Investigating cluster astrophysics and cosmology with cross-correlation of the thermal Sunyaev-Zel'dovich effect and weak lensing

NASA Astrophysics Data System (ADS)

Osato, Ken; Flender, Samuel; Nagai, Daisuke; Shirasaki, Masato; Yoshida, Naoki

2018-03-01

Recent detections of the cross-correlation of the thermal Sunyaev-Zel'dovich (tSZ) effect and weak gravitational lensing (WL) enable unique studies of cluster astrophysics and cosmology. In this work, we present constraints on the amplitude of the non-thermal pressure fraction in galaxy clusters, α0, and the amplitude of the matter power spectrum, σ8, using measurements of the tSZ power spectrum from Planck, and the tSZ-WL cross-correlation from Planck and the Red Cluster Sequence Lensing Survey. We fit the data to a semi-analytic model with the covariance matrix using N-body simulations. We find that the tSZ power spectrum alone prefers σ8 ˜ 0.85 and a large fraction of non-thermal pressure (α0 ˜ 0.2-0.3). The tSZ-WL cross-correlation on the other hand prefers a significantly lower σ8 ˜ 0.6 and low α0 ˜ 0.05. We show that this tension can be mitigated by allowing for a steep slope in the stellar mass-halo mass relation, which would cause a reduction of the gas in low-mass haloes. In such a model, the combined data prefer σ8 ˜ 0.7 and α0 ˜ 0.2, consistent with predictions from hydrodynamical simulations.

Dissecting the thermal Sunyaev-Zeldovich-gravitational lensing cross-correlation with hydrodynamical simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hojjati, Alireza; Harnois-Deraps, Joachim; Waerbeke, Ludovic Van

2015-10-01

We use the cosmo-OWLS suite of cosmological hydrodynamical simulations, which includes different galactic feedback models, to predict the cross-correlation signal between weak gravitational lensing and the thermal Sunyaev-Zeldovich (tSZ) y-parameter. The predictions are compared to the recent detection reported by van Waerbeke and collaborators. The simulations reproduce the weak lensing-tSZ cross-correlation, ξ{sub yκ}(θ), well. The uncertainty arising from different possible feedback models appears to be important on small scales only (0θ ∼< 1 arcmin), while the amplitude of the correlation on all scales is sensitive to cosmological parameters that control the growth rate of structure (such as σ{sub 8}, Ω{sub m} andmore » Ω{sub b}). This study confirms our previous claim (in Ma et al.) that a significant proportion of the signal originates from the diffuse gas component in low-mass (M{sub halo} ∼< 10{sup 14} M{sub ⊙}) clusters as well as from the region beyond the virial radius. We estimate that approximately 20% of the detected signal comes from low-mass clusters, which corresponds to about 30% of the baryon density of the Universe. The simulations also suggest that more than half of the baryons in the Universe are in the form of diffuse gas outside halos (∼> 5 times the virial radius) which is not hot or dense enough to produce a significant tSZ signal or be observed by X-ray experiments. Finally, we show that future high-resolution tSZ-lensing cross-correlation observations will serve as a powerful tool for discriminating between different galactic feedback models.« less

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

NASA Astrophysics Data System (ADS)

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 <50 per cent increment on the 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.

A Novel Approach in the Weakly Interacting Massive Particle Quest: Cross-correlation of Gamma-Ray Anisotropies and Cosmic Shear

NASA Astrophysics Data System (ADS)

Camera, Stefano; Fornasa, Mattia; Fornengo, Nicolao; Regis, Marco

2013-07-01

Both cosmic shear and cosmological gamma-ray emission stem from the presence of dark matter (DM) in the universe: DM structures are responsible for the bending of light in the weak-lensing regime and those same objects can emit gamma rays, either because they host astrophysical sources (active galactic nuclei or star-forming galaxies) or directly by DM annihilations (or decays, depending on the properties of the DM particle). Such gamma rays should therefore exhibit strong correlation with the cosmic shear signal. In this Letter, we compute the cross-correlation angular power spectrum of cosmic shear and gamma rays produced by the annihilation/decay of weakly interacting massive particle DM, as well as by astrophysical sources. We show that this observable provides novel information on the composition of the extragalactic gamma-ray background (EGB), since the amplitude and shape of the cross-correlation signal strongly depend on which class of sources is responsible for the gamma-ray emission. If the DM contribution to the EGB is significant (at least in a definite energy range), although compatible with current observational bounds, its strong correlation with the cosmic shear makes such signal potentially detectable by combining Fermi Large Area Telescope data with forthcoming galaxy surveys, like the Dark Energy Survey and Euclid. At the same time, the same signal would demonstrate that the weak-lensing observables are indeed due to particle DM matter and not to possible modifications of general relativity.

Wide-field lensing mass maps from Dark Energy Survey science verification data: Methodology and detailed analysis

DOE PAGES

Vikram, V.

2015-07-29

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 data. 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. We demonstrate that candidatemore » superclusters and voids along the line of sight can be identified, exploiting the tight scatter of the cluster photometric redshifts. We cross-correlate the mass map with a foreground magnitude-limited galaxy sample from the same data. Our measurement gives results consistent with mock catalogs from N-body simulations 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 6.8σ level with 20 arcminute smoothing. We find that the contribution of systematics to the lensing mass maps is generally within measurement uncertainties. In this study, we analyze less than 3% of the final area that will be mapped by the DES; the tools and analysis techniques developed in this paper can be applied to forthcoming larger data sets from the survey.« less

Dark Energy Survey Year 1 Results: Cross-Correlation Redshifts in the DES -- Calibration of the Weak Lensing Source Redshift Distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, C.; et al.

We present the calibration of the Dark Energy Survey Year 1 (DES Y1) weak lensing source galaxy redshift distributions from clustering measurements. By cross-correlating the positions of source galaxies with luminous red galaxies selected by the redMaGiC algorithm we measure the redshift distributions of the source galaxies as placed into different tomographic bins. These measurements constrain any such shifts to an accuracy ofmore » $$\\sim0.02$$ and can be computed even when the clustering measurements do not span the full redshift range. The highest-redshift source bin is not constrained by the clustering measurements because of the minimal redshift overlap with the redMaGiC galaxies. We compare our constraints with those obtained from $$\\texttt{COSMOS}$$ 30-band photometry and find that our two very different methods produce consistent constraints.« less

Weak lensing magnification of SpARCS galaxy clusters

NASA Astrophysics Data System (ADS)

Tudorica, A.; Hildebrandt, H.; Tewes, M.; Hoekstra, H.; Morrison, C. B.; Muzzin, A.; Wilson, G.; Yee, H. K. C.; Lidman, C.; Hicks, A.; Nantais, J.; Erben, T.; van der Burg, R. F. J.; Demarco, R.

2017-12-01

Context. Measuring and calibrating relations between cluster observables is critical for resource-limited studies. The mass-richness relation of clusters offers an observationally inexpensive way of estimating masses. Its calibration is essential for cluster and cosmological studies, especially for high-redshift clusters. Weak gravitational lensing magnification is a promising and complementary method to shear studies, that can be applied at higher redshifts. Aims: We aim to employ the weak lensing magnification method to calibrate the mass-richness relation up to a redshift of 1.4. We used the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS) galaxy cluster candidates (0.2 < z < 1.4) and optical data from the Canada France Hawaii Telescope (CFHT) to test whether magnification can be effectively used to constrain the mass of high-redshift clusters. Methods: Lyman-break galaxies (LBGs) selected using the u-band dropout technique and their colours were used as a background sample of sources. LBG positions were cross-correlated with the centres of the sample of SpARCS clusters to estimate the magnification signal, which was optimally-weighted using an externally-calibrated LBG luminosity function. The signal was measured for cluster sub-samples, binned in both redshift and richness. Results: We measured the cross-correlation between the positions of galaxy cluster candidates and LBGs and detected a weak lensing magnification signal for all bins at a detection significance of 2.6-5.5σ. In particular, the significance of the measurement for clusters with z> 1.0 is 4.1σ; for the entire cluster sample we obtained an average M200 of 1.28 -0.21+0.23 × 1014 M⊙. Conclusions: Our measurements demonstrated the feasibility of using weak lensing magnification as a viable tool for determining the average halo masses for samples of high redshift galaxy clusters. The results also established the success of using galaxy over-densities to select massive clusters at z > 1. Additional studies are necessary for further modelling of the various systematic effects we discussed.

Rotation of the cosmic microwave background polarization from weak gravitational lensing.

PubMed

Dai, Liang

2014-01-31

When a cosmic microwave background (CMB) photon travels from the surface of last scatter through spacetime metric perturbations, the polarization vector may rotate about its direction of propagation. This gravitational rotation is distinct from, and occurs in addition to, the lensing deflection of the photon trajectory. This rotation can be sourced by linear vector or tensor metric perturbations and is fully coherent with the curl deflection field. Therefore, lensing corrections to the CMB polarization power spectra as well as the temperature-polarization cross correlations due to nonscalar perturbations are modified. The rotation does not affect lensing by linear scalar perturbations, but needs to be included when calculations go to higher orders. We present complete results for weak lensing of the full-sky CMB power spectra by general linear metric perturbations, taking into account both deflection of the photon trajectory and rotation of the polarization. For the case of lensing by gravitational waves, we show that the B modes induced by the rotation largely cancel those induced by the curl component of deflection.

Cross-correlating Planck tSZ with RCSLenS weak lensing: implications for cosmology and AGN feedback

NASA Astrophysics Data System (ADS)

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.

Dark Energy Survey Year 1 results: curved-sky weak lensing mass map

NASA Astrophysics Data System (ADS)

Chang, C.; Pujol, A.; Mawdsley, B.; Bacon, D.; Elvin-Poole, J.; Melchior, P.; Kovács, A.; Jain, B.; Leistedt, B.; Giannantonio, T.; Alarcon, A.; Baxter, E.; Bechtol, K.; Becker, M. R.; Benoit-Lévy, A.; Bernstein, G. M.; Bonnett, C.; Busha, M. T.; Rosell, A. Carnero; Castander, F. J.; Cawthon, R.; da Costa, L. N.; Davis, C.; De Vicente, J.; DeRose, J.; Drlica-Wagner, A.; Fosalba, P.; Gatti, M.; Gaztanaga, E.; Gruen, D.; Gschwend, J.; Hartley, W. G.; Hoyle, B.; Huff, E. M.; Jarvis, M.; Jeffrey, N.; Kacprzak, T.; Lin, H.; MacCrann, N.; Maia, M. A. G.; Ogando, R. L. C.; Prat, J.; Rau, M. M.; Rollins, R. P.; Roodman, A.; Rozo, E.; Rykoff, E. S.; Samuroff, S.; Sánchez, C.; Sevilla-Noarbe, I.; Sheldon, E.; Troxel, M. A.; Varga, T. N.; Vielzeuf, P.; Vikram, V.; Wechsler, R. H.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Kind, M. Carrasco; Carretero, J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Doel, P.; Estrada, J.; Neto, A. Fausti; Fernandez, E.; Flaugher, B.; Frieman, J.; García-Bellido, J.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jeltema, T.; Johnson, M. W. G.; Johnson, M. D.; Kent, S.; Kirk, D.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Lahav, O.; Li, T. S.; Lima, M.; March, M.; Martini, P.; Menanteau, F.; Miquel, R.; Mohr, J. J.; Neilsen, E.; Nichol, R. C.; Petravick, D.; Plazas, A. A.; Romer, A. K.; Sako, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Smith, M.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Thomas, D.; Tucker, D. L.; Walker, A. R.; Wester, W.; Zhang, Y.

2018-04-01

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 the previous work, is constructed over a contiguous ≈1500 deg2, covering a comoving volume of ≈10 Gpc3. The effects of masking, sampling, and noise are tested using simulations. We generate weak lensing maps from two DES Y1 shear catalogues, METACALIBRATION and IM3SHAPE, with sources at redshift 0.2 < z < 1.3, and in each of four bins in this range. In the highest signal-to-noise map, the ratio between the mean signal to noise in the E-mode map and the B-mode map is ˜1.5 (˜2) when smoothed with a Gaussian filter of σG = 30 (80) arcmin. The second and third moments of the convergence κ in the maps are in agreement with simulations. We also find no significant correlation of κ with maps of potential systematic contaminants. Finally, we demonstrate two applications of the mass maps: (1) cross-correlation

Metric Tests for Curvature from Weak Lensing and Baryon Acoustic Oscillations

NASA Astrophysics Data System (ADS)

Bernstein, G.

2006-02-01

We describe a practical measurement of the curvature of the universe which, unlike current constraints, relies purely on the properties of the Robertson-Walker metric rather than any assumed model for the dynamics and content of the universe. The observable quantity is the cross-correlation between foreground mass and gravitational shear of background galaxies, which depends on the angular diameter distances dA(zl), dA(zs), and dA(zs,zl) on the degenerate triangle formed by observer, source, and lens. In a flat universe, dA(zl,zs)=dA(zs)-dA(zl), but in curved universes an additional term ~Ωk appears and alters the lensing observables even if dA(z) is fixed. We describe a method whereby weak-lensing data can be used to solve simultaneously for dA and the curvature. This method is completely insensitive to the equation of state of the contents of the universe, or amendments to general relativity that alter the gravitational deflection of light or the growth of structure. The curvature estimate is also independent of biases in the photometric redshift scale. This measurement is shown to be subject to a degeneracy among dA, Ωk, and the galaxy bias factors that may be broken by using the same imaging data to measure the angular scale of baryon acoustic oscillations. Simplified estimates of the accuracy attainable by this method indicate that ambitious weak-lensing + baryon-oscillation surveys would measure Ωk to an accuracy ~0.04f-1/2sky(σlnz/0.04)1/2, where σlnz is the photometric redshift error. The Fisher-matrix formalism developed here is also useful for predicting bounds on curvature and other characteristics of parametric dark energy models. We forecast some representative error levels and compare ours to other analyses of the weak-lensing cross-correlation method. We find both curvature and parametric constraints to be surprisingly insensitive to the systematic shear calibration errors.

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

DOE PAGES

Chang, C.; Sheldon, E.; Pujol, A.; ...

2018-01-04

We construct the largest curved-sky galaxy weak lensing mass map to date from the DES firstyear (DES Y1) data. The map, about 10 times larger than previous work, is constructed over a contiguous ≈1;500 deg 2, covering a comoving volume of ≈10 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 < z < 1:3; and in each of four bins in this range. In the highest signal-to-noise map, the ratio between the mean signal-to-noise in themore » E-mode and the B-mode map is ~1.5 (~2) when smoothed with a Gaussian filter of sG =30 (80) arcminutes. The second and third moments of the convergence k in the maps are in agreement with simulations. We also find no significant correlation of k with maps of potential systematic contaminants. Finally, we demonstrate two applications of the mass maps: (1) cross-correlation with different foreground tracers of mass and (2) exploration of the largest peaks and voids in the maps.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, C.; Sheldon, E.; Pujol, A.

We construct the largest curved-sky galaxy weak lensing mass map to date from the DES firstyear (DES Y1) data. The map, about 10 times larger than previous work, is constructed over a contiguous ≈1;500 deg 2, covering a comoving volume of ≈10 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 < z < 1:3; and in each of four bins in this range. In the highest signal-to-noise map, the ratio between the mean signal-to-noise in themore » E-mode and the B-mode map is ~1.5 (~2) when smoothed with a Gaussian filter of sG =30 (80) arcminutes. The second and third moments of the convergence k in the maps are in agreement with simulations. We also find no significant correlation of k with maps of potential systematic contaminants. Finally, we demonstrate two applications of the mass maps: (1) cross-correlation with different foreground tracers of mass and (2) exploration of the largest peaks and voids in the maps.« less

Constraints on the dark matter and dark energy interactions from weak lensing bispectrum tomography

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Rui; Feng, Chang; Wang, Bin, E-mail: an_rui@sjtu.edu.cn, E-mail: chang.feng@uci.edu, E-mail: wang_b@sjtu.edu.cn

We estimate uncertainties of cosmological parameters for phenomenological interacting dark energy models using weak lensing convergence power spectrum and bispectrum. We focus on the bispectrum tomography and examine how well the weak lensing bispectrum with tomography can constrain the interactions between dark sectors, as well as other cosmological parameters. Employing the Fisher matrix analysis, we forecast parameter uncertainties derived from weak lensing bispectra with a two-bin tomography and place upper bounds on strength of the interactions between the dark sectors. The cosmic shear will be measured from upcoming weak lensing surveys with high sensitivity, thus it enables us to usemore » the higher order correlation functions of weak lensing to constrain the interaction between dark sectors and will potentially provide more stringent results with other observations combined.« less

Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

NASA Astrophysics Data System (ADS)

Davis, C.; Rozo, E.; Roodman, A.; Alarcon, A.; Cawthon, R.; Gatti, M.; Lin, H.; Miquel, R.; Rykoff, E. S.; Troxel, M. A.; Vielzeuf, P.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; Crocce, M.; Cunha, C. E.; D'Andrea, C. B.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Doel, P.; Drlica-Wagner, A.; Fausti Neto, A.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Giannantonio, T.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Jain, B.; James, D. J.; Jeltema, T.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; March, M.; Marshall, J. L.; Martini, P.; Melchior, P.; Ogando, R. L. C.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Scarpine, V.; Schindler, R.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Vikram, V.; Walker, A. R.; Wechsler, R. H.

2018-06-01

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogues with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty of Δz ˜ ±0.01. We forecast that our proposal can, in principle, control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Our results provide strong motivation to launch a programme to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.

Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

DOE PAGES

Davis, C.; Rozo, E.; Roodman, A.; ...

2018-03-26

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogs with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty ofmore » $$\\Delta z \\sim \\pm 0.01$$. We forecast that our proposal can in principle control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Here, our results provide strong motivation to launch a program to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.« less

Cross-correlation redshift calibration without spectroscopic calibration samples in DES Science Verification Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, C.; Rozo, E.; Roodman, A.

Galaxy cross-correlations with high-fidelity redshift samples hold the potential to precisely calibrate systematic photometric redshift uncertainties arising from the unavailability of complete and representative training and validation samples of galaxies. However, application of this technique in the Dark Energy Survey (DES) is hampered by the relatively low number density, small area, and modest redshift overlap between photometric and spectroscopic samples. We propose instead using photometric catalogs with reliable photometric redshifts for photo-z calibration via cross-correlations. We verify the viability of our proposal using redMaPPer clusters from the Sloan Digital Sky Survey (SDSS) to successfully recover the redshift distribution of SDSS spectroscopic galaxies. We demonstrate how to combine photo-z with cross-correlation data to calibrate photometric redshift biases while marginalizing over possible clustering bias evolution in either the calibration or unknown photometric samples. We apply our method to DES Science Verification (DES SV) data in order to constrain the photometric redshift distribution of a galaxy sample selected for weak lensing studies, constraining the mean of the tomographic redshift distributions to a statistical uncertainty ofmore » $$\\Delta z \\sim \\pm 0.01$$. We forecast that our proposal can in principle control photometric redshift uncertainties in DES weak lensing experiments at a level near the intrinsic statistical noise of the experiment over the range of redshifts where redMaPPer clusters are available. Here, our results provide strong motivation to launch a program to fully characterize the systematic errors from bias evolution and photo-z shapes in our calibration procedure.« less

Gravitational Lensing Effect on the Two-Point Correlation of Hot Spots in the Cosmic Microwave Background.

PubMed

Takada; Komatsu; Futamase

2000-04-20

We investigate the weak gravitational lensing effect that is due to the large-scale structure of the universe on two-point correlations of local maxima (hot spots) in the two-dimensional sky map of the cosmic microwave background (CMB) anisotropy. According to the Gaussian random statistics, as most inflationary scenarios predict, the hot spots are discretely distributed, with some characteristic angular separations on the last scattering surface that are due to oscillations of the CMB angular power spectrum. The weak lensing then causes pairs of hot spots, which are separated with the characteristic scale, to be observed with various separations. We found that the lensing fairly smooths out the oscillatory features of the two-point correlation function of hot spots. This indicates that the hot spot correlations can be a new statistical tool for measuring the shape and normalization of the power spectrum of matter fluctuations from the lensing signatures.

RCSLenS: The Red Cluster Sequence Lensing Survey

NASA Astrophysics Data System (ADS)

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.

Evidence for gravitational lensing of the cosmic microwave background polarization from cross-correlation with the cosmic infrared background.

PubMed

Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Borys, C; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Leitch, E M; Linder, E; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Poletti, D; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Rotermund, K; Schanning, I; Schenck, D E; Sherwin, B D; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tikhomirov, A; Tomaru, T; Wilson, B; Yadav, A; Zahn, O

2014-04-04

We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.

The effect of Limber and flat-sky approximations on galaxy weak lensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lemos, Pablo; Challinor, Anthony; Efstathiou, George, E-mail: pl411@cam.ac.uk, E-mail: a.d.challinor@ast.cam.ac.uk, E-mail: gpe@ast.cam.ac.uk

We review the effect of the commonly-used Limber and flat-sky approximations on the calculation of shear power spectra and correlation functions for galaxy weak lensing. These approximations are accurate at small scales, but it has been claimed recently that their impact on low multipoles could lead to an increase in the amplitude of the mass fluctuations inferred from surveys such as CFHTLenS, reducing the tension between galaxy weak lensing and the amplitude determined by Planck from observations of the cosmic microwave background. Here, we explore the impact of these approximations on cosmological parameters derived from weak lensing surveys, using themore » CFHTLenS data as a test case. We conclude that the use of small-angle approximations for cosmological parameter estimation is negligible for current data, and does not contribute to the tension between current weak lensing surveys and Planck.« less

Weak lensing mass map and peak statistics in Canada-France-Hawaii Telescope Stripe 82 survey

NASA Astrophysics Data System (ADS)

Shan, Huan Yuan; Kneib, Jean-Paul; Comparat, Johan; Jullo, Eric; Charbonnier, Aldée; Erben, Thomas; Makler, Martin; Moraes, Bruno; Van Waerbeke, Ludovic; Courbin, Frédéric; Meylan, Georges; Tao, Charling; Taylor, James E.

2014-08-01

We present a weak lensing mass map covering ˜124 deg2 of the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82). We study the statistics of rare peaks in the map, including peak abundance, the peak-peak correlation functions and the tangential-shear profiles around peaks. We find that the abundance of peaks detected in CS82 is consistent with predictions from a Λ cold dark matter cosmological model, once noise effects are properly included. The correlation functions of peaks with different signal-to-noise ratio (SNR) are well described by power laws, and there is a clear cross-correlation between the Sloan Digital Sky Survey III/Constant Mass galaxies and high SNR peaks. The tangential-shear profiles around peaks increase with peak SNR. We fit analytical models to the tangential-shear profiles, including a projected singular isothermal sphere (SIS) model and a projected Navarro, Frenk & White (NFW) model, plus a two-halo term. For the high SNR peaks, the SIS model is rejected at ˜3σ. The NFW model plus a two-halo term gives more acceptable fits to the data. Some peaks match the positions of optically detected clusters, while others are relatively dark. Comparing dark and matched peaks, we find a difference in lensing signal of a factor of 2, suggesting that about half of the dark peaks are false detections.

Galaxy-galaxy weak gravitational lensing in f(R) gravity

NASA Astrophysics Data System (ADS)

Li, Baojiu; Shirasaki, Masato

2018-03-01

We present an analysis of galaxy-galaxy weak gravitational lensing (GGL) in chameleon f(R) gravity - a leading candidate of non-standard gravity models. For the analysis, we have created mock galaxy catalogues based on dark matter haloes from two sets of numerical simulations, using a halo occupation distribution (HOD) prescription which allows a redshift dependence of galaxy number density. To make a fairer comparison between the f(R) and Λ cold dark matter (ΛCDM) models, their HOD parameters are tuned so that the galaxy two-point correlation functions in real space (and therefore the projected two-point correlation functions) match. While the f(R) model predicts an enhancement of the convergence power spectrum by up to ˜ 30 per cent compared to the standard ΛCDM model with the same parameters, the maximum enhancement of GGL is only half as large and less than 5 per cent on separations above ˜1-2 h-1 Mpc, because the latter is a cross-correlation of shear (or matter, which is more strongly affected by modified gravity) and galaxy (which is weakly affected given the good match between galaxy autocorrelations in the two models) fields. We also study the possibility of reconstructing the matter power spectrum by combination of GGL and galaxy clustering in f(R) gravity. We find that the galaxy-matter cross-correlation coefficient remains at unity down to ˜2-3 h-1 Mpc at relevant redshifts even in f(R) gravity, indicating joint analysis of GGL and galaxy clustering can be a powerful probe of matter density fluctuations in chameleon gravity. The scale dependence of the model differences in their predictions of GGL can potentially allows us to break the degeneracy between f(R) gravity and other cosmological parameters such as Ωm and σ8.

Lensing as a probe of early universe: from CMB to galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassani, Farbod; Baghram, Shant; Firouzjahi, Hassan, E-mail: farbod@physics.sharif.edu, E-mail: baghram@sharif.edu, E-mail: firouz@ipm.ir

The Cosmic Microwave Background (CMB) radiation lensing is a promising tool to study the physics of early universe. In this work we probe the imprints of deviations from isotropy and scale invariance of primordial curvature perturbation power spectrum on CMB lensing potential and convergence. Specifically, we consider a scale-dependent hemispherical asymmetry in primordial power spectrum. We show that the CMB lensing potential and convergence and also the cross-correlation of the CMB lensing and late time galaxy convergence can probe the amplitude and the scale dependence of the dipole modulation. As another example, we consider a primordial power spectrum with localmore » feature. We show that the CMB lensing and the cross-correlation of the CMB lensing and galaxy lensing can probe the amplitude and the shape of the local feature. We show that the cross correlation of CMB lensing convergence and galaxy lensing is capable to probe the effects of local features in power spectrum on smaller scales than the CMB lensing. Finally we showed that the current data can constrain the amplitude and moment dependence of dipole asymmetry.« less

Contact lens deposits, adverse responses, and clinical ocular surface parameters.

PubMed

Zhao, Zhenjun; Naduvilath, Thomas; Flanagan, Judith L; Carnt, Nicole A; Wei, Xiaojia; Diec, Jennie; Evans, Vicki; Willcox, Mark D P

2010-09-01

To correlate clinical responses during contact lens wear with the amount of protein or cholesterol extracted from lenses after wear. Clinical parameters, including adverse response rates and corneal staining, and symptomatology rating during lens wear were collected from a series of clinical tests comprising four different silicone hydrogel lenses with four different multipurpose solutions. To test for correlates, the amount of total protein or cholesterol extracted from lenses after daily wear were compared statistically to clinical parameters. The amount of protein (p = 0.008) or cholesterol (p = 0.01) extracted from lenses was higher for those subjects who showed solution-induced corneal staining. Amount of protein extracted was correlated (p < 0.01) with conjunctival staining (R = -0.23), lens front surface wetting (r = 0.14), and lens fit tightness (R = -0.20). These clinical parameters accounted for 48% of lens protein deposition. The amount of cholesterol extracted from lenses was much more weakly associated with clinical variables. Amount of protein or cholesterol extracted from lenses was not associated with the production of any corneal infiltrative or mechanical adverse event during wear and was only very weakly correlated with insertion comfort of lenses. These results suggest that there may be no physiologically relevant consequence of cholesterol depositing on silicone hydrogel lenses. The amount of protein that deposits onto silicone hydrogel lenses during wear may have more affect on lens performance on-eye. However, the correlations were generally small and may still not indicate any causative relevant physiological response. Further work is required to determine whether there is any direct causative effect to support these correlative findings.

Weak lensing in the Dark Energy Survey

NASA Astrophysics Data System (ADS)

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.

Particle dark matter searches in the anisotropic sky

NASA Astrophysics Data System (ADS)

Fornengo, Nicolao; Regis, Marco

2014-02-01

Anisotropies in the electromagnetic emission produced by dark matter annihilation or decay in the extragalactic sky are a recent tool in the quest for a particle dark matter evidence. We review the formalism to compute the two-point angular power spectrum in the halo-model approach and discuss the features and the relative size of the various auto- and cross-correlation signals that can be envisaged for anisotropy studies. From the side of particle dark matter signals, we consider the full multi-wavelength spectrum, from the radio emission to X-ray and gamma-ray productions. We discuss the angular power spectra of the auto-correlation of each of these signals and of the cross-correlation between any pair of them. We then extend the search to comprise specific gravitational tracers of dark matter distribution in the Universe: weak-lensing cosmic shear, large-scale-structure matter distribution and CMB-lensing. We have shown that cross-correlating a multi-wavelength dark matter signal (which is a direct manifestation of its particle physics nature) with a gravitational tracer (which is a manifestation of the presence of large amounts of unseen matter in the Universe) may offer a promising tool to demonstrate that what we call DM is indeed formed by elementary particles.

Self-calibration of photometric redshift scatter in weak-lensing surveys

DOE PAGES

Zhang, Pengjie; Pen, Ue -Li; Bernstein, Gary

2010-06-11

Photo-z errors, especially catastrophic errors, are a major uncertainty for precision weak lensing cosmology. We find that the shear-(galaxy number) density and density-density cross correlation measurements between photo-z bins, available from the same lensing surveys, contain valuable information for self-calibration of the scattering probabilities between the true-z and photo-z bins. The self-calibration technique we propose does not rely on cosmological priors nor parameterization of the photo-z probability distribution function, and preserves all of the cosmological information available from shear-shear measurement. We estimate the calibration accuracy through the Fisher matrix formalism. We find that, for advanced lensing surveys such as themore » planned stage IV surveys, the rate of photo-z outliers can be determined with statistical uncertainties of 0.01-1% for z < 2 galaxies. Among the several sources of calibration error that we identify and investigate, the galaxy distribution bias is likely the most dominant systematic error, whereby photo-z outliers have different redshift distributions and/or bias than non-outliers from the same bin. This bias affects all photo-z calibration techniques based on correlation measurements. As a result, galaxy bias variations of O(0.1) produce biases in photo-z outlier rates similar to the statistical errors of our method, so this galaxy distribution bias may bias the reconstructed scatters at several-σ level, but is unlikely to completely invalidate the self-calibration technique.« less

Gravitational corrections to light propagation in a perturbed FLRW universe and corresponding weak-lensing spectra

NASA Astrophysics Data System (ADS)

Cuesta-Lazaro, Carolina; Quera-Bofarull, Arnau; Reischke, Robert; Schäfer, Björn Malte

2018-06-01

When the gravitational lensing of the large-scale structure is calculated from a cosmological model a few assumptions enter: (i) one assumes that the photons follow unperturbed background geodesics, which is usually referred to as the Born approximation, (ii) the lenses move slowly, (iii) the source-redshift distribution is evaluated relative to the background quantities, and (iv) the lensing effect is linear in the gravitational potential. Even though these approximations are small individually they could sum up, especially since they include local effects such as the Sachs-Wolfe and peculiar motion, but also non-local ones like the Born approximation and the integrated Sachs-Wolfe effect. In this work, we will address all points mentioned and perturbatively calculate the effect on a tomographic cosmic shear power spectrum of each effect individually as well as all cross-correlations. Our findings show that each effect is at least 4-5 orders of magnitude below the leading order lensing signal. Finally, we sum up all effects to estimate the overall impact on parameter estimation by a future cosmological weak-lensing survey such as Euclid in a wcold dark matter cosmology with parametrization Ωm, σ8, ns, h, w0, and wa, using five tomographic bins. We consistently find a parameter bias of 10-5, which is therefore completely negligible for all practical purposes, confirming that other effects such as intrinsic alignments, magnification bias and uncertainties in the redshift distribution will be the dominant systematic source in future surveys.

Halo Pressure Profile through the Skew Cross-power Spectrum of the Sunyaev-Zel’dovich Effect and CMB Lensing in Planck

NASA Astrophysics Data System (ADS)

Timmons, Nicholas; Cooray, Asantha; Feng, Chang; Keating, Brian

2017-11-01

We measure the cosmic microwave background (CMB) skewness power spectrum in Planck, using frequency maps of the HFI instrument and the Sunyaev-Zel’dovich (SZ) component map. The two-to-one skewness power spectrum measures the cross-correlation between CMB lensing and the thermal SZ effect. We also directly measure the same cross-correlation using the Planck CMB lensing map and the SZ map and compare it to the cross-correlation derived from the skewness power spectrum. We model fit the SZ power spectrum and CMB lensing-SZ cross-power spectrum via the skewness power spectrum to constrain the gas pressure profile of dark matter halos. The gas pressure profile is compared to existing measurements in the literature including a direct estimate based on the stacking of SZ clusters in Planck.

Noise estimates for measurements of weak lensing from the Ly α forest

NASA Astrophysics Data System (ADS)

Metcalf, R. Benton; Croft, Rupert A. C.; Romeo, Alessandro

2018-06-01

Lensing changes the apparent separation between pixels in the Ly α forest of separate quasars or high-redshift objects by changing their observed positions on the sky. This changes the implied correlations in the absorption and in particular makes the Ly α forest correlation function, or power spectrum, locally anisotropic in the plane of the sky. We have proposed a method for measuring weak lensing using this effect. Here, we estimate the noise expected in weak lensing maps and power spectra for different sets of observational parameters. We find that surveys of the size and quality of the ones being done today and ones planned for the future will be able to measure the lensing power spectrum at a source redshift of z ≃ 2.5 with high precision and even be able to image the distribution of foreground matter with high fidelity on degree scales. For example, we predict that Ly α forest lensing measurements from the DESI and WEAVE surveys should yield the mass fluctuation amplitude with a statistical error of ˜3 per cent, eBOSS ˜6 per cent. and the proposed MSE survey less than 1 per cent. By dividing the redshift range into multiple bins, some tomographic lensing information should be accessible as well. This would allow for cosmological lensing measurements at higher redshift than are accessible with galaxy shear surveys and correspondingly better constraints on the evolution of dark energy at relatively early times.

Removing the Impact of Correlated PSF Uncertainties in Weak Lensing

NASA Astrophysics Data System (ADS)

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

2018-05-01

Accurate reconstruction of the spatial distributions of the point-spread function (PSF) is crucial for high precision cosmic shear measurements. Nevertheless, current methods are not good at recovering the PSF fluctuations of high spatial frequencies. In general, the residual PSF fluctuations are spatially correlated, and therefore can significantly contaminate the correlation functions of the weak lensing signals. We propose a method to correct for this contamination statistically, without any assumptions on the PSF and galaxy morphologies or their spatial distribution. We demonstrate our idea with the data from the W2 field of CFHTLenS.

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

NASA Astrophysics Data System (ADS)

Kesden, Michael

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

Predicting weak lensing statistics from halo mass reconstructions - Final Paper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everett, Spencer

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 makemore » 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.« less

Full-sky Ray-tracing Simulation of Weak Lensing Using ELUCID Simulations: Exploring Galaxy Intrinsic Alignment and Cosmic Shear Correlations

NASA Astrophysics Data System (ADS)

Wei, Chengliang; Li, Guoliang; Kang, Xi; Luo, Yu; Xia, Qianli; Wang, Peng; Yang, Xiaohu; Wang, Huiyuan; Jing, Yipeng; Mo, Houjun; Lin, Weipeng; Wang, Yang; Li, Shijie; Lu, Yi; Zhang, Youcai; Lim, S. H.; Tweed, Dylan; Cui, Weiguang

2018-01-01

The intrinsic alignment of galaxies is an important systematic effect in weak-lensing surveys, which can affect the derived cosmological parameters. One direct way to distinguish different alignment models and quantify their effects on the measurement is to produce mock weak-lensing surveys. In this work, we use the full-sky ray-tracing technique to produce mock images of galaxies from the ELUCID N-body simulation run with WMAP9 cosmology. In our model, we assume that the shape of the central elliptical galaxy follows that of the dark matter halo, and that of the spiral galaxy follows the halo spin. Using the mock galaxy images, a combination of galaxy intrinsic shape and the gravitational shear, we compare the predicted tomographic shear correlations to the results of the Kilo-Degree Survey (KiDS) and Deep Lens Survey (DLS). We find that our predictions stay between the KiDS and DLS results. We rule out a model in which the satellite galaxies are radially aligned with the center galaxy; otherwise, the shear correlations on small scales are too high. Most importantly, we find that although the intrinsic alignment of spiral galaxies is very weak, they induce a positive correlation between the gravitational shear signal and the intrinsic galaxy orientation (GI). This is because the spiral galaxy is tangentially aligned with the nearby large-scale overdensity, contrary to the radial alignment of the elliptical galaxy. Our results explain the origin of the detected positive GI term in the weak-lensing surveys. We conclude that in future analyses, the GI model must include the dependence on galaxy types in more detail.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rozo, Eduardo; /U. Chicago /Chicago U., KICP; Wu, Hao-Yi

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 havemore » 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.« less

Weak lensing Study in VOICE Survey I: Shear Measurement

NASA Astrophysics Data System (ADS)

Fu, Liping; Liu, Dezi; Radovich, Mario; Liu, Xiangkun; Pan, Chuzhong; Fan, Zuhui; Covone, Giovanni; Vaccari, Mattia; Amaro, Valeria; Brescia, Massimo; Capaccioli, Massimo; De Cicco, Demetra; Grado, Aniello; Limatola, Luca; Miller, Lance; Napolitano, Nicola R.; Paolillo, Maurizio; Pignata, Giuliano

2018-06-01

The VST Optical Imaging of the CDFS and ES1 Fields (VOICE) Survey is a Guaranteed Time program carried out with the ESO/VST telescope to provide deep optical imaging over two 4 deg2 patches of the sky centred on the CDFS and ES1 pointings. We present the cosmic shear measurement over the 4 deg2 covering the CDFS region in the r-band using LensFit. Each of the four tiles of 1 deg2 has more than one hundred exposures, of which more than 50 exposures passed a series of image quality selection criteria for weak lensing study. The 5σ limiting magnitude in r- band is 26.1 for point sources, which is ≳1 mag deeper than other weak lensing survey in the literature (e.g. the Kilo Degree Survey, KiDS, at VST). The photometric redshifts are estimated using the VOICE u, g, r, i together with near-infrared VIDEO data Y, J, H, Ks. The mean redshift of the shear catalogue is 0.87, considering the shear weight. The effective galaxy number density is 16.35 gal/arcmin2, which is nearly twice the one of KiDS. The performance of LensFit on such a deep dataset was calibrated using VOICE-like mock image simulations. Furthermore, we have analyzed the reliability of the shear catalogue by calculating the star-galaxy cross-correlations, the tomographic shear correlations of two redshift bins and the contaminations of the blended galaxies. As a further sanity check, we have constrained cosmological parameters by exploring the parameter space with Population Monte Carlo sampling. For a flat ΛCDM model we have obtained Σ _8 = σ _8(Ω _m/0.3)^{0.5} = 0.68^{+0.11}_{-0.15}.

A 2500 deg 2 CMB Lensing Map from Combined South Pole Telescope and Planck Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omori, Y.; Chown, R.; Simard, G.

Here, we present a cosmic microwave background (CMB) lensing map produced from a linear combination of South Pole Telescope (SPT) and Planck temperature data. The 150 GHz temperature data from the 2500 deg 2 SPT-SZ survey is combined with the Planck 143 GHz data in harmonic space to obtain a temperature map that has a broader ℓ coverage and less noise than either individual map. Using a quadratic estimator technique on this combined temperature map, we produce a map of the gravitational lensing potential projected along the line of sight. We measure the auto-spectrum of the lensing potentialmore » $${C}_{L}^{\\phi \\phi }$$, and compare it to the theoretical prediction for a ΛCDM cosmology consistent with the Planck 2015 data set, finding a best-fit amplitude of $${0.95}_{-0.06}^{+0.06}(\\mathrm{stat}.{)}_{-0.01}^{+0.01}(\\mathrm{sys}.)$$. The null hypothesis of no lensing is rejected at a significance of 24σ. One important use of such a lensing potential map is in cross-correlations with other dark matter tracers. We demonstrate this cross-correlation in practice by calculating the cross-spectrum, $${C}_{L}^{\\phi G}$$, between the SPT+Planck lensing map and Wide-field Infrared Survey Explorer (WISE) galaxies. We fit $${C}_{L}^{\\phi G}$$ to a power law of the form $${p}_{L}=a{(L/{L}_{0})}^{-b}$$ with a, L 0, and b fixed, and find $${\\eta }^{\\phi G}={C}_{L}^{\\phi G}/{p}_{L}={0.94}_{-0.04}^{+0.04}$$, which is marginally lower, but in good agreement with $${\\eta }^{\\phi G}={1.00}_{-0.01}^{+0.02}$$, the best-fit amplitude for the cross-correlation of Planck-2015 CMB lensing and WISE galaxies over ~67% of the sky. Finally, the lensing potential map presented here will be used for cross-correlation studies with the Dark Energy Survey, whose footprint nearly completely covers the SPT 2500 deg 2 field.« less

A 2500 deg 2 CMB Lensing Map from Combined South Pole Telescope and Planck Data

DOE PAGES

Omori, Y.; Chown, R.; Simard, G.; ...

2017-11-07

Here, we present a cosmic microwave background (CMB) lensing map produced from a linear combination of South Pole Telescope (SPT) and Planck temperature data. The 150 GHz temperature data from the 2500 deg 2 SPT-SZ survey is combined with the Planck 143 GHz data in harmonic space to obtain a temperature map that has a broader ℓ coverage and less noise than either individual map. Using a quadratic estimator technique on this combined temperature map, we produce a map of the gravitational lensing potential projected along the line of sight. We measure the auto-spectrum of the lensing potentialmore » $${C}_{L}^{\\phi \\phi }$$, and compare it to the theoretical prediction for a ΛCDM cosmology consistent with the Planck 2015 data set, finding a best-fit amplitude of $${0.95}_{-0.06}^{+0.06}(\\mathrm{stat}.{)}_{-0.01}^{+0.01}(\\mathrm{sys}.)$$. The null hypothesis of no lensing is rejected at a significance of 24σ. One important use of such a lensing potential map is in cross-correlations with other dark matter tracers. We demonstrate this cross-correlation in practice by calculating the cross-spectrum, $${C}_{L}^{\\phi G}$$, between the SPT+Planck lensing map and Wide-field Infrared Survey Explorer (WISE) galaxies. We fit $${C}_{L}^{\\phi G}$$ to a power law of the form $${p}_{L}=a{(L/{L}_{0})}^{-b}$$ with a, L 0, and b fixed, and find $${\\eta }^{\\phi G}={C}_{L}^{\\phi G}/{p}_{L}={0.94}_{-0.04}^{+0.04}$$, which is marginally lower, but in good agreement with $${\\eta }^{\\phi G}={1.00}_{-0.01}^{+0.02}$$, the best-fit amplitude for the cross-correlation of Planck-2015 CMB lensing and WISE galaxies over ~67% of the sky. Finally, the lensing potential map presented here will be used for cross-correlation studies with the Dark Energy Survey, whose footprint nearly completely covers the SPT 2500 deg 2 field.« less

Non-negative Matrix Factorization for Self-calibration of Photometric Redshift Scatter in Weak-lensing Surveys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Le; Yu, Yu; Zhang, Pengjie, E-mail: lezhang@sjtu.edu.cn

Photo- z error is one of the major sources of systematics degrading the accuracy of weak-lensing cosmological inferences. Zhang et al. proposed a self-calibration method combining galaxy–galaxy correlations and galaxy–shear correlations between different photo- z bins. Fisher matrix analysis shows that it can determine the rate of photo- z outliers at a level of 0.01%–1% merely using photometric data and do not rely on any prior knowledge. In this paper, we develop a new algorithm to implement this method by solving a constrained nonlinear optimization problem arising in the self-calibration process. Based on the techniques of fixed-point iteration and non-negativemore » matrix factorization, the proposed algorithm can efficiently and robustly reconstruct the scattering probabilities between the true- z and photo- z bins. The algorithm has been tested extensively by applying it to mock data from simulated stage IV weak-lensing projects. We find that the algorithm provides a successful recovery of the scatter rates at the level of 0.01%–1%, and the true mean redshifts of photo- z bins at the level of 0.001, which may satisfy the requirements in future lensing surveys.« less

Probing dark energy with lensing magnification in photometric surveys.

PubMed

Schneider, Michael D

2014-02-14

I present an estimator for the angular cross correlation of two tracers of the cosmological large-scale structure that utilizes redshift information to isolate separate physical contributions. The estimator is derived by solving the Limber equation for a reweighting of the foreground tracer that nulls either clustering or lensing contributions to the cross correlation function. Applied to future photometric surveys, the estimator can enhance the measurement of gravitational lensing magnification effects to provide a competitive independent constraint on the dark energy equation of state.

Imitating intrinsic alignments: a bias to the CMB lensing-galaxy shape cross-correlation power spectrum induced by the large-scale structure bispectrum

NASA Astrophysics Data System (ADS)

Merkel, Philipp M.; Schäfer, Björn Malte

2017-10-01

Cross-correlating the lensing signals of galaxies and comic microwave background (CMB) fluctuations is expected to provide valuable cosmological information. In particular, it may help tighten constraints on parameters describing the properties of intrinsically aligned galaxies at high redshift. To access the information conveyed by the cross-correlation signal, its accurate theoretical description is required. We compute the bias to CMB lensing-galaxy shape cross-correlation measurements induced by non-linear structure growth. Using tree-level perturbation theory for the large-scale structure bispectrum, we find that the bias is negative on most angular scales, therefore mimicking the signal of intrinsic alignments. Combining Euclid-like galaxy lensing data with a CMB experiment comparable to the Planck satellite mission, the bias becomes significant only on smallest scales (ℓ ≳ 2500). For improved CMB observations, however, the corrections amount to 10-15 per cent of the CMB lensing-intrinsic alignment signal over a wide multipole range (10 ≲ ℓ ≲ 2000). Accordingly, the power spectrum bias, if uncorrected, translates into 2σ and 3σ errors in the determination of the intrinsic alignment amplitude in the case of CMB stage III and stage IV experiments, respectively.

Cosmological parameter constraints from galaxy-galaxy lensing and galaxy clustering with the SDSS DR7

NASA Astrophysics Data System (ADS)

Mandelbaum, Rachel; Slosar, Anže; Baldauf, Tobias; Seljak, Uroš; Hirata, Christopher M.; Nakajima, Reiko; Reyes, Reinabelle; Smith, Robert E.

2013-06-01

Recent studies have shown that the cross-correlation coefficient between galaxies and dark matter is very close to unity on scales outside a few virial radii of galaxy haloes, independent of the details of how galaxies populate dark matter haloes. This finding makes it possible to determine the dark matter clustering from measurements of galaxy-galaxy weak lensing and galaxy clustering. We present new cosmological parameter constraints based on large-scale measurements of spectroscopic galaxy samples from the Sloan Digital Sky Survey (SDSS) data release 7. We generalize the approach of Baldauf et al. to remove small-scale information (below 2 and 4 h-1 Mpc for lensing and clustering measurements, respectively), where the cross-correlation coefficient differs from unity. We derive constraints for three galaxy samples covering 7131 deg2, containing 69 150, 62 150 and 35 088 galaxies with mean redshifts of 0.11, 0.28 and 0.40. We clearly detect scale-dependent galaxy bias for the more luminous galaxy samples, at a level consistent with theoretical expectations. When we vary both σ8 and Ωm (and marginalize over non-linear galaxy bias) in a flat Λ cold dark matter model, the best-constrained quantity is σ8(Ωm/0.25)0.57 = 0.80 ± 0.05 (1σ, stat. + sys.), where statistical and systematic errors (photometric redshift and shear calibration) have comparable contributions, and we have fixed ns = 0.96 and h = 0.7. These strong constraints on the matter clustering suggest that this method is competitive with cosmic shear in current data, while having very complementary and in some ways less serious systematics. We therefore expect that this method will play a prominent role in future weak lensing surveys. When we combine these data with Wilkinson Microwave Anisotropy Probe 7-year (WMAP7) cosmic microwave background (CMB) data, constraints on σ8, Ωm, H0, wde and ∑mν become 30-80 per cent tighter than with CMB data alone, since our data break several parameter degeneracies.

SKA weak lensing- II. Simulated performance and survey design considerations

NASA Astrophysics Data System (ADS)

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

2016-12-01

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 optimize a 2-yr 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 on to consider survey size, finding that an area of 5000 deg2 is optimal for most SKA1 instrumental configurations. Finally, we forecast the performance of a weak lensing survey with the second deployment of the SKA. The increased survey size (3π steradian) and sensitivity improves both the signal to noise and the dark energy metrics by two orders of magnitude.

Halo Pressure Profile through the Skew Cross-power Spectrum of the Sunyaev–Zel’dovich Effect and CMB Lensing in Planck

DOE Office of Scientific and Technical Information (OSTI.GOV)

Timmons, Nicholas; Cooray, Asantha; Feng, Chang

2017-11-01

We measure the cosmic microwave background (CMB) skewness power spectrum in Planck , using frequency maps of the HFI instrument and the Sunyaev–Zel’dovich (SZ) component map. The two-to-one skewness power spectrum measures the cross-correlation between CMB lensing and the thermal SZ effect. We also directly measure the same cross-correlation using the Planck CMB lensing map and the SZ map and compare it to the cross-correlation derived from the skewness power spectrum. We model fit the SZ power spectrum and CMB lensing–SZ cross-power spectrum via the skewness power spectrum to constrain the gas pressure profile of dark matter halos. The gasmore » pressure profile is compared to existing measurements in the literature including a direct estimate based on the stacking of SZ clusters in Planck .« less

Weak lensing magnification in the Dark Energy Survey Science Verification Data

DOE PAGES

Garcia-Fernandez, M.; et al.

2018-02-02

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 themore » $0.2 < z < 0.4$ 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.« less

Weak lensing magnification in the Dark Energy Survey Science Verification Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garcia-Fernandez, M.; et al.

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 themore » $0.2 < z < 0.4$ 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.« less

Weak lensing magnification in the Dark Energy Survey Science Verification Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 themore » $0.2 < z < 0.4$ 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.« less

A 2500 deg 2 CMB Lensing Map from Combined South Pole Telescope and Planck Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Omori, Y.; Chown, R.; Simard, G.

We present a cosmic microwave background (CMB) lensing map produced from a linear combination of South Pole Telescope (SPT) and \\emph{Planck} temperature data. The 150 GHz temperature data from themore » $$2500\\ {\\rm deg}^{2}$$ SPT-SZ survey is combined with the \\emph{Planck} 143 GHz data in harmonic space, to obtain a temperature map that has a broader $$\\ell$$ coverage and less noise than either individual map. Using a quadratic estimator technique on this combined temperature map, we produce a map of the gravitational lensing potential projected along the line of sight. We measure the auto-spectrum of the lensing potential $$C_{L}^{\\phi\\phi}$$, and compare it to the theoretical prediction for a $$\\Lambda$$CDM cosmology consistent with the \\emph{Planck} 2015 data set, finding a best-fit amplitude of $$0.95_{-0.06}^{+0.06}({\\rm Stat.})\\! _{-0.01}^{+0.01}({\\rm Sys.})$$. The null hypothesis of no lensing is rejected at a significance of $$24\\,\\sigma$$. One important use of such a lensing potential map is in cross-correlations with other dark matter tracers. We demonstrate this cross-correlation in practice by calculating the cross-spectrum, $$C_{L}^{\\phi G}$$, between the SPT+\\emph{Planck} lensing map and Wide-field Infrared Survey Explorer (\\emph{WISE}) galaxies. We fit $$C_{L}^{\\phi G}$$ to a power law of the form $$p_{L}=a(L/L_{0})^{-b}$$ with $$a=2.15 \\times 10^{-8}$$, $b=1.35$, $$L_{0}=490$$, and find $$\\eta^{\\phi G}=0.94^{+0.04}_{-0.04}$$, which is marginally lower, but in good agreement with $$\\eta^{\\phi G}=1.00^{+0.02}_{-0.01}$$, the best-fit amplitude for the cross-correlation of \\emph{Planck}-2015 CMB lensing and \\emph{WISE} galaxies over $$\\sim67\\%$$ of the sky. The lensing potential map presented here will be used for cross-correlation studies with the Dark Energy Survey (DES), whose footprint nearly completely covers the SPT $$2500\\ {\\rm deg}^2$$ field.« less

A 2500 deg 2 CMB Lensing Map from Combined South Pole Telescope and Planck Data

DOE PAGES

Omori, Y.; Chown, R.; Simard, G.; ...

2017-11-07

We present a cosmic microwave background (CMB) lensing map produced from a linear combination of South Pole Telescope (SPT) and \\emph{Planck} temperature data. The 150 GHz temperature data from themore » $$2500\\ {\\rm deg}^{2}$$ SPT-SZ survey is combined with the \\emph{Planck} 143 GHz data in harmonic space, to obtain a temperature map that has a broader $$\\ell$$ coverage and less noise than either individual map. Using a quadratic estimator technique on this combined temperature map, we produce a map of the gravitational lensing potential projected along the line of sight. We measure the auto-spectrum of the lensing potential $$C_{L}^{\\phi\\phi}$$, and compare it to the theoretical prediction for a $$\\Lambda$$CDM cosmology consistent with the \\emph{Planck} 2015 data set, finding a best-fit amplitude of $$0.95_{-0.06}^{+0.06}({\\rm Stat.})\\! _{-0.01}^{+0.01}({\\rm Sys.})$$. The null hypothesis of no lensing is rejected at a significance of $$24\\,\\sigma$$. One important use of such a lensing potential map is in cross-correlations with other dark matter tracers. We demonstrate this cross-correlation in practice by calculating the cross-spectrum, $$C_{L}^{\\phi G}$$, between the SPT+\\emph{Planck} lensing map and Wide-field Infrared Survey Explorer (\\emph{WISE}) galaxies. We fit $$C_{L}^{\\phi G}$$ to a power law of the form $$p_{L}=a(L/L_{0})^{-b}$$ with $$a=2.15 \\times 10^{-8}$$, $b=1.35$, $$L_{0}=490$$, and find $$\\eta^{\\phi G}=0.94^{+0.04}_{-0.04}$$, which is marginally lower, but in good agreement with $$\\eta^{\\phi G}=1.00^{+0.02}_{-0.01}$$, the best-fit amplitude for the cross-correlation of \\emph{Planck}-2015 CMB lensing and \\emph{WISE} galaxies over $$\\sim67\\%$$ of the sky. The lensing potential map presented here will be used for cross-correlation studies with the Dark Energy Survey (DES), whose footprint nearly completely covers the SPT $$2500\\ {\\rm deg}^2$$ field.« less

Cluster mass calibration at high redshift: HST weak lensing analysis of 13 distant galaxy clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey

NASA Astrophysics Data System (ADS)

Schrabback, T.; Applegate, D.; 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.

2018-02-01

We present an HST/Advanced Camera for Surveys (ACS) weak gravitational lensing analysis of 13 massive high-redshift (zmedian = 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 Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (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 concentration-mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass-temperature scaling relation ln (E(z)M500c/1014 M⊙) = A + 1.5ln (kT/7.2 keV) 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}.

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel'dovich Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrabback, T.; et al.

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 sourcemore » 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}.« less

The Atacama Cosmology Telescope: Cross-Correlation of Cosmic Microwave Background Lensing and Quasars

NASA Technical Reports Server (NTRS)

Sherwin, Blake D; Das, Sudeep; Haijian, Amir; Addison, Graeme; Bond, Richard; Crichton, Devin; Devlin, Mark J.; Dunkley, Joanna; Gralla, Megan B.; Halpern, Mark;

Statistical and systematic errors in the measurement of weak-lensing Minkowski functionals: Application to the Canada-France-Hawaii Lensing Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirasaki, Masato; Yoshida, Naoki, E-mail: masato.shirasaki@utap.phys.s.u-tokyo.ac.jp

2014-05-01

The measurement of cosmic shear using weak gravitational lensing is a challenging task that involves a number of complicated procedures. We study in detail the systematic errors in the measurement of weak-lensing Minkowski Functionals (MFs). Specifically, we focus on systematics associated with galaxy shape measurements, photometric redshift errors, and shear calibration correction. We first generate mock weak-lensing catalogs that directly incorporate the actual observational characteristics of the Canada-France-Hawaii Lensing Survey (CFHTLenS). We then perform a Fisher analysis using the large set of mock catalogs for various cosmological models. We find that the statistical error associated with the observational effects degradesmore » the cosmological parameter constraints by a factor of a few. The Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of ∼1400 deg{sup 2} will constrain the dark energy equation of the state parameter with an error of Δw {sub 0} ∼ 0.25 by the lensing MFs alone, but biases induced by the systematics can be comparable to the 1σ error. We conclude that the lensing MFs are powerful statistics beyond the two-point statistics only if well-calibrated measurement of both the redshifts and the shapes of source galaxies is performed. Finally, we analyze the CFHTLenS data to explore the ability of the MFs to break degeneracies between a few cosmological parameters. Using a combined analysis of the MFs and the shear correlation function, we derive the matter density Ω{sub m0}=0.256±{sub 0.046}{sup 0.054}.« less

Cosmology with cosmic shear observations: a review.

PubMed

Kilbinger, Martin

2015-07-01

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 the implications for cosmology. We then conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.

Cosmic variance of the galaxy cluster weak lensing signal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruen, D.; Seitz, S.; Becker, M. R.

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 15h –1M ⊙, z = 0.25…0.5 in a cosmological simulation. We show that weak lensing measurements of clusters significantly underestimate massmore » 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 15h –1M ⊙ and z = 0.25), but significant also under typical ground-based conditions. We show that neglecting intrinsic profile variations leads to biases in the mass-observable relation constrained with weak lensing, both for intrinsic scatter and overall scale (the latter at the 15 per cent level). Furthermore, these biases are in excess of the statistical errors of upcoming surveys and can be avoided if the cosmic variance of cluster profiles is accounted for.« less

Cosmic variance of the galaxy cluster weak lensing signal

DOE PAGES

Gruen, D.; Seitz, S.; Becker, M. R.; ...

2015-04-13

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 15h –1M ⊙, z = 0.25…0.5 in a cosmological simulation. We show that weak lensing measurements of clusters significantly underestimate massmore » 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 15h –1M ⊙ and z = 0.25), but significant also under typical ground-based conditions. We show that neglecting intrinsic profile variations leads to biases in the mass-observable relation constrained with weak lensing, both for intrinsic scatter and overall scale (the latter at the 15 per cent level). Furthermore, these biases are in excess of the statistical errors of upcoming surveys and can be avoided if the cosmic variance of cluster profiles is accounted for.« less

KiDS-450: the tomographic weak lensing power spectrum and constraints on cosmological parameters

NASA Astrophysics Data System (ADS)

Köhlinger, F.; Viola, M.; Joachimi, B.; Hoekstra, H.; van Uitert, E.; Hildebrandt, H.; Choi, A.; Erben, T.; Heymans, C.; Joudaki, S.; Klaes, D.; Kuijken, K.; Merten, J.; Miller, L.; Schneider, P.; Valentijn, E. A.

2017-11-01

We present measurements of the weak gravitational lensing shear power spectrum based on 450 ° ^2 of imaging data from the Kilo Degree Survey. We employ a quadratic estimator in two and three redshift bins and extract band powers of redshift autocorrelation and cross-correlation spectra in the multipole range 76 ≤ ℓ ≤ 1310. The cosmological interpretation of the measured shear power spectra is performed in a Bayesian framework assuming a ΛCDM model with spatially flat geometry, while accounting for small residual uncertainties in the shear calibration and redshift distributions as well as marginalizing over intrinsic alignments, baryon feedback and an excess-noise power model. Moreover, massive neutrinos are included in the modelling. The cosmological main result is expressed in terms of the parameter combination S_8 ≡ σ _8 √{Ω_m/0.3} yielding S8 = 0.651 ± 0.058 (three z-bins), confirming the recently reported tension in this parameter with constraints from Planck at 3.2σ (three z-bins). We cross-check the results of the three z-bin analysis with the weaker constraints from the two z-bin analysis and find them to be consistent. The high-level data products of this analysis, such as the band power measurements, covariance matrices, redshift distributions and likelihood evaluation chains are available at http://kids.strw.leidenuniv.nl.

Angular spectra of the intrinsic galaxy ellipticity field, their observability and their impact on lensing in tomographic surveys

NASA Astrophysics Data System (ADS)

Schäfer, Björn Malte; Merkel, Philipp M.

2017-09-01

This paper describes intrinsic ellipticity correlations between galaxies, their statistical properties, their observability with future surveys and their interference with weak gravitational lensing measurements. Using an angular-momentum-based, quadratic intrinsic alignment model we derive correlation functions of the ellipticity components and project them to yield the four non-zero angular ellipticity spectra C^ɛ _E(ℓ), C^ɛ _B(ℓ), C^ɛ _C(ℓ) and C^ɛ _S(ℓ) in their generalization to tomographic surveys. For a Euclid-like survey, these spectra would have amplitudes smaller than the weak lensing effect on non-linear structures, but would constitute an important systematics. Computing estimation biases for cosmological parameters derived from an alignment-contaminated survey suggests biases of +5σw for the dark energy equation of state parameter w, -20σ _{Ω _m} for the matter density Ωm and -12σ _{σ _8} for the spectrum normalization σ8. Intrinsic alignments yield a signal that is easily observable with a survey similar to Euclid: while not independent, significances for estimates of each of the four spectra reach values of tens of σ if weak lensing and shape noise are considered as noise sources, which suggests relative uncertainties on alignment parameters at the percent level, implying that galaxy alignment mechanisms can be investigated by future surveys.

Weak Gravitational Lensing by the Nearby Cluster Abell 3667.

PubMed

Joffre; Fischer; Frieman; McKay; Mohr; Nichol; Johnston; Sheldon; Bernstein

2000-05-10

We present two weak lensing reconstructions of the nearby (zcl=0.055) merging cluster Abell 3667, based on observations taken approximately 1 yr apart under different seeing conditions. This is the lowest redshift cluster with a weak lensing mass reconstruction to date. The reproducibility of features in the two mass maps demonstrates that weak lensing studies of low-redshift clusters are feasible. These data constitute the first results from an X-ray luminosity-selected weak lensing survey of 19 low-redshift (z<0.1) southern clusters.

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

NASA Astrophysics Data System (ADS)

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.

Planck 2015 results. XV. Gravitational lensing

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartlett, J. G.; Bartolo, N.; Basak, S.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Fergusson, J.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Lewis, A.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rowan-Robinson, M.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; White, M.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-09-01

We present the most significant measurement of the cosmic microwave background (CMB) lensing potential to date (at a level of 40σ), using temperature and polarization data from the Planck 2015 full-mission release. Using a polarization-only estimator, we detect lensing at a significance of 5σ. We cross-check the accuracy of our measurement using the wide frequency coverage and complementarity of the temperature and polarization measurements. Public products based on this measurement include an estimate of the lensing potential over approximately 70% of the sky, an estimate of the lensing potential power spectrum in bandpowers for the multipole range 40 ≤ L ≤ 400, and an associated likelihood for cosmological parameter constraints. We find good agreement between our measurement of the lensing potential power spectrum and that found in the ΛCDM model that best fits the Planck temperature and polarization power spectra. Using the lensing likelihood alone we obtain a percent-level measurement of the parameter combination σ8Ω0.25m = 0.591 ± 0.021. We combine our determination of the lensing potential with the E-mode polarization, also measured by Planck, to generate an estimate of the lensing B-mode. We show that this lensing B-mode estimate is correlated with the B-modes observed directly by Planck at the expected level and with a statistical significance of 10σ, confirming Planck's sensitivity to this known sky signal. We also correlate our lensing potential estimate with the large-scale temperature anisotropies, detecting a cross-correlation at the 3σ level, as expected because of dark energy in the concordance ΛCDM model.

Planck 2015 results: XV. Gravitational lensing

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Arnaud, M.; ...

2016-09-20

Here, we present the most significant measurement of the cosmic microwave background (CMB) lensing potential to date (at a level of 40σ), using temperature and polarization data from the Planck 2015 full-mission release. Using a polarization-only estimator, we detect lensing at a significance of 5σ. We cross-check the accuracy of our measurement using the wide frequency coverage and complementarity of the temperature and polarization measurements. Public products based on this measurement include an estimate of the lensing potential over approximately 70% of the sky, an estimate of the lensing potential power spectrum in bandpowers for the multipole range 40 ≤more » L ≤ 400, and an associated likelihood for cosmological parameter constraints. We find good agreement between our measurement of the lensing potential power spectrum and that found in the ΛCDM model that best fits the Planck temperature and polarization power spectra. Using the lensing likelihood alone we obtain a percent-level measurement of the parameter combination σ 8Ω 0.25 m = 0.591 ± 0.021. We combine our determination of the lensing potential with the E-mode polarization, also measured by Planck, to generate an estimate of the lensing B-mode. We show that this lensing B-mode estimate is correlated with the B-modes observed directly by Planck at the expected level and with a statistical significance of 10σ, confirming Planck’s sensitivity to this known sky signal. Finally, we also correlate our lensing potential estimate with the large-scale temperature anisotropies, detecting a cross-correlation at the 3σ level, as expected because of dark energy in the concordance ΛCDM model.« less

A Bayesian hierarchical approach to galaxy-galaxy lensing

NASA Astrophysics Data System (ADS)

Sonnenfeld, Alessandro; Leauthaud, Alexie

2018-07-01

We present a Bayesian hierarchical inference formalism to study the relation between the properties of dark matter haloes and those of their central galaxies using weak gravitational lensing. Unlike traditional methods, this technique does not resort to stacking the weak lensing signal in bins, and thus allows for a more efficient use of the information content in the data. Our method is particularly useful for constraining scaling relations between two or more galaxy properties and dark matter halo mass, and can also be used to constrain the intrinsic scatter in these scaling relations. We show that, if observational scatter is not properly accounted for, the traditional stacking method can produce biased results when exploring correlations between multiple galaxy properties and halo mass. For example, this bias can affect studies of the joint correlation between galaxy mass, halo mass, and galaxy size, or galaxy colour. In contrast, our method easily and efficiently handles the intrinsic and observational scatter in multiple galaxy properties and halo mass. We test our method on mocks with varying degrees of complexity. We find that we can recover the mean halo mass and concentration, each with a 0.1 dex accuracy, and the intrinsic scatter in halo mass with a 0.05 dex accuracy. In its current version, our method will be most useful for studying the weak lensing signal around central galaxies in groups and clusters, as well as massive galaxies samples with log M* > 11, which have low satellite fractions.

A Bayesian Hierarchical Approach to Galaxy-Galaxy Lensing

NASA Astrophysics Data System (ADS)

Sonnenfeld, Alessandro; Leauthaud, Alexie

2018-04-01

We present a Bayesian hierarchical inference formalism to study the relation between the properties of dark matter halos and those of their central galaxies using weak gravitational lensing. Unlike traditional methods, this technique does not resort to stacking the weak lensing signal in bins, and thus allows for a more efficient use of the information content in the data. Our method is particularly useful for constraining scaling relations between two or more galaxy properties and dark matter halo mass, and can also be used to constrain the intrinsic scatter in these scaling relations. We show that, if observational scatter is not properly accounted for, the traditional stacking method can produce biased results when exploring correlations between multiple galaxy properties and halo mass. For example, this bias can affect studies of the joint correlation between galaxy mass, halo mass, and galaxy size, or galaxy colour. In contrast, our method easily and efficiently handles the intrinsic and observational scatter in multiple galaxy properties and halo mass. We test our method on mocks with varying degrees of complexity. We find that we can recover the mean halo mass and concentration, each with a 0.1 dex accuracy, and the intrinsic scatter in halo mass with a 0.05 dex accuracy. In its current version, our method will be most useful for studying the weak lensing signal around central galaxies in groups and clusters, as well as massive galaxies samples with log M* > 11, which have low satellite fractions.

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel’dovich Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrabback, T.; Applegate, D.; Dietrich, J. P.

Here we present an HST/Advanced Camera for Surveys (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 Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (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 concentration–mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass–temperature scaling relation ln (E(z)M 500c/10 14 M ⊙) = A + 1.5ln (kT/7.2 keV) to A=1.81more » $$+0.24\\atop{-0.14}$$(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$$+3.7\\atop{-1.8}$$.« less

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel’dovich Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schrabback, T.; Applegate, D.; Dietrich, J. P.

We present an HST/Advanced Camera for Surveys (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 Vmore » - I colour. Our estimate of the source redshift distribution is based on Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (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 concentration-mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass-temperature scaling relation ln (E(z) M-500c/10(14)M(circle dot)) = A + 1.5ln (kT/7.2 keV) to A = 1.81(-0.14)(+0.24)(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(-1.8)(+3.7).« less

Cluster Mass Calibration at High Redshift: HST Weak Lensing Analysis of 13 Distant Galaxy Clusters from the South Pole Telescope Sunyaev-Zel’dovich Survey

DOE PAGES

Schrabback, T.; Applegate, D.; Dietrich, J. P.; ...

