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Arxiv: Differencing and Coadding JWST Images with Matched Point Spread Function Published: 9/17/2023 6:18:26 AM Updated: 4/28/2024 8:10:18 PM

Paper abstract: We present an algorithm to derive difference images for data taken with theJWST with matched point-spread functions (PSFs). It is based on the saccadicfast Fourier transform (SFFT) method but with revisions to accommodate therotations and spatial variations of the PSFs. It allows for spatially varyingkernels in B-spline form with separately controlled photometric scaling andTikhonov kernel regularization for harnessing the ultimate fitting flexibility.We present this method using the JWST/NIRCam images of galaxy cluster Abell2744 acquired in JWST Cycle 1 as the test data. The algorithm can be useful fortime-domain source detection and differential photometry with the JWST. It canalso coadd images of multiple exposures taken at different field orientations.The coadded images preserve the sharpness of the central cores of the PSFs, andthe positions and shapes of the objects are matched precisely with B-splinesacross the field.