Galaxy Clusters Formed Early

February 17, 2005
The most distant galaxy claster known

Only one billion years after the Big Bang, clusters of galaxies were already forming. This discovery pushes back the age of the youngest known galaxy cluster by a third, and shows that the largest astronomical objects in the Universe had already begun to form in one of the earliest epochs of the Universe that astronomers have been able to observe. This work was conducted by researchers from the University of Tokyo, the National Astronomical Observatory of Japan, and elsewhere using the Subaru telescope.

Galaxies often congregate to form clusters of galaxies. At the present day, clusters have tens and hundreds of member galaxies and are the largest astronomical objects in the Universe. Knowing how they formed is a key to understanding the past and future of the Universe.

To study how the Universe has changed over large scales in space and time, it is essential to observe deeply a wide area of the sky. A large number of researchers are now studying the Subaru-XMM Deep Survey Field (SXDS), an approximately one square degree area of the sky in the direction of the constellation Cetus, the Whale, at many wavelengths using several telescopes.

To understand the origin of galaxy clusters, Masami Ouchi, currently at the Space Telescope Science Institute, decided to study how galaxies approximately 12.7 billion light years away (a red shift of 5.7) were distributed in the SXDS. By using the color of galaxies as a guide to their distance, Ouchi and his collaborators found 515 galaxies in a volume 500 million light years in height and width and 100 million light years in depth in images from Subaru's prime focus camera (Suprime-Cam).

Figure 1 shows a density map of the galaxies in this volume as seen on the sky. This map represents the physical structures in the Universe at the farthest distances and the earliest times that astronomers have been able to observe to date. The yellow regions are where there are the highest concentration of galaxies.

In the bottom portion of this map, the researchers found a concentration of galaxies that could not be explained by chance. By obtaining accurate distance estimates to these galaxies using Subaru's Faint Object Camera and Spectrograph (FOCAS), the researchers confirmed that there were six galaxies concentrated in a small volume only 3 million light years in diameter, forming a galaxy cluster. Figure 2 identifies the six member galaxies of the cluster.

The cluster has several properties that reveal its young age. It is one hundred times less massive than present day galaxy clusters and has significantly fewer members. Moreover, its member galaxies are producing stars at one hundred times the rate of galaxies outside the cluster.

Figure2

The infant galaxy cluster existed at a time when the Universe was only one billion years old. The youngest portraits of galaxy clusters that astronomers previously had were from the Universe at an age of one and a half billion years. As any parent would attest, young children change rapidly. The portrait of a galaxy cluster at a younger age fills a significant gap in our knowledge of the early history of the Universe when stars, galaxies, and clusters were first forming.

"The fact that a cluster is already forming so soon after the Big Bang puts strong constraints on the fundamental structure of the Universe", says Ouchi. The prevailing theory of cosmology postulates that smaller mass structures form first and then grow into more massive structures. "Our results seem to contradict the prevailing wisdom, but the real challenge is in understanding how well the distribution of visible matter such as galaxies correlates with the distribution of mass in general. As we continue to fill in the gaps in the early history of clusters, we should be able to resolve such ambiguities", he says.

These results were published in the February 10, 2005, edition of the Astrophysical Journal (ApJ 620, L1-L4) and will be presented at the meeting "The Future of cosmology with clusters of Galaxies" beginning on February 26, 2005, in Waikoloa, Hawaii.

Explore further: Scientists confirm the universe has no direction

Related Stories

Galactic fireworks illuminate monster hydrogen blob

September 21, 2016

An international team of researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) and other telescopes has discovered the power source illuminating a so-called Lyman-alpha Blob – a rare, brightly glowing, ...

Galaxy cluster discovered at record-breaking distance

August 31, 2016

A new record for the most distant galaxy cluster has been set using NASA's Chandra X-ray Observatory and other telescopes. This galaxy cluster may have been caught right after birth, a brief, but important stage of evolution ...

The rise and fall of galaxy formation

August 30, 2016

An international team of astronomers, including Carnegie's Eric Persson, has charted the rise and fall of galaxies over 90 percent of cosmic history. Their work, which includes some of the most sensitive astronomical measurements ...

Dark matter—hot or not?

August 31, 2016

For almost a century, astronomers and cosmologists have postulated that space is filled with an invisible mass known as "dark matter". Accounting for 27% of the mass and energy in the observable universe, the existence of ...

Recommended for you

Photons do the twist, and scientists can now measure it

September 26, 2016

Researchers in the University of Minnesota's College of Science and Engineering have measured the twisting force, or torque, generated by light on a silicon chip. Their work holds promise for applications such as miniaturized ...

Click and declick of amine and thiol coupling reaction

September 26, 2016

(Phys.org)—A group of researchers from the University of Texas have developed a sequential, two-step amine and thiol coupling reaction via click chemistry using a derivative of Meldrum's acid. This reaction is reversible ...

Pulsar discovered in an ultraluminous X-ray source

September 26, 2016

(Phys.org)—A team of European astronomers has discovered a new pulsar in a variable ultraluminous X-ray source (ULX) known as NGC 7793 P13. The newly found object is the third ultraluminous X-ray pulsar detected so far, ...

Yeast knockouts peel back secrets of cell protein function

September 26, 2016

Proteins are the hammers and tongs of life, with fundamental roles in most of what happens in biology. But biologists still don't know what thousands of proteins do, and how their presence or absence affects the cell.

0 comments

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.