A Cosmic Web Connecting the Universe Shapes Dark Matter In Galaxies, Study Finds

An anonymous reader quotes a report from Motherboard: Our universe is connected by a cosmic web made of giant threads of dark matter and gas that stretch across millions of light years and intersect at "nodes" populated by dense clusters of galaxies. This vast network shapes the distribution and evolution of galaxies in fundamental ways that scientists are trying to unravel with ever-sharper observations and advanced simulations. Now, a team led by Callum Donnan, a postgraduate student in astronomy at the University of Edinburgh, have identified a key correlation between the chemical makeup of galaxies and their location within the cosmic web. Using both real-life observations and computer simulations, the team found that "galaxies closer to nodes [display] higher chemical enrichment than those farther away," a discovery that reveals some of the mysterious dynamics that link the universe, according to a study published on Monday in Nature Astronomy.

To home in on this question, Donnan and his colleagues examined galaxies within about a billion light years of the Milky Way observed by the Sloan Digital Sky Survey in New Mexico, which covers a huge area of the sky. The team studied the elemental makeup of gasses in the interstellar spaces within these real-life galaxies, a property that is known as gas-phase metallicity. The results revealed that galaxies close to the nodes of the cosmic web were richer in "metals," which in astronomy refers to any element heavier than helium. A weaker correlation was also observed with proximity to the web's filaments, which are the threads that stretch across the universe and link nodes together. The team ran sophisticated cosmological simulations using the IllustrisTNG platform, which supported the observational findings. Significantly, the approach revealed that a galaxy's position in the cosmic web modulates its chemical content even when other factors, such as the density of a particular region in the universe, are taken into account.

Naturally, that raises the question of why galaxies located near nodes are enriched with more metals compared to those distributed along filaments or in empty "voids" within the cosmic web. Donnan's team isolated two major drivers of this relationship: The absorption of gas from outside of galaxies and the evolution of stars and dark matter inside of them. Galaxies feed on gasses that are strewn across space in the intergalactic medium, but those that are further from nodes consume much more of this outside material than those close to nodes. Since intergalactic gas is metal-poor, it dilutes the enriched gas of far-flung galaxies, lowering their overall gas-phase metallicities. Galaxies near nodes don't consume as much of this metal-poor material, which helps to keep them chemically enriched with higher concentrations of heavier elements. In addition, galaxies close to nodes seem to have matured earlier than those located at a distance. These galaxies had a head-start in birthing new stars and collecting dark matter, which is a mysterious substance that makes up most of the matter in the universe.

I can answer that

[Growlley]

it's the simulations API's framework and libraries.

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[narcc]

That's funny until you realize that there are people that seriously believe that.

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[gweihir]

That's funny until you realize that there are people that seriously believe that.

Well, it is not completely impossible, but these people believe, like all religious and quasi-religious idiots, that they of course have the truth.

So it was spiders after all.

[Anonymous Coward]

Sorry, turtles.

Re: was spiders after all [Sorry, turtles.]

[Tablizer]

Spiders are just leggy turtles.

The Brain?

[Dewiltse]

It's nerons in some giant brain!?! XD (kidding) But in a more serious note, it's really cool that it's collected in this strange web. I'll have to go look up more about it. :)

Maybe caused by life forms?

[Narcocide]

Know what else would largely be focused on the more mineral-rich galaxies? Space travelers. Maybe it's warp field pollution, like they predicted in Star Trek.

How the universer works.

[UsRanger175]

This story is identical to the how the universe works episode that Just came out.

Puff Puff Give

[CubicleZombie]

It sounds like they made up something to explain something nobody understands. I feel that way about anything I read regarding "Dark Matter", like we're 2-Dimensional people trying to explain a sphere and there's something fundamentally missing.

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[Jamu]

It sounds like they made up something to explain something nobody understands.

Ah, science.

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[Admiral Krunch]

It sounds like they made up something to explain something nobody understands.

Ah, science.

Yea, religion would never do anything like that...

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[MikeDataLink]

It sounds like they made up something to explain something nobody understands.

You are confusing science with religion. Religion makes something up and then kills you for not believing it.

Science makes a hypothesis, and then tests it to see if it is correct. If it is not correct, we change our hypothesis based on what we discovered and and test again.

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[Potor]

True. So strangely enough, religion is about certainty, whereas science never is. At best, science is only certain until proven wrong, so it is essentially about doubt (i.e. falsification). Religion cannot be falsified.

Based on the history of science, and especially based on the fact that dark matter is postulated to explain phenomena but it itself is postulated as non-phenomenal, I expect dark matter to be like phlogiston or epicycles. But of course I will be willing to stand corrected.

The mixing problem

[Okian Warrior]

It sounds like they made up something to explain something nobody understands. I feel that way about anything I read regarding "Dark Matter", like we're 2-Dimensional people trying to explain a sphere and there's something fundamentally missing.

