Clearest picture yet of dark matter points the way to better understanding of dark energy

Jan 09, 2012
Teams from Fermilab and Berkeley Lab used galaxies from wide-ranging SDSS Stripe 82, a tiny detail of which is shown here, to plot new maps of dark matter based on the largest direct measurements of cosmic shear to date. Credit: SDSS

(PhysOrg.com) -- Two teams of physicists at the U.S. Department of Energy's Fermilab and Lawrence Berkeley National Laboratory (Berkeley Lab) have independently made the largest direct measurements of the invisible scaffolding of the universe, building maps of dark matter using new methods that, in turn, will remove key hurdles for understanding dark energy with ground-based telescopes.

The teams' measurements look for tiny distortions in the images of distant galaxies, called "cosmic shear," caused by the of massive, invisible dark matter structures in the foreground. Accurately mapping out these dark-matter structures and their evolution over time is likely to be the most sensitive of the few tools available to physicists in their ongoing effort to understand the mysterious space-stretching effects of .

Both teams depended upon extensive databases of cosmic images collected by the Sloan Digital Sky Survey (SDSS), which were compiled in large part with the help of Berkeley Lab and Fermilab.

"These results are very encouraging for future large sky surveys. The images produced lead to a picture of the galaxies in the universe that is about six times deeper, or further back in time, than is available from single images," says Huan Lin, a Fermilab physicist and member of the SDSS and the Dark Energy Survey (DES).

Layering photos of one area of sky taken at various time periods, a process called coaddition, can increase the sensitivity of the images six-fold, by removing errors and enhancing faint light signals. The image on the left shows a single picture of galaxies from SDSS Stripe 82. The image on the right shows the same area after layering, increasing the number of visible, distant galaxies. Credit: SDSS

Melanie Simet, a member of the SDSS collaboration from the University of Chicago, will outline the new techniques for improving maps of cosmic shear and explain how these techniques can expand the reach of upcoming international sky survey experiments during a talk at 2 p.m. CST on Monday, January 9, at the (AAS) conference in Austin, Texas. In her talk she will demonstrate a unique way to analyze dark matter's distortion of galaxies to get a better picture of the universe's past.

Eric Huff, an SDSS member from Berkeley Lab and the University of California at Berkeley, will present a poster describing the full cosmic shear measurement, including the new constraints on dark energy, on Thursday, January 12, at the AAS conference.

Several large astronomical surveys, such as the Dark Energy Survey, the Large Synoptic Survey Telescope, and the HyperSuprimeCam survey, will try to measure cosmic shear in the coming years. Weak lensing distortions are so subtle, however, that the same atmospheric effects that cause stars to twinkle at night pose a formidable challenge for cosmic shear measurements. Until now, no ground-based cosmic-shear measurement has been able to completely and provably separate weak lensing effects from the atmospheric distortions.

Constraints on cosmological parameters from SDSS Stripe 82 cosmic shear at the 1- and 2-sigma level. Also shown are the constraints from WMAP. The innermost region is the combined constraint from both WMAP and Stripe 82. Credit: SDSS

"The community has been building towards cosmic shear measurements for a number of years now," says Huff, an astronomer at Berkeley Lab, "but there's also been some skepticism as to whether they can be done accurately enough to constrain dark energy. Showing that we can achieve the required accuracy with these pathfinding studies is important for the next generation of large surveys."

To construct dark matter maps, the Berkeley Lab and Fermilab teams used images of galaxies collected between 2000 and 2009 by SDSS surveys I and II, using the Sloan Telescope at Apache Point Observatory in New Mexico. Berkeley Lab also used updated calibrations from SDSS III, which continues today. The galaxies lie within a continuous ribbon of sky known as SDSS Stripe 82, lying along the celestial equator and encompassing 275 square degrees. The galaxy images were captured in multiple passes over many years.

Gravity tends to pull matter together into dense concentrations, but dark energy acts as a repulsive force that slows down the collapse. Thus the clumpiness of the maps provides a measurement of the amount of dark energy in the universe.

When they compared their final results before the AAS meeting, both teams found somewhat less structure than would have been expected from other measurements such as the Wilkinson Microwave Anisotropy Probe (WMAP), but, says Berkeley Lab's Huff, "the results are not yet different enough from previous experiments to ring any alarm bells."

