Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

XMM-Newton probes formation of galaxy clusters

01.09.2005


ESA’s X-ray observatory, XMM-Newton, has for the first time allowed scientists to study in detail the formation history of galaxy clusters, not only with single arbitrarily selected objects, but with a complete representative sample of clusters.


XMM-Newton image of galaxy cluster RXCJ0658.5-5556


XMM-Newton image of galaxy cluster RXCJ2337.6+0016



Knowing how these massive objects formed is a key to understanding the past and future of the Universe. Scientists currently base their well-founded picture of cosmic evolution on a model of structure formation where small structures form first and these then make up larger astronomical objects.

Galaxy clusters are the largest and most recently formed objects in the known Universe, and they have many properties that make them great astrophysical ‘laboratories’. For example, they are important witnesses of the structure formation process and important ‘probes’ to test cosmological models.


To successfully test such cosmological models, we must have a good observational understanding of the dynamical structure of the individual galaxy clusters from representative cluster samples.

For example, we need to know how many clusters are well evolved. We also need to know which clusters have experienced a recent substantial gravitational accretion of mass, and which clusters are in a stage of collision and merging. In addition, a precise cluster mass measurement, performed with the same XMM-Newton data, is also a necessary prerequisite for quantitative cosmological studies.

The most easily visible part of galaxy clusters, i.e. the stars in all the galaxies, make up only a small fraction of the total of what makes up the cluster. Most of the observable matter of the cluster is composed of a hot gas (10-100 million degrees) trapped by the gravitational potential force of the cluster. This gas is completely invisible to human eyes, but because of its temperature, it is visible by its X-ray emission.

This is where XMM-Newton comes in. With its unprecedented photon-collecting power and capability of spatially resolved spectroscopy, XMM-Newton has enabled scientists to perform these studies so effectively that not only single objects, but also whole representative samples can be studied routinely.

XMM-Newton produces a combination of X-ray images (in different x-ray energy bands, which can be thought of as different X-ray ‘colours’), and makes spectroscopic measurements of different regions in the cluster.

While the image brightness gives information on the gas density in the cluster, the colours and spectra provide an indication of the cluster’s internal gas temperature. From the temperature and density distribution, the physically very important parameters of pressure and ‘entropy’ can be also derived. Entropy is a measure of the heating and cooling history of a physical system.

The accompanying three images illustrate the use of entropy distribution in the ‘X-ray luminous’ gas as a way of identifying various physical processes. Entropy has the unique property of decreasing with radiative cooling, increasing due to heating processes, but staying constant with compression or expansion under energy conservation.

The latter ensures that a ‘fossil record’ of any heating or cooling is kept even if the gas subsequently changes its pressure adiabatically (under energy conservation).

These examples are drawn from the REFLEX-DXL sample, a statistically complete sample of some of the most X-ray luminous clusters found in the ROSAT All-Sky Survey. ROSAT was an X-ray observatory developed in the 1990s in co-operation between Germany, USA and UK.

The images provide views of the entropy distribution coded in colour where the values increase from blue, green, yellow to red and white.

Norbert Schartel | alfa
Further information:
http://www.esa.int/esaSC/SEMDW5A5QCE_index_0.html

More articles from Physics and Astronomy:

nachricht New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center

nachricht Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology

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: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>