Movement of Galaxy Clusters Opens New Window on the Universe --May Unlock Key to Dark Energy
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April 02, 2013

Movement of Galaxy Clusters Opens New Window on the Universe --May Unlock Key to Dark Energy

 

 

           Rdcs1252_xray_opt

 

A large research team from two major astronomy surveys reports that scientists detected the movement of distant galaxy clusters via the kinematic Sunyaev-Zel’dovich (kSZ) effect, which has never before been seen. First proposed in 1972 by Russian physicists Rashid Sunyaev and Yakov Zel’dovich, the kSZ effect results when the hot gas in galaxy clusters distorts the cosmic microwave background radiation—which is the glow of the heat left over from the Big Bang—that fills our universe. Radiation passing through a galaxy cluster moving toward Earth appears hotter by a few millionths of a degree, while radiation passing through a cluster moving away appears slightly cooler.

Pedro Ferreira, an astrophysics professor at the University of Oxford, calls the paper a “beautiful piece of work” that neatly demonstrates an accurate method for studying the evolution of the universe and the distribution of matter in it. Ferreira had no role in the research but is familiar with it. “This is the first time the kSZ effect has been unambiguously detected, which in and of itself is a really important result,” Ferreira says. “By probing how galaxies and clusters of galaxies move around in the universe, the kSZ effect is directly probing how objects gather and evolve in the universe,” he says. “Therefore it is hugely dependent on dark matter and dark energy. You can then think of the kSZ effect as a completely new window on the large-scale structure of the universe.”

Now that it has been detected, the kSZ effect could prove to be an exceptional tool for measuring the velocity of objects in the distant universe, the researchers report. It could provide insight into the strength of the gravitational forces pulling on galaxy clusters and other bodies.

Chief among these forces are the still-hypothetical dark energy and dark matter, which are thought to drive the universe’s expansion and the motions of galaxies. In addition, the strength of the kSZ effect’s signal depends on the distribution of electrons in and around galaxies. As a result, the effect also can be used to trace the location of atoms in the nearby universe, which can reveal how galaxies form.

The benefits of the kSZ effect stem from a unique ability to pinpoint velocity, says Hand, a 2011 Princeton graduate who is now a graduate student in astronomy at the University of California-Berkeley. The researchers detected the motion of galaxy clusters that are several billion light years away moving at velocities of up to 600 kilometers (372 miles) per second.

“Traditional methods of measuring velocities require very precise distance measurements, which is difficult. So, these methods are most useful when objects are closer to Earth,” Hand says.

“One of the main advantages of the kSZ effect is that its magnitude is independent of a galaxy cluster’s distance from us, so we can measure the velocity of an object’s motion toward or away from Earth at much larger distances than we can now,” Hand says. “In the future, it can provide an additional statistical check that is independent of our other methods of measuring cosmological parameters and understanding how the universe forms on a larger scale.”

To find the kSZ effect, the researchers combined and analyzed data from the ACT and BOSS projects. The kSZ effect is so small that it is not visible from the interaction with an individual galaxy cluster with the cosmic microwave background (CMB), but can be detected by compiling signals from several clusters, the researchers discovered.

ACT is a custom-designed 6-meter telescope in Chile built to produce a detailed map of the CMB using microwave frequencies. The ACT collaboration involves a dozen universities with leading contributions from Princeton and the University of Pennsylvania, and includes important detector technology from NASA’s Goddard Space Flight Center, the National Institute of Standards and Technology, and the University of British Columbia.

BOSS, a visible-light survey based at the Apache Point Observatory in New Mexico, has captured spectra of thousands of luminous galaxies and quasars to improve understanding of the large-scale structure of the universe. BOSS is a part of the Sloan Digital Sky Survey III, the third phase of the most productive astronomy project in history, and a joint effort among 27 universities and institutions from around the world.

For the current project, researchers from ACT compiled a catalog of 27,291 luminous galaxies from BOSS that appeared in the same region of sky mapped by ACT between 2008 and 2010. Because each galaxy likely resides in a galaxy cluster, their positions were used to determine the locations of clusters that would distort the CMB radiation that was detected by ACT.

Hand used the 7,500 brightest galaxies from the BOSS data to uncover the predicted kSZ signal produced as galaxy clusters interacted with CMB radiation. ACT collaborator Arthur Kosowsky, an associate professor of physics and astronomy at the University of Pittsburgh, suggested a particular mathematical average that reflects the slight tendency for pairs of galaxy clusters to move toward each other due to their mutual gravitational attraction, which made the kSZ effect more apparent in the data.

