Direct detection of dark energy ?

[Royston]

Just found this...

 

http://physicsworld.com/cws/article/news/35368;jsessionid=48833536D0AA1CF3FDDE27AE83B7112D

 

from the Physicsworld article...

 

A group of astrophysicists led by István Szapudi at the University of Hawaii. They have analyzed the glow of microwave photons emanating from space to see how the size of massive galaxy “superclusters” changes over time. If our universe is flat — and observations suggest this is indeed the case — Einstein’s theory of gravity predicts supercluster size should stay the same. However, the Hawaii researchers have found that the superclusters are being stretched apart — the hallmark of repulsive dark energy.

 

The microwave photons in question, known as the cosmic microwave background (CMB), have permeated the entire cosmos since matter and radiation first “decoupled” some 380,000 years after the Big Bang. In fact, the glow of the CMB is so regular that astrophysicists can use it to illuminate the dynamics of large structures like galaxy clusters and superclusters. Taking data from a galaxy catalogue called the Sloan Digital Sky Survey, Szapudi’s team plot the location of superclusters on a map of the CMB. They can then compare how the CMB map looks in regions where there are superclusters with regions where there is empty space, or supervoids.

 

Is Szapudi’s team the first to see this extra energy?

 

No. The phenomenon is called the Integrated Sachs–Wolfe (ISW) effect, and the idea of using it to look at the dynamics of superclusters was first proposed by cosmologists Rob Crittenden and Neil Turok while they were at Princeton University in 1995. Since then a handful of astrophysicists have taken up the challenge, including teams led by Bob Nichol and Crittenden of Portsmouth University in the UK, Enrique Gaztanaga of the Institute of Space Sciences in Spain and Nikhil Padmanabhan of Lawrence Berkeley Laboratory in the US. In the past few years these teams have detected the ISW effect with increasing confidence.

 

Not sure if this means the death of measuring expansion via the Type Ia Supernovae technique, but this is certainly good news.

[Arch2008]

Type Ia supernovae are “standard candles” in that the light that these stars emit is at a known rate during the phase after they explode. Thus the distance to a galaxy with a Type Ia can be measured by detecting the brightness of the supernova. Realization that Type Ia’s were dimmer than they should have been was evidence that the expansion of the universe was accelerating.

The ISW effect detects stretching in microwaves that pass through galaxy clusters and superclusters. I don’t believe that this can be used to measure distance to the supercluster or acceleration in the expansion of the universe.

http://www.ifa.hawaii.edu/cosmowave/supervoids/

 

It wouldn't be the first time I was wrong though.

[Royston]

The ISW effect detects stretching in microwaves that pass through galaxy clusters and superclusters. I don’t believe that this can be used to measure distance to the supercluster or acceleration in the expansion of the universe.

http://www.ifa.hawaii.edu/cosmowave/supervoids/

 

It wouldn't be the first time I was wrong though.

 

I was assuming that acceleration could be extracted from the ISW data, or maybe I read it somewhere...not sure, but I'll have a browze and see if I can find more on this.

 

I'm sure you're more knowledgable in this subject than me...so I may pick your brains on this topic (especially as I'm looking to do an MSc in this field)

[Arch2008]

I was able to find this:

http://biblioteca.universia.net/html_bura/ficha/params/id/36186330.html

“The ISW effect gives us information about dark energy (DE), because DE modifies the evolution of dark matter gravitational potential. In principle, the ISW effect can probe dark energy independently from other observations, such as Supernovae Ia.”

 

So, right you are! It might still be interesting to correlate data from Type Ia with ISW to see if they are in agreement.

[Royston]

I was able to find this:

http://biblioteca.universia.net/html_bura/ficha/params/id/36186330.html

“The ISW effect gives us information about dark energy (DE), because DE modifies the evolution of dark matter gravitational potential. In principle, the ISW effect can probe dark energy independently from other observations, such as Supernovae Ia.”

 

Thanks for finding this Arch2008, I was at work earlier and didn't have time to look for related articles.

 

It might still be interesting to correlate data from Type Ia with ISW to see if they are in agreement.

 

Good point, if there are any attempts to do this, as well as any other developments, I'll be sure to keep my eye out and post anything I find under this thread.