UFig v1: The ultra-fast image generator

Abstract

With the rise of simulation-based inference (SBI) methods, simulations need to be fast as well as realistic. $\text{UFig v1}$ is a public Python package that simulates astronomical images with exceptional speed, taking approximately the same time as source extraction. This makes it particularly well-suited for SBI methods where computational efficiency is crucial. To render an image, $\text{UFig}$ requires a galaxy catalog, and a description of the point spread function (PSF). It can also add background noise, sample stars using the Besançon model of the Milky Way, and run $\text{SExtractor}$ to extract sources from the rendered image. The extracted sources can be matched to the intrinsic catalog, flagged based on $\text{SExtractor}$ output and survey masks, and emulators can be used to bypass the image simulation and extraction steps. A first version of $\text{UFig}$ was presented in Bergé et al. (2013) and the software has since been used and further developed in a variety of forward modelling applications.

8 pages, 4 figures, accepted for publication in JOSS