KICP in the News, 2012



 
Discovery science pays off
Arete, The University of Chicago, January 12, 2012
Astrophysicist Michael Turner predicts some very exciting science coming from the Kavli Institute's Physics Frontier Center in the next 10 years.  <i>Photo by Lloyd DeGrane</i>
Astrophysicist Michael Turner predicts some very exciting science coming from the Kavli Institute's Physics Frontier Center in the next 10 years.

Photo by Lloyd DeGrane
by Greg Borzo, Arete, The University of Chicago

When quantum mechanics was developed, scientists had no idea that this esoteric branch of physics would ever have any practical application. Today society depends upon it.

"Take away quantum mechanics and you wouldn't have computers, the Internet or modern communication systems that make the information age possible," says Michael Turner, director of the Physics Frontier Center at the University of Chicago's Kavli Institute for Cosmological Physics and professor of astronomy and astrophysics, and physics at the University.

This is just one example of the need for pure "discovery" science, which will continue to power the economy and influence all of society, he adds.

There will be a lot more discovery science going on at the University over the coming years thanks to a recent National Science Foundation grant to KICP's Physics Frontier Center of $3.4 million per year for five years, hopefully longer. About half the money will support fellows and graduate students; about half will fund ongoing research projects, conferences, workshops and visitors; and $300,000 a year will seed new initiatives.

The Center will use the money to continue studying three of the most fundamental questions that cosmologists are asking: What comprises dark matter, the mysterious stuff that holds together our solar system and all other structures in the universe? Was there a period of cosmic "inflation," or exponential expansion, in the first moments of the universe? And what is the nature of dark energy, the puzzling energy that permeates space and is causing the expansion of the universe to speed up?

"We're in the 'dark matter decade' and by 2020 should be able to determine whether dark matter is made of WIMPs," Turner says. "Progress on inflation is less certain, and dark energy may be a 'problem for the ages'."

"The main topics that the Center researches are on the frontier of physics, and the team is well balanced between theorists and experimentalists," says Matthew Christian, co-director of Arete and assistant vice president for research program development in the Office of the Vice President for Research and National Laboratories. "We're going to see some very exciting science coming out of the Center in the next several years."

Center reinvents itself
Created in 2001 with an earlier NSF grant, the Center spent the last decade training scientists and building and operating big projects, including the South Pole Telescope in Antarctica, Chicagoland Observatory for Underground Particle Physics, and the Dark Energy Survey.

"The first ten years were devoted to building these projects, and the next five will be all about getting the science out," Turner says. "To do so, we need to engage scientists all around the world, especially those at the Fermi National Accelerator Laboratory and Argonne National Laboratory."

Since the Center has existed for ten years, Turner realized that winning a new NSF grant was going to be extremely challenging. "NSF could have said, 'the University of Chicago has had our support for ten years; let's give someone else a chance,' especially considering that there were 60 pre-proposals in the running and 11 finalists invited to make oral presentations."

Ultimately, the KICP Center was one of only four or five PFC proposals that NSF funded, and Arete was a big part of securing the grant, Turner says. It read the proposals and gave invaluable feedback, helped interpret NSF reviews, and prepared the team for its oral presentation.

"Now that we have the grant, we'll certainly find other ways to take advantage of what Arete has to offer," he adds.

The Center funds a director of education and outreach, Randall Landsberg, because a big requirement of its grants is education and outreach. Turner finds this work the easiest and the most fun since the Center wrestles with questions that the public is extremely interested in: Where do we come from? Where are we going? Are we alone?

"We like to discuss such issues with students because it gets them interested in pursuing careers in science, technology, engineering and mathematics," he says. "We're the Pied Pipers for STEM careers."

Read more >>

Related Links:
KICP Members: Randall H. Landsberg; Michael S. Turner
 
Baby pulsars spawn universe's most energetic particles
New Scientist, February 2, 2012
Pulsars may unleash high-energy cosmic rays.  <i>Image: NASA/Goddard Space Flight Center Conceptual Image Lab</i>
Pulsars may unleash high-energy cosmic rays.

Image: NASA/Goddard Space Flight Center Conceptual Image Lab
by Maggie McKee, New Scientist

Talk about enfants terribles. Baby pulsars may unleash torrents of the highest energy particles known, explaining the provenance of the ultra-high-energy cosmic rays that hit Earth.

Charged particles with energies of at least 1019 electronvolts slam into our atmosphere from time to time - since 2008, 5000 have been detected by the Auger observatory in Argentina.

Their source has been a mystery. Pulsars - ultradense stars formed during supernova blasts - are one candidate, but it has not been clear if the particles they shed could make it through the dense shroud of stellar shrapnel that surrounds them.

Now Ke Fang and colleagues at the University of Chicago have modelled these particles and found that they can escape within the first year of a pulsar's life.

At that time, the pulsar's spin, which gradually slows, is still fast enough to shoot out high-energy particles, and the supernova debris has spread out enough to allow those particles to escape. "The most energetic particles may come from the smallest stars," says Fang.

'Violent fellows'
If pulsars are the source of ultra-high-energy cosmic rays, it could explain a puzzling finding by Auger. Unlike the majority of low-energy cosmic rays, ultra-high-energy cosmic rays seem to be made up of the nuclei of heavy atoms, such as iron.

Pulsars - whose cores are made of neutrons - are thought to have charged particles such as iron nuclei in their crusts. When the stars spin, their electromagnetic fields accelerate these heavy, charged particles outwards. Because each iron nuclei has 26 protons, each of which feels the pull of the field, the resulting cosmic rays will be of a higher energy than any single protons thrown out by the pulsar.

"We set out to search for energetic cosmic accelerators that have iron, and [pulsars] seem to be an obvious place," says team member Angela Olinto, also at the University of Chicago.

"Pulsars are certainly violent little fellows," agrees Jim Matthews of Louisiana State University in Baton Rouge, a spokesman for the Auger observatory.

Nearby pulsar
The plot could thicken further, however. Auger doesn't detect cosmic rays directly, but the shower of secondary particles created when these rays slam into the atmosphere. So it's possible that the signals being picked up aren't from iron nuclei but single protons interacting with atmospheric particles in a previously unknown way.

We may one day get a chance to test whether pulsars really are the source of ultra-high-energy cosmic rays, says Matthews.

To date, the highest energy cosmic rays measured by Auger seem to be scattered fairly evenly across the sky, suggesting they originated beyond our galaxy and were deflected by cosmic magnetic fields before they hit Auger's detectors. This makes it impossible to trace them back to a source such as a pulsar.

But if a supernova one day explodes in our galaxy, producing a pulsar, it would be close enough that Auger could trace any cosmic rays back to it. "Then it should just be shining iron nuclei on us," says Matthews.

