AstroAI Workshop 2025
Antoine Bourdin
Diffusing Galaxies onto Dark Matter Fields over Multiple Cosmologies and Astrophysics
Presenter: Antoine Bourdin
Title: Diffusing Galaxies onto Dark Matter Fields over Multiple Cosmologies and Astrophysics
Date/Time: Monday, July 7th, 3:30 - 5:00 PM
Abstract: Cosmological hydrodynamical simulations, while the state-of-the art methodology for generating theoretical predictions for the large-scale structures of the Universe, are among the most expensive simulation tools, requiring upwards of 100 million CPU hours per simulation. N-body simulations, which exclusively model dark matter and its purely gravitational interactions, represent a less resource-intensive alternative, however, they do not model galaxies, and as such cannot directly be compared to observations. We use conditional score-based models to learn a mapping from N-body to hydrodynamical simulations, specifically from dark matter density fields to the observable distribution of galaxies. Our field emulator replicates the summary statistics of hydrodynamical simulations over multiple cosmology and astrophysics at a fraction of the computational cost. Furthermore, our model can serve as a likelihood in a simulation-based inference framework to obtain posterior distributions over cosmological parameters. Our emulator is significantly more precise than the traditional Halo Occupancy Distribution over the non-linear scales 0.36 h/Mpc ≤ k ≤3.88 h/Mpc, and provides tighter and unbiased constraints on matter density and fluctuations.