## Hubble Provides Most Detailed Dark Matter Map Yet

by Nancy Atkinson[/caption]

Using Hubble’s Advanced Camera for Surveys, astronomers have been able to chart invisible dark matter in a distant galaxy, which enabled them to create one of the sharpest and most detailed maps of dark matter in the universe. Looking for invisible and indeterminate matter is a difficult job, but one that astronomers have been trying to do for over a decade. This new map also might provide clues on that other mysterious stuff in the universe — dark energy – and what role it played in the universe’s early formative years.

A team led by Dan Coe at JPL used Hubble to look at Abell 1689, located 2.2 billion light-years away. The cluster’s gravity, which mostly comes from dark matter, acts like a cosmic magnifying glass, bending and amplifying the light from distant galaxies behind it. This effect, called gravitational lensing, produces multiple, warped, and greatly magnified images of those galaxies, making the galaxies look distorted and fuzzy. By studying the distorted images, astronomers estimated the amount of dark matter within the cluster. If the cluster’s gravity only came from the visible galaxies, the lensing distortions would be much weaker.

What they found suggests that galaxy clusters may have formed earlier than expected, before the push of dark energy inhibited their growth.

Dark energy pushes galaxies apart from one another by stretching the space between them, thereby suppressing the formation of giant structures called galaxy clusters. One way astronomers can probe this primeval tug-of-war is through mapping the distribution of dark matter in clusters.

“The lensed images are like a big puzzle,” Coe said. “Here we have figured out, for the first time, a way to arrange the mass of Abell 1689 such that it lenses all of these background galaxies to their observed positions.” Coe used this information to produce a higher-resolution map of the cluster’s dark matter distribution than was possible before.

Based on their higher-resolution mass map, Coe and his collaborators confirm previous results showing that the core of Abell 1689 is much denser in dark matter than expected for a cluster of its size, based on computer simulations of structure growth. Abell 1689 joins a handful of other well-studied clusters found to have similarly dense cores. The finding is surprising, because the push of dark energy early in the universe’s history would have stunted the growth of all galaxy clusters.

“Galaxy clusters, therefore, would had to have started forming billions of years earlier in order to build up to the numbers we see today,” Coe said. “At earlier times, the universe was smaller and more densely packed with dark matter. Abell 1689 appears to have been well fed at birth by the dense matter surrounding it in the early universe. The cluster has carried this bulk with it through its adult life to appear as we observe it today.”

Astronomers are planning to study more clusters to confirm the possible influence of dark energy. A major Hubble program that will analyze dark matter in gigantic galaxy clusters is the Cluster Lensing and Supernova survey with Hubble (CLASH). In this survey, the telescope will study 25 clusters for a total of one month over the next three years. The CLASH clusters were selected because of their strong X-ray emission, indicating they contain large quantities of hot gas. This abundance means the clusters are extremely massive. By observing these clusters, astronomers will map the dark matter distributions and look for more conclusive evidence of early cluster formation, and possibly early dark energy.

For more information see the HubbleSite.

Abell 1689, Gravitational Lensing, Hubble

Due to the large concentration in the center, this looks like a great confirmation of the “Great Attractor” theory for our own cluster. Maybe like super-massive black holes are a normality for the center of galaxies, this super-massive dark matter center could be some part of a greater explanation of how galaxy clusters form.

Dark energy began to dominate the universe about 4 billion years ago, or around the time the solar system formed. Before then the universe was matter dominated, so galaxy clusters had plenty of time to coalesce. Galaxy dynamics maven can then compute the upper bound on galaxy cluster mass given a 9 billion year time frame.

This image is a keeper.

LC

So the Flying Spaghetti Monster is real!?

It stands to reason that DM influenced the visible universe more than we earlier accounted for. But since the old cosmology made local sense DM’s influence must be stealthed analogous to the fashion seen here.

While this is long, it pretty much covers the basic stuff — this is not my personal theory, but is based on standard concepts of cosmology.

The FLRW cosmology is comparatively simple to understand. The motion of the space is given by a scale factor which evolves with time. The Hamiltonian for the scale factor a in FLRW logic is

(a’/a)^2 = (8pi G rho/3) – k/a^2, ( ‘ = d/dt)

which has different solutions for different densities rho. This leads to a dynamical equation of motion when considered as a Hamiltonian

d^2a/dt^2 = (8pi G?/3)a – k/a^2.

