“Gamma Rays from the Milky Way’s Galactic Center –Evidence of Dark Matter”

 

           Gamhalo_egret

 

Gamma-ray photons seen emanating from the center of the Milky Way galaxy are consistent with the intriguing possibility that dark-matter particles are annihilating each other in space, according to research conducted by  UC Irvine astrophysicists. 


Analyzing data collected between August 2008 and June 2012 from NASA’s Fermi Gamma-ray Space Telescope orbiting Earth, the team found more gamma-ray photons coming from the Milky Way galactic center than they had expected, based on previous scientific models. Gamma-rays are electromagnetic radiation emitted during radioactive decay or other high-energy particle processes.

“This is the first time this new source has been observed with such high statistical significance, and the most striking part is how the shape, spectrum and rate of the observed gamma rays are very consistent with the leading theories for dark matter,” said Kevork Abazajian, assistant professorof the Department of Physics & Astronomy. “Future observations of regions with less astrophysical emission, such as dwarf galaxies, will be able to conclusively determine if this is actually from the dark matter.”

Nonluminous and not directly detectable, dark matter is thought to account for 85 percent of the universe’s mass. Its existence can only be inferred from its gravitational effects on other, visible matter. The UCI researchers’ findings could support its presumed presence at the center of galaxies.

The prevailing hypothesis is that dark matter is composed of weakly interacting massive particles, or WIMPs. When two WIMPs meet, they annihilate each other to produce more familiar particles – including gamma rays.

Although the data interpretation seems to be consistent with dark-matter theory, the gamma rays could be coming from a source other than WIMP destruction, noted Manoj Kaplinghat, associate professor. “The signal we see is also consistent with photons emitted by pulsars,” he said, “or from high-energy particles interacting with gas in the galactic center.”

In this false color all-sky image at the top of the page centered on the Milky Way, the brown and green regions indicate brighter, known sources of gamma-rays. The galactic center and plane clearly standout as do some distant galaxies seen near the top and bottom of the picture. The dim, blue regions above and below the plane correspond to our Galaxy's unexpected gamma-ray halo. 

The Daily Galaxy via http://today.uci.edu

Image credit: D. Dixon (UCR), D. Hartmann (Clemson), E. Kolaczyk (U. Chicago), NASA

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