Caustics: Simulating Gravitational Lensing


Yashar Hezaveh, Director, Ciela Institute 

Laurence Perreault-Levasseur, Assistant Professor, Ciela Institute 

Connor Stone, Astrophysics Postdoctoral Fellow, Ciela Institute 

SSEC Engineers

Don Setiawan, Senior Research Software Engineer

Cordero Core, Senior Research Software Engineer

Gravitational lensing occurs when a large mass (e.g. a galaxy) lies between an observer (Earth) and a light source (another galaxy). These chance alignments magnify and multiply image the background source in a variety of interesting configurations. Scientists can leverage these naturally occurring telescopes to study phenomena such as distant galaxies, cosmology, and dark matter. 

Caustics is a lensing simulator developed by researchers at University of Montreal’s Ciela Institute. The present Python Package focuses on strong lensing. 

SSEC is working to expand the flexible modeling framework to meet the needs of the broader lensing community. In adding standard packaging conventions, detailed documentation, and enabling GitHub Codespaces, SSEC aims to increase accessibility to the software. Bringing caustics into open-source Scientific Python ecosystems will allow for sustained contributions and greater engagement. Features such as CI/CD, API specifications, data validation, and save-state will facilitate robust code that is easily shared, understood, and reproduced amongst researchers. 

Those new to gravitational lensing will learn the field while working through examples in caustics; then continue their science using the tool. The ultimate aspiration for caustics is a comprehensive/one-stop-shop modeling framework, one that meets the science needs of any scientist who explores gravitational lensing phenomena.

The SSEC team contributed to a lot of features to the codebase as reflected in the release of caustics version 0.10.0. The installable package is hosted on Python Packaging Index and the Anaconda Conda Package Repository.

A virtual poster session will be held for caustics at the 2024 SciPy Conference. Connor Stone will also present development best practices that he has learned during SSEC’s engagement with caustics at his talk for AstroPhot, a software that he developed in parallel with caustics.