For a constant density rho = /\/(8pi G) for /\ = “Lambda” the cosmological constant. This solution for k = 0 is an exponential solution

a ~ exp(sqrt{8pi G rho/3}t),

which is the inflationary solution. However, for k = 1 there is this perturbing term which does damp out as the scale factor a increases.

The distance to the horizon is

R = int^t dt’/a(t’) = sqrt{3/8pi G?} = sqrt{3//\}.

The entropy is S ~ 4?A/L_p^2 = 12?/(?L_p^2). But if k = +1 it is clear the solution is different, but only early on. The observed universe is k = 0, which is spatially flat with curvature in the “time direction,” and this describes the inflationary period of the universe. The most early universe was some sort of closed spherical “blob” with k = 1, and there was a topology change which shifted to k = 0. This I will ignore for this post. This dynamics also curiously describes the universe now for a much smaller rho. The early inflationary period had rho = 10^{-15}L_p^{-4} = 10^{60}GeV^4, which is very large and now rho ~ 1GeV^4. So the current phase of the universe is a slow “eternal inflationary phase.”

The eternal inflationary phase has some interesting consequences which many people do not quite fathom. The CMB is the surface of last scatter and is interestingly giga light year distant. The cosmological horizon is at the point where v = Hd equals the speed of light. For the FLRW equation

(a’/a)^2 = C*rho, a’ = da/dt.and C = (8pi G/3)

then H = a’/a. For rho = (1/3)/\ then v = c = 1 is the case where 1 = sqrt{/\ /3}d, and d = sqrt{/\ /3}. This is the cosmological horizon, which is about 11 giga ly out. The redshift factor z is often measured by astronomers, and z ~ (d/c)H in the linear approximation of the de Sitter metric. Currently the most distant galaxies observed have z ~ 8. These are beyond the cosmological horizon and are commoving out at 8 times the speed of light. The CMB has z ~ 1000 and is moving out at v = zc. Remember, the speed of light is an invariant in a local inertial frame. For large regions of space or spacetime, where the local Lorentz frame does not apply, the dynamics of space and spacetime may drag points around in a way which apparently violates v sqrt{/\ /3}.

There are two intermediary periods between the early explosive inflationary phase and the current slow eternal inflationary phase. These are radiation and matter dominated periods. The density for matter depends on the scale factor by the volume V = (4pi/3)a^3. For matter the energy is constant so rho ~ a^{-3}. So the density of matter is rho ~ (3/4pi)a^{-3}. So the FLRW equation is a’ = Ca^{-1/2}. We set a = ct^n, where a’ = nct^{n-1} and c^{-1/2} = (1/c)^{1/2}t^{-n/2}. We compute the coefficient n so that n-1 = -n/2, and we get n = 2/3. The density for radiation depends on the scale factor a in two ways. First with volume V = (4pi/3)a^3. Then for radiation the wavelength is stretched out by the scale factor lambda ~ a, and the energy of a photon decreases by E ~ 1/a. So the density of radiation is rho ~ (3/4pi)a^{-4}. So the FLRW equation is a’ = C’a^{-1}, where by the same analysis we get n = 1/2. The C and C’ constants are not terribly relevant here, though one can compute them without much trouble.

So for radiation period the scale factor evolved as a ~ t^{1/2} and the matter dominated period it shifted to a ~ t^{2/3}. The CMB is the region where the universe transitioned from radiation dominated to matter dominated. About 4 billion years ago the universe shifted from matter dominated to vacuum dominated, or where the small quantum vacuum is larger in energy density than matter. This is the source of the cosmological constant and the now observed accelerated expansion of the universe.

LC

strong evidence for what we like to call “dark matter”. dark matter therory un-RIP!

possible further evidence to suggest that (once again) mans’ estimate of the age of the universe is incorrect.

therory

Capper or madcapper? In any case, opinion doesn’t cap the facts, and the fact is that this was a *successful* test of standard cosmology – it survived!

@LBC

You are only making assumptions.

“The entropy is S ~ 4?A/L_p^2 = 12?/(?L_p^2). But if k = +1 it is clear the solution is different, but only early on. The observed universe is k = 0, which is spatially flat with curvature in the “time direction,” and this describes the inflationary period of the universe.”

