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Dwarf galaxies are dark matter-dominated and therefore promising targets forthe search for weakly interacting massive particles (WIMPs), which arewell-known candidates for dark matter. Annihilation of WIMPs produceultra-relativistic cosmic-ray electrons and positrons that emit synchrotronradiation in the presence of magnetic fields. For typical magnetic fieldstrengths (few $\mu $G) and $\mathcal O$(GeV--TeV) WIMP masses, this emissionpeaks at hundreds of MHz. Here, we use the non-detection of 150-MHz radiocontinuum emission from the dwarf spheroidal galaxy Canes Venatici I with theLOw-Frequency ARray (LOFAR) to derive constraints on the annihilation crosssection of WIMPs into primary electron-positron and other fundamentalparticle-antiparticle pairs. Our main underlying assumption is that thetransport of the cosmic rays can be described by the diffusion approximation,thus requiring a non-zero magnetic field strength with small-scale structure.In particular, by adopting magnetic field strengths of $\mathcal O(1\,\mu$G)and diffusion coefficients $\sim 10^{27}~\rm cm^2\,s^{-1}$, we obtain limitsthat are comparable with those set by \emph{Fermi} Large Area Telescope usinggamma-ray observations of this particular galaxy. Assuming s-wave annihilationand WIMPs making up 100 per cent of the DM density, our benchmark limitsexclude several thermal WIMP realisations in the $[2,20]$-GeV mass range. Wecaution, however, that our limits for the cross section are subject to enormousuncertainties which we also quantitatively assess. In particular, variations onthe propagation parameters or on the DM halo can shift our limits up by severalorders of magnitude (in the pessimistic scenario).

Radio constraints on dark matter annihilation in Canes Venatici I with LOFAR