2017-10-14

Here we present an HST/Advanced Camera for Surveys (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 Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (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 concentration–mass relation using simulations. In combination with temperature estimates from Chandra we constrain the normalization of the mass–temperature scaling relation ln (E(z)M 500c/10 14 M ⊙) = A + 1.5ln (kT/7.2 keV) to A=1.81more » $$+0.24\\atop{-0.14}$$(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$$+3.7\\atop{-1.8}$$.« less

The Weak Lensing Masses of Filaments between Luminous Red Galaxies

NASA Astrophysics Data System (ADS)

Epps, Seth D.; Hudson, Michael J.

2017-07-01

In the standard model of non-linear structure formation, a cosmic web of dark-matter-dominated filaments connects dark matter haloes. In this paper, we stack the weak lensing signal of an ensemble of filaments between groups and clusters of galaxies. Specifically, we detect the weak lensing signal, using CFHTLenS galaxy ellipticities, from stacked filaments between Sloan Digital Sky Survey (SDSS)-III/Baryon Oscillation Spectroscopic Survey luminous red galaxies (LRGs). As a control, we compare the physical LRG pairs with projected LRG pairs that are more widely separated in redshift space. We detect the excess filament mass density in the projected pairs at the 5σ level, finding a mass of (1.6 ± 0.3) × 1013 M⊙ for a stacked filament region 7.1 h-1 Mpc long and 2.5 h-1 Mpc wide. This filament signal is compared with a model based on the three-point galaxy-galaxy-convergence correlation function, as developed in Clampitt et al., yielding reasonable agreement.

Lensing bias to CMB measurements of compensated isocurvature perturbations

NASA Astrophysics Data System (ADS)

Heinrich, Chen He; Grin, Daniel; Hu, Wayne

2016-08-01

Compensated isocurvature perturbations (CIPs) are modes in which the baryon and dark matter density fluctuations cancel. They arise in the curvaton scenario as well as some models of baryogenesis. While they leave no observable effects on the cosmic microwave background (CMB) at linear order, they do spatially modulate two-point CMB statistics and can be reconstructed in a manner similar to gravitational lensing. Due to the similarity between the effects of CMB lensing and CIPs, lensing contributes nearly Gaussian random noise to the CIP estimator that approximately doubles the reconstruction noise power. Additionally, the cross correlation between lensing and the integrated Sachs-Wolfe effect generates a correlation between the CIP estimator and the temperature field even in the absence of a correlated CIP signal. For cosmic-variance limited temperature measurements out to multipoles l ≤2500 , subtracting a fixed lensing bias degrades the detection threshold for CIPs by a factor of 1.3, whether or not they are correlated with the adiabatic mode.

Needlet estimation of cross-correlation between CMB lensing maps and LSS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bianchini, Federico; Renzi, Alessandro; Marinucci, Domenico, E-mail: fbianchini@sissa.it, E-mail: renzi@mat.uniroma2.it, E-mail: marinucc@mat.uniroma2.it

In this paper we develop a novel needlet-based estimator to investigate the cross-correlation between cosmic microwave background (CMB) lensing maps and large-scale structure (LSS) data. We compare this estimator with its harmonic counterpart and, in particular, we analyze the bias effects of different forms of masking. In order to address this bias, we also implement a MASTER-like technique in the needlet case. The resulting estimator turns out to have an extremely good signal-to-noise performance. Our analysis aims at expanding and optimizing the operating domains in CMB-LSS cross-correlation studies, similarly to CMB needlet data analysis. It is motivated especially by nextmore » generation experiments (such as Euclid) which will allow us to derive much tighter constraints on cosmological and astrophysical parameters through cross-correlation measurements between CMB and LSS.« less

First Weak-lensing Results from “See Change”: Quantifying Dark Matter in the Two z ≳ 1.5 High-redshift Galaxy Clusters SPT-CL J2040-4451 and IDCS J1426+3508

NASA Astrophysics Data System (ADS)

Jee, M. James; Ko, Jongwan; Perlmutter, Saul; Gonzalez, Anthony; Brodwin, Mark; Linder, Eric; Eisenhardt, Peter

2017-10-01

We present a weak-lensing study of SPT-CL J2040-4451 and IDCS J1426+3508 at z = 1.48 and 1.75, respectively. The two clusters were observed in our “See Change” program, a Hubble Space Telescope survey of 12 massive high-redshift clusters aimed at high-z supernova measurements and weak-lensing estimation of accurate cluster masses. We detect weak but significant galaxy shape distortions using infrared images from the Wide Field Camera 3 (WFC3), which has not yet been used for weak-lensing studies. Both clusters appear to possess relaxed morphology in projected mass distribution, and their mass centroids agree nicely with those defined by both the galaxy luminosity and X-ray emission. Using a Navarro-Frenk-White profile, for which we assume that the mass is tightly correlated with the concentration parameter, we determine the masses of SPT-CL J2040-4451 and IDCS J1426 + 3508 to be {M}200={8.6}-1.4+1.7× {10}14 {M}⊙ and {2.2}-0.7+1.1× {10}14 {M}⊙ , respectively. The weak-lensing mass of SPT-CL J2040-4451 shows that the cluster is clearly a rare object. Adopting the central value, the expected abundance of such a massive cluster at z≳ 1.48 is only ˜ 0.07 in the parent 2500 sq. deg. survey. However, it is yet premature to claim that the presence of this cluster creates a serious tension with the current ΛCDM paradigm unless that tension will remain in future studies after marginalizing over many sources of uncertainties such as the accuracy of the mass function and the mass-concentration relation at the high-mass end. The mass of IDCS J1426+3508 is in excellent agreement with our previous Advanced Camera for Surveys-based weak-lensing result, while the much higher source density from our WFC3 imaging data makes the current statistical uncertainty ˜ 40% smaller.

KiDS-i-800: comparing weak gravitational lensing measurements from same-sky surveys

NASA Astrophysics Data System (ADS)

Amon, A.; Heymans, C.; Klaes, D.; Erben, T.; Blake, C.; Hildebrandt, H.; Hoekstra, H.; Kuijken, K.; Miller, L.; Morrison, C. B.; Choi, A.; de Jong, J. T. A.; Glazebrook, K.; Irisarri, N.; Joachimi, B.; Joudaki, S.; Kannawadi, A.; Lidman, C.; Napolitano, N.; Parkinson, D.; Schneider, P.; van Uitert, E.; Viola, M.; Wolf, C.

2018-07-01

We present a weak gravitational lensing analysis of 815 deg2 of i-band imaging from the Kilo-Degree Survey (KiDS-i-800). In contrast to the deep r-band observations, which take priority during excellent seeing conditions and form the primary KiDS data set (KiDS-r-450), the complementary yet shallower KiDS-i-800 spans a wide range of observing conditions. The overlapping KiDS-i-800 and KiDS-r-450 imaging therefore provides a unique opportunity to assess the robustness of weak lensing measurements. In our analysis we introduce two new `null' tests. The `nulled' two-point shear correlation function uses a matched catalogue to show that the calibrated KiDS-i-800 and KiDS-r-450 shear measurements agree at the level of 1 ± 4 per cent. We use five galaxy lens samples to determine a `nulled' galaxy-galaxy lensing signal from the full KiDS-i-800 and KiDS-r-450 surveys and find that the measurements agree to 7 ± 5 per cent when the KiDS-i-800 source redshift distribution is calibrated using either spectroscopic redshifts, or the 30-band photometric redshifts from the COSMOS survey.

KiDS-i-800: Comparing weak gravitational lensing measurements from same-sky surveys

NASA Astrophysics Data System (ADS)

Amon, A.; Heymans, C.; Klaes, D.; Erben, T.; Blake, C.; Hildebrandt, H.; Hoekstra, H.; Kuijken, K.; Miller, L.; Morrison, C. B.; Choi, A.; de Jong, J. T. A.; Glazebrook, K.; Irisarri, N.; Joachimi, B.; Joudaki, S.; Kannawadi, A.; Lidman, C.; Napolitano, N.; Parkinson, D.; Schneider, P.; van Uitert, E.; Viola, M.; Wolf, C.

2018-04-01

We present a weak gravitational lensing analysis of 815deg2 of i-band imaging from the Kilo-Degree Survey (KiDS-i-800). In contrast to the deep r-band observations, which take priority during excellent seeing conditions and form the primary KiDS dataset (KiDS-r-450), the complementary yet shallower KiDS-i-800 spans a wide range of observing conditions. The overlapping KiDS-i-800 and KiDS-r-450 imaging therefore provides a unique opportunity to assess the robustness of weak lensing measurements. In our analysis we introduce two new `null' tests. The `nulled' two-point shear correlation function uses a matched catalogue to show that the calibrated KiDS-i-800 and KiDS-r-450 shear measurements agree at the level of 1 ± 4%. We use five galaxy lens samples to determine a `nulled' galaxy-galaxy lensing signal from the full KiDS-i-800 and KiDS-r-450 surveys and find that the measurements agree to 7 ± 5% when the KiDS-i-800 source redshift distribution is calibrated using either spectroscopic redshifts, or the 30-band photometric redshifts from the COSMOS survey.

Bias of damped Lyman-α systems from their cross-correlation with CMB lensing

DOE PAGES

Alonso, D.; Colosimo, J.; Font-Ribera, A.; ...

2018-04-20

We cross-correlate the positions of damped Lyman-α systems (DLAs) and their parent quasar catalog with a convergence map derived from the Planck cosmic microwave background (CMB) temperature data. We then make consistent measurements of the lensing signal of both samples in both Fourier and configuration space. By interpreting the excess signal present in the DLA catalog with respect to the parent quasar catalog as caused by the large scale structure traced by DLAs, we are able to infer the bias of these objects: b DLA=2.6±0.9. These results are consistent with previous measurements made in cross-correlation with the Lyman-α forest, althoughmore » the current noise in the lensing data and the low number density of DLAs limits the constraining power of this measurement. We discuss the robustness of the analysis with respect to a number different systematic effects and forecast prospects of carrying out this measurement with data from future experiments.« less

Bias of damped Lyman-α systems from their cross-correlation with CMB lensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alonso, D.; Colosimo, J.; Font-Ribera, A.

We cross-correlate the positions of damped Lyman-α systems (DLAs) and their parent quasar catalog with a convergence map derived from the Planck cosmic microwave background (CMB) temperature data. We then make consistent measurements of the lensing signal of both samples in both Fourier and configuration space. By interpreting the excess signal present in the DLA catalog with respect to the parent quasar catalog as caused by the large scale structure traced by DLAs, we are able to infer the bias of these objects: b DLA=2.6±0.9. These results are consistent with previous measurements made in cross-correlation with the Lyman-α forest, althoughmore » the current noise in the lensing data and the low number density of DLAs limits the constraining power of this measurement. We discuss the robustness of the analysis with respect to a number different systematic effects and forecast prospects of carrying out this measurement with data from future experiments.« less

Bias of damped Lyman-α systems from their cross-correlation with CMB lensing

NASA Astrophysics Data System (ADS)

Alonso, D.; Colosimo, J.; Font-Ribera, A.; Slosar, A.

2018-04-01

We cross-correlate the positions of damped Lyman-α systems (DLAs) and their parent quasar catalog with a convergence map derived from the Planck cosmic microwave background (CMB) temperature data. We make consistent measurements of the lensing signal of both samples in both Fourier and configuration space. By interpreting the excess signal present in the DLA catalog with respect to the parent quasar catalog as caused by the large scale structure traced by DLAs, we are able to infer the bias of these objects: bDLA=2.6±0.9. These results are consistent with previous measurements made in cross-correlation with the Lyman-α forest, although the current noise in the lensing data and the low number density of DLAs limits the constraining power of this measurement. We discuss the robustness of the analysis with respect to a number different systematic effects and forecast prospects of carrying out this measurement with data from future experiments.

Lenses in the forest: cross correlation of the Lyman-alpha flux with cosmic microwave background lensing.

PubMed

Vallinotto, Alberto; Das, Sudeep; Spergel, David N; Viel, Matteo

2009-08-28

We present a theoretical estimate for a new observable: the cross correlation between the Lyman-alpha flux fluctuations in quasar spectra and the convergence of the cosmic microwave background as measured along the same line of sight. As a first step toward the assessment of its detectability, we estimate the signal-to-noise ratio using linear theory. Although the signal-to-noise is small for a single line of sight and peaks at somewhat smaller redshifts than those probed by the Lyman-alpha forest, we estimate a total signal-to-noise of 9 for cross correlating quasar spectra of SDSS-III with Planck and 20 for cross correlating with a future polarization based cosmic microwave background experiment. The detection of this effect would be a direct measure of the neutral hydrogen-matter cross correlation and could provide important information on the growth of structures at large scales in a redshift range which is still poorly probed.

On the insufficiency of arbitrarily precise covariance matrices: non-Gaussian weak-lensing likelihoods

NASA Astrophysics Data System (ADS)

Sellentin, Elena; Heavens, Alan F.

2018-01-01

We investigate whether a Gaussian likelihood, as routinely assumed in the analysis of cosmological data, is supported by simulated survey data. We define test statistics, based on a novel method that first destroys Gaussian correlations in a data set, and then measures the non-Gaussian correlations that remain. This procedure flags pairs of data points that depend on each other in a non-Gaussian fashion, and thereby identifies where the assumption of a Gaussian likelihood breaks down. Using this diagnosis, we find that non-Gaussian correlations in the CFHTLenS cosmic shear correlation functions are significant. With a simple exclusion of the most contaminated data points, the posterior for s8 is shifted without broadening, but we find no significant reduction in the tension with s8 derived from Planck cosmic microwave background data. However, we also show that the one-point distributions of the correlation statistics are noticeably skewed, such that sound weak-lensing data sets are intrinsically likely to lead to a systematically low lensing amplitude being inferred. The detected non-Gaussianities get larger with increasing angular scale such that for future wide-angle surveys such as Euclid or LSST, with their very small statistical errors, the large-scale modes are expected to be increasingly affected. The shifts in posteriors may then not be negligible and we recommend that these diagnostic tests be run as part of future analyses.

Combining weak-lensing tomography and spectroscopic redshift surveys

DOE PAGES

Cai, Yan -Chuan; Bernstein, Gary

2012-05-11

Redshift space distortion (RSD) is a powerful way of measuring the growth of structure and testing General Relativity, but it is limited by cosmic variance and the degeneracy between galaxy bias b and the growth rate factor f. The cross-correlation of lensing shear with the galaxy density field can in principle measure b in a manner free from cosmic variance limits, breaking the f-b degeneracy and allowing inference of the matter power spectrum from the galaxy survey. We analyze the growth constraints from a realistic tomographic weak lensing photo-z survey combined with a spectroscopic galaxy redshift survey over the samemore » sky area. For sky coverage f sky = 0.5, analysis of the transverse modes measures b to 2-3% accuracy per Δz = 0.1 bin at z < 1 when ~10 galaxies arcmin –2 are measured in the lensing survey and all halos with M > M min = 10 13h –1M ⊙ have spectra. For the gravitational growth parameter parameter γ (f = Ω γ m), combining the lensing information with RSD analysis of non-transverse modes yields accuracy σ(γ) ≈ 0.01. Adding lensing information to the RSD survey improves \\sigma(\\gamma) by an amount equivalent to a 3x (10x) increase in RSD survey area when the spectroscopic survey extends down to halo mass 10 13.5 (10 14) h –1 M ⊙. We also find that the σ(γ) of overlapping surveys is equivalent to that of surveys 1.5-2 times larger if they are separated on the sky. This gain is greatest when the spectroscopic mass threshold is 10 13 -10 14 h –1 M ⊙, similar to LRG surveys. The gain of overlapping surveys is reduced for very deep or very shallow spectroscopic surveys, but any practical surveys are more powerful when overlapped than when separated. As a result, the gain of overlapped surveys is larger in the case when the primordial power spectrum normalization is uncertain by > 0.5%.« less

Optimizing weak lensing mass estimates for cluster profile uncertainty

DOE PAGES

Gruen, D.; Bernstein, G. M.; Lam, T. Y.; ...

2011-09-11

Weak lensing measurements of cluster masses are necessary for calibrating mass-observable relations (MORs) to investigate the growth of structure and the properties of dark energy. However, the measured cluster shear signal varies at fixed mass M 200m due to inherent ellipticity of background galaxies, intervening structures along the line of sight, and variations in the cluster structure due to scatter in concentrations, asphericity and substructure. We use N-body simulated halos to derive and evaluate a weak lensing circular aperture mass measurement M ap that minimizes the mass estimate variance <(M ap - M 200m) 2> in the presence of allmore » these forms of variability. Depending on halo mass and observational conditions, the resulting mass estimator improves on M ap filters optimized for circular NFW-profile clusters in the presence of uncorrelated large scale structure (LSS) about as much as the latter improve on an estimator that only minimizes the influence of shape noise. Optimizing for uncorrelated LSS while ignoring the variation of internal cluster structure puts too much weight on the profile near the cores of halos, and under some circumstances can even be worse than not accounting for LSS at all. As a result, we discuss the impact of variability in cluster structure and correlated structures on the design and performance of weak lensing surveys intended to calibrate cluster MORs.« less

Wide-Field Lensing Mass Maps from Dark Energy Survey Science Verification Data

DOE PAGES

Chang, C.

2015-07-29

We present a mass map reconstructed from weak gravitational lensing shear measurements over 139 deg 2 from the Dark Energy Survey science verification data. The mass map probes both luminous and dark matter, thus providing a tool for studying cosmology. We also find good agreement between the mass map and the distribution of massive galaxy clusters identified using a red-sequence cluster finder. Potential candidates for superclusters 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 6.8σ level with 20 arc min smoothing.more » These measurements are consistent with simulated galaxy catalogs based on N-body simulations from a cold dark matter model with a cosmological constant. This suggests low systematics uncertainties in the map. Finally, we summarize our key findings in this Letter; the detailed methodology and tests for systematics are presented in a companion paper.« less

Wide-Field Lensing Mass Maps from Dark Energy Survey Science Verification Data.

PubMed

Chang, C; Vikram, V; 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; Kovács, A; Lahav, O; Lin, H; Melchior, P; Peiris, H; Rozo, E; Rykoff, E; Sánchez, C; Sheldon, E; Troxel, M A; Wechsler, R; Zuntz, J; Abbott, T; Abdalla, F B; Allam, S; Annis, J; Bauer, A H; Benoit-Lévy, A; Brooks, D; Buckley-Geer, E; Burke, D L; Capozzi, D; Carnero Rosell, A; Carrasco Kind, M; 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; Fausti Neto, A; 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

2015-07-31

We present a mass map reconstructed from weak gravitational lensing shear measurements over 139  deg2 from the Dark Energy Survey 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 superclusters 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 6.8σ level with 20 arc min smoothing. These measurements are consistent with simulated galaxy catalogs based on N-body simulations from a cold dark matter model with a cosmological constant. This suggests 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.

Clustering redshift distributions for the Dark Energy Survey

NASA Astrophysics Data System (ADS)

Helsby, Jennifer

Accurate determination of photometric redshifts and their errors is critical for large scale structure and weak lensing studies for constraining cosmology from deep, wide imaging surveys. Current photometric redshift methods suffer from bias and scatter due to incomplete training sets. Exploiting the clustering between a sample of galaxies for which we have spectroscopic redshifts and a sample of galaxies for which the redshifts are unknown can allow us to reconstruct the true redshift distribution of the unknown sample. Here we use this method in both simulations and early data from the Dark Energy Survey (DES) to determine the true redshift distributions of galaxies in photometric redshift bins. We find that cross-correlating with the spectroscopic samples currently used for training provides a useful test of photometric redshifts and provides reliable estimates of the true redshift distribution in a photometric redshift bin. We discuss the use of the cross-correlation method in validating template- or learning-based approaches to redshift estimation and its future use in Stage IV surveys.

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

NASA Technical Reports Server (NTRS)

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.

The skewed weak lensing likelihood: why biases arise, despite data and theory being sound

NASA Astrophysics Data System (ADS)

Sellentin, Elena; Heymans, Catherine; Harnois-Déraps, Joachim

2018-07-01

We derive the essentials of the skewed weak lensing likelihood via a simple hierarchical forward model. Our likelihood passes four objective and cosmology-independent tests which a standard Gaussian likelihood fails. We demonstrate that sound weak lensing data are naturally biased low, since they are drawn from a skewed distribution. This occurs already in the framework of Lambda cold dark matter. Mathematically, the biases arise because noisy two-point functions follow skewed distributions. This form of bias is already known from cosmic microwave background analyses, where the low multipoles have asymmetric error bars. Weak lensing is more strongly affected by this asymmetry as galaxies form a discrete set of shear tracer particles, in contrast to a smooth shear field. We demonstrate that the biases can be up to 30 per cent of the standard deviation per data point, dependent on the properties of the weak lensing survey and the employed filter function. Our likelihood provides a versatile framework with which to address this bias in future weak lensing analyses.

The skewed weak lensing likelihood: why biases arise, despite data and theory being sound.

NASA Astrophysics Data System (ADS)

Sellentin, Elena; Heymans, Catherine; Harnois-Déraps, Joachim

2018-04-01

We derive the essentials of the skewed weak lensing likelihood via a simple Hierarchical Forward Model. Our likelihood passes four objective and cosmology-independent tests which a standard Gaussian likelihood fails. We demonstrate that sound weak lensing data are naturally biased low, since they are drawn from a skewed distribution. This occurs already in the framework of ΛCDM. Mathematically, the biases arise because noisy two-point functions follow skewed distributions. This form of bias is already known from CMB analyses, where the low multipoles have asymmetric error bars. Weak lensing is more strongly affected by this asymmetry as galaxies form a discrete set of shear tracer particles, in contrast to a smooth shear field. We demonstrate that the biases can be up to 30% of the standard deviation per data point, dependent on the properties of the weak lensing survey and the employed filter function. Our likelihood provides a versatile framework with which to address this bias in future weak lensing analyses.

On weak lensing shape noise

NASA Astrophysics Data System (ADS)

Niemi, Sami-Matias; Kitching, Thomas D.; Cropper, Mark

2015-12-01

One of the most powerful techniques to study the dark sector of the Universe is weak gravitational lensing. In practice, to infer the reduced shear, weak lensing measures galaxy shapes, which are the consequence of both the intrinsic ellipticity of the sources and of the integrated gravitational lensing effect along the line of sight. Hence, a very large number of galaxies is required in order to average over their individual properties and to isolate the weak lensing cosmic shear signal. If this `shape noise' can be reduced, significant advances in the power of a weak lensing surveys can be expected. This paper describes a general method for extracting the probability distributions of parameters from catalogues of data using Voronoi cells, which has several applications, and has synergies with Bayesian hierarchical modelling approaches. This allows us to construct a probability distribution for the variance of the intrinsic ellipticity as a function of galaxy property using only photometric data, allowing a reduction of shape noise. As a proof of concept the method is applied to the CFHTLenS survey data. We use this approach to investigate trends of galaxy properties in the data and apply this to the case of weak lensing power spectra.

A weak lensing analysis of the PLCK G100.2-30.4 cluster

NASA Astrophysics Data System (ADS)

Radovich, M.; Formicola, I.; Meneghetti, M.; Bartalucci, I.; Bourdin, H.; Mazzotta, P.; Moscardini, L.; Ettori, S.; Arnaud, M.; Pratt, G. W.; Aghanim, N.; Dahle, H.; Douspis, M.; Pointecouteau, E.; Grado, A.

2015-07-01

We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4, derived from a weak lensing analysis of deep Subaru griz images. We perform a careful selection of the background galaxies using the multi-band imaging data, and undertake the weak lensing analysis on the deep (1 h) r -band image. The shape measurement is based on the Kaiser-Squires-Broadhurst algorithm; we adopt the PSFex software to model the point spread function (PSF) across the field and correct for this in the shape measurement. The weak lensing analysis is validated through extensive image simulations. We compare the resulting weak lensing mass profile and total mass estimate to those obtained from our re-analysis of XMM-Newton observations, derived under the hypothesis of hydrostatic equilibrium. The total integrated mass profiles agree remarkably well, within 1σ across their common radial range. A mass M500 ~ 7 × 1014M⊙ is derived for the cluster from our weak lensing analysis. Comparing this value to that obtained from our reanalysis of XMM-Newton data, we obtain a bias factor of (1-b) = 0.8 ± 0.1. This is compatible within 1σ with the value of (1-b) obtained in Planck 2015 from the calibration of the bias factor using newly available weak lensing reconstructed masses. Based on data collected at Subaru Telescope (University of Tokyo).

On Using a Space Telescope to Detect Weak-lensing Shear

NASA Astrophysics Data System (ADS)

Tung, Nathan; Wright, Edward

2017-11-01

Ignoring redshift dependence, the statistical performance of a weak-lensing survey is set by two numbers: the effective shape noise of the sources, which includes the intrinsic ellipticity dispersion and the measurement noise, and the density of sources that are useful for weak-lensing measurements. In this paper, we provide some general guidance for weak-lensing shear measurements from a “generic” space telescope by looking for the optimum wavelength bands to maximize the galaxy flux signal-to-noise ratio (S/N) and minimize ellipticity measurement error. We also calculate an effective galaxy number per square degree across different wavelength bands, taking into account the density of sources that are useful for weak-lensing measurements and the effective shape noise of sources. Galaxy data collected from the ultra-deep UltraVISTA Ks-selected and R-selected photometric catalogs (Muzzin et al. 2013) are fitted to radially symmetric Sérsic galaxy light profiles. The Sérsic galaxy profiles are then stretched to impose an artificial weak-lensing shear, and then convolved with a pure Airy Disk PSF to simulate imaging of weak gravitationally lensed galaxies from a hypothetical diffraction-limited space telescope. For our model calculations and sets of galaxies, our results show that the peak in the average galaxy flux S/N, the minimum average ellipticity measurement error, and the highest effective galaxy number counts all lie around the K-band near 2.2 μm.

Estimating the weak-lensing rotation signal in radio cosmic shear surveys

NASA Astrophysics Data System (ADS)

Thomas, Daniel B.; Whittaker, Lee; Camera, Stefano; Brown, Michael L.

2017-09-01

Weak lensing has become an increasingly important tool in cosmology and the use of galaxy shapes to measure cosmic shear has become routine. The weak-lensing distortion tensor contains two other effects in addition to the two components of shear: the convergence and rotation. The rotation mode is not measurable using the standard cosmic shear estimators based on galaxy shapes, as there is no information on the original shapes of the images before they were lensed. Due to this, no estimator has been proposed for the rotation mode in cosmological weak-lensing surveys, and the rotation mode has never been constrained. Here, we derive an estimator for this quantity, which is based on the use of radio polarization measurements of the intrinsic position angles of galaxies. The rotation mode can be sourced by physics beyond Λ cold dark matter (ΛCDM), and also offers the chance to perform consistency checks of ΛCDM and of weak-lensing surveys themselves. We present simulations of this estimator and show that, for the pedagogical example of cosmic string spectra, this estimator could detect a signal that is consistent with the constraints from Planck. We examine the connection between the rotation mode and the shear B modes and thus how this estimator could help control systematics in future radio weak-lensing surveys.

Lensing bias to CMB polarization measurements of compensated isocurvature perturbations

NASA Astrophysics Data System (ADS)

Heinrich, Chen

2018-01-01

Compensated isocurvature perturbations (CIPs) are opposite spatial fluctuations in the baryon and dark matter (DM) densities. They arise in the curvaton model and some models of baryogenesis. While the gravitational effects of baryon fluctuations are compensated by those of DM, leaving no observable impacts on the cosmic microwave background (CMB) at first order, they modulate the sound horizon at recombination, thereby correlating CMB anisotropies at different multipoles. As a result, CIPs can be reconstructed using quadratic estimators similarly to CMB detection of gravitational lensing. Because of these similarities, however, the CIP estimators are biased with lensing contributions that must be subtracted. These lensing contributions for CMB polarization measurement of CIPs are found to roughly triple the noise power of the total CIP estimator on large scales. In addition, the cross power with temperature and E -mode polarization are contaminated by lensing-ISW (integrated Sachs-Wolfe) correlations and reionization-lensing correlations respectively. For a cosmic-variance-limited temperature and polarization experiment measuring out to multipoles lmax=2500 , the lensing noise raises the detection threshold by a factor of 1.5, leaving a 2.7 σ detection possible for the maximal CIP signal in the curvaton model.

Gauge-invariant formalism of cosmological weak lensing

NASA Astrophysics Data System (ADS)

Yoo, Jaiyul; Grimm, Nastassia; Mitsou, Ermis; Amara, Adam; Refregier, Alexandre

2018-04-01

We present the gauge-invariant formalism of cosmological weak lensing, accounting for all the relativistic effects due to the scalar, vector, and tensor perturbations at the linear order. While the light propagation is fully described by the geodesic equation, the relation of the photon wavevector to the physical quantities requires the specification of the frames, where they are defined. By constructing the local tetrad bases at the observer and the source positions, we clarify the relation of the weak lensing observables such as the convergence, the shear, and the rotation to the physical size and shape defined in the source rest-frame and the observed angle and redshift measured in the observer rest-frame. Compared to the standard lensing formalism, additional relativistic effects contribute to all the lensing observables. We explicitly verify the gauge-invariance of the lensing observables and compare our results to previous work. In particular, we demonstrate that even in the presence of the vector and tensor perturbations, the physical rotation of the lensing observables vanishes at the linear order, while the tetrad basis rotates along the light propagation compared to a FRW coordinate. Though the latter is often used as a probe of primordial gravitational waves, the rotation of the tetrad basis is indeed not a physical observable. We further clarify its relation to the E-B decomposition in weak lensing. Our formalism provides a transparent and comprehensive perspective of cosmological weak lensing.

The weak lensing analysis of the CFHTLS and NGVS RedGOLD galaxy clusters

NASA Astrophysics Data System (ADS)

Parroni, C.; Mei, S.; Erben, T.; Van Waerbeke, L.; Raichoor, A.; Ford, J.; Licitra, R.; Meneghetti, M.; Hildebrandt, H.; Miller, L.; Côté, P.; Covone, G.; Cuillandre, J.-C.; Duc, P.-A.; Ferrarese, L.; Gwyn, S. D. J.; Puzia, T. H.

2017-12-01

An accurate estimation of galaxy cluster masses is essential for their use in cosmological and astrophysical studies. We studied the accuracy of the optical richness obtained by our RedGOLD cluster detection algorithm tep{licitra2016a, licitra2016b} as a mass proxy, using weak lensing and X-ray mass measurements. We measured stacked weak lensing cluster masses for a sample of 1323 galaxy clusters in the Canada-France-Hawaii Telescope Legacy Survey W1 and the Next Generation Virgo Cluster Survey at 0.2

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shaikh, Shabbir; Mukherjee, Suvodip; 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 and 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 (Ω{sub GW}) of the SGWB, sourced at different redshifts, without assuming anymore » particular model for its origin. We present these bounds on Ω{sub GW} for different power-law models characterizing the SGWB, indicating the threshold above which observable imprints of SGWB must be present in CMB.« less

Precise weak lensing constraints from deep high-resolution Ks images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2 J 232727.7-020437 at z = 0.70

NASA Astrophysics Data System (ADS)

Schrabback, Tim; Schirmer, Mischa; van der Burg, Remco F. J.; Hoekstra, Henk; Buddendiek, Axel; Applegate, Douglas; Bradač, Maruša; Eifler, Tim; Erben, Thomas; Gladders, Michael D.; Hernández-Martín, Beatriz; Hildebrandt, Hendrik; Hoag, Austin; Klaes, Dominik; von der Linden, Anja; Marchesini, Danilo; Muzzin, Adam; Sharon, Keren; Stefanon, Mauro

2018-03-01

We demonstrate that deep good-seeing VLT/HAWK-I Ks images complemented with g + z-band photometry can yield a sensitivity for weak lensing studies of massive galaxy clusters at redshifts 0.7 ≲ z ≲ 1.1, which is almost identical to the sensitivity of HST/ACS mosaics of single-orbit depth. Key reasons for this good performance are the excellent image quality frequently achievable for Ks imaging from the ground, a highly effective photometric selection of background galaxies, and a galaxy ellipticity dispersion that is noticeably lower than for optically observed high-redshift galaxy samples. Incorporating results from the 3D-HST and UltraVISTA surveys we also obtained a more accurate calibration of the source redshift distribution than previously achieved for similar optical weak lensing data sets. Here we studied the extremely massive galaxy cluster RCS2 J232727.7-020437 (z = 0.699), combining deep VLT/HAWK-I Ks images (point spread function with a 0.''35 full width at half maximum) with LBT/LBC photometry. The resulting weak lensing mass reconstruction suggests that the cluster consists of a single overdensity, which is detected with a peak significance of 10.1σ. We constrained the cluster mass to M200c/(1015 M⊙) = 2.06-0.26+0.28(stat.) ± 0.12(sys.) assuming a spherical Navarro, Frenk & White model and simulation-based priors on the concentration, making it one of the most massive galaxy clusters known in the z ≳ 0.7 Universe. We also cross-checked the HAWK-I measurements through an analysis of overlapping HST/ACS images, yielding fully consistent estimates of the lensing signal. Based on observations conducted with the ESO Very Large Telescope, the Large Binocular Telescope, and the NASA/ESA Hubble Space Telescope, as detailed in the acknowledgements.

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

PubMed

Cooray; Hu; Miralda-Escudé

2000-05-20

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

Magnification bias as a novel probe for primordial magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Camera, S.; Fedeli, C.; Moscardini, L., E-mail: stefano.camera@tecnico.ulisboa.pt, E-mail: cosimo.fedeli@oabo.inaf.it, E-mail: lauro.moscardini@unibo.it

2014-03-01

In this paper we investigate magnetic fields generated in the early Universe. These fields are important candidates at explaining the origin of astrophysical magnetism observed in galaxies and galaxy clusters, whose genesis is still by and large unclear. Compared to the standard inflationary power spectrum, intermediate to small scales would experience further substantial matter clustering, were a cosmological magnetic field present prior to recombination. As a consequence, the bias and redshift distribution of galaxies would also be modified. Hitherto, primordial magnetic fields (PMFs) have been tested and constrained with a number of cosmological observables, e.g. the cosmic microwave background radiation,more » galaxy clustering and, more recently, weak gravitational lensing. Here, we explore the constraining potential of the density fluctuation bias induced by gravitational lensing magnification onto the galaxy-galaxy angular power spectrum. Such an effect is known as magnification bias. Compared to the usual galaxy clustering approach, magnification bias helps in lifting the pathological degeneracy present amongst power spectrum normalisation and galaxy bias. This is because magnification bias cross-correlates galaxy number density fluctuations of nearby objects with weak lensing distortions of high-redshift sources. Thus, it takes advantage of the gravitational deflection of light, which is insensitive to galaxy bias but powerful in constraining the density fluctuation amplitude. To scrutinise the potentiality of this method, we adopt a deep and wide-field spectroscopic galaxy survey. We show that magnification bias does contain important information on primordial magnetism, which will be useful in combination with galaxy clustering and shear. We find we shall be able to rule out at 95.4% CL amplitudes of PMFs larger than 5 × 10{sup −4} nG for values of the PMF power spectral index n{sub B} ∼ 0.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, C.; Pujol, A.; Gaztañaga, E.

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 amore » $$\\sim$$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.« less

Evidence of Cross-correlation between the CMB Lensing and the γ-Ray Sky

NASA Astrophysics Data System (ADS)

Fornengo, Nicolao; Perotto, Laurence; Regis, Marco; Camera, Stefano

2015-03-01

We report the measurement of the angular power spectrum of cross-correlation between the unresolved component of the Fermi-LAT γ-ray sky maps and the cosmic microwave background lensing potential map reconstructed by the Planck satellite. The matter distribution in the universe determines the bending of light coming from the last scattering surface. At the same time, the matter density drives the growth history of astrophysical objects, including their capability at generating non-thermal phenomena, which in turn give rise to γ-ray emissions. The Planck lensing map provides information on the integrated distribution of matter, while the integrated history of γ-ray emitters is imprinted in the Fermi-LAT sky maps. We report here the first evidence of their correlation. We find that the multipole dependence of the cross-correlation measurement is in agreement with current models of the γ-ray luminosity function for active galactic nuclei and star-forming galaxies, with a statistical evidence of 3.0σ. Moreover, its amplitude can in general be matched only assuming that these extragalactic emitters are also the bulk contribution of the measured isotopic γ-ray background (IGRB) intensity. This leaves little room for a big contribution from galactic sources to the IGRB measured by Fermi-LAT, pointing toward direct evidence of the extragalactic origin of the IGRB.

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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.

Bias to CMB lensing reconstruction from temperature anisotropies due to large-scale galaxy motions

NASA Astrophysics Data System (ADS)

Ferraro, Simone; Hill, J. Colin

2018-01-01

Gravitational lensing of the cosmic microwave background (CMB) is expected to be amongst the most powerful cosmological tools for ongoing and upcoming CMB experiments. In this work, we investigate a bias to CMB lensing reconstruction from temperature anisotropies due to the kinematic Sunyaev-Zel'dovich (kSZ) effect, that is, the Doppler shift of CMB photons induced by Compton scattering off moving electrons. The kSZ signal yields biases due to both its own intrinsic non-Gaussianity and its nonzero cross-correlation with the CMB lensing field (and other fields that trace the large-scale structure). This kSZ-induced bias affects both the CMB lensing autopower spectrum and its cross-correlation with low-redshift tracers. Furthermore, it cannot be removed by multifrequency foreground separation techniques because the kSZ effect preserves the blackbody spectrum of the CMB. While statistically negligible for current data sets, we show that it will be important for upcoming surveys, and failure to account for it can lead to large biases in constraints on neutrino masses or the properties of dark energy. For a stage 4 CMB experiment, the bias can be as large as ≈15 % or 12% in cross-correlation with LSST galaxy lensing convergence or galaxy overdensity maps, respectively, when the maximum temperature multipole used in the reconstruction is ℓmax=4000 , and about half of that when ℓmax=3000 . Similarly, we find that the CMB lensing autopower spectrum can be biased by up to several percent. These biases are many times larger than the expected statistical errors. We validate our analytical predictions with cosmological simulations and present the first complete estimate of secondary-induced CMB lensing biases. The predicted bias is sensitive to the small-scale gas distribution, which is affected by pressure and feedback mechanisms, thus making removal via "bias-hardened" estimators challenging. Reducing ℓmax can significantly mitigate the bias at the cost of a decrease in the overall lensing reconstruction signal-to-noise. A bias ≲1 % on large scales requires ℓmax≲2000 , which leads to a reduction in signal-to-noise by a factor of ≈3 - 5 for a stage 4 CMB experiment. Polarization-only reconstruction may be the most robust mitigation strategy.

Non-Gaussian information from weak lensing data via deep learning

NASA Astrophysics Data System (ADS)

Gupta, Arushi; Matilla, José Manuel Zorrilla; Hsu, Daniel; Haiman, Zoltán

2018-05-01

Weak lensing maps contain information beyond two-point statistics on small scales. Much recent work has tried to extract this information through a range of different observables or via nonlinear transformations of the lensing field. Here we train and apply a two-dimensional convolutional neural network to simulated noiseless lensing maps covering 96 different cosmological models over a range of {Ωm,σ8} . Using the area of the confidence contour in the {Ωm,σ8} plane as a figure of merit, derived from simulated convergence maps smoothed on a scale of 1.0 arcmin, we show that the neural network yields ≈5 × tighter constraints than the power spectrum, and ≈4 × tighter than the lensing peaks. Such gains illustrate the extent to which weak lensing data encode cosmological information not accessible to the power spectrum or even other, non-Gaussian statistics such as lensing peaks.

Planck intermediate results: XLI. A map of lensing-induced B-modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ade, P. A. R.; Aghanim, N.; Ashdown, M.

The secondary cosmic microwave background (CMB) B-modes stem from the post-decoupling distortion of the polarization E-modes due to the gravitational lensing effect of large-scale structures. These lensing-induced B-modes constitute both a valuable probe of the dark matter distribution and an important contaminant for the extraction of the primary CMB B-modes from inflation. Planck provides accurate nearly all-sky measurements of both the polarization E-modes and the integrated mass distribution via the reconstruction of the CMB lensing potential. By combining these two data products, we have produced in this paper an all-sky template map of the lensing-induced B-modes using a real-space algorithmmore » that minimizes the impact of sky masks. The cross-correlation of this template with an observed (primordial and secondary) B-mode map can be used to measure the lensing B-mode power spectrum at multipoles up to 2000. In particular, when cross-correlating with the B-mode contribution directly derived from the Planck polarization maps, we obtain lensing-induced B-mode power spectrum measurement at a significance level of 12σ, which agrees with the theoretical expectation derived from the Planck best-fit Λ cold dark matter model. This unique nearly all-sky secondary B-mode template, which includes the lensing-induced information from intermediate to small (10 ≲ ℓ ≲ 1000) angular scales, is delivered as part of the Planck 2015 public data release. Finally, it will be particularly useful for experiments searching for primordial B-modes, such as BICEP2/Keck Array or LiteBIRD, since it will enable an estimate to be made of the lensing-induced contribution to the measured total CMB B-modes.« less

Planck intermediate results. XLI. A map of lensing-induced B-modes

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Basak, S.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Catalano, A.; Chiang, H. C.; Christensen, P. R.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davis, R. J.; de Bernardis, P.; de Zotti, G.; Delabrouille, J.; Dickinson, C.; Diego, J. M.; Doré, O.; Ducout, A.; Dupac, X.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gruppuso, A.; Gudmundsson, J. E.; Harrison, D. L.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hornstrup, A.; Hovest, W.; Hurier, G.; Jaffe, A. H.; Jones, W. C.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Leonardi, R.; Levrier, F.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Meinhold, P. R.; Melchiorri, A.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Novikov, D.; Novikov, I.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pointecouteau, E.; Polenta, G.; Pratt, G. W.; Rachen, J. P.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-12-01

The secondary cosmic microwave background (CMB) B-modes stem from the post-decoupling distortion of the polarization E-modes due to the gravitational lensing effect of large-scale structures. These lensing-induced B-modes constitute both a valuable probe of the dark matter distribution and an important contaminant for the extraction of the primary CMB B-modes from inflation. Planck provides accurate nearly all-sky measurements of both the polarization E-modes and the integrated mass distribution via the reconstruction of the CMB lensing potential. By combining these two data products, we have produced an all-sky template map of the lensing-induced B-modes using a real-space algorithm that minimizes the impact of sky masks. The cross-correlation of this template with an observed (primordial and secondary) B-mode map can be used to measure the lensing B-mode power spectrum at multipoles up to 2000. In particular, when cross-correlating with the B-mode contribution directly derived from the Planck polarization maps, we obtain lensing-induced B-mode power spectrum measurement at a significance level of 12σ, which agrees with the theoretical expectation derived from the Planck best-fit Λ cold dark matter model. This unique nearly all-sky secondary B-mode template, which includes the lensing-induced information from intermediate to small (10 ≲ ℓ ≲ 1000) angular scales, is delivered as part of the Planck 2015 public data release. It will be particularly useful for experiments searching for primordial B-modes, such as BICEP2/Keck Array or LiteBIRD, since it will enable an estimate to be made of the lensing-induced contribution to the measured total CMB B-modes.

Planck intermediate results: XLI. A map of lensing-induced B-modes

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Ashdown, M.; ...

2016-12-12

The secondary cosmic microwave background (CMB) B-modes stem from the post-decoupling distortion of the polarization E-modes due to the gravitational lensing effect of large-scale structures. These lensing-induced B-modes constitute both a valuable probe of the dark matter distribution and an important contaminant for the extraction of the primary CMB B-modes from inflation. Planck provides accurate nearly all-sky measurements of both the polarization E-modes and the integrated mass distribution via the reconstruction of the CMB lensing potential. By combining these two data products, we have produced in this paper an all-sky template map of the lensing-induced B-modes using a real-space algorithmmore » that minimizes the impact of sky masks. The cross-correlation of this template with an observed (primordial and secondary) B-mode map can be used to measure the lensing B-mode power spectrum at multipoles up to 2000. In particular, when cross-correlating with the B-mode contribution directly derived from the Planck polarization maps, we obtain lensing-induced B-mode power spectrum measurement at a significance level of 12σ, which agrees with the theoretical expectation derived from the Planck best-fit Λ cold dark matter model. This unique nearly all-sky secondary B-mode template, which includes the lensing-induced information from intermediate to small (10 ≲ ℓ ≲ 1000) angular scales, is delivered as part of the Planck 2015 public data release. Finally, it will be particularly useful for experiments searching for primordial B-modes, such as BICEP2/Keck Array or LiteBIRD, since it will enable an estimate to be made of the lensing-induced contribution to the measured total CMB B-modes.« less

Weak Lensing Results of the Merging Cluster A1758

NASA Technical Reports Server (NTRS)

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

2011-01-01

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

The Subaru FMOS galaxy redshift survey (FastSound). V. Intrinsic alignments of emission-line galaxies at z ˜ 1.4

NASA Astrophysics Data System (ADS)

Tonegawa, Motonari; Okumura, Teppei; Totani, Tomonori; Dalton, Gavin; Glazebrook, Karl; Yabe, Kiyoto

2018-06-01

Intrinsic alignments (IA), the coherent alignment of intrinsic galaxy orientations, can be a source of a systematic error of weak lensing surveys. The redshift evolution of IA also contains information about the physics of galaxy formation and evolution. This paper presents the first measurement of IA at high redshift, z ˜ 1.4, using the spectroscopic catalog of blue star-forming galaxies of the FastSound redshift survey, with the galaxy shape information from the Canada-Hawaii-France telescope lensing survey. The IA signal is consistent with zero with power-law amplitudes fitted to the projected correlation functions for density-shape and shape-shape correlation components, Aδ+ = -0.0071 ± 0.1340 and A++ = -0.0505 ± 0.0848, respectively. These results are consistent with those obtained from blue galaxies at lower redshifts (e.g., A _{δ +}=0.0035_{-0.0389}^{+0.0387} and A_{++}=0.0045_{-0.0168}^{+0.0166} at z = 0.51 from the WiggleZ survey). The upper limit of the constrained IA amplitude corresponds to a few percent contamination to the weak-lensing shear power spectrum, resulting in systematic uncertainties on the cosmological parameter estimations by -0.052 < Δσ8 < 0.039 and -0.039 < ΔΩm < 0.030.

The Subaru FMOS galaxy redshift survey (FastSound). V. Intrinsic alignments of emission-line galaxies at z ˜ 1.4

NASA Astrophysics Data System (ADS)

Tonegawa, Motonari; Okumura, Teppei; Totani, Tomonori; Dalton, Gavin; Glazebrook, Karl; Yabe, Kiyoto

2018-04-01

Intrinsic alignments (IA), the coherent alignment of intrinsic galaxy orientations, can be a source of a systematic error of weak lensing surveys. The redshift evolution of IA also contains information about the physics of galaxy formation and evolution. This paper presents the first measurement of IA at high redshift, z ˜ 1.4, using the spectroscopic catalog of blue star-forming galaxies of the FastSound redshift survey, with the galaxy shape information from the Canada-Hawaii-France telescope lensing survey. The IA signal is consistent with zero with power-law amplitudes fitted to the projected correlation functions for density-shape and shape-shape correlation components, Aδ+ = -0.0071 ± 0.1340 and A++ = -0.0505 ± 0.0848, respectively. These results are consistent with those obtained from blue galaxies at lower redshifts (e.g., A _{δ +}=0.0035_{-0.0389}^{+0.0387} and A_{++}=0.0045_{-0.0168}^{+0.0166} at z = 0.51 from the WiggleZ survey). The upper limit of the constrained IA amplitude corresponds to a few percent contamination to the weak-lensing shear power spectrum, resulting in systematic uncertainties on the cosmological parameter estimations by -0.052 < Δσ8 < 0.039 and -0.039 < ΔΩm < 0.030.

Planck 2015 results: XXI. The integrated Sachs-Wolfe effect

DOE PAGES

Ade, P. A. R.; Aghanim, N.; Arnaud, M.; ...

2016-09-20

Here, this paper presents a study of the integrated Sachs-Wolfe (ISW) effect from the Planck 2015 temperature and polarization data release. This secondary cosmic microwave background (CMB) anisotropy caused by the large-scale time-evolving gravitational potential is probed from different perspectives. The CMB is cross-correlated with different large-scale structure (LSS) tracers: radio sources from the NVSS catalogue; galaxies from the optical SDSS and the infrared WISE surveys; and the Planck 2015 convergence lensing map. The joint cross-correlation of the CMB with the tracers yields a detection at 4σ where most of the signal-to-noise is due to the Planck lensing and themore » NVSS radio catalogue. In fact, the ISW effect is detected from the Planck data only at ≈3σ (through the ISW-lensing bispectrum), which is similar to the detection level achieved by combining the cross-correlation signal coming from all the galaxy catalogues mentioned above. We study the ability of the ISW effect to place constraints on the dark-energy parameters; in particular, we show that Ω Λ is detected at more than 3σ. This cross-correlation analysis is performed only with the Planck temperature data, since the polarization scales available in the 2015 release do not permit significant improvement of the CMB-LSS cross-correlation detectability. Nevertheless, the Planck polarization data are used to study the anomalously large ISW signal previously reported through the aperture photometry on stacked CMB features at the locations of known superclusters and supervoids, which is in conflict with ΛCDM expectations. We find that the current Planck polarization data do not exclude that this signal could be caused by the ISW effect. In addition, the stacking of the Planck lensing map on the locations of superstructures exhibits a positive cross-correlation with these large-scale structures. Finally, we have improved our previous reconstruction of the ISW temperature fluctuations by combining the information encoded in all the previously mentioned LSS tracers. In particular, we construct a map of the ISW secondary anisotropies and the corresponding uncertainties map, obtained from simulations. Lastly, we also explore the reconstruction of the ISW anisotropies caused by the large-scale structure traced by the 2MASS Photometric Redshift Survey (2MPZ) by directly inverting the density field into the gravitational potential field.« less

Planck 2015 results. XXI. The integrated Sachs-Wolfe effect

NASA Astrophysics Data System (ADS)

Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Basak, S.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bock, J. J.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Bucher, M.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Casaponsa, B.; Catalano, A.; Challinor, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Fergusson, J.; Fernandez-Cobos, R.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Galeotta, S.; Galli, S.; Ganga, K.; Génova-Santos, R. T.; Giard, M.; Giraud-Héraud, Y.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Ilić, S.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lähteenmäki, A.; Lamarre, J.-M.; Langer, M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Lesgourgues, J.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Ma, Y.-Z.; Macías-Pérez, J. F.; Maggio, G.; Maino, D.; Mandolesi, N.; Mangilli, A.; Marcos-Caballero, A.; Maris, M.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Moss, A.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; Noviello, F.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Renzi, A.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Rossetti, M.; Roudier, G.; Rubiño-Martín, J. A.; Rusholme, B.; Sandri, M.; Santos, D.; Savelainen, M.; Savini, G.; Schaefer, B. M.; Scott, D.; Seiffert, M. D.; Shellard, E. P. S.; Spencer, L. D.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Tuovinen, J.; Valenziano, L.; Valiviita, J.; Van Tent, F.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

2016-09-01

This paper presents a study of the integrated Sachs-Wolfe (ISW) effect from the Planck 2015 temperature and polarization data release. This secondary cosmic microwave background (CMB) anisotropy caused by the large-scale time-evolving gravitational potential is probed from different perspectives. The CMB is cross-correlated with different large-scale structure (LSS) tracers: radio sources from the NVSS catalogue; galaxies from the optical SDSS and the infrared WISE surveys; and the Planck 2015 convergence lensing map. The joint cross-correlation of the CMB with the tracers yields a detection at 4σ where most of the signal-to-noise is due to the Planck lensing and the NVSS radio catalogue. In fact, the ISW effect is detected from the Planck data only at ≈3σ (through the ISW-lensing bispectrum), which is similar to the detection level achieved by combining the cross-correlation signal coming from all the galaxy catalogues mentioned above. We study the ability of the ISW effect to place constraints on the dark-energy parameters; in particular, we show that ΩΛ is detected at more than 3σ. This cross-correlation analysis is performed only with the Planck temperature data, since the polarization scales available in the 2015 release do not permit significant improvement of the CMB-LSS cross-correlation detectability. Nevertheless, the Planck polarization data are used to study the anomalously large ISW signal previously reported through the aperture photometry on stacked CMB features at the locations of known superclusters and supervoids, which is in conflict with ΛCDM expectations. We find that the current Planck polarization data do not exclude that this signal could be caused by the ISW effect. In addition, the stacking of the Planck lensing map on the locations of superstructures exhibits a positive cross-correlation with these large-scale structures. Finally, we have improved our previous reconstruction of the ISW temperature fluctuations by combining the information encoded in all the previously mentioned LSS tracers. In particular, we construct a map of the ISW secondary anisotropies and the corresponding uncertainties map, obtained from simulations. We also explore the reconstruction of the ISW anisotropies caused by the large-scale structure traced by the 2MASS Photometric Redshift Survey (2MPZ) by directly inverting the density field into the gravitational potential field.

Planck 2015 results: XXI. The integrated Sachs-Wolfe effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ade, P. A. R.; Aghanim, N.; Arnaud, M.

Here, this paper presents a study of the integrated Sachs-Wolfe (ISW) effect from the Planck 2015 temperature and polarization data release. This secondary cosmic microwave background (CMB) anisotropy caused by the large-scale time-evolving gravitational potential is probed from different perspectives. The CMB is cross-correlated with different large-scale structure (LSS) tracers: radio sources from the NVSS catalogue; galaxies from the optical SDSS and the infrared WISE surveys; and the Planck 2015 convergence lensing map. The joint cross-correlation of the CMB with the tracers yields a detection at 4σ where most of the signal-to-noise is due to the Planck lensing and themore » NVSS radio catalogue. In fact, the ISW effect is detected from the Planck data only at ≈3σ (through the ISW-lensing bispectrum), which is similar to the detection level achieved by combining the cross-correlation signal coming from all the galaxy catalogues mentioned above. We study the ability of the ISW effect to place constraints on the dark-energy parameters; in particular, we show that Ω Λ is detected at more than 3σ. This cross-correlation analysis is performed only with the Planck temperature data, since the polarization scales available in the 2015 release do not permit significant improvement of the CMB-LSS cross-correlation detectability. Nevertheless, the Planck polarization data are used to study the anomalously large ISW signal previously reported through the aperture photometry on stacked CMB features at the locations of known superclusters and supervoids, which is in conflict with ΛCDM expectations. We find that the current Planck polarization data do not exclude that this signal could be caused by the ISW effect. In addition, the stacking of the Planck lensing map on the locations of superstructures exhibits a positive cross-correlation with these large-scale structures. Finally, we have improved our previous reconstruction of the ISW temperature fluctuations by combining the information encoded in all the previously mentioned LSS tracers. In particular, we construct a map of the ISW secondary anisotropies and the corresponding uncertainties map, obtained from simulations. Lastly, we also explore the reconstruction of the ISW anisotropies caused by the large-scale structure traced by the 2MASS Photometric Redshift Survey (2MPZ) by directly inverting the density field into the gravitational potential field.« less

H-ATLAS/GAMA: magnification bias tomography. Astrophysical constraints above ∼1 arcmin

DOE Office of Scientific and Technical Information (OSTI.GOV)

González-Nuevo, J.; Bonavera, L.; Lapi, A.

An unambiguous manifestation of the magnification bias is the cross-correlation between two source samples with non-overlapping redshift distributions. In this work we measure and study the cross-correlation signal between a foreground sample of GAMA galaxies with spectroscopic redshifts in the range 0.2< z <0.8, and a background sample of H-ATLAS galaxies with photometric redshifts ∼>1.2. It constitutes a substantial improvement over the cross-correlation measurements made by Gonzalez-Nuevo et al. (2014) with updated catalogues and wider area (with S / N ∼> 5 below 10 arcmin and reaching S / N ∼ 20 below 30 arcsec). The better statistics allow usmore » to split the sample in different redshift bins and to perform a tomographic analysis (with S / N ∼> 3 below 10 arcmin and reaching S / N ∼ 15 below 30 arcsec). Moreover, we implement a halo model to extract astrophysical information about the background galaxies and the deflectors that are producing the lensing link between the foreground (lenses) and background (sources) samples. In the case of the sources, we find typical mass values in agreement with previous studies: a minimum halo mass to host a central galaxy, M {sub min}∼ 10{sup 12.26} M {sub ⊙}, and a pivot halo mass to have at least one sub-halo satellite, M {sub 1∼} 10{sup 12.84} M {sub ⊙}. However, the lenses are massive galaxies or even galaxy groups/clusters, with minimum mass of M {sub min}{sup lens}∼ 10{sup 13.06} M {sub ⊙}. Above a mass of M {sub 1}{sup lens}∼ 10{sup 14.57} M {sub ⊙} they contain at least one additional satellite galaxy which contributes to the lensing effect. The tomographic analysis shows that, while M {sub 1}{sup lens} is almost redshift independent, there is a clear evolution of increase M {sub min}{sup lens} with redshift in agreement with theoretical estimations. Finally, the halo modeling allows us to identify a strong lensing contribution to the cross-correlation for angular scales below 30 arcsec. This interpretation is supported by the results of basic but effective simulations.« less

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

NASA Astrophysics Data System (ADS)

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.

Mass Mapping Abell 2261 with Kinematic Weak Lensing: A Pilot Study for NASAs WFIRST mission

NASA Astrophysics Data System (ADS)

Eifler, Tim

2015-02-01

We propose to investigate a new method to extract cosmological information from weak gravitational lensing in the context of the mission design and requirements of NASAs Wide-Field Infrared Survey Telescope (WFIRST). In a recent paper (Huff, Krause, Eifler, George, Schlegel 2013) we describe a new method for reducing the shape noise in weak lensing measurements by an order of magnitude. Our method relies on spectroscopic measurements of disk galaxy rotation and makes use of the well-established Tully-Fisher (TF) relation in order to control for the intrinsic orientations of galaxy disks. Whereas shape noise is one of the major limitations for current weak lensing experiments it ceases to be an important source of statistical error in our new proposed technique. Specifically, we propose a pilot study that maps the projected mass distribution in the massive cluster Abell 2261 (z=0.225) to infer whether this promising technique faces systematics that prohibit its application to WFIRST. In addition to the cosmological weak lensing prospects, these measurements will also allow us to test kinematic lensing in the context of cluster mass reconstruction with a drastically improved signal-to-noise (S/N) per galaxy.

THE MASS-RICHNESS RELATION OF MaxBCG CLUSTERS FROM QUASAR LENSING MAGNIFICATION USING VARIABILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Anne H.; Baltay, Charles; Ellman, Nancy

2012-04-10

Accurate measurement of galaxy cluster masses is an essential component not only in studies of cluster physics but also for probes of cosmology. However, different mass measurement techniques frequently yield discrepant results. The Sloan Digital Sky Survey MaxBCG catalog's mass-richness relation has previously been constrained using weak lensing shear, Sunyaev-Zeldovich (SZ), and X-ray measurements. The mass normalization of the clusters as measured by weak lensing shear is {approx}>25% higher than that measured using SZ and X-ray methods, a difference much larger than the stated measurement errors in the analyses. We constrain the mass-richness relation of the MaxBCG galaxy cluster catalogmore » by measuring the gravitational lensing magnification of type I quasars in the background of the clusters. The magnification is determined using the quasars' variability and the correlation between quasars' variability amplitude and intrinsic luminosity. The mass-richness relation determined through magnification is in agreement with that measured using shear, confirming that the lensing strength of the clusters implies a high mass normalization and that the discrepancy with other methods is not due to a shear-related systematic measurement error. We study the dependence of the measured mass normalization on the cluster halo orientation. As expected, line-of-sight clusters yield a higher normalization; however, this minority of haloes does not significantly bias the average mass-richness relation of the catalog.« less

Cosmology from large-scale galaxy clustering and galaxy–galaxy lensing with Dark Energy Survey Science Verification data

DOE PAGES

Kwan, J.; Sánchez, C.; Clampitt, J.; ...

2016-10-05

We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe asmore » $$\\Omega_m = 0.31 \\pm 0.09$$ and the clustering amplitude of the matter power spectrum as $$\\sigma_8 = 0.74 +\\pm 0.13$$ after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into $$S_8$$ = $$\\sigma_8(\\Omega_m/0.3)^{0.16} = 0.74 \\pm 0.12$$ for our fiducial lens redshift bin at 0.35 < z < 0.5, while $$S_8 = 0.78 \\pm 0.09$$ using two bins over the range 0.2 < z < 0.5. We study the robustness of the results under changes in the data vectors, modelling and systematics treatment, including photometric redshift and shear calibration uncertainties, and find consistency in the derived cosmological parameters. We show that our results are consistent with previous cosmological analyses from DES and other data sets and conclude with a joint analysis of DES angular clustering and galaxy-galaxy lensing with Planck CMB data, Baryon Accoustic Oscillations and Supernova type Ia measurements.« less

Cosmology from large-scale galaxy clustering and galaxy–galaxy lensing with Dark Energy Survey Science Verification data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwan, J.; Sánchez, C.; Clampitt, J.

We present cosmological constraints from the Dark Energy Survey (DES) using a combined analysis of angular clustering of red galaxies and their cross-correlation with weak gravitational lensing of background galaxies. We use a 139 square degree contiguous patch of DES data from the Science Verification (SV) period of observations. Using large scale measurements, we constrain the matter density of the Universe asmore » $$\\Omega_m = 0.31 \\pm 0.09$$ and the clustering amplitude of the matter power spectrum as $$\\sigma_8 = 0.74 +\\pm 0.13$$ after marginalizing over seven nuisance parameters and three additional cosmological parameters. This translates into $$S_8$$ = $$\\sigma_8(\\Omega_m/0.3)^{0.16} = 0.74 \\pm 0.12$$ for our fiducial lens redshift bin at 0.35 < z < 0.5, while $$S_8 = 0.78 \\pm 0.09$$ using two bins over the range 0.2 < z < 0.5. We study the robustness of the results under changes in the data vectors, modelling and systematics treatment, including photometric redshift and shear calibration uncertainties, and find consistency in the derived cosmological parameters. We show that our results are consistent with previous cosmological analyses from DES and other data sets and conclude with a joint analysis of DES angular clustering and galaxy-galaxy lensing with Planck CMB data, Baryon Accoustic Oscillations and Supernova type Ia measurements.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hearin, Andrew P.; Zentner, Andrew R., E-mail: aph15@pitt.edu, E-mail: zentner@pitt.edu

Forthcoming projects such as the Dark Energy Survey, Joint Dark Energy Mission, and the Large Synoptic Survey Telescope, aim to measure weak lensing shear correlations with unprecedented accuracy. Weak lensing observables are sensitive to both the distance-redshift relation and the growth of structure in the Universe. If the cause of accelerated cosmic expansion is dark energy within general relativity, both cosmic distances and structure growth are governed by the properties of dark energy. Consequently, one may use lensing to check for this consistency and test general relativity. After reviewing the phenomenology of such tests, we address a major challenge tomore » such a program. The evolution of the baryonic component of the Universe is highly uncertain and can influence lensing observables, manifesting as modified structure growth for a fixed cosmic distance scale. Using two proposed methods, we show that one could be led to reject the null hypothesis of general relativity when it is the true theory if this uncertainty in baryonic processes is neglected. Recent simulations suggest that we can correct for baryonic effects using a parameterized model in which the halo mass-concentration relation is modified. The correction suffices to render biases small compared to statistical uncertainties. We study the ability of future weak lensing surveys to constrain the internal structures of halos and test the null hypothesis of general relativity simultaneously. Compared to alternative methods which null information from small-scales to mitigate sensitivity to baryonic physics, this internal calibration program should provide limits on deviations from general relativity that are several times more constraining. Specifically, we find that limits on general relativity in the case of internal calibration are degraded by only {approx} 30% or less compared to the case of perfect knowledge of nonlinear structure.« less

Weak Gravitational Lensing of Finite Beams.

PubMed

Fleury, Pierre; Larena, Julien; Uzan, Jean-Philippe

2017-11-10

The standard theory of weak gravitational lensing relies on the infinitesimal light beam approximation. In this context, images are distorted by convergence and shear, the respective sources of which unphysically depend on the resolution of the distribution of matter-the so-called Ricci-Weyl problem. In this Letter, we propose a strong-lensing-inspired formalism to describe the lensing of finite beams. We address the Ricci-Weyl problem by showing explicitly that convergence is caused by the matter enclosed by the beam, regardless of its distribution. Furthermore, shear turns out to be systematically enhanced by the finiteness of the beam. This implies, in particular, that the Kaiser-Squires relation between shear and convergence is violated, which could have profound consequences on the interpretation of weak-lensing surveys.

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

NASA Astrophysics Data System (ADS)

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.

Calibration of colour gradient bias in shear measurement using HST/CANDELS data

NASA Astrophysics Data System (ADS)

Er, X.; Hoekstra, H.; Schrabback, T.; Cardone, V. F.; Scaramella, R.; Maoli, R.; Vicinanza, M.; Gillis, B.; Rhodes, J.

2018-06-01

Accurate shape measurements are essential to infer cosmological parameters from large area weak gravitational lensing studies. The compact diffraction-limited point spread function (PSF) in space-based observations is greatly beneficial, but its chromaticity for a broad-band observation can lead to new subtle effects that could hitherto be ignored: the PSF of a galaxy is no longer uniquely defined and spatial variations in the colours of galaxies result in biases in the inferred lensing signal. Taking Euclid as a reference, we show that this colour gradient bias (CG bias) can be quantified with high accuracy using available multicolour Hubble Space Telescope (HST) data. In particular we study how noise in the HST observations might impact such measurements and find this to be negligible. We determine the CG bias using HST observations in the F606W and F814W filters and observe a correlation with the colour, in line with expectations, whereas the dependence with redshift is weak. The biases for individual galaxies are generally well below 1 per cent, which may be reduced further using morphological information from the Euclid data. Our results demonstrate that CG bias should not be ignored, but it is possible to determine its amplitude with sufficient precision, so that it will not significantly bias the weak lensing measurements using Euclid data.

Weak-Lensing Mass Calibration of the Atacama Cosmology Telescope Equatorial Sunyaev-Zeldovich Cluster Sample with the Canada-France-Hawaii Telescope Stripe 82 Survey

NASA Technical Reports Server (NTRS)

Battaglia, N.; Leauthaud, A.; Miyatake, H.; Hasseleld, M.; Gralla, M. B.; Allison, R.; Bond, J. R.; Calabrese, E.; Crichton, D.; Devlin, M. J.;

Weak-lensing mass calibration of the Atacama Cosmology Telescope equatorial Sunyaev-Zeldovich cluster sample with the Canada-France-Hawaii telescope stripe 82 survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Battaglia, N.; Miyatake, H.; Hasselfield, M.

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) ×10{sup 14} M{sub ⊙}, consistent with the tSZ mass estimate of (4.70±1.0) ×10{sup 14} M{sub ⊙} which assumes a universal pressure profile for the cluster gas. Our results are consistentmore » 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.« less

Precision cosmology with weak gravitational lensing

NASA Astrophysics Data System (ADS)

Hearin, Andrew P.

In recent years, cosmological science has developed a highly predictive model for the universe on large scales that is in quantitative agreement with a wide range of astronomical observations. While the number and diversity of successes of this model provide great confidence that our general picture of cosmology is correct, numerous puzzles remain. In this dissertation, I analyze the potential of planned and near future galaxy surveys to provide new understanding of several unanswered questions in cosmology, and address some of the leading challenges to this observational program. In particular, I study an emerging technique called cosmic shear, the weak gravitational lensing produced by large scale structure. I focus on developing strategies to optimally use the cosmic shear signal observed in galaxy imaging surveys to uncover the physics of dark energy and the early universe. In chapter 1 I give an overview of a few unsolved mysteries in cosmology and I motivate weak lensing as a cosmological probe. I discuss the use of weak lensing as a test of general relativity in chapter 2 and assess the threat to such tests presented by our uncertainty in the physics of galaxy formation. Interpreting the cosmic shear signal requires knowledge of the redshift distribution of the lensed galaxies. This redshift distribution will be significantly uncertain since it must be determined photometrically. In chapter 3 I investigate the influence of photometric redshift errors on our ability to constrain dark energy models with weak lensing. The ability to study dark energy with cosmic shear is also limited by the imprecision in our understanding of the physics of gravitational collapse. In chapter 4 I present the stringent calibration requirements on this source of uncertainty. I study the potential of weak lensing to resolve a debate over a long-standing anomaly in CMB measurements in chapter 5. Finally, in chapter 6 I summarize my findings and conclude with a brief discussion of my outlook on the future of weak lensing studies of cosmology.

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

NASA Astrophysics Data System (ADS)

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 .

