Self-Calibration for 3-point Intrinsic Alignment Auto-Correlations in
  Weak Lensing Surveys
  The weak lensing signal (cosmic shear) has been shown to be strongly
contaminated by the various types of galaxy intrinsic alignment (IA)
correlations, which poses a barrier to precision weak lensing measurements. The
redshift dependence of the IA signal has been used at the 2-point level to
reduce this contamination by only measuring cross-correlations between large
redshift bins, which significantly reduces the galaxy intrinsic ellipticity -
intrinsic ellipticity (II) correlation. A self-calibration technique based on
the redshift dependences of the IA correlations has also been proposed as a
means to remove the 2-point IA contamination from the lensing signal. We
explore here the redshift dependences of the IA and lensing bispectra in order
to propose a self-calibration of the IA auto-correlations at the 3-point level
(i.e. GGI, GII, and III), which can be well understood without the assumption
of any particular IA model. We find that future weak lensing surveys will be
able to measure the distinctive IA redshift dependence over ranges of $|\Delta
z^P|\le 0.2$. Using conservative estimates of photo-z accuracy, we describe the
3-point self-calibration technique for the total IA signal, which can be
accomplished through lensing tomography of photo-z bin size $\sim 0.01$. We
find that the 3-point self-calibration can function at the accuracy of the
2-point technique with modest constraints in redshift separation. This allows
the 3-point IA auto-correlation self-calibration technique proposed here to
significantly reduce the contamination of the IA contamination to the weak
lensing bispectrum.
