First star-forming structures in fuzzy cosmic filaments

TL;DR

This study uses advanced simulations to explore how the first galaxies form within fuzzy dark matter filaments, revealing unique wave-like structures and potential observational signatures of ultralight dark matter.

Contribution

It presents the first cosmological hydrodynamical simulation of galaxy formation in fuzzy dark matter, highlighting the impact of wave phenomena on structure development.

Findings

Dark matter filaments show interference patterns at the de Broglie scale.

Cylindrical soliton-like cores form and collapse into spherical solitons.

Gas and stars develop central cores influenced by dark matter structures.

Abstract

In hierarchical models of structure formation, the first galaxies form in low-mass dark matter potential wells, probing the behavior of dark matter on kiloparsec (kpc) scales. Even though these objects are below the detection threshold of current telescopes, future missions will open an observational window into this emergent world. In this Letter we investigate how the first galaxies are assembled in a `fuzzy' dark matter (FDM) cosmology where dark matter is an ultralight $\sim 10^{-22}$~eV boson and the primordial stars are expected to form along dense dark matter filaments. Using a first-of-its-kind cosmological hydrodynamical simulation, we explore the interplay between baryonic physics and unique wavelike features inherent to FDM. In our simulation, the dark matter filaments show coherent interference patterns on the boson de Broglie scale and develop cylindrical soliton-like cores which are unstable under gravity and collapse into kpc-scale spherical solitons. Features of the dark matter distribution are largely unaffected by the baryonic feedback. On the contrary, the distributions of gas and stars, which do form along the entire filament, exhibit central cores imprinted by dark matter -- a smoking gun signature of FDM.