“Two recent studies by teams in the U.S. and the Netherlands have shown that the gamma-ray excess at the galactic center is speckled, not smooth as we would expect for a dark matter signal. Those results suggest the speckles may be due to point sources that we can’t see as individual sources…” -Eric Charles
When NASA’s Fermi satellite began operations, it didn’t take long before we had constructed the most accurate, comprehensive gamma ray map of the galaxy. While many outstanding astrophysics findings ensued, including the discovery of many new pulsars, there was one particular mystery that came about as well: an unexplained excess of gamma rays from the galactic center. Many possible explanations emerged, but one gathered a disproportionately large and exciting amount of attention: that of dark matter annihilations.
According to models and simulations, all galaxies should be embedded in dark matter halos, whose densities peak at the galactic centers. However, unless the dark matter obeys very particular models and exhibits specific properties, it will be difficult to account for a gamma ray excess with dark matter. Image credit: NASA, ESA, and T. Brown and J. Tumlinson (STScI).
In some models of dark matter, it’s a particle that’s ...