Survey Reveals Building Block Process For Biggest Galaxies

Apr 12, 2006

A new study of the universe's most massive galaxy clusters shows how mergers play a critical role in their evolution. Astronomers used the twin Gemini Observatory instruments in Hawaii and Chile, and the Hubble Space Telescope to study populations of stars in the universe's most massive galaxy clusters over a range of epochs - the earliest being nearly 7 billion years old, or half the age of the universe.

The team used the Hubble images to map the light distribution of the galaxies in the cluster. Data from the Gemini Multi-Object Spectrograph allowed the team to analyze the light from galaxies to determine their masses, ages and chemical compositions.

"We still don't have a clear picture of how galaxies develop over the history of the Universe, said team leader Jordi Barr of Oxford University. "The strength of this study is that we are able to look at galaxy clusters over a range of epochs."

Barr presented some of the first results of the Gemini/HST Galaxy Cluster Project at a meeting of the Royal Astronomical.

Galaxy clusters contain the most massive galaxies in the universe, but until recently astronomers thought all galaxies in the centers of clusters formed rapidly and then aged without any further changes to their structure in a process known as passive evolution. Results from the Gemini/HST Galaxy Cluster Project show this cannot be the case.

"When we're looking at the most distant galaxy clusters, we are looking back in time to clusters that are in early stages of their formation," Barr said. "The young galaxies in distant clusters appear to be very different from those in the mature clusters that we see in the local Universe."

Barr said his team discovered that the earliest galaxy clusters display a huge variation in their abundances of elements such as oxygen and magnesium, while the chemistry of galaxies in the sample of closer clusters appears to be much more homogenous.

"This difference in chemistry proves that the clusters must actively change over time," Barr said. "If the galaxies in the old clusters have acquired a complete set of elements, it's most likely that they have formed from the mergers of several young galaxies."

The team found star formation is most dependent on galactic mass, and in lower-mass galaxies star formation continues longer. The most massive galaxies in clusters appear to have formed all their stars by the time the universe is just over 1 billion years old, while lower-mass galaxies finish forming their stars some 4 billion years later.

"We see the effects of star-formation in low-mass galaxies, but are unsure about why it's happening," Barr said. "It's possible that star-formation can be shut down very rapidly in dense environments and that the lower-mass galaxies are recent arrivals that are forming stars over a longer period outside the cluster, then falling in - but we are still speculating."

The observations of merging galaxy clusters showed a large proportion of the galaxies in those clusters have undergone recent bursts of star formation. This indicates star formation may be triggered if galaxies are thrown, during the course of a merger, into contact with the gaseous medium pervading the cluster.

The team plans more observations at X-ray wavelengths to study the interactions between galaxies and the distribution and temperature of the surrounding gas.

Copyright 2006 by Space Daily, Distributed United Press International

Explore further: What's the brightest star in the sky, past and future?

add to favorites email to friend print save as pdf

Related Stories

The controversy over interstellar messaging

Feb 20, 2015

Should we beam messages into deep space, announcing our presence to any extraterrestrial civilizations that might be out there? Or, should we just listen? Since the beginnings of the modern Search for Extraterrestrial ...

Why does the Milky Way rotate?

Feb 11, 2015

We live in a galaxy that is called the Milky Way. It's called a barred spiral galaxy, which means that it has a spiral shape with a bar of stars across its middle. The galaxy is rather huge—at least 100,000 ...

Image: Smile, and the universe smiles with you

Feb 11, 2015

An upbeat-looking galaxy cluster appears to smile at us in a newly released image from the NASA/ESA Hubble Space Telescope. The cluster - designated as SDSS J1038+4849 - appears to have two eyes and a nose ...

Dark matter guides growth of supermassive black holes

Feb 18, 2015

Every massive galaxy has a black hole at its center, and the heftier the galaxy, the bigger its black hole. But why are the two related? After all, the black hole is millions of times smaller and less massive ...

Recommended for you

Could the Milky Way become a quasar?

Feb 27, 2015

A quasar is what you get when a supermassive black hole is actively feeding on material at the core of a galaxy. The region around the black hole gets really hot and blasts out radiation that we can see billions ...

Galactic dinosaurs not extinct

Feb 27, 2015

One of the biggest mysteries in galaxy evolution is the fate of the compact massive galaxies that roamed the early Universe.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

JukriS
1 / 5 (1) Jul 12, 2009
Galaxies are huge particles who move in space who dont expanding.

All galaxies energy moving very fast before our stuff and time born.

Today galaxies move almost same direction, but young Universe time, galaxies moving more other direction.

All visible Universe galaxies move far away from one point, who is far away outside visible Universe.

One moment all visible Universe energy move out this space where we are now and next moment out that space where we just moved etc.

Nucleus of atoms expanding/exploding all a time and emit/radiate waves of energy who have a nature of electrons and particle who also expanding/exploding and emit/radiate waves of energy etc......

http://www.onesim....com/296

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.