Astronomers find a dark matter galaxy far, far away

Jan 18, 2012
At the center of this infrared image is a massive red galaxy, 9.8 billion light-years from Earth, which acts like a cosmic magnifying glass, distorting the light from an even more distant galaxy, 17.3 billion light-years away. The result is a spectacular Einstein ring image of the background galaxy. The observations were made with the 10-meter Keck-11 Telescope on Mauna Kea, Hawaii. Image: David Lagattuta/W. M. Keck Observatory

(PhysOrg.com) -- A faint “satellite galaxy” 10 billion light years from Earth is the lowest-mass object ever detected at such a distance, says University of California, Davis, physics professor Chris Fassnacht, who aided in the satellite’s discovery.

The find, described in a paper published online today (Jan. 18) in the journal Nature, could help astronomers find similar objects and confirm or reject theories about the structure of the cosmos.

Theory predicts that galaxies should be surrounded by halos of smaller, satellite blobs of mass, according to Fassnacht. Astronomers have detected such satellites around our own galaxy, the Milky Way, and nearby.

But they had not previously detected the predicted satellites of more distant galaxies.

Because most of the mass of galaxies is made up, not of stars, but of “,” which does not absorb or emit light, these distant objects may be very faint or even completely dark.

The team looked for faint or dark satellites of distant galaxies using a method called gravitational lensing. Using the Keck II telescope at the W.M. Keck Observatory on Mauna Kea, Hawaii, with “adaptive optics,” they found two galaxies aligned with each other, as viewed from Earth.

The nearer object’s gravitational field deflects the light from the more distant object as the light passes through or near the other object’s gravitational field, creating a distorted image as if passed through a lens. By analyzing these distorted images, the researchers could determine if there were any satellite galaxies clustered around the “lens” galaxy.

Adaptive optics make constant, tiny adjustments to the telescope mirror to compensate for the effects of the Earth’s atmosphere. As a result, the Keck telescopes can achieve higher resolution than the Hubble Space Telescope.

The technique can now be applied to many more , Fassnacht said. “As we collect more objects, we can do more precise tests of our simulations and make predictions about the structure of the universe,” he said.

First author Simona Vegetti, a postdoctoral researcher at the Massachusetts Institute of Technology, said: “Now we have one dark satellite, but suppose that we don’t find enough of them — then we will have to change the properties of dark matter.

“Or, we might find as many satellites as we see in the simulations, and that will tell us that dark matter has the properties we think it has.”

Fassnacht and Vegetti worked with Leon Koopmans of the University of Groningen, Netherlands; David Lagattuta, now at the Swinburne University of Technology, Australia; Matthew Auger, UC Santa Barbara; and John McKean of the Netherlands Foundation for Research in Astronomy. Lagattuta and Auger are former graduate students in Fassnacht’s lab, and McKean was a postdoctoral researcher at UC Davis.

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More information: www.nature.com/nature/journal/… ull/nature10669.html

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Postman1
1 / 5 (10) Jan 18, 2012
The satellite galaxy is at 7 bly, at the lensing galaxy. The distorted galaxy is at 10 bly.
From the report: "Because it is so far and hard to see, astronomers can't be sure if the newly discovered galaxy really is made almost exclusively of dark matter, or if it just contains stars that are too dim to be visible at this distance."

So this entire article may be so much bunk. Nice....
Seems to make much more sense for this to be a massive black hole, flung off into space during a galactic collision, or just a faint galaxy, rather than unproven dark matter. Occams Razor would favor a simpler explanation.
Parsec
4.1 / 5 (7) Jan 18, 2012
The satellite galaxy is at 7 bly, at the lensing galaxy. The distorted galaxy is at 10 bly.
From the report: "Because it is so far and hard to see, astronomers can't be sure if the newly discovered galaxy really is made almost exclusively of dark matter, or if it just contains stars that are too dim to be visible at this distance."

So this entire article may be so much bunk. Nice....
Seems to make much more sense for this to be a massive black hole, flung off into space during a galactic collision, or just a faint galaxy, rather than unproven dark matter. Occams Razor would favor a simpler explanation.

It would be very easy to show the difference between a point gravity source like a black hole, and one with a small but discernible radius.

The authors are pointing out that they cannot tell how luminous it is (or even if its luminous at all), just that it has sufficient mass to act as a gravitational lens. Hence their fudging about its nature.
bewertow
2.8 / 5 (6) Jan 19, 2012
in before neutron repulsion
Mayday
3 / 5 (3) Jan 19, 2012
I think it's just one of the rivets holding the CMB in place.
Sonhouse
not rated yet Jan 19, 2012
I liked the idea it was at 17 billion ly away better:)
BabaNovac
3 / 5 (2) Jan 20, 2012
The idea the it was 17 billion ly away made me ask a few questions...
1. How come we can see 17 bly away if the Universe is only 13.7 by old... And I got an answer, the Universe is that old, but observable Universe is bigger.
Fair enough, I researched observable Universe and I discovered that from one end to the other of the bubble should be around 93 bly ... But then I got to my second question...
2. Because we can only see so far in the Universe from us to an edge of the Universe is about 46 bly... But we can't see that far, so why do scientists put our galaxy in the centre of the Universe? How can we be sure of our position if we can just see about 17 bly away?
Because of the discrepancy between observable Universe and actual age I came to the conclusion that there is something moving faster than light in the Universe and that is the Universe's expansion.. I would appreciate if someone could answer my questions...

Benni
1 / 5 (1) Jan 25, 2012
so why do scientists put our galaxy in the centre of the Universe?


Could you show us a link for this? I'd be curious as who is saying this.

A "centre" implies a non-inflationary "big bang", but if you go by the "inflation theory" there is no "centre" due to the fact galactic density is observed to be almost exactly the same no matter what direction the universe is observed through the most powerful telescopes. We had this discussion recently in one of Astronomy Club meetings.

Maybe the final answer can be found out there on a "sliderule".
Benni
1 / 5 (1) Jan 25, 2012
I might add to my above post, that at the time the "big bang" was originally proposed, and up until about the 90's, it was assumed the oldest galaxies would be the smallest due to the effects of the "big bang" explosion which dictates that the least dense accumulations of galaxies would occur near the perimeter of the sphere of the explosion & the galaxies would be much smaller.

However, after the Hubble telescope came online, "galactic size & density" were not observed to be in comport with a "big bang", so "inflation" became the new catchphrase to explain the shortcomings of the "big bang", which is the "galactic density" & "size" dilemna.

With "inflation" you get an explanation of why the universe is expanding without doing away with the "big bang", the two theories standing alone negate one another, but melded together becomes an intellectual concept to in comport with Hubble Ultra-DeepField observations...this is what we discussed in our Astronomy club...seems reasonable.