Cosmic shear analysis with CFHTLS deep data

Semboloni, Elisabetta; Mellier, Y.; Waerbeke, Ludovic Van; Hoekstra, Henk; Tereno, I.; Benabed, K.; Gwyn, Stephen; Fu, Liping; Hudson, Michael J.; Maoli, R.; Parker, Laura C.

doi:10.1051/0004-6361:20054479

Cited by 167 publications

(238 citation statements)

References 48 publications

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“…Prominent examples include the supernova and weak lensing programs of the CFHT Legacy Survey (CFHTLS; Conley et al 2011;Semboloni et al 2006a;Heymans et al 2012b), the ESSENCE supernova survey (Wood-Vasey et al, 2007), BAO measurements from the Sloan Digital Sky Survey (SDSS; Eisenstein et al 2005;Percival et al 2010;Padmanabhan et al 2012), and the SDSS-II supernova survey . These have been complemented by extensive multi-wavelength studies of local and high-redshift supernovae such as the Carnegie Supernova Project (Hamuy et al, 2006;Freedman et al, 2009), by systematic searches for z > 1 supernovae with Hubble Space Telescope Suzuki et al, 2012), by dark energy constraints from the evolution of X-ray or optically selected clusters (Henry et al, 2009;Vikhlinin et al, 2009;Rozo et al, 2010), by improved measurements of the Hubble constant (Riess et al, , 2011Freedman et al, 2012), and by CMB data from the WMAP satellite (Bennett et al, 2003;Larson et al, 2011) and from ground-based experiments that probe smaller angular scales.…”

Section: Looking Forwardmentioning

confidence: 99%

“…Several wide-field optical surveys were ongoing at the time, including the deep 170 deg 2 CFHT Legacy Survey (for which cosmic shear was a key science driver) and the very deep multiwavelength COSMOS survey with high-resolution optical imaging from HST/ACS (Massey et al, 2007b;Schrabback et al, 2010). The CFHTLS presented some early results Semboloni et al, 2006a;Fu et al, 2008), but following this there was a rather bleak period of time.…”

Section: Cosmic Shearmentioning

confidence: 99%

“…The prototype moments-based method was that of Kaiser, Squires, and Broadhurst (KSB;Kaiser et al 1995; improved by Luppino and Kaiser 1997;Hoekstra et al 1998). Many improvements of these methods have been made -e.g., in computing better conversion factors from shear to quadrupole moments 50 (Semboloni et al, 2006b). Elliptical-weighted moments and the concept of shear-covariance were introduced by Bernstein and Jarvis (2002) and have been used extensively in SDSS (Hirata and Seljak, 2003b).…”

Section: Measuring Shearsmentioning

confidence: 99%

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Observational probes of cosmic acceleration

et al. 2013

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The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of "dark energy" with exotic physical properties, or that Einstein's theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit "Stage IV" dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant H 0 . We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever larger scales.

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Section: Looking Forwardmentioning

confidence: 99%

Section: Cosmic Shearmentioning

confidence: 99%

Section: Measuring Shearsmentioning

confidence: 99%

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Observational probes of cosmic acceleration

et al. 2013

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“…Larger surveys have significantly reduced statistical uncertainties (e.g. Hoekstra et al 2002;Brown et al 2003;Jarvis et al 2003;Van Waerbeke et al 2005;Hoekstra et al 2006;Semboloni et al 2006;Hetterscheidt et al 2007;Fu et al 2008), while tests on simulated data have led to better understanding of PSF systematics (Heymans et al 2006a;Massey et al 2007a;Bridle et al 2010, and references therein). Finally, because it is a geometric effect, gravitational lensing depends on the source redshift distribution, where most earlier measurements have had to rely on external redshift calibrations from the small Hubble Deep Fields.…”

