Systematic tests for position-dependent additive shear bias

We study projected underdensities in the cosmic galaxy density field known as 'troughs', and their overdense counterparts, which we call 'ridges'. We identify these regions using a bright sample of foreground galaxies from the photometric Kilo-Degree Survey (KiDS), specifically selected to mimic the spectroscopic Galaxy And Mass Assembly survey (GAMA). Using background galaxies from KiDS, we measure the weak gravitational lensing profiles of the troughs/ridges. We quantify the amplitude of their lensing strength A as a function of galaxy density percentile rank P and galaxy overdensity δ, and find that the skewness in the galaxy density distribution is reflected in the total mass distribution measured by weak lensing. We interpret our results using the mock galaxy catalogue from the Marenostrum Institut de Ciències de l'Espai (MICE) simulation, and find a good agreement with our observations. Using signal-to-noise weights derived from the Scinet LIghtCone Simulations (SLICS) mock catalogue we optimally stack the lensing signal of KiDS troughs with an angular radius θ A = {5, 10, 15, 20} arcmin, resulting in {16.8, 14.9, 10.13, 7.55} σ detections. Finally, we select troughs using a volume-limited sample of galaxies, split into two redshift bins between 0.1 < z < 0.3. For troughs/ridges with transverse comoving radius R A = 1.9 h −1 70 Mpc, we find no significant difference in the comoving Excess Surface Density as a function of P and δ between the low-and high-redshift sample. Using the MICE and SLICS mocks we predict that trough and ridge evolution could be detected with gravitational lensing using deeper and wider lensing surveys, such as those from the Large Synoptic Survey Telescope and Euclid.

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“…The same effect can be seen in Fig. 15 of van Uitert & Schneider (2016), who conclude that it originates from the boundaries of the survey tiles.…”

Section: Lensing Measurementsupporting

confidence: 72%

Studying galaxy troughs and ridges using weak gravitational lensing with the Kilo-Degree Survey

Brouwer

Demchenko

Harnois-Déraps

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Additive biases (equation 14) are mainly caused by a residual PSF ellipticity in the shape of galaxies (e.g. Hoekstra 2004;van Uitert & Schneider 2016). More generally, any effect causing a preferential alignment of shapes in the galaxy source sample will create an additive bias.…”

Section: Appendix E: Sensitivity To Large-scale Additive Biasmentioning

confidence: 99%

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

Köhlinger

Viola

Joachimi

et al. 2017

Monthly Notices of the Royal Astronomical Society

218

276

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We present measurements of the weak gravitational lensing shear power spectrum based on 450 deg 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 ≤ ≤ 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 marginalising 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 S 8 = 0.651 ± 0.058 (3 z-bins), confirming the recently reported tension in this parameter with constraints from Planck at 3.2σ (3 z-bins). We cross-check the results of the 3 z-bin analysis with the weaker constraints from the 2 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.

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Consistent cosmic shear in the face of systematics: a B-mode analysis of KiDS-450, DES-SV and CFHTLenS

Asgari

Heymans

Hildebrandt³

et al. 2019

A&A

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We analyse three public cosmic shear surveys; the Kilo-Degree Survey (KiDS-450), the Dark Energy Survey (DES-SV) and the Canada France Hawaii Telescope Lensing Survey (CFHTLenS). Adopting the 'COSEBIs' statistic to cleanly and completely separate the lensing E-modes from the non-lensing B-modes, we detect B-modes in KiDS-450 and CFHTLenS at the level of ∼ 2.7σ. For DES-SV we detect B-modes at the level of 2.8σ in a non-tomographic analysis, increasing to a 5.5σ B-mode detection in a tomographic analysis. In order to understand the origin of these detected B-modes we measure the B-mode signature of a range of different simulated systematics including PSF leakage, random but correlated PSF modelling errors, camera-based additive shear bias and photometric redshift selection bias. We show that any correlation between photometric-noise and the relative orientation of the galaxy to the point-spread-function leads to an ellipticity selection bias in tomographic analyses. This work therefore introduces a new systematic for future lensing surveys to consider. We find that the B-modes in DES-SV appear similar to a superposition of the Bmode signatures from all of the systematics simulated. The KiDS-450 and CFHTLenS B-mode measurements show features that are consistent with a repeating additive shear bias.1 Contributions beyond the first-order Born approximation (Schneider et al. 1998) and source clustering (Schneider et al. 2002b) can produce insignificant levels of B-modes for the current generation of shear surveys.Article number, page 1 of 32Theoretically the 2PCFs can be calculated through their relation to the shear power spectrum, P γ ,ξ − (θ) = ∞ 0 d 2π J 4 ( θ) P γ ( ) , Article number, page 2 of 32 Article number, page 4 of 32

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Systematic tests for position-dependent additive shear bias

Cited by 5 publications

References 35 publications

Studying galaxy troughs and ridges using weak gravitational lensing with the Kilo-Degree Survey

Studying galaxy troughs and ridges using weak gravitational lensing with the Kilo-Degree Survey

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

Consistent cosmic shear in the face of systematics: a B-mode analysis of KiDS-450, DES-SV and CFHTLenS

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