Dark Energy Survey reveals most accurate measurement of dark matter structure in the universe

August 3, 2017, Fermi National Accelerator Laboratory
Map of dark matter made from gravitational lensing measurements of 26 million galaxies in the Dark Energy Survey. The map covers about 1/30th of the entire sky and spans several billion light-years in extent. Red regions have more dark matter than average, blue regions less dark matter. Credit: Chihway Chang of the Kavli Institute for Cosmological Physics at the University of Chicago and the DES collaboration.

Imagine planting a single seed and, with great precision, being able to predict the exact height of the tree that grows from it. Now imagine traveling to the future and snapping photographic proof that you were right.

If you think of the seed as the early , and the tree as the universe the way it looks now, you have an idea of what the Dark Energy Survey (DES) collaboration has just done. In a presentation today at the American Physical Society Division of Particles and Fields meeting at the U.S. Department of Energy's (DOE) Fermi National Accelerator Laboratory, DES scientists will unveil the most accurate measurement ever made of the present large-scale structure of the universe.

These measurements of the amount and "clumpiness" (or distribution) of in the present-day cosmos were made with a precision that, for the first time, rivals that of inferences from the early universe by the European Space Agency's orbiting Planck observatory. The new DES result (the tree, in the above metaphor) is close to "forecasts" made from the Planck measurements of the distant past (the seed), allowing scientists to understand more about the ways the universe has evolved over 14 billion years.

"This result is beyond exciting," said Scott Dodelson of Fermilab, one of the lead scientists on this result. "For the first time, we're able to see the current structure of the universe with the same clarity that we can see its infancy, and we can follow the threads from one to the other, confirming many predictions along the way."

Most notably, this result supports the theory that 26 percent of the universe is in the form of mysterious dark matter and that space is filled with an also-unseen dark energy, which is causing the accelerating expansion of the universe and makes up 70 percent.

Composite picture of stars over the Cerro Tololo Inter-American Observatory in Chile. Credit: Reidar Hahn/Fermilab

Paradoxically, it is easier to measure the large-scale clumpiness of the universe in the distant past than it is to measure it today. In the first 400,000 years following the Big Bang, the universe was filled with a glowing gas, the light from which survives to this day. Planck's map of this cosmic microwave background radiation gives us a snapshot of the universe at that very early time. Since then, the gravity of dark matter has pulled mass together and made the universe clumpier over time. But dark energy has been fighting back, pushing matter apart. Using the Planck map as a start, cosmologists can calculate precisely how this battle plays out over 14 billion years.

"The DES measurements, when compared with the Planck map, support the simplest version of the dark matter/dark energy theory," said Joe Zuntz, of the University of Edinburgh, who worked on the analysis. "The moment we realized that our measurement matched the Planck result within 7 percent was thrilling for the entire collaboration."

The primary instrument for DES is the 570-megapixel Dark Energy Camera, one of the most powerful in existence, able to capture digital images of light from galaxies eight billion light-years from Earth. The camera was built and tested at Fermilab, the lead laboratory on the Dark Energy Survey, and is mounted on the National Science Foundation's 4-meter Blanco telescope, part of the Cerro Tololo Inter-American Observatory in Chile, a division of the National Optical Astronomy Observatory. The DES data are processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

Scientists on DES are using the camera to map an eighth of the sky in unprecedented detail over five years. The fifth year of observation will begin in August. The new results released today draw from data collected only during the survey's first year, which covers 1/30th of the sky.

"It is amazing that the team has managed to achieve such precision from only the first year of their survey," said National Science Foundation Program Director Nigel Sharp. "Now that their analysis techniques are developed and tested, we look forward with eager anticipation to breakthrough results as the survey continues."

This image of the NGC 1398 galaxy was taken with the Dark Energy Camera. This galaxy lives in the Fornax cluster, roughly 65 million light-years from Earth. It is 135,000 light-years in diameter, just slightly larger than our own Milky Way galaxy, and contains more than a billion stars. Credit: Dark Energy Survey

DES scientists used two methods to measure dark matter. First, they created maps of galaxy positions as tracers, and second, they precisely measured the shapes of 26 million galaxies to directly map the patterns of dark matter over billions of light-years, using a technique called gravitational lensing.

