XMM-Newton's massive discovery

August 25, 2008
The optical image that confirmed that 2XMM J083026+524133 is a distant cluster of galaxies, taken by the Large Binocular Telescope in Arizona. The X-ray emission from the cluster of galaxies is shown in blue at the centre of the image. The individual galaxies in the cluster are the small dots inside the blue glow. Credits: ESA XMM-Newton/EPIC, LBT/LBC, AIP (J. Kohnert)

(PhysOrg.com) -- ESA's orbiting X-ray observatory XMM-Newton has discovered the most massive cluster of galaxies seen in the distant Universe until now. The galaxy cluster is so big that there can only be a handful of them at that distance, making this a rare catch indeed. The discovery confirms the existence of dark energy.

The newly-discovered monster, known only by the catalogue number 2XMM J083026+524133, is estimated to contain as much mass as a thousand large galaxies. Much of it is in the form of 100-million-degree hot gas. It was first observed by chance as XMM-Newton was studying another celestial object and 2XMM J083026+524133 was placed in a catalogue for a future follow-up.

Georg Lamer, Astrophysikalisches Institut Potsdam, Germany, and a team of astronomers discovered the record-breaking cluster as they were performing a systematic analysis of the catalogue. Based on 3500 observations performed with XMM-Newton's European Photon Imaging Camera (EPIC) covering about 1% of the entire sky, the catalogue contains more than 190 000 individual X-ray sources. The team were looking for extended patches of X-rays that could either be nearby galaxies or distant clusters of galaxies.

J083026+524133 stood out because it was so bright. While checking visual images from the Sloan Digital Sky Survey, the team could not find any obvious nearby galaxy in that location. So they turned to the Large Binocular Telescope in Arizona and took a deep exposure.

Sure enough, they found a cluster of galaxies. So the team calculated a distance of 7.7 thousand million light-years and the cluster's mass using the XMM-Newton data. This was not a surprise because XMM-Newton is sensitive enough to routinely find galaxy clusters at this distance. The surprise was that the cluster contains a thousand times the mass of our own galaxy, the Milky Way.

“Such massive galaxy clusters are thought to be rare objects in the distant Universe. They can be used to test cosmological theories,” says Lamer. Indeed, the very presence of this cluster confirms the existence of a mysterious component of the Universe called dark energy.

No one knows what dark energy is, but it is causing the expansion of the Universe to accelerate. This hampers the growth of massive galaxy clusters in more recent times, indicating that they must have formed earlier in the Universe. “The existence of the cluster can only be explained with dark energy,” says Lamer.

Yet he does not expect to find more of them in the XMM-Newton catalogue. “According to the current cosmological theories, we should only expect to find this one cluster in the 1% of sky that we have searched,” says Lamer.

In other words, the team have found a cosmic ‘needle in a haystack’.

Citation: '2XMM J083026+524133: The most X-ray luminous cluster at redshift 1' by G. Lamer, M. Hoeft, J. Kohnert, A. Schwope, and J. Storm will be published in a forthcoming issue of the journal Astronomy & Astrophysics.

Provided by ESA

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4.1 / 5 (9) Aug 25, 2008
How exactly does this 'confirm' dark energy? If the current model requires dark energy to explain such a massive old galaxy then the model could very well be wrong. This same model also predicted that this galaxy should be a 'needle in a haystack' but we found it on a telescope that searches 1% of the sky? I'd wager this haystack has a lot of needles in it.

It's an awesome discovery, but throwing in the 'confirmation' of dark matter is reaching.
4.6 / 5 (9) Aug 25, 2008
How does existence of 2XMM J083026 524133 confirm
dark energy?
4.4 / 5 (7) Aug 25, 2008
Agreed, from the article: "No one knows what dark energy is, but it is causing the expansion of the Universe to accelerate." How do you know if you have found something when you don't know what you are looking for? Is there no other model that explains the find?

Like Glis, I find the discovery quite interesting, but the additional statement is a bit much.
4.2 / 5 (5) Aug 25, 2008
i would like to know also how this "confirms" it. the article doesn't say how it just says that its needed for the expansion of the universe.
4.8 / 5 (9) Aug 25, 2008
My understanding is that dark energy is just a tag for something driving the accelerating expansion of the universe. This finding suggests that expansion is indeed accelerating, hence... it corroborates the existence of 'dark energy', by definition.
3.4 / 5 (5) Aug 25, 2008
The guy wants to go down in the record books as the researcher who confirmed dark energy. Unfortunately for him, he'll now go down as the researcher who was too overzealous about his own theory and put his foot in his mouth.
not rated yet Aug 25, 2008
What I find puzzling about this ESA press release is that after reading the original paper by Dr Lamer (http://arXiv.org/....3817v2) I see on mention of Dark Energy OR Dark Matter. Either the paper is wrong & should be retracted or(more likely) the ESA press people mis-interpreted the paper's conclusions. I, too, am bewildered by the ESA press release. Maybe they were alluding to Dark Matter in this distant cluster, with the XMM data. Seeing that Dr. Lamer is both lead author of the paper & quoted in the ESA press release, maybe he can shed some light on the 'Dark Energy' press release.
5 / 5 (1) Aug 25, 2008
Link t paper should be http://arXiv.org/...5.3817v3 .It's only 5 pages long & no mention of DE. What gives?
5 / 5 (1) Aug 25, 2008
After comparing v2 & v3 of this paper, I see only that the total luminosity & temperature are slightly higher. Certainly, this makes this cluster one of the brightest & hottest known at this redshift(z=0.99), but still no link to DE or DM. Personally, I've got no problem with either DE or DM, just that this paper does not mention either(both v2 & v3). DM mapping of this cluster (by looking for micro- or macrolensing) might just be possible with Hubble, its' great distance will make this a tough project. The paper does mention an upcoming planned observation by the Chandra X-ray telescope, but this will only help pin down this cluster's luminosity & temp. I still believe the ESA PR people misstated what the paper on the cluster was all about, hence the confusion. CXO observations may clarify if this is a 'cooling core' cluster, but not have anything to do with DE and possibly constrain the total mass (including DM).

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