Section: Introductionmentioning

confidence: 99%

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

Schrabback

Hartlap

Joachimi

et al. 2010

A&A

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346

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We present a comprehensive analysis of weak gravitational lensing by large-scale structure in the Hubble Space Telescope Cosmic Evolution Survey (COSMOS), in which we combine space-based galaxy shape measurements with ground-based photometric redshifts to study the redshift dependence of the lensing signal and constrain cosmological parameters. After applying our weak lensingoptimized data reduction, principal-component interpolation for the spatially, and temporally varying ACS point-spread function, and improved modelling of charge-transfer inefficiency, we measured a lensing signal that is consistent with pure gravitational modes and no significant shape systematics. We carefully estimated the statistical uncertainty from simulated COSMOS-like fields obtained from ray-tracing through the Millennium Simulation, including the full non-Gaussian sampling variance. We tested our lensing pipeline on simulated space-based data, recalibrated non-linear power spectrum corrections using the ray-tracing analysis, employed photometric redshift information to reduce potential contamination by intrinsic galaxy alignments, and marginalized over systematic uncertainties. We find that the weak lensing signal scales with redshift as expected from general relativity for a concordance ΛCDM cosmology, including the full cross-correlations between different redshift bins. Assuming a flat ΛCDM cosmology, we measure σ 8 (Ω m /0.3) 0.51 = 0.75 ± 0.08 from lensing, in perfect agreement with WMAP-5, yielding joint constraints Ω m = 0.266 +0.025 −0.023 , σ 8 = 0.802 +0.028 −0.029 (all 68.3% conf.). Dropping the assumption of flatness and using priors from the HST Key Project and Big-Bang nucleosynthesis only, we find a negative deceleration parameter q 0 at 94.3% confidence from the tomographic lensing analysis, providing independent evidence of the accelerated expansion of the Universe. For a flat wCDM cosmology and prior w ∈ [−2, 0], we obtain w < −0.41 (90% conf.). Our dark energy constraints are still relatively weak solely due to the limited area of COSMOS. However, they provide an important demonstration of the usefulness of tomographic weak lensing measurements from space.

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“…Jarvis et al 2006;Hoekstra et al 2006;Semboloni et al 2006;Hetterscheidt et al 2007;Benjamin et al 2007;Fu et al 2008), planned surveys with instruments like Euclid, JDEM, LSST, or SKA will provide weak lensing data with unprecedented precision. The anticipated high quality of data enforces a careful and complete treatment of systematic errors, which has become one focus of current work in the field -consider for instance Heymans et al (2006), Massey et al (2007), and Bridle et al (2009) regarding galaxy shape measurements.…”

Section: Introductionmentioning

confidence: 99%

The removal of shear-ellipticity correlations from the cosmic shear signal

Joachimi¹,

Schneider²

2009

A&A

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Aims. Cosmic shear, the gravitational lensing on cosmological scales, is regarded as one of the most powerful probes for revealing the properties of dark matter and dark energy. To fully utilize its potential, one has to be able to control systematic effects down to below the level of the statistical parameter errors. Particularly worrisome in this respect is the intrinsic alignment of galaxies, causing considerable parameter biases via correlations between the intrinsic ellipticities of galaxies and the gravitational shear, which mimic lensing. Since our understanding of the underlying processes of intrinsic alignment is still poor, purely geometrical methods are required to control this systematic. In an earlier work we proposed a nulling technique that downweights this systematic, only making use of its well-known redshift dependence. We assess the practicability of nulling, given realistic conditions on photometric redshift information. Methods. For several simplified intrinsic alignment models and a wide range of photometric redshift characteristics, we calculate an average bias before and after nulling. Modifications of the technique are introduced to optimize the bias removal and minimize the information loss by nulling. We demonstrate that one of the presented versions of nulling is close to optimal in terms of bias removal, given the high quality of photometric redshifts. Although the nulling weights depend on cosmology, being composed of comoving distances, we show that the technique is robust against an incorrect choice of cosmological parameters when calculating the weights. Moreover, general aspects such as the behavior of the Fisher matrix under parameter-dependent transformations and the range of validity of the bias formalism are discussed in an appendix. Results. Given excellent photometric redshift information, i.e. at least 10 bins with a dispersion σ ph 0.03, a negligible fraction of catastrophic outliers, and precise knowledge about the bin-wise redshift distributions as characterized by a scatter of 0.001 or less on the median redshifts, one version of nulling is capable of reducing the shear-intrinsic ellipticity contamination by at least a factor of 100. Alternatively, we describe a robust nulling variant which suppresses the systematic signal by about 10 for a very broad range of photometric redshift configurations, provided basic information about σ ph in each of 10 photometric redshift bins is available. Irrespective of the photometric redshift quality, a loss of statistical power is inherent to nulling, which amounts to a decrease of the order 50% in terms of our figure of merit under conservative assumptions.

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Cosmic shear analysis with CFHTLS deep data

Cited by 167 publications

References 48 publications

Observational probes of cosmic acceleration

Observational probes of cosmic acceleration

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

The removal of shear-ellipticity correlations from the cosmic shear signal

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