Could primordial galactic Magnetic Fields be generated by Charged Ultra-Light Boson Dark Matter?

TL;DR

This paper explores whether charged ultra-light boson dark matter halos can generate primordial galactic magnetic fields and reproduce observed rotation curves, providing constraints on the bosons' charge based on observational data.

Contribution

It introduces a model where charged ultra-light bosons produce magnetic fields and galactic rotation curves, constraining the bosons' charge using observational data and classical solutions of the Klein-Gordon-Maxwell system.

Findings

Charged ultra-light boson dark matter can generate microgauss magnetic fields.

The model can reproduce observed galaxy rotation curves.

Charge constraints are set at less than 10^{-13}e to 10^{-14}e.

Abstract

In this work we study the possibility that primordial magnetic fields observed in galaxies could be produced by a dark matter halo made of charged ultra-light bosons. In the model, we assume that ultra-light bosons arise as excitations of a complex scalar field described by the Klein-Gordon equation with local $U(1)$ symmetry which introduces electromagnetic fields that minimally couple to the complex scalar current. We use classical solutions of the Klein-Gordon-Maxwell system to describe the density profile of dark matter and magnetic fields in the galaxies. We consider two cases assuming spherical and dipolar spatial symmetries respectively. For the particular case of the LSB spherical galaxy F563, we test the sensitivity of the predicted rotation curves in the charged scalar field dark matter (cSFDM) model to variations of the electromagnetic coupling and, by using the Fisher matrix error estimator, we set a constraint over that coupling by requiring that theoretical rotation curves lay inside the $1\sigma$ confidence region of observational data . We find that cSFDM haloes are able to generate magnetic fields of the order of $\mu G$ and reproduce the observed rotation curves of F563-V2 at the same time if the ultra-light boson has a charge lower than $\sim 10^{-13}e$ for the monopole-like density profile and lower than $10^{-14}e$ for the dipole-like one.