'Cosmic own goal' another clue in hunt for dark matter

Jun 25, 2014
Description: The visible galaxies in the Local Group simulation, shown in the lower right, only trace a tiny fraction of the vast number of dark matter halos, revealed in the upper left. Credit: John Helly, Till Sawala, James Trayford, Durham University

The hunt for dark matter has taken another step forward thanks to new supercomputer simulations showing the evolution of our "local Universe" from the Big Bang to the present day.

Physicists at Durham University, UK, who are leading the research, say their simulations could improve understanding of , a mysterious substance believed to make up 85 per cent of the mass of the Universe.

Professor Carlos Frenk, Director of Durham University's Institute for Computational Cosmology, said: "I've been losing sleep over this for the last 30 years.

"Dark matter is the key to everything we know about , but we still don't know its exact nature. Understanding how galaxies formed holds the key to the dark matter mystery."

Scientists believe clumps of dark matter – or halos – that emerged from the early Universe, trapped intergalactic gas and became the birthplaces of galaxies.

Cosmological theory predicts that our own cosmic neighbourhood should be teeming with millions of small halos, but only a few dozen small galaxies have been observed around the Milky Way.

Professor Frenk added: "We know there can't be a galaxy in every halo. The question is: 'Why not?'."

The Durham researchers believe their simulations answer this question, showing explicitly how and why millions of halos around our galaxy and neighbouring Andromeda failed to produce galaxies and became barren worlds. They say the gas that would have made the galaxy was sterilized by the heat from the first stars that formed in the Universe and was prevented from cooling and turning into stars.

Description: Gas in the EAGLE Simulation, showing hot bubbles (red colors) surrounding large galaxies, connected by colder filaments (blue and green colors). Inserts zoom in on the Local Group around the Milky Way and show the distribution of gas, stars and dark matter. Credit: Richard Bower, John Helly, Sarah Nixon, Till Sawala, James Trayford, Durham University

However, a few halos managed to bypass this cosmic furnace by growing early and fast enough to hold on to their gas and eventually form galaxies.

The findings will be presented at the Royal Astronomical Society's National Astronomy Meeting in Portsmouth today.

Professor Frenk, who will today receive the Royal Astronomical Society's top award, the Gold Medal for Astronomy, added: "We have learned that most dark matter halos are quite different from the 'chosen few' that are lit up by starlight.

"Thanks to our simulations we know that if our theories of dark matter are correct then the Universe around us should be full of halos that failed to make a galaxy. Perhaps astronomers will one day figure out a way to find them."

Lead researcher Dr Till Sawala, in the Institute for Computational Cosmology, at Durham University, said the research was the first to simulate the evolution of our "Local Group" of galaxies, including the Milky Way, Andromeda, their satellites and several isolated small galaxies, in its entirety.

Dr Sawala said: "What we've seen in our simulations is a cosmic own goal.

Description: The DiRAC Cosmology Machine, operated by Durham University has 6720 Intel Xeon Cores and 53,760 GByte of RAM. Credit: Till Sawala, Durham University

"We already knew that the first generation of stars emitted intense radiation, heating intergalactic gas to temperatures hotter than the surface of the sun. After that, the gas is so hot that further star formation gets a lot more difficult, leaving halos with little chance to form galaxies.

"We were able to show that the cosmic heating was not simply a lottery with a few lucky winners. Instead, it was a rigorous selection process and only halos that grew fast enough were fit for galaxy formation."

The close-up look at the Local Group is part of the larger EAGLE project currently being undertaken by cosmologists at Durham University and the University of Leiden in the Netherlands. EAGLE is one of the first attempts to simulate from the beginning the formation of galaxies in a representative volume of the Universe. By peering into the virtual Universe, the researchers find galaxies that look remarkably like our own, surrounded by countless , only a small fraction of which contain galaxies.

The Durham-led simulation was carried out on the "Cosmology Machine", which is the part of the DiRAC national supercomputing facility for research in astrophysics and particle physics funded by the Department for Business, Innovation and Skills through the STFC.

