Either neutralino dark matter or cuspy dark halos

Abstract

We show that if the neutralino in the minimal supersymmetric standard model is the dark matter in our galaxy, there cannot be a dark matter cusp extending to the galactic center. Conversely, if a dark matter cusp extends to the galactic center, the neutralino cannot be the dark matter in our galaxy. We obtain these results considering the synchrotron emission from neutralino annihilations around the black hole at the galactic center.

Figures (3)

• Figure 1: Comparison of the Sgr A$^*$ spectrum with the synchrotron emission from neutralino annihilation in the spike. The figure shows four typical synchrotron spectra: two points in supersymmetric parameter space (thick and thin lines), and two models for the magnetic field (solid and dashed lines). The spectra are normalized to the upper bound at 408 MHz.
• Figure 2: Expected radio emission from the galactic center at 408 MHz from neutralino annihilations in the dark matter spike, assuming a Navarro-Frenk-White profile and (a) a uniform magnetic field of 1 mG, (b) a magnetic field at the equipartition value. All models exceed the present upper bound by several orders of magnitude.
• Figure 3: Upper bound on the inner halo slope $\gamma$ imposed by the constraint on the radio emission from the galactic center at 408 MHz, assuming (a) a uniform magnetic field of 1 mG, and (b) a magnetic field at the equipartition value. Each dot corresponds to a point in supersymmetric parameter space. The results of cold dark matter simulations are much higher than the upper bounds.