Dark matter annihilation energy output and its effects on the high-z IGM

ARAYA, IGNACIO J.; PADILLA, NELSON D.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2014 vol. 445 p. 850 - 868

0035-8711

We study the case of dark matter (DM) self-annihilation, in order to assess its importance as an energy injection mechanism, to the intergalactic medium (IGM) in general, and to the medium within particular DM haloes. We consider thermal relic WIMP (weakly interacting massive particle) particles with masses of 10GeV and 1 TeV, and we analyse in detail the clustering properties of DM in a cold dark matter cosmology, on all hierarchy levels, from haloes and their mass function, to subhaloes and the DM density profiles within them, considering adiabatic contraction by the presence of a supermassive black hole. We then compute the corresponding energy output, concluding thatDMannihilation does not constitute an important feedback mechanism. We also calculate the effects that DM annihilation has on the IGM temperature and ionization fraction, and we find that assuming maximal energy absorption, at z ~ 10, for the case of a 1 TeV WIMP, the ionization fraction could be raised to 6 × 10-4 and the temperature to 10K, and in the case of a 10 GeV WIMP, the IGM temperature could be raised to 200K and the ionization fraction to 8 × 10-3. We conclude that DM annihilations cannot be regarded as an alternative reionization scenario. Regarding the detectability of the WIMP through the modifications to the 21 cm differential brightness temperature signal (δTb), we conclude that a thermal relic WIMP with mass of 1 TeV is not likely to be detected from the global signal alone, except perhaps at the 1-3mK level in the frequency range 30 < ν < 35MHz corresponding to 40 < z < 46. However, a 10 GeV mass WIMP may be detectable at the 1-3mK level in the frequency range 55 < ν < 119MHz corresponding to 11