Scientists Report Breakthrough Mapping Dark Matter

Model prediction of what the four images of the background quasar RXJ 1131-1231 should look like, as lensed by an intervening galaxy (left). Chandra X-ray observations show a strong anomaly in the middle of the three images on the left side of the panel (right).

/ D. Pooley (Eureka Scientific)

By Mike Wall This story originally appeared on Space.com

SEATTLE - Researchers have mapped out mysterious dark matter in a sample of huge galaxies, determining where the strange stuff resides and how much of it there is.

Dark matter is thought to make up much of the universe but remains invisible to astronomers. Its existence is inferred by its gravitational effects, which can be measured.

Astronomers made the map by studying how the faraway galaxies bend light thrown off from even more distant objects. The results could yield insights about galaxy formation as well as the nature of dark matter, researchers said. [Image of map]

"This is one of the most direct measurements of the amount of dark matter at a specific location in a galaxy," said study lead author David Pooley, of Eureka Scientific, Inc., in a statement. Pooley presented the results today (Jan. 13) here at the 217th meeting of the American Astronomical Society.

Peering Through a Gravitational Lens

Pooley and his team used NASA's Chandra X-ray Observatory to study 14 massive elliptical galaxies, which are about 6 billion light-years from Earth on average. Each one sits almost directly in front of an even more distant galaxy, nearly three times farther away.

Each of the more distant galaxies harbors a quasar at its core. Quasars — active supermassive black holes that exude huge amounts of radiation — are some of the brightest objects in the universe.

The huge gravity of the closer-in galaxies bends the quasars' light significantly. These intervening "gravitational lenses" thus produce four images of the background quasar as seen from Chandra's vantage point.

"We compared what those four images were supposed to look like according to lensing theory to what we actually saw with Chandra," Pooley said. "We found some major differences."

These differences are likely due to the makeup of the matter in the lensing galaxies, researchers said.

Details of the lensing galaxies' composition — such as how many stars they possess, and how much dark matter is found in the locations where the light passes through — can affect the quasars' light, beyond simply generating four images.

The researchers figured out that, to produce what Chandra saw, the lensing galaxies must consist of about 85 to 95 percent dark matter in the regions where the quasars' light passes through. [Video: Dark Matter in 3-D]

In general, those regions are located about 15,000 to 25,000 light-years from the centers of the lensing galaxies, similar to the distance of our solar system from the center of the Milky Way, researchers said.

Other studies have determined the amount of dark matter in clusters of galaxies, but the dark matter being studied has mostly been in the vast spaces between the galaxies. The new study, on the other hand, probes deep inside individual galaxies, researchers said.

The team will refine these results further, as more gravitationally lensed quasars are discovered and then observed with Chandra. Such discoveries will be aided by large-area surveys by ground-based observatories, such as the Panoramic Survey Telescope & Rapid Response System project and the future Large Synoptic Survey Telescope, researchers said.

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[mafer1]

These researchers appear to be on a roll of enthusiasm and might also be missing some other possible answers. One of which is that a black hole not in the center of a galaxy and actually quite removed from the center of associated galaxies could also provide for distortion, which they are apparently, automatically saying is dark matter.
We are dealing with a place we know but a scratchings worth about, and yet, the report makes it sound like researchers have an absolute answer. I am sure, that in 100 years, the will be more imaginative ideas, and many more questions too.

[enough-already]

What I'd love to know is: who is paying for all the expensive toys it takes to research/study all this useless stuff? Taxpayers?

[rf35]

I can help these scientists observe some dark matter. I flush some down my toilet every day.

[RedWings_ninety_one]

They are currently trying to detect dark matter down below the earth. They have these sensors in a giant freezer at absolute zero so that the atoms will not move on their own and thus they can detect the slightest vibrations..

Problem 1..Dark matter supposedly exists is space and they have their sensors in freezers 1 mile below the surface of the earth.

Problem 2..They claim that dark matter can and has gone through the earth, thus it can go through atoms making it so that their sensors are expensive pieces of junk.

I know of another problem..but I forgot it at this time so I will comment later when I remember it.

[nic1234567-2009]

Actually, he is partly right the more popular dark matter candidate is something called Weakly Interacting Massive Particles (WIMPs). If the dark matter within our galaxy is made up of WIMPs, then a large number must pass through the Earth each second. There are many experiments planned, which would be similar to those used for detecting 'neutrinos'. These experiments would search for the scattering of dark matter particles off atomic nuclei within a detector. Although WIMPs are a more popular dark matter candidate, there are also experiments searching for other particle candidates such as axions. It is also possible that dark matter consists of very heavy hidden sector particles which only interact with ordinary matter via gravity.