Simulating image coaddition with the Nancy Grace Roman Space Telescope: I. Simulation methodology and general results

Kavli Affiliate: Katrin Heitmann

| Authors: Christopher M. Hirata, Masaya Yamamoto, Katherine Laliotis, Emily Macbeth, M. A. Troxel, Tianqing Zhang, Ami Choi, Jahmour Givans, Katrin Heitmann, Mustapha Ishak, Mike Jarvis, Eve Kovacs, Heyang Long, Rachel Mandelbaum, Andy Park, Anna Porredon, Christopher W. Walter, W. Michael Wood-Vasey

| Summary:

The upcoming Nancy Grace Roman Space Telescope will carry out a wide-area
survey in the near infrared. A key science objective is the measurement of
cosmic structure via weak gravitational lensing. Roman data will be
undersampled, which introduces new challenges in the measurement of source
galaxy shapes; a potential solution is to use linear algebra-based coaddition
techniques such as Imcom that combine multiple undersampled images to produce a
single oversampled output mosaic with a desired “target” point spread function
(PSF). We present here an initial application of Imcom to 0.64 square degrees
of simulated Roman data, based on the Roman branch of the Legacy Survey of
Space and Time (LSST) Dark Energy Science Collaboration (DESC) Data Challenge 2
(DC2) simulation. We show that Imcom runs successfully on simulated data that
includes features such as plate scale distortions, chip gaps, detector defects,
and cosmic ray masks. We simultaneously propagate grids of injected sources and
simulated noise fields as well as the full simulation. We quantify the residual
deviations of the PSF from the target (the “fidelity”), as well as noise
properties of the output images; we discuss how the overall tiling pattern as
well as Moir’e patterns appear in the final fidelity and noise maps. We
include appendices on interpolation algorithms and the interaction of
undersampling with image processing operations that may be of broader
applicability. The companion paper (“Paper II”) explores the implications for
weak lensing analyses.

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