Constraining scalar fields with stellar kinematics and collisional dark matter

TL;DR

This paper uses astronomical observations, especially stellar dynamics at the Galactic center, to constrain properties of scalar fields as dark matter candidates, significantly narrowing their possible parameter space and implications.

Contribution

It provides new observational constraints on self-interacting scalar fields, linking stellar kinematics to limits on scalar dark matter properties and their role in galactic structures.

Findings

Scalar fields are tightly constrained by stellar dynamics data.

Scalar dark matter cannot explain both halos and dark compact objects simultaneously.

Constraints on scalar field parameters are significantly improved.

Abstract

The existence and detection of scalar fields could provide solutions to long-standing puzzles about the nature of dark matter, the dark compact objects at the centre of most galaxies, and other phenomena. Yet, self-interacting scalar fields are very poorly constrained by astronomical observations, leading to great uncertainties in estimates of the mass $m_\phi$ and the self-interacting coupling constant $\lambda$ of these fields. To counter this, we have systematically employed available astronomical observations to develop new constraints, considerably restricting this parameter space. In particular, by exploiting precise observations of stellar dynamics at the centre of our Galaxy and assuming that these dynamics can be explained by a single boson star, we determine an upper limit for the boson star compactness and impose significant limits on the values of the properties of possible scalar fields. Requiring the scalar field particle to follow a collisional dark matter model further narrows these constraints. Most importantly, we find that if a scalar dark matter particle does exist, then it cannot account for both the dark-matter halos and the existence of dark compact objects in galactic nuclei