Self-Calibration Techniques for 3-point Intrinsic Alignment Correlations in Weak Gravitational Lensing Surveys

The weak lensing signal (cosmic shear) has been shown to be contaminated by correlations between the intrinsic alignment (IA) of galaxies, which poses a barrier to precision weak lensing measurements in planned surveys. We review recent work to extend the self-calibration approach to the cosmic shear bispectrum. The self-calibration techniques use the redshift separation dependencies of the IA bispectra and the non-linear galaxy bias in order to isolate and remove the impact of the IA correlations on the cosmic shear signal. We outline the proposed self-calibration techniques for the 3-point cosmic shear auto- and cross-correlations and summarize their performance. Using conservative estimates of photo-z accuracy, we find that planned surveys will be able to measure the IA redshift separation dependence over ranges of $|\Delta z^P|\le 0.2$ in the 3-point ellipticity auto-correlation. For the 3-point cross-correlations, we find that the self-calibration technique allows for reductions in the IA contamination by a factor of 10 or more over most scales and redshift bin choices and in all cases by a factor of 3-5 or more. The 3-point self-calibration techniques thus provide a means to greatly reduce the impact of IA on the cosmic shear signal.