The Cosmology Machine – based at Durham University – has more than 5,000 times the computing power of typical PCs, and over 10,000 times the amount of memory.

Explore further: Map of universe questioned: Dwarf galaxies don't fit standard model

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Quantum Flux
1.6 / 5 (9) Jun 25, 2014
I predict that dark matter is a escape goat to fix the errors in the relativity theories.
Uncle Ira
3.7 / 5 (9) Jun 25, 2014
I predict that dark matter is a escape goat to fix the errors in the relativity theories.


Well Skippy as long as we are predicting,, Ol Ira predicts that you probably won't be making much of a living with your predictions. Wonder who has the prediction that will come true, what you think Cher?
Quantum Flux
3.6 / 5 (5) Jun 25, 2014
Now according to Scientific American; http://www.scient...-matter/ dark matter is suppose to be causing the gamma radiation emanating from the galactic core where no object rests but Sgr A*. I have some questions.

When did dark matter become gamma radiation? Why can't dark matter, which is suppose to make stars orbit the Milky Way faster, be observed at the edge of the Milky Way?

Let me get this straight, dark matter has a huge influence on the movement of stars near the outer edge of the Milky Way but cannot be detected. And the dark matter said to be concentrated or dense near the center of the Milky way does not influence the movement of the stars at all but can be detected.

Why does dark matter not influence the stars more-so where it is supposedly denser?
Quantum Flux
not rated yet Jun 25, 2014
You are right Ol Ira. I will not make one cent off of any of my predictions.
Uncle Ira
1 / 5 (4) Jun 25, 2014
@ Quantity-Skippy. I'm not the scientist really, I just read the physorg stuffs and the google-Skippy's stuffs. But I will do the best I can but don't hold me to it, okayeeei Cher?

When did dark matter become gamma radiation?


I don't think that it did become that no. If it did then they got the things to see that with.

Why can't dark matter, which is suppose to make stars orbit the Milky Way faster, be observed at the edge of the Milky Way?


Now that one I am not sure about but I think it is invisible so they can't see it with regular things they use to look with.

I'm going to have to P.S. to you because I will run out of the letters between the questions, that okayeei with you Cher?
IMP-9
4.5 / 5 (8) Jun 25, 2014
the galactic core where no object rests but Sgr A*.


There are lots of things in the core, tens of billions of stars for one. That map is of a very large region.

The hypotheses with the gamma ray data was that dark matter particles could collide and annihilate producing gamma rays, like positions and electrons. It would be stronger in the centre because the density is highest there and collision rate often varies with density squared.

Dark matter would influence the stars in the center but it wouldn't strongly affect the shape of the velocity curve due to the way the distributions work. The core is affected less than the outer reaches because they don't feel the gravity of the mass outside their radius as long as it is symmetric. Just like digging down into the earth decreases the acceleration due to gravity.
Uncle Ira
1 / 5 (3) Jun 25, 2014
P.S. for you Quantity-Skippy.

dark matter has a huge influence on the movement of stars near the outer edge of the Milky Way


Yeah, I think you got that part right.

but cannot be detected.


Yeah, I think that is right too me. But we both could be wrong about that. I think it's because none of the scientist-Skippys has found a thing to look at it with yet. I think they are looking for something that isn't like anything else so they working on a way to find it or something.

And the dark matter said to be concentrated or dense near the center of the Milky way does not influence the movement of the stars at all but can be detected.


Hooweei, that is another one I'll say say some foolishment on. I think it is spread out all around the Milky Way bothering everything in it. But that could be wrong.

Why does dark matter not influence the stars more-so where it is supposedly denser


I don't think that is right. Where all the smart-Skippys when you need one?
Uncle Ira
1 / 5 (3) Jun 25, 2014
There are lots of things in the core, tens of billions of stars for one. That map is of a very large region.

The hypotheses with the gamma ray data was that dark matter particles could collide and annihilate producing gamma rays, like positions and electrons. It would be stronger in the centre because the density is highest there and collision rate often varies with density squared.

