Anomalous gamma-ray excess emissions

Several theories have been proposed for this "Galactic centre excess". They include self-annihilation of dark-matter particles, an unresolved population of millisecond pulsars, an unresolved population of young pulsars, or a series of burst events.

Here, we report on an analysis that exploits hydrodynamical modelling to register the position of interstellar gas associated with diffuse Galactic gamma-ray emission. We find evidence that the Galactic centre excess gamma rays are statistically better described by the stellar over-density in the Galactic bulge and the nuclear stellar bulge, rather than a spherical excess. Given its non-spherical nature, we argue that the Galactic centre excess is not a dark-matter phenomenon but rather associated with the stellar population of the Galactic bulge and the nuclear bulge.