Monster Clusters in the Young Universe? Weak-lensing Masses of SPT-CL J0205-5829 and MOO1014+0038 with HST Observations

NASA Astrophysics Data System (ADS)

Feilx Kim, Seojin; Jee, Myungkook James

2018-01-01

Measuring High-z clusters’ masses is very important as the cluster abundance is extremely sensitive to the cosmological parameters. However, deriving their masses from the intracluster medium properties (i.e., Sunyaev-Zel’dovich or X-ray observations) is not the best method because of their departure from the hydrostatic equilibrium. Fortunately, the “See Change” Hubble Space Telescope program offers a rare opportunity to measure them using weak gravitational lensing. We study SPT-CL J0205-5829 (z=1.322) and MOO1014+0038 (z=1.24) discovered in the SPT-SZ and MaDCoW Surveys, respectively. Previous non-lensing based approaches suggest that both targets might be extremely massive clusters. After carefully addressing various possible systematics from the Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) images, we successfully detect clear weak lensing signals. We present their 2-dimensional mass maps and compare our weak-lensing masses with previous ICM-based results.

Modeling CMB lensing cross correlations with CLEFT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Modi, Chirag; White, Martin; Vlah, Zvonimir, E-mail: modichirag@berkeley.edu, E-mail: mwhite@berkeley.edu, E-mail: zvlah@stanford.edu

2017-08-01

A new generation of surveys will soon map large fractions of sky to ever greater depths and their science goals can be enhanced by exploiting cross correlations between them. In this paper we study cross correlations between the lensing of the CMB and biased tracers of large-scale structure at high z . We motivate the need for more sophisticated bias models for modeling increasingly biased tracers at these redshifts and propose the use of perturbation theories, specifically Convolution Lagrangian Effective Field Theory (CLEFT). Since such signals reside at large scales and redshifts, they can be well described by perturbative approaches.more » We compare our model with the current approach of using scale independent bias coupled with fitting functions for non-linear matter power spectra, showing that the latter will not be sufficient for upcoming surveys. We illustrate our ideas by estimating σ{sub 8} from the auto- and cross-spectra of mock surveys, finding that CLEFT returns accurate and unbiased results at high z . We discuss uncertainties due to the redshift distribution of the tracers, and several avenues for future development.« less

Searching for massive clusters in weak lensing surveys

NASA Astrophysics Data System (ADS)

Hamana, Takashi; Takada, Masahiro; Yoshida, Naoki

2004-05-01

We explore the ability of weak lensing surveys to locate massive clusters. We use both analytic models of dark matter haloes and mock weak lensing surveys generated from a large cosmological N-body simulation. The analytic models describe the average properties of weak lensing haloes and predict the number counts, enabling us to compute an effective survey selection function. We argue that the detectability of massive haloes depends not only on the halo mass but also strongly on the redshift where the halo is located. We test the model prediction for the peak number counts in weak lensing mass maps against mock numerical data, and find that the noise resulting from intrinsic galaxy ellipticities causes a systematic effect which increases the peak counts. We develop a correction scheme for the systematic effect in an empirical manner, and show that, after correction, the model prediction agrees well with the mock data. The mock data is also used to examine the completeness and efficiency of the weak lensing halo search by fully taking into account the noise and the projection effect by large-scale structures. We show that the detection threshold of S/N = 4 ~ 5 gives an optimal balance between completeness and efficiency. Our results suggest that, for a weak lensing survey with a galaxy number density of ng= 30 arcmin-2 with a mean redshift of z= 1, the mean number of haloes which are expected to cause lensing signals above S/N = 4 is Nhalo(S/N > 4) = 37 per 10 deg2, whereas 23 of the haloes are actually detected with S/N > 4, giving the effective completeness as good as 63 per cent. Alternatively, the mean number of peaks in the same area is Npeak= 62 for a detection threshold of S/N = 4. Among the 62 peaks, 23 are caused by haloes with the expected peak height S/N > 4, 13 result from haloes with 3 < S/N < 4 and the remaining 26 peaks are either the false peaks caused by the noise or haloes with a lower expected peak height. Therefore the contamination rate is 44 per cent (this could be an overestimation). Weak lensing surveys thus provide a reasonably efficient way to search for massive clusters.

The Effects of Physically Unrelated Near Neighbors on the Weak Galaxy-Galaxy Lensing Signal

NASA Astrophysics Data System (ADS)

Brainerd, Tereasa

2018-01-01

The effects of physically unrelated near neighbors on the weak galaxy-galaxy lensing signal are explored. Physically unrelated near neighbors are galaxies that are close to a given lens galaxy in projection on the sky, but are located at substantially different redshifts. Typically, the effects of such physically unrelated near neighbors are assumed to cancel. If that were truly the case, these objects would not contribute to the mean tangential shear around the lenses and they can be ignored when using an observed weak lensing signal to infer the excess surface mass density surrounding a set of lens galaxies. Here, observed galaxies with known redshifts and luminosities are used as the basis of a suite of Monte Carlo simluations of weak galaxy-galaxy lensing. The simulations incorporate the intrinsic clustering of the lens galaxies, as well as the intrinsic distribution of the lens galaxy masses. Dark matter halos of appropriate sizes and masses are assigned to each of the lens galaxies, and the net effect of all lenses on a set of background source galaxies is determined. The net weak lensing signal (i.e., the mean tangential shear due to all lenses along the line of sight) is computed and then compared to the excess surface mass density surrounding the lenses. Due to the broad redshift and mass distributions of the lenses, the effects of physically unrelated near neighbors in the simulations do not cancel. On scales equal to or greater than the scale for which the two-halo term contributes substantially to the shear, this non-cancellation of the effects of physically unrelated near neighbors significantly affects the accuracy with which the excess surface mass density may be inferred from the mean tangential shear via the standard formula: < ΔΣ > = < Σc γt > . The effects of physically unrelated near neighbors are greatest for the least massive lens galaxies but can also be important for the most massive lens galaxies.

On mass concentrations and magnitude gaps of galaxy systems in the CS82 survey

NASA Astrophysics Data System (ADS)

Vitorelli, André Z.; Cypriano, Eduardo S.; Makler, Martín; Pereira, Maria E. S.; Erben, Thomas; Moraes, Bruno

2018-02-01

Galaxy systems with large magnitude gaps - defined as the difference in magnitude between the central galaxy and the brightest satellite in the central region, such as fossil groups - are claimed to have earlier formation times. In this study, we measure the mass concentration, as an indicator of the formation epoch, of ensembles of galaxy systems divided by redshift and magnitude gaps in the r band. We use cross-correlation weak-lensing measurements with NFW parametric mass profiles to measure masses and concentrations of these ensembles from a catalogue of systems built from the SDSS Coadd by the redMaPPer algorithm. The lensing shear data come from the CFHT Stripe 82 (CS82) survey, and consists of i-band images of the SDSS Stripe 82 region. We find that the stack made up of systems with larger magnitude gaps has a high probability of being more concentrated, in the lowest redshift slice (0.2 < z < 0.4), both when dividing in quartiles (P = 0.98) and tertiles (P = 0.85). These results lend credibility to the claim that systems with large magnitude gaps tend to have been formed early.

Weak lensing by galaxy troughs in DES Science Verification data

DOE PAGES

Gruen, D.; Friedrich, O.; Amara, A.; ...

2015-11-29

In this study, 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 ofmore » the matter density with Poissonian noise, we find agreement of our measurements with predictions in a fiducial Λ cold dark matter 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 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. 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.« less

Direct Shear Mapping: Prospects for Weak Lensing Studies of Individual Galaxy-Galaxy Lensing Systems

NASA Astrophysics Data System (ADS)

de Burgh-Day, C. O.; Taylor, E. N.; Webster, R. L.; Hopkins, A. M.

2015-11-01

Using both a theoretical and an empirical approach, we have investigated the frequency of low redshift galaxy-galaxy lensing systems in which the signature of 3D weak lensing might be directly detectable. We find good agreement between these two approaches. Using data from the Galaxy and Mass Assembly redshift survey we estimate the frequency of detectable weak lensing at low redshift. We find that below a redshift of z ~ 0.6, the probability of a galaxy being weakly lensed by γ ⩾ 0.02 is ~ 0.01. We have also investigated the feasibility of measuring the scatter in the M * - Mh relation using shear statistics. We estimate that for a shear measurement error of Δγ = 0.02 (consistent with the sensitivity of the Direct Shear Mapping technique), with a sample of ~50,000 spatially and spectrally resolved galaxies, the scatter in the M * - Mh relation could be measured. While there are currently no existing IFU surveys of this size, there are upcoming surveys that will provide this data (e.g The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX), surveys with Hector, and the Square Kilometre Array (SKA)).

How the cosmic web induces intrinsic alignments of galaxies

NASA Astrophysics Data System (ADS)

Codis, S.; Dubois, Y.; Pichon, C.; Devriendt, J.; Slyz, A.

2016-10-01

Intrinsic alignments are believed to be a major source of systematics for future generation of weak gravitational lensing surveys like Euclid or LSST. Direct measurements of the alignment of the projected light distribution of galaxies in wide field imaging data seem to agree on a contamination at a level of a few per cent of the shear correlation functions, although the amplitude of the effect depends on the population of galaxies considered. Given this dependency, it is difficult to use dark matter-only simulations as the sole resource to predict and control intrinsic alignments. We report here estimates on the level of intrinsic alignment in the cosmological hydrodynamical simulation Horizon-AGN that could be a major source of systematic errors in weak gravitational lensing measurements. In particular, assuming that the spin of galaxies is a good proxy for their ellipticity, we show how those spins are spatially correlated and how they couple to the tidal field in which they are embedded. We will also present theoretical calculations that illustrate and qualitatively explain the observed signals.

Dark Energy Survey Year 1 results: cross-correlation redshifts - methods and systematics characterization

NASA Astrophysics Data System (ADS)

Gatti, M.; Vielzeuf, P.; Davis, C.; Cawthon, R.; Rau, M. M.; DeRose, J.; De Vicente, J.; Alarcon, A.; Rozo, E.; Gaztanaga, E.; Hoyle, B.; Miquel, R.; Bernstein, G. M.; Bonnett, C.; Carnero Rosell, A.; Castander, F. J.; Chang, C.; da Costa, L. N.; Gruen, D.; Gschwend, J.; Hartley, W. G.; Lin, H.; MacCrann, N.; Maia, M. A. G.; Ogando, R. L. C.; Roodman, A.; Sevilla-Noarbe, I.; Troxel, M. A.; Wechsler, R. H.; Asorey, J.; Davis, T. M.; Glazebrook, K.; Hinton, S. R.; Lewis, G.; Lidman, C.; Macaulay, E.; Möller, A.; O'Neill, C. R.; Sommer, N. E.; Uddin, S. A.; Yuan, F.; Zhang, B.; Abbott, T. M. C.; Allam, S.; Annis, J.; Bechtol, K.; Brooks, D.; Burke, D. L.; Carollo, D.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; D'Andrea, C. B.; DePoy, D. L.; Desai, S.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gerdes, D. W.; Goldstein, D. A.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; Hoormann, J. K.; Jain, B.; James, D. J.; Jarvis, M.; Jeltema, T.; Johnson, M. W. G.; Johnson, M. D.; Krause, E.; Kuehn, K.; Kuhlmann, S.; Kuropatkin, N.; Li, T. S.; Lima, M.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Nichol, R. C.; Nord, B.; Plazas, A. A.; Reil, K.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sheldon, E.; Smith, M.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, B. E.; Tucker, D. L.; Vikram, V.; Walker, A. R.; Weller, J.; Wester, W.; Wolf, R. C.

2018-06-01

We use numerical simulations to characterize the performance of a clustering-based method to calibrate photometric redshift biases. In particular, we cross-correlate the weak lensing source galaxies from the Dark Energy Survey Year 1 sample with redMaGiC galaxies (luminous red galaxies with secure photometric redshifts) to estimate the redshift distribution of the former sample. The recovered redshift distributions are used to calibrate the photometric redshift bias of standard photo-z methods applied to the same source galaxy sample. We apply the method to two photo-z codes run in our simulated data: Bayesian Photometric Redshift and Directional Neighbourhood Fitting. We characterize the systematic uncertainties of our calibration procedure, and find that these systematic uncertainties dominate our error budget. The dominant systematics are due to our assumption of unevolving bias and clustering across each redshift bin, and to differences between the shapes of the redshift distributions derived by clustering versus photo-zs. The systematic uncertainty in the mean redshift bias of the source galaxy sample is Δz ≲ 0.02, though the precise value depends on the redshift bin under consideration. We discuss possible ways to mitigate the impact of our dominant systematics in future analyses.

AzTEC Millimetre Survey of the COSMOS field - II. Source count overdensity and correlations with large-scale structure

NASA Astrophysics Data System (ADS)

Austermann, J. E.; Aretxaga, I.; Hughes, D. H.; Kang, Y.; Kim, S.; Lowenthal, J. D.; Perera, T. A.; Sanders, D. B.; Scott, K. S.; Scoville, N.; Wilson, G. W.; Yun, M. S.

2009-03-01

We report an overdensity of bright submillimetre galaxies (SMGs) in the 0.15 deg2 AzTEC/COSMOS survey and a spatial correlation between the SMGs and the optical-IR galaxy density at z <~ 1.1. This portion of the COSMOS field shows a ~3σ overdensity of robust SMG detections when compared to a background, or `blank-field', population model that is consistent with SMG surveys of fields with no extragalactic bias. The SMG overdensity is most significant in the number of very bright detections (14 sources with measured fluxes S1.1mm > 6 mJy), which is entirely incompatible with sample variance within our adopted blank-field number densities and infers an overdensity significance of >> 4σ. We find that the overdensity and spatial correlation to optical-IR galaxy density are most consistent with lensing of a background SMG population by foreground mass structures along the line of sight, rather than physical association of the SMGs with the z <~ 1.1 galaxies/clusters. The SMG positions are only weakly correlated with weak-lensing maps, suggesting that the dominant sources of correlation are individual galaxies and the more tenuous structures in the survey region, and not the massive and compact clusters. These results highlight the important roles cosmic variance and large-scale structure can play in the study of SMGs.

Cosmology with weak lensing surveys.

PubMed

Munshi, Dipak; Valageas, Patrick

2005-12-15

Weak gravitational lensing is responsible for the shearing and magnification of the images of high-redshift sources due to the presence of intervening mass. Since the lensing effects arise from deflections of the light rays due to fluctuations of the gravitational potential, they can be directly related to the underlying density field of the large-scale structures. Weak gravitational surveys are complementary to both galaxy surveys and cosmic microwave background observations as they probe unbiased nonlinear matter power spectra at medium redshift. Ongoing CMBR experiments such as WMAP and a future Planck satellite mission will measure the standard cosmological parameters with unprecedented accuracy. The focus of attention will then shift to understanding the nature of dark matter and vacuum energy: several recent studies suggest that lensing is the best method for constraining the dark energy equation of state. During the next 5 year period, ongoing and future weak lensing surveys such as the Joint Dark Energy Mission (JDEM; e.g. SNAP) or the Large-aperture Synoptic Survey Telescope will play a major role in advancing our understanding of the universe in this direction. In this review article, we describe various aspects of probing the matter power spectrum and the bi-spectrum and other related statistics with weak lensing surveys. This can be used to probe the background dynamics of the universe as well as the nature of dark matter and dark energy.

Effect of Masked Regions on Weak-lensing Statistics

NASA Astrophysics Data System (ADS)

Shirasaki, Masato; Yoshida, Naoki; Hamana, Takashi

2013-09-01

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 cosmological ray-tracing simulations to examine in detail the impact of masked regions on the weak-lensing Minkowski Functionals (MFs). We consider actual sky masks used for a Subaru Suprime-Cam imaging survey. The masks increase the variance of the convergence field and the expected values of the MFs are biased. The bias then compromises the non-Gaussian signals induced by the gravitational growth of structure. We then explore how masks affect cosmological parameter estimation. We calculate the cumulative signal-to-noise ratio (S/N) for masked maps to study the information content of lensing MFs. We show that the degradation of S/N for masked maps is mainly determined by the effective survey area. We also perform simple χ2 analysis to show the impact of lensing MF bias due to masked regions. Finally, we compare ray-tracing simulations with data from a Subaru 2 deg2 survey in order to address if the observed lensing MFs are consistent with those of the standard cosmology. The resulting χ2/n dof = 29.6/30 for three combined MFs, obtained with the mask effects taken into account, suggests that the observational data are indeed consistent with the standard ΛCDM model. We conclude that the lensing MFs are a powerful probe of cosmology only if mask effects are correctly taken into account.

Weak lensing of the Lyman α forest

NASA Astrophysics Data System (ADS)

Croft, Rupert A. C.; Romeo, Alessandro; Metcalf, R. Benton

2018-06-01

The angular positions of quasars are deflected by the gravitational lensing effect of foreground matter. The Lyman α (Lyα) forest seen in the spectra of these quasars is therefore also lensed. We propose that the signature of weak gravitational lensing of the Lyα forest could be measured using similar techniques that have been applied to the lensed cosmic microwave background (CMB), and which have also been proposed for application to spectral data from 21-cm radio telescopes. As with 21-cm data, the forest has the advantage of spectral information, potentially yielding many lensed `slices' at different redshifts. We perform an illustrative idealized test, generating a high-resolution angular grid of quasars (of order arcminute separation), and lensing the Lyα forest spectra at redshifts z = 2-3 using a foreground density field. We find that standard quadratic estimators can be used to reconstruct images of the foreground mass distribution at z ˜ 1. There currently exists a wealth of Lyα forest data from quasar and galaxy spectral surveys, with smaller sightline separations expected in the future. Lyα forest lensing is sensitive to the foreground mass distribution at redshifts intermediate between CMB lensing and galaxy shear, and avoids the difficulties of shape measurement associated with the latter. With further refinement and application of mass reconstruction techniques, weak gravitational lensing of the high-redshift Lyα forest may become a useful new cosmological probe.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, C.; Pujol, A.; Gaztañaga, E.

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 deg 2 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 inmore » 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. Moreover, 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.« less

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

DOE PAGES

Chang, C.; Pujol, A.; Gaztañaga, E.; ...

2016-04-15

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 deg 2 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 inmore » 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. Moreover, 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.« less

CFHTLenS and RCSLenS: testing photometric redshift distributions using angular cross-correlations with spectroscopic galaxy surveys

NASA Astrophysics Data System (ADS)

Choi, A.; Heymans, C.; Blake, C.; Hildebrandt, H.; Duncan, C. A. J.; Erben, T.; Nakajima, R.; Van Waerbeke, L.; Viola, M.

2016-12-01

We determine the accuracy of galaxy redshift distributions as estimated from photometric redshift probability distributions p(z). Our method utilizes measurements of the angular cross-correlation between photometric galaxies and an overlapping sample of galaxies with spectroscopic redshifts. We describe the redshift leakage from a galaxy photometric redshift bin j into a spectroscopic redshift bin I using the sum of the p(z) for the galaxies residing in bin j. We can then predict the angular cross-correlation between photometric and spectroscopic galaxies due to intrinsic galaxy clustering when I ≠ j as a function of the measured angular cross-correlation when I = j. We also account for enhanced clustering arising from lensing magnification using a halo model. The comparison of this prediction with the measured signal provides a consistency check on the validity of using the summed p(z) to determine galaxy redshift distributions in cosmological analyses, as advocated by the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). We present an analysis of the photometric redshifts measured by CFHTLenS, which overlaps the Baryon Oscillation Spectroscopic Survey (BOSS). We also analyse the Red-sequence Cluster Lensing Survey, which overlaps both BOSS and the WiggleZ Dark Energy Survey. We find that the summed p(z) from both surveys are generally biased with respect to the true underlying distributions. If unaccounted for, this bias would lead to errors in cosmological parameter estimation from CFHTLenS by less than ˜4 per cent. For photometric redshift bins which spatially overlap in 3D with our spectroscopic sample, we determine redshift bias corrections which can be used in future cosmological analyses that rely on accurate galaxy redshift distributions.

Weighing the Giants - I. Weak-lensing masses for 51 massive galaxy clusters: project overview, data analysis methods and cluster images

NASA Astrophysics Data System (ADS)

von der Linden, Anja; Allen, Mark T.; 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

2014-03-01

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 ≲ zCl ≲ 0.7, in order to calibrate X-ray and other mass proxies for cosmological cluster experiments. The primary aim is to improve the absolute mass calibration of cluster observables, currently the dominant systematic uncertainty for cluster count experiments. Key elements of this work are the rigorous quantification of systematic uncertainties, high-quality data reduction and photometric calibration, and the `blind' nature of the analysis to avoid confirmation bias. Our target clusters are drawn from X-ray catalogues based on the ROSAT All-Sky Survey, and provide a versatile calibration sample for many aspects of cluster cosmology. We have acquired wide-field, high-quality imaging using the Subaru Telescope and Canada-France-Hawaii Telescope for all 51 clusters, in at least three bands per cluster. For a subset of 27 clusters, we have data in at least five bands, allowing accurate photometric redshift estimates of lensed galaxies. In this paper, we describe the cluster sample and observations, and detail the processing of the SuprimeCam data to yield high-quality images suitable for robust weak-lensing shape measurements and precision photometry. For each cluster, we present wide-field three-colour optical images and maps of the weak-lensing mass distribution, the optical light distribution and the X-ray emission. These provide insights into the large-scale structure in which the clusters are embedded. We measure the offsets between X-ray flux centroids and the brightest cluster galaxies in the clusters, finding these to be small in general, with a median of 20 kpc. For offsets ≲100 kpc, weak-lensing mass measurements centred on the brightest cluster galaxies agree well with values determined relative to the X-ray centroids; miscentring is therefore not a significant source of systematic uncertainty for our weak-lensing mass measurements. In accompanying papers, we discuss the key aspects of our photometric calibration and photometric redshift measurements (Kelly et al.), and measure cluster masses using two methods, including a novel Bayesian weak-lensing approach that makes full use of the photometric redshift probability distributions for individual background galaxies (Applegate et al.). In subsequent papers, we will incorporate these weak-lensing mass measurements into a self-consistent framework to simultaneously determine cluster scaling relations and cosmological parameters.

Statistics of Dark Matter Halos from Gravitational Lensing.

PubMed

Jain; Van Waerbeke L

2000-02-10

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Yan -Chuan; Bernstein, Gary

Redshift space distortion (RSD) is a powerful way of measuring the growth of structure and testing General Relativity, but it is limited by cosmic variance and the degeneracy between galaxy bias b and the growth rate factor f. The cross-correlation of lensing shear with the galaxy density field can in principle measure b in a manner free from cosmic variance limits, breaking the f-b degeneracy and allowing inference of the matter power spectrum from the galaxy survey. We analyze the growth constraints from a realistic tomographic weak lensing photo-z survey combined with a spectroscopic galaxy redshift survey over the samemore » sky area. For sky coverage f sky = 0.5, analysis of the transverse modes measures b to 2-3% accuracy per Δz = 0.1 bin at z < 1 when ~10 galaxies arcmin –2 are measured in the lensing survey and all halos with M > M min = 10 13h –1M ⊙ have spectra. For the gravitational growth parameter parameter γ (f = Ω γ m), combining the lensing information with RSD analysis of non-transverse modes yields accuracy σ(γ) ≈ 0.01. Adding lensing information to the RSD survey improves \\sigma(\\gamma) by an amount equivalent to a 3x (10x) increase in RSD survey area when the spectroscopic survey extends down to halo mass 10 13.5 (10 14) h –1 M ⊙. We also find that the σ(γ) of overlapping surveys is equivalent to that of surveys 1.5-2 times larger if they are separated on the sky. This gain is greatest when the spectroscopic mass threshold is 10 13 -10 14 h –1 M ⊙, similar to LRG surveys. The gain of overlapping surveys is reduced for very deep or very shallow spectroscopic surveys, but any practical surveys are more powerful when overlapped than when separated. As a result, the gain of overlapped surveys is larger in the case when the primordial power spectrum normalization is uncertain by > 0.5%.« less

Weak Gravitational Lensing

NASA Astrophysics Data System (ADS)

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

2012-03-01

This chapter reviews the data mining methods recently developed to solve standard data problems in weak gravitational lensing. We detail the different steps of the weak lensing data analysis along with the different techniques dedicated to these applications. An overview of the different techniques currently used will be given along with future prospects. Until about 30 years ago, astronomers thought that the Universe was composed almost entirely of ordinary matter: protons, neutrons, electrons, and atoms. The field of weak lensing has been motivated by the observations made in the last decades showing that visible matter represents only about 4-5% of the Universe (see Figure 14.1). Currently, the majority of the Universe is thought to be dark, that is, does not emit electromagnetic radiation. The Universe is thought to be mostly composed of an invisible, pressure less matter - potentially relic from higher energy theories - called "dark matter" (20-21%) and by an even more mysterious term, described in Einstein equations as a vacuum energy density, called "dark energy" (70%). This "dark" Universe is not well described or even understood; its presence is inferred indirectly from its gravitational effects, both on the motions of astronomical objects and on light propagation. So this point could be the next breakthrough in cosmology. Today's cosmology is based on a cosmological model that contains various parameters that need to be determined precisely, such as the matter density parameter Omega_m or the dark energy density parameter Omega_lambda. Weak gravitational lensing is believed to be the most promising tool to understand the nature of dark matter and to constrain the cosmological parameters used to describe the Universe because it provides a method to directly map the distribution of dark matter (see [1,6,60,63,70]). From this dark matter distribution, the nature of dark matter can be better understood and better constraints can be placed on dark energy, which affects the evolution of structures. Gravitational lensing is the process by which light from distant galaxies is bent by the gravity of intervening mass in the Universe as it travels toward us. This bending causes the images of background galaxies to appear slightly distorted, and can be used to extract important cosmological information. In the beginning of the twentieth century, A. Einstein predicted that massive bodies could be seen as gravitational lenses that bend the path of light rays by creating a local curvature in space time. One of the first confirmations of Einstein's new theory was the observation during the 1919 solar eclipse of the deflection of light from distant stars by the sun. Since then, a wide range of lensing phenomena have been detected. The gravitational deflection of light by mass concentrations along light paths produces magnification, multiplication, and distortion of images. These lensing effects are illustrated by Figure 14.2, which shows one of the strongest lenses observed: Abell 2218, a very massive and distant cluster of galaxies in the constellation Draco. The observed gravitational arcs are actually the magnified and strongly distorted images of galaxies that are about 10 times more distant than the cluster itself. These strong gravitational lensing effects are very impressive but they are very rare. Far more prevalent are weak gravitational lensing effects, which we consider in this chapter, and in which the induced distortion in galaxy images is much weaker. These gravitational lensing effects are now widely used, but the amplitude of the weak lensing signal is so weak that its detection relies on the accuracy of the techniques used to analyze the data. Future weak lensing surveys are already planned in order to cover a large fraction of the sky with high accuracy, such as Euclid [68]. However, improving accuracy also places greater demands on the methods used to extract the available information.

KiDS+GAMA: cosmology constraints from a joint analysis of cosmic shear, galaxy-galaxy lensing, and angular clustering

NASA Astrophysics Data System (ADS)

van Uitert, Edo; Joachimi, Benjamin; Joudaki, Shahab; Amon, Alexandra; Heymans, Catherine; Köhlinger, Fabian; Asgari, Marika; Blake, Chris; Choi, Ami; Erben, Thomas; Farrow, Daniel J.; Harnois-Déraps, Joachim; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D.; Klaes, Dominik; Kuijken, Konrad; Merten, Julian; Miller, Lance; Nakajima, Reiko; Schneider, Peter; Valentijn, Edwin; Viola, Massimo

2018-06-01

We present cosmological parameter constraints from a joint analysis of three cosmological probes: the tomographic cosmic shear signal in ˜450 deg2 of data from the Kilo Degree Survey (KiDS), the galaxy-matter cross-correlation signal of galaxies from the Galaxies And Mass Assembly (GAMA) survey determined with KiDS weak lensing, and the angular correlation function of the same GAMA galaxies. We use fast power spectrum estimators that are based on simple integrals over the real-space correlation functions, and show that they are practically unbiased over relevant angular frequency ranges. We test our full pipeline on numerical simulations that are tailored to KiDS and retrieve the input cosmology. By fitting different combinations of power spectra, we demonstrate that the three probes are internally consistent. For all probes combined, we obtain S_8≡ σ _8 √{Ω _m/0.3}=0.800_{-0.027}^{+0.029}, consistent with Planck and the fiducial KiDS-450 cosmic shear correlation function results. Marginalizing over wide priors on the mean of the tomographic redshift distributions yields consistent results for S8 with an increase of 28 {per cent} in the error. The combination of probes results in a 26 per cent reduction in uncertainties of S8 over using the cosmic shear power spectra alone. The main gain from these additional probes comes through their constraining power on nuisance parameters, such as the galaxy intrinsic alignment amplitude or potential shifts in the redshift distributions, which are up to a factor of 2 better constrained compared to using cosmic shear alone, demonstrating the value of large-scale structure probe combination.

EFFECT OF MASKED REGIONS ON WEAK-LENSING STATISTICS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shirasaki, Masato; Yoshida, Naoki; Hamana, Takashi, E-mail: masato.shirasaki@utap.phys.s.u-tokyo.ac.jp

2013-09-10

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

Precision calculations of the cosmic shear power spectrum projection

NASA Astrophysics Data System (ADS)

Kilbinger, Martin; Heymans, Catherine; Asgari, Marika; Joudaki, Shahab; Schneider, Peter; Simon, Patrick; Van Waerbeke, Ludovic; Harnois-Déraps, Joachim; Hildebrandt, Hendrik; Köhlinger, Fabian; Kuijken, Konrad; Viola, Massimo

2017-12-01

We compute the spherical-sky weak-lensing power spectrum of the shear and convergence. We discuss various approximations, such as flat-sky, and first- and second-order Limber equations for the projection. We find that the impact of adopting these approximations is negligible when constraining cosmological parameters from current weak-lensing surveys. This is demonstrated using data from the Canada-France-Hawaii Telescope Lensing Survey. We find that the reported tension with Planck cosmic microwave background temperature anisotropy results cannot be alleviated. For future large-scale surveys with unprecedented precision, we show that the spherical second-order Limber approximation will provide sufficient accuracy. In this case, the cosmic-shear power spectrum is shown to be in agreement with the full projection at the sub-percent level for ℓ > 3, with the corresponding errors an order of magnitude below cosmic variance for all ℓ. When computing the two-point shear correlation function, we show that the flat-sky fast Hankel transformation results in errors below two percent compared to the full spherical transformation. In the spirit of reproducible research, our numerical implementation of all approximations and the full projection are publicly available within the package NICAEA at http://www.cosmostat.org/software/nicaea.

Dark Energy Survey Year 1 Results: Weak Lensing Mass Calibration of redMaPPer Galaxy Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

McClintock, T.; et al.

We constrain the mass--richness scaling relation of redMaPPer galaxy clusters identified in the Dark Energy Survey Year 1 data using weak gravitational lensing. We split clusters intomore » $$4\\times3$$ bins of richness $$\\lambda$$ and redshift $z$ for $$\\lambda\\geq20$$ and $$0.2 \\leq z \\leq 0.65$$ and measure the mean masses of these bins using their stacked weak lensing signal. By modeling the scaling relation as $$\\langle M_{\\rm 200m}|\\lambda,z\\rangle = M_0 (\\lambda/40)^F ((1+z)/1.35)^G$$, we constrain the normalization of the scaling relation at the 5.0 per cent level as $$M_0 = [3.081 \\pm 0.075 ({\\rm stat}) \\pm 0.133 ({\\rm sys})] \\cdot 10^{14}\\ {\\rm M}_\\odot$$ at $$\\lambda=40$$ and $z=0.35$. The richness scaling index is constrained to be $$F=1.356 \\pm 0.051\\ ({\\rm stat})\\pm 0.008\\ ({\\rm sys})$$ and the redshift scaling index $$G=-0.30\\pm 0.30\\ ({\\rm stat})\\pm 0.06\\ ({\\rm sys})$$. These are the tightest measurements of the normalization and richness scaling index made to date. We use a semi-analytic covariance matrix to characterize the statistical errors in the recovered weak lensing profiles. Our analysis accounts for the following sources of systematic error: shear and photometric redshift errors, cluster miscentering, cluster member dilution of the source sample, systematic uncertainties in the modeling of the halo--mass correlation function, halo triaxiality, and projection effects. We discuss prospects for reducing this systematic error budget, which dominates the uncertainty on $$M_0$$. Our result is in excellent agreement with, but has significantly smaller uncertainties than, previous measurements in the literature, and augurs well for the power of the DES cluster survey as a tool for precision cosmology and upcoming galaxy surveys such as LSST, Euclid and WFIRST.« less

Multiwavelength study of X-ray luminous clusters in the Hyper Suprime-Cam Subaru Strategic Program S16A field

NASA Astrophysics Data System (ADS)

Miyaoka, Keita; Okabe, Nobuhiro; Kitaguchi, Takao; Oguri, Masamune; Fukazawa, Yasushi; Mandelbaum, Rachel; Medezinski, Elinor; Babazaki, Yasunori; Nishizawa, Atsushi J.; Hamana, Takashi; Lin, Yen-Ting; Akamatsu, Hiroki; Chiu, I.-Non; Fujita, Yutaka; Ichinohe, Yuto; Komiyama, Yutaka; Sasaki, Toru; Takizawa, Motokazu; Ueda, Shutaro; Umetsu, Keiichi; Coupon, Jean; Hikage, Chiaki; Hoshino, Akio; Leauthaud, Alexie; Matsushita, Kyoko; Mitsuishi, Ikuyuki; Miyatake, Hironao; Miyazaki, Satoshi; More, Surhud; Nakazawa, Kazuhiro; Ota, Naomi; Sato, Kousuke; Spergel, David; Tamura, Takayuki; Tanaka, Masayuki; Tanaka, Manobu M.; Utsumi, Yousuke

2018-01-01

We present a joint X-ray, optical, and weak-lensing analysis for X-ray luminous galaxy clusters selected from the MCXC (Meta-Catalog of X-Ray Detected Clusters of Galaxies) cluster catalog in the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) survey field with S16A data. As a pilot study for a series of papers, we measure hydrostatic equilibrium (HE) masses using XMM-Newton data for four clusters in the current coverage area out of a sample of 22 MCXC clusters. We additionally analyze a non-MCXC cluster associated with one MCXC cluster. We show that HE masses for the MCXC clusters are correlated with cluster richness from the CAMIRA catalog, while that for the non-MCXC cluster deviates from the scaling relation. The mass normalization of the relationship between cluster richness and HE mass is compatible with one inferred by matching CAMIRA cluster abundance with a theoretical halo mass function. The mean gas mass fraction based on HE masses for the MCXC clusters is = 0.125 ± 0.012 at spherical overdensity Δ = 500, which is ˜80%-90% of the cosmic mean baryon fraction, Ωb/Ωm, measured by cosmic microwave background experiments. We find that the mean baryon fraction estimated from X-ray and HSC-SSP optical data is comparable to Ωb/Ωm. A weak-lensing shear catalog of background galaxies, combined with photometric redshifts, is currently available only for three clusters in our sample. Hydrostatic equilibrium masses roughly agree with weak-lensing masses, albeit with large uncertainty. This study demonstrates that further multiwavelength study for a large sample of clusters using X-ray, HSC-SSP optical, and weak-lensing data will enable us to understand cluster physics and utilize cluster-based cosmology.

Subaru Weak-lensing Survey of Dark Matter Subhalos in the Coma Cluster: Subhalo Mass Function and Statistical Properties

NASA Astrophysics Data System (ADS)

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

2014-04-01

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

Lensing-induced morphology changes in CMB temperature maps in modified gravity theories

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munshi, D.; Coles, P.; Hu, B.

2016-04-01

Lensing of the Cosmic Microwave Background (CMB) changes the morphology of pattern of temperature fluctuations, so topological descriptors such as Minkowski Functionals can probe the gravity model responsible for the lensing. We show how the recently introduced two-to-two and three-to-one kurt-spectra (and their associated correlation functions), which depend on the power spectrum of the lensing potential, can be used to probe modified gravity theories such as f ( R ) theories of gravity and quintessence models. We also investigate models based on effective field theory, which include the constant-Ω model, and low-energy Hořava theories. Estimates of the cumulative signal-to-noise formore » detection of lensing-induced morphology changes, reaches O(10{sup 3}) for the future planned CMB polarization mission COrE{sup +}. Assuming foreground removal is possible to ℓ{sub max}=3000, we show that many modified gravity theories can be rejected with a high level of significance, making this technique comparable in power to galaxy weak lensing or redshift surveys. These topological estimators are also useful in distinguishing lensing from other scattering secondaries at the level of the four-point function or trispectrum. Examples include the kinetic Sunyaev-Zel'dovich (kSZ) effect which shares, with lensing, a lack of spectral distortion. We also discuss the complication of foreground contamination from unsubtracted point sources.« less

Weak deflection gravitational lensing for photons coupled to Weyl tensor in a Schwarzschild black hole

NASA Astrophysics Data System (ADS)

Cao, Wei-Guang; Xie, Yi

2018-03-01

Beyond the Einstein-Maxwell model, electromagnetic field might couple with gravitational field through the Weyl tensor. In order to provide one of the missing puzzles of the whole physical picture, we investigate weak deflection lensing for photons coupled to the Weyl tensor in a Schwarzschild black hole under a unified framework that is valid for its two possible polarizations. We obtain its coordinate-independent expressions for all observables of the geometric optics lensing up to the second order in the terms of ɛ which is the ratio of the angular gravitational radius to angular Einstein radius of the lens. These observables include bending angle, image position, magnification, centroid and time delay. The contributions of such a coupling on some astrophysical scenarios are also studied. We find that, in the cases of weak deflection lensing on a star orbiting the Galactic Center Sgr A*, Galactic microlensing on a star in the bulge and astrometric microlensing by a nearby object, these effects are beyond the current limits of technology. However, measuring the variation of the total flux of two weak deflection lensing images caused by the Sgr A* might be a promising way for testing such a coupling in the future.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pujol, Arnau; Chang, Chihway; Gaztañaga, Enrique

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 / ormore » /. 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.« less

Reionization and CMB non-Gaussianity

NASA Astrophysics Data System (ADS)

Munshi, D.; Corasaniti, P. S.; Coles, P.; Heavens, A.; Pandolfi, S.

2014-08-01

We show how cross-correlating a high-redshift external tracer field, such as the 21-cm neutral hydrogen distribution and product maps involving cosmic microwave background (CMB) temperature and polarization fields, that probe mixed bispectrum involving these fields, can help to determine the reionization history of the Universe, beyond what can be achieved from cross-spectrum analysis. Taking clues from recent studies for the detection of primordial non-Gaussianity, we develop a set of estimators that can study reionization using a power spectrum associated with the bispectrum (or skew-spectrum). We use the matched filtering inherent in this method to investigate different reionization histories. We check to what extent they can be used to rule out various models of reionization and study cross-contamination from different sources such as the lensing of the CMB. The estimators can be fine-tuned to optimize study of a specific reionization history. We consider three different types of tracers in our study, namely: proto-galaxies; 21-cm maps of neutral hydrogen; and quasars. We also consider four alternative models of reionization. We find that the cumulative signal-to-noise ratio (S/N) for detection at ℓmax = 2000 can reach O(70) for cosmic variance limited all-sky experiments. Combining 100 GHz, 143 GHz and 217 GHz channels of the Planck experiment, we find that the S/N lies in the range O(5)-O(35). The S/N depends on the specific choice of a tracer field, and multiple tracers can be effectively used to map out the entire reionization history with reasonable S/N. Contamination from weak lensing is investigated and found to be negligible, and the effects of Thomson scattering from patchy reionization are also considered.

Weak-lensing magnification as a probe for the dark Universe

DOE Office of Scientific and Technical Information (OSTI.GOV)

García Fernández, Manuel

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.

Merging Galaxy Clusters: A Case Study of ZwCl 2341.1+0000 and the Development of a New Forward Modeled Lensing Technique

NASA Astrophysics Data System (ADS)

Benson, Bryant Joseph

Context: Galaxy clusters are the most massive gravitationally bound structures in the universe and are formed through the process of hierarchical clustering, in which smaller systems undergo a series of mergers to form ever larger clusters. Because of the masses involved, mergers between these giants provide a unique laboratory for observing many interesting astrophysical processes. These merging systems also act as large dark matter colliders, because the dark matter halos of the clusters involved pass through each other during of the merger. This offers us a means to observe if dark matter-dark matter collisions result in momentum exchange beyond what occurs from gravity alone. Such observations can help us to unravel some of the mysteries behind dark matter, such as does it interact with itself through mechanisms beyond gravity, and how strong are those interactions. Answers to questions like these are what will eventually allow us to discover what dark matter really is. However, the extremely long time scales for these mergers (˜several billion years) make each observation a single snapshot in the long merger history, and we must infer many of the details necessary for understanding the full merger process. Furthermore, current weak lensing analyses lack the precision required to detect a signal from self-interacting dark matter. Uncertain weak lensing mass and position estimates also yield large uncertainties in the dynamical reconstruction of the merger scenarios. Need: In order to better model the dynamics of merging galaxy cluster systems, and to potentially measure any signal from self-interacting dark matter, we need to obtain more precise measurements on the masses and positions of the dark matter halos involved. Gravitational lensing offers a robust method for mapping the mass in these clusters because it directly measures the gravitational field, and does not depend on the dynamical state of the system that has been disturbed in the merger process. Of the lensing methods, weak gravitational lensing is the only way that we can probe a wide field and measure the total mass of the cluster. However, the precision of conventional weak lensing techniques is currently limited by shape noise (uncertainty in the shear due to the dispersion in the intrinsic shapes and orientations of unlensed galaxies). A possible avenue forward is to eliminate shape noise as a source of uncertainty in shear measurements via a technique to be described below. This would eliminate the largest source of uncertainty in weak lensing analyses, and enable us to obtain mass and position estimates of dark matter halos with a much higher level of precision. Task: In this dissertation we perform statistical clustering, conventional weak lensing analyses, and dynamical reconstruction on the merging galaxy cluster system ZwCl 2341.1+0000 in order to test the capabilities of the dynamical modeling on a complex, multiple merger. We use targeted optical spectroscopy to identify cluster member galaxies, which we then use to model the galaxy substructures. We also obtain a dynamical mass estimate using the galaxy velocity dispersions, and perform weak lensing analyses in the forms of aperture densitometry to place an upper bound on the total cluster mass, and multiple NFW profile halo fitting to approximate the masses and positions of the individual dark matter halos present in the merger. The masses, positions, and line of sight velocities of those clusters are then used to constrain the parameters describing the best fit merger scenario, with radio relic positions and polarization used to further tighten those constraints. We also develop a new method for obtaining weak lensing data from individual source galaxies in the form of shear measurements that are independent of shape noise, and direct measurements of the convergence. We accomplish this by simultaneously modeling the pre-lensing velocity and intensity profiles of a lensed, rotating disk galaxy, and the lensing transform required to distort those into the lensed profiles we observe. We test this method with a host of idealized simulations to characterize its capabilities in a best-case scenario and forecast the possible improvements it can bring to the precision of weak lensing analyses on galaxy clusters. (Abstract shortened by ProQuest.).

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

We present cosmological results from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 degmore » $^2$ 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 ...« less

Dark Energy Survey Year 1 Results: Methodology and Projections for Joint Analysis of Galaxy Clustering, Galaxy Lensing, and CMB Lensing Two-point Functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giannantonio, T.; et al.

Optical imaging surveys measure both the galaxy density and the gravitational lensing-induced shear fields across the sky. Recently, the Dark Energy Survey (DES) collaboration used a joint fit to two-point correlations between these observables to place tight constraints on cosmology (DES Collaboration et al. 2017). In this work, we develop the methodology to extend the DES Collaboration et al. (2017) analysis to include cross-correlations of the optical survey observables with gravitational lensing of the cosmic microwave background (CMB) as measured by the South Pole Telescope (SPT) and Planck. Using simulated analyses, we show how the resulting set of five two-pointmore » functions increases the robustness of the cosmological constraints to systematic errors in galaxy lensing shear calibration. Additionally, we show that contamination of the SPT+Planck CMB lensing map by the thermal Sunyaev-Zel'dovich effect is a potentially large source of systematic error for two-point function analyses, but show that it can be reduced to acceptable levels in our analysis by masking clusters of galaxies and imposing angular scale cuts on the two-point functions. The methodology developed here will be applied to the analysis of data from the DES, the SPT, and Planck in a companion work.« less

ICE-COLA: fast simulations for weak lensing observables

NASA Astrophysics Data System (ADS)

Izard, Albert; Fosalba, Pablo; Crocce, Martin

2018-01-01

Approximate methods to full N-body simulations provide a fast and accurate solution to the development of mock catalogues for the modelling of galaxy clustering observables. In this paper we extend ICE-COLA, based on an optimized implementation of the approximate COLA method, to produce weak lensing maps and halo catalogues in the light-cone using an integrated and self-consistent approach. We show that despite the approximate dynamics, the catalogues thus produced enable an accurate modelling of weak lensing observables one decade beyond the characteristic scale where the growth becomes non-linear. In particular, we compare ICE-COLA to the MICE Grand Challenge N-body simulation for some fiducial cases representative of upcoming surveys and find that, for sources at redshift z = 1, their convergence power spectra agree to within 1 per cent up to high multipoles (i.e. of order 1000). The corresponding shear two point functions, ξ+ and ξ-, yield similar accuracy down to 2 and 20 arcmin respectively, while tangential shear around a z = 0.5 lens sample is accurate down to 4 arcmin. We show that such accuracy is stable against an increased angular resolution of the weak lensing maps. Hence, this opens the possibility of using approximate methods for the joint modelling of galaxy clustering and weak lensing observables and their covariance in ongoing and future galaxy surveys.

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

PubMed

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

2003-06-06

We use cosmic microwave background (CMB) observations together with the red-sequence cluster survey weak lensing results to derive constraints on a range of cosmological parameters. This particular choice of observations is motivated by their robust physical interpretation and complementarity. Our combined analysis, including a weak nucleosynthesis constraint, yields accurate determinations of a number of parameters including the amplitude of fluctuations sigma(8)=0.89+/-0.05 and matter density Omega(m)=0.30+/-0.03. We also find a value for the Hubble parameter of H(0)=70+/-3 km s(-1) Mpc(-1), in good agreement with the Hubble Space Telescope key-project result. We conclude that the combination of CMB and weak lensing data provides some of the most powerful constraints available in cosmology today.

Searching for modified growth patterns with tomographic surveys

NASA Astrophysics Data System (ADS)

Zhao, Gong-Bo; Pogosian, Levon; Silvestri, Alessandra; Zylberberg, Joel

2009-04-01

In alternative theories of gravity, designed to produce cosmic acceleration at the current epoch, the growth of large scale structure can be modified. We study the potential of upcoming and future tomographic surveys such as Dark Energy Survey (DES) and Large Synoptic Survey Telescope (LSST), with the aid of cosmic microwave background (CMB) and supernovae data, to detect departures from the growth of cosmic structure expected within general relativity. We employ parametric forms to quantify the potential time- and scale-dependent variation of the effective gravitational constant and the differences between the two Newtonian potentials. We then apply the Fisher matrix technique to forecast the errors on the modified growth parameters from galaxy clustering, weak lensing, CMB, and their cross correlations across multiple photometric redshift bins. We find that even with conservative assumptions about the data, DES will produce nontrivial constraints on modified growth and that LSST will do significantly better.

SEARCHING FOR COOLING SIGNATURES IN STRONG LENSING GALAXY CLUSTERS: EVIDENCE AGAINST BARYONS SHAPING THE MATTER DISTRIBUTION IN CLUSTER CORES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanchard, Peter K.; Bayliss, Matthew B.; McDonald, Michael

2013-07-20

The process by which the mass density profile of certain galaxy clusters becomes centrally concentrated enough to produce high strong lensing (SL) cross-sections is not well understood. It has been suggested that the baryonic condensation of the intracluster medium (ICM) due to cooling may drag dark matter to the cores and thus steepen the profile. In this work, we search for evidence of ongoing ICM cooling in the first large, well-defined sample of SL selected galaxy clusters in the range 0.1 < z < 0.6. Based on known correlations between the ICM cooling rate and both optical emission line luminositymore » and star formation, we measure, for a sample of 89 SL clusters, the fraction of clusters that have [O II]{lambda}{lambda}3727 emission in their brightest cluster galaxy (BCG). We find that the fraction of line-emitting BCGs is constant as a function of redshift for z > 0.2 and shows no statistically significant deviation from the total cluster population. Specific star formation rates, as traced by the strength of the 4000 A break, D{sub 4000}, are also consistent with the general cluster population. Finally, we use optical imaging of the SL clusters to measure the angular separation, R{sub arc}, between the arc and the center of mass of each lensing cluster in our sample and test for evidence of changing [O II] emission and D{sub 4000} as a function of R{sub arc}, a proxy observable for SL cross-sections. D{sub 4000} is constant with all values of R{sub arc}, and the [O II] emission fractions show no dependence on R{sub arc} for R{sub arc} > 10'' and only very marginal evidence of increased weak [O II] emission for systems with R{sub arc} < 10''. These results argue against the ability of baryonic cooling associated with cool core activity in the cores of galaxy clusters to strongly modify the underlying dark matter potential, leading to an increase in SL cross-sections.« less

EDITORIAL: Focus on Gravitational Lensing

NASA Astrophysics Data System (ADS)

Jain, Bhuvnesh

2007-11-01

Gravitational lensing emerged as an observational field following the 1979 discovery of a doubly imaged quasar lensed by a foreground galaxy. In the 1980s and '90s dozens of other multiply imaged systems were observed, as well as time delay measurements, weak and strong lensing by galaxies and galaxy clusters, and the discovery of microlensing in our galaxy. The rapid pace of advances has continued into the new century. Lensing is currently one of best techniques for finding and mapping dark matter over a wide range of scales, and also addresses broader cosmological questions such as understanding the nature of dark energy. This focus issue of New Journal of Physics presents a snapshot of current research in some of the exciting areas of lensing. It provides an occasion to look back at the advances of the last decade and ahead to the potential of the coming years. Just about a decade ago, microlensing was discovered through the magnification of stars in our galaxy by invisible objects with masses between that of Jupiter and a tenth the mass of the Sun. Thus a new component of the mass of our galaxy, dubbed MACHOs, was established (though a diffuse, cold dark matter-like component is still needed to make up most of the galaxy mass). More recently, microlensing led to another exciting discovery—of extra-solar planets with masses ranging from about five times that of Earth to that of Neptune. We can expect many more planets to be discovered through ongoing surveys. Microlensing is the best technique for finding Earth mass planets, though it is not as productive overall as other methods and does not allow for follow up observations. Beyond planet hunting, microlensing has enabled us to observe previously inaccessible systems, ranging from the surfaces of other stars to the accretion disks around the black holes powering distant quasars. Galaxies and galaxy clusters at cosmological distances can produce dramatic lensing effects: multiple images of background galaxies or quasars which are strongly magnified and sheared. In the last decade, double and quadruply imaged systems due to galactic lenses have been studied with optical and radio observations. An interesting result obtained from the flux ratio 'anomalies' of quadruply imaged systems is the statistical detection of dark sub-clumps in galaxy halos. More broadly, while we have learned a lot about the mass distribution in lens galaxies and improved time delay constraints on the Hubble constant, the limitations of cosmological studies with strong lensing due to uncertainties in lens mass models have also come to be appreciated. That said, progress will no doubt continue with qualitative advances in observations such as astrometric counterparts to the flux anomalies, clever ideas such as the use of spectroscopic signatures to assemble the SLACS lens sample, and combining optical imaging, spectroscopy and radio data to continue the quest for a set of golden lenses to measure the Hubble constant. Galaxy clusters are a fascinating arena for studying the distribution of dark and baryonic matter. Weak and strong lensing information can be combined with dynamical information from the spectroscopic measurements of member galaxies and x-ray/Sunyaev Zeldovich measurements of the hot ionized gas. Hubble Space Telescope observations have yielded spectacular images of clusters, such as Abell 1689, which has over a hundred multiply imaged arcs. Mass measurements have progressed to the level of 10 percent accuracy for several clusters. Unfortunately, it is unclear if one can do much better for individual clusters given inherent limitations such as unknown projection effects. The statistical study of clusters is likely to remain a promising way to study dark matter, gravity theories, and cosmology. Techniques to combine weak and strong lensing information to obtain the mass distribution of clusters have also advanced, and work continues on parameter-free techniques that are agnostic to the relation of cluster light and mass. An interesting twist in cluster lensing was provided by the post-merger Bullet Cluster (identified as 1E0657-558). In this and other merging clusters, the lensing mass is displaced from the baryonic center of mass, presenting a challenge to theories that attempt to explain away dark matter by positing a modification to the law of gravity. Detailed modeling and multi-wavelength data on these systems will provide interesting limits on dark matter as well as the possibility of a major surprise. Other advances may come from the gravitational telescope effect of galaxy clusters: regions with very high magnification can be used to image proto-galaxies at z ~ 10. Statistical studies of galaxy and cluster lenses and of invisible, diffuse large-scale structures via weak lensing have come into their own in recent years. A census of the mass distribution at low redshift has been made using the technique of galaxy galaxy lensing: the mean mass profiles of galaxies and clusters have been measured using the weak tangential shear imprinted on background galaxies. These can be correlated with a variety of luminous tracers to study galaxy/cluster properties at a level of detail not possible until recently. Equally impressive is the measurement of excess mass correlations out to ~30 Mpc from these halos, requiring measurements of shear signals below 0.01%. These measurements account for the total matter density inferred from the CMB plus other observations, thus providing a direct measure of dark matter in the present day universe. Cosmic shear refers to the more challenging measurement of shear shear correlations without the use of foreground objects to orient the shear. The first detections of such correlations were published in 2001; since then measurements from arcminute to degree scales have been made with much improved accuracy. Theoretical techniques of lensing tomography and advances in analysis methods to eliminate systematic errors have progressed rapidly. That cosmic shear is now regarded as a key element of major missions aimed at probing dark energy is a feat of scientific persuasion—a decade ago not many believed it was realistic to even detect this tiny shear signal, let alone measure it with the percent-level accuracy needed to advance dark energy measurements. If weak lensing measurements deliver on their promise, then, in combination with other imaging and spectroscopic probes, they may well impact fundamental physics and cosmology. For example they may find evidence for an evolving dark energy component or signatures of departures from general relativity. These exciting prospects rest on new optical surveys planned for the next five years which will image a thousand square degrees or more of the sky to redshifts ~1 (compared to about a hundred square degrees imaged currently). Further, through photometric redshifts based on galaxy colors, lensing tomography methods will be applied to learn about the three-dimensional distribution of dark matter. Lensing measurements in other wavelengths, such as planned 21-cm surveys and CMB lensing, would add valuable diversity to measurement techniques. The case for the next generation optical surveys from the ground and space is compelling as well: they will produce another order of magnitude in data quantity and deliver images with minimal distortions due to the atmosphere and telescope optics. The coming decade therefore has the potential for exciting discoveries in gravitational lensing. Focus on Gravitational Lensing Contents A Bayesian approach to strong lensing modelling of galaxy clusters E Jullo, J-P Kneib, M Limousin, Á Elíasdóttir, P J Marshall and T Verdugo Probing dark energy with cluster counts and cosmic shear power spectra: including the full covariance Masahiro Takada and Sarah Bridle How robust are the constraints on cosmology and galaxy evolution from the lens-redshift test? Pedro R Capelo and Priyamvada Natarajan Dark energy constraints from cosmic shear power spectra: impact of intrinsic alignments on photometric redshift requirements Sarah Bridle and Lindsay King An integral-field spectroscopic strong lens survey Adam S Bolton and Scott Burles Is there a quad problem among optical gravitational lenses? Masamune Oguri Cluster mass estimators from CMB temperature and polarization lensing Wayne Hu, Simon DeDeo and Chris Vale

Measuring the lensing potential with tomographic galaxy number counts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montanari, Francesco; Durrer, Ruth, E-mail: francesco.montanari@unige.ch, E-mail: ruth.durrer@unige.ch

2015-10-01

We investigate how the lensing potential can be measured tomographically with future galaxy surveys using their number counts. Such a measurement is an independent test of the standard ΛCDM framework and can be used to discern modified theories of gravity. We perform a Fisher matrix forecast based on galaxy angular-redshift power spectra, assuming specifications consistent with future photometric Euclid-like surveys and spectroscopic SKA-like surveys. For the Euclid-like survey we derive a fitting formula for the magnification bias. Our analysis suggests that the cross correlation between different redshift bins is very sensitive to the lensing potential such that the survey canmore » measure the amplitude of the lensing potential at the same level of precision as other standard ΛCDM cosmological parameters.« less

Fundamental physics from future weak-lensing calibrated Sunyaev-Zel'dovich galaxy cluster counts

NASA Astrophysics Data System (ADS)

Madhavacheril, Mathew S.; Battaglia, Nicholas; Miyatake, Hironao

2017-11-01

Future high-resolution measurements of the cosmic microwave background (CMB) will produce catalogs of tens of thousands of galaxy clusters through the thermal Sunyaev-Zel'dovich (tSZ) effect. We forecast how well different configurations of a CMB Stage-4 experiment can constrain cosmological parameters, in particular, the amplitude of structure as a function of redshift σ8(z ) , the sum of neutrino masses Σ mν, and the dark energy equation of state w (z ). A key element of this effort is calibrating the tSZ scaling relation by measuring the lensing signal around clusters. We examine how the mass calibration from future optical surveys like the Large Synoptic Survey Telescope (LSST) compares with a purely internal calibration using lensing of the CMB itself. We find that, due to its high-redshift leverage, internal calibration gives constraints on cosmological parameters comparable to the optical calibration, and can be used as a cross-check of systematics in the optical measurement. We also show that in contrast to the constraints using the CMB lensing power spectrum, lensing-calibrated tSZ cluster counts can detect a minimal Σ mν at the 3 - 5 σ level even when the dark energy equation of state is freed up.

Probabilistic cosmological mass mapping from weak lensing shear

DOE PAGES

Schneider, M. D.; Ng, K. Y.; Dawson, W. A.; ...

2017-04-10

Here, 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 ormore » 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.« less

Probabilistic Cosmological Mass Mapping from Weak Lensing Shear

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, M. D.; Dawson, W. A.; Ng, K. Y.

2017-04-10

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-distributedmore » 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.« less

Deep Learning the Universe

NASA Astrophysics Data System (ADS)

Singh, Shiwangi; Bard, Deborah

2017-01-01

Weak gravitational lensing is an effective tool to map the structure of matter in the universe, and has been used for more than ten years as a probe of the nature of dark energy. Beyond the well-established two-point summary statistics, attention is now turning to methods that use the full statistical information available in the lensing observables, through analysis of the reconstructed shear field. This offers an opportunity to take advantage of powerful deep learning methods for image analysis. We present two early studies that demonstrate that deep learning can be used to characterise features in weak lensing convergence maps, and to identify the underlying cosmological model that produced them.We developed an unsupervised Denoising Convolutional Autoencoder model in order to learn an abstract representation directly from our data. This model uses a convolution-deconvolution architecture, which is fed with input data (corrupted with binomial noise to prevent over-fitting). Our model effectively trains itself to minimize the mean-squared error between the input and the output using gradient descent, resulting in a model which, theoretically, is broad enough to tackle other similarly structured problems. Using this model we were able to successfully reconstruct simulated convergence maps and identify the structures in them. We also determined which structures had the highest “importance” - i.e. which structures were most typical of the data. We note that the structures that had the highest importance in our reconstruction were around high mass concentrations, but were highly non-Gaussian.We also developed a supervised Convolutional Neural Network (CNN) for classification of weak lensing convergence maps from two different simulated theoretical models. The CNN uses a softmax classifier which minimizes a binary cross-entropy loss between the estimated distribution and true distribution. In other words, given an unseen convergence map the trained CNN determines probabilistically which theoretical model fits the data best. This preliminary work demonstrates that we can classify the cosmological model that produced the convergence maps with 80% accuracy.

Galaxy cluster center detection methods with weak lensing

NASA Astrophysics Data System (ADS)

Simet, Melanie

The precise location of galaxy cluster centers is a persistent problem in weak lensing mass estimates and in interpretations of clusters in a cosmological context. In this work, we test methods of centroid determination from weak lensing data and examine the effects of such self-calibration on the measured masses. Drawing on lensing data from the Sloan Digital Sky Survey Stripe 82, a 275 square degree region of coadded data in the Southern Galactic Cap, together with a catalog of MaxBCG clusters, we show that halo substructure as well as shape noise and stochasticity in galaxy positions limit the precision of such a self-calibration (in the context of Stripe 82, to ˜ 500 h-1 kpc or larger) and bias the mass estimates around these points to a level that is likely unacceptable for the purposes of making cosmological measurements. We also project the usefulness of this technique in future surveys.

Weak lensing probe of cubic Galileon model

NASA Astrophysics Data System (ADS)

Dinda, Bikash R.

2018-06-01

The cubic Galileon model containing the lowest non-trivial order action of the full Galileon action can produce the stable late-time cosmic acceleration. This model can have a significant role in the growth of structures. The signatures of the cubic Galileon model in the structure formation can be probed by the weak lensing statistics. Weak lensing convergence statistics is one of the strongest probes to the structure formation and hence it can probe the dark energy or modified theories of gravity models. In this work, we investigate the detectability of the cubic Galileon model from the ΛCDM model or from the canonical quintessence model through the convergence power spectrum and bi-spectrum.

Optical study of the DAFT/FADA galaxy cluster survey

NASA Astrophysics Data System (ADS)

Martinet, N.; Durret, F.; Clowe, D.; Adami, C.

2013-11-01

DAFT/FADA (Dark energy American French Team) is a large survey of ˜90 high redshift (0.42×10^{14} M_{⊙}) clusters with HST weak lensing oriented data, plus BVRIZJ 4m ground based follow up to compute photometric redshifts. The main goals of this survey are to constrain dark energy parameters using weak lensing tomography and to study a large homogeneous sample of high redshift massive clusters. We will briefly review the latest results of this optical survey, focusing on two ongoing works: the calculation of galaxy luminosity functions from photometric redshift catalogs and the weak lensing analysis of ground based data.

Probing Primordial Non-Gaussianity with Weak-lensing Minkowski Functionals

NASA Astrophysics Data System (ADS)

Shirasaki, Masato; Yoshida, Naoki; Hamana, Takashi; Nishimichi, Takahiro

2012-11-01

We study the cosmological information contained in the Minkowski functionals (MFs) of weak gravitational lensing convergence maps. We show that the MFs provide strong constraints on the local-type primordial non-Gaussianity parameter f NL. We run a set of cosmological N-body simulations and perform ray-tracing simulations of weak lensing to generate 100 independent convergence maps of a 25 deg2 field of view for f NL = -100, 0 and 100. We perform a Fisher analysis to study the degeneracy among other cosmological parameters such as the dark energy equation of state parameter w and the fluctuation amplitude σ8. We use fully nonlinear covariance matrices evaluated from 1000 ray-tracing simulations. For upcoming wide-field observations such as those from the Subaru Hyper Suprime-Cam survey with a proposed survey area of 1500 deg2, the primordial non-Gaussianity can be constrained with a level of f NL ~ 80 and w ~ 0.036 by weak-lensing MFs. If simply scaled by the effective survey area, a 20,000 deg2 lensing survey using the Large Synoptic Survey Telescope will yield constraints of f NL ~ 25 and w ~ 0.013. We show that these constraints can be further improved by a tomographic method using source galaxies in multiple redshift bins.

High resolution microphotonic needle for endoscopic imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tadayon, Mohammad Amin; Mohanty, Aseema; Roberts, Samantha P.; Barbosa, Felippe; Lipson, Michal

2017-02-01

GRIN (Graded index) lens have revolutionized micro endoscopy enabling deep tissue imaging with high resolution. The challenges of traditional GRIN lenses are their large size (when compared with the field of view) and their limited resolution. This is because of the relatively weak NA in standard graded index lenses. Here we introduce a novel micro-needle platform for endoscopy with much higher resolution than traditional GRIN lenses and a FOV that corresponds to the whole cross section of the needle. The platform is based on polymeric (SU-8) waveguide integrated with a microlens micro fabricated on a silicon substrate using a unique molding process. Due to the high index of refraction of the material the NA of the needle is much higher than traditional GRIN lenses. We tested the probe in a fluorescent dye solution (19.6 µM Alexa Flour 647 solution) and measured a numerical aperture of 0.25, focal length of about 175 µm and minimal spot size of about 1.6 µm. We show that the platform can image a sample with the field of view corresponding to the cross sectional area of the waveguide (80x100 µm2). The waveguide size can in principle be modified to vary size of the imaging field of view. This demonstration, combined with our previous work demonstrating our ability to implant the high NA needle in a live animal, shows that the proposed system can be used for deep tissue imaging with very high resolution and high field of view.

Baryons, universe and everything in between

NASA Astrophysics Data System (ADS)

Ho, Shirley

2008-06-01

This thesis is a tour of topics in cosmology, unified by their diversity and pursuits in better understanding of our Universe. The first chapter measures the Integrated Sachs-Wolfe effect as a function of redshift utilizing a large range of large scale structure observations and the cosmic microwave background. We combine the ISW likelihood function with weak lensing of CMB (which is described in Chapter 2) and CMB powerspectrum to constrain the equation of state of dark energy and the curvature of the Universe. The second chapter investigates the correlation of gravitational lensing of the cosmic microwave background (CMB) with several tracers of large-scale structure, and we find evidence for a positive cross-correlation at the 2.5s level. The third chapter explores the statistical properties of Luminous Red Galaxies in a sample of X-ray selected galaxy clusters, including the halo occupation distribution, how Poisson is the satellite distribution of LRGs and the radial profile of LRGs within clusters. The forth chapter explores the idea of using multiplicity of galaxies to understand their merging timescales. We find that (by using the multiplicity function of LRGs in Chapter 3) Massive halos (~ 10 14 M [Special characters omitted.] ) at low redshift have, for example, been bombarded by several ~ 10 13 M [Special characters omitted.] halos throughout their history and these accreted LRGs merge on relatively short timescales (~ 2 Gyr). The fifth chapter presents a new method for generating a template for the kinematic Sunyaev-Zel'dovich effect that can be used to detect the missing baryons. We assessed the feasibility of the method by investigating combinations of differeng galaxy surveys and CMB observations and find that we can detect the gas-momentum kSZ correlation, and thus the ionized gas, at significant signal-to-noise level.

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

NASA Astrophysics Data System (ADS)

Reyes, R.; Mandelbaum, R.; Hirata, C.; Bahcall, N.; Seljak, U.

2008-11-01

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 ~13000 optically selected clusters from the Sloan Digital Sky Survey (SDSS) maxBCG catalogue, 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 various 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, N200, and the luminosity of the BCG, LBCG: , where is the observed mean BCG luminosity at a given richness. This improved mass tracer will enable the use of galaxy clusters as a more powerful tool for constraining cosmological parameters.

Shear Recovery Accuracy in Weak-Lensing Analysis with the Elliptical Gauss-Laguerre Method

NASA Astrophysics Data System (ADS)

Nakajima, Reiko; Bernstein, Gary

2007-04-01

We implement the elliptical Gauss-Laguerre (EGL) galaxy-shape measurement method proposed by Bernstein & Jarvis and quantify the shear recovery accuracy in weak-lensing analysis. This method uses a deconvolution fitting scheme to remove the effects of the point-spread function (PSF). The test simulates >107 noisy galaxy images convolved with anisotropic PSFs and attempts to recover an input shear. The tests are designed to be immune to statistical (random) distributions of shapes, selection biases, and crowding, in order to test more rigorously the effects of detection significance (signal-to-noise ratio [S/N]), PSF, and galaxy resolution. The systematic error in shear recovery is divided into two classes, calibration (multiplicative) and additive, with the latter arising from PSF anisotropy. At S/N > 50, the deconvolution method measures the galaxy shape and input shear to ~1% multiplicative accuracy and suppresses >99% of the PSF anisotropy. These systematic errors increase to ~4% for the worst conditions, with poorly resolved galaxies at S/N simeq 20. The EGL weak-lensing analysis has the best demonstrated accuracy to date, sufficient for the next generation of weak-lensing surveys.

Anisotropic Galaxy-Galaxy Lensing in the Illustris-1 Simulation

NASA Astrophysics Data System (ADS)

Brainerd, Tereasa G.

2017-06-01

In Cold Dark Matter universes, the dark matter halos of galaxies are expected to be triaxial, leading to a surface mass density that is not circularly symmetric. In principle, this "flattening" of the dark matter halos of galaxies should be observable as an anisotropy in the weak galaxy-galaxy lensing signal. The degree to which the weak lensing signal is observed to be anisotropic, however, will depend strongly on the degree to which mass (i.e., the dark matter) is aligned with light in the lensing galaxies. That is, the anisotropy will be maximized when the major axis of the projected mass distribution is well aligned with the projected light distribution of the lens galaxies. Observational studies of anisotropic galaxy-galaxy lensing have found an anisotropic weak lensing signal around massive, red galaxies. Detecting the signal around blue, disky galaxies has, however, been more elusive. A possible explanation for this is that mass and light are well aligned within red galaxies and poorly aligned within blue galaxies (an explanation that is supported by studies of the locations of satellites of large, relatively isolated galaxies). Here we compute the weak lensing signal of isolated central galaxies in the Illustris-1 simulation. We compute the anisotropy of the weak lensing signal using two definitions of the geometry: [1] the major axis of the projected dark matter mass distribution and [2] the major axis of the projected stellar mass. On projected scales less than 15% of the virial radius, an anisotropy of order 10% is found for both definitions of the geometry. On larger scales, the anisotropy computed relative to the major axis of the projected light distribution is less than the anisotropy computed relative to the major axis of the projected dark matter. On projected scales of order the virial radius, the anisotropy obtained when using the major axis of the light is an order of magnitude less than the anisotropy obtained when using the major axis of the dark matter. The suppression of the anisotropy when using the major axis of the light to define the geometry is indicative of a significant misalignment of mass and light in the Illustris-1 galaxies at large physical radii.

