. The resultant mass maps are distinctly bimodal, tracing the galaxy centers and remaining anisotropic up to scales much larger than the galaxy separation. At larger scales, the shear is approximately tangential about the center of the pair but with small...

  3. Reconstruction of Cluster Masses using Particle Based Lensing I: Application to Weak Lensing

    CERN Document Server

    Deb, Sanghamitra; Ramdass, Vede J

    2008-01-01

    Combining strong and weak (S+W) lensing is becoming an important tool in mass measurements of clusters. Determining mass maps of clusters using S+W analysis can be challenging because of the difference in length scales associated with the different signals. Traditionally researchers have used grid based methods to reconstruct the density fields. In this paper we develop PBL, a particle based method that incorporates these two scales without the necessity of regularization. We apply the particle based method to do mass reconstruction using ellipticities only, but show that PBL can be easily generalized to include strong lensing information as well. We apply these techniques to a number of test cases and find excellent agreement between the reconstructed and input mass distribution. In particular we reconstruct the mass distribution of a softened isothermal sphere with a $\\chi^2$ of 1.1. We have also applied PBL to ``Bullet Cluster'' (1E0657-56) data and compared the resulting mass distribution with the publicl...

  4. Weak lensing reconstructions in 2D & 3D: implications for cluster studies

    CERN Document Server

    Leonard, Adrienne; Starck, Jean-Luc

    2015-01-01

    We compare the efficiency with which 2D and 3D weak lensing mass mapping techniques are able to detect clusters of galaxies using two state-of-the-art mass reconstruction techniques: MRLens in 2D and GLIMPSE in 3D. We simulate otherwise-empty cluster fields for 96 different virial mass-redshift combinations spanning the ranges $3\\times10^{13}h^{-1}M_\\odot \\le M_{vir}\\le 10^{15}h^{-1}M_\\odot$ and $0.05 \\le z_{\\rm cl} \\le 0.75$, and for each generate 1000 realisations of noisy shear data in 2D and 3D. For each field, we then compute the cluster (false) detection rate as the mean number of cluster (false) detections per reconstruction over the sample of 1000 reconstructions. We show that both MRLens and GLIMPSE are effective tools for the detection of clusters from weak lensing measurements, and provide comparable quality reconstructions at low redshift. At high redshift, GLIMPSE reconstructions offer increased sensitivity in the detection of clusters, yielding cluster detection rates up to a factor of $\\sim 10\\...

  5. Dark Energy Survey Year 1 Results: Curved-Sky Weak Lensing Mass Map

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; et al.

    2017-08-04

    We construct the largest curved-sky galaxy weak lensing mass map to date from the DES first-year (DES Y1) data. The map, about 10 times larger than previous work, is constructed over a contiguous $\\approx1,500 $deg$^2$, covering a comoving volume of $\\approx10 $Gpc$^3$. The effects of masking, sampling, and noise are tested using simulations. We generate weak lensing maps from two DES Y1 shear catalogs, Metacalibration and Im3shape, with sources at redshift $0.2

  6. Weak lensing study of 16 DAFT/FADA clusters: substructures and filaments

    CERN Document Server

    Martinet, Nicolas; Durret, Florence; Adami, Christophe; Acebrón, Ana; Hernandez-García, Lorena; Márquez, Isabel; Guennou, Loic; Sarron, Florian; Ulmer, Mel

    2016-01-01

    While our current cosmological model places galaxy clusters at the nodes of a filament network (the cosmic web), we still struggle to detect these filaments at high redshifts. We perform a weak lensing study for a sample of 16 massive, medium-high redshift (0.4shear profile measured in a KSB-like method, adding our contribution to the calibration of the observable-mass relation required for cluster abundance cosmological studies. We compute convergence maps and select structures within, securing their detection with noise re-sampling techniques. Taking advantage of the large field of view of our data, we study cluster environment, adding information from galaxy density maps at the cluster redshift and from X-ray images when available. We find that clusters show a large variety of weak lensing maps at large scale...

  7. Gravitational Lensing and the New Method in Weak Gravitational Lensing%引力透镜和弱引力透镜的新方法

    Institute of Scientific and Technical Information of China (English)

    杨晓峰

    2011-01-01

    Gravitational lensing is one of the most powerful tools in astrophysics. In particular it is significant in the explorations of extra-solar planets, in the investigations of the dark universe (dark matter and dark energy), and in testing gravity at cosmological scales. The great advantage of gravitational lensing is that it is directly dependent on gravity only, and does not depend on the nature of dark matter or complicated baryonic physics.First, we review the fundamental theory and approximations of gravitational lensing in which matter distribution (such as a stars, galaxies, galaxy clusters or large scale structure (LSS)) bends light propagating between a distant source and the observer. We discuss three types of gravitational lensing based on the scale of the lensing system: micro, weak, and strong lensing and their applications in extra-solar planet searches (micro lensing) and constraining density profile of dark matter halos (strong lensing). Then we report and review new progresses in gravitational lensing and introduce a new interpretation of gravitational lensing by employing the split of wavefront.Second, we discuss the use of weak lensing in cosmology. Gravitational lensing can be split into convergence and shear terms. The convergence magnifies the fluxes of background galaxies by increasing their sizes, while the shear stretches them tangentially around the foreground mass. Since the distortion of the shape and size of the galaxies is weak and tiny, significant shear effects can only be detected statistically using large number of background galaxies. This effect is known as cosmic shear. In the past decade, there are a number of works focusing on using cosmic shear effect to study the LSS and to constrain cosmological parameters. However, weak lensing measurements through cosmic shear still suffers from observational uncertainties and systematics such as the intrinsic alignment and the shapeerror of galaxies.Finally, we introduce a new method to

  8. Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data

    CERN Document Server

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

    2012-01-01

    The synoptic imaging survey proposed for the Large Synoptic Survey Telescope (LSST) will generate large numbers of short exposure ($\\simeq$15 seconds) images. A primary science driver for this project is to measure the cosmic shear signal from weak lensing to extreme accuracy. One difficulty, however, is that in these short exposure images, the spatial variation of the Point Spread Function (PSF) shapes may be dominated by the atmosphere, in addition to optics errors. In particular, the atmosphere generates stochastic structures on a wide range of angular scales. Since the PSF patterns in these images can only be inferred by interpolating the sparsely sampled stars in the field, these multi-scale, complex patterns from the atmosphere complicates the PSF interpolation problem. In this paper we present a new method, PSFent, for interpolating atmospheric PSF shape parameters, based on reconstructing underlying shape parameter maps with a multi-scale maximum entropy algorithm. We demonstrate, using images from th...

  9. The impact of correlated noise on galaxy shape estimation for weak lensing

    CERN Document Server

    Gurvich, Alex

    2015-01-01

    The robust estimation of the tiny distortions (shears) of galaxy shapes caused by weak gravitational lensing in the presence of much larger shape distortions due to the point-spread function (PSF) has been widely investigated. One major problem is that most galaxy shape measurement methods are subject to bias due to pixel noise in the images ("noise bias"). Noise bias is usually characterized using uncorrelated noise fields; however, real images typically have low-level noise correlations due to galaxies below the detection threshold, and some types of image processing can induce further noise correlations. We investigate the effective detection significance and its impact on noise bias in the presence of correlated noise for one method of galaxy shape estimation. For a fixed noise variance, the biases in galaxy shape estimates can differ substantially for uncorrelated versus correlated noise. However, use of an estimate of detection significance that accounts for the noise correlations can almost entirely re...

  10. Shear-induced solidification of athermal systems with weak attraction

    Science.gov (United States)

    Zheng, Wen; Liu, Hao; Xu, Ning

    2016-12-01

    We find that unjammed packings of frictionless particles with rather weak attraction can always be driven into solidlike states by shear. The structure of shear-driven solids evolves continuously with packing fraction from gel-like to jamminglike, but is almost independent of the shear stress. In contrast, both the density of vibrational states (DOVS) and force network evolve progressively with the shear stress. There exists a packing fraction independent shear stress σc, at which the shear-driven solids are isostatic and have a flattened DOVS. Solidlike states induced by a shear stress greater than σc possess properties of marginally jammed solids and are thus strictly defined shear jammed states. Below σc, shear-driven solids with rather different structures are all under isostaticity and share common features in the DOVS and force network. Our study leads to a jamming phase diagram for weakly attractive particles, which reveals the significance of the shear stress in determining properties of shear-driven solids and the connections and distinctions between jamminglike and gel-like states.

  11. Cross correlation of Cosmic Microwave background and Weak Lensing

    CERN Document Server

    Lee, Seokcheon

    2015-01-01

    The integrated Sachs-Wolfe (ISW) effect and its non-linear extension Rees-Sciama (RS) effect provide us the information of the time evolution of gravitational potential. The cross-correlation between the cosmic microwave background (CMB) and the large scale structure (LSS) is known as a promising way to extract the ISW (RS) effect. It is known that the RS effect shows the unique behavior by changing the anti-correlated cross correlation between the CMB and the mass tracer into the positively correlated cross correlation compared to the linear ISW effect. We show that the dependence of this flipping scale of the cross-correlation between RS and weak lensing on dark energy models. However, there exists the degeneracy between DE and $\\Omega_{\\rm{m}0}$ which might be broken by redshift dependent observables. The cross-correlation between the momentum field and the density field might be served as the better observable to be used for this purpose.

  12. Measuring weak lensing correlations of Type Ia Supernovae

    CERN Document Server

    Scovacricchi, D; Macaulay, E; Bacon, D

    2016-01-01

    We study the feasibility of detecting weak lensing spatial correlations between Supernova (SN) Type Ia magnitudes with present (Dark Energy Survey, DES) and future (Large Synoptic Survey Telescope, LSST) surveys. We investigate the angular auto-correlation function of SN magnitudes (once the background cosmology has been subtracted) and cross-correlation with galaxy catalogues. We examine both analytical and numerical predictions, the latter using simulated galaxy catalogues from the MICE Grand Challenge Simulation. We predict that we will be unable to detect the SN auto-correlation in DES, while it should be detectable with the LSST SN deep fields (15,000 SNe on 70 deg^2) at ~6sigma level of confidence (assuming 0.15 magnitudes of intrinsic dispersion). The SN-galaxy cross-correlation function will deliver much higher signal-to-noise, being detectable in both surveys with an integrated signal-to-noise of ~100 (up to 30 arcmin separations). We predict joint constraints on the matter density parameter (Omega_m...

  13. Measuring weak lensing correlations of Type Ia supernovae

    Science.gov (United States)

    Scovacricchi, D.; Nichol, R. C.; Macaulay, E.; Bacon, D.

    2017-03-01

    We study the feasibility of detecting weak lensing spatial correlations between supernova (SN) Type Ia magnitudes with present (Dark Energy Survey, DES) and future (Large Synoptic Survey Telescope, LSST) surveys. We investigate the angular auto-correlation function of SN magnitudes (once the background cosmology has been subtracted) and cross-correlation with galaxy catalogues. We examine both analytical and numerical predictions, the latter using simulated galaxy catalogues from the MICE Grand Challenge Simulation. We predict that we will be unable to detect the SN auto-correlation in DES, while it should be detectable with the LSST SN deep fields (15 000 SNe on 70 deg2) at ≃6σ level of confidence (assuming 0.15 mag of intrinsic dispersion). The SN-galaxy cross-correlation function will deliver much higher signal to noise, being detectable in both surveys with an integrated signal to noise of ∼100 (up to 30 arcmin separations). We predict joint constraints on the matter density parameter (Ωm) and the clustering amplitude (σ8) by fitting the auto-correlation function of our mock LSST deep fields. When assuming a Gaussian prior for Ωm, we can achieve a 25 per cent measurement of σ8 from just these LSST supernovae (assuming 0.15 mag of intrinsic dispersion). These constraints will improve significantly if the intrinsic dispersion of SNe Ia can be reduced.

  14. Fingerprinting Dark Energy II: weak lensing and galaxy clustering tests

    CERN Document Server

    Sapone, Domenico; Amendola, Luca

    2010-01-01

    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 $c_{s}\\lesssim0.01$ (in units of $c$). For larger sound speeds the error grows to 100% and more. We conclude that large scale structure...

  15. Cosmology with photometric weak lensing surveys: Constraints with redshift tomography of convergence peaks and moments

    Science.gov (United States)

    Petri, Andrea; May, Morgan; Haiman, Zoltán

    2016-09-01

    Weak gravitational lensing is becoming a mature technique for constraining cosmological parameters, and future surveys will be able to constrain the dark energy equation of state w . When analyzing galaxy surveys, redshift information has proven to be a valuable addition to angular shear correlations. We forecast parameter constraints on the triplet (Ωm,w ,σ8) for a LSST-like photometric galaxy survey, using tomography of the shear-shear power spectrum, convergence peak counts and higher convergence moments. We find that redshift tomography with the power spectrum reduces the area of the 1 σ confidence interval in (Ωm,w ) space by a factor of 8 with respect to the case of the single highest redshift bin. We also find that adding non-Gaussian information from the peak counts and higher-order moments of the convergence field and its spatial derivatives further reduces the constrained area in (Ωm,w ) by factors of 3 and 4, respectively. When we add cosmic microwave background parameter priors from Planck to our analysis, tomography improves power spectrum constraints by a factor of 3. Adding moments yields an improvement by an additional factor of 2, and adding both moments and peaks improves by almost a factor of 3 over power spectrum tomography alone. We evaluate the effect of uncorrected systematic photometric redshift errors on the parameter constraints. We find that different statistics lead to different bias directions in parameter space, suggesting the possibility of eliminating this bias via self-calibration.

  16. Detection of large scale intrinsic ellipticity-density correlation from the Sloan Digital Sky Survey and implications for weak lensing surveys

    CERN Document Server

    Mandelbaum, R; Ishak, M; Seljak, U; Brinkmann, J; Mandelbaum, Rachel; Hirata, Christopher M.; Ishak, Mustapha; Seljak, Uros; Brinkmann, Jonathan

    2006-01-01

    The power spectrum of weak lensing shear caused by large-scale structure is an emerging tool for precision cosmology, in particular for measuring the effects of dark energy on the growth of structure at low redshift. One potential source of systematic error is intrinsic alignments of ellipticities of neighbouring galaxies (II correlation) that could mimic the correlations due to lensing. A related possibility pointed out by Hirata and Seljak (2004) is correlation between the intrinsic ellipticities of galaxies and the density field responsible for gravitational lensing shear (GI correlation). We present constraints on both the II and GI correlations using 265 908 spectroscopic galaxies from the SDSS, and using galaxies as tracers of the mass in the case of the GI analysis. The availability of redshifts in the SDSS allows us to select galaxies at small radial separations, which both reduces noise in the intrinsic alignment measurement and suppresses galaxy- galaxy lensing (which otherwise swamps the GI correla...

  17. A Subaru Weak Lensing Survey I: Cluster Candidates and Spectroscopic Verification

    CERN Document Server

    Miyazaki, Satoshi; Ellis, Richard S; Kashikawa, Nobunari; Massey, Richard J; Taylor, James; Refregier, Alexandre

    2007-01-01

    We present the results of an ongoing weak lensing survey conducted with the Subaru telescope whose initial goal is to locate and study the distribution of shear-selected structures or halos. Using a Suprime-cam imaging survey spanning 21.82 square degree, we present a catalog of 100 candidate halos located from lensing convergence maps. Our sample is reliably drawn from that subset of our survey area, (totaling 16.72 square degree) uncontaminated by bright stars and edge effects and limited at a convergence signal to noise ratio of 3.69. To validate the sample detailed spectroscopic measures have been made for 26 candidates using the Subaru multi-object spectrograph, FOCAS. All are confirmed as clusters of galaxies but two arise as the superposition of multiple clusters viewed along the line of sight. Including data available in the literature and an ongoing Keck spectroscopic campaign, a total of 41 halos now have reliable redshifts. For one of our survey fields, the XMM LSS (Pierre et al. 2004) field, we co...

  18. Halo ellipticity of GAMA galaxy groups from KiDS weak lensing

    CERN Document Server

    van Uitert, Edo; Joachimi, Benjamin; Schneider, Peter; Bland-Hawthorn, Joss; Choi, Ami; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Hopkins, Andrew M; Klaes, Dominik; Kuijken, Konrad; Nakajima, Reiko; Napolitano, Nicola R; Schrabback, Tim; Valentijn, Edwin; Viola, Massimo

    2016-01-01

    We constrain the average halo ellipticity of ~2 600 galaxy groups from the Galaxy And Mass Assembly (GAMA) survey, using the weak gravitational lensing signal measured from the overlapping Kilo Degree Survey (KiDS). To do so, we quantify the azimuthal dependence of the stacked lensing signal around seven different proxies for the orientation of the dark matter distribution, as it is a priori unknown which one traces the orientation best. On small scales, the major axis of the brightest group/cluster member (BCG) provides the best proxy, leading to a clear detection of an anisotropic signal. In order to relate that to a halo ellipticity, we have to adopt a model density profile. We derive new expressions for the quadrupole moments of the shear field given an elliptical model surface mass density profile. Modeling the signal with an elliptical Navarro-Frenk-White (NFW) profile on scales < 250 kpc, which roughly corresponds to half the virial radius, and assuming that the BCG is perfectly aligned with the dar...

  19. Galaxy bias from the DES Science Verification Data: combining galaxy density maps and weak lensing maps

    CERN Document Server

    Chang, C; Gaztanaga, E; Amara, A; Refregier, A; Bacon, D; Becker, M R; Bonnett, C; Carretero, J; Castander, F J; Crocce, M; Fosalba, P; Giannantonio, T; Hartley, W; Jain, B; Jarvis, M; Kacprzak, T; Ross, A J; Sheldon, E; Troxel, M A; Vikram, V; Zuntz, J; Abbott, T M C; Abdalla, F B; Allam, S; Annis, J; Benoit-Levy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Cunha, C E; D'Andrea, C B; da Costa, L N; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Eifler, T F; Estrada, J; Evrard, A E; Flaugher, B; Frieman, J; Goldstein, D A; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; Marshall, J L; Martini, P; Melchior, P; Miller, C J; Miquel, R; Mohr, J J; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Rykoff, E S; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thomas, D; Walker, A R

    2016-01-01

    We measure the redshift evolution of galaxy bias from a magnitude-limited galaxy sample by combining the galaxy density maps and weak lensing shear maps for a $\\sim$116 deg$^{2}$ area of the Dark Energy Survey (DES) Science Verification data. This method was first developed in Amara et al. (2012) and later re-examined in a companion paper (Pujol et al., in prep) with rigorous simulation tests and analytical treatment of tomographic measurements. In this work we apply this method to the DES SV data and measure the galaxy bias for a magnitude-limited galaxy sample. We find the galaxy bias and 1$\\sigma$ error bars in 4 photometric redshift bins to be 1.33$\\pm$0.18 (z=0.2-0.4), 1.19$\\pm$0.23 (z=0.4-0.6), 0.99$\\pm$0.36 ( z=0.6-0.8), and 1.66$\\pm$0.56 (z=0.8-1.0). These measurements are consistent at the 1-2$\\sigma$ level with mea- surements on the same dataset using galaxy clustering and cross-correlation of galaxies with CMB lensing. In addition, our method provides the only $\\sigma_8$-independent constraint amon...

  20. Frontier Fields: Subaru Weak-Lensing Analysis of the Merging Galaxy Cluster A2744

    CERN Document Server

    Medezinski, Elinor; Okabe, Nobuhiro; Nonino, Mario; Molnar, Sandor; Massey, Richard; Dupke, Renato; Merten, Julian

    2015-01-01

    We present a weak-lensing analysis of the merging {\\em Frontier Fields} (FF) cluster Abell~2744 using new Subaru/Suprime-Cam imaging. The wide-field lensing mass distribution reveals this cluster is comprised of four distinct substructures. Simultaneously modeling the two-dimensional reduced shear field using a combination of a Navarro--Frenk--White (NFW) model for the main core and truncated NFW models for the subhalos, we determine their masses and locations. The total mass of the system is constrained as $M_\\mathrm{200c} = (2.06\\pm0.42)\\times10^{15}\\,M_\\odot$. The most massive clump is the southern component with $M_\\mathrm{200c} = (7.7\\pm3.4)\\times10^{14}\\,M_\\odot$, followed by the western substructure ($M_\\mathrm{200c} = (4.5\\pm2.0)\\times10^{14}\\,M_\\odot$) and two smaller substructures to the northeast ($M_\\mathrm{200c} = (2.8\\pm1.6)\\times10^{14}\\,M_\\odot$) and northwest ($M_\\mathrm{200c} = (1.9\\pm1.2)\\times10^{14}\\,M_\\odot$). The presence of the four substructures supports the picture of multiple merger...

  1. Ellipticity of dark matter halos with galaxy-galaxy weak lensing

    CERN Document Server

    Mandelbaum, R; Broderick, T; Seljak, U; Brinkmann, J; Mandelbaum, Rachel; Hirata, Christopher M.; Broderick, Tamara; Seljak, Uros; Brinkmann, Jonathan

    2005-01-01

    We present the results of attempts to detect the ellipticity of dark matter halos using galaxy-galaxy weak lensing with SDSS data. We use 2,020,256 galaxies brighter than r=19 with photometric redshifts (divided into colour and luminosity subsamples) as lenses and 31,697,869 source galaxies. We search for and identify several signal contaminants, which if not removed lead to a spurious detection. These include systematic shear that leads to a slight spurious alignment of lens and source ellipticities, intrinsic alignments (due to contamination of the source sample by physically-associated lens source pairs), and anisotropic magnification bias. We develop methods that allow us to remove these contaminants to the signal. We split the analysis into blue (spiral) and red (elliptical) galaxies. Assuming Gaussian errors as in previous work and a power-law profile, we find f_h=e_h/e_g=0.1+/-0.06 for red galaxies and -0.8+/-0.4 for blue galaxies using 20-300 kpc/h, averaged over luminosity. Inclusion of the more real...

  2. Statistical connection of peak counts to power spectrum and moments in weak-lensing field

    Science.gov (United States)

    Shirasaki, Masato

    2017-02-01

    The number density of local maxima of weak-lensing field, referred to as weak-lensing peak counts, can be used as a cosmological probe. However, its relevant cosmological information is still unclear. We study the relationship between the peak counts and other statistics in weak-lensing field by using 1000 ray-tracing simulations. We construct a local transformation of lensing field K to a new Gaussian field y, named local-Gaussianized transformation. We calibrate the transformation with numerical simulations so that the one-point distribution and the power spectrum of K can be reproduced from a single Gaussian field y and monotonic relation between y and K. Therefore, the correct information of two-point clustering and any order of moments in weak-lensing field should be preserved under local-Gaussianized transformation. We then examine if local-Gaussianized transformation can predict weak-lensing peak counts in simulations. The local-Gaussianized transformation is insufficient to explain weak-lensing peak counts in the absence of shape noise. The prediction by local-Gaussianized transformation underestimates the simulated peak counts with a level of ˜20-30 per cent over a wide range of peak heights. Local-Gaussianized transformation can predict the weak-lensing peak counts with an ˜10 per cent accuracy in the presence of shape noise. Our analyses suggest that the cosmological information beyond power spectrum and its moments would be necessary to predict the weak-lensing peak counts with a percent-level accuracy, which is an expected statistical uncertainty in upcoming wide-field galaxy surveys.

  3. Sub-pixel calibration for Weak Lensing and Astrometry

    Science.gov (United States)

    Shao, Michael

    We have recently developed and demonstrated a new method of sub-pixel detector calibration that offers orders of magnitude improvement in astrometry with CCD focal planes. Using this technique we have demonstrated centroiding of images to 1e 5 lambda/D in laboratory conditions. Our method allows reconstructing the true optical point spread function (PSF) of a telescope from pixelated stellar images. Although this technique was originally developed for centroiding of images across a large focal plane, it can also be applied to weak lensing program on WFIRST. We use a laser metrology technique to measure geometric imperfections in the focal plane array from pixel placement errors to non-uniform quantum efficiency (QE) within every pixel. With precise sub-pixel calibration one can use dithered images (e.g., a 2×2 dither) to derive Nyquist-sampled image of stars. The WFIRST telescope has a large 0.28 sq.deg field of view (FOV) with theoretical PSF varying considerably over that FOV. However, even at high galactic latitude there will be over 1,000 stars brighter than 16 mag and, with Nyquist-sampled images, it should be possible to calculate the spatially varying PSF at 1,000 locations in the focal plane. With knowledge of the optical PSF and sub-pixel calibration of the detector, one can remove biases in the shapes of galaxies introduced by the spatially varying PSF. The technique of sub-pixel calibration has so far only been demonstrated in with visible CCD detectors and applied to achieve ultra-precise image centroiding. The purpose of this proposal is to extend the technique of removing biases in the shape of galaxies due to pixilation and spatially varying PSF and to extend the calibration of visible detectors to NIR detectors. The new technique could be used to enable 4 10 microarcsecond (μas) astrometry within the 0.28 sq.deg FOV of the WFIRST telescope. Using the upcoming Gaia catalogue accurate to ~10 μas, we will be able to stitch the HgCdTe arrays on

  4. Constraining f (R ) Gravity Theory Using Weak Lensing Peak Statistics from the Canada-France-Hawii-Telescope Lensing Survey

    Science.gov (United States)

    Liu, Xiangkun; Li, Baojiu; Zhao, Gong-Bo; Chiu, Mu-Chen; Fang, Wei; Pan, Chuzhong; Wang, Qiao; Du, Wei; Yuan, Shuo; Fu, Liping; Fan, Zuhui

    2016-07-01

    In this Letter, we report the observational constraints on the Hu-Sawicki f (R ) theory derived from weak lensing peak abundances, which are closely related to the mass function of massive halos. In comparison with studies using optical or x-ray clusters of galaxies, weak lensing peak analyses have the advantages of not relying on mass-baryonic observable calibrations. With observations from the Canada-France-Hawaii-Telescope Lensing Survey, our peak analyses give rise to a tight constraint on the model parameter |fR 0| for n =1 . The 95% C.L. is log10|fR 0|<-4.82 given WMAP9 priors on (Ωm , As ). With Planck15 priors, the corresponding result is log10|fR 0|<-5.16 .

  5. Constraining stochastic gravitational wave background from weak lensing of CMB B-modes

    CERN Document Server

    Shaikh, Shabbir; Rotti, Aditya; Souradeep, Tarun

    2016-01-01

    A stochastic gravitational wave background (SGWB) will affect the CMB anisotropies via weak lensing. Unlike weak lensing due to large scale structure which only deflects photon trajectories, a SGWB has an additional effect of rotating the polarization vector along the trajectory. We study the relative importance of these two effects, deflection \\& rotation, specifically in the context of E-mode to B-mode power transfer caused by weak lensing due to SGWB. Using weak lensing distortion of the CMB as a probe, we derive constraints on the spectral energy density ($\\Omega_{GW}$) of the SGWB, sourced at different redshifts, without assuming any particular model for its origin. We present these bounds on $\\Omega_{GW}$ for different power-law models characterizing the SGWB, indicating the threshold above which observable imprints of SGWB must be present in CMB.

  6. Constraining stochastic gravitational wave background from weak lensing of CMB B-modes

    Science.gov (United States)

    Shaikh, Shabbir; Mukherjee, Suvodip; Rotti, Aditya; Souradeep, Tarun

    2016-09-01

    A stochastic gravitational wave background (SGWB) will affect the CMB anisotropies via weak lensing. Unlike weak lensing due to large scale structure which only deflects photon trajectories, a SGWB has an additional effect of rotating the polarization vector along the trajectory. We study the relative importance of these two effects, deflection & rotation, specifically in the context of E-mode to B-mode power transfer caused by weak lensing due to SGWB. Using weak lensing distortion of the CMB as a probe, we derive constraints on the spectral energy density (ΩGW) of the SGWB, sourced at different redshifts, without assuming any particular model for its origin. We present these bounds on ΩGW for different power-law models characterizing the SGWB, indicating the threshold above which observable imprints of SGWB must be present in CMB.

  7. A CFH12k lensing survey of X-ray luminous galaxy clusters - II. Weak lensing analysis and global correlations

    NARCIS (Netherlands)

    Bardeau, S.; Soucail, G.; Kneib, J.-P.; Czoske, O.; Ebeling, H.; Hudelot, P.; Smail, I.; Smith, G. P.

    2007-01-01

    Aims. We present a wide-field multi-color survey of a homogeneous sample of eleven clusters of galaxies for which we measure total masses and mass distributions from weak lensing. This sample, spanning a small range in both X-ray luminosity and redshift, is ideally suited to determining the normalis

  8. Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-09-19

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

  9. KiDS-450: cosmological parameter constraints from tomographic weak gravitational lensing

    Science.gov (United States)

    Hildebrandt, H.; Viola, M.; Heymans, C.; Joudaki, S.; Kuijken, K.; Blake, C.; Erben, T.; Joachimi, B.; Klaes, D.; Miller, L.; Morrison, C. B.; Nakajima, R.; Verdoes Kleijn, G.; Amon, A.; Choi, A.; Covone, G.; de Jong, J. T. A.; Dvornik, A.; Fenech Conti, I.; Grado, A.; Harnois-Déraps, J.; Herbonnet, R.; Hoekstra, H.; Köhlinger, F.; McFarland, J.; Mead, A.; Merten, J.; Napolitano, N.; Peacock, J. A.; Radovich, M.; Schneider, P.; Simon, P.; Valentijn, E. A.; van den Busch, J. L.; van Uitert, E.; Van Waerbeke, L.

    2017-02-01

    We present cosmological parameter constraints from a tomographic weak gravitational lensing analysis of ˜450 deg2 of imaging data from the Kilo Degree Survey (KiDS). For a flat Λ cold dark matter (ΛCDM) cosmology with a prior on H0 that encompasses the most recent direct measurements, we find S_8≡ σ _8√{Ω _m/0.3}=0.745± 0.039. This result is in good agreement with other low-redshift probes of large-scale structure, including recent cosmic shear results, along with pre-Planck cosmic microwave background constraints. A 2.3σ tension in S8 and 'substantial discordance' in the full parameter space is found with respect to the Planck 2015 results. We use shear measurements for nearly 15 million galaxies, determined with a new improved 'self-calibrating' version of lensFIT validated using an extensive suite of image simulations. Four-band ugri photometric redshifts are calibrated directly with deep spectroscopic surveys. The redshift calibration is confirmed using two independent techniques based on angular cross-correlations and the properties of the photometric redshift probability distributions. Our covariance matrix is determined using an analytical approach, verified numerically with large mock galaxy catalogues. We account for uncertainties in the modelling of intrinsic galaxy alignments and the impact of baryon feedback on the shape of the non-linear matter power spectrum, in addition to the small residual uncertainties in the shear and redshift calibration. The cosmology analysis was performed blind. Our high-level data products, including shear correlation functions, covariance matrices, redshift distributions, and Monte Carlo Markov chains are available at http://kids.strw.leidenuniv.nl.

  10. SKA Engineering Change Proposal: Gridded Visibilities to Enable Precision Cosmology with Radio Weak Lensing

    CERN Document Server

    Harrison, Ian

    2015-01-01

    This document was submitted as supporting material to an Engineering Change Proposal (ECP) for the Square Kilometre Array (SKA). This ECP requests gridded visibilities as an extra imaging data product from the SKA, in order to enable bespoke analysis techniques to measure source morphologies to the accuracy necessary for precision cosmology with radio weak lensing. We also discuss the properties of an SKA weak lensing data set and potential overlaps with other cosmology science goals.

  11. Mask effects on cosmological studies with weak-lensing peak statistics

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiangkun; Pan, Chuzhong; Fan, Zuhui [Department of Astronomy, Peking University, Beijing 100871 (China); Wang, Qiao, E-mail: fanzuhui@pku.edu.cn [National Astronomical Observatories, Chinese Academy of Science, Beijing 100012 (China)

    2014-03-20

    With numerical simulations, we analyze in detail how the bad data removal, i.e., the mask effect, can influence the peak statistics of the weak-lensing convergence field reconstructed from the shear measurement of background galaxies. It is found that high peak fractions are systematically enhanced because of the presence of masks; the larger the masked area is, the higher the enhancement is. In the case where the total masked area is about 13% of the survey area, the fraction of peaks with signal-to-noise ratio ν ≥ 3 is ∼11% of the total number of peaks, compared with ∼7% of the mask-free case in our considered cosmological model. This can have significant effects on cosmological studies with weak-lensing convergence peak statistics, inducing a large bias in the parameter constraints if the effects are not taken into account properly. Even for a survey area of 9 deg{sup 2}, the bias in (Ω {sub m}, σ{sub 8}) is already intolerably large and close to 3σ. It is noted that most of the affected peaks are close to the masked regions. Therefore, excluding peaks in those regions in the peak statistics can reduce the bias effect but at the expense of losing usable survey areas. Further investigations find that the enhancement of the number of high peaks around the masked regions can be largely attributed to the smaller number of galaxies usable in the weak-lensing convergence reconstruction, leading to higher noise than that of the areas away from the masks. We thus develop a model in which we exclude only those very large masks with radius larger than 3' but keep all the other masked regions in peak counting statistics. For the remaining part, we treat the areas close to and away from the masked regions separately with different noise levels. It is shown that this two-noise-level model can account for the mask effect on peak statistics very well, and the bias in cosmological parameters is significantly reduced if this model is applied in the parameter

  12. KiDS-450: Cosmological parameter constraints from tomographic weak gravitational lensing

    CERN Document Server

    Hildebrandt, H; Heymans, C; Joudaki, S; Kuijken, K; Blake, C; Erben, T; Joachimi, B; Klaes, D; Miller, L; Morrison, C B; Nakajima, R; Kleijn, G Verdoes; Amon, A; Choi, A; Covone, G; de Jong, J T A; Dvornik, A; Conti, I Fenech; Grado, A; Harnois-Déraps, J; Herbonnet, R; Hoekstra, H; Köhlinger, F; McFarland, J; Mead, A; Merten, J; Napolitano, N; Peacock, J A; Radovich, M; Schneider, P; Simon, P; Valentijn, E A; Busch, J L van den; van Uitert, E; Van Waerbeke, L

    2016-01-01

    We present cosmological parameter constraints from a tomographic weak gravitational lensing analysis of ~450deg$^2$ of imaging data from the Kilo Degree Survey (KiDS). For a flat $\\Lambda$CDM cosmology with a prior on $H_0$ that encompasses the most recent direct measurements, we find $S_8\\equiv\\sigma_8\\sqrt{\\Omega_{\\rm m}/0.3}=0.745\\pm0.039$. This result is in good agreement with other low redshift probes of large scale structure, including recent cosmic shear results, along with pre-Planck cosmic microwave background constraints. A $2.3$-$\\sigma$ tension in $S_8$ and `substantial discordance' in the full parameter space is found with respect to the Planck 2015 results. We use shear measurements for nearly 15 million galaxies, determined with a new improved `self-calibrating' version of $lens$fit validated using an extensive suite of image simulations. Four-band $ugri$ photometric redshifts are calibrated directly with deep spectroscopic surveys. The redshift calibration is confirmed using two independent te...

  13. A new model to predict weak-lensing peak counts III. Filtering technique comparisons

    CERN Document Server

    Lin, Chieh-An; Pires, Sandrine

    2016-01-01

    This is the third in a series of papers that develop a new and flexible model to predict weak-lensing (WL) peak counts, which have been shown to be a very valuable non-Gaussian probe of cosmology. In this paper, we compare the cosmological information extracted from WL peak counts using different filtering techniques of the galaxy shear data, including linear filtering with a Gaussian and two compensated filters (the starlet wavelet and the aperture mass), and the nonlinear filtering method MRLens. We present improvements to our model that account for realistic survey conditions, which are masks, shear-to-convergence transformations, and non-constant noise. We create simulated peak counts from our stochastic model, from which we obtain constraints on the matter density $\\Omega_\\mathrm{m}$, the power spectrum normalization $\\sigma_8$, and the dark-energy parameter $w_0^\\mathrm{de}$. We use two methods for parameter inference, a copula likelihood, and approximate Bayesian computation (ABC). We measure the conto...

  14. Weak lensing mass map and peak statistics in CFHT/Stripe82 survey

    CERN Document Server

    Shan, HuanYuan; Comparat, Johan; Jullo, Eric; Charbonnier, Aldee; Erben, Thomas; Makler, Martin; Moraes, Bruno; Van Waerbeke, Ludovic; Courbin, Frederic; Meylan, George; Tao, Charling; Taylor, James E

    2013-01-01

    We present the weak lensing mass map of the 173 tiles Canada-France-Hawaii Telescope Stripe82 Survey (CS82) with the effective area ~124 square degrees and study the peak statistics, including peak abundance, correlation functions and tangential-shear profile of peaks with the mass map. We find that (1) peak abundance detected in CS82 are consistent with predictions from a Lambda-CDM cosmological model, once noise effects are properly included; (2) correlation function of peaks with different signal-to-noise ratio (SNR) can be well fitted with power laws. Combining with the SDSS-III/Constant Mass (CMASS) galaxies, the cross-correlation between CMASS galaxies and high SNR peaks can be well-fitted with a power law; (3) the tangential shear profiles of the peaks increase with SNR. We concentrate on fitting spherical models to the tangential profiles with both singular isothermal sphere (SIS) and Navarro Frenk & White (NFW) models. For the high SNR peaks, the SIS model is rejected at ~3-sigma. Comparing the D...

  15. A New Method for Measuring Weak Lensing Magnification With Weighted Number Counts

    CERN Document Server

    Gillis, Bryan

    2015-01-01

    We present a new local method for optimally estimating the local effects of magnification from weak gravitational lensing, using a comparison of number counts in an arbitrary region of space to the expected unmagnified number counts. This method has equivalent statistical power to the optimally-weighted correlation function method previously employed to measure magnification, but has the potential to be used for purposes such as mass mapping, and is also significantly computationally faster. We present a proof-of-principle test of this method on data from the CFHTLenS, showing that its calculated magnification signals agree with predictions from model fits to shear data. Finally, we investigate how magnification data can be used to supplement shear data in determining the best-fit model mass profiles for galaxy dark matter haloes. We find that at redshifts greater than z~0.6, the inclusion of magnification can often significantly improve the constraints on the components of the mass profile which relate to ga...

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

    CERN Document Server

    Thomas, Daniel B; Magueijo, Joao

    2009-01-01

    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.

  17. Fast generation of weak lensing maps by the inverse-Gaussianization method

    Science.gov (United States)

    Yu, Yu; Zhang, Pengjie; Jing, Yipeng

    2016-10-01

    To take full advantage of the unprecedented power of upcoming weak lensing surveys, understanding the noise, such as cosmic variance and geometry/mask effects, is as important as understanding the signal itself. Accurately quantifying the noise requires a large number of statistically independent mocks for a variety of cosmologies. This is impractical for weak lensing simulations, which are costly for simultaneous requirements of large box size (to cover a significant fraction of the past light cone) and high resolution (to robustly probe the small scale where most lensing signal resides). Therefore, fast mock generation methods are desired and are under intensive investigation. We propose a new fast weak lensing map generation method, named the inverse-Gaussianization method, based on the finding that a lensing convergence field can be Gaussianized to excellent accuracy by a local transformation [43 Y. Yu, P. Zhang, W. Lin, W. Cui, and J. N. Fry, Phys. Rev. D 84, 023523 (2011).]. Given a simulation, it enables us to produce as many as infinite statistically independent lensing maps as fast as producing the simulation initial conditions. The proposed method is tested against simulations for each tomography bin centered at lens redshift z ˜0.5 , 1, and 2, with various statistics. We find that the lensing maps generated by our method have reasonably accurate power spectra, bispectra, and power spectrum covariance matrix. Therefore, it will be useful for weak lensing surveys to generate realistic mocks. As an example of application, we measure the probability distribution function of the lensing power spectrum, from 16384 lensing maps produced by the inverse-Gaussianization method.

  18. The dark matter distribution in z~0.5 clusters of galaxies. I : Determining scaling relations with weak lensing masses

    CERN Document Server

    Foëx, G; Pointecouteau, E; Arnaud, M; Limousin, M; Pratt, G W

    2012-01-01

    The total mass of clusters of galaxies is a key parameter to study massive halos. It relates to numerous gravitational and baryonic processes at play in the framework of large scale structure formation, thus rendering its determination important but challenging. From a sample of the 11 X-ray bright clusters selected from the excpres sample, we investigate the optical and X-ray properties of clusters with respect to their total mass derived from weak gravitational lensing. From multi-color wide field imaging obtained with MegaCam at CFHT, we derive the shear profile of each individual cluster of galaxies. We perform a careful investigation of all systematic sources related to the weak lensing mass determination. The weak lensing masses are then compared to the X-ray masses obtained from the analysis of XMM observations and assuming hydrostatic equilibrium. We find a good agreement between the two mass proxies although a few outliers with either perturbed morphology or poor quality data prevent to derive robust...

  19. Statistical connection of peak counts to power spectrum and moments in weak lensing field

    CERN Document Server

    Shirasaki, Masato

    2016-01-01

    The number density of local maxima of weak lensing field, referred to as weak-lensing peak counts, can be used as a cosmological probe. However, its relevant cosmological information is still unclear. We study the relationship between the peak counts and other statistics in weak lensing field by using 1000 ray-tracing simulations. We construct a local transformation of lensing field $\\cal K$ to a new Gaussian field $y$, named local-Gaussianized transformation. We calibrate the transformation with numerical simulations so that the one-point distribution and the power spectrum of $\\cal K$ can be reproduced from a single Gaussian field $y$ and monotonic relation between $y$ and $\\cal K$. Therefore, the correct information of two-point clustering and any order of moments in weak lensing field should be preserved under local-Gaussianized transformation. We then examine if local-Gaussianized transformation can predict weak-lensing peak counts in simulations. The local-Gaussianized transformation is insufficient to ...

  20. Intrinsic alignment-lensing interference as a contaminant of cosmic shear

    CERN Document Server

    Hirata, C M; Hirata, Christopher M.; Seljak, Uros

    2004-01-01

    Cosmic shear surveys have great promise as tools for precision cosmology, but can be subject to systematic errors including intrinsic ellipticity correlations of the source galaxies. The intrinsic alignments are believed to be small for deep surveys, but this is based on intrinsic and lensing distortions being uncorrelated. Here we show that the gravitational lensing shear and intrinsic shear need not be independent: correlations between the tidal field and the intrinsic shear cause the intrinsic shear of nearby galaxies to be correlated with the gravitational shear acting on more distant galaxies. We estimate the magnitude of this effect for two simple intrinsic alignment models: one in which the galaxy ellipticity is linearly related to the tidal field, and one in which it is quadratic in the tidal field as suggested by tidal torque theory. The first model predicts a gravitational-intrinsic (GI) correlation that can be much greater than the intrinsic-intrinsic (II) correlation for broad redshift distributio...

  1. Weak lensing by galaxy troughs with modified gravity

    Science.gov (United States)

    Barreira, Alexandre; Bose, Sownak; Li, Baojiu; Llinares, Claudio

    2017-02-01

    We study the imprints that theories of gravity beyond GR can leave on the lensing signal around line of sight directions that are predominantly halo-underdense (called troughs) and halo-overdense. To carry out our investigations, we consider the normal branch of DGP gravity, as well as a phenomenological variant thereof that directly modifies the lensing potential. The predictions of these models are obtained with N-body simulation and ray-tracing methods using the ECOSMOG and Ray-Ramses codes. We analyse the stacked lensing convergence profiles around the underdense and overdense lines of sight, which exhibit, respectively, a suppression and a boost w.r.t. the mean in the field of view. The modifications to gravity in these models strengthen the signal w.r.t. ΛCDM in a scale-independent way. We find that the size of this effect is the same for both underdense and overdense lines of sight, which implies that the density field along the overdense directions on the sky is not sufficiently evolved to trigger the suppression effects of the screening mechanism. These results are robust to variations in the minimum halo mass and redshift ranges used to identify the lines of sight, as well as to different line of sight aperture sizes and criteria for their underdensity and overdensity thresholds.

  2. Galaxy Bias from the DES Science Verification Data: Combining Galaxy Density Maps and Weak Lensing Maps

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; et al.

    2016-01-04

    We measure the redshift evolution of galaxy bias from a magnitude-limited galaxy sample by combining the galaxy density maps and weak lensing shear maps for a $\\sim$116 deg$^{2}$ area of the Dark Energy Survey (DES) Science Verification data. This method was first developed in Amara et al. (2012) and later re-examined in a companion paper (Pujol et al., in prep) with rigorous simulation tests and analytical treatment of tomographic measurements. In this work we apply this method to the DES SV data and measure the galaxy bias for a magnitude-limited galaxy sample. We find the galaxy bias and 1$\\sigma$ error bars in 4 photometric redshift bins to be 1.33$\\pm$0.18 (z=0.2-0.4), 1.19$\\pm$0.23 (z=0.4-0.6), 0.99$\\pm$0.36 ( z=0.6-0.8), and 1.66$\\pm$0.56 (z=0.8-1.0). These measurements are consistent at the 1-2$\\sigma$ level with mea- surements on the same dataset using galaxy clustering and cross-correlation of galaxies with CMB lensing. In addition, our method provides the only $\\sigma_8$-independent constraint among the three. We forward-model the main observational effects using mock galaxy catalogs by including shape noise, photo-z errors and masking effects. We show that our bias measurement from the data is consistent with that expected from simulations. With the forthcoming full DES data set, we expect this method to provide additional constraints on the galaxy bias measurement from more traditional methods. Furthermore, in the process of our measurement, we build up a 3D mass map that allows further exploration of the dark matter distribution and its relation to galaxy evolution.

  3. Limitations for shapelet-based weak-lensing measurements

    CERN Document Server

    Melchior, P; Lombardi, M; Bartelmann, M

    2009-01-01

    We seek to understand the impact on shape estimators obtained from circular and elliptical shapelet models under two realistic conditions: (a) only a limited number of shapelet modes is available for the model, and (b) the intrinsic galactic shapes are not restricted to shapelet models. We create a set of simplistic simulations, in which the galactic shapes follow a Sersic profile. By varying the Sersic index and applied shear, we quantify the amount of bias on shear estimates which arises from insufficient modeling. Additional complications due to PSF convolution, pixelation and pixel noise are also discussed. Steep and highly elliptical galaxy shapes cannot be accurately modeled within the circular shapelet basis system and are biased towards shallower and less elongated shapes. This problem can be cured partially by allowing elliptical basis functions, but for steep profiles elliptical shapelet models still depend critically on accurate ellipticity priors. As a result, shear estimates are typically biased ...

  4. Testing a Phenomenologically Extended DGP Model with Upcoming Weak Lensing Surveys

    CERN Document Server

    Camera, Stefano; Cardone, Vincenzo F

    2011-01-01

    A phenomenological extension of the well-known brane-world cosmology of Dvali, Gabadadze and Porrati (eDGP) has recently been proposed. In this model, a cosmological-constant-like term is explicitly present as a non-vanishing tension sigma on the brane, and an extra parameter alpha tunes the cross-over scale r_c, the scale at which higher dimensional gravity effects become non negligible. Since the Hubble parameter in this cosmology reproduces the same LCDM expansion history, we study how upcoming weak lensing surveys, such as Euclid and DES (Dark Energy Survey), can confirm or rule out this class of models. We perform Markov Chain Monte Carlo simulations to determine the parameters of the model, using Type Ia Supernov\\ae, H(z) data, Gamma Ray Bursts and Baryon Acoustic Oscillations. We also fit the power spectrum of the temperature anisotropies of the Cosmic Microwave Background to obtain the correct normalisation for the density perturbation power spectrum. Then, we compute the matter and the cosmic shear p...

