Updated constraints on WIMP dark matter annihilation by radio observations of M31

The present work derived the robust constraints on annihilating weakly interacting massive particle (WIMP) parameters utilizing new radio observations of M31 as well as new studies of its dark matter distribution and other properties. The characteristics of emission due to dark matter (DM) annihilation were computed in the frame of a 2D galactic model employing GALPROP code adapted specifically for M31. This enabled us to refine various inaccuracies of previous studies on the subject. DM constraints were obtained for two representative annihilation channels: chi chi -> b (b) over bar and chi chi -> tau(+)tau(-). A wide variety of radio data was utilized in the frequency range approximate to(0.1-10)GHz. As the result, the thermal WIMP lighter than fiducially approximate to 70 GeV for b (b) over bar channel and approximate to 40 GeV for tau(+)tau(-) was excluded. The corresponding mass threshold uncertainty ranges were estimated to be 20-210 GeV and 18-89 GeV. The obtained exclusions are competitive to those from Fermi-LAT observations of dwarfs and AMS-02 measurements of antiprotons. Our constraints do not exclude the explanation of the gamma-ray outer halo of M31 and the Galactic Center excess by annihilating DM. The thermal WIMP with m(x) approximate to 70 GeV, which explains the outer halo, would make a significant contribution to the nonthermal radio flux in M31 nucleus, fitting well both the spectrum and morphology. And, finally, we questioned the possibility claimed in other studies to robustly constrain heavy thermal WIMP with m(x) > 100 GeV by radio data on M31.

Automated summary

This study derived robust constraints on annihilating weakly interacting massive particle (WIMP) parameters based on new radio observations and dark matter distribution studies of M31. The obtained constraints exclude thermal WIMPs with lighter masses for specific annihilation channels and provide competitive results compared to other observations. The study also suggests that the explanation of the gamma-ray outer halo of M31 and the Galactic Center excess by annihilating dark matter is not excluded. The results indicate that a thermal WIMP with a mass of approximately 70 GeV could contribute significantly to nonthermal radio flux in M31 nucleus.