The overlap of data from the two projects was essential because the amplitude of the signal from the kSZ effect is so small, says ACT collaborator David Spergel, professor and department chair of astrophysical sciences at Princeton, as well as Hand’s senior thesis adviser. By averaging the ACT’s CMB maps with thousands of BOSS galaxy locations, the kSZ signal got stronger in comparison to unrelated signals and measurement errors, Spergel says.

“The kSZ signal is small because the odds of a microwave hitting an electron while passing through a galaxy cluster are low, and the change in the microwave’s energy from this collision is slight,” says Spergel. “Including several thousand galaxies in the dataset reduced distortion and we were left with a strong signal.”

In fact, if analyzed separately, neither the ACT nor the BOSS data would have revealed the kSZ effect, Kosowsky says. “This result is a great example of an important scientific discovery relying on the rich data from more than one large astronomy survey,” he says. “The researchers of the ACT and BOSS collaborations did not have this in mind when they first designed their experiments.”

The paper was initiated at Princeton University by lead author Nick Hand. Fifty-eight collaborators from the Atacama Cosmology Telescope (ACT) and the Baryon Oscillation Spectroscopic Survey (BOSS) projects are listed as co-authors. The paper was submitted to the journal Physical Review Letters.

The image at the top of the page is a color composite image of the galaxy cluster RDCS 1252.9-2927 shows the X-ray (purple) light from 70-million-degree Celsius gas in the cluster, and the optical (red, yellow and green) light from the galaxies in the cluster. X-ray data from Chandra and the XMM-Newton Observatory show that this cluster was fully formed more than 8 billion years ago, and has a mass at least 200 trillion times that of the Sun.

At a distance of 8.5 billion light years, it is the most massive cluster ever observed at such an early stage in the evolution of the universe.Even though the cluster is seen as it was only 5 billion years after the Big Bang, it has an abundance of elements such as silicon, sulfur, and iron similar to that of clusters observed at more recent epochs. The cluster gas must have been enriched by heavy elements synthesized in stars and ultimately ejected from the galaxies. The relative abundances of these heavy elements are indicators of the star formation history of the galaxies. The observations of RDCS 1252.9-2927 are consistent with the theory that most of the heavy elements were produced by massive stars some 11 billion years ago. 

The Daily Galaxy via Princeton University

Image credit: Credit: X-ray: NASA/CXC/ESO/P.Rosati et al.; Optical: ESO/VLT/P.Rosati et al.

Comments

The fact that heavy elements were plentiful only 5 billion years after the big bang is a very good sign about the possibility of alien-life evolving in the very earlier universe.

But of course that then leads to the annoying and now cliche Fermi paradoxical question:

If alien life had several billion years to get started earlier than we might have initially expected, then where the heck are they?

Consider this:

If a hyper intelligent civilization arose when the universe was only 5 billion years old, then it should have had time to effectively colonize every galaxy in the universe, simply by sending out replicating-machines and probes to every visible galaxy at once, simultaneously.

And of course once each probe reached the target galaxy, it would only take a few hundred thousands years (or perhaps a couple of million years at most) to establish replicating probes in every star system of that galaxy.

So really once life reaches hyper intelligence, then it doesn't take very long to colonize not only a single galaxy, but the entire universe.

Thus there really should be aliens amongst us.

Some answers to the paradox might include:

1) It really is much more difficult to evolve intelligence than we suspect.

But... I'm not sure I fully buy that. We see sophisticated intelligence evolving multiple times in multiple species, including dolphins, whales, chimpanzees, bonobos... heck even crows and parots show sophisticated intelligence at times. Even the lowly octopus, which is a very alien creature to mamals, is said to exhibit cat-like intelligence.

2) Hyper intelligent civilizations always end up self destructing pretty quickly.

I guess, sadly, this seems to be them most plausible explanation... but even this explanation doesn't feel fully correct... as you just need 1 civilization, out of millions to not self destruct, and then they can take over the universe.

3) The aliens are already amongst us -- observing!

But as forensic scientists say, you can't enter a room without leaving some sort of trace... it would seem based upon the laws of physics as we know it, and chaos theory, that there should be some trace of them, no matter how careful they are, that can be detected.

4) We are living in a simulation.

I once read a theory that says it is far more likely we are living in a simulation, as opposed to the "real" universe.

The reasoning behind that is simply this: imagine that there is a vast universe, in which a few million hyper intelligent civilizations have evolved, that have computer technology.

Each of those civilizations will in turn likely run billions of simulations.

Thus if you look at the numbers: there are only a few million "real" civilizations, and multiple billions (probably trillions!) of simulated civilizations.

