Galaxy formation with wave/fuzzy dark matter: The core-halo structure and the solitonic imprint

TL;DR

This paper compares cosmological simulations of cold dark matter, warm dark matter, and wave/fuzzy dark matter to predict stellar profiles, revealing distinctive core-halo structures and asymmetries in the fuzzy dark matter scenario.

Contribution

It demonstrates that wave/fuzzy dark matter predicts unique core-halo stellar structures and asymmetries, unlike CDM and WDM, providing potential observational signatures.

Findings

Core-halo structures are distinguishable in $\\psi$DM simulations.

Stellar density is enhanced in the core due to the soliton.

Asymmetry in stellar distribution is observed in $\\psi$DM.

Abstract

Dark matter-dominated cores have long been claimed for the well-studied local group dwarf galaxies. More recently, extended stellar halos have been uncovered around several of these dwarfs through deeper imaging and spectroscopy. Such core-halo structures are not a feature of conventional cold dark matter (CDM). In contrast, smooth and prominent dark matter cores are predicted for wave/fuzzy dark matter ($\psi$DM). The question arises as to what extent the visible stellar profiles should reflect this dark matter core structure. Here we compare cosmological hydrodynamical simulations of CDM, ``WDM'' (model used as a proxy for $\psi$DM) \& $\psi$DM, aiming to predict the stellar profiles for these three DM scenarios. We show that cores surrounded by extended halos are distinguishable for $\psi$DM, where the stellar density is enhanced in the core due to the presence of the relatively dense soliton. Our analysis demonstrates that, in our simulations, a distinctive core-halo structure does not appear in the case of CDM in the DM, gas, or stars. Whereas we do find a core-halo transition for DM, gas, and stars for $\psi$DM, and the scale of this transition is in line with the predicted core radius set by the soliton scale anticipated for the adopted boson mass of 2.5$\times10^{-22}$eV. The presence of a core-halo structure in the stellar profile for Galaxy 1 for $\psi$DM is visible for the most massive and the first galaxy to form in the simulation. Clearly, further simulations are needed to establish how strict this possible relationship is between the DM and stellar core-halo profile as a potential observational discriminator. Furthermore, we observe the anticipated asymmetry for $\psi$DM due to the soliton's motion (jumping and random walk), a distinctive characteristic not found in the symmetric distributions of stars in the warm and CDM models.