Meanwhile, says Fermilab's Lin, "Our image-correction processes should prove a valuable tool for the next generation of weak-lensing surveys."

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More information:
Fermilab/ University of Chicago scientific papers:

coadd data: arxiv.org/abs/1111.6619
photometric redshifts: arxiv.org/abs/1111.6620
cluster lensing: arxiv.org/abs/1111.6621
cosmic shear: arxiv.org/abs/1111.6622

Berkeley Lab/ University of California at Berkeley scientific papers:

coadd data: arxiv.org/abs/1111.6958
cosmic shear: arxiv.org/abs/1112.3143

Provided by Fermi National Accelerator Laboratory

4.9 /5 (14 votes)

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User comments : 16

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TombSyphon2317
1.4 / 5 (10) Jan 10, 2012
Can we please stop trying to MAKE UP our own solutions, and re-evaluate our guess at how gravity works!!!!!!!!!!!!!!!!!
TombSyphon2317
1.4 / 5 (11) Jan 10, 2012
"In her talk she will demonstrate a unique way to analyze dark matter's distortion of galaxies to get a better picture of the universe's past."

SERIOUSLY I want to see her evidence/proof/math/anything for dark matter before i'm willing to invest my mental capacity.
LJW
3 / 5 (2) Jan 10, 2012
Can we please stop trying to MAKE UP our own solutions, and re-evaluate our guess at how gravity works!!!!!!!!!!!!!!!!!

this is called being a theoretical physicist
vidyunmaya
1 / 5 (8) Jan 10, 2012
Please provide me more information- Limiting function of Dark Matter and why are you projecting or mentioning Dark Energy- both are Undefined for Space-Cosmology studies.See alternaives-Origins-Cosmology Vedas Interlinks
http://vidyardhic...spot.com
TombSyphon2317
1.6 / 5 (7) Jan 10, 2012
Theoretical.......please help me! In this instance it's no more then arrogance. (dark matter/energy) is compensating for our lack of mathematical knowledge.
We're making shit up and complicating the matter b/c we're not willing to let go of what has worked for this long. Sorry Einstein but it's time we move on.
rawa1
1 / 5 (8) Jan 10, 2012
Can we please stop trying to MAKE UP our own solutions, and re-evaluate our guess at how gravity works!
Such approach is disadvantageous for theorists from many practical and psychosocial reasons. Every theorist wants to promote hist own theory of particular phenomena to become famous, but he don't want to change the underlying theories (relativity, quantum mechanics), on which this particular theory is based. Or he would risk the accusation from crackpotism immediately. From this reason, the theorists have no reason/motivation to speculate, on which these underlying theories are based and WHY they're working at all. They just need them working in their present state. This is just a reason, why contemporary theorists are so dismissive regarding the answering of WHY questions. These questions could expand our understanding, but it could threat the existing theories too.

For more detailed info about this subject please refer to http://www.youtub...FPe-DwUL
rawa1
1 / 5 (9) Jan 10, 2012
In particle environment representing the vacuum only two kind of waves exist: longitudinal and transverse ones and the transverse waves of light are too slow to explain gravity effects (including the bending of light). The longitudinal waves are much faster than these transverse ones. Therefore in AWT (dense aether model) the gravity results from shielding of superluminal gravitational waves with massive bodies. If you think about it, it's the only mechanism, which can apply to particle environment without further assumptions about the system and it explains the inverse square law for gravity force in 3D space easily.
http://en.wikiped...vitation
Now the question remains about dark matter. The simplest explanation is, the dark matter is the result of gravity of neighbouring massive objects, i.e. the shielding of shielding with all other massive objects in the observable Universe. Such model minimizes the number of assumptions about geometry of system.
Ethelred
3.7 / 5 (6) Jan 10, 2012
Zephir you are completely wrong about nearly everything. AWITABS is based on ludicrous ideas that include such idiocies as fluctuations in INFINITE densities.

