Searching for Dark Matter with X-ray Observations of Local Dwarf Galaxies

Abstract

A generic feature of weakly interacting massive particle (WIMP) dark matter models is the emission of photons over a broad energy band resulting from the stable yields of dark matter pair annihilation. Inverse Compton scattering off cosmic microwave background photons of energetic electrons and positrons produced in dark matter annihilation is expected to produce significant diffuse X-ray emission. Dwarf galaxies are ideal targets for this type of dark matter search technique, being nearby, dark matter dominated systems free of any astrophysical diffuse X-ray background. In this paper, we present the first systematic study of X-ray observations of local dwarf galaxies aimed at the search for WIMP dark matter. We outline the optimal energy and angular ranges for current telescopes, and analyze the systematic uncertainties connected to electron/positron diffusion. We do not observe any significant X-ray excess, and translate this null result into limits on the mass and pair annihilation cross section for particle dark matter. Our results indicate that X-ray observations of dwarf galaxies currently constrain dark matter models at the same level or even more strongly than gamma-ray observations of the same systems, although at the expenses of introducing additional assumptions and related uncertainties in the modeling of diffusion and energy loss processes. The limits we find constrain portions of the supersymmetric parameter space, particularly if the effect of dark matter substructures is included. Finally, we comment on the role of future X-ray satellites (e.g. Constellation-X, XEUS) and on their complementarity with GLAST and other gamma-ray telescopes in the quest for particle dark matter.

30 pages, 5 figures; accepted for publication in ApJ

References in corpus (17)

• Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Interpretation
• Dark Matter and Collider Phenomenology of Universal Extra Dimensions
• Precise constraints on the dark matter content of Milky Way dwarf galaxies for gamma-ray experiments
• Evidence Of Dark Matter Annihilations In The WMAP Haze
• The Dark Matter Annihilation Signal from Galactic Substructure: Predictions for GLAST
• The Most Dark Matter Dominated Galaxies: Predicted Gamma-ray Signals from the Faintest Milky Way Dwarfs
• The XMM-Newton EPIC Background and the production of Background Blank Sky Event Files
• TeV gamma-rays and the largest masses and annihilation cross sections of neutralino dark matter
• The galactic antiproton spectrum at high energies: background expectation vs. exotic contributions
• Multi-wavelength signals of dark matter annihilations at the Galactic center
• The Role of Antimatter Searches in the Hunt for Supersymmetric Dark Matter
• Hunting the lightest lightest neutralinos
• Antiproton and Positron Signal Enhancement in Dark Matter Mini-Spikes Scenarios
• Constraining Supersymmetric Dark Matter With Synchrotron Measurements
• Prospects For Detecting Dark Matter With GLAST In Light Of The WMAP Haze
• Non-thermal X-rays from the Ophiuchus galaxy cluster and dark matter annihilation
• Direct probes of Dark Matter in the cluster 1ES0657-556 through microwave observations

Cited by in corpus (3)

• Fitting the Gamma-Ray Spectrum from Dark Matter with DMFIT: GLAST and the Galactic Center Region
• Gamma Rays from Clusters and Groups of Galaxies: Cosmic Rays versus Dark Matter
• Non-thermal X-rays from the Ophiuchus galaxy cluster and dark matter annihilation