Read more >>

Related Links:
KICP Members: Angela V. Olinto
KICP Students: Ke Fang
Scientific projects: Pierre Auger Observatory (AUGER)
 
Hubble Zooms in on a Magnified Galaxy
Hubble News Release, February 6, 2012
A team of astronomers aimed Hubble at one of the most striking examples of gravitational lensing, a nearly 90-degree arc of light in the galaxy cluster RCS2 032727-132623. Hubble's view of the distant background galaxy, which lies nearly 10 billion light-years away, is significantly more detailed than could ever be achieved without the help of the gravitational lens. This observation provides a unique opportunity to study the physical properties of a galaxy vigorously forming stars when the universe was only one-third its present age. The results have been accepted for publication in The Astrophysical Journal.
A team of astronomers aimed Hubble at one of the most striking examples of gravitational lensing, a nearly 90-degree arc of light in the galaxy cluster RCS2 032727-132623. Hubble's view of the distant background galaxy, which lies nearly 10 billion light-years away, is significantly more detailed than could ever be achieved without the help of the gravitational lens.
This observation provides a unique opportunity to study the physical properties of a galaxy vigorously forming stars when the universe was only one-third its present age. The results have been accepted for publication in The Astrophysical Journal.
by Ray Villard and Jane Rigby, Hubble News Release

Thanks to the presence of a natural "zoom lens" in space, NASA's Hubble Space Telescope got a uniquely close-up look at the brightest "magnified" galaxy yet discovered.

This observation provides a unique opportunity to study the physical properties of a galaxy vigorously forming stars when the universe was only one-third its present age.

A so-called gravitational lens is produced when space is warped by a massive foreground object, whether it is the Sun, a black hole, or an entire cluster of galaxies. The light from more-distant background objects is distorted, brightened, and magnified as it passes through this gravitationally disturbed region.

A team of astronomers led by Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md., aimed Hubble at one of the most striking examples of gravitational lensing, a nearly 90-degree arc of light in the galaxy cluster RCS2 032727-132623. Hubble's view of the distant background galaxy is significantly more detailed than could ever be achieved without the help of the gravitational lens.

The results have been accepted for publication in The Astrophysical Journal, in a paper led by Keren Sharon of the Kavli Institute for Cosmological Physics at the University of Chicago. Professor Michael Gladders and graduate student Eva Wuyts of the University of Chicago were also key team members.

The presence of the lens helps show how galaxies evolved from 10 billion years ago to today. While nearby galaxies are fully mature and are at the tail end of their star-formation histories, distant galaxies tell us about the universe's formative years. The light from those early events is just now arriving at Earth. Very distant galaxies are not only faint but also appear small on the sky. Astronomers would like to see how star formation progressed deep within these galaxies. Such details would be beyond the reach of Hubble's vision were it not for the magnification made possible by gravity in the intervening lens region.

In 2006 a team of astronomers using the Very Large Telescope in Chile measured the arc's distance and calculated that the galaxy appears more than three times brighter than previously discovered lensed galaxies. In 2011 astronomers used Hubble to image and analyze the lensed galaxy with the observatory's Wide Field Camera 3.

The distorted image of the galaxy is repeated several times in the foreground lensing cluster, as is typical of gravitational lenses. The challenge for astronomers was to reconstruct what the galaxy really looked like, were it not distorted by the cluster's funhouse-mirror effect.

Hubble's sharp vision allowed astronomers to remove the distortions and reconstruct the galaxy image as it would normally look. The reconstruction revealed regions of star formation glowing like bright Christmas tree bulbs. These are much brighter than any star-formation region in our Milky Way galaxy.

Through spectroscopy, the spreading out of light into its constituent colors, the team plans to analyze these star-forming regions from the inside out to better understand why they are forming so many stars.

Link to published paper:
Keren Sharon, Michael D. Gladders, Jane R. Rigby, Eva Wuyts, Benjamin P. Koester, Matthew B. Bayliss and L. Felipe Barrientos, SOURCE-PLANE RECONSTRUCTION OF THE BRIGHT LENSED GALAXY RCSGA 032727-132609*, The Astrophysical Journal, Volume 746, Number 2

CONTACT
Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514

Jane Rigby
NASA Goddard Space Flight Center, Greenbelt, Md.
301-286-1507

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Related Links:
KICP Members: Michael D. Gladders; Keren Sharon
KICP Students: Eva Wuyts
 
Hubble Captures Giant Lensed Galaxy Arc
Universe Today, February 6, 2012
This graphic shows a reconstruction (at lower left) of the brightest galaxy whose image has been distorted by the gravity of a distant galaxy cluster. The small rectangle in the center shows the location of the background galaxy on the sky if the intervening galaxy cluster were not there. The rounded outlines show distinct, distorted images of the background galaxy resulting from lensing by the mass in the cluster. The image at lower left is a reconstruction of what the lensed galaxy would look like in the absence of the cluster, based on a model of the cluster's mass distribution derived from studying the distorted galaxy images.   <i>Illustration Credit: NASA, ESA, and Z. Levay (STScI) Science Credit: NASA, ESA, J. Rigby (NASA Goddard Space Flight Center), K. Sharon (Kavli Institute for Cosmological Physics, University of Chicago), and M. Gladders and E. Wuyts (University of Chicago)</i>
This graphic shows a reconstruction (at lower left) of the brightest galaxy whose image has been distorted by the gravity of a distant galaxy cluster. The small rectangle in the center shows the location of the background galaxy on the sky if the intervening galaxy cluster were not there. The rounded outlines show distinct, distorted images of the background galaxy resulting from lensing by the mass in the cluster. The image at lower left is a reconstruction of what the lensed galaxy would look like in the absence of the cluster, based on a model of the cluster's mass distribution derived from studying the distorted galaxy images.

Illustration Credit: NASA, ESA, and Z. Levay (STScI) Science Credit: NASA, ESA, J. Rigby (NASA Goddard Space Flight Center), K. Sharon (Kavli Institute for Cosmological Physics, University of Chicago), and M. Gladders and E. Wuyts (University of Chicago)
by Tammy Plotner, Universe Today

Less than a year ago, the Hubble Space Telescope's Wide Field Camera 3 captured an amazing image - a giant lensed galaxy arc. Gravitational lensing produces a natural "zoom" to observations and this is a look at one of the brightest distant galaxies so far known. Located some 10 billion light years away, the galaxy has been magnified as a nearly 90-degree arc of light against the galaxy cluster RCS2 032727-132623 - which is only half the distance. In this unusual case, the background galaxy is over three times brighter than typically lensed galaxies... and a unique look back in time as to what a powerful star-forming galaxy looked like when the Universe was only about one third its present age.

A team of astronomers led by Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Maryland are the parties responsible for this incredible look back into time. It is one of the most detailed looks at an incredibly distant object to date and their results have been accepted for publication in The Astrophysical Journal, in a paper led by Keren Sharon of the Kavli Institute for Cosmological Physics at the University of Chicago. Professor Michael Gladders and graduate student Eva Wuyts of the University of Chicago were also key team members.

"The presence of the lens helps show how galaxies evolved from 10 billion years ago to today. While nearby galaxies are fully mature and are at the tail end of their star-formation histories, distant galaxies tell us about the universe's formative years. The light from those early events is just now arriving at Earth." says the team. "Very distant galaxies are not only faint but also appear small on the sky. Astronomers would like to see how star formation progressed deep within these galaxies. Such details would be beyond the reach of Hubble's vision were it not for the magnification made possible by gravity in the intervening lens region."