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

    CERN Document Server

    Mohammed, Irshad; Teyssier, Romain; Amara, Adam

    2014-01-01

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

  6. Mocking the Weak Lensing universe: the LensTools python computing package

    CERN Document Server

    Petri, Andrea

    2016-01-01

    We present a newly developed software package which implements a wide range of routines frequently used in Weak Gravitational Lensing (WL). With the continuously increasing size of the WL scientific community we feel that easy to use Application Program Interfaces (APIs) for common calculations are a necessity to ensure efficiency and coordination across different working groups. Coupled with existing open source codes, such as CAMB and Gadget2, LensTools brings together a cosmic shear simulation pipeline which, complemented with a variety of WL feature measurement tools and parameter sampling routines, provides easy access to the numerics for theoretical studies of WL as well as for experiment forecasts. Being implemented in python, LensTools takes full advantage of a range of state--of--the art techniques developed by the large and growing open--source software community (scipy,pandas,astropy,scikit-learn,emcee). We made the LensTools code available on the Python Package Index and published its documentatio...

  7. Selecting background galaxies in weak-lensing analysis of galaxy clusters

    CERN Document Server

    Formicola, I; Meneghetti, M; Mazzotta, P; Grado, A; Giocoli, C

    2016-01-01

    In this paper, we present a new method to select the faint, background galaxies used to derive the mass of galaxy clusters by weak lensing. The method is based on the simultaneous analysis of the shear signal, that should be consistent with zero for the foreground, unlensed galaxies, and of the colors of the galaxies: photometric data from the COSMic evOlution Survey are used to train the color selection. In order to validate this methodology, we test it against a set of state-of-the-art image simulations of mock galaxy clusters in different redshift [$0.23-0.45$] and mass [$0.5-1.55\\times10^{15}M_\\odot$] ranges, mimicking medium-deep multicolor imaging observations (e.g. SUBARU, LBT). The performance of our method in terms of contamination by unlensed sources is comparable to a selection based on photometric redshifts, which however requires a good spectral coverage and is thus much more observationally demanding. The application of our method to simulations gives an average ratio between estimated and true ...

  8. Mocking the weak lensing universe: The LensTools Python computing package

    Science.gov (United States)

    Petri, A.

    2016-10-01

    We present a newly developed software package which implements a wide range of routines frequently used in Weak Gravitational Lensing (WL). With the continuously increasing size of the WL scientific community we feel that easy to use Application Program Interfaces (APIs) for common calculations are a necessity to ensure efficiency and coordination across different working groups. Coupled with existing open source codes, such as CAMB (Lewis et al., 2000) and Gadget2 (Springel, 2005), LensTools brings together a cosmic shear simulation pipeline which, complemented with a variety of WL feature measurement tools and parameter sampling routines, provides easy access to the numerics for theoretical studies of WL as well as for experiment forecasts. Being implemented in PYTHON (Rossum, 1995), LensTools takes full advantage of a range of state-of-the art techniques developed by the large and growing open-source software community (Jones et al., 2001; McKinney, 2010; Astrophy Collaboration, 2013; Pedregosa et al., 2011; Foreman-Mackey et al., 2013). We made the LensTools code available on the Python Package Index and published its documentation on http://lenstools.readthedocs.io.

  9. Statistical uncertainties and systematic errors in weak lensing mass estimates of galaxy clusters

    CERN Document Server

    Köhlinger, F; Eriksen, M

    2015-01-01

    Upcoming and ongoing large area weak lensing surveys will also discover large samples of galaxy clusters. Accurate and precise masses of galaxy clusters are of major importance for cosmology, for example, in establishing well calibrated observational halo mass functions for comparison with cosmological predictions. We investigate the level of statistical uncertainties and sources of systematic errors expected for weak lensing mass estimates. Future surveys that will cover large areas on the sky, such as Euclid or LSST and to lesser extent DES, will provide the largest weak lensing cluster samples with the lowest level of statistical noise regarding ensembles of galaxy clusters. However, the expected low level of statistical uncertainties requires us to scrutinize various sources of systematic errors. In particular, we investigate the bias due to cluster member galaxies which are erroneously treated as background source galaxies due to wrongly assigned photometric redshifts. We find that this effect is signifi...

  10. Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

    CERN Document Server

    Tröster, Tilman; Fornasa, Mattia; Regis, Marco; van Waerbeke, Ludovic; Harnois-Déraps, Joachim; Ando, Shin'ichiro; Bilicki, Maciej; Erben, Thomas; Fornengo, Nicolao; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kuijken, Konrad; Viola, Massimo

    2016-01-01

    We measure the cross-correlation between Fermi-LAT gamma-ray photons and over 1000 deg$^2$ of weak lensing data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the Red Cluster Sequence Lensing Survey (RCSLenS), and the Kilo Degree Survey (KiDS). We present the first measurement of tomographic weak lensing cross-correlations and the first application of spectral binning to cross-correlations between gamma rays and weak lensing. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. We verify the accuracy of our covariance estimate by comparing it to two internal covariance estimators. Based on the non-detection of a cross-correlation signal, we derive constraints on weakly interacting massive particle (WIMP) dark matter. We compute exclusion limits on the dark matter annihilation cross-section $\\langle\\sigma_\\rm{ann} v \\rangle$, decay rate $\\Gamma_\\rm{dec}$, and particle mass $m_\\rm{DM}$. We find that in th...

  11. Cross-correlation of weak lensing and gamma rays: implications for the nature of dark matter

    Science.gov (United States)

    Tröster, Tilman; Camera, Stefano; Fornasa, Mattia; Regis, Marco; van Waerbeke, Ludovic; Harnois-Déraps, Joachim; Ando, Shin'ichiro; Bilicki, Maciej; Erben, Thomas; Fornengo, Nicolao; Heymans, Catherine; Hildebrandt, Hendrik; Hoekstra, Henk; Kuijken, Konrad; Viola, Massimo

    2017-05-01

    We measure the cross-correlation between Fermi gamma-ray photons and over 1000 deg2 of weak lensing data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), the Red Cluster Sequence Lensing Survey (RCSLenS), and the Kilo Degree Survey (KiDS). We present the first measurement of tomographic weak lensing cross-correlations and the first application of spectral binning to cross-correlations between gamma rays and weak lensing. The measurements are performed using an angular power spectrum estimator while the covariance is estimated using an analytical prescription. We verify the accuracy of our covariance estimate by comparing it to two internal covariance estimators. Based on the non-detection of a cross-correlation signal, we derive constraints on weakly interacting massive particle (WIMP) dark matter. We compute exclusion limits on the dark matter annihilation cross-section , decay rate Γdec and particle mass mDM. We find that in the absence of a cross-correlation signal, tomography does not significantly improve the constraining power of the analysis. Assuming a strong contribution to the gamma-ray flux due to small-scale clustering of dark matter and accounting for known astrophysical sources of gamma rays, we exclude the thermal relic cross-section for particle masses of mDM ≲ 20 GeV.

  12. Testing a phenomenologically extended DGP model with upcoming weak lensing surveys

    Energy Technology Data Exchange (ETDEWEB)

    Camera, Stefano; Diaferio, Antonaldo [Dipartimento di Fisica Generale ' ' A. Avogadro' ' , Università di Torino, via P. Giuria 1, 10125 Torino (Italy); Cardone, Vincenzo F., E-mail: camera@ph.unito.it, E-mail: diaferio@ph.unito.it, E-mail: winnyenodrac@gmail.com [Dipartimento di Scienze e Tecnologie per l' Ambiente e il Territorio, Università degli Studi del Molise, Contrada Fonte Lappone, 86090 Pesche (Italy)

    2011-01-01

    A phenomenological extension of the well-known brane-world cosmology of Dvali, Gabadadze and Porrati (eDGP) has recently been proposed. In this model, a cosmological-constant-like term is explicitly present as a non-vanishing tension σ on the brane, and an extra parameter α tunes the cross-over scale r{sub c}, the scale at which higher dimensional gravity effects become non negligible. Since the Hubble parameter in this cosmology reproduces the same ΛCDM expansion history, we study how upcoming weak lensing surveys, such as Euclid and DES (Dark Energy Survey), can confirm or rule out this class of models. We perform Monte Carlo Markov Chain simulations to determine the parameters of the model, using Type Ia Supernovæ, H(z) data, Gamma Ray Bursts and Baryon Acoustic Oscillations. We also fit the power spectrum of the temperature anisotropies of the Cosmic Microwave Background to obtain the correct normalisation for the density perturbation power spectrum. Then, we compute the matter and the cosmic shear power spectra, both in the linear and non-linear régimes. The latter is calculated with the two different approaches of Hu and Sawicki (2007) (HS) and Khoury and Wyman (2009) (KW). With the eDGP parameters coming from the Markov Chains, KW reproduces the ΛCDM matter power spectrum at both linear and non-linear scales and the ΛCDM and eDGP shear signals are degenerate. This result does not hold with the HS prescription. Indeed, Euclid can distinguish the eDGP model from ΛCDM because their expected power spectra roughly differ by the 3σ uncertainty in the angular scale range 700∼

  13. Weak-lensing magnification as a probe for the dark Universe

    Energy Technology Data Exchange (ETDEWEB)

    García Fernández, Manuel [Autonomous Univ. of Madrid (Spain)

    2017-06-01

    This Thesis is devoted to the analysis of weak-lensing magnification on the Dark Energy Survey. Two analysis with different goals each are made on different data-sets: the Science Verification (DES-SV) and the Year 1 (DES-Y1). The DES-SV analysis aims the development of techniques to detect the weak-lensing number count magnification signal and the mitigation of systematic errors. The DES-Y1 analysis employs the methods used with the DES-SV data to measure the convergence profile of the emptiest regions of the Universe –voids and troughs–to use them as a new cosmological probe.

  14. Gravitational lensing beyond the weak-field approximation

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-01-14

    Gravitational lensing is considered in the full spacetime formalism of general relativity, assuming that the light rays are lightlike geodesics in a Lorentzian manifold. The review consists of three parts. The first part is devoted to spherically symmetric and static spacetimes. In particular, an exact lens map for this situation is discussed. The second part is on axisymmetric and stationary spacetimes. It concentrates on the investigation of the photon region, i.e., the region filled by spherical lightlike geodesics, in the Kerr spacetime. The photon region is of crucial relevance for the formation of a shadow. Finally, the third part briefly addresses two topics that apply to spacetimes without symmetry, namely Fermat’s principle and the exact lens map of Frittelli and Newman.

  15. Galaxy-Galaxy Weak Lensing Measurements from SDSS: I. Image Processing and Lensing signals

    CERN Document Server

    Luo, Wentao; Zhang, Jun; Tweed, Dylan; Fu, Liping; Mo, H J; Bosch, Frank C van den; Shu, Chenggang; Li, Ran; Li, Nan; Liu, Xiangkun; Pan, Chuzhong; Wang, Yiran; Radovich, Mario

    2016-01-01

    As the first paper in a series on the study of the galaxy-galaxy lensing from Sloan Digital Sky Survey Data Release 7 (SDSS DR7), we present our image processing pipeline that corrects the systematics primarily introduced by the Point Spread Function (PSF). Using this pipeline, we processed SDSS DR7 imaging data in $r$ band and generated a background galaxy catalog containing the shape information of each galaxy. Based on our own shape measurements of the galaxy images from SDSS DR7, we extract the galaxy-galaxy (GG) lensing signals around foreground spectroscopic galaxies binned in different luminosity and stellar mass. The overall signals are in good agreement with those obtained by \\citet{Mandelbaum2005, Mandelbaum2006} from the SDSS DR4. The results in this paper with higher signal to noise ratio is due to the larger survey area than SDSS DR4, confirm that more luminous/massive galaxies bear stronger GG lensing signal. We also divide the foreground galaxies into red/blue and star forming/quenched subsampl...

  16. RHEOLOGY OF CONFINED POLYMER MELTS UNDER SHEAR-FLOW - WEAK ADSORPTION LIMIT : Weak Adsorption Limit

    NARCIS (Netherlands)

    Subbotin, A.V.; Semenov, A.N.; Hadziioannou, G; ten Brinke, G.

    1995-01-01

    The dynamics of a confined polymer melt between weakly adsorbing surfaces is considered theoretically. The finite chain extensibility is taken into account explicitly, and the tangential stress and the first and the second normal-stress differences are calculated as functions of shear rate gamma.

  17. Weak lensing measurement of the mass-richness relation using the SDSS database

    CERN Document Server

    Johana, Gonzalez Elizabeth; Diego, García Lambas; Manuel, Merchán; Gael, Foëx; Martín, Chalela

    2016-01-01

    We study the mass-richness relation using galaxy catalogues and images from the Sloan Digital Sky Survey. We use two independent methods, in the first one, we calibrate the scaling relation with weak-lensing mass estimates. In the second procedure we apply a background subtraction technique to derive the probability distribution, $P(M \\mid N)$, that groups with $N$-members have a virialized halo mass $M$. Lensing masses are derived in different richness bins for two galaxy systems sets: the maxBCG catalogue and a catalogue based on a group finder algorithm developed by Yang et al. MaxBCG results are used to test the lensing methodology. The lensing mass-richness relation for the Yang et al. group sample shows a good agreement with $P(M \\mid N)$ obtained independently with a straightforward procedure.

  18. Weak-lensing measurement of the mass-richness relation using the SDSS data base

    Science.gov (United States)

    Gonzalez, Elizabeth Johana; Rodriguez, Facundo; García Lambas, Diego; Merchán, Manuel; Foëx, Gael; Chalela, Martín

    2017-02-01

    We study the mass-richness relation using galaxy catalogues and images from the Sloan Digital Sky Survey. We use two independent methods: In the first one, we calibrate the scaling relation with weak-lensing mass estimates. In the second procedure, we apply a background subtraction technique to derive the probability distribution, P(M∣N), that groups with N-members have a virialized halo mass M. Lensing masses are derived in different richness bins for two galaxy systems sets: the maxBCG catalogue and a catalogue based on a group finder algorithm developed by Yang et al. Results of maxBCG are used to test the lensing methodology. The lensing mass-richness relation for the Yang et al. group sample shows a good agreement with P(M∣N) obtained independently with a straightforward procedure.

  19. Analyzing weak lensing of the cosmic microwave background using the likelihood function

    CERN Document Server

    Hirata, C M; Hirata, Christopher M.; Seljak, Uros

    2003-01-01

    Future experiments will produce high-resolution temperature maps of the cosmic microwave background (CMB) and are expected to reveal the signature of gravitational lensing by intervening large-scale structures. We construct all-sky maximum-likelihood estimators that use the lensing effect to estimate the projected density (convergence) of these structures, its power spectrum, and cross-correlation with other observables. This contrasts with earlier quadratic-estimator approaches that Taylor-expanded the observed CMB temperature to linear order in the lensing deflection angle; these approaches gave estimators for the temperature-convergence correlation in terms of the CMB three-point correlation function and for the convergence power spectrum in terms of the CMB four-point correlation function, which can be biased and non-optimal due to terms beyond the linear order. We show that for sufficiently weak lensing, the maximum-likelihood estimator reduces to the computationally less demanding quadratic estimator. T...

  20. Cosmological parameter estimation from weak lensing. The case of $\\Omega_m$, $\\sigma_8$

    CERN Document Server

    Castañeda, Leonardo

    2014-01-01

    Propagation of light in the universe with structure which amplify and modify the shape of distant galaxies, producing a correlation between nearby and distant density of galaxies, is a phenomena very important in cosmology for determining cosmological parameters as the {\\Lambda}CDM. In this paper, we discuss the estimation of the two point correlation function in the gravitational shear produced by the large scale structure. We will compare the result given by gravitational lensing with the use of another alternatives such as a counting galaxy clusters. We also describe some software used in the gravitational lensing study for determining mass distribution models and images formation.

  1. Controlling intrinsic alignments in weak lensing statistics: The nulling and boosting techniques

    CERN Document Server

    Joachimi, B

    2010-01-01

    The intrinsic alignment of galaxies constitutes the major astrophysical source of systematic errors in surveys of weak gravitational lensing by the large-scale structure. We discuss the principles, summarise the implementation, and highlight the performance of two model-independent methods that control intrinsic alignment signals in weak lensing data: the nulling technique which eliminates intrinsic alignments to ensure unbiased constraints on cosmology, and the boosting technique which extracts intrinsic alignments and hence allows one to further study this contribution. Making only use of the characteristic dependence on redshift of the signals, both approaches are robust, but reduce the statistical power due to the similar redshift scaling of intrinsic alignment and lensing signals.

  2. Constraining $f(R)$ Gravity Theory Using CFHTLenS Weak Lensing Peak Statistics

    CERN Document Server

    Liu, Xiangkun; Zhao, Gong-Bo; Chiu, Mu-Chen; Fang, Wei; Pan, Chuzhong; Wang, Qiao; Du, Wei; Yuan, Shuo; Fu, Liping; Fan, Zuhui

    2016-01-01

    In this Letter, we report the observational constraints on the Hu-Sawicki $f(R)$ theory derived from weak lensing peak abundances, which are closely related to the mass function of massive halos. In comparison with studies using optical or X-ray clusters of galaxies, weak lensing peak analyses have the advantages of not relying on mass-baryonic observable calibrations. With observations from the Canada-France-Hawaii-Telescope Lensing Survey, our peak analyses give rise to a tight constraint on the model parameter $|f_{R0}|$ for $n=1$. The $95\\%$ CL limit is $\\log_{10}|f_{R0}| < -4.82$ given WMAP9 priors on $(\\Omega_{\\rm m}, A_{\\rm s})$. With Planck15 priors, the corresponding result is $\\log_{10}|f_{R0}| < -5.16$.

  3. Wavelet Helmholtz decomposition for weak lensing mass map reconstruction

    Science.gov (United States)

    Deriaz, E.; Starck, J.-L.; Pires, S.

    2012-04-01

    To derive the convergence field from the gravitational shear γ of the background galaxy images, the classical methods require a convolution of the shear to be performed over the entire sky, usually expressed by the fast Fourier transform (FFT). However, it is not optimal for an imperfect geometry survey. Furthermore, FFT implicitly uses periodic conditions that introduce errors into the reconstruction. A method has been proposed that relies on computation of an intermediate field u that combines the derivatives of γ and on convolution with a Green kernel. In this paper, we study the wavelet Helmholtz decomposition as a new approach to reconstructing the dark matter mass map. We show that a link exists between the Helmholtz decomposition and the electric and magnetic component separation. We introduce a new wavelet construction that has a property that gives us more flexibility in handling the border problem, and we propose a new method of reconstructing the dark matter mass map in the wavelet space. A set of experiments based on noise-free images illustrates that this Wavelet Helmholtz decomposition reconstructs the borders better than all other existing methods.

  4. Weak lensing analysis of C1 1358+62 using Hubble Space Telescope observations

    NARCIS (Netherlands)

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

    1998-01-01

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

  5. KiDS-450 : cosmological parameter constraints from tomographic weak gravitational lensing

    NARCIS (Netherlands)

    Hildebrandt, H.; Viola, M.; Heymans, C.; Joudaki, S.; Kuijken, K.; Blake, C.; Erben, T.; Joachimi, B.; Klaes, D.; Miller, L.; Morrison, C. B.; Nakajima, R.; Verdoes Kleijn, G.; Amon, A.; Choi, A.; Covone, G.; de Jong, J.T.A.; Dvornik, A.; Fenech Conti, I.; Grado, A.; Harnois-Déraps, J.; Herbonnet, R.; Hoekstra, H.; Köhlinger, F.; McFarland, J.; Mead, A.; Merten, J.; Napolitano, N.; Peacock, J. A.; Radovich, M.; Schneider, P.; Simon, P.; Valentijn, E. A.; van den Busch, J. L.; van Uitert, E.; Van Waerbeke, L.

    2017-01-01

    We present cosmological parameter constraints from a tomographic weak gravitational lensing analysis of ~450deg$^2$ of imaging data from the Kilo Degree Survey (KiDS). For a flat $\\Lambda$CDM cosmology with a prior on $H_0$ that encompasses the most recent direct measurements, we find $S_8\\equiv\\sig

  6. Dark Energy Survey Year 1 Results: Cosmological Constraints from Galaxy Clustering and Weak Lensing

    Energy Technology Data Exchange (ETDEWEB)

    Abbott, T.M.C.; et al.

    2017-08-04

    We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg$^2$ of $griz$ imaging data from the first year of the Dark Energy Survey (DES Y1). We combine three two-point functions: (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. To demonstrate the robustness of these results, we use independent pairs of galaxy shape, photometric redshift estimation and validation, and likelihood analysis pipelines. To prevent confirmation bias, the bulk of the analysis was carried out while blind to the true results; we describe an extensive suite of systematics checks performed and passed during this blinded phase. The data are modeled in flat $\\Lambda$CDM and $w$CDM cosmologies, marginalizing over 20 nuisance parameters, varying 6 (for $\\Lambda$CDM) or 7 (for $w$CDM) cosmological parameters including the neutrino mass density and including the 457 $\\times$ 457 element analytic covariance matrix. We find consistent cosmological results from these three two-point functions, and from their combination obtain $S_8 \\equiv \\sigma_8 (\\Omega_m/0.3)^{0.5} = 0.783^{+0.021}_{-0.025}$ and $\\Omega_m = 0.264^{+0.032}_{-0.019}$ for $\\Lambda$CDM for $w$CDM, we find $S_8 = 0.794^{+0.029}_{-0.027}$, $\\Omega_m = 0.279^{+0.043}_{-0.022}$, and $w=-0.80^{+0.20}_{-0.22}$ at 68% CL. The precision of these DES Y1 results rivals that from the Planck cosmic microwave background measurements, allowing a comparison of structure in the very early and late Universe on equal terms. Although the DES Y1 best-fit values for $S_8$ and $\\Omega_m$ are lower than the central values from Planck ...

  7. Weak-lensing Mass Calibration of RedMaPPer Galaxy Clusters in Dark Energy Survey Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Melchior, P.; et al.

    2016-10-21

    We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8,000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter $5 \\leq \\lambda \\leq 180$ and redshift $0.2 \\leq z \\leq 0.8$, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentering; deviations from the NFW halo profile; halo triaxiality; and line-of-sight projections. We combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift, $\\mathcal{M}(\\lambda,z) \\varpropto M_0 \\lambda^{F} (1+z)^{G}$. We find $M_0 \\equiv \\langle M_{200\\mathrm{m}}\\,|\\,\\lambda=30,z=0.5\\rangle=\\left[ 2.35 \\pm 0.22\\ \\rm{(stat)} \\pm 0.12\\ \\rm{(sys)} \\right] \\cdot 10^{14}\\ M_\\odot$, with $F = 1.12\\,\\pm\\,0.20\\ \\rm{(stat)}\\, \\pm\\, 0.06\\ \\rm{(sys)}$ and $G = 0.18\\,\\pm\\, 0.75\\ \\rm{(stat)}\\, \\pm\\, 0.24\\ \\rm{(sys)}$. The amplitude of the mass-richness relation is in excellent agreement with the weak-lensing calibration of redMaPPer clusters in SDSS by Simet et al. (2016) and with the Saro et al. (2015) calibration based on abundance matching of SPT-detected clusters. Our results extend the redshift range over which the mass-richness relation of redMaPPer clusters has been calibrated with weak lensing from $z\\leq 0.3$ to $z\\leq0.8$. Calibration uncertainties of shear measurements and photometric redshift estimates dominate our systematic error budget and require substantial improvements for forthcoming studies.

  8. DEMNUni: ISW, Rees-Sciama, and weak-lensing in the presence of massive neutrinos

    CERN Document Server

    Carbone, Carmelita; Dolag, Klaus

    2016-01-01

    We present, for the first time in the literature, a full reconstruction of the total (linear and non-linear) ISW/Rees-Sciama effect in the presence of massive neutrinos, together with its cross-correlations with CMB-lensing and weak-lensing signals. The present analyses make use of all-sky maps extracted via ray-tracing across the gravitational potential distribution provided by the "Dark Energy and Massive Neutrino Universe" (DEMNUni) project, a set of large-volume, high-resolution cosmological N-body simulations, where neutrinos are treated as separate collisionless particles. We correctly recover, at $1-2\\%$ accuracy, the linear predictions from CAMB. Concerning the CMB-lensing and weak-lensing signals, we also recover, with similar accuracy, the signal predicted by Boltzmann codes, once non-linear neutrino corrections to Halofit are accounted for. Interestingly, in the ISW/Rees-Sciama signal, and its cross correlation with lensing, we find an excess of power with respect to the massless case, due to free ...

  9. Detection of dark matter concentrations in the field of Cl 1604+4304 from weak lensing analysis

    CERN Document Server

    Umetsu, K; Umetsu, Keiichi; Futamase, Toshifumi

    2000-01-01

    We present a weak-lensing analysis of a region around the galaxy cluster Cl 1604+4304 (z=0.897) on the basis of the deep observations with the {\\sl HST}/WFPC2. We apply a variant of Schneider's aperture mass technique to the observed WFPC2 field and obtain the distribution of weak-lensing signal-to-noise (S/N) ratio within the field. The resulting S/N map reveals a clear pronounced peak located about $1\\farcm 7$ ($850h_{50}^{-1}$ kpc at z=0.897) southwest of the second peak associated with the optical cluster center determined from the dynamical analysis of Postman et al. A non-linear finite-field inversion method has been used to reconstruct the projected mass distribution from the observed shear field. The reconstructed mass map shows a super-critical feature at the location of the S/N peak as well as in the cluster central region. Assuming the redshift distribution of field galaxies, we obtain the total mass in the observed field to be $1.0 h_{50}^{-1}\\times 10^{15} M_{\\odot}$ for $=1.0$. The estimated mas...

  10. Origins of weak lensing systematics, and requirements on future instrumentation (or knowledge of instrumentation)

    Energy Technology Data Exchange (ETDEWEB)

    Massey, Richard [Durham Univ., Durham (United Kingdom); Hoekstra, Henk [Leiden Univ., Leiden (Netherlands); Kitching, Thomas [Univ. of Edinburg, Edinburg (United Kingdom); Rhodes, Jason [California Institute of Technology, Pasadena, CA (United States); Cropper, Mark [Univ. College London, Surrey (United Kingdom); Amiaux, Jerome [CEA Saclay, Gif sur Yvette (France); Harvey, David [Univ. of Edinburg, Edinburg (United Kingdom); Mellier, Yannick [Univ. Pierre et Marie Curie, Paris (France); CEA Saclay, Gif sur Yvette (France); Meneghetti, Massimo [Istituto Nazionale di Astrofisica (INAF), Bologna (Italy); Miller, Lance [Univ. of Oxford, Oxford (United Kingdom); Paulin-Henriksson, Stephane [CEA Saclay, Gif sur Yvette (France); Pires, Sandrine [CEA Saclay, Gif sur Yvette (France); Scaramella, Roberto [Istituto Nazionale di Astrofisica (INAF), Monteporzio Catone (Italy); Schrabback, Tim [Stanford Univ., Stanford, CA (United States); Argelander-Institut fur Astronomie, Bonn (Germany)

    2012-12-13

    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. In addition, these now explain the additive A(ℓ) and multiplicative M(ℓ) 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.

  11. Weak lensing calibrated M-T scaling relation of galaxy groups in the cosmos field

    Energy Technology Data Exchange (ETDEWEB)

    Kettula, K.; Finoguenov, A. [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, FI-00014 Helsinki (Finland); Massey, R. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Rhodes, J. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Hoekstra, H. [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333-CA Leiden (Netherlands); Taylor, J. E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Spinelli, P. F. [Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG), Rua do Matão, 1226 Cidade Universitária 05508-090, São Paulo, SP (Brazil); Tanaka, M. [National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Ilbert, O. [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, F-13013 Marseille (France); Capak, P. [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard Pasadena, CA 91125 (United States); McCracken, H. J. [Institut d' Astrophysique de Paris, UMR 7095, 98 bis Boulevard Arago, F-75014 Paris (France); Koekemoer, A., E-mail: kimmo.kettula@iki.fi [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2013-11-20

    The scaling between X-ray observables and mass for galaxy clusters and groups is instrumental for cluster-based cosmology and an important probe for the thermodynamics of the intracluster gas. We calibrate a scaling relation between the weak lensing mass and X-ray spectroscopic temperature for 10 galaxy groups in the COSMOS field, combined with 55 higher-mass clusters from the literature. The COSMOS data includes Hubble Space Telescope imaging and redshift measurements of 46 source galaxies per arcminute{sup 2}, enabling us to perform unique weak lensing measurements of low-mass systems. Our sample extends the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study, resulting in a power-law slope of 1.48{sub −0.09}{sup +0.13}. The slope is consistent with the self-similar model, predictions from simulations, and observations of clusters. However, X-ray observations relying on mass measurements derived under the assumption of hydrostatic equilibrium have indicated that masses at group scales are lower than expected. Both simulations and observations suggest that hydrostatic mass measurements can be biased low. Our external weak lensing masses provide the first observational support for hydrostatic mass bias at group level, showing an increasing bias with decreasing temperature and reaching a level of 30%-50% at 1 keV.

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

    Energy Technology Data Exchange (ETDEWEB)

    Cevallos, Marissa; /Caltech /SLAC

    2006-01-04

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

  13. Comparison of halo detection from noisy weak lensing convergence maps with Gaussian smoothing and MRLens treatment *

    Institute of Scientific and Technical Information of China (English)

    Yang-Xiu Jiao; Huan-Yuan Shan; Zu-Hui Fan

    2011-01-01

    Taking into account the noise from intrinsic ellipticities of source galaxies,we study the efficiency and completeness of halo detections from weak lensing convergence maps. Particularly, with numerical simulations, we compare the Gaussian filter with the so called MRLens treatment based on the modification of the Maximum Entropy Method. For a pure noise field without lensing signals, a Gaussian smoothing results in a residual noise field that is approximately Gaussian in terms of statistics if a large enough number of galaxies are included in the smoothing window. On the other hand, the noise field after the MRLens treatment is significantly non-Gaussian, resulting in complications in characterizing the noise effects. Considering weak-lensing cluster detections, although the MRLens treatment effectively deletes false peaks arising from noise, it removes the real peaks heavily due to its inability to distinguish real signals with relatively low amplitudes from noise in its restoration process. The higher the noise level is, the larger the removal effects are for the real peaks. For a survey with a source density ng ~ 30 arcmin-2, the number of peaks found in an area of 3 × 3 deg2 after MRLens filtering is only ~ 50 for the detection threshold k = 0.02, while the number of halos with M > 5 × 1013 M⊙ and with redshift z ≤ 2 in the same area is expected to be ~ 530. For the Gaussian smoothing treatment, the number of detections is ~ 260, much larger than that of the MRLens. The Gaussianity of the noise statistics in the Gaussian smoothing case adds further advantages for this method to circumvent the problem of the relatively low efficiency in weak-lensing cluster detections.Therefore, in studies aiming to construct large cluster samples from weak-lensing surveys, the Gaussian smoothing method performs significantly better than the MRLens treatment.

  14. Subaru weak-lensing survey of dark matter subhalos in the Coma cluster: Subhalo mass function and statistical properties

    Energy Technology Data Exchange (ETDEWEB)

    Okabe, Nobuhiro [Kavli Institute for the Physics and Mathematics of the Universe (WPI), Todai Institutes for Advanced Study, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan); Futamase, Toshifumi; Kuroshima, Risa [Astronomical Institute, Tohoku University, Sendai 980-8578 (Japan); Kajisawa, Masaru, E-mail: nobuhiro.okabe@ipmu.jp [Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan)

    2014-04-01

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

  15. Mass Calibration of Galaxy Clusters at Redshift 0.1-1.0 using Weak Lensing in the Sloan Digital Sky Survey Stripe 82 Co-add

    CERN Document Server

    Wiesner, Matthew P; Soares-Santos, Marcelle

    2015-01-01

    We present mass-richness relations found in the Sloan Digital Sky Survey Stripe 82 co-add. These relations were found using stacked weak lensing shear observed in a large sample of galaxy clusters. These mass-richness relations are presented for four redshift bins, $0.1 < z \\leq 0.4$, $0.4 < z \\leq 0.7$, $0.7 < z \\leq 1.0$ and $0.1 < z \\leq 1.0$. We describe the sample of galaxy clusters and explain how these clusters were found using a Voronoi Tessellation cluster finder. We fit an NFW profile to the stacked weak lensing shear signal in redshift and richness bins in order to measure virial mass $(M_{200})$. We describe several effects that can bias weak lensing measurements, including photometric redshift bias, the effect of the central BCG, halo miscentering, photometric redshift uncertainty and foreground galaxy contamination. We present mass-richness relations using richness measure $N_{VT}$ with each of these effects considered separately as well as considered altogether. We present values fo...

  16. A test of the Suyama-Yamaguchi inequality from weak lensing

    Science.gov (United States)

    Grassi, Alessandra; Heisenberg, Lavinia; Byrnes, Christian T.; Schäfer, Björn Malte

    2014-08-01

    We investigate the weak lensing signature of primordial non-Gaussianities of the local type by constraining the magnitude of the weak convergence bi- and trispectra expected for the Euclid weak lensing survey. Starting from expressions for the weak convergence spectra, bispectra and trispectra, whose relative magnitudes we investigate as a function of scale, we compute their respective signal-to-noise ratios by relating the polyspectra's amplitude to their Gaussian covariance using a Monte Carlo technique for carrying out the configuration space integrations. In computing the Fisher matrix on the non-Gaussianity parameters fNL, gNL and τNL with a very similar technique, we can derive pieces of Bayesian evidence for a violation of the Suyama-Yamaguchi (SY) relation τNL ≥ (6fNL/5)2 as a function of the true fNL- and τNL-values and show that the relation can be probed down to levels of fNL ≃ 102 and τNL ≃ 105. In a related study, we derive analytical expressions for the probability density that the SY relation is exactly fulfilled, as required by models in which any one field generates the perturbations. We conclude with an outlook on the levels of non-Gaussianity that can be probed with tomographic lensing surveys.

  17. Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

    CERN Document Server

    Johnston, David E; Wechsler, Risa H; Rozo, Eduardo; Koester, Benjamin P; Frieman, Joshua A; McKay, Timothy A; Evrard, August E; Becker, Matthew R; Annis, James

    2007-01-01

    We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. 2007 (Paper I). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of 13% including both statistical and systematic errors. We also constrain the halo concentration para...

  18. Multipolar moments of weak lensing signal around clusters. Weighing filaments in harmonic space

    Science.gov (United States)

    Gouin, C.; Gavazzi, R.; Codis, S.; Pichon, C.; Peirani, S.; Dubois, Y.

    2017-09-01

    Context. Upcoming weak lensing surveys such as Euclid will provide an unprecedented opportunity to quantify the geometry and topology of the cosmic web, in particular in the vicinity of lensing clusters. Aims: Understanding the connectivity of the cosmic web with unbiased mass tracers, such as weak lensing, is of prime importance to probe the underlying cosmology, seek dynamical signatures of dark matter, and quantify environmental effects on galaxy formation. Methods: Mock catalogues of galaxy clusters are extracted from the N-body PLUS simulation. For each cluster, the aperture multipolar moments of the convergence are calculated in two annuli (inside and outside the virial radius). By stacking their modulus, a statistical estimator is built to characterise the angular mass distribution around clusters. The moments are compared to predictions from perturbation theory and spherical collapse. Results: The main weakly chromatic excess of multipolar power on large scales is understood as arising from the contraction of the primordial cosmic web driven by the growing potential well of the cluster. Besides this boost, the quadrupole prevails in the cluster (ellipsoidal) core, while at the outskirts, harmonic distortions are spread on small angular modes, and trace the non-linear sharpening of the filamentary structures. Predictions for the signal amplitude as a function of the cluster-centric distance, mass, and redshift are presented. The prospects of measuring this signal are estimated for current and future lensing data sets. Conclusions: The Euclid mission should provide all the necessary information for studying the cosmic evolution of the connectivity of the cosmic web around lensing clusters using multipolar moments and probing unique signatures of, for example, baryons and warm dark matter.

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

    CERN Document Server

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

    2014-01-01

    We conduct a joint X-ray and weak-lensing study of four relaxed galaxy clusters (Hydra A, A478, A1689 and A1835) observed by both Suzaku and Subaru out to virial radii, with an aim to understand recently-discovered unexpected feature of the ICM in cluster outskirts. We show that the average hydrostatic-to-lensing total mass ratio for the four clusters decreases from \\sim 70% to \\sim 40% as the overdensity contrast decreases from 500 to the virial value.The average gas mass fraction from lensing total mass estimates increases with cluster radius and agrees with the cosmic mean baryon fraction within the virial radius, whereas the X-ray-based gas fraction considerably exceeds the cosmic values due to underestimation of the hydrostatic mass. We also develop a new advanced method for determining normalized cluster radial profiles for multiple X-ray observables by simultaneously taking into account both their radial dependence and multivariate scaling relations with weak-lensing masses. Although the four clusters ...

  20. Estimating small angular scale CMB anisotropy with high resolution N-body simulations: weak lensing

    CERN Document Server

    Fullana, M J; Thacker, R J; Couchman, H M P; Sáez, D

    2010-01-01

    We estimate the impact of weak lensing by strongly nonlinear cosmological structures on the cosmic microwave background. Accurate calculation of large $\\ell$ 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 (AP3M) 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 3-D 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 t...

  1. Accurate covariance estimation of galaxy-galaxy weak lensing: limitations of jackknife covariance

    CERN Document Server

    Shirasaki, Masato; Miyatake, Hironao; Takahashi, Ryuichi; Hamana, Takashi; Nishimichi, Takahiro; Murata, Ryoma

    2016-01-01

    We develop a method to simulate galaxy-galaxy weak lensing by utilizing all-sky, light-cone simulations. We populate a real catalog of source galaxies into a light-cone simulation realization, simulate the lensing effect on each galaxy, and then identify lensing halos that are considered to host galaxies or clusters of interest. We use the mock catalog to study the error covariance matrix of galaxy-galaxy weak lensing and find that the super-sample covariance (SSC), which arises from density fluctuations with length scales comparable with or greater than a size of survey area, gives a dominant source of the sample variance. We then compare the full covariance with the jackknife (JK) covariance, the method that estimates the covariance from the resamples of the data itself. We show that, although the JK method gives an unbiased estimator of the covariance in the shot noise or Gaussian regime, it always over-estimates the true covariance in the sample variance regime, because the JK covariance turns out to be a...

  2. The influence of weak lensing on measurements of the Hubble constant with quad-image gravitational lenses

    Science.gov (United States)

    Jaroszyński, M.; Skowron, J.

    2016-10-01

    We investigate the influence of matter along the line of sight and in the strong lens vicinity on the properties of quad-image configurations and on the measurements of the Hubble constant (H0). We use simulations of light propagation in a non-uniform universe model with the distribution of matter in space based on the data from Millennium Simulation. For a given strong lens and haloes in its environment we model the matter distribution along the line of sight many times, using different combinations of pre-computed deflection maps representing subsequent layers of matter on the path of rays. We fit the simulated quad-image configurations with time delays using non-singular isothermal ellipsoids with external shear as lens models, treating the Hubble constant as a free parameter. We get a large artificial catalogue of lenses with derived values of the Hubble constant, Hfit. The average and median of Hfit differ from the true value used in simulations by ≤0.5 km s-1 Mpc-1 which includes the influence of matter along the line of sight and in the lens vicinity, and uncertainty in lens parameters, except the slope of the matter distribution, which is fixed. The characteristic uncertainty of Hfit is ˜3 km s-1 Mpc-1. Substituting the lens shear parameters with values estimated from the simulations reduces the uncertainty to ˜2 km s-1 Mpc-1.

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

    CERN Document Server

    Sereno, Mauro

    2014-01-01

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

  4. A KiDS weak lensing analysis of assembly bias in GAMA galaxy groups

    Science.gov (United States)

    Dvornik, Andrej; Cacciato, Marcello; Kuijken, Konrad; Viola, Massimo; Hoekstra, Henk; Nakajima, Reiko; van Uitert, Edo; Brouwer, Margot; Choi, Ami; Erben, Thomas; Fenech Conti, Ian; Farrow, Daniel J.; Herbonnet, Ricardo; Heymans, Catherine; Hildebrandt, Hendrik; Hopkins, Andrew M.; McFarland, John; Norberg, Peder; Schneider, Peter; Sifón, Cristóbal; Valentijn, Edwin; Wang, Lingyu

    2017-07-01

    We investigate possible signatures of halo assembly bias for spectroscopically selected galaxy groups from the Galaxy And Mass Assembly (GAMA) survey using weak lensing measurements from the spatially overlapping regions of the deeper, high-imaging-quality photometric Kilo-Degree Survey. We use GAMA groups with an apparent richness larger than 4 to identify samples with comparable mean host halo masses but with a different radial distribution of satellite galaxies, which is a proxy for the formation time of the haloes. We measure the weak lensing signal for groups with a steeper than average and with a shallower than average satellite distribution and find no sign of halo assembly bias, with the bias ratio of 0.85^{+0.37}_{-0.25}, which is consistent with the Λ cold dark matter prediction. Our galaxy groups have typical masses of 1013 M⊙ h-1, naturally complementing previous studies of halo assembly bias on galaxy cluster scales.

  5. A new model to predict weak-lensing peak counts II. Parameter constraint strategies

    CERN Document Server

    Lin, Chieh-An

    2015-01-01

    Peak counts have been shown to be an excellent tool to extract the non-Gaussian part of the weak lensing signal. Recently, we developped a fast stochastic forward model to predict weak-lensing peak counts. Our model is able to reconstruct the underlying distribution of observables for analyses. In this work, we explore and compare various strategies for constraining parameter using our model, focusing on the matter density $\\Omega_\\mathrm{m}$ and the density fluctuation amplitude $\\sigma_8$. First, we examine the impact from the cosmological dependency of covariances (CDC). Second, we perform the analysis with the copula likelihood, a technique which makes a weaker assumption compared to the Gaussian likelihood. Third, direct, non-analytic parameter estimations are applied using the full information of the distribution. Fourth, we obtain constraints with approximate Bayesian computation (ABC), an efficient, robust, and likelihood-free algorithm based on accept-reject sampling. We find that neglecting the CDC ...

  6. KiDS-450: tomographic cross-correlation of galaxy shear with Planck lensing

    Science.gov (United States)

    Harnois-Déraps, Joachim; Tröster, Tilman; Chisari, Nora Elisa; Heymans, Catherine; van Waerbeke, Ludovic; Asgari, Marika; Bilicki, Maciej; Choi, Ami; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Joudaki, Shahab; Kuijken, Konrad; Merten, Julian; Miller, Lance; Robertson, Naomi; Schneider, Peter; Viola, Massimo

    2017-10-01

    We present the tomographic cross-correlation between galaxy lensing measured in the Kilo Degree Survey (KiDS-450) with overlapping lensing measurements of the cosmic microwave background (CMB), as detected by Planck 2015. We compare our joint probe measurement to the theoretical expectation for a flat Λ cold dark matter cosmology, assuming the best-fitting cosmological parameters from the KiDS-450 cosmic shear and Planck CMB analyses. We find that our results are consistent within 1σ with the KiDS-450 cosmology, with an amplitude re-scaling parameter AKiDS = 0.86 ± 0.19. Adopting a Planck cosmology, we find our results are consistent within 2σ, with APlanck = 0.68 ± 0.15. We show that the agreement is improved in both cases when the contamination to the signal by intrinsic galaxy alignments is accounted for, increasing A by ∼0.1. This is the first tomographic analysis of the galaxy lensing - CMB lensing cross-correlation signal, and is based on five photometric redshift bins. We use this measurement as an independent validation of the multiplicative shear calibration and of the calibrated source redshift distribution at high redshifts. We find that constraints on these two quantities are strongly correlated when obtained from this technique, which should therefore not be considered as a stand-alone competitive calibration tool.

  7. Cosmological Constraints From Weak Lensing Peak Statistics With CFHT Stripe-82 Survey

    CERN Document Server

    Liu, Xiangkun; Li, Ran; Shan, Huanyuan; Wang, Qiao; Fu, Liping; Fan, Zuhui; Kneib, Jean-Paul; Leauthaud, Alexie; Van Waerbeke, Ludovic; Makler, Martin; Moraes, Bruno; Erben, Thomas; Charbonnier, Aldée

    2014-01-01

    We derived constraints on cosmological parameters using weak lensing peak statistics measured on the $\\sim130~\\rm{deg}^2$ of the Canada-France-Hawaii Telescope Stripe82 Survey (CS82). This analysis, based on a fast GPU code, demonstrates the feasibility of using peak statistics in cosmological studies. For our measurements, we considered peaks with signal-to-noise ratio in the range of $\

  8. Problems using ratios of galaxy shape moments in requirements for weak lensing surveys

    Science.gov (United States)

    Israel, H.; Kitching, T. D.; Massey, R.; Cropper, M.

    2017-01-01

    Context. The shapes of galaxies are typically quantified by ratios of their quadrupole moments. Knowledge of these ratios (i.e. their measured standard deviation) is commonly used to assess the efficiency of weak gravitational lensing surveys. For faint galaxies, observational noise can make the denominator close to zero, so the ratios become ill-defined. Aims: Since the requirements cannot be formally tested for faint galaxies, we explore two complementary mitigation strategies. In many weak lensing contexts, the most problematic sources can be removed by a cut in measured size. This first technique is applied frequently. As our second strategy, we propose requirements directly on the quadrupole moments rather than their ratio. Methods: As an example of the first strategy, we have investigated how a size cut affects the required precision of the charge transfer inefficiency model for two shape measurement settings. For the second strategy, we analysed the joint likelihood distribution of the image quadrupole moments measured from simulated galaxies, and propagate their (correlated) uncertainties into ellipticities. Results: Using a size cut, we find slightly wider tolerance margins for the charge transfer inefficiency parameters compared to the full size distribution. However, subtle biases in the data analysis chain may be introduced. These can be avoided using the second strategy. To optimally exploit a Stage-IV dark energy survey, we find that the mean and standard deviation of a population of galaxies' quadrupole moments must to be known to better than 1.4 × 10-3 arcsec2, or the Stokes parameters to 1.9 × 10-3 arcsec2. Conclusions: Cuts in measured size remove sources that otherwise make ellipticity statistics of weak lensing galaxy samples diverge. However, size cuts bias the source population non-trivially. Assessing weak lensing data quality directly on the quadrupole moments instead mitigates the need for size cuts. Such testable requirements can form

  9. For information: Geneva University - Weak lensing et énergie sombre

    CERN Multimedia

    2005-01-01

    UNIVERSITE DE GENEVE ECOLE DE PHYSIQUE Département de physique nucléaire et corspusculaire 24, Quai Ernest-Ansermet - 1211 GENEVE 4 Tél : (022) 379 62 73 Fax: (022) 379 69 92 Wednesday 4 May PARTICLE PHYSICS SEMINAR at 17:00 - Stückelberg Auditorium Weak lensing et énergie sombre by Prof. Alexandre Refregier / CEA, Saclay L'effet de cisaillement gravitationnel faible, ou 'weak lensing', permet de cartographier directement la distribution de la matière sombre dans l'univers. Cette distribution peut être comparée aux prédictions des modèles de formation des structures afin de contraindre les paramètres cosmologiques. Après un rappel des principes du weak lensing, je résumerai le statut observationnel de ce domaine en évolution très rapide. Je présenterai ensuite les perspectives offertes par les futurs relevés grand...

  10. An optimal survey geometry of weak lensing survey: minimizing super-sample covariance

    CERN Document Server

    Takahashi, Ryuichi; Takada, Masahiro; Kayo, Issha

    2014-01-01

    Upcoming wide-area weak lensing surveys are expensive both in time and cost and require an optimal survey design in order to attain maximum scientific returns from a fixed amount of available telescope time. The super-sample covariance (SSC), which arises from unobservable modes that are larger than the survey size, significantly degrades the statistical precision of weak lensing power spectrum measurement even for a wide-area survey. Using the 1000 mock realizations of the log-normal model, which approximates the weak lensing field for a $\\Lambda$-dominated cold dark matter model, we study an optimal survey geometry to minimize the impact of SSC contamination. For a continuous survey geometry with a fixed survey area, a more elongated geometry such as a rectangular shape of 1:400 side-length ratio reduces the SSC effect and allows for a factor 2 improvement in the cumulative signal-to-noise ratio ($S/N$) of power spectrum measurement up to $\\ell_{\\rm max}\\simeq $ a few $10^3$, compared to compact geometries ...

