A new cosmic shear function: optimized E/Bmode decomposition on a finite interval
Abstract
The decomposition of the cosmic shear field into E and B mode is an important diagnostic in weak gravitational lensing. However, commonly used techniques to perform this separation suffer from modemixing on very small or very large scales. We introduce a new E/Bmode decomposition of the cosmic shear twopoint correlation on a finite interval. This new statistic is optimized for cosmological applications, by maximizing the signaltonoise ratio (S/N) and a figure of merit (FoM) based on the Fisher matrix of the cosmological parameters Ω_{m} and σ_{8}.
We improve both S/N and FoM results substantially with respect to the recently introduced ring statistic, which also provides E/Bmode separation on a finite angular range. The S/N (FoM) is larger by a factor of 3 (2) on angular scales between 1 and 220 arcmin. In addition, it yields better results than for the aperturemass dispersion <M^{2}_{ap}>, with improvements of 20 per cent (10 per cent) for S/N (FoM). Our results depend on the survey parameters, most importantly on the covariance of the twopoint shear correlation function. Although we assume parameters according to the CFHTLSWide survey, our method and optimization scheme can be applied easily to any given survey settings and observing parameters. Arbitrary quantities, with respect to which the E/Bmode filter is optimized, can be defined, therefore generalizing the aim and context of the new shear statistic.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 January 2010
 DOI:
 10.1111/j.13652966.2009.15720.x
 arXiv:
 arXiv:0907.0795
 Bibcode:
 2010MNRAS.401.1264F
 Keywords:

 gravitational lensing;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 11 pages, 7 figures, 2 tables. MNRAS accepted. Cprogram freely available at http://www2.iap.fr/users/kilbinge/decomp_eb/