Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Most Distant Group of Galaxies Known in the Universe

09.04.2002


New VLT Discovery Pushes Back the Beginnings

Using the ESO Very Large Telescope (VLT), a team of astronomers from The Netherlands, Germany and the USA [1] have discovered the most distant group of galaxies ever seen, about 13.5 billion light-years away.


The Photo shows the sky region near the powerful radio galaxy TN J1338-1942 at a redshift of 4.1 [2], i.e. at a distance of about 13.5 billion light-years from the Earth (we see it as it was when the Universe was just 1.5 billion years old). The photo is a "negative" rendering (the objects are dark on a bright background) of an image obtained with the FORS2 multi-mode instrument on the 8.2-m VLT KUEYEN telescope (ESO Paranal Observatory, Chile) through a narrow-band optical filter, centered at the wavelength of the redshifted Lyman-alpha line. The 20 galaxies that have been confirmed to be emitting the sharp colours due to glowing hydrogen gas at the distance of the radio galaxy are encircled in blue. The green rectangle marks the radio galaxy, from which a stream of hydrogen gas stretches to the northwest, over a distance of about 300,000 light-years. The size of the sky field corresponds to about 10 million light-years at the distance of these galaxies. North is up and East is left. Technical information about the photo is available below.



It has taken the light now recorded by the VLT about nine-tenths of the age of the Universe to cover the huge distance. We therefore observe those galaxies as they were at a time when the Universe was only about 10% of its present age.

The astronomers conclude that this group of early galaxies will develop into a rich cluster of galaxies, such as those seen in the nearby Universe. The newly discovered structure provides the best opportunity so far for studying when and how galaxies began to form clusters after the initial Big Bang, one of the greatest puzzles in modern cosmology.

Radio Galaxies as cosmic signposts

A most intriguing question in modern astronomy is how the first groupings or "clusters" of galaxies emerged from the gas produced in the Big Bang.

Some theoretical models predict that densely populated galaxy clusters ("rich clusters" in current astronomical terminology) are built up through a step-wise process. Clumps develop in the primeval gas, and stars condense out of these clumps to form small galaxies. Then these small galaxies merge together to form larger units.

The peculiar class of "radio galaxies" is particularly important for investigating such scenarios. They are called so because their radio emission - a result of violent processes believed to be related to massive black holes located at the centres of these galaxies - is stronger by 5 - 10 orders of magnitude than that of our own Milky Way galaxy. In fact, this radio emission is often so intense that the galaxies can be spotted at extremely large distances, and thus at the remote epoch when the Universe was very young, just a small fraction of its present age.

The radio galaxies are amongst the most massive objects in the early Universe and there has long been circumstantial evidence that they are located at the heart of young clusters of galaxies, still in the process of formation. In this sense, they act as signposts of early cosmic "meeting points".

Radio galaxies are therefore potential beacons for pinpointing regions of the Universe in which large galaxies and clusters of galaxies are being formed.

VLT observations of the environment of radio galaxy TN J1338-1942

Following up this conjecture, the Leiden astronomers and their colleagues in the USA and Germany [1] proposed a large observing programme with the ESO VLT at Paranal (Chile) to search for groupings of galaxies in the vicinity of distant radio galaxies that might be the ancestors of rich clusters.

For this, they first used the FORS2 multi-mode instrument on the 8.2-m VLT KUEYEN telescope to take very "deep" pictures of sky regions around several radio galaxies, each field measuring about one-fifth of the diameter of the full moon. The most distant of these was an object called TN J1338-1942, a radio galaxy at a distance of about 13.5 billion light years from the Earth.

To search for galaxies at the same distance as the radio galaxy, the pictures were optimised in sensitivity for the sharp colour emitted by glowing hydrogen gas at the distance of the radio galaxy [2]. Images were taken through two red filters, one that is "tuned" to light produced by the hydrogen gas (the redshifted Lyman-alpha line) and the other that is dominated by light from stars (the R-band), cf. PR Photo 11a/02. An earlier example of this observational technique is described in ESO PR 13/99.

These images revealed 28 galaxies that are likely to be at the distance of the radio galaxy. More detailed information was obtained for 23 of these with the FORS2 instrument in the spectrographic mode, now confirming 20 of them to be indeed located at the same distance as the radio galaxy, cf. PR Photo 11b/02.

