Spectraluntersuchungen �ber die Energie der Einwirkung von Brom auf aromatische Kohlenwasserstoffe

Schramm, Julian; Zakrzewski, Ignaz

doi:10.1007/bf01510052

Cited by 8 publications

(6 citation statements)

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“…w a is the weight associated with the measured ellipticity at x x x a and t/× are the tangential and cross components of the measured ellipticity (Schneider et al 2002a). Here the ellipticity is defined such that its expectation value is equal to the reduced shear, in absence of systematics (Schramm & Kayser 1995;Seitz & Schneider 1997). If the ellipticity measurements require a multiplicative correction, m (see for example Miller et al 2013), then the correlation functions may be calibrated by dividing them with the following correction, where is the Fourier conjugate of θ and J 0 and J 4 are the ordinary Bessel functions of zeroth and fourth order (see Kaiser 1992, for example).…”

Section: Methodsmentioning

confidence: 99%

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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Section: Methodsmentioning

confidence: 99%

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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“…In addition, we show that weakly lensed arcs can be uniquely decomposed into the spin-1 first flexion, and a new component which has not previously been considered, the second flexion which we show has spin-3 properties. Schramm & Kayser (1995) suggested an alternative complex representation for lensing; we introduce a complex gradient operator which simplifies the analysis considerably.…”

Section: Complex Representationmentioning

confidence: 99%

Weak gravitational flexion

Bacon

Goldberg

Rowe

et al. 2006

Monthly Notices of the Royal Astronomical Society

131

183

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Flexion is the significant third‐order weak gravitational lensing effect responsible for the weakly skewed and arc‐like appearance of lensed galaxies. Here we demonstrate how flexion measurements can be used to measure galaxy halo density profiles and large‐scale structure on non‐linear scales, via galaxy–galaxy lensing, dark matter mapping and cosmic flexion correlation functions. We describe the origin of gravitational flexion, and discuss its four components, two of which are first described here. We also introduce an efficient complex formalism for all orders of lensing distortion. We proceed to examine the flexion predictions for galaxy–galaxy lensing, examining isothermal sphere and Navarro–Frenk–White (NFW) profiles and both circularly symmetric and elliptical cases. We show that in combination with shear we can precisely measure galaxy masses and NFW halo concentrations. We also show how flexion measurements can be used to reconstruct mass maps in two‐dimensional projection on the sky, and in three dimensions in combination with redshift data. Finally, we examine the predictions for cosmic flexion, including convergence–flexion cross‐correlations, and we find that the signal is an effective probe of structure on non‐linear scales.

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“…With our definition for the ellipticity parameter ǫ, the expectation value for observed image ellipticities is equal to the reduced shear: ǫ ǫs = g (Schramm & Kayser 1995, Seitz & Schneider 1997. Therefore, each observed image ellipticity ǫi is an unbiased -though very noisy -estimate for the reduced shear gi = γi/(1 − κi) at the image position, and γti can be replaced by ǫti (1 − κi) in the above equation.…”

Section: Kaisermentioning

confidence: 99%

Constraining the mass distribution of cluster galaxies by weak lensing

Geiger

Schneider

1998

Monthly Notices of the Royal Astronomical Society

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Analysing the weak lensing distortions of the images of faint background galaxies provides a means to constrain the average mass distribution of cluster galaxies and potentially to test the extent of their dark matter haloes as a function of the density of their environment. The observable image distortions are a consequence of the interplay between the effects of a global cluster mass distribution and the perturbations resulting from individual cluster galaxies. Starting from a reconstruction of the cluster mass distribution with conventional techniques, we apply a maximum likelihood method to infer the average properties of an ensemble of cluster galaxies. From simulations this approach is found to be reliable as long as the galaxies including their dark matter haloes only contribute a small fraction to the total mass of the system. If their haloes are extended, the galaxies contain a substantial mass fraction. In this case our method is still applicable in the outer regions of clusters, where the surface mass density is low, but yields biased estimates of the parameters describing the mass profiles of the cluster galaxies in the central part of the cluster. In that case it will be necessary to resort to more sophisticated strategies by modelling cluster galaxies and an underlying global mass distribution simultaneously. We conclude that galaxy–galaxy lensing in clusters provides a unique means to probe the presence and extent of dark haloes of cluster galaxies.

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Spectraluntersuchungen �ber die Energie der Einwirkung von Brom auf aromatische Kohlenwasserstoffe

Cited by 8 publications

References 0 publications

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

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

Weak gravitational flexion

Constraining the mass distribution of cluster galaxies by weak lensing

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