Princeton University Gravity Group Lunch Seminar - New Speaker

The near-century-old dark matter (DM) problem is one of the most intriguing mysteries in modern physics. We do not know the nature of 84% of matter in the Universe, yet it is thought to govern cosmic structure and hold galaxies and clusters together. In this talk, I will present pioneering simulations of what the Universe would look like if DM were ultra-light, in the so-called `fuzzy dark matter' (FDM) limit where DM is a ~10^-22 eV boson. In hierarchical models of structure formation, the first galaxies form in low-mass DM potential wells, probing the behavior of DM on kiloparsec (kpc) scales. Even though these objects have not yet been observed, telescopes such as the James Webb Space Telescope (JWST) will soon offer an observational window into this emergent world. In this talk, I show how the first galaxies are assembled in FDM cosmology along dense DM filaments. Using first-of-its-kind cosmological hydrodynamical simulations, I explore the interplay between baryonic physics and unique wavelike features inherent to FDM. In the simulations, the DM filaments show coherent interference patterns on the boson de Broglie scale, develop cylindrical soliton-like cores, and form stars along the entire structure. The filaments are unstable under gravity and collapse into kpc-scale spherical solitons. Features of the DM distribution are largely unaffected by the realistic baryonic feedback; on the contrary, gas and stars follow DM filaments and their profiles exhibit flattened cores -- smoking gun signatures of FDM. I contrast these results against first structures in cold and warm DM cosmologies. I will also discuss a variety of other small-scale astrophysical consequences of FDM due to its unique substructure, which place independent constraints on the FDM particle mass, and present prospects for the future to validate or rule-out FDM.