Galaxy masses in large surveys: Connecting luminous and dark matter with weak lensing and kinematics

NASA Astrophysics Data System (ADS)

Reyes, Reinabelle

2011-01-01

Galaxy masses are difficult to determine because light traces stars and gas in a non-trivial way, and does not trace dark matter, which extends well beyond the luminous regions of galaxies. In this thesis, I use the most direct probes of dark matter available---weak gravitational lensing and galaxy kinematics---to trace the total mass in galaxies (and galaxy clusters) in large surveys. In particular, I use the large, homogeneous dataset from the Sloan Digital Sky Survey (SDSS), which provides spectroscopic redshifts for a large sample of galaxies at z ≲ 0.2 and imaging data to a depth of r < 22. By combining complementary probes, I am able to obtain robust observational constraints that cannot be obtained from any single technique alone. First, I use weak lensing of galaxy clusters to derive an optimal optical tracer of cluster mass, which was found to be a combination of cluster richness and the luminosity of the brightest cluster galaxy. Next, I combine weak lensing of luminous red galaxies with redshift distortions and clustering measurements to derive a robust probe of gravity on cosmological scales. Finally, I combine weak lensing with the kinematics of disk galaxies to constrain the total mass profile over several orders of magnitude. I derive a minimal-scatter relation between disk velocity and stellar mass (also known as the Tully-Fisher relation) that can be used, by construction, on a similarly-selected lens sample. Then, I combine this relation with halo mass measurements from weak lensing to place constraints on the ratio of the optical to virial velocities, as well as the ratio of halo to stellar masses, both as a function of stellar mass. These results will serve as inputs to and constraints on disk galaxy formation models, which will be explored in future work.

CLASH: COMPLETE LENSING ANALYSIS OF THE LARGEST COSMIC LENS MACS J0717.5+3745 AND SURROUNDING STRUCTURES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Medezinski, Elinor; Lemze, Doron; Ford, Holland

2013-11-01

The galaxy cluster MACS J0717.5+3745 (z = 0.55) is the largest known cosmic lens, with complex internal structures seen in deep X-ray, Sunyaev-Zel'dovich effect, and dynamical observations. We perform a combined weak- and strong-lensing analysis with wide-field BVR{sub c} i'z' Subaru/Suprime-Cam observations and 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble. We find consistent weak distortion and magnification measurements of background galaxies and combine these signals to construct an optimally estimated radial mass profile of the cluster and its surrounding large-scale structure out to 5 Mpc h {sup –1}. We findmore » consistency between strong-lensing and weak-lensing in the region where these independent data overlap, <500 kpc h {sup –1}. The two-dimensional weak-lensing map reveals a clear filamentary structure traced by distinct mass halos. We model the lensing shear field with nine halos, including the main cluster, corresponding to mass peaks detected above 2.5σ{sub κ}. The total mass of the cluster as determined by the different methods is M{sub vir} ≈ (2.8 ± 0.4) × 10{sup 15} M{sub ☉}. Although this is the most massive cluster known at z > 0.5, in terms of extreme value statistics, we conclude that the mass of MACS J0717.5+3745 by itself is not in serious tension with ΛCDM, representing only a ∼2σ departure above the maximum simulated halo mass at this redshift.« less

Probing high-redshift clusters with HST/ACS gravitational weak-lensing and Chandra x-ray observations

NASA Astrophysics Data System (ADS)

Jee, Myungkook James

2006-06-01

Clusters of galaxies, the largest gravitationally bound objects in the Universe, are useful tracers of cosmic evolution, and particularly detailed studies of still-forming clusters at high-redshifts can considerably enhance our understanding of the structure formation. We use two powerful methods that have become recently available for the study of these distant clusters: spaced- based gravitational weak-lensing and high-resolution X-ray observations. Detailed analyses of five high-redshift (0.8 < z < 1.3) clusters are presented based on the deep Advanced Camera for Surveys (ACS) and Chandra X-ray images. We show that, when the instrumental characteristics are properly understood, the newly installed ACS on the Hubble Space Telescope (HST) can detect subtle shape distortions of background galaxies down to the limiting magnitudes of the observations, which enables the mapping of the cluster dark matter in unprecedented high-resolution. The cluster masses derived from this HST /ACS weak-lensing study have been compared with those from the re-analyses of the archival Chandra X-ray data. We find that there are interesting offsets between the cluster galaxy, intracluster medium (ICM), and dark matter centroids, and possible scenarios are discussed. If the offset is confirmed to be uniquitous in other clusters, the explanation may necessitate major refinements in our current understanding of the nature of dark matter, as well as the cluster galaxy dynamics. CL0848+4452, the highest-redshift ( z = 1.27) cluster yet detected in weak-lensing, has a significant discrepancy between the weak- lensing and X-ray masses. If this trend is found to be severe and common also for other X-ray weak clusters at redshifts beyond the unity, the conventional X-ray determination of cluster mass functions, often inferred from their immediate X-ray properties such as the X-ray luminosity and temperature via the so-called mass-luminosity (M-L) and mass-temperature (M-T) relations, will become highly unstable in this redshift regime. Therefore, the relatively unbiased weak-lensing measurements of the cluster mass properties can be used to adequately calibrate the scaling relations in future high-redshift cluster investigations.

Galaxy bias from galaxy–galaxy lensing in the DES science verification data

DOE PAGES

Prat, J.; Sánchez, C.; Miquel, R.; ...

2017-09-25

Here, we present a measurement of galaxy–galaxy lensing around a magnitude-limited (i AB < 22.5) sample of galaxies from the dark energy survey science verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias b and cross-correlation coefficient between the galaxy and dark matter overdensity fields r in each bin, using scales above 4 h –1 Mpc comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy–galaxy lensing with those obtained from galaxy clusteringmore » and CMB lensing for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al., while, in the lowest redshift bin (z ~ 0.3), they show some tension with the findings in Giannantonio et al. We measure b · r to be 0.87 ± 0.11, 1.12 ± 0.16 and 1.24 ± 0.23, respectively, for the three redshift bins of width Δz = 0.2 in the range 0.2 < z < 0.8, defined with the photometric-redshift algorithm bpz. Using a different code to split the lens sample, tpz, leads to changes in the measured biases at the 10–20 per cent level, but it does not alter the main conclusion of this work: when comparing with Crocce et al. we do not find strong evidence for a cross-correlation parameter significantly below one in this galaxy sample, except possibly at the lowest redshift bin (z ~ 0.3), where we find r = 0.71 ± 0.11 when using tpz, and 0.83 ± 0.12 with bpz.« less

Galaxy bias from galaxy–galaxy lensing in the DES science verification data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prat, J.; Sánchez, C.; Miquel, R.

Here, we present a measurement of galaxy–galaxy lensing around a magnitude-limited (i AB < 22.5) sample of galaxies from the dark energy survey science verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias b and cross-correlation coefficient between the galaxy and dark matter overdensity fields r in each bin, using scales above 4 h –1 Mpc comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy–galaxy lensing with those obtained from galaxy clusteringmore » and CMB lensing for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al., while, in the lowest redshift bin (z ~ 0.3), they show some tension with the findings in Giannantonio et al. We measure b · r to be 0.87 ± 0.11, 1.12 ± 0.16 and 1.24 ± 0.23, respectively, for the three redshift bins of width Δz = 0.2 in the range 0.2 < z < 0.8, defined with the photometric-redshift algorithm bpz. Using a different code to split the lens sample, tpz, leads to changes in the measured biases at the 10–20 per cent level, but it does not alter the main conclusion of this work: when comparing with Crocce et al. we do not find strong evidence for a cross-correlation parameter significantly below one in this galaxy sample, except possibly at the lowest redshift bin (z ~ 0.3), where we find r = 0.71 ± 0.11 when using tpz, and 0.83 ± 0.12 with bpz.« less

Galaxy bias from galaxy-galaxy lensing in the DES science verification data

NASA Astrophysics Data System (ADS)

Prat, J.; Sánchez, C.; Miquel, R.; Kwan, J.; Blazek, J.; Bonnett, C.; Amara, A.; Bridle, S. L.; Clampitt, J.; Crocce, M.; Fosalba, P.; Gaztanaga, E.; Giannantonio, T.; Hartley, W. G.; Jarvis, M.; MacCrann, N.; Percival, W. J.; Ross, A. J.; Sheldon, E.; Zuntz, J.; Abbott, T. M. C.; Abdalla, F. B.; Annis, J.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Burke, D. L.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Castander, F. J.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Fausti Neto, A.; Flaugher, B.; 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.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Nord, B.; Plazas, A. A.; Reil, K.; Romer, A. K.; Roodman, A.; 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.

2018-01-01

We present a measurement of galaxy-galaxy lensing around a magnitude-limited (iAB < 22.5) sample of galaxies from the dark energy survey science verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias b and cross-correlation coefficient between the galaxy and dark matter overdensity fields r in each bin, using scales above 4 h-1 Mpc comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering and CMB lensing for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al., while, in the lowest redshift bin (z ∼ 0.3), they show some tension with the findings in Giannantonio et al. We measure b · r to be 0.87 ± 0.11, 1.12 ± 0.16 and 1.24 ± 0.23, respectively, for the three redshift bins of width Δz = 0.2 in the range 0.2 < z < 0.8, defined with the photometric-redshift algorithm BPZ. Using a different code to split the lens sample, TPZ, leads to changes in the measured biases at the 10-20 per cent level, but it does not alter the main conclusion of this work: when comparing with Crocce et al. we do not find strong evidence for a cross-correlation parameter significantly below one in this galaxy sample, except possibly at the lowest redshift bin (z ∼ 0.3), where we find r = 0.71 ± 0.11 when using TPZ, and 0.83 ± 0.12 with BPZ.

A large sample of shear-selected clusters from the Hyper Suprime-Cam Subaru Strategic Program S16A Wide field mass maps

NASA Astrophysics Data System (ADS)

Miyazaki, Satoshi; Oguri, Masamune; Hamana, Takashi; Shirasaki, Masato; Koike, Michitaro; Komiyama, Yutaka; Umetsu, Keiichi; Utsumi, Yousuke; Okabe, Nobuhiro; More, Surhud; Medezinski, Elinor; Lin, Yen-Ting; Miyatake, Hironao; Murayama, Hitoshi; Ota, Naomi; Mitsuishi, Ikuyuki

2018-01-01

We present the result of searching for clusters of galaxies based on weak gravitational lensing analysis of the ˜160 deg2 area surveyed by Hyper Suprime-Cam (HSC) as a Subaru Strategic Program. HSC is a new prime focus optical imager with a 1.5°-diameter field of view on the 8.2 m Subaru telescope. The superb median seeing on the HSC i-band images of 0.56" allows the reconstruction of high angular resolution mass maps via weak lensing, which is crucial for the weak lensing cluster search. We identify 65 mass map peaks with a signal-to-noise (S/N) ratio larger than 4.7, and carefully examine their properties by cross-matching the clusters with optical and X-ray cluster catalogs. We find that all the 39 peaks with S/N > 5.1 have counterparts in the optical cluster catalogs, and only 2 out of the 65 peaks are probably false positives. The upper limits of X-ray luminosities from the ROSAT All Sky Survey (RASS) imply the existence of an X-ray underluminous cluster population. We show that the X-rays from the shear-selected clusters can be statistically detected by stacking the RASS images. The inferred average X-ray luminosity is about half that of the X-ray-selected clusters of the same mass. The radial profile of the dark matter distribution derived from the stacking analysis is well modeled by the Navarro-Frenk-White profile with a small concentration parameter value of c500 ˜ 2.5, which suggests that the selection bias on the orientation or the internal structure for our shear-selected cluster sample is not strong.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kettula, K.; Finoguenov, A.; Massey, R.

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 anmore » 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.« less

Gravitational Lensing 2.0

NASA Astrophysics Data System (ADS)

Wittman, David M.; Benson, Bryant

2018-06-01

Weak lensing analyses use the image---the intensity field---of a distant galaxy to infer gravitational effects on that line of sight. What if we analyze the velocity field instead? We show that lensing imprints much more information onto a highly ordered velocity field, such as that of a rotating disk galaxy, than onto an intensity field. This is because shuffling intensity pixels yields a post-lensed image quite similar to an unlensed galaxy with a different orientation, a problem known as "shape noise." We show that velocity field analysis can eliminate shape noise and yield much more precise lensing constraints. Furthermore, convergence as well as shear can be constrained using the same target, and there is no need to assume the weak lensing limit of small convergence. We present Fisher matrix forecasts of the precision achievable with this method. Velocity field observations are expensive, so we derive guidelines for choosing suitable targets by exploring how precision varies with source parameters such as inclination angle and redshift. Finally, we present simulations that support our Fisher matrix forecasts.

Cluster-lensing: A Python Package for Galaxy Clusters and Miscentering

NASA Astrophysics Data System (ADS)

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/.

Investigations of Galaxy Clusters Using Gravitational Lensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiesner, Matthew P.

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 andmore » 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.« less

Weak-Lensing Detection of Cl 1604+4304 at z=0.90

NASA Astrophysics Data System (ADS)

Margoniner, V. E.; Lubin, L. M.; Wittman, D. M.; Squires, G. K.

2005-01-01

We present a weak-lensing analysis of the high-redshift cluster Cl 1604+4304. At z=0.90, this is the highest redshift cluster yet detected with weak lensing. It is also one of a sample of high-redshift, optically selected clusters whose X-ray temperatures are lower than expected based on their velocity dispersions. Both the gas temperature and galaxy velocity dispersion are proxies for its mass, which can be determined more directly by a lensing analysis. Modeling the cluster as a singular isothermal sphere, we find that the mass contained within projected radius R is (3.69+/-1.47)[R/(500 kpc)]×1014 Msolar. This corresponds to an inferred velocity dispersion of 1004+/-199 km s-1, which agrees well with the velocity dispersion of 989+98-76 km s-1 recently measured by Gal & Lubin. These numbers are higher than the 575+110-85 km s-1 inferred from Cl 1604+4304's X-ray temperature; however, all three velocity dispersion estimates are consistent within ~1.9 σ.

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

NASA Astrophysics Data System (ADS)

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

2009-04-01

We study the correlation between the locations of galaxy-galaxy strong-lensing candidates and tracers of large-scale structure from both weak lensing (WL) or X-ray emission. The Cosmological Evolution Survey (COSMOS) is a unique data set, combining deep, high resolution and contiguous imaging in which strong lenses have been discovered, plus unparalleled multiwavelength coverage. To help interpret the COSMOS data, we have also produced mock COSMOS strong- and WL observations, based on ray-tracing through the Millennium 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 observation is not true of the simulations, which predict an increasing fraction of strong lenses in dense environments. The discrepancy may be a real effect, but could also be explained by various limitations of our analysis. For example, our visual search of strong lens systems could be incomplete and suffer from selection bias; the luminosity function of elliptical galaxies may differ between our real and simulated data; or the simplifying assumptions and approximations used in our lensing simulations may be inadequate. Work is therefore ongoing. Automated searches for strong lens systems will be particularly important in better constraining the selection function.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marrone, Daniel P.; Carlstrom, John E.; Gralla, Megan

2012-08-01

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tessore, Nicolas; Metcalf, R. Benton; Winther, Hans A.

A number of alternatives to general relativity exhibit gravitational screening in the non-linear regime of structure formation. We describe a set of algorithms that can produce weak lensing maps of large scale structure in such theories and can be used to generate mock surveys for cosmological analysis. By analysing a few basic statistics we indicate how these alternatives can be distinguished from general relativity with future weak lensing surveys.

Weak lensing measurement of the mass–richness relation of SDSS redMaPPer clusters

DOE PAGES

Simet, Melanie; McClintock, Tom; Mandelbaum, Rachel; ...

2016-12-15

Here, 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 carefully characterized a broad range of systematic uncertainties, including shear calibration errors, photo-zz biases, dilution by member galaxies, source obscuration, magnification bias, incorrect assumptions about cluster mass profiles, cluster centering, halo triaxiality, and projection effects. We then 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 ≤ zz ≤ 0.33, the normalization of our power-law mass vs. λ relation is log 10[M 200m/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+0.09-0.101.33more » $$+0.09\\atop{-0.10}$$ (1σ). Finally, the detailed systematics characterization in this work renders it the definitive weak lensing mass calibration for SDSS redMaPPer clusters at this time.« less

Hubble confirms cosmic acceleration with weak lensing

NASA Image and Video Library

2017-12-08

NASA/ESA Hubble Release Date: March 25, 2010 This image shows a smoothed reconstruction of the total (mostly dark) matter distribution in the COSMOS field, created from data taken by the NASA/ESA Hubble Space Telescope and ground-based telescopes. It was inferred from the weak gravitational lensing distortions that are imprinted onto the shapes of background galaxies. The colour coding indicates the distance of the foreground mass concentrations as gathered from the weak lensing effect. Structures shown in white, cyan, and green are typically closer to us than those indicated in orange and red. To improve the resolution of the map, data from galaxies both with and without redshift information were used. The new study presents the most comprehensive analysis of data from the COSMOS survey. The researchers have, for the first time ever, used Hubble and the natural "weak lenses" in space to characterise the accelerated expansion of the Universe. Credit: NASA, ESA, P. Simon (University of Bonn) and T. Schrabback (Leiden Observatory) To learn more abou this image go to: www.spacetelescope.org/news/html/heic1005.html For more information about Goddard Space Flight Center go here: www.nasa.gov/centers/goddard/home/index.html

LoCuSS: comparison of observed X-ray and lensing galaxy cluster scaling relations with simulations

NASA Astrophysics Data System (ADS)

Zhang, Y.-Y.; Finoguenov, A.; Böhringer, H.; Kneib, J.-P.; Smith, G. P.; Kneissl, R.; Okabe, N.; Dahle, H.

2008-05-01

The Local Cluster Substructure Survey (LoCuSS, Smith et al.) is a systematic multi-wavelength survey of more than 100 X-ray luminous galaxy clusters in the redshift range 0.14-0.3 selected from the ROSAT All Sky Survey. We used data on 37 LoCuSS clusters from the XMM-Newton archive to investigate the global scaling relations of galaxy clusters. The scaling relations based solely on the X-ray data (S-T, S-Y_X, P-Y_X, M-T, M-Y_X, M-M_gas, M_gas-T, L-T, L-Y_X, and L-M) obey empirical self-similarity and reveal no additional evolution beyond the large-scale structure growth. They also reveal up to 17 per cent segregation between all 37 clusters and non-cool core clusters. Weak lensing mass measurements are also available in the literature for 19 of the clusters with XMM-Newton data. The average of the weak lensing mass to X-ray based mass ratio is 1.09± 0.08, setting the limit of the non-thermal pressure support to 9 ± 8 per cent. The mean of the weak lensing mass to X-ray based mass ratio of these clusters is ~1, indicating good agreement between X-ray and weak lensing masses for most clusters, although with 31-51 per cent scatter. The scatter in the mass-observable relations (M-Y_X, M-M_gas, and M-T) is smaller using X-ray based masses than using weak lensing masses by a factor of 2. With the scaled radius defined by the YX profile - r500 Y_X,X, r500YX,wl, and r500Y_X,si, we obtain lower scatter in the weak lensing mass based mass-observable relations, which means the origin of the scatter is M^wl and MX instead of Y_X. The normalization of the M-YX relation using X-ray mass estimates is lower than the one from simulations by up to 18-24 per cent at 3σ significance. This agrees with the M-YX relation based on weak lensing masses, the normalization of the latter being ~20 per cent lower than the one from simulations at ~2σ significance. This difference between observations and simulations is also indicated in the M-M_gas and M-T relations. Despite the large scatter in the comparison of X-ray to lensing, the agreement between these two completely independent observational methods is an important step towards controlling astrophysical and measurement systematics in cosmological scaling relations. This work is based on observations made with the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA). Appendices A-C are only available in electronic form at http://www.aanda.org

Neutrino mass and dark energy from weak lensing.

PubMed

Abazajian, Kevork N; Dodelson, Scott

2003-07-25

Weak gravitational lensing of background galaxies by intervening matter directly probes the mass distribution in the Universe. This distribution is sensitive to both the dark energy and neutrino mass. We examine the potential of lensing experiments to measure features of both simultaneously. Focusing on the radial information contained in a future deep 4000 deg(2) survey, we find that the expected (1-sigma) error on a neutrino mass is 0.1 eV, if the dark-energy parameters are allowed to vary. The constraints on dark-energy parameters are similarly restrictive, with errors on w of 0.09.

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

DOE PAGES

Gruen, D.; Brimioulle, F.

2017-02-23

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 paper, 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 colour. We use this framework to quantify biases in empirically estimated p(z) caused bymore » selection effects present in realistic reference and weak lensing source catalogues, 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 clusters, and for depths and filter combinations appropriate for ongoing lensing surveys, we find that (1) spectroscopic selection can cause biases above the 10 per cent level, which can be reduced to ≈5 per cent by optimal lensing weighting, while (2) selection effects in the shape catalogue bias mass estimates at or below the 2 per cent level. Finally, this illustrates the importance of completeness of the reference catalogues for empirical redshift estimation.« less

Robust covariance estimation of galaxy-galaxy weak lensing: validation and limitation of jackknife covariance

NASA Astrophysics Data System (ADS)

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

2017-09-01

We develop a method to simulate galaxy-galaxy weak lensing by utilizing all-sky, light-cone simulations and their inherent halo catalogues. Using the mock catalogue to study the error covariance matrix of galaxy-galaxy weak lensing, we compare the full covariance with the 'jackknife' (JK) covariance, the method often used in the literature that estimates the covariance from the resamples of the data itself. We show that there exists the variation of JK covariance over realizations of mock lensing measurements, while the average JK covariance over mocks can give a reasonably accurate estimation of the true covariance up to separations comparable with the size of JK subregion. The scatter in JK covariances is found to be ∼10 per cent after we subtract the lensing measurement around random points. However, the JK method tends to underestimate the covariance at the larger separations, more increasingly for a survey with a higher number density of source galaxies. We apply our method to the Sloan Digital Sky Survey (SDSS) data, and show that the 48 mock SDSS catalogues nicely reproduce the signals and the JK covariance measured from the real data. We then argue that the use of the accurate covariance, compared to the JK covariance, allows us to use the lensing signals at large scales beyond a size of the JK subregion, which contains cleaner cosmological information in the linear regime.

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

NASA Astrophysics Data System (ADS)

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

2009-08-01

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

MATTER IN THE BEAM: WEAK LENSING, SUBSTRUCTURES, AND THE TEMPERATURE OF DARK MATTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahdi, Hareth S.; Elahi, Pascal J.; Lewis, Geraint F.

2016-08-01

Warm dark matter (WDM) models offer an attractive alternative to the current cold dark matter (CDM) cosmological model. We present a novel method to differentiate between WDM and CDM cosmologies, namely, using weak lensing; this provides a unique probe as it is sensitive to all of the “matter in the beam,” not just dark matter haloes and the galaxies that reside in them, but also the diffuse material between haloes. We compare the weak lensing maps of CDM clusters to those in a WDM model corresponding to a thermally produced 0.5 keV dark matter particle. Our analysis clearly shows thatmore » the weak lensing magnification, convergence, and shear distributions can be used to distinguish between CDM and WDM models. WDM models increase the probability of weak magnifications, with the differences being significant to ≳5 σ , while leaving no significant imprint on the shear distribution. WDM clusters analyzed in this work are more homogeneous than CDM ones, and the fractional decrease in the amount of material in haloes is proportional to the average increase in the magnification. This difference arises from matter that would be bound in compact haloes in CDM being smoothly distributed over much larger volumes at lower densities in WDM. Moreover, the signature does not solely lie in the probability distribution function but in the full spatial distribution of the convergence field.« less

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

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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

2014-10-01

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

Dark Energy Survey Year 1 Results: Cross-Correlation Redshifts - Methods and Systematics Characterization

DOE PAGES

Gatti, M.

2018-02-22

We use numerical simulations to characterize the performance of a clustering-based method to calibrate photometric redshift biases. In particular, we cross-correlate the weak lensing (WL) source galaxies from the Dark Energy Survey Year 1 (DES Y1) sample with redMaGiC galaxies (luminous red galaxies with secure photometric red- shifts) to estimate the redshift distribution of the former sample. The recovered redshift distributions are used to calibrate the photometric redshift bias of standard photo-z methods applied to the same source galaxy sample. We also apply the method to three photo-z codes run in our simulated data: Bayesian Photometric Redshift (BPZ), Directional Neighborhoodmore » Fitting (DNF), and Random Forest-based photo-z (RF). We characterize the systematic uncertainties of our calibration procedure, and find that these systematic uncertainties dominate our error budget. The dominant systematics are due to our assumption of unevolving bias and clustering across each redshift bin, and to differences between the shapes of the redshift distributions derived by clustering vs photo-z's. The systematic uncertainty in the mean redshift bias of the source galaxy sample is z ≲ 0.02, though the precise value depends on the redshift bin under consideration. Here, we discuss possible ways to mitigate the impact of our dominant systematics in future analyses.« less

Dark Energy Survey Year 1 Results: Cross-Correlation Redshifts - Methods and Systematics Characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gatti, M.

We use numerical simulations to characterize the performance of a clustering-based method to calibrate photometric redshift biases. In particular, we cross-correlate the weak lensing (WL) source galaxies from the Dark Energy Survey Year 1 (DES Y1) sample with redMaGiC galaxies (luminous red galaxies with secure photometric red- shifts) to estimate the redshift distribution of the former sample. The recovered redshift distributions are used to calibrate the photometric redshift bias of standard photo-z methods applied to the same source galaxy sample. We also apply the method to three photo-z codes run in our simulated data: Bayesian Photometric Redshift (BPZ), Directional Neighborhoodmore » Fitting (DNF), and Random Forest-based photo-z (RF). We characterize the systematic uncertainties of our calibration procedure, and find that these systematic uncertainties dominate our error budget. The dominant systematics are due to our assumption of unevolving bias and clustering across each redshift bin, and to differences between the shapes of the redshift distributions derived by clustering vs photo-z's. The systematic uncertainty in the mean redshift bias of the source galaxy sample is z ≲ 0.02, though the precise value depends on the redshift bin under consideration. Here, we discuss possible ways to mitigate the impact of our dominant systematics in future analyses.« less

Invited Review Article: Development of crystal lenses for energetic photons

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smither, Robert K.

2014-08-15

This paper follows the development of crystal diffraction lenses designed to focus energetic photons. It begins with the search for a solution to the astrophysics problem of how to detect weak astrophysics sources of gamma rays and x-rays. This led to the basic designs for a lens and to the understanding of basic limitations of lens design. The discussion of the development of crystal diffraction lenses is divided into two parts: lenses using crystals with mosaic structure, and lenses that use crystals with curved crystal planes. This second group divides into two sub-groups: (1) Curved crystals that are used tomore » increase the acceptance angle of the diffraction of a monochromatic beam and to increase the energy bandwidth of the diffraction. (2) Curved crystals used to focus gamma ray beams. The paper describes how these two types of crystals affect the design of the corresponding crystal lenses in different fields: astrophysics, medical imaging, detection of weak, distant, gamma-ray sources, etc. The designs of crystal lenses for these applications are given in enough detail to allow the reader to design a lens for his own application.« less

Sunyaev-Zel'dovich Effect and X-ray Scaling Relations from Weak-Lensing Mass Calibration of 32 SPT Selected Galaxy Clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dietrich, J.P.; et al.

Uncertainty in the mass-observable scaling relations is currently the limiting factor for galaxy cluster based cosmology. Weak gravitational lensing can provide a direct mass calibration and reduce the mass uncertainty. We present new ground-based weak lensing observations of 19 South Pole Telescope (SPT) selected clusters and combine them with previously reported space-based observations of 13 galaxy clusters to constrain the cluster mass scaling relations with the Sunyaev-Zel'dovich effect (SZE), the cluster gas massmore » $$M_\\mathrm{gas}$$, and $$Y_\\mathrm{X}$$, the product of $$M_\\mathrm{gas}$$ and X-ray temperature. We extend a previously used framework for the analysis of scaling relations and cosmological constraints obtained from SPT-selected clusters to make use of weak lensing information. We introduce a new approach to estimate the effective average redshift distribution of background galaxies and quantify a number of systematic errors affecting the weak lensing modelling. These errors include a calibration of the bias incurred by fitting a Navarro-Frenk-White profile to the reduced shear using $N$-body simulations. We blind the analysis to avoid confirmation bias. We are able to limit the systematic uncertainties to 6.4% in cluster mass (68% confidence). Our constraints on the mass-X-ray observable scaling relations parameters are consistent with those obtained by earlier studies, and our constraints for the mass-SZE scaling relation are consistent with the the simulation-based prior used in the most recent SPT-SZ cosmology analysis. We can now replace the external mass calibration priors used in previous SPT-SZ cosmology studies with a direct, internal calibration obtained on the same clusters.« less

Modeling fine-scale geological heterogeneity--examples of sand lenses in tills.

PubMed

Kessler, Timo Christian; Comunian, Alessandro; Oriani, Fabio; Renard, Philippe; Nilsson, Bertel; Klint, Knud Erik; Bjerg, Poul Løgstrup

2013-01-01

Sand lenses at various spatial scales are recognized to add heterogeneity to glacial sediments. They have high hydraulic conductivities relative to the surrounding till matrix and may affect the advective transport of water and contaminants in clayey till settings. Sand lenses were investigated on till outcrops producing binary images of geological cross-sections capturing the size, shape and distribution of individual features. Sand lenses occur as elongated, anisotropic geobodies that vary in size and extent. Besides, sand lenses show strong non-stationary patterns on section images that hamper subsequent simulation. Transition probability (TP) and multiple-point statistics (MPS) were employed to simulate sand lens heterogeneity. We used one cross-section to parameterize the spatial correlation and a second, parallel section as a reference: it allowed testing the quality of the simulations as a function of the amount of conditioning data under realistic conditions. The performance of the simulations was evaluated on the faithful reproduction of the specific geological structure caused by sand lenses. Multiple-point statistics offer a better reproduction of sand lens geometry. However, two-dimensional training images acquired by outcrop mapping are of limited use to generate three-dimensional realizations with MPS. One can use a technique that consists in splitting the 3D domain into a set of slices in various directions that are sequentially simulated and reassembled into a 3D block. The identification of flow paths through a network of elongated sand lenses and the impact on the equivalent permeability in tills are essential to perform solute transport modeling in the low-permeability sediments. © 2012, The Author(s). Groundwater © 2012, National Ground Water Association.

The DES Science Verification Weak Lensing Shear Catalogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarvis, M.

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 also 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 SVmore » data. Furthermore, we 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.« less

The DES Science Verification Weak Lensing Shear Catalogs

DOE PAGES

Jarvis, M.

2016-05-01

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 also 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 SVmore » data. Furthermore, we 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.« less

Reconstruction of cluster masses using particle based lensing

NASA Astrophysics Data System (ADS)

Deb, Sanghamitra

Clusters of galaxies are among the richest astrophysical data systems, but to truly understand these systems, we need a detailed study of the relationship between observables and the underlying cluster dark matter distribution. Gravitational lensing is the most direct probe of dark matter, but many mass reconstruction techniques assume that cluster light traces mass, or combine different lensing signals in an ad hoc way. In this talk, we will describe "Particle Based Lensing" (PBL), a new method for cluster mass reconstruction, that avoids many of the pitfalls of previous techniques. PBL optimally combines lensing information of varying signal-to-noise, and makes no assumptions about the relationship between mass and light. We will describe mass reconstructions in three very different, but very illuminating cluster systems: the "Bullet Cluster" (lE 0657-56), A901/902 and A1689. The "Bullet Cluster" is a system of merging clusters made famous by the first unambiguous lensing detection of dark matter. A901/902 is a multi-cluster system with four peaks, and provides an ideal laboratory for studying cluster interaction. We are particularly interested in measuring and correlating the dark matter clump ellipticities. A1689 is one of the richest clusters known, and has significant substructure at the core. It is also my first exercise in optimally combining weak and strong gravitational lensing in a cluster reconstruction. We find that the dark matter distribution is significantly clumpier than indicated by X-ray maps of the gas. We conclude by discussing various potential applications of PBL to existing and future data.

Time delay and magnification centroid due to gravitational lensing by black holes and naked singularities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Virbhadra, K. S.; Keeton, C. R.; Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854

We model the massive dark object at the center of the Galaxy as a Schwarzschild black hole as well as Janis-Newman-Winicour naked singularities, characterized by the mass and scalar charge parameters, and study gravitational lensing (particularly time delay, magnification centroid, and total magnification) by them. We find that the lensing features are qualitatively similar (though quantitatively different) for Schwarzschild black holes, weakly naked, and marginally strongly naked singularities. However, the lensing characteristics of strongly naked singularities are qualitatively very different from those due to Schwarzschild black holes. The images produced by Schwarzschild black hole lenses and weakly naked and marginallymore » strongly naked singularity lenses always have positive time delays. On the other hand, strongly naked singularity lenses can give rise to images with positive, zero, or negative time delays. In particular, for a large angular source position the direct image (the outermost image on the same side as the source) due to strongly naked singularity lensing always has a negative time delay. We also found that the scalar field decreases the time delay and increases the total magnification of images; this result could have important implications for cosmology. As the Janis-Newman-Winicour metric also describes the exterior gravitational field of a scalar star, naked singularities as well as scalar star lenses, if these exist in nature, will serve as more efficient cosmic telescopes than regular gravitational lenses.« less

Dark Energy Survey Year 1 Results: redshift distributions of the weak-lensing source galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hoyle, B.; Gruen, D.; Bernstein, G. M.

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 distributionsmore » $$n^i_{PZ}(z)$$ 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« less

Dark Energy Survey Year 1 Results: redshift distributions of the weak-lensing source galaxies

DOE PAGES

Hoyle, B.; Gruen, D.; Bernstein, G. M.; ...

2018-04-18

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 distributionsmore » $$n^i_{PZ}(z)$$ 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« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 distributionsmore » $$n^i_{PZ}(z)$$ 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« less

Probing supervoids with weak lensing

NASA Astrophysics Data System (ADS)

Higuchi, Yuichi; Inoue, Kaiki Taro

2018-05-01

The cosmic microwave background (CMB) has non-Gaussian features in the temperature fluctuations. An anomalous cold spot surrounded with a hot ring, called the Cold Spot, is one of such features. If a large underdense region (supervoid) resides towards the Cold Spot, we would be able to detect a systematic shape distortion in the images of background source galaxies via weak lensing effect. In order to estimate the detectability of such signals, we used the data of N-body simulations to simulate full-sky ray-tracing of source galaxies. We searched for a most prominent underdense region using the simulated convergence maps smoothed at a scale of 20° and obtained tangential shears around it. The lensing signal expected in a concordant Λ cold dark matter model can be detected at a signal-to-noise ratio S/N ˜ 3. If a supervoid with a radius of ˜200 h-1 Mpc and a density contrast δ0 ˜ -0.3 at the centre resides at a redshift z ˜ 0.2, on-going and near-future weak gravitational lensing surveys would detect a lensing signal with S/N ≳ 4 without resorting to stacking. From the tangential shear profile, we can obtain a constraint on the projected mass distribution of the supervoid.

KiDS-450: cosmological constraints from weak lensing peak statistics - I. Inference from analytical prediction of high signal-to-noise ratio convergence peaks

NASA Astrophysics Data System (ADS)

Shan, HuanYuan; Liu, Xiangkun; Hildebrandt, Hendrik; Pan, Chuzhong; Martinet, Nicolas; Fan, Zuhui; Schneider, Peter; Asgari, Marika; Harnois-Déraps, Joachim; Hoekstra, Henk; Wright, Angus; Dietrich, Jörg P.; Erben, Thomas; Getman, Fedor; Grado, Aniello; Heymans, Catherine; Klaes, Dominik; Kuijken, Konrad; Merten, Julian; Puddu, Emanuella; Radovich, Mario; Wang, Qiao

2018-02-01

This paper is the first of a series of papers constraining cosmological parameters with weak lensing peak statistics using ˜ 450 deg2 of imaging data from the Kilo Degree Survey (KiDS-450). We measure high signal-to-noise ratio (SNR: ν) weak lensing convergence peaks in the range of 3 < ν < 5, and employ theoretical models to derive expected values. These models are validated using a suite of simulations. We take into account two major systematic effects, the boost factor and the effect of baryons on the mass-concentration relation of dark matter haloes. In addition, we investigate the impacts of other potential astrophysical systematics including the projection effects of large-scale structures, intrinsic galaxy alignments, as well as residual measurement uncertainties in the shear and redshift calibration. Assuming a flat Λ cold dark matter model, we find constraints for S_8=σ _8(Ω _m/0.3)^{0.5}=0.746^{+0.046}_{-0.107} according to the degeneracy direction of the cosmic shear analysis and Σ _8=σ _8(Ω _m/0.3)^{0.38}=0.696^{+0.048}_{-0.050} based on the derived degeneracy direction of our high-SNR peak statistics. The difference between the power index of S8 and in Σ8 indicates that combining cosmic shear with peak statistics has the potential to break the degeneracy in σ8 and Ωm. Our results are consistent with the cosmic shear tomographic correlation analysis of the same data set and ˜2σ lower than the Planck 2016 results.

The Double Galaxy Cluster A2465. III. X-Ray and Weak-lensing Observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wegner, Gary A.; Umetsu, Keiichi; Molnar, Sandor M.

We report Chandra X-ray observations and optical weak-lensing measurements from Subaru/Suprime-Cam images of the double galaxy cluster A2465 ( z = 0.245). The X-ray brightness data are fit to a β model to obtain the radial gas density profiles of the northeast (NE) and southwest (SW) subcomponents, which are seen to differ in structure. We determine core radii, central temperatures, the gas masses within r {sub 500c}, and the total masses for the broader NE and sharper SW components assuming hydrostatic equilibrium. There is no large X-ray excess between the two components. The central entropy of the NE subcluster ismore » about two times higher than the SW. Along with its structural properties and an apparent radio halo that is a sign of a merger, this suggests that the NE component has undergone merging on its own. The weak-lensing analysis gives virial masses for each substructure, which compare well with earlier dynamical results. The derived outer mass contours of the SW sub-component from weak lensing are more irregular and extended than those of the NE. Although there is a weak enhancement and small offsets between X-ray gas and mass centers from weak lensing, the lack of large amounts of gas between the two subclusters indicates that A2465 is in a pre-merger state. We discuss star formation enhancement in this system resulting from its dynamics and shock-induced star formation scenarios. A dynamical model that is consistent with the observed cluster data, based on the FLASH program and the radial infall model, is constructed, where the subclusters currently separated by ∼1.2 Mpc are approaching each other at ∼2000 km s{sup −1} and will meet in ∼0.4 Gyr.« less

The Double Galaxy Cluster A2465. III. X-Ray and Weak-lensing Observations

NASA Astrophysics Data System (ADS)

Wegner, Gary A.; Umetsu, Keiichi; Molnar, Sandor M.; Nonino, Mario; Medezinski, Elinor; Andrade-Santos, Felipe; Bogdan, Akos; Lovisari, Lorenzo; Forman, William R.; Jones, Christine

2017-07-01

We report Chandra X-ray observations and optical weak-lensing measurements from Subaru/Suprime-Cam images of the double galaxy cluster A2465 (z = 0.245). The X-ray brightness data are fit to a β model to obtain the radial gas density profiles of the northeast (NE) and southwest (SW) subcomponents, which are seen to differ in structure. We determine core radii, central temperatures, the gas masses within r 500c, and the total masses for the broader NE and sharper SW components assuming hydrostatic equilibrium. There is no large X-ray excess between the two components. The central entropy of the NE subcluster is about two times higher than the SW. Along with its structural properties and an apparent radio halo that is a sign of a merger, this suggests that the NE component has undergone merging on its own. The weak-lensing analysis gives virial masses for each substructure, which compare well with earlier dynamical results. The derived outer mass contours of the SW sub-component from weak lensing are more irregular and extended than those of the NE. Although there is a weak enhancement and small offsets between X-ray gas and mass centers from weak lensing, the lack of large amounts of gas between the two subclusters indicates that A2465 is in a pre-merger state. We discuss star formation enhancement in this system resulting from its dynamics and shock-induced star formation scenarios. A dynamical model that is consistent with the observed cluster data, based on the FLASH program and the radial infall model, is constructed, where the subclusters currently separated by ˜1.2 Mpc are approaching each other at ˜2000 km s-1 and will meet in ˜0.4 Gyr. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.

MEASURING LENSING MAGNIFICATION OF QUASARS BY LARGE SCALE STRUCTURE USING THE VARIABILITY-LUMINOSITY RELATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauer, Anne H.; Seitz, Stella; Jerke, Jonathan

2011-05-10

We introduce a technique to measure gravitational lensing magnification using the variability of type I quasars. Quasars' variability amplitudes and luminosities are tightly correlated, on average. Magnification due to gravitational lensing increases the quasars' apparent luminosity, while leaving the variability amplitude unchanged. Therefore, the mean magnification of an ensemble of quasars can be measured through the mean shift in the variability-luminosity relation. As a proof of principle, we use this technique to measure the magnification of quasars spectroscopically identified in the Sloan Digital Sky Survey (SDSS), due to gravitational lensing by galaxy clusters in the SDSS MaxBCG catalog. The Palomar-QUESTmore » Variability Survey, reduced using the DeepSky pipeline, provides variability data for the sources. We measure the average quasar magnification as a function of scaled distance (r/R{sub 200}) from the nearest cluster; our measurements are consistent with expectations assuming Navarro-Frenk-White cluster profiles, particularly after accounting for the known uncertainty in the clusters' centers. Variability-based lensing measurements are a valuable complement to shape-based techniques because their systematic errors are very different, and also because the variability measurements are amenable to photometric errors of a few percent and to depths seen in current wide-field surveys. Given the volume data of the expected from current and upcoming surveys, this new technique has the potential to be competitive with weak lensing shear measurements of large-scale structure.« less

Scale dependence of galaxy biasing investigated by weak gravitational lensing: An assessment using semi-analytic galaxies and simulated lensing data

NASA Astrophysics Data System (ADS)

Simon, Patrick; Hilbert, Stefan

2018-05-01

Galaxies are biased tracers of the matter density on cosmological scales. For future tests of galaxy models, we refine and assess a method to measure galaxy biasing as a function of physical scale k with weak gravitational lensing. This method enables us to reconstruct the galaxy bias factor b(k) as well as the galaxy-matter correlation r(k) on spatial scales between 0.01 h Mpc-1 ≲ k ≲ 10 h Mpc-1 for redshift-binned lens galaxies below redshift z ≲ 0.6. In the refinement, we account for an intrinsic alignment of source ellipticities, and we correct for the magnification bias of the lens galaxies, relevant for the galaxy-galaxy lensing signal, to improve the accuracy of the reconstructed r(k). For simulated data, the reconstructions achieve an accuracy of 3-7% (68% confidence level) over the above k-range for a survey area and a typical depth of contemporary ground-based surveys. Realistically the accuracy is, however, probably reduced to about 10-15%, mainly by systematic uncertainties in the assumed intrinsic source alignment, the fiducial cosmology, and the redshift distributions of lens and source galaxies (in that order). Furthermore, our reconstruction technique employs physical templates for b(k) and r(k) that elucidate the impact of central galaxies and the halo-occupation statistics of satellite galaxies on the scale-dependence of galaxy bias, which we discuss in the paper. In a first demonstration, we apply this method to previous measurements in the Garching-Bonn Deep Survey and give a physical interpretation of the lens population.

Direct shear mapping - a new weak lensing tool

NASA Astrophysics Data System (ADS)

de Burgh-Day, C. O.; Taylor, E. N.; Webster, R. L.; Hopkins, A. M.

2015-08-01

We have developed a new technique called direct shear mapping (DSM) to measure gravitational lensing shear directly from observations of a single background source. The technique assumes the velocity map of an unlensed, stably rotating galaxy will be rotationally symmetric. Lensing distorts the velocity map making it asymmetric. The degree of lensing can be inferred by determining the transformation required to restore axisymmetry. This technique is in contrast to traditional weak lensing methods, which require averaging an ensemble of background galaxy ellipticity measurements, to obtain a single shear measurement. We have tested the efficacy of our fitting algorithm with a suite of systematic tests on simulated data. We demonstrate that we are in principle able to measure shears as small as 0.01. In practice, we have fitted for the shear in very low redshift (and hence unlensed) velocity maps, and have obtained null result with an error of ±0.01. This high-sensitivity results from analysing spatially resolved spectroscopic images (i.e. 3D data cubes), including not just shape information (as in traditional weak lensing measurements) but velocity information as well. Spirals and rotating ellipticals are ideal targets for this new technique. Data from any large Integral Field Unit (IFU) or radio telescope is suitable, or indeed any instrument with spatially resolved spectroscopy such as the Sydney-Australian-Astronomical Observatory Multi-Object Integral Field Spectrograph (SAMI), the Atacama Large Millimeter/submillimeter Array (ALMA), the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) and the Square Kilometer Array (SKA).

Anisotropic magnification distortion of the 3D galaxy correlation. I. Real space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hui, Lam; LoVerde, Marilena; Department of Physics, Columbia University, New York, New York 10027

2007-11-15

It has long been known that gravitational lensing, primarily via magnification bias, modifies the observed galaxy (or quasar) clustering. Such discussions have largely focused on the 2D angular correlation function. Here and in paper II [L. Hui, E. Gaztanaga, and M. LoVerde, arXiv:0710.4191] we explore how magnification bias distorts the 3D correlation function and power spectrum, as first considered by Matsubara [Astrophys. J. Lett. 537, L77 (2000).]. The interesting point is that the distortion is anisotropic. Magnification bias in general preferentially enhances the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. For instance, at a LOS separationmore » of {approx}100 Mpc/h, where the intrinsic galaxy-galaxy correlation is rather weak, the observed correlation can be enhanced by lensing by a factor of a few, even at a modest redshift of z{approx}0.35. This effect presents an interesting opportunity as well as a challenge. The opportunity: this lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification, and magnification-magnification correlations, without measuring galaxy shapes. The anisotropy is distinguishable from the well-known distortion due to peculiar motions, as will be discussed in paper II. The challenge: the magnification distortion of the galaxy correlation must be accounted for in interpreting data as precision improves. For instance, the {approx}100 Mpc/h baryon acoustic oscillation scale in the correlation function is shifted by up to {approx}3% in the LOS orientation, and up to {approx}0.6% in the monopole, depending on the galaxy bias, redshift, and number count slope. The corresponding shifts in the inferred Hubble parameter and angular diameter distance, if ignored, could significantly bias measurements of the dark energy equation of state. Lastly, magnification distortion offers a plausible explanation for the well-known excess correlations seen in pencil beam surveys.« less

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

NASA Astrophysics Data System (ADS)

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.

Mass and galaxy distributions of four massive galaxy clusters from Dark Energy Survey Science Verification data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melchior, P.; Suchyta, E.; Huff, E.

2015-03-31

We measure the weak-lensing masses and galaxy distributions of four massive galaxy clusters observed during the Science Verification phase of the Dark Energy Survey. This pathfinder study is meant to 1) validate the DECam imager for the task of measuring weak-lensing shapes, and 2) utilize DECam's large field of view to map out the clusters and their environments over 90 arcmin. We conduct a series of rigorous tests on astrometry, photometry, image quality, PSF modeling, and shear measurement accuracy to single out flaws in the data and also to identify the optimal data processing steps and parameters. We find Sciencemore » Verification data from DECam to be suitable for the lensing analysis described in this paper. The PSF is generally well-behaved, but the modeling is rendered difficult by a flux-dependent PSF width and ellipticity. We employ photometric redshifts to distinguish between foreground and background galaxies, and a red-sequence cluster finder to provide cluster richness estimates and cluster-galaxy distributions. By fitting NFW profiles to the clusters in this study, we determine weak-lensing masses that are in agreement with previous work. For Abell 3261, we provide the first estimates of redshift, weak-lensing mass, and richness. In addition, the cluster-galaxy distributions indicate the presence of filamentary structures attached to 1E 0657-56 and RXC J2248.7-4431, stretching out as far as 1 degree (approximately 20 Mpc), showcasing the potential of DECam and DES for detailed studies of degree-scale features on the sky.« less

Mass and galaxy distributions of four massive galaxy clusters from Dark Energy Survey Science Verification data

DOE PAGES

Melchior, P.; Suchyta, E.; Huff, E.; ...

2015-03-31

We measure the weak-lensing masses and galaxy distributions of four massive galaxy clusters observed during the Science Verification phase of the Dark Energy Survey. This pathfinder study is meant to 1) validate the DECam imager for the task of measuring weak-lensing shapes, and 2) utilize DECam's large field of view to map out the clusters and their environments over 90 arcmin. We conduct a series of rigorous tests on astrometry, photometry, image quality, PSF modelling, and shear measurement accuracy to single out flaws in the data and also to identify the optimal data processing steps and parameters. We find Sciencemore » Verification data from DECam to be suitable for the lensing analysis described in this paper. The PSF is generally well-behaved, but the modelling is rendered difficult by a flux-dependent PSF width and ellipticity. We employ photometric redshifts to distinguish between foreground and background galaxies, and a red-sequence cluster finder to provide cluster richness estimates and cluster-galaxy distributions. By fitting NFW profiles to the clusters in this study, we determine weak-lensing masses that are in agreement with previous work. For Abell 3261, we provide the first estimates of redshift, weak-lensing mass, and richness. Additionally, the cluster-galaxy distributions indicate the presence of filamentary structures attached to 1E 0657-56 and RXC J2248.7-4431, stretching out as far as 1degree (approximately 20 Mpc), showcasing the potential of DECam and DES for detailed studies of degree-scale features on the sky.« less

Weak gravitational lensing analysis of Sloan Digital Sky Survey data

NASA Astrophysics Data System (ADS)

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 that may constrain the underlying cosmological model. The results of this study are consistent with commonly accepted cosmological models.

The Projected Dark and Baryonic Ellipsoidal Structure of 20 CLASH Galaxy Clusters

NASA Astrophysics Data System (ADS)

Umetsu, Keiichi; Sereno, Mauro; Tam, Sut-Ieng; Chiu, I.-Non; Fan, Zuhui; Ettori, Stefano; Gruen, Daniel; Okumura, Teppei; Medezinski, Elinor; Donahue, Megan; Meneghetti, Massimo; Frye, Brenda; Koekemoer, Anton; Broadhurst, Tom; Zitrin, Adi; Balestra, Italo; Benítez, Narciso; Higuchi, Yuichi; Melchior, Peter; Mercurio, Amata; Merten, Julian; Molino, Alberto; Nonino, Mario; Postman, Marc; Rosati, Piero; Sayers, Jack; Seitz, Stella

2018-06-01

We reconstruct the two-dimensional (2D) matter distributions in 20 high-mass galaxy clusters selected from the CLASH survey by using the new approach of performing a joint weak gravitational lensing analysis of 2D shear and azimuthally averaged magnification measurements. This combination allows for a complete analysis of the field, effectively breaking the mass-sheet degeneracy. In a Bayesian framework, we simultaneously constrain the mass profile and morphology of each individual cluster, assuming an elliptical Navarro–Frenk–White halo characterized by the mass, concentration, projected axis ratio, and position angle (PA) of the projected major axis. We find that spherical mass estimates of the clusters from azimuthally averaged weak-lensing measurements in previous work are in excellent agreement with our results from a full 2D analysis. Combining all 20 clusters in our sample, we detect the elliptical shape of weak-lensing halos at the 5σ significance level within a scale of 2 {Mpc} {h}-1. The median projected axis ratio is 0.67 ± 0.07 at a virial mass of {M}vir}=(15.2+/- 2.8)× {10}14 {M}ȯ , which is in agreement with theoretical predictions from recent numerical simulations of the standard collisionless cold dark matter model. We also study misalignment statistics of the brightest cluster galaxy, X-ray, thermal Sunyaev–Zel’dovich effect, and strong-lensing morphologies with respect to the weak-lensing signal. Among the three baryonic tracers studied here, we find that the X-ray morphology is best aligned with the weak-lensing mass distribution, with a median misalignment angle of | {{Δ }}{PA}| =21^\\circ +/- 7^\\circ . We also conduct a stacked quadrupole shear analysis of the 20 clusters assuming that the X-ray major axis is aligned with that of the projected mass distribution. This yields a consistent axis ratio of 0.67 ± 0.10, suggesting again a tight alignment between the intracluster gas and dark matter. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.

Dark Energy Survey Year 1 Results: Calibration of redMaGiC Redshift Distributions in DES and SDSS from Cross-Correlations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cawthon, R.; et al.

We present calibrations of the redshift distributions of redMaGiC galaxies in the Dark Energy Survey Year 1 (DES Y1) and Sloan Digital Sky Survey (SDSS) DR8 data. These results determine the priors of the redshift distribution of redMaGiC galaxies, which were used for galaxy clustering measurements and as lenses for galaxy-galaxy lensing measurements in DES Y1 cosmological analyses. We empirically determine the bias in redMaGiC photometric redshift estimates using angular cross-correlations with Baryon Oscillation Spectroscopic Survey (BOSS) galaxies. For DES, we calibrate a single parameter redshift bias in three photometric redshift bins:more » $$z \\in[0.15,0.3]$$, [0.3,0.45], and [0.45,0.6]. Our best fit results in each bin give photometric redshift biases of $$|\\Delta z|<0.01$$. To further test the redMaGiC algorithm, we apply our calibration procedure to SDSS redMaGiC galaxies, where the statistical precision of the cross-correlation measurement is much higher due to a greater overlap with BOSS galaxies. For SDSS, we also find best fit results of $$|\\Delta z|<0.01$$. We compare our results to other analyses of redMaGiC photometric redshifts.« less

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

DOE PAGES

Liu, Jia; May, Morgan; Petri, Andrea; ...

2015-03-04

Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters Ω m, σ 8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build anmore » 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 (Ω m, σ 8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (Ω m, σ 8) plane reduces by a factor of ≈ two, compared to using the power spectrum alone. For a flat Λ cold dark matter model, combining both statistics, we obtain the constraint σ 8(Ω m/0.27)0.63 = 0.85 +0.03 -0.03.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jia; May, Morgan; Petri, Andrea

Lensing peaks have been proposed as a useful statistic, containing cosmological information from non-Gaussianities that is inaccessible from traditional two-point statistics such as the power spectrum or two-point correlation functions. Here we examine constraints on cosmological parameters from weak lensing peak counts, using the publicly available data from the 154 deg2 CFHTLenS survey. We utilize a new suite of ray-tracing N-body simulations on a grid of 91 cosmological models, covering broad ranges of the three parameters Ω m, σ 8, and w, and replicating the galaxy sky positions, redshifts, and shape noise in the CFHTLenS observations. We then build anmore » 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 (Ω m, σ 8, w) from both observables. We find that constraints from peak counts are comparable to those from the power spectrum, and somewhat tighter when different smoothing scales are combined. Neither observable can constrain w without external data. When the power spectrum and peak counts are combined, the area of the error “banana” in the (Ω m, σ 8) plane reduces by a factor of ≈ two, compared to using the power spectrum alone. For a flat Λ cold dark matter model, combining both statistics, we obtain the constraint σ 8(Ω m/0.27)0.63 = 0.85 +0.03 -0.03.« less

KiDS-450: cosmological constraints from weak-lensing peak statistics - II: Inference from shear peaks using N-body simulations

NASA Astrophysics Data System (ADS)

Martinet, Nicolas; Schneider, Peter; Hildebrandt, Hendrik; Shan, HuanYuan; Asgari, Marika; Dietrich, Jörg P.; Harnois-Déraps, Joachim; Erben, Thomas; Grado, Aniello; Heymans, Catherine; Hoekstra, Henk; Klaes, Dominik; Kuijken, Konrad; Merten, Julian; Nakajima, Reiko

2018-02-01

We study the statistics of peaks in a weak-lensing reconstructed mass map of the first 450 deg2 of the Kilo Degree Survey (KiDS-450). The map is computed with aperture masses directly applied to the shear field with an NFW-like compensated filter. We compare the peak statistics in the observations with that of simulations for various cosmologies to constrain the cosmological parameter S_8 = σ _8 √{Ω _m/0.3}, which probes the (Ωm, σ8) plane perpendicularly to its main degeneracy. We estimate S8 = 0.750 ± 0.059, using peaks in the signal-to-noise range 0 ≤ S/N ≤ 4, and accounting for various systematics, such as multiplicative shear bias, mean redshift bias, baryon feedback, intrinsic alignment, and shear-position coupling. These constraints are ˜ 25 per cent tighter than the constraints from the high significance peaks alone (3 ≤ S/N ≤ 4) which typically trace single-massive haloes. This demonstrates the gain of information from low-S/N peaks. However, we find that including S/N < 0 peaks does not add further information. Our results are in good agreement with the tomographic shear two-point correlation function measurement in KiDS-450. Combining shear peaks with non-tomographic measurements of the shear two-point correlation functions yields a ˜20 per cent improvement in the uncertainty on S8 compared to the shear two-point correlation functions alone, highlighting the great potential of peaks as a cosmological probe.

An assessment of the measurement of the Lense Thirring effect in the Earth gravity field, in reply to: “On the measurement of the Lense Thirring effect using the nodes of the LAGEOS satellites, in reply to “On the reliability of the so far performed tests for measuring the Lense Thirring effect with the LAGEOS satellites” by L. Iorio,” by I. Ciufolini and E. Pavlis

NASA Astrophysics Data System (ADS)

Iorio, L.

2007-03-01

In this paper we reply to recent claims by Ciufolini and Pavlis about certain aspects of the measurement of the general relativistic Lense-Thirring effect in the gravitational field of the Earth. (I) The proposal by such authors of using the existing satellites endowed with some active mechanism of compensation of the non-gravitational perturbations as an alternative strategy to improve the currently ongoing Lense-Thirring tests is unfeasible because of the impact of the uncancelled even zonal harmonics of the geopotential and of some time-dependent tidal perturbations. (II) It is shown that their criticisms about the possibility of using the existing altimeter Jason-1 and laser-ranged Ajisai satellites are groundless. (III) Ciufolini and Pavlis also claimed that we would have explicitly proposed to use the mean anomaly of the LAGEOS satellites in order to improve the accuracy of the Lense-Thirring tests. We prove that it is false. In regard to the mean anomaly of the LAGEOS satellites, Ciufolini himself did use such an orbital element in some previously published tests. About the latest test performed with the LAGEOS satellites, (IV) we discuss the cross-coupling between the inclination errors and the first even zonal harmonic as another possible source of systematic error affecting it with an additional 9% bias. (V) Finally, we stress the weak points of the claims about the origin of the two-nodes LAGEOS-LAGEOS II combination used in that test.

Gravitational lensing frequencies - Galaxy cross-sections and selection effects

NASA Technical Reports Server (NTRS)

Fukugita, Masataka; Turner, Edwin L.

1991-01-01

Four issues - (1) the best currently available data on the galaxy velocity-dispersion distribution, (2) the effects of finite core radii potential ellipticity on lensing cross sections, (3) the predicted distribution of lens image separations compared to observational angular resolutions, and (4) the preferential inclusion of lens systems in flux limited samples - are considered in order to facilitate more realistic predictions of multiple image galaxy-quasar lensing frequencies. It is found that (1) the SIS lensing parameter F equals 0.047 +/-0.019 with almost 90 percent contributed by E and S0 galaxies, (2) observed E and S0 core radii are remarkably small, yielding a factor of less than about 2 reduction in total lensing cross sections, (3) 50 percent of galaxy-quasar lenses have image separations greater than about 1.3 arcsec, and (4) amplification bias factors are large and must be carefully taken into account. It is concluded that flat universe models excessively dominated by the cosmological constant are not favored by the small observed galaxy-quasar lensing rate.

SUZAKU OBSERVATIONS OF SUBHALOS IN THE COMA CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sasaki, Toru; Matsushita, Kyoko; Sato, Kosuke

2015-06-10

We observed three massive subhalos in the Coma cluster with Suzaku. These subhalos, labeled “ID 1,” “ID 2,” and “ID 32,” were detected with a weak-lensing survey using Subaru/Suprime-Cam, and are located at the projected distances of 1.4 r{sub 500}, 1.2 r{sub 500}, and 1.6 r{sub 500} from the center of the Coma cluster, respectively. The subhalo “ID 1” has a compact X-ray excess emission close to the center of the weak-lensing mass contour, and the gas mass to weak-lensing mass ratio is about 0.001. The temperature of the emission is about 3 keV, which is slightly lower than thatmore » of the surrounding intracluster medium (ICM) and that expected for the temperature versus mass relation of clusters of galaxies. The subhalo “ID 32” shows an excess emission whose peak is shifted toward the opposite direction from the center of the Coma cluster. The gas mass to weak-lensing mass ratio is also about 0.001, which is significantly smaller than regular galaxy groups. The temperature of the excess is about 0.5 keV and significantly lower than that of the surrounding ICM and far from the temperature versus mass relation of clusters. However, there is no significant excess X-ray emission in the “ID 2” subhalo. Assuming an infall velocity of about 2000 km s{sup −1}, at the border of the excess X-ray emission, the ram pressures for “ID 1” and “ID 32” are comparable to the gravitational restoring force per area. We also studied the effect of the Kelvin–Helmholtz instability to strip the gas. Although we found X-ray clumps associated with the weak-lensing subhalos, their X-ray luminosities are much lower than the total ICM luminosity in the cluster outskirts.« less

Weak gravitational lensing effects on the determination of Omega_mega_m and Omega_mega Lambda from SNeIa

NASA Astrophysics Data System (ADS)

Valageas, P.

2000-02-01

In this article we present an analytical calculation of the probability distribution of the magnification of distant sources due to weak gravitational lensing from non-linear scales. We use a realistic description of the non-linear density field, which has already been compared with numerical simulations of structure formation within hierarchical scenarios. Then, we can directly express the probability distribution P(mu ) of the magnification in terms of the probability distribution of the density contrast realized on non-linear scales (typical of galaxies) where the local slope of the initial linear power-spectrum is n=-2. We recover the behaviour seen by numerical simulations: P(mu ) peaks at a value slightly smaller than the mean < mu >=1 and it shows an extended large mu tail (as described in another article our predictions also show a good quantitative agreement with results from N-body simulations for a finite smoothing angle). Then, we study the effects of weak lensing on the derivation of the cosmological parameters from SNeIa. We show that the inaccuracy introduced by weak lensing is not negligible: {cal D}lta Omega_mega_m >~ 0.3 for two observations at z_s=0.5 and z_s=1. However, observations can unambiguously discriminate between Omega_mega_m =0.3 and Omega_mega_m =1. Moreover, in the case of a low-density universe one can clearly distinguish an open model from a flat cosmology (besides, the error decreases as the number of observ ed SNeIa increases). Since distant sources are more likely to be ``demagnified'' the most probable value of the observed density parameter Omega_mega_m is slightly smaller than its actual value. On the other hand, one may obtain some valuable information on the properties of the underlying non-linear density field from the measure of weak lensing distortions.

Cluster mass estimators from CMB temperature and polarization lensing

NASA Astrophysics Data System (ADS)

Hu, Wayne; DeDeo, Simon; Vale, Chris

2007-12-01

Upcoming Sunyaev Zel'dovich surveys are expected to return ~104 intermediate mass clusters at high redshift. Their average masses must be known to the same accuracy as desired for the dark energy properties. Internal to the surveys, the cosmic microwave background (CMB) potentially provides a source for lensing mass measurements whose distance is precisely known and behind all clusters. We develop statistical mass estimators from six quadratic combinations of CMB temperature and polarization fields that can simultaneously recover large-scale structure and cluster mass profiles. The performance of these estimators on idealized Navarro Frenk White (NFW) clusters suggests that surveys with a ~1' beam and 10\\,\\muK^{\\prime} noise in uncontaminated temperature maps can make a ~10σ detection, or equivalently a ~10% mass measurement for each 103 set of clusters. With internal or external acoustic scale E-polarization measurements, the ET cross-correlation estimator can provide a stringent test for contaminants on a first detection at ~1/3 the significance. For surveys that reach below 3\\,\\muK^{\\prime}, the EB cross-correlation estimator should provide the most precise measurements and potentially the strongest control over contaminants.

Individual set-point and gain of emmetropization in chickens.

PubMed

Tepelus, Tudor Cosmin; Schaeffel, Frank

2010-01-01

During the developmental process of emmetropization evidence shows that visual feedback guides the eye as it approaches a refractive state close to zero, or slightly hyperopic. How this "set-point" is internally defined, in the presence of continuous shifts of the focal plane with different viewing distances and accommodation, remains unclear. Minimizing defocus blur over time should produce similar end-point refractions in different individuals. However, we found that individual chickens display considerable variability in their set-point refractive states, despite that they all had the same visual experience. This variability is not random since the refractions in both eyes were highly correlated - even though it is known that they can emmetropize independently. Furthermore, if chicks underwent a period of experimentally induced ametropia, they returned to their individual set-point refractions during recovery (correlation of the refractions before treatment versus after recovery: n=19 chicks, 38 eyes, left eyes: slope 1.01, R=0.860; right eyes: slope 0.85, R=0.610, p<0.001, linear regression). Also, the induced deprivation myopia was correlated in both eyes (n=18 chicks, 36 eyes, p<0.01, orthogonal regression). If chicks were treated with spectacle lenses, the compensatory changes in refraction were, on average, appropriate but individual chicks displayed variable responses. Again, the refractions of both eyes remained correlated (negative lenses, n=18 chicks, 36 eyes, slope 0.89, R=0.504, p<0.01, positive lenses: n=21 chicks, 42 eyes, slope 1.14, R=0.791, p<0.001). The amount of deprivation myopia that developed in two successive treatment cycles, with an intermittent period of recovery, was not correlated; only vitreous chamber growth was almost significantly correlated in both cycles (n=7 chicks, 14 eyes; p<0.05). The amounts of ametropia and vitreous chamber changes induced in two successive cycles of treatment, first with lenses and then with diffusers, were also not correlated, suggesting that the "gains of lens compensation" are different from those in deprivation myopia. In summary, (1) there appears to be an endogenous, possibly genetic, definition of the set-point of emmetropization in each individual, which is similar in both eyes, (2) visual conditions that induce ametropia produce variable changes in refractions, with high correlations between both eyes, (3) overall, the "gain of emmetropization" appears only weakly controlled by endogenous factors.

General relativistic corrections to the weak lensing convergence power spectrum

NASA Astrophysics Data System (ADS)

Giblin, John T.; Mertens, James B.; Starkman, Glenn D.; Zentner, Andrew R.

2017-11-01

We compute the weak lensing convergence power spectrum, Cℓκκ, in a dust-filled universe using fully nonlinear general relativistic simulations. The spectrum is then compared to more standard, approximate calculations by computing the Bardeen (Newtonian) potentials in linearized gravity and partially utilizing the Born approximation. We find corrections to the angular power spectrum amplitude of order ten percent at very large angular scales, ℓ˜2 - 3 , and percent-level corrections at intermediate angular scales of ℓ˜20 - 30 .

Spectroscopy of Giant Arcs Behind the Strongest Lenses in the Universe

NASA Astrophysics Data System (ADS)

Hennawi, Joseph F.; Gladders, Michael; Oguri, Masamune; Koester, Benjamin; Bayliss, Matt; Dahle, Hakon; Natarajan, Priya

2009-02-01

We have conducted a deep ((mu)_g ≲ 24) imaging survey using the WIYN 4-m telescope, the UH 88-inch telescope, and the 2.5m Nordic Optical Telescope (NOT) to search for giant arcs behind the richest clusters identified in the Gpc^3 volume of the SDSS. By imaging nearly 500 massive clusters, this ongoing survey has uncovered some of the most dramatic examples of gravitational lensing ever discovered, similar to `poster-children' like Abell 1689 and CL0024+1654. We propose to use GMOS on Gemini-North and the Blue Channel Spectrograph on the MMT to determine arc redshifts in these new lenses. When combined with our GMOS data from a similar program in 2008A, this proposal will result in a sample of 60 gravitationally lensed galaxies behind ~ 25 clusters. These arc redshifts pinpoint the mass of dark matter interior to the Einstein radius in the cluster core (R < 200 kpc; comoving). The larger scale (R ~ 1-5 Mpc) weak lensing shear has been measured for more than half of our targets from deep imaging at NOT, WIYN, Subaru, and using archival data from HST. GMOS arc redshifts combined with weak and strong lensing will allow us to measure the density profile of dark matter halos on scales 200 kpc < R < 5 Mpc for the statistical sample of lensing clusters, providing a powerful test of the (Lambda)CDM paradigm.

