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

TL;DR

This paper evaluates how the persistence effect in the Roman Space Telescope's NIR detectors impacts weak lensing measurements, finding it to be a minor systematic error compared to the mission's error budget.

Contribution

It introduces image simulations incorporating persistence to quantify its impact on galaxy shape measurements and weak lensing signals.

Findings

Persistence has negligible spatial correlation effects on galaxy shapes.

The impact of persistence is two orders of magnitude below the systematic error budget.

Persistence is a subdominant systematic for the Roman Space Telescope's weak lensing analysis.

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.