Ignacio J. Araya, Nelson D. Padilla
We study the case of DM self annihilation, in order to asses its importance as an energy injection mechanism, to the IGM in general, and to the medium within particular DM haloes. We consider two well motivated WIMP candidates, the SUSY neutralino and the first KK excited state of the B electroweak boson. We explicitly compute the energy output (or luminosity) of DM haloes due to annihilations, and compare the obtained luminosities with the standard AGN feedback process, concluding that DM annihilation does not provide the necessary output as to constitute an important feedback mechanism. We then compute the energy injection rate per baryon of annihilations on the IGM, in order to calculate the effects that it has on its temperature and ionization fraction. We find significant deviations in the evolutions of the temperature and ionization fraction of the IGM, in scenarios that take into account the clustering of DM at all levels, such that a 1TeV WIMP may, for example, maintain the temperature of the IGM on the ~100K level, or contribute to the ionization fraction maintaining it in a value of ~10^(-2) (not considering POPIII stars). We conclude that although the DM annihilation can have a significant impact on the properties of the IGM, it 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 (?Tb), we conclude that, considering the adiabatic compression and the substructure, and assuming a maximal absorption fraction of fabs = 1, a 1TeV WIMP with thermal relic cross section may be detected with a peak signal of ~18mK at a redshift of ~50, corresponding to a frequency of 30MHz.
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http://arxiv.org/abs/1302.5462
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