Continuous quantum measurement with independent detector cross correlations.

PubMed

Jordan, Andrew N; Büttiker, Markus

2005-11-25

We investigate the advantages of using two independent, linear detectors for continuous quantum measurement. For single-shot measurement, the detection process may be quantum limited if the detectors are twins. For weak continuous measurement, cross correlations allow a violation of the Korotkov-Averin bound for the detector's signal-to-noise ratio. The joint weak measurement of noncommuting observables is also investigated, and we find the cross correlation changes sign as a function of frequency, reflecting a crossover from incoherent relaxation to coherent, out of phase oscillations. Our results are applied to a double quantum-dot charge qubit, simultaneously measured by two quantum point contacts.

The dependence of halo mass on galaxy size at fixed stellar mass using weak lensing

NASA Astrophysics Data System (ADS)

Charlton, Paul J. L.; Hudson, Michael J.; Balogh, Michael L.; Khatri, Sumeet

2017-12-01

Stellar mass has been shown to correlate with halo mass, with non-negligible scatter. The stellar mass-size and luminosity-size relationships of galaxies also show significant scatter in galaxy size at fixed stellar mass. It is possible that, at fixed stellar mass and galaxy colour, the halo mass is correlated with galaxy size. Galaxy-galaxy lensing allows us to measure the mean masses of dark matter haloes for stacked samples of galaxies. We extend the analysis of the galaxies in the CFHTLenS catalogue by fitting single Sérsic surface brightness profiles to the lens galaxies in order to recover half-light radius values, allowing us to determine halo masses for lenses according to their size. Comparing our halo masses and sizes to baselines for that stellar mass yields a differential measurement of the halo mass-galaxy size relationship at fixed stellar mass, defined as Mh(M_{*}) ∝ r_{eff}^{η }(M_{*}). We find that, on average, our lens galaxies have an η = 0.42 ± 0.12, i.e. larger galaxies live in more massive dark matter haloes. The η is strongest for high-mass luminous red galaxies. Investigation of this relationship in hydrodynamical simulations suggests that, at a fixed M*, satellite galaxies have a larger η and greater scatter in the Mh and reff relationship compared to central galaxies.

LSST Probes of Dark Energy: New Energy vs New Gravity

NASA Astrophysics Data System (ADS)

Bradshaw, Andrew; Tyson, A.; Jee, M. J.; Zhan, H.; Bard, D.; Bean, R.; Bosch, J.; Chang, C.; Clowe, D.; Dell'Antonio, I.; Gawiser, E.; Jain, B.; Jarvis, M.; Kahn, S.; Knox, L.; Newman, J.; Wittman, D.; Weak Lensing, LSST; LSS Science Collaborations

2012-01-01

Is the late time acceleration of the universe due to new physics in the form of stress-energy or a departure from General Relativity? LSST will measure the shape, magnitude, and color of 4x109 galaxies to high S/N over 18,000 square degrees. These data will be used to separately measure the gravitational growth of mass structure and distance vs redshift to unprecedented precision by combining multiple probes in a joint analysis. Of the five LSST probes of dark energy, weak gravitational lensing (WL) and baryon acoustic oscillation (BAO) probes are particularly effective in combination. By measuring the 2-D BAO scale in ugrizy-band photometric redshift-selected samples, LSST will determine the angular diameter distance to a dozen redshifts with sub percent-level errors. Reconstruction of the WL shear power spectrum on linear and weakly non-linear scales, and of the cross-correlation of shear measured in different photometric redshift bins provides a constraint on the evolution of dark energy that is complementary to the purely geometric measures provided by supernovae and BAO. Cross-correlation of the WL shear and BAO signal within redshift shells minimizes the sensitivity to systematics. LSST will also detect shear peaks, providing independent constraints. Tomographic study of the shear of background galaxies as a function of redshift allows a geometric test of dark energy. To extract the dark energy signal and distinguish between the two forms of new physics, LSST will rely on accurate stellar point-spread functions (PSF) and unbiased reconstruction of galaxy image shapes from hundreds of exposures. Although a weighted co-added deep image has high S/N, it is a form of lossy compression. Bayesian forward modeling algorithms can in principle use all the information. We explore systematic effects on shape measurements and present tests of an algorithm called Multi-Fit, which appears to avoid PSF-induced shear systematics in a computationally efficient way.

The DAFT/FADA Survey status and latest results

NASA Astrophysics Data System (ADS)

Guennou, L.

2011-12-01

We present here the latest results obtained from the American French collaboration called the Dark energy American French Team/French American DArk energy Team (DAFT/FADA). The goal of the DAFT/FADA collaboration is to carry out a weak lensing tomography survey of z = 0.4-0.9 rich clusters of galaxies. Unlike supernovae or other methods such as cluster of galaxy counts, weak lensing tomography is purely based on geometry and does not depend on knowledge of the physics of the objects used as distance indicators. In addition, the reason for analyzing observations in the direction of clusters is that the shear signal is enhanced by about 10 over the field. Our work will eventually contain results obtained on 91 rich clusters from the HST archive combined with ground based work to obtain photo-zs. This combination of photo-z and weak lensing tomography will enable us to constrain the equation of state of dark energy. We present here the latest results obtained so far in this study.

Impact of theoretical priors in cosmological analyses: The case of single field quintessence

NASA Astrophysics Data System (ADS)

Peirone, Simone; Martinelli, Matteo; Raveri, Marco; Silvestri, Alessandra

2017-09-01

We investigate the impact of general conditions of theoretical stability and cosmological viability on dynamical dark energy models. As a powerful example, we study whether minimally coupled, single field quintessence models that are safe from ghost instabilities, can source the Chevallier-Polarski-Linder (CPL) expansion history recently shown to be mildly favored by a combination of cosmic microwave background (Planck) and weak lensing (KiDS) data. We find that in their most conservative form, the theoretical conditions impact the analysis in such a way that smooth single field quintessence becomes significantly disfavored with respect to the standard Λ CDM cosmological model. This is due to the fact that these conditions cut a significant portion of the (w0,wa) parameter space for CPL, in particular, eliminating the region that would be favored by weak lensing data. Within the scenario of a smooth dynamical dark energy parametrized with CPL, weak lensing data favors a region that would require multiple fields to ensure gravitational stability.

Weak Lensing from Space I: Instrumentation and Survey Strategy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rhodes, Jason; Refregier, Alexandre; Massey, Richard

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 currentmore » 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.« less

Lensing of 21-cm fluctuations by primordial gravitational waves.

PubMed

Book, Laura; Kamionkowski, Marc; Schmidt, Fabian

2012-05-25

Weak-gravitational-lensing distortions to the intensity pattern of 21-cm radiation from the dark ages can be decomposed geometrically into curl and curl-free components. Lensing by primordial gravitational waves induces a curl component, while the contribution from lensing by density fluctuations is strongly suppressed. Angular fluctuations in the 21-cm background extend to very small angular scales, and measurements at different frequencies probe different shells in redshift space. There is thus a huge trove of information with which to reconstruct the curl component of the lensing field, allowing tensor-to-scalar ratios conceivably as small as r~10(-9)-far smaller than those currently accessible-to be probed.

Calibrating the Planck cluster mass scale with CLASH

NASA Astrophysics Data System (ADS)

Penna-Lima, M.; Bartlett, J. G.; Rozo, E.; Melin, J.-B.; Merten, J.; Evrard, A. E.; Postman, M.; Rykoff, E.

2017-08-01

We determine the mass scale of Planck galaxy clusters using gravitational lensing mass measurements from the Cluster Lensing And Supernova survey with Hubble (CLASH). We have compared the lensing masses to the Planck Sunyaev-Zeldovich (SZ) mass proxy for 21 clusters in common, employing a Bayesian analysis to simultaneously fit an idealized CLASH selection function and the distribution between the measured observables and true cluster mass. We used a tiered analysis strategy to explicitly demonstrate the importance of priors on weak lensing mass accuracy. In the case of an assumed constant bias, bSZ, between true cluster mass, M500, and the Planck mass proxy, MPL, our analysis constrains 1-bSZ = 0.73 ± 0.10 when moderate priors on weak lensing accuracy are used, including a zero-mean Gaussian with standard deviation of 8% to account for possible bias in lensing mass estimations. Our analysis explicitly accounts for possible selection bias effects in this calibration sourced by the CLASH selection function. Our constraint on the cluster mass scale is consistent with recent results from the Weighing the Giants program and the Canadian Cluster Comparison Project. It is also consistent, at 1.34σ, with the value needed to reconcile the Planck SZ cluster counts with Planck's base ΛCDM model fit to the primary cosmic microwave background anisotropies.

Magnification-temperature correlation: The dark side of integrated Sachs-Wolfe measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

LoVerde, Marilena; Hui, Lam; Gaztanaga, Enrique

2007-02-15

Integrated Sachs-Wolfe (ISW) measurements, which involve cross-correlating the microwave background anisotropies with the foreground large-scale structure (e.g. traced by galaxies/quasars), have proven to be an interesting probe of dark energy. We show that magnification bias, which is the inevitable modulation of the foreground number counts by gravitational lensing, alters both the scale dependence and amplitude of the observed ISW signal. This is true especially at high redshifts because (1) the intrinsic galaxy-temperature signal diminishes greatly back in the matter-dominated era, (2) the lensing efficiency increases with redshift and (3) the number count slope generally steepens with redshift in a magnitudemore » limited sample. At z > or approx. 2, the magnification-temperature correlation dominates over the intrinsic galaxy-temperature correlation and causes the observed ISW signal to increase with redshift, despite dark energy subdominance--a result of the fact that magnification probes structures all the way from the observer to the sources. Ignoring magnification bias therefore can lead to (significantly) erroneous conclusions about dark energy. While the lensing modulation opens up an interesting high z window for ISW measurements, high redshift measurements are not expected to add much new information to low redshift ones if dark energy is indeed the cosmological constant. This is because lensing introduces significant covariance across redshifts. The most compelling reasons for pursuing high redshift ISW measurements are to look for potential surprises such as early dark energy domination or signatures of modified gravity. We conclude with a discussion of existing measurements, the highest redshift of which is at the margin of being sensitive to the magnification effect. We also develop a formalism which might be of more general interest: to predict biases in estimating parameters when certain physical effects are ignored in interpreting observations.« less

Next Generation Virgo Cluster Survey. XXI. The Weak Lensing Masses of the CFHTLS and NGVS RedGOLD Galaxy Clusters and Calibration of the Optical Richness

NASA Astrophysics Data System (ADS)

Parroni, Carolina; Mei, Simona; Erben, Thomas; Van Waerbeke, Ludovic; Raichoor, Anand; Ford, Jes; Licitra, Rossella; Meneghetti, Massimo; Hildebrandt, Hendrik; Miller, Lance; Côté, Patrick; Covone, Giovanni; Cuillandre, Jean-Charles; Duc, Pierre-Alain; Ferrarese, Laura; Gwyn, Stephen D. J.; Puzia, Thomas H.

2017-10-01

We measured stacked weak lensing cluster masses for a sample of 1323 galaxy clusters detected by the RedGOLD algorithm in the Canada-France-Hawaii Telescope Legacy Survey W1 and the Next Generation Virgo Cluster Survey at 0.2< z< 0.5, in the optical richness range 10< λ < 70. This is the most comprehensive lensing study of a ˜ 100 % complete and ˜ 80 % pure optical cluster catalog in this redshift range. We test different mass models, and our final model includes a basic halo model with a Navarro Frenk and White profile, as well as correction terms that take into account cluster miscentering, non-weak shear, the two-halo term, the contribution of the Brightest Cluster Galaxy, and an a posteriori correction for the intrinsic scatter in the mass-richness relation. With this model, we obtain a mass-richness relation of {log}{M}200/{M}⊙ =(14.46+/- 0.02)+(1.04+/- 0.09){log}(λ /40) (statistical uncertainties). This result is consistent with other published lensing mass-richness relations. We give the coefficients of the scaling relations between the lensing mass and X-ray mass proxies, L X and T X, and compare them with previous results. When compared to X-ray masses and mass proxies, our results are in agreement with most previous results and simulations, and consistent with the expected deviations from self-similarity.

MEASURING THE GEOMETRY OF THE UNIVERSE FROM WEAK GRAVITATIONAL LENSING BEHIND GALAXY GROUPS IN THE HST COSMOS SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, James E.; Massey, Richard J.; Leauthaud, Alexie

2012-04-20

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

A PLANETARY LENSING FEATURE IN CAUSTIC-CROSSING HIGH-MAGNIFICATION MICROLENSING EVENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Sun-Ju; Hwang, Kyu-Ha; Ryu, Yoon-Hyun

Current microlensing follow-up observations focus on high-magnification events because of the high efficiency of planet detection. However, central perturbations of high-magnification events caused by a planet can also be produced by a very close or a very wide binary companion, and the two kinds of central perturbations are not generally distinguished without time consuming detailed modeling (a planet-binary degeneracy). Hence, it is important to resolve the planet-binary degeneracy that occurs in high-magnification events. In this paper, we investigate caustic-crossing high-magnification events caused by a planet and a wide binary companion. From this investigation, we find that because of the differentmore » magnification excess patterns inside the central caustics induced by the planet and the binary companion, the light curves of the caustic-crossing planetary-lensing events exhibit a feature that is discriminated from those of the caustic-crossing binary-lensing events, and the feature can be used to immediately distinguish between the planetary and binary companions. The planetary-lensing feature appears in the interpeak region between the two peaks of the caustic-crossings. The structure of the interpeak region for the planetary-lensing events is smooth and convex or boxy, whereas the structure for the binary-lensing events is smooth and concave. We also investigate the effect of a finite background source star on the planetary-lensing feature in the caustic-crossing high-magnification events. From this, we find that the convex-shaped interpeak structure appears in a certain range that changes with the mass ratio of the planet to the planet-hosting star.« less

Designing future dark energy space missions. II. Photometric redshift of space weak lensing optimized surveys

NASA Astrophysics Data System (ADS)

Jouvel, S.; Kneib, J.-P.; Bernstein, G.; Ilbert, O.; Jelinsky, P.; Milliard, B.; Ealet, A.; Schimd, C.; Dahlen, T.; Arnouts, S.

2011-08-01

Context. With the discovery of the accelerated expansion of the universe, different observational probes have been proposed to investigate the presence of dark energy, including possible modifications to the gravitation laws by accurately measuring the expansion of the Universe and the growth of structures. We need to optimize the return from future dark energy surveys to obtain the best results from these probes. Aims: A high precision weak-lensing analysis requires not an only accurate measurement of galaxy shapes but also a precise and unbiased measurement of galaxy redshifts. The survey strategy has to be defined following both the photometric redshift and shape measurement accuracy. Methods: We define the key properties of the weak-lensing instrument and compute the effective PSF and the overall throughput and sensitivities. We then investigate the impact of the pixel scale on the sampling of the effective PSF, and place upper limits on the pixel scale. We then define the survey strategy computing the survey area including in particular both the Galactic absorption and Zodiacal light variation accross the sky. Using the Le Phare photometric redshift code and realistic galaxy mock catalog, we investigate the properties of different filter-sets and the importance of the u-band photometry quality to optimize the photometric redshift and the dark energy figure of merit (FoM). Results: Using the predicted photometric redshift quality, simple shape measurement requirements, and a proper sky model, we explore what could be an optimal weak-lensing dark energy mission based on FoM calculation. We find that we can derive the most accurate the photometric redshifts for the bulk of the faint galaxy population when filters have a resolution ℛ ~ 3.2. We show that an optimal mission would survey the sky through eight filters using two cameras (visible and near infrared). Assuming a five-year mission duration, a mirror size of 1.5 m and a 0.5 deg2 FOV with a visible pixel scale of 0.15'', we found that a homogeneous survey reaching a survey population of IAB = 25.6 (10σ) with a sky coverage of ~11 000 deg2 maximizes the weak lensing FoM. The effective number density of galaxies used for WL is then ~45 gal/arcmin2, which is at least a factor of two higher than ground-based surveys. Conclusions: This study demonstrates that a full account of the observational strategy is required to properly optimize the instrument parameters and maximize the FoM of the future weak-lensing space dark energy mission.

Gravitational lensing by rotating naked singularities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyulchev, Galin N.; Yazadjiev, Stoytcho S.; Institut fuer Theoretische Physik, Universitaet Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen

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

Constraining dark sector perturbations I: cosmic shear and CMB lensing

NASA Astrophysics Data System (ADS)

Battye, Richard A.; Moss, Adam; Pearson, Jonathan A.

2015-04-01

We present current and future constraints on equations of state for dark sector perturbations. The equations of state considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant Script L(g) theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity. We develop a theoretical understanding of the observable impact of these models. In order to constrain these models we use CMB temperature data from Planck, BAO measurements, CMB lensing data from Planck and the South Pole Telescope, and weak galaxy lensing data from CFHTLenS. We find non-trivial exclusions on the range of parameters, although the data remains compatible with w=-1. We gauge how future experiments will help to constrain the parameters. This is done via a likelihood analysis for CMB experiments such as CoRE and PRISM, and tomographic galaxy weak lensing surveys, focussing in on the potential discriminatory power of Euclid on mildly non-linear scales.

Gravitational Lensing Corrections in Flat ΛCDM Cosmology

NASA Astrophysics Data System (ADS)

Kantowski, Ronald; Chen, Bin; Dai, Xinyu

2010-08-01

We compute the deflection angle to order (m/r 0)2 and m/r 0 × Λr 2 0 for a light ray traveling in a flat ΛCDM cosmology that encounters a completely condensed mass region. We use a Swiss cheese model for the inhomogeneities and find that the most significant correction to the Einstein angle occurs not because of the nonlinear terms but instead occurs because the condensed mass is embedded in a background cosmology. The Swiss cheese model predicts a decrease in the deflection angle of ~2% for weakly lensed galaxies behind the rich cluster A1689 and that the reduction can be as large as ~5% for similar rich clusters at z ≈ 1. Weak-lensing deflection angles caused by galaxies can likewise be reduced by as much as ~4%. We show that the lowest order correction in which Λ appears is proportional to m/r_0× √{Λ r_0^2}}} and could cause as much as a ~0.02% increase in the deflection angle for light that passes through a rich cluster. The lowest order nonlinear correction in the mass is proportional to m/r_0× √{m/r_0} and can increase the deflection angle by ~0.005% for weak lensing by galaxies.

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

NASA Astrophysics Data System (ADS)

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.

Galilean-invariant scalar fields can strengthen gravitational lensing.

PubMed

Wyman, Mark

2011-05-20

The mystery of dark energy suggests that there is new gravitational physics on long length scales. Yet light degrees of freedom in gravity are strictly limited by Solar System observations. We can resolve this apparent contradiction by adding a Galilean-invariant scalar field to gravity. Called Galileons, these scalars have strong self-interactions near overdensities, like the Solar System, that suppress their dynamical effect. These nonlinearities are weak on cosmological scales, permitting new physics to operate. In this Letter, we point out that a massive-gravity-inspired coupling of Galileons to stress energy can enhance gravitational lensing. Because the enhancement appears at a fixed scaled location for dark matter halos of a wide range of masses, stacked cluster analysis of weak lensing data should be able to detect or constrain this effect.

Constraining modified gravitational theories by weak lensing with Euclid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martinelli, Matteo; Calabrese, Erminia; De Bernardis, Francesco

2011-01-15

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

A Measurement of the Cosmic Microwave Background Gravitational Lensing Potential from 100 Square Degrees of SPTpol Data

NASA Astrophysics Data System (ADS)

Story, K. T.; Hanson, D.; Ade, P. A. R.; Aird, K. A.; Austermann, J. E.; Beall, J. A.; Bender, A. N.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Chiang, H. C.; Cho, H.-M.; Citron, R.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Everett, W.; Gallicchio, J.; Gao, J.; George, E. M.; Gilbert, A.; Halverson, N. W.; Harrington, N.; Henning, J. W.; Hilton, G. C.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hou, Z.; Hrubes, J. D.; Huang, N.; Hubmayr, J.; Irwin, K. D.; Keisler, R.; Knox, L.; Lee, A. T.; Leitch, E. M.; Li, D.; Liang, C.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Mocanu, L.; Montroy, T. E.; Natoli, T.; Nibarger, J. P.; Novosad, V.; Padin, S.; Pryke, C.; Reichardt, C. L.; Ruhl, J. E.; Saliwanchik, B. R.; Sayre, J. T.; Schaffer, K. K.; Smecher, G.; Stark, A. A.; Tucker, C.; Vanderlinde, K.; Vieira, J. D.; Wang, G.; Whitehorn, N.; Yefremenko, V.; Zahn, O.

2015-09-01

We present a measurement of the cosmic microwave background (CMB) gravitational lensing potential using data from the first two seasons of observations with SPTpol, the polarization-sensitive receiver currently installed on the South Pole Telescope. The observations used in this work cover 100 deg2 of sky with arcminute resolution at 150 GHz. Using a quadratic estimator, we make maps of the CMB lensing potential from combinations of CMB temperature and polarization maps. We combine these lensing potential maps to form a minimum-variance (MV) map. The lensing potential is measured with a signal-to-noise ratio of greater than one for angular multipoles between 100\\lt L\\lt 250. This is the highest signal-to-noise mass map made from the CMB to date and will be powerful in cross-correlation with other tracers of large-scale structure. We calculate the power spectrum of the lensing potential for each estimator, and we report the value of the MV power spectrum between 100\\lt L\\lt 2000 as our primary result. We constrain the ratio of the spectrum to a fiducial ΛCDM model to be AMV = 0.92 ± 0.14 (Stat.) ± 0.08 (Sys.). Restricting ourselves to polarized data only, we find APOL = 0.92 ± 0.24 (Stat.) ± 0.11 (Sys.). This measurement rejects the hypothesis of no lensing at 5.9σ using polarization data alone, and at 14σ using both temperature and polarization data.

Gravitational Lensing in Astronomy

NASA Astrophysics Data System (ADS)

Wambsganss, Joachim

1998-11-01

In addition to multiply-imaged quasars, a number of other aspects of lensing have been discovered: For example, giant luminous arcs, quasar microlensing, Einstein rings, galactic microlensing events, arclets, and weak gravitational lensing. At present, literally hundreds of individual gravitational lens phenomena are known. Although still in its childhood, lensing has established itself as a very useful astrophysical tool with some remarkable successes. It has contributed significant new results in areas as different as the cosmological distance scale, the large scale matter distribution in the universe, mass and mass distribution of galaxy clusters, the physics of quasars, dark matter in galaxy halos, and galaxy structure. Looking at these successes in the recent past we predict an even more luminous future for gravitational lensing.

2dFLenS and KiDS: determining source redshift distributions with cross-correlations

NASA Astrophysics Data System (ADS)

Johnson, Andrew; Blake, Chris; Amon, Alexandra; Erben, Thomas; Glazebrook, Karl; Harnois-Deraps, Joachim; Heymans, Catherine; Hildebrandt, Hendrik; Joudaki, Shahab; Klaes, Dominik; Kuijken, Konrad; Lidman, Chris; Marin, Felipe A.; McFarland, John; Morrison, Christopher B.; Parkinson, David; Poole, Gregory B.; Radovich, Mario; Wolf, Christian

2017-03-01

We develop a statistical estimator to infer the redshift probability distribution of a photometric sample of galaxies from its angular cross-correlation in redshift bins with an overlapping spectroscopic sample. This estimator is a minimum-variance weighted quadratic function of the data: a quadratic estimator. This extends and modifies the methodology presented by McQuinn & White. The derived source redshift distribution is degenerate with the source galaxy bias, which must be constrained via additional assumptions. We apply this estimator to constrain source galaxy redshift distributions in the Kilo-Degree imaging survey through cross-correlation with the spectroscopic 2-degree Field Lensing Survey, presenting results first as a binned step-wise distribution in the range z < 0.8, and then building a continuous distribution using a Gaussian process model. We demonstrate the robustness of our methodology using mock catalogues constructed from N-body simulations, and comparisons with other techniques for inferring the redshift distribution.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shan Huanyuan; Tao Charling; Kneib, Jean-Paul

2012-03-20

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

Lossy compression of weak lensing data

DOE PAGES

Vanderveld, R. Ali; Bernstein, Gary M.; Stoughton, Chris; ...

2011-07-12

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

Discrepancies between CFHTLenS cosmic shear and Planck: new physics or systematic effects?

NASA Astrophysics Data System (ADS)

Kitching, Thomas D.; Verde, Licia; Heavens, Alan F.; Jimenez, Raul

2016-06-01

There is currently a discrepancy in the measured value of the amplitude of matter clustering, parametrized using σ8, inferred from galaxy weak lensing, and cosmic microwave background (CMB) data, which could be an indication of new physics, such as massive neutrinos or a modification to the gravity law, or baryon feedback. In this paper we make the assumption that the cosmological parameters are well determined by Planck, and use weak lensing data to investigate the implications for baryon feedback and massive neutrinos, as well as possible contributions from intrinsic alignments and biases in photometric redshifts. We apply a non-parametric approach to model the baryonic feedback on the dark matter clustering, which is flexible enough to reproduce the OWLS (OverWhelmingly Large Simulations) and Illustris simulation results. 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. We analyse the CFHTLenS weak lensing data and, assuming best-fitting cosmological parameters from the Planck CMB experiment, find that there is no evidence for baryonic feedback on the dark matter power spectrum, but there is evidence for a bias in the photometric redshifts in the CFHTLenS data, consistent with a completely independent analysis by Choi et al., based on spectroscopic redshifts, and that these conclusions are robust to assumptions about the intrinsic alignment systematic. We also find an upper limit, of <0.28 eV (1σ), to the sum of neutrino masses conditional on other Λ-cold-dark-matter parameters being fixed.

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

NASA Astrophysics Data System (ADS)

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.

X-Ray Temperatures, Luminosities, and Masses from XMM-Newton Follow-up of the First Shear-selected Galaxy Cluster Sample

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deshpande, Amruta J.; Hughes, John P.; Wittman, David, E-mail: amrejd@physics.rutgers.edu, E-mail: jph@physics.rutgers.edu, E-mail: dwittman@physics.ucdavis.edu

We continue the study of the first sample of shear-selected clusters from the initial 8.6 square degrees of the Deep Lens Survey (DLS); a sample with well-defined selection criteria corresponding to the highest ranked shear peaks in the survey area. We aim to characterize the weak lensing selection by examining the sample’s X-ray properties. There are multiple X-ray clusters associated with nearly all the shear peaks: 14 X-ray clusters corresponding to seven DLS shear peaks. An additional three X-ray clusters cannot be definitively associated with shear peaks, mainly due to large positional offsets between the X-ray centroid and the shearmore » peak. Here we report on the XMM-Newton properties of the 17 X-ray clusters. The X-ray clusters display a wide range of luminosities and temperatures; the L {sub X} − T {sub X} relation we determine for the shear-associated X-ray clusters is consistent with X-ray cluster samples selected without regard to dynamical state, while it is inconsistent with self-similarity. For a subset of the sample, we measure X-ray masses using temperature as a proxy, and compare to weak lensing masses determined by the DLS team. The resulting mass comparison is consistent with equality. The X-ray and weak lensing masses show considerable intrinsic scatter (∼48%), which is consistent with X-ray selected samples when their X-ray and weak lensing masses are independently determined.« less

swot: Super W Of Theta

NASA Astrophysics Data System (ADS)

Coupon, Jean; Leauthaud, Alexie; Kilbinger, Martin; Medezinski, Elinor

2017-07-01

SWOT (Super W Of Theta) computes two-point statistics for very large data sets, based on “divide and conquer” algorithms, mainly, but not limited to data storage in binary trees, approximation at large scale, parellelization (open MPI), and bootstrap and jackknife resampling methods “on the fly”. It currently supports projected and 3D galaxy auto and cross correlations, galaxy-galaxy lensing, and weighted histograms.

CMB lensing tomography with the DES Science Verification galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giannantonio, T.

We measure the cross-correlation between the galaxy density in the Dark Energy Survey (DES) Science Verification data and the lensing of the cosmic microwave background (CMB) as reconstructed with the Planck satellite and the South Pole Telescope (SPT). When using the DES main galaxy sample over the full redshift range 0.2 < z phot < 1.2, a cross-correlation signal is detected at 6σ and 4σ with SPT and Planck respectively. We then divide the DES galaxies into five photometric redshift bins, finding significant (>2σ) detections in all bins. Comparing to the fiducial Planck cosmology, we find the redshift evolution ofmore » the signal matches expectations, although the amplitude is consistently lower than predicted across redshift bins. We test for possible systematics that could affect our result and find no evidence for significant contamination. Finally, we demonstrate how these measurements can be used to constrain the growth of structure across cosmic time. We find the data are fit by a model in which the amplitude of structure in the z < 1.2 universe is 0.73 ± 0.16 times as large as predicted in the LCDM Planck cosmology, a 1.7σ deviation.« less

CMB lensing tomography with the DES Science Verification galaxies

DOE PAGES

Giannantonio, T.

2016-01-07

We measure the cross-correlation between the galaxy density in the Dark Energy Survey (DES) Science Verification data and the lensing of the cosmic microwave background (CMB) as reconstructed with the Planck satellite and the South Pole Telescope (SPT). When using the DES main galaxy sample over the full redshift range 0.2 < z phot < 1.2, a cross-correlation signal is detected at 6σ and 4σ with SPT and Planck respectively. We then divide the DES galaxies into five photometric redshift bins, finding significant (>2σ) detections in all bins. Comparing to the fiducial Planck cosmology, we find the redshift evolution ofmore » the signal matches expectations, although the amplitude is consistently lower than predicted across redshift bins. We test for possible systematics that could affect our result and find no evidence for significant contamination. Finally, we demonstrate how these measurements can be used to constrain the growth of structure across cosmic time. We find the data are fit by a model in which the amplitude of structure in the z < 1.2 universe is 0.73 ± 0.16 times as large as predicted in the LCDM Planck cosmology, a 1.7σ deviation.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Yong-Seon; Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Portsmouth, PO1 3FX; Zhao Gongbo

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

Multifractal detrended cross-correlations between the CSI 300 index futures and the spot markets based on high-frequency data

NASA Astrophysics Data System (ADS)

Cao, Guangxi; Han, Yan; Cui, Weijun; Guo, Yu

2014-11-01

The cross-correlation between the China Securities Index 300 (CSI 300) index futures and the spot markets based on high-frequency data is discussed in this paper. We empirically analyze the cross-correlation by using the multifractal detrended cross-correlation analysis (MF-DCCA), and investigate further the characteristics of asymmetry, frequency difference, and transmission direction of the cross-correlation. The results indicate that the cross-correlation between the two markets is significant and multifractal. Meanwhile, weak asymmetries exist in the cross-correlation, and higher data frequency results in a lower multifractality degree of the cross-correlation. The causal relationship between the two markets is bidirectional, but the CSI 300 index futures market has greater impact on the spot market.

The third data release of the Kilo-Degree Survey and associated data products

NASA Astrophysics Data System (ADS)

de Jong, Jelte T. A.; Verdois Kleijn, Gijs A.; Erben, Thomas; Hildebrandt, Hendrik; Kuijken, Konrad; Sikkema, Gert; Brescia, Massimo; Bilicki, Maciej; Napolitano, Nicola R.; Amaro, Valeria; Begeman, Kor G.; Boxhoorn, Danny R.; Buddelmeijer, Hugo; Cavuoti, Stefano; Getman, Fedor; Grado, Aniello; Helmich, Ewout; Huang, Zhuoyi; Irisarri, Nancy; La Barbera, Francesco; Longo, Giuseppe; McFarland, John P.; Nakajima, Reiko; Paolillo, Maurizio; Puddu, Emanuella; Radovich, Mario; Rifatto, Agatino; Tortora, Crescenzo; Valentijn, Edwin A.; Vellucci, Civita; Vriend, Willem-Jan; Amon, Alexandra; Blake, Chris; Choi, Ami; Conti, Ian Fenech; Gwyn, Stephen D. J.; Herbonnet, Ricardo; Heymans, Catherine; Hoekstra, Henk; Klaes, Dominik; Merten, Julian; Miller, Lance; Schneider, Peter; Viola, Massimo

2017-08-01

Context. The Kilo-Degree Survey (KiDS) is an ongoing optical wide-field imaging survey with the OmegaCAM camera at the VLT Survey Telescope. It aims to image 1500 square degrees in four filters (ugri). The core science driver is mapping the large-scale matter distribution in the Universe, using weak lensing shear and photometric redshift measurements. Further science cases include galaxy evolution, Milky Way structure, detection of high-redshift clusters, and finding rare sources such as strong lenses and quasars. Aims: Here we present the third public data release and several associated data products, adding further area, homogenized photometric calibration, photometric redshifts and weak lensing shear measurements to the first two releases. Methods: A dedicated pipeline embedded in the Astro-WISE information system is used for the production of the main release. Modifications with respect to earlier releases are described in detail. Photometric redshifts have been derived using both Bayesian template fitting, and machine-learning techniques. For the weak lensing measurements, optimized procedures based on the THELI data reduction and lensfit shear measurement packages are used. Results: In this third data release an additional 292 new survey tiles (≈300 deg2) stacked ugri images are made available, accompanied by weight maps, masks, and source lists. The multi-band catalogue, including homogenized photometry and photometric redshifts, covers the combined DR1, DR2 and DR3 footprint of 440 survey tiles (44 deg2). Limiting magnitudes are typically 24.3, 25.1, 24.9, 23.8 (5σ in a 2'' aperture) in ugri, respectively, and the typical r-band PSF size is less than 0.7''. The photometric homogenization scheme ensures accurate colours and an absolute calibration stable to ≈2% for gri and ≈3% in u. Separately released for the combined area of all KiDS releases to date are a weak lensing shear catalogue and photometric redshifts based on two different machine-learning techniques.

THE SYSTEMATIC ERROR TEST FOR PSF CORRECTION IN WEAK GRAVITATIONAL LENSING SHEAR MEASUREMENT BY THE ERA METHOD BY IDEALIZING PSF

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okura, Yuki; Futamase, Toshifumi, E-mail: yuki.okura@riken.jp

We improve the ellipticity of re-smeared artificial image (ERA) method of point-spread function (PSF) correction in a weak lensing shear analysis in order to treat the realistic shape of galaxies and the PSF. This is done by re-smearing the PSF and the observed galaxy image using a re-smearing function (RSF) and allows us to use a new PSF with a simple shape and to correct the PSF effect without any approximations or assumptions. We perform a numerical test to show that the method applied for galaxies and PSF with some complicated shapes can correct the PSF effect with a systematicmore » error of less than 0.1%. We also apply the ERA method for real data of the Abell 1689 cluster to confirm that it is able to detect the systematic weak lensing shear pattern. The ERA method requires less than 0.1 or 1 s to correct the PSF for each object in a numerical test and a real data analysis, respectively.« less

Photometric redshift requirements for lens galaxies in galaxy-galaxy lensing analyses

NASA Astrophysics Data System (ADS)

Nakajima, R.; Mandelbaum, R.; Seljak, U.; Cohn, J. D.; Reyes, R.; Cool, R.

2012-03-01

Weak gravitational lensing is a valuable probe of galaxy formation and cosmology. Here we quantify the effects of using photometric redshifts (photo-z) in galaxy-galaxy lensing, for both sources and lenses, both for the immediate goal of using galaxies with photo-z as lenses in the Sloan Digital Sky Survey (SDSS) and as a demonstration of methodology for large, upcoming weak lensing surveys that will by necessity be dominated by lens samples with photo-z. We calculate the bias in the lensing mass calibration as well as consequences for absolute magnitude (i.e. k-corrections) and stellar mass estimates for a large sample of SDSS Data Release 8 (DR8) galaxies. The redshifts are obtained with the template-based photo-z code ZEBRA on the SDSS DR8 ugriz photometry. We assemble and characterize the calibration samples (˜9000 spectroscopic redshifts from four surveys) to obtain photometric redshift errors and lensing biases corresponding to our full SDSS DR8 lens and source catalogues. Our tests of the calibration sample also highlight the impact of observing conditions in the imaging survey when the spectroscopic calibration covers a small fraction of its footprint; atypical imaging conditions in calibration fields can lead to incorrect conclusions regarding the photo-z of the full survey. For the SDSS DR8 catalogue, we find σΔz/(1+z)= 0.096 and 0.113 for the lens and source catalogues, with flux limits of r= 21 and 21.8, respectively. The photo-z bias and scatter is a function of photo-z and template types, which we exploit to apply photo-z quality cuts. By using photo-z rather than spectroscopy for lenses, dim blue galaxies and L* galaxies up to z˜ 0.4 can be used as lenses, thus expanding into unexplored areas of parameter space. We also explore the systematic uncertainty in the lensing signal calibration when using source photo-z, and both lens and source photo-z; given the size of existing training samples, we can constrain the lensing signal calibration (and therefore the normalization of the surface mass density) to within 2 and 4 per cent, respectively.

Gradient Refractive Index Lenses.

ERIC Educational Resources Information Center

Morton, N.

1984-01-01

Describes the nature of gradient refractive index (GRIN) lenses, focusing on refraction in these materials, focal length of a thin Wood lens, and on manufacturing of such lenses. Indicates that GRIN lenses of small cross section are in limited production with applications suggested for optical communication and photocopying fields. (JN)

Implications of a wavelength-dependent PSF for weak lensing measurements

NASA Astrophysics Data System (ADS)

Eriksen, Martin; Hoekstra, Henk

2018-07-01

The convolution of galaxy images by the point spread function (PSF) is the dominant source of bias for weak gravitational lensing studies, and an accurate estimate of the PSF is required to obtain unbiased shape measurements. The PSF estimate for a galaxy depends on its spectral energy distribution (SED), because the instrumental PSF is generally a function of the wavelength. In this paper we explore various approaches to determine the resulting `effective' PSF using broad-band data. Considering the Euclid mission as a reference, we find that standard SED template fitting methods result in biases that depend on source redshift, although this may be remedied if the algorithms can be optimized for this purpose. Using a machine learning algorithm we show that, at least in principle, the required accuracy can be achieved with the current survey parameters. It is also possible to account for the correlations between photometric redshift and PSF estimates that arise from the use of the same photometry. We explore the impact of errors in photometric calibration, errors in the assumed wavelength dependence of the PSF model, and limitations of the adopted template libraries. Our results indicate that the required accuracy for Euclid can be achieved using the data that are planned to determine photometric redshifts.

Implications of a wavelength dependent PSF for weak lensing measurements.

NASA Astrophysics Data System (ADS)

Eriksen, Martin; Hoekstra, Henk

2018-05-01

The convolution of galaxy images by the point-spread function (PSF) is the dominant source of bias for weak gravitational lensing studies, and an accurate estimate of the PSF is required to obtain unbiased shape measurements. The PSF estimate for a galaxy depends on its spectral energy distribution (SED), because the instrumental PSF is generally a function of the wavelength. In this paper we explore various approaches to determine the resulting `effective' PSF using broad-band data. Considering the Euclid mission as a reference, we find that standard SED template fitting methods result in biases that depend on source redshift, although this may be remedied if the algorithms can be optimised for this purpose. Using a machine-learning algorithm we show that, at least in principle, the required accuracy can be achieved with the current survey parameters. It is also possible to account for the correlations between photometric redshift and PSF estimates that arise from the use of the same photometry. We explore the impact of errors in photometric calibration, errors in the assumed wavelength dependence of the PSF model and limitations of the adopted template libraries. Our results indicate that the required accuracy for Euclid can be achieved using the data that are planned to determine photometric redshifts.

21 CFR 886.1840 - Simulatan (including crossed cylinder).

Code of Federal Regulations, 2010 CFR

2010-04-01

... of cylinder lenses that provides various equal plus and minus refractive strengths. The lenses are arranged so that the user can exchange the positions of plus and minus cylinder lenses of equal strengths... given object is clearly in focus, as the examiner uses different lenses). (b) Classification. Class I...

Compact Groups analysis using weak gravitational lensing

NASA Astrophysics Data System (ADS)

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

2017-05-01

We present a weak lensing analysis of a sample of Sloan Digital Sky Survey 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 CG 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 CG 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 yield σV ≈ 230 km s-1 in agreement with our lensing results.

H0LiCOW VIII. A weak-lensing measurement of the external convergence in the field of the lensed quasar HE 0435-1223

NASA Astrophysics Data System (ADS)

Tihhonova, O.; Courbin, F.; Harvey, D.; Hilbert, S.; Rusu, C. E.; Fassnacht, C. D.; Bonvin, V.; Marshall, P. J.; Meylan, G.; Sluse, D.; Suyu, S. H.; Treu, T.; Wong, K. C.

2018-07-01

We present a weak gravitational lensing measurement of the external convergence along the line of sight to the quadruply lensed quasar HE 0435-1223. Using deep r-band images from Subaru Suprime Cam, we observe galaxies down to a 3σ limiting magnitude of ˜26 mag resulting in a source galaxy density of 14 galaxies per square arcminute after redshift-based cuts. Using an inpainting technique and multiscale entropy filtering algorithm, we find that the region in close proximity to the lens has an estimated external convergence of κ =-0.012^{+0.020}_{-0.013} and is hence marginally underdense. We also rule out the presence of any halo with a mass greater than Mvir = 1.6 × 1014h-1M⊙ (68 per cent confidence limit). Our results, consistent with previous studies of this lens, confirm that the intervening mass along the line of sight to HE 0435-1223 does not affect significantly the cosmological results inferred from the time-delay measurements of that specific object.

H0LiCOW VIII. A weak lensing measurement of the external convergence in the field of the lensed quasar HE 0435-1223

NASA Astrophysics Data System (ADS)

Tihhonova, O.; Courbin, F.; Harvey, D.; Hilbert, S.; Rusu, C. E.; Fassnacht, C. D.; Bonvin, V.; Marshall, P. J.; Meylan, G.; Sluse, D.; Suyu, S. H.; Treu, T.; Wong, K. C.

2018-04-01

We present a weak gravitational lensing measurement of the external convergence along the line of sight to the quadruply lensed quasar HE 0435-1223. Using deep r-band images from Subaru-Suprime-Cam we observe galaxies down to a 3σ limiting magnitude of ˜26 mags resulting in a source galaxy density of 14 galaxies / arcmin2 after redshift-based cuts. Using an inpainting technique and Multi-Scale Entropy filtering algorithm, we find that the region in close proximity to the lens has an estimated external convergence of κ =-0.012^{+0.020}_{-0.013} and is hence marginally under-dense. We also rule out the presence of any halo with a mass greater than Mvir = 1.6 × 1014h-1M⊙ (68% confidence limit). Our results, consistent with previous studies of this lens, confirm that the intervening mass along the line of sight to HE 0435-1223 does not affect significantly the cosmological results inferred from the time delay measurements of that specific object.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Applegate, D. E; Mantz, A.; Allen, S. W.

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 measures the combined bias of X-ray hydrostatic masses from both astrophysical and instrumental sources. While we cannot disentangle the two sources of bias, only the combined bias is relevant for calibrating cosmological measurements using relaxed clusters. Assuming a fixed cosmology, and within amore » 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. Our results imply that any departures from hydrostatic equilibrium at these radii are offset by calibration errors of comparable magnitude, with large departures of tens-of-percent unlikely. In addition, we find a mean concentration of the sample measured from lensing data of c 200 = 3.0 +4.4 –1.8. In conclusion, anticipated short-term improvements in lensing systematics, and a modest expansion of the relaxed lensing sample, can easily increase the measurement precision by 30–50%, leading to similar improvements in cosmological constraints that employ X-ray hydrostatic mass estimates, such as on Ω m from the cluster gas mass fraction.« less

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

DOE PAGES

Applegate, D. E; Mantz, A.; Allen, S. W.; ...

2016-02-04

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 measures the combined bias of X-ray hydrostatic masses from both astrophysical and instrumental sources. While we cannot disentangle the two sources of bias, only the combined bias is relevant for calibrating cosmological measurements using relaxed clusters. Assuming a fixed cosmology, and within amore » 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. Our results imply that any departures from hydrostatic equilibrium at these radii are offset by calibration errors of comparable magnitude, with large departures of tens-of-percent unlikely. In addition, we find a mean concentration of the sample measured from lensing data of c 200 = 3.0 +4.4 –1.8. In conclusion, anticipated short-term improvements in lensing systematics, and a modest expansion of the relaxed lensing sample, can easily increase the measurement precision by 30–50%, leading to similar improvements in cosmological constraints that employ X-ray hydrostatic mass estimates, such as on Ω m from the cluster gas mass fraction.« less

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

NASA Astrophysics Data System (ADS)

Applegate, D. E.; Mantz, A.; Allen, S. W.; von der Linden, A.; Morris, R. Glenn; Hilbert, S.; Kelly, Patrick L.; Burke, D. L.; Ebeling, H.; Rapetti, D. A.; Schmidt, R. W.

2016-04-01

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 measures the combined bias of X-ray hydrostatic masses from both astrophysical and instrumental sources. While we cannot disentangle the two sources of bias, only the combined bias is relevant for calibrating cosmological measurements using relaxed clusters. Assuming a fixed cosmology, and within a characteristic radius (r2500) determined from the X-ray data, we measure a lensing to X-ray mass ratio of 0.96 ± 9 per cent (stat) ± 9 per cent (sys). We find no significant trends of this ratio with mass, redshift or the morphological indicators used to select the sample. Our results imply that any departures from hydrostatic equilibrium at these radii are offset by calibration errors of comparable magnitude, with large departures of tens-of-percent unlikely. In addition, we find a mean concentration of the sample measured from lensing data of c_{200} = 3.0_{-1.8}^{+4.4}. Anticipated short-term improvements in lensing systematics, and a modest expansion of the relaxed lensing sample, can easily increase the measurement precision by 30-50 per cent, leading to similar improvements in cosmological constraints that employ X-ray hydrostatic mass estimates, such as on Ωm from the cluster gas mass fraction.

Weak lensing shear and aperture mass from linear to non-linear scales

NASA Astrophysics Data System (ADS)

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

2004-05-01

We describe the predictions for the smoothed weak lensing shear, γs, and aperture mass,Map, of two simple analytical models of the density field: the minimal tree model and the stellar model. Both models give identical results for the statistics of the three-dimensional density contrast smoothed over spherical cells and only differ by the detailed angular dependence of the many-body density correlations. We have shown in previous work that they also yield almost identical results for the probability distribution function (PDF) of the smoothed convergence, κs. We find that the two models give rather close results for both the shear and the positive tail of the aperture mass. However, we note that at small angular scales (θs<~ 2 arcmin) the tail of the PDF, , for negative Map shows a strong variation between the two models, and the stellar model actually breaks down for θs<~ 0.4 arcmin and Map < 0. This shows that the statistics of the aperture mass provides a very precise probe of the detailed structure of the density field, as it is sensitive to both the amplitude and the detailed angular behaviour of the many-body correlations. On the other hand, the minimal tree model shows good agreement with numerical simulations over all the scales and redshifts of interest, while both models provide a good description of the PDF, , of the smoothed shear components. Therefore, the shear and the aperture mass provide robust and complementary tools to measure the cosmological parameters as well as the detailed statistical properties of the density field.

Weak-Lensing Determination of the Mass in Galaxy Halos

NASA Astrophysics Data System (ADS)

Smith, D. R.; Bernstein, G. M.; Fischer, P.; Jarvis, M.

2001-04-01

We detect the weak gravitational lensing distortion of 450,000 background galaxies (20

Binary Microlensing Events from the MACHO Project

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Baines, D.; Becker, A. C.; Bennett, D. P.; Bourke, A.; Brakel, A.; Cook, K. H.; Crook, B.; Crouch, A.; Dan, J.; Drake, A. J.; Fragile, P. C.; Freeman, K. C.; Gal-Yam, A.; Geha, M.; Gray, J.; Griest, K.; Gurtierrez, A.; Heller, A.; Howard, J.; Johnson, B. R.; Kaspi, S.; Keane, M.; Kovo, O.; Leach, C.; Leach, T.; Leibowitz, E. M.; Lehner, M. J.; Lipkin, Y.; Maoz, D.; Marshall, S. L.; McDowell, D.; McKeown, S.; Mendelson, H.; Messenger, B.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pozza, E.; Purcell, P.; Pratt, M. R.; Quinn, J.; Quinn, P. J.; Rhie, S. H.; Rodgers, A. W.; Salmon, A.; Shemmer, O.; Stetson, P.; Stubbs, C. W.; Sutherland, W.; Thomson, S.; Tomaney, A.; Vandehei, T.; Walker, A.; Ward, K.; Wyper, G.

2000-09-01

We present the light curves of 21 gravitational microlensing events from the first six years of the MACHO Project gravitational microlensing survey that are likely examples of lensing by binary systems. These events were manually selected from a total sample of ~350 candidate microlensing events that were either detected by the MACHO Alert System or discovered through retrospective analyses of the MACHO database. At least 14 of these 21 events exhibit strong (caustic) features, and four of the events are well fit with lensing by large mass ratio (brown dwarf or planetary) systems, although these fits are not necessarily unique. The total binary event rate is roughly consistent with predictions based upon our knowledge of the properties of binary stars, but a precise comparison cannot be made without a determination of our binary lens event detection efficiency. Toward the Galactic bulge, we find a ratio of caustic crossing to noncaustic crossing binary lensing events of 12:4, excluding one event for which we present two fits. This suggests significant incompleteness in our ability to detect and characterize noncaustic crossing binary lensing. The distribution of mass ratios, N(q), for these binary lenses appears relatively flat. We are also able to reliably measure source-face crossing times in four of the bulge caustic crossing events, and recover from them a distribution of lens proper motions, masses, and distances consistent with a population of Galactic bulge lenses at a distance of 7+/-1 kpc. This analysis yields two systems with companions of ~0.05 Msolar.

An end of service life assessment of PMMA lenses from veteran concentrator photovoltaic systems

DOE PAGES

Miller, David C.; Khonkar, Hussameldin I.; Herrero, Rebeca; ...

2017-04-04

The optical performance of poly(methyl methacrylate) lenses from veteran concentrator photovoltaic modules was examined after the end of their service life. Lenses from the Martin-Marietta and Intersol module designs were examined from the 'Solar Village' site near Riyadh, Saudi Arabia, as well as the Phoenix Sky Harbor airport, followed by the Arizona Public Service Solar Test and Research (APS-STaR) center in Tempe, Arizona. The various lens specimens were deployed for 20, 27, and 22 years, respectively. Optical characterizations included lens efficiency (Solar Simulator instrument), material transmittance and haze (of coupons cut from veteran lenses, then measured again after their facetedmore » back surface was polished, and then measured again after the incident front surface was polished), and direct transmittance (as a function of detector's acceptance angle, using the Very Low Angular Beam Spread ('VLABS') instrument). Lens efficiency measurements compared the central region to the entire lens, also using hot and cold mirror measurements to diagnose differences in performance. A series of subsequent characterizations was performed because a decrease in performance of greater than 10% was observed for some of the veteran lenses. The optimal focal distance of the lenses was quantified using the Solar Simulator, and then correlated to lens curvature using a recently developed measurement technique. Surface roughness was examined using atomic force microscopy and scanning electron microscopy. Facet geometry (tip and valley radius) was quantified on cross-sectioned specimens. As a result, molecular weight was compared between the incident and faceted surfaces of the lenses.« less

A measurement of the cosmic microwave background gravitational lensing potential from 100 square degrees of SPTpol data

DOE PAGES

Story, K. T.; Hanson, D.; Ade, P. A. R.; ...

2015-08-28

Here, we present a measurement of the cosmic microwave background (CMB) gravitational lensing potential using data from the first two seasons of observations with SPTpol, the polarization-sensitive receiver currently installed on the South Pole Telescope. The observations used in this work cover 100 deg 2 of sky with arcminute resolution at 150 GHz. Using a quadratic estimator, we make maps of the CMB lensing potential from combinations of CMB temperature and polarization maps. We combine these lensing potential maps to form a minimum-variance (MV) map. The lensing potential is measured with a signal-to-noise ratio of greater than one for angular multipoles betweenmore » $$100\\lt L\\lt 250$$. This is the highest signal-to-noise mass map made from the CMB to date and will be powerful in cross-correlation with other tracers of large-scale structure. We calculate the power spectrum of the lensing potential for each estimator, and we report the value of the MV power spectrum between $$100\\lt L\\lt 2000$$ as our primary result. We constrain the ratio of the spectrum to a fiducial ΛCDM model to be AMV = 0.92 ± 0.14 (Stat.) ± 0.08 (Sys.). Restricting ourselves to polarized data only, we find A POL = 0.92 ± 0.24 (Stat.) ± 0.11 (Sys.). This measurement rejects the hypothesis of no lensing at $$5.9\\sigma $$ using polarization data alone, and at $$14\\sigma $$ using both temperature and polarization data.« less

An end of service life assessment of PMMA lenses from veteran concentrator photovoltaic systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, David C.; Khonkar, Hussameldin I.; Herrero, Rebeca

The optical performance of poly(methyl methacrylate) lenses from veteran concentrator photovoltaic modules was examined after the end of their service life. Lenses from the Martin-Marietta and Intersol module designs were examined from the 'Solar Village' site near Riyadh, Saudi Arabia, as well as the Phoenix Sky Harbor airport, followed by the Arizona Public Service Solar Test and Research (APS-STaR) center in Tempe, Arizona. The various lens specimens were deployed for 20, 27, and 22 years, respectively. Optical characterizations included lens efficiency (Solar Simulator instrument), material transmittance and haze (of coupons cut from veteran lenses, then measured again after their facetedmore » back surface was polished, and then measured again after the incident front surface was polished), and direct transmittance (as a function of detector's acceptance angle, using the Very Low Angular Beam Spread ('VLABS') instrument). Lens efficiency measurements compared the central region to the entire lens, also using hot and cold mirror measurements to diagnose differences in performance. A series of subsequent characterizations was performed because a decrease in performance of greater than 10% was observed for some of the veteran lenses. The optimal focal distance of the lenses was quantified using the Solar Simulator, and then correlated to lens curvature using a recently developed measurement technique. Surface roughness was examined using atomic force microscopy and scanning electron microscopy. Facet geometry (tip and valley radius) was quantified on cross-sectioned specimens. As a result, molecular weight was compared between the incident and faceted surfaces of the lenses.« less

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

NASA Astrophysics Data System (ADS)

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.

THE CLUSTER LENSING AND SUPERNOVA SURVEY WITH HUBBLE (CLASH): STRONG-LENSING ANALYSIS OF A383 FROM 16-BAND HST/WFC3/ACS IMAGING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zitrin, A.; Broadhurst, T.; Coe, D.

2011-12-01

We examine the inner mass distribution of the relaxed galaxy cluster A383 (z = 0.189), in deep 16 band Hubble Space Telescope/ACS+WFC3 imaging taken as part of the Cluster Lensing And Supernova survey with Hubble (CLASH) multi-cycle treasury program. Our program is designed to study the dark matter distribution in 25 massive clusters, and balances depth with a wide wavelength coverage, 2000-16000 A, to better identify lensed systems and generate precise photometric redshifts. This photometric information together with the predictive strength of our strong-lensing analysis method identifies 13 new multiply lensed images and candidates, so that a total of 27more » multiple images of nine systems are used to tightly constrain the inner mass profile gradient, dlog {Sigma}/dlog r {approx_equal} -0.6 {+-} 0.1 (r < 160 kpc). We find consistency with the standard distance-redshift relation for the full range spanned by the lensed images, 1.01 < z < 6.03, with the higher-redshift sources deflected through larger angles as expected. The inner mass profile derived here is consistent with the results of our independent weak-lensing analysis of wide-field Subaru images, with good agreement in the region of overlap ({approx}0.7-1 arcmin). Combining weak and strong lensing, the overall mass profile is well fitted by a Navarro-Frenk-White profile with M{sub vir} = (5.37{sup +0.70}{sub -0.63} {+-} 0.26) Multiplication-Sign 10{sup 14} M{sub Sun} h{sup -1} and a relatively high concentration, c{sub vir} = 8.77{sup +0.44}{sub -0.42} {+-} 0.23, which lies above the standard c-M relation similar to other well-studied clusters. The critical radius of A383 is modest by the standards of other lensing clusters, r{sub E} {approx_equal} 16 {+-} 2'' (for z{sub s} = 2.55), so the relatively large number of lensed images uncovered here with precise photometric redshifts validates our imaging strategy for the CLASH survey. In total we aim to provide similarly high-quality lensing data for 25 clusters, 20 of which are X-ray-selected relaxed clusters, enabling a precise determination of the representative mass profile free from lensing bias.« less

X-Ray Temperatures, Luminosities, and Masses from XMM-Newton Follow-upof the First Shear-selected Galaxy Cluster Sample

NASA Astrophysics Data System (ADS)

Deshpande, Amruta J.; Hughes, John P.; Wittman, David

2017-04-01

We continue the study of the first sample of shear-selected clusters from the initial 8.6 square degrees of the Deep Lens Survey (DLS); a sample with well-defined selection criteria corresponding to the highest ranked shear peaks in the survey area. We aim to characterize the weak lensing selection by examining the sample’s X-ray properties. There are multiple X-ray clusters associated with nearly all the shear peaks: 14 X-ray clusters corresponding to seven DLS shear peaks. An additional three X-ray clusters cannot be definitively associated with shear peaks, mainly due to large positional offsets between the X-ray centroid and the shear peak. Here we report on the XMM-Newton properties of the 17 X-ray clusters. The X-ray clusters display a wide range of luminosities and temperatures; the L X -T X relation we determine for the shear-associated X-ray clusters is consistent with X-ray cluster samples selected without regard to dynamical state, while it is inconsistent with self-similarity. For a subset of the sample, we measure X-ray masses using temperature as a proxy, and compare to weak lensing masses determined by the DLS team. The resulting mass comparison is consistent with equality. The X-ray and weak lensing masses show considerable intrinsic scatter (˜48%), which is consistent with X-ray selected samples when their X-ray and weak lensing masses are independently determined. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

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

NASA Astrophysics Data System (ADS)

Lin, Chieh-An; Kilbinger, Martin

2015-11-01

Context. Peak counts have been shown to be an excellent tool for extracting the non-Gaussian part of the weak lensing signal. Recently, we developed a fast stochastic forward model to predict weak-lensing peak counts. Our model is able to reconstruct the underlying distribution of observables for analysis. Aims: In this work, we explore and compare various strategies for constraining a parameter using our model, focusing on the matter density Ωm and the density fluctuation amplitude σ8. Methods: First, we examine the impact from the cosmological dependency of covariances (CDC). Second, we perform the analysis with the copula likelihood, a technique that makes a weaker assumption than does 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. Results: We find that neglecting the CDC effect enlarges parameter contours by 22% and that the covariance-varying copula likelihood is a very good approximation to the true likelihood. The direct techniques work well in spite of noisier contours. Concerning ABC, the iterative process converges quickly to a posterior distribution that is in excellent agreement with results from our other analyses. The time cost for ABC is reduced by two orders of magnitude. Conclusions: The stochastic nature of our weak-lensing peak count model allows us to use various techniques that approach the true underlying probability distribution of observables, without making simplifying assumptions. Our work can be generalized to other observables where forward simulations provide samples of the underlying distribution.

The impact of baryons on massive galaxy clusters: halo structure and cluster mass estimates

NASA Astrophysics Data System (ADS)

Henson, Monique A.; Barnes, David J.; Kay, Scott T.; McCarthy, Ian G.; Schaye, Joop

2017-03-01

We use the BAHAMAS (BAryons and HAloes of MAssive Systems) and MACSIS (MAssive ClusterS and Intercluster Structures) hydrodynamic simulations to quantify the impact of baryons on the mass distribution and dynamics of massive galaxy clusters, as well as the bias in X-ray and weak lensing mass estimates. These simulations use the subgrid physics models calibrated in the BAHAMAS project, which include feedback from both supernovae and active galactic nuclei. They form a cluster population covering almost two orders of magnitude in mass, with more than 3500 clusters with masses greater than 1014 M⊙ at z = 0. We start by characterizing the clusters in terms of their spin, shape and density profile, before considering the bias in both weak lensing and hydrostatic mass estimates. Whilst including baryonic effects leads to more spherical, centrally concentrated clusters, the median weak lensing mass bias is unaffected by the presence of baryons. In both the dark matter only and hydrodynamic simulations, the weak lensing measurements underestimate cluster masses by ≈10 per cent for clusters with M200 ≤ 1015 M⊙ and this bias tends to zero at higher masses. We also consider the hydrostatic bias when using both the true density and temperature profiles, and those derived from X-ray spectroscopy. When using spectroscopic temperatures and densities, the hydrostatic bias decreases as a function of mass, leading to a bias of ≈40 per cent for clusters with M500 ≥ 1015 M⊙. This is due to the presence of cooler gas in the cluster outskirts. Using mass weighted temperatures and the true density profile reduces this bias to 5-15 per cent.

LoCuSS: weak-lensing mass calibration of galaxy clusters

NASA Astrophysics Data System (ADS)

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.

Discovery of a Lensed Ultrabright Submillimeter Galaxy at z = 2.0439

NASA Astrophysics Data System (ADS)

Díaz-Sánchez, A.; Iglesias-Groth, S.; Rebolo, R.; Dannerbauer, H.

2017-07-01

We report an ultrabright lensed submillimeter galaxy (SMG) at z = 2.0439, WISE J132934.18+224327.3, identified as a result of a full-sky cross-correlation of the AllWISE and Planck compact source catalogs aimed to search for bright analogs of the SMG SMM J2135, the Cosmic Eyelash. Inspection of archival SCUBA-2 observations of the candidates revealed a source with fluxes ({S}850μ {{m}}=130 mJy) consistent with the Planck measurements. The centroid of the SCUBA-2 source coincides within 1 arcsec with the position of the AllWISE mid-IR source, and, remarkably, with an arc-shaped lensed galaxy in HST images at visible wavelengths. Low-resolution rest-frame UV-optical spectroscopy of this lensed galaxy obtained with 10.4 m GTC reveals the typical absorption lines of a starburst galaxy. Gemini-N near-IR spectroscopy provided a clear detection of {{{H}}}α emission. The lensed source appears to be gravitationally magnified by a massive foreground galaxy cluster lens at z = 0.44 modeling with Lenstool indicates a lensing amplification factor of 11 ± 2. We determine an intrinsic rest-frame 8-1000 μm luminosity, {L}{IR}, of (1.3+/- 0.1)× {10}13 {L}⊙ , and a likely star formation rate (SFR) of ˜ 500{--}2000 {M}⊙ {{yr}}-1. The SED shows a remarkable similarity with the Cosmic Eyelash from optical-mid/IR to submillimeter/radio, albeit at higher fluxes.

Exploring cosmic origins with CORE: Gravitational lensing of the CMB

NASA Astrophysics Data System (ADS)

Challinor, A.; Allison, R.; Carron, J.; Errard, J.; Feeney, S.; Kitching, T.; Lesgourgues, J.; Lewis, A.; Zubeldía, Í.; Achucarro, A.; Ade, P.; Ashdown, M.; Ballardini, M.; Banday, A. J.; Banerji, R.; Bartlett, J.; Bartolo, N.; Basak, S.; Baumann, D.; Bersanelli, M.; Bonaldi, A.; Bonato, M.; Borrill, J.; Bouchet, F.; Boulanger, F.; Brinckmann, T.; Bucher, M.; Burigana, C.; Buzzelli, A.; Cai, Z.-Y.; Calvo, M.; Carvalho, C.-S.; Castellano, G.; Chluba, J.; Clesse, S.; Colantoni, I.; Coppolecchia, A.; Crook, M.; d'Alessandro, G.; de Bernardis, P.; de Gasperis, G.; De Zotti, G.; Delabrouille, J.; Di Valentino, E.; Diego, J.-M.; Fernandez-Cobos, R.; Ferraro, S.; Finelli, F.; Forastieri, F.; Galli, S.; Genova-Santos, R.; Gerbino, M.; González-Nuevo, J.; Grandis, S.; Greenslade, J.; Hagstotz, S.; Hanany, S.; Handley, W.; Hernandez-Monteagudo, C.; Hervías-Caimapo, C.; Hills, M.; Hivon, E.; Kiiveri, K.; Kisner, T.; Kunz, M.; Kurki-Suonio, H.; Lamagna, L.; Lasenby, A.; Lattanzi, M.; Liguori, M.; Lindholm, V.; López-Caniego, M.; Luzzi, G.; Maffei, B.; Martinez-González, E.; Martins, C. J. A. P.; Masi, S.; Matarrese, S.; McCarthy, D.; Melchiorri, A.; Melin, J.-B.; Molinari, D.; Monfardini, A.; Natoli, P.; Negrello, M.; Notari, A.; Paiella, A.; Paoletti, D.; Patanchon, G.; Piat, M.; Pisano, G.; Polastri, L.; Polenta, G.; Pollo, A.; Poulin, V.; Quartin, M.; Remazeilles, M.; Roman, M.; Rubino-Martin, J.-A.; Salvati, L.; Tartari, A.; Tomasi, M.; Tramonte, D.; Trappe, N.; Trombetti, T.; Tucker, C.; Valiviita, J.; Van de Weijgaert, R.; van Tent, B.; Vennin, V.; Vielva, P.; Vittorio, N.; Young, K.; Zannoni, M.

2018-04-01

Lensing of the cosmic microwave background (CMB) is now a well-developed probe of the clustering of the large-scale mass distribution over a broad range of redshifts. By exploiting the non-Gaussian imprints of lensing in the polarization of the CMB, the CORE mission will allow production of a clean map of the lensing deflections over nearly the full-sky. The number of high-S/N modes in this map will exceed current CMB lensing maps by a factor of 40, and the measurement will be sample-variance limited on all scales where linear theory is valid. Here, we summarise this mission product and discuss the science that will follow from its power spectrum and the cross-correlation with other clustering data. For example, the summed mass of neutrinos will be determined to an accuracy of 17 meV combining CORE lensing and CMB two-point information with contemporaneous measurements of the baryon acoustic oscillation feature in the clustering of galaxies, three times smaller than the minimum total mass allowed by neutrino oscillation measurements. Lensing has applications across many other science goals of CORE, including the search for B-mode polarization from primordial gravitational waves. Here, lens-induced B-modes will dominate over instrument noise, limiting constraints on the power spectrum amplitude of primordial gravitational waves. With lensing reconstructed by CORE, one can "delens" the observed polarization internally, reducing the lensing B-mode power by 60 %. This can be improved to 70 % by combining lensing and measurements of the cosmic infrared background from CORE, leading to an improvement of a factor of 2.5 in the error on the amplitude of primordial gravitational waves compared to no delensing (in the null hypothesis of no primordial B-modes). Lensing measurements from CORE will allow calibration of the halo masses of the tens of thousands of galaxy clusters that it will find, with constraints dominated by the clean polarization-based estimators. The 19 frequency channels proposed for CORE will allow accurate removal of Galactic emission from CMB maps. We present initial findings that show that residual Galactic foreground contamination will not be a significant source of bias for lensing power spectrum measurements with CORE.

Dependence of GAMA galaxy halo masses on the cosmic web environment from 100 deg2 of KiDS weak lensing data

NASA Astrophysics Data System (ADS)

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.

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

NASA Astrophysics Data System (ADS)

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 = 0.70. 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 ξ± suggests that a combined analysis would yield tighter constraints than either measure alone. As expected, w0de cannot be well constrained without a tomographic analysis, but its degeneracy directions with the other two varied parameters are still clear for both peaks and ξ±.

The relative impact of baryons and cluster shape on weak lensing mass estimates of galaxy clusters

NASA Astrophysics Data System (ADS)

Lee, B. E.; Le Brun, A. M. C.; Haq, M. E.; Deering, N. J.; King, L. J.; Applegate, D.; McCarthy, I. G.

2018-05-01

Weak gravitational lensing depends on the integrated mass along the line of sight. Baryons contribute to the mass distribution of galaxy clusters and the resulting mass estimates from lensing analysis. We use the cosmo-OWLS suite of hydrodynamic simulations to investigate the impact of baryonic processes on the bias and scatter of weak lensing mass estimates of clusters. These estimates are obtained by fitting NFW profiles to mock data using MCMC techniques. In particular, we examine the difference in estimates between dark matter-only runs and those including various prescriptions for baryonic physics. We find no significant difference in the mass bias when baryonic physics is included, though the overall mass estimates are suppressed when feedback from AGN is included. For lowest-mass systems for which a reliable mass can be obtained (M200 ≈ 2 × 1014M⊙), we find a bias of ≈-10 per cent. The magnitude of the bias tends to decrease for higher mass clusters, consistent with no bias for the most massive clusters which have masses comparable to those found in the CLASH and HFF samples. For the lowest mass clusters, the mass bias is particularly sensitive to the fit radii and the limits placed on the concentration prior, rendering reliable mass estimates difficult. The scatter in mass estimates between the dark matter-only and the various baryonic runs is less than between different projections of individual clusters, highlighting the importance of triaxiality.