But the Hubble isn't the only eye on the sky examining this phenomenon. A little over 10 years ago a team of astronomers using the Very Large Telescope in Chile also measured and examined the arc and reported the distant galaxy seems to be more than three times brighter than those previously discovered. However, there's more to the picture than meets the eye. Original images show the magnified galaxy as hugely distorted and it shows itself more than once in the foreground lensing cluster. The challenge was to create a image that was "true to life" and thanks to Hubble's resolution capabilities, the team was able to remove the distortions from the equation. In this image they found several incredibly bright star-forming regions and through the use of spectroscopy, they hope to better understand them.

Read more >>

Related Links:
KICP Members: Michael D. Gladders; Keren Sharon
KICP Students: Eva Wuyts
 
New Kavli Institute Announced at the University of Tokyo
Kavli Foundation, February 8, 2012
New Kavli Institute Announced at the University of Tokyo
Kavli Foundation

Institute for the Physics and Mathematics of the Universe Receives Major Endowment from The Kavli Foundation, Joining Family of Kavli Institutes

(Originally published by the University of Tokyo)

February 7, 2012

(TOKYO, JAPAN) The University of Tokyo (Todai) announced today the establishment of an endowment by The Kavli Foundation for the Institute for the Physics and Mathematics of the Universe (IPMU).

The Institute, which will now be known as the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), probes the biggest mysteries in modern cosmology: How did the universe begin, and how will it end? What is it made of, and what laws govern its behavior? How did we come to exist? The Institute is seeking answers through collaborative research conducted by a wide range of scientists, including mathematicians, theoretical physicists, experimental physicists and astronomers. Together, they focus on topics such as dark matter and dark energy, which make up nearly 96 percent of the universe but today are completely unknown, and the possibility of a single unified theory that can explain the cosmos at the smallest and largest scales.


Read a roundtable discussion with the Director and Deputy Directors of the Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, about research at the Institute and plans for the future. Click here.


"It is a great honor for the University of Tokyo that the world-renowned Kavli Foundation has chosen the Institute for the Mathematics and Physics of the Universe as the recipient of a major donation, and to become the newest member of the Kavli group of research institutes as the Kavli IPMU," said University of Tokyo President Junichi Hamada. "Mr. Kavli's generous donation ensures a secure foundation for the Kavli IPMU today and guarantees that the institute will remain at the forefront of its field tomorrow. In addition, this donation has provided the occasion to reexamine and reform our systems for managing donated funds. Seizing this opportunity, I hope to build on this momentum and redouble our efforts to pursue reform at the University of Tokyo."

Said Daisuke Yoshida, Director-General, Research Promotion Bureau, Ministry of Education, Culture, Sports, Science and Technology (MEXT), "IPMU was established in 2007 and has been supported by the World Premier International Research Center Initiative (WPI) of the Japanese government. The WPI program is designed to promote world-class science in Japan and its international visibility. Within just four years, IPMU has established itself as a world-renowned institute starting from zero. I also congratulate IPMU for receiving wonderful recognition by such an international foundation supporting basic science as The Kavli Foundation. We believe that the prestige associated with the endowment will bring a wider global recognition and help sustain the long-term success of IPMU."

The Kavli IPMU will be the first of the university's Todai Institutes of Advanced Study (TODIAS), an initiative announced last year by President Hamada. The goal of TODIAS is to pursue excellence in academics and research, boost academic diversity, promote world-class science, and strengthen the university's international ties.

"The establishment of the Kavli Institute for the Physics and Mathematics of the Universe is a wonderful development," said Sadanori Okamura, TODIAS director. "Kavli IPMU is presently the only institute under TODIAS, and this generous gift from The Kavli Foundation is a testimony that the Foundation appreciates the high quality of scientists at the Institute, assembled by Director Murayama. As the Kavli IPMU was established by the WPI, which currently limits funding to no more than 10 years, we are extremely grateful this endowment will provide income in perpetuity. This is an important step toward providing the institute a long-term financial base. I also sincerely hope that Kavli's generous gift has many positive effects on the University's efforts to ask for further contributions to the University Fund from the society at large."

The Kavli Foundation, based in Southern California, sponsors research in astrophysics, nanoscience, neuroscience and theoretical physics at institutes across the globe, including China, England, Netherlands, Norway and the United States. Kavli IPMU is The Kavli Foundation's 16th institute, its sixth in astrophysics and third in theoretical physics, and the first to be established in Japan.

"I am very glad to welcome the Kavli IPMU to our community of institutes," said Fred Kavli, Founder and Chairman of The Kavli Foundation. "By bringing together disciplines ranging from mathematics to theoretical and experimental physics, the Institute is certain to inspire creative collaborations that will lead to exciting discoveries about the universe. I also hope that our support of science in Japan can demonstrate that the quest for knowledge has no boundaries, and that finding the answers to some of science's biggest and most fundamental questions itself requires international collaboration."

The Kavli IPMU is comprised of about 200 researchers from 15 fields, with almost half coming from outside Japan. Reflecting its dedication to multi-disciplinary collaboration, the Institute is embodied in a five-story research building at the Kashiwa campus, outside of Tokyo in Chiba prefecture, where researchers from different fields typically alternate offices, and the hallways gradually ramp from floor-to-floor to encourage informal connections.

"We are very excited by the vision for this institute," said Robert W. Conn, President of The Kavli Foundation. "The Kavli IPMU is dedicated to attracting an international body of excellent researchers from many fields to focus on topics of science that are of profound interest to all humankind. This Institute's program also fits with our focus on supporting four areas of science: Astrophysics, Nanoscience, Neuroscience and Theoretical Physics. The Kavli IPMU spans two of these four areas - Astrophysics and Theoretical Physics - and demonstrates that the pursuit of scientific knowledge very often requires collaborative efforts across many disciplines. We have been extraordinarily impressed by the leadership of Todai and IPMU, and wish everyone at the University the very best as they pursue some of the most fundamental scientific questions of our day."

The Kavli IPMU director is Professor Hitoshi Murayama, a particle physicist from the University of California, Berkeley who, like the Institute he leads, works on a wide range of subjects. These include developing strategies for new particle collider experiments, dark matter theory, the genesis of ordinary matter in the universe, the theory of inflation, which postulates the rapid expansion of the universe in the first moments of the Big Bang, and models of physics beyond the standard explanation for the nature of the universe.

Deputy directors include Professor Hiroaki Aihara, a particle physicist who is working on a new survey of distant galaxies to learn about the nature of dark energy, and Professor Yoichiro Suzuki, who is deeply involved in an underground experiment to detect dark matter.

"I'm super-excited about the IPMU becoming a Kavli Institute," Murayama said. "It brings an international visibility to the Institute that will help us recruit the best minds from around the world. Meanwhile, the connection to the other Kavli institutes will boost our collaborative research opportunities."

IPMU was established in the fall of 2007 as part of the World Premier International Research Center Initiative, a program of the Japanese government to promote interdisciplinary science in Japan, its international visibility, and globalization of the Japanese universities. Proposed as part of the University of Tokyo, the IPMU was one of six research proposals around the country that won sponsorship from the Ministry of Education, Culture, Sports, Science and Technology. Other WPI institutes are involved in materials research, cell biology, immunology, nanotechnology, and alternative energy development. IPMU receives funding support from the government and the university, but the Institute must eventually identify other sources of support to become a permanent research center.

"The endowment income will help sustain the research program at the Kavli IPMU beyond the current initiative by the Japanese government," Murayama said. "Now we can press on to attack the most basic and biggest mysteries of the Universe!"

