New Limits on Charged Dark Matter from Large-Scale Coherent Magnetic Fields

Understand

We study the interaction of an electrically charged component of the dark matter with a magnetized galactic interstellar medium (ISM) of (rotating) spiral galaxies.

• For the observed ordered component of the field, $B\sim \mu$G, we find that the accumulated Lorentz interactions between the charged particles and the ISM will extract an order unity fraction of the disk angular momentum over the few Gyr Galactic lifetime unless $q/e \lesssim 10^{-13\pm 1}\,m\,c^2/$ GeV if all the dark matter is charged.
• The bound is weakened by factor $f_{\rm qdm}^{-1/2}$ if only a mass fraction $f_{\rm qdm}\gtrsim0.13$ of the dark matter is charged.
• Here $q$ and $m$ are the dark matter particle mass and charge.