PSFs of coadded images
Abstract
We provide a detailed exploration of the connection between choice of coaddition schemes and the point-spread function (PSF) of the resulting coadded images. In particular, we investigate what properties of the coaddition algorithm lead to the final coadded image having a well-defined PSF. The key elements of this discussion are as follows: 1. We provide an illustration of how linear coaddition schemes can produce a coadd that lacks a well-defined PSF even for relatively simple scenarios and choices of weight functions. 2. We provide a more formal demonstration of the fact that a linear coadd only has a well-defined PSF in the case that either (a) each input image has the same PSF or (b) the coadd is produced with weights that are independent of the signal. 3. We discuss some reasons that two plausible nonlinear coaddition algorithms (median and clipped-mean) fail to produce a consistent PSF profile for stars. 4. We demonstrate that all nonlinear coaddition procedures fail to produce a well-defined PSF for extended objects. In the end, we conclude that, for any purpose where a well-defined PSF is desired, one should use a linear coaddition scheme with weights that do not correlate with the signal and are approximately uniform across typical objects of interest.
Keywords
Cite
@article{arxiv.2209.09253,
title = {PSFs of coadded images},
author = {Rachel Mandelbaum and Mike Jarvis and Robert H. Lupton and James Bosch and Arun Kannawadi and Michael D. Murphy and Tianqing Zhang and the LSST Dark Energy Science Collaboration},
journal= {arXiv preprint arXiv:2209.09253},
year = {2023}
}
Comments
13 pages, 4 figures; pedagogical article; v2 accepted for publication in the Open Journal of Astrophysics