Testing the Prediction of Fuzzy Dark Matter Theory in the Milky Way Center

TL;DR

This study tests fuzzy dark matter theory by simulating gas flow in the Milky Way to see if a soliton core can explain the Central Molecular Zone, providing constraints on dark matter properties.

Contribution

The paper presents high-resolution hydrodynamical simulations incorporating a soliton core to evaluate its role in forming the Milky Way's CMZ, offering new constraints on fuzzy dark matter parameters.

Findings

A dense center is necessary for the formation of the CMZ.

A soliton core with ~4.0×10^8 solar masses and 0.05 kpc radius fits observations.

A boson mass of 2-7×10^-22 eV is consistent with the data.

Abstract

The fuzzy dark matter model (FDM, also known as quantum wave dark matter model) argues that light bosons with a mass of $\sim10^{-22}{\;{\rm eV}}$ are a possible candidate for dark matter in the Universe. One of the most important predictions of FDM is the formation of a soliton core instead of a density cusp at the center of galaxies. If FDM is the correct theory of dark matter, then the predicted soliton core can help to form the Central Molecular Zone (CMZ) in the Milky Way. We present high-resolution hydrodynamical simulations of gas flow patterns to constrain the properties of the soliton core based on a realistic Milky Way potential. We find that a dense center is required to form a reasonable CMZ. The size and kinematics of the CMZ offer a relatively strong constraint on the inner enclosed mass profile of the Galaxy. If a soliton core is not considered, a compact nuclear bulge alone with a radially varying mass-to-light ratio can match the observed size and kinematics of the CMZ. A soliton core model with a mass of $\approx4.0\times10^8{\; {\rm M}_{\odot}}$ and a core radius of $\approx0.05{\;{\rm kpc}}$, together with a less massive nuclear bulge with a constant mass-to-light ratio, also agrees nicely with the current data. Such a FDM soliton core corresponds to a boson mass of $\sim2-7\times10^{-22}{\;{\rm eV}}$, which could be further constrained by the improved determination of the mass-to-light ratio in the Galactic center.