Dark matter ghosts its way through powerful (and messy) collision of galaxy clusters

[Admin]

Using data from the Hubble and Chandra space telescopes, scientists have determined that dark matter ghosted through the wreckage of two colliding galaxy clusters over 5 billion light-years away.

Dark matter ghosts its way through powerful (and messy) collision of galaxy clusters : Read more

 

[Unclear Engineer]

So, this result seems inconsistent with the result in the other article about merging black holes. See https://www.space.com/dark-matter-final-parsec-problem , which says that study concluded that dark matter scatters off other dark matter, effectively creating a friction-like effect.

And, scattering aside, the "collisions" of galaxies are not so much actual physical collisions of their stars as they are gravitational interactions of multiple bodies. So, I am not seeing the explanation of why regular matter and dark matter should go separate ways during galaxy collisions if they both are mainly and mutually affected by gravitational interactions in the same way.

Does baryonic gas get separated from the stars in galaxies when galaxies collide?

 

[Questioner]

The graphic makes each DM halo seem like it has a stronger affinity for either the external galaxy’s DM &/or visible matter than its own visible matter. (Selective gravity?)

Otherwise it requires the DM to gain vector energy (inertia) from somewhere.

From the graphic DM seems to have inconsistent gravitational characteristics.
De-linking its inertia from its mass? huh?

I would be curious to find out what the two galactic central black holes were doing during this intersection/collision.

If the two central black holes broke out and raced ahead of the rest of their respective galaxies it would fit with my idea that the mass halo was a secondary mass curve of black holes,
if not my notion needs a serious rethink.

 

[Unclear Engineer]

I notice the same thing about the "dark matter" seeming to be more attracted to the opposite galaxy than to its own galaxy.

But, considering that "dark matter" is not directly imaged, but instead it is somehow inferred from other data, I think the whole video needs much better explanation and discussion. The written conclusions don't seem to be supported by the visual evidence provided.

I am not seeing anything that looks like an undisturbed pass-through. I am seeing something that looks like a decoupling, with unexplained movement. And, considering that "unexplained movement" is the initial basis for the concept of "dark matter", I would expect whatever movement seems to be associated with "dark matter" to be consistent with its concept of interacting only by gravity and in the same way that normal matter interacts by gravity.

 

[Cdr. Shepard]

I notice the same thing about the "dark matter" seeming to be more attracted to the opposite galaxy than to its own galaxy.

But, considering that "dark matter" is not directly imaged, but instead it is somehow inferred from other data, I think the whole video needs much better explanation and discussion. The written conclusions don't seem to be supported by the visual evidence provided.

I am not seeing anything that looks like an undisturbed pass-through. I am seeing something that looks like a decoupling, with unexplained movement. And, considering that "unexplained movement" is the initial basis for the concept of "dark matter", I would expect whatever movement seems to be associated with "dark matter" to be consistent with its concept of interacting only by gravity and in the same way that normal matter interacts by gravity.

I came here hoping you or Billslugg or somebody could help resolve my confusion, but at least I'm not the only one with questions.

In regards to the unexplained movement, I wondered why the DM halos decoupled prior to collision of the baryonic matter. Would some sort of collision of galactic bow shocks slow the two galaxies prior to collision? From the gif in the article, it actually seems (to me) as though the DM halos accelerated ahead of their respective galaxies while the two galaxies continued on at a seemingly steady velocity until the moment of "collision". Will have to do my own google sleuthing later I suppose.

 

[Unclear Engineer]

First remember that we are talking about a video of a simulation, not an observation. So, whoever made that simulation should be able to address why the dark matter does what they simulated it do do.

One thing that seems to make sense in the beginning is that the dark matter halos are the first parts of the two galaxies to get close together, so they might tend to be getting drawn towards each other earlier than the visible matter that is still at greater separation. But, that explanation falls apart as the galaxies "pass through each other" because the simulated dark matter tends to keep going while the regular matter tends to stick together. That just may be an assumption that regular matter interacts with itself and dark matter does not interact with itself or regular matter except by gravity. But, it still doesn't seem to explain why the dark matter would first be attracted and then not attracted by its own gravity or the gravity of regular matter.

But, again, this is just a simulation using a model that may not be right, or even self consistent. It is somebody's concept, not an observation. So, I would like to hear their explanation.

To expand a bit, not knowing much about "dark matter" makes it easy to speculate, but hard to prove or disprove anything.

One speculation on my part is that the central supermassive black hole in the center of each galaxy has some sort of effect over a volume that exceeds the volume of visible stars in the galaxy, shaping the "dark matter halo". Perhaps by material ejection in polar jets that is recaptured by gravity? Perhaps by extremely large magnetic fields? Perhaps by some force carrier that affects "dark matter" that we cannot sense?

I welcome studies that produce observations that raise questions about the limits to our current understanding. And, I appreciate attempts to explain them with new physics. I am just skeptical of explanations that have not been tested against other observations.

 

[billslugg]

The artist illustration does not match the article's explanation. Per the explanation, two clusters collided. The DM kept going but the galaxies interacted somehow and slowed down. In the artist illustration, the DM appears to accelerate but not the regular matter. Ignore the illustration. Use the "dump trucks carrying sand colliding" model. Dump trucks represent regular matter, sand the DM. Dump trucks slow down, sand keeps going. Similarly, when two galaxy clusters collide, the regular matter coalesces and forms new galaxies. This is because galaxies only represent a tiny percentage of the regular mass in the universe. Much of it is intergalactic dust. The article decouples the velocity of dark matter and regular matter. In a collision the DM goes right on, unimpeded. The regular matter clumps and slows down.

