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Giant filament structures give rare insight into galaxy clusterevolution (Forwarded)



 
 
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Old April 6th 06, 04:52 PM posted to sci.space.news
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Default Giant filament structures give rare insight into galaxy clusterevolution (Forwarded)

ROYAL ASTRONOMICAL SOCIETY PRESS INFORMATION NOTE

Issued by RAS Communications Officers:

Anita Heward
Tel: +44 (0)1483-420904
AND
Peter Bond
Tel: +44 (0)1483-268672 Fax: +44 (0)1483-274047

National Astronomy Meeting Press Room (4 - 7 April only):
Tel: +44 (0)116-229-7474 or 229-7475 or 252-3312 or 252-3531
Fax: +44 (0)116-252-3531

RAS Web site:
http://www.ras.org.uk/

RAS National Astronomy Meeting web site:
http://www.nam2006.le.ac.uk/index.shtml

CONTACT DETAILS ARE LISTED AT THE END OF THIS RELEASE.

EMBARGOED FOR 00:01 BST, WEDNESDAY, 5 APRIL 2006

Ref.: PN 06/20 (NAM13)

GIANT FILAMENT STRUCTURES GIVE RARE INSIGHT INTO GALAXY CLUSTER
EVOLUTION

A new image of the centre of a cluster of galaxies has revealed
massive filamentary structures that give a rare insight into
the evolution of galaxy clusters.

"The star forming regions in the cluster that we'd observed
previously were just the tip of the iceberg. We've now observed
filaments of gas streaming out from these regions that are
approximately 490 thousand light years across. The gaseous
trails mark the path of galaxies travelling at high speed through
the cluster. The origin of these unique features is still a
matter for debate, but we think the combined action of tidal
forces among galaxies in the cluster and of ram-pressure by the
ambient medium caused the galaxies to fragment and blast out the
ionized gas," said Dr Luca Cortese, who is presenting the results
at the Royal Astronomical Society's National Astronomy Meeting on
5th April.

An international team, lead by Dr Cortese, studied the physical
properties of a compact group that is falling towards the centre
of a cluster of galaxies known as Abell1367 at a rate of 1700 km/s.
The group, which was discovered in 2002, has the highest density
of star forming objects ever observed in local clusters. It
contains two giant galaxies, at least ten dwarf galaxies or
extragalactic clouds of gas and over a billion solar masses of
diffuse gas filaments.

Scientists believe that clusters of galaxies are formed from the
accretion of compact groups like the one observed in Abell 1367.
Formation of clusters of galaxies peaked 5 billion years ago. Now
the rate is at least three times lower and it will slow dramatically
due to the effects of the acceleration of the Universe. The Abell
1367 group is particularly important as it is only 300 million light
years from Earth -- 'local' in terms of the Universe -- and so the
scientists can see the processes at work in unprecedented detail. Dr
Cortese explains, "The physical processes seen here are typical of
young clusters, found far away in space and a long time ago. To
really understand what's going on, we need a close up view. This is
the first time we have found an example of a galaxy group mid-way
through its transformation that is close enough for us to have a
really good look at the structures surrounding the galaxies."

The results suggest that at least part of the changes to the
structure of cluster galaxies that took place in earlier epochs
happened very differently to ones observed in today's clusters. In
today's clusters of galaxies, the galaxies are travelling faster
than in the infalling groups, which means that gravitational
interactions between galaxies happen much faster.

The study was carried out using the Italian National Telescope
Galileo in La Palma in April 2004 and February 2006.

The results of this study are accepted for publication on Astronomy
and Astrophysics

IMAGES

For images of the filament structures, see:
http://goldmine.mib.infn.it/papers/preprocessing.html

FURTHER INFORMATION

This study has been undertaken in collaboration with:

Prof. Giuseppe Gavazzi
Universita' degli Studi di Milano-Bicocca, Italy

Dott. Alessandro Boselli
Laboratoire d'Astrophysique de Marseille, France

Dott. Paolo Franzetti
IASF-INAF Milano, Italy

Prof. Robert Kennicutt
Institute of Astronomy, Cambridge, UK

Dott. Karen O'Neil
NRAO, USA

Dott. Shoko Sakai
UCLA, USA

Telescopio Nazionale Galileo (TNG)

The Telescopio Nazionale Galileo (TNG), with a primary mirror of
3.58m, is the national facility of the Italian astronomical
community. It is located at Roque de Los Muchachos Observatory on
La Palma, Canary Islands, and is operated by the Italian National
Institute of Astrophysics (INAF).

TNG is equipped with 5 instruments which are permanently operating
on its foci and offer a large variety of observing modes covering
the optical and near infrared wavelength ranges and spanning from
broad band imaging to high resolution spectroscopy.

For more information, visit:
http://www.tng.iac.es/info/whatstng.html

NOTES FOR EDITORS

Royal Astronomical Society's National Astronomy Meeting

The 2006 RAS National Astronomy Meeting is hosted by the University
of Leicester. It is sponsored by the Royal Astronomical Society,
the UK Particle Physics and Astronomy Research Council (PPARC), the
University of Leicester and the National Space Centre, Leicester.

CONTACTS

Dr Luca Cortese
School of Physics and Astronomy
Cardiff University
5, The Parade
Cardiff CF24 3YB
Tel. +44 (0)2920876992
Fax. +44 (0)2920874056

From Wednesday 5th until Thursday 6th April, Dr Cortese can be
contacted via the NAM press office (see above).


 




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