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The shear testing programme 2 : Factors affecting high-precision weak-lensing analyses

Massey, R.; Heymans, C.; Bergé, J.; Bernstein, G.; Bridle, S.; Clowe, D.; Dahle, H.; Ellis, R.; Erben, T.; Hetterscheidt, M.; High, F.W.; Hirata, C.; Hoekstra, H.; Hudelot, P.; Jarvis, M.; Johnston, D.; Kuijken, K.; Margoniner, V.; Mandelbaum, R.; Mellier, Y.; Nakajima, R.; Paulin-Henriksson, S.; Peeples, M.; Roat, C.; Refregier, A.; Rhodes, J.; Schrabback, T.; Schirmer, M.; Seljak, U.; Semboloni, E.; Van Waerbeke, L.

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Authors

C. Heymans

J. Bergé

G. Bernstein

S. Bridle

D. Clowe

H. Dahle

R. Ellis

T. Erben

M. Hetterscheidt

F.W. High

C. Hirata

H. Hoekstra

P. Hudelot

M. Jarvis

D. Johnston

K. Kuijken

V. Margoniner

R. Mandelbaum

Y. Mellier

R. Nakajima

S. Paulin-Henriksson

M. Peeples

C. Roat

A. Refregier

J. Rhodes

T. Schrabback

M. Schirmer

U. Seljak

E. Semboloni

L. Van Waerbeke



Abstract

The Shear Testing Programme (STEP) is a collaborative project to improve the accuracy and reliability of weak-lensing measurement, in preparation for the next generation of wide-field surveys. We review 16 current and emerging shear-measurement methods in a common language, and assess their performance by running them (blindly) on simulated images that contain a known shear signal. We determine the common features of algorithms that most successfully recover the input parameters. A desirable goal would be the combination of their best elements into one ultimate shear-measurement method. In this analysis, we achieve previously unattained discriminatory precision via a combination of more extensive simulations and pairs of galaxy images that have been rotated with respect to each other. That removes the otherwise overwhelming noise from their intrinsic ellipticities. Finally, the robustness of our simulation approach is confirmed by testing the relative calibration of methods on real data. Weak-lensing measurements have improved since the first STEP paper. Several methods now consistently achieve better than 2 per cent precision, and are still being developed. However, we can now distinguish all methods from perfect performance. Our main concern continues to be the potential for a multiplicative shear calibration bias: not least because this cannot be internally calibrated with real data. We determine which galaxy populations are responsible for bias and, by adjusting the simulated observing conditions, we also investigate the effects of instrumental and atmospheric parameters. The simulated point spread functions are not allowed to vary spatially, to avoid additional confusion from interpolation errors. We have isolated several previously unrecognized aspects of galaxy shape measurement, in which focused development could provide further progress towards the sub-per cent level of precision desired for future surveys. These areas include the suitable treatment of image pixellization and galaxy morphology evolution. Ignoring the former effect affects the measurement of shear in different directions, leading to an overall underestimation of shear and hence the amplitude of the matter power spectrum. Ignoring the second effect could affect the calibration of shear estimators as a function of galaxy redshift, and the evolution of the lensing signal, which will be vital to measure parameters including the dark energy equation of state.

Citation

Massey, R., Heymans, C., Bergé, J., Bernstein, G., Bridle, S., Clowe, D., …Van Waerbeke, L. (2007). The shear testing programme 2 : Factors affecting high-precision weak-lensing analyses. Monthly Notices of the Royal Astronomical Society, 376(1), 13-38. https://doi.org/10.1111/j.1365-2966.2006.11315.x

Journal Article Type Article
Publication Date Mar 21, 2007
Deposit Date Mar 21, 2013
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 376
Issue 1
Pages 13-38
DOI https://doi.org/10.1111/j.1365-2966.2006.11315.x
Keywords Gravitational lensing, Methods: data analysis, Cosmology: observations.

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Copyright Statement
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2007 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.





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