Warm–hot intergalactic medium

From Wikipedia, the free encyclopedia
Jump to: navigation, search

The warm–hot intergalactic medium (WHIM) refers to a sparse, warm-to-hot (105 to 107 K) plasma that cosmologists believe to exist in the spaces between galaxies and to contain 40–50%[1] of the baryons (that is, 'normal matter' which exists as plasma or as atoms and molecules, in contrast to dark matter) in the universe at the current epoch.[2] Because of the high temperature of the medium, it is more readily observed from the ultraviolet and low energy X-ray emission. This was detected in the 0.4–0.6 keV energy band as of 2010 using the orbiting XMM-Newton observatory. This emission forms 12% ± 5% of the diffuse X-ray background radiation.[3]

Within the WHIM, gas shocks are created as a result of active galactic nuclei, along with the gravitationally-driven processes of merging and accretion. Part of the gravitational energy supplied by these effects is converted into thermal emissions of the matter by collisionless shock heating.[1]

In May 2010 a giant reservoir of WHIM was detected by the Chandra X-ray Observatory lying along the wall shaped structure of galaxies (Sculptor Wall) some 400 million light-years from Earth.[4][5]

References[edit]

  1. ^ a b Bykov, A. M.; Paerels, F. B. S.; Petrosian, V. (February 2008), "Equilibration Processes in the Warm-Hot Intergalactic Medium", Space Science Reviews 134 (1–4): 141–153, arXiv:0801.1008, Bibcode:2008SSRv..134..141B, doi:10.1007/s11214-008-9309-4 
  2. ^ Reimers, D. (2002), "Baryons in the diffuse intergalactic medium", Space Science Reviews 100 (1/4): 89, Bibcode:2002SSRv..100...89R, doi:10.1023/A:1015861926654 
  3. ^ Gupta, Anjali; Galeazzi, M.; Ursino, E. (May 2010), "Detection and Characterization of the Warm-Hot Intergalactic Medium", Bulletin of the American Astronomical Society 41: 908, Bibcode:2010AAS...21631808G 
  4. ^ http://www.space.com/scienceastronomy/chandra-missing-matter-100511.html
  5. ^ http://www.skyandtelescope.com/news/93797364.html

See also[edit]