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To render cosmic shear an astronomical tool of high precision, it isessential to eliminate systematic effects upon its signal, one of the mostsignificant ones being correlations between the gravitational shear and theintrinsic ellipticity of source galaxies. Because of the crudeness of currentmodels of intrinsic alignment, we have developed a model-independent, purelygeometrical method to remove shear-ellipticity correlations. We eliminate thecontributions to a tomographic cosmic shear signal that may be subject tocontamination by shear-ellipticity correlations, making use of thecharacteristic dependence of these correlations on redshift. By introducing anappropriately chosen weight function to the lensing efficiency that nullssignals stemming from certain distances, new second-order measures of cosmicshear, free of intrinsic alignment, can be constructed. The loss of informationinduced by this nulling technique and the subsequent degradation of constraintson cosmological parameters is quantified in a likelihood analysis. Concerningthe construction of optimal weight functions, good agreement is achievedbetween all approaches considered. For a survey divided into 20 redshift binswe find that the area of credible regions increases by 20% up to about 50%after the application of nulling, depending on the cosmological parametersconsidered. We demonstrate that due to an optimization of the weight functionsnearly all information is contained in a small subset of the new second-ordermeasures. The use of a significantly smaller number of redshift bins than 20for the nulling considerably degrades parameter constraints under conservativeassumptions, emphasizing the need for detailed redshift information.

The removal of shear-ellipticity correlations from the cosmic shear signal via nulling techniques