Giant filament structures give a rare insight into galaxy cluster evolution

Apr 05, 2006
The RGB image of the BIG group
The RGB image of the BIG group. Blue is Halpha Net band, Red is r' band and Green is Halpha on band.

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 Abell1367. 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 Abell1367 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.

Source: Royal Astronomical Society

Explore further: Short, sharp shocks let slip the stories of supernovae

Related Stories

Scientists discover the fluffiest galaxies

May 14, 2015

An international team of researchers led by Pieter van Dokkum at Yale University have used the W. M. Keck Observatory to confirm the existence of the most diffuse class of galaxies known in the universe. ...

VLT discovers new kind of globular star cluster

May 13, 2015

Observations with ESO's Very Large Telescope in Chile have discovered a new class of 'dark' globular star clusters around the giant galaxy Centaurus A. These mysterious objects look similar to normal clusters, ...

More evidence that the Milky Way has four spiral arms

May 12, 2015

Astronomers have been arguing over just how many spiral arms our galaxy exhibits. Is the Milky Way a four or two-armed spiral galaxy? Astronomers had often assumed the Milky Way was potentially a four-armed ...

Birth of a radio phoenix

Apr 28, 2015

Abell 1033 is a cluster of over 350 galaxies located about 1.7 billion light-years away. Collisions between galaxies in clusters are common events, and each merger heats and shocks the nearby gas. The rapidly ...

Giant cosmic tsunami wakes up comatose galaxies

Apr 24, 2015

Galaxies are often found in clusters, with many 'red and dead' neighbours that stopped forming stars in the distant past. Now an international team of astronomers, led by Andra Stroe of Leiden Observatory ...

Recommended for you

How bad can solar storms get?

8 hours ago

Our sun regularly pelts the Earth with all kinds of radiation and charged particles. How bad can these solar storms get?

Mars rover's ChemCam instrument gets sharper vision

8 hours ago

NASA's Mars Curiosity Rover's "ChemCam" instrument just got a major capability fix, as Los Alamos National Laboratory scientists uploaded a software repair for the auto-focus system on the instrument.

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.