Detecting dark matter WIMPs in the Draco dwarf: A multiwavelength perspective

Abstract

We explore the possible signatures of dark matter pair annihilations in the nearby dwarf spheroidal galaxy Draco. After investigating the mass models for Draco in the light of available observational data, we carefully model the dark matter density profile, taking advantage of numerical simulations of hierarchical structure formation. We then analyze the gamma-ray and electron/positron yield expected for weakly interacting dark matter particle (WIMP) models, including an accurate treatment of the propagation of the charged particle species. We show that unlike in larger dark matter structures—such as galaxy clusters—spatial diffusion plays here an important role. While Draco would appear as a pointlike gamma-ray source, synchrotron emission from electrons and positrons produced by WIMP annihilations features a spatially extended structure. Depending upon the cosmic ray propagation setup and the size of the magnetic fields, the search for a diffuse radio emission from Draco can be a more sensitive indirect dark matter search probe than gamma rays. Finally, we show that available data are consistent with the presence of a black hole at the center of Draco: if this is indeed the case, very significant enhancements of the rates for gamma rays and other emissions related to dark matter annihilations are expected.