Fast GPU-powered and auto-differentiable forward modeling for cosmological hydrodynamical simulations

On Thursday 15th May, we celebrated the ‘Young RSE Award’ winners from 2023, 2024 and 2025 with a presentation from each of them on the research topic that won them the award. We welcome the 2025 Award Winner - Anna Lena Schaible Abstract: In the field of extragalactic astronomy we have typical two groups: The observers and the theorists. The nature of the data these two groups work with is very different: Observers count photons with the instrument detectors and theorists work with particles that have specific physical properties. This results in a rather small scientific exchange between both groups. Generally, there are two ways to bring observational data and simulation data closer together to allow a direct comparison between them: Forward modeling and inverse modeling. Forward modeling calculates what should be observed for a particular model. The forward model takes certain parameters and produces data that are comparable to actual observations. Here, we present RUBIX, a novel python framework that aims at bridging the gap between observation and modeling. Inverse modeling is the process of starting with the result - the observational data - and calculating the causal factors that produce these data, which means constructing a model that accounts for the given set of observations. In the future, RUBIX will also allow for inverse modeling of observational data of galaxies. To this end, it leverages the sophisticated features of the JAX ecosystem and implements a pipeline structure that naturally supports differentiability of the computations. Besides the pure software side, I will spent part time of the talk on how to start writing a research software from scratch. I will discuss the experiences and lessons learned in the journey from being a PhD student with no prior experience in research software engineering to developing an innovative open-source scientific software that uses cutting edge technologies. The presentation recording is available on the HiRSE YouTube Channel: https://www.youtube.com/@Helmholtz_Platform_for_RSE/videos?view=0&sort=dd&shelf_id=3https://www.youtube.com/watch?v=kY7aP3tgG6E Learn more about the HiRSE Seminar Series: https://www.helmholtz-hirse.de/series.html