  11. Joint likelihood function of cluster number counts and weak lensing power spectrum

    CERN Document Server

    Takada, Masahiro

    2013-01-01

    A coherent over- or under-density contrast across a finite survey volume causes an upward- or downward- fluctuation in the number of halos. This fluctuation in halo number adds a significant co-variant scatter in the observed amplitudes of weak lensing power spectrum at nonlinear, small scales. Because of this covariance, the amount of information that can be extracted from a measurement of the weak lensing power spectrum is significantly smaller than naive estimates. In this paper, we show that by measuring both the number counts of clusters and the power spectrum in the same survey region, we can mitigate this loss of information and significantly enhance the scientific return from the upcoming surveys. First, using the halo model approach, we derive the joint likelihood function of the halo number counts and the weak lensing power spectrum, taking into account the super-sample co-variance effect on the two observables. We show that the analytical model matches the distributions measured from 1000 realizati...

  12. Improved optical mass tracer for galaxy clusters calibrated using weak lensing measurements

    CERN Document Server

    Reyes, Reinabelle; Hirata, Christopher M; Bahcall, Neta; Seljak, Uros

    2008-01-01

    We develop an improved mass tracer for clusters of galaxies from optically observed parameters, and calibrate the mass relation using weak gravitational lensing measurements. We employ a sample of ~ 13,000 optically-selected clusters from the Sloan Digital Sky Survey (SDSS) maxBCG catalog, with photometric redshifts in the range 0.1-0.3. The optical tracers we consider are cluster richness, cluster luminosity, luminosity of the brightest cluster galaxy (BCG), and combinations of these parameters. We measure the weak lensing signal around stacked clusters as a function of the different tracers, and use it to determine the tracer with the least amount of scatter. We further use the weak lensing data to calibrate the mass normalization. We find that the best mass estimator for massive clusters is a combination of cluster richness, N_{200}, and the luminosity of the brightest cluster galaxy, L_{BCG}: M_{200\\bar{\\rho}} = (1.27 +/- 0.08) (N_{200}/20)^{1.20 +/- 0.09} (L_{BCG}/\\bar{L}_{BCG}(N_{200}))^{0.71 +/- 0.14} ...

  13. Full-sky lensing shear at second order

    CERN Document Server

    Bernardeau, Francis; Vernizzi, Filippo

    2009-01-01

    We compute the reduced cosmic shear up to second order in the gravitational potential without relying on the small angle or thin-lens approximation. This is obtained by solving the Sachs equation which describes the deformation of the infinitesimal cross-section of light bundle in the optical limit, and maps galaxy intrinsic shapes into their angular images. The calculation is done in the Poisson gauge without a specific matter content, including vector and tensor perturbations generated at second order and taking account of the inhomogeneities of a fixed redshift source plane. Our final result is expressed in terms of spin-2 operators on the sphere and is valid on the full sky. Beside the well known lens-lens and Born corrections that dominate on small angular scales, we find new non-linear couplings. These are a purely general relativistic intrinsic contribution, a coupling between the gravitational potential at the source with the lens, couplings between the time delay with the lens, couplings between two ...

  14. Improving three-dimensional mass mapping with weak gravitational lensing through a synergy with galaxy clustering

    CERN Document Server

    Simon, Patrick

    2012-01-01

    The weak gravitational lensing distortion of distant galaxy images ("sources") probes the projected large-scale matter distribution in the Universe. The availability of redshift information in galaxy surveys also allows us to recover the radial matter distribution to a certain degree. To improve the S/N in the mass mapping, we combine the lensing information with the spatial clustering of a population of galaxies that trace the matter density with a known galaxy bias. We construct a minimum-variance estimator for the 3D matter density that incorporates the angular distribution of galaxy tracers, which are coarsely binned in redshift. Merely the second-order biasing of the tracers has to be known, which can in principle be self-consistently constrained in the data by lensing techniques. To study the new estimator, we generate a mock survey with galaxies that trace the matter density with a Gaussian linear stochastic bias. The filter smoothes and linearly mixes the individual lensing mass and tracer number dens...

  15. First test of Verlinde's theory of emergent gravity using weak gravitational lensing measurements

    Science.gov (United States)

    Brouwer, Margot M.; Visser, Manus R.; Dvornik, Andrej; Hoekstra, Henk; Kuijken, Konrad; Valentijn, Edwin A.; Bilicki, Maciej; Blake, Chris; Brough, Sarah; Buddelmeijer, Hugo; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Holwerda, Benne W.; Hopkins, Andrew M.; Klaes, Dominik; Liske, Jochen; Loveday, Jon; McFarland, John; Nakajima, Reiko; Sifón, Cristóbal; Taylor, Edward N.

    2017-04-01

    Verlinde proposed that the observed excess gravity in galaxies and clusters is the consequence of emergent gravity (EG). In this theory, the standard gravitational laws are modified on galactic and larger scales due to the displacement of dark energy by baryonic matter. EG gives an estimate of the excess gravity (described as an apparent dark matter density) in terms of the baryonic mass distribution and the Hubble parameter. In this work, we present the first test of EG using weak gravitational lensing, within the regime of validity of the current model. Although there is no direct description of lensing and cosmology in EG yet, we can make a reasonable estimate of the expected lensing signal of low-redshift galaxies by assuming a background Lambda cold dark matter cosmology. We measure the (apparent) average surface mass density profiles of 33 613 isolated central galaxies and compare them to those predicted by EG based on the galaxies' baryonic masses. To this end, we employ the ∼180 deg2 overlap of the Kilo-Degree Survey with the spectroscopic Galaxy And Mass Assembly survey. We find that the prediction from EG, despite requiring no free parameters, is in good agreement with the observed galaxy-galaxy lensing profiles in four different stellar mass bins. Although this performance is remarkable, this study is only a first step. Further advancements on both the theoretical framework and observational tests of EG are needed before it can be considered a fully developed and solidly tested theory.

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

    CERN Document Server

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

    2013-01-01

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

  17. Selection biases in empirical p(z) methods for weak lensing

    CERN Document Server

    Gruen, Daniel

    2016-01-01

    To measure the mass of foreground objects with weak gravitational lensing, one needs to estimate the redshift distribution of lensed background sources. This is commonly done in an empirical fashion, i.e. with a reference sample of galaxies of known spectroscopic redshift, matched to the source population. In this work, we develop a simple decision tree framework that, under the ideal conditions of a large, purely magnitude-limited reference sample, allows an unbiased recovery of the source redshift probability density function p(z), as a function of magnitude and color. We use this framework to quantify biases in empirically estimated p(z) caused by selection effects present in realistic reference and weak lensing source catalogs, namely (1) complex selection of reference objects by the targeting strategy and success rate of existing spectroscopic surveys and (2) selection of background sources by the success of object detection and shape measurement at low signal-to-noise. For intermediate-to-high redshift ...

  18. A test of the Suyama-Yamaguchi inequality from weak lensing

    CERN Document Server

    Grassi, Alessandra; Byrnes, Chris T; Schaefer, Bjoern Malte

    2013-01-01

    We investigate the weak lensing signature of primordial non-Gaussianities of the local type by constraining the magnitude of the weak convergence bi- and trispectra expected for the EUCLID weak lensing survey. Starting from expressions for the weak convergence spectra, bispectra and trispectra, whose relative magnitudes we investigate as a function of scale, we compute their respective signal to noise ratios by relating the polyspectra's amplitude to their Gaussian covariance using a Monte-Carlo technique for carrying out the configuration space integrations. In computing the Fisher-matrix on the non-Gaussianity parameters f_nl, g_nl and tau_nl with a very similar technique, we can derive Bayesian evidences for a violation of the Suyama-Yamaguchi relation tau_nl>=(6 f_nl/5)^2 as a function of the true f_nl and tau_nl-values and show that the relation can be probed down to levels of f_nl~10^2 and tau_nl~10^5. In a related study, we derive analytical expressions for the probability density that the SY-relation ...

  19. Cosmological constraints with weak lensing peak counts and second-order statistics in a large-field survey

    Science.gov (United States)

    Peel, Austin; Lin, Chieh-An; Lanusse, Francois; Leonard, Adrienne; Starck, Jean-Luc; Kilbinger, Martin

    2017-01-01

    Peak statistics in weak lensing maps access the non-Gaussian information contained in the large-scale distribution of matter in the Universe. They are therefore a promising complementary probe to two-point and higher-order statistics to constrain our cosmological models. To prepare for the high precision afforded by next-generation weak lensing surveys, we assess the constraining power of peak counts in a simulated Euclid-like survey on the cosmological parameters Ωm, σ8, and w0de. In particular, we study how CAMELUS---a fast stochastic model for predicting peaks---can be applied to such large surveys. The algorithm avoids the need for time-costly N-body simulations, and its stochastic approach provides full PDF information of observables. We measure the abundance histogram of peaks in a mock shear catalogue of approximately 5,000 deg2 using a multiscale mass map filtering technique, and we then constrain the parameters of the mock survey using CAMELUS combined with approximate Bayesian computation, a robust likelihood-free inference algorithm. We find that peak statistics yield a tight but significantly biased constraint in the σ8-Ωm plane, indicating the need to better understand and control the model's systematics before applying it to a real survey of this size or larger. We perform a calibration of the model to remove the bias and compare results to those from the two-point correlation functions (2PCF) measured on the same field. In this case, we find the derived parameter Σ8 = σ8(Ωm/0.27)α = 0.76 (-0.03 +0.02) with α = 0.65 for peaks, while for 2PCF the values are Σ8 = 0.76 (-0.01 +0.02) and α = 0.70. We conclude that the constraining power can therefore be comparable between the two weak lensing observables in large-field surveys. Furthermore, the tilt in the σ8-Ωm degeneracy direction for peaks with respect to that of 2PCF suggests that a combined analysis would yield tighter constraints than either measure alone. As expected, w0de cannot be

  20. Weak-lensing mass calibration of redMaPPer galaxy clusters in Dark Energy Survey Science Verification data

    CERN Document Server

    Melchior, P; McClintock, T; Varga, T N; Sheldon, E; Rozo, E; Amara, A; Becker, M R; Benson, B A; Bermeo, A; Bridle, S L; Clampitt, J; Dietrich, J P; Hartley, W G; Hollowood, D; Jain, B; Jarvis, M; Jeltema, T; Kacprzak, T; MacCrann, N; Rykoff, E S; Saro, A; Suchyta, E; Troxel, M A; Zuntz, J; Bonnett, C; Plazas, A A; Abbott, T M C; Abdalla, F B; Annis, J; Benoit-Lévy, A; Bernstein, G M; Bertin, E; Brooks, D; Buckley-Geer, E; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Cunha, C E; D'Andrea, C B; da Costa, L N; Desai, S; Eifler, T F; Flaugher, B; Fosalba, P; García-Bellido, J; Gaztanaga, E; Gerdes, D W; Gruendl, R A; Gschwend, J; Gutierrez, G; Honscheid, K; James, D J; Kirk, D; Krause, E; Kuehn, K; Kuropatkin, N; Lahav, O; Lima, M; Maia, M A G; March, M; Martini, P; Menanteau, F; Miller, C J; Miquel, R; Mohr, J J; Nichol, R C; Ogando, R; Romer, A K; Sanchez, E; Scarpine, V; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Swanson, M E C; Tarle, G; Thomas, D; Walker, A R; Weller, J; Zhang, Y

    2016-01-01

    We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8,000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter $5 \\leq \\lambda \\leq 180$ and redshift $0.2 \\leq z \\leq 0.8$, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentering; deviations from the NFW halo profile; halo triaxiality; and line-of-sight projections. We combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift, $\\mathcal{M}(\\lambda,z) \\varpropto M_0 \\lambda^{F} (1+z)^{G}$. We find $M_0 \\equiv \\langle M_{200\\mathrm{m}}\\,|\\,\\lambda=30,z=0.5\\rangle=\\left[ 2.35 \\pm 0.22\\ \\rm{(stat)} \\pm 0.12\\ \\rm{(sys)} \\right] \\cdot 10^{14}\\ M_\\odot$, with $F = 1.12...

  1. The influence of weak lensing on measurements of the Hubble constant with quad-image gravitational lenses

    CERN Document Server

    Jaroszynski, M

    2016-01-01

    We investigate the influence of matter along the line of sight and in the strong lens vicinity on the properties of quad image configurations and on the measurements of the Hubble constant (H0). We use simulations of light propagation in a nonuniform universe model with the distribution of matter in space based on the data from Millennium Simulation. For a given strong lens and haloes in its environment we model the matter distribution along the line of sight many times, using different combinations of precomputed deflection maps representing subsequent layers of matter on the path of rays. We fit the simulated quad image configurations with time delays using nonsingular isothermal ellipsoids (NSIE) with external shear as lens models, treating the Hubble constant as a free parameter. We get a large artificial catalog of lenses with derived values of the Hubble constant, Hfit. The average and median of Hfit differ from the true value used in simulations by < 0.5 km/s/Mpc which includes the influence of matt...

  2. The mass of high-z massive galaxy cluster, SPT-CL J2106-5844 using weak-lensing analysis with HST observations

    Science.gov (United States)

    Kim, Jinhyub; Jee, James; Ko, Jongwan

    2017-01-01

    We present a weak-lensing analysis of the galaxy cluster SPT-CL J2106-5844 at z~1.132 using images from the Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) on-board on the Hubble Space Telescope (HST). This cluster discovered in the South Pole Telescope Sunyaev-Zel’dovich (SPT-SZ) survey is known to be the most massive system at z > 1 in the survey. Within the current ΛCDM hierarchical structure formation paradigm, the mass of the cluster at such a high redshift inferred by SZ, X-ray, and galaxy velocity dispersion data is somewhat unusual. The previous mass estimates, however, rely on assumptions on the dynamical state of the system, which may become questionable when the universe was young (about 40% of the current age). In this work, we present the first weak-lensing mass estimates of this interesting cluster. We describe how we derive a mass from the HST/ACS and HST/WFC3 deep imaging data and show a two-dimensional mass reconstruction. We find that the mass distribution of the cluster is unimodal with a centroid consistent (~1σ) with both galaxy luminosity and number density distributions. Based on tangential shear fitting with an NFW halo assumption, our weak-lensing mass estimates agree well with the previous estimates.

  3. Weak lensing study of 16 DAFT/FADA clusters: Substructures and filaments

    Science.gov (United States)

    Martinet, Nicolas; Clowe, Douglas; Durret, Florence; Adami, Christophe; Acebrón, Ana; Hernandez-García, Lorena; Márquez, Isabel; Guennou, Loic; Sarron, Florian; Ulmer, Mel

    2016-05-01

    While our current cosmological model places galaxy clusters at the nodes of a filament network (the cosmic web), we still struggle to detect these filaments at high redshifts. We perform a weak lensing study for a sample of 16 massive, medium-high redshift (0.4 detection with noise resampling techniques. Taking advantage of the large field of view of our data, we study cluster environment, adding information from galaxy density maps at the cluster redshift and from X-ray images when available. We find that clusters show a large variety of weak lensing maps at large scales and that they may all be embedded in filamentary structures at megaparsec scale. We classify these clusters in three categories according to the smoothness of their weak lensing contours and to the amount of substructures: relaxed (~7%), past mergers (~21.5%), and recent or present mergers (~71.5%). The fraction of clusters undergoing merging events observationally supports the hierarchical scenario of cluster growth, and implies that massive clusters are strongly evolving at the studied redshifts. Finally, we report the detection of unusually elongated structures in CLJ0152, MACSJ0454, MACSJ0717, A851, BMW1226, MACSJ1621, and MS1621. This study is based on observations obtained with MegaCam, a joint project of CFHT and CEA/IRFU, at the Canada-France-Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. The study is also based on archive data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. This research made use of data obtained from the Chandra Data Archive provided by the Chandra X-ray Center (CXC) and data obtained from the XMM-Newton Data Archive provided by the XMM-Newton Science Archive (XSA).

  4. A new method to measure galaxy bias by combining the density and weak lensing fields

    CERN Document Server

    Pujol, Arnau; Gaztañaga, Enrique; Amara, Adam; Refregier, Alexandre; Bacon, David J; Carretero, Jorge; Castander, Francisco J; Crocce, Martin; Fosalba, Pablo; Manera, Marc; Vikram, Vinu

    2016-01-01

    We present a new method to measure the redshift-dependent galaxy bias by combining information from the galaxy density field and the weak lensing field. This method is based on Amara et al. (2012), where they use the galaxy density field to construct a bias-weighted convergence field kg. The main difference between Amara et al. (2012) and our new implementation is that here we present another way to measure galaxy bias using tomography instead of bias parameterizations. The correlation between kg and the true lensing field k allows us to measure galaxy bias using different zero-lag correlations, such as / or /. This paper is the first that studies and systematically tests the robustness of this method in simulations. We use the MICE simulation suite, which includes a set of self-consistent N-body simulations, lensing maps, and mock galaxy catalogues. We study the accuracy and systematic uncertainties associated with the implementation of the method, and the regime where it is consistent with the linear galaxy...

  5. Cosmology and astrophysics from relaxed galaxy clusters - IV: Robustly calibrating hydrostatic masses with weak lensing

    CERN Document Server

    Applegate, D E; Allen, S W; von der Linden, A; Morris, R G; Hilbert, S; Kelly, P L; Burke, D L; Ebeling, H; Rapetti, D A; Schmidt, R W

    2015-01-01

    This is the fourth in a series of papers studying the astrophysics and cosmology of massive, dynamically relaxed galaxy clusters. Here, we use measurements of weak gravitational lensing from the Weighing the Giants project to calibrate Chandra X-ray measurements of total mass that rely on the assumption of hydrostatic equilibrium. This comparison of X-ray and lensing masses provides a measurement of the combined bias of X-ray hydrostatic masses due to both astrophysical and instrumental sources. Assuming a fixed cosmology, and within a characteristic radius (r_2500) determined from the X-ray data, we measure a lensing to X-ray mass ratio of 0.96 +/- 9% (stat) +/- 9% (sys). We find no significant trends of this ratio with mass, redshift or the morphological indicators used to select the sample. In accordance with predictions from hydro simulations for the most massive, relaxed clusters, our results disfavor strong, tens-of-percent departures from hydrostatic equilibrium at these radii. In addition, we find a m...

  6. A measurement of weak lensing by large scale structure in RCS fields

    CERN Document Server

    Hoekstra, H; Gladders, M D; Barrientos, L F; Hall, P B; Infante, L; Hoekstra, Henk; Yee, Howard K.C.; Gladders, Michael D.; Hall, Patrick B.; Infante, Leopoldo

    2002-01-01

    We have analysed ~24 square degrees of R_C-band imaging data from the Red-Sequence Cluster Survey (RCS), and measured the excess correlations between galaxy ellipticities on scales ranging from 1 to 30 arcminutes. We have used data from two different telescopes: ~16.4 square degrees of CFHT data and ~7.6 square degrees of CTIO 4-meter data, distributed over 13 widely separated patches. For the first time, a direct comparison can be made of the lensing signal measured using different instruments, which provides an important test of the weak lensing analysis itself. The measurements obtained from the two telescopes agree well. For the lensing analysis we use galaxies down to a limiting magnitude of R_C=24, for which the redshift distribution is known relatively well. This allows us to constrain some cosmological parameters. For the currently favored $\\Lambda$CDM model $(\\Omega_m=0.3, \\Omega_\\Lambda=0.7, \\Gamma=0.21)$ we obtain $\\sigma_8=0.81^{+0.14}_{-0.19}$ (95% confidence), in agreement with the results from ...

  7. CFHTLenS: Weak lensing constraints on the ellipticity of galaxy-scale matter haloes and the galaxy-halo misalignment

    CERN Document Server

    Schrabback, Tim; Hoekstra, Henk; Simon, Patrick; van Uitert, Edo; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bett, Philip; Coupon, Jean; Fu, Liping; Hudson, Michael J; Joachimi, Benjamin; Kilbinger, Martin; Kuijken, Konrad

    2015-01-01

    We present weak lensing constraints on the ellipticity of galaxy-scale matter haloes and the galaxy-halo misalignment. Using data from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS), we measure the weighted-average ratio of the aligned projected ellipticity components of galaxy matter haloes and their embedded galaxies, $f_\\mathrm{h}$, split by galaxy type. We then compare our observations to measurements taken from the Millennium Simulation, assuming different models of galaxy-halo misalignment. Using the Millennium Simulation we verify that the statistical estimator used removes contamination from cosmic shear. We also detect an additional signal in the simulation, which we interpret as the impact of intrinsic shape-shear alignments between the lenses and their large-scale structure environment. These alignments are likely to have caused some of the previous observational constraints on $f_\\mathrm{h}$ to be biased high. From CFHTLenS we find $f_\\mathrm{h}=-0.04 \\pm 0.25$ for early-type galaxie...

  8. Cross-correlation Weak Lensing of SDSS galaxy Clusters II: Cluster Density Profiles and the Mass--Richness Relation

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, David E.; Sheldon, Erin S.; Wechsler, Risa H.; Rozo, Eduardo; Koester, Benjamin P.; Frieman, Joshua A.; McKay, Timothy A.; Evrard, August E.; Becker, Matthew; Annis, James

    2007-09-28

    We interpret and model the statistical weak lensing measurements around 130,000 groups and clusters of galaxies in the Sloan Digital Sky Survey presented by Sheldon et al. (2007). We present non-parametric inversions of the 2D shear profiles to the mean 3D cluster density and mass profiles in bins of both optical richness and cluster i-band luminosity. Since the mean cluster density profile is proportional to the cluster-mass correlation function, the mean profile is spherically symmetric by the assumptions of large-scale homogeneity and isotropy. We correct the inferred 3D profiles for systematic effects, including non-linear shear and the fact that cluster halos are not all precisely centered on their brightest galaxies. We also model the measured cluster shear profile as a sum of contributions from the brightest central galaxy, the cluster dark matter halo, and neighboring halos. We infer the relations between mean cluster virial mass and optical richness and luminosity over two orders of magnitude in cluster mass; the virial mass at fixed richness or luminosity is determined with a precision of {approx} 13% including both statistical and systematic errors. We also constrain the halo concentration parameter and halo bias as a function of cluster mass; both are in good agreement with predictions from N-body simulations of LCDM models. The methods employed here will be applicable to deeper, wide-area optical surveys that aim to constrain the nature of the dark energy, such as the Dark Energy Survey, the Large Synoptic Survey Telescope and space-based surveys.

  9. Hubble Space Telescope Combined Strong and Weak Lensing Analysis of the CLASH Sample: Mass and Magnification Models and Systematic Uncertainties

    CERN Document Server

    Zitrin, Adi; Merten, Julian; Melchior, Peter; Meneghetti, Massimo; Koekemoer, Anton; Coe, Dan; Maturi, Matteo; Bartelmann, Matthias; Postman, Marc; Umetsu, Keiichi; Seidel, Gregor; Sendra, Irene; Broadhurst, Tom; Balestra, Italo; Biviano, Andrea; Grillo, Claudio; Mercurio, Amata; Nonino, Mario; Rosati, Piero; Bradley, Larry; Carrasco, Mauricio; Donahue, Megan; Ford, Holland; Frye, Brenda L; Moustakas, John

    2014-01-01

    [ABRIDGED] We present results from an HST lensing analysis of the complete Cluster Lensing And Supernova survey with Hubble (CLASH) cluster sample. We identify various new multiple-images previously undiscovered, allowing improved or first constraints on the cluster inner mass distributions and profiles. We combine these strong-lensing constraints with weak lensing shape measurements within the HST FOV to jointly constrain the mass distributions. The analysis is performed in two different common parameterizations (one adopts light-traces-mass for both galaxies and dark matter while the other adopts an analytical, elliptical NFW form for the dark matter), to provide a better assessment of the underlying systematics - which is most important for deep lensing surveys such as CLASH and the Hubble Frontier Fields, especially when studying high-redshift magnified objects. We find that the typical (median), relative systematic differences throughout the central FOV are $\\sim40\\%$ in the (dimensionless) mass density,...

  10. Herschel-ATLAS/GAMA: SDSS cross-correlation induced by weak lensing

    CERN Document Server

    González-Nuevo, J; Negrello, M; Danese, L; De Zotti, G; Amber, S; Baes, M; Bland-Hawthorn, J; Bourne, N; Brough, S; Bussmann, R S; Cai, Z -Y; Cooray, A; Dunne, L; Dye, S; Eales, S; Ibar, E; Ivison, R; Liske, J; Loveday, J; Maddox, S; Michałowski, M J; Schneider, M D; Scott, D; Smith, M W L; Valiante, E; Xia, J -Q

    2014-01-01

    We report a highly significant ($>10\\sigma$) spatial correlation between galaxies with $S_{350\\mu\\rm m}\\ge 30\\,$mJy detected in the equatorial fields of the \\textsl{Herschel} Astrophysical Terahertz Large Area Survey (H-ATLAS) with estimated redshifts $\\gtrsim 1.5$, and SDSS or GAMA galaxies at $0.2\\le z\\le 0.6$. The significance of the cross-correlation is much higher than those reported so far for samples with non-overlapping redshift distributions selected in other wavebands. Extensive, realistic simulations of clustered sub-mm galaxies amplified by foreground structures confirm that the cross-correlation is explained by weak gravitational lensing ($\\mu<2$). The simulations also show that the measured amplitude and range of angular scales of the signal are larger than can be accounted for by galaxy-galaxy weak lensing. However, for scales $\\lesssim 2\\,$arcmin, the signal can be reproduced if SDSS/GAMA galaxies act as signposts of galaxy groups/clusters with halo masses in the range ~$10^{13.2}$--$10^{14...

  11. LoCuSS: Weak-lensing mass calibration of galaxy clusters

    CERN Document Server

    Okabe, Nobuhiro

    2015-01-01

    We present weak-lensing mass measurements of 50 X-ray luminous galaxy clusters at $0.15\\le z\\le0.3$, based on high quality observations with Suprime-Cam mounted on the 8.2-m Subaru telescope. We pay close attention to possible systematic biases, aiming to control them at the $\\lt4$ per cent level. The dominant source of systematic bias in weak-lensing measurements of the mass of individual galaxy clusters is contamination of background galaxy catalogues by faint cluster and foreground galaxies. We extend our conservative method for selecting background galaxies with $(V-i')$ colours redder than the red sequence of cluster members to use a colour-cut that depends on cluster-centric radius. This allows us to define background galaxy samples that suffer $\\le1$ per cent contamination, and comprise $13$ galaxies per square arcminute. Thanks to the purity of our background galaxy catalogue, the largest systematic in our measurement is a shape measurement bias of $3$ per cent, that we measure using custom-made simul...

  12. Stacking weak lensing signals of SZ clusters to constrain cluster physics

    CERN Document Server

    Sealfon, C; Verde, L; Jimenez, Raul; Sealfon, Carolyn; Verde, Licia

    2006-01-01

    We show how to place constraints on cluster physics by stacking the weak lensing signals from multiple clusters found through the Sunyaev-Zeldovich (SZ) effect. For a survey that covers about 200 sq. deg. both in SZ and weak lensing observations, the slope and amplitude of the mass vs. SZ luminosity relation can be measured with few percent error for clusters at z~0.5. This can be used to constrain cluster physics, such as the nature of feedback. For example, we can distinguish a pre-heated model from a model with a decreased accretion rate at more than 5sigma. The power to discriminate among different non-gravitational processes in the ICM becomes even stronger if we use the central Compton parameter y_0, which could allow one to distinguish between models with pre-heating, SN feedback and AGN feedback, for example, at more than 5sigma. Measurement of these scaling relations as a function of redshift makes it possible to directly observe e.g., the evolution of the hot gas in clusters. With this approach the ...

  13. A weak lensing view of the downsizing of star-forming galaxies

    CERN Document Server

    Utsumi, Yousuke; Dell'Antonio, Ian P; Kamata, Yukiko; Kawanomoto, Satoshi; Koike, Michitaro; Komiyama, Yutaka; Koshida, Shintaro; Mineo, Sogo; Miyazaki, Satoshi; Sakurai, Jyunya; Tait, Philip J; Terai, Tsuyoshi; Tomono, Daigo; Usuda, Tomonori; Yamada, Yoshihiko; Zahid, Harus J

    2016-01-01

    We describe a weak lensing view of the downsizing of star forming galaxies based on cross correlating a weak lensing ($\\kappa$) map with a predicted map constructed from a redshift survey. Moderately deep and high resolution images with Subaru/Hyper Suprime-Cam covering the 4 deg^2 DLS F2 field provide a $\\kappa$ map with 1 arcmin resolution. A dense complete redshift survey of the F2 field including 12,705 galaxies with $R\\leq20.6$ is the basis for construction of the predicted map. The zero-lag cross-correlation between the \\kappa and predicted maps is significant at the $30\\sigma$ level. The width of the cross-correlation peak is comparable with the angular scale of rich cluster at $z\\sim0.3$, the median depth of the redshift survey. Slices of the predicted map in $\\delta{z} = 0.05$ redshift bins enable exploration of the impact of structure as a function of redshift. The zero-lag normalised cross-correlation has significant local maxima at redshifts coinciding with known massive X-ray clusters. Even in sl...

  14. Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps

    CERN Document Server

    Clerkin, L; Manera, M; Lahav, O; Abdalla, F; Amara, A; Bacon, D; Chang, C; Gaztañaga, E; Hawken, A; Jain, B; Joachimi, B; Vikram, V; Abbott, T; Allam, S; Armstrong, R; Benoit-Lévy, A; Bernstein, G M; Bertin, E; Brooks, D; Burk, D L; Rosell, A Carnero; Kind, M Carrasco; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; Desai, S; Diehl, H T; Dietrich, J P; Eifler, T F; Evrard, A E; Flaugher, B; Fosalba, P; Frieman, J; Gerdes, D W; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kent, S; Kuehn, K; Kuropatkin, N; Lima, M; Melchior, P; Miquel, R; Nord, B; Plazas, A A; Romer, A K; Sanchez, E; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Santos, M Soares; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Walker, A R

    2016-01-01

    It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence (kappa_WL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the Counts in Cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey (DES) Science Verification data over 139 deg^2. We test whether the underlying density contrast is well described by a lognormal distribution for the galaxies, the convergence and their joint PDF. We confirm that the galaxy density contrast distribution is well modeled by a lognormal PDF convolved with Poisson noise at angular scales from 10-40 arcmin (corresponding to physical scales of 3-10 Mpc). We note that as kappa_WL is a weighted sum of the mass fluctuations along the line of sight, its PDF is expected to be only approximately lognormal. We find that the kappa_WL d...

  15. Galaxy bias from the Dark Energy Survey Science Verification data: combining galaxy density maps and weak lensing maps

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; Pujol, A.; Gaztañaga, E.; Amara, A.; Réfrégier, A.; Bacon, D.; Becker, M. R.; Bonnett, C.; Carretero, J.; Castander, F. J.; Crocce, M.; Fosalba, P.; Giannantonio, T.; Hartley, W.; Jarvis, M.; Kacprzak, T.; Ross, A. J.; Sheldon, E.; Troxel, M. A.; Vikram, V.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Kind, M. Carrasco; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.

    2016-04-15

    We measure the redshift evolution of galaxy bias from a magnitude-limited galaxy sample by combining the galaxy density maps and weak lensing shear maps for a $\\sim$116 deg$^{2}$ area of the Dark Energy Survey (DES) Science Verification data. This method was first developed in Amara et al. (2012) and later re-examined in a companion paper (Pujol et al., in prep) with rigorous simulation tests and analytical treatment of tomographic measurements. In this work we apply this method to the DES SV data and measure the galaxy bias for a magnitude-limited galaxy sample. We find the galaxy bias and 1$\\sigma$ error bars in 4 photometric redshift bins to be 1.33$\\pm$0.18 (z=0.2-0.4), 1.19$\\pm$0.23 (z=0.4-0.6), 0.99$\\pm$0.36 ( z=0.6-0.8), and 1.66$\\pm$0.56 (z=0.8-1.0). These measurements are consistent at the 1-2$\\sigma$ level with mea- surements on the same dataset using galaxy clustering and cross-correlation of galaxies with CMB lensing. In addition, our method provides the only $\\sigma_8$-independent constraint among the three. We forward-model the main observational effects using mock galaxy catalogs by including shape noise, photo-z errors and masking effects. We show that our bias measurement from the data is consistent with that expected from simulations. With the forthcoming full DES data set, we expect this method to provide additional constraints on the galaxy bias measurement from more traditional methods. Furthermore, in the process of our measurement, we build up a 3D mass map that allows further exploration of the dark matter distribution and its relation to galaxy evolution.

  16. Galaxy bias from the Dark Energy Survey Science Verification data: combining galaxy density maps and weak lensing maps

    Science.gov (United States)

    Chang, C.; Pujol, A.; Gaztañaga, E.; Amara, A.; Réfrégier, A.; Bacon, D.; Becker, M. R.; Bonnett, C.; Carretero, J.; Castander, F. J.; Crocce, M.; Fosalba, P.; Giannantonio, T.; Hartley, W.; Jarvis, M.; Kacprzak, T.; Ross, A. J.; Sheldon, E.; Troxel, M. A.; Vikram, V.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Rosell, A. Carnero; Kind, M. Carrasco; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Mohr, J. J.; Nichol, R. C.; Nord, B.; Ogando, R.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.

    2016-07-01

    We measure the redshift evolution of galaxy bias for a magnitude-limited galaxy sample by combining the galaxy density maps and weak lensing shear maps for a ˜116 deg2 area of the Dark Energy Survey (DES) Science Verification (SV) data. This method was first developed in Amara et al. and later re-examined in a companion paper with rigorous simulation tests and analytical treatment of tomographic measurements. In this work we apply this method to the DES SV data and measure the galaxy bias for a i < 22.5 galaxy sample. We find the galaxy bias and 1σ error bars in four photometric redshift bins to be 1.12 ± 0.19 (z = 0.2-0.4), 0.97 ± 0.15 (z = 0.4-0.6), 1.38 ± 0.39 (z = 0.6-0.8), and 1.45 ± 0.56 (z = 0.8-1.0). These measurements are consistent at the 2σ level with measurements on the same data set using galaxy clustering and cross-correlation of galaxies with cosmic microwave background lensing, with most of the redshift bins consistent within the 1σ error bars. In addition, our method provides the only σ8 independent constraint among the three. We forward model the main observational effects using mock galaxy catalogues by including shape noise, photo-z errors, and masking effects. We show that our bias measurement from the data is consistent with that expected from simulations. With the forthcoming full DES data set, we expect this method to provide additional constraints on the galaxy bias measurement from more traditional methods. Furthermore, in the process of our measurement, we build up a 3D mass map that allows further exploration of the dark matter distribution and its relation to galaxy evolution.

  17. Dark Energy Survey Year 1 Results: Redshift distributions of the weak lensing source galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hoyle, B.; et al.

    2017-08-04

    We describe the derivation and validation of redshift distribution estimates and their uncertainties for the galaxies used as weak lensing sources in the Dark Energy Survey (DES) Year 1 cosmological analyses. The Bayesian Photometric Redshift (BPZ) code is used to assign galaxies to four redshift bins between z=0.2 and 1.3, and to produce initial estimates of the lensing-weighted redshift distributions $n^i_{PZ}(z)$ for bin i. Accurate determination of cosmological parameters depends critically on knowledge of $n^i$ but is insensitive to bin assignments or redshift errors for individual galaxies. The cosmological analyses allow for shifts $n^i(z)=n^i_{PZ}(z-\\Delta z^i)$ to correct the mean redshift of $n^i(z)$ for biases in $n^i_{\\rm PZ}$. The $\\Delta z^i$ are constrained by comparison of independently estimated 30-band photometric redshifts of galaxies in the COSMOS field to BPZ estimates made from the DES griz fluxes, for a sample matched in fluxes, pre-seeing size, and lensing weight to the DES weak-lensing sources. In companion papers, the $\\Delta z^i$ are further constrained by the angular clustering of the source galaxies around red galaxies with secure photometric redshifts at 0.15

  18. The dark matter distribution of merging galaxy cluster PLCKG287.0+32.9 by weak lensing

    Science.gov (United States)

    Finner, Kyle; Jee, James; Dawson, William; Golovich, Nathan; Gruen, Daniel; Lemaux, Brian; Wittman, David M.

    2017-01-01

    The merging galaxy cluster, PLCKG287.0+32.9, is the second most significant detection of the Planck SZ survey. As part of a sample of galaxy clusters being investigated by the Merging Cluster Collaboration ($MC^2$), PLCKG287.0+32.9 is studied to further constrain dark matter properties and improve our understanding of galaxy cluster physics. The galaxy cluster hosts two megaparsec sized radio relics and a radio halo, evidence of its merger nature. The radio relics are located approximately one and three megaparsecs from the X-ray peak, requiring a somewhat complex merging scenario. A detailed study of the dark matter distribution will provide key information to constrain the merger scenario. With Subaru g- and r-band data, we perform a weak-lensing analysis and determine the dark matter distribution of the merging galaxy cluster. We fit a 2-parameter NFW profile to the tangential shear to quantify the mass. We find that the dark matter peak is aligned with the luminosity peak. Using the dark matter mass distribution, we discuss the significance of the merging constituents and their relation to the luminous emissions.

  19. Consequences of CCD imperfections for cosmology determined by weak lensing surveys: From laboratory measurements to cosmological parameter bias

    CERN Document Server

    Okura, Yuki; May, Morgan; Plazas, Andrés A; Tamagawa, Toru

    2016-01-01

    Weak gravitational lensing causes subtle changes in the apparent shapes of galaxies due to the bending of light by the gravity of foreground masses. By measuring the shapes of large numbers of galaxies (millions in recent surveys, up to tens of billions in future surveys) we can infer the parameters that determine cosmology. Imperfections in the detectors used to record images of the sky can introduce changes in the apparent shape of galaxies, which in turn can bias the inferred cosmological parameters. In this paper we consider the effect of two widely discussed sensor imperfections: tree-rings, due to impurity gradients which cause transverse electric fields in the Charge-Coupled Devices (CCD), and pixel-size variation, due to periodic CCD fabrication errors. These imperfections can be observed when the detectors are subject to uniform illumination (flat field images). We develop methods to determine the spurious shear and convergence (due to the imperfections) from the flat-field images. We calculate how t...

  20. A Weak Lensing View of the Downsizing of Star-forming Galaxies

    Science.gov (United States)

    Utsumi, Yousuke; Geller, Margaret J.; Dell'Antonio, Ian P.; Kamata, Yukiko; Kawanomoto, Satoshi; Koike, Michitaro; Komiyama, Yutaka; Koshida, Shintaro; Mineo, Sogo; Miyazaki, Satoshi; Sakurai, Junya; Tait, Philip J.; Terai, Tsuyoshi; Tomono, Daigo; Usuda, Tomonori; Yamada, Yoshihiko; Zahid, Harus J.

    2016-12-01

    We describe a weak lensing view of the downsizing of star-forming galaxies based on cross-correlating a weak lensing (κ) map with a predicted map constructed from a redshift survey. Moderately deep and high-resolution images with Subaru/Hyper Suprime-Cam covering the 4 {\\deg }2 DLS F2 field provide a κ map with 1 arcmin resolution. A dense complete redshift survey of the F2 field including 12,705 galaxies with R≤slant 20.6 is the basis for construction of the predicted map. The zero-lag cross-correlation between the κ and predicted maps is significant at the 30σ level. The width of the cross-correlation peak is comparable to the angular scale of rich clusters at z˜ 0.3, the median depth of the redshift survey. Slices of the predicted map in δ z=0.05 redshift bins enable exploration of the impact of structure as a function of redshift. The zero-lag normalized cross-correlation has significant local maxima at redshifts coinciding with known massive X-ray clusters. Even in slices where there are no known massive clusters, there is a significant signal in the cross-correlation originating from lower mass groups that trace the large-scale of the universe. Spectroscopic {D}n4000 measurements enable division of the sample into star-forming and quiescent populations. In regions surrounding massive clusters of galaxies, the significance of the cross-correlation with maps based on star-forming galaxies increases with redshift from 5σ at z = 0.3 to 7σ at z=0.5; the fractional contribution of the star-forming population to the total cross-correlation signal also increases with redshift. This weak lensing view is consistent with the downsizing picture of galaxy evolution established from other independent studies. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  1. Parameter constraints from weak-lensing tomography of galaxy shapes and cosmic microwave background fluctuations

    Science.gov (United States)

    Merkel, Philipp M.; Schäfer, Björn Malte

    2017-08-01

    Recently, it has been shown that cross-correlating cosmic microwave background (CMB) lensing and three-dimensional (3D) cosmic shear allows to considerably tighten cosmological parameter constraints. We investigate whether similar improvement can be achieved in a conventional tomographic setup. We present Fisher parameter forecasts for a Euclid-like galaxy survey in combination with different ongoing and forthcoming CMB experiments. In contrast to a fully 3D analysis, we find only marginal improvement. Assuming Planck-like CMB data, we show that including the full covariance of the combined CMB and cosmic shear data improves the dark energy figure of merit (FOM) by only 3 per cent. The marginalized error on the sum of neutrino masses is reduced at the same level. For a next generation CMB satellite mission such as Prism, the predicted improvement of the dark energy FOM amounts to approximately 25 per cent. Furthermore, we show that the small improvement is contrasted by an increased bias in the dark energy parameters when the intrinsic alignment of galaxies is not correctly accounted for in the full covariance matrix.

  2. Detection of universality of dark matter profile from Subaru weak lensing measurements of 50 massive clusters

    CERN Document Server

    Niikura, Hiroko; Okabe, Nobuhiro; Martino, Rossella; Takahashi, Ryuichi

    2015-01-01

    We develop a novel method of measuring the lensing distortion profiles of clusters with stacking the scaled amplitudes of background galaxy ellipticities as a function of the scaled centric radius according to the NFW prediction of each cluster, based on the assumption that the different clusters in a sample follow the universal NFW profile. First we demonstrate the feasibility of this method using both the analytical NFW model and simulated halos in high-resolution $N$-body simulations. We then apply, as a proof of concept, this method to the Subaru weak lensing data and the XMM/Chandra X-ray observables for a sample of 50 massive clusters in the redshift range $0.15\\le z\\le 0.3$, where their halo masses range over an order of magnitude. To estimate the NFW parameters of each cluster, we use the halo mass proxy relation of X-ray observables, based on either the hydrostatic equilibrium or the gas mass, and then infer the halo concentration from the model $c(M)$ relation. We evaluate a performance of the NFW s...

  3. Information content of weak lensing bispectrum: including the non-Gaussian error covariance matrix

    CERN Document Server

    Kayo, Issha; Jain, Bhuvnesh

    2013-01-01

    We address a long-standing problem, how can we extract information in the non-Gaussian regime of weak lensing surveys, by accurate modeling of all relevant covariances between the power spectra and bispectra. We use 1000 ray-tracing simulation realizations for a Lambda-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, which extend to 6-point correlation functions. We include a new contribution arising from coupling of the lensing Fourier modes with large-scale mass fluctuations on scales comparable with the survey region via halo bias theory, which we call the halo sample variance (HSV) effect. We show that the model predictions are in excellent agreement with the simulation results for the power spectrum and bispectrum covariances. The HSV effect gives a dominant contribution to the covariances at multipoles l > 10^3, which arise from massive halos with masses of about 10^14 solar masses and at rel...

  4. Cosmology Constraints from the Weak Lensing Peak Counts and the Power Spectrum in CFHTLenS

    CERN Document Server

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

    2014-01-01

    Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg^2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters Omega_m, sigma_8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build an emulator that interpolates the power spectrum and the peak counts to an accuracy of <= 5%, and compute the likelihood in the three-dimensional parameter space (Omega_m, sigma_8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales...

  5. Towards Precision LSST Weak-Lensing Measurement - I: Impacts of Atmospheric Turbulence and Optical Aberration

    CERN Document Server

    Tyson, M James Jee And J Anthony

    2010-01-01

    The weak-lensing science of the LSST project drives the need to carefully model and separate the instrumental artifacts from the intrinsic lensing signal. The dominant source of the systematics for all ground based telescopes is the spatial correlation of the PSF modulated by both atmospheric turbulence and optical aberrations. In this paper, we present a full FOV simulation of the LSST images by modeling both the atmosphere and the telescope optics with the most current data for the telescope specifications and the environment. To simulate the effects of atmospheric turbulence, we generated six-layer phase screens with the parameters estimated from the on-site measurements. For the optics, we combined the ray-tracing tool ZEMAX and our simulated focal plane data to introduce realistic aberrations and focal plane height fluctuations. Although this expected flatness deviation for LSST is small compared with that of other existing cameras, the fast f-ratio of the LSST optics makes this focal plane flatness vari...

  6. The Weak Lensing Signal and the Clustering of BOSS Galaxies: Cosmological Constraints

    CERN Document Server

    More, Surhud; Mandelbaum, Rachel; Takada, Masahiro; Spergel, David; Brownstein, Joel; Schneider, Donald P

    2014-01-01

    We perform a joint analysis of the abundance, the clustering and the galaxy-galaxy lensing signal of galaxies from Data Release 11 of the Sloan Digital Sky Survey III Baryon Oscillation Spectroscopic Survey. We fit halo occupation parameters and cosmological parameters ($\\Omega_m$ and $\\sigma_8$) to both of these observables simultaneously, and thus break the degeneracy between galaxy bias and cosmology. The cosmological analysis is the first of its kind to be performed at a redshift as high as 0.53. We present measurements of the clustering signal of galaxies by utilizing various stellar mass threshold samples. The galaxy-galaxy weak lensing signal is obtained by using the shape catalog of background galaxies from the Canada France Hawaii Telescope Legacy Survey, which was made publicly available by the CFHTLenS collaboration, with an area overlap of about 100 deg$^2$. We analyze these measurements in the framework of the halo model. Adopting a flat {\\Lambda}CDM cosmology with priors on $\\Omega_bh^2$, $n_s$ ...

  7. Cosmological parameters from weak lensing power spectrum and bispectrum tomography: including the non-Gaussian errors

    CERN Document Server

    Kayo, Issha

    2013-01-01

    We re-examine a genuine power of weak lensing bispectrum tomography for constraining cosmological parameters, when combined with the power spectrum tomography, based on the Fisher information matrix formalism. To account for the full information at two- and three-point levels, we include all the power spectrum and bispectrum information built from all-available combinations of tomographic redshift bins, multipole bins and different triangle configurations over a range of angular scales (up to lmax=2000 as our fiducial choice). For the parameter forecast, we use the halo model approach in Kayo, Takada & Jain (2013) to model the non-Gaussian error covariances as well as the cross-covariance between the power spectrum and the bispectrum, including the halo sample variance or the nonlinear version of beat-coupling. We find that adding the bispectrum information leads to about 60% improvement in the dark energy figure-of-merit compared to the lensing power spectrum tomography alone, for three redshift-bin tomo...

  8. Scaling Relations and Overabundance of Massive Clusters at z>~1 from Weak-Lensing Studies with HST

    CERN Document Server

    Jee, M J; Hoekstra, H; Perlmutter, S; Rosati, P; Brodwin, M; Suzuki, N; Koester, B; Postman, M; Lubin, L; Meyers, J; Stanford, S A; Barbary, K; Barrientos, F; Eisenhardt, P; Ford, H C; Gilbank, D G; Gladders, M D; Gonzalez, A; Harris, D W; Huang, X; Lidman, C; Rykoff, E S; Rubin, D; Spadafora, A L

    2011-01-01

    We present weak gravitational lensing analysis of 22 high-redshift (z >~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 LambdaCDM 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 >~ 1. For the power law slope of the M-TX relation (M propto T^{\\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 s...

