Impact of Image Persistence in the Roman Space Telescope High-Latitude Survey

Abstract

The High Latitude Survey of the Nancy Grace Roman Space Telescope is expected to measure the positions and shapes of hundreds of millions of galaxies in an area of 2220 deg 2 . This survey will provide high-quality weak lensing data with unprecedented systematics control. The Roman Space Telescope will survey the sky in near infrared (NIR) bands using Teledyne H4RG HgCdTe photodiode arrays. These NIR arrays exhibit an effect called persistence: charges that are trapped in the photodiodes during earlier exposures are gradually released into later exposures, leading to contamination of the images and potentially to errors in measured galaxy properties such as fluxes and shapes. In this work, we use image simulations that incorporate the persistence effect to study its impact on galaxy shape measurements and weak lensing signals. No significant spatial correlations are found between the galaxy shape changes induced by persistence. On the scales of interest for weak lensing cosmology, the effect of persistence on the weak lensing correlation function is about two orders of magnitude lower than the Roman Space Telescope additive shear error budget, indicating that the persistence effect is expected to be a subdominant contributor to the systematic error budget for weak lensing with the Roman Space Telescope given its current design.

Weak Gravitational Lensing Shear Estimation with Metacalibration for the Roman High-Latitude Imaging Survey

“…The bias can be introduced in places such as PSF modeling, blending, and the undersampling of the image (e.g., . Additionally, complex detector effects such as the brighter-fatter effect are potential sources of bias (Choi & Hirata 2020), while it has been shown that for Roman the effect of persistence will not be an issue (Lin et al 2021). Qualitatively, if the recovered shear is biased by 1% (𝑚 = 0.01), from the cosmic shear power spectrum 𝑆 8 = 𝜎 8 √︁ Ω 𝑚 /0.3 could be estimated to be biased about 1.5% in the final cosmology result.…”