Dark Energy Survey Year 3 Results: Point-Spread Function Modeling

TL;DR

This paper presents Piff, a new software for modeling the PSF in astronomical images, applied to DES Year 3 data, showing improved accuracy over previous models for weak lensing analysis.

Contribution

Introduction of Piff, a novel PSF modeling software, with demonstrated small systematic errors in DES Year 3 data compared to Year 1.

Findings

PSF modeling errors are very small for DES Y3.

Systematic errors are significantly reduced compared to DES Y1.

Piff's improvements enhance weak lensing analysis accuracy.

Abstract

We introduce a new software package for modeling the point-spread function (PSF) of astronomical images, called Piff (PSFs In the Full FOV), which we apply to the first three years (known as Y3) of the Dark Energy Survey (DES) data. We describe the relevant details about the algorithms used by Piff to model the PSF, including how the PSF model varies across the field of view (FOV). Diagnostic results show that the systematic errors from the PSF modeling are very small over the range of scales that are important for the DES Y3 weak lensing analysis. In particular, the systematic errors from the PSF modeling are significantly smaller than the corresponding results from the DES year one (Y1) analysis. We also briefly describe some planned improvements to Piff that we expect to further reduce the modeling errors in future analyses.