Ergo, the odds are much greater that an individual will exist in a simulated universe, rather than the real universe.

Suddenly I'm beginning to think that the lack of evidence of aliens, may simply be that we are indeed a simulation, and aliens are not programmed into this particular simulation!

Probability/mathematically this is beginning to sound like the most reasonable explanation...

But it's also the explanation I am most uncomfortable with, so I hope it is wrong!

PS: Sorry just as a 5th point to my comment above, I also forgot to mention this:

Some people say that the reason we do not seem to detect or observe aliens is simply that they are not interested in us.

But I'm not sure I fully buy that explanation to the Fermi paradox either!

For example, some might say that I am "hyper intelligent" as compared to my pet cat.

I can do calculus, but my cat can not! (At least I don't think he can!)

I can drive/navigate an automobile at high speeds... my cat can not. I can read, program computers, etc... but my cat can not do these things.

Really, all my cat does is meow, purr, and sleep.

And yet... despite this great difference in observed intelligence, I still spend lots of time with my cat! I'm very curious about my cat, and enjoy and seek out some interactions with my cat. I love my cat, and care for it. My cat is in fact a friend. (Not like a human friend, but still it is a friend.)

Also, the greater the intelligence of a species, the more curious that species seems to become.

Thus an ultra-hyper-intelligent alien species might in fact be ultra-hyper-curious!

And of course any hyper-curious creature would indeed seek out contact and interaction with humans. They wouldn't be able to just ignore us for very long.

It's the same reason humans are driven to visit zoos: we're fascinated and curious about other life forms and species.

An alien life form might be able to perform multidimensional varying-base mathematics rapidly in it's head, in the blink of it's alien eye...

But I think that same alien would still have a curiosity and interest, and perhaps even a strong social drive to interact with humans.

Some might, "Well, instead of cats, we probably seem more like ants to a hyper alien creature! And there's not much interest in humans to interact with ants."

But I don't buy that either. I think there is a minimum threshold of intelligence, that once an animal species crosses that threshold they then become interesting.

I think humans have crosses that minimum threshold: we are changing an entire planet, evolving a planetary society, and sending robotic probes into space.

So no, I don't think humans would seem like "ants" to an alien... rather we would probably seem more like cats or dogs appear to us.

Similarly, most of the animals at zoos have crossed some type of threshold that makes them much more interesting to us than ants. Lions, tigers, bears, kangaroos, monkeys... all those zoo animals have crossed a threshold that makes them interesting.

And heck... even plants seem very interesting... I visit biodomes and botanical gardens...

So in short... we are more interesting than ants, and aliens would likely find us interesting.

So I don't think the "we seem like ants" explanation is a plausible solution to the fermi paradox.

Re: Velocity Wave, it is possible to have incredibly many alien civilizations and no contact. Note that we seem to be a long time from being able to design Von Neumann Probes, may be as much as a century, during that century we will develop the ability to enhance our intelligence via genetic engineering and direct brain/computer interfaces. This means that we are going to evolve our intellect/intelligence at an accelerating rate. Any entity that leaves their home system will come back to world populated by a more advanced species. Consider a member of the human/chimp common ancestor of several million years ago returning to Earth today after a time dilated trip. Earth is no longer home to this traveler. The point being the longer the trip the less like home it becomes. The point to Von Neumann probes is the info sent back, if it was programmed by a chimp, the info is useless. So no aliens, no probes.

Birds have dropped seeds and successfully allowed for plants to colonize every island on Earth; So is similar the purpose of man with his wings of intelligence to spread the seeds of the biosphere out into the cosmos.
Intelligence does not occur by chance but is a requirement of a progressing universe.

Very interesting pls read my comment below

This life is a Simulation, let me start by laying out any Fermi Paradox issues anyone may have.
The issue of traces of evidence of any Alien lifeforms/Drones visiting is quickly dispelled by this - They are watching us and they know our limitations even sometimes they have a hand in limiting us - once you know someones limitations then you can abuse that, needless to say they would know how the human race would trace visitations and therefore they would avoid that measure.
The comment about Birds dropping seeds is very good and well noticed - this is the spreading of life on a smaller scale but still important.
Many times the question 'why run a life simulation' that the user cannot stop' - the main use of a full life simulation is the answer to what in the future is known as 'Massive Travel', this is travelling from one star to another (or as you may know it from one universe to another) - it takes many years and those on board literally get Bored. So a full life simulation is given to them to pass time and use minimum food water resources.
This is your life - you are on that ship, to another star.


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