Dark Matter in our Galaxy may produce a linearly polarized synchrotron signal through the secondary emission of electrons and positrons originating, for example, from dark matter annihilations. Using the latest Planck data release, we use for the first time microwave synchrotron polarization to constrain Dark Matter annihilation in the Galaxy.
We demonstrate that polarization is more constraining than synchrotron intensity by about one order of magnitude, independently from uncertainties in the modeling of electron and positron propagation and the model of Galactic magnetic field.
We discuss the extension of these constraints to further exotic electron and positron injections in the Galaxy such as primordial black holes, as well as improvements in the modeling of the background emissions coming from Galactic sources.