The Shear Testing Programme – I. Weak lensing analysis of simulated ground-based observations

By Catherine Heymans, L. Waerbeke, D. Bacon, J. Bergé, G. Bernstein, E. Bertin, Sarah Bridle, Michael L. Brown, D. Clowe, H. Dahle and 15 more. 2005

376 citations recorded by the source corpus.

The Shear Testing Programme (STEP) is a collaborative project to improve the accuracy and reliability of all weak lensing measurements in preparation for the next generation of wide-field surveys. In this first STEP paper, we present the results of a blind analysis of simulated ground-based observations of relatively simple galaxy morphologies. The most successful methods are shown to achieve percent level accuracy. From the cosmic shear pipelines that have been used to constrain cosmology, we find weak lensing shear measured to an accuracy that is within the statistical errors of current weak lensing analyses, with shear measurements accurate to better than 7 per cent. The dominant source of measurement error is shown to arise from calibration uncertainties where the measured shear is over or underestimated by a constant multiplicative factor. This is of concern as calibration errors cannot be detected through standard diagnostic tests. The measured calibration errors appear to result from stellar contamination, false object detection, the shear measurement method itself, selection bias and/or the use of biased weights. Additive systematics (false detections of shear) resulting from residual point-spread function anisotropy are, in most cases, reduced to below an equivalent shear of 0.001, an order of magnitude below cosmic shear distortions on the scales probed by current surveys. Our results provide a snapshot view of the accuracy of current ground-based weak lensing methods and a benchmark upon which we can improve. To this end we provide descriptions of each method tested and include details of the eight different implementations of the commonly used Kaiser, Squires & Broadhurst method (KSB+) to aid the improvement of future KSB+ analyses.

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Citations in the corpus

Results of the GREAT08 Challenge?: an image analysis competition for cosmological lensing: Results o (2009, methodology): “(iii) STEP1 required participants to determine which objects were stars and therefore could be used for a PSF determination.”
Weighing the Giants – III. Methods and measurements of accurate galaxy cluster weak-lensing masses (2012, methodology): “The STEP simulation studies (Heymans et al. 2006; Massey et al. 2007) parameterize this bias as a function of shear using a multiplicative biasm and an additive biasc (Eq.”
Cosmology from the Chinese Space Station Optical Survey (CSS-OS) (2019, unknown): “…on the estimates of STEP (the Shear Testing Programme) and GREAT10 (the Gravitational Lensing Accuracy Testing 2010), the N̄add can be controlled within 10 −10 with S/N ∼ 10 in the Stage IV weak lensing surveys (Heymans et al. 2006; Massey et al. 2007; Kitching et al. 2012; Massey et al. 2013).”
The DES Science Verification weak lensing shear catalogues (2015, methodology): “…have been carried out to assess progress in a uniform way across the international shear measurement community: the Shear TEsting Programme (STEP Heymans et al. 2006; Massey et al. 2007) and the GRavitational lEnsing Accuracy Testing (GREAT) Challenges (Bridle et al. 2009, 2010; Kitching et al.…”
CLASH: WEAK-LENSING SHEAR-AND-MAGNIFICATION ANALYSIS OF 20 GALAXY CLUSTERS (2014, background): “…we found in Umetsu et al. (2010) that the lensing signal can be recovered with |m| ∼ 5% of the multiplicative shear calibration bias (as defined by Heymans et al. 2006; Massey et al. 2007), and c ∼ 10−3 of the residual shear offset, which is about one order of magnitude smaller than the typical…”
KiDS-450: The tomographic weak lensing power spectrum and constraints on cosmological parameters (2017, methodology): “The quadratic estimator (Hu & White 2001) was applied to the COMBO-17 data set (Brown et al. 2003) and the GEMS data set (Heymans et al. 2005).”
KiDS+VIKING-450: Cosmic shear tomography with optical and infrared data (2018, methodology): “To quantify the shear bias, we adopt the commonly used linear parametrisation (Heymans et al. 2006; Massey et al. 2007), expressed as a multiplicative bias term mi and an additive bias term ci, ĝi = (1 + mi)gtruei + ci, (1) where i = 1, 2 refers to the two components of the reduced shear g, and ĝ…”
Potential sources of contamination to weak lensing measurements: constraints from N-body simulations (2006, background): “The resultingei ellipticity distributions have a mean〈ei〉 = 0 and a widthσe = 0.33 which is very similar to what is measured from space-based data (Heymans et al. 2006).”
Combined strong and weak lensing analysis of 28 clusters from the Sloan Giant Arcs Survey (2011, methodology): “We find that the resulting shear multiplicative error (the parameter m in Heymans et al. 2006; Massey et al. 2007) depends on both seeing size and β such that m is smaller for larger seeing sizes or smaller β, but our algorithm generally yields |m| .”
NEW CONSTRAINTS ON THE EVOLUTION OF THE STELLAR-TO-DARK MATTER CONNECTION: A COMBINED ANALYSIS OF GALAXY–GALAXY LENSING, CLUSTERING, AND STELLAR MASS FUNCTIONS FROM z = 0.2 to z = 1 (2011, methodology): “First, Heymans et al. (2006a) fit an NFW profile to the g–g lensing signal and so the masses that they measure will reflect the mean halo mass at fixed stellar mass, 25 For example, the UltraVista survey of the COSMOS field will obtain IR imaging to Y = 26.7, J = 26.6, H = 26.1, and Ks = 25.6 mag,…”
Very weak lensing in the CFHTLS Wide: Cosmology from cosmic shear in the linear regime (2007, methodology): “As described in Heymans et al. (2006a) and Massey et al. (2007b), the shear bias parameter m often depends on object sizes, rg, and magnitudes mag.”
Gravitational lensing (2010, methodology): “The shear testing programme (STEP, [186, 311]) was launched to test and improve the accuracy of shear measurements from weakly distorted images of distant galaxies in the presence of several perturbing effects.”
A comparison of weak-lensing masses and X-ray properties of galaxy clusters (2007, background): “These results suggest that we can recover the shear with an accuracy of ∼2 per cent (Heymans et al. 2005).”