Spatial Tests of Dark Matter

Dark matter constitutes roughly one quarter of the energy density of the Universe, but its composition remains unknown. Indirect searches aim to determine the presence and nature of dark matter by detecting photons produced when it decays or annihilates. Recent observations of a spectral line at 3.5 kilo-electron-volts from certain galaxy clusters and of a gamma-ray excess from the Galactic Center have been interpreted as possible dark matter signatures. However, more mundane origins of the signals, e.g., pulsars or emission from potassium atoms, have not yet been ruled out. Now, a research group led by Peter Graham at Stanford University, California, has proposed that high-spatial-resolution observations of the sky could provide a “smoking gun” for decaying dark matter.