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The Sciences

Dark Matter: Still Dark.

Cosmic VarianceBy Julianne DalcantonJanuary 17, 2008 4:01 AM

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ESA has just done the first big press release for the Integral gamma-ray telescope, and the big woosh you're hearing is the sound of numerous dark matter models flushing down the toilet. For several years the community has been carefully eyeing an extended, apparently spherical excess of gamma-rays from the center of the galaxy. Theorists have been busy generating crafty models where the excess in gamma-rays comes from the direct annhilation of dark matter particles, or from a decay chain from the dark matter particles themselves. These models were attractive because the shape and extent of the gamma-ray detection was wrong for just about any Galactic source except for the dark matter halo itself. The dark matter halo would produce just the right sort of signal, since it's presumably highly cuspy in the center, leading to high rates of the sorts of interactions which might lead to detectable photons, but only near the center of the galaxy. The halo is also expected to be mostly spherical, as was consistent with the previous observations.

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Well, with the higher resolution of the new Integral telescope, the distribution of gamma-rays looks distinctly disklike and lopsided, which smells much more like a boring old astronomical explanation (where "boring" means something to do with neutron stars and black holes, but still -- no one's expecting the Nobel Prize for this one, yet).

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