Shear calibration for multi-redshift blended galaxies

Develop a treatment of multi-redshift blending in which blended components at different redshifts experience different shears, including calibration of the resulting source-redshift-distribution and shear-estimation effects for photometric-redshift-based tomographic weak-lensing analyses.

Background

The analytical correction developed in the paper addresses shear-estimation bias caused by photometric-redshift-based tomographic selection. It does not address blends whose components lie at substantially different redshifts. Such components experience different gravitational shears, so the effective redshift distribution probed by the measured shear can differ from the redshift distribution inferred from the source catalogue.

The paper states that external simulations may be required to calibrate this effect and explicitly leaves its treatment unresolved. This problem is therefore distinct from the successfully validated photo-z selection-bias correction presented in the paper.

References

We note that external simulations may still be required to calibrate the source redshift distribution in the presence of blending between galaxies at different redshifts, which experience different shears \citep{DESY3_BlendshearCalib_MacCrann2021}. In this work, however, we focus specifically on the shear-estimation bias induced by photo-$z$-based selection and leave the treatment of multi-redshift blending to future work.

— Weak-Lensing Shear Response for Photometric Redshift-Based Tomographic Binning  (2610.00999 - Li et al., 1 Oct 2026) in Section 1, Introduction