  9. The topology of weak lensing field in the neighborhood of MS1054-03

    CERN Document Server

    Sato, J; Futamase, T; Yamada, T; Sato, Jun'ichi; Umetsu, Keiichi; Futamase, Toshifumi; Yamada, Toru

    2003-01-01

    We report the first measurement of genus curves for the two-dimensional mass map in the neighborhood of rich, X-ray luminous galaxy cluster MS1054-03 at z=0.83, reconstructed from weak lensing data obtained by Suprime-Cam on the prime focus of 8.2m Subaru telescope. We find that the genus curve measured in the whole survey field deviates from that expected from a random Gaussian field. We show that this non-Gaussianity is induced by the rich cluster in this region, and that the genus curve for the region without the cluster is consistent with the prediction for a random Gaussian field. The results demonstrate the feasibility of the genus statistics to examine the non-Gaussianity due to the large scale structures and to probe the statistical properties of the large scale clustering.

  10. CODEX weak lensing: concentration of galaxy clusters at z ˜ 0.5

    Science.gov (United States)

    Cibirka, N.; Cypriano, E. S.; Brimioulle, F.; Gruen, D.; Erben, T.; van Waerbeke, L.; Miller, L.; Finoguenov, A.; Kirkpatrick, C.; Henry, J. Patrick; Rykoff, E.; Rozo, E.; Dupke, R.; Kneib, J.-P.; Shan, H.; Spinelli, P.

    2017-06-01

    We present a stacked weak-lensing analysis of 27 richness selected galaxy clusters at 0.40 ≤ z ≤ 0.62 in the COnstrain Dark Energy with X-ray galaxy clusters (CODEX) survey. The fields were observed in five bands with the Canada-France-Hawaii Telescope (CFHT). We measure the stacked surface mass density profile with a 14σ significance in the radial range 0.1 CODEX sample. Comparing our best-fitting values for M200c and c200c with other observational surveys at different redshifts, we find no evidence for evolution in the concentration-mass relation, though it could be mitigated by particular selection functions. Similar to previous studies investigating the X-ray luminosity-mass relation, our data suggest a lower evolution than expected from self-similarity.

  11. Integrated approach to cosmology: Combining CMB, large-scale structure and weak lensing

    CERN Document Server

    Nicola, Andrina; Amara, Adam

    2016-01-01

    Recent observational progress has led to the establishment of the standard $\\Lambda$CDM model for cosmology. This development is based on different cosmological probes that are usually combined through their likelihoods at the latest stage in the analysis. We implement here an integrated scheme for cosmological probes, which are combined in a common framework starting at the map level. This treatment is necessary as the probes are generally derived from overlapping maps and are thus not independent. It also allows for a thorough test of the cosmological model and of systematics through the consistency of different physical tracers. As a first application, we combine current measurements of the Cosmic Microwave Background (CMB) from the Planck satellite, and galaxy clustering and weak lensing from SDSS. We consider the spherical harmonic power spectra of these probes including all six auto- and cross-correlations along with the associated full gaussian covariance matrix. This provides an integrated treatment o...

  12. Spherical particle sedimenting in weakly viscoelastic shear flow

    CERN Document Server

    Einarsson, J

    2016-01-01

    We consider the dynamics of a small spherical particle driven through an unbounded viscoelastic shear flow by an external force. We give analytical solutions to both the mobility problem (velocity of forced particle) and the resistance problem (force on fixed particle), valid to second order in the dimensionless Deborah and Weissenberg numbers, which represent the elastic relaxation time of the fluid relative to the rate of translation and the imposed shear rate. We find a shear-induced lift at $O({\\rm Wi})$, a modified drag at $O({\\rm De}^2)$ and $O({\\rm Wi}^2)$, and a second lift that is orthogonal to the first, at $O({\\rm Wi}^2)$. The relative importance of these effects depends strongly on the orientation of the forcing relative to the shear. We discuss how these forces affect the terminal settling velocity in an inclined shear flow. We also describe a new basis set of symmetric Cartesian tensors, and demonstrate how they enable general tensorial perturbation calculations such as the present theory. In pa...

  13. Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps

    Energy Technology Data Exchange (ETDEWEB)

    Clerkin, L.; Kirk, D.; Manera, M.; Lahav, O.; Abdalla, F.; Amara, A.; Bacon, D.; Chang, C.; Gaztañaga, E.; Hawken, A.; Jain, B.; Joachimi, B.; Vikram, V.; Abbott, T.; Allam, S.; Armstrong, R.; Benoit-Lévy, A.; Bernstein, G. M.; Bernstein, R. A.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Carrasco Kind, M.; Crocce, M.; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Melchior, P.; Miquel, R.; Nord, B.; Plazas, A. A.; Romer, A. K.; Roodman, A.; Sanchez, E.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Walker, A. R.

    2016-08-30

    It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence (kappa_WL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the Counts in Cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey (DES) Science Verification data over 139 deg^2. We test whether the underlying density contrast is well described by a lognormal distribution for the galaxies, the convergence and their joint PDF. We confirm that the galaxy density contrast distribution is well modeled by a lognormal PDF convolved with Poisson noise at angular scales from 10-40 arcmin (corresponding to physical scales of 3-10 Mpc). We note that as kappa_WL is a weighted sum of the mass fluctuations along the line of sight, its PDF is expected to be only approximately lognormal. We find that the kappa_WL distribution is well modeled by a lognormal PDF convolved with Gaussian shape noise at scales between 10 and 20 arcmin, with a best-fit chi^2/DOF of 1.11 compared to 1.84 for a Gaussian model, corresponding to p-values 0.35 and 0.07 respectively, at a scale of 10 arcmin. Above 20 arcmin a simple Gaussian model is sufficient. The joint PDF is also reasonably fitted by a bivariate lognormal. As a consistency check we compare the variances derived from the lognormal modelling with those directly measured via CiC. Our methods are validated against maps from the MICE Grand Challenge N-body simulation.

  14. Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps

    Energy Technology Data Exchange (ETDEWEB)

    Clerkin, L.; et al.

    2016-05-06

    It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence (kappa_WL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the Counts in Cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey (DES) Science Verification data over 139 deg^2. We test whether the underlying density contrast is well described by a lognormal distribution for the galaxies, the convergence and their joint PDF. We confirm that the galaxy density contrast distribution is well modeled by a lognormal PDF convolved with Poisson noise at angular scales from 10-40 arcmin (corresponding to physical scales of 3-10 Mpc). We note that as kappa_WL is a weighted sum of the mass fluctuations along the line of sight, its PDF is expected to be only approximately lognormal. We find that the kappa_WL distribution is well modeled by a lognormal PDF convolved with Gaussian shape noise at scales between 10 and 20 arcmin, with a best-fit chi^2/DOF of 1.11 compared to 1.84 for a Gaussian model, corresponding to p-values 0.35 and 0.07 respectively, at a scale of 10 arcmin. Above 20 arcmin a simple Gaussian model is sufficient. The joint PDF is also reasonably fitted by a bivariate lognormal. As a consistency check we compare the variances derived from the lognormal modelling with those directly measured via CiC. Our methods are validated against maps from the MICE Grand Challenge N-body simulation.

  15. Testing the lognormality of the galaxy and weak lensing convergence distributions from Dark Energy Survey maps

    Science.gov (United States)

    Clerkin, L.; Kirk, D.; Manera, M.; Lahav, O.; Abdalla, F.; Amara, A.; Bacon, D.; Chang, C.; Gaztañaga, E.; Hawken, A.; Jain, B.; Joachimi, B.; Vikram, V.; Abbott, T.; Allam, S.; Armstrong, R.; Benoit-Lévy, A.; Bernstein, G. M.; Bernstein, R. A.; Bertin, E.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Carrasco Kind, M.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Melchior, P.; Miquel, R.; Nord, B.; Plazas, A. A.; Romer, A. K.; Roodman, A.; Sanchez, E.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Walker, A. R.

    2017-04-01

    It is well known that the probability distribution function (PDF) of galaxy density contrast is approximately lognormal; whether the PDF of mass fluctuations derived from weak lensing convergence (κWL) is lognormal is less well established. We derive PDFs of the galaxy and projected matter density distributions via the counts-in-cells (CiC) method. We use maps of galaxies and weak lensing convergence produced from the Dark Energy Survey Science Verification data over 139 deg2. We test whether the underlying density contrast is well described by a lognormal distribution for the galaxies, the convergence and their joint PDF. We confirm that the galaxy density contrast distribution is well modelled by a lognormal PDF convolved with Poisson noise at angular scales from 10 to 40 arcmin (corresponding to physical scales of 3-10 Mpc). We note that as κWL is a weighted sum of the mass fluctuations along the line of sight, its PDF is expected to be only approximately lognormal. We find that the κWL distribution is well modelled by a lognormal PDF convolved with Gaussian shape noise at scales between 10 and 20 arcmin, with a best-fitting χ2/dof of 1.11 compared to 1.84 for a Gaussian model, corresponding to p-values 0.35 and 0.07, respectively, at a scale of 10 arcmin. Above 20 arcmin a simple Gaussian model is sufficient. The joint PDF is also reasonably fitted by a bivariate lognormal. As a consistency check, we compare the variances derived from the lognormal modelling with those directly measured via CiC. Our methods are validated against maps from the MICE Grand Challenge N-body simulation.

  16. Weak lensing calibration of mass bias in the REFLEX+BCS X-ray galaxy cluster catalogue

    Science.gov (United States)

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

    2017-04-01

    The use of large, X-ray-selected Galaxy cluster catalogues for cosmological analyses requires a thorough understanding of the X-ray mass estimates. Weak gravitational lensing is an ideal method to shed light on such issues, due to its insensitivity to the cluster dynamical state. We perform a weak lensing calibration of 166 galaxy clusters from the REFLEX and BCS cluster catalogue and compare our results to the X-ray masses based on scaled luminosities from that catalogue. To interpret the weak lensing signal in terms of cluster masses, we compare the lensing signal to simple theoretical Navarro-Frenk-White models and to simulated cluster lensing profiles, including complications such as cluster substructure, projected large-scale structure and Eddington bias. We find evidence of underestimation in the X-ray masses, as expected, with = 0.75 ± 0.07 stat. ±0.05 sys. for our best-fitting model. The biases in cosmological parameters in a typical cluster abundance measurement that ignores this mass bias will typically exceed the statistical errors.

  17. Cosmological constraints with weak-lensing peak counts and second-order statistics in a large-field survey

    Science.gov (United States)

    Peel, Austin; Lin, Chieh-An; Lanusse, François; Leonard, Adrienne; Starck, Jean-Luc; Kilbinger, Martin

    2017-03-01

    Peak statistics in weak-lensing maps access the non-Gaussian information contained in the large-scale distribution of matter in the Universe. They are therefore a promising complementary probe to two-point and higher-order statistics to constrain our cosmological models. Next-generation galaxy surveys, with their advanced optics and large areas, will measure the cosmic weak-lensing signal with unprecedented precision. To prepare for these anticipated data sets, we assess the constraining power of peak counts in a simulated Euclid-like survey on the cosmological parameters Ωm, σ8, and w0de. In particular, we study how Camelus, a fast stochastic model for predicting peaks, can be applied to such large surveys. The algorithm avoids the need for time-costly N-body simulations, and its stochastic approach provides full PDF information of observables. Considering peaks with a signal-to-noise ratio ≥ 1, we measure the abundance histogram in a mock shear catalogue of approximately 5000 deg2 using a multiscale mass-map filtering technique. We constrain the parameters of the mock survey using Camelus combined with approximate Bayesian computation, a robust likelihood-free inference algorithm. Peak statistics yield a tight but significantly biased constraint in the σ8-Ωm plane, as measured by the width ΔΣ8 of the 1σ contour. We find Σ8 = σ8(Ωm/ 0.27)α = 0.77-0.05+0.06 with α = 0.75 for a flat ΛCDM model. The strong bias indicates the need to better understand and control the model systematics before applying it to a real survey of this size or larger. We perform a calibration of the model and compare results to those from the two-point correlation functions ξ± measured on the same field. We calibrate the ξ± result as well, since its contours are also biased, although not as severely as for peaks. In this case, we find for peaks Σ8 = 0.76-0.03+0.02 with α = 0.65, while for the combined ξ+ and ξ- statistics the values are Σ8 = 0.76-0.01+0.02 and α = 0

  18. A new method to measure galaxy bias by combining the density and weak lensing fields

    Science.gov (United States)

    Pujol, Arnau; Chang, Chihway; Gaztañaga, Enrique; Amara, Adam; Refregier, Alexandre; Bacon, David J.; Carretero, Jorge; Castander, Francisco J.; Crocce, Martin; Fosalba, Pablo; Manera, Marc; Vikram, Vinu

    2016-10-01

    We present a new method to measure redshift-dependent galaxy bias by combining information from the galaxy density field and the weak lensing field. This method is based on the work of Amara et al., who use the galaxy density field to construct a bias-weighted convergence field κg. The main difference between Amara et al.'s work and our new implementation is that here we present another way to measure galaxy bias, using tomography instead of bias parametrizations. The correlation between κg and the true lensing field κ allows us to measure galaxy bias using different zero-lag correlations, such as / or /. Our method measures the linear bias factor on linear scales, under the assumption of no stochasticity between galaxies and matter. We use the Marenostrum Institut de Ciències de l'Espai (MICE) simulation to measure the linear galaxy bias for a flux-limited sample (i < 22.5) in tomographic redshift bins using this method. This article is the first that studies the accuracy and systematic uncertainties associated with the implementation of the method and the regime in which it is consistent with the linear galaxy bias defined by projected two-point correlation functions (2PCF). We find that our method is consistent with a linear bias at the per cent level for scales larger than 30 arcmin, while non-linearities appear at smaller scales. This measurement is a good complement to other measurements of bias, since it does not depend strongly on σ8 as do the 2PCF measurements. We will apply this method to the Dark Energy Survey Science Verification data in a follow-up article.

  19. The imprint of $f(R)$ gravity on weak gravitational lensing I: Connection between observables and large scale structure

    CERN Document Server

    Higuchi, Yuichi

    2016-01-01

    We study the effect of $f(R)$ gravity on the statistical properties of various large-scale structures which can be probed in weak gravitational lensing measurements. A set of ray-tracing simulations of gravitational lensing in $f(R)$ gravity enables us to explore cosmological information on (i) stacking analyses of weak lensing observables and (ii) peak statistics in reconstructed lensing mass maps. For the $f(R)$ model proposed by Hu & Sawicki, the measured lensing signals of dark matter haloes in the stacking analysis would show a $\\simlt10\\%$ difference between the standard $\\Lambda$CDM and the $f(R)$ model when the additional degree of freedom in $f(R)$ model would be $|f_{\\rm R0}|\\sim10^{-5}$. Among various large-scale structures to be studied in stacking analysis, troughs, i.e, underdensity regions in projected plane of foreground massive haloes, could be promising to constrain the model with $|f_{\\rm R0}|\\sim10^{-5}$, while stacking analysis around voids is found to be difficult to improve the cons...

  20. Intrinsic galaxy alignments from the 2SLAQ and SDSS surveys: luminosity and redshift scalings and implications for weak lensing surveys

    CERN Document Server

    Hirata, C M; Ishak, M; Seljak, U; Nichol, R; Pimbblet, K A; Ross, N P; Wake, D; Hirata, Christopher M.; Mandelbaum, Rachel; Ishak, Mustapha; Seljak, Uros; Nichol, Robert; Pimbblet, Kevin A.; Ross, Nicholas P.; Wake, David

    2007-01-01

    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 SDSS data. Here we present a more detailed characterization of this effect, which can cause anti-correlations between gravitational lensing shear and intrinsic ellipticity (GI correlations). This measurement uses 36278 Luminous Red Galaxies (LRGs) from the SDSS spectroscopic sample with 0.153sigma detections of the effect for all galaxy subsamples within the SDSS LRG sample; for the 2SLAQ sample, we find a 2sigma 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. We estimate contamination in the measurement of sigma_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...

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-09-28

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

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

    CERN Document Server

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

    2007-01-01

    We present measurements of the excess mass-to-light ratio (M/L) measured around MaxBCG galaxy clusters observed in the SDSS. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean \\Delta \\rho(r) = \\rho(r) - \\bar{\\rho} for clusters in bins of richness and optical luminosity. We also measure the excess ^{0.25}i-band luminosity density \\Delta l(r) = l(r) - \\bar{l}. For both mass and light, we de-project the profiles to produce 3D mass and light profiles over scales from 25 kpc/h to 22 Mpc/h. From these profiles we calculate the cumulative excess mass \\Delta M(r) and excess light \\Delta L(r) as a function of separation from the BCG. On small scales, where \\rho(r) >> \\bar{\\rho}, the integrated M/L profile may be interpreted as the cluster M/L. We find the (\\Delta M/\\Delta L)_{200}, the M/L within r_{200}, scales with cluster mass as a power law with index 0.33+/-0.02. On large scales, where \\rho(r) . We find /b^2_{ml} = 362+/-54 h measured in the ^{0.25}i-bandpass...

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

    CERN Document Server

    Sheldon, Erin S; 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

    2007-01-01

    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 ~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 lu...

  4. Evaluating the effect of stellar multiplicity on the PSF of space-based weak lensing surveys

    CERN Document Server

    Kuntzer, T; Meylan, G

    2016-01-01

    The next generation of space-based telescopes used for weak lensing surveys will require exquisite point spread function (PSF) determination. Previously negligible effects may become important in the reconstruction of the PSF, in part because of the improved spatial resolution. In this paper, we show that unresolved multiple star systems can affect the ellipticity and size of the PSF and that this effect is not cancelled even when using many stars in the reconstruction process. We estimate the error in the reconstruction of the PSF due to the binaries in the star sample both analytically and with image simulations for different PSFs and stellar populations. The simulations support our analytical finding that the error on the size of the PSF is a function of the multiple stars distribution and of the intrinsic value of the size of the PSF, i.e. if all stars were single. Similarly, the modification of each of the complex ellipticity components (e1,e2) depends on the distribution of multiple stars and on the int...

  5. From linear to non-linear scales: analytical and numerical predictions for the weak lensing convergence

    CERN Document Server

    Barber, A J; Valageas, P; Barber, Andrew J.; Munshi, Dipak; Valageas, Patrick

    2004-01-01

    Weak lensing convergence can be used directly to map and probe the dark mass distribution in the universe. Building on earlier studies, we recall how the statistics of the convergence field are related to the statistics of the underlying mass distribution, in particular to the many-body density correlations. We describe two model-independent approximations which provide two simple methods to compute the probability distribution function, pdf, of the convergence. We apply one of these to the case where the density field can be described by a log-normal pdf. Next, we discuss two hierarchical models for the high-order correlations which allow one to perform exact calculations and evaluate the previous approximations in such specific cases. Finally, we apply these methods to a very simple model for the evolution of the density field from linear to highly non-linear scales. Comparisons with the results obtained from numerical simulations, obtained from a number of different realizations, show excellent agreement w...

  6. Probe combination in large galaxy surveys : Application of Fisher information and Shannon entropy to weak lensing

    CERN Document Server

    Carron, Julien; Lilly, Simon

    2011-01-01

    This paper is aimed at developing a better understanding of the structure of the information that in contained in galaxy surveys, so as to find optimal ways to combine observables from such surveys. We first show how Jaynes' Maximal Entropy Principle allows us, in the general case, to express the Fisher information content of data sets in terms of the curvature of the Shannon entropy surface with respect to the relevant observables. This allows us to understand the Fisher information content of a data set, once a physical model is specified, independently of the specific way that the data will be processed, and without any assumptions of Gaussianity. This includes as a special case the standard Fisher matrix prescriptions for Gaussian variables widely used in the cosmological community, for instance for power spectra extraction. As an application of this approach, we evaluate the prospects of a joint analysis of weak lensing tracers up to second order in the shapes distortions, in the case that the noise in e...

  7. Weak lensing magnification in the Dark Energy Survey Science Verification Data

    CERN Document Server

    Garcia-Fernandez, M; Sevilla-Noarbe, I; Suchyta, E; Huff, E M; Gaztanaga, E; Aleksić, J; Ponce, R; Castander, F J; Hoyle, B; Abbott, T M C; Abdalla, F B; Allam, S; Annis, J; Benoit-Lévy, A; Bernstein, G M; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Eifler, T F; Evrard, A E; Fernandez, E; Flaugher, B; Fosalba, P; Frieman, J; García-Bellido, J; Gerdes, D W; Giannantonio, T; Gruen, D; Gruendl, R A; Gschwend, J; Gutierrez, G; James, D J; Jarvis, M; Kirk, D; Krause, E; Kuehn, K; Kuropatkin, N; Lahav, O; Lima, M; MacCrann, N; Maia, M A G; March, M; Marshall, J L; Melchior, P; Miquel, R; Mohr, J J; Plazas, A A; Romer, A K; Roodman, A; Rykoff, E S; Scarpine, V; Schubnell, M; Smith, R C; Soares-Santos, M; Sobreira, F; Tarle, G; Thomas, D; Walker, A R; Wester, W

    2016-01-01

    In this paper the effect of weak lensing magnification on galaxy number counts is studied by cross-correlating the positions of two galaxy samples, separated by redshift, using data from the Dark Energy Survey Science Verification dataset. The analysis is carried out for two photometrically-selected galaxy samples, with mean photometric redshifts in the $0.2 < z < 0.4$ and $0.7 < z < 1.0$ ranges, in the riz bands. A signal is detected with a $3.5\\sigma$ significance level in each of the bands tested, and is compatible with the magnification predicted by the $\\Lambda$CDM model. After an extensive analysis, it cannot be attributed to any known systematic effect. The detection of the magnification signal is robust to estimated uncertainties in the outlier rate of the pho- tometric redshifts, but this will be an important issue for use of photometric redshifts in magnification mesurements from larger samples. In addition to the detection of the magnification signal, a method to select the sample with ...

  8. The effect of detector nonlinearity on WFIRST PSF profiles for weak gravitational lensing measurements

    CERN Document Server

    Plazas, Andrés A; Kannawadi, Arun; Mandelbaum, Rachel; Rhodes, Jason D; Smith, Roger

    2016-01-01

    Weak gravitational lensing (WL) is one of the most powerful techniques to learn about the dark sector of the universe. To extract the WL signal from astronomical observations, galaxy shapes must be measured and corrected for the point spread function (PSF) of the imaging system with extreme accuracy. Future WL missions (such as the Wide-Field Infrared Survey Telescope, WFIRST) will use a family of hybrid nearinfrared CMOS detectors (HAWAII-4RG) that are untested for accurate WL measurements. Like all image sensors, these devices are subject to conversion gain nonlinearities (voltage response to collected photo-charge) that bias the shape and size of bright objects such as reference stars that are used in PSF determination. We study this type of detector nonlinearity (NL) and show how to derive requirements on it from WFIRST PSF size and ellipticity requirements. We simulate the PSF optical profiles expected for WFIRST and measure the fractional error in the PSF size and the absolute error in the PSF elliptici...

  9. Weak lensing magnification in the Dark Energy Survey Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Fernandez, M.; et al.

    2016-11-30

    In this paper the effect of weak lensing magnification on galaxy number counts is studied by cross-correlating the positions of two galaxy samples, separated by redshift, using data from the Dark Energy Survey Science Verification dataset. The analysis is carried out for two photometrically-selected galaxy samples, with mean photometric redshifts in the $0.2 < z < 0.4$ and $0.7 < z < 1.0$ ranges, in the riz bands. A signal is detected with a $3.5\\sigma$ significance level in each of the bands tested, and is compatible with the magnification predicted by the $\\Lambda$CDM model. After an extensive analysis, it cannot be attributed to any known systematic effect. The detection of the magnification signal is robust to estimated uncertainties in the outlier rate of the pho- tometric redshifts, but this will be an important issue for use of photometric redshifts in magnification mesurements from larger samples. In addition to the detection of the magnification signal, a method to select the sample with the maximum signal-to-noise is proposed and validated with data.

  10. Weak Lensing from Space I: Prospects for The Supernova/Acceleration Probe

    CERN Document Server

    Rhodes, J; Aldering, G; Amanullah, R; Astier, Pierre; Barrelet, E; Bebek, C; Bergstr, L; Bercovitz, J; Bester, M; Bonissent, A; Bower, C; Carithers, W C; Commins, Eugene D; Day, C; Deustua, S; Di Gennaro, R S; Ealet, A; Eriksson, M; Fruchter, A S; Genat, J F; Goldhaber, G; Goobar, A; Groom, D; Harris, S; Harvey, P; Heetderks, H; Holland, S; Huterer, D; Karcher, A; Kolbe, W F; Krieger, B; Lafever, R; Lamoureux, J; Levi, M; Levin, D; Linder, E V; Loken, S; Malina, R; McKee, S; Miquel, R; Mostek, N; Mufson, S L; Musser, J; Nugent, P; Oluseyi, H; Pain, R; Palaio, N; Pankow, D; Perlmutter, S; Pratt, R; Prieto, E; Robinson, K; Roe, N; Sholl, M; Schubnell, M S; Smadja, G; Smoot, G F; Spadafora, A; Tarl, G; Tomasch, A; Von der Lippe, H; Vincent, D; Walder, J P; Wang, G; Rhodes, Jason; Refregier, Alexandre; Massey, Richard

    2003-01-01

    The proposed Supernova/Acceleration Probe (SNAP) satellite has been recognized as an ideal instrument to measure the accelerating expansion of the universe through the distance moduli to type Ia supernovae. We show that SNAP will also be excellent for surveys of weak gravitational lensing by large-scale structure. Many of the requirements for precise photometry are compatible with those to accurately measure the shapes of background galaxies. We describe two surveys to be performed by SNAP. A 15 square degree ``deep'' survey will find clusters/groups and allow two-and three-dimensional dark matter maps to be made. A 300 square degree ``wide'' survey will be used to provide global constraints on cosmological parameters including Omega_M and w, the dark energy equation of state parameter. Both surveys will be conducted in 9 wide-band optical and near-IR filters, enabling photometric redshifts to be calculated. This first paper in a three part series outlines the survey strategies and introduces the SNAP instrum...

  11. Subaru Weak Lensing Study of Seven Merging Clusters: Distributions of Mass and Baryons

    CERN Document Server

    Okabe, N; Okabe, Nobuhiro; Umetsu, Keiichi

    2007-01-01

    We present and compare projected distributions of mass, galaxies, and the intracluster medium (ICM) for a sample of merging clusters of galaxies based on the joint weak-lensing, optical, and X-ray analysis. Our sample comprises seven nearby Abell clusters ($0.0542 \\le z \\le 0.279$), for which we have conducted systematic, deep imaging observations with Suprime-Cam on Subaru telescope. Our seven target clusters, representing various merging stages and conditions, allow us to investigate in details the physical interplay between dark matter, ICM, and galaxies associated with cluster formation and evolution. A1750 and A1758 are binary systems consisting of two cluster-sized components, A520, A754, A1758, and A1914 are on-going cluster mergers, and A2034 and A2142 are cold-front clusters. In the binary clusters, which are presumably in an early phase of mergers, the projected mass, optical light, and X-ray distributions are overall similar and regular without significant substructures. On-going merging clusters, ...

  12. Scaling Relations and Overabundance of Massive Clusters at z >~ 1 from Weak-lensing Studies with the Hubble Space Telescope

    Science.gov (United States)

    Jee, M. J.; Dawson, K. S.; Hoekstra, H.; Perlmutter, S.; Rosati, P.; Brodwin, M.; Suzuki, N.; Koester, B.; Postman, M.; Lubin, L.; Meyers, J.; Stanford, S. A.; Barbary, K.; Barrientos, F.; Eisenhardt, P.; Ford, H. C.; Gilbank, D. G.; Gladders, M. D.; Gonzalez, A.; Harris, D. W.; Huang, X.; Lidman, C.; Rykoff, E. S.; Rubin, D.; Spadafora, A. L.

    2011-08-01

    We present weak gravitational lensing analysis of 22 high-redshift (z >~ 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 ΛCDM 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 >~ 1. For the power-law slope of the M-TX relation (MvpropT α), we obtain α = 1.54 ± 0.23. This is consistent with the theoretical self-similar prediction α = 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-TX 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 ΛCDM model. The combined probability of finding the four most massive clusters in this sample after the marginalization over cosmological parameters is less than 1%. 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, under program 9290, 9919, and 10496.

  13. A robust lower limit on the amplitude of matter fluctuations in the universe from cluster abundance and weak lensing

    CERN Document Server

    Mandelbaum, R; Mandelbaum, Rachel; Seljak, Uros

    2007-01-01

    Cluster abundance measurements are among the most sensitive probes of the amplitude of matter fluctuations in the universe, which in turn can help constrain other cosmological parameters, like the dark energy equation of state or neutrino mass. However, difficulties in calibrating the relation between the cluster observable and halo mass, and the lack of completeness information, make this technique particularly susceptible to systematic errors. Here we argue that a cluster abundance analysis using statistical weak lensing on the stacked clusters leads to a robust lower limit on the amplitude of fluctuations. The method compares the average weak lensing signal measured around the whole cluster sample to a theoretical prediction, assuming that the clusters occupy the centers of all of the most massive halos above some minimum mass threshold. If the amplitude of fluctuations is below a certain limiting value, there are too few massive clusters in this model and the theoretical prediction falls below the observa...

  14. Cosmological Constraint on the Light Gravitino Mass from CMB Lensing and Cosmic Shear

    CERN Document Server

    Osato, Ken; Shirasaki, Masato; Kamada, Ayuki; Yoshida, Naoki

    2016-01-01

    Light gravitinos of mass $\\lesssim \\mathcal{O} (10)$ eV are of particular interest in cosmology, offering various baryogenesis scenarios without suffering from the cosmological gravitino problem. The gravitino may contribute considerably to the total matter content of the universe and affect structure formation through early to present epochs. After the gravitinos decouple from other particles in the early Universe, they free-stream and consequently suppress density fluctuations of (sub-)galactic length scales. Observations of structure at the relevant length-scales can be used to infer or constrain the mass and the abundance of light gravitinos. We derive constraints on the light gravitino mass using the data of cosmic microwave background (CMB) lensing from Planck and of cosmic shear from the CHFTLenS survey, combined with analyses of the primary CMB anisotropies and the signature of baryon acoustic oscillations in galaxy distributions. The obtained constraint on the gravitino mass is $m_{3/2} < 4.7$ eV ...

  15. The Effect of Detector Nonlinearity on WFIRST PSF Profiles for Weak Gravitational Lensing Measurements

    Science.gov (United States)

    Plazas, A. A.; Shapiro, C.; Kannawadi, A.; Mandelbaum, R.; Rhodes, J.; Smith, R.

    2016-10-01

    Weak gravitational lensing (WL) is one of the most powerful techniques to learn about the dark sector of the universe. To extract the WL signal from astronomical observations, galaxy shapes must be measured and corrected for the point-spread function (PSF) of the imaging system with extreme accuracy. Future WL missions—such as NASA’s Wide-Field Infrared Survey Telescope (WFIRST)—will use a family of hybrid near-infrared complementary metal-oxide-semiconductor detectors (HAWAII-4RG) that are untested for accurate WL measurements. Like all image sensors, these devices are subject to conversion gain nonlinearities (voltage response to collected photo-charge) that bias the shape and size of bright objects such as reference stars that are used in PSF determination. We study this type of detector nonlinearity (NL) and show how to derive requirements on it from WFIRST PSF size and ellipticity requirements. We simulate the PSF optical profiles expected for WFIRST and measure the fractional error in the PSF size (ΔR/R) and the absolute error in the PSF ellipticity (Δe) as a function of star magnitude and the NL model. For our nominal NL model (a quadratic correction), we find that, uncalibrated, NL can induce an error of ΔR/R = 1 × 10-2 and Δe 2 = 1.75 × 10-3 in the H158 bandpass for the brightest unsaturated stars in WFIRST. In addition, our simulations show that to limit the bias of ΔR/R and Δe in the H158 band to ˜10% of the estimated WFIRST error budget, the quadratic NL model parameter β must be calibrated to ˜1% and ˜2.4%, respectively. We present a fitting formula that can be used to estimate WFIRST detector NL requirements once a true PSF error budget is established.

  16. Weak lensing and spectroscopic analysis of the nearby dissociative merging galaxy cluster Abell 3376

    Science.gov (United States)

    Monteiro-Oliveira, R.; Lima Neto, G. B.; Cypriano, E. S.; Machado, R. E. G.; Capelato, H. V.; Laganá, T. F.; Durret, F.; Bagchi, J.

    2017-07-01

    The galaxy cluster Abell 3376 is a nearby (\\bar{z}=0.046) dissociative merging cluster surrounded by two prominent radio relics and showing an X-ray comet-like morphology. The merger system is comprised of the subclusters A3376W and A3376E. Based on new deep multiwavelength large-field images and published redshifts, we bring new insights about the history of this merger. Despite the difficulty of applying the weak lensing technique at such low redshift, we successfully recovered the mass distribution in the cluster field. Moreover, with the application of a two-body model, we have addressed the dynamics of this merging system. We have found the individual masses of M_{200}^W=3.0_{-1.7}^{+1.3}× 10^{14} M⊙ and M_{200}^E=0.9_{-0.8}^{+0.5}× 10^{14} M⊙. The cometary-shaped X-ray distribution shows only one peak spatially coincident with both eastern BCG and the A3376E mass peak whereas the gas content of A3376W seems to be stripped out. Our data allowed us to confirm the existence of a third subcluster located at the north, 1147 ± 62 kpc apart from the neighbour subcluster A3376E and having a mass M_{200}^N=1.4_{-1.0}^{+0.7}× 10^{14} M⊙. From our dynamical analysis, we found the merging is taking place very close to the plane of the sky, with the merger axis just 10° ± 11° from it. The application of a two-body analysis code showed that the merging cluster is seen 0.9_{-0.3}^{+0.2} Gyr after the pericentric passage and it is currently going to the point of maximum separation between the subclusters.

  17. Effects of Shear Fracture on In-depth Profile Modification of Weak Gels

    Institute of Scientific and Technical Information of China (English)

    Li Xianjie; Song Xinwang; Yue Xiang'an; Hou Jirui; Fang Lichun; Zhang Huazhen

    2007-01-01

    Two sand packs were filled with fine glass beads and quartz sand respectively. The characteristics of crosslinked polymer flowing through the sand packs as well as the influence of shear fracture of porous media on the in-depth profile modification of the weak gel generated from the crosslinked polymer were investigated. The results indicated that under the dynamic condition crosslinking reaction happened in both sand packs,and the weak gels in these two cases became small gel particles after water flooding. The differences were:the dynamic gelation time in the quartz sand pack was longer than that in the glass bead pack. Residual resistance factor (FRR) caused by the weak gel in the quartz sand pack was smaller than that in the glass bead pack. The weak gel became gel particles after being scoured by subsequent flood water. A weak gel with uniform apparent viscosity and sealing characteristics was generated in every part of the glass bead pack,which could not only move deeply into the sand pack but also seal the high capacity channels again when it reached the deep part. The weak gel performed in-depth profile modification in the glass bead pack,while in the quartz sand pack,the weak gel was concentrated with 100 cm from the entrance of the sand pack. When propelled by the subsequent flood water,the weak gel could move towards the deep part of the sand pack but then became tiny gel particles and could not effectively seal the high capacity channels there. The in-depth profile modification of the weak gel was very weak in the quartz sand pack. It was the shear fracture of porous media that mainly affected the properties and weakened the in-depth profile modification of the weak gel.

  18. A study of the sensitivity of shape measurements to the input parameters of weak lensing image simulations

    CERN Document Server

    Hoekstra, Henk; Herbonnet, Ricardo

    2016-01-01

    Improvements in the accuracy of shape measurements are essential to exploit the statistical power of planned imaging surveys that aim to constrain cosmological parameters using weak lensing by large-scale structure. Although a range of tests can be performed using the measurements, the performance of the algorithm can only be quantified using simulated images. This yields, however, only meaningful results if the simulated images resemble the real observations sufficiently well. In this paper we explore the sensitivity of the multiplicative bias to the input parameters of Euclid-like image simulations.We find that algorithms will need to account for the local density of sources. In particular the impact of galaxies below the detection limit warrants further study, because magnification changes their number density, resulting in correlations between the lensing signal and multiplicative bias. Although achieving sub-percent accuracy will require further study, we estimate that sufficient archival Hubble Space Te...

  19. Formulating Weak Lensing from the Boltzmann Equation and Application to Lens-lens Couplings

    CERN Document Server

    Su, S -C

    2014-01-01

    The Planck mission has conclusively detected lensing of the Cosmic Microwave Background (CMB) radiation from foreground sources to an overall significance of greater than $25\\sigma$. The high precision of this measurement motivates the development of a more complete formulation of the calculation of this effect. While most effects on the CMB anisotropies are widely studied through direct solutions of the Boltzmann equation, the non-linear effect of CMB lensing is formulated through the solutions of the geodesic equation. In this paper, we present a new formalism to the calculation of the lensing effect by \\emph{directly solving the Boltzmann equation}, as we did in the calculation of the CMB anisotropies at recombination. In particular, we developed a diagrammatic approach to efficiently keep track of all the interaction terms and calculate all possible non-trivial correlations to arbitrary high orders. Using this formalism, we explicitly articulate the approximations required to recover the usual remapping a...

  20. Cross-correlation of CMB with large-scale structure: weak gravitational lensing

    CERN Document Server

    Hirata, C M; Seljak, U; Schlegel, D J; Brinkmann, J; Hirata, Christopher M.; Padmanabhan, Nikhil; Seljak, Uros; Schlegel, David; Brinkmann, Jonathan

    2004-01-01

    We present the results of a search for gravitational lensing of the cosmic microwave background (CMB) in cross-correlation with the projected density of luminous red galaxies (LRGs). The CMB lensing reconstruction is performed using the first year of Wilkinson Microwave Anisotropy Probe (WMAP) data, and the galaxy maps are obtained using the Sloan Digital Sky Survey (SDSS) imaging data. We find no detection of lensing; our constraint on the galaxy bias derived from the galaxy-convergence cross-spectrum is $b_g=1.81\\pm 1.92$ ($1\\sigma$, statistical), as compared to the expected result of $b_g\\sim 1.7$ for this sample. We discuss possible instrument-related systematic errors and show that the Galactic foregrounds are not important. We do not find any evidence for point source or thermal Sunyaev-Zel'dovich effect contamination.

  1. Galaxy and Mass Assembly (GAMA): The halo mass of galaxy groups from maximum-likelihood weak lensing

    CERN Document Server

    Han, Jiaxin; Frenk, Carlos S; Mandelbaum, Rachel; Norberg, Peder; Schneider, Michael D; Peacock, John A; Jing, Yipeng; Baldry, Ivan; Bland-Hawthorn, Joss; Brough, Sarah; Brown, Michael J I; Loveday, Jon

    2014-01-01

    We present a maximum-likelihood weak lensing analysis of the mass distribution in optically selected spectroscopic Galaxy Groups (G3Cv1) in the Galaxy And Mass Assembly (GAMA) survey, using background Sloan Digital Sky Survey (SDSS) photometric galaxies. The scaling of halo mass, $M_h$, with various group observables is investigated. Our main results are: 1) the measured relations of halo mass with group luminosity, virial volume and central galaxy stellar mass, $M_\\star$, agree very well with predictions from mock group catalogues constructed from a GALFORM semi-analytical galaxy formation model implemented in the Millennim $\\Lambda$CDM N-body simulation; 2) the measured relations of halo mass with velocity dispersion and projected half-abundance radius show weak tension with mock predictions, hinting at problems in the mock galaxy dynamics and their small scale distribution; 3) the median $M_h|M_\\star$ measured from weak lensing depends more sensitively on the dispersion in $M_\\star$ at fixed $M_h$ than it ...

  2. CFHTLenS: The relation between galaxy dark matter haloes and baryons from weak gravitational lensing

    CERN Document Server

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

    2013-01-01

    We present a study of the relation between dark matter halo mass and the baryonic content of host galaxies, quantified through luminosity and stellar mass. Our investigation uses 154 deg2 of Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) lensing and photometric data, obtained from the CFHT Legacy Survey. We employ a galaxy-galaxy lensing halo model which allows us to constrain the halo mass and the satellite fraction, and our analysis is limited to lenses at redshifts between 0.2 and 0.4. We express the relationship between halo mass and baryonic observable as a power law. For the luminosity-halo mass relation we find a slope of 1.56+0.04-0.06 and a normalisation of 1.26+0.07-0.06x10^13 h70^-1 Msun for red galaxies, while for blue galaxies the best-fit slope is 0.73+0.09-0.08 and the normalisation is 0.16+/-0.03x10^13 h70^-1 Msun. Similarly, we find a best-fit slope of 1.49+0.06-0.04 and a normalisation of 1.30+0.05-0.09x10^13 h70^-1 Msun for the stellar mass-halo mass relation of red galaxies, whil...

  3. Existence of Weakly Damped Kinetic Alfven Eigenmodes in Reversed Shear Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    N. N. Gorelenkov

    2008-08-12

    A kinetic theory of weakly damped Alfven Eigenmode (AE) solutions strongly interacting with the continuum is developed for tokamak plasmas with reversed magnetic shear. We show that the ideal MHD model is not sufficient for the eigenmode solutions if the standard causality condition bypass rule is applied. Finite Larmor radius effects are required, which introduce multiple kinetic subeigenmodes and collisionless radiative damping. The theory explains the existence of experimentally observed Alfvenic instabilities with frequencies sweeping down and reaching their minimum (bottom).

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

    CERN Document Server

    Reyes, Reinabelle; Seljak, Uros; Baldauf, Tobias; Gunn, James E; Lombriser, Lucas; Smith, Robert E; 10.1038/nature08857

    2010-01-01

    Although general relativity underlies modern cosmology, its applicability on cosmological length scales has yet to be stringently tested. Such a test has recently been proposed, using a quantity, EG, that combines measures of large-scale gravitational lensing, galaxy clustering and structure growth rate. The combination is insensitive to 'galaxy bias' (the difference between the clustering of visible galaxies and invisible dark matter) and is thus robust to the uncertainty in this parameter. Modified theories of gravity generally predict values of EG different from the general relativistic prediction because, in these theories, the 'gravitational slip' (the difference between the two potentials that describe perturbations in the gravitational metric) is non-zero, which leads to changes in the growth of structure and the strength of the gravitational lensing effect3. Here we report that EG = 0.39 +/- 0.06 on length scales of tens of megaparsecs, in agreement with the general relativistic prediction of EG $\\app...

  5. Deep Generative Models of Galaxy Images for the Calibration of the Next Generation of Weak Lensing Surveys

    Science.gov (United States)

    Lanusse, Francois; Ravanbakhsh, Siamak; Mandelbaum, Rachel; Schneider, Jeff; Poczos, Barnabas

    2017-01-01

    Weak gravitational lensing has long been identified as one of the most powerful probes to investigate the nature of dark energy. As such, weak lensing is at the heart of the next generation of cosmological surveys such as LSST, Euclid or WFIRST.One particularly crititcal source of systematic errors in these surveys comes from the shape measurement algorithms tasked with estimating galaxy shapes. GREAT3, the last community challenge to assess the quality of state-of-the-art shape measurement algorithms has in particular demonstrated that all current methods are biased to various degrees and, more importantly, that these biases depend on the details of the galaxy morphologies. These biases can be measured and calibrated by generating mock observations where a known lensing signal has been introduced and comparing the resulting measurements to the ground-truth. Producing these mock observations however requires input galaxy images of higher resolution and S/N than the simulated survey, which typically implies acquiring extremely expensive space-based observations.The goal of this work is to train a deep generative model on already available Hubble Space Telescope data which can then be used to sample new galaxy images conditioned on parameters such as magnitude, size or redshift and exhibiting complex morphologies. Such model can allow us to inexpensively produce large set of realistic realistic images for calibration purposes.We implement a conditional generative model based on state-of-the-art deep learning methods and fit it to deep galaxy images from the COSMOS survey. The quality of the model is assessed by computing an extensive set of galaxy morphology statistics on the generated images. Beyond simple second moment statistics such as size and ellipticity, we apply more complex statistics specifically designed to be sensitive to disturbed galaxy morphologies. We find excellent agreement between the morphologies of real and model generated galaxies.Our results

  6. Studies of instability and transport in tokamak plasmas with very weak magnetic shear

    Energy Technology Data Exchange (ETDEWEB)

    Dong, J.Q.; Zhang, Y.Z. [Southwestern Inst. of Physics, Chengdu (China)]|[International Center for Theoretical Physics, Trieste (Italy); Mahajan, S.M. [Texas Univ., Austin, TX (United States). Inst. for Fusion Studies

    1997-04-01

    Ion temperature gradient (ITG or {eta}{sub i}) driven microinstabilities are studied, using kinetic theory, for tokamak plasmas with very weak (positive or negative) magnetic shear (VWS). The gradient of magnetic shear as well as the effects of parallel and perpendicular velocity shear (v{prime}{sub {parallel}} and v{prime}{sub E}) are included in the defining equations. Two eigenmodes: the double (D) and the global (G) are found to coexist. Parametric dependence of these instabilities, and of the corresponding quasilinear transport is systematically analyzed. It is shown that, in VWS plasmas, a parallel velocity shear (PVS) may stabilize or destabilize the modes, depending on the individual as well as the relative signs of PVS and of the gradient of magnetic shear. The quasilinear transport induced by the instabilities may be significantly reduced with PVS in VWS plasmas. The v{prime}{sub E} values required to completely suppress the instabilities are much lower in VWS plasmas than they are in normal plasmas. Possible correlations with tokamak experiments are discussed.

  7. Dark energy constraints and correlations with systematics from CFHTLS weak lensing, SNLS supernovae Ia and WMAP5

    CERN Document Server

    Kilbinger, M; Guy, J; Astier, Pierre; Tereno, I; Fu, L; Wraith, D; Coupon, J; Mellier, Y; Balland, C; Bouchet, F R; Hamana, T; Hardin, D; McCracken, H J; Pain, R; Regnault, N; Schultheiss, M; Yahagi, H

    2008-01-01

    We combine measurements of weak gravitational lensing from the CFHTLS-Wide survey, supernovae Ia from CFHT SNLS and CMB anisotropies from WMAP5 to obtain joint constraints on cosmological parameters, in particular, the dark energy equation of state parameter w. We assess the influence of systematics in the data on the results and look for possible correlations with cosmological parameters. We implement an MCMC algorithm to sample the parameter space of a flat CDM model with a dark-energy component of constant w. Systematics in the data are parametrised and included in the analysis. We determine the influence of photometric calibration of SNIa data on cosmological results by calculating the response of the distance modulus to photometric zero-point variations. The weak lensing data set is tested for anomalous field-to-field variations and a systematic shape measurement bias for high-z galaxies. Ignoring photometric uncertainties for SNLS biases cosmological parameters by at most 20% of the statistical errors, ...

  8. CoMaLit-V. Mass forecasting with proxies. Method and application to weak lensing calibrated samples

    CERN Document Server

    Sereno, Mauro

    2016-01-01

    Mass measurements of astronomical objects are most wanted but still elusive. We need them to trace the formation and evolution of cosmic structure but we can get direct measurements only for a minority. This lack can be circumvented with a proxy and a scaling relation. The twofold goal of estimating the unbiased relation and finding the right proxy value to plug in can be hampered by systematics, selection effects, Eddington/Malmquist biases and time evolution. We present a Bayesian hierarchical method which deals with these issues. Masses to be predicted are treated as missing data in the regression and are estimated together with the scaling parameters. The calibration subsample with measured masses does not need to be representative of the full sample. We apply the method to forecast weak lensing calibrated masses of the Planck, redMaPPer and MCXC clusters. Planck masses are biased low with respect to weak lensing calibrated masses, with a bias more pronounced for high redshift clusters. MCXC masses are un...

