PDA

View Full Version : Galaxy Cluster Collision Creates a Dark Matter Core



Fraser
2007-Aug-16, 08:13 PM
This strange photograph is a composite image of Abell 520, a massive cluster of galaxies in the process of colliding with one another - it's one of the most massive structures in the Universe. ...

Read the full blog entry (http://www.universetoday.com/2007/08/16/galaxy-cluster-collision-creates-a-dark-matter-core/)

Fortunate
2007-Aug-17, 05:12 AM
Since nothing I think of here seems right to me, I'll propose something that doesn't seem right. Please don't tear me up. No one (as I understand it) can figure out how the collision could have stripped the dark matter away from the galaxies. What occurred to me is that maybe there was a lot of nonluminous matter in the collision that was never associated with the galaxies in the first place. What or why or how I don't know.

Anyway, if I were a pro, I'd being looking for sets of colliding galaxies clusters to study.

RussT
2007-Aug-17, 07:24 AM
So, which one of these clusters was/is NOT following the Hubble Flow><?

antoniseb
2007-Aug-17, 10:28 AM
which one of these clusters was/is NOT following the Hubble Flow

That is an interesting question that I have wondered about too. I suspect that the answer is that all clusters were imparted some initial velocity beyond the Hubble flow. As you and I have discussed tangentially, it may also be possible that clusters formed near voids are imparted some extra velocity away from the voids. This is all highly speculative, and if measured so far, only with the most meager of signal-to-noise ratios.

iantresman
2007-Aug-17, 02:16 PM
The original Chandra press release (http://chandra.harvard.edu/press/07_releases/press_081607.html) says that the "theory of dark matter predicts that dark matter and galaxies should stay together, even during a violent collision".

They didn't. The results contradict the theory. QED.

antoniseb
2007-Aug-17, 02:24 PM
The original Chandra press release (http://chandra.harvard.edu/press/07_releases/press_081607.html) says ... The results contradict the theory. QED.
Press releases are not proof or disproof. They are not written for scientists.
The Bullet Cluster, and the dark matter ring both show that it is possible to separate reactive matter from dark matter. This is a third example.

John Mendenhall
2007-Aug-17, 03:09 PM
Since nothing I think of here seems right to me, I'll propose something that doesn't seem right. (snip) What occurred to me is that maybe there was a lot of nonluminous matter in the collision that was never associated with the galaxies in the first place. What or why or how I don't know. (snip)

Good suggestion.

Michael Noonan
2007-Aug-17, 04:01 PM
Press releases are not proof or disproof. They are not written for scientists.
The Bullet Cluster, and the dark matter ring both show that it is possible to separate reactive matter from dark matter. This is a third example.

Curious, I was wondering if there is anything available to check for extreme red shift or blue shift anomalies?

Fortunate
2007-Aug-18, 12:27 AM
The article seems to say that the GALAXIES collided with each other, but I actually think that the Bullet Cluster and Abell 520 result from the collision of CLUSTERS of galaxies. The actual galaxies occupy such a tiny fraction of the total space in each cluster that virtually none of the galaxies collide with each other. In the Bullet Cluster the intergalactic gas from one cluster exerted a drag on the intergalactic gas in the other custer, slowing the gas down while the galaxies and the dark matter just sped on through the collision unimpeded, so the dark matter and the galaxies stayed together while the gas got separated from them. So what happened in Abell 520 to separate the dark matter from the galaxies?

Maybe this seems like a repetitive recapitulation, but it just wasn't, for the most part, galaxies that collided.

Infralever
2007-Aug-28, 06:02 AM
The Tully Fisher (http://pbfred1.googlepages.com/untitled.PNG)> law could mean what it says it means.

The spreading infrared luminosity from the central cloud of hot gas in between the two clusters of Abell 520 could actually be causing the gravitational light bending. In the 1919 solar eclipse study, it could have been the hot spreading luminosity from the sun that was causing the light bending an not the yet-to-be-specified (http://pbfred1.googlepages.com/InalettertoRichardBentley.pdf) property of the mass of the sun that was producing the warping of the nearby space so that the background starlight would appear as bent.

I have been trying for years to get someone to replicate my experiments so someone besides myself would begin to believe that spreading infrared radiation is gravitationally attractive. And now maybe Mahdavi et al also have found evidence that support the notion that spreading heat is attractive (http://pbfred1.googlepages.com/theory)

Peter Fred

Maybe its not the dark matter that is difficult to see it's the light (http://pbfred1.googlepages.com/centerofgalaxie.jpg).

Fortunate
2007-Oct-20, 01:57 AM
The November issue of Scientific American has an article, Dark Riddles, about possible explanations for the picture presented by Abell 520 - nothing uniquely convincing, just various speculations, including inaccurate weak lensing measurements (the original authors are using the Hubble to get better observations), a fifth force, MOND (group is working on showing that result is consistent with MOND), and the possibilty that some concentrations of dark matter might not automatically spawn stars.