FPFS: A fast, accurate shear estimator#
Fourier Power Function Shapelets (FPFS) is an innovative estimator for the shear responses of galaxy shape, flux, and detection. Utilizing leading-order perturbations of shear (a vector perturbation) and image noise (a tensor perturbation), FPFS determines shear and noise responses for both measurements and detections. Unlike traditional methods that distort each observed galaxy repeatedly, FPFS employs analytical shear responses of select basis functions, including Shapelets basis and peak basis. Remarkably efficient, FPFS can process approximately 1,000 galaxies within a single CPU second. Testing under simple simulations has proven its capability to maintain a multiplicative shear estimation bias below 0.5%, even amidst blending challenges.