On scale-dependent cosmic shear systematic effects

Kitching, Thomas D.; Taylor, Andy; Cropper, Mark; Hoekstra, Henk; Hood, Rosie; Massey, Richard; Niemi, S. M.

doi:10.1093/mnras/stv2523

Cited by 15 publications

(25 citation statements)

References 28 publications

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“…We note that these studies considered requirements under the assumption that systematic effects do not depend on scale. This can result in conservative limits, as was discussed in Kitching et al (2016). Nonetheless, in order to minimize the multiplicative bias caused by shortcomings of the image simulations, we consider an ambitious value of |µsim| = 10 −4 .…”

Section: The Need For a Calibrated Algorithmmentioning

confidence: 99%

See 1 more Smart Citation

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

Hoekstra¹,

Viola²,

Herbonnet³

2017

Monthly Notices of the Royal Astronomical Society

107

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

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Section: The Need For a Calibrated Algorithmmentioning

confidence: 99%

“…Small scale effects that do not correlate between detectors or exposures merely increase the measurement noise slightly, which is negligible compared to the intrinsic shape noise on such small scales (see e.g. Kitching et al 2016).…”

Section: Sensitivity To Noisementioning

confidence: 99%

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

Hoekstra¹,

Viola²,

Herbonnet³

2017

Monthly Notices of the Royal Astronomical Society

107

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“…How these shape measurement biases propagate in cosmic shear studies is investigated in several works (see e.g. Massey et al 2013;Cropper et al 2013;Kitching et al 2016, and references therein).…”

Section: Introductionmentioning

confidence: 99%

Systematic tests for position-dependent additive shear bias

Uitert

Schneider²

2016

A&A

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We present new tests to identify stationary position-dependent additive shear biases in weak gravitational lensing data sets. These tests are important diagnostics for currently ongoing and planned cosmic shear surveys, as such biases induce coherent shear patterns that can mimic and potentially bias the cosmic shear signal. The central idea of these tests is to determine the average ellipticity of all galaxies with shape measurements in a grid in the pixel plane. The distribution of the absolute values of these averaged ellipticities can be compared to randomised catalogues; a difference points to systematics in the data. In addition, we introduce a method to quantify the spatial correlation of the additive bias, which suppresses the contribution from cosmic shear and therefore eases the identification of a position-dependent additive shear bias in the data. We apply these tests to the publicly available shear catalogues from the CanadaFrance-Hawaii Telescope Lensing Survey (CFHTLenS) and the Kilo Degree Survey (KiDS) and find evidence for a small but non-negligible residual additive bias at small scales. As this residual bias is smaller than the error on the shear correlation signal at those scales, it is highly unlikely that it causes a significant bias in the published cosmic shear results of CFHTLenS. In CFHTLenS, the amplitude of this systematic signal is consistent with zero in fields where the number of stars used to model the point spread function (PSF) is higher than average, suggesting that the position-dependent additive shear bias originates from undersampled PSF variations across the image.

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“…This represents a worst case because the residual power spectra are assumed to be proportional to the cosmological signal (apart from the additive offset). In Kitching et al (2016), simple models for systematic effects are used to create simplified but realistic δC( ) values. In the constant multiplicative and additive formulation is generalised to include the propagation of real-space multiplicative effects into power spectra as a convolution.…”

Section: Comparison To Previous Workmentioning

confidence: 99%

“…This is particularly true for CTI, which is exacerbated by radiation damage, and thus increases with time (Massey et al 2014;Israel et al 2015). An initial study of the implications of scale-dependent scenarios was presented in Kitching et al (2016), who find that survey strategy can play a critical role in the case of time-dependent effects. Their results suggest the expected biases in cosmological parameters may be reduced if the correct scale dependences are considered.…”

Section: Introductionmentioning

confidence: 99%

Euclid preparation

Paykari¹,

Kitching

Hoekstra

et al. 2020

A&A

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Aims. Our aim is to quantify the impact of systematic effects on the inference of cosmological parameters from cosmic shear. Methods. We present an "end-to-end" approach that introduces sources of bias in a modelled weak lensing survey on a galaxy-by-galaxy level. We propagated residual biases through a pipeline from galaxy properties at one end to cosmic shear power spectra and cosmological parameter estimates at the other end. We did this to quantify how imperfect knowledge of the pipeline changes the maximum likelihood values of dark energy parameters. Results. We quantify the impact of an imperfect correction for charge transfer inefficiency and modelling uncertainties of the point spread function for Euclid, and find that the biases introduced can be corrected to acceptable levels.

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On scale-dependent cosmic shear systematic effects

Cited by 15 publications

References 28 publications

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

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

Systematic tests for position-dependent additive shear bias

Euclid preparation

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