E- and B-mode mixing from incomplete knowledge of the shear correlation

Free access article

Issue		A&A Volume 457, Number 1, October I 2006


Page(s)		15 - 19
Section		Cosmology (including clusters of galaxies)
DOI		http://dx.doi.org/10.1051/0004-6361:20065495

A&A 457, 15-19 (2006)
DOI: 10.1051/0004-6361:20065495

E- and B-mode mixing from incomplete knowledge of the shear correlation

M. Kilbinger, P. Schneider and T. Eifler

Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
e-mail: kilbinge@astro.uni-bonn.de

(Received 25 April 2005 / Accepted 20 June 2006 )

Abstract
Context.
Aims. We quantify the mixing of the measured cosmic-shear E- and B-modes caused by the lack of shear-correlation measurements on small and large scales, arising from a lack of close projected galaxy pairs and the finite field size, respectively.
Methods. We calculate the aperture-mass statistics $\langle M_{\rm ap, \perp}^2 \rangle$ and the E-/B-mode shear-correlation functions $\xi_{\rm E, B \pm}$ where small- and large-scale cutoffs are taken into account. We assess the deviation of the obtained E-mode to the true E-mode and the introduction of a spurious B-mode.
Results. The measured aperture-mass dispersion is underestimated by more than 10% on scales smaller than 12 times the lower cutoff. For a precise measurement of the E- and B-modes at the percent level using a combination of $\xi_{\rm E, B +}$ and $\xi_{\rm E, B -}$ , a field as large as 7 (2.4) degrees is necessary for ground-based (space-based) observations.

Key words: gravitational lensing -- large-scale structure of Universe -- cosmological parameters

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