Source–lens clustering effects on the skewness of the lensing convergence
1 For more information about the DESCART project, see http://terapix.iap.fr/Descart/
2 The lensing convergence is not a direct observable but is obtained via a convergence reconstruction technique ( Van Waerbeke, Bernardeau & Mellier 1999) or the aperture mass ( Schneider et al. 1998) from a lensing shear map.
3 It should be noted, however, that to break the degeneracy between cosmological parameters, one still has to measure cosmic shear statistics at linear scales, i.e. θ>1° ( Jain & Seljak 1997).
4 Notice the difference of sign convention that we use for κ, to enforce positively for the convergence skewness.
Abstract
The correlation between source galaxies and lensing potentials causes a systematic effect on measurements of cosmic shear statistics, known as the source–lens clustering (SLC) effect. The SLC effect on the skewness of lensing convergence, S3, is examined using a non-linear semi-analytic approach and is checked against numerical simulations. The semi-analytic calculations have been performed in a wide variety of generic models for the redshift distribution of source galaxies and power-law models for the bias parameter between the galaxy and dark matter distributions. The semi-analytic predictions are tested successfully against numerical simulations. We find the relative amplitude of the SLC effect on S3 to be of the order of 5–40 per cent. It depends significantly on the redshift distribution of sources and on the way in which the bias parameter evolves. We discuss possible measurement strategies to minimize the SLC effects.
