Universe  ID: 10943

Fermi Observations of Dwarf Galaxies Provide New Insights on Dark Matter

There's more to the cosmos than meets the eye. About 80 percent of the matter in the universe is invisible to telescopes, yet its gravitational influence is manifest in the orbital speeds of stars around galaxies and in the motions of clusters of galaxies. Yet, despite decades of effort, no one knows what this "dark matter" really is. Many scientists think it's likely that the mystery will be solved with the discovery of new kinds of subatomic particles, types necessarily different from those composing atoms of the ordinary matter all around us. The search to detect and identify these particles is underway in experiments both around the globe and above it.

Scientists working with data from NASA's Fermi Gamma-ray Space Telescope have looked for signals from some of these hypothetical particles by zeroing in on 10 small, faint galaxies that orbit our own. Although no signals have been detected, a novel analysis technique applied to two years of data from the observatory's Large Area Telescope (LAT) has essentially eliminated these particle candidates for the first time.

WIMPs, or Weakly Interacting Massive Particles, represent a favored class of dark matter candidates. Some WIMPs may mutually annihilate when pairs of them interact, a process expected to produce gamma rays — the most energetic form of light — that the LAT is designed to detect.

The team examined two years of LAT-detected gamma rays with energies in the range from 200 million to 100 billion electron volts (GeV) from 10 of the roughly two dozen dwarf galaxies known to orbit the Milky Way. Instead of analyzing the results for each galaxy separately, the scientists developed a statistical technique — they call it a "joint likelihood analysis" — that evaluates all of the galaxies at once without merging the data together. No gamma-ray signal consistent with the annihilations expected from four different types of commonly considered WIMP particles was found.

For the first time, the results show that WIMP candidates within a specific range of masses and interaction rates cannot be dark matter. A paper detailing these results appeared in the Dec. 9, 2011, issue of Physical Review Letters.

 

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For More Information

http://www.nasa.gov/mission_pages/GLAST/news/dark-matter-insights.html


Credits

Scott Wiessinger (USRA): Lead Animator
Walt Feimer (HTSI): Animator
Donna Cox (AVL NCSA/University of Illinois): Animator
Ralf Kaehler (KIPAC/Standford): Animator
Scott Wiessinger (USRA): Video Editor
Scott Wiessinger (USRA): Narrator
Scott Wiessinger (USRA): Producer
Scott Wiessinger (USRA): Writer
Francis Reddy (Syneren Technologies): Writer
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Mission:
Fermi Gamma-ray Space Telescope

Data Used:
Fermi
Fermi/LAT
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This item is part of these series:
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Goddard TV Tape:
G2012-036 -- Dark Matter Limits

Keywords:
SVS >> Galaxy
SVS >> HDTV
SVS >> Music
SVS >> Neutron Star
SVS >> Satellite
SVS >> Simulation
GCMD >> Earth Science >> Spectral/Engineering >> Gamma Ray
SVS >> Hyperwall
SVS >> Astrophysics
SVS >> Universe
SVS >> Edited Feature
SVS >> Dark Matter
SVS >> Fermi
DLESE >> Narrated
SVS >> Galaxy Cluster
SVS >> Space Science
NASA Science >> Universe

GCMD keywords can be found on the Internet with the following citation: Olsen, L.M., G. Major, K. Shein, J. Scialdone, S. Ritz, T. Stevens, M. Morahan, A. Aleman, R. Vogel, S. Leicester, H. Weir, M. Meaux, S. Grebas, C.Solomon, M. Holland, T. Northcutt, R. A. Restrepo, R. Bilodeau, 2013. NASA/Global Change Master Directory (GCMD) Earth Science Keywords. Version 8.0.0.0.0