The Kavli IPMU's research spans physics and cosmology from subatomic neutrinos and other fundamental particles to the cosmic web of galaxies that formed from the seeds of density perturbations in the Cosmic Microwave Background - the afterglow energy from the Big Bang that emerged less than 400,000 years after that event nearly 14 billion years ago.

Mathematicians at the Institute are working on, for example, new geometric tools to help string theorists, who propose that the smallest constituents of all matter are vibrating strings of energy, describe their ideas.

Particle physicists, such as Kavli IPMU Deputy Director Aihara, are working with astrophysicists at the Subaru Telescope atop Mauna Kea on the Big Island of Hawaii to study the nature of dark energy, the mysterious force that makes up more than 70 percent of the universe and is causing it to accelerate at an ever increasing rate. Meanwhile, researchers such as Kavli IPMU Deputy Director Suzuki are working on ambitious projects such as XMASS, a stunningly sensitive detector deep underground being designed to detect dark matter, which makes up nearly a quarter of the universe and permeates the cosmos like a scaffold upon which galaxies congregate.

Other researchers at the IPMU have published recent papers on the distribution of dark matter in the universe, vigorous star formation in one of the most distant and oldest galaxies yet seen, the growth of supermassive black holes, and other topics.

Astrophysicist Roger Blandford, director of the Kavli Institute for Particle Astrophysics and Cosmology and Professor at Stanford University in California, said IPMU has accomplished much since it was established less than five years ago. "I am thrilled that IPMU will become the Kavli IPMU," Blandford said. "It has already become an outstanding cosmological research center, and this will allow it to contribute even more to this exciting field. My colleagues and I at the Kavli Institute for Particle Astrophysics and Cosmology look forward to many future collaborations and send our congratulations."

About the University of Tokyo
The University of Tokyo, also known as "Todai," was established in 1877 as the first national university in Japan. As a leading research university, Todai offers courses in essentially all academic disciplines at both undergraduate and graduate levels and conducts research across the full spectrum of academic activity. The university aims to provide its students with a rich and varied academic environment that ensures opportunities for both intellectual development and the acquisition of professional knowledge and skills. The University of Tokyo enrolls 28,000 students, evenly divided between undergraduates and graduates. More than ten percent of all students were from overseas in 2011, and more than 3,300 researchers visited the campus in 2010 for short and extended stays. More than 9,000 of the university's researchers visited partner institutions around the world.

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University of Chicago Cosmology & Astronomy Scientists "Launch Off" To Outreach with Project Exploration!
Project Exploration Blog, February 10, 2012
The awesome KICP scientists ready to share their passion and knowledge with Project Exploration students!
The awesome KICP scientists ready to share their passion and knowledge with Project Exploration students!
Project Exploration Blog

The importance of scientist trainings and workshops for Project Exploration's work: At the heart of Project Exploration's youth programming is bringing together scientists and young people to work together and engage in authentic science. As we grow our programs and opportunities for youth, we are also diversifying and expanding the cadre of wonderful scientists with whom we work. Project Exploration's commitment to increasing access and equity in science means that we also work with scientists to discuss what effective outreach looks like, how to communicate science to youth, share methods of building personal relationships with young people, and how to design youth-centered activities where students and scientists are engaged in the nature of science.

What's "out there?" How do we count the stars? What is space made of? What role does the moon play in our everyday lives? Why does the sun look like it's moving, when it's not?

These are some of the great questions that a group of professors, graduate students, and post-doc fellows of University of Chicago's Kavli Institute for Cosmological Physics (KICP) came up with during a scientist training on effective outreach.

KICP is one of the foremost national research institutes dedicated to interdisciplinary cosmological physics. The scientists at KICP are studying amazing questions about the universe: What is dark energy? What happened during the first moments of the universe's birth? What clues do high energy particles offer about the universe and its evolution? All of this amazing research happens on Chicago's southside, which is also home to many of the under-resourced schools with whom Project Exploration works. By working with scientists at KICP, Project Exploration youth will have an opportunity to discover, explore, and pursue the fields of astronomy, cosmology, and physics alongside professional scientists in their community.

Randy Landsberg, KICP's Director of Education and Outreach, and Project Exploration have been looking for fruitful ways to work together for some time. With Project Exploration's strategic plan calling for us to double the number of students served and diversify our offerings, astronomy and physics seemed like a perfect way to bring scientists and Project Exploration together.

The training was a great opportunity for KICP scientists to learn about Project Exploration and it's youth-centered programming. After discussing effective instructional strategies, the scientists were ready to start developing their "big ideas" about the work they do. With Brothers4Science starting next week, the male scientists were excited about developing activities and sharing their passion for asking questions about the universe with young boys in the community. Many of the female scientists are developing sessions for Sisters4Science. For example, post-doctoral appointee and KICP Fellow Elise Jennings will be working with Sisters4Science in March on understanding the phases of the moon!

Christopher Greer, a graduate student at KICP who has worked with Project Exploration in the past, said that one of the most interesting questions he once heard was "What is the most wonderous thing you have seen in nature?" These are the types of questions that spark the mind and invite inquiry. We look forward to learning about the wonderous universe together with youth and KICP scientists!

Thank you to Randy Landsberg and Professor Daniel Holz for bringing the training to KICP. A big thank you to the participants of the workshop - we can't wait for your exciting sessions with youth!

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Related Links:
KICP Members: Scott Dodelson; Daniel E. Holz; Elise Jennings; Yuko Kakazu; Claudio Ugalde
KICP Students: Immanuel Buder; Ke Fang; Christopher Greer; Christopher M. Kelso; Jing Zhou
 
Leading the quest to crack cosmological mysteries
The University of Chicago News Office, February 13, 2012
Kavli Institute for Cosmological Physics directs national collaboration on deepest questions of dark energy, dark matter, and cosmic inflation.
Kavli Institute for Cosmological Physics directs national collaboration on deepest questions of dark energy, dark matter, and cosmic inflation.
by Steve Koppes, The University of Chicago News Office

Main feature by Steve Koppes
Main photo courtesy of NASA, ESA, M.J. Jee and H. Ford (Johns Hopkins University)


Sometimes a scientist can only laugh in the face of a seemingly insurmountable challenge.

Such is the case with cracking the mystery of dark energy and its repulsive gravity, which is causing the expansion of the universe to accelerate.


"The time is ripe to solve the dark matter problem. Our Physics Frontiers Center hopes to shed critical light on dark matter."
- Prof. Rocky Kolb


"People don't even get the term 'repulsive gravity' because the defining feature of gravity is that it's attractive," says Michael Turner, director of the Kavli Institute for Cosmological Physics. "What do you mean, repulsive gravity? Do you mean the theory is repulsive?" he jokes.

Turner calls dark energy "the most profound mystery in all of science." Cracking the problem requires collaborations of original thinkers working beyond the limits of current theories. That's why dark energy is one of three cosmological puzzles that the Kavli Institute will tackle over the next five years with $17 million in new funding from the National Science Foundation as a Physics Frontiers Center.

Also high on the institute's research agenda are the riddles of dark matter and cosmic inflation. Along with dark energy, these are the three pillars of modern cosmological theory, "and none of them can be explained with physics that we know," Turner says. "They're all pointing to new physics."

