Weakly interacting massive particles (WIMPs) are one of the current best Dark Matter candidates. WIMPs can self-annihilate and thus provide us with the possibility for an indirect detection. Dwarf spheroidal (dSph) galaxies are excellent places to search for annihilation signals because they are rich in Dark Matter and background emission is low. If microGauss magnetic fields in dSph exist, the particles produced in DM annihilation emit synchrotron radiation in the radio band.
I will talk about how we use the non-detection of 150 MHz radio continuum emission from dSph galaxies with the LOw Frequency ARray (LOFAR) to derive constraints on the annihilation cross-section of WIMPs into electron-positron pairs. Our limits will be compared to limits set by Fermi-LAT using gamma-ray observations of dwarf galaxies. I will also discuss the potentially high uncertainty of radio limits due to the assumptions on the average magnetic field and diffusion coefficient in dSph.