The outgoing force of a spinning object is F = m*(V^2)/r, and the gravitational force is G*M*m/(r^2).

For an orbiting object, these have to be equal. Setting them equal the little m (mass of the object) cancels, one of the r's cancels, and you're left with the relation r = K/(V^2), so r (distance from the sun) is inversely proportional to the square of the velocity.

So the mass of an orbiting object doesn't matter, and we see that in our own solar system: when we plot the distance versus orbital velocity, the planets fall exactly on the 1/V^2 curve regardless of planetary mass.

This works all the way down to the surface of the sun. You can extend it inside the sun (as a thought problem) by noting that in a uniform sphere the gravitational attraction is linear with distance to the center.

So the typical and expected Newtonian physics predicts the orbital velocities as a function of distance from the center: starting at zero in the exact center, rising to a maximum at the surface of the central body, then falling as a 1/V^2 curve out to infinity.

Note that the orbital velocities is wildly different on this plot: Mercury goes around 49 times while Jupiter goes around once, as the Earth goes around 12 times. This means that at any point in time, it's highly likely that the planets are distributed evenly in their orbits, relative to each other. If you were to start the planets in a straight line pointing to the sun, it's analogous to drawing a line of chocolate on the surface of a cup of milk and then stirring: the orbits would quickly "mix" until everything was evenly distributed.

The orbital velocity of our galaxy is about 1/4 billion years (it takes 260,000,000 years for the Earth to orbit around), the universe is about 14 billion years old, so our galaxy has made about 56 revolutions in that time...

...and yet, our galaxy still has identifiable "arms". Somehow the stars formed in a line, and this line has not mixed over time.

Indeed, one can easily find Bar Spiral galaxies [wikipedia.org], which still have spiral arms *and* a central bar that has rotated in lock step with the rest of the galaxy (!).

In fact, you can easily find galaxies [case.edu] which are almost entirely central bar. The bar, almost all of the galaxy, rotates in step while the spiral arms show less than 1 full orbital rotation.

This is "the mixing problem", and was known since Kepler's time.

We can measure the galactic rotation by measuring the red/blue shift of individual stars on either side of a galaxy.

We can estimate the amount of mass in a galaxy by the total brightness of the stars, which is about 1/5 of what would be required by the measured orbital velocities.

Gravitational lensing indicates that galaxies do, indeed, have about 5x the mass we estimate from star census calculations.

So from all this, we believe that galaxies have about 5x as much mass as we can see, our own galaxy has extra mass that we can't see, and other explanations (such as modifications to Newtonian gravity) have been ruled out.

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[CubicleZombie]

Thanks for a very good reply.

I think my issue with "Dark Matter" is that the term implies there's something there, we just can't see it because somehow it doesn't interact with light.

I just have this feeling that if we could somehow get a box full of whatever dark matter is that we'd still have no idea what it is. Much like a 2D being trying to figure out what a sphere is.

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[kbahey]

Came here to say thanks a lot for the step by step explanation ... wonderful ...

Much simpler than it sounds

[burtosis]

Cosmic filaments or “web” are just regions of slightly higher density that have then pulled themselves together under gravity bringing regular and dark matter together. The filaments also branch and at regions where they intersect the density is higher still creating points or nodes where the density becomes quite a bit higher than average, even along the filaments themselves.

Stars burn hydrogen and helium left over from the Big Bang to form heavier elements, the higher the density the large

cause and effect

[algaeman]

Since we have such a poor understanding of what the process is generating these threads and nodes, it seems impossible to say whether the physics governing the nodes are generating the increased metallicity, or if the increased density (causing greater levels of supernovae) are then creating the superstructure of the filaments.

"Dark Web"?

[Tablizer]

I knew that was coming, per Dark X meme for everything that baffles astronomers. I have Dark People Skills.

Interesting

[jd]

We know that the large scale structure of the universe matches very well the structure of the cosmic microwave background radiation. According to wikipedia, dark matter also leaves an imprint on the CMBR but in a different way. If we go with this cosmic web model of dark matter, then it would presumably follow that the structure of the imprint of dark matter must match the structure of the web calculated for dark matter, after you correct for the different nature of the interaction. Therefore a more detaile

cosmic web

[Mr. Goodprobe]

Almost sounds like the eldar webways...

Sounds like birkeland currents.

[danda]

cosmic web made of giant threads

This is what people like Birkeland, Alfven, Peratt, Thornhill have been saying for 100+ years now.

gee, could it be that the universe is electric?

ps: doesn't require any "dark matter", unless one equates "dark matter" to the dynamic ether (which Dayton Miller and others have detected).

Giant Brain?

[benthurston27]

All these nodes and interconnections really sounds like the whole universe is some kind of neural network.