Earliest known group of galaxies

The spectra also showed that the galaxies are moving around with speeds of a few hundred kilometers per second. The observed structure of galaxies is more than 10 million light-years across and its existence means that galaxies must have begun to form groups already at this early epoch, i.e. still within the first 10% of the history of the Universe.

From the excess number of detected galaxies and the observed volume of the structure, its combined mass can be estimated. The derived number is 1000 million million (1015) times the mass of the Sun - this is comparable with the masses of nearby rich clusters of galaxies. For the present structure to evolve into a nearby rich cluster, it must contract in volume by an order of magnitude in about one billion years.

This newly discovered group of galaxies is the most remote discovered so far and hence the earliest known at this moment - another, less distant one was recently described in ESO PR 03/02.

The VLT observations also establish a crucial link between the ancestors of rich galaxy clusters and the bright galaxies whose active nuclei produce the bright radio emission. Based on the 4 radio galaxies surveyed by the VLT so far, the team concludes that every forming cluster may house a bright galaxy that is or has been a powerful radio source. The radio sources are believed to be powered by massive black holes located deep within their nuclei.

Next steps

The next step in the present project will be to use the VLT to establish the boundaries of the proto-cluster. Also, the colours and shapes of galaxies in the structure will be studied intensively by the Advanced Camera for Surveys (ACS), recently fitted to the Hubble Space Telescope (HST).

George Miley, also a member of the ACS Science Team, is enthusiastic: "We have now scheduled this particular target for one of the deepest observations ever to be made with the HST. Our project is an example of the great possibilities now opening to astronomers by combining the complementary strengths of the wonderful new ground- and space-based observational facilities!"

More information

The results described in this Press Release are about to appear in print in the research journal Astrophysical Journal ("The Most Distant Structure of Galaxies Known: a Protocluster at z = 4.1" by B.P. Venemans and co-authors), cf. astro-ph/0203249.

The text of this ESO Press Release, with two photos and all weblinks, will be found at

http://www.eso.org/outreach/press-rel/pr-2002/pr-07-02.html

Notes

[1]: The team is led by George Miley (Leiden University, The Netherlands) and the first author of the resulting research paper is Bram Venemans, a graduate student of Miley`s. Other members are Jaron Kurk and Huub Röttgering (also Leiden University), Laura Pentericci (MPIA, Heidelberg, Germany), Wil van Breugel (University of California, USA), Chris Carilli (US National Radio Astronomy Observatory, Charlottesville, USA), Carlos De Breuck (Institut d`Astrophysique, Paris), France) Holland Ford and Tim Heckman (Johns Hopkins University, Baltimore, USA) and Pat McCarthy (Carnegie Institute, Pasadena, USA).

[2]: The measured redshift of TN J1338-1942 is z = 4.1. In astronomy, the redshift denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a remote galaxy provides an estimate of its distance. The distances indicated in the present text are based on an age of the Universe of 15 billion years. At the indicated redshift, the Lyman-alpha line of atomic hydrogen (rest wavelength 121.6 nm) is observed at 620 nm, i.e. in the red spectral region.

Richard West | alphagalileo

More articles from Physics and Astronomy:

nachricht Artificial Intelligence Helps in the Discovery of New Materials
21.09.2016 | Universität Basel

nachricht Magnetic polaron imaged for the first time
19.09.2016 | Aalto University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

Im Focus: Launch of New Industry Working Group for Process Control in Laser Material Processing

At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.

In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...

Im Focus: New laser joining technologies at ‘K 2016’ trade fair

Every three years, the plastics industry gathers at K, the international trade fair for plastics and rubber in Düsseldorf. The Fraunhofer Institute for Laser Technology ILT will also be attending again and presenting many innovative technologies, such as for joining plastics and metals using ultrashort pulse lasers. From October 19 to 26, you can find the Fraunhofer ILT at the joint Fraunhofer booth SC01 in Hall 7.

K is the world’s largest trade fair for the plastics and rubber industry. As in previous years, the organizers are expecting 3,000 exhibitors and more than...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

ICPE in Graz for the seventh time

20.09.2016 | Event News

Using mathematical models to understand our brain

16.09.2016 | Event News

 
Latest News

Chains of nanogold – forged with atomic precision

23.09.2016 | Life Sciences

New leukemia treatment offers hope

23.09.2016 | Health and Medicine

Self-assembled nanostructures hit their target

23.09.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>