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: SDO captures images of two mid-level flares

add to favorites email to friend print save as pdf

Related Stories

Kepler proves it can still find planets

Dec 18, 2014

To paraphrase Mark Twain, the report of the Kepler spacecraft's death was greatly exaggerated. Despite a malfunction that ended its primary mission in May 2013, Kepler is still alive and working. The evidence ...

Staying warm: The hot gas in clusters of galaxies

Nov 28, 2014

Most galaxies lie in clusters, groupings of a few to many thousands of galaxies. Our Milky Way galaxy itself is a member of the "Local Group," a band of about fifty galaxies whose other large member is the ...

WikiGalaxy turns Wikipedia into a galaxy of stars

Dec 10, 2014

Owen Cornec, an engineering student studying in Paris, has released a web browser application called WikiGalaxy that gives using Wikipedia a whole new spin. He's used a star/galaxy based analog as a basis ...

Two spiral galaxies in the process of merging

Dec 12, 2014

At this time of year, there are lots of gatherings often decorated with festive lights. When galaxies get together, there is the chance of a spectacular light show as is the case with NGC 2207 and IC 2163

Recommended for you

SDO captures images of two mid-level flares

Dec 19, 2014

The sun emitted a mid-level flare on Dec. 18, 2014, at 4:58 p.m. EST. NASA's Solar Dynamics Observatory, which watches the sun constantly, captured an image of the event. Solar flares are powerful bursts ...

Why is Venus so horrible?

Dec 19, 2014

Venus sucks. Seriously, it's the worst. The global temperature is as hot as an oven, the atmospheric pressure is 90 times Earth, and it rains sulfuric acid. Every part of the surface of Venus would kill you ...

Image: Christmas wrapping the Sentinel-3A antenna

Dec 19, 2014

The moment a team of technicians, gowned like hospital surgeons, wraps the Sentinel-3A radar altimeter in multilayer insulation to protect it from the temperature extremes found in Earth orbit.

Video: Flying over Becquerel

Dec 19, 2014

This latest release from the camera on ESA's Mars Express is a simulated flight over the Becquerel crater, showing large-scale deposits of sedimentary material.

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.