Gamma-ray and synchrotron emission from neutralino annihilation in the Large Magellanic Cloud

Abstract

We calculate the expected flux of gamma-ray and radio emission from the LMC due to neutralino annihilation. Using rotation curve data to probe the density profile and assuming a minimum disk, we describe the dark matter halo of the LMC using models predicted by N-body simulations. We consider a range of density profiles including the NFW profile, a modified NFW profile proposed by Hayashi et al.(2003) to account for the effects of tidal stripping, and an isothermal sphere with a core. We find that the gamma-ray flux expected from these models may be detectable by GLAST for a significant part of the neutralino parameter space. The prospects for existing and upcoming Atmospheric Cherenkov Telescopes are less optimistic, as unrealistically long exposures are required for detection. However, the effects of adiabatic compression due to the baryonic component may improve the chances for detection by ACTs. The maximum flux we predict is well below EGRET's measurements and thus EGRET does not constrain the parameter space. The expected synchrotron emission generally lies below the observed radio emission from the LMC in the frequency range of 19.7 to 8550 MHz. As long as <2x 10^-26 cm^3 s^-1 for a neutralino mass of 50 GeV, the observed radio emission is not primarily due to neutralinos and is consistent with the assumption that the main source is cosmic rays. We find that the predicted fluxes, obtained by integrating over the entire LMC, are not very strongly dependent on the inner slope of the halo profile, varying by less than an order of magnitude for the range of profiles we considered.