2016 Volume 71 Issue 9 Pages 617-622
About 25% of energy density of the universe today is in the form of non-baryonic cold dark matter, and Weakly Interacting Massive Particles (WIMPs) are one of the most promising candidates. Annihilation of WIMPs could produce detectable gamma-ray signal depending on their mass and number density. The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope is sensitive to GeV gamma rays and is suitable for indirect search of WIMP signals. Recent studies of gamma rays in the direction of Galactic center reveal an extended excess emission in 1–10 GeV energies over the standard Galactic diffuse gamma-ray emission. Although the excess can be explained by annihilation of WIMPs with the mass of a few 10s GeV, the spectrum is strongly affected by the uncertainty of the Galactic diffuse emission. No significant gamma-ray excess was found coincident with known dwarf spheroidal galaxies which are known to be dark matter rich and lack of non-thermal astrophysical processes. Instead, WIMP mass less than 100 GeV are excluded by 95% confidence. If the most of the Galactic center excess is not due to WIMP annihilation, more observations by Fermi-LAT with future observations in TeV gamma rays by Cherenkov Telescope Array, will enable us to search for WIMP signal of mass range from 10 GeV up to a few TeV.