Speaker
Description
Galactic magnetic fields with strengths of order microgauss and coherence lengths of kiloparsecs have been observed in galaxies. These fields tend to follow the interarm regions of spiral galaxies, but their origin remains an open question. In this work, we investigate the possibility that the large-scale magnetic fields observed in galaxies arise naturally from a complex Scalar Field Dark Matter (SFDM) halo charged under a local $U(1)$ symmetry. The scalar field is minimally coupled to a gauge field $B_\mu$, with a charge $q\sim 10^{-45}e$. Treating the gauge field as a perturbation, we study the evolution of density perturbations in an expanding Universe. We show that the presence of the gauge field does not significantly modify the distribution of the multistate SFDM halo. We derive analytical expressions for the temporal and spatial components of the gauge field in terms of Bessel functions and use them to calculate the corresponding electric and magnetic fields. We find that the model can naturally generate magnetic fields with strengths of order microgauss, with their magnitude determined by the free parameters of the model. Interestingly, the strength of the resulting galactic magnetic fields increases towards the past.