Transforming cosmology
During its first decade as a Physics Frontier Center, the Kavli Institute helped to establish the current cosmological paradigm. Originally called the Center for Cosmological Physics, the Institute was founded in 2001 with a $15 million NSF grant. The Institute is launching its second decade with 21 key collaborators around the country and 15 institutional partners, including Argonne National Laboratory and Fermi National Accelerator Laboratory.

The NSF created the Physics Frontiers Centers program to make significant advances at some of the most important intellectual frontiers in diverse physics subfields, says Joseph Dehmer, director of NSF's division of physics.

"By all measures, this has happened, and the 10 PFCs now operating reflect the extremely high standards of scholarship and synergy hoped for," Dehmer says. "An unexpected and most welcome benefit is that the PFCs act as talent magnets, drawing high levels of talent into physics. Another not unexpected benefit is that the triennial PFC competition constitutes a serious, high-level discussion across the subfields of physics - a rare 'unity of physics' event in an increasingly specialized field."

Argonne is a new partner in the UChicago PFC. Argonne and Kavli Institute scientists will develop large-scale cosmological simulations on the laboratory's supercomputers, as well as sensitive new detectors for the South Pole Telescope, which studies the cosmic microwave background radiation leftover from the birth of the universe. Kavli Institute scientists will investigate the dark energy question with the SPT and the Dark Energy Survey. The latter project, led by Fermilab, will collect data on approximately 300 million galaxies spanning two-thirds the history of the universe in order to measure dark energy with new precision.

New form of matter?
The mystery of dark matter may be easier to solve. Kavli Institute scientists hope to accomplish this feat within the next decade. They suspect that dark matter is made of a new form of matter, something that does not consist of quarks, neutrons or protons.

Dark matter may reveal itself through any or all of three means: direct detection via ground-based detectors at the Chicagoland Observatory for Underground Particle Physics (COUPP), indirect detection in the galaxy halo via satellites, and production of the particles at the Large Hadron Collider at CERN, the European particle physics laboratory.

"Right now, there is confusion - claims of possible detections, counter-claims, and spirited debate - and the time is ripe to solve the dark matter problem. Our PFC hopes to shed critical light on dark matter," says Rocky Kolb, the University's Arthur Holly Compton Distinguished Service Professor in Astronomy & Astrophysics, who leads the PFC's dark matter effort.

Cosmic inflation is a different kind of problem. It has emerged as the most important cosmological concept since the Big Bang theory, but many of its claims have not yet been thoroughly tested. Inflation proposes that the universe expanded extremely rapidly in a tiny fraction of a second after the Big Bang. Such a swift expansion would explain some important questions that Big Bang theory alone has been unable to answer.

"We have some circumstantial evidence that inflation took place, but we'd like to make the case very strongly," says John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics. A more direct indication of inflation would be to look for a minute sign of polarization in the cosmic microwave background, the afterglow of the Big Bang.

For the last decade, center scientists, including Carlstrom and the late Bruce Winstein, have been developing a technology capable of measuring this polarization. Now they need to deploy that technology to see what they can find.

The successful Kavli Institute proposal for the Physics Frontiers Center was more than two years in the making and included significant support from the University administration and behind-the-scenes personnel.

Winstein, the Samuel K. Allison Distinguished Service Professor in Physics and founder of the original PFC, also played a big role in developing the proposal for renewed funding. Winstein, who lost a four-year battle with cancer last February, worked on the proposal until his last days, Turner says.

"During the last months of his life, he was parceling out his time only to the most important things, and we got a lot of his time. Our PFC is part of Bruce's legacy."

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Related Links:
KICP Members: John E. Carlstrom; Edward W. Kolb; Michael S. Turner; Bruce D. Winstein
Scientific projects: COUPP/PICO; Dark Energy Survey (DES); South Pole Telescope (SPT)
 
Cosmologists Seek Unified Picture of the Universe
The University of Chicago News Office, February 14, 2012
Michael Turner, Director of the Kavli Institue of Cosmological Physics
Michael Turner, Director of the Kavli Institue of Cosmological Physics
The University of Chicago News Office

Michael Turner, Director of the Kavli Institue of Cosmological Physics, speaks about theories, scientists and the universe.

Video

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Related Links:
KICP Members: Michael S. Turner
 
Cosmologists Michael Turner and Joshua Frieman discuss Dark Energy and DES in an article in The Economist
The Economist, February 22, 2012
The Cerro Tololo Inter-American Observatory  <i>Image credit:</i> T.Abbott/NOAO/AURA/NSF
The Cerro Tololo Inter-American Observatory

Image credit: T.Abbott/NOAO/AURA/NSF
The Economist

The dark side of the universe
Scientists are trying to understand why the universe is running away from them

AT FIVE tonnes and 520 megapixels, it is the biggest digital camera ever built-which is fitting, because it is designed to tackle the biggest problem in the universe. On February 20th researchers at the Cerro Tololo Inter-American Observatory, which sits 2,200 metres (7,200 feet) above sea level in the Atacama desert of northern Chile, will begin installing this behemoth on a telescope called Blanco. It is the centrepiece of the Dark Energy Survey (DES), the most ambitious attempt yet to understand a mystery as perplexing as any that faces physics: what is driving the universe to expand at an ever greater rate.

It has been known since the late 1920s that the universe is getting bigger. But it was thought that the expansion was slowing. When in 1998 two independent studies reached the opposite conclusion, cosmology was knocked head over heels. Since then, 5,000 papers have been written to try to explain (or explain away) this result. "That's more than one a day," marvels Saul Perlmutter, of the Lawrence Berkeley National Laboratory, who led the Supernova Cosmology Project-one of the studies that was responsible for dropping the bombshell. Last October that work earned Dr Perlmutter the Nobel prize for physics, which he shared with Brian Schmidt and Adam Riess, who led the other study, the High-Z Supernova Search.

Many of those 5,000 papers deal with something that has come to be known as dark energy. One reason for its popularity is that, at one fell swoop, it explains another big cosmological find of recent years. In the early 1990s studies of the cosmic microwave background (CMB), an all-pervading sea of microwaves which reveals what the universe looked like when it was just 380,000 years old, showed that the universe, then and now, was "flat". However big a triangle you draw on it-the corners could be billions of light years apart-the angles in it would add up to 180o, just as they do in a school exercise book.

That might not surprise people whose geometrical endeavours have never gone beyond such books. But it surprised many physicists. At some scales space is not at all flat: the power of Albert Einstein's theory of general relativity lies in its interpretation of gravity in terms of curved space. Cosmologists were quite prepared for it to be curved at the grandest of scales, and intrigued to discover that it was not.

Dark thoughts
Relativity says that for the universe to be flat, it has to have a very particular density-which in relativity is a measure not just of the mass contained in a certain volume, but also of the energy. The puzzle was that various lines of evidence showed that the universe's endowment of ordinary matter (the stuff that people, planets and stars are made of) would give it just 4% of that density. Adding in extraordinary matter-"dark matter", not made of atoms, that interacts with the rest of the universe almost only by means of gravity-gets at most an extra 22%. That left almost three-quarters of the critical density unaccounted for. Theorists such as Michael Turner, of the University of Chicago, became convinced that there was something big missing from their picture of the universe.