Please tell me first what entropy really means, I see no insight here. Do not feel offended personally btw. Nobody actually knows what entropy means.

“Nobody actually knows what entropy means.”

What do you mean? Maybe nobody knows what it means in some sort of deep existential sense, such as ‘nobody knows what quantum mechanics really means’, but just like QM the concept of entropy is clearly defined, as is the mathematical framework in which it appears. What are you trying to say?

Hannes: the formula for entropy can be derived, but is a bit complicated to work through. Entropy is well enough defined, and has a number of different forms. In statistical mechanics it is the number of ways microstates may be rearranged without changing a macrostate. The entropy is then measured by the size of this macrostate V, as S = -k log(V). In information theory for a set of bits with probability P_i so S = -k sum_i P_i log(P_i). For these probabilities corresponding to entangled states there is a corresponding entanglement entropy — in a bipartite Q-bit form. Things get really fun in a multi-partite form.

LC

why should somebody be happy if dark matter was conclusively disproved?? EM forces can explain dark matter and black holes in the plasma labs. ARP’S 2003 quasar catalogue shows many photos of luminous filaments connecting quasars with a nearby host galaxy. All quasars except one disc are near a galaxy, and are believed to form by galaxy collisions mergers. Arp says they are ejected at higher redshifts, and are intrinsic redshifts that falsify the big-bang model of dark energy expansion. Just recently the first reverse gravitational lens was discovered, where a foreground quasar only 1.6 billion light years away supposedly lenses a galaxy 7 billion light years behind it. the photo only reveals a bright flash behind the quasar, and is unconvincing. if the quasar source was moving towards us, then maybe the redshift by distance method is flawed, and this background galaxy is really near the quasar? Einstein said, “if the speed of light is in the least way affected by the speed of the light source, then my theory of gravity and relativity is false.” quasars ejected from the galaxy at higher redshifts explains the gravitational lens effect predicted by Einstein, and why we need a better theory then the big-bang. evidence is that there is no time dilation of quasars, and that THE CMB HAS NO DISCERNABLE GRAVITATIONAL LENS, which Lieu and Mitaz disc in 2005 was shocking and means there are serious flaws the big-bang theory.

[i] “Capper or madcapper? In any case, opinion doesn’t cap the facts, and the fact is that this was a *successful* test of standard cosmology – it survived!” [/i]

//////////////////

There don’t seem to be any caps in modern cosmology. Anything goes! Nevertheless, I’m glad that “standard” cosmology survived this (previously unknown by me) threat to its existence.

I’m actually not opposed to dark matter theory, I simply have issues with the seemingly 100% conclusiveness with which it has often been presented in the last several years. Is it likely? Maybe. Has enough evidence of its existence been shown to me that I can now assume with almost absolute certainty that dark matter is there and never question its existence? No. You may feel otherwise, and that’s your right (I’ll happily examine your evidence).

This article is a good example of what I mean (no offense to Nancy, who is awesome): Stronger than expected gravitational lensing is occuring in a distant galaxy cluster. As a result, the cluster is reasonably assumed to be more massive than what was previously assumed based on the amount of currently detectable visual matter in the cluster… but then: …Therefore, dark matter MUST be causing this obseravtion. From this, the connection is made to dark enegy and how it was competing with the dark matter in the early universe, then we start down a path that eventually leads to the assumption that galaxy clusters formed much more early than previously thought.

I’d be happy for dark matter to finally be proven conclusively. It would make some things more easy to explain. I guess I’d just like to hear a little more uncertainty every now and then, and not see quite so many theories built upon other not yet proven theories.

The dark matter issue does come from the anomalous motion of stars in the galaxy. It is not hard to show with the Poisson equation &_i&^i? = 4?G rho, &_i = 3 dimensional directional derivative, that for a region of constant density rho an integration over a volume is constant on the right hand side. One the left hand side one can use Stokes rule to get

(&_iU)*A = 4?G rho V

for A the area bounding the volume V, and U is the potential function of gravity. For A = 4?r^2 and the volume V = 4?r^3/3 you get the force F = &^iU ~ constant*r. So this is a spring force and gives dynamics similar to what we see with the motion of stars in a galaxy. This is different from the motion one expects of a central force of gravity with F = GMm/r^2. This is one reason that dark matter was initially inferred.