Dark matter would influence the stars in the center but it wouldn't strongly affect the shape of the velocity curve due to the way the distributions work. The core is affected less than the outer reaches because they don't feel the gravity of the mass outside their radius as long as it is symmetric. Just like digging down into the earth decreases the acceleration due to gravity.


I'm sure glad to see you show up, I was making the fool of me for real. Can you grade my paper too IMP-Skippy? It don't hurt my feeling for the bad grade. I just want to know how I did. Thanks if you can.
otero
Jun 25, 2014
This comment has been removed by a moderator.
MrPressure
Jun 26, 2014
This comment has been removed by a moderator.
Whydening Gyre
3.4 / 5 (5) Jun 26, 2014
I dunno... This Dark Matter is beginning to sound "aether"ish...
Liquid1474
5 / 5 (1) Jun 26, 2014
Intriguing how 'natural selection' processes were around since the beginning;
"Everything small is a small version of something big"
---Finn, Adventure Time
cantdrive85
1.6 / 5 (7) Jun 26, 2014
Own goal is a perfect analogy, rewrite the code and cherry pick data until you find what ye seek.
dogbert
1 / 5 (3) Jun 26, 2014
"Thanks to our simulations we know that if our theories of dark matter are correct then the Universe around us should be full of halos that failed to make a galaxy. Perhaps astronomers will one day figure out a way to find them."


Wonder how that works. Billions of dark matter halos which did not form galaxies but somehow don't participate in gravitational lensing.

Dark matter is truly magical.
DeliriousNeuron
2 / 5 (4) Jun 26, 2014
Ok Aunt Ira....call me Skippy...no worries here man! I'm highly confident you'll eat your words one day.
So someone programmed the simulation with flawed data, only to pacify mainstream physics.

So if I were a computer programmer, I could program the outcome to simulate dark matter is a giant turd in a vacuum right?
If something is flawed from the beginning, how on earth could the outcome be correct?
IMP-9
4 / 5 (4) Jun 26, 2014
Wonder how that works. Billions of dark matter halos which did not form galaxies but somehow don't participate in gravitational lensing.


Who says it doesn't? The fidelity of weak lensing maps isn't high enough to see individual galactic halos yet.
dogbert
1 / 5 (2) Jun 26, 2014
IMP-9
Who says it doesn't? The fidelity of weak lensing maps isn't high enough to see individual galactic halos yet.


It can be "seen" in the bullet cluster where it is supposed to have been stripped of normal matter, but it can't be "seen" in galactic halos which never contained normal matter?
yyz
5 / 5 (2) Jun 26, 2014
"It can be "seen" in the bullet cluster where it is supposed to have been stripped of normal matter, but it can't be "seen" in galactic halos which never contained normal matter?"

dogbert, you're comparing galaxy clusters to galaxies. Weak lensing has never been observed in the context of individual galaxies, only in galaxy clusters. As IMP-9 pointed out, weak lensing studies aren't sufficiently detailed enough to detect DM halos around individual galaxies.....yet.
dogbert
1 / 5 (3) Jun 28, 2014
yyz,
dogbert, you're comparing galaxy clusters to galaxies. Weak lensing has never been observed in the context of individual galaxies, only in galaxy clusters. As IMP-9 pointed out, weak lensing studies aren't sufficiently detailed enough to detect DM halos around individual galaxies.....yet.


There are numerous articles on phys.org about gravitational lensing from single galaxies. Here are a couple:

http://phys.org/n...nal.html

http://phys.org/n...ens.html

IMP-9
5 / 5 (2) Jun 28, 2014
There are numerous articles on phys.org about gravitational lensing from single galaxies.


