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It's in the constellation of Phoenix at a distance of 7.2 billion light years and is the most massive and hottest of all the known galaxy clusters at such large distances. It is a very bright X-ray source and represents an excellent laboratory for studying the standard cosmological model.
Given its size, it has been nick-named "El Gordo" (the fat one) and is actually the result of a merger between two smaller clusters.
The cluster was found by researchers led by Felipe Menanteau (Rutgers University in New Brunswick, N.J.), that made use of the Sunyaev-Zeldovich effect, that causes the hot gas in clusters to distort the emission from the cosmic microwave background. It was then photographed by the X-ray satellite Chandra, the infrared satellite Spitzer, and ESO's VLT at optical wavelengths.
Of all the matter visible in the cluster, stars make up only 1%, all the rest is either gas or the dominant dark matter. In fact, during the collision between the two clusters the dark matter of the two clusters did not collide, interacting only gravitationally, whereas the gas collided violently, heating up dramatically.
It can be seen that this cluster is the result of an almost completed merger, according to Menanteau and colleagues, thanks to the brightest region in the image, representing where the two brightest galaxies in each cluster met (a 'tail' can be seen, resulting from the interaction, suggesting it was a glancing rather than direct collision).
The results of Menanteau's team on El Gordo were presented at the 219th meeting of the American Astronomical Society, currently in progress in Austin Texas, and will soon be published in The Astrophysical Journal.
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by Michele Ferrara & Marcel
Clemens |
credit:
X-ray: NASA/CXC/Rutgers/J.Hughes et al,
Optical: ESO/VLT/Pontificia Universidad. Catolica de Chile/L.Infante & SOAR (MSU/NOAO/UNC/CNPq-Brazil)/Rutgers/F.Menanteau,
IR: NASA/JPL/Rutgers/F.Menanteau |
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