Updated constraints on dark matter (WIMP) annihilation by radio
  observations of M31
  The present work derived the robust constraints on annihilating 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 DM annihilation were computed in the frame of 2D galactic model
employing GALPROP code adapted specifically for M31. This enabled to refine
various inaccuracies of previous studies on the subject. DM constraints were
obtained for two representative annihilation channels: $\chi\chi \rightarrow
b\bar{b}$ and $\chi\chi \rightarrow \tau^+\tau^-$. A wide variety of radio data
was utilized in the frequency range $\approx$(0.1-10) GHz. As the result the
thermal WIMP lighter than $\approx$ 72 GeV for $b\bar{b}$ channel and $\approx$
39 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 does not exclude the
explanation of the gamma-ray outer halo of M31 and Galactic center excess by
annihilating DM. The thermal WIMP with $m_x \approx 70$ GeV, which explains the
outer halo, would make a significant contribution into the non-thermal radio
flux in M31 nucleus fitting well both the spectrum and morphology. And finally
we questioned the possibility to robustly constrain heavy thermal WIMP with
$m_x > 100$ GeV by radio data on M31 claimed in other studies.
