Diverse dark matter haloes in Two-field Fuzzy Dark Matter

TL;DR

This paper explores how two-field fuzzy dark matter models, inspired by string theory, can produce diverse dark matter halo structures, addressing limitations of single-field models in explaining dwarf galaxy diversity.

Contribution

It introduces the first cosmological simulation of two-field fuzzy dark matter, demonstrating diverse halo structures and nested soliton cores.

Findings

Diverse dark matter halo structures observed in 2FDM simulations.

Late-time haloes can host nested soliton cores or dominant species solitons.

Simulation reveals potential resolutions to dwarf galaxy diversity issues.

Abstract

Fuzzy dark matter (FDM) is a compelling candidate for dark matter, offering a natural explanation for the structure of diffuse low-mass haloes. However, the canonical FDM model with a mass of $10^{-22}~{\rm eV}$ encounters challenges in reproducing the observed diversity of dwarf galaxies, except for possibly scenarios where strong galactic feedback is invoked. The introduction of multiple-field FDM can provide a potential resolution to this diversity issue. The theoretical plausibility of this dark matter model is also enhanced by the fact that multiple axion species with logarithmically-distributed mass spectrum exist as a generic prediction of string theory. In this paper, we consider the axiverse hypothesis and investigate non-linear structure formation in the two-field fuzzy dark matter (2FDM) model. Our cosmological simulation with an unprecedented resolution and self-consistent initial conditions reveals the diverse structures of dark matter haloes in the 2FDM model for the first time. Depending on the formation time and local tidal activities, late-time haloes can host solitons of nested cores or solitons of one dominant species.