Can We Constrain Warm Dark Matter Masses with Individual Galaxies?

We study the impact of warm dark matter (WDM) mass on the internal properties of individual galaxies using a large suite of 1024 state-of-the-art cosmological hydrodynamic simulations from the DREAMS project. We take individual galaxies’ properties from the simulations, which have different cosmologies, astrophysics, and WDM masses, and train normalizing flows to learn the posterior of the parameters. We find that our models cannot infer the value of the WDM mass, even when the values of the cosmological and astrophysical parameters are given explicitly. This result holds for galaxies with stellar mass larger than 2 × 10 ^8 M _⊙ h ^−1 at both low and high redshifts. We calculate the mutual information and find no significant dependence between the WDM mass and galaxy properties. On the other hand, our models can infer the value of Ω _m with a ∼10% accuracy from the properties of individual galaxies while marginalizing astrophysics and WDM masses.