A new research paper co-authored by Prof. Shunsaku Horiuchi and appearing in the journal Physical Review D has strongly ruled out the possibility that dark matter physics is behind a mysterious excess of gamma rays from the center of the Milky Way galaxy.

The mysterious gamma-ray signal was detected more than a decade ago by NASA's Fermi Gamma Ray Space Telescope, which convinced some physicists that they were seeing evidence of the annihilation of dark matter particles. However, many sources of gamma rays crowd the field, from star-formation activity to high-energy outflows and pulsars. "We looked at all of the different modeling that goes on in the Galactic Center, including molecular gas, stellar emissions and high-energy electrons that scatter low-energy photons," said co-author Oscar Macias, a former postdoctoral scholar at Virginia Tech's Center for Neutrino Physics and now joint postdoctoral researcher at the University of Tokyo and the University of Amsterdam. Horiuchi explained that especially crucial was the distribution of stars which is shaped like a bar in the Galactic Center, rather than symmetric as expected from dark matter. By including these in the analysis, the authors were able to strongly exclude the dark matter explanation, and set the strongest constraints yet on the properties of the most popularly theorized models of dark matter.

The Milky Way Galaxy seen over the Virgina Tech Campus. The center of the Milky Way is the source of an excess of high energy gamma rays that may have been evidence of dark matter, a hypothesis now debunked by Prof. Horiuchi and his collaborators.

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