Whatever it is that is driving the universe's accelerating expansion fits the bill rather well. Add the amount of energy needed to keep cosmic acceleration going to the amount of matter and energy in the universe already accounted for and you have more or less exactly the density of matter and energy needed to make the universe flat. But there is a catch; for the sums to tally, that "dark energy" - Dr Turner is thought to have coined the term - must be very strange stuff indeed. According to Einstein's theory of relativity, energy in the form of radiation has the same sort of gravitational effect as matter does - the photons of which light is made exert a pressure, and this in turn gives rise to a gravitational attraction. In order to drive its acceleration, then, dark energy must instead have a repulsive effect. It must, in other words, exert a negative pressure.

Divide dark energy's pressure (negative) by its energy density (positive) and you get something cosmologists label "w". It is easy to see that w must be negative. Observations made since 1998 suggest that w is pretty close to -1. If it were found to be exactly -1, that would make dark energy something physicists call a cosmological constant. A cosmological constant is the same no matter where in the universe you look - an inherent, unchanging feature of the fabric of creation, however much it expands, twists or ties itself in knots.

The cosmological constant is another thing first dreamed up by Einstein. On realising that the equations of general relativity allowed for the universe's expansion (or, indeed, contraction), he added a parameter describing just such a constant in order to keep it from doing either. For all his notoriously counterintuitive predictions, an expanding universe was one he was not prepared to countenance, at least not in 1917, when he published his theory. After Edwin Hubble's discovery 12 years later that other galaxies were indeed streaming away from Earth's Milky Way backyard, Einstein dropped the tweak. No doubt miffed that he had not trusted his maths in the first place, he later called the cosmological constant his "biggest blunder".

By then, though, the cosmological constant had been seized upon by quantum theorists, themselves in the midst of turning physics on its head. Quantum theory says that the seemingly empty vacuum of space is, in fact, not empty at all. Instead it is constantly abuzz with "virtual" particles flitting in and out of existence. The energy resulting from all this buzzing - vacuum energy - should be a fixed feature of space - in other words, a cosmological constant.

Stringing it all together
And, in principle, it could also propel the universe's expansion. Thus vacuum energy and dark energy might be the same thing. But this theoretical neatness runs into a practical problem. A naive approach to quantum theory says that vacuum energy should be a whopping 1060 to 10120 times bigger than dark energy's estimated energy density. Some physicists call this "the worst prediction ever". Working out why vacuum energy is not so vast has been a problem for physics ever since.

Cliff Burgess, from Perimeter Institute for Theoretical Physics in Waterloo, Ontario, and the author of a handful of the 5,000 papers Dr Perlmutter has dug up, thinks he has a solution; the vacuum energy is vast, but it is almost all hidden away in extra spatial dimensions. Unlike the familiar three of length, breadth and height, these extra dimensions are curled up so tightly that they elude detection (though scientists are trying to prise them open in particle accelerators like the Large Hadron Collider near Geneva). Extra dimensions are of interest because string theory, a class of mathematical models based on quantum theory that seeks to describe reality in the most fundamental way, requires that there be at least six of them, maybe more.

What makes Dr Burgess's proposal unusual is that he went out on a limb and suggested that these energy-sapping, curled-up extra dimensions should be as big as a few microns across, gargantuan by string-theory standards. The reason they have not been noticed by chipmakers, virologists and others who pay attention to things on the micron scale, he contends, is that, like dark matter, they are sensitive only to gravity, and relatively oblivious to the other three of nature's fundamental interactions: electromagnetism and the weak and strong nuclear forces. This may sound like a cheap excuse but it makes robust mathematical sense. And it makes predictions; at micron scales the attraction between two masses will no longer depend on the square of the distance between them in the way that physicists since Newton have required it to.

An experiment under way at the University of Washington, led by Eric Adelberger, tests this idea using the world's most sensitive torsion balance, a souped-up version of the kit Henry Cavendish, an English physicist, used to measure gravity directly for the first time in the late 18th century. It consists of a disk with holes around its edge hanging horizontally from a cord, microns above another, similarly perforated plate. When the bottom disk is rotated the material between its holes exerts a tiny gravitational tug on the material between the holes of the top disk, causing it to rotate, albeit only by billionths of a degree. So far, Sir Isaac is winning. Dr Adelberger has confirmed that Newton's predictions are correct down to 44 microns. But the experiment continues, and Dr Burgess is taking bets that Newton's winning streak will not last much longer.

If Dr Burgess is right, vacuum energy and dark energy are the same thing, a cosmological constant, and w is exactly equal to -1. What, though, if it is not? Then dark energy would have to be something that varies in space, time, or both, and is close to -1 today just by coincidence. Names applied to this something else include quintessence, k-essence, phantom energy and a bunch more, depending on which theorist you ask and what properties you think likely. It would be a new fundamental force, one that rears its head only at vast cosmic distances.

An alternative is to monkey with one of the existing forces. Some physicists would rather fiddle with Einstein's theory of relativity, for instance by making gravity weaker at extremely long ranges. This is tricky. It is notoriously hard to modify the equations of general relativity without damaging the theory beyond repair. That is one reason for their enduring appeal. Another is that they have been confirmed time and again by tests that range from minute measurements of bodies circling the solar system to observations of the farthest known light sources, quasars, billions of light years from Earth. Any new theory, then, has its work cut out-which has not, of course, stopped theorists trying.

The more precisely w comes to look like -1, the more enthusiasm there will be for cosmological constant theories, which require that value, and the less enthusiasm there will be for fifth forces and modified gravity, part of the charm of which is that they can work with other values. This is where telescopes like Cerro Tololo come in. Existing data from ground-based and space telescopes put w at between -1.1 and -0.9. DES will aim to narrow the margin of uncertainty down to just 0.01. To do so, it will take 400 one-gigabyte snaps a night for 525 nights over five years (the remaining telescope time will be split between other science projects). And it will use an array of clever techniques to analyse the data.

The first is a time-honoured method borrowed from Dr Perlmutter, Dr Schmidt and Dr Riess and used to study exploding stars called supernovae. These come in different varieties. Some, called type Ia, always explode with almost exactly the same energy. They are, therefore, equally bright. Since brightness decreases in a predictable way with distance, type Ia supernovae make excellent cosmic yardsticks. Since the speed of light is constant, knowing how far away such a "standard candle" is (calculated from its apparent brightness seen from Earth) is to know how long ago it exploded. The rate at which stars and galaxies are moving away from Earth, meanwhile, can be worked out from their redshift. As light travels across space, which is stretching, its wavelength, too, is stretched and its frequency shifts towards the red end of the spectrum. The faster the expansion, the greater the redshift.

What the Supernova Cosmology Project and the High-z Supernova Search both found, and what others have later confirmed, is that distant exploding stars are dimmer, and so farther away, than their redshift implies they should be if the universe has been expanding at a steady clip throughout. The expansion must therefore have sped up recently.

The two groups originally based this conclusion on data from a mere 50-odd supernovae. The number has since grown tenfold, but it still leaves plenty of wriggle room for the cosmological constant to prove, well, not so constant after all. Joshua Frieman, who heads DES, hopes his team will eventually analyse over 4,000 exploding stars, some as far away as 7 billion light years. They exploded when the universe was half its current age and, researchers now reckon, still dominated by the gravity of the matter it contained, which was putting the brakes on expansion. Dark energy, it is thought, revved things up some 5 billion years ago. A better estimate of the time at which one gave way to the other helps determine w.

