On the maximum disk heating attributable to fuzzy dark matter

TL;DR

This paper examines how fuzzy dark matter influences stellar disk heating and migration, suggesting previous bounds on dark matter particle mass should be increased due to less efficient heating observed in our galaxy.

Contribution

It provides a revised estimate for the lower bound of fuzzy dark matter particle mass based on the discrepancy between expected and observed stellar disk heating.

Findings

Radial heating due to FDM is less than previously assumed.

Lower bounds on FDM particle mass should be increased.

Galactic disk kinematics constrain FDM properties.

Abstract

Fuzzy dark matter (FDM) granulations would drive orbital transport of stars in galactic disks, and in particular would produce roughly equal amounts of radial heating and radial migration. However, observations suggest that heating has been much less efficient than migration in our Galaxy. We argue that this decreases the amount of radial heating, $\mathcal{H}_\mathrm{FDM}$, that can safely be attributed to FDM. Consequently, lower bounds on the FDM particle mass $m$ derived through Galactic disk kinematics should be revised upwards; a rough estimate is $m \gtrsim 1.3\times 10^{-22} \mathrm{eV} \times [(\mathcal{H}_\mathrm{FDM}/\mathcal{H})/0.1]^{-1/2}$, where $\mathcal{H}$ is the total observed radial heating.