A proposal on the galaxy intrinsic alignment self-calibration in weak lensing surveys

The galaxy intrinsic alignment causes the galaxy ellipticity-ellipticity power spectrum between two photometric redshifts to decrease faster with respect to the redshift separation Delta z(P), for fixed mean redshift. This offers a valuable diagnosis on the intrinsic alignment. We show that the distinctive dependences of the GG, II and GI correlations on Delta z(P) over the range vertical bar Delta z(P)vertical bar less than or similar to 0.2 can be understood robustly without strong assumptions on the intrinsic alignment. This allows us to measure the intrinsic alignment within each conventional photo-z bin of typical size greater than or similar to 0.2, through lensing tomography of photo-z bin size similar to 0.01. Both the statistical and systematical errors in the lensing cosmology can be reduced by this self-calibration technique.