The density of dark matter in the galaxy is about 10^{-24}kg/m^3. A spherical volume that encloses the solar system some 5e^{9}km out or 5e^{11}m is then a volume of about 5e^{34}m^3. Hence the mass contained in the solar system in the form of dark matter is only about 10^{10}kg. This is not a whole lot when compared to the mass of planets and certainly the sun. So this is why it does not make a significant contribution to the dynamics of the solar system.

LC

@ Hannes:

Of course we know, or we wouldn’t be able to use it. LC gave the most fundamental definition, which the classical definition builds on in an effective (i.e useful in theory but not fundamental) form.

More broader, these aren’t assumptions but testable hypotheses. For example inflation is tested as part of standard cosmology. (Though direct tests still fall just shy of 3 sigma. Wait for Planck!) The same goes for DM.

@ Capper:

That you claim so, right after I stated the relevant facts, means there is no basis for a rational discussion. It as inane as rejecting gravity.

I can only recommend that you try to learn something about science if you are able. For example, nothing is “proven” in science, and this cryptoinductionist scheme (which nowadays finds its support in religious circles) is actually what leads to “theories built upon other … theories”.

Testing breaks that ironic induction proof of how inductionism doesn’t work, and supplies precisely that quantified (un)certainty you ask for. (See above on testing inflation – direct tests are now at ~ 2.6 sigma IIRC.)

increased order is lower entropy, and higher entropy is increased randomness or disorder. if you heat ice crystals or boil water, they gain entrophy becoming gas particles that have less order and more chances for random collisions, then when held in a crystalline form or liquid state.

@ nobody actually knows what the universe is or means, perhaps it is a collective theory

“Nobody actually knows what entropy means.”

Anyone reading the progression of deterioration comments here will see entropy in action!

Not one person here has commented on the “strong X-ray emission” (observations) of the selected CLASH clusters that might be suppressing the “growth of all galaxy clusters” (the theory.) This rest of the comments are frankly just the usual irrelevant claptrap — avoiding the story completely. Frankly, Nancy should be deleting most of them as just “personal theory.”

Hon. Salacious B. Crumb: I wrote the expository above due to the usual confusion over dark matter and dark energy, and problems people have with cosmology. What I wrote is basically the standard model, and is not my personal theory.

I also repost my argument for dark matter above, which is based on textbook standard Newtonian gravity. I wrote this with unicode symbols that I did not change here and they showed up as ? marks.

The dark matter issue does come from the anomalous motion of stars in the galaxy. It is not hard to show with the Poisson equation &_i&^iU = 4pi G rho, &_i = 3 dimensional directional derivative, U the gravitational potential, and for a region of constant density rho an integration over a volume is constant on the right hand side. One the left hand side one can use Stokes rule to get

(&_iU)*A = 4pi G rho V

for A the area bounding the volume V, and U is the potential function of gravity. For A = 4pi r^2 and the volume V = 4pi r^3/3 you get the force F = &^iU ~ constant*r. So this is a spring force and gives dynamics similar to what we see with the motion of stars in a galaxy. This is different from the motion one expects of a central force of gravity with F = GMm/r^2. This is one reason that dark matter was initially inferred.

The density of dark matter in the galaxy is about 10^{-24}kg/m^3. A spherical volume that encloses the solar system some 5e^{9}km out or 5e^{11}m is then a volume of about 5e^{34}m^3. Hence the mass contained in the solar system in the form of dark matter is only about 10^{10}kg. This is not a whole lot when compared to the mass of planets and certainly the sun. So this is why it does not make a significant contribution to the dynamics of the solar system.

LC

John von Neumann: “…nobody knows what entropy really is”

–Conversation between Claude Shannon and John von Neumann regarding what name to give to the “measure of uncertainty” or attenuation in phone-line signals (1949)

We don’t know if a blackhole [if it exists] has the maximum allowed entropy.

Other option: look at the no-hair theorem, there is zero entropy. But 2nd law of thermodynamics problem in that case.

Larsson:

“That you claim so, right after I stated the relevant facts, means there is no basis for a rational discussion. It as inane as rejecting gravity.