Relativistic weak lensing from a fully non-linear cosmological density field

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, D.B.; Bruni, M.; Wands, D., E-mail: thomas.daniel@ucy.ac.cy, E-mail: marco.bruni@port.ac.uk, E-mail: david.wands@port.ac.uk

2015-09-01

In this paper we examine cosmological weak lensing on non-linear scales and show that there are Newtonian and relativistic contributions and that the latter can also be extracted from standard Newtonian simulations. We use the post-Friedmann formalism, a post-Newtonian type framework for cosmology, to derive the full weak-lensing deflection angle valid on non-linear scales for any metric theory of gravity. We show that the only contributing term that is quadratic in the first order deflection is the expected Born correction and lens-lens coupling term. We use this deflection angle to analyse the vector and tensor contributions to the E- andmore » B- mode cosmic shear power spectra. In our approach, once the gravitational theory has been specified, the metric components are related to the matter content in a well-defined manner. Specifying General Relativity, we write down a complete set of equations for a GR+ΛCDM universe for computing all of the possible lensing terms from Newtonian N-body simulations. We illustrate this with the vector potential and show that, in a GR+ΛCDM universe, its contribution to the E-mode is negligible with respect to that of the conventional Newtonian scalar potential, even on non-linear scales. Thus, under the standard assumption that Newtonian N-body simulations give a good approximation of the matter dynamics, we show that the standard ray tracing approach gives a good description for a ΛCDM cosmology.« less

Joint measurement of lensing-galaxy correlations using SPT and DES SV data

DOE PAGES

Baxter, E. J.

2016-07-04

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 favoredmore » $$\\Lambda$$CDM cosmological model. In conclusion, it also demonstrates that joint lensing-galaxy correlation measurement considered here contains a wealth of information that can be extracted using current and future surveys.« less

Joint measurement of lensing-galaxy correlations using SPT and DES SV data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baxter, E. J.

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 favoredmore » $$\\Lambda$$CDM cosmological model. In conclusion, it also demonstrates that joint lensing-galaxy correlation measurement considered here contains a wealth of information that can be extracted using current and future surveys.« less

Galaxy bias from galaxy-galaxy lensing in the DES Science Verification Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prat, J.; et al.

We present a measurement of galaxy-galaxy lensing around a magnitude-limited (more » $$i_{AB} < 22.5$$) sample of galaxies selected from the Dark Energy Survey Science Verification (DES-SV) data. We split these lenses into three photometric-redshift bins from 0.2 to 0.8, and determine the product of the galaxy bias $b$ and cross-correlation coefficient between the galaxy and dark matter overdensity fields $r$ in each bin, using scales above 4 Mpc/$h$ comoving, where we find the linear bias model to be valid given our current uncertainties. We compare our galaxy bias results from galaxy-galaxy lensing with those obtained from galaxy clustering (Crocce et al. 2016) and CMB lensing (Giannantonio et al. 2016) for the same sample of galaxies, and find our measurements to be in good agreement with those in Crocce et al. (2016), while, in the lowest redshift bin ($$z\\sim0.3$$), they show some tension with the findings in Giannantonio et al. (2016). Our results are found to be rather insensitive to a large range of systematic effects. We measure $$b\\cdot r$$ to be $$0.87\\pm 0.11$$, $$1.12 \\pm 0.16$$ and $$1.24\\pm 0.23$$, respectively for the three redshift bins of width $$\\Delta z = 0.2$$ in the range $0.2« less

The MICE Grand Challenge light-cone simulation - III. Galaxy lensing mocks from all-sky lensing maps

NASA Astrophysics Data System (ADS)

Fosalba, P.; Gaztañaga, E.; Castander, F. J.; Crocce, M.

2015-02-01

In Paper I of this series, we presented a new N-body light-cone simulation from the MICE Collaboration, the MICE Grand Challenge (MICE-GC), containing about 70 billion dark-matter particles in a (3 h-1 Gpc)3 comoving volume, from which we built halo and galaxy catalogues using a Halo Occupation Distribution and Halo Abundance Matching technique, as presented in the companion Paper II. Given its large volume and fine mass resolution, the MICE-GC simulation also allows an accurate modelling of the lensing observables from upcoming wide and deep galaxy surveys. In the last paper of this series (Paper III), we describe the construction of all-sky lensing maps, following the `Onion Universe' approach, and discuss their properties in the light-cone up to z = 1.4 with sub-arcminute spatial resolution. By comparing the convergence power spectrum in the MICE-GC to lower mass-resolution (i.e. particle mass ˜1011 h-1 M⊙) simulations, we find that resolution effects are at the 5 per cent level for multipoles ℓ ˜ 103 and 20 per cent for ℓ ˜ 104. Resolution effects have a much lower impact on our simulation, as shown by comparing the MICE-GC to recent numerical fits by Takahashi. We use the all-sky lensing maps to model galaxy lensing properties, such as the convergence, shear, and lensed magnitudes and positions, and validate them thoroughly using galaxy shear auto and cross-correlations in harmonic and configuration space. Our results show that the galaxy lensing mocks here presented can be used to accurately model lensing observables down to arcminute scales. Accompanying this series of papers, we make a first public data release of the MICE-GC galaxy mock, the MICECAT v1.0, through a dedicated web-portal for the MICE simulations, http://cosmohub.pic.es, to help developing and exploiting the new generation of astronomical surveys.

Cross-correlations between crude oil and agricultural commodity markets

NASA Astrophysics Data System (ADS)

Liu, Li

2014-02-01

In this paper, we investigate cross-correlations between crude oil and agricultural commodity markets. Based on a popular statistical test proposed by Podobnik et al. (2009), we find that the linear return cross-correlations are significant at larger lag lengths and the volatility cross-correlations are highly significant at all of the lag lengths under consideration. Using a detrended cross-correlation analysis (DCCA), we find that the return cross-correlations are persistent for corn and soybean and anti-persistent for oat and soybean. The volatility cross-correlations are strongly persistent. Using a nonlinear cross-correlation measure, our results show that cross-correlations are relatively weak but they are significant for smaller time scales. For larger time scales, the cross-correlations are not significant. The reason may be that information transmission from crude oil market to agriculture markets can complete within a certain period of time. Finally, based on multifractal extension of DCCA, we find that the cross-correlations are multifractal and high oil prices partly contribute to food crisis during the period of 2006-mid-2008.

Cosmology without cosmic variance

DOE PAGES

Bernstein, Gary M.; Cai, Yan -Chuan

2011-10-01

The growth of structures in the Universe is described by a function G that is predicted by the combination of the expansion history of the Universe and the laws of gravity within it. We examine the improvements in constraints on G that are available from the combination of a large-scale galaxy redshift survey with a weak gravitational lensing survey of background sources. We describe a new combination of such observations that in principle this yields a measure of the growth rate that is free of sample variance, i.e. the uncertainty in G can be reduced without bound by increasing themore » number of redshifts obtained within a finite survey volume. The addition of background weak lensing data to a redshift survey increases information on G by an amount equivalent to a 10-fold increase in the volume of a standard redshift-space distortion measurement - if the lensing signal can be measured to sub-per cent accuracy. This argues that a combined lensing and redshift survey over a common low-redshift volume of the Universe is a more powerful test of general relativity than an isolated redshift survey over larger volume at high redshift, especially as surveys begin to cover most of the available sky.« less

Compact Groups analysis using weak gravitational lensing II: CFHT Stripe 82 data

NASA Astrophysics Data System (ADS)

Chalela, Martín; Gonzalez, Elizabeth Johana; Makler, Martín; Lambas, Diego García; Pereira, Maria E. S.; O'mill, Ana; Shan, HuanYuan

2018-06-01

In this work we present a lensing study of Compact Groups (CGs) using data obtained from the high quality Canada-France-Hawaii Telescope Stripe 82 Survey. Using stacking techniques we obtain the average density contrast profile. We analyse the lensing signal dependence on the groups surface brightness and morphological content, for CGs in the redshift range z = 0.2 - 0.4. We obtain a larger lensing signal for CGs with higher surface brightness, probably due to their lower contamination by interlopers. Also, we find a strong dependence of the lensing signal on the group concentration parameter, with the most concentrated quintile showing a significant lensing signal, consistent with an isothermal sphere with σV = 336 ± 28 km/s and a NFW profile with R200 = 0.60 ± 0.05 h_{70}^{-1}Mpc. We also compare lensing results with dynamical estimates finding a good agreement with lensing determinations for CGs with higher surface brightness and higher concentration indexes. On the other hand, CGs that are more contaminated by interlopers show larger dynamical dispersions, since interlopers bias dynamical estimates to larger values, although the lensing signal is weakened.

The signal of weak gravitational lensing from galaxy groups and clusters

NASA Astrophysics Data System (ADS)

Markert, Sean

2017-02-01

The weak gravitational lensing of galaxy clusters is a valuable tool. The deflection of light around a lens is solely dependent on the underlying distribution of foreground mass, and independent of tracers of mass such as the mass to light ratio and kinematics. As a direct probe of mass, weak lensing serves as an independent calibration of mass-observable relationships. These massive clusters are objects of great interest to astronomers, as their abundance is dependent on the conditions of the early universe, and accurate counts of clusters serve as a test of cosmological model. Upcoming surveys, such as LSST and DES, promise to push the limit of observable weak lensing, detecting clusters and sources at higher redshift than has ever been detected before. This makes accurate counts of clusters of a given mass and redshift, and proper calibration of mass-observable relationships, vital to cosmological studies. We used M> 1013.5 h-1M ⊙ halos from the MultiDark Planck simulation at z 0.5 to study the behavior of the reduced shear in clusters. We generated 2D maps of convergence and shear the halos using the GLAMER lensing library. Using these maps, we simulated observations of randomly placed background sources, and generate azimuthal averages of the shear. This reduced shear profile, and the true reduced shear profile of the halo, is fit using analytical solutions for shear of the NFW, Einasto, and truncated NFW density profile. The masses of these density profiles are then compared to the total halo masses from the halo catalogs. We find that fits to the reduced shear for halos extending past ≈ 2 h-1Mpc are fits to the noise of large scale structure along the line of sight. This noise is largely in the 45° rotated component to the reduced tangential shear, and is a breakdown in the approximation of gtan ≈ gnot required for density profile fitting of clusters. If fits are constrained to a projected radii of < 2 h-1Mpc, we see massively improved fits insensitive to the amount of structure present along the line of sight.

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

NASA Astrophysics Data System (ADS)

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 suggest that such deep generative models represent a reliable alternative to the acquisition of expensive high quality observations for generating the calibration data needed by the next generation of weak lensing surveys.

Disentangling dark energy and cosmic tests of gravity from weak lensing systematics

NASA Astrophysics Data System (ADS)

Laszlo, Istvan; Bean, Rachel; Kirk, Donnacha; Bridle, Sarah

2012-06-01

We consider the impact of key astrophysical and measurement systematics on constraints on dark energy and modifications to gravity on cosmic scales. We focus on upcoming photometric ‘stage III’ and ‘stage IV’ large-scale structure surveys such as the Dark Energy Survey (DES), the Subaru Measurement of Images and Redshifts survey, the Euclid survey, the Large Synoptic Survey Telescope (LSST) and Wide Field Infra-Red Space Telescope (WFIRST). We illustrate the different redshift dependencies of gravity modifications compared to intrinsic alignments, the main astrophysical systematic. The way in which systematic uncertainties, such as galaxy bias and intrinsic alignments, are modelled can change dark energy equation-of-state parameter and modified gravity figures of merit by a factor of 4. The inclusion of cross-correlations of cosmic shear and galaxy position measurements helps reduce the loss of constraining power from the lensing shear surveys. When forecasts for Planck cosmic microwave background and stage IV surveys are combined, constraints on the dark energy equation-of-state parameter and modified gravity model are recovered, relative to those from shear data with no systematic uncertainties, provided fewer than 36 free parameters in total are used to describe the galaxy bias and intrinsic alignment models as a function of scale and redshift. While some uncertainty in the intrinsic alignment (IA) model can be tolerated, it is going to be important to be able to parametrize IAs well in order to realize the full potential of upcoming surveys. To facilitate future investigations, we also provide a fitting function for the matter power spectrum arising from the phenomenological modified gravity model we consider.

Solar concentration properties of flat fresnel lenses with large F-numbers

NASA Technical Reports Server (NTRS)

Cosby, R. M.

1978-01-01

The solar concentration performances of flat, line-focusing sun-tracking Fresnel lenses with selected f-numbers between 0.9 and 2.0 were analyzed. Lens transmittance was found to have a weak dependence on f-number, with a 2% increase occuring as the f-number is increased from 0.9 to 2.0. The geometric concentration ratio for perfectly tracking lenses peaked for an f-number near 1.35. Intensity profiles were more uniform over the image extent for large f-number lenses when compared to the f/0.9 lens results. Substantial decreases in geometri concentration ratios were observed for transverse tracking errors equal to or below 1 degree for all f-number lenses. With respect to tracking errors, the solar performance is optimum for f-numbers between 1.25 and 1.5.

Parabolic crossed planar polymeric x-ray lenses

NASA Astrophysics Data System (ADS)

Nazmov, V.; Reznikova, E.; Mohr, J.; Saile, V.; Vincze, L.; Vekemans, B.; Bohic, S.; Somogyi, A.

2011-01-01

The principles of design and manufacturing of the polymer planar x-ray lenses focusing in one and two directions, as well as the peculiarities of optical behaviors and the results of the lens test are reported in this paper. The methods of electron and deep x-ray lithography used in lens manufacturing allow the manufacture of ten or more x-ray lenses on one substrate; the lenses show focal lengths down to several centimeters for photon energies between 5 and 40 keV. The measured focus size was 105 nm for a linear lens with an intensity gain of about 407, and 300 × 770 nm for a crossed lens with an intensity gain of 6470.

The Hidden Fortress: structure and substructure of the complex strong lensing cluster SDSS J1029+2623

NASA Astrophysics Data System (ADS)

Oguri, Masamune; Schrabback, Tim; Jullo, Eric; Ota, Naomi; Kochanek, Christopher S.; Dai, Xinyu; Ofek, Eran O.; Richards, Gordon T.; Blandford, Roger D.; Falco, Emilio E.; Fohlmeister, Janine

2013-02-01

We present Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) and Wide Field Camera 3 (WFC3) observations of SDSS J1029+2623, a three-image quasar lens system produced by a foreground cluster at z = 0.584. Our strong lensing analysis reveals six additional multiply imaged galaxies in addition to the multiply imaged quasar. We confirm the complex nature of the mass distribution of the lensing cluster, with a bimodal dark matter distribution which deviates from the Chandra X-ray surface brightness distribution. The Einstein radius of the lensing cluster is estimated to be θE = 15.2 ± 0.5 arcsec for the quasar redshift of z = 2.197. We derive a radial mass distribution from the combination of strong lensing, HST/ACS weak lensing and Subaru/Suprime-cam weak lensing analysis results, finding a best-fitting virial mass of Mvir = 1.55+ 0.40- 0.35 × 1014 h- 1 M⊙ and a concentration parameter of cvir = 25.7+ 14.1- 7.5. The lensing mass estimate at the outer radius is smaller than the X-ray mass estimate by a factor of ˜2. We ascribe this large mass discrepancy to shock heating of the intracluster gas during a merger, which is also suggested by the complex mass and gas distributions and the high value of the concentration parameter. In the HST image, we also identify a probable galaxy, GX, in the vicinity of the faintest quasar image C. In strong lens models, the inclusion of GX explains the anomalous flux ratios between the quasar images. The morphology of the highly elongated quasar host galaxy is also well reproduced. The best-fitting model suggests large total magnifications of 30 for the quasar and 35 for the quasar host galaxy, and has an AB time delay consistent with the measured value.

Practical Weak-lensing Shear Measurement with Metacalibration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheldon, Erin S.; Huff, Eric M.

2017-05-20

Metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observe that for imagesmore » with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.« less

Calibrating the Planck Cluster Mass Scale with Cluster Velocity Dispersions

NASA Astrophysics Data System (ADS)

Amodeo, Stefania; Mei, Simona; Stanford, Spencer A.; Bartlett, James G.; Melin, Jean-Baptiste; Lawrence, Charles R.; Chary, Ranga-Ram; Shim, Hyunjin; Marleau, Francine; Stern, Daniel

2017-08-01

We measure the Planck cluster mass bias using dynamical mass measurements based on velocity dispersions of a subsample of 17 Planck-detected clusters. The velocity dispersions were calculated using redshifts determined from spectra that were obtained at the Gemini observatory with the GMOS multi-object spectrograph. We correct our estimates for effects due to finite aperture, Eddington bias, and correlated scatter between velocity dispersion and the Planck mass proxy. The result for the mass bias parameter, (1-b), depends on the value of the galaxy velocity bias, {b}{{v}}, adopted from simulations: (1-b)=(0.51+/- 0.09){b}{{v}}3. Using a velocity bias of {b}{{v}}=1.08 from Munari et al., we obtain (1-b)=0.64+/- 0.11, I.e., an error of 17% on the mass bias measurement with 17 clusters. This mass bias value is consistent with most previous weak-lensing determinations. It lies within 1σ of the value that is needed to reconcile the Planck cluster counts with the Planck primary cosmic microwave background constraints. We emphasize that uncertainty in the velocity bias severely hampers the precision of the measurements of the mass bias using velocity dispersions. On the other hand, when we fix the Planck mass bias using the constraints from Penna-Lima et al., based on weak-lensing measurements, we obtain a positive velocity bias of {b}{{v}}≳ 0.9 at 3σ .

Simulating the effect of non-linear mode coupling in cosmological parameter estimation

NASA Astrophysics Data System (ADS)

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

2011-09-01

Fisher Information Matrix methods are commonly used in cosmology to estimate the accuracy that cosmological parameters can be measured with a given experiment and to optimize the design of experiments. However, the standard approach usually assumes both data and parameter estimates are Gaussian-distributed. Further, for survey forecasts and optimization it is usually assumed that the power-spectrum covariance matrix is diagonal in Fourier space. However, in the low-redshift Universe, non-linear mode coupling will tend to correlate small-scale power, moving information from lower to higher order moments of the field. This movement of information will change the predictions of cosmological parameter accuracy. In this paper we quantify this loss of information by comparing naïve Gaussian Fisher matrix forecasts with a maximum likelihood parameter estimation analysis of a suite of mock weak lensing catalogues derived from N-body simulations, based on the SUNGLASS pipeline, for a 2D and tomographic shear analysis of a Euclid-like survey. In both cases, we find that the 68 per cent confidence area of the Ωm-σ8 plane increases by a factor of 5. However, the marginal errors increase by just 20-40 per cent. We propose a new method to model the effects of non-linear shear-power mode coupling in the Fisher matrix by approximating the shear-power distribution as a multivariate Gaussian with a covariance matrix derived from the mock weak lensing survey. We find that this approximation can reproduce the 68 per cent confidence regions of the full maximum likelihood analysis in the Ωm-σ8 plane to high accuracy for both 2D and tomographic weak lensing surveys. Finally, we perform a multiparameter analysis of Ωm, σ8, h, ns, w0 and wa to compare the Gaussian and non-linear mode-coupled Fisher matrix contours. The 6D volume of the 1σ error contours for the non-linear Fisher analysis is a factor of 3 larger than for the Gaussian case, and the shape of the 68 per cent confidence volume is modified. We propose that future Fisher matrix estimates of cosmological parameter accuracies should include mode-coupling effects.

Only marginal alignment of disc galaxies

NASA Astrophysics Data System (ADS)

Andrae, René; Jahnke, Knud

2011-12-01

Testing theories of angular-momentum acquisition of rotationally supported disc galaxies is the key to understanding the formation of this type of galaxies. The tidal-torque theory aims to explain this acquisition process in a cosmological framework and predicts positive autocorrelations of angular-momentum orientation and spiral-arm handedness, i.e. alignment of disc galaxies, on short distance scales of 1 Mpc h-1. This disc alignment can also cause systematic effects in weak-lensing measurements. Previous observations claimed discovering these correlations but are overly optimistic in the reported level of statistical significance of the detections. Errors in redshift, ellipticity and morphological classifications were not taken into account, although they have a significant impact. We explain how to rigorously propagate all the important errors through the estimation process. Analysing disc galaxies in the Sloan Digital Sky Survey (SDSS) data base, we find that positive autocorrelations of spiral-arm handedness and angular-momentum orientations on distance scales of 1 Mpc h-1 are plausible but not statistically significant. Current data appear not good enough to constrain parameters of theory. This result agrees with a simple hypothesis test in the Local Group, where we also find no evidence for disc alignment. Moreover, we demonstrate that ellipticity estimates based on second moments are strongly biased by galactic bulges even for Scd galaxies, thereby corrupting correlation estimates and overestimating the impact of disc alignment on weak-lensing studies. Finally, we discuss the potential of future sky surveys. We argue that photometric redshifts have too large errors, i.e. PanSTARRS and LSST cannot be used. Conversely, the EUCLID project will not cover the relevant redshift regime. We also discuss the potentials and problems of front-edge classifications of galaxy discs in order to improve the autocorrelation estimates of angular-momentum orientation.

Improving Weak Lensing Mass Map Reconstructions using Gaussian and Sparsity Priors: Application to DES SV

NASA Astrophysics Data System (ADS)

Jeffrey, N.; Abdalla, F. B.; Lahav, O.; Lanusse, F.; Starck, J.-L.; Leonard, A.; Kirk, D.; Chang, C.; Baxter, E.; Kacprzak, T.; Seitz, S.; Vikram, V.; Whiteway, L.; Abbott, T. M. C.; Allam, S.; Avila, S.; Bertin, E.; Brooks, 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.; Davis, C.; De Vicente, J.; Desai, S.; Doel, P.; Eifler, T. F.; Evrard, A. E.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; Hartley, W. G.; Honscheid, K.; Hoyle, B.; James, D. J.; Jarvis, M.; Kuehn, K.; Lima, M.; Lin, H.; March, M.; Melchior, P.; Menanteau, F.; Miquel, R.; Plazas, A. A.; Reil, K.; Roodman, A.; Sanchez, E.; Scarpine, V.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Walker, A. R.

2018-05-01

Mapping the underlying density field, including non-visible dark matter, using weak gravitational lensing measurements is now a standard tool in cosmology. Due to its importance to the science results of current and upcoming surveys, the quality of the convergence reconstruction methods should be well understood. We compare three methods: Kaiser-Squires (KS), Wiener filter, and GLIMPSE. KS is a direct inversion, not accounting for survey masks or noise. The Wiener filter is well-motivated for Gaussian density fields in a Bayesian framework. GLIMPSE uses sparsity, aiming to reconstruct non-linearities in the density field. We compare these methods with several tests using public Dark Energy Survey (DES) Science Verification (SV) data and realistic DES simulations. The Wiener filter and GLIMPSE offer substantial improvements over smoothed KS with a range of metrics. Both the Wiener filter and GLIMPSE convergence reconstructions show a 12% improvement in Pearson correlation with the underlying truth from simulations. To compare the mapping methods' abilities to find mass peaks, we measure the difference between peak counts from simulated ΛCDM shear catalogues and catalogues with no mass fluctuations (a standard data vector when inferring cosmology from peak statistics); the maximum signal-to-noise of these peak statistics is increased by a factor of 3.5 for the Wiener filter and 9 for GLIMPSE. With simulations we measure the reconstruction of the harmonic phases; the phase residuals' concentration is improved 17% by GLIMPSE and 18% by the Wiener filter. The correlation between reconstructions from data and foreground redMaPPer clusters is increased 18% by the Wiener filter and 32% by GLIMPSE.

CMB lensing forecasts for constraining the primordial perturbations: adding to the CMB temperature and polarization information

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kasanda, Simon Muya; Moodley, Kavilan, E-mail: simon.muya.kasanda@gmail.com, E-mail: moodleyk41@ukzn.ac.za

2014-12-01

We forecast how current (PLANCK) and future (PRISM) cosmic microwave background (CMB) experiments constrain the adiabatic mode and its admixtures with primordial isocurvature modes. The forecasts are based on measurements of the reconstructed CMB lensing potential and lensing-induced CMB B-mode polarization anisotropies in combination with the CMB temperature and E-mode polarization anisotropies. We first study the characteristic features of the CMB temperature, polarization and lensing spectra for adiabatic and isocurvature modes. We then consider how information from the CMB lensing potential and B-mode polarization induced by lensing can improve constraints on an admixture of adiabatic and three correlated isocurvature modes.more » We find that the CMB lensing spectrum improves constraints on isocurvature modes by at most 10% for the PLANCK and PRISM experiments. The limited improvement is a result of the low amplitude of isocurvature lensing spectra and cancellations between these spectra that render them only slightly detectable. There is a larger gain from using the lensing-induced B-mode polarization spectrum measured by PRISM. In this case constraints on isocurvature mode amplitudes improve by as much as 40% relative to the CMB temperature and E-mode polarization constraints. The addition of both lensing and lensing-induced B-mode polarization information constrains isocurvature mode amplitudes at the few percent level or better. In the case of admixtures of the adiabatic mode with one or two correlated isocurvature modes we find that constraints at the percent level or better are possible. We investigate the dependence of our results to various assumptions in our analysis, such as the inclusion of dark energy parameters, the CMB temperature-lensing correlation, and the presence of primordial tensor modes, and find that these assumptions do not significantly change our main results.« less

Weak Lensing by Galaxy Clusters: from Pixels to Cosmology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gruen, Daniel

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 clustermore » 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 J2248.7--4431 our lensing analysis constrains mass and concentration of the cluster halo and we confirm the large mass predicted by X-ray and Sunyaev-Zel’dovich (SZ) observations. The study of cluster members shows the relation of galaxy morphology to luminosity and environment. (ii) Our lensing mass measurements for 12 clusters are consistent with X-ray masses derived under the assumption of hydrostatic equilibrium of the intra-cluster gas. We confirm the MORs derived by the South Pole Telescope collaboration for the detection significance of the cluster SZ signal in their survey. We find discrepancies, however, with the Planck SZ MOR. We hypothesize that these are related either to a shallower slope of the MOR or a size-, redshift- or noise-dependent bias in SZ signal extraction. (iii) Finally, using a combination of simulations and theoretical models for the variation of cluster profiles at fixed mass, we find that the latter is a significant contribution to the uncertainty of cluster lensing mass measurements. A cosmic variance model, such as the one we develop, is necessary for MOR constraints to be accurate at the level required for future surveys.« less

Testing a generalized cubic Galileon gravity model with the Coma Cluster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terukina, Ayumu; Yamamoto, Kazuhiro; Okabe, Nobuhiro

2015-10-01

We obtain a constraint on the parameters of a generalized cubic Galileon gravity model exhibiting the Vainshtein mechanism by using multi-wavelength observations of the Coma Cluster. The generalized cubic Galileon model is characterized by three parameters of the turning scale associated with the Vainshtein mechanism, and the amplitude of modifying a gravitational potential and a lensing potential. X-ray and Sunyaev-Zel'dovich (SZ) observations of the intra-cluster medium are sensitive to the gravitational potential, while the weak-lensing (WL) measurement is specified by the lensing potential. A joint fit of a complementary multi-wavelength dataset of X-ray, SZ and WL measurements enables us tomore » simultaneously constrain these three parameters of the generalized cubic Galileon model for the first time. We also find a degeneracy between the cluster mass parameters and the gravitational modification parameters, which is influential in the limit of the weak screening of the fifth force.« less

Projection Effects of Large-scale Structures on Weak-lensing Peak Abundances

NASA Astrophysics Data System (ADS)

Yuan, Shuo; Liu, Xiangkun; Pan, Chuzhong; Wang, Qiao; Fan, Zuhui

2018-04-01

High peaks in weak lensing (WL) maps originate dominantly from the lensing effects of single massive halos. Their abundance is therefore closely related to the halo mass function and thus a powerful cosmological probe. However, besides individual massive halos, large-scale structures (LSS) along lines of sight also contribute to the peak signals. In this paper, with ray-tracing simulations, we investigate the LSS projection effects. We show that for current surveys with a large shape noise, the stochastic LSS effects are subdominant. For future WL surveys with source galaxies having a median redshift z med ∼ 1 or higher, however, they are significant. For the cosmological constraints derived from observed WL high-peak counts, severe biases can occur if the LSS effects are not taken into account properly. We extend the model of Fan et al. by incorporating the LSS projection effects into the theoretical considerations. By comparing with simulation results, we demonstrate the good performance of the improved model and its applicability in cosmological studies.

Attenuation of harmonic noise in vibroseis data using Simulated Annealing

NASA Astrophysics Data System (ADS)

Sharma, S. P.; Tildy, Peter; Iranpour, Kambiz; Scholtz, Peter

2009-04-01

Processing of high productivity vibroseis seismic data (such as slip-sweep acquisition records) suffers from the well known disadvantage of harmonic distortion. Harmonic distortions are observed after cross-correlation of the recorded seismic signal with the pilot sweep and affect the signals in negative time (before the actual strong reflection event). Weak reflection events of the earlier sweeps falling in the negative time window of the cross-correlation sequence are being masked by harmonic distortions. Though the amplitude of the harmonic distortion is small (up to 10-20 %) compared to the fundamental amplitude of the reflection events, but it is significant enough to mask weak reflected signals. Elimination of harmonic noise due to source signal distortion from the cross-correlated seismic trace is a challenging task since the application of vibratory sources started and it still needs improvement. An approach has been worked out that minimizes the level of harmonic distortion by designing the signal similar to the harmonic distortion. An arbitrary length filter is optimized using the Simulated Annealing global optimization approach to design a harmonic signal. The approach deals with the convolution of a ratio trace (ratio of the harmonics with respect to the fundamental sweep) with the correlated "positive time" recorded signal and an arbitrary filter. Synthetic data study has revealed that this procedure of designing a signal similar to the desired harmonics using convolution of a suitable filter with theoretical ratio of harmonics with fundamental sweep helps in reducing the problem of harmonic distortion. Once we generate a similar signal for a vibroseis source using an optimized filter, then, this filter could be used to generate harmonics, which can be subtracted from the main cross-correlated trace to get the better, undistorted image of the subsurface. Designing the predicted harmonics to reduce the energy in the trace by considering weak reflection and observed harmonics together yields the desired result (resolution of weak reflected signal from the harmonic distortion). As optimization steps proceeds forward it is possible to observe from the difference plots of desired and predicted harmonics how weak reflections evolved from the harmonic distortion gradually during later iterations of global optimization. The procedure is applied in resolving weak reflections from a number of traces considered together. For a more precise design of harmonics SA procedure needs longer computation time which is impractical to deal with voluminous seismic data. However, the objective of resolving weak reflection signal in the strong harmonic noise can be achieved with fast computation using faster cooling schedule and less number of iterations and number of moves in simulated annealing procedure. This process could help in reducing the harmonics distortion and achieving the objective of resolving the lost weak reflection events in the cross-correlated seismic traces. Acknowledgements: The research was supported under the European Marie Curie Host Fellowships for Transfer of Knowledge (TOK) Development Host Scheme (contract no. MTKD-CT-2006-042537).

Are Large Core Radius Clusters Merging Systems?

NASA Technical Reports Server (NTRS)

Forman, William R.

1997-01-01

We have analyzed observations for two lensing clusters of galaxies, A1689 and A2218. Our investigations have explored the implications of their X-ray properties for mass determinations both in X-rays and through both weak and strong gravitational lensing. The work on these two clusters is summarized below and copies of the two papers submitted to the Astrophysical Journal and accepted for publication are attached.

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

DOE PAGES

Melchior, P.; Gruen, D.; McClintock, T.; ...

2017-05-16

Here, 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 8000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter 5 ≤ λ ≤ 180 and redshift 0.2 ≤ z ≤ 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; miscentring; deviations from the NFW halo profile; halo triaxiality and line-of-sight projections.

XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster Cl J120958.9+495352 ( z = 0.902)

DOE PAGES

Tholken, Sophia; Schrabback, Tim; Reiprich, Thomas H.; ...

2018-03-05

Here, observations of relaxed, massive, and distant clusters can provide important tests of standard cosmological models, for example by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to be investigated. X-ray analyses provide one of the best opportunities to access this information and to determine important properties such as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analyses are complementary independent probes that are essential in order to test whether X-ray masses could be biased.

XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster Cl J120958.9+495352 ( z = 0.902)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tholken, Sophia; Schrabback, Tim; Reiprich, Thomas H.

Here, observations of relaxed, massive, and distant clusters can provide important tests of standard cosmological models, for example by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to be investigated. X-ray analyses provide one of the best opportunities to access this information and to determine important properties such as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analyses are complementary independent probes that are essential in order to test whether X-ray masses could be biased.

Relieving the tension between weak lensing and cosmic microwave background with interacting dark matter and dark energy models

NASA Astrophysics Data System (ADS)

An, Rui; Feng, Chang; Wang, Bin

2018-02-01

We constrain interacting dark matter and dark energy (IDMDE) models using a 450-degree-square cosmic shear data from the Kilo Degree Survey (KiDS) and the angular power spectra from Planck's latest cosmic microwave background measurements. We revisit the discordance problem in the standard Lambda cold dark matter (ΛCDM) model between weak lensing and Planck datasets and extend the discussion by introducing interacting dark sectors. The IDMDE models are found to be able to alleviate the discordance between KiDS and Planck as previously inferred from the ΛCDM model, and moderately favored by a combination of the two datasets.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melchior, P.; Gruen, D.; McClintock, T.

Here, 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 8000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter 5 ≤ λ ≤ 180 and redshift 0.2 ≤ z ≤ 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; miscentring; deviations from the NFW halo profile; halo triaxiality and line-of-sight projections.

Microbiologic Examination of Bandage Contact Lenses Used after Corneal Collagen Cross-linking Treatment.

PubMed

Yuksel, Erdem; Yalcin, Nuriye Gokçen; Kilic, Gaye; Cubuk, Mehmet Ozgur; Ozmen, Mehmet Cuneyt; Altay, Aylin; Çağlar, Kayhan; Bilgihan, Kamil

2016-01-01

To investigate the agents of bacterial contamination of contact lenses after corneal collagen cross-linking (CCL), and to present the possible changes of ocular flora after riboflavin/ultraviolet A. Seventy-two contact lenses of patients who underwent CCL and 41 contact lenses of patients who underwent photorefractive keratectomy (PRK) as control group were enrolled to the study. After 48 h of incubation, broth culture media was transferred to plates. Samples were accepted as positive if one or more colony-forming units were shown. There were positive cultures in 12 (16.7%) contact lenses in the CCL group and 5 (12.2%) had positive cultures in PRK group. Coagulase-negative staphlycocci (CNS) were the most frequent microorganism. Alpha hemolytic streptococci and Diphteroid spp. were the other isolated microorganisms. Bacterial colonization can occur during and early after the CCL procedure in epithelial healing. To prevent corneal infections after the treatment, prophylactic antibiotics should be prescribed.

Weak Lensing Peaks in Simulated Light-Cones: Investigating the Coupling between Dark Matter and Dark Energy

NASA Astrophysics Data System (ADS)

Giocoli, Carlo; Moscardini, Lauro; Baldi, Marco; Meneghetti, Massimo; Metcalf, Robert B.

2018-05-01

In this paper, we study the statistical properties of weak lensing peaks in light-cones generated from cosmological simulations. In order to assess the prospects of such observable as a cosmological probe, we consider simulations that include interacting Dark Energy (hereafter DE) models with coupling term between DE and Dark Matter. Cosmological models that produce a larger population of massive clusters have more numerous high signal-to-noise peaks; among models with comparable numbers of clusters those with more concentrated haloes produce more peaks. The most extreme model under investigation shows a difference in peak counts of about 20% with respect to the reference ΛCDM model. We find that peak statistics can be used to distinguish a coupling DE model from a reference one with the same power spectrum normalisation. The differences in the expansion history and the growth rate of structure formation are reflected in their halo counts, non-linear scale features and, through them, in the properties of the lensing peaks. For a source redshift distribution consistent with the expectations of future space-based wide field surveys, we find that typically seventy percent of the cluster population contributes to weak-lensing peaks with signal-to-noise ratios larger than two, and that the fraction of clusters in peaks approaches one-hundred percent for haloes with redshift z ≤ 0.5. Our analysis demonstrates that peak statistics are an important tool for disentangling DE models by accurately tracing the structure formation processes as a function of the cosmic time.

ELLIPTICAL WEIGHTED HOLICs FOR WEAK LENSING SHEAR MEASUREMENT. III. THE EFFECT OF RANDOM COUNT NOISE ON IMAGE MOMENTS IN WEAK LENSING ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okura, Yuki; Futamase, Toshifumi, E-mail: yuki.okura@nao.ac.jp, E-mail: tof@astr.tohoku.ac.jp

This is the third paper on the improvement of systematic errors in weak lensing analysis using an elliptical weight function, referred to as E-HOLICs. In previous papers, we succeeded in avoiding errors that depend on the ellipticity of the background image. In this paper, we investigate the systematic error that depends on the signal-to-noise ratio of the background image. We find that the origin of this error is the random count noise that comes from the Poisson noise of sky counts. The random count noise makes additional moments and centroid shift error, and those first-order effects are canceled in averaging,more » but the second-order effects are not canceled. We derive the formulae that correct this systematic error due to the random count noise in measuring the moments and ellipticity of the background image. The correction formulae obtained are expressed as combinations of complex moments of the image, and thus can correct the systematic errors caused by each object. We test their validity using a simulated image and find that the systematic error becomes less than 1% in the measured ellipticity for objects with an IMCAT significance threshold of {nu} {approx} 11.7.« less

Dark Energy Survey Year 1 Results: redshift distributions of the weak-lensing source galaxies

NASA Astrophysics Data System (ADS)

Hoyle, B.; Gruen, D.; Bernstein, G. M.; Rau, M. M.; De Vicente, J.; Hartley, W. G.; Gaztanaga, E.; DeRose, J.; Troxel, M. A.; Davis, C.; Alarcon, A.; MacCrann, N.; Prat, J.; Sánchez, C.; Sheldon, E.; Wechsler, R. H.; Asorey, J.; Becker, M. R.; Bonnett, C.; Carnero Rosell, A.; Carollo, D.; Carrasco Kind, M.; Castander, F. J.; Cawthon, R.; Chang, C.; Childress, M.; Davis, T. M.; Drlica-Wagner, A.; Gatti, M.; Glazebrook, K.; Gschwend, J.; Hinton, S. R.; Hoormann, J. K.; Kim, A. G.; King, A.; Kuehn, K.; Lewis, G.; Lidman, C.; Lin, H.; Macaulay, E.; Maia, M. A. G.; Martini, P.; Mudd, D.; Möller, A.; Nichol, R. C.; Ogando, R. L. C.; Rollins, R. P.; Roodman, A.; Ross, A. J.; Rozo, E.; Rykoff, E. S.; Samuroff, S.; Sevilla-Noarbe, I.; Sharp, R.; Sommer, N. E.; Tucker, B. E.; Uddin, S. A.; Varga, T. N.; Vielzeuf, P.; Yuan, F.; Zhang, B.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Busha, M. T.; Capozzi, D.; Carretero, J.; Crocce, M.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Fernandez, E.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gerdes, D. W.; Giannantonio, T.; Goldstein, D. A.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jarvis, M.; Jeltema, T.; Johnson, M. W. G.; Johnson, M. D.; Kirk, D.; Krause, E.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; March, M.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Miquel, R.; Nord, B.; O'Neill, C. R.; Plazas, A. A.; Romer, A. K.; Sako, M.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schindler, R.; Schubnell, M.; Smith, M.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D. L.; Vikram, V.; Walker, A. R.; Weller, J.; Wester, W.; Wolf, R. C.; Yanny, B.; Zuntz, J.

2018-07-01

We describe the derivation and validation of redshift distribution estimates and their uncertainties for the populations of 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)∝ dn^i/dz for members of bin i. Accurate determination of cosmological parameters depends critically on knowledge of ni, 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-Δ z^i) to correct the mean redshift of ni(z) for biases in n^i_PZ. The Δzi are constrained by comparison of independently estimated 30-band photometric redshifts of galaxies in the Cosmic Evolution Survey (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 Δzi of the three lowest redshift bins are further constrained by the angular clustering of the source galaxies around red galaxies with secure photometric redshifts at 0.15 < z < 0.9. This paper details the BPZ and COSMOS procedures, and demonstrates that the cosmological inference is insensitive to details of the ni(z) beyond the choice of Δzi. The clustering and COSMOS validation methods produce consistent estimates of Δzi in the bins where both can be applied, with combined uncertainties of σ_{Δ z^i}=0.015, 0.013, 0.011, and 0.022 in the four bins. Repeating the photo-z procedure instead using the Directional Neighbourhood Fitting algorithm, or using the ni(z) estimated from the matched sample in COSMOS, yields no discernible difference in cosmological inferences.

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

NASA Astrophysics Data System (ADS)

Hoyle, B.; Gruen, D.; Bernstein, G. M.; Rau, M. M.; De Vicente, J.; Hartley, W. G.; Gaztanaga, E.; DeRose, J.; Troxel, M. A.; Davis, C.; Alarcon, A.; MacCrann, N.; Prat, J.; Sánchez, C.; Sheldon, E.; Wechsler, R. H.; Asorey, J.; Becker, M. R.; Bonnett, C.; Carnero Rosell, A.; Carollo, D.; Carrasco Kind, M.; Castander, F. J.; Cawthon, R.; Chang, C.; Childress, M.; Davis, T. M.; Drlica-Wagner, A.; Gatti, M.; Glazebrook, K.; Gschwend, J.; Hinton, S. R.; Hoormann, J. K.; Kim, A. G.; King, A.; Kuehn, K.; Lewis, G.; Lidman, C.; Lin, H.; Macaulay, E.; Maia, M. A. G.; Martini, P.; Mudd, D.; Möller, A.; Nichol, R. C.; Ogando, R. L. C.; Rollins, R. P.; Roodman, A.; Ross, A. J.; Rozo, E.; Rykoff, E. S.; Samuroff, S.; Sevilla-Noarbe, I.; Sharp, R.; Sommer, N. E.; Tucker, B. E.; Uddin, S. A.; Varga, T. N.; Vielzeuf, P.; Yuan, F.; Zhang, B.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Buckley-Geer, E.; Burke, D. L.; Busha, M. T.; Capozzi, D.; Carretero, J.; Crocce, M.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Doel, P.; Eifler, T. F.; Estrada, J.; Evrard, A. E.; Fernandez, E.; Flaugher, B.; Fosalba, P.; Frieman, J.; García-Bellido, J.; Gerdes, D. W.; Giannantonio, T.; Goldstein, D. A.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Jarvis, M.; Jeltema, T.; Johnson, M. W. G.; Johnson, M. D.; Kirk, D.; Krause, E.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Li, T. S.; Lima, M.; March, M.; Marshall, J. L.; Melchior, P.; Menanteau, F.; Miquel, R.; Nord, B.; O'Neill, C. R.; Plazas, A. A.; Romer, A. K.; Sako, M.; Sanchez, E.; Santiago, B.; Scarpine, V.; Schindler, R.; Schubnell, M.; Smith, M.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thomas, D.; Tucker, D. L.; Vikram, V.; Walker, A. R.; Weller, J.; Wester, W.; Wolf, R. C.; Yanny, B.; Zuntz, J.; DES Collaboration

2018-04-01

We describe the derivation and validation of redshift distribution estimates and their uncertainties for the populations of 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)∝ dn^i/dz for members of bin i. Accurate determination of cosmological parameters depends critically on knowledge of ni 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-Δ z^i) to correct the mean redshift of ni(z) for biases in n^i_PZ. The Δzi 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 Δzi of the three lowest redshift bins are further constrained by the angular clustering of the source galaxies around red galaxies with secure photometric redshifts at 0.15 < z < 0.9. This paper details the BPZ and COSMOS procedures, and demonstrates that the cosmological inference is insensitive to details of the ni(z) beyond the choice of Δzi. The clustering and COSMOS validation methods produce consistent estimates of Δzi in the bins where both can be applied, with combined uncertainties of σ _{Δ z^i}=0.015, 0.013, 0.011, and 0.022 in the four bins. Repeating the photo-z proceedure instead using the Directional Neighborhood Fitting (DNF) algorithm, or using the ni(z) estimated from the matched sample in COSMOS, yields no discernible difference in cosmological inferences.

Dipolar modulation in the size of galaxies: the effect of Doppler magnification

NASA Astrophysics Data System (ADS)

Bonvin, Camille; Andrianomena, Sambatra; Bacon, David; Clarkson, Chris; Maartens, Roy; Moloi, Teboho; Bull, Philip

2017-12-01

Objects falling into an overdensity appear larger on its near side and smaller on its far side than other objects at the same redshift. This produces a dipolar pattern of magnification, primarily as a consequence of the Doppler effect. At low redshift, this Doppler magnification completely dominates the usual integrated gravitational lensing contribution to the lensing magnification. We show that one can optimally observe this pattern by extracting the dipole in the cross-correlation of number counts and galaxy sizes. This dipole allows us to almost completely remove the contribution from gravitational lensing up to redshift ≲0.5, and even at high redshift z ≃ 1, the dipole picks up the Doppler magnification predominantly. Doppler magnification should be easily detectable in current and upcoming optical and radio surveys; by forecasting for telescopes such as the SKA, we show that this technique is competitive with using peculiar velocities via redshift-space distortions to constrain dark energy. It produces similar yet complementary constraints on the cosmological model to those found using measurements of the cosmic shear.

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

NASA Astrophysics Data System (ADS)

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.

Mass calibration of galaxy clusters at redshift 0.1–1.0 using weak lensing in the Sloan Digital Sky Survey Stripe 82 co-add

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiesner, Matthew P.; Lin, Huan; Soares-Santos, Marcelle

We present galaxy cluster mass–richness relations found in the Sloan Digital Sky Survey Stripe 82 co-add using clusters found using a Voronoi tessellation cluster finder. 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 ≤ 0.4, 0.4 < z ≤ 0.7, 0.7 < z ≤ 1.0 and 0.1 < z ≤ 1.0. We describe the sample of galaxy clusters and explain how these clusters were found using a Voronoi tessellation cluster finder. We fit a Navarro-Frenk-White profile to the stackedmore » 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 also examine redshift evolution of the mass–richness relation. As a result, we present measurements of the mass coefficient (M 200|20) and the power-law slope (α) for power-law fits to the mass and richness values in each of the redshift bins. We find values of the mass coefficient of 8.49 ± 0.526, 14.1 ± 1.78, 30.2 ± 8.74 and 9.23 ± 0.525 × 10 13 h –1 M ⊙ for each of the four redshift bins, respectively. As a result, we find values of the power-law slope of 0.905 ± 0.0585, 0.948 ± 0.100, 1.33 ± 0.260 and 0.883 ± 0.0500, respectively.« less

Mass calibration of galaxy clusters at redshift 0.1–1.0 using weak lensing in the Sloan Digital Sky Survey Stripe 82 co-add

DOE PAGES

Wiesner, Matthew P.; Lin, Huan; Soares-Santos, Marcelle

2015-07-08

We present galaxy cluster mass–richness relations found in the Sloan Digital Sky Survey Stripe 82 co-add using clusters found using a Voronoi tessellation cluster finder. 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 ≤ 0.4, 0.4 < z ≤ 0.7, 0.7 < z ≤ 1.0 and 0.1 < z ≤ 1.0. We describe the sample of galaxy clusters and explain how these clusters were found using a Voronoi tessellation cluster finder. We fit a Navarro-Frenk-White profile to the stackedmore » 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 also examine redshift evolution of the mass–richness relation. As a result, we present measurements of the mass coefficient (M 200|20) and the power-law slope (α) for power-law fits to the mass and richness values in each of the redshift bins. We find values of the mass coefficient of 8.49 ± 0.526, 14.1 ± 1.78, 30.2 ± 8.74 and 9.23 ± 0.525 × 10 13 h –1 M ⊙ for each of the four redshift bins, respectively. As a result, we find values of the power-law slope of 0.905 ± 0.0585, 0.948 ± 0.100, 1.33 ± 0.260 and 0.883 ± 0.0500, respectively.« less

The Splashback Feature around DES Galaxy Clusters: Galaxy Density and Weak Lensing Profiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Chihway; et al.

Splashback refers to the process of matter that is accreting onto a dark matter halo reaching its first orbital apocenter and turning around in its orbit. The cluster-centric radius at which this process occurs, r_sp, defines a halo boundary that is connected to the dynamics of the cluster, in contrast with other common halo boundary definitions such as R_200. A rapid decline in the matter density profile of the halo is expected near r_sp. We measure the galaxy number density and weak lensing mass profiles around RedMapper galaxy clusters in the first year Dark Energy Survey (DES) data. For amore » cluster sample with mean mass ~2.5 x 10^14 solar masses, we find strong evidence of a splashback-like steepening of the galaxy density profile and measure r_sp=1.16 +/- 0.08 Mpc/h, consistent with earlier SDSS measurements of More et al. (2016) and Baxter et al. (2017). Moreover, our weak lensing measurement demonstrates for the first time the existence of a splashback-like steepening of the matter profile of galaxy clusters. We measure r_sp=1.28 +/- 0.18 Mpc/h from the weak lensing data, in good agreement with our galaxy density measurements. Applying our analysis to different cluster and galaxy samples, we find that consistent with LambdaCDM simulations, r_sp scales with R_200m and does not evolve with redshift over the redshift range of 0.3--0.6. We also find that potential systematic effects associated with the RedMapper algorithm may impact the location of r_sp, in particular the choice of scale used to estimate cluster richness. We discuss progress needed to understand the systematic uncertainties and fully exploit forthcoming data from DES and future surveys, emphasizing the importance of more realistic mock catalogs and independent cluster samples.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melchior, P.; Gruen, D.; McClintock, T.

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 parametermore » $$5 \\leq \\lambda \\leq 180$$ 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.« less

The Atacama Cosmology Telescope: temperature and gravitational lensing power spectrum measurements from three seasons of data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Das, Sudeep; Louis, Thibaut; Calabrese, Erminia

2014-04-01

We present the temperature power spectra of the cosmic microwave background (CMB) derived from the three seasons of data from the Atacama Cosmology Telescope (ACT) at 148 GHz and 218 GHz, as well as the cross-frequency spectrum between the two channels. We detect and correct for contamination due to the Galactic cirrus in our equatorial maps. We present the results of a number of tests for possible systematic error and conclude that any effects are not significant compared to the statistical errors we quote. Where they overlap, we cross-correlate the ACT and the South Pole Telescope (SPT) maps and showmore » they are consistent. The measurements of higher-order peaks in the CMB power spectrum provide an additional test of the ΛCDM cosmological model, and help constrain extensions beyond the standard model. The small angular scale power spectrum also provides constraining power on the Sunyaev-Zel'dovich effects and extragalactic foregrounds. We also present a measurement of the CMB gravitational lensing convergence power spectrum at 4.6σ detection significance.« less

The Atacama Cosmology Telescope: Temperature and Gravitational Lensing Power Spectrum Measurements from Three Seasons of Data

NASA Technical Reports Server (NTRS)

Das, Sudeep; Louis, Thibaut; Nolta, Michael R.; Addison, Graeme E.; Battisetti, Elia S.; Bond, J. Richard; Calabrese, Erminia; Crichton, Devin; Devlin, Mark J.; Dicker, Simon;

The ellipticity of galaxy cluster haloes from satellite galaxies and weak lensing

DOE PAGES

Shin, Tae-hyeon; Clampitt, Joseph; Jain, Bhuvnesh; ...

2018-01-04

Here, we study the ellipticity of galaxy cluster haloes as characterized by the distribution of cluster galaxies and as measured with weak lensing. We use Monte Carlo simulations of elliptical cluster density profiles to estimate and correct for Poisson noise bias, edge bias and projection effects. We apply our methodology to 10 428 Sloan Digital Sky Survey clusters identified by the redMaPPer algorithm with richness above 20. We find a mean ellipticity =0.271 ± 0.002 (stat) ±0.031 (sys) corresponding to an axis ratio = 0.573 ± 0.002 (stat) ±0.039 (sys). We compare this ellipticity of the satellites to the halomore » shape, through a stacked lensing measurement using optimal estimators of the lensing quadrupole based on Clampitt and Jain (2016). We find a best-fitting axis ratio of 0.56 ± 0.09 (stat) ±0.03 (sys), consistent with the ellipticity of the satellite distribution. Thus, cluster galaxies trace the shape of the dark matter halo to within our estimated uncertainties. Finally, we restack the satellite and lensing ellipticity measurements along the major axis of the cluster central galaxy's light distribution. From the lensing measurements, we infer a misalignment angle with an root-mean-square of 30° ± 10° when stacking on the central galaxy. We discuss applications of halo shape measurements to test the effects of the baryonic gas and active galactic nucleus feedback, as well as dark matter and gravity. The major improvements in signal-to-noise ratio expected with the ongoing Dark Energy Survey and future surveys from Large Synoptic Survey Telescope, Euclid, and Wide Field Infrared Survey Telescope will make halo shapes a useful probe of these effects.« less

The ellipticity of galaxy cluster haloes from satellite galaxies and weak lensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Tae-hyeon; Clampitt, Joseph; Jain, Bhuvnesh

Here, we study the ellipticity of galaxy cluster haloes as characterized by the distribution of cluster galaxies and as measured with weak lensing. We use Monte Carlo simulations of elliptical cluster density profiles to estimate and correct for Poisson noise bias, edge bias and projection effects. We apply our methodology to 10 428 Sloan Digital Sky Survey clusters identified by the redMaPPer algorithm with richness above 20. We find a mean ellipticity =0.271 ± 0.002 (stat) ±0.031 (sys) corresponding to an axis ratio = 0.573 ± 0.002 (stat) ±0.039 (sys). We compare this ellipticity of the satellites to the halomore » shape, through a stacked lensing measurement using optimal estimators of the lensing quadrupole based on Clampitt and Jain (2016). We find a best-fitting axis ratio of 0.56 ± 0.09 (stat) ±0.03 (sys), consistent with the ellipticity of the satellite distribution. Thus, cluster galaxies trace the shape of the dark matter halo to within our estimated uncertainties. Finally, we restack the satellite and lensing ellipticity measurements along the major axis of the cluster central galaxy's light distribution. From the lensing measurements, we infer a misalignment angle with an root-mean-square of 30° ± 10° when stacking on the central galaxy. We discuss applications of halo shape measurements to test the effects of the baryonic gas and active galactic nucleus feedback, as well as dark matter and gravity. The major improvements in signal-to-noise ratio expected with the ongoing Dark Energy Survey and future surveys from Large Synoptic Survey Telescope, Euclid, and Wide Field Infrared Survey Telescope will make halo shapes a useful probe of these effects.« less

The ellipticity of galaxy cluster haloes from satellite galaxies and weak lensing

NASA Astrophysics Data System (ADS)

Shin, Tae-hyeon; Clampitt, Joseph; Jain, Bhuvnesh; Bernstein, Gary; Neil, Andrew; Rozo, Eduardo; Rykoff, Eli

2018-04-01

We study the ellipticity of galaxy cluster haloes as characterized by the distribution of cluster galaxies and as measured with weak lensing. We use Monte Carlo simulations of elliptical cluster density profiles to estimate and correct for Poisson noise bias, edge bias and projection effects. We apply our methodology to 10 428 Sloan Digital Sky Survey clusters identified by the redMaPPer algorithm with richness above 20. We find a mean ellipticity =0.271 ± 0.002 (stat) ±0.031 (sys) corresponding to an axis ratio = 0.573 ± 0.002 (stat) ±0.039 (sys). We compare this ellipticity of the satellites to the halo shape, through a stacked lensing measurement using optimal estimators of the lensing quadrupole based on Clampitt and Jain (2016). We find a best-fitting axis ratio of 0.56 ± 0.09 (stat) ±0.03 (sys), consistent with the ellipticity of the satellite distribution. Thus, cluster galaxies trace the shape of the dark matter halo to within our estimated uncertainties. Finally, we restack the satellite and lensing ellipticity measurements along the major axis of the cluster central galaxy's light distribution. From the lensing measurements, we infer a misalignment angle with an root-mean-square of 30° ± 10° when stacking on the central galaxy. We discuss applications of halo shape measurements to test the effects of the baryonic gas and active galactic nucleus feedback, as well as dark matter and gravity. The major improvements in signal-to-noise ratio expected with the ongoing Dark Energy Survey and future surveys from Large Synoptic Survey Telescope, Euclid, and Wide Field Infrared Survey Telescope will make halo shapes a useful probe of these effects.

XMM-Newton X-ray and HST weak gravitational lensing study of the extremely X-ray luminous galaxy cluster Cl J120958.9+495352 (z = 0.902)

NASA Astrophysics Data System (ADS)

Thölken, Sophia; Schrabback, Tim; Reiprich, Thomas H.; Lovisari, Lorenzo; Allen, Steven W.; Hoekstra, Henk; Applegate, Douglas; Buddendiek, Axel; Hicks, Amalia

2018-03-01

Context. Observations of relaxed, massive, and distant clusters can provide important tests of standard cosmological models, for example by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to be investigated. X-ray analyses provide one of the best opportunities to access this information and to determine important properties such as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analyses are complementary independent probes that are essential in order to test whether X-ray masses could be biased. Aims: We study the very luminous, high redshift (z = 0.902) galaxy cluster Cl J120958.9+495352 using XMM-Newton data. We measure global cluster properties and study the temperature profile and the cooling time to investigate the dynamical status with respect to the presence of a cool core. We use Hubble Space Telescope (HST) weak lensing data to estimate its total mass and determine the gas mass fraction. Methods: We perform a spectral analysis using an XMM-Newton observation of 15 ks cleaned exposure time. As the treatment of the background is crucial, we use two different approaches to account for the background emission to verify our results. We account for point spread function effects and deproject our results to estimate the gas mass fraction of the cluster. We measure weak lensing galaxy shapes from mosaic HST imaging and select background galaxies photometrically in combination with imaging data from the William Herschel Telescope. Results: The X-ray luminosity of Cl J120958.9+495352 in the 0.1-2.4 keV band estimated from our XMM-Newton data is LX = (13.4+1.2-1.0) × 1044 erg/s and thus it is one of the most X-ray luminous clusters known at similarly high redshift. We find clear indications for the presence of a cool core from the temperature profile and the central cooling time, which is very rare at such high redshifts. Based on the weak lensing analysis, we estimate a cluster mass of M500/1014 M⊙ = 4.4+2.2-2.0 (stat.) + 0.6 (sys.) and a gas mass fraction of fgas,2500 = 0.11-0.03+0.06 in good agreement with previous findings for high redshift and local clusters.

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

NASA Astrophysics Data System (ADS)

Jee, M. James; Hughes, John P.; Menanteau, Felipe; Sifón, Cristóbal; Mandelbaum, Rachel; Barrientos, L. Felipe; Infante, Leopoldo; Ng, Karen Y.

2014-04-01

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 deg2 survey. Our weak-lensing analysis confirms that ACT-CL J0102-4915 is indeed an extreme system consisting of two massive (gsim 1015 M ⊙ each) subclusters with a projected separation of {\\sim }0.7\\,h_{70}^{-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_{200c}=(1.38+/- 0.22)\\times 10^{15} \\,h_{70}^{-1}\\, M_{\\odot } and (0.78+/- 0.20)\\times 10^{15} \\,h_{70}^{-1}\\, M_{\\odot }, 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_{-61}^{+58}\\; km\\; s^{-1} and 1064_{-66} ^{+62}\\; km\\; s^{-1} for the NW and SE components, respectively, which are consistent with their spectroscopic measurements (1290 ± 134 km s-1 and 1089 ± 200 km s-1, respectively). The centroids of both components are tightly constrained (~4'') and close to the optical luminosity centers. The X-ray and mass peaks are spatially offset by ~8'' ({\\sim }62\\,h_{70}^{-1} kpc), which is significant at the ~2σ confidence level. The mass peak, however, does not lead the gas peak in the direction expected if we are viewing the cluster soon after first core passage during a high speed merger. Under the assumption that the merger is happening in the plane of the sky, extrapolation of the two NFW halos to a radius r_{200a}=2.4\\,h_{70}^{-1} Mpc yields a combined mass of M_{200a}=(3.13+/- 0.56)\\times 10^{15}\\,h_{70}^{-1}\\, M_{\\odot }. This extrapolated total mass is consistent with our two-component-based dynamical analysis and previous X-ray measurements, projecting ACT-CL J0102-4915 to be the most massive cluster at z > 0.6 known to date.

Probing galaxy assembly bias with LRG weak lensing observations

NASA Astrophysics Data System (ADS)

Niemiec, A.; Jullo, E.; Montero-Dorta, A. D.; Prada, F.; Rodriguez-Torres, S.; Perez, E.; Klypin, A.; Erben, T.; Makler, M.; Moraes, B.; Pereira, M. E. S.; Shan, H.

2018-06-01

In Montero-Dorta et al., we show that luminous red galaxies (LRGs) from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS) at z ˜ 0.55 can be divided into two groups based on their star formation histories. So-called fast-growing LRGs assemble 80 per cent of their stellar mass at z ˜ 5, whereas slow-growing LRGs reach the same evolutionary state at z ˜ 1.5. We further demonstrate that these two subpopulations present significantly different clustering properties on scales of ˜1-30 Mpc. Here, we measure the mean halo mass of each subsample using the galaxy-galaxy lensing technique, in the ˜ 190°^2 overlap of the LRG catalogue and the CS82 and CFHTLenS shear catalogues. We show that fast- and slow-growing LRGs have similar lensing profiles, which implies that they live in haloes of similar mass: log (M_halo^fast/h^{-1}M_{⊙}) = 12.85^{+0.16}_{-0.26} and log (M_halo^slow/h^{-1}M_{⊙}) =12.92^{+0.16}_{-0.22}. This result, combined with the clustering difference, suggests the existence of galaxy assembly bias, although the effect is too subtle to be definitively proven, given the errors on our current weak-lensing measurement. We show that this can soon be achieved with upcoming surveys like DES.

Line-of-sight effects in strong lensing: putting theory into practice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birrer, Simon; Welschen, Cyril; Amara, Adam

2017-04-01

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 ± 0.003 (statistical error) for an HST-like dataset. 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 estimatemore » 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 galaxies. Joint constraints of multiple strong lens systems may add valuable information to the galaxy-halo connection and may allow independent weak lensing shear measurement calibrations.« less

Optimizing Spectroscopic and Photometric Galaxy Surveys: Same-Sky Benefits for Dark Energy and Modified Gravity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kirk, Donnacha; Lahav, Ofer; Bridle, Sarah

The combination of multiple cosmological probes can produce measurements of cosmological parameters much more stringent than those possible with any individual probe. We examine the combination of two highly correlated probes of late-time structure growth: (i) weak gravitational lensing from a survey with photometric redshifts and (ii) galaxy clustering and redshift space distortions from a survey with spectroscopic redshifts. We choose generic survey designs so that our results are applicable to a range of current and future photometric redshift (e.g. KiDS, DES, HSC, Euclid) and spectroscopic redshift (e.g. DESI, 4MOST, Sumire) surveys. Combining the surveys greatly improves their power tomore » measure both dark energy and modified gravity. An independent, non-overlapping combination sees a dark energy figure of merit more than 4 times larger than that produced by either survey alone. The powerful synergies between the surveys are strongest for modified gravity, where their constraints are orthogonal, producing a non-overlapping joint figure of merit nearly 2 orders of magnitude larger than either alone. Our projected angular power spectrum formalism makes it easy to model the cross-correlation observable when the surveys overlap on the sky, producing a joint data vector and full covariance matrix. We calculate a same-sky improvement factor, from the inclusion of these cross-correlations, relative to non-overlapping surveys. We find nearly a factor of 4 for dark energy and more than a factor of 2 for modified gravity. The exact forecast figures of merit and same-sky benefits can be radically affected by a range of forecasts assumption, which we explore methodically in a sensitivity analysis. We show that that our fiducial assumptions produce robust results which give a good average picture of the science return from combining photometric and spectroscopic surveys.« less

Heat Coma Temperature and Supercooling Point in Oceanic Sea Skaters (Heteroptera, Gerridae)

PubMed Central

Harada, Tetsuo

2018-01-01

Heat coma temperatures (HCTs) and super cooling points (SCPs) were examined for nearly 1000 oceanic sea skaters collected from in the Pacific and Indian Oceans representing four Halobates species; H. germanus, H. micans, H. sericeus, and H. sp. Analysis was conducted using the entire dataset because a negative correlation was seen between the HCTs and SCPs in all four species. A weak negative correlation was seen between HCTs and SCPs with a cross tolerance between warmer HCTs and colder SCPs. The weakness of the correlation may be due to the large size of the dataset and to the variability in ocean surface temperature. The negative correlation does however suggest that oceanic sea skaters may have some form of cross tolerance with a common physiological mechanism for their high and low temperature tolerances. PMID:29401693

Linear and non-linear Modified Gravity forecasts with future surveys

NASA Astrophysics Data System (ADS)

Casas, Santiago; Kunz, Martin; Martinelli, Matteo; Pettorino, Valeria

2017-12-01

Modified Gravity theories generally affect the Poisson equation and the gravitational slip in an observable way, that can be parameterized by two generic functions (η and μ) of time and space. We bin their time dependence in redshift and present forecasts on each bin for future surveys like Euclid. We consider both Galaxy Clustering and Weak Lensing surveys, showing the impact of the non-linear regime, with two different semi-analytical approximations. In addition to these future observables, we use a prior covariance matrix derived from the Planck observations of the Cosmic Microwave Background. In this work we neglect the information from the cross correlation of these observables, and treat them as independent. Our results show that η and μ in different redshift bins are significantly correlated, but including non-linear scales reduces or even eliminates the correlation, breaking the degeneracy between Modified Gravity parameters and the overall amplitude of the matter power spectrum. We further apply a Zero-phase Component Analysis and identify which combinations of the Modified Gravity parameter amplitudes, in different redshift bins, are best constrained by future surveys. We extend the analysis to two particular parameterizations of μ and η and consider, in addition to Euclid, also SKA1, SKA2, DESI: we find in this case that future surveys will be able to constrain the current values of η and μ at the 2-5% level when using only linear scales (wavevector k < 0 . 15 h/Mpc), depending on the specific time parameterization; sensitivity improves to about 1% when non-linearities are included.

Clinical Evaluation of Large Diameter Rigid-Gas Permeable Versus Soft Toric Contact Lenses for the Correction of Refractive Astigmatism. A MultiCenter Study.

PubMed

Michaud, Langis; Bennett, Edward S; Woo, Stephanie L; Reeder, Renee; Morgan, Bruce W; Dinardo, Amy; Harthan, Jennifer S

2018-05-01

This study aims to address the clinical performance of a large diameter rigid gas permeable lens (LRGP) in a group of subjects with low-to-moderate (0.75-2.75 D) refractive astigmatism. An additional goal was to determine whether soft toric or LRGP contact lenses performed better objectively in the correction of astigmatism and to determine which modality is preferred by subjects. This was a multisite prospective cross-over clinical study. Ten asymptomatic contact lens wearers per site (four university clinics) were recruited and randomly assigned to group A or group B. Group A was assigned to start wearing Comfilcon A soft toric lens first, for two weeks, and then crossed over to LRGP lenses (Boston XO, 14.3 mm diameter miniscleral lens). Group B initially wore LRGP lenses and then crossed over to soft toric lenses. For each type of lens worn, low-contrast and high-contrast visual acuity (VA) were evaluated at distance. At the conclusion of the study, after two months, all subjects completed a questionnaire in which they were asked to indicate their preference for one type of lens (soft toric or LRGP) and to rate the quality of vision in day-to-day activities. Thirty-six of 38 (94.7%) subjects completed the study with 75% preferring the vision of the LRGP lens as compared to the soft toric lenses worn in the study. 52.7% expressed a preference to continue with this modality despite only 38.8% reporting that these LRGP lenses are easy or very easy to handle. Wear time, subjective comfort, and subjective vision ratings exhibited no significant difference between the two groups. In a population of asymptomatic contact lens wearers, LRGP lenses can be considered as a good alternative to soft toric lenses for the correction of refractive astigmatism.

Cross-correlations between Renminbi and four major currencies in the Renminbi currency basket

NASA Astrophysics Data System (ADS)

Wang, Gang-Jin; Xie, Chi

2013-03-01

We investigate the cross-correlations between Renminbi (CNY) and four major currencies (USD, EUR, JPY, and KRW) in the Renminbi currency basket, i.e., the cross-correlations of CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW. Qualitatively, using a statistical test in analogy to the Ljung-Box test, we find that cross-correlations significantly exist in CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW. Quantitatively, employing the detrended cross-correlation analysis (DCCA) method, we find that the cross-correlations of CNY-USD, CNY-EUR, CNY-JPY, and CNY-KRW are weakly persistent. We use the DCCA cross-correlation coefficient ρ to quantify the level of cross-correlations and find the currency weight in the Renminbi currency basket is arranged in the order of USD>EUR>JPY >KRW. Using the method of rolling windows, which can capture the time-varying cross-correlation scaling exponents, we find that: (i) CNY and USD are positively cross-correlated over time, but the cross-correlations of CNY-USD are anti-persistent during the US sub-prime crisis and the European debt crisis. (ii) The cross-correlation scaling exponents of CNY-EUR have the cyclical fluctuation with a nearly two-year cycle. (iii) CNY-JPY has long-term negative cross-correlations, during the European debt crisis, but CNY and KRW are positively cross-correlated.

