Dark Matter constraints from Planck observations of the Galactic polarized synchrotron emission

TL;DR

This paper uses Planck satellite polarization data to set new constraints on dark matter annihilation, showing polarization provides stronger limits than intensity and is competitive with CMB bounds for certain models.

Contribution

First use of synchrotron polarization to constrain dark matter annihilation cross section with Planck data, improving bounds over intensity measurements.

Findings

Polarization constraints are about ten times more restrictive than intensity.

Bounds are comparable to CMB limits for leptophilic dark matter.

Results are robust against uncertainties in electron propagation and magnetic field modeling.

Abstract

Dark Matter (DM) annihilation in our Galaxy may produce a linearly polarized synchrotron signal. We use, for the first time, synchrotron polarization to constrain the DM annihilation cross section by comparing theoretical predictions with the latest polarization maps obtained by the Planck satellite collaboration. We find that synchrotron polarization is typically more constraining than synchrotron intensity by about one order of magnitude, independently of uncertainties in the modeling of electron and positron propagation, or of the Galactic magnetic field. Our bounds compete with Cosmic Microwave Background limits in the case of leptophilic DM.