Dark Matter a Dark Horse

 

citation -- https://phys.org/news/2020-08-dark-destruction-extra-galaxy-center.html?

Study rules out dark matter destruction as origin of extra radiation in galaxy center

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"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 postdoctoral scholar in physics and astronomy at the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo whose visit to UCI in 2017 initiated this project. "We took over three years to pull all of these new, better models together and examine the emissions, finding that there is little room left for dark matter."

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The group tested all classes of models used in the Galactic Center region for excess emission analyses, and its conclusions remained unchanged. "One would have to craft a diffuse emission model that leaves a big 'hole' in them to relax our constraints, and science doesn't work that way," Macias said.

Kaplinghat noted that physicists have predicted that radiation from dark matter annihilation would be represented in a neat spherical or elliptical shape emanating from the Galactic Center, but the gamma ray excess detected by the Fermi space telescope after its June 2008 deployment shows up as a triaxial, bar-like structure.

"If you peer at the Galactic Center, you see that the stars are distributed in a boxy way," he said. "There's a disk of stars, and right in the center, there's a bulge that's about 10 degrees on the sky, and it's actually a very specific shape—sort of an asymmetric box—and this shape leaves very little room for additional dark matter."

Does this research rule out the existence of dark matter in the galaxy? "No," Kaplinghat said. "Our study constrains the kind of particle that dark matter could be. The multiple lines of evidence for dark matter in the galaxy are robust and unaffected by our work."

Far from considering the team's findings to be discouraging, Abazajian said they should encourage physicists to focus on concepts other than the most popular ones.

"There are a lot of alternative dark matter candidates out there," he said. "The search is going to be more like a fishing expedition where you don't already know where the fish are."