Elmo Tempel, Andi Hektor, Martti Raidal
We analyze publicly available Fermi-LAT high-energy gamma-ray data and confirm the existence of clear spectral feature peaked at $E_\gamma= 130$ GeV. Scanning over the Galaxy we identify several disconnected regions where the observed excess originates from. Our best optimized fit is obtained for the central region of Galaxy with a clear peak at 130 GeV with statistical significance $4.5\sigma ,$ while for the other regions the peak significances vary between $3.2\sigma$ and $1.6\sigma.$ The observed excess is not correlated with Fermi bubbles. We compute the photon spectra induced by dark matter annihilations into two and four standard model particles, the latter via two light intermediate states, and fit the spectra with data. Since our fits indicate sharper and higher signal peak than in the previous works, data disfavours all but the dark matter direct two-body annihilation channels into photons. Due to the final state radiation our fits prefer dark matter mass 145 GeV for the $\gamma\gamma$ channel. We obtain large gamma-ray fluxes from Galactic centre that imply large annihilation cross-sections of order thermal freeze-out cross-section, if the Einasto halo profile correctly predicts the central cusp. If the observed gamma-ray excess comes from dark matter annihilations, we have identified the most dense dark matter sub-structures of our Galaxy. The large dark matter two-body annihilation cross-section to photons may signal a new resonance that should be searched for at the CERN LHC experiments.
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http://arxiv.org/abs/1205.1045
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