 

[Unclear Engineer]

But, the dark matter is still gravitationally attracted to the regular matter, as well as itself. So, the dark matter should not just go right on by the collision without showing any effect at all.

If it is really cold dark matter, which is hypothesized to not interact with itself as well as to not interact (except gravitationally) with regular matter, then there would not be so much clumping as seen in the regular matter, but the dark matter should still be gravitationally attracted to the regular matter that "stops" at the collision site.

On the other hand, if dark matter does interact with itself, then it should appear to also clump like the visible matter, although maybe to a different extent.

The theorists have been looking for some explanation about how all of the "cold dark matter" could be stripped out of a galaxy, ever since finding the galaxy that seems to have none. So, this seems to be their hypothesis. But, it still doesn't look "right" to me.

 

[Questioner]

Since the only assigned attribute of hypothetical DM is mass
& the only potential way of deducing its supposed existence is its effect on visible matter,
one can only think they are 'locating' DM by its influence on visible matter.

Since in galactic 'collisions' almost nothing actually collides,
so there is virtually no visible matter clumping from the 'collision'.
The clumping of visible matter is already clumped.

Honestly if their detection of unseen mass are correct,
something very non-standard is going on if DM is any kind of matter.

I repeat I'm curious what the two galactic central black holes are doing. I don't know how tightly they can track them.

Because if the DM attributed halos coincide with the central black hole's positions my theory could be correct, in which case it would overhaul astrophysics in a major way.

 

[Unclear Engineer]

Regular matter apparently does effectively "clump" because the visible parts of galaxies apparently often do merge into one galaxy when they collide.

While it is true that few if any stars actually run into each other in such a galactic collision, the net effect of a large number of N-body star gravitational "collisions" (or interactions without touching) still allow the transfer of momentum between the 2 large masses of stars.

Viewed from a distance, collisions between 2 stars look the same in transfer of momentum as what occurs when 2 billiard balls hit each other. But, when there are lots of stars, not just a pair, the net gravity of the whole group tends to keep the stars from just scattering away from the galaxies. So, the net effect is that the 2 groups of stars tend to average their net momentums through intergalactic space and merge together.

Now, what that means for "dark matter" that we cannot directly see is going to depend on what that dark matter really is. If it is "another world" of matter with "dark atoms", "dark stars" etc. then I would expect it to have the same merging effect as the visible matter. But, if it is particles or waves of some sort that do not interact with each other the same way that regular matter interacts with itself, then the dark matter may do something entirely different.

But, if it really does just "pass through", it still should be attracted to the visible matter that stops at the merge volume. So, in that speculative "artist's illustration" where it seems to be attracted out ahead of the visible matter as the separate galaxies approach each other, I would expect it to also slow down as it moves away from the merged visible matter when it gets to the other side and is moving away.

If it does not end up staying with the visible matter, then there should be some sort of dark-matter-only clumps sailing around the cosmos from previous collisions, which should be detectable by their lensing effects on background light from visible matter. Do, we see anything like that - lensing with no visible foreground object to account for it? Considering that dark matter is supposedly the majority mass of galaxies, even including the central supermassive black hole, the lensing of a blob of dark matter with no visible matter in it and no black hole in it should still make a substantial lens.

 

[Questioner]

I believe there are lensing locations without identifiable visible matter,
so those are generally attributed to DM.

Is regular gravitational interactions of mass fields considered 'clumping',
because i wouldn't call that 'clumping'.

Clumping would have to be electromagnetic or some other similar force where electro-polar (or similar) entwinements possibly including electron cloud linkages happen.
Namely something beyond gravitational mass interactions.

Presumably if DM has mass it would also have mass field gravitational interactions,
but it's not at all clear that is the case.

Inertia is (should be?) a function of mass and mass is the only currently assigned property of DM.

These graphics indicate something beyond mass and its inertia alone is going on with the hypothesized DM.

My idea the halo of mass is an additional function of black holes does require a superluminal 'speed of gravity',
which is why if happens to correct will overhaul standing conventions.

 

[Unclear Engineer]

I thought you were referring to the visible galaxies as "clumps". And, the two clumps merge to one clump. I would expect gravity to be able to make clumps of various sizes without magnetism. although I am not surprised that magnetism is present wherever there is ionization of baryonic matter and motion.

 

[Questioner]

The gravitational effect is ephemeral & incredibly weaker than any of the major forces,
although the gravitational effect extends much farther with greater constancy than those.

Alone, gravity is fragile & often transitory.

Only when electromagnetism comes into play [likely facilitated by gravity derived proximity] is there any more tenacious interaction(s) involved.

 

[Unclear Engineer]

Not understanding why you think gravity extends farther than other forces.

Electrical force and gravitational force both diminish by the square of the distance.

The difference is that the electrical force between 2 objects depend on them having opposite charges, so if there are 2 opposite charges that are not separated by much distance, then the net effect beyond their distance of separation is no longer a simple relationship to the square of the distance from either. It become a dipole field.

But, with gravity, there is only one version of mass, with no anti-mass to make dipoles (at least as far as we can tell). Even "antimatter" seems to have positive mass, from the few experiments that were done to try to measure that.

If there were 2 galaxies with significant net charges of opposite polarity, they would interact much more strongly than they do by gravity. But, as far as we know, the net charge of a galaxy seems to be neutral or small.

However, I do wonder what those jets of matter emanating from the poles of central supermassive black holes do in the way of making electrical dipoles and/or magnetic dipoles that might engulf galaxies.