  9. Forecasting Constraints on the Evolution of the Hubble Parameter and the Growth Function by Future Weak Lensing Surveys

    CERN Document Server

    Vollmer, Adrian

    2011-01-01

    The cosmological information encapsulated within a weak lensing signal can be accessed via the power spectrum of the so called convergence. We use the Fisher information matrix formalism with the convergence power spectrum as the observable to predict how future weak lensing surveys will constrain the expansion rate and the growth function as functions of redshift without using any specific model to parameterize these two quantities. To do this, we divide redshift space into bins and linearly interpolate the functions with the centers of the redshift bins as sampling points, using a fiducial set of parameters. At the same time, we use these redshift bins for power spectrum tomography, where we analyze not only the power spectrum in each bin but also their cross-correlation in order to maximize the extracted information. We find that a small number of bins with the given photometric redshift mea- surement precision is sufficient to access most of the information content and that the projected constraints are c...

  10. Alfvenic Ion Temperature Gradient Activities in a Weak Magnetic Shear Plasma

    CERN Document Server

    Chen, W; Li, Y Y; Shi, Z B; Du, H R; Jiang, M; Yu, L M; Yuan, B S; Li, Y G; Yang, Z C; Shi, P W; Ding, X T; Dong, J Q; Liu, Yi; Xu, M; Xu, Y H; Yang, Q W; Duan, X R

    2016-01-01

    We report the first experimental evidence of Alfvenic ion temperature gradient (AITG) modes in HL-2A Ohmic plasmas. A group of oscillations with $f=15-40$ kHz and $n=3-6$ is detected by various diagnostics in high-density Ohmic regimes. They appear in the plasmas with peaked density profiles and weak magnetic shear, which indicates that corresponding instabilities are excited by pressure gradients. The time trace of the fluctuation spectrogram can be either a frequency staircase, with different modes excited at different times or multiple modes may simultaneously coexist. Theoretical analyses by the extended generalized fishbone-like dispersion relation (GFLDR-E) reveal that mode frequencies scale with ion diamagnetic drift frequency and $\\eta_i$, and they lie in KBM-AITG-BAE frequency ranges. AITG modes are most unstable when the magnetic shear is small in low pressure gradient regions. Numerical solutions of the AITG/KBM equation also illuminate why AITG modes can be unstable for weak shear and low pressure...

  11. A Numerical Investigation of a Slow-Moving Convective Line in a Weakly Sheared Environment

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    A series of three-dimensional, cloud-resolving numerical simulations are performed to examine a slowpropagating, quasi-two-dimensional convective system in a weakly sheared environment during the Tropical Rainfall Measuring Mission Large-Scale Biosphere-Atmosphere (TRMM-LBA) field campaign. The focus is on the kinematics and thermodynamics, organization mechanisms, and dynamical effects of low-level shear, ice microphysics and tropospheric humidity. The control simulation, which is initialized with the observed sounding and includes full microphysics, successfully replicates many observed features of the convective system, such as the linear structure, spatial orientation, life cycle, and sluggish translation.The system at the mature stage displays a line-normal structure similar to that associated with squalltype convective systems, but the corresponding mesoscale circulation and thermodynamic modification are much weaker. Ice-phase microphysical processes are not necessary to the formation of the convective system, but they play a non-trivial role in the late evolution stage. In contrast, the low-level shear, albeit shallow and weak, is critical to the realistic realization of the convective line. The tropospheric moisture above the planetary boundary layer has an important impact on the behavior of convective organization.In particular, a dry layer in the lower troposphere significantly suppresses convective development and inhibits the generation of organized convection even though the convective available potential energy is substantial. The free-atmosphere humidity has received little attention in previous studies of organized convection and warrants further investigation.

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

    Science.gov (United States)

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

    2010-03-11

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

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

    CERN Document Server

    Hirata, Christopher M; Padmanabhan, Nikhil; Seljak, Uros; Bahcall, Neta

    2008-01-01

    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 $1.06\\pm 0.42$ 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 signa...

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

    CERN Document Server

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

    2006-01-01

    We present results of a measurement of the shape of the density profile of galaxy groups and clusters traced by 43 335 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 modeled 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 100 kpc/h of LRGs which we remove using photometric redshift information. The resulting lensing signal is consistent with NFW profile dark matter halos; the 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 40 kpc/h and 2 Mpc/h with total signal-to-noise of 19 and 25 for the ...

  15. LoCuSS: Exploring the selection of faint blue background galaxies for cluster weak-lensing

    Science.gov (United States)

    Ziparo, Felicia; Smith, Graham P.; Okabe, Nobuhiro; Haines, Chris P.; Pereira, Maria J.; Egami, Eiichi

    2016-10-01

    Cosmological constraints from galaxy clusters rely on accurate measurements of the mass and internal structure of clusters. An important source of systematic uncertainty in cluster mass and structure measurements is the secure selection of background galaxies that are gravitationally lensed by clusters. This issue has been shown to be particular severe for faint blue galaxies. We therefore explore the selection of faint blue background galaxies, by reference to photometric redshift catalogues derived from the COSMOS survey and our own observations of massive galaxy clusters at z ≃ 0.2. We show that methods relying on photometric redshifts of galaxies in/behind clusters based on observations through five filters, and on deep 30-band COSMOS photometric redshifts are both inadequate to safely identify faint blue background galaxies with the same 1 per cent contamination level that we have achieved with red galaxies. This is due to the small number of filters used by the former, and absence of massive galaxy clusters at redshifts of interest in the latter. Nevertheless, our least contaminated blue galaxy sample yields stacked weak-lensing results consistent with our previously published results based on red galaxies, and we show that the stacked clustercentric number density profile of these faint blue galaxies is consistent with expectations from consideration of the lens magnification signal of the clusters. Indeed, the observed number density of blue background galaxies changes by ˜10 - 30 per cent across the radial range over which other surveys assume it to be flat.

  16. A weak gravitational lensing recalibration of the scaling relations linking the gas properties of dark halos to their mass

    CERN Document Server

    Wang, Wenting; Mandelbaum, Rachel; Henriques, Bruno; Anderson, Michael E; Han, Jiaxin

    2015-01-01

    We use weak gravitational lensing to measure mean mass profiles around Locally Brightest Galaxies (LBGs). These are selected from the SDSS/DR7 spectroscopic and photometric catalogues to be brighter than any neighbour projected within 1.0 Mpc and differing in redshift by $ 83\\%$) are expected to be the central galaxies of their dark matter halos. Previous stacking analyses have used this LBG sample to measure mean Sunyaev-Zeldovich flux and mean X-ray luminosity as a function of LBG stellar mass. In both cases, a simulation of the formation of the galaxy population was used to estimate effective halo mass for LBGs of given stellar mass, allowing the derivation of scaling relations between the gas properties of halos and their mass. By comparing results from a variety of simulations to our lensing data, we show that this procedure has significant model dependence reflecting: (i) the failure of any given simulation to reproduce observed galaxy abundances exactly; (ii) a dependence on the cosmology underlying th...

  17. Implications for Primordial Non-Gaussianity ($f_{NL}$) from weak lensing masses of high-z galaxy clusters

    CERN Document Server

    Jimenez, Raul

    2009-01-01

    The recent weak lensing measurement of the dark matter mass of the high-redshift galaxy cluster XMMUJ2235.3-2557 of (8.5 +- 1.7) x 10^{14} Msun 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 LCDM model, then its abundance should be 3-10 if the non-Gaussianity parameter f^local_NL is in the range 150-200. This value is comparable to the limit for f_NL obtained by current constraints from the CMB. We conclude that mass determination of high-redshift, massive clusters can offer a complementary probe of primordial non-gaussianity.

  18. On Dark Peaks and Missing Mass: A Weak-Lensing Mass Reconstruction of the Merging Cluster System A520

    Science.gov (United States)

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

    2012-01-01

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

  19. Statistical Cluster-QSO Weak Lensing in the Sloan Digital Sky Survey

    Institute of Scientific and Technical Information of China (English)

    Zhong-Lue Wen; Yan-Bin Yang; Xu Zhou; Qi-Rong Yuan; Jun Ma

    2006-01-01

    We investigate the cross-correlation between galaxy clusters and QSOs using Sloan Digital Sky Survey (SDSS) DR4 ~ 5000 deg2 data. With photometric redshifts of galaxies,we select galaxy clusters based on the local projected densities of LRGs brighter than Mr'=-22. The QSOs are from the mainsample of SDSS QSO spectroscopic survey to i' = 19. A significant positive correlation is found between the clusters and QSOs. Under the assumption that the signal is caused by gravitational lensing, we fit the signal with singular isothermal sphere (SIS) model and NFW profile halo model. The velocity dispersion σv = 766 km s-1 is derived for the best-fit of SIS model. Best-fit for the NFW model requires the dark matter halo mass within 1.5 h-1 Mpc to be 4.6 × 1014 h-1 M⊙. The mass parameter Ωcl of the cluster sample is deduced as 0.077 with the SIS model and 0.083 with the NFW model. Our results of Ωcl are smaller than those given by Croom & Shanks and by Myers et al.

  20. Detection of weak gravitational lensing magnification from Galaxy-QSO cross-correlation in the SDSS

    CERN Document Server

    Gaztañaga, E

    2003-01-01

    We report a detection of galaxy-QSO cross-correlation w_{GQ} in the Sloan Digital Sky Survey (SDSS) Early Data Release (EDR) over 0.2-30 arc-minute scales. We cross-correlate galaxy samples of different mean depths r'=19-22 (z_G =0.15-0.35) with the main QSO population (i'_Q <19.2) at \\zbar_Q \\simeq 1.6. We find positive detection in most cases (except for the faintest QSOs as expeceted) with up to 8-sigma significance. The amplitude of the signal on arc-minute scales is about 20% at z_G=0.15 decreasing to 10% at z_G =0.35 This is a few times larger than currently expected from structure formation LCDM models o but confirms, at a higher significance, previous measurements by several groups. The shape and redshift evolution agrees well with being a lensing signal. We also find a 3-sigma detection for the (pseudo) skewness (galaxy-galaxy-QSO correlation): S_3 = 18.6 \\pm 5.7$ The data indicates very strong non-linear amplitude for the underlaying matter fluctuations scales of 0.2$ Mpc/h, in apparent contradic...

  1. Lyman-{\\alpha} Forest and Cosmic Weak Lensing in a Warm Dark Matter Universe

    CERN Document Server

    Markovič, Katarina

    2013-01-01

    We review the current state of the theory of large scale structure in a warm dark matter (WDM) cosmological model. In particular, we focus on the non-linear modelling of the matter power spectrum and on the mass function of dark matter haloes. We describe the results of N-body simulations with WDM and mention the effects that could be induced by baryonic physics. We also examine the halo model of large scale structure and its recently suggested modifications for a WDM cosmology, which account for the small scale smoothness of the initial matter density field and better fit the results of N-body simulations. Having described the theoretical models, we discuss the current lower limits on the WDM particle mass, m_w, which correspond to upper limits on the WDM temperature under the assumption that the particles are thermal relics. The best such constraints come from the Ly{\\alpha} forest and exclude all masses below 3.3 keV at the 2{\\sigma} confidence level. We finally review the forecasts for future lensing surv...

  2. The Jubilee ISW Project I: simulated ISW and weak lensing maps and initial power spectra results

    CERN Document Server

    Watson, W A; Gottlöber, S; Iliev, I T; Knebe, A; Martínez-González, E; Yepes, G; Barreiro, R B; González-Nuevo, J; Hotchkiss, S; Marcos-Caballero, A; Nadathur, S; Vielva, P; .,

    2013-01-01

    We present initial results from the Jubilee ISW project, which models the expected \\LambdaCDM Integrated Sachs-Wolfe (ISW) effect in the Jubilee simulation. The simulation volume is (6 Gpc/h)^3, allowing power on very large-scales to be incorporated into the calculation. Haloes are resolved down to a mass of 1.5x10^12 M_sun/h, which allows us to derive a catalogue of mock Luminous Red Galaxies (LRGs) for cross-correlation analysis with the ISW signal. We find the ISW effect observed on a projected sky to grow stronger at late times with the evolution of the ISW power spectrum matching expectations from linear theory. Maps of the gravitational lensing effect, including the convergence and deflection fields, are calculated using the same potential as for the ISW. We calculate the redshift dependence of the ISW-LRG cross-correlation signal for a full sky survey with no noise considerations. For l 30 the signal is best observed with surveys covering z ~ 0.6-1.0.

  3. Weak-Lensing Mass Calibration of the Atacama Cosmology Telescope Equatorial Sunyaev-Zeldovich Cluster Sample with the Canada-France-Hawaii Telescope Stripe 82 Survey

    CERN Document Server

    Battaglia, N; Miyatake, H; Hasselfield, M; Gralla, M B; Allison, R; Bond, J R; Calabrese, E; Crichton, D; Devlin, M J; Dunkley, J; Dünner, R; Erben, T; Ferrara, S; Halpern, M; Hilton, M; Hill, J C; Hincks, A D; Hložek, R; Huffenberger, K M; Hughes, J P; Kneib, J P; Kosowsky, A; Makler, M; Marriage, T A; Menanteau, F; Miller, L; Moodley, K; Moraes, B; Niemack, M D; Page, L; Shan, H; Sehgal, N; Sherwin, B D; Sievers, J L; Sifón, C; Spergel, D N; Staggs, S T; Taylor, J; Thornton, R; van Waerbeke, L; Wollack, E J

    2015-01-01

    Mass calibration uncertainty is the largest systematic effect for using clusters of galaxies to constrain cosmological parameters. We present weak lensing mass measurements from the Canada-France-Hawaii Telescope Stripe 82 Survey for galaxy clusters selected through their high signal-to-noise thermal Sunyaev-Zeldovich (tSZ) signal measured with the Atacama Cosmology Telescope (ACT). The average weak lensing mass is $\\left(4.8\\pm0.8\\right)\\,\\times10^{14}\\,\\mathrm{M}_\\odot$, consistent with the tSZ mass estimate of $\\left(4.70\\pm1.0\\right)\\,\\times10^{14}\\,\\mathrm{M}_\\odot$ which assumes a universal pressure profile for the cluster gas. Our results are consistent with previous weak-lensing measurements of tSZ-detected clusters from the Planck satellite. When comparing our results, we estimate the Eddington bias correction for the sample intersection of Planck and weak-lensing clusters which was previously neglected.

  4. Weak-lensing mass calibration of the Atacama Cosmology Telescope equatorial Sunyaev-Zeldovich cluster sample with the Canada-France-Hawaii telescope stripe 82 survey

    Science.gov (United States)

    Battaglia, N.; Leauthaud, A.; Miyatake, H.; Hasselfield, M.; Gralla, M. B.; Allison, R.; Bond, J. R.; Calabrese, E.; Crichton, D.; Devlin, M. J.; Dunkley, J.; Dünner, R.; Erben, T.; Ferrara, S.; Halpern, M.; Hilton, M.; Hill, J. C.; Hincks, A. D.; Hložek, R.; Huffenberger, K. M.; Hughes, J. P.; Kneib, J. P.; Kosowsky, A.; Makler, M.; Marriage, T. A.; Menanteau, F.; Miller, L.; Moodley, K.; Moraes, B.; Niemack, M. D.; Page, L.; Shan, H.; Sehgal, N.; Sherwin, B. D.; Sievers, J. L.; Sifón, C.; Spergel, D. N.; Staggs, S. T.; Taylor, J. E.; Thornton, R.; van Waerbeke, L.; Wollack, E. J.

    2016-08-01

    Mass calibration uncertainty is the largest systematic effect for using clusters of galaxies to constrain cosmological parameters. We present weak lensing mass measurements from the Canada-France-Hawaii Telescope Stripe 82 Survey for galaxy clusters selected through their high signal-to-noise thermal Sunyaev-Zeldovich (tSZ) signal measured with the Atacama Cosmology Telescope (ACT). For a sample of 9 ACT clusters with a tSZ signal-to-noise greater than five the average weak lensing mass is (4.8±0.8) ×1014 Msolar, consistent with the tSZ mass estimate of (4.70±1.0) ×1014 Msolar which assumes a universal pressure profile for the cluster gas. Our results are consistent with previous weak-lensing measurements of tSZ-detected clusters from the Planck satellite. When comparing our results, we estimate the Eddington bias correction for the sample intersection of Planck and weak-lensing clusters which was previously excluded.

  5. Constraining Source Redshift Distributions with Gravitational Lensing

    CERN Document Server

    Wittman, D

    2012-01-01

    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 ($\\sigma_v=1200$ km/s) 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 $N_{lens}^0.5$, but the improvement slows as one is forced to use lenses further ...

  6. Dark Synergy Gravitational Lensing and the CMB

    CERN Document Server

    Hu, W

    2002-01-01

    Power spectra and cross-correlation measurements from the weak gravitational lensing of the cosmic microwave background (CMB) and the cosmic shearing of faint galaxies images will help shed light on quantities hidden from the CMB temperature anisotropies: the dark energy, the end of the dark ages, and the inflationary gravitational wave amplitude. Even with modest surveys, both types of lensing power spectra break CMB degeneracies and they can ultimately improve constraints on the dark energy equation of state w by over an order of magnitude. In its cross correlation with the integrated Sachs-Wolfe effect, CMB lensing offers a unique opportunity for a more direct detection of the dark energy and enables study of its clustering properties. By obtaining source redshifts and cross-correlations with CMB lensing, cosmic shear surveys provide tomographic handles on the evolution of clustering correspondingly better precision on the dark energy equation of state and density. Both can indirectly provide detections of...

  7. Cross-correlating Planck tSZ with RCSLenS weak lensing: implications for cosmology and AGN feedback

    Science.gov (United States)

    Hojjati, Alireza; Tröster, Tilman; Harnois-Déraps, Joachim; McCarthy, Ian G.; van Waerbeke, Ludovic; Choi, Ami; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Hinshaw, Gary; Ma, Yin-Zhe; Miller, Lance; Viola, Massimo; Tanimura, Hideki

    2017-10-01

    We present measurements of the spatial mapping between (hot) baryons and the total matter in the Universe, via the cross-correlation between the thermal Sunyaev-Zeldovich (tSZ) map from Planck and the weak gravitational lensing maps from the Red Cluster Sequence Lensing Survey (RCSLenS). The cross-correlations are performed on the map level where all the sources (including diffuse intergalactic gas) contribute to the signal. We consider two configuration-space correlation function estimators, ξy-κ and ξ ^ {y-γ t}, and a Fourier-space estimator, C_{ℓ}^{y-κ}, in our analysis. We detect a significant correlation out to 3° of angular separation on the sky. Based on statistical noise only, we can report 13σ and 17σ detections of the cross-correlation using the configuration-space y-κ and y-γt estimators, respectively. Including a heuristic estimate of the sampling variance yields a detection significance of 7σ and 8σ, respectively. A similar level of detection is obtained from the Fourier-space estimator, C_{ℓ}^{y-κ}. As each estimator probes different dynamical ranges, their combination improves the significance of the detection. We compare our measurements with predictions from the cosmo-OverWhelmingly Large Simulations suite of cosmological hydrodynamical simulations, where different galactic feedback models are implemented. We find that a model with considerable active galactic nuclei (AGN) feedback that removes large quantities of hot gas from galaxy groups and Wilkinson Microwave Anisotropy Probe 7-yr best-fitting cosmological parameters provides the best match to the measurements. All baryonic models in the context of a Planck cosmology overpredict the observed signal. Similar cosmological conclusions are drawn when we employ a halo model with the observed 'universal' pressure profile.

  8. Describing galaxy weak lensing measurements from tenths to tens of Mpc and up to z~0.6 with a single model

    CERN Document Server

    Cacciato, Marcello; Hoekstra, Henk

    2013-01-01

    The clustering of galaxies and the matter distribution around them can be described using the halo model complemented with a realistic description of the way galaxies populate dark matter haloes. This has been used successfully to describe statistical properties of samples of galaxies at z<0.2. Without adjusting any model parameters, we compare the predicted weak lensing signal induced by Luminous Red Galaxies to measurements from SDSS DR7 on much larger scales (up to ~90 h_{70}^{-1} Mpc) and at higher redshift (z~0.4). We find excellent agreement, suggesting that the model captures the main properties of the galaxy-dark matter connection. To extend the comparison to lenses at even higher redshifts we complement the SDSS data with shape measurements from the deeper RCS2, resulting in precise lensing measurements for lenses up to z~0.6. These measurements are also well described using the same model. Considering solely these weak lensing measurements, we robustly assess that, up to z~0.6, the number of cent...

  9. Cluster Lenses

    CERN Document Server

    Kneib, Jean-Paul; 10.1007/s00159-011-0047-3

    2012-01-01

    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...

  10. Intrinsic alignment of simulated galaxies in the cosmic web: implications for weak lensing surveys

    CERN Document Server

    Codis, Sandrine; Dubois, Yohan; Pichon, Christophe; Benabed, Karim; Desjacques, Vincent; Pogosyan, Dmitry; Devriendt, Julien; Slyz, Adrianne

    2014-01-01

    The intrinsic alignment of galaxy shapes and their cross-correlation with the surrounding dark matter tidal field are investigated using the 160 000, z=1.2 synthetic galaxies extracted from the high-resolution cosmological hydrodynamical simulation Horizon-AGN. One- and two-point statistics of the spin of the stellar component are measured as a function of mass and colour. For the low-mass galaxies, this spin is locally aligned with the tidal field `filamentary' direction while, for the high-mass galaxies, it is perpendicular to both filaments and walls. The bluest galaxies of our synthetic catalog are more strongly correlated with the surrounding tidal field than the reddest galaxies, and this correlation extends up to 10 Mpc/h comoving distance. We also report a correlation of the projected ellipticities of blue, intermediate mass galaxies on a similar scale at a level of 10^(-4) which could be a concern for cosmic shear measurements. We do not report any measurable intrinsic alignments of the reddest galax...

  11. Transport and performance in DIII-D discharges with weak or negative central magnetic shear

    Energy Technology Data Exchange (ETDEWEB)

    Greenfield, C.M.; Schissel, D.P.; Stallard, B.W. [and others

    1996-12-01

    Discharges exhibiting the highest plasma energy and fusion reactivity yet realized in the DIII-D tokamak have been produced by combining the benefits of a hollow or weakly sheared central current profile with a high confinement (H-mode) edge. In these discharges, low power neutral beam injection heats the electrons during the initial current ramp, and {open_quotes}freezes in{close_quotes} a hollow or flat central current profile. When the neutral beam power is increased, formation of a region of reduced transport and highly peaked profiles in the core often results. Shortly before these plasmas would otherwise disrupt, a transition is triggered from the low (L-mode) to high (H-mode) confinement regimes, thereby broadening the pressure profile and avoiding the disruption. These plasmas continue to evolve until the high performance phase is terminated nondisruptively at much higher {beta}{sub T} (ratio of plasma pressure to toroidal magnetic field pressure) than would be attainable with peaked profiles and an L-mode edge. Transport analysis indicates that in this phase, the ion diffusivity is equivalent to that predicted by Chang-Hinton neoclassical theory over the entire plasma volume. This result is consistent with suppression of turbulence by locally enhanced E x B flow shear, and is supported by observations of reduced fluctuations in the plasma. Calculations of performance in these discharges extrapolated to a deuterium-tritium fuel mixture indicates that such plasmas could produce a DT fusion gain Q{sub DT} = 0.32.

  12. Baryon impact on weak lensing peaks and power spectrum: low-bias statistics and self-calibration in future surveys

    CERN Document Server

    Yang, Xiuyuan; Huffenberger, Kevin; Haiman, Zoltán; May, Morgan

    2012-01-01

    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 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 ...

  13. Dark matter halo properties of GAMA galaxy groups from 100 square degrees of KiDS weak lensing data

    CERN Document Server

    Viola, M; Brouwer, M; Kuijken, K; Hoekstra, H; Norberg, P; Robotham, A S G; van Uitert, E; Alpaslan, M; Baldry, I K; Choi, A; de Jong, J T A; Driver, S P; Erben, T; Grado, A; Graham, Alister W; Heymans, C; Hildebrandt, H; Hopkins, A M; Irisarri, N; Joachimi, B; Loveday, J; Miller, L; Nakajima, R; Schneider, P; Sifón, C; Kleijn, G Verdoes

    2015-01-01

    The Kilo-Degree Survey (KiDS) is an optical wide-field survey designed to map the matter distribution in the Universe using weak gravitational lensing. In this paper, we use these data to measure the density profiles and masses of a sample of $\\sim \\mathrm{1400}$ spectroscopically identified galaxy groups and clusters from the Galaxy And Mass Assembly (GAMA) survey. We detect a highly significant signal (signal-to-noise-ratio $\\sim$ 120), allowing us to study the properties of dark matter haloes over one and a half order of magnitude in mass, from $M \\sim 10^{13}-10^{14.5} h^{-1}\\mathrm{M_{\\odot}}$. We interpret the results for various subsamples of groups using a halo model framework which accounts for the mis-centring of the Brightest Cluster Galaxy (used as the tracer of the group centre) with respect to the centre of the group's dark matter halo. We find that the density profiles of the haloes are well described by an NFW profile with concentrations that agree with predictions from numerical simulations. ...

  14. The XXL Survey X: K-band luminosity - weak-lensing mass relation for groups and clusters of galaxies

    CERN Document Server

    Ziparo, F; Mulroy, S L; Lieu, M; Willis, J P; Hudelot, P; McGee, S L; Fotopoulou, S; Lidman, C; Lavoie, S; Pierre, M; Adami, C; Chiappetti, L; Clerc, N; Giles, P; Maughan, B; Pacaud, F; Sadibekova, T

    2015-01-01

    We present the K-band luminosity-halo mass relation, $L_{K,500}-M_{500,WL}$, for a subsample of 20 of the 100 brightest clusters in the XXL Survey observed with WIRCam at the Canada-France-Hawaii Telescope (CFHT). For the first time, we have measured this relation via weak-lensing analysis down to $M_{500,WL} =3.5 \\times 10^{13}\\,M_\\odot$. This allows us to investigate whether the slope of the $L_K-M$ relation is different for groups and clusters, as seen in other works. The clusters in our sample span a wide range in mass, $M_{500,WL} =0.35-12.10 \\times 10^{14}\\,M_\\odot$, at $0

  15. Nbody Simulations and Weak Gravitational Lensing using new HPC-Grid resources: the PI2S2 project

    Science.gov (United States)

    Becciani, U.; Antonuccio-Delogu, V.; Costa, A.; Comparato, M.

    2008-08-01

    We present the main project of the new grid infrastructure and the researches, that have been already started in Sicily and will be completed by next year. The PI2S2 project of the COMETA consortium is funded by the Italian Ministry of University and Research and will be completed in 2009. Funds are from the European Union Structural Funds for Objective 1 regions. The project, together with a similar project called Trinacria GRID Virtual Laboratory (Trigrid VL), aims to create in Sicily a computational grid for e-science and e-commerce applications with the main goal of increasing the technological innovation of local enterprises and their competition on the global market. PI2S2 project aims to build and develop an e-Infrastructure in Sicily, based on the grid paradigm, mainly for research activity using the grid environment and High Performance Computer systems. As an example we present the first results of a new grid version of FLY a tree Nbody code developed by INAF Astrophysical Observatory of Catania, already published in the CPC program Library, that will be used in the Weak Gravitational Lensing field.

  16. Cross-correlating Planck tSZ with RCSLenS weak lensing: Implications for cosmology and AGN feedback

    CERN Document Server

    Hojjati, Alireza; Harnois-Déraps, Joachim; McCarthy, Ian G; van Waerbeke, Ludovic; Choi, Ami; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Hinshaw, Gary; Ma, Yin-Zhe; Miller, Lance; Viola, Massimo; Tanimura, Hideki

    2016-01-01

    We present measurements of the spatial mapping between (hot) baryons and the total matter in the Universe, via the cross-correlation between the thermal Sunyaev-Zeldovich (tSZ) map from Planck and the weak gravitational lensing maps from the Red Sequence Cluster Survey (RCSLenS). The cross-correlations are performed on the map level where all the sources (including diffuse intergalactic gas) contribute to the signal. We consider two configuration-space correlation function estimators, $\\xi^{ y-\\kappa}$ and $\\xi^ {y-\\gamma_{t}}$, and a Fourier space estimator, $C_{\\ell}^{y-\\kappa}$, in our analysis. We detect a significant correlation out to three degrees of angular separation on the sky. Based on statistical noise only, we can report 13$\\sigma$ and 17$\\sigma$ detections of the cross-correlation using the configuration-space $y-\\kappa$ and $y-\\gamma_{t}$ estimators, respectively. Including a heuristic estimate of the sampling variance yields a detection significance of 6$\\sigma$ and 8$\\sigma$, respectively. A ...

  17. Weighing the Giants I: Weak Lensing Masses for 51 Massive Galaxy Clusters - Project Overview, Data Analysis Methods, and Cluster Images

    CERN Document Server

    von der Linden, Anja; Applegate, Douglas E; Kelly, Patrick L; Allen, Steven W; Ebeling, Harald; Burchat, Patricia R; Burke, David L; Donovan, David; Morris, R Glenn; Blandford, Roger; Erben, Thomas; Mantz, Adam

    2012-01-01

    This is the first in a series of papers in which we measure accurate weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known at redshifts 0.15

  18. Generalized shear-ratio tests: A new relation between cosmological distances, and a diagnostic for a redshift-dependent multiplicative bias in shear measurements

    CERN Document Server

    Schneider, Peter

    2016-01-01

    We derive a new relation between cosological distances, valid in any (statistically) isotropic space-time and independent of cosmological parameters or even the validity of the field equation of General Relativity. In particular, this relation yields an equation between those distance ratios which are the geometrical factors determining the strength of the gravitational lensing effect of mass concentrations. Considering a combination of weak lensing shear ratios, based on lenses at two different redshifts, and sources at three different redshifts, we derive a relation between shear-ratio tests which must be identically satisfied. A redshift-dependent multiplicative bias in shear estimates will violate this relation, and thus can be probed by this generalized shear-ratio test. Combining the lensing effect for lenses at three different redshifts and three different source redshifts, a relation between shear ratios is derived which must be valid independent of a multiplicative bias. We propose these generalized ...

  19. A weak lensing mass reconstruction of the large-scale filament feeding the massive galaxy cluster MACS J0717.5+3745

    Science.gov (United States)

    Jauzac, Mathilde; Jullo, Eric; Kneib, Jean-Paul; Ebeling, Harald; Leauthaud, Alexie; Ma, Cheng-Jiun; Limousin, Marceau; Massey, Richard; Richard, Johan

    2012-11-01

    We report the first weak lensing detection of a large-scale filament funnelling matter on to the core of the massive galaxy cluster MACS J0717.5+3745. Our analysis is based on a mosaic of 18 multipassband images obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope, covering an area of ˜10 × 20 arcmin2. We use a weak lensing pipeline developed for the Cosmic Evolution Survey, modified for the analysis of galaxy clusters, to produce a weak lensing catalogue. A mass map is then computed by applying a weak gravitational lensing multiscale reconstruction technique designed to describe irregular mass distributions such as the one investigated here. We test the resulting mass map by comparing the mass distribution inferred for the cluster core with the one derived from strong lensing constraints and find excellent agreement. Our analysis detects the MACS J0717.5+3745 filament within the 3σ detection contour of the lensing mass reconstruction, and underlines the importance of filaments for theoretical and numerical models of the mass distribution in the cosmic web. We measure the filament's projected length as ˜4.5 h74-1 Mpc, and its mean density as (2.92 ± 0.66) × 108 h74 M⊙ kpc-2. Combined with the redshift distribution of galaxies obtained after an extensive spectroscopic follow-up in the area, we can rule out any projection effect resulting from the chance alignment on the sky of unrelated galaxy group-scale structures. Assuming plausible constraints concerning the structure's geometry based on its galaxy velocity field, we construct a three-dimensional (3D) model of the large-scale filament. Within this framework, we derive the 3D length of the filament to be 18 h74-1 Mpc. The filament's deprojected density in terms of the critical density of the Universe is measured as (206 ± 46) ρcrit, a value that lies at the very high end of the range predicted by numerical simulations. Finally, we study the distribution of stellar mass in the

  20. A Weak Lensing Study of X-ray Groups in the COSMOS survey: Form and Evolution of the Mass-Luminosity Relation

    CERN Document Server

    Leauthaud, A; Taylor, J E; Massey, R; Rhodes, J; Ilbert, O; Bundy, K; Tinker, J; George, M R; Capak, P; Koekemoer, A M; Johnston, D E; Cappelluti, N; Ellis, Richard S; Elvis, M; Heymans, C; Le Fèvre, O; Lilly, S; McCraken, H J; Mellier, Y; Réfrégier, A; Salvato, M; Scoville, N; Smoot, G; Tanaka, M; Van Waerbeke, L; Wolk, M

    2009-01-01

    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 (Lx) and halo mass (M00) where M200 is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 square degrees of contiguous imaging with the Advanced Camera for Surveys (ACS) and deep XMM-Newton/Chandra imaging. 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, M200 ~ Lx^a, with a slope...

  1. The Dark Matter Halos of Moderate Luminosity X-ray AGN as Determined from Weak Gravitational Lensing and Host Stellar Masses

    CERN Document Server

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

    2014-01-01

    Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modeling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to a fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z<1 fro...

  2. Linear and weakly nonlinear aspects of free shear layer instability, roll-up, subharmonic interaction and wall influence

    Science.gov (United States)

    Cain, A. B.; Thompson, M. W.

    1986-01-01

    The growth of the momentum thickness and the modal disturbance energies are examined to study the nature and onset of nonlinearity in a temporally growing free shear layer. A shooting technique is used to find solutions to the linearized eigenvalue problem, and pseudospectral weakly nonlinear simulations of this flow are obtained for comparison. The roll-up of a fundamental disturbance follows linear theory predictions even with a 20 percent disturbance amplitude. A weak nonlinear interaction of the disturbance creates a finite-amplitude mean shear stress which dominates the growth of the layer momentum thickness, and the disturbance growth rate changes until the fundamental disturbance dominates. The fundamental then becomes an energy source for the harmonic, resulting in an increase in the growth rate of the subharmonic over the linear prediction even when the fundamental has no energy to give. Also considered are phase relations and the wall influence.

  3. Gravitational lensing

    CERN Document Server

    Dodelson, Scott

    2017-01-01

    Gravitational lensing is a consequence of general relativity, where the gravitational force due to a massive object bends the paths of light originating from distant objects lying behind it. Using very little general relativity and no higher level mathematics, this text presents the basics of gravitational lensing, focusing on the equations needed to understand the phenomena. It then applies them to a diverse set of topics, including multiply imaged objects, time delays, extrasolar planets, microlensing, cluster masses, galaxy shape measurements, cosmic shear, and lensing of the cosmic microwave background. This approach allows undergraduate students and others to get quickly up to speed on the basics and the important issues. The text will be especially relevant as large surveys such as LSST and Euclid begin to dominate the astronomical landscape. Designed for a one semester course, it is accessible to anyone with two years of undergraduate physics background.

  4. The Normal Cluster Weak Lensing Survey Mass Profiles and M\\/L Ratios of Eight Clusters at z=0.2

    CERN Document Server

    Wittman, D; Tyson, T; Bernstein, G; Fischer, P; Smith, D; Wittman, David; Antonio, Ian Dell'; Tyson, Tony; Bernstein, Gary; Fischer, Philippe; Smith, Deano

    2000-01-01

    We present a survey of mass profiles and mass-to-light ratios of eight typical galaxy clusters at a common redshift (z ~ 0.2). We use weak gravitational lensing as a probe because it is unique in avoiding any assumptions about the dynamical state of the clusters. To avoid bias toward the rare and spectacular clusters that are easy targets for lensing work, we selected an ensemble of much more common clusters with moderate X-ray luminosity. Although the survey is still in progress, two conclusions are emerging: (1) within a cluster, mass follows light very closely on the angular scales that we can measure, $0.2-2h^{-1}$ Mpc, and (2) there is a significant cluster-to-cluster scatter in mass-to-light (M/L) ratios despite uniformity of observing, reduction, and analysis procedures. We also derive an estimate of $\\Omega_{matter}$ based on extrapolation from the mass properties of these typical clusters. Finally, we discuss the discovery of other clusters in our fields through their lensing signal.

  5. Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey

    CERN Document Server

    Schrabback, T; Dietrich, J P; Hoekstra, H; Bocquet, S; Gonzalez, A H; von der Linden, A; McDonald, M; Morrison, C B; Raihan, S F; Allen, S W; Bayliss, M; Benson, B A; Bleem, L E; Chiu, I; Desai, S; Foley, R J; de Haan, T; High, F W; Hilbert, S; Mantz, A B; Massey, R; Mohr, J; Reichardt, C L; Saro, A; Simon, P; Stern, C; Stubbs, C W; Zenteno, A

    2016-01-01

    We present an HST/ACS weak gravitational lensing analysis of 13 massive high-redshift (z_median=0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev-Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour. Our estimate of the source redshift distribution is based on CANDELS data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing...

  6. Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey

    Energy Technology Data Exchange (ETDEWEB)

    Schrabback, T.; et al.

    2016-11-11

    We present an HST/ACS weak gravitational lensing analysis of 13 massive high-redshift (z_median=0.88) galaxy clusters discovered in the South Pole Telescope (SPT) Sunyaev-Zel'dovich Survey. This study is part of a larger campaign that aims to robustly calibrate mass-observable scaling relations over a wide range in redshift to enable improved cosmological constraints from the SPT cluster sample. We introduce new strategies to ensure that systematics in the lensing analysis do not degrade constraints on cluster scaling relations significantly. First, we efficiently remove cluster members from the source sample by selecting very blue galaxies in V-I colour. Our estimate of the source redshift distribution is based on CANDELS data, where we carefully mimic the source selection criteria of the cluster fields. We apply a statistical correction for systematic photometric redshift errors as derived from Hubble Ultra Deep Field data and verified through spatial cross-correlations. We account for the impact of lensing magnification on the source redshift distribution, finding that this is particularly relevant for shallower surveys. Finally, we account for biases in the mass modelling caused by miscentring and uncertainties in the mass-concentration relation using simulations. In combination with temperature estimates from Chandra we constrain the normalisation of the mass-temperature scaling relation ln(E(z) M_500c/10^14 M_sun)=A+1.5 ln(kT/7.2keV) to A=1.81^{+0.24}_{-0.14}(stat.) +/- 0.09(sys.), consistent with self-similar redshift evolution when compared to lower redshift samples. Additionally, the lensing data constrain the average concentration of the clusters to c_200c=5.6^{+3.7}_{-1.8}.

  7. The massive galaxy cluster XMMU J1230.3+1339 at z ˜ 1: colour-magnitude relation, Butcher-Oemler effect, X-ray and weak lensing mass estimates

    Science.gov (United States)

    Lerchster, M.; Seitz, S.; Brimioulle, F.; Fassbender, R.; Rovilos, M.; Böhringer, H.; Pierini, D.; Kilbinger, M.; Finoguenov, A.; Quintana, H.; Bender, R.

    2011-03-01

    We present results from the multiwavelength study of XMMU J1230.3+1339 at z˜ 1. We analyse deep multiband wide-field images from the Large Binocular Telescope (LBT), multi-object spectroscopy observations from VLT, as well as space-based serendipitous observations, from the GALEX and Chandra X-ray observatories. We apply a Bayesian photometric redshift code to derive the redshifts using the far-UV (FUV), near-UV (NUV) and the deep U, B, V, r, i, z data. We make further use of spectroscopic data from FORS2 to calibrate our photometric redshifts, and investigate the photometric and spectral properties of the early-type galaxies. We achieve an accuracy of ▵z/(1 +z)= 0.07 (0.04) and the fraction of catastrophic outliers is η= 13 (0) per cent, when using all (secure) spectroscopic data, respectively. The i-z against z colour-magnitude relation of the photo-z members shows a tight red sequence with a zero-point of 0.935 mag, and slope equal to -0.027. We observe evidence for a truncation at the faint end of the red-cluster-sequence and the Butcher-Oemler effect, finding a fraction of blue galaxies fb≈ 0.5. Further, we conduct a weak lensing analysis of the deep 26 × 26 arcmin r-band LBC image. The observed shear is fitted with a Single-Isothermal-Sphere and a Navarro-Frenk-White model to obtain the velocity dispersion and the model parameters, respectively. Our best-fitting values are, for the velocity dispersion σSIS= 1308 ± 284 km s-1, concentration parameter c= 4.0+14-2 and scale radius rs= 345+50-57 kpc. From a 38 ks Chandra X-ray observation we obtain an independent estimate of the cluster mass. In addition, we create a signal-to-noise ratio (S/N) map for the detection of the matter mass distribution of the cluster using the mass-aperture technique. We find excellent agreement of the mass concentration identified with weak lensing and the X-ray surface brightness. Combining our mass estimates from the kinematic, X-ray and weak lensing analyses we obtain a

  8. JOINT ANALYSIS OF CLUSTER OBSERVATIONS. II. CHANDRA/XMM-NEWTON X-RAY AND WEAK LENSING SCALING RELATIONS FOR A SAMPLE OF 50 RICH CLUSTERS OF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Mahdavi, Andisheh [Department of Physics and Astronomy, San Francisco State University, San Francisco, CA 94131 (United States); Hoekstra, Henk [Leiden Observatory, Leiden University, Niels Bohrweg 2, NL-2333 CA Leiden (Netherlands); Babul, Arif; Bildfell, Chris [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada); Jeltema, Tesla [Santa Cruz Institute for Particle Physics, UC Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Henry, J. Patrick [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2013-04-20

    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{sub 500}{sup WL} (the pseudo-pressure Y{sub X} 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 Y{sub X} 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{sub 500}{sup 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{sub 2500}{sup WL} and r{sub 500}{sup 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.

  9. First Frontier Field Constraints on the Cosmic Star-Formation Rate Density at z~10 - The Impact of Lensing Shear on Completeness of High-Redshift Galaxy Samples

    CERN Document Server

    Oesch, P A; Illingworth, G D; Franx, M; Ammons, S M; van Dokkum, P G; Trenti, M; Labbe, I

    2014-01-01

    We search the complete Hubble Frontier Field dataset of Abell 2744 and its parallel field for z~10 sources to further refine the evolution of the cosmic star-formation rate density (SFRD) at z>8. We independently confirm two images of the recently discovered triply-imaged z~9.8 source by Zitrin et al. (2014) and set an upper limit for similar z~10 galaxies with red colors of J_125-H_160>1.2 in the parallel field of Abell 2744. We utilize extensive simulations to derive the effective selection volume of Lyman-break galaxies at z~10, both in the lensed cluster field and in the adjacent parallel field. Particular care is taken to include position-dependent lensing shear to accurately account for the expected sizes and morphologies of highly-magnified sources. We show that both source blending and shear reduce the completeness at a given observed magnitude in the cluster, particularly near the critical curves. These effects have a significant, but largely overlooked, impact on the detectability of high-redshift s...

  10. Testing gravity on large scales by combining weak lensing with galaxy clustering using CFHTLenS and BOSS CMASS

    CERN Document Server

    Alam, Shadab; More, Surhud; Ho, Shirley; Mandelbaum, Rachel

    2016-01-01

    We measure a combination of gravitational lensing, galaxy clustering, and redshift-space distortions called $E_G$. The quantity $E_G$ probes both parts of metric potential and is insensitive to galaxy bias and $\\sigma_8$. These properties make it an attractive statistic to test $\\Lambda$CDM, General Relativity and its alternate theories. We have combined CMASS DR11 with CFHTLenS and recent measurements of $\\beta$ from RSD analysis, and find $E_G(z = 0.57) = 0.42 \\pm 0.056$, an 13\\% measurement in agreement with the prediction of general relativity $E_G(z = 0.57) = 0.396 \\pm 0.011$ using the Planck 2015 cosmological parameters. We have corrected our measurement for various observational and theoretical systematics. Our measurement is consistent with the first measurement of $E_G$ using CMB lensing in place of galaxy lensing (Pullen et. al. 2015a) at small scales, but shows 2.8$\\sigma$ tension when compared with their final results including large scales. This analysis with future surveys will provide improved ...

  11. Testing gravity on large scales by combining weak lensing with galaxy clustering using CFHTLenS and BOSS CMASS

    Science.gov (United States)

    Alam, Shadab; Miyatake, Hironao; More, Surhud; Ho, Shirley; Mandelbaum, Rachel

    2017-03-01

    We measure a combination of gravitational lensing, galaxy clustering and redshift-space distortions (RSDs) called EG. The quantity EG probes both parts of metric potential and is insensitive to galaxy bias and σ8. These properties make it an attractive statistic to test lambda cold dark matter, general relativity and its alternate theories. We have combined CMASS Data Release 11 with CFHTLenS and recent measurements of β from RSD analysis, and find EG(z = 0.57) = 0.42 ± 0.056, a 13 per cent measurement in agreement with the prediction of general relativity EG(z = 0.57) = 0.396 ± 0.011 using the Planck 2015 cosmological parameters. We have corrected our measurement for various observational and theoretical systematics. Our measurement is consistent with the first measurement of EG using cosmic microwave background lensing in place of galaxy lensing at small scales, but shows 2.8σ tension when compared with their final results including large scales. This analysis with future surveys will provide improved statistical error and better control over systematics to test general relativity and its alternate theories.

  12. Mixed-mode shear-compression failure criterion for weak snowpack layers

    Science.gov (United States)

    Reiweger, Ingrid; Gaume, Johan; Schweizer, Jürg

    2015-04-01

    The failure of a weak snow layer below a cohesive slab is a prerequisite for the release of a dry-snow snow slab avalanche. Once an initial failure in the weak layer reaches its critical size to become self-propagating, the slab will release as an avalanche - provided the slope is steep enough. However, the nature of the initial failure within the weak layer is still unknown - but strongly debated among avalanche researchers. Moreover, different avalanche release models assume contradictory failure criteria as input parameters. We analysed a unique data set stemming from laboratory experiments on snow failure with samples containing a weak snow layer of either depth hoar or buried surface hoar. Depth and surface hoar layers are the most relevant weak layers for avalanche release. The failure behaviour of these types of weak layers can well be described with a modified Mohr-Coulomb model. We therefore propose a mixed-mode failure criterion to be used in avalanche release models.

  13. Systematic tests for position-dependent additive shear bias

    CERN Document Server

    van Uitert, Edo

    2016-01-01

    We present new tests to identify stationary position-dependent additive shear biases in weak gravitational lensing data sets. These tests are important diagnostics for currently ongoing and planned cosmic shear surveys, as such biases induce coherent shear patterns that can mimic and potentially bias the cosmic shear signal. The central idea of these tests is to determine the average ellipticity of all galaxies with shape measurements in a grid in the pixel plane. The distribution of the absolute values of these averaged ellipticities can be compared to randomized catalogues; a difference points to systematics in the data. In addition, we introduce a method to quantify the spatial correlation of the additive bias, which suppresses the contribution from cosmic shear and therefore eases the identification of a position-dependent additive shear bias in the data. We apply these tests to the publicly available shear catalogues from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) and the Kilo Degree Su...

  14. EDITORIAL: Focus on Gravitational Lensing

    Science.gov (United States)

    Jain, Bhuvnesh

    2007-11-01

    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

  15. Finite-amplitude shear-Alfv\\'en waves do not propagate in weakly magnetized collisionless plasmas

    CERN Document Server

    Squire, J; Schekochihin, A A

    2016-01-01

    It is shown that low-collisionality plasmas cannot support linearly polarized shear-Alfv\\'en fluctuations above a critical amplitude $\\delta B_{\\perp}/B_{0} \\sim \\beta^{\\,-1/2}$, where $\\beta$ is the ratio of thermal to magnetic pressure. Above this cutoff, a developing fluctuation will generate a pressure anisotropy that is sufficient to destabilize itself through the parallel firehose instability. This causes the wave frequency to approach zero, interrupting the fluctuation before any oscillation. The magnetic field lines rapidly relax into a sequence of angular zig-zag structures. Such a restrictive bound on shear-Alfv\\'en-wave amplitudes has far-reaching implications for the physics of magnetized turbulence in the high-$\\beta$ conditions prevalent in many astrophysical plasmas, as well as for the solar wind at $\\sim 1 \\mathrm{AU}$ where $\\beta \\gtrsim 1$.