Achieving diffraction-limited nanometer-scale X-ray point focus with two crossed multilayer Laue lenses: alignment challenges

DOE PAGES

Yan, Hanfei; Huang, Xiaojing; Bouet, Nathalie; ...

2017-10-16

In this article, we discuss misalignment-induced aberrations in a pair of crossed multilayer Laue lenses used for achieving a nanometer-scale x-ray point focus. We thoroughly investigate the impacts of two most important contributions, the orthogonality and the separation distance between two lenses. We find that misalignment in the orthogonality results in astigmatism at 45º and other inclination angles when coupled with a separation distance error. Theoretical explanation and experimental verification are provided. We show that to achieve a diffraction-limited point focus, accurate alignment of the azimuthal angle is required to ensure orthogonality between two lenses, and the required accuracy ismore » scaled with the ratio of the focus size to the aperture size.« less

Cross-correlations between agricultural commodity futures markets in the US and China

NASA Astrophysics Data System (ADS)

Li, Zhihui; Lu, Xinsheng

2012-08-01

This paper examines the cross-correlation properties of agricultural futures markets between the US and China using a cross-correlation statistic test and multifractal detrended cross-correlation analysis (MF-DCCA). The results show that the cross-correlations between the two geographically distant markets for four pairs of important agricultural commodities futures are significantly multifractal. By introducing the concept of a “crossover”, we find that the multifractality of cross-correlations between the two markets is not long lasting. The cross-correlations in the short term are more strongly multifractal, but they are weakly so in the long term. Moreover, cross-correlations of small fluctuations are persistent and those of large fluctuations are anti-persistent in the short term while cross-correlations of all kinds of fluctuations for soy bean and soy meal futures are persistent and for corn and wheat futures are anti-persistent in the long term. We also find that cross-correlation exponents are less than the averaged generalized Hurst exponent when q<0 and more than the averaged generalized Hurst exponent when q>0 in the short term, while in the long term they are almost the same.

Calibrating the Galaxy Color-Redshift Relation: A Critical Foundation for Weak Lensing Cosmology with WFIRST and Euclid

NASA Astrophysics Data System (ADS)

Stern, Daniel

2016-08-01

A primary objective of both WFIRST and Euclid is to provide a 3D map of the distribution of matter across a significant fraction of the universe from the weak lensing shear field, but to do so requires robust distances to billions of galaxies. We propose a 4-semester, 20-night Key Strategic Mission Support program, supporting both the NASA PCOS and COR science goals, to obtain the necessary galaxy spectroscopy to calibrate the color-redshift relation. Combined with a coordinated, similarly sized Caltech Keck proposal, the proposed program will achieve the photometric redshift calibration requirements for Euclid, and make significant progress towards the WFIRST requirements. [2016B is the 2nd semester of our 4-semester request.

Correction of Hydrostatic Cluster Masses through Power Ratios and Weak Lensing

NASA Astrophysics Data System (ADS)

Mahdavi, Andisheh

2009-09-01

The evolution of rich, X-ray emitting clusters of galaxies has given us precise measurements of the cosmological parameters, with dramatic constraints on the dark energy equation of state. Built into these measurements are wholesale corrections for the infamous "X-ray mass underestimate"---the fact that X-ray masses are systematically low due to the incomplete thermalization of the intracluster plasma. We seek to refine the mass correction for cosmological use through morphological power ratios. Power ratios deliver more accurate correction factors because they take into account variations in substructure from cluster to cluster. We will test their ability to correct X-ray masses by comparing hydrostatic and weak lensing mass profiles for a sample of 44 rich clusters of galaxies.

Instantaneous phase estimation to measure weak velocity variations: application to noise correlation on seismic data at the exploration scale

NASA Astrophysics Data System (ADS)

Corciulo, M.; Roux, P.; Campillo, M.; Dubucq, D.

2010-12-01

Passive imaging from noise cross-correlation is a consolidated analysis applied at continental and regional scale whereas its use at local scale for seismic exploration purposes is still uncertain. The development of passive imaging by cross-correlation analysis is based on the extraction of the Green’s function from seismic noise data. In a completely random field in time and space, the cross-correlation permits to retrieve the complete Green’s function whatever the complexity of the medium. At the exploration scale and at frequency above 2 Hz, the noise sources are not ideally distributed around the stations which strongly affect the extraction of the direct arrivals from the noise cross-correlation process. In order to overcome this problem, the coda waves extracted from noise correlation could be useful. Coda waves describe long and scattered paths sampling the medium in different ways such that they become sensitive to weak velocity variations without being dependent on the noise source distribution. Indeed, scatters in the medium behave as a set of secondary noise sources which randomize the spatial distribution of noise sources contributing to the coda waves in the correlation process. We developed a new technique to measure weak velocity changes based on the computation of the local phase variations (instantaneous phase variation or IPV) of the cross-correlated signals. This newly-developed technique takes advantage from the doublet and stretching techniques classically used to monitor weak velocity variation from coda waves. We apply IPV to data acquired in Northern America (Canada) on a 1-km side square seismic network laid out by 397 stations. Data used to study temporal variations are cross-correlated signals computed on 10-minutes ambient noise in the frequency band 2-5 Hz. As the data set was acquired over five days, about 660 files are processed to perform a complete temporal analysis for each stations pair. The IPV permits to estimate the phase shift all over the signal length without any assumption on the medium velocity. The instantaneous phase is computed using the Hilbert transform of the signal. For each stations pair, we measure the phase difference between successive correlation functions calculated for 10 minutes of ambient noise. We then fit the instantaneous phase shift using a first-order polynomial function. The measure of the velocity variation corresponds to the slope of this fit. Compared to other techniques, the advantage of IPV is a very fast procedure which efficiently provides the measure of velocity variation on large data sets. Both experimental results and numerical tests on synthetic signals will be presented to assess the reliability of the IPV technique, with comparison to the doublet and stretching methods.

A WEAK LENSING STUDY OF X-RAY GROUPS IN THE COSMOS SURVEY: FORM AND EVOLUTION OF THE MASS-LUMINOSITY RELATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leauthaud, Alexie; Finoguenov, Alexis; Cappelluti, Nico

2010-01-20

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

Characterization and correction of charge-induced pixel shifts in DECam

DOE PAGES

Gruen, D.; Bernstein, G. M.; Jarvis, M.; ...

2015-05-28

Interaction of charges in CCDs with the already accumulated charge distribution causes both a flux dependence of the point-spread function (an increase of observed size with flux, also known as the brighter/fatter effect) and pixel-to-pixel correlations of the Poissonian noise in flat fields. We describe these effects in the Dark Energy Camera (DECam) with charge dependent shifts of effective pixel borders, i.e. the Antilogus et al. (2014) model, which we fit to measurements of flat-field Poissonian noise correlations. The latter fall off approximately as a power-law r -2.5 with pixel separation r, are isotropic except for an asymmetry in themore » direct neighbors along rows and columns, are stable in time, and are weakly dependent on wavelength. They show variations from chip to chip at the 20% level that correlate with the silicon resistivity. The charge shifts predicted by the model cause biased shape measurements, primarily due to their effect on bright stars, at levels exceeding weak lensing science requirements. We measure the flux dependence of star images and show that the effect can be mitigated by applying the reverse charge shifts at the pixel level during image processing. Differences in stellar size, however, remain significant due to residuals at larger distance from the centroid.« less

Kinoform optics applied to X-ray photon correlation spectroscopy.

PubMed

Sandy, A R; Narayanan, S; Sprung, M; Su, J-D; Evans-Lutterodt, K; Isakovic, A F; Stein, A

2010-05-01

Moderate-demagnification higher-order silicon kinoform focusing lenses have been fabricated to facilitate small-angle X-ray photon correlation spectroscopy (XPCS) experiments. The geometric properties of such lenses, their focusing performance and their applicability for XPCS measurements are described. It is concluded that one-dimensional vertical X-ray focusing via silicon kinoform lenses significantly increases the usable coherent flux from third-generation storage-ring light sources for small-angle XPCS experiments.

The Grism Lens-Amplified Survey from Space (GLASS). VI. Comparing the Mass and Light in MACS J0416.1-2403 Using Frontier Field Imaging and GLASS Spectroscopy

NASA Astrophysics Data System (ADS)

Hoag, A.; Huang, K.-H.; Treu, T.; Bradač, M.; Schmidt, K. B.; Wang, X.; Brammer, G. B.; Broussard, A.; Amorin, R.; Castellano, M.; Fontana, A.; Merlin, E.; Schrabback, T.; Trenti, M.; Vulcani, B.

2016-11-01

We present a model using both strong and weak gravitational lensing of the galaxy cluster MACS J0416.1-2403, constrained using spectroscopy from the Grism Lens-Amplified Survey from Space (GLASS) and Hubble Frontier Fields (HFF) imaging data. We search for emission lines in known multiply imaged sources in the GLASS spectra, obtaining secure spectroscopic redshifts of 30 multiple images belonging to 15 distinct source galaxies. The GLASS spectra provide the first spectroscopic measurements for five of the source galaxies. The weak lensing signal is acquired from 884 galaxies in the F606W HFF image. By combining the weak lensing constraints with 15 multiple image systems with spectroscopic redshifts and nine multiple image systems with photometric redshifts, we reconstruct the gravitational potential of the cluster on an adaptive grid. The resulting map of total mass density is compared with a map of stellar mass density obtained from the deep Spitzer Frontier Fields imaging data to study the relative distribution of stellar and total mass in the cluster. We find that the projected stellar mass to total mass ratio, f ⋆, varies considerably with the stellar surface mass density. The mean projected stellar mass to total mass ratio is < {f}\\star > =0.009+/- 0.003 (stat.), but with a systematic error as large as 0.004-0.005, dominated by the choice of the initial mass function. We find agreement with several recent measurements of f ⋆ in massive cluster environments. The lensing maps of convergence, shear, and magnification are made available to the broader community in the standard HFF format.

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

NASA Astrophysics Data System (ADS)

Becker, Matthew Rand

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

Cosmic discordance: are Planck CMB and CFHTLenS weak lensing measurements out of tune?

DOE PAGES

MacCrann, Niall; Zuntz, Joe; Bridle, Sarah; ...

2015-06-17

We examine the level of agreement between low-redshift weak lensing data and the cosmic microwave background using measurements from the Canada–France–Hawaii Telescope Lensing Survey (CFHTLenS) and Planck+Wilkinson Microwave Anisotropy Probe (WMAP) polarization. We perform an independent analysis of the CFHTLenS six bin tomography results of Heymans et al. We extend their systematics treatment and find the cosmological constraints to be relatively robust to the choice of non-linear modelling, extension to the intrinsic alignment model and inclusion of baryons. We find that when marginalized in the Ωm–σ8 plane, the 95 percent confidence contours of CFHTLenS and Planck+WMAP only just touch, butmore » the discrepancy is less significant in the full six-dimensional parameter space of Λ cold dark matter (ΛCDM). Allowing a massive active neutrino or tensor modes does not significantly resolve the tension in the full n-dimensional parameter space. Our results differ from some in the literature because we use the full tomographic information in the weak lensing data and marginalize over systematics. We note that adding a sterile neutrino to ΛCDM brings the 2D marginalized contours into greater overlap, mainly due to the extra effective number of neutrino species, which we find to be 0.88 ± 0.43 (68 per cent) greater than standard on combining the data sets. We discuss why this is not a completely satisfactory resolution, leaving open the possibility of other new physics or observational systematics as contributing factors. We provide updated cosmology fitting functions for the CFHTLenS constraints and discuss the differences from ones used in the literature.« less

Practical Weak-lensing Shear Measurement with Metacalibration

DOE PAGES

Sheldon, Erin S.; Huff, Eric M.

2017-05-19

We report that metacalibration is a recently introduced method to accurately measure weak gravitational lensing shear using only the available imaging data, without need for prior information about galaxy properties or calibration from simulations. The method involves distorting the image with a small known shear, and calculating the response of a shear estimator to that applied shear. The method was shown to be accurate in moderate-sized simulations with galaxy images that had relatively high signal-to-noise ratios, and without significant selection effects. In this work we introduce a formalism to correct for both shear response and selection biases. We also observemore » that for images with relatively low signal-to-noise ratios, the correlated noise that arises during the metacalibration process results in significant bias, for which we develop a simple empirical correction. To test this formalism, we created large image simulations based on both parametric models and real galaxy images, including tests with realistic point-spread functions. We varied the point-spread function ellipticity at the five-percent level. In each simulation we applied a small few-percent shear to the galaxy images. We introduced additional challenges that arise in real data, such as detection thresholds, stellar contamination, and missing data. We applied cuts on the measured galaxy properties to induce significant selection effects. Finally, using our formalism, we recovered the input shear with an accuracy better than a part in a thousand in all cases.« less

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

NASA Astrophysics Data System (ADS)

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.

CMB-lensing beyond the Born approximation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marozzi, Giovanni; Fanizza, Giuseppe; 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 ∼< 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-Gaussianmore » 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.« less

CLASH: Joint analysis of strong-lensing, weak-lensing shear, and magnification data for 20 galaxy clusters*

DOE PAGES

Umetsu, Keiichi; Zitrin, Adi; Gruen, Daniel; ...

2016-04-20

Here, 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 atmore » $$0.19\\lesssim z\\lesssim 0.69$$ 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 $$c{| }_{z=0.34}=3.95\\pm 0.35$$ at M200c sime 14 × 1014 M⊙ and an intrinsic scatter of $$\\sigma (\\mathrm{ln}{c}_{200{\\rm{c}}})=0.13\\pm 0.06$$, 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 power-law, cored isothermal and Burkert density profiles are disfavored by the data. We show that cuspy halo models that include the large-scale two-halo term provide improved agreement with the data. For the NFW halo model, we measure a mean concentration of $${c}_{200{\\rm{c}}}={3.79}_{-0.28}^{+0.30}$$ at $${M}_{200{\\rm{c}}}={14.1}_{-1.0}^{+1.0}\\times {10}^{14}\\;{M}_{\\odot }$$, demonstrating consistency between the complementary analysis methods.« less

Gravitational Lensing in Astronomy.

PubMed

Wambsganss, Joachim

1998-01-01

Deflection of light by gravity was predicted by General Relativity and observationally confirmed in 1919. In the following decades, various aspects of the gravitational lens effect were explored theoretically. Among them were: the possibility of multiple or ring-like images of background sources, the use of lensing as a gravitational telescope on very faint and distant objects, and the possibility of determining Hubble's constant with lensing. It is only relatively recently, (after the discovery of the first doubly imaged quasar in 1979), that gravitational lensing has became an observational science. Today lensing is a booming part of astrophysics. In addition to multiply-imaged quasars, a number of other aspects of lensing have been discovered: For example, giant luminous arcs, quasar microlensing, Einstein rings, galactic microlensing events, arclets, and weak gravitational lensing. At present, literally hundreds of individual gravitational lens phenomena are known. Although still in its childhood, lensing has established itself as a very useful astrophysical tool with some remarkable successes. It has contributed significant new results in areas as different as the cosmological distance scale, the large scale matter distribution in the universe, mass and mass distribution of galaxy clusters, the physics of quasars, dark matter in galaxy halos, and galaxy structure. Looking at these successes in the recent past we predict an even more luminous future for gravitational lensing. Supplementary material is available for this article at 10.12942/lrr-1998-12.

Sparse Reconstruction of the Merging A520 Cluster System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peel, Austin; Lanusse, François; Starck, Jean-Luc, E-mail: austin.peel@cea.fr

2017-09-20

Merging galaxy clusters present a unique opportunity to study the properties of dark matter in an astrophysical context. These are rare and extreme cosmic events in which the bulk of the baryonic matter becomes displaced from the dark matter halos of the colliding subclusters. Since all mass bends light, weak gravitational lensing is a primary tool to study the total mass distribution in such systems. Combined with X-ray and optical analyses, mass maps of cluster mergers reconstructed from weak-lensing observations have been used to constrain the self-interaction cross-section of dark matter. The dynamically complex Abell 520 (A520) cluster is anmore » exceptional case, even among merging systems: multi-wavelength observations have revealed a surprising high mass-to-light concentration of dark mass, the interpretation of which is difficult under the standard assumption of effectively collisionless dark matter. We revisit A520 using a new sparsity-based mass-mapping algorithm to independently assess the presence of the puzzling dark core. We obtain high-resolution mass reconstructions from two separate galaxy shape catalogs derived from Hubble Space Telescope observations of the system. Our mass maps agree well overall with the results of previous studies, but we find important differences. In particular, although we are able to identify the dark core at a certain level in both data sets, it is at much lower significance than has been reported before using the same data. As we cannot confirm the detection in our analysis, we do not consider A520 as posing a significant challenge to the collisionless dark matter scenario.« less

RAY-RAMSES: a code for ray tracing on the fly in N-body simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barreira, Alexandre; Llinares, Claudio; Bose, Sownak

2016-05-01

We present a ray tracing code to compute integrated cosmological observables on the fly in AMR N-body simulations. Unlike conventional ray tracing techniques, our code takes full advantage of the time and spatial resolution attained by the N-body simulation by computing the integrals along the line of sight on a cell-by-cell basis through the AMR simulation grid. Moroever, since it runs on the fly in the N-body run, our code can produce maps of the desired observables without storing large (or any) amounts of data for post-processing. We implemented our routines in the RAMSES N-body code and tested the implementationmore » using an example of weak lensing simulation. We analyse basic statistics of lensing convergence maps and find good agreement with semi-analytical methods. The ray tracing methodology presented here can be used in several cosmological analysis such as Sunyaev-Zel'dovich and integrated Sachs-Wolfe effect studies as well as modified gravity. Our code can also be used in cross-checks of the more conventional methods, which can be important in tests of theory systematics in preparation for upcoming large scale structure surveys.« less

The integrated bispectrum and beyond

NASA Astrophysics Data System (ADS)

Munshi, Dipak; Coles, Peter

2017-02-01

The position-dependent power spectrum has been recently proposed as a descriptor of gravitationally induced non-Gaussianity in galaxy clustering, as it is sensitive to the "soft limit" of the bispectrum (i.e. when one of the wave number tends to zero). We generalise this concept to higher order and clarify their relationship to other known statistics such as the skew-spectrum, the kurt-spectra and their real-space counterparts the cumulants correlators. Using the Hierarchical Ansatz (HA) as a toy model for the higher order correlation hierarchy, we show how in the soft limit, polyspectra at a given order can be identified with lower order polyspectra with the same geometrical dependence but with renormalised amplitudes expressed in terms of amplitudes of the original polyspectra. We extend the concept of position-dependent bispectrum to bispectrum of the divergence of the velocity field Θ and mixed multispectra involving δ and Θ in the 3D perturbative regime. To quantify the effects of transients in numerical simulations, we also present results for lowest order in Lagrangian perturbation theory (LPT) or the Zel'dovich approximation (ZA). Finally, we discuss how to extend the position-dependent spectrum concept to encompass cross-spectra. And finally study the application of this concept to two dimensions (2D), for projected galaxy maps, convergence κ maps from weak-lensing surveys or maps of CMB secondaries e.g. the frequency cleaned y-parameter maps of thermal Sunyaev-Zel'dovich (tSZ) effect from CMB surveys.

The integrated bispectrum and beyond

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munshi, Dipak; Coles, Peter, E-mail: D.Munshi@sussex.ac.uk, E-mail: P.Coles@sussex.ac.uk

2017-02-01

The position-dependent power spectrum has been recently proposed as a descriptor of gravitationally induced non-Gaussianity in galaxy clustering, as it is sensitive to the 'soft limit' of the bispectrum (i.e. when one of the wave number tends to zero). We generalise this concept to higher order and clarify their relationship to other known statistics such as the skew-spectrum, the kurt-spectra and their real-space counterparts the cumulants correlators. Using the Hierarchical Ansatz (HA) as a toy model for the higher order correlation hierarchy, we show how in the soft limit, polyspectra at a given order can be identified with lower ordermore » polyspectra with the same geometrical dependence but with renormalised amplitudes expressed in terms of amplitudes of the original polyspectra. We extend the concept of position-dependent bispectrum to bispectrum of the divergence of the velocity field Θ and mixed multispectra involving δ and Θ in the 3D perturbative regime. To quantify the effects of transients in numerical simulations, we also present results for lowest order in Lagrangian perturbation theory (LPT) or the Zel'dovich approximation (ZA). Finally, we discuss how to extend the position-dependent spectrum concept to encompass cross-spectra. And finally study the application of this concept to two dimensions (2D), for projected galaxy maps, convergence κ maps from weak-lensing surveys or maps of CMB secondaries e.g. the frequency cleaned y -parameter maps of thermal Sunyaev-Zel'dovich (tSZ) effect from CMB surveys.« less

Redshift distributions of galaxies in the Dark Energy Survey Science Verification shear catalogue and implications for weak lensing

DOE PAGES

Bonnett, C.; Troxel, M. A.; Hartley, W.; ...

2016-08-30

Here 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 analyzed. 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-z’s. From the galaxies in the DES SV shear catalogue, which have meanmore » redshift 0.72±0.01 over the range 0.38 of approximately 3%. This shift is within the one sigma statistical errors on σ8 for the DES SV shear catalogue. We further study the potential impact of systematic differences on the critical surface density, Σ crit, finding levels of bias safely less than the statistical power of DES SV data. In conclusion, 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.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kantowski, Ronald; Chen Bin; Dai Xinyu, E-mail: kantowski@nhn.ou.ed, E-mail: Bin.Chen-1@ou.ed, E-mail: dai@nhn.ou.ed

We compute the deflection angle to order (m/r {sub 0}){sup 2} and m/r{sub 0} x {Lambda}r {sup 2}{sub 0} for a light ray traveling in a flat {Lambda}CDM cosmology that encounters a completely condensed mass region. We use a Swiss cheese model for the inhomogeneities and find that the most significant correction to the Einstein angle occurs not because of the nonlinear terms but instead occurs because the condensed mass is embedded in a background cosmology. The Swiss cheese model predicts a decrease in the deflection angle of {approx}2% for weakly lensed galaxies behind the rich cluster A1689 and thatmore » the reduction can be as large as {approx}5% for similar rich clusters at z {approx} 1. Weak-lensing deflection angles caused by galaxies can likewise be reduced by as much as {approx}4%. We show that the lowest order correction in which {Lambda} appears is proportional to m/r{sub 0} x {radical}({Lambda}r{sub 0}{sup 2}) and could cause as much as a {approx}0.02% increase in the deflection angle for light that passes through a rich cluster. The lowest order nonlinear correction in the mass is proportional to m/r{sub 0}x{radical}(m/r{sub 0}) and can increase the deflection angle by {approx}0.005% for weak lensing by galaxies.« less

Bounds on graviton mass using weak lensing and SZ effect in galaxy clusters

NASA Astrophysics Data System (ADS)

Rana, Akshay; Jain, Deepak; Mahajan, Shobhit; Mukherjee, Amitabha

2018-06-01

In General Relativity (GR), the graviton is massless. However, a common feature in several theoretical alternatives of GR is a non-zero mass for the graviton. These theories can be described as massive gravity theories. Despite many theoretical complexities in these theories, on phenomenological grounds the implications of massive gravity have been widely used to put bounds on graviton mass. One of the generic implications of giving a mass to the graviton is that the gravitational potential will follow a Yukawa-like fall off. We use this feature of massive gravity theories to probe the mass of graviton by using the largest gravitationally bound objects, namely galaxy clusters. In this work, we use the mass estimates of galaxy clusters measured at various cosmologically defined radial distances measured via weak lensing (WL) and Sunyaev-Zel'dovich (SZ) effect. We also use the model independent values of Hubble parameter H (z) smoothed by a non-parametric method, Gaussian process. Within 1σ confidence region, we obtain the mass of graviton mg < 5.9 ×10-30 eV with the corresponding Compton length scale λg > 6.82 Mpc from weak lensing and mg < 8.31 ×10-30 eV with λg > 5.012 Mpc from SZ effect. This analysis improves the upper bound on graviton mass obtained earlier from galaxy clusters.

Complete Calibration of the Color-Redshift Relation (C3R2): A Critical Foundation for Weak Lensing Cosmology with Euclid and WFIRST

NASA Astrophysics Data System (ADS)

Masters, Daniel C.; Stern, Daniel; Cohen, Judy; Capak, Peter

2018-01-01

A primary objective of both WFIRST and Euclid is to provide a 3D map of the distribution of matter across a significant fraction of the universe from the weak lensing shear field. Doing so will require accurate redshifts to the billions of galaxies that comprise the weak lensing samples of these surveys; achieving the required accuracy is a “tall pole” challenge for both missions. Here we present the ongoing Complete Calibration of the Color-Redshift Relation (C3R2) survey, designed specifically to calibrate the empirical galaxy color-redshift relation to Euclid depth. C3R2 is an ambitious Keck spectroscopy program, with a survey design based on a machine learning technique that allows us to optimally select the most important galaxies to sample the full range of galaxy colors. C3R2 is a multi-center program with time from all the primary Keck partners (Caltech, UC, Hawaii, and NASA), with a total of 34.5 Keck nights allocated to this project. Data Release 1, including 1283 high-confidence spectroscopic redshifts, is published as Masters, Stern, Cohen, Capak, et al. (2017), and we are currently completing Data Release 2, which will include >2000 additional high-confidence spectroscopic redshifts (Masters et al., in prep.). We will discuss current results and prospects for the survey going forward.

Redshift distributions of galaxies in the Dark Energy Survey Science Verification shear catalogue and implications for weak lensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonnett, C.; Troxel, M. A.; Hartley, W.

Here 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 analyzed. 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-z’s. From the galaxies in the DES SV shear catalogue, which have meanmore » redshift 0.72±0.01 over the range 0.38 of approximately 3%. This shift is within the one sigma statistical errors on σ8 for the DES SV shear catalogue. We further study the potential impact of systematic differences on the critical surface density, Σ crit, finding levels of bias safely less than the statistical power of DES SV data. In conclusion, 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.« less

Variations of cosmic large-scale structure covariance matrices across parameter space

NASA Astrophysics Data System (ADS)

Reischke, Robert; Kiessling, Alina; Schäfer, Björn Malte

2017-03-01

The likelihood function for cosmological parameters, given by e.g. weak lensing shear measurements, depends on contributions to the covariance induced by the non-linear evolution of the cosmic web. As highly non-linear clustering to date has only been described by numerical N-body simulations in a reliable and sufficiently precise way, the necessary computational costs for estimating those covariances at different points in parameter space are tremendous. In this work, we describe the change of the matter covariance and the weak lensing covariance matrix as a function of cosmological parameters by constructing a suitable basis, where we model the contribution to the covariance from non-linear structure formation using Eulerian perturbation theory at third order. We show that our formalism is capable of dealing with large matrices and reproduces expected degeneracies and scaling with cosmological parameters in a reliable way. Comparing our analytical results to numerical simulations, we find that the method describes the variation of the covariance matrix found in the SUNGLASS weak lensing simulation pipeline within the errors at one-loop and tree-level for the spectrum and the trispectrum, respectively, for multipoles up to ℓ ≤ 1300. We show that it is possible to optimize the sampling of parameter space where numerical simulations should be carried out by minimizing interpolation errors and propose a corresponding method to distribute points in parameter space in an economical way.

Silicone hydrogel mini-scleral contact lenses in early stage after corneal collagen cross-linking for keratoconus: a retrospective case series.

PubMed

Severinsky, Boris; Wajnsztajn, Denise; Frucht-Pery, Joseph

2013-11-01

 The aim was to the evaluate performance of a novel silicone hydrogel mini-scleral contact lens (SHmS) for optical correction of keratoconus in the early stages after the corneal collagen cross-linking procedure (CXL).  We retrospectively analysed the visual acuity improvement and corneal adaptation in the first 10 eyes of nine patients fitted with SHmS lenses one to 3.5 months after corneal collagen cross-linking. The lenses were designed to rest over the patients' sclera and peri-limbal cornea and vault the central cornea with minimal support over it. Visual acuities with manifest refraction and contact lenses, refractive and topographical values (Kmin and Kmax) were evaluated on lens dispensing and after six month of lens wearing. Ocular physiological responses were evaluated using the Institute of Eye Research (IER) grading scales.  SHmS fitting was performed 2.1 ± 0.97 (SD) months after collagen cross-linking. Mean follow up was 10.9 ± 4.41 months (range six to 18 months). Mean decimal visual acuity with SHmS was 0.66 ± 0.22 (approximately 6/9 Snellen fraction, range 0.3 to 0.1) or 0.75 ± 0.14 (approximately 6/8.1, range 0.5 to 1.0), when omitting two amblyopic eyes. Nine (90 per cent) eyes were successfully fitted, that is, able to wear the lenses for 10 hours per day or longer. Mean wearing time was 11.7 hours (range six to 14) per day. No corneal neovascularisation or papillary reaction was found in all fitted eyes.  SHmS contact lenses provide successful visual rehabilitation shortly after corneal collagen cross-linking. This new soft contact lens design with scleral fixation and minimal apical touch was demonstrated to be safe shortly after collagen cross-linking, as the avoidance of contact with the treated zone minimises contact lens influence on corneal recovery. © 2013 The Authors. Clinical and Experimental Optometry © 2013 Optometrists Association Australia.

Origin of weak lensing convergence peaks

NASA Astrophysics Data System (ADS)

Liu, Jia; Haiman, Zoltán

2016-08-01

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 Ωm and σ8 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 deg2 Canada-France-Hawaii Telescope Lensing Survey. We found that while high peaks (with height κ >3.5 σκ , where σκ is the rms of the convergence κ ) are typically due to one single massive halo of ≈1 015M⊙ , low peaks (κ ≲σκ ) are associated with constellations of 2-8 smaller halos (≲1 013M⊙ ). In addition, halos responsible for forming low peaks are found to be significantly offset from the line of sight towards the peak center (impact parameter ≳ 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 findings are in good agreement with results from the simulation work by Yang et al. [Phys. Rev. D 84, 043529 (2011)].

First Predictions of the Angular Power Spectrum of the Astrophysical Gravitational Wave Background

NASA Astrophysics Data System (ADS)

Cusin, Giulia; Dvorkin, Irina; Pitrou, Cyril; Uzan, Jean-Philippe

2018-06-01

We present the first predictions for the angular power spectrum of the astrophysical gravitational wave background constituted of the radiation emitted by all resolved and unresolved astrophysical sources. Its shape and amplitude depend on both the astrophysical properties on galactic scales and on cosmological properties. We show that the angular power spectrum behaves as Cℓ∝1 /ℓ on large scales and that relative fluctuations of the signal are of order 30% at 100 Hz. We also present the correlations of the astrophysical gravitational wave background with weak lensing and galaxy distribution. These numerical results pave the way to the study of a new observable at the crossroad between general relativity, astrophysics, and cosmology.

Glimpse: Sparsity based weak lensing mass-mapping tool

NASA Astrophysics Data System (ADS)

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

2018-02-01

Glimpse, also known as Glimpse2D, is a weak lensing mass-mapping tool that relies on a robust sparsity-based regularization scheme to recover high resolution convergence from either gravitational shear alone or from a combination of shear and flexion. Including flexion allows the supplementation of the shear on small scales in order to increase the sensitivity to substructures and the overall resolution of the convergence map. To preserve all available small scale information, Glimpse avoids any binning of the irregularly sampled input shear and flexion fields and treats the mass-mapping problem as a general ill-posed inverse problem, regularized using a 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.

Setting limits on q0 from gravitational lensing

NASA Technical Reports Server (NTRS)

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

1989-01-01

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

The impact of baryonic matter on gravitational lensing by galaxy clusters

NASA Astrophysics Data System (ADS)

Lee, Brandyn E.; King, Lindsay; Applegate, Douglas; McCarthy, Ian

2017-01-01

Since the bulk of the matter comprising galaxy clusters exists in the form of dark matter, gravitational N-body simulations have historically been an effective way to investigate large scale structure formation and the astrophysics of galaxy clusters. However, upcoming telescopes such as the Large Synoptic Survey Telescope are expected to have lower systematic errors than older generations, reducing measurement uncertainties and requiring that astrophysicists better quantify the impact of baryonic matter on the cluster lensing signal. Here we outline the effects of baryonic processes on cluster density profiles and on weak lensing mass and concentration estimates. Our analysis is done using clusters grown in the suite of cosmological hydrodynamical simulations known as cosmo-OWLS.

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

NASA Technical Reports Server (NTRS)

Isaacson, Jeffrey A.; Canizares, Claude R.

1989-01-01

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

Problems with small area surveys: lensing covariance of supernova distance measurements.

PubMed

Cooray, Asantha; Huterer, Dragan; Holz, Daniel E

2006-01-20

While luminosity distances from type Ia supernovae (SNe) are a powerful probe of cosmology, the accuracy with which these distances can be measured is limited by cosmic magnification due to gravitational lensing by the intervening large-scale structure. Spatial clustering of foreground mass leads to correlated errors in SNe distances. By including the full covariance matrix of SNe, we show that future wide-field surveys will remain largely unaffected by lensing correlations. However, "pencil beam" surveys, and those with narrow (but possibly long) fields of view, can be strongly affected. For a survey with 30 arcmin mean separation between SNe, lensing covariance leads to a approximately 45% increase in the expected errors in dark energy parameters.

The microscopic protein structure of the lens with a theory for cataract formation as determined by Raman spectroscopy of intact bovine lenses.

PubMed

Schachar, R A; Solin, S A

1975-05-01

Intact bovine lenses have been studied using the polarized Raman spectroscopic technique. A brief theoretical and experimental review of Raman spectroscopy is presented. From the dependence of the Raman depolarization ratio on the propagation direction of the incident radiation we have determined that the uniaxial qualities of the lens result from microscopic anisotropy and have established the quantitative positional correlation of specific chemical bonds with respect to the lens optic axis. In particular, the hydrogen bonded linear CONH groups of the antiparallel beta-pleated sheet are preferentially oriented in directions orthogonal to the lens optic axis. The Raman spectra of intact lenses do not exhibit bands at positions characteristic of either the alpha-helix or the random coil protein structure. The antiparallel beta-pleated sheet protein microstructure and the lens fiber cross-sectional macrostructure exhibit a remarkable similarity. This similarity may be causal and is consistent with the protein concentration of the lens, the birefringent properties observed by both Lenhard and Brewster, the CONH bond angle distribution with respect to the optic axis, and the lens anatomy. It is suggested that cortical cataracts are caused by fluctuations in protein orientational order.

Galaxy cluster lensing masses in modified lensing potentials

DOE PAGES

Barreira, Alexandre; Li, Baojiu; Jennings, Elise; ...

2015-10-28

In this study, we determine the concentration–mass relation of 19 X-ray selected galaxy clusters from the Cluster Lensing and Supernova Survey with Hubble survey in theories of gravity that directly modify the lensing potential. We model the clusters as Navarro–Frenk–White haloes and fit their lensing signal, in the Cubic Galileon and Nonlocal gravity models, to the lensing convergence profiles of the clusters. We discuss a number of important issues that need to be taken into account, associated with the use of non-parametric and parametric lensing methods, as well as assumptions about the background cosmology. Our results show that the concentrationmore » and mass estimates in the modified gravity models are, within the error bars, the same as in Λ cold dark matter. This result demonstrates that, for the Nonlocal model, the modifications to gravity are too weak at the cluster redshifts, and for the Galileon model, the screening mechanism is very efficient inside the cluster radius. However, at distances ~ [2–20] Mpc/h from the cluster centre, we find that the surrounding force profiles are enhanced by ~ 20–40% in the Cubic Galileon model. This has an impact on dynamical mass estimates, which means that tests of gravity based on comparisons between lensing and dynamical masses can also be applied to the Cubic Galileon model.« less

A new detection of an UFO in the X-ray spectrum of a lensed QSO

NASA Astrophysics Data System (ADS)

Dadina, M.

2017-10-01

The discovery of the "M_{SMBH}-σ relation" indicated that a connection between the central black-hole and the hosting galaxies acted during the cosmic time. With the discovery in X-rays of the ultra-fast outflows in nearby AGN, we have most probably probed one of the ingredients that are needed to build-up this mechanism. At high-z, however, such measurements were possible only in an handful of objects and this was possible mainly for the presence of gravitational lenses that magnified otherwise X-ray weak QSO. Following this, we proposed a program to use XMM-Newton and gravitational lenses as telescopes to point bright, lensed and distant QSO to characterize in detail their X-ray spectrum and to detect blushifted absorption lines at E˜7-10 keV (rest frame). Here we present the preliminary results obtained for the z=2.64 QSO MG J0414+0534.

Corneal, Conjunctival effects and blood flow changes related to silicone hydrogel lens wear and their correlations with end of day comfort.

PubMed

Sorbara, Luigina; Maram, Jyotsna; Simpson, Trefford; Hutchings, Natalie

2018-04-01

First, to examine how wearing high and low modulus lenses with two different base curves affected lens fit, and the corneal tissue and bulbar conjunctival vascular tissue (bulbar redness and blood velocity). Secondly, to quantify the associations between these baseline and outcome variables and the third purpose was to correlate these variables with end of day comfort. Thirty participants wore higher (PureVision (PV) 8.3, 8.6) and lower (Acuvue Advance (AA) 8.3, 8.7) modulus silicone hydrogel lenses for two weeks on a daily wear basis. Lens fitting characteristics were examined. Corneal epithelial thickness was measured and the cornea and conjunctiva were assessed. RBC velocity was estimated from high magnification bulbar conjunctival images. Subjective comfort/dryness was reported by participants using visual analogue scales. AA lenses were rated the most comfortable (ANOVA, p=0.041). The least movement was while using the AA 8.3 base curve lens (Tukey p=0.028). Steep AA and PV lenses showed significantly higher conjunctival staining at the 2 week visit (ANOVA, p=0.029). There was a significant decrease in RBC velocity with both steeper AA lenses vs PV lenses (Tukey, p=0.001). Comparing baseline and 2 week visits, there was a significant negative correlation for the PV 8.3 between comfort and superior bulbar staining (r=-0.53). For both the PV 8.3 and AA 8.3 reduced RBC velocity was correlated with dryness (r=0.61 and r=0.91, respectively). Physical differences in contact lenses affect structural and vascular functional aspects of the ocular surface and these may be associated with symptoms of dryness. Copyright © 2017 British Contact Lens Association. All rights reserved.

Cosmological parameter constraints with the Deep Lens Survey using galaxy-shear correlations and galaxy clustering properties

NASA Astrophysics Data System (ADS)

Yoon, Mijin; Jee, Myungkook James; Tyson, Tony

2018-01-01

The Deep Lens Survey (DLS), a precursor to the Large Synoptic Survey Telescope (LSST), is a 20 sq. deg survey carried out with NOAO’s Blanco and Mayall telescopes. The strength of the survey lies in its depth reaching down to ~27th mag in BVRz bands. This enables a broad redshift baseline study and allows us to investigate cosmological evolution of the large-scale structure. In this poster, we present the first cosmological analysis from the DLS using galaxy-shear correlations and galaxy clustering signals. Our DLS shear calibration accuracy has been validated through the most recent public weak-lensing data challenge. Photometric redshift systematic errors are tested by performing lens-source flip tests. Instead of real-space correlations, we reconstruct band-limited power spectra for cosmological parameter constraints. Our analysis puts a tight constraint on the matter density and the power spectrum normalization parameters. Our results are highly consistent with our previous cosmic shear analysis and also with the Planck CMB results.

Bacterial adhesion to unworn and worn silicone hydrogel lenses.

PubMed

Vijay, Ajay Kumar; Zhu, Hua; Ozkan, Jerome; Wu, Duojia; Masoudi, Simin; Bandara, Rani; Borazjani, Roya N; Willcox, Mark D P

2012-08-01

The objective of this study was to determine the bacterial adhesion to various silicone hydrogel lens materials and to determine whether lens wear modulated adhesion. Bacterial adhesion (total and viable cells) of Staphylococcus aureus (31, 38, and ATCC 6538) and Pseudomonas aeruginosa (6294, 6206, and GSU-3) to 10 commercially available different unworn and worn silicone hydrogel lenses was measured. Results of adhesion were correlated to polymer and surface properties of contact lenses. S. aureus adhesion to unworn lenses ranged from 2.8 × 10 to 4.4 × 10 colony forming units per lens. The highest adhesion was to lotrafilcon A lenses, and the lowest adhesion was to asmofilcon A lenses. P. aeruginosa adhesion to unworn lenses ranged from 8.9 × 10 to 3.2 × 10 colony forming units per lens. The highest adhesion was to comfilcon A lenses, and the lowest adhesion was to asmofilcon A and balafilcon A lenses. Lens wear altered bacterial adhesion, but the effect was specific to lens and strain type. Adhesion of bacteria, regardless of genera/species or lens wear, was generally correlated with the hydrophobicity of the lens; the less hydrophobic the lens surface, the greater the adhesion. P. aeruginosa adhered in higher numbers to lenses in comparison with S. aureus strains, regardless of the lens type or lens wear. The effect of lens wear was specific to strain and lens. Hydrophobicity of the silicone hydrogel lens surface influenced the adhesion of bacterial cells.

CLASH: MASS DISTRIBUTION IN AND AROUND MACS J1206.2-0847 FROM A FULL CLUSTER LENSING ANALYSIS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Umetsu, Keiichi; Koch, Patrick M.; Lin, Kai-Yang

2012-08-10

We derive an accurate mass distribution of the galaxy cluster MACS J1206.2-0847 (z = 0.439) from a combined weak-lensing distortion, magnification, and strong-lensing analysis of wide-field Subaru BVR{sub c} I{sub c} z' imaging and our recent 16-band Hubble Space Telescope observations taken as part of the Cluster Lensing And Supernova survey with Hubble program. We find good agreement in the regions of overlap between several weak- and strong-lensing mass reconstructions using a wide variety of modeling methods, ensuring consistency. The Subaru data reveal the presence of a surrounding large-scale structure with the major axis running approximately northwest-southeast (NW-SE), aligned withmore » the cluster and its brightest galaxy shapes, showing elongation with a {approx}2: 1 axis ratio in the plane of the sky. Our full-lensing mass profile exhibits a shallow profile slope dln {Sigma}/dln R {approx} -1 at cluster outskirts (R {approx}> 1 Mpc h{sup -1}), whereas the mass distribution excluding the NW-SE excess regions steepens farther out, well described by the Navarro-Frenk-White form. Assuming a spherical halo, we obtain a virial mass M{sub vir} = (1.1 {+-} 0.2 {+-} 0.1) Multiplication-Sign 10{sup 15} M{sub Sun} h{sup -1} and a halo concentration c{sub vir} = 6.9 {+-} 1.0 {+-} 1.2 (c{sub vir} {approx} 5.7 when the central 50 kpc h{sup -1} is excluded), which falls in the range 4 {approx}< (c) {approx}< 7 of average c(M, z) predictions for relaxed clusters from recent {Lambda} cold dark matter simulations. Our full-lensing results are found to be in agreement with X-ray mass measurements where the data overlap, and when combined with Chandra gas mass measurements, they yield a cumulative gas mass fraction of 13.7{sup +4.5}{sub -3.0}% at 0.7 Mpc h{sup -1}( Almost-Equal-To 1.7 r{sub 2500}), a typical value observed for high-mass clusters.« less

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg2 SPT-SZ and Planck Gravitational Lensing Map

NASA Astrophysics Data System (ADS)

Simard, G.; Omori, Y.; Aylor, K.; Baxter, E. J.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H.-M.; Chown, R.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Everett, W. B.; George, E. M.; Halverson, N. W.; Harrington, N. L.; Henning, J. W.; Holder, G. P.; Hou, Z.; Holzapfel, W. L.; Hrubes, J. D.; Knox, L.; Lee, A. T.; Leitch, E. M.; Luong-Van, D.; Manzotti, A.; McMahon, J. J.; Meyer, S. S.; Mocanu, L. M.; Mohr, J. J.; Natoli, T.; Padin, S.; Pryke, C.; Reichardt, C. L.; Ruhl, J. E.; Sayre, J. T.; Schaffer, K. K.; Shirokoff, E.; Staniszewski, Z.; Stark, A. A.; Story, K. T.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.; Wu, W. L. K.

2018-06-01

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 deg2 of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the lensing power spectrum to a model including cold dark matter and a cosmological constant ({{Λ }}{CDM}), and to models with single-parameter extensions to {{Λ }}{CDM}. We find constraints that are comparable to and consistent with those found using the full-sky Planck CMB lensing data, e.g., {σ }8{{{Ω }}}{{m}}0.25 = 0.598 ± 0.024 from the lensing data alone with weak priors placed on other parameters. Combining with primary CMB data, we explore single-parameter extensions to {{Λ }}{CDM}. We find {{{Ω }}}k =-{0.012}-0.023+0.021 or {M}ν < 0.70 eV at 95% confidence, in good agreement with results including the lensing potential as measured by Planck. We include two parameters that scale the effect of lensing on the CMB: {A}L, which scales the lensing power spectrum in both the lens reconstruction power and in the smearing of the acoustic peaks, and {A}φ φ , which scales only the amplitude of the lensing reconstruction power spectrum. We find {A}φ φ × {A}L = 1.01 ± 0.08 for the lensing map made from combined SPT and Planck data, indicating that the amount of lensing is in excellent agreement with expectations from the observed CMB angular power spectrum when not including the information from smearing of the acoustic peaks.

General relativistic corrections in density-shear correlations

NASA Astrophysics Data System (ADS)

Ghosh, Basundhara; Durrer, Ruth; Sellentin, Elena

2018-06-01

We investigate the corrections which relativistic light-cone computations induce on the correlation of the tangential shear with galaxy number counts, also known as galaxy-galaxy lensing. The standard-approach to galaxy-galaxy lensing treats the number density of sources in a foreground bin as observable, whereas it is in reality unobservable due to the presence of relativistic corrections. We find that already in the redshift range covered by the DES first year data, these currently neglected relativistic terms lead to a systematic correction of up to 50% in the density-shear correlation function for the highest redshift bins. This correction is dominated by the fact that a redshift bin of number counts does not only lens sources in a background bin, but is itself again lensed by all masses between the observer and the counted source population. Relativistic corrections are currently ignored in the standard galaxy-galaxy analyses, and the additional lensing of a counted source populations is only included in the error budget (via the covariance matrix). At increasingly higher redshifts and larger scales, these relativistic and lensing corrections become however increasingly more important, and we here argue that it is then more efficient, and also cleaner, to account for these corrections in the density-shear correlations.

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

NASA Astrophysics Data System (ADS)

Huff, Eric Michael

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

Improving Weak Lensing Mass Map Reconstructions using Gaussian and Sparsity Priors: Application to DES SV

DOE PAGES

Jeffrey, N.; Abdalla, F. B.; Lahav, O.; ...

2018-05-15

Mapping the underlying density field, including non-visible dark matter, using weak gravitational lensing measurements is now a standard tool in cosmology. Due to its importance to the science results of current and upcoming surveys, the quality of the convergence reconstruction methods should be well understood. We compare three different mass map reconstruction methods: Kaiser-Squires (KS), Wiener filter, and GLIMPSE. KS is a direct inversion method, taking no account of survey masks or noise. The Wiener filter is well motivated for Gaussian density fields in a Bayesian framework. The GLIMPSE method uses sparsity, with the aim of reconstructing non-linearities in themore » density field. We compare these methods with a series of tests on the public Dark Energy Survey (DES) Science Verification (SV) data and on realistic DES simulations. The Wiener filter and GLIMPSE methods offer substantial improvement on the standard smoothed KS with a range of metrics. For both the Wiener filter and GLIMPSE convergence reconstructions we present a 12% improvement in Pearson correlation with the underlying truth from simulations. To compare the mapping methods' abilities to find mass peaks, we measure the difference between peak counts from simulated {\\Lambda}CDM shear catalogues and catalogues with no mass fluctuations. This is a standard data vector when inferring cosmology from peak statistics. The maximum signal-to-noise value of these peak statistic data vectors was increased by a factor of 3.5 for the Wiener filter and by a factor of 9 using GLIMPSE. With simulations we measure the reconstruction of the harmonic phases, showing that the concentration of the phase residuals is improved 17% by GLIMPSE and 18% by the Wiener filter. We show that the correlation between the reconstructions from data and the foreground redMaPPer clusters is increased 18% by the Wiener filter and 32% by GLIMPSE. [Abridged]« less

Cosmological information in Gaussianized weak lensing signals

NASA Astrophysics Data System (ADS)

Joachimi, B.; Taylor, A. N.; Kiessling, A.

2011-11-01

Gaussianizing the one-point distribution of the weak gravitational lensing convergence has recently been shown to increase the signal-to-noise ratio contained in two-point statistics. We investigate the information on cosmology that can be extracted from the transformed convergence fields. Employing Box-Cox transformations to determine optimal transformations to Gaussianity, we develop analytical models for the transformed power spectrum, including effects of noise and smoothing. We find that optimized Box-Cox transformations perform substantially better than an offset logarithmic transformation in Gaussianizing the convergence, but both yield very similar results for the signal-to-noise ratio. None of the transformations is capable of eliminating correlations of the power spectra between different angular frequencies, which we demonstrate to have a significant impact on the errors in cosmology. Analytic models of the Gaussianized power spectrum yield good fits to the simulations and produce unbiased parameter estimates in the majority of cases, where the exceptions can be traced back to the limitations in modelling the higher order correlations of the original convergence. In the ideal case, without galaxy shape noise, we find an increase in the cumulative signal-to-noise ratio by a factor of 2.6 for angular frequencies up to ℓ= 1500, and a decrease in the area of the confidence region in the Ωm-σ8 plane, measured in terms of q-values, by a factor of 4.4 for the best performing transformation. When adding a realistic level of shape noise, all transformations perform poorly with little decorrelation of angular frequencies, a maximum increase in signal-to-noise ratio of 34 per cent, and even slightly degraded errors on cosmological parameters. We argue that to find Gaussianizing transformations of practical use, it will be necessary to go beyond transformations of the one-point distribution of the convergence, extend the analysis deeper into the non-linear regime and resort to an exploration of parameter space via simulations.

Improving Weak Lensing Mass Map Reconstructions using Gaussian and Sparsity Priors: Application to DES SV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeffrey, N.; et al.

2018-01-26

Mapping the underlying density field, including non-visible dark matter, using weak gravitational lensing measurements is now a standard tool in cosmology. Due to its importance to the science results of current and upcoming surveys, the quality of the convergence reconstruction methods should be well understood. We compare three different mass map reconstruction methods: Kaiser-Squires (KS), Wiener filter, and GLIMPSE. KS is a direct inversion method, taking no account of survey masks or noise. The Wiener filter is well motivated for Gaussian density fields in a Bayesian framework. The GLIMPSE method uses sparsity, with the aim of reconstructing non-linearities in themore » density field. We compare these methods with a series of tests on the public Dark Energy Survey (DES) Science Verification (SV) data and on realistic DES simulations. The Wiener filter and GLIMPSE methods offer substantial improvement on the standard smoothed KS with a range of metrics. For both the Wiener filter and GLIMPSE convergence reconstructions we present a 12% improvement in Pearson correlation with the underlying truth from simulations. To compare the mapping methods' abilities to find mass peaks, we measure the difference between peak counts from simulated {\\Lambda}CDM shear catalogues and catalogues with no mass fluctuations. This is a standard data vector when inferring cosmology from peak statistics. The maximum signal-to-noise value of these peak statistic data vectors was increased by a factor of 3.5 for the Wiener filter and by a factor of 9 using GLIMPSE. With simulations we measure the reconstruction of the harmonic phases, showing that the concentration of the phase residuals is improved 17% by GLIMPSE and 18% by the Wiener filter. We show that the correlation between the reconstructions from data and the foreground redMaPPer clusters is increased 18% by the Wiener filter and 32% by GLIMPSE. [Abridged]« less

Improving Weak Lensing Mass Map Reconstructions using Gaussian and Sparsity Priors: Application to DES SV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeffrey, N.; Abdalla, F. B.; Lahav, O.

Mapping the underlying density field, including non-visible dark matter, using weak gravitational lensing measurements is now a standard tool in cosmology. Due to its importance to the science results of current and upcoming surveys, the quality of the convergence reconstruction methods should be well understood. We compare three different mass map reconstruction methods: Kaiser-Squires (KS), Wiener filter, and GLIMPSE. KS is a direct inversion method, taking no account of survey masks or noise. The Wiener filter is well motivated for Gaussian density fields in a Bayesian framework. The GLIMPSE method uses sparsity, with the aim of reconstructing non-linearities in themore » density field. We compare these methods with a series of tests on the public Dark Energy Survey (DES) Science Verification (SV) data and on realistic DES simulations. The Wiener filter and GLIMPSE methods offer substantial improvement on the standard smoothed KS with a range of metrics. For both the Wiener filter and GLIMPSE convergence reconstructions we present a 12% improvement in Pearson correlation with the underlying truth from simulations. To compare the mapping methods' abilities to find mass peaks, we measure the difference between peak counts from simulated {\\Lambda}CDM shear catalogues and catalogues with no mass fluctuations. This is a standard data vector when inferring cosmology from peak statistics. The maximum signal-to-noise value of these peak statistic data vectors was increased by a factor of 3.5 for the Wiener filter and by a factor of 9 using GLIMPSE. With simulations we measure the reconstruction of the harmonic phases, showing that the concentration of the phase residuals is improved 17% by GLIMPSE and 18% by the Wiener filter. We show that the correlation between the reconstructions from data and the foreground redMaPPer clusters is increased 18% by the Wiener filter and 32% by GLIMPSE. [Abridged]« less

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

NASA Astrophysics Data System (ADS)

Kettula, K.; Finoguenov, A.; Massey, R.; Rhodes, J.; Hoekstra, H.; Taylor, J. E.; Spinelli, P. F.; Tanaka, M.; Ilbert, O.; Capak, P.; McCracken, H. J.; Koekemoer, A.

2013-11-01

The scaling between X-ray observables and mass for galaxy clusters and groups is instrumental for cluster-based cosmology and an important probe for the thermodynamics of the intracluster gas. We calibrate a scaling relation between the weak lensing mass and X-ray spectroscopic temperature for 10 galaxy groups in the COSMOS field, combined with 55 higher-mass clusters from the literature. The COSMOS data includes Hubble Space Telescope imaging and redshift measurements of 46 source galaxies per arcminute2, enabling us to perform unique weak lensing measurements of low-mass systems. Our sample extends the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study, resulting in a power-law slope of 1.48^{+0.13}_{-0.09}. The slope is consistent with the self-similar model, predictions from simulations, and observations of clusters. However, X-ray observations relying on mass measurements derived under the assumption of hydrostatic equilibrium have indicated that masses at group scales are lower than expected. Both simulations and observations suggest that hydrostatic mass measurements can be biased low. Our external weak lensing masses provide the first observational support for hydrostatic mass bias at group level, showing an increasing bias with decreasing temperature and reaching a level of 30%-50% at 1 keV. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555. Also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation; the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.; and the Canada-France-Hawaii Telescope (CFHT) with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the National Research Council of Canada, the Canadian Astronomy Data Centre, the Centre National de la Recherche Scientifique de France, TERAPIX, and the University of Hawaii.

The BAHAMAS project: the CMB-large-scale structure tension and the roles of massive neutrinos and galaxy formation

NASA Astrophysics Data System (ADS)

McCarthy, Ian G.; Bird, Simeon; Schaye, Joop; Harnois-Deraps, Joachim; Font, Andreea S.; van Waerbeke, Ludovic

2018-05-01

Recent studies have presented evidence for tension between the constraints on Ωm and σ8 from the cosmic microwave background (CMB) and measurements of large-scale structure (LSS). This tension can potentially be resolved by appealing to extensions of the standard model of cosmology and/or untreated systematic errors in the modelling of LSS, of which baryonic physics has been frequently suggested. We revisit this tension using, for the first time, carefully calibrated cosmological hydrodynamical simulations, which thus capture the backreaction of the baryons on the total matter distribution. We have extended the BAryons and HAloes of MAssive Sysmtes simulations to include a treatment of massive neutrinos, which currently represents the best-motivated extension to the standard model. We make synthetic thermal Sunyaev-Zel'dovich effect, weak galaxy lensing, and CMB lensing maps and compare to observed auto- and cross-power spectra from a wide range of recent observational surveys. We conclude that: (i) in general, there is tension between the primary CMB and LSS when adopting the standard model with minimal neutrino mass; (ii) after calibrating feedback processes to match the gas fractions of clusters, the remaining uncertainties in the baryonic physics modelling are insufficient to reconcile this tension; and (iii) if one accounts for internal tensions in the Planck CMB data set (by allowing the lensing amplitude, ALens, to vary), invoking a non-minimal neutrino mass, typically of 0.2-0.4 eV, can resolve the tension. This solution is fully consistent with separate constraints from the primary CMB and baryon acoustic oscillations.

Statistical analysis on multifractal detrended cross-correlation coefficient for return interval by oriented percolation

NASA Astrophysics Data System (ADS)

Deng, Wei; Wang, Jun

2015-06-01

We investigate and quantify the multifractal detrended cross-correlation of return interval series for Chinese stock markets and a proposed price model, the price model is established by oriented percolation. The return interval describes the waiting time between two successive price volatilities which are above some threshold, the present work is an attempt to quantify the level of multifractal detrended cross-correlation for the return intervals. Further, the concept of MF-DCCA coefficient of return intervals is introduced, and the corresponding empirical research is performed. The empirical results show that the return intervals of SSE and SZSE are weakly positive multifractal power-law cross-correlated, and exhibit the fluctuation patterns of MF-DCCA coefficients. The similar behaviors of return intervals for the price model is also demonstrated.

Recommended coordinate systems for thin spherocylindrical lenses.

PubMed

Deal, F C; Toop, J

1993-05-01

Because the set of thin spherocylindrical lenses forms a vector space, any such lens can be expressed in terms of its cartesian coordinates with respect to whatever set of basis lenses we may choose. Two types of cartesian coordinate systems have become prominent, those having coordinates associated with the lens power matrix and those having coordinates associated with the Humphrey Vision Analyzer. This paper emphasizes the value of a particular cartesian coordinate system of the latter type, and the cylindrical coordinate system related to it, by showing how it can simplify the trigonometry of adding lenses and how it preserves symmetry in depicting the sets of all spherical lenses, all Jackson crossed-cylinders, and all cylindrical lenses. It also discusses appropriate coordinates for keeping statistics on lenses and shows that an easy extension of the lens vector space to include general optical systems is not possible.

HectoMAPping the Universe. Karl Schwarzschild Award Lecture 2014

NASA Astrophysics Data System (ADS)

Geller, Margaret J.; Hwang, Ho Seong

2015-06-01

During the last three decades progress in mapping the Universe from an age of 400 000 years to the present has been stunning. Instrument/telescope combinations have naturally determined the sampling of various redshift ranges. Here we outline the impact of the Hectospec on the MMT on exploration of the Universe in the redshift range 0.2 ⪉ z ⪉ 0.8. We focus on dense redshift surveys, SHELS and HectoMAP. SHELS is a complete magnitude limited survey covering 8 square degrees. The HectoMAP survey combines a red-selected dense redshift survey and a weak lensing map covering 50 square degrees. Combining the dense redshift survey with a Subaru HyperSuprimeCam (HSC) weak lensing map will provide a powerful probe of the way galaxies trace the distribution of dark matter on a wide range of physical scales.

CALIBRATED ULTRA FAST IMAGE SIMULATIONS FOR THE DARK ENERGY SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruderer, Claudio; Chang, Chihway; Refregier, Alexandre

2016-01-20

Image simulations are becoming increasingly important in understanding the measurement process of the shapes of galaxies for weak lensing and the associated systematic effects. For this purpose we present the first implementation of the Monte Carlo Control Loops (MCCL), a coherent framework for studying systematic effects in weak lensing. It allows us to model and calibrate the shear measurement process using image simulations from the Ultra Fast Image Generator (UFig) and the image analysis software SExtractor. We apply this framework to a subset of the data taken during the Science Verification period (SV) of the Dark Energy Survey (DES). Wemore » calibrate the UFig simulations to be statistically consistent with one of the SV images, which covers ∼0.5 square degrees. We then perform tolerance analyses by perturbing six simulation parameters and study their impact on the shear measurement at the one-point level. This allows us to determine the relative importance of different parameters. For spatially constant systematic errors and point-spread function, the calibration of the simulation reaches the weak lensing precision needed for the DES SV survey area. Furthermore, we find a sensitivity of the shear measurement to the intrinsic ellipticity distribution, and an interplay between the magnitude-size and the pixel value diagnostics in constraining the noise model. This work is the first application of the MCCL framework to data and shows how it can be used to methodically study the impact of systematics on the cosmic shear measurement.« less

Correlation function of the luminosity distances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biern, Sang Gyu; Yoo, Jaiyul, E-mail: sgbiern@physik.uzh.ch, E-mail: jyoo@physik.uzh.ch

We present the correlation function of the luminosity distances in a flat ΛCDM universe. Decomposing the luminosity distance fluctuation into the velocity, the gravitational potential, and the lensing contributions in linear perturbation theory, we study their individual contributions to the correlation function. The lensing contribution is important at large redshift ( z ∼> 0.5) but only for small angular separation (θ ∼< 3°), while the velocity contribution dominates over the other contributions at low redshift or at larger separation. However, the gravitational potential contribution is always subdominant at all scale, if the correct gauge-invariant expression is used. The correlation functionmore » of the luminosity distances depends significantly on the matter content, especially for the lensing contribution, thus providing a novel tool of estimating cosmological parameters.« less

A study of correlations between crude oil spot and futures markets: A rolling sample test

NASA Astrophysics Data System (ADS)

Liu, Li; Wan, Jieqiu

2011-10-01

In this article, we investigate the asymmetries of exceedance correlations and cross-correlations between West Texas Intermediate (WTI) spot and futures markets. First, employing the test statistic proposed by Hong et al. [Asymmetries in stock returns: statistical tests and economic evaluation, Review of Financial Studies 20 (2007) 1547-1581], we find that the exceedance correlations were overall symmetric. However, the results from rolling windows show that some occasional events could induce the significant asymmetries of the exceedance correlations. Second, employing the test statistic proposed by Podobnik et al. [Quantifying cross-correlations using local and global detrending approaches, European Physics Journal B 71 (2009) 243-250], we find that the cross-correlations were significant even for large lagged orders. Using the detrended cross-correlation analysis proposed by Podobnik and Stanley [Detrended cross-correlation analysis: a new method for analyzing two nonstationary time series, Physics Review Letters 100 (2008) 084102], we find that the cross-correlations were weakly persistent and were stronger between spot and futures contract with larger maturity. Our results from rolling sample test also show the apparent effects of the exogenous events. Additionally, we have some relevant discussions on the obtained evidence.

Quantifying systematics from the shear inversion on weak-lensing peak counts

NASA Astrophysics Data System (ADS)

Lin, Chieh-An; Kilbinger, Martin

2018-06-01

Weak-lensing peak counts provide a straightforward way to constrain cosmology by linking local maxima of the lensing signal to the mass function. Recent applications to data have already been numerous and fruitful. However, the importance of understanding and dealing with systematics increases as data quality reaches an unprecedented level. One of the sources of systematics is the convergence-shear inversion. This effect, inevitable when carrying out a convergence field from observations, is usually neglected by theoretical peak models. Thus, it could have an impact on cosmological results. In this paper, we study the bias from neglecting (mis-modeling) the inversion. Our tests show a small but non-negligible bias. The cosmological dependence of this bias seems to be related to the parameter Σ8 ≡ (Ωm/(1 - α))1 - α(σ8/α)α, where α = 2/3. When this bias propagates to the parameter estimation, we discovered that constraint contours involving the dark energy equation of state can differ by 2σ. Such an effect can be even larger for future high-precision surveys and we argue that the inversion should be properly modeled for theoretical peak models.

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

DOE PAGES

Petri, Andrea; May, Morgan; Haiman, Zoltán

2016-09-30

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 (Ω m,w,σ 8) for a LSST-like photometric galaxy survey, using tomography of the shear-shear power spectrum, convergence peak counts and higher convergence moments. Here we find that redshift tomography with the power spectrum reduces the area of the 1σ confidence interval in (Ω m,w) space by a factor ofmore » 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 (Ω m,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. In conclusion, we find that different statistics lead to different bias directions in parameter space, suggesting the possibility of eliminating this bias via self-calibration.« less

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg$^2$ SPT-SZ and Planck Gravitational Lensing Map

DOE PAGES

Simard, G.; et al.

2018-06-20

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 degmore » $^2$ of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the corresponding lensing angular power spectrum to a model including cold dark matter and a cosmological constant ($$\\Lambda$$CDM), and to models with single-parameter extensions to $$\\Lambda$$CDM. We find constraints that are comparable to and consistent with constraints found using the full-sky Planck CMB lensing data. Specifically, we find $$\\sigma_8 \\Omega_{\\rm m}^{0.25}=0.598 \\pm 0.024$$ from the lensing data alone with relatively weak priors placed on the other $$\\Lambda$$CDM parameters. In combination with primary CMB data from Planck, we explore single-parameter extensions to the $$\\Lambda$$CDM model. We find $$\\Omega_k = -0.012^{+0.021}_{-0.023}$$ or $$M_{\

Constraints on Cosmological Parameters from the Angular Power Spectrum of a Combined 2500 deg$^2$ SPT-SZ and Planck Gravitational Lensing Map

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simard, G.; et al.

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 degmore » $^2$ of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the corresponding lensing angular power spectrum to a model including cold dark matter and a cosmological constant ($$\\Lambda$$CDM), and to models with single-parameter extensions to $$\\Lambda$$CDM. We find constraints that are comparable to and consistent with constraints found using the full-sky Planck CMB lensing data. Specifically, we find $$\\sigma_8 \\Omega_{\\rm m}^{0.25}=0.598 \\pm 0.024$$ from the lensing data alone with relatively weak priors placed on the other $$\\Lambda$$CDM parameters. In combination with primary CMB data from Planck, we explore single-parameter extensions to the $$\\Lambda$$CDM model. We find $$\\Omega_k = -0.012^{+0.021}_{-0.023}$$ or $$M_{\

Conformal bootstrap at large charge

NASA Astrophysics Data System (ADS)

Jafferis, Daniel; Mukhametzhanov, Baur; Zhiboedov, Alexander

2018-05-01

We consider unitary CFTs with continuous global symmetries in d > 2. We consider a state created by the lightest operator of large charge Q ≫ 1 and analyze the correlator of two light charged operators in this state. We assume that the correlator admits a well-defined large Q expansion and, relatedly, that the macroscopic (thermodynamic) limit of the correlator exists. We find that the crossing equations admit a consistent truncation, where only a finite number N of Regge trajectories contribute to the correlator at leading nontrivial order. We classify all such truncated solutions to the crossing. For one Regge trajectory N = 1, the solution is unique and given by the effective field theory of a Goldstone mode. For two or more Regge trajectories N ≥ 2, the solutions are encoded in roots of a certain degree N polynomial. Some of the solutions admit a simple weakly coupled EFT description, whereas others do not. In the weakly coupled case, each Regge trajectory corresponds to a field in the effective Lagrangian.

A redshift survey of the strong-lensing cluster ABELL 383

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geller, Margaret J.; Hwang, Ho Seong; Kurtz, Michael J.

