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

TL;DR

This paper proposes a self-calibration method for galaxy intrinsic alignment in weak lensing surveys, leveraging the dependence of correlation functions on redshift separation to improve cosmological measurements.

Contribution

It introduces a novel approach to measure intrinsic alignment within photo-z bins using lensing tomography, reducing errors without strong assumptions.

Findings

Intrinsic alignment decreases faster with redshift separation.

The method allows measurement within small photo-z bins (~0.01).

Both statistical and systematic errors can be reduced.

Abstract

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 $|\Delta z^P|\la 0.2$ 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 $\ga 0.2$, through lensing tomography of photo-z bin size $\sim 0.01$. Both the statistical and systematical errors in the lensing cosmology can be reduced by this self-calibration technique.