  16. Weak Lensing with the Hyper Suprime-Cam Survey: Connecting the Mass Profiles of Massive Galaxies with their Dark Matter Halos

    Science.gov (United States)

    Leauthaud, Alexie; HSC Survey Collaboration

    2017-01-01

    The HSC survey is an ambitious multi-wavelength (g,r,i,z,y) weak-lensing program to map out 1400 square degrees of the sky with the 8.2m Subaru Telescope to a 5 sigma point-source depth of i~26 mag. This is a truly unique combination of deep imaging over a wide area which makes this a well suited data-set for studying the mass profiles and assembly histories of the most rare and massive galaxies in the universe. Furthermore, the lensing capabilities of HSC means that we can tie the luminous properties of massive galaxies to the properties of their dark matter halos. With 240 deg^2 of excellent quality imaging data already in hand, I will show that HSC can simultaneously map the light profiles of massive galaxies out to 100 kpc and characterize the profiles of their host dark matter halos to radii greater than 10 Mpc. By comparing with modern hydrodynamic simulations of galaxy formation, I will show that the combination of these two measurements provides strong observational constraints on the strength of feedback mechanisms in massive galaxies.

  17. LoCuSS: Exploring the selection of faint blue background galaxies for cluster weak-lensing

    CERN Document Server

    Ziparo, Felicia; Okabe, Nobuhiro; Haines, Chris P; Pereira, Maria J; Egami, Eiichi

    2015-01-01

    Cosmological constraints from galaxy clusters rely on accurate measurements of the mass and internal structure of clusters. An important source of systematic uncertainty in cluster mass and structure measurements is the secure selection of background galaxies that are gravitationally lensed by clusters. This issue has been shown to be particular severe for faint blue galaxies. We therefore explore the selection of faint blue background galaxies, by reference to photometric redshift catalogs derived from the COSMOS survey and our own observations of massive galaxy clusters at z~0.2. We show that methods relying on photometric redshifts of galaxies in/behind clusters based on observations through five filters, and on deep 30-band COSMOS photometric redshifts are both inadequate to identify safely faint blue background galaxies. This is due to the small number of filters used by the former, and absence of massive galaxy clusters at redshifts of interest in the latter. We therefore develop a pragmatic method to c...

  18. Comparing Masses in Literature (CoMaLit)-I. Bias and scatter in weak lensing and X-ray mass estimates of clusters

    CERN Document Server

    Sereno, Mauro

    2014-01-01

    The first building block for using galaxy clusters in astrophysics and cosmology is an accurate determination of their mass, which can be estimated with weak lensing (WL) determinations or X-ray analyses assuming hydrostatic equilibrium (HE). By comparing the two mass proxies in well observed samples of rich clusters, we determined the intrinsic scatters, sigma_{WL}~15 per cent for WL masses and sigma_{HE}~25 per cent for HE masses. The certain assessment of the bias is hampered by differences as large as ~40 per cent in either WL or HE mass estimates reported by different groups. If the scatter in the mass proxy is not considered, the slope of any scaling relation `mass--observable' is biased towards shallower values, whereas the intrinsic scatter of the scaling is over-estimated.

  19. 3D Cosmic Shear: Cosmology from CFHTLenS

    CERN Document Server

    Kitching, T D; Alsing, J; Erben, T; Heymans, C; Hildebrandt, H; Hoekstra, H; Jaffe, A; Kiessling, A; Mellier, Y; Miller, L; van Waerbeke, L; Benjamin, J; Coupon, J; Fu, L; Hudson, M J; Kilbinger, M; Kuijken, K; Rowe, B T P; Schrabback, T; Semboloni, E; Velander, M

    2014-01-01

    This paper presents the first application of 3D cosmic shear to a wide-field weak lensing survey. 3D cosmic shear is a technique that analyses weak lensing in three dimensions using a spherical harmonic approach, and does not bin data in the redshift direction. This is applied to CFHTLenS, a 154 square degree imaging survey with a median redshift of 0.7 and an effective number density of 11 galaxies per square arcminute usable for weak lensing. To account for survey masks we apply a 3D pseudo-Cl approach on weak lensing data, and to avoid uncertainties in the highly non-linear regime, we separately analyse radial wavenumbers k<=1.5h/Mpc and k<=5.0h/Mpc, and angular wavenumbers l~400-5000. We show how one can recover 2D and tomographic power spectra from the full 3D cosmic shear power spectra and present a measurement of the 2D cosmic shear power spectrum, and measurements of a set of 2-bin and 6-bin cosmic shear tomographic power spectra; in doing so we find that using the 3D power in the calculation of...

  20. Review article: Cosmology with cosmic shear observations

    CERN Document Server

    Kilbinger, Martin

    2014-01-01

    Cosmic shear is the distortion of images of distant galaxies due to weak gravitational lensing by the large-scale structure in the Universe. Such images are coherently deformed by the tidal field of matter inhomogeneities along the line of sight. By measuring galaxy shape correlations, we can study the properties and evolution of structure on large scales as well as the geometry of the Universe. Thus, cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. We review here the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then we give an overview of weak-lensing measurements, and present the main observational cosmic-shear results since it was discovered 15 years ago, as well as ...

  1. A Weak Lensing Study of X-ray Groups in the Cosmos Survey: Form and Evolution of the Mass-Luminosity Relation

    Science.gov (United States)

    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

    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)α, with a slope of α = 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, α = 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 3.7σ level with the self-similar prediction of α = 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

  2. An overview of the completed Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS)

    CERN Document Server

    Hildebrandt, Hendrik

    2014-01-01

    The Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) represents the most powerful weak lensing survey carried out to date. The CFHTLenS (Canada-France-Hawaii Telescope Lensing Survey) team was formed in 2008 to analyse the data from the CFHTLS focussing on a rigorous treatment of systematic effects in shape measurements and photometric redshifts. Here we review the technical challenges that we faced in analysing these data and their solutions which set the current standard for weak lensing analyses. We also present some science highlights that were made possible by this effort including cosmic shear tomography, tests for modified gravity models, and the mapping of dark matter structures over unprecedentedly large scales. An outlook is given on current and future surveys that are analysed with the tools prepared for CFHTLenS. CFHTLenS represents the first and only weak lensing data set that has been made publicly available so far. We encourage other surveys to follow this example.

  3. Dark Energy Survey Year 1 Results: The Impact of Galaxy Neighbours on Weak Lensing Cosmology with im3shape

    Energy Technology Data Exchange (ETDEWEB)

    Samuroff, S.; et al.

    2017-08-04

    We use a suite of simulated images based on Year 1 of the Dark Energy Survey to explore the impact of galaxy neighbours on shape measurement and shear cosmology. The hoopoe image simulations include realistic blending, galaxy positions, and spatial variations in depth and PSF properties. Using the im3shape maximum-likelihood shape measurement code, we identify four mechanisms by which neighbours can have a non-negligible influence on shear estimation. These effects, if ignored, would contribute a net multiplicative bias of $m \\sim 0.03 - 0.09$ in the DES Y1 im3shape catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied. This can be reduced to percentage level or less by removing objects with close neighbours, at a cost to the effective number density of galaxies $n_\\mathrm{eff}$ of 30%. We use the cosmological inference pipeline of DES Y1 to explore the cosmological implications of neighbour bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude $S_8\\equiv \\sigma_8 (\\Omega _\\mathrm{m} /0.3)^{0.5}$ by $2 \\sigma$ towards low values. Finally, we use the hoopoe simulations to test the effect of neighbour-induced spatial correlations in the multiplicative bias. We find the impact on the recovered $S_8$ of ignoring such correlations to be subdominant to statistical error at the current level of precision.

  4. On the existence of weak solution to the coupled fluid-structure interaction problem for non-Newtonian shear-dependent fluid

    OpenAIRE

    Hundertmark-Zaušková, A.; Lukáčová-Medviďová, M.; Nečasová, Š. (Šárka)

    2016-01-01

    We study the existence of weak solution for unsteady fluid-structure interaction problem for shear-thickening flow. The time dependent domain has at one part a flexible elastic wall. The evolution of fluid domain is governed by the generalized string equation with action of the fluid forces. The power-law viscosity model is applied to describe shear-dependent non-Newtonian fluids.

  5. Improving lensing cluster mass estimate with flexion

    CERN Document Server

    Cardone, Vincenzo F; Er, Xinzhong; Maoli, Roberto; Scaramella, Roberto

    2016-01-01

    Gravitational lensing has long been considered as a valuable tool to determine the total mass of galaxy clusters. The shear profile as inferred from the statistics of ellipticity of background galaxies allows to probe the cluster intermediate and outer regions thus determining the virial mass estimate. However, the mass sheet degeneracy and the need for a large number of background galaxies motivate the search for alternative tracers which can break the degeneracy among model parameters and hence improve the accuracy of the mass estimate. Lensing flexion, i.e. the third derivative of the lensing potential, has been suggested as a good answer to the above quest since it probes the details of the mass profile. We investigate here whether this is indeed the case considering jointly using weak lensing, magnification and flexion. We use a Fisher matrix analysis to forecast the relative improvement in the mass accuracy for different assumptions on the shear and flexion signal - to - noise (S/N) ratio also varying t...

  6. RCSLenS: The Red Cluster Sequence Lensing Survey

    Science.gov (United States)

    Hildebrandt, H.; Choi, A.; Heymans, C.; Blake, C.; Erben, T.; Miller, L.; Nakajima, R.; van Waerbeke, L.; Viola, M.; Buddendiek, A.; Harnois-Déraps, J.; Hojjati, A.; Joachimi, B.; Joudaki, S.; Kitching, T. D.; Wolf, C.; Gwyn, S.; Johnson, N.; Kuijken, K.; Sheikhbahaee, Z.; Tudorica, A.; Yee, H. K. C.

    2016-11-01

    We present the Red Cluster Sequence Lensing Survey (RCSLenS), an application of the methods developed for the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) to the ˜785 deg2, multi-band imaging data of the Red-sequence Cluster Survey 2. This project represents the largest public, sub-arcsecond seeing, multi-band survey to date that is suited for weak gravitational lensing measurements. With a careful assessment of systematic errors in shape measurements and photometric redshifts, we extend the use of this data set to allow cross-correlation analyses between weak lensing observables and other data sets. We describe the imaging data, the data reduction, masking, multi-colour photometry, photometric redshifts, shape measurements, tests for systematic errors, and a blinding scheme to allow for more objective measurements. In total, we analyse 761 pointings with r-band coverage, which constitutes our lensing sample. Residual large-scale B-mode systematics prevent the use of this shear catalogue for cosmic shear science. The effective number density of lensing sources over an unmasked area of 571.7 deg2 and down to a magnitude limit of r ˜ 24.5 is 8.1 galaxies per arcmin2 (weighted: 5.5 arcmin-2) distributed over 14 patches on the sky. Photometric redshifts based on four-band griz data are available for 513 pointings covering an unmasked area of 383.5 deg2. We present weak lensing mass reconstructions of some example clusters as well as the full survey representing the largest areas that have been mapped in this way. All our data products are publicly available through Canadian Astronomy Data Centre at http://www.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/en/community/rcslens/query.html in a format very similar to the CFHTLenS data release.

  7. Lateral shear interferometry with holo shear lens

    Science.gov (United States)

    Joenathan, C.; Mohanty, R. K.; Sirohi, R. S.

    1984-12-01

    A simple method for obtaining lateral shear using holo shear lenses (HSL) has been discussed. This simple device which produces lateral shears in the orthogonal directions has been used for lens testing. The holo shear lens is placed at or near the focus of the lens to be tested. It has also been shown that HSL can be used in speckle shear interferometry as it performs both the functions of shearing and imaging.

  8. MC2: Mapping the Dark Matter Distribution of the "Toothbrush" Cluster RX J0603.3+4214 with Hubble Space Telescope and Subaru Weak Lensing

    Science.gov (United States)

    Jee, M. James; Dawson, William A.; Stroe, Andra; Wittman, David; van Weeren, Reinout J.; Brüggen, Marcus; Bradač, Maruša; Röttgering, Huub

    2016-02-01

    The galaxy cluster RX J0603.3+4214 at z = 0.225 is one of the rarest clusters boasting an extremely large (˜2 Mpc) radio relic. Because of the remarkable morphology of the relic, the cluster is nicknamed the “Toothbrush Cluster.” Although the cluster's underlying mass distribution is one of the critical pieces of information needed to reconstruct the merger scenario responsible for the puzzling radio relic morphology, its proximity to the Galactic plane b ˜ 10° has imposed significant observational challenges. We present a high-resolution weak-lensing study of the cluster with Subaru/Suprime Cam and Hubble Space Telescope imaging data. Our mass reconstruction reveals that the cluster is composed of complicated dark matter substructures closely tracing the galaxy distribution, in contrast, however, with the relatively simple binary X-ray morphology. Nevertheless, we find that the cluster mass is still dominated by the two most massive clumps aligned north-south with a ˜3:1 mass ratio ({M}200={6.29}-1.62+2.24× {10}14 {M}⊙ and {1.98}-0.74+1.24× {10}14 {M}⊙ for the northern and southern clumps, respectively). The southern mass peak is ˜2‧ offset toward the south with respect to the corresponding X-ray peak, which has a “bullet”-like morphology pointing south. Comparison of the current weak-lensing result with the X-ray, galaxy, and radio relic suggests that perhaps the dominant mechanism responsible for the observed relic may be a high-speed collision of the two most massive subclusters, although the peculiarity of the morphology necessitates involvement of additional subclusters. Careful numerical simulations should follow in order to obtain more complete understanding of the merger scenario utilizing all existing observations. 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.

  9. Constraining the Scatter in the Mass-Richness Relation of maxBCG Clusters With Weak Lensing and X-ray Data

    Energy Technology Data Exchange (ETDEWEB)

    Rozo, Eduardo; /Ohio State U.; Rykoff, Eli S.; /UC, Santa Barbara; Evrard, August; /Michigan U.; Becker, Matthew R.; /Chicago U.; McKay, Timothy; /Michigan U.; Wechsler, Risa H.; /SLAC; Koester, Benjamin P.; /Chicago U. /KICP, Chicago; Hao, Jiangang; /Michigan U.; Hansen, Sarah; /Chicago U. /KICP, Chicago; Sheldon, Erin; /New York U.; Johnston, David; /Houston U.; Annis, James T.; /Fermilab; Frieman, Joshua A.; /Chicago U. /KICP, Chicago /Fermilab

    2009-08-03

    We measure the logarithmic scatter in mass at fixed richness for clusters in the maxBCG cluster catalog, an optically selected cluster sample drawn from SDSS imaging data. Our measurement is achieved by demanding consistency between available weak lensing and X-ray measurements of the maxBCG clusters, and the X-ray luminosity-mass relation inferred from the 400d X-ray cluster survey, a flux limited X-ray cluster survey. We find {sigma}{sub lnM|N{sub 200}} = 0.45{sub -0.18}{sup +0.20} (95%CL) at N{sub 200} {approx} 40, where N{sub 200} is the number of red sequence galaxies in a cluster. As a byproduct of our analysis, we also obtain a constraint on the correlation coefficient between lnL{sub X} and lnM at fixed richness, which is best expressed as a lower limit, r{sub L,M|N} {ge} 0.85 (95% CL). This is the first observational constraint placed on a correlation coefficient involving two different cluster mass tracers. We use our results to produce a state of the art estimate of the halo mass function at z = 0.23 - the median redshift of the maxBCG cluster sample - and find that it is consistent with the WMAP5 cosmology. Both the mass function data and its covariance matrix are presented.

  10. Constraining the Scatter in the Mass-Richness Relation of maxBCG Clusters With Weak Lensing and X-ray Data

    CERN Document Server

    Rozo, Eduardo; Evrard, August; Becker, Matthew; McKay, Timothy; Wechsler, Risa H; Koester, Benjamin P; Hao, Jiangang; Hansen, Sarah; Sheldon, Erin; Johnston, David; Annis, James; Frieman, Joshua

    2008-01-01

    We measure the logarithmic scatter in mass at fixed richness for clusters in the maxBCG cluster catalog, an optically selected cluster sample drawn from SDSS imaging data. Our measurement is achieved by demanding consistency between available weak lensing and X-ray measurements of the maxBCG clusters, and the X-ray luminosity--mass relation inferred from the 400d X-ray cluster survey, a flux limited X-ray cluster survey. We find \\sigma_{\\ln M|N_{200}}=0.45^{+0.20}_{-0.18} (95% CL) at N_{200} ~ 40, where N_{200} is the number of red sequence galaxies in a cluster. As a byproduct of our analysis, we also obtain a constraint on the correlation coefficient between \\ln Lx and \\ln M at fixed richness, which is best expressed as a lower limit, r_{L,M|N} >= 0.85 (95% CL). This is the first observational constraint placed on a correlation coefficient involving two different cluster mass tracers. We use our results to produce a state of the art estimate of the halo mass function at z=0.23 -- the median redshift of the ...

  11. MC^2: Mapping the Dark Matter Distribution of the "Toothbrush" Cluster RX J0603.3+4214 with Hubble Space Telescope and Subaru Weak-lensing

    CERN Document Server

    Jee, M James; Stroe, Andra; Wittman, David; Van Weeren, Reinout J; Bruggen, Marcus; Bradac, Marusa; Rottgering, Huub

    2015-01-01

    The galaxy cluster RX J0603.3+4214 at z=0.225 is one of the rarest clusters boasting an extremely large (~2 Mpc) radio-relic. Because of the remarkable morphology of the relic, the cluster is nicknamed "Toothbrush Cluster". Although the cluster's underlying mass distribution is one of the critical pieces of information needed to reconstruct the merger scenario responsible for the puzzling radio-relic morphology, its proximity to the Galactic plane b~10 deg has imposed significant observational challenges. We present a high-resolution weak-lensing study of the cluster with Subaru/Suprime Cam and Hubble Space Telescope imaging data. Our mass reconstruction reveals that the cluster is comprised of complicated dark matter substructures closely tracing the galaxy distribution, however in contrast with the relatively simple binary X-ray morphology. Nevertheless, we find that the cluster mass is still dominated by the two most massive clumps aligned north-south with a ~3:1 mass ratio (M_{200}=6.29_{-1.62}^{+2.24} x ...

  12. Determination of the shear force at the balance between bacterial attachment and detachment in weak-adherence systems, using a flow displacement chamber

    NARCIS (Netherlands)

    Nejadnik, M. Reza; van der Mei, Hermy C.; Busscher, Henk J.; Norde, Willem

    2008-01-01

    We introduce a procedure for determining shear forces at the balance between attachment and detachment of bacteria under flow. This procedure can be applied to derive adhesion forces in weak-adherence systems, such as polymer brush coatings, which are currently at the center of attention for their c

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

    CERN Document Server

    Mead, James M G; McCarthy, Ian G

    2009-01-01

    The problem of detecting dark matter filaments in the cosmic web is considered. Weak lensing is an ideal probe of dark matter, and therefore forms the basis of particularly promising detection methods. We consider and develop a number of weak lensing techniques that could be used to detect filaments in individual or stacked cluster fields, and apply them to synthetic lensing data sets in the fields of clusters from the Millennium Simulation. These techniques are multipole moments of the shear and convergence, mass reconstruction, and parameterized fits to filament mass profiles using a Markov Chain Monte Carlo approach. In particular, two new filament detection techniques are explored (multipole shear filters and Markov Chain Monte Carlo mass profile fits), and we outline the quality of data required to be able to identify and quantify filament profiles. We also consider the effects of large scale structure on filament detection. We conclude that using these techniques, there will be realistic prospects of de...

  14. Discrepancies between CFHTLenS cosmic shear & Planck: new physics or systematic effects?

    CERN Document Server

    Kitching, Thomas D; Heavens, Alan F; Jimenez, Raul

    2016-01-01

    There is currently a discrepancy in the measured value of the amplitude of matter clustering, parameterised using sigma_8, inferred from galaxy weak lensing and CMB data. In this paper we investigate what could mitigate this discrepancy. We consider systematic effects in the weak lensing data and include intrinsic galaxy alignments, and biases in photometric redshift estimates. We also apply a non-parametric approach to model the baryonic feedback on the dark matter clustering, which is flexible enough to reproduce the OWLS and Illustris simulation results. Finally we extend the cosmological analysis of the weak lensing data to include the effect of massive neutrinos. The statistic we use, 3D cosmic shear, is a method that extracts cosmological information from weak lensing data using a spherical-Bessel function power spectrum approach. There are several advantages that this affords, in particular that the method does not rely on binning in redshift, or covariance estimation from simulations. It also allows f...

  15. Weighing "El Gordo" with a Pecision Scale: Hubble Space Telescope Weak-lensing Analysis of the Merging Galaxy Cluster ACT-CL J0102-4915 at z=0.87

    CERN Document Server

    Jee, M James; Menanteau, Felipe; Sifon, Cristobal; Mandelbaum, Rachel; Barrientos, L Felipe; Infante, Leopoldo; Ng, Karen Y

    2013-01-01

    (Abridged) We present a HST weak-lensing study of the merging galaxy cluster "El Gordo" (ACT-CL J0102-4915) at z=0.87 discovered by the Atacama Cosmology Telescope collaboration as the strongest SZ decrement in its ~1000 sq. deg survey. Our weak-lensing analysis confirms that ACT-CL J0102-4915 is indeed an extreme system consisting of two massive (~10^15 Msun each) subclusters with a projected separation of ~0.7 Mpc. This binary mass structure revealed by our lensing study is consistent with the cluster galaxy distribution and the dynamical study carried out with 89 spectroscopic members. We estimate the mass of ACT-CL J0102-4915 by simultaneously fitting two axisymmetric NFW profiles allowing their centers to vary. Our MCMC analysis shows that the masses of the northwestern (NW) and the southeastern (SE) components are M200c=(1.40+-0.31) x 10^15 Msun and (0.75+-0.17) x 10^15 Msun, respectively. The lensing-based velocity dispersions are consistent with their spectroscopic measurements. The centroids of both ...

  16. N-body lensed CMB maps: lensing extraction and characterization

    CERN Document Server

    Antolini, Claudia; Martinelli, Matteo; Carbone, Carmelita; Baccigalupi, Carlo

    2013-01-01

    We reconstruct shear maps and angular power spectra from simulated weakly lensed total intensity (TT) and polarised (EB) maps of the Cosmic Microwave Background (CMB) anisotropies, obtained using Born approximated ray-tracing through the N-body simulated Cold Dark Matter (CDM) structures in the Millennium Simulations (MS). We compare the recovered signal with the ${\\Lambda}$CDM prediction, on the whole interval of angular scales which is allowed by the finite box size, extending from the degree scale to the arcminute, by applying a quadratic estimator in the flat sky limit; we consider PRISM-like instrumental specification for future generation CMB satellites, corresponding to arcminute angular resolution of 3.2' and sensitivity of 2.43 ${\\mu}$K-arcmin. The noise bias in the simulations closely follows the estimator prediction, becoming dominated by limits in the angular resolution for the EB signal, at l ${\\simeq}$ 1500. The de-biased signal shows no visible departure from predictions of the weak lensing pow...

  17. Cluster-lensing: A Python Package for Galaxy Clusters & Miscentering

    CERN Document Server

    Ford, Jes

    2016-01-01

    We describe a new open source package for calculating properties of galaxy clusters, including NFW halo profiles with and without the effects of cluster miscentering. This pure-Python package, cluster-lensing, provides well-documented and easy-to-use classes and functions for calculating cluster scaling relations, including mass-richness and mass-concentration relations from the literature, as well as the surface mass density $\\Sigma(R)$ and differential surface mass density $\\Delta\\Sigma(R)$ profiles, probed by weak lensing magnification and shear. Galaxy cluster miscentering is especially a concern for stacked weak lensing shear studies of galaxy clusters, where offsets between the assumed and the true underlying matter distribution can lead to a significant bias in the mass estimates if not accounted for. This software has been developed and released in a public GitHub repository, and is licensed under the permissive MIT license. The cluster-lensing package is archived on Zenodo (Ford 2016). Full documenta...

  18. RCSLenS: The Red Cluster Sequence Lensing Survey

    CERN Document Server

    Hildebrandt, H; Heymans, C; Blake, C; Erben, T; Miller, L; Nakajima, R; van Waerbeke, L; Viola, M; Buddendiek, A; Harnois-Déraps, J; Hojjati, A; Joachimi, B; Joudaki, S; Kitching, T D; Wolf, C; Gwyn, S; Kuijken, K; Sheikhbahaee, Z; Tudorica, A; Yee, H K C

    2016-01-01

    We present the Red-sequence Cluster Lensing Survey (RCSLenS), an application of the methods developed for the Canada France Hawaii Telescope Lensing Survey (CFHTLenS) to the ~785deg$^2$, multi-band imaging data of the Red-sequence Cluster Survey 2 (RCS2). This project represents the largest public, sub-arcsecond seeing, multi-band survey to date that is suited for weak gravitational lensing measurements. With a careful assessment of systematic errors in shape measurements and photometric redshifts we extend the use of this data set to allow cross-correlation analyses between weak lensing observables and other data sets. We describe the imaging data, the data reduction, masking, multi-colour photometry, photometric redshifts, shape measurements, tests for systematic errors, and a blinding scheme to allow for more objective measurements. In total we analyse 761 pointings with r-band coverage, which constitutes our lensing sample. Residual large-scale B-mode systematics prevent the use of this shear catalogue fo...

  19. Gravitational lensing properties of an isothermal universal halo profile

    Institute of Scientific and Technical Information of China (English)

    Xin-Zhong Er

    2013-01-01

    N-body simulations predict that dark matter halos with different mass scales are described by a universal model,the Navarro-Frenk-White (NFW) density profiles.As a consequence of baryonic cooling effects,these halos will become more concentrated,and similar to an isothermal sphere over a large range in radii (~ 300 h-1 kpc).The singular isothermal sphere (SIS) model however has to be truncated artificially at large radii since it extends to infinity.We model a massive galaxy halo as a combination of an isothermal sphere and an NFW density profile.We give an approximation for the mass concentration at different baryon fractions and present exact expressions for the weak lensing shear and flexion for such a halo.We compare the lensing properties with the SIS and NFW profiles.We find that the combined profile can generate higher order lensing signals at small radii and is more efficient in generating strong lensing events.In order to distinguish such a halo profile from the SIS or NFW profiles,one needs to combine strong and weak lensing constraints for small and large radii.

  20. Reconstruction of small-scale galaxy cluster substructure with lensing flexion

    Science.gov (United States)

    Cain, Benjamin; Bradač, Maruša; Levinson, Rebecca

    2016-09-01

    We present reconstructions of galaxy-cluster-scale mass distributions from simulated gravitational lensing data sets including strong lensing, weak lensing shear, and measurements of quadratic image distortions - flexion. The lensing data is constructed to make a direct comparison between mass reconstructions with and without flexion. We show that in the absence of flexion measurements, significant galaxy-group scale substructure can remain undetected in the reconstructed mass profiles, and that the resulting profiles underestimate the aperture mass in the substructure regions by ˜25 - 40%. When flexion is included, subhaloes down to a mass of ˜3 × 1012 M⊙ can be detected at an angular resolution smaller than 10″. Aperture masses from profiles reconstructed with flexion match the input distribution values to within an error of ˜13%, including both statistical error and scatter. This demonstrates the important constraint that flexion measurements place on substructure in galaxy clusters and its utility for producing high-fidelity mass reconstructions.

  1. On the validity of the Born approximation for weak cosmic flexions

    CERN Document Server

    Schaefer, Bjoern Malte; Kalovidouris, Angelos Fotios; Bacon, David J

    2011-01-01

    Weak lensing calculations are often made under the assumption of the Born approximation, where the ray path is approximated as a straight radial line. In addition, lens-lens couplings where there are several deflections along the light ray are often neglected. We examine the effect of dropping the Born approximation and taking lens-lens couplings into account, for weak lensing effects up to second order (cosmic flexion), by making a perturbative expansion in the light path. We present a diagrammatic representation of the resulting corrections to the lensing effects. The flexion signal, which measures the derivative of the density field, acquires correction terms proportional to the squared gravitational shear; we also find that by dropping the Born approximation, two further degrees of freedom of the lensing distortion can be excited (the twist components), in addition to the four standard flexion components. We derive angular power spectra of the flexion and twist, with and without the Born-approximation and...

  2. Cross-correlation of gravitational lensing from DES Science Verification data with SPT and Planck lensing

    Science.gov (United States)

    Kirk, D.; Omori, Y.; Benoit-Lévy, A.; Cawthon, R.; Chang, C.; Larsen, P.; Amara, A.; Bacon, D.; Crawford, T. M.; Dodelson, S.; Fosalba, P.; Giannantonio, T.; Holder, G.; Jain, B.; Kacprzak, T.; Lahav, O.; MacCrann, N.; Nicola, A.; Refregier, A.; Sheldon, E.; Story, K. T.; Troxel, M. A.; Vieira, J. D.; Vikram, V.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Becker, M. R.; Benson, B. A.; Bernstein, G. M.; Bernstein, R. A.; Bleem, L. E.; Bonnett, C.; Bridle, S. L.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Carlstrom, J. E.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D. J.; Jarvis, M.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lima, M.; March, M.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Nichol, R. C.; Ogando, R.; Plazas, A. A.; Reichardt, C. L.; Roodman, A.; Rozo, E.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Simard, G.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Wechsler, R. H.; Weller, J.

    2016-06-01

    We measure the cross-correlation between weak lensing of galaxy images and of the cosmic microwave background (CMB). The effects of gravitational lensing on different sources will be correlated if the lensing is caused by the same mass fluctuations. We use galaxy shape measurements from 139 deg2 of the Dark Energy Survey (DES) Science Verification data and overlapping CMB lensing from the South Pole Telescope (SPT) and Planck. The DES source galaxies have a median redshift of zmed ˜ 0.7, while the CMB lensing kernel is broad and peaks at z ˜ 2. The resulting cross-correlation is maximally sensitive to mass fluctuations at z ˜ 0.44. Assuming the Planck 2015 best-fitting cosmology, the amplitude of the DES×SPT cross-power is found to be ASPT = 0.88 ± 0.30 and that from DES×Planck to be APlanck = 0.86 ± 0.39, where A = 1 corresponds to the theoretical prediction. These are consistent with the expected signal and correspond to significances of 2.9σ and 2.2σ, respectively. We demonstrate that our results are robust to a number of important systematic effects including the shear measurement method, estimator choice, photo-z uncertainty and CMB lensing systematics. We calculate a value of A = 1.08 ± 0.36 for DES×SPT when we correct the observations with a simple intrinsic alignment model. With three measurements of this cross-correlation now existing in the literature, there is not yet reliable evidence for any deviation from the expected LCDM level of cross-correlation. We provide forecasts for the expected signal-to-noise ratio of the combination of the five-year DES survey and SPT-3G.

  3. COSMOLOGY WITH GRAVITATIONAL LENSES

    Directory of Open Access Journals (Sweden)

    Emilio E. Falco

    2009-01-01

    Full Text Available Gravitational lenses yield a very high rate of return on observational investment. Given their scarcity, their impact on our knowledge of the universe is very signi cant. In the weak- eld limit, lensing studies are based on well-established physics and thus o er a straightforward approach to pursue many currently pressing problems of astrophysics. Examples of these are the signi cance of dark matter and the density, age and size of the universe. I present recent developments in cosmological applications of gravitational lenses, regarding estimates of the Hubble constant using strong lensing of quasars. I describe our recent measurements of time delays for the images of SDSS J1004+4112, and discuss prospects for the future utilizing synoptic telescopes, planned and under construction.

  4. Cluster-lensing: A Python Package for Galaxy Clusters and Miscentering

    Science.gov (United States)

    Ford, Jes; VanderPlas, Jake

    2016-12-01

    We describe a new open source package for calculating properties of galaxy clusters, including Navarro, Frenk, and White halo profiles with and without the effects of cluster miscentering. This pure-Python package, cluster-lensing, provides well-documented and easy-to-use classes and functions for calculating cluster scaling relations, including mass-richness and mass-concentration relations from the literature, as well as the surface mass density {{Σ }}(R) and differential surface mass density {{Δ }}{{Σ }}(R) profiles, probed by weak lensing magnification and shear. Galaxy cluster miscentering is especially a concern for stacked weak lensing shear studies of galaxy clusters, where offsets between the assumed and the true underlying matter distribution can lead to a significant bias in the mass estimates if not accounted for. This software has been developed and released in a public GitHub repository, and is licensed under the permissive MIT license. The cluster-lensing package is archived on Zenodo. Full documentation, source code, and installation instructions are available at http://jesford.github.io/cluster-lensing/.

  5. Weakly nonlinear analysis of Rayleigh-Bénard convection in a non-Newtonian fluid between plates of finite conductivity: Influence of shear-thinning effects.

    Science.gov (United States)

    Bouteraa, Mondher; Nouar, Chérif

    2015-12-01

    Finite-amplitude thermal convection in a shear-thinning fluid layer between two horizontal plates of finite thermal conductivity is considered. Weakly nonlinear analysis is adopted as a first approach to investigate nonlinear effects. The rheological behavior of the fluid is described by the Carreau model. As a first step, the critical conditions for the onset of convection are computed as a function of the ratio ξ of the thermal conductivity of the plates to the thermal conductivity of the fluid. In agreement with the literature, the critical Rayleigh number Ra(c) and the critical wave number k(c) decrease from 1708 to 720 and from 3.11 to 0, when ξ decreases from infinity to zero. In the second step, the critical value α(c) of the shear-thinning degree above which the bifurcation becomes subcritical is determined. It is shown that α(c) increases with decreasing ξ. The stability of rolls and squares is then investigated as a function of ξ and the rheological parameters. The limit value ξ(c), below which squares are stable, decreases with increasing shear-thinning effects. This is related to the fact that shear-thinning effects increase the nonlinear interactions between sets of rolls that constitute the square patterns [M. Bouteraa et al., J. Fluid Mech. 767, 696 (2015)]. For a significant deviation from the critical conditions, nonlinear convection terms and nonlinear viscous terms become stronger, leading to a further diminution of ξ(c). The dependency of the heat transfer on ξ and the rheological parameters is reported. It is consistent with the maximum heat transfer principle. Finally, the flow structure and the viscosity field are represented for weakly and highly conducting plates.

  6. CFHTLenS: The Canada-France-Hawaii Telescope Lensing Survey

    CERN Document Server

    Heymans, Catherine; Miller, Lance; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D; Mellier, Yannick; Simon, Patrick; Bonnett, Christopher; Coupon, Jean; Fu, Liping; Harnois-D'eraps, Joachim; Hudson, Michael J; Kilbinger, Martin; Kuijken, Koenraad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta; van Uitert, Edo; Vafaei, Sanaz; Velander, Malin

    2012-01-01

    We present the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) that accurately determines a weak gravitational lensing signal from the full 154 square degrees of deep multi-colour data obtained by the CFHT Legacy Survey. Weak gravitational lensing by large-scale structure is widely recognised as one of the most powerful but technically challenging probes of cosmology. We outline the CFHTLenS analysis pipeline, describing how and why every step of the chain from the raw pixel data to the lensing shear and photometric redshift measurement has been revised and improved compared to previous analyses of a subset of the same data. We present a novel method to identify data which contributes a non-negligible contamination to our sample and quantify the required level of calibration for the survey. Through a series of cosmology-insensitive tests we demonstrate the robustness of the resulting cosmic shear signal, presenting a science-ready shear and photometric redshift catalogue for future exploitation.

  7. GREAT3 results I: systematic errors in shear estimation and the impact of real galaxy morphology

    CERN Document Server

    Mandelbaum, Rachel; Armstrong, Robert; Bard, Deborah; Bertin, Emmanuel; Bosch, James; Boutigny, Dominique; Courbin, Frederic; Dawson, William A; Donnarumma, Annamaria; Conti, Ian Fenech; Gavazzi, Raphael; Gentile, Marc; Gill, Mandeep; Hogg, David W; Huff, Eric M; Jee, M James; Kacprzak, Tomasz; Kilbinger, Martin; Kuntzer, Thibault; Lang, Dustin; Luo, Wentao; March, Marisa C; Marshall, Philip J; Meyers, Joshua E; Miller, Lance; Miyatake, Hironao; Nakajima, Reiko; Mboula, Fred Maurice Ngole; Nurbaeva, Guldariya; Okura, Yuki; Paulin-Henriksson, Stephane; Rhodes, Jason; Schneider, Michael D; Shan, Huanyuan; Sheldon, Erin S; Simet, Melanie; Starck, Jean-Luc; Sureau, Florent; Tewes, Malte; Adami, Kristian Zarb; Zhang, Jun; Zuntz, Joe

    2014-01-01

    We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included simulated space- and ground-based data with constant or cosmologically-varying shear fields. The simplest (control) experiment included parametric galaxies with a realistic distribution of signal-to-noise, size, and ellipticity, and a complex point spread function (PSF). The other experiments tested the additional impact of realistic galaxy morphology, multiple exposure imaging, and the uncertainty about a spatially-varying PSF; the last two questions will be explored in Paper II. The 24 participating teams competed to estimate lensing shears to within systematic error tolerances for upcoming Stage-IV dark energy surveys, making 1525 submissions overall. GREAT3 saw considerable variety a...

  8. Systematic errors in the measurement of neutrino masses due to baryonic feedback processes: Prospects for stage IV lensing surveys

    CERN Document Server

    Natarajan, Aravind; Battaglia, Nicholas; Trac, Hy

    2014-01-01

    We examine the importance of baryonic feedback effects on the matter power spectrum on small scales, and the implications for the precise measurement of neutrino masses through gravitational weak lensing. Planned large galaxy surveys such as the Large Synoptic Sky Telescope (LSST) and Euclid are expected to measure the sum of neutrino masses to extremely high precision, sufficient to detect non-zero neutrino masses even in the minimal mass normal hierarchy. We show that weak lensing of galaxies while being a very good probe of neutrino masses, is extremely sensitive to baryonic feedback processes. We use publicly available results from the Overwhelmingly Large Simulations (OWLS) project to investigate the effects of active galactic nuclei feedback, the nature of the stellar initial mass function, and gas cooling rates, on the measured weak lensing shear power spectrum. Using the Fisher matrix formalism and priors from CMB+BAO data, we show that when one does not account for feedback, the measured neutrino mas...

  9. Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 deg2 of KiDS weak lensing data

    Science.gov (United States)

    Brouwer, Margot M.; Cacciato, Marcello; Dvornik, Andrej; Eardley, Lizzie; Heymans, Catherine; Hoekstra, Henk; Kuijken, Konrad; McNaught-Roberts, Tamsyn; Sifón, Cristóbal; Viola, Massimo; Alpaslan, Mehmet; Bilicki, Maciej; Bland-Hawthorn, Joss; Brough, Sarah; Choi, Ami; Driver, Simon P.; Erben, Thomas; Grado, Aniello; Hildebrandt, Hendrik; Holwerda, Benne W.; Hopkins, Andrew M.; de Jong, Jelte T. A.; Liske, Jochen; McFarland, John; Nakajima, Reiko; Napolitano, Nicola R.; Norberg, Peder; Peacock, John A.; Radovich, Mario; Robotham, Aaron S. G.; Schneider, Peter; Sikkema, Gert; van Uitert, Edo; Verdoes Kleijn, Gijs; Valentijn, Edwin A.

    2016-11-01

    Galaxies and their dark matter haloes are part of a complex network of mass structures, collectively called the cosmic web. Using the tidal tensor prescription these structures can be classified into four cosmic environments: voids, sheets, filaments and knots. As the cosmic web may influence the formation and evolution of dark matter haloes and the galaxies they host, we aim to study the effect of these cosmic environments on the average mass of galactic haloes. To this end we measure the galaxy-galaxy lensing profile of 91 195 galaxies, within 0.039 < z < 0.263, from the spectroscopic Galaxy And Mass Assembly survey, using {˜ }100 ° ^2 of overlapping data from the Kilo-Degree Survey. In each of the four cosmic environments we model the contributions from group centrals, satellites and neighbouring groups to the stacked galaxy-galaxy lensing profiles. After correcting the lens samples for differences in the stellar mass distribution, we find no dependence of the average halo mass of central galaxies on their cosmic environment. We do find a significant increase in the average contribution of neighbouring groups to the lensing profile in increasingly dense cosmic environments. We show, however, that the observed effect can be entirely attributed to the galaxy density at much smaller scales (within 4 h-1 Mpc), which is correlated with the density of the cosmic environments. Within our current uncertainties we find no direct dependence of galaxy halo mass on their cosmic environment.

  10. Shear Wave Splitting analysis of borehole microseismic reveals weak azimuthal anisotropy hidden behind strong VTI fabric of Lower Paleozoic shales in northern Poland

    Science.gov (United States)

    Gajek, Wojciech; Verdon, James; Malinowski, Michał; Trojanowski, Jacek

    2017-04-01

    Azimuthal anisotropy plays a key-role in hydraulic fracturing experiments, since it provides information on stress orientation and pre-existing fracture system presence. The Lower Paleozoic shale plays in northern Poland are characterized by a strong (15-18%) Vertical Transverse Isotropy (VTI) fabric which dominates weak azimuthal anisotropy being of order of 1-2%. A shear wave travelling in the subsurface after entering an anisotropic medium splits into two orthogonally polarized waves travelling with different velocities. Splitting parameters which can be assessed using a microseismic array are polarization of the fast shear wave and time delay between two modes. Polarization of the fast wave characterizes the anisotropic system on the wave path while the time delay is proportional to the magnitude of anisotropy. We employ Shear Wave Splitting (SWS) technique using a borehole microseismic dataset collected during a hydraulic stimulation treatment located in northern Poland, to image fracture strike masked by a strong VTI signature. During the inversion part, the VTI background parameters were kept constant using information from 3D seismic (VTI model used for pre-stack depth migration). Obtained fracture azimuths averaged over fracturing stages are consistent with the available XRMI imager logs from the nearby vertical well, however they are different from the large-scale maximum stress direction (by 40-45 degrees). Inverted Hudson's crack density (ca. 2%) are compatible with the low shear-wave anisotropy observed in the cross-dipole sonic logs (1-2%). This work has been funded by the Polish National Centre for Research and Development within the Blue Gas project (No BG2/SHALEMECH/14). Data were provided by the PGNiG SA. Collaboration with University of Bristol was supported within TIDES COST Action ES1401.

  11. Measurement of Cosmic Shear with the Space Telescope Imaging Spectrograph

    Science.gov (United States)

    Rhodes, Jason; Refregier, Alexandre; Collins, Nicholas R.; Gardner, Jonathan P.; Groth, Edward J.; Hill, Robert S.

    2004-04-01

    Weak lensing by large-scale structure allows a direct measure of the dark matter distribution. We have used parallel images taken with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope to measure weak lensing, or cosmic shear. We measure the shapes of 26,036 galaxies in 1292 STIS fields and measure the shear variance at a scale of 0.51m. The charge transfer efficiency (CTE) of STIS has degraded over time and introduces a spurious ellipticity into galaxy shapes during the readout process. We correct for this effect as a function of signal-to-noise ratio and CCD position. We further show that the detected cosmic shear signal is nearly constant in time over the approximately 4 yr of observation. We detect cosmic shear at the 5.1 σ level, and our measurement of the shear variance is consistent with theoretical predictions in a ΛCDM universe. This provides a measure of the normalization of the mass power spectrum σ8=(1.02+/-0.16)(0.3/Ωm)0.46(0.21/Γ)0.18. The 1 σ error includes noise, cosmic variance, systematics, and the redshift uncertainty of the source galaxies. This is consistent with previous cosmic shear measurements, but tends to favor those with a high value of σ8. It is also consistent with the recent determination of σ8 from the Wilkinson Microwave Anisotropy Probe (WMAP) experiment.

  12. Reconstructing the lensing mass in the Universe from photometric catalogue data

    NARCIS (Netherlands)

    Collett, Thomas E.; Marshall, Philip J.; Auger, Matthew W.; Hilbert, Stefan; Suyu, Sherry H.; Greene, Zachary; Treu, Tommaso; Fassnacht, Christopher D.; Koopmans, Leon V. E.; Bradac, Marusa; Blandford, Roger D.

    2013-01-01

    High precision cosmological distance measurements towards individual objects such as time delay gravitational lenses or Type Ia supernovae are affected by weak lensing perturbations by galaxies and groups along the line of sight. In time delay gravitational lenses, 'external convergence',

  13. Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 square degrees of KiDS weak lensing data

    CERN Document Server

    Brouwer, Margot M; Dvornik, Andrej; Eardley, Lizzie; Heymans, Catherine; Hoekstra, Henk; Kuijken, Konrad; McNaught-Roberts, Tamsyn; Sifón, Cristóbal; Viola, Massimo; Alpaslan, Mehmet; Bilicki, Maciej; Bland-Hawthorn, Joss; Brough, Sarah; Choi, Ami; Driver, Simon P; Erben, Thomas; Grado, Aniello; Hildebrandt, Hendrik; Holwerda, Benne W; Hopkins, Andrew M; de Jong, Jelte T A; Liske, Jochen; McFarland, John; Nakajima, Reiko; Napolitano, Nicola R; Norberg, Peder; Peacock, John A; Radovich, Mario; Robotham, Aaron S G; Schneider, Peter; Sikkema, Gert; van Uitert, Edo; Kleijn, Gijs Verdoes

    2016-01-01

    Galaxies and their dark matter haloes are part of a complex network of mass structures, collectively called the cosmic web. Using the tidal tensor prescription these structures can be classified into four cosmic environments: voids, sheets, filaments and knots. As the cosmic web may influence the formation and evolution of dark matter haloes and the galaxies they host, we aim to study the effect of these cosmic environments on the average mass of galactic haloes. To this end we measure the galaxy-galaxy lensing profile of 91,195 galaxies, within 0.039 < z < 0.263, from the spectroscopic Galaxy And Mass Assembly (GAMA) survey, using ~100 square degrees of overlapping data from the Kilo-Degree Survey (KiDS). In each of the four cosmic environments we model the contributions from group centrals, satellites and neighbouring groups to the stacked galaxy-galaxy lensing profiles. After correcting the lens samples for differences in the stellar mass distribution, we find no dependence of the average halo mass o...

  14. Shear and Bulk Viscosities of a Weakly Coupled Quark Gluon Plasma with Finite Chemical Potential and Temperature---Leading-Log Results

    CERN Document Server

    Chen, Jiunn-Wei; Song, Yu-Kun; Wang, Qun

    2012-01-01

    We calculate the shear (eta) and bulk (zeta) viscosities of a weakly coupled quark gluon plasma at the leading-log order with finite temperature T and quark chemical potential mu. We find that the shear viscosity to entropy density ratio eta/s increases monotonically with mu and eventually scales as (mu/T)^2 at large mu. In contrary, zeta/s is insensitive to mu. Both eta/s and zeta/s are monotonically decreasing functions of the quark flavor number N_f when N_f \\geq 2. This property is also observed in pion gas systems. Our perturbative calculation suggests that QCD becomes the most perfect (i.e. with the smallest eta/s) at mu=0 and N_f = 16 (the maximum N_f with asymptotic freedom). It would be interesting to test whether the currently smallest eta/s computed close to the phase transition with mu=0 and N_f = 0 can be further reduced by increasing N_f.