2014-03-01

Abell 383 is a famous rich cluster (z = 0.1887) imaged extensively as a basis for intensive strong- and weak-lensing studies. Nonetheless, there are few spectroscopic observations. We enable dynamical analyses by measuring 2360 new redshifts for galaxies with r {sub Petro} ≤ 20.5 and within 50' of the Brightest Cluster Galaxy (BCG; R.A.{sub 2000} = 42.°014125, decl.{sub 2000} = –03.°529228). We apply the caustic technique to identify 275 cluster members within 7 h {sup –1} Mpc of the hierarchical cluster center. The BCG lies within –11 ± 110 km s{sup –1} and 21 ± 56 h {sup –1} kpcmore » of the hierarchical cluster center; the velocity dispersion profile of the BCG appears to be an extension of the velocity dispersion profile based on cluster members. The distribution of cluster members on the sky corresponds impressively with the weak-lensing contours of Okabe et al. especially when the impact of foreground and background structure is included. The values of R {sub 200} = 1.22 ± 0.01 h {sup –1} Mpc and M {sub 200} = (5.07 ± 0.09) × 10{sup 14} h {sup –1} M {sub ☉} obtained by application of the caustic technique agree well with recent completely independent lensing measures. The caustic estimate extends direct measurement of the cluster mass profile to a radius of ∼5 h {sup –1} Mpc.« less

The 2-degree Field Lensing Survey: design and clustering measurements

NASA Astrophysics Data System (ADS)

Blake, Chris; Amon, Alexandra; Childress, Michael; Erben, Thomas; Glazebrook, Karl; Harnois-Deraps, Joachim; Heymans, Catherine; Hildebrandt, Hendrik; Hinton, Samuel R.; Janssens, Steven; Johnson, Andrew; Joudaki, Shahab; Klaes, Dominik; Kuijken, Konrad; Lidman, Chris; Marin, Felipe A.; Parkinson, David; Poole, Gregory B.; Wolf, Christian

2016-11-01

We present the 2-degree Field Lensing Survey (2dFLenS), a new galaxy redshift survey performed at the Anglo-Australian Telescope. 2dFLenS is the first wide-area spectroscopic survey specifically targeting the area mapped by deep-imaging gravitational lensing fields, in this case the Kilo-Degree Survey. 2dFLenS obtained 70 079 redshifts in the range z < 0.9 over an area of 731 deg2, and is designed to extend the data sets available for testing gravitational physics and promote the development of relevant algorithms for joint imaging and spectroscopic analysis. The redshift sample consists first of 40 531 Luminous Red Galaxies (LRGs), which enable analyses of galaxy-galaxy lensing, redshift-space distortion, and the overlapping source redshift distribution by cross-correlation. An additional 28 269 redshifts form a magnitude-limited (r < 19.5) nearly complete subsample, allowing direct source classification and photometric-redshift calibration. In this paper, we describe the motivation, target selection, spectroscopic observations, and clustering analysis of 2dFLenS. We use power spectrum multipole measurements to fit the redshift-space distortion parameter of the LRG sample in two redshift ranges 0.15 < z < 0.43 and 0.43 < z < 0.7 as β = 0.49 ± 0.15 and β = 0.26 ± 0.09, respectively. These values are consistent with those obtained from LRGs in the Baryon Oscillation Spectroscopic Survey. 2dFLenS data products will be released via our website http://2dflens.swin.edu.au.

Lensing corrections to features in the angular two-point correlation function and power spectrum

DOE Office of Scientific and Technical Information (OSTI.GOV)

LoVerde, Marilena; Department of Physics, Columbia University, New York, New York 10027; Hui, Lam

2008-01-15

It is well known that magnification bias, the modulation of galaxy or quasar source counts by gravitational lensing, can change the observed angular correlation function. We investigate magnification-induced changes to the shape of the observed correlation function w({theta}), and the angular power spectrum C{sub l}, paying special attention to the matter-radiation equality peak and the baryon wiggles. Lensing effectively mixes the correlation function of the source galaxies with that of the matter correlation at the lower redshifts of the lenses distorting the observed correlation function. We quantify how the lensing corrections depend on the width of the selection function, themore » galaxy bias b, and the number count slope s. The lensing correction increases with redshift and larger corrections are present for sources with steep number count slopes and/or broad redshift distributions. The most drastic changes to C{sub l} occur for measurements at high redshifts (z > or approx. 1.5) and low multipole moment (l < or approx. 100). For the source distributions we consider, magnification bias can shift the location of the matter-radiation equality scale by 1%-6% at z{approx}1.5 and by z{approx}3.5 the shift can be as large as 30%. The baryon bump in {theta}{sup 2}w({theta}) is shifted by < or approx. 1% and the width is typically increased by {approx}10%. Shifts of > or approx. 0.5% and broadening > or approx. 20% occur only for very broad selection functions and/or galaxies with (5s-2)/b > or approx. 2. However, near the baryon bump the magnification correction is not constant but is a gently varying function which depends on the source population. Depending on how the w({theta}) data is fitted, this correction may need to be accounted for when using the baryon acoustic scale for precision cosmology.« less

A relativistic signature in large-scale structure

NASA Astrophysics Data System (ADS)

Bartolo, Nicola; Bertacca, Daniele; Bruni, Marco; Koyama, Kazuya; Maartens, Roy; Matarrese, Sabino; Sasaki, Misao; Verde, Licia; Wands, David

2016-09-01

In General Relativity, the constraint equation relating metric and density perturbations is inherently nonlinear, leading to an effective non-Gaussianity in the dark matter density field on large scales-even if the primordial metric perturbation is Gaussian. Intrinsic non-Gaussianity in the large-scale dark matter overdensity in GR is real and physical. However, the variance smoothed on a local physical scale is not correlated with the large-scale curvature perturbation, so that there is no relativistic signature in the galaxy bias when using the simplest model of bias. It is an open question whether the observable mass proxies such as luminosity or weak lensing correspond directly to the physical mass in the simple halo bias model. If not, there may be observables that encode this relativistic signature.

Statistical tests for power-law cross-correlated processes

NASA Astrophysics Data System (ADS)

Podobnik, Boris; Jiang, Zhi-Qiang; Zhou, Wei-Xing; Stanley, H. Eugene

2011-12-01

For stationary time series, the cross-covariance and the cross-correlation as functions of time lag n serve to quantify the similarity of two time series. The latter measure is also used to assess whether the cross-correlations are statistically significant. For nonstationary time series, the analogous measures are detrended cross-correlations analysis (DCCA) and the recently proposed detrended cross-correlation coefficient, ρDCCA(T,n), where T is the total length of the time series and n the window size. For ρDCCA(T,n), we numerically calculated the Cauchy inequality -1≤ρDCCA(T,n)≤1. Here we derive -1≤ρDCCA(T,n)≤1 for a standard variance-covariance approach and for a detrending approach. For overlapping windows, we find the range of ρDCCA within which the cross-correlations become statistically significant. For overlapping windows we numerically determine—and for nonoverlapping windows we derive—that the standard deviation of ρDCCA(T,n) tends with increasing T to 1/T. Using ρDCCA(T,n) we show that the Chinese financial market's tendency to follow the U.S. market is extremely weak. We also propose an additional statistical test that can be used to quantify the existence of cross-correlations between two power-law correlated time series.

Potential sources of bacteria that are isolated from contact lenses during wear.

PubMed

Willcox, M D; Power, K N; Stapleton, F; Leitch, C; Harmis, N; Sweeney, D F

1997-12-01

The aim of this paper was to determine the possible contamination sources of contact lenses during wear. Potential sources of the microbiota that colonized hydrogel contact lenses during wear were examined. The microorganisms that colonize contact lenses were grown, identified, and compared to those microorganisms that colonized the lower lid margins, upper bulbar conjunctiva, hands, and contact lens cases of contact lens wearers. In addition, the incidence of contamination of the domestic water supply in the Sydney area was obtained, and this was compared to the incidence of colonization of contact lenses by microorganisms in general and gram-negative bacteria in particular. There was a wide diversity of bacteria that were isolated from each site sampled. Coagulase-negative staphylococci and Propionibacterium spp. were the most common isolates from all ocular sites examined, and constituted the normal ocular microbiota. Other bacteria, including members of the families Enterobacteriaceae and Pseudomonadaceae, were isolated infrequently from all sites, but most frequently from contact lens cases. Statistical analysis revealed that there was a correlation between the isolation of bacteria from the contact lens and the lower lid margin (p < 0.001). Analysis of this correlation revealed that this was true for the normal microbiota. A correlation was also noted between the colonization of contact lenses by gram-negative bacteria and contamination of the domestic water supply. This study has demonstrated that the likely route for the normal ocular microbiota colonizing contact lenses is via the lid margins, whereas colonization by gram-negative bacteria, including potential agents of microbial keratitis, is likely to be from the domestic water supply.

Defect inspection of actuator lenses using swept-source optical coherence tomography

NASA Astrophysics Data System (ADS)

Lee, Jaeyul; Shirazi, Muhammad Faizan; Park, Kibeom; Jeon, Mansik; Kim, Jeehyun

2017-12-01

Actuator lens industries have gained an enormous interest with the enhancement of various latest communication devices, such as mobile phone and notebooks. The quality of the aforementioned devices can be degraded due to the internal defects of actuator lenses. Therefore, in this study, we implemented swept-source optical coherence tomography (SS-OCT) system to inspect defects of actuator lenses. Owing to the high-resolution of the SS-OCT system, defected foreign substances between the actuator lenses, defective regions of lenses and surface stains were more clearly distinguished through three-dimensional (3D) and two-dimensional (2D) cross-sectional OCT images. Therefore, the implemented SS-OCT system can be considered as a potential application to defect inspection of actuator lens.

AMI SZ observation of galaxy-cluster merger CIZA J2242+5301: perpendicular flows of gas and dark matter

NASA Astrophysics Data System (ADS)

Rumsey, Clare; Perrott, Yvette C.; Olamaie, Malak; Saunders, Richard D. E.; Hobson, Michael P.; Stroe, Andra; Schammel, Michel P.; Grainge, Keith J. B.

2017-10-01

Arcminute Microkelvin Imager observations towards CIZA J2242+5301, in comparison with observations of weak gravitational lensing and X-ray emission from the literature, are used to investigate the behaviour of non-baryonic dark matter (NBDM) and gas during the merger. Analysis of the Sunyaev-Zel'dovich (SZ) signal indicates the presence of high pressure gas elongated perpendicularly to the X-ray and weak-lensing morphologies, which, given the merger-axis constraints in the literature, implies that high pressure gas is pushed out into a linear structure during core passing. Simulations in the literature closely matching the inferred merger scenario show the formation of gas density and temperature structures perpendicular to the merger axis. These SZ observations are challenging for modified gravity theories in which NBDM is not the dominant contributor to galaxy-cluster gravity.

Optics ellipticity performance of an unobscured off-axis space telescope.

PubMed

Zeng, Fei; Zhang, Xin; Zhang, Jianping; Shi, Guangwei; Wu, Hongbo

2014-10-20

With the development of astronomy, more and more attention is paid to the survey of dark matter. Dark matter cannot be seen directly but can be detected by weak gravitational lensing measurement. Ellipticity is an important parameter used to define the shape of a galaxy. Galaxy ellipticity changes with weak gravitational lensing and nonideal optics. With our design of an unobscured off-axis telescope, we implement the simulation and calculation of optics ellipticity. With an accurate model of optics PSF, the characteristic of ellipticity is modeled and analyzed. It is shown that with good optical design, the full field ellipticity can be quite small. The spatial ellipticity change can be modeled by cubic interpolation with very high accuracy. We also modeled the ellipticity variance with time and analyzed the tolerance. It is shown that the unobscured off-axis telescope has good ellipticity performance and fulfills the requirement of dark matter survey.

MODEL-FREE MULTI-PROBE LENSING RECONSTRUCTION OF CLUSTER MASS PROFILES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Umetsu, Keiichi

2013-05-20

Lens magnification by galaxy clusters induces characteristic spatial variations in the number counts of background sources, amplifying their observed fluxes and expanding the area of sky, the net effect of which, known as magnification bias, depends on the intrinsic faint-end slope of the source luminosity function. The bias is strongly negative for red galaxies, dominated by the geometric area distortion, whereas it is mildly positive for blue galaxies, enhancing the blue counts toward the cluster center. We generalize the Bayesian approach of Umetsu et al. for reconstructing projected cluster mass profiles, by incorporating multiple populations of background sources for magnification-biasmore » measurements and combining them with complementary lens-distortion measurements, effectively breaking the mass-sheet degeneracy and improving the statistical precision of cluster mass measurements. The approach can be further extended to include strong-lensing projected mass estimates, thus allowing for non-parametric absolute mass determinations in both the weak and strong regimes. We apply this method to our recent CLASH lensing measurements of MACS J1206.2-0847, and demonstrate how combining multi-probe lensing constraints can improve the reconstruction of cluster mass profiles. This method will also be useful for a stacked lensing analysis, combining all lensing-related effects in the cluster regime, for a definitive determination of the averaged mass profile.« less

Magnifying Lenses with Weak Achromatic Bends for High-Energy Electron Radiography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walstrom, Peter Lowell

2015-02-27

This memo briefly describes bremsstrahlung background effects in GeV-range electron radiography systems and the use of weak bending magnets to deflect the image to the side of the forward bremsstrahlung spot to reduce background. The image deflection introduces first-order chromatic image blur due to dispersion. Two approaches to eliminating the dispersion effect to first order by use of magnifying lens with achromatic bends are described. Also, higher-order image blur terms caused by weak bends are also discussed, and shown to be negligibly small in most cases of interest.

Multi-centre evaluation of two daily disposable contact lenses.

PubMed

Walker, Jon; Young, Graeme; Hunt, Chris; Henderson, Terri

2007-05-01

To evaluate the clinical performance of two daily disposable contact lenses: 1-DAY ACUVUE (1DA) (etafilcon A, Johnson & Johnson Vision Care) and FOCUS DAILIES with AquaComfort (FD) (nelfilcon A, CIBA Vision, Inc.), which contains a quickly released moisture enhancing agent, polyvinyl alcohol (PVA). This was a 1-week, daily wear, subject-masked, bilateral, parallel group study with subjects randomly assigned to one of two daily disposable soft contact lenses. Subjects were existing soft contact lens wearers in the age range 18-39 years with a spherical refraction between -0.50 and -6.00 D. Subjects were assessed at baseline and after 1 week. Assessments included both subjective (symptoms, wearing time, vision) and objective (lens fit and ocular health) outcomes. Twenty clinical sites enrolled 282 subjects (74% female) of whom 276 (98%) successfully completed the study. Significantly more 1DA wearers reported higher mean comfort scores than with FD (3.95 versus 3.41, respectively, P<0.0001). End-of-day comfort means were also significantly higher with the 1DA group compared to the FD group (3.3 versus 3.0, P=0.03). The 1DA group reported significantly longer mean overall wearing time (1DA was worn on average 0.66+/-0.30 h longer than FD, P=0.03) and longer mean comfortable wearing time (1DA was worn on average 1.73+/-0.35 h longer than FD, P<0.0001). The 1DA lens generally showed significantly better on-eye fitting in terms of movement in primary (P<0.0001) and upgaze (P<0.0001) and ease of removal from the eye (92% versus 63%, P<0.0001) compared to FD. There was significantly less corneal staining observed with the 1DA wearing eyes compared with the FD wearing eyes (23% versus 45%, respectively, P<0.0001). Finally, there was a weak correlation between corneal staining and comfort for FD (r=0.27, P=0.002, n=136), but not for 1DA (r=-0.11, P=0.18, n=140). Subjective and objective clinical performance differences between two commonly used daily disposable lenses highlight that, although both lenses may be considered as clinically acceptable, these lenses should not be regarded as interchangeable.

An Empirical Examination of the Anomie Theory of Drug Use.

ERIC Educational Resources Information Center

Dull, R. Thomas

1983-01-01

Investigated the relationship between anomie theory, as measured by Srole's Anomie Scale, and self-admitted drug use in an adult population (N=1,449). Bivariate cross-comparison correlations indicated anomie was significantly correlated with several drug variables, but these associations were extremely weak and of little explanatory value.…

Light on curved backgrounds

NASA Astrophysics Data System (ADS)

Batic, D.; Nelson, S.; Nowakowski, M.

2015-05-01

We consider the motion of light on different spacetime manifolds by calculating the deflection angle, lensing properties and by probing into the possibility of bound states. The metrics in which we examine the light motion include, among other items, a general relativistic dark matter metric, a dirty black hole, and a worm hole metric, the last two inspired by noncommutative geometry. The lensing in a holographic screen metric is discussed in detail. We study also the bending of light around naked singularities like, e.g., the Janis-Newman-Winicour metric and include other cases. A generic property of light behavior in these exotic metrics is pointed out. For the standard metric like the Schwarzschild and Schwarzschild-de Sitter cases, we improve the accuracy of the lensing results for the weak and strong regimes.

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

NASA Astrophysics Data System (ADS)

Simon, Patrick; Schneider, Peter

2017-08-01

In weak gravitational lensing, weighted quadrupole moments of the brightness profile in galaxy images are a common way to estimate gravitational shear. We have employed general adaptive moments (GLAM ) to study causes of shear bias on a fundamental level and for a practical definition of an image ellipticity. The GLAM ellipticity has useful properties for any chosen weight profile: the weighted ellipticity is identical to that of isophotes of elliptical images, and in absence of noise and pixellation it is always an unbiased estimator of reduced shear. We show that moment-based techniques, adaptive or unweighted, are similar to a model-based approach in the sense that they can be seen as imperfect fit of an elliptical profile to the image. Due to residuals in the fit, moment-based estimates of ellipticities are prone to underfitting bias when inferred from observed images. The estimation is fundamentally limited mainly by pixellation which destroys information on the original, pre-seeing image. We give an optimised estimator for the pre-seeing GLAM ellipticity and quantify its bias for noise-free images. To deal with images where pixel noise is prominent, we consider a Bayesian approach to infer GLAM ellipticity where, similar to the noise-free case, the ellipticity posterior can be inconsistent with the true ellipticity if we do not properly account for our ignorance about fit residuals. This underfitting bias, quantified in the paper, does not vary with the overall noise level but changes with the pre-seeing brightness profile and the correlation or heterogeneity of pixel noise over the image. Furthermore, when inferring a constant ellipticity or, more relevantly, constant shear from a source sample with a distribution of intrinsic properties (sizes, centroid positions, intrinsic shapes), an additional, now noise-dependent bias arises towards low signal-to-noise if incorrect prior densities for the intrinsic properties are used. We discuss the origin of this prior bias. With regard to a fully-Bayesian lensing analysis, we point out that passing tests with source samples subject to constant shear may not be sufficient for an analysis of sources with varying shear.

A near/mid infrared search for ultra-bright submillimetre galaxies: Searching for Cosmic Eyelash Analogues

NASA Astrophysics Data System (ADS)

Iglesias-Groth, S.; Díaz-Sánchez, A.; Rebolo, R.; Dannerbauer, H.

2017-05-01

We present results from a near-/mid-IR search for submillimetre galaxies over a region of 6230 deg2 of the southern sky. We used a cross-correlation of the VISTA Hemispheric Survey (VHS) and the WISE data base to identify bright galaxies (Ks ≤ 18.2) with near-/mid-IR colours similar to those of the high-redshift lensed submm galaxy SMM J2135-0102. We find seven galaxies that fulfil all five adopted near-/mid-IR colour (NMIRQC) criteria and resemble the SED of the reference galaxy at these wavelengths. For these galaxies, which are broadly distributed in the sky, we determined photometric redshifts in the range z = 1.6-3.2. We searched the VHS for clusters of galaxies, which may be acting as gravitational lenses, and found that six out of the seven galaxies are located within 3.5 arcmin of a cluster/group of galaxies. Using the J-Ks versus J sequences, we determine photometric redshifts for these clusters/groups in the range z = 0.2-0.9. We propose the newly identified sources are ultrabright high-redshift lensed SMG candidates. Follow-up observations in the submm and mm are key to determine the ultimate nature of these objects.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simard, G.; et al.

We report constraints on cosmological parameters from the angular power spectrum of a cosmic microwave background (CMB) gravitational lensing potential map created using temperature data from 2500 degmore » $^2$ of South Pole Telescope (SPT) data supplemented with data from Planck in the same sky region, with the statistical power in the combined map primarily from the SPT data. We fit the corresponding lensing angular power spectrum to a model including cold dark matter and a cosmological constant ($$\\Lambda$$CDM), and to models with single-parameter extensions to $$\\Lambda$$CDM. We find constraints that are comparable to and consistent with constraints found using the full-sky Planck CMB lensing data. Specifically, we find $$\\sigma_8 \\Omega_{\\rm m}^{0.25}=0.598 \\pm 0.024$$ from the lensing data alone with relatively weak priors placed on the other $$\\Lambda$$CDM parameters. In combination with primary CMB data from Planck, we explore single-parameter extensions to the $$\\Lambda$$CDM model. We find $$\\Omega_k = -0.012^{+0.021}_{-0.023}$$ or $$M_{\

Saw-tooth refractive x-ray optics with sub-micron resolution

NASA Astrophysics Data System (ADS)

Cederstrom, Bjorn; Ribbing, Carolina; Lundqvist, Mats

2002-11-01

Saw-tooth refractive x-ray lenses have been used to focus a synchrotron beam to sub-μm line width. These lenses are free from spherical aberration and work in analogy with 1-D focusing parabolic compound refractive lenses. However, the focal length can be varied by a simple mechanical procedure. Silicon lenses were fabricated by wet anisotropic etching, and epoxy replicas were molded from the silicon masters. Theses lenses provided 1-D intensity gains up to a factor of 40 and the smallest focal line width was 0.74 μm, very close to the theoretical expectation. Two crossed lenses were put in series to obtain 2-D focusing and the 80 μm by 275 μm source was imaged to 1.0 μm by 5.4 μm. Beryllium lenses were fabricated using conventional computer-controlled milling. The focal line width was 1.7 μm, nearly 3 times larger than predicted by theory. This can be attributed to large surface roughness and a bent lens shape.

Tomographic-spectral approach for dark matter detection in the cross-correlation between cosmic shear and diffuse γ-ray emission

NASA Astrophysics Data System (ADS)

Camera, S.; Fornasa, M.; Fornengo, N.; Regis, M.

2015-06-01

We recently proposed to cross-correlate the diffuse extragalactic γ-ray background with the gravitational lensing signal of cosmic shear. This represents a novel and promising strategy to search for annihilating or decaying particle dark matter (DM) candidates. In the present work, we demonstrate the potential of a tomographic-spectral approach: measuring the cross-correlation in separate bins of redshift and energy significantly improves the sensitivity to a DM signal. Indeed, the technique proposed here takes advantage of the different scaling of the astrophysical and DM components with redshift and, simultaneously of their different energy spectra and different angular extensions. The sensitivity to a particle DM signal is extremely promising even when the DM-induced emission is quite faint. We first quantify the prospects of detecting DM by cross-correlating the Fermi Large Area Telescope (LAT) diffuse γ-ray background with the cosmic shear expected from the Dark Energy Survey. Under the hypothesis of a significant subhalo boost, such a measurement can deliver a 5σ detection of DM, if the DM particle is lighter than 300 GeV and has a thermal annihilation rate. We then forecast the capability of the European Space Agency Euclid satellite (whose launch is planned for 2020), in combination with an hypothetical future γ-ray detector with slightly improved specifications compared to current telescopes. We predict that the cross-correlation of their data will allow a measurement of the DM mass with an uncertainty of a factor of 1.5-2, even for moderate subhalo boosts, for DM masses up to few hundreds of GeV and thermal annihilation rates.

The internalization of posterior subcapsular cataracts (PSCs) in Royal College of Surgeons (RCS) rats. II. The inter-relationship of optical quality and structure as a function of age.

PubMed

Kuszak, J R; Al-Ghoul, K J; Novak, L A; Peterson, K L; Herbert, K L; Sivak, J G

1999-05-06

The Royal College of Surgeons (RCS) rat is an animal model for human retinal degenerative disease and posterior subcapsular cataracts (PSCs). The purpose of this study was to correlate the structure and optical quality of RCS lenses with PSCs as a function of their internalization, with normal, non-cataractous, age-matched control lenses. Correlative light (LM), scanning electron microscopic (SEM), three-dimensional computer assisted drawings (3D-CADs) and low power helium-neon laser scan analysis were used to examine the structure and function of lenses. The optical properties (average focal length variability; sharpness of focus) of RCS rat lenses are quantitatively compromised by PSCs. Correlative LM and SEM analysis of RCS lenses at various stages of PSC internalization (1.5, 3, 6, 9, 12 and 15 months of age), revealed that the sutures formed by additional fiber growth were progressively more abnormal. During PSC internalization, two to nine small suture branches were formed and arranged in modified line to multiple y configurations rather than the normal three branch y sutures. These temporal changes were also chronicled in animated 3D-CAD videos derived from lens reconstructions based on LM and SEM micrographs from the selected time points stated above. However, laser scan analysis also revealed that as the PSCs of RCS rat lenses were progressively internalized, there was a steady improvement in total sharpness of focus that reached normal levels by 12 months of age. The correlation of laser scan and structural data from specific regions of lenses revealed the following: 1. The abnormal posterior sutures of RCS rats with internalized PSCs effect a greater reduction in optical quality than normal posterior sutures of age-matched controls; 2. However, the resulting abnormal suture plane area was cumulatively similar to that of age-matched controls; 3. Thus, total optical quality was similar between RCS lenses with internalized PSCs and age-matched controls by 12 months of age. The results of this study show that RCS lenses with internalized PSCs can appear grossly, and indeed optically perform, at levels comparable to aged lenses. These findings are consistent with clinical observations of spontaneous recovery from PSC. The results suggest that human PSCs that occur as a consequence of retinal degenerative disease could also be the result of abnormal posterior suture growth. If this is proven to be the case, such PSCs may have some capacity for repair or recovery thereby obviating their surgical removal.

CFHTLenS: co-evolution of galaxies and their dark matter haloes

NASA Astrophysics Data System (ADS)

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

2015-02-01

Galaxy-galaxy weak lensing is a direct probe of the mean matter distribution around galaxies. The depth and sky coverage of the Canada-France-Hawaii Telescope Legacy Survey yield statistically significant galaxy halo mass measurements over a much wider range of stellar masses (108.75 to 1011.3 M⊙) and redshifts (0.2 < z < 0.8) than previous weak lensing studies. At redshift z ˜ 0.5, the stellar-to-halo mass ratio (SHMR) reaches a maximum of 4.0 ± 0.2 per cent as a function of halo mass at ˜1012.25 M⊙. We find, for the first time from weak lensing alone, evidence for significant evolution in the SHMR: the peak ratio falls as a function of cosmic time from 4.5 ± 0.3 per cent at z ˜ 0.7 to 3.4 ± 0.2 per cent at z ˜ 0.3, and shifts to lower stellar mass haloes. These evolutionary trends are dominated by red galaxies, and are consistent with a model in which the stellar mass above which star formation is quenched `downsizes' with cosmic time. In contrast, the SHMR of blue, star-forming galaxies is well fitted by a power law that does not evolve with time. This suggests that blue galaxies form stars at a rate that is balanced with their dark matter accretion in such a way that they evolve along the SHMR locus. The redshift dependence of the SHMR can be used to constrain the evolution of the galaxy population over cosmic time.

Radio weak lensing shear measurement in the visibility domain - II. Source extraction

NASA Astrophysics Data System (ADS)

Rivi, M.; Miller, L.

2018-05-01

This paper extends the method introduced in Rivi et al. (2016b) to measure galaxy ellipticities in the visibility domain for radio weak lensing surveys. In that paper, we focused on the development and testing of the method for the simple case of individual galaxies located at the phase centre, and proposed to extend it to the realistic case of many sources in the field of view by isolating visibilities of each source with a faceting technique. In this second paper, we present a detailed algorithm for source extraction in the visibility domain and show its effectiveness as a function of the source number density by running simulations of SKA1-MID observations in the band 950-1150 MHz and comparing original and measured values of galaxies' ellipticities. Shear measurements from a realistic population of 104 galaxies randomly located in a field of view of 1 \\deg ^2 (i.e. the source density expected for the current radio weak lensing survey proposal with SKA1) are also performed. At SNR ≥ 10, the multiplicative bias is only a factor 1.5 worse than what found when analysing individual sources, and is still comparable to the bias values reported for similar measurement methods at optical wavelengths. The additive bias is unchanged from the case of individual sources, but it is significantly larger than typically found in optical surveys. This bias depends on the shape of the uv coverage and we suggest that a uv-plane weighting scheme to produce a more isotropic shape could reduce and control additive bias.

Deep observation of A2163: studying a new bullet cluster

NASA Astrophysics Data System (ADS)

Bourdin, Herve

2011-10-01

Exhibiting a clear spatial separation between the gas and dark matter component of a fastly accreted subcluster, the `bullet cluster', 1E 0657-56, has provided us a unique laboratory to investigate the impact of violent cluster mergers on the Intra-Cluster Medium, galaxies and dark matter properties. In recent analyses of X-ray, optical and weak-lensing data, we show that the massive cluster A2163 also exhibits a crossing gas bullet separated from a galaxy and dark matter over-density, and suggest that both A2163 and 1E 0657-56 share a common merging scenario possibly just differing in the time elapsed after the closest cluster encounters. With this deeper XMM observation of A2163, we propose to refine our knowledge of the dynamics and geometry of the on-going subcluster accretion.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jee, M. James; Ng, Karen Y.; Hughes, John P.

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.more » 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 centers. The X-ray and mass peaks are spatially offset by ∼8'' (∼62 h{sub 70}{sup −1} kpc), which is significant at the ∼2σ confidence level. The mass peak, however, does not lead the gas peak in the direction expected if we are viewing the cluster soon after first core passage during a high speed merger. Under the assumption that the merger is happening in the plane of the sky, extrapolation of the two NFW halos to a radius r{sub 200a}=2.4 h{sub 70}{sup −1} Mpc yields a combined mass of M{sub 200a}=(3.13±0.56)×10{sup 15} h{sub 70}{sup −1} M{sub ⊙}. This extrapolated total mass is consistent with our two-component-based dynamical analysis and previous X-ray measurements, projecting ACT-CL J0102–4915 to be the most massive cluster at z > 0.6 known to date.« less

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

NASA Astrophysics Data System (ADS)

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

Magnification of photometric LRGs by foreground LRGs and clusters in the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Bauer, Anne H.; Gaztañaga, Enrique; Martí, Pol; Miquel, Ramon

2014-06-01

The magnification effect of gravitational lensing is a powerful probe of the distribution of matter in the universe, yet it is frequently overlooked due to the fact that its signal-to-noise ratio is smaller than that of lensing shear. Because its systematic errors are quite different from those of shear, magnification is nevertheless an important approach with which to study the distribution of large-scale structure. We present lensing mass profiles of spectroscopic luminous red galaxies (LRGs) and galaxy clusters determined through measurements of the weak lensing magnification of photometric LRGs in their background. We measure the change in detected galaxy counts as well as the increased average galaxy flux behind the lenses. In addition, we examine the average change in source colour due to extinction by dust in the lenses. By simultaneously fitting these three probes we constrain the mass profiles and dust-to-mass ratios of the lenses in six bins of lens richness. For each richness bin we fit a Navarro-Frenk-White halo mass, brightest cluster galaxy mass, second halo term, and dust-to-mass ratio. The resulting mass-richness relation is consistent with previous analyses of the catalogues, and limits on the dust-to-mass ratio in the lenses are in agreement with expectations. We explore the effects of including the (low signal-to-noise ratio) flux magnification and reddening measurements in the analysis compared to using only the counts magnification data; the additional probes significantly improve the agreement between our measured mass-richness relation and previous results.

Weighing the giants- V. Galaxy cluster scaling relations

NASA Astrophysics Data System (ADS)

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn; von der Linden, Anja; Applegate, Douglas E.; Kelly, Patrick L.; Burke, David L.; Donovan, David; Ebeling, Harald

2016-12-01

We present constraints on the scaling relations of galaxy cluster X-ray luminosity, temperature and gas mass (and derived quantities) with mass and redshift, employing masses from robust weak gravitational lensing measurements. These are the first such results obtained from an analysis that simultaneously accounts for selection effects and the underlying mass function, and directly incorporates lensing data to constrain total masses. Our constraints on the scaling relations and their intrinsic scatters are in good agreement with previous studies, and reinforce a picture in which departures from self-similar scaling laws are primarily limited to cluster cores. However, the data are beginning to reveal new features that have implications for cluster astrophysics and provide new tests for hydrodynamical simulations. We find a positive correlation in the intrinsic scatters of luminosity and temperature at fixed mass, which is related to the dynamical state of the clusters. While the evolution of the nominal scaling relations over the redshift range 0.0 < z < 0.5 is consistent with self-similarity, we find tentative evidence that the luminosity and temperature scatters, respectively, decrease and increase with redshift. Physically, this likely related to the development of cool cores and the rate of major mergers. We also examine the scaling relations of redMaPPer richness and Compton Y from Planck. While the richness-mass relation is in excellent agreement with recent work, the measured Y-mass relation departs strongly from that assumed in the Planck cluster cosmology analysis. The latter result is consistent with earlier comparisons of lensing and Planck scaling relation-derived masses.

Erratum: Weighing the giants – V. Galaxy cluster scaling relations

DOE PAGES

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn; ...

2017-02-21

We present constraints on the scaling relations of galaxy cluster X-ray luminosity, temperature and gas mass (and derived quantities) with mass and redshift, employing masses from robust weak gravitational lensing measurements. These are the first such results obtained from an analysis that simultaneously accounts for selection effects and the underlying mass function, and directly incorporates lensing data to constrain total masses. Our constraints on the scaling relations and their intrinsic scatters are in good agreement with previous studies, and reinforce a picture in which departures from self-similar scaling laws are primarily limited to cluster cores. However, the data are beginningmore » to reveal new features that have implications for cluster astrophysics and provide new tests for hydrodynamical simulations. We find a positive correlation in the intrinsic scatters of luminosity and temperature at fixed mass, which is related to the dynamical state of the clusters. While the evolution of the nominal scaling relations over the redshift range 0.0 < z < 0.5 is consistent with self similarity, we find tentative evidence that the luminosity and temperature scatters respectively decrease and increase with redshift. Physically, this likely related to the development of cool cores and the rate of major mergers. We also examine the scaling relations of redMaPPer richness and Compton Y from Planck. While the richness{mass relation is in excellent agreement with recent work, the measured Y {mass relation departs strongly from that assumed in the Planck cluster cosmology analysis. Furthermore, the latter result is consistent with earlier comparisons of lensing and Planck scaling-relation-derived masses.« less

Weighing the giants– V. Galaxy cluster scaling relations

DOE PAGES

Mantz, Adam B.; Allen, Steven W.; Morris, R. Glenn; ...

2016-09-07

Here, we present constraints on the scaling relations of galaxy cluster X-ray luminosity, temperature and gas mass (and derived quantities) with mass and redshift, employing masses from robust weak gravitational lensing measurements. These are the first such results obtained from an analysis that simultaneously accounts for selection effects and the underlying mass function, and directly incorporates lensing data to constrain total masses. Our constraints on the scaling relations and their intrinsic scatters are in good agreement with previous studies, and reinforce a picture in which departures from self-similar scaling laws are primarily limited to cluster cores. However, the data aremore » beginning to reveal new features that have implications for cluster astrophysics and provide new tests for hydrodynamical simulations. We find a positive correlation in the intrinsic scatters of luminosity and temperature at fixed mass, which is related to the dynamical state of the clusters. While the evolution of the nominal scaling relations over the redshift range 0.0 < z < 0.5 is consistent with self-similarity, we find tentative evidence that the luminosity and temperature scatters, respectively, decrease and increase with redshift. Physically, this likely related to the development of cool cores and the rate of major mergers. We also examine the scaling relations of redMaPPer richness and Compton Y from Planck. While the richness–mass relation is in excellent agreement with recent work, the measured Y–mass relation departs strongly from that assumed in the Planck cluster cosmology analysis. Furthermore, the latter result is consistent with earlier comparisons of lensing and Planck scaling relation-derived masses.« less

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okura, Yuki; Petri, Andrea; May, Morgan

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. Here in this paper we consider the effect of two widely discussed sensor imperfections: tree-rings, due to impuritymore » 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 the spurious shear when added to the lensing shear will bias the determination of cosmological parameters. We apply our methods to candidate sensors of the Large Synoptic Survey Telescope (LSST) as a timely and important example, analyzing flat field images recorded with LSST prototype CCDs in the laboratory. In conclusion, we find that tree-rings and periodic pixel-size variation present in the LSST CCDs will introduce negligible bias to cosmological parameters determined from the lensing power spectrum, specifically w,Ω m and σ 8.« less

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

DOE PAGES

Okura, Yuki; Petri, Andrea; May, Morgan; ...

2016-06-27

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. Here in this paper we consider the effect of two widely discussed sensor imperfections: tree-rings, due to impuritymore » 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 the spurious shear when added to the lensing shear will bias the determination of cosmological parameters. We apply our methods to candidate sensors of the Large Synoptic Survey Telescope (LSST) as a timely and important example, analyzing flat field images recorded with LSST prototype CCDs in the laboratory. In conclusion, we find that tree-rings and periodic pixel-size variation present in the LSST CCDs will introduce negligible bias to cosmological parameters determined from the lensing power spectrum, specifically w,Ω m and σ 8.« less

Halo ellipticity of GAMA galaxy groups from KiDS weak lensing

NASA Astrophysics Data System (ADS)

van Uitert, Edo; Hoekstra, Henk; 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

2017-06-01

We constrain the average halo ellipticity of ˜2600 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. Modelling the signal with an elliptical Navarro-Frenk-White profile on scales R < 250 kpc, and assuming that the BCG is perfectly aligned with the dark matter, we find an average halo ellipticity of ɛh = 0.38 ± 0.12, in fair agreement with results from cold dark matter only simulations. On larger scales, the lensing signal around the BCGs becomes isotropic and the distribution of group satellites provides a better proxy for the halo's orientation instead, leading to a 3σ-4σ detection of a non-zero halo ellipticity at 250 < R < 750 kpc. Our results suggest that the distribution of stars enclosed within a certain radius forms a good proxy for the orientation of the dark matter within that radius, which has also been observed in hydrodynamical simulations.

Detection of enhancement in number densities of background galaxies due to magnification by massive galaxy clusters

DOE PAGES

Chiu, I.; Dietrich, J. P.; Mohr, J.; ...

2016-02-18

We present a detection of the enhancement in the number densities of background galaxies induced from lensing magnification and use it to test the Sunyaev-Zel'dovich effect (SZE) inferred masses in a sample of 19 galaxy clusters with median redshift z≃0.42 selected from the South Pole Telescope SPT-SZ survey. Two background galaxy populations are selected for this study through their photometric colours; they have median redshifts z median≃0.9 (low-z background) and z median≃1.8 (high-z background). Stacking these populations, we detect the magnification bias effect at 3.3σ and 1.3σ for the low- and high-z backgrounds, respectively. We fit NFW models simultaneously tomore » all observed magnification bias profiles to estimate the multiplicative factor η that describes the ratio of the weak lensing mass to the mass inferred from the SZE observable-mass relation. We further quantify systematic uncertainties in η resulting from the photometric noise and bias, the cluster galaxy contamination and the estimations of the background properties. The resulting η for the combined background populations with 1σ uncertainties is 0.83 ± 0.24(stat) ± 0.074(sys), indicating good consistency between the lensing and the SZE-inferred masses. We also use our best-fit η to predict the weak lensing shear profiles and compare these predictions with observations, showing agreement between the magnification and shear mass constraints. Our work demonstrates the promise of using the magnification as a complementary method to estimate cluster masses in large surveys.« less

Constraints on a new post-general relativity cosmological parameter

NASA Astrophysics Data System (ADS)

Caldwell, Robert; Cooray, Asantha; Melchiorri, Alessandro

2007-07-01

A new cosmological variable is introduced to characterize the degree of departure from Einstein’s general relativity with a cosmological constant. The new parameter, ϖ, is the cosmological analog of γ, the parametrized post-Newtonian variable which measures the amount of spacetime curvature per unit mass. In the cosmological context, ϖ measures the difference between the Newtonian and longitudinal potentials in response to the same matter sources, as occurs in certain scalar-tensor theories of gravity. Equivalently, ϖ measures the scalar shear fluctuation in a dark-energy component. In the context of a vanilla, cosmological constant-dominated universe, a nonzero ϖ signals a departure from general relativity or a fluctuating cosmological constant. Using a phenomenological model for the time evolution ϖ=ϖ0ρDE/ρM which depends on the ratio of energy density in the cosmological constant to the matter density at each epoch, it is shown that the observed cosmic microwave background temperature anisotropies limit the overall normalization constant to be -0.4<ϖ0<0.1 at the 95% confidence level. Existing measurements of the cross-correlations of the cosmic microwave background with large-scale structure further limit ϖ0>-0.2 at the 95% CL. In the future, integrated Sachs-Wolfe and weak lensing measurements can more tightly constrain ϖ0, providing a valuable clue to the nature of dark energy and the validity of general relativity.

Mass Modeling of Frontier Fields Cluster MACS J1149.5+2223 Using Strong and Weak Lensing

NASA Astrophysics Data System (ADS)

Finney, Emily Quinn; Bradač, Maruša; Huang, Kuang-Han; Hoag, Austin; Morishita, Takahiro; Schrabback, Tim; Treu, Tommaso; Borello Schmidt, Kasper; Lemaux, Brian C.; Wang, Xin; Mason, Charlotte

2018-05-01

We present a gravitational-lensing model of MACS J1149.5+2223 using ultra-deep Hubble Frontier Fields imaging data and spectroscopic redshifts from HST grism and Very Large Telescope (VLT)/MUSE spectroscopic data. We create total mass maps using 38 multiple images (13 sources) and 608 weak-lensing galaxies, as well as 100 multiple images of 31 star-forming regions in the galaxy that hosts supernova Refsdal. We find good agreement with a range of recent models within the HST field of view. We present a map of the ratio of projected stellar mass to total mass (f ⋆) and find that the stellar mass fraction for this cluster peaks on the primary BCG. Averaging within a radius of 0.3 Mpc, we obtain a value of < {f}\\star > ={0.012}-0.003+0.004, consistent with other recent results for this ratio in cluster environments, though with a large global error (up to δf ⋆ = 0.005) primarily due to the choice of IMF. We compare values of f ⋆ and measures of star formation efficiency for this cluster to other Hubble Frontier Fields clusters studied in the literature, finding that MACS1149 has a higher stellar mass fraction than these other clusters but a star formation efficiency typical of massive clusters.

Integrated cosmological probes: concordance quantified

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nicola, Andrina; Amara, Adam; Refregier, Alexandre, E-mail: andrina.nicola@phys.ethz.ch, E-mail: adam.amara@phys.ethz.ch, E-mail: alexandre.refregier@phys.ethz.ch

2017-10-01

Assessing the consistency of parameter constraints derived from different cosmological probes is an important way to test the validity of the underlying cosmological model. In an earlier work [1], we computed constraints on cosmological parameters for ΛCDM from an integrated analysis of CMB temperature anisotropies and CMB lensing from Planck, galaxy clustering and weak lensing from SDSS, weak lensing from DES SV as well as Type Ia supernovae and Hubble parameter measurements. In this work, we extend this analysis and quantify the concordance between the derived constraints and those derived by the Planck Collaboration as well as WMAP9, SPT andmore » ACT. As a measure for consistency, we use the Surprise statistic [2], which is based on the relative entropy. In the framework of a flat ΛCDM cosmological model, we find all data sets to be consistent with one another at a level of less than 1σ. We highlight that the relative entropy is sensitive to inconsistencies in the models that are used in different parts of the analysis. In particular, inconsistent assumptions for the neutrino mass break its invariance on the parameter choice. When consistent model assumptions are used, the data sets considered in this work all agree with each other and ΛCDM, without evidence for tensions.« less

Prospects for Determining the Mass Distributions of Galaxy Clusters on Large Scales Using Weak Gravitational Lensing

NASA Astrophysics Data System (ADS)

Fong, M.; Bowyer, R.; Whitehead, A.; Lee, B.; King, L.; Applegate, D.; McCarthy, I.

2018-05-01

For more than two decades, the Navarro, Frenk, and White (NFW) model has stood the test of time; it has been used to describe the distribution of mass in galaxy clusters out to their outskirts. Stacked weak lensing measurements of clusters are now revealing the distribution of mass out to and beyond their virial radii, where the NFW model is no longer applicable. In this study we assess how well the parameterised Diemer & Kravstov (DK) density profile describes the characteristic mass distribution of galaxy clusters extracted from cosmological simulations. This is determined from stacked synthetic lensing measurements of the 50 most massive clusters extracted from the Cosmo-OWLS simulations, using the Dark Matter Only run and also the run that most closely matches observations. The characteristics of the data reflect the Weighing the Giants survey and data from the future Large Synoptic Survey Telescope (LSST). In comparison with the NFW model, the DK model favored by the stacked data, in particular for the future LSST data, where the number density of background galaxies is higher. The DK profile depends on the accretion history of clusters which is specified in the current study. Eventually however subsamples of galaxy clusters with qualities indicative of disparate accretion histories could be studied.

MAGNIFICENT MAGNIFICATION: EXPLOITING THE OTHER HALF OF THE LENSING SIGNAL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huff, Eric M.; Graves, Genevieve J.

2014-01-10

We describe a new method for measuring galaxy magnification due to weak gravitational lensing. Our method makes use of a tight scaling relation between galaxy properties that are modified by gravitational lensing, such as apparent size, and other properties that are not, such as surface brightness. In particular, we use a version of the well-known fundamental plane relation for early-type galaxies. This modified ''photometric fundamental plane'' uses only photometric galaxy properties, eliminating the need for spectroscopic data. We present the first detection of magnification using this method by applying it to photometric catalogs from the Sloan Digital Sky Survey. Thismore » analysis shows that the derived magnification signal is within a factor of three of that available from conventional methods using gravitational shear. We suppress the dominant sources of systematic error and discuss modest improvements that may further enhance the lensing signal-to-noise available with this method. Moreover, some of the dominant sources of systematic error are substantially different from those of shear-based techniques. With this new technique, magnification becomes a useful measurement tool for the coming era of large ground-based surveys intending to measure gravitational lensing.« less

Discovery and Characterization of a Caustic Crossing Microlensing Event in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.; King, L. J.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Pratt, M. R.; Quinn, P. J.; Rhie, S. H.; Rodgers, A. W.; Stetson, P. B.; Stubbs, C. W.; Sutherland, W.; Tomaney, A.; Vandehei, T.

1999-06-01

We present photometric observations and analysis of the second microlensing event detected toward the Small Magellanic Cloud (SMC), MACHO Alert 98-SMC-1. This event was detected early enough to allow intensive observation of the light curve. These observations revealed 98-SMC-1 to be the first caustic crossing binary microlensing event toward the Magellanic Clouds to be discovered in progress. Frequent coverage of the evolving light curve allowed an accurate prediction for the date of the source crossing out of the lens caustic structure. The caustic crossing temporal width, along with the angular size of the source star, measures the proper motion of the lens with respect to the source and thus allows an estimate of the location of the lens. Lenses located in the Galactic halo would have a velocity projected to the SMC of v̂~1500 kms-1, while an SMC lens would typically have v̂~60 kms-1. The event light curve allows us to obtain a unique fit to the parameters of the binary lens and to estimate the proper motion of the lensing system. We have performed a joint fit to the MACHO/GMAN data presented here, including recent EROS data of this event from Afonso and collaborators. These joint data are sufficient to constrain the time t* for the lens to move an angle equal to the source angular radius: t*=0.116+/-0.010 days. We estimate a radius for the lensed source of R*=1.1+/-0.1 Rsolar from its unblended color and magnitude. This yields a projected velocity of v̂=76+/-10 kms-1. Only 0.12% of halo lenses would be expected to have a v̂ value at least as small as this, while 38% of SMC lenses would be expected to have v̂ as large as this. This implies that the lensing system is more likely to reside in the SMC than in the Galactic halo. Similar observations of future Magellanic Cloud microlensing events will help to determine the contribution of MACHOS to the Galaxy's dark halo.

Lensing is low: cosmology, galaxy formation or new physics?

NASA Astrophysics Data System (ADS)

Leauthaud, Alexie; Saito, Shun; Hilbert, Stefan; Barreira, Alexandre; More, Surhud; White, Martin; Alam, Shadab; Behroozi, Peter; Bundy, Kevin; Coupon, Jean; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Mandelbaum, Rachel; Miller, Lance; Moraes, Bruno; Pereira, Maria E. S.; Rodríguez-Torres, Sergio A.; Schmidt, Fabian; Shan, Huan-Yuan; Viel, Matteo; Villaescusa-Navarro, Francisco

2017-05-01

We present high signal-to-noise galaxy-galaxy lensing measurements of the Baryon Oscillation Spectroscopic Survey constant mass (CMASS) sample using 250 deg2 of weak-lensing data from Canada-France-Hawaii Telescope Lensing Survey and Canada-France-Hawaii Telescope Stripe 82 Survey. We compare this signal with predictions from mock catalogues trained to match observables including the stellar mass function and the projected and two-dimensional clustering of CMASS. We show that the clustering of CMASS, together with standard models of the galaxy-halo connection, robustly predicts a lensing signal that is 20-40 per cent larger than observed. Detailed tests show that our results are robust to a variety of systematic effects. Lowering the value of S_8=σ _8 \\sqrt{Ω _m/0.3} compared to Planck Collaboration XIII reconciles the lensing with clustering. However, given the scale of our measurement (r < 10 h-1 Mpc), other effects may also be at play and need to be taken into consideration. We explore the impact of baryon physics, assembly bias, massive neutrinos and modifications to general relativity on ΔΣ and show that several of these effects may be non-negligible given the precision of our measurement. Disentangling cosmological effects from the details of the galaxy-halo connection, the effect of baryons, and massive neutrinos, is the next challenge facing joint lensing and clustering analyses. This is especially true in the context of large galaxy samples from Baryon Acoustic Oscillation surveys with precise measurements but complex selection functions.

Complete super-sample lensing covariance in the response approach

NASA Astrophysics Data System (ADS)

Barreira, Alexandre; Krause, Elisabeth; Schmidt, Fabian

2018-06-01

We derive the complete super-sample covariance (SSC) of the matter and weak lensing convergence power spectra using the power spectrum response formalism to accurately describe the coupling of super- to sub-survey modes. The SSC term is completely characterized by the survey window function, the nonlinear matter power spectrum and the full first-order nonlinear power spectrum response function, which describes the response to super-survey density and tidal field perturbations. Generalized separate universe simulations can efficiently measure these responses in the nonlinear regime of structure formation, which is necessary for lensing applications. We derive the lensing SSC formulae for two cases: one under the Limber and flat-sky approximations, and a more general one that goes beyond the Limber approximation in the super-survey mode and is valid for curved sky applications. Quantitatively, we find that for sky fractions fsky ≈ 0.3 and a single source redshift at zS=1, the use of the flat-sky and Limber approximation underestimates the total SSC contribution by ≈ 10%. The contribution from super-survey tidal fields to the lensing SSC, which has not been included in cosmological analyses so far, is shown to represent about 5% of the total lensing covariance on multipoles l1,l2 gtrsim 300. The SSC is the dominant off-diagonal contribution to the total lensing covariance, making it appropriate to include these tidal terms and beyond flat-sky/Limber corrections in cosmic shear analyses.

The Morphologies and Alignments of Gas, Mass, and the Central Galaxies of CLASH Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Donahue, Megan; Ettori, Stefano; Rasia, Elena; Sayers, Jack; Zitrin, Adi; Meneghetti, Massimo; Voit, G. Mark; Golwala, Sunil; Czakon, Nicole; Yepes, Gustavo; Baldi, Alessandro; Koekemoer, Anton; Postman, Marc

2016-03-01

Morphology is often used to infer the state of relaxation of galaxy clusters. The regularity, symmetry, and degree to which a cluster is centrally concentrated inform quantitative measures of cluster morphology. The Cluster Lensing and Supernova survey with Hubble Space Telescope (CLASH) used weak and strong lensing to measure the distribution of matter within a sample of 25 clusters, 20 of which were deemed to be “relaxed” based on their X-ray morphology and alignment of the X-ray emission with the Brightest Cluster Galaxy. Toward a quantitative characterization of this important sample of clusters, we present uniformly estimated X-ray morphological statistics for all 25 CLASH clusters. We compare X-ray morphologies of CLASH clusters with those identically measured for a large sample of simulated clusters from the MUSIC-2 simulations, selected by mass. We confirm a threshold in X-ray surface brightness concentration of C ≳ 0.4 for cool-core clusters, where C is the ratio of X-ray emission inside 100 h70-1 kpc compared to inside 500 {h}70-1 kpc. We report and compare morphologies of these clusters inferred from Sunyaev-Zeldovich Effect (SZE) maps of the hot gas and in from projected mass maps based on strong and weak lensing. We find a strong agreement in alignments of the orientation of major axes for the lensing, X-ray, and SZE maps of nearly all of the CLASH clusters at radii of 500 kpc (approximately 1/2 R500 for these clusters). We also find a striking alignment of clusters shapes at the 500 kpc scale, as measured with X-ray, SZE, and lensing, with that of the near-infrared stellar light at 10 kpc scales for the 20 “relaxed” clusters. This strong alignment indicates a powerful coupling between the cluster- and galaxy-scale galaxy formation processes.

Cross-Grade Comparison of Students' Conceptual Understanding with Lenses in Geometric Optics

ERIC Educational Resources Information Center

Tural, G.

2015-01-01

Students commonly find the field of physics difficult. Therefore, they generally have learning problems. One of the subjects with which they have difficulties is optics within a physics discipline. This study aims to determine students' conceptual understanding levels at different education levels relating to lenses in geometric optics. A…

Synthetic aperture radar correlator phase histories

NASA Technical Reports Server (NTRS)

1977-01-01

This report supplements the design of the following subsystems: (1) zoom azimuth telescope, zooming range from 3X to 6X. (2) range curvature correcting lenses. (3) Sphero-cylindrical shift lens. (4) Auxiliary lenses (tilted cylinder and matching lens).

Anisotropic magnification distortion of the 3D galaxy correlation. II. Fourier and redshift space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hui Lam; Department of Physics, Columbia University, New York, New York 10027; Institute of Theoretical Physics, Chinese University of Hong Kong

2008-03-15

In paper I of this series we discuss how magnification bias distorts the 3D correlation function by enhancing the observed correlation in the line-of-sight (LOS) orientation, especially on large scales. This lensing anisotropy is distinctive, making it possible to separately measure the galaxy-galaxy, galaxy-magnification and magnification-magnification correlations. Here we extend the discussion to the power spectrum and also to redshift space. In real space, pairs oriented close to the LOS direction are not protected against nonlinearity even if the pair separation is large; this is because nonlinear fluctuations can enter through gravitational lensing at a small transverse separation (or i.e.more » impact parameter). The situation in Fourier space is different: by focusing on a small wave number k, as is usually done, linearity is guaranteed because both the LOS and transverse wave numbers must be small. This is why magnification distortion of the galaxy correlation appears less severe in Fourier space. Nonetheless, the effect is non-negligible, especially for the transverse Fourier modes, and should be taken into account in interpreting precision measurements of the galaxy power spectrum, for instance those that focus on the baryon oscillations. The lensing induced anisotropy of the power spectrum has a shape that is distinct from the more well-known redshift space anisotropies due to peculiar motions and the Alcock-Paczynski effect. The lensing anisotropy is highly localized in Fourier space while redshift space distortions are more spread out. This means that one could separate the magnification bias component in real observations, implying that potentially it is possible to perform a gravitational lensing measurement without measuring galaxy shapes.« less

21-cm lensing and the cold spot in the cosmic microwave background.

PubMed

Kovetz, Ely D; Kamionkowski, Marc

2013-04-26

An extremely large void and a cosmic texture are two possible explanations for the cold spot seen in the cosmic microwave background. We investigate how well these two hypotheses can be tested with weak lensing of 21-cm fluctuations from the epoch of reionization measured with the Square Kilometer Array. While the void explanation for the cold spot can be tested with Square Kilometer Array, given enough observation time, the texture scenario requires significantly prolonged observations, at the highest frequencies that correspond to the epoch of reionization, over the field of view containing the cold spot.

Analytical transmission cross-coefficients for pink beam X-ray microscopy based on compound refractive lenses.

PubMed

Falch, Ken Vidar; Detlefs, Carsten; Snigirev, Anatoly; Mathiesen, Ragnvald H

2018-01-01

Analytical expressions for the transmission cross-coefficients for x-ray microscopes based on compound refractive lenses are derived based on Gaussian approximations of the source shape and energy spectrum. The effects of partial coherence, defocus, beam convergence, as well as lateral and longitudinal chromatic aberrations are accounted for and discussed. Taking the incoherent limit of the transmission cross-coefficients, a compact analytical expression for the modulation transfer function of the system is obtained, and the resulting point, line and edge spread functions are presented. Finally, analytical expressions for optimal numerical aperture, coherence ratio, and bandwidth are given. Copyright © 2017 Elsevier B.V. All rights reserved.

Looking for dark matter trails in colliding galaxy clusters

NASA Astrophysics Data System (ADS)

Harvey, David; Robertson, Andrew; Massey, Richard; Kneib, Jean-Paul

2017-02-01

If dark matter interacts, even weakly, via non-gravitational forces, simulations predict that it will be preferentially scattered towards the trailing edge of the halo during collisions between galaxy clusters. This will temporarily create a non-symmetric mass profile, with a trailing overdensity along the direction of motion. To test this hypothesis, we fit (and subtract) symmetric haloes to the weak gravitational data of 72 merging galaxy clusters observed with the Hubble Space Telescope. We convert the shear directly into excess κ and project in to a one-dimensional profile. We generate numerical simulations and find that the one-dimensional profile is well described with simple Gaussian approximations. We detect the weak lensing signal of trailing gas at a 4σ confidence, finding a mean gas fraction of Mgas/Mdm = 0.13 ± 0.035. We find no evidence for scattered dark matter particles with an estimated scattering fraction of f = 0.03 ± 0.05. Finally, we find that if we can reduce the statistical error on the positional estimate of a single dark matter halo to <2.5 arcsec, then we will be able to detect a scattering fraction of 10 per cent at the 3σ level with current surveys. This potentially interesting new method can provide an important independent test for other complimentary studies of the self-interaction cross-section of dark matter.

The effect of clulstering of galaxies on the statistics of gravitational lenses

NASA Technical Reports Server (NTRS)

Anderson, N.; Alcock, C.

1986-01-01

It is examined whether clustering of galaxies can significantly alter the statistical properties of gravitational lenses? Only models of clustering that resemble the observed distribution of galaxies in the properties of the two-point correlation function are considered. Monte-Carlo simulations of the imaging process are described. It is found that the effect of clustering is too small to be significant, unless the mass of the deflectors is so large that gravitational lenses become common occurrences. A special model is described which was concocted to optimize the effect of clustering on gravitational lensing but still resemble the observed distribution of galaxies; even this simulation did not satisfactorily produce large numbers of wide-angle lenses.

Simulations for 21 cm radiation lensing at EoR redshifts

NASA Astrophysics Data System (ADS)

Romeo, Alessandro; Metcalf, Robert Benton; Pourtsidou, Alkistis

2018-02-01

We introduce simulations aimed at assessing how well weak gravitational lensing of 21cm radiation from the Epoch of Reionization (z ˜ 8) can be measured by a Square Kilometre Array (SKA)-like radio telescope. A simulation pipeline has been implemented to study the performance of lensing reconstruction techniques. We show how well the lensing signal can be reconstructed using the 3D quadratic lensing estimator in Fourier space assuming different survey strategies. The numerical code introduced in this work is capable of dealing with issues that cannot be treated analytically such as the discreteness of visibility measurements and the inclusion of a realistic model for the antennas distribution. This paves the way for future numerical studies implementing more realistic re-ionization models, foreground subtraction schemes, and testing the performance of lensing estimators that take into account the non-Gaussian distribution of HI after re-ionization. If multiple frequency channels covering z ˜ 7-11.6 are combined, Phase 1 of SKA-Low should be able to obtain good quality images of the lensing potential with a total resolution of ˜1.6 arcmin. The SKA-Low Phase 2 should be capable of providing images with high fidelity even using data from z ˜ 7.7 to 8.3. We perform tests aimed at evaluating the numerical implementation of the mapping reconstruction. We also discuss the possibility of measuring an accurate lensing power spectrum. Combining data from z ˜ 7 to 11.6 using the SKA2-Low telescope model, we find constraints comparable to sample variance in the range L < 1000, even for survey areas as small as 25 deg2.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Wentao; Yang, Xiaohu; Zhang, Jun

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% atmore » 2 σ levels. The overall GG lensing signals we measured are in good agreement with Mandelbaum et al. The reduced χ {sup 2} between the two measurements in different luminosity bins are from 0.43 to 0.83. Larger reduced χ {sup 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.« less

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

DOE PAGES

Clerkin, L.; Kirk, D.; Manera, M.; ...

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 confirmmore » 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.« less

Weak Lensing Study in VOICE Survey II: Shear Bias Calibrations

NASA Astrophysics Data System (ADS)

Liu, Dezi; Fu, Liping; Liu, Xiangkun; Radovich, Mario; Wang, Chao; Pan, Chuzhong; Fan, Zuhui; Covone, Giovanni; Vaccari, Mattia; Botticella, Maria Teresa; Capaccioli, Massimo; De Cicco, Demetra; Grado, Aniello; Miller, Lance; Napolitano, Nicola; Paolillo, Maurizio; Pignata, Giuliano

2018-05-01

The VST Optical Imaging of the CDFS and ES1 Fields (VOICE) Survey is proposed to obtain deep optical ugri imaging of the CDFS and ES1 fields using the VLT Survey Telescope (VST). At present, the observations for the CDFS field have been completed, and comprise in total about 4.9 deg2 down to rAB ˜ 26 mag. In the companion paper by Fu et al. (2018), we present the weak lensing shear measurements for r-band images with seeing ≤ 0.9 arcsec. In this paper, we perform image simulations to calibrate possible biases of the measured shear signals. Statistically, the properties of the simulated point spread function (PSF) and galaxies show good agreements with those of observations. The multiplicative bias is calibrated to reach an accuracy of ˜3.0%. We study the bias sensitivities to the undetected faint galaxies and to the neighboring galaxies. We find that undetected galaxies contribute to the multiplicative bias at the level of ˜0.3%. Further analysis shows that galaxies with lower signal-to-noise ratio (SNR) are impacted more significantly because the undetected galaxies skew the background noise distribution. For the neighboring galaxies, we find that although most have been rejected in the shape measurement procedure, about one third of them still remain in the final shear sample. They show a larger ellipticity dispersion and contribute to ˜0.2% of the multiplicative bias. Such a bias can be removed by further eliminating these neighboring galaxies. But the effective number density of the galaxies can be reduced considerably. Therefore efficient methods should be developed for future weak lensing deep surveys.

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

NASA Astrophysics Data System (ADS)

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.

MC 2: A Deeper Look at ZwCl 2341.1+0000 with Bayesian Galaxy Clustering and Weak Lensing Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, B.; Wittman, D. M.; Golovich, N.

ZwCl 2341.1+0000, a merging galaxy cluster with disturbed X-ray morphology and widely separated (~3 Mpc) double radio relics, was thought to be an extremely massive (10 - 30 X 10 14M⊙) and complex system with little known about its merger history. We present JVLA 2-4 GHz observations of the cluster, along with new spectroscopy from our Keck/DEIMOS survey, and apply Gaussian Mixture Modeling to the three-dimensional distribution of 227 con rmed cluster galaxies. After adopting the Bayesian Information Criterion to avoid over tting, which we discover can bias total dynamical mass estimates high, we nd that a three-substructure model withmore » a total dynamical mass estimate of 9:39 ± 0:81 X 10 14M⊙ is favored. We also present deep Subaru imaging and perform the rst weak lensing analysis on this system, obtaining a weak lensing mass estimate of 5:57±2:47X10 14M⊙. This is a more robust estimate because it does not depend on the dynamical state of the system, which is disturbed due to the merger. Our results indicate that ZwCl 2341.1+0000 is a multiple merger system comprised of at least three substructures, with the main merger that produced the radio relics occurring near to the plane of the sky, and a younger merger in the North occurring closer to the line of sight. Dynamical modeling of the main merger reproduces observed quantities (relic positions and polarizations, subcluster separation and radial velocity difference), if the merger axis angle of ~10 +34 -6 degrees and the collision speed at pericenter is ~1900 +300 -200 km/s.« less

Information gains from cosmological probes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grandis, S.; Seehars, S.; Refregier, A.

In light of the growing number of cosmological observations, it is important to develop versatile tools to quantify the constraining power and consistency of cosmological probes. Originally motivated from information theory, we use the relative entropy to compute the information gained by Bayesian updates in units of bits. This measure quantifies both the improvement in precision and the 'surprise', i.e. the tension arising from shifts in central values. Our starting point is a WMAP9 prior which we update with observations of the distance ladder, supernovae (SNe), baryon acoustic oscillations (BAO), and weak lensing as well as the 2015 Planck release.more » We consider the parameters of the flat ΛCDM concordance model and some of its extensions which include curvature and Dark Energy equation of state parameter w . We find that, relative to WMAP9 and within these model spaces, the probes that have provided the greatest gains are Planck (10 bits), followed by BAO surveys (5.1 bits) and SNe experiments (3.1 bits). The other cosmological probes, including weak lensing (1.7 bits) and (H{sub 0}) measures (1.7 bits), have contributed information but at a lower level. Furthermore, we do not find any significant surprise when updating the constraints of WMAP9 with any of the other experiments, meaning that they are consistent with WMAP9. However, when we choose Planck15 as the prior, we find that, accounting for the full multi-dimensionality of the parameter space, the weak lensing measurements of CFHTLenS produce a large surprise of 4.4 bits which is statistically significant at the 8 σ level. We discuss how the relative entropy provides a versatile and robust framework to compare cosmological probes in the context of current and future surveys.« less

MC 2: A Deeper Look at ZwCl 2341.1+0000 with Bayesian Galaxy Clustering and Weak Lensing Analyses

DOE PAGES

Benson, B.; Wittman, D. M.; Golovich, N.; ...

2017-05-16

ZwCl 2341.1+0000, a merging galaxy cluster with disturbed X-ray morphology and widely separated (~3 Mpc) double radio relics, was thought to be an extremely massive (10 - 30 X 10 14M⊙) and complex system with little known about its merger history. We present JVLA 2-4 GHz observations of the cluster, along with new spectroscopy from our Keck/DEIMOS survey, and apply Gaussian Mixture Modeling to the three-dimensional distribution of 227 con rmed cluster galaxies. After adopting the Bayesian Information Criterion to avoid over tting, which we discover can bias total dynamical mass estimates high, we nd that a three-substructure model withmore » a total dynamical mass estimate of 9:39 ± 0:81 X 10 14M⊙ is favored. We also present deep Subaru imaging and perform the rst weak lensing analysis on this system, obtaining a weak lensing mass estimate of 5:57±2:47X10 14M⊙. This is a more robust estimate because it does not depend on the dynamical state of the system, which is disturbed due to the merger. Our results indicate that ZwCl 2341.1+0000 is a multiple merger system comprised of at least three substructures, with the main merger that produced the radio relics occurring near to the plane of the sky, and a younger merger in the North occurring closer to the line of sight. Dynamical modeling of the main merger reproduces observed quantities (relic positions and polarizations, subcluster separation and radial velocity difference), if the merger axis angle of ~10 +34 -6 degrees and the collision speed at pericenter is ~1900 +300 -200 km/s.« less

Redshift distributions of galaxies in the Dark Energy Survey Science Verification shear catalogue and implications for weak lensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonnett, C.; Troxel, M. A.; Hartley, W.

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 SVmore » 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 δ z ≲ 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 σ 8 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, Σ crit, 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.« less

The projected gravitational potential of the galaxy cluster MACS J1206 derived from galaxy kinematics

NASA Astrophysics Data System (ADS)

Stock, Dennis; Meyer, Sven; Sarli, Eleonora; Bartelmann, Matthias; Balestra, Italo; Grillo, Claudio; Koekemoer, Anton; Mercurio, Amata; Nonino, Mario; Rosati, Piero

2015-12-01

We reconstruct the radial profile of the projected gravitational potential of the galaxy cluster MACS J1206 from 592 spectroscopic measurements of velocities of cluster members. To accomplish this, we use a method we have developed recently based on the Richardson-Lucy deprojection algorithm and an inversion of the spherically-symmetric Jeans equation. We find that, within the uncertainties, our reconstruction agrees very well with a potential reconstruction from weak and strong gravitational lensing as well as with a potential obtained from X-ray measurements. In addition, our reconstruction is in good agreement with several common analytic profiles of the lensing potential. Varying the anisotropy parameter in the Jeans equation, we find that isotropy parameters, which are either small, β ≲ 0.2, or decrease with radius, yield potential profiles that strongly disagree with that obtained from gravitational lensing. We achieve the best agreement between our potential profile and the profile from gravitational lensing if the anisotropy parameter rises steeply to β ≈ 0.6 within ≈ 0.5 Mpc and stays constant further out.

Strong field gravitational lensing by a charged Galileon black hole

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Shan-Shan; Xie, Yi, E-mail: clefairy035@163.com, E-mail: yixie@nju.edu.cn

Strong field gravitational lensings are dramatically disparate from those in the weak field by representing relativistic images due to light winds one to infinity loops around a lens before escaping. We study such a lensing caused by a charged Galileon black hole, which is expected to have possibility to evade no-hair theorem. We calculate the angular separations and time delays between different relativistic images of the charged Galileon black hole. All these observables can potentially be used to discriminate a charged Galileon black hole from others. We estimate the magnitudes of these observables for the closest supermassive black hole Sgrmore » A*. The strong field lensing observables of the charged Galileon black hole can be close to those of a tidal Reissner-Nordström black hole or those of a Reissner-Nordström black hole. It will be helpful to distinguish these black holes if we can separate the outermost relativistic images and determine their angular separation, brightness difference and time delay, although it requires techniques beyond the current limit.« less