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A&A press release
Released on May 7th, 2008
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XMM-Newton discovers part of the missing matter in the Universe
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“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 &
Astrophysics.
Astronomy & Astrophysics is publishing the
discovery by Dutch
and German astronomers [1] 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 newly-detected bridge connecting Abell 222 and Abell 223
would be part of this missing baryonic matter. Matter in the Universe
is distributed in a web-like structure, and clusters of galaxies are
the dense nodes of this cosmic web [2]. For 10 years, astronomers
suspected that the missing baryonic matter is hot gas at very low
density permeating the filamentary structure of the cosmic web. Because
of its low density, detecting this hot gas was a very challenging task.
This discovery was made possible because of the very fortunate geometry
of the two clusters. As seen from the Earth, the filament connecting
the two clusters is aligned along our line-of-sight, so that the entire
emission from the filament is concentrated in a small region of the
sky, thereby making its detection possible. Previous observations, at a
lower sensitivity level, only allowed astronomers to detect
the clusters and some groups of galaxies, the dense knots of
the web. The high-sensitivity level now achieved with in-depth
XMM-Newton observations makes it possible to observe the connecting
wires of the cosmic web. This discovery is a step toward understanding
the distribution of the matter within the large-scale structure of the
Universe.
[1] 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).
[2] 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.
Detection
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
Contacts:
Dr.
Norbert Werner
SRON
Sorbonnelaan 2
3584 CA Utrecht, The Netherlands
Email: N.Werner (at) sron.nl
Phone: +31 30 253 5721
Dr.
Jennifer Martin
Journal Astronomy & Astrophysics
61, avenue de l'Observatoire
75014 Paris, France
Email: aanda.paris (at) obspm.fr
Phone: +33 1 43 29 05 41
© Astronomy
& Astrophysics 2008
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