To make these ultraprecise measurements, the DES team developed new ways to detect the tiny lensing distortions of galaxy images, an effect not even visible to the eye, enabling revolutionary advances in understanding these cosmic signals. In the process, they created the largest guide to spotting dark matter in the cosmos ever drawn (see image). The new dark matter map is 10 times the size of the one DES released in 2015 and will eventually be three times larger than it is now.

"It's an enormous team effort and the culmination of years of focused work," said Erin Sheldon, a physicist at the DOE's Brookhaven National Laboratory, who co-developed the new method for detecting lensing distortions.

These results and others from the first year of the Dark Energy Survey will be released today online and announced during a talk by Daniel Gruen, NASA Einstein fellow at the Kavli Institute for Particle Astrophysics and Cosmology at DOE's SLAC National Accelerator Laboratory, at 5 p.m. Central time. The talk is part of the APS Division of Particles and Fields meeting at Fermilab and will be streamed live.

The results will also be presented by Kavli fellow Elisabeth Krause of the Kavli Insitute for Particle Astrophysics and Cosmology at SLAC at the TeV Particle Astrophysics Conference in Columbus, Ohio, on Aug. 9; and by Michael Troxel, postdoctoral fellow at the Center for Cosmology and AstroParticle Physics at Ohio State University, at the International Symposium on Lepton Photon Interactions at High Energies in Guanzhou, China, on Aug. 10. All three of these speakers are coordinators of DES science working groups and made key contributions to the analysis.

"The Dark Energy Survey has already delivered some remarkable discoveries and measurements, and they have barely scratched the surface of their data," said Fermilab Director Nigel Lockyer. "Today's world-leading results point forward to the great strides DES will make toward understanding in the coming years."

Explore further: Cosmologists produce new maps of dark matter dynamics

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Tuxford
2 / 5 (4) Aug 03, 2017
Most notably, this result supports the theory that 26 percent of the universe is in the form of mysterious dark matter and that space is filled with an also-unseen dark energy, which is causing the accelerating expansion of the universe and makes up 70 percent.

Fairy tales gone mainstream. Fake science!
setnom
4.3 / 5 (6) Aug 07, 2017
Fairy tales gone mainstream. Fake science!


Study hard, go into the field, write your own scientific papers, publish them and get them peer-reviewed, collect your Nobel prize. Go for it! Prove these guys wrong!
setnom
5 / 5 (4) Aug 09, 2017
How can anyone write this much but say so little?

This very article shows that something was MEASURED to be correct (at least within 7% of the predictions). There is no logical fallacy. If there was, what logical fallacy were you talking about, anyway?

If Tuxford is up for it, he can come up with his own set of peer-reviewed scientific conclusions. Is he? What do you think? Do you think he's able to?
setnom
5 / 5 (2) Aug 09, 2017
His conclusion is 100% accurate...as one of his peers I have reviewed it and accept his conclusion.


Hahaha. Check-mate, I guess? But really, you have "reviewed" what? A comment on a website? Is that what passes as conclusions in your "informed" opinion? Well, how valid and scientific, then.

Come on, is "Fairy tales gone mainstream. Fake science!" enough for you to accept this scientific work as incorrect? Who cares about being informed, educated, to work in the field, make your measurements, publish your own science papers?

Theory vs. proven reality...learn the difference.


Juding from the acceptance of a "fact" based on an INCREDIBLE lack of scientific information (a single comment) and apparent refusal to delve deeper into the science behind the article in order to efficiently argue what the scientists found out - doing the work yourself in order to come to a better conclusion or prove the work incorrect -, I'd say you don't WANT to know the difference.
setnom
5 / 5 (1) Aug 10, 2017
They're testable! These scientists are testing it!