Ethelred
Benni
3 / 5 (6) Jan 10, 2012
@rawa1: What makes you think gravity functions in a superluminol fashion? Everything I know about "conservation of momentum" does not allow for it. Earth's orbital trajectory in the gravity field around the sun follows a "steady flow" principle which always points to the true position of the sun but this is not superluminol as some try to make it out to be, it's just a steady flow until an exterior force acts upon the two bodies.
Ethelred
3.9 / 5 (7) Jan 10, 2012
@rawa1: What makes you think gravity functions in a superluminol fashion?


en.wikipedia.org/wiki/Le_Sage%27s_theory_of_gravitation

He thinks that link somehow supports his AWITSBS nonsense. The fact that the link shows how bad the idea was and is doesn't seem to phase him at all. Probably due to his ability to believe in fluctuations in density of a vacuum that has infinite density according to him. Why he thinks there can be fluctuation in anything with infinite density is something he evaded answering. Pretended the question wasn't asked.

Ethelred
Callippo
1 / 5 (7) Jan 10, 2012
What makes you think gravity functions in a superluminol fashion?
In dense aether theory the two types of waves are mediating energy spreading: the transverse and longitudinal waves. The light waves are known to be transverse waves, so that the gravitational waves must be longitudinal. In analogy of space-time with water surface the surface waves are transverse and longitudinal waves are much faster, being represented with sound waves of underwater.

Actually, even the four hundred years old physicists like the Fatio de Duillier and later Le Sage realized, the gravity must be mediated with "ultramundanne particles", i.e. particles outside of our Universe and faster than light. They actually assumed multiverse, foamy space-time structure and many other super modern things - which is quite impressive, if we realize, how subtle experimental background they really had. But their insights originated from even older Arabians roots, namely the Al Kindi from 9th century.
Callippo
1 / 5 (3) Jan 10, 2012
Why he thinks there can be fluctuation in anything with infinite density is something he evaded answering. Pretended the question wasn't asked.
For example, the natural numbers are countable easily, although they're forming an infinite series. Everyone can imagine the segment of line, although such a line is actually infinite.AWT is actually as abstract model as every other physical theory - it just uses the emergent particle model for explanation of space-time geometry. Infinitely tiny density fluctuations of infinitely dense particle environment would appear like the quite real, finite and observable stuff in such model. Unfortunately I have no explanation for composition for the substance or fields which are forming us - I just believe, they're forming us in the same way, like smaller particles are forming larger density fluctuations inside of particle gas. If we would compress such fluctuations heavily, the complexity of these fluctuations would increase into Boltzmann brain
Benni
2.3 / 5 (6) Jan 10, 2012
What makes you think gravity functions in a superluminol fashion?
In dense aether theory the two types of waves are mediating energy spreading: the transverse and longitudinal waves. The light waves are known to be transverse waves, so that the gravitational waves must be longitudinal. /q]

We know light waves exist, but what makes you think "gravity waves" exist? Sure, gravity has an "attracting area of influence" between bodies of mass, but this is nothing like the known flux fields between the north & south poles of a magnet that you can see by dropping iron filings on a sheet of paper & observing how the filings line up along the flux lines of the electro-magnetic field between the north & south poles.

Gravity & energy have no known similar characteristics, including the "waveforms" you're trying to create for gravity. Nothing in the Universe is "infinite", your "infinitely dense particle environment" is a perpetual motion machine.


Ethelred
2.3 / 5 (3) Jan 12, 2012
For example, the natural numbers are countable easily, although they're forming an infinite series.
That is a false analolgy. Blatantly so. YOU are claiming infinite density of energy carrying material in a push gravity Universe. The first is impossible and the second was dubious at best back when Newton was laughing it and it completely ridiculous now.

Read the wiki you linked to. The idea simply is completely broken.

I was amazed that all you had was a self contradictory concept of your own and a ludicrously broken 300 year old crank idea that simply cannot work.

Ethelred
bluehigh
1.7 / 5 (12) Jan 12, 2012
.. in a push gravity Universe


Just to play the devils advocate Ethelred. There is reputable evidence that supports the concept. I'll look it up and post some links soonest. Off the top of my head, its some tests done with accelerometers in Iceland. (I am time poor tonight, maybe someone else here has heard of the experiments).

Not support just FYI

Rohitasch
5 / 5 (1) Jan 14, 2012
Please provide me more information- Limiting function of Dark Matter and why are you projecting or mentioning Dark Energy- both are Undefined for Space-Cosmology studies.
.
.

Pick up your school books, mate. Just for kicks, try reading them once again.

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