I can only recommend that you try to learn something about science if you are able…”

/////////////////////////

Above is the type of comment made by a frustrated person. What’s worse is that you didn’t even address what I was writing about. If you are not prepared to deal with questions in earnest, why bother trolling?

Here are your “facts” from this thread (unless there is some mysterious missing post):

First comment:

“So the Flying Spaghetti Monster is real!?

It stands to reason that DM influenced the visible universe more than we earlier accounted for. But since the old cosmology made local sense DM’s influence must be stealthed analogous to the fashion seen here…”

Second comment:

“Capper or madcapper? In any case, opinion doesn’t cap the facts, and the fact is that this was a *successful* test of standard cosmology – it survived!”

Hmmm… I just can’t seem to find any “facts” in those comments; only opinion.

As far as I can see, LBC is the only one who made an effort to be helpful. The other guys are arguing about entropy and Crumb comes in just in time to engage in some late-thread trolling of his own.

So thank you LBC, although I wouldn’t dare to argue with your numbers, I would like to at least inject uncertainty regarding what these numbers show and they should not be conclusively determined to indicate invisible matter until more solid practical observation has been conducted and any other (admittedly) less likely causes are ruled out.

Remember both how relatively young the “dark” theories are and how often we have been wrong in the past.

Capper

Your out of you depth, sonny. Entropy, and what you are rabbiting on about) is totally irrelevant to this article. End of story.

Hannes (obviously related to the PC/EU nutter, after their messiah, Hannes Alfvin) is likely just an Anaconda clone. Again, entropy has nothing to do with this story.I’d take no notice of such jackasses.

As for LBC’s comments, I just accept them as they are written.

gravity waves nor graviton particles have never even been detected. Get real and admit that the space telescope failure indicates that we won’t find dark matter, which has an even smaller chance then gravity to actually exist. Visible mater produces “undetectable gravity” but “extra gravity” to fit the “big-bang theory” produces “actual dark matter particles that we will find because our math predicts it’?? The math is brilliant for many cases including explaining the constant orbital star velocities that model a galaxy using Hooke’s Law. I’ve asked brlliant scientists to please explain things,, and some wrote me that EM forces can replace dark matter and black holes, but EM forces cannot explain Dark Energy. these dark matter maps, are better explained as flowing currents pathways visible objects of plasma mass follows to form galaxies, and EM is a fundamentally different force then gravity.

Crumb, you never cease to disappoint me. Each thing that I read from your keyboard makes me angry.

My response for this latest irritation:

1. I did not mention entropy, other than to point out that other posters were disagreeing about the definition of it. I guess you must have (unsurprisingly) ignored most of the posts in this thread.

2. Use correct grammar when spewing out insults in order to avoid making yourself look like an even lower form of troll (ex: a youtube troll).

3. Until your peer decided to insult me for no reason (which I happily look at as a challenge) dark matter was the subject that i was “rabbiting” about. Even after being attacked by Larsson, I attempted to continue with the subject of dark matter, which he ignored, as is typical for his kind. So if my attempted discussion of dark matter “is totally irrelevant to this article”, which is exclusively about dark matter, then i ask you troll, what is a relevant discussion for this article? Don’t bother answering because you don’t know.

This is the way I see it thread after thread:

This forum consists of genuinely helpful people like Gnat, LBC, Aqua, and many others. Then there are the pseudo-intellectuals like Larsson and Ivan3man, then there are the plain trolls like you, who have driven many of the old timers away from this forum and forced others to lurk.

“Irrelevant”…? Don’t make me laugh Crumb. Look at your post above trying to bring up EU theory and calling people jackasses. As I wrote before, you never cease to disappoint me.

“Crumb, you never cease to disappoint me.”

Funny. I thought I was trying to totally ignore you.

the orbits of 7 inner stars from 1995-2010 around our milky way’s galactic black hole center is shown by Keck/UCLA at http://www.astro.ucla.edu.~ghezgroup/gc/

the stars have elliptical looking orbits that intersect at points where perhaps a collision would form a supernova standard candle believed by computer models to be by accretion reaching the critical mass.

http://www.astro.ucla.edu/~ghezgroup/gc/

Am I doing a good job lurking? …. wait, oppsies..