"The primary instrument for DES is the 570-megapixel Dark Energy Camera, one of the most powerful in existence, able to capture digital images of light from galaxies eight billion light-years from Earth." [...] "DES scientists used two methods to measure dark matter. First, they created maps of galaxy positions as tracers, and second, they precisely measured the shapes of 26 million galaxies to directly map the patterns of dark matter over billions of light-years, using a technique called gravitational lensing. To make these ultraprecise measurements, the DES team developed new ways to detect the tiny lensing distortions of galaxy images" [...] ""The DES measurements, when compared with the Planck map, support the simplest version of the dark matter/dark energy theory. The moment we realized that our measurement matched the Planck result within 7 percent was thrilling for the entire collaboration".
setnom
5 / 5 (1) Aug 10, 2017
You haven't answered my question, though. These scientists (there are many more doing the same work in this field), are gathering a treasure trove of scientific data regarding dark matter that you refuse to aknowledge.

But on the other hand, you willfully agree with Tuxford based on a single comment on a website ("Fairy tales gone mainstream. Fake science!"). Why? This is neither fairies nor fake science. Do you think they are photoshopping the images from the DEC camera or something? :P

Why do you put aside scientific work that has measurements that support it but accept two unscientific phrases as fact without any scientific backing whatsoever?
setnom
5 / 5 (1) Aug 10, 2017
The observations these scientists gathered are publicly available here: http://archive.noao.edu/

If you think they are full of sh*t, do the work yourself and come up with your own conclusions. Yes, I will keep repeating this, wether you like it or not. Doing science, doing the work, is the best way to correct who you think is wrong. Posting negative comments on a website is not enough! That is not science.
setnom
5 / 5 (1) Aug 10, 2017
By the way, are you knowledgeable of the subject matter? Do you have a science background? In what field?

Have you read and examined their publications? https://www.darke...-papers/

Care to post in-depth reviews of each of 10 scientific papers? Pointing out all the inaccuracies the scientists made there?
setnom
5 / 5 (1) Aug 11, 2017
I read what you wrote and it shows you don't understand the science, the methods of gathering the evidence and the measurements the scientists from the DES collaboration are making.

Like I asked: are you educated on the matter? What's your scientific background? Do you work in the field? Care to do your own work from the raw data publicly available ( http://archive.noao.edu/ )? Show me that you understand the subject matter better than the DES scientists. Posting comments is not enough. Do the hard work.

Have you even read the 10 scientific papers? https://www.darke...-papers/

You don't seem to have read them because I haven't seen a single specific rebuttal of what they write there. Or if you did, you didn't understand them. If you don't understand the subject, if you haven't read them carefully, how can you put them into question? I'm sorry, but you sound like the anti-vaccer analogue of cosmology.
setnom
5 / 5 (1) Aug 11, 2017
Like I asked: do in-depths reviews of the 10 scientific papers. That will show that you understand what they are talking about, that will be something with more scientific "juice" on it than just pseudo-arguments rehashed time and time again.

You also don't appear to have read what I wrote, because I already asked you twice why do you refuse to accept this work, with measured and testable evidence, and at the same time willfully accept one unscientific comment published here (regarding Tuxford's comment).

By the way: ever thought about contacting the team behind the DES collaboration? E-mail them, show them your arguments against their work. Schedule a meeting face to face to debate their results. It would be interesting if you recorded that meeting and posted here what happened. Will you do it? There's no better way to dispute their results. I'm not part of that team, arguing with me is kinda pointless. Will you do it? Keep us posted: http://www.darken...tact-us/
setnom
5 / 5 (1) Aug 12, 2017
Way to go straw man.

I said arguing with me is kinda pointless in the sense that it would be better if you discussed this with the scientists behind the DES collaboration, it's their work. And THEN tell us all about it. How did you not get that? I was very clear on the matter... be honest, you did it on purpose, didn't you?

Of course you won't bother doing the work, it's easier to be lazy, remain ignorant and troll away on the internet.

You won't even read the papers. You won't reach out to the actual DES scientists and try to have a discussion, you won't educate yourself on the matter, you won't do your own work on the data available.

Like I said, you're no better than an anti-vaccer. Shame, shame, SHAME!

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