The first is a strong lens, the other is microlensing neither are weak lensing. The trouble with strong lensing is it requires very fine alignment (dumb luck). It will depend strongly on the density and mass of the lens, we don't know what those are so you have no idea if we should be seeing them. It is rare for individual galaxies to do this. Note importantly that it was discovered by intentionally studying the lensing radio galaxy, if it was a dark matter halo it wouldn't have been found. The second example is microlensing which wasn't apparent until a supernova occurred behind it, this is very rare and so not very useful. Secondly the way it was confirmed to be a lens was by detecting the lensing galaxy. These methods work on chance, weak lensing on the other hand allows 3D tomography of the mass distribution, things can't hide.
yyz
5 / 5 (2) Jun 28, 2014
@dogbert,

What I should have stated in my earlier comment is that weak lensing by individual galaxies (or more correctly DM halos) of the masses described in this article (10^4-10^7 solar mass) has not been observed. Weak lensing by such low-mass objects is currently below the threshold of detection by current methods.

"There are numerous articles on phys.org about gravitational lensing from single galaxies. Here are a couple:"

Those are examples of strong lensing: http://en.wikiped..._lensing

Strong lensing is not expected to be observed in such low-mass DM halos as this article describes. The bottom line is that weak or strong gravitational lensing is not expected to be useful (or practicable) for detecting such low-mass objects.
Returners
1.7 / 5 (6) Jun 29, 2014

Now that one I am not sure about but I think it is invisible so they can't see it with regular things they use to look with.


No un-accounted for gravitational influences have been noticed within 1000 light years of Earth. That is to say, no object within 1000 light years has any motion which cannot be entirely explained, to margin of error, by known ordinary matter.

This contradicts Dark Matter theory, since 80 to 85% of the universe is supposedly Dark Matter according to the theory.

We reside in a part of the galaxy where the concentration of DM would need to be maximized, under their interpretation of the facts, in order for their theory to be true.

However, I have proved by elementary examples that the common interpretation of Newton's gravity in the context of galactic stellar orbits is wrong, and have been able to show that the observed motion is entirely explained by Newtonian dynamics, properly applied, and ordinary matter.

Nobody listens, even though It's proven.
Returners
1 / 5 (4) Jun 29, 2014
Ironically, my predictions, based on Newtonian Dynamics, actually agree with the observation of stars within 1000 light year radius of Earth, and can explain why there is no observed "Dark Matter," namely because it simply does not exist, and there is no need for it to exist to explain stellar orbits.

The "mass" you feel in a disk is related to the disks volume. You can express the mass of a concentric disk(cylinder) as "d*h*Pi*r^2," for each distance, r, from the center. Here "d" is average density.

Once you substitute this term for the big "M" in the gravity equation, you have expressed, roughly, the average mass the orbiting star should "feel".

You'll notice that when you plug this in the standard gravitational acceleration equation, the "r" terms from the denominator cancel, and you are left with a solution which is approximately CONSTANT with distance from the center.

The observations are CONSTANT orbital velocities when away from the hub of the galaxy.

DM does not exist.
Returners
1.7 / 5 (6) Jun 29, 2014
There is another way to prove Dark matter "halos" do not exist within galaxies, because they would be eaten by the central black hole, or by ordinary stellar mass black holes.

Dark Matter supposedly does not interact mechanically except by gravity, which means it cannot "clump" like normal matter. It can only end up in orbits around itself or ordinary matter, or in pogo orbits, where it passes through other DM particles and oscillates like that.

Nevertheless, if it crosses an event horizon it would get captured.

If there was 4 to 6 times as much DM as ordinary matter, then SMBH and even stellar mass black holes within the spiral bands of spiral galaxies (where DM is supposed to be densest) would grow out of control in relatively short time periods. Now the average density of DM in the universe is low, but the average density of DM in a galaxy, according to their interpretation, would need to be very high...

In reality, we observe no DM within the Milky Way anywhere within 1000 ly.
dogbert
1 / 5 (5) Jun 29, 2014
Returners,

You make a valid point. If Dark Matter were real, then our little section of the universe is uniquely devoid of it. There is absolutely no reason to expect our section of the universe to be unique devoid of DM.
Returners
1.7 / 5 (6) Jun 29, 2014
Sombrero Galaxy:

http://en.wikiped...o_Galaxy

Now galaxies are not perfectly uniform, which is where the orbital velocity curve with distance is not perfectly linear, and grows as you go out from the center, until a maximum is hit near the edge of the hub, then it levels off.