Music of the spheres
In addition to supernova searches, which will train the telescope at ten patches of the sky where Dr Frieman and his colleagues hope to spot and track the explosions, DES will be scouring one-eighth of the night sky for other clues, using three other methods. These all rely on throwing cartloads of computing power at seemingly random data in order to tease out tiny statistical anomalies.

One method looks for the effects of sound waves which originated in the Big Bang: baryon-acoustic oscillations (BAO). In the Big Bang's primordial soup of particles, known as a baryon-photon fluid, there were density waves like the sound waves in air, though far vaster. When the fluid cooled down enough, though, the baryons (particles from which atomic nuclei are made) and photons parted company. The photons became what is now the CMB; it is the fact that they have had nothing to do with matter since the Big Bang that makes the CMB such a remarkable window into the early universe.

With the photons no longer willing to play, there could be no more baryon-photon fluid. The baryons were stuck in position. Where the oscillations in the fluid had bunched the baryons tightly, they remained bunched; where they had been rarefied they remained sparse. The higher density regions became the seeds of galaxies-and the average separation of those galaxies thus reveals the wavelength of the oscillations in the primordial fluid. That characteristic scale has been stretched out to around 450m light years; measuring it at earlier times is another way to show how quickly the universe has been expanding.

The last two of DES's techniques measure not just rates of expansion, as supernovae and BAO searches do, but also the growth of cosmic structures like clusters of galaxies. Tracking the size and shape of clusters through time gives an idea of the tug-of-war between gravity, pulling them together, and dark energy, pushing them apart. This could help answer the question whether expansion is down to dark energy alone, in which case physicists expect a correlation between results from all four techniques, or to modified gravity, if the last two do not square with the first two.

One way to probe structure is to count the number of clusters of a given mass in a given volume of space at different redshifts. This is harder than it sounds because 85% of the mass is invisible dark matter. But it can be measured indirectly, for instance by looking at how hot clouds of gas get as they are pulled towards the cluster's dark-matter core by its gravity.

Alternatively, the distribution of matter, both dark and humdrum, can be gleaned from the effect it has on light. Relativity requires the path of light to be bent by massive objects. The heavier the object, the more an image of something behind it is warped. Most of the time, this warping is tiny-images of galaxies are typically stretched by 2% or so by the clumps of matter they pass on their way to telescopes on Earth. To complicate matters further, few galaxies are perfectly round to start with, so it is hard to tell whether stretching has taken place by looking at any particular galaxy. Fortunately, light from all the galaxies in a given region of the sky passes by the same clumps of matter on the way to Earth. So galaxies as seen from Earth ought all to be distorted in a preferred direction. Observe enough of them, 300m in DES's case, and a pattern should emerge, allowing astronomers to model the structures responsible for the bending.

Combine all four techniques and a clearer picture of the causes of cosmic acceleration will emerge. That, at least, is the hope. Ofer Lahav from University College, London, who is in charge of DES's science programme, says the odds are that DES will home in on w being equal to -1 -- some sort of a cosmological constant.

Saving the best 'til LSST
Other, even more ambitious projects, will strive to increase the precision of the measurement of W. Last year ground was broken on the Large Synoptic Survey Telescope (LSST), a much bigger instrument which will be perched atop Cerro Pachon, 10km (6 miles) from Cerro Tololo. Though its $620m budget awaits final approval from America's National Science Foundation and Department of Energy, scientists hope to have it up and running by 2021. The LSST's mammoth camera will boast 3.2 gigapixels.

Then there are two space telescopes, each with a price tag of $1 billion or so. The European Space Agency plans to launch Euclid in 2019 and NASA hopes to put WFIRST in orbit three years later.

These projects are not solely dedicated to probing the nature of dark energy. LSST, for example, will discover asteroids by the bushel-including some that might be hazardous to Earth. But one way or another it is cosmic expansion that they, and all sorts of other astronomical ventures, will be addressing.

The rub is that no amount of observations can ever pin down the figure for w with perfect accuracy. That would require infinite precision, something impossible to achieve even in an ever-expanding universe. And the whole constant idea falls to pieces if w is even a smidgen off -1.

More than any other scientific problem the cosmic-expansion conundrum presents scientists with an existential quandary. "It could be a 22nd-century problem we stumbled upon in the 20th century," says Dr Turner. Some researchers may begin to feel time would be better spent on other scientific pursuits.

Many astronomers, including Dr Perlmutter, are quietly hoping that as DES and the host of other acronyms come online, they will spring another surprise, like the one that first propelled cosmic acceleration into the limelight in 1998. Whether they do or not, though, dark energy-or whatever else is causing the universe to speed up-is probably too big a conundrum for one generation to crack. It will cause boffins to rack their brains for years to come.

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Related Links:
KICP Members: Joshua A. Frieman; Michael S. Turner
Scientific projects: Dark Energy Survey (DES)
 
Gravitational lens reveals details of distant, ancient galaxy
The University of Chicago News Office, March 8, 2012
This graphic shows a reconstruction (at lower left) of the brightest galaxy, whose image has been distorted by the gravity of a distant galaxy cluster. The small rectangle in the center shows the location of the background galaxy on the sky if the intervening galaxy cluster were not there. The rounded outlines show distinct, distorted images of the background galaxy resulting from lensing by the mass in the cluster. The image at lower left is a reconstruction of what the lensed galaxy would look like in the absence of the cluster, based on a model of the cluster's mass distribution derived from studying the distorted galaxy images.  <i>Courtesy of NASA; ESA; J. Rigby (NASA Goddard Space Flight Center); K. Sharon (Kavli Institute for Cosmological Physics); and and M. Gladders and E. Wuyts (University of Chicago)</i>
This graphic shows a reconstruction (at lower left) of the brightest galaxy, whose image has been distorted by the gravity of a distant galaxy cluster. The small rectangle in the center shows the location of the background galaxy on the sky if the intervening galaxy cluster were not there. The rounded outlines show distinct, distorted images of the background galaxy resulting from lensing by the mass in the cluster. The image at lower left is a reconstruction of what the lensed galaxy would look like in the absence of the cluster, based on a model of the cluster's mass distribution derived from studying the distorted galaxy images.

Courtesy of NASA; ESA; J. Rigby (NASA Goddard Space Flight Center); K. Sharon (Kavli Institute for Cosmological Physics); and and M. Gladders and E. Wuyts (University of Chicago)
by Steve Koppes and Ray Villard, The University of Chicago News Office

Thanks to the presence of a natural "zoom lens" in space, University of Chicago scientists working with NASA's Hubble Space Telescope have obtained a uniquely close-up look at the brightest gravitationally magnified galaxy yet discovered.

The imagery offers a visually striking example of gravitational lensing, in which one massive object's gravitational field can magnify and distort the light coming from another object behind it. Such optical tricks stem from Einstein's theory of general relativity, which describes how gravity can warp space and time, including bending the path that light travels.

In this case, gravity from the galaxy cluster RCS2 032727-132623 bent and amplified the light coming from a much more distant galaxy, 10 billion light-years from Earth. This "gravitational telescope" creates a vast arc of light, as if the distant galaxy had been reflected in a funhouse mirror. The UChicago team reconstructed what the distant galaxy really looks like, using computational tools that reversed the effect of gravitational lensing.