  15. CMB lensing from SPT+Planck and cross-correlations

    Science.gov (United States)

    Omori, Yuuki; SPT Collaboration; DES Collaboration

    2017-01-01

    The South Pole Telescope (SPT) SZ survey has observed 2500 square degrees of the Cosmic Microwave Background (CMB) to high accuracy down to 1 arcminute resolution at 150GHz. The Planck satellite has also observed the same patch of the CMB sky at 143GHz, but the two experiments were designed to measure temperature anisotropies optimally at different angular scales. By combining data from these two experiments, we are able to produce a temperature map that has an improved signal-to-noise ratio at all scales. This combined temperature map is used to produce a CMB weak lensing map, which we use for cosmological parameter and cross-correlation analyses. In particular, the SPT footprint has significant overlap with the Dark Energy Survey (DES) observing region, which allows us to cross-correlate the CMB lensing map with galaxy density and galaxy shear measurements obtained by DES. In this talk, I will present the SPT+Planck combining procedure, the CMB lensing reconstruction pipeline, tests performed to verify the lensing map, and finally the cross-correlation measurements.

  16. The stellar-to-halo mass relation of GAMA galaxies from 100 square degrees of KiDS weak lensing data

    CERN Document Server

    van Uitert, Edo; Hoekstra, Henk; Brouwer, Margot; Sifón, Cristóbal; Viola, Massimo; Baldry, Ivan; Bland-Hawthorn, Joss; Brough, Sarah; Brown, M J I; Choi, Ami; Driver, Simon P; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Joachimi, Benjamin; Kuijken, Konrad; Liske, Jochen; Loveday, Jon; McFarland, John; Miller, Lance; Nakajima, Reiko; Peacock, John; Radovich, Mario; Robotham, A S G; Schneider, Peter; Sikkema, Gert; Taylor, Edward N; Kleijn, Gijs Verdoes

    2016-01-01

    We study the stellar-to-halo mass relation of central galaxies in the range 9.75x10^10 h^-2 M_sun, the stellar mass increases with halo mass as ~M_h^0.25. The ratio of dark matter to stellar mass has a minimum at a halo mass of 8x10^11 h^-1 M_sun with a value of M_h/M_*=56_-10^+16 [h]. We also use the GAMA group catalogue to select centrals and satellites in groups with five or more members, which trace regions in space where the local matter density is higher than average, and determine for the first time the stellar-to-halo mass relation in these denser environments. We find no significant differences compared to the relation from the full sample, which suggests that the stellar-to-halo mass relation does not vary strongly with local density. Furthermore, we find that the stellar-to-halo mass relation of central galaxies can also be obtained by modelling the lensing signal and stellar mass function of satellite galaxies only, which shows that the assumptions to model the satellite contribution in the halo m...

  17. Weak-lensing-inferred scaling relations of galaxy clusters in the RCS2: mass-richness, mass-concentration, mass-bias and more

    CERN Document Server

    van Uitert, Edo; Hoekstra, Henk; Semboloni, Elisabetta; Gladders, Michael D; Yee, H K C

    2016-01-01

    We study a sample of ~10^4 galaxy clusters in the redshift range 0.2 5x10^13 h_70^-1 M_sun, discovered in the second Red-sequence Cluster Survey (RCS2). The depth and excellent image quality of the RCS2 enable us to detect the cluster-mass cross-correlation up to z~0.7. To obtain cluster masses, concentrations and halo biases, we fit a cluster halo model simultaneously to the lensing signal and to the projected density profile of red-sequence cluster members, as the latter provides tight constraints on the cluster miscentring distribution. We parametrise the mass-richness relation as M_200 = A x (N_200/20)^alpha, and find A = (16.7 +- 1.2) x 10^13 h_70^-1 M_sun and alpha = 0.73 +- 0.09 at low redshift (0.2

  18. Cosmic Shear Bias and Calibration in Cosmic Shear Studies

    CERN Document Server

    Taylor, A N

    2016-01-01

    With the advent of large-scale weak lensing surveys there is a need to understand how realistic, scale-dependent systematics bias cosmic shear and dark energy measurements, and how they can be removed. Here we describe how spatial variations in the amplitude and orientation of realistic image distortions convolve with the measured shear field, mixing the even-parity convergence and odd-parity modes, and bias the shear power spectrum. Many of these biases can be removed by calibration to external data, the survey itself, or by modelling in simulations. The uncertainty in the calibration must be marginalised over and we calculate how this propagates into parameter estimation, degrading the dark energy Figure-of-Merit. We find that noise-like biases affect dark energy measurements the most, while spikes in the bias power have the least impact, reflecting their correlation with the effect of cosmological parameters. We argue that in order to remove systematic biases in cosmic shear surveys and maintain statistica...

  19. Weighing 'El Gordo' with a precision scale: Hubble space telescope weak-lensing analysis of the merging galaxy cluster ACT-CL J0102–4915 at z = 0.87

    Energy Technology Data Exchange (ETDEWEB)

    Jee, M. James; Ng, Karen Y. [Department of Physics, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States); Hughes, John P.; Menanteau, Felipe [Department of Physics and Astronomy, Rutgers University, 136 Frelinghysen Rd., Piscataway, NJ 08854 (United States); Sifón, Cristóbal [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Mandelbaum, Rachel [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States); Barrientos, L. Felipe; Infante, Leopoldo [Departamento de Astronomía y Astrofísica, Facultad de Física, Ponticia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile)

    2014-04-10

    We present a Hubble Space Telescope weak-lensing study of the merging galaxy cluster 'El Gordo' (ACT-CL J0102–4915) at z = 0.87 discovered by the Atacama Cosmology Telescope (ACT) collaboration as the strongest Sunyaev-Zel'dovich decrement in its ∼1000 deg{sup 2} survey. Our weak-lensing analysis confirms that ACT-CL J0102–4915 is indeed an extreme system consisting of two massive (≳ 10{sup 15} M {sub ☉} each) subclusters with a projected separation of ∼0.7 h{sub 70}{sup −1} Mpc. This binary mass structure revealed by our lensing study is consistent with the cluster galaxy distribution and the dynamical study carried out with 89 spectroscopic members. We estimate the mass of ACT-CL J0102–4915 by simultaneously fitting two axisymmetric Navarro-Frenk-White (NFW) profiles allowing their centers to vary. We use only a single parameter for the NFW mass profile by enforcing the mass-concentration relation from numerical simulations. Our Markov-Chain-Monte-Carlo analysis shows that the masses of the northwestern (NW) and the southeastern (SE) components are M{sub 200c}=(1.38±0.22)×10{sup 15} h{sub 70}{sup −1} M{sub ⊙} and (0.78±0.20)×10{sup 15} h{sub 70}{sup −1} M{sub ⊙}, respectively, where the quoted errors include only 1σ statistical uncertainties determined by the finite number of source galaxies. These mass estimates are subject to additional uncertainties (20%-30%) due to the possible presence of triaxiality, correlated/uncorrelated large scale structure, and departure of the cluster profile from the NFW model. The lensing-based velocity dispersions are 1133{sub −61}{sup +58} km s{sup −1} and 1064{sub −66}{sup +62} km s{sup −1} for the NW and SE components, respectively, which are consistent with their spectroscopic measurements (1290 ± 134 km s{sup –1} and 1089 ± 200 km s{sup –1}, respectively). The centroids of both components are tightly constrained (∼4'') and close to the optical luminosity

  20. Systematic tests for position-dependent additive shear bias

    Science.gov (United States)

    van Uitert, Edo; Schneider, Peter

    2016-11-01

    We present new tests to identify stationary position-dependent additive shear biases in weak gravitational lensing data sets. These tests are important diagnostics for currently ongoing and planned cosmic shear surveys, as such biases induce coherent shear patterns that can mimic and potentially bias the cosmic shear signal. The central idea of these tests is to determine the average ellipticity of all galaxies with shape measurements in a grid in the pixel plane. The distribution of the absolute values of these averaged ellipticities can be compared to randomised catalogues; a difference points to systematics in the data. In addition, we introduce a method to quantify the spatial correlation of the additive bias, which suppresses the contribution from cosmic shear and therefore eases the identification of a position-dependent additive shear bias in the data. We apply these tests to the publicly available shear catalogues from the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) and the Kilo Degree Survey (KiDS) and find evidence for a small but non-negligible residual additive bias at small scales. As this residual bias is smaller than the error on the shear correlation signal at those scales, it is highly unlikely that it causes a significant bias in the published cosmic shear results of CFHTLenS. In CFHTLenS, the amplitude of this systematic signal is consistent with zero in fields where the number of stars used to model the point spread function (PSF) is higher than average, suggesting that the position-dependent additive shear bias originates from undersampled PSF variations across the image.

  1. Gravitational lensing in standard and non-standard frameworks as a probe for precision cosmology: Challenges and applications

    Science.gov (United States)

    Troxel, Michael A.

    Gravitational lensing has been identified as a critical cosmological tool in studying the evolution of large scale structure in the universe as well as the nature of dark matter and dark energy. One of the primary physical systematics of weak lensing due to large scale structure (cosmic shear) is the intrinsic alignment (IA) of galaxies, which poses a barrier to precision weak lensing measurements. Methods for identifying and removing its effects on cosmological information are key to the success of weak lensing survey science goals. We have expanded model-independent techniques to isolate and remove the IA contamination from the lensing signal. These self-calibration techniques take advantage of complementary survey information to self-calibrate the lensing signal, which along with unique lensing and IA geometry and separation dependencies, allow us to reconstruct the IA correlations at the level of the spectrum and bispectrum. We have demonstrated that the self-calibration approach can reduce the IA bias over most relevant scale and redshift ranges by up to a factor of 10 or more. This could reduce a potential 10-20% bias in some cosmological information down to the 1-2% level. The self-calibration techniques have the added benefit of preserving the IA signal, which itself provides additional information that can be used in studying the formation and evolution of large scale structure in the universe. We have also identified a new source of intrinsic alignment contamination in cross-correlations with cosmic microwave background lensing and proposed a method to calibrate it, and we explored the potential of future surveys to measure directly various 2- and 3-point intrinsic alignment correlations. Finally, we have investigated the use of exact anisotropic and inhomogeneous models in general relativity for large- and small-scale structures in the universe, developing the frameworks necessary to analyze gravitational lensing in such models, and have compared them to

  2. On the validity of the Born approximation for weak cosmic flexions

    Science.gov (United States)

    Schäfer, Björn Malte; Heisenberg, Lavinia; Kalovidouris, Angelos F.; Bacon, David J.

    2012-02-01

    Weak lensing calculations are often made under the assumption of the Born approximation, where the ray path is approximated as a straight radial line. In addition, lens-lens couplings where there are several deflections along the light ray are often neglected. We examine the effect of dropping the Born approximation and taking lens-lens couplings into account, for weak lensing effects up to second order (cosmic flexion), by making a perturbative expansion in the light path. We present a diagrammatic representation of the resulting corrections to the lensing effects. The flexion signal, which measures the derivative of the density field, acquires correction terms proportional to the squared gravitational shear; we also find that by dropping the Born approximation, two further degrees of freedom of the lensing distortion can be excited (the twist components), in addition to the four standard flexion components. We derive angular power spectra of the flexion and twist, with and without the Born approximation and lens-lens couplings and confirm that the Born approximation is an excellent approximation for weak cosmic flexions, but may fail in the strong lensing regime.

  3. The Effects of Physically Unrelated Near Neighbors on the Galaxy-Galaxy Lensing Signal

    Science.gov (United States)

    Brainerd, Tereasa G.

    2017-01-01

    A suite of Monte Carlo simulations was used to investigate the effects of near neighbors on the galaxy-galaxy lensing signal. The simulated lenses were drawn from a set of observed galaxies with known spectroscopic redshifts and known luminosities. The relative locations of the lenses were obtained from the actual locations of the observed galaxies on the sky. The simulations take into account the weak lensing deflections of central lenses and their nearest neighbor galaxies on the sky. The relative depths of the gravitational potentials of the lenses were obtained from their rest-frame blue luminosities using a Faber-Jackson type of relationship, and they naturally incorporate the intrinsic clustering of galaxies. In the first set of simulations, all lenses were assigned a single, fixed redshift. In this case, as expected, the mean tangential shear about the central lenses, γT, was found to be identically equal to the excess surface mass density, ΔΣ, divided by the critical surface mass density, Σc. In the second set of simulations, the lenses were assigned their actual, observed spectroscopic redshifts and Σc was taken to be the critical surface mass density of the central lens. In the second set of simulations, the relationship γT = ΔΣ/Σc was found to be violated on large scales because more than 90% of the near neighbors for a given central lens are located at redshifts that differ significantly from that of the central lens. That is, the simulations show the “two-halo” term in galaxy-galaxy lensing can have a significant contribution from galaxies that are not physically associated with the central lens. For a given central lens, physically unrelated near neighbors give rise to a ratio of γT to ΔΣ/Σc that spans a wide range from 0.5 to 1.5 at a projected distance ~1 Mpc. The magnitude and the sense of the discrepancy between γT and the ratio ΔΣ/Σc are functions of both the projected radius and the velocity dispersions of the central lens

  4. Cross-correlation of gravitational lensing from DES Science Verification data with SPT and Planck lensing

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, D.; et al.

    2015-12-14

    We measure the cross-correlation between weak lensing of galaxy images and of the cosmic microwave background (CMB). The effects of gravitational lensing on different sources will be correlated if the lensing is caused by the same mass fluctuations. We use galaxy shape measurements from 139 deg$^{2}$ of the Dark Energy Survey (DES) Science Verification data and overlapping CMB lensing from the South Pole Telescope (SPT) and Planck. The DES source galaxies have a median redshift of $z_{\\rm med} {\\sim} 0.7$, while the CMB lensing kernel is broad and peaks at $z{\\sim}2$. The resulting cross-correlation is maximally sensitive to mass fluctuations at $z{\\sim}0.44$. Assuming the Planck 2015 best-fit cosmology, the amplitude of the DES$\\times$SPT cross-power is found to be $A = 0.88 \\pm 0.30$ and that from DES$\\times$Planck to be $A = 0.86 \\pm 0.39$, where $A=1$ corresponds to the theoretical prediction. These are consistent with the expected signal and correspond to significances of $2.9 \\sigma$ and $2.2 \\sigma$ respectively. We demonstrate that our results are robust to a number of important systematic effects including the shear measurement method, estimator choice, photometric redshift uncertainty and CMB lensing systematics. Significant intrinsic alignment of galaxy shapes would increase the cross-correlation signal inferred from the data; we calculate a value of $A = 1.08 \\pm 0.36$ for DES$\\times$SPT when we correct the observations with a simple IA model. With three measurements of this cross-correlation now existing in the literature, there is not yet reliable evidence for any deviation from the expected LCDM level of cross-correlation, given the size of the statistical uncertainties and the significant impact of systematic errors, particularly IAs. We provide forecasts for the expected signal-to-noise of the combination of the five-year DES survey and SPT-3G.

  5. Ophthalmic Lenses

    CERN Document Server

    Bhootra, Ajay Kumar

    2009-01-01

    This book is uniquely meant for the ophthalmologists, optometrists and opticians to help the world see better by excellent vision through the services of technicians and clinical principle based ophthalmology so that the management of ocular problems can be done for a better vision . Informs that a wide range of material and design of ophthalmic lenses with innovative developments is available. This book presents comprehensively rich information about the ophthalmic lenses and their dispensing tips . It will be highly useful mainly for the students of optometry and opticians, ophthalmologists,

  6. Cross-correlating Planck CMB lensing with SDSS: lensing-lensing and galaxy-lensing cross-correlations

    Science.gov (United States)

    Singh, Sukhdeep; Mandelbaum, Rachel; Brownstein, Joel R.

    2017-01-01

    We present results from cross-correlating Planck cosmic microwave background (CMB) lensing maps with the Sloan Digital Sky Survey (SDSS) galaxy lensing shape catalogue and BOSS (Baryon Oscillation Spectroscopic Survey) galaxy catalogues. For galaxy position versus CMB lensing cross-correlations, we measure the convergence signal around the galaxies in configuration space, using the BOSS LOWZ (z ˜ 0.30) and CMASS (z ˜ 0.57) samples. With fixed Planck 2015 cosmology, doing a joint fit with the galaxy clustering measurement, for the LOWZ (CMASS) sample we find a galaxy bias bg = 1.75 ± 0.04 (1.95 ± 0.02) and galaxy-matter cross-correlation coefficient rcc = 1.0 ± 0.2 (0.8 ± 0.1) using 20 < rp < 70 h-1 Mpc, consistent with results from galaxy-galaxy lensing. Using the same scales and including the galaxy-galaxy lensing measurements, we constrain Ωm = 0.284 ± 0.024 and relative calibration bias between the CMB lensing and galaxy lensing to be b_γ =0.82^{+0.15}_{-0.14}. The combination of galaxy lensing and CMB lensing also allows us to measure the cosmological distance ratios (with zl ˜ 0.3, zs ˜ 0.5) R=D_s D_{l,*}/D_{* D_{l,s}}=2.68± 0.29, consistent with predictions from the Planck 2015 cosmology (R=2.35). We detect the galaxy position-CMB convergence cross-correlation at small scales, rp < 1 h-1 Mpc, and find consistency with lensing by NFW haloes of mass Mh ˜ 1013 h-1 M⊙. Finally, we measure the CMB lensing-galaxy shear cross-correlation, finding an amplitude of A = 0.76 ± 0.23 (zeff = 0.35, θ < 2°) with respect to Planck 2015 Λ cold dark matter predictions (1σ level consistency). We do not find evidence for relative systematics between the CMB and SDSS galaxy lensing.

  7. Is Gravitational Lensing by Intercluster Filaments Always Negligible?

    CERN Document Server

    Xu, Dong; Shan, HuanYuan; Famaey, Benoit; Limousin, Marceau; Zhao, HongSheng

    2007-01-01

    Intercluster filaments negligibly contribute to the weak lensing signal in General Relativity (GR), $\\gamma_{N}\\sim 10^{-4}-10^{-3}$. In the context of relativistic Modified Newtonian Dynamics (MOND) (Bekenstein 2004), however, a single filament inclined by $\\approx 45^\\circ$ from the line of sight can cause substantial distortion of background sources pointing towards the filament's axis ($\\kappa=\\gamma=(1-A^{-1})/2\\sim 0.01$); this is rigourous for infinitely long uniform filaments, but also qualitatively true for short filaments ($\\sim 30$Mpc), and even in regions where the projected matter density of the filament equals to zero. Since galaxies and galaxy clusters are generally embedded in filaments or are projected on such structures, this contribution complicates the interpretation of the weak lensing shear map in the context of MOND. While our analysis is of mainly theoretical interest providing order-of-magnitude estimates only, it seems safe to conclude that when modeling systems with anomalous weak l...

  8. The Massive Galaxy Cluster XMMU J1230.3+1339 at z ~ 1: Colour-magnitude relation, Butcher-Oemler effect, X-ray and weak lensing mass estimates

    CERN Document Server

    Lerchster, M; Brimioulle, F; Fassbender, R; Rovilos, M; Böhringer, H; Pierini, D; Kilbinger, M; Finoguenov, A; Quintana, H; Bender, R

    2010-01-01

    We present results from the multi-wavelength study of XMMU J1230.3+1339 at z ~ 1. We analyze deep multi-band wide-field images from the Large Binocular Telescope, multi-object spectroscopy observations from VLT, as well as space-based serendipitous observations, from the GALEX and Chandra X-ray observatories. We apply a Bayesian photometric redshift code to derive the redshifts using the FUV, NUV and the deep U, B, V, r, i, z data. We achieve an accuracy of $\\triangle z/(1+z)$ = 0.07 (0.04) and the fraction of catastrophic outliers is $\\eta$ = 13 (0)%, when using all (secure) spectroscopic data, respectively. The i - z against z colour-magnitude relation of the photo-z members shows a tight red-sequence with a zero point of 0.935 mag, and slope equal to -0.027. We observe evidence for a truncation at the faint end of the red-cluster-sequence and the Butcher-Oemler effect, finding a fraction of blue galaxies $f_b \\approx$ 0.5. Further we conduct a weak lensing analysis of the deep 26' $\\times$ 26' r-band LBC i...

  9. Measuring the Deviation from the Linear and Deterministic Bias through Cosmic Gravitational Lensing Effects

    CERN Document Server

    Fan, Z H

    2003-01-01

    Since gravitational lensing effects directly probe inhomogeneities of dark matter, lensing-galaxy cross-correlations can provide us important information on the relation between dark matter and galaxy distributions, i.e., the bias. In this paper, we propose a method to measure the stochasticity/nonlinearity of the galaxy bias through correlation studies of the cosmic shear and galaxy number fluctuations. Specifically, we employ the aperture mass statistics $M_{ap}$ to describe the cosmic shear. We divide the foreground galaxy redshift $z_f^2/$ for each redshift bin. Then the ratio of the summation of $^2/$ over the bins to $$ gives a measure of the nonlinear/stochastic bias. Here $N_g(z_f)$ is the projected surface number density fluctuation of foreground galaxies at redshift $z_f$, and $M_{ap}$ is the aperture mass from the cosmic-shear analysis. We estimate that for a moderately deep weak-lensing survey with $z_s=1$, source galaxy surface number density $n_b=30 \\hbox {gal}/\\hbox {arcmin}^2$ and a survey are...

  10. Lensing Measurements of the Ellipticity of LRG Dark Matter Halos

    CERN Document Server

    Clampitt, Joseph

    2015-01-01

    Lensing measurements of the shapes of dark matter halos can provide tests of gravity theories and possible dark matter interactions. We measure the quadrupole weak lensing signal from the elliptical halos of 70,000 SDSS Luminous Red Galaxies. We use a new estimator that nulls the spherical halo lensing signal, isolating the shear due to anisotropy in the dark matter distribution. One of the two Cartesian components of our estimator is insensitive to the primary systematic, a spurious alignment of lens and source ellipticities, allowing us to make robust measurements of halo ellipticity. Our best-fit value for the ellipticity of the surface mass density is 0.24, which translates to an axis ratio of 0.78. We rule out the hypothesis of no ellipticity at the 4-sigma confidence level, and ellipticity 0.89) at the 2-sigma level. We discuss how our measurements of halo ellipticity are revised to higher values using estimates of the misalignment of mass and light from simulations. Finally, we apply the same techniqu...

  11. Gravitational Lensing Analysis of the Kilo Degree Survey

    CERN Document Server

    Kuijken, Konrad; Hildebrandt, Hendrik; Nakajima, Reiko; Erben, Thomas; de Jong, Jelte T A; Viola, Massimo; Choi, Ami; Hoekstra, Henk; Miller, Lance; van Uitert, Edo; Amon, Alexandra; Blake, Chris; Brouwer, Margot; Buddendiek, Axel; Conti, Ian Fenech; Eriksen, Martin; Grado, Aniello; Harnois-Déraps, Joachim; Helmich, Ewout; Herbonnet, Ricardo; Irisarri, Nancy; Kitching, Thomas; Klaes, Dominik; Labarbera, Francesco; Napolitano, Nicola; Radovich, Mario; Schneider, Peter; Sifón, Cristóbal; Sikkema, Gert; Simon, Patrick; Tudorica, Alexandru; Valentijn, Edwin; Kleijn, Gijs Verdoes; van Waerbeke, Ludovic

    2015-01-01

    The Kilo-Degree Survey (KiDS) is a multi-band imaging survey designed for cosmological studies from weak lensing and photometric redshifts. It uses the ESO VLT Survey Telescope with its wide-field camera OmegaCAM. KiDS images are taken in four filters similar to the SDSS ugri bands. The best-seeing time is reserved for deep r-band observations that reach a median 5-sigma limiting AB magnitude of 24.9 with a median seeing that is better than 0.7arcsec. Initial KiDS observations have concentrated on the GAMA regions near the celestial equator, where extensive, highly complete redshift catalogues are available. A total of 101 survey tiles, one square degree each, form the basis of the first set of lensing analyses, which focus on measurements of halo properties of GAMA galaxies. 9 galaxies per square arcminute enter the lensing analysis, for an effective inverse shear variance of 69 per square arcminute. Accounting for the shape measurement weight, the median redshift of the sources is 0.53. KiDS data processing...

  12. epsnoise: Pixel noise in ellipticity and shear measurements

    Science.gov (United States)

    Melchior, Peter; Viola, Massimo

    2012-04-01

    epsnoise simulates pixel noise in weak-lensing ellipticity and shear measurements. This open-source python code can efficiently create an intrinsic ellipticity distribution, shear it, and add noise, thereby mimicking a "perfect" measurement that is not affected by shape-measurement biases. For theoretical studies, we provide the Marsaglia distribution, which describes the ratio of normal variables in the general case of non-zero mean and correlation. We also added a convenience method that evaluates the Marsaglia distribution for the ratio of moments of a Gaussian-shaped brightness distribution, which gives a very good approximation of the measured ellipticity distribution also for galaxies with different radial profiles. We provide four shear estimators, two based on the ɛ ellipticity measure, two on χ. While three of them are essentially plain averages, we introduce a new estimator which requires a functional minimization.

  13. 坝基软弱夹层剪切蠕变及其长期强度试验研究%EXPERIMENTAL RESEARCH ON SHEAR CREEP AND ITS LONG-TERM STRENGTH OF WEAK INTERCALATION IN DAM FOUNDATION

    Institute of Scientific and Technical Information of China (English)

    王宇; 李建林; 刘锋

    2013-01-01

    为了更准确认识坝基岩体中的软弱夹层剪切蠕变特性,进行不同正应力水平下的剪切蠕变试验,采用不同正应力水平下分级加载剪应力的方式,重点研究软弱夹层的剪切蠕变变形规律、破裂机制及其长期抗剪强度。研究结果表明,经验公式u=u0+A[1-exp(-Bt)]+Ctn能较好反映软弱夹层的剪切蠕变变形规律,不同正应力水平下的平均及稳态剪切蠕变速率随剪应力增加呈指数函数增大,且软弱夹层剪切蠕变破坏呈现典型的延性破坏特征。通过新提出的拐点法确定不同正应力水平下的长期抗剪强度,并与稳态速率法的计算结果进行对比,验证了拐点法的合理性和适用性,该方法大大提高了确定岩体长期抗剪强度的准确性,对工程实际具有重要的参考价值。%In order to understand exactly the creep property of weak intercalation in dam foundation rock,the shear creep test is carried out under different normal stresses by using step loading shear stress. The shear creep deformation law,failure mechanism and long-term shear strength of weak intercalation are concerned in this study. The results indicate that the empirical formulation u=u0+A[1-exp(-Bt)]+Ctn can reflect the shear creep deformation law of weak intercalation properly,the average and steady-state shear creep rates increase at a exponential function with the shear stress increasing,and the shear creep failure of weak intercalation shows typical ductility failure characteristics. Based on a new method,called inflection-point method,the long-term shear strength of weak intercalation under different normal stresses is determined. The calculation results of inflection-point method are compared with that of steady-state rate method,and the rationality and validity of inflection-point method are test. The research results show that this method greatly improves the accuracy of determining the rock mass long-term shear strength

  14. Precision simulation of ground-based lensing data using observations from space

    CERN Document Server

    Mandelbaum, Rachel; Leauthaud, Alexie; Massey, Richard J; Rhodes, Jason

    2011-01-01

    Current and upcoming wide-field, ground-based, broad-band imaging surveys promise to address a wide range of outstanding problems in galaxy formation and cosmology. Several such uses of ground-based data, especially weak gravitational lensing, require highly precise measurements of galaxy image statistics with careful correction for the effects of the point-spread function (PSF). In this paper, we introduce the SHERA (SHEar Reconvolution Analysis) software to simulate ground-based imaging data with realistic galaxy morphologies and observing conditions, starting from space-based data (from COSMOS, the Cosmological Evolution Survey) and accounting for the effects of the space-based PSF. This code simulates ground-based data, optionally with a weak lensing shear applied, in a model-independent way using a general Fourier space formalism. The utility of this pipeline is that it allows for a precise, realistic assessment of systematic errors due to the method of data processing, for example in extracting weak len...

  15. Investigations of Galaxy Clusters Using Gravitational Lensing

    Energy Technology Data Exchange (ETDEWEB)

    Wiesner, Matthew P. [Northern Illinois Univ., DeKalb, IL (United States)

    2014-08-01

    In this dissertation, we discuss the properties of galaxy clusters that have been determined using strong and weak gravitational lensing. A galaxy cluster is a collection of galaxies that are bound together by the force of gravity, while gravitational lensing is the bending of light by gravity. Strong lensing is the formation of arcs or rings of light surrounding clusters and weak lensing is a change in the apparent shapes of many galaxies. In this work we examine the properties of several samples of galaxy clusters using gravitational lensing. In Chapter 1 we introduce astrophysical theory of galaxy clusters and gravitational lensing. In Chapter 2 we examine evidence from our data that galaxy clusters are more concentrated than cosmology would predict. In Chapter 3 we investigate whether our assumptions about the number of galaxies in our clusters was valid by examining new data. In Chapter 4 we describe a determination of a relationship between mass and number of galaxies in a cluster at higher redshift than has been found before. In Chapter 5 we describe a model of the mass distribution in one of the ten lensing systems discovered by our group at Fermilab. Finally in Chapter 6 we summarize our conclusions.

  16. Cross-correlation of gravitational lensing from DES Science Verification data with SPT and Planck lensing

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, D.; Omori, Y.; Benoit-Lévy, A.; Cawthon, R.; Chang, C.; Larsen, P.; Amara, A.; Bacon, D.; Crawford, T. M.; Dodelson, S.; Fosalba, P.; Giannantonio, T.; Holder, G.; Jain, B.; Kacprzak, T.; Lahav, O.; MacCrann, N.; Nicola, A.; Refregier, A.; Sheldon, E.; Story, K. T.; Troxel, M. A.; Vieira, J. D.; Vikram, V.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Becker, M. R.; Benson, B. A.; Bernstein, G. M.; Bernstein, R. A.; Bleem, L. E.; Bonnett, C.; Bridle, S. L.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Capozzi, D.; Carlstrom, J. E.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; Crocce, M.; Cunha, C. E.; D' Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D. J.; Jarvis, M.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lima, M.; March, M.; Martini, P.; Melchior, P.; Miller, C. J.; Miquel, R.; Nichol, R. C.; Ogando, R.; Plazas, A. A.; Reichardt, C. L.; Roodman, A.; Rozo, E.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Simard, G.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Wechsler, R. H.; Weller, J.

    2016-03-10

    We measure the cross-correlation between weak lensing of galaxy images and of the cosmic microwave background (CMB). The effects of gravitational lensing on different sources will be correlated if the lensing is caused by the same mass fluctuations. We use galaxy shape measurements from 139 deg$^{2}$ of the Dark Energy Survey (DES) Science Verification data and overlapping CMB lensing from the South Pole Telescope (SPT) and Planck. The DES source galaxies have a median redshift of $z_{\\rm med} {\\sim} 0.7$, while the CMB lensing kernel is broad and peaks at $z{\\sim}2$. The resulting cross-correlation is maximally sensitive to mass fluctuations at $z{\\sim}0.44$. Assuming the Planck 2015 best-fit cosmology, the amplitude of the DES$\\times$SPT cross-power is found to be $A = 0.88 \\pm 0.30$ and that from DES$\\times$Planck to be $A = 0.86 \\pm 0.39$, where $A=1$ corresponds to the theoretical prediction. These are consistent with the expected signal and correspond to significances of $2.9 \\sigma$ and $2.2 \\sigma$ respectively. We demonstrate that our results are robust to a number of important systematic effects including the shear measurement method, estimator choice, photometric redshift uncertainty and CMB lensing systematics. Significant intrinsic alignment of galaxy shapes would increase the cross-correlation signal inferred from the data; we calculate a value of $A = 1.08 \\pm 0.36$ for DES$\\times$SPT when we correct the observations with a simple IA model. With three measurements of this cross-correlation now existing in the literature, there is not yet reliable evidence for any deviation from the expected LCDM level of cross-correlation, given the size of the statistical uncertainties and the significant impact of systematic errors, particularly IAs. We provide forecasts for the expected signal-to-noise of the combination of the five-year DES survey and SPT-3G.

  17. Preliminary study of microstructural properties and chemical modifications of interlayer shear weakness zone in Baihetan%白鹤滩层间错动带微结构特性及其化学改性初探

    Institute of Scientific and Technical Information of China (English)

    史存鹏; 冯夏庭; 江权; 徐鼎平

    2013-01-01

      白鹤滩水电站层间错动带结构疏松、性状软弱、空间展布范围大、力学强度低,严重影响着地下厂房洞室的稳定性。为了揭示并改良层间错动带的力学特性,首先通过矿物成分分析试验、扫描电镜试验和压汞试验,从微观结构角度对层间错动带的矿物组成特征、颗粒排列规律、孔隙分布规律进行了详细的研究,阐明了层间错动带的微观结构特性及其对灌浆材料选择的影响,进而开展了层间错动带化学溶液浸泡对比试验。试验表明,硅酸钠溶液可以有效改善层间错动带的完整性,明显提高层间错动带的弹性波速、抗压强度、弹性模量和凝聚力。其研究结果对白鹤滩层间错动带的工程加固和改性设计具有一定的借鉴意义。%Interlayer shear weakness zone has a series of features such as loose structure, easy to be softening, large spatial distribution and poor mechanical properties in Baihetan hydropower station. The existence of interlayer shear weakness zone seriously affects the stability of underground cavern groups of hydropower station. In order to reveal and improve the mechanical properties of interlayer shear weakness zone, X-ray diffractometer, scanning electron microscope and mercury intrusion porosimetry tests are applied separately to observe and determine the main mineral composition, the orientated range of particles and the distribution of pore structure in samples. Microstructural properties of interlayer shear weakness zone and its effect on the selection of grouting materials are discussed in detail combining with the testing data. What’s more, chemical modification experiments are carried out based on above experiments. Comparative experiment between samples immersed with or without sodium silicate solution indicates that chemical modification can improve the integrality, elastic wave velocity, compressive strength, elastic modulus and cohesion of

  18. Wide-Field Lensing Mass Maps from DES Science Verification Data

    CERN Document Server

    Vikram, V; Jain, B; Bacon, D; Amara, A; Becker, M; Bernstein, G; Bonnett, C; Bridle, S; Brout, D; Busha, M; Frieman, J; Gaztanaga, E; Hartley, W; Jarvis, M; Kacprzak, T; Lahav, O; Leistedt, B; Lin, H; Melchior, P; Peiris, H; Rozo, E; Rykoff, E; Sanchez, C; Sheldon, E; Troxel, M; Wechsler, R; Zuntz, J; Abbott, T; Abdalla, F B; Armstrong, R; Banerji, M; Bauer, A H; Benoit-Levy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Castander, F J; Crocce, M; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Cunha, C E; Estrada, J; Evrard, A E; Neto, A Fausti; Fernandez, E; Flaugher, B; Fosalba, P; Gerdes, D; Gruen, D; Gruendl, R A; Honscheid, K; James, D; Kent, S; Kuehn, K; Kuropatkin, N; Li, T S; Maia, M A G; Makler, M; March, M; Marshall, J; Martini, Paul; Merritt, K W; Miller, C J; Miquel, R; Neilsen, E; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Romer, A K; Roodman, A; Sanchez, E; Scarpine, V; Sevilla, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Walker, A R; Weller, J

    2015-01-01

    Weak gravitational lensing allows one to reconstruct the spatial distribution of the projected mass density across the sky. These "mass maps" provide a powerful tool for studying cosmology as they probe both luminous and dark matter. In this paper, we present a weak lensing mass map reconstructed from shear measurements in a 139 deg^2 area from the Dark Energy Survey (DES) Science Verification (SV) data overlapping with the South Pole Telescope survey. We compare the distribution of mass with that of the foreground distribution of galaxies and clusters. The overdensities in the reconstructed map correlate well with the distribution of optically detected clusters. Cross-correlating the mass map with the foreground galaxies from the same DES SV data gives results consistent with mock catalogs that include the primary sources of statistical uncertainties in the galaxy, lensing, and photo-z catalogs. The statistical significance of the cross-correlation is at the 6.8 sigma level with 20 arcminute smoothing. A maj...

  19. Size magnification as a complement to Cosmic Shear

    CERN Document Server

    Casaponsa, Biuse; Kitching, Tom D; Miller, Lance; Barreiro, Rita Belén; Martínez-Gonzalez, Enrique

    2012-01-01

    We investigate the extent to which cosmic size magnification may be used to com- plement cosmic shear in weak gravitational lensing surveys, with a view to obtaining high-precision estimates of cosmological parameters. Using simulated galaxy images, we find that size estimation can be an excellent complement, finding that unbiased estimation of the convergence field is possible with galaxies with angular sizes larger than the point-spread function (PSF) and signal-to-noise ratio in excess of 10. The statistical power is similar to, but not quite as good as, cosmic shear, and it is subject to different systematic effects. Application to ground-based data will be challeng- ing, with relatively large empirical corrections required to account for with biases for galaxies which are smaller than the PSF, but for space-based data with 0.1 arcsecond resolution, the size distribution of galaxies brighter than i=24 is ideal for accurate estimation of cosmic size magnification.

  20. The cross-correlation between 3d cosmic shear and the integrated Sachs-Wolfe effect

    CERN Document Server

    Zieser, Britta

    2016-01-01

    We present the first calculation of the cross-correlation between three-dimensional cosmic shear and the integrated Sachs-Wolfe (iSW) effect. Both signals are combined in a single formalism, which permits the computation of the full covariance matrix. In order to avoid the uncertainties presented by the non-linear evolution of the matter power spectrum and intrinsic alignments of galaxies, our analysis is restricted to large scales, i.e. multipoles below l=1000. We demonstrate in a Fisher analysis that this reduction compared to other studies of three-dimensional weak lensing extending to smaller scales is compensated by the information that is gained if the additional iSW signal and in particular its cross-correlation with lensing data are considered. Given the observational standards of upcoming weak lensing surveys like Euclid, marginal errors on cosmological parameters decrease by ten per cent compared to a cosmic shear experiment if both types of information are combined without a CMB prior. Once the con...

  1. Types of Contact Lenses

    Science.gov (United States)

    ... back to top ] Rigid Gas Permeable (RGP) Contact Lenses Rigid gas permeable contact lenses (RGPs) are more durable ... Ortho-K) Orthokeratology, or Ortho-K, is a lens fitting procedure that uses specially designed rigid gas permeable (RGP) contact lenses to change the ...

  2. Gravitational Lensing - Einstein's Unfinished Symphony

    CERN Document Server

    Treu, Tommaso

    2014-01-01

    Gravitational lensing - the deflection of light rays by gravitating matter - has become a major tool in the armoury of the modern cosmologist. Proposed nearly a hundred years ago as a key feature of Einstein's theory of General Relativity, we trace the historical development since its verification at a solar eclipse in 1919. Einstein was apparently cautious about its practical utility and the subject lay dormant observationally for nearly 60 years. Nonetheless there has been rapid progress over the past twenty years. The technique allows astronomers to chart the distribution of dark matter on large and small scales thereby testing predictions of the standard cosmological model which assumes dark matter comprises a massive weakly-interacting particle. By measuring distances and tracing the growth of dark matter structure over cosmic time, gravitational lensing also holds great promise in determining whether the dark energy, postulated to explain the accelerated cosmic expansion, is a vacuum energy density or a...

  3. Galaxy-galaxy lensing estimators and their covariance properties

    CERN Document Server

    Singh, Sukhdeep; Seljak, Uroš; Slosar, Anže; Gonzalez, Jose Vazquez

    2016-01-01

    We study the covariance properties of real space correlation function estimators -- primarily galaxy-shear correlations, or galaxy-galaxy lensing -- using SDSS data for both shear catalogs and lenses (specifically the BOSS LOWZ sample). Using mock catalogs of lenses and sources, we disentangle the various contributions to the covariance matrix and compare them with a simple analytical model. We show that not subtracting the lensing measurement around random points from the measurement around the lens sample is equivalent to performing the measurement using the density field instead of the over-density field, and that this leads to a significant error increase due to an additional term in the covariance. Therefore, this subtraction should be performed regardless of its beneficial effects on systematics. Comparing the error estimates from data and mocks for estimators that involve the over-density, we find that the errors are dominated by the shape noise and lens clustering, that empirically estimated covarianc...

  4. GREAT3 results - I. Systematic errors in shear estimation and the impact of real galaxy morphology

    Energy Technology Data Exchange (ETDEWEB)

    Mandelbaum, R.; Rowe, B.; Armstrong, R.; Bard, D.; Bertin, E.; Bosch, J.; Boutigny, D.; Courbin, F.; Dawson, W. A.; Donnarumma, A.; Fenech Conti, I.; Gavazzi, R.; Gentile, M.; Gill, M. S. S.; Hogg, D. W.; Huff, E. M.; Jee, M. J.; Kacprzak, T.; Kilbinger, M.; Kuntzer, T.; Lang, D.; Luo, W.; March, M. C.; Marshall, P. J.; Meyers, J. E.; Miller, L.; Miyatake, H.; Nakajima, R.; Ngole Mboula, F. M.; Nurbaeva, G.; Okura, Y.; Paulin-Henriksson, S.; Rhodes, J.; Schneider, M. D.; Shan, H.; Sheldon, E. S.; Simet, M.; Starck, J. -L.; Sureau, F.; Tewes, M.; Zarb Adami, K.; Zhang, J.; Zuntz, J.

    2015-05-01

    We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was divided into experiments to test three specific questions, and included simulated space- and ground-based data with constant or cosmologically varying shear fields. The simplest (control) experiment included parametric galaxies with a realistic distribution of signal-to-noise, size, and ellipticity, and a complex point spread function (PSF). The other experiments tested the additional impact of realistic galaxy morphology, multiple exposure imaging, and the uncertainty about a spatially varying PSF; the last two questions will be explored in Paper II. The 24 participating teams competed to estimate lensing shears to within systematic error tolerances for upcoming Stage-IV dark energy surveys, making 1525 submissions overall. GREAT3 saw considerable variety and innovation in the types of methods applied. Several teams now meet or exceed the targets in many of the tests conducted (to within the statistical errors). We conclude that the presence of realistic galaxy morphology in simulations changes shear calibration biases by ~1 per cent for a wide range of methods. Other effects such as truncation biases due to finite galaxy postage stamps, and the impact of galaxy type as measured by the Sérsic index, are quantified for the first time. Our results generalize previous studies regarding sensitivities to galaxy size and signal-to-noise, and to PSF properties such as seeing and defocus. Almost all methods’ results support the simple model in which additive shear biases depend linearly on PSF ellipticity.

  5. Scalar-field quintessence by cosmic shear: CFHT data analysis and forecasts for DUNE

    CERN Document Server

    Schimd, C; Schimd, Carlo; Tereno, Ismael

    2006-01-01

    A light scalar field, minimally or not-minimally coupled to the metric field, is a well-defined candidate for the dark energy, overcoming the coincidence problem intrinsic to the cosmological constant and avoiding the difficulties of parameterizations. We present a general description of the weak gravitational lensing valid for every metric theory of gravity, including vector and tensor perturbations for a non-flat spatial metric. Based on this description, we investigate two minimally-coupled scalar field quintessence models using VIRMOS-Descart and CFHTLS cosmic shear data, and forecast the constraints for the proposed space-borne wide-field imager DUNE.

  6. Gravitational lensing in plasmic medium

    Energy Technology Data Exchange (ETDEWEB)

    Bisnovatyi-Kogan, G. S., E-mail: gkogan@iki.rssi.ru; Tsupko, O. Yu., E-mail: tsupko@iki.rssi.ru [Russian Academy of Sciences, Space Research Institute (Russian Federation)

    2015-07-15

    The influence of plasma on different effects of gravitational lensing is reviewed. Using the Hamiltonian approach for geometrical optics in a medium in the presence of gravity, an exact formula for the photon deflection angle by a black hole (or another body with a Schwarzschild metric) embedded in plasma with a spherically symmetric density distribution is derived. The deflection angle in this case is determined by the mutual combination of different factors: gravity, dispersion, and refraction. While the effects of deflection by the gravity in vacuum and the refractive deflection in a nonhomogeneous medium are well known, the new effect is that, in the case of a homogeneous plasma, in the absence of refractive deflection, the gravitational deflection differs from the vacuum deflection and depends on the photon frequency. In the presence of a plasma nonhomogeneity, the chromatic refractive deflection also occurs, so the presence of plasma always makes gravitational lensing chromatic. In particular, the presence of plasma leads to different angular positions of the same image if it is observed at different wavelengths. It is discussed in detail how to apply the presented formulas for the calculation of the deflection angle in different situations. Gravitational lensing in plasma beyond the weak deflection approximation is also considered.

  7. Line-of-sight effects in strong lensing: Putting theory into practice

    CERN Document Server

    Birrer, Simon; Amara, Adam; Refregier, Alexandre

    2016-01-01

    We present a simple method to accurately infer line of sight (LOS) integrated lensing effects for galaxy scale strong lens systems through image reconstruction. Our approach enables us to separate weak lensing LOS effects from the main strong lens deflector. We test our method using mock data and show that strong lens systems can be accurate probes of cosmic shear with a precision on the shear terms of $\\pm 0.003$. We apply our formalism to reconstruct the lens COSMOS 0038+4133 and its LOS. In addition, we estimate the LOS properties with a halo-rendering estimate based on the COSMOS field galaxies and a galaxy-halo connection. The two approaches are independent and complementary in their information content. We find that when estimating the convergence at the strong lens system, performing a joint analysis improves the measure by a factor of two compared to a halo model only analysis. Furthermore, the constraints of the strong lens reconstruction lead to tighter constraints on the halo masses of the LOS gala...

  8. Scalar field haloes as gravitational lenses

    CERN Document Server

    Schunck, F E; Mielke, E W

    2006-01-01

    A non-topological soliton model with a repulsive scalar self-interaction of the Emden type provides a constant density core,similarly as the empirical Burkert profile of dark matter haloes. As a further test, we derive the gravitational lens properties of our model, in particular, the demarcation curves between `weak' and `strong' lensing. Accordingly, strong lensing with typically three images is almost three times more probable for our solitonic model than for the Burkert fit. Moreover, some prospective consequences of a possible flattening of dark matter haloes are indicated.

  9. Hierarchical probabilistic inference of cosmic shear

    CERN Document Server

    Schneider, Michael D; Marshall, Philip J; Dawson, William A; Meyers, Joshua; Bard, Deborah J; Lang, Dustin

    2014-01-01

    Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the glo...

  10. One Episode, Two Lenses

    Science.gov (United States)

    Drijvers, Paul; Godino, Juan D.; Font, Vicenc; Trouche, Luc

    2013-01-01

    A deep understanding of students' learning processes is one of the core challenges of research in mathematics education. To achieve this, different theoretical lenses are available. The question is how these different lenses compare and contrast, and how they can be coordinated and combined to provide a more comprehensive view on the topic of…

  11. On conformal lenses

    CERN Document Server

    Chen, Huanyang; Li, Hui

    2011-01-01

    Plane mirror can make one object into two for observers on the object's side. Yet, there seems no way to achieve the same effect for observers from all directions. In this letter, we will design a new class of gradient index lenses from multivalued optical conformal mapping. We shall call them the conformal lenses. Such lenses can transform one source into two (or even many) omnidirectionally. Like the overlapped illusion optics does, they can even transform multiple sources into one. Rather than using negative index materials, implementation here only needs isotropic positive index materials like other gradient index lenses. One obvious drawback however, is that they have singular permittivity values which restrict them to functioning at one single frequency. This however, needs not be the case when applying transmutation methods, which enable the lenses to work in a broadband frequency range.

