Galaxy Cluster Far, Far Away Smashes Distance Record
Written by Nancy Atkinson
A galaxy cluster located about 10.2 billion light years from Earth has been discovered by combining data from NASA's Chandra X-ray Observatory with optical and infrared telescopes. The cluster, JKCS041, is the most distant galaxy cluster yet observed, and we see it as when the Universe was only about a quarter of its present age. The cluster's distance beats the previous record holder by about a billion light years.
Galaxy clusters are the largest gravitationally bound objects in the Universe. Finding such a large structure at this very early epoch can reveal important information about how the Universe evolved at this crucial stage.
JKCS041 is at the brink of when scientists think galaxy clusters can exist in the early Universe based on how long it should take for them to assemble. Therefore, studying its characteristics – such as composition, mass, and temperature – will reveal more about how the Universe took shape.
"This object is close to the distance limit expected for a galaxy cluster," said Stefano Andreon of the National Institute for Astrophysics (INAF) in Milan, Italy. "We don't think gravity can work fast enough to make galaxy clusters much earlier."
JKCS041 was originally detected in 2006 in a survey from the United Kingdom Infrared Telescope (UKIRT). The distance to the cluster was then determined from optical and infrared observations from UKIRT, the Canada-France-Hawaii telescope in Hawaii and NASA's Spitzer Space Telescope. Infrared observations are important because the optical light from the galaxies at large distances is shifted into infrared wavelengths because of the expansion of the universe.
The Chandra data were the final – but crucial – piece of evidence as they showed that JKCS041 was, indeed, a genuine galaxy cluster. The extended X-ray emission seen by Chandra shows that hot gas has been detected between the galaxies, as expected for a true galaxy cluster rather than one that has been caught in the act of forming.
Also, without the X-ray observations, the possibility remained that this object could have been a blend of different groups of galaxies along the line of sight, or a filament, a long stream of galaxies and gas, viewed front on. The mass and temperature of the hot gas detected estimated from the Chandra observations rule out both of those alternatives.
The extent and shape of the X-ray emission, along with the lack of a central radio source argue against the possibility that the X-ray emission is caused by scattering of cosmic microwave background light by particles emitting radio waves.
It is not yet possible, with the detection of just one extremely distant galaxy cluster, to test cosmological models, but searches are underway to find other galaxy clusters at extreme distances.
"This discovery is exciting because it is like finding a Tyrannosaurus Rex fossil that is much older than any other known," said co-author Ben Maughan, from the University of Bristol in the United Kingdom. "One fossil might just fit in with our understanding of dinosaurs, but if you found many more, you would have to start rethinking how dinosaurs evolved. The same is true for galaxy clusters and our understanding of cosmology."
The previous record holder for a galaxy cluster was 9.2 billion light years away, XMMXCS J2215.9-1738, discovered by ESA's XMM-Newton in 2006. This broke the previous distance record by only about 0.1 billion light years, while JKCS041 surpasses XMMXCS J2215.9 by about ten times that.
"What's exciting about this discovery is the astrophysics that can be done with detailed follow-up studies," said Andreon.
Among the questions scientists hope to address by further studying JKCS041 are: What is the build-up of elements (such as iron) like in such a young object? Are there signs that the cluster is still forming? Do the temperature and X-ray brightness of such a distant cluster relate to its mass in the same simple way as they do for nearby clusters?
Source: EurekAlert
Filed under: galaxies
Tags: Chandra, Galactic ClusterRelated stories on Universe Today
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October 22nd, 2009 at 11:09 am
Once upon a time in a galaxy cluster very, very, very far away……
Couldn't resist
October 22nd, 2009 at 3:22 pm
I recently came across this paper on the arXiv site & was hoping UT would write it up. The article includes only a mediocre image of the cluster embedded in the blue X-ray glow. An awesome 3 color image obtained with the 3.6m CFHT is well worth a gander here: http://www.brera.mi.astro.it/~andreon/JKCS041_WIRDS_gzK_T0002.jpg . These really are some distant, red galaxies (see link). The paper mentions that a 12 hour spectrum across the cluster taken with one of the 8 meter VLT 'scopes detected NO galaxies, hence the redshift is derived photometrically. Detailed spectra and direct imaging of this cluster sounds like a perfect job for Hubble.
October 22nd, 2009 at 3:25 pm
Oh yeah, the paper on the discovery of JKCS 041 can be found here: http://arxiv.org/PS_cache/arxiv/pdf/0812/0812.1699v2.pdf .
October 22nd, 2009 at 4:49 pm
The observed values of z are quoted as 1.91 in
http://arxiv.org/PS_cache/arxiv/pdf/0812/0812.1699v2.pdf .
The FLRW spacetime metric result on the Doppler shift is for R(T) = radius of cosmic region now, R(t) = radius of same region at previous time t is
z = R(T)/R(t) – 1
so R(t) =~ R(T)/2.9. If I assume a "coasting universe," or where the mutual gravitation of galaxies on average is small and the accelerated expansion of the universe is small enough that would give a similar ratio of times T/t =~ 2.9. That is about 4.7 billion years after the big bang. If I ignore frame dragging effects then that would be about 9 billion Ly away. So the numbers seem to match.
What appears to make these interesting is they are clusters of galaxies, so they represent the largest identified gravtiationally bound objects identified this early in the unvierse. There are some z = 7 objects which have been identified, which puts them out to 2 billion years after the BB.
LC
October 22nd, 2009 at 6:18 pm
Boy, thats a long way…
October 22nd, 2009 at 10:36 pm
Meh – I guess it's kind of far… I've seen further.
October 28th, 2009 at 3:31 pm
OK, this is something that confuses me, perhaps because I do not understand the underlying maths.
If something is 10 billion LY away from us today, then 10 billion years ago it must have been a lot closer (if we are to assume the expanding universe/big bang theory).
So, to see something that is now 10 billion LY away from us means that it is no longer there but a lot further away from us as we are seeing it where it was 10 billion years ago.
If the universe is (for all approximations and averages) about 15 billion years old, how can something be seen as being that far away, or even further if some of the other objects are used (13+ billion LY distant)?
If someone can explain this to me it will help me sleep at night.
And for the record, I feel that the explanation behind red shift is flawed. I feel it is a measure of distance, but not of how fast something is receding from us. But that is another argument.