UFig v1: The ultra-fast image generator

TL;DR

UFig v1 is a Python package that rapidly simulates realistic astronomical images, enabling efficient simulation-based inference by matching the speed of source extraction processes.

Contribution

It introduces a highly efficient, publicly available image generator for astronomy that integrates with existing analysis tools and supports emulators to accelerate simulations.

Findings

Simulation time matches source extraction time

Supports realistic galaxy and star sampling

Enables fast forward modeling in astronomy

Abstract

With the rise of simulation-based inference (SBI) methods, simulations need to be fast as well as realistic. $\texttt{UFig v1}$ 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, $\texttt{UFig}$ requires a galaxy catalog, and a description of the point spread function (PSF). It can also add background noise, sample stars using the Besan\c{c}on model of the Milky Way, and run $\texttt{SExtractor}$ to extract sources from the rendered image. The extracted sources can be matched to the intrinsic catalog, flagged based on $\texttt{SExtractor}$ output and survey masks, and emulators can be used to bypass the image simulation and extraction steps. A first version of $\texttt{UFig}$ was presented in Berg\'e et al. (2013) and the software has since been used and further developed in a variety of forward modelling applications.