  12. Aspherics in spectacle lenses

    Science.gov (United States)

    Dürsteler, Juan Carlos

    2016-12-01

    A review of the use of aspherics in the last decades, understood in a broad sense as encompassing single-vision lenses with conicoid surfaces and free-form and progressive addition lenses (PALs) as well, is provided. The appearance of conicoid surfaces to correct aphakia and later to provide thinner and more aesthetically appealing plus lenses and the introduction of PALs and free-form surfaces have shaped the advances in spectacle lenses in the last three decades. This document basically considers the main target optical aberrations, the idiosyncrasy of single lenses for correction of refractive errors and the restrictions and particularities of PAL design and their links to science vision and perception.

  13. CMB-lensing beyond the Born approximation

    Science.gov (United States)

    Marozzi, Giovanni; Fanizza, Giuseppe; Di Dio, Enea; Durrer, Ruth

    2016-09-01

    We investigate the weak lensing corrections to the cosmic microwave background temperature anisotropies considering effects beyond the Born approximation. To this aim, we use the small deflection angle approximation, to connect the lensed and unlensed power spectra, via expressions for the deflection angles up to third order in the gravitational potential. While the small deflection angle approximation has the drawback to be reliable only for multipoles l lesssim 2500, it allows us to consistently take into account the non-Gaussian nature of cosmological perturbation theory beyond the linear level. The contribution to the lensed temperature power spectrum coming from the non-Gaussian nature of the deflection angle at higher order is a new effect which has not been taken into account in the literature so far. It turns out to be the leading contribution among the post-Born lensing corrections. On the other hand, the effect is smaller than corrections coming from non-linearities in the matter power spectrum, and its imprint on CMB lensing is too small to be seen in present experiments.

  14. Wide-Field Lensing Mass Maps from DES Science Verification Data

    CERN Document Server

    Chang, C; Jain, B; Bacon, D; Amara, A; Becker, M R; Bernstein, G; Bonnett, C; Bridle, S; Brout, D; Busha, M; Frieman, J; Gaztanaga, E; Hartley, W; Jarvis, M; Kacprzak, T; Kovacs, A; Lahav, O; Lin, H; Melchior, P; Peiris, H; Rozo, E; Rykoff, E; Sanchez, C; Sheldon, E; Troxel, M A; Wechsler, R; Zuntz, J; Abbott, T; Abdalla, F B; Allam, S; Annis, J; Bauer, A H; Benoit-Levy, A; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Castander, F J; Crocce, M; D'Andrea, C B; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Eifler, T F; Evrard, A E; Neto, A Fausti; Flaugher, B; Fosalba, P; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D; Kent, S; Kuehn, K; Kuropatkin, N; Maia, M A G; March, M; Martini, P; Merritt, K W; Miller, C J; Miquel, R; Neilsen, E; Nichol, R C; Ogando, R; Plazas, A A; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Sevilla, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Tarle, G; Thaler, J; Thomas, D; Tucker, D; Walker, A R

    2015-01-01

    We present a mass map reconstructed from weak gravitational lensing shear measurements over 139 sq. deg from the Dark Energy Survey (DES) Science Verification data. The mass map probes both luminous and dark matter, thus providing a tool for studying cosmology. We find good agreement between the mass map and the distribution of massive galaxy clusters identified using a red-sequence cluster finder. Potential candidates for super-clusters and voids are identified using these maps. We measure the cross-correlation between the mass map and a magnitude-limited foreground galaxy sample and find a detection at the 5-7 sigma level on a large range of scales. These measurements are consistent with simulated galaxy catalogs based on LCDM N-body simulations, suggesting low systematics uncertainties in the map. We summarize our key findings in this letter; the detailed methodology and tests for systematics are presented in a companion paper.

  15. Seeing in the dark -- II. Cosmic shear in the Sloan Digital Sky Survey

    CERN Document Server

    Huff, Eric M; Hirata, Christopher M; Mandelbaum, Rachel; Schlegel, David; Seljak, Uros

    2011-01-01

    Statistical weak lensing by large-scale structure -- cosmic shear -- is a promising cosmological tool, which has motivated the design of several large upcoming surveys. Here, we present a measurement of cosmic shear using coadded Sloan Digital Sky Survey (SDSS) imaging in 168 square degrees of the equatorial region, with r<23.5 and i<22.5, a source number density of 2.2 galaxies per square arcminute and median redshift of 0.52. These coadds were generated using a new method described in the companion Paper I that was intended to minimise systematic errors in the lensing measurement due to coherent PSF anisotropies that are otherwise prevalent in the SDSS imaging data. We present measurements of cosmic shear out to angular separations of 2 degrees, along with systematics tests that (combined with those from Paper I on the catalogue generation) demonstrate that our results are dominated by statistical rather than systematic errors. Assuming a cosmological model corresponding to WMAP7 and allowing only the...

  16. Cosmic shear measurement with maximum likelihood and maximum a posteriori inference

    CERN Document Server

    Hall, Alex

    2016-01-01

    We investigate the problem of noise bias in maximum likelihood and maximum a posteriori estimators for cosmic shear. We derive the leading and next-to-leading order biases and compute them in the context of galaxy ellipticity measurements, extending previous work on maximum likelihood inference for weak lensing. We show that a large part of the bias on these point estimators can be removed using information already contained in the likelihood when a galaxy model is specified, without the need for external calibration. We test these bias-corrected estimators on simulated galaxy images similar to those expected from planned space-based weak lensing surveys, with very promising results. We find that the introduction of an intrinsic shape prior mitigates noise bias, such that the maximum a posteriori estimate can be made less biased than the maximum likelihood estimate. Second-order terms offer a check on the convergence of the estimators, but are largely sub-dominant. We show how biases propagate to shear estima...

  17. Cosmology constraints from shear peak statistics in Dark Energy Survey Science Verification data

    CERN Document Server

    Kacprzak, T; Friedrich, O; Amara, A; Refregier, A; Marian, L; Dietrich, J P; Suchyta, E; Aleksić, J; Bacon, D; Becker, M R; Bonnett, C; Bridle, S L; Chang, C; Eifler, T F; Hartley, W; Huff, E M; Krause, E; MacCrann, N; Melchior, P; Nicola, A; Samuroff, S; Sheldon, E; Troxel, M A; Weller, J; Zuntz, J; Abbott, T M C; Abdalla, F B; Armstrong, R; Benoit-Lévy, A; Bernstein, R A; Bertin, E; Brooks, D; Burke, D L; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; Crocce, M; D'Andrea, C B; da Costa, L N; Desai, S; Diehl, H T; Evrard, A E; Neto, A Fausti; Flaugher, B; Fosalba, P; Frieman, J; Gerdes, D W; Goldstein, D A; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Lima, M; March, M; Marshall, J L; Martini, P; Miller, C J; Miquel, R; Mohr, J J; Nichol, R C; Nord, B; Plazas, A A; Romer, A K; Roodman, A; Rykoff, E S; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Swanson, M E C; Tarle, G; Thomas, D; Vikram, V; Walker, A R; Zhang, Y

    2016-01-01

    Shear peak statistics has gained a lot of attention recently as a practical alternative to the two point statistics for constraining cosmological parameters. We perform a shear peak statistics analysis of the Dark Energy Survey (DES) Science Verification (SV) data, using weak gravitational lensing measurements from a 139 deg$^2$ field. We measure the abundance of peaks identified in aperture mass maps, as a function of their signal-to-noise ratio, in the signal-to-noise range $04$ would require significant corrections, which is why we do not include them in our analysis. We compare our results to the cosmological constraints from the two point analysis on the SV field and find them to be in good agreement in both the central value and its uncertainty. We discuss prospects for future peak statistics analysis with upcoming DES data.

  18. Higher order moments of lensing convergence - I. Estimate from simulations

    CERN Document Server

    Vicinanza, M; Maoli, R; Scaramella, R; Er, X

    2016-01-01

    Large area lensing surveys are expected to make it possible to use cosmic shear tomography as a tool to severely constrain cosmological parameters. To this end, one typically relies on second order statistics such as the two - point correlation fucntion and its Fourier counterpart, the power spectrum. Moving a step forward, we wonder whether and to which extent higher order stastistics can improve the lensing Figure of Merit (FoM). In this first paper of a series, we investigate how second, third and fourth order lensing convergence moments can be measured and use as probe of the underlying cosmological model. We use simulated data and investigate the impact on moments estimate of the map reconstruction procedure, the cosmic variance, and the intrinsic ellipticity noise. We demonstrate that, under realistic assumptions, it is indeed possible to use higher order moments as a further lensing probe.

  19. Gravitational lensing of quasars

    CERN Document Server

    Eigenbrod, Alexander

    2013-01-01

    The universe, in all its richness, diversity and complexity, is populated by a myriad of intriguing celestial objects. Among the most exotic of them are gravitationally lensed quasars. A quasar is an extremely bright nucleus of a galaxy, and when such an object is gravitationally lensed, multiple images of the quasar are produced – this phenomenon of cosmic mirage can provide invaluable insights on burning questions, such as the nature of dark matter and dark energy. After presenting the basics of modern cosmology, the book describes active galactic nuclei, the theory of gravitational lensing, and presents a particular numerical technique to improve the resolution of astronomical data. The book then enters the heart of the subject with the description of important applications of gravitational lensing of quasars, such as the measurement of the famous Hubble constant, the determination of the dark matter distribution in galaxies, and the observation of the mysterious inner parts of quasars with much higher r...

  20. Gravitational Lenses of Wormholes

    CERN Document Server

    Nandi, K K; Zhang, Y Z; Nandi, Kamal Kanti; Zakharov, Alexander V.; Zhang, Yuan-Zhong

    2006-01-01

    Gravitational lensing by traversable Lorentzian wormholes is a new possibility and is analyzed in the strong field limit. Wormhole solutions are considered in the Einstein minimally coupled theory and in the brane world model. The observables in both the theories show significant differences from those in the Schwarzschild black hole lensing. It is shown that the zero mass wormholes act as photon sinks. Some special features of the considered solutions are pointed out.

  1. Detections of Planets in Binaries Through the Channel of Chang–Refsdal Gravitational Lensing Events

    Science.gov (United States)

    Han, Cheongho; Shin, In-Gu; Jung, Youn Kil

    2017-02-01

    Chang–Refsdal (C–R) lensing, which refers to the gravitational lensing of a point mass perturbed by a constant external shear, provides a good approximation in describing lensing behaviors of either a very wide or a very close binary lens. C–R lensing events, which are identified by short-term anomalies near the peak of high-magnification lensing light curves, are routinely detected from lensing surveys, but not much attention is paid to them. In this paper, we point out that C–R lensing events provide an important channel to detect planets in binaries, both in close and wide binary systems. Detecting planets through the C–R lensing event channel is possible because the planet-induced perturbation occurs in the same region of the C–R lensing-induced anomaly and thus the existence of the planet can be identified by the additional deviation in the central perturbation. By presenting the analysis of the actually observed C–R lensing event OGLE-2015-BLG-1319, we demonstrate that dense and high-precision coverage of a C–R lensing-induced perturbation can provide a strong constraint on the existence of a planet in a wide range of planet parameters. The sample of an increased number of microlensing planets in binary systems will provide important observational constraints in giving shape to the details of planet formation, which have been restricted to the case of single stars to date.

  2. Cosmology from Cosmic Shear with DES Science Verification Data

    CERN Document Server

    Abbott, T; Allam, S; Amara, A; Annis, J; Armstrong, R; Bacon, D; Banerji, M; Bauer, A H; Baxter, E; Becker, M R; Benoit-Lévy, A; Bernstein, R A; Bernstein, G M; Bertin, E; Blazek, J; Bonnett, C; Bridle, S L; Brooks, D; Bruderer, C; Buckley-Geer, E; Burke, D L; Busha, M T; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; Chang, C; Clampitt, J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; Das, R; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Dodelson, S; Doel, P; Drlica-Wagner, A; Efstathiou, G; Eifler, T F; Erickson, B; Estrada, J; Evrard, A E; Neto, A Fausti; Fernandez, E; Finley, D A; Flaugher, B; Fosalba, P; Friedrich, O; Frieman, J; Gangkofner, C; Garcia-Bellido, J; Gaztanaga, E; Gerdes, D W; Gruen, D; Gruendl, R A; Gutierrez, G; Hartley, W; Hirsch, M; Honscheid, K; Huff, E M; Jain, B; James, D J; Jarvis, M; Kacprzak, T; Kent, S; Kirk, D; Krause, E; Kravtsov, A; Kuehn, K; Kuropatkin, N; Kwan, J; Lahav, O; Leistedt, B; Li, T S; Lima, M; Lin, H; MacCrann, N; March, M; Marshall, J L; Martini, P; McMahon, R G; Melchior, P; Miller, C J; Miquel, R; Mohr, J J; Neilsen, E; Nichol, R C; Nicola, A; Nord, B; Ogando, R; Palmese, A; Peiris, H V; Plazas, A A; Refregier, A; Roe, N; Romer, A K; Roodman, A; Rowe, B; Rykoff, E S; Sabiu, C; Sadeh, I; Sako, M; Samuroff, S; Sánchez, C; Sanchez, E; Seo, H; Sevilla-Noarbe, I; Sheldon, E; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Troxel, M A; Vikram, V; Walker, A R; Wechsler, R H; Weller, J; Zhang, Y; Zuntz, J

    2015-01-01

    We present the first constraints on cosmology from the Dark Energy Survey (DES), using weak lensing measurements from the preliminary Science Verification (SV) data. We use 139 square degrees of SV data, which is less than 3\\% of the full DES survey area. Using cosmic shear 2-point measurements over three redshift bins we find $\\sigma_8 (\\Omega_{\\rm m}/0.3)^{0.5} = 0.81 \\pm 0.06$ (68\\% confidence), after marginalising over 7 systematics parameters and 3 other cosmological parameters. We examine the robustness of our results to the choice of data vector and systematics assumed, and find them to be stable. About $20$\\% of our error bar comes from marginalising over shear and photometric redshift calibration uncertainties. The current state-of-the-art cosmic shear measurements from CFHTLenS are mildly discrepant with the cosmological constraints from Planck CMB data; our results are consistent with both datasets. Our uncertainties are $\\sim$30\\% larger than those from CFHTLenS when we carry out a comparable anal...

  3. Cosmic Shear Measurements with DES Science Verification Data

    CERN Document Server

    Becker, M R; MacCrann, N; Krause, E; Eifler, T F; Friedrich, O; Nicola, A; Refregier, A; Amara, A; Bacon, D; Bernstein, G M; Bonnett, C; Bridle, S L; Busha, M T; Chang, C; Dodelson, S; Erickson, B; Evrard, A E; Frieman, J; Gaztanaga, E; Gruen, D; Hartley, W; Jain, B; Jarvis, M; Kacprzak, T; Kirk, D; Kravtsov, A; Leistedt, B; Rykoff, E S; Sabiu, C; Sanchez, C; Seo, H; Sheldon, E; Wechsler, R H; Zuntz, J; Abbott, T; Abdalla, F B; Allam, S; Armstrong, R; Banerji, M; Bauer, A H; Benoit-Levy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Castander, F J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Neto, A Fausti; Fernandez, E; Finley, D A; Flaugher, B; Fosalba, P; Gerdes, D W; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; Maia, M A G; March, M; Martini, P; Melchior, P; Miller, C J; Miquel, R; Mohr, J J; Nichol, R C; Nord, B; Ogando, R; Plazas, A A; Reil, K; Romer, A K; Roodman, A; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Thomas, D; Vikram, V; Walker, A R

    2015-01-01

    We present measurements of weak gravitational lensing cosmic shear two-point statistics using Dark Energy Survey Science Verification data. We demonstrate that our results are robust to the choice of shear measurement pipeline, either ngmix or im3shape, and robust to the choice of two-point statistic, including both real and Fourier-space statistics. Our results pass a suite of null tests including tests for B-mode contamination and direct tests for any dependence of the two-point functions on a set of 16 observing conditions and galaxy properties, such as seeing, airmass, galaxy color, galaxy magnitude, etc. We furthermore use a large suite of simulations to compute the covariance matrix of the cosmic shear measurements and assign statistical significance to our null tests. We find that our covariance matrix is consistent with the halo model prediction, indicating that it has the appropriate level of halo sample variance. We compare the same jackknife procedure applied to the data and the simulations in orde...

  4. On the contribution of large scale structure to strong gravitational lensing

    CERN Document Server

    Faure, C; Hilbert, S; Massey, R; Covone, G; Finoguenov, A; Leauthaud, A; Taylor, J E; Pires, S; Scoville, N

    2008-01-01

    We study the correlation between the locations of galaxy-galaxy strong lensing candidates and tracers of large-scale structure from both weak lensing or X-ray emission. The COSMOS survey is a unique data set, combining deep, high resolution and contiguous imaging in which strong lenses have been discovered, plus unparalleled multiwavelength coverage. To help interpret the COSMOS data, we have also produced mock COSMOS strong and weak lensing observations, based on ray-tracing through the Millenium simulation. In agreement with the simulations, we find that strongly lensed images with the largest angular separations are found in the densest regions of the COSMOS field. This is explained by a prevalence among the lens population in dense environments of elliptical galaxies with high total-to-stellar mass ratios, which can deflect light through larger angles. However, we also find that the overall fraction of elliptical galaxies with strong gravitational lensing is independent of the local mass density; this obs...

  5. Cosmological parameters, shear maps and power spectra from CFHTLenS using Bayesian hierarchical inference

    CERN Document Server

    Alsing, Justin; Jaffe, Andrew H

    2016-01-01

    We apply two Bayesian hierarchical inference schemes to infer shear power spectra, shear maps and cosmological parameters from the CFHTLenS weak lensing survey - the first application of this method to data. In the first approach, we sample the joint posterior distribution of the shear maps and power spectra by Gibbs sampling, with minimal model assumptions. In the second approach, we sample the joint posterior of the shear maps and cosmological parameters, providing a new, accurate and principled approach to cosmological parameter inference from cosmic shear data. As a first demonstration on data we perform a 2-bin tomographic analysis to constrain cosmological parameters and investigate the possibility of photometric redshift bias in the CFHTLenS data. Under the baseline $\\Lambda$CDM model we constrain $S_8 = \\sigma_8(\\Omega_\\mathrm{m}/0.3)^{0.5} = 0.67 ^{\\scriptscriptstyle+ 0.03 }_{\\scriptscriptstyle- 0.03 }$ $(68\\%)$, consistent with previous CFHTLenS analysis but in tension with Planck. Adding neutrino m...

  6. Prediction of galaxy ellipticities and reduction of shape noise in cosmic shear measurements

    Science.gov (United States)

    Croft, Rupert A. C.; Freeman, Peter E.; Schuster, Thomas S.; Schafer, Chad M.

    2017-08-01

    The intrinsic scatter in the ellipticities of galaxies about the mean shape, known as `shape noise', is the most important source of noise in weak lensing shear measurements. Several approaches for reducing shape noise have recently been put forward, using information beyond photometry, such as radio polarization and optical spectroscopy. Here we investigate how well the intrinsic ellipticities of galaxies can be predicted using other exclusively photometric parameters. These (such as galaxy colours) are already available in the data and do not necessitate additional, often expensive observations. We apply a regression technique, generalized additive models to the publicly released galaxy property data from CFHTLenS. We find that the individual galaxy ellipticities can be predicted from other photometric parameters to better precision than the scatter about the mean ellipticity. The ellipticity contribution to the shear can apparently therefore be measured to higher precision, comparable to using a larger sample of galaxies. Using only parameters unaffected by lensing (e.g. surface brightness, colour), our best-fitting model leads to a gain (for the ellipticity contribution only) equivalent to having 12 per cent more galaxies in the sample. Allowing parameters correlated with lensing increases the apparent gains (we find 52.5 per cent), but these would likely be negated by correlations between the predictor and measured shear. We caution that the ultimate usefulness of this method will depend on careful treatment of the effect of the point spread function and input parameter measurement. This is to avoid information on the ellipticity contaminating the estimated ellipticity through observational effects rather than true physical correlations.

  7. Cross-correlation of gravitational lensing from DES Science Verification data with SPT and Planck lensing

    CERN Document Server

    Kirk, D; Benoit-Lévy, A; Cawthon, R; Chang, C; Larsen, P; Amara, A; Bacon, D; Crawford, T M; Dodelson, S; Fosalba, P; Giannantonio, T; Holder, G; Jain, B; Kacprzak, T; Lahav, O; MacCrann, N; Nicola, A; Refregier, A; Sheldon, E; Story, K T; Troxel, M A; Vieira, J D; Vikram, V; Zuntz, J; Abbott, T M C; Abdalla, F B; Becker, M R; Benson, B A; Bernstein, G M; Bernstein, R A; Bleem, L E; Bonnett, C; Bridle, S L; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Carlstrom, J E; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Eifler, T F; Evrard, A E; Flaugher, B; Frieman, J; Gerdes, D W; Goldstein, D A; Gruen, D; Gruendl, R A; Honscheid, K; James, D J; Jarvis, M; Kent, S; Kuehn, K; Kuropatkin, N; Lima, M; March, M; Martini, P; Melchior, P; Miller, C J; Miquel, R; Nichol, R C; Ogando, R; Plazas, A A; Reichardt, C L; Roodman, A; Rozo, E; Rykoff, E S; Sako, M; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Simard, G; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thomas, D; Wechsler, R H; Weller, J

    2015-01-01

    We measure the cross-correlation between weak lensing of galaxy images and of the cosmic microwave background (CMB). The effects of gravitational lensing on different sources will be correlated if the lensing is caused by the same mass fluctuations. We use galaxy shape measurements from 139 deg$^{2}$ of the Dark Energy Survey (DES) Science Verification data and overlapping CMB lensing from the South Pole Telescope (SPT) and Planck. The DES source galaxies have a median redshift of $z_{\\rm med} {\\sim} 0.7$, while the CMB lensing kernel is broad and peaks at $z{\\sim}2$. The resulting cross-correlation is maximally sensitive to mass fluctuations at $z{\\sim}0.44$. Assuming the Planck 2015 best-fit cosmology, the amplitude of the DES$\\times$SPT cross-power is found to be $A = 0.88 \\pm 0.30$ and that from DES$\\times$Planck to be $A = 0.86 \\pm 0.39$, where $A=1$ corresponds to the theoretical prediction. These are consistent with the expected signal and correspond to significances of $2.9 \\sigma$ and $2.2 \\sigma$ re...

  8. Strong gravitational lensing versus dynamic galactic mass

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, Antonio C.C.; Sodre Junior, Laerte [Universidade de Sao Paulo (USP), SP (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas. Dept. de Astronomia

    2006-07-01

    The mass associated to a galaxy is a fundamental property necessary for its description and for the understating of its structure, formation and evolution. In the cosmological context, the mass and density profile of galaxies and galaxy clusters is relevant for the understanding of dark matter properties and the formation dynamics of structures in the Universe. We find the masses of 15 galaxies from the SLACS Survey through two methods: using the stellar velocity dispersion (dynamic method) and using strong gravitational lensing. We discover a discrepancy between the masses obtained through these two methods and develop several models to explain it. We test the models suggested by calculating {chi}{sup 2} statistics and the Bayesian information criteria. Statistical fluctuation and a constant systematic error are strongly discarded as explanations for the mass discrepancy. Our results show evidence of projection effects on the line of sight that add a contamination mass in the strong lensing galactic mass determination. This effect was already observed in greater detail in weak and strong gravitational lensing measures of cluster of galaxies, but was little explored before in the case of strong lensing by galaxies. (author)

  9. CMB-lensing beyond the Born approximation

    CERN Document Server

    Marozzi, Giovanni; Di Dio, Enea; Durrer, Ruth

    2016-01-01

    We investigate the weak lensing corrections to the cosmic microwave background temperature anisotropies considering effects beyond the Born approximation. To this aim, we use the small deflection angle approximation, to connect the lensed and unlensed power spectra, via expressions for the deflection angles up to third order in the gravitational potential. While the small deflection angle approximation has the drawback to be reliable only for multipoles $\\ell\\lesssim 2500$, it allows us to consistently take into account the non-Gaussian nature of cosmological perturbation theory beyond the linear level. The contribution to the lensed temperature power spectrum coming from the non-Gaussian nature of the deflection angle at higher order is a new effect which has not been taken into account in the literature so far. It turns out to be the leading contribution among the post-Born lensing corrections. On the other hand, the effect is smaller than corrections coming from non-linearities in the matter power spectrum...

  10. Galaxy-Galaxy Lensing in the DES Science Verification Data

    Energy Technology Data Exchange (ETDEWEB)

    Clampitt, J.; et al.

    2016-03-18

    We present galaxy-galaxy lensing results from 139 square degrees of Dark Energy Survey (DES) Science Verification (SV) data. Our lens sample consists of red galaxies, known as redMaGiC, which are specifically selected to have a low photometric redshift error and outlier rate. The lensing measurement has a total signal-to-noise of 29, including all lenses over a wide redshift range $0.2 < z < 0.8$. Dividing the lenses into three redshift bins, we find no evidence for evolution in the halo mass with redshift. We obtain consistent results for the lensing measurement with two independent shear pipelines, ngmix and im3shape. We perform a number of null tests on the shear and photometric redshift catalogs and quantify resulting systematic errors. Covariances from jackknife subsamples of the data are validated with a suite of 50 mock surveys. The results and systematics checks in this work provide a critical input for future cosmological and galaxy evolution studies with the DES data and redMaGiC galaxy samples. We fit a Halo Occupation Distribution (HOD) model, and demonstrate that our data constrains the mean halo mass of the lens galaxies, despite strong degeneracies between individual HOD parameters.

  11. Galaxy-Galaxy Lensing in the DES Science Verification Data

    CERN Document Server

    Clampitt, J; Kwan, J; Krause, E; MacCrann, N; Park, Y; Troxel, M A; Jain, B; Rozo, E; Rykoff, E S; Wechsler, R H; Blazek, J; Bonnett, C; Crocce, M; Fang, Y; Gaztanaga, E; Gruen, D; Jarvis, M; Miquel, R; Prat, J; Ross, A J; Sheldon, E; Zuntz, J; Abbott, T M C; Abdalla, F B; Armstrong, R; Becker, M R; Benoit-Lévy, A; Bernstein, G M; Bertin, E; Brooks, D; Burke, D L; Rosell, A Carnero; Kind, M Carrasco; Cunha, C E; D'Andrea, C B; da Costa, L N; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Estrada, J; Evrard, A E; Neto, A Fausti; Flaugher, B; Fosalba, P; Frieman, J; Gruendl, R A; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lima, M; March, M; Marshall, J L; Martini, P; Melchior, P; Mohr, J J; Nichol, R C; Nord, B; Plazas, A A; Romer, A K; Sanchez, E; Scarpine, V; Schubnell, M; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thomas, D; Vikram, V; Walker, A R

    2016-01-01

    We present galaxy-galaxy lensing results from 139 square degrees of Dark Energy Survey (DES) Science Verification (SV) data. Our lens sample consists of red galaxies, known as redMaGiC, which are specifically selected to have a low photometric redshift error and outlier rate. The lensing measurement has a total signal-to-noise of 29, including all lenses over a wide redshift range $0.2 < z < 0.8$. Dividing the lenses into three redshift bins, we find no evidence for evolution in the halo mass with redshift. We obtain consistent results for the lensing measurement with two independent shear pipelines, ngmix and im3shape. We perform a number of null tests on the shear and photometric redshift catalogs and quantify resulting systematic errors. Covariances from jackknife subsamples of the data are validated with a suite of 50 mock surveys. The results and systematics checks in this work provide a critical input for future cosmological and galaxy evolution studies with the DES data and redMaGiC galaxy sample...

  12. Experimental and theoretical studies on the effects of water content on shear creep behavior of weak structural plane of sandstone%不同含水率软弱结构面剪切蠕变试验及模型研究

    Institute of Scientific and Technical Information of China (English)

    李鹏; 刘建

    2009-01-01

    软弱结构面的蠕变特性是岩体重要力学特性之一,其蠕变特性常控制着岩体的蠕变变形和长期强度.软弱结构面中充填物的含水率是影响其蠕变特性的重要因素之一,通过开展不同含水率砂岩软弱结构面剪切蠕变试验,得到了具不同含水率的砂岩软弱结构面剪切蠕变试验曲线.基于得到的剪切蠕变试验曲线,分析了含水率对软弱结构面剪切蠕变特性及长期抗剪强度的影响规律.最后通过模型辨识,采用改进的粘弹塑性模型来描述考虑含水率变化的砂岩软弱结构面蠕变特性.%Creep behavior of weak structural plane is one of the most important mechanical characteristics of rock mass and always has an important influence on deformation and long-term strength of rock mass. Water content of the fillings is a significant factor influencing the creep properties of the weak structural plane. In this study, by multi-stage loading, a series of shear creep tests on the weak structural plane of sandstone with different water contents are conducted. The curves of the shear creep deformation vs. time under different water content of the fillings are derived. The effects of water content on the shear creep behavior and long-term shear strength of weak structural plane of sandstone are analyzed. Compared with the shear strength by rapid shear test, the long-term strength has sharply decreased. Based on the test results and analysis, modified viscoelastoplastic model is identified to describe the behavior of water content influencing on the weak structural plane of sandstones and parameters of this model are also given through back analysis.

  13. Polyadic devil's lenses.

    Science.gov (United States)

    Calatayud, Arnau; Monsoriu, Juan A; Mendoza-Yero, Omel; Furlan, Walter D

    2009-12-01

    Devil's lenses (DLs) were recently proposed as a new kind of kinoform lens in which the phase structure is characterized by the "devil's staircase" function. DLs are considered fractal lenses because they are constructed following the geometry of the triadic Cantor set and because they provide self-similar foci along the optical axis. Here, DLs are generalized allowing the inclusion of polyadic Cantor distributions in their design. The lacunarity of the selected polyadic fractal distribution is an additional design parameter. The results are coined polyadic DLs. Construction requirements and interrelations among the different parameters of these new fractal lenses are also presented. It is shown that the lacunarity parameter affects drastically the irradiance profile along the optical axis, appodizing higher-order foci, and these features are proved to improve the behavior of conventional DLs under polychromatic illumination.

  14. Gravitational Lensing & Stellar Dynamics

    CERN Document Server

    Koopmans, L V E

    2005-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-anisotropy degeneracies. Second, observational results are presented from the Lenses Structure & Dynamics (LSD) Survey and the Sloan Lens ACS (SLACS) Survey collaborations to illustrate this new methodology in constraining the dark and stellar density profiles, and mass structure, of early-type galaxies to redshifts of unity.

  15. Weak Convergence and Weak Convergence

    Directory of Open Access Journals (Sweden)

    Narita Keiko

    2015-09-01

    Full Text Available In this article, we deal with weak convergence on sequences in real normed spaces, and weak* convergence on sequences in dual spaces of real normed spaces. In the first section, we proved some topological properties of dual spaces of real normed spaces. We used these theorems for proofs of Section 3. In Section 2, we defined weak convergence and weak* convergence, and proved some properties. By RNS_Real Mizar functor, real normed spaces as real number spaces already defined in the article [18], we regarded sequences of real numbers as sequences of RNS_Real. So we proved the last theorem in this section using the theorem (8 from [25]. In Section 3, we defined weak sequential compactness of real normed spaces. We showed some lemmas for the proof and proved the theorem of weak sequential compactness of reflexive real Banach spaces. We referred to [36], [23], [24] and [3] in the formalization.

  16. Masses of galaxy clusters from gravitational lensing

    CERN Document Server

    Hoekstra, Henk; Dahle, Haakon; Israel, Holger; Limousin, Marceau; Meneghetti, Massimo

    2013-01-01

    Despite consistent progress in numerical simulations, the observable properties of galaxy clusters are difficult to predict ab initio. It is therefore important to compare both theoretical and observational results to a direct measure of the cluster mass. This can be done by measuring the gravitational lensing effects caused by the bending of light by the cluster mass distribution. In this review we discuss how this phenomenon can be used to determine cluster masses and study the mass distribution itself. As sample sizes increase, the accuracy of the weak lensing mass estimates needs to improve accordingly. We discuss the main practical aspects of these measurements. We review a number of applications and highlight some recent results.

  17. Gravitational lensing & stellar dynamics

    NARCIS (Netherlands)

    Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B

    2006-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-ani

  18. Gravitational lensing & stellar dynamics

    NARCIS (Netherlands)

    Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B

    2006-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and

  19. Gravitational lensing & stellar dynamics

    NARCIS (Netherlands)

    Koopmans, L. V. E.; Mamon, GA; Combes, F; Deffayet, C; Fort, B

    2006-01-01

    Strong gravitational lensing and stellar dynamics provide two complementary and orthogonal constraints on the density profiles of galaxies. Based on spherically symmetric, scale-free, mass models, it is shown that the combination of both techniques is powerful in breaking the mass-sheet and mass-ani

  20. A pseudo-spectrum analysis of galaxy-galaxy lensing

    Science.gov (United States)

    Hikage, Chiaki; Oguri, Masamune

    2016-10-01

    We present the application of the pseudo-spectrum method to galaxy-galaxy lensing. We derive explicit expressions for the pseudo-spectrum analysis of the galaxy-shear cross-spectrum, which is the Fourier space counterpart of the stacked galaxy-galaxy lensing profile. The pseudo-spectrum method corrects observational issues such as the survey geometry, masks of bright stars and their spikes, and inhomogeneous noise, which distort the spectrum and also mix the E-mode and the B-mode signals. Using ray-tracing simulations in N-body simulations including realistic masks, we confirm that the pseudo-spectrum method successfully recovers the input galaxy-shear cross-spectrum. We also show that the galaxy-shear cross-spectrum has an excess covariance relative to the Gaussian covariance at small scales (k ≳ 1h Mpc-1) where the shot noise is dominated in the Gaussian approximation. We find that the excess is consistent with the expectation from the halo sample variance (HSV), which originates from the matter fluctuations at scales larger than the survey area. We apply the pseudo-spectrum method to the observational data of Canada-France-Hawaii Telescope Lensing survey shear catalogue and three different spectroscopic samples of Sloan Digital Sky Survey Luminous Red Galaxy, and Baryon Oscillation Spectroscopic Survey CMASS and LOWZ galaxies. The galaxy-shear cross-spectra are significantly detected at the level of 7-10σ using the analytic covariance with the HSV contribution included. We also confirm that the observed spectra are consistent with the halo model predictions with the halo occupation distribution parameters estimated from previous work. This work demonstrates the viability of galaxy-galaxy lensing analysis in the Fourier space.

  1. The Third Gravitational Lensing Accuracy Testing (GREAT3) Challenge Handbook

    CERN Document Server

    Mandelbaum, Rachel; Bosch, James; Chang, Chihway; Courbin, Frederic; Gill, Mandeep; Jarvis, Mike; Kannawadi, Arun; Kacprzak, Tomasz; Lackner, Claire; Leauthaud, Alexie; Miyatake, Hironao; Nakajima, Reiko; Rhodes, Jason; Simet, Melanie; Zuntz, Joe; Armstrong, Bob; Bridle, Sarah; Coupon, Jean; Dietrich, Jörg P; Gentile, Marc; Heymans, Catherine; Jurling, Alden S; Kent, Stephen M; Kirkby, David; Margala, Daniel; Massey, Richard; Melchior, Peter; Peterson, John; Roodman, Aaron; Schrabback, Tim

    2013-01-01

    The GRavitational lEnsing Accuracy Testing 3 (GREAT3) challenge is the third in a series of image analysis challenges, with a goal of testing and facilitating the development of methods for analyzing astronomical images that will be used to measure weak gravitational lensing. This measurement requires extremely precise estimation of very small galaxy shape distortions, in the presence of far larger intrinsic galaxy shapes and distortions due to the blurring kernel caused by the atmosphere, telescope optics, and instrumental effects. The GREAT3 challenge is posed to the astronomy, machine learning, and statistics communities, and includes tests of three specific effects that are of immediate relevance to upcoming weak lensing surveys, two of which have never been tested in a community challenge before. These effects include realistically complex galaxy models based on high-resolution imaging from space; spatially varying blurring kernel; and combination of multiple different exposures. To facilitate entry by p...

  2. Obituary--rigid contact lenses.

    Science.gov (United States)

    Efron, Nathan

    2010-10-01

    Scleral and corneal rigid lenses represented 100 per cent of the contact lens market immediately prior to the invention of soft lenses in the mid-1960s. In the United Kingdom today, rigid lenses comprise 2 per cent of all new lens fits. Low rates of rigid lens fitting are also apparent in 27 other countries which have recently been surveyed. Thus, the 1998 prediction of the author that rigid lenses--also referred to as 'rigid gas permeable' (RGP) lenses or 'gas permeable' (GP) lenses--would be obsolete by the year 2010 has essentially turned out to be correct. In this obituary, the author offers 10 reasons for the demise of rigid lens fitting: initial rigid lens discomfort; intractable rigid lens-induced corneal and lid pathology; extensive soft lens advertising; superior soft lens fitting logistics; lack of rigid lens training opportunities; redundancy of the rigid lens 'problem solver' function; improved soft toric and bifocal/varifocal lenses; limited uptake of orthokeratology; lack of investment in rigid lenses; and the emergence of aberration control soft lenses. Rigid lenses are now being fitted by a minority of practitioners with specialist skills/training. Certainly, rigid lenses can no longer be considered as a mainstream form of contact lens correction. May their dear souls (bulk properties) rest in peace.

  3. LHC beam-beam compensation using wires and electron lenses

    CERN Document Server

    Dorda, U; Shiltsev, V; Zimmermann, F

    2007-01-01

    We present weak-strong simulation results for a possible application of current-carrying wires and electron lenses to compensate the LHC long-range and head-on beambeam interaction, respectively, for nominal and PACMAN bunches. We show that these measures have the potential to considerably increase the beam-beam limit, allowing for a corresponding increase in peak luminosity.

  4. HIERARCHICAL PROBABILISTIC INFERENCE OF COSMIC SHEAR

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Michael D.; Dawson, William A. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Hogg, David W. [Center for Cosmology and Particle Physics, New York University, New York, NY 10003 (United States); Marshall, Philip J.; Bard, Deborah J. [SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Meyers, Joshua [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94035 (United States); Lang, Dustin, E-mail: schneider42@llnl.gov [Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213 (United States)

    2015-07-01

    Point estimators for the shearing of galaxy images induced by gravitational lensing involve a complex inverse problem in the presence of noise, pixelization, and model uncertainties. We present a probabilistic forward modeling approach to gravitational lensing inference that has the potential to mitigate the biased inferences in most common point estimators and is practical for upcoming lensing surveys. The first part of our statistical framework requires specification of a likelihood function for the pixel data in an imaging survey given parameterized models for the galaxies in the images. We derive the lensing shear posterior by marginalizing over all intrinsic galaxy properties that contribute to the pixel data (i.e., not limited to galaxy ellipticities) and learn the distributions for the intrinsic galaxy properties via hierarchical inference with a suitably flexible conditional probabilitiy distribution specification. We use importance sampling to separate the modeling of small imaging areas from the global shear inference, thereby rendering our algorithm computationally tractable for large surveys. With simple numerical examples we demonstrate the improvements in accuracy from our importance sampling approach, as well as the significance of the conditional distribution specification for the intrinsic galaxy properties when the data are generated from an unknown number of distinct galaxy populations with different morphological characteristics.

  5. Learning unit: Thin lenses

    Science.gov (United States)

    Nita, L.-S.

    2012-04-01

    Learning unit: Thin lenses "Why objects seen through lenses are sometimes upright and sometimes reversed" Nita Laura Simona National College of Arts and Crafts "Constantin Brancusi", Craiova, Romania 1. GEOMETRIC OPTICS. 13 hours Introduction (models, axioms, principles, conventions) 1. Thin lenses (Types of lenses. Defining elements. Path of light rays through lenses. Image formation. Required physical quantities. Lens formulas). 2. Lens systems (Non-collated lenses. Focalless systems). 3. Human eye (Functioning as an optical system. Sight defects and their corrections). 4. Optical instruments (Characteristics exemplified by a magnifying glass. Paths of light rays through a simplified photo camera. Path of light rays through a classical microscope) (Physics curriculum for the IXth grade/ 2011). This scenario exposes a learning unit based on experimental sequences (defining specific competencies), as a succession of lessons started by noticing a problem whose solution assumes the setup of an experiment under laboratory conditions. Progressive learning of theme objectives are realised with sequential experimental steps. The central cognitive process is the induction or the generalization (development of new knowledge based on observation of examples or counterexamples of the concept to be learnt). Pupil interest in theme objectives is triggered by problem-situations, for example: "In order to better see small objects I need a magnifying glass. But when using a magnifier, small object images are sometimes seen upright and sometimes seen reversed!" Along the way, pupils' reasoning will converge to the idea: "The image of an object through a lens depends on the relative distances among object, lens, and observer". Associated learning model: EXPERIMENT Specific competencies: derived from the experiment model, in agreement with the following learning unit steps I. Evoking - Anticipation: Size of the problem, formulation of hypotheses and planning of experiment. II

  6. Weak Force

    CERN Multimedia

    Without the weak force, the sun wouldn't shine. The weak force causes beta decay, a form of radioactivity that triggers nuclear fusion in the heart of the sun. The weak force is unlike other forces: it is characterised by disintegration. In beta decay, a down quark transforms into an up quark and an electron is emitted. Some materials are more radioactive than others because the delicate balance between the strong force and the weak force varies depending on the number of particles in the atomic nucleus. We live in the midst of a natural radioactive background that varies from region to region. For example, in Cornwall where there is a lot of granite, levels of background radiation are much higher than in the Geneva region. Text for the interactive: Move the Geiger counter to find out which samples are radioactive - you may be surprised. It is the weak force that is responsible for the Beta radioactivity here. The electrons emitted do not cross the plastic cover. Why do you think there is some detected radioa...

  7. Pulsar lensing geometry

    CERN Document Server

    Liu, Siqi; Macquart, J-P; Brisken, Walter; Deller, Adam

    2015-01-01

    Our analysis of archival VLBI data of PSR 0834+06 revealed that its scintillation properties can be precisely modelled using the inclined sheet model (Pen & Levin 2014), resulting in two distinct lens planes. These data strongly favour the grazing sheet model over turbulence as the primary source of pulsar scattering. This model can reproduce the parameters of the observed diffractive scintillation with an accuracy at the percent level. Comparison with new VLBI proper motion results in a direct measure of the ionized ISM screen transverse velocity. The results are consistent with ISM velocities local to the PSR 0834+06 sight-line (through the Galaxy). The simple 1D structure of the lenses opens up the possibility of using interstellar lenses as precision probes for pulsar lens mapping, precision transverse motions in the ISM, and new opportunities for removing scattering to improve pulsar timing. We describe the parameters and observables of this double screen system. While relative screen distances can i...

  8. The removal of shear-ellipticity correlations from the cosmic shear signal by nulling techniques

    CERN Document Server

    Joachimi, B

    2008-01-01

    In order to render cosmic shear an astronomical tool of high precision, it is essential to eliminate systematic effects upon its signal, one of the most significant ones being correlations between the gravitational shear and the intrinsic ellipticity of source galaxies. Regarding the crudeness of current models of intrinsic alignment, we have developed a model-independent, purely geometrical method to remove shear-ellipticity correlations. We eliminate the contributions to a tomographic cosmic shear signal that may be subject to contamination by shear-ellipticity correlations, making use of the characteristic dependence of these correlations on redshift. By introducing an appropriately chosen weight function to the lensing efficiency that nulls signals stemming from certain distances, new second-order measures of cosmic shear, free from intrinsic alignment, can be constructed. The loss of information induced by this nulling technique and the subsequent degradation of constraints on cosmological parameters is ...

  9. Joint Measurement of Lensing-Galaxy Correlations Using SPT and DES SV Data

    CERN Document Server

    Baxter, E J; Giannantonio, T; Dodelson, S; Jain, B; Huterer, D; Bleem, L E; Crawford, T M; Efstathiou, G; Fosalba, P; Kirk, D; Kwan, J; Sánchez, C; Story, K T; Troxel, M A; Abbott, T M C; Abdalla, F B; Armstrong, R; Benoit-Lévy, A; Benson, B A; Bernstein, G M; Bernstein, R A; Bertin, E; Brooks, D; Carlstrom, J E; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Chown, R; Crocce, M; Cunha, C E; D'Andrea, C B; da Costa, L N; Desai, S; Diehl, H T; Dietrich, J P; Doel, P; Evrard, A E; Neto, A Fausti; Flaugher, B; Frieman, J; Gruen, D; Gruendl, R A; Gutierrez, G; de Haan, T; Holder, G P; Honscheid, K; Hou, Z; James, D J; Kuehn, K; Kuropatkin, N; Lima, M; March, M; Marshall, J L; Martini, P; Melchior, P; Miller, C J; Miquel, R; Mohr, J J; Nord, B; Omori, Y; Plazas, A A; Reichardt, C L; Romer, A K; Rykoff, E S; Sanchez, E; Sevilla-Noarbe, I; Sheldon, E; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Stark, A A; Swanson, M E C; Tarle, G; Thomas, D; Walker, A R; Wechsler, R H

    2016-01-01

    We measure the correlation of galaxy lensing and cosmic microwave background lensing with a set of galaxies expected to trace the matter density field. The measurements are performed using pre-survey Dark Energy Survey (DES) Science Verification optical imaging data and millimeter-wave data from the 2500 square degree South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. The two lensing-galaxy correlations are jointly fit to extract constraints on cosmological parameters, constraints on the redshift distribution of the lens galaxies, and constraints on the absolute shear calibration of DES galaxy lensing measurements. We show that an attractive feature of these fits is that they are fairly insensitive to the clustering bias of the galaxies used as matter tracers. The measurement presented in this work confirms that DES and SPT data are consistent with each other and with the currently favored $\\Lambda$CDM cosmological model. It also demonstrates that joint lensing-galaxy correlation measurement considered ...

  10. CFHTLenS: Mapping the Large Scale Structure with Gravitational Lensing

    CERN Document Server

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

    2013-01-01

    We present a quantitative analysis of the largest contiguous maps of projected mass density obtained from gravitational lensing shear. We use data from the 154 deg2 covered by the Canada France Hawaii Telescope Lensing Survey. Our study is the first attempt to quantitatively characterize the scientific value of lensing maps, which could serve in the future as a complementary approach to the study of the dark universe with gravitational lensing. We show that mass maps contain unique cosmological information beyond that of traditional two-points statistical analysis techniques. Using a series of numerical simulations, we first show that gravitational lensing inversion provides a reliable probe of the projected matter distribution of large scale structure. We validate our analysis by quantifying the robustness of the maps with various statistical estimators. The same process is then applied to the CFHTLenS data. It is found that the statistical properties of the projected mass are fully consistent with the cosmo...

  11. AGN-selected clusters as revealed by weak lensing

    Science.gov (United States)

    Wold, M.; Lacy, M.; Dahle, H.; Lilje, P. B.; Ridgway, S. E.

    2002-01-01

    We discuss the results in light of the cooling flow and the merger/interaction scenarios for triggering and fuelling AGN in clusters, but find that the data do not point unambiguously to neither of the two.

  12. Modified Gravity: the CMB, Weak Lensing and General Parameterisations

    CERN Document Server

    Thomas, Shaun A; Weller, Jochen

    2011-01-01

    We examine general physical parameterisations for viable gravitational models in the $f(R)$ framework. This is related to the mass of an additional scalar field, called the scalaron, that is introduced by the theories. Using a simple parameterisation for the scalaron mass $M(a)$ we show there is an exact correspondence between the model and popular parameterisations of the modified Poisson equation $\\mu(a,k)$ and the ratio of the Newtonian potentials $\\eta(a,k)$. However, by comparing the aforementioned model against other viable scalaron theories we highlight that the common form of $\\mu(a,k)$ and $\\eta(a,k)$ in the literature does not accurately represent $f(R)$ behaviour. We subsequently construct an improved description for the scalaron mass (and therefore $\\mu(a,k)$ and $\\eta(a,k)$) which captures their essential features and has benefits derived from a more physical origin. We study the scalaron's observational signatures and show the modifica