A&A press release: XMM-Newton discovers part of the missing matter in the Universe (7 May 2008)
- Published on 06 May 2008
A&A press release
Released on May 7th, 2008
XMM-Newton discovers part of the missing matter in the Universe
“Detection of hot gas in the filament connecting the clusters of galaxies Abell 222 and Abell 223”, by Werner et al.
Published in Astronomy & Astrophysics Letters, 2008, vol. 482-3, pp. L29
A team of Dutch and German astronomers have
discovered part of the missing matter in the Universe using the
European X-ray satellite XMM-Newton. They observed a filament of hot
gas connecting two clusters of galaxies. This tenuous hot gas could be
part of the missing “baryonic” matter. Their
findings are being published in Astronomy &
Astronomy & Astrophysics is publishing the discovery by Dutch and German astronomers  of a filament of tenuous hot gas connecting two clusters of galaxies. The existence of this hot gas (with a temperature of 100 000 - 10 000 000 degrees), known as a warm-hot intergalactic medium, was predicted 10 years ago as a possible source for the missing dark matter. Gas at such high temperature and low density is very difficult to detect and many attempts have failed in past years. The team observed a pair of clusters of galaxies (Abell 222 and Abell 223) using the European X-ray satellite XMM-Newton. Their observations (see Fig. 1) clearly show a bridge connecting both clusters. The gas they observed there is probably the hottest and densest part of the diffuse gas in the cosmic web, which would be part of the missing “baryonic” dark matter.
Most of the matter and energy in the Universe is of unknown nature, so they are called “dark matter” and “dark energy”. Dark energy accounts for 72% of the total energy in the Universe, while some 23% of the total amount of matter/energy is made of this so-called “dark matter”, which is composed of heavy particles still waiting to be discovered by particle physicists. The remaining 5% of the Universe is made of ordinary matter, the one we know on Earth that constitutes stars and planets. It consists of protons and neutrons – called baryons – and of electrons, all the building blocks of the atoms. But part of this 5% of “baryonic” matter is also missing. Stars, galaxies, and gas that astronomers observed in the Universe account for less than half of the baryonic matter.
Fig. 1 - Composite optical/X-ray image of two clusters of galaxies Abell 222 and Abell 223. The two clusters are connected by a filament of hot, low-density gas. The optical image was obtained by SuprimeCam at the Subaru telescope, and the X-ray image showing the distribution of the diffuse hot gas (yellow to red) was obtained by XMM-Newton. Image processing by Jörg Dietrich, Norbert Werner, and Alexis Finoguenov.
 The team of astronomers includes N. Werner (SRON, Netherlands), A. Finoguenov, A. Simionescu, H. Böhringer (MPI, Germany), J. S. Kaastra (SRON and Utrecht University, Netherlands), J. P. Dietrich (ESO, Germany), J. Vink (Utrecht University, Netherlands).
 A movie with a flight through a cosmic web is available at http://www.mpa-garching.mpg.de/galform/data_vis/index.shtml#flying_filament.
of hot gas in the filament connecting the clusters of galaxies Abell
222 and Abell 223
by N. Werner, A. Finoguenov, J. S. Kaastra, A. Simionescu, J. P. Dietrich, J. Vink, H. Böhringer
Astronomy & Astrophysics Letters, 2008, volume 482-3, pp. L29. Full article available in PDF format
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