Some have argued that the average density of stars falls off from the Hub, I see no evidence of that.

This galaxy certainly appears to have similar, or possibly even greater density of stars and dust in the outer bands.

yeah, the density of the disk is less than the hub, but the hub is not 100% of mass, as you move away from the hub, the hub's influence is less important, and the disk-like shape becomes more important, producing an approximately constant stellar orbital speed with distance, excluding local effects from star clusters.

http://en.wikiped...file.svg

continued.
Returners
1.7 / 5 (6) Jun 29, 2014
Note the second link above, incorrectly shows Dark Matter in a Spherical Halo, contrary to how it would need to be in order to explain the CONSTANT stellar orbits.

These idiots don't even know the mathematics of what they are trying to explain, as a Spherical distribution would result in an "r" term remaining in the numerator of the gravity equation, and would therefore result in stars actually having faster orbits the farther they are away from the center of the galaxy.

Observe spherical distribution in terms of volume and density:

A = (4/3)*G*d*pi*r^3 / r^2 = (4/3)*G*d*pi*r....

which is a linearly increasing acceleration, therefore linearly increasing stellar orbital velocity, with distance, which is NOT observed.

idiots.

Not to mention that a spherical distribution of DM would not even be stable when circumscribed around a disk of ordinary matter, as it would collapse into the plane of the disk anyway, and would be over-concentrated in the center, where it doesn't need to be.
Returners
1.7 / 5 (6) Jun 29, 2014
The reason a collapse would happen is related to the SMBH and early stellar mass black holes from alleged super-massive first generation stars. That's why a spherical shell of DM is not stable, and certainly not over billions of years.

I believe that's:

T = 2pi*sqrt(a^3/GM)

Since galaxies are nearly circular, we allow "r ~ a"...

If we write "M" in terms of volume of a disk, and density, we have:

M = pi*h*d*r^2 =~ pi*h*d*a^2

Now re-write period equation:

T = 2pi *sqrt(a^3/(G*pi*h*d*a^2)) = 2pi*sqrt(a/(G*pi*h*d))

All of the bottom terms are approximately constant, once outside the hub, based on observable, ordinary matter, so we can re-write this as a constant, k, for each galaxy...

T =~ 2pi*sqrt(a/k)

T =~ 2pi*sqrt(a) / sqrt(k)

Which is approximately what is observed.
Returners
2.1 / 5 (7) Jun 29, 2014
The reason cosmologists can't get galaxies to form in simulations without simulating "Dark Matter" is because they incorrectly assume the universe started as a random bunch of crap, with galaxies forming only by chance in certain lucky locations.

No, it really is THAT hard to form a stable orbiting system. They just can't get over the fact it doesn't happen by chance, so they have to add more and more fudge factors to try to make it happen by chance, which is a ridiculous contradiction.
DeliriousNeuron
1 / 5 (2) Jun 29, 2014
http://m.youtube.com/watch?v=qHrBhgwq__Q
Gravity creates motion. Motion of mass creates static electricity.
IMP-9
4 / 5 (4) Jun 29, 2014
they incorrectly assume the universe started as a random bunch of crap


No. Most of these simulations start with the density perturbations observed with the CMBR. Testable crap rather than "there is a reason" untestable nonsense.

Dark Matter in a Spherical Halo


Are you intentionally misrepresenting the science or do you just have no knowledge of it? People don't use spherical distributions, people use distributions such as NFW profiles and the like.

if it crosses an event horizon it would get captured.

Consider the schwarzschild radius of a SMBH vs the radius of a dark matter halo, then shut up, it's a tiny amount. It wouldn't be swallowed because unlike barionic matter there is no friction to accrete with.

no object within 1000 light years has any motion which cannot be entirely explained, to margin of error, by known ordinary matter.


That's wrong, there are conflicting studies but the best point to DM and explain previous biases.

Nonsense.