Dark matter and the CACTUS gamma-ray excess from Draco
The CACTUS atmospheric Cherenkov telescope collaboration recently reported a gamma-ray excess from the Draco dwarf spheroidal galaxy. Draco features a very low gas content and a large mass-to-light ratio, suggesting as a possible explanation annihilation of weakly interacting massive particles (WIMPs) in the Draco dark-matter halo. We show that with improved angular resolution, future measurements can determine whether the halo is cored or cuspy, as well as its scale radius. We find the relevant WIMP masses and annihilation cross sections and show that supersymmetric models can account for the required gamma-ray flux. The annihilation cross section range is found to be not compatible with a standard thermal relic dark-matter production. We compute for these supersymmetric models the resulting Draco gamma-ray flux in the GLAST energy range and the rates for direct neutralino detection and for the flux of neutrinos from neutralino annihilation in the Sun. We also discuss the possibility that the bulk of the signal detected by CACTUS comes from direct WIMP annihilation to two photons and point out that a decaying-dark-matter scenario for Draco is not compatible with the gamma-ray flux from the Galactic centre and in the diffuse gamma-ray background.
Additional Information© Institute of Physics and IOP Publishing Limited 2006. Received 17 January 2006; Accepted 16 February 2006; Published 6 March 2006 We would like to thank Max Chertok, Francesc Ferrer, Jeter Hall, Reshmi Mukherjee, Mani Tripathi, and Piero Ullio for helpful discussions. This work was supported in part by DoE DE-FG03-92-ER40701 and FG02-05ER41361 and NASA NNG05GF69G. ArXiv ePrint: astro-ph/0601249
Published - PROjcap06.pdf