CONSTRAINING THE DISTRIBUTION OF DARK MATTER IN THE INNER GALAXY WITH AN INDIRECT DETECTION SIGNAL: THE CASE OF A TENTATIVE 130 GeV γ-RAY LINE

Abstract

The dark matter distribution in the very inner region of our Galaxy is still in debate. In the N-body simulations a cuspy dark matter halo density profile is favored. Several dissipative baryonic processes however are found to be able to significantly flatten dark matter distribution and a cored dark matter halo density profile is possible. The baryons dominate the gravitational potential in the inner Galaxy, hence a direct constrain on the abundance of the dark matter particles is rather challenging. Recently, a few groups have identified a tentative 130 GeV line signal in the Galactic center, which could be interpreted as the signal of the dark matter annihilation. With current 130 GeV line data and adopting the generalized Navarro-Frenk-White profile of the dark matter halo, for local dark matter density \rho_0=0.4 GeV cm^{-3} and r_s=20 kpc we obtain a 95% confidence level lower (upper) limit on the inner slope of dark matter density distribution \alpha = 1.06 (the cross section of dark matter annihilation into gamma-rays <\sigma v >_{\chi\chi -> \gamma\gamma}= 1.3\times 10^{-27} cm^3 s^{-1}). Such a slope is consistent with the results of some N-body simulations, and if the signal is due to dark matter, suggests that baryonic processes may be unimportant.