Testing Shear Recovery with Field Distortion

Understand

The tilt, rotation, or offset of each CCD with respect to the focal plane, as well as the distortion of the focal plane itself, cause shape distortions to the observed objects, an effect typically known as field distortion (FD).

• We point out that FD provides a unique way of quantifying the accuracy of cosmic shear measurement.
• The idea is to stack the shear estimators from galaxies that share similar FD-induced shape distortions.
• Given that the latter can be calculated with parameters from astrometric calibrations, the accuracy of the shear estimator can be directly tested on real images.