"What's happening here is a manifestation of general relativity," said Michael Gladders, assistant professor in astronomy & astrophysics at UChicago. "Instead of seeing the normal, faint image of that distant source, you see highly distorted, highly magnified, and in this case, multiple images of the source caused by the intervening gravitational mass."

The cosmic lens gave the UChicago team the unusual opportunity to see what a galaxy looked like 10 billion years ago. The reconstructed image of the galaxy revealed regions of star formation glowing like bright points of light. These are much brighter than any star-formation region in Earth's home galaxy, the Milky Way.

'Looking at the nature of dark matter'
In 2006 the Chicago astronomers used the Very Large Telescope in Chile to measure the arc's distance and calculated that the galaxy appears more than three times brighter than previously discovered lensed galaxies. Then last year, Jane Rigby of NASA's Goddard Space Flight Center in Greenbelt, Md., and the Chicago team imaged the arc with the Hubble Space Telescope's Wide Field Camera 3.

Using this gravitational lens as a telescope offers two major scientific opportunities, Gladders said. First, "It gives us a look at that very distant source with a precision and fidelity that we couldn't otherwise achieve," he said.

And second, it provides an opportunity to learn something about the lens-forming mass, which is dominated by dark matter. "It's really a way of looking at the nature of dark matter," Gladders said. Dark matter accounts for nearly 90 percent of all matter in the universe, yet its identity remains one of the biggest mysteries of modern science.

Keren Sharon, a postdoctoral scholar at UChicago's Kavli Institute for Cosmological Physics, led the effort to perform a detailed reconstruction of the lensed galaxy. She and her co-authors, including Gladders, NASA's Rigby and UChicago graduate student Eva Wuyts, published their findings last month in the Astrophysical Journal.

Sharon painstakingly created a computer reconstruction of the gravitational lens, then reverse-engineered the distorted image to determine the distant galaxy's actual appearance. "It's a little bit of an art, but there's a lot of physics in it. That's the beauty of it," Sharon said. "It was a fun puzzle to solve, especially when we had such great data."

Gladders said Sharon is "one of the world experts on exactly how to do this. Combine that degree of finesse with this quality of data, and you get a very nice result. This object now becomes not only the brightest-lensed source known, but because of this analysis, it is also going to be one of the best-understood sources."

Through spectroscopy, the spreading out of light into its constituent colors, the team plans to analyze the distant galaxy's star-forming regions from the inside out to better understand why they are forming so many stars.

The team also has obtained data from one of the twin Magellan Telescopes to help them determine why the galaxy, which is 10 billion light years away, looks so irregular.

"It's not like we have something to compare it to," Sharon said. "We don't know what other galaxies at the same distance look like at this level of detail."

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Related Links:
KICP Members: Michael D. Gladders; Keren Sharon
KICP Students: Eva Wuyts
 
South Pole Telescope Finishes Five-year Survey of Galaxy Clusters
SpaceRef, March 30, 2012
Construction workers on a lift assemble the metal superstructure for the ground shield on the South Pole Telescope during the 2011-12 field season. The shield will eliminate ground reflection inteference as the telescope begins a new experiment on cosmic inflation.   Photo Credit: Peter Rejcek
Construction workers on a lift assemble the metal superstructure for the ground shield on the South Pole Telescope during the 2011-12 field season. The shield will eliminate ground reflection inteference as the telescope begins a new experiment on cosmic inflation.

Photo Credit: Peter Rejcek
SpaceRef

Peter Rejcek, Antarctic Sun Editor: Its five-year mission: To survey the early universe for massive galaxy clusters, a search designed to understand more about one of cosmology's greatest mysteries -- dark energy. Mission complete. Now it's time for something new.

The South Pole Telescope (SPT), the largest such instrument ever installed at the U.S. Antarctic Program's research station at the bottom of the world, completed its scan of 2,500-square degrees of night sky at the end of the 2011 winter. The 10-meter telescope has spied hundreds of previously unseen galaxy clusters, including the most massive ever detected, since seeing its first light at the beginning of the 2007 South Pole winter.

"We're trying to understand what dark energy could be, and our way of looking at it is to see the structures involved," explained John Carlstrom, principal investigator for the experiment, which includes dozens of collaborators. "The project as a whole has been more successful than any of us thought."

Galaxy clusters, thanks to the pull of gravity, are the largest structures to have evolved in the cosmos. The SPT hunts for them using the Sunyaev-Zel'dovich (SZ) effect -- a small distortion in the cosmic microwave background (CMB), a "glow" left over from the Big Bang some 14 billion years ago. Such distortions are created as background radiation passes through a large galaxy cluster -- effectively creating a shadow from the cluster in the microwave background.

In 2008, the telescope detected its first galaxy clusters using the SZ effect. Two years later, astronomers announced the discovery of the most massive galaxy cluster yet, tipping the scales at the equivalent of 800 trillion suns, and holding hundreds of galaxies.

Mapping the number of such clusters over the history of the universe can tell researchers how much influence dark energy had on their growth, according to Bradford Benson, a postdoctoral research fellow at the University of Chicago. He is also the lead author of a recent paper that puts additional constraints, based on SPT data, on the models cosmologists use to understand a universe increasingly dominated by dark energy.

It sounds like a disembodied entity that Captain Kirk and company might battle in an episode of Star Trek. Dark energy is the prevalent explanation for the accelerating expansion of the universe. Dark energy appears to counteract the gravitational attraction between galaxies.

In a younger, smaller universe billions of years ago, gravity had a greater influence, allowing galaxy clusters to grow and clump together like dust bunnies on a wood floor. In a study last year using SPT data, lead author Christian L Reichardt, with the University of California, Berkeley, and colleagues found that dark energy accounted for no more than 1.8 percent of the total energy-density of the universe at a time when it was only 400,000 years old. Today, dark energy accounts for more than 70 percent of all the matter and energy in the universe.

"Everything is getting diluted. Dark energy is just sitting there," said Carlstrom, director of the Kavli Institute of Cosmological Physics at the University of Chicago. "In the future, it dominates. Right now it is two-thirds of the energy-density of the universe."

Now, Carlstrom, Benson and their team want to peer back to near the beginning of time, a fraction of a moment after the Big Bang, when the universe expanded exponentially, a theory known as inflation.

During the 2011-12 season, they swapped the telescope's high-tech "camera" purposefully designed to detect the SZ effect with one sensitive to the signature left by cosmic inflation on the pattern of the CMB.

CMB radiation, often referred to as a faint hiss of microwaves, comes from every direction in the sky. It is almost a perfectly uniform plasma, with a temperature of 2.7 degrees above absolute zero on the Kelvin scale.

But it contains "hot" and "cold" spots that are slight irregularities in its near-perfect uniformity, which is known as anisotropy. These spots can tell cosmologists something about the geometry of the universe, the amounts and types of dark matter and energy that make up the cosmos, and even something about the universe's ultimate fate.

The inflation theory holds that the rapid expansion of space-time would generate gravity waves and leave a unique signature when they interact with the plasma. This signature would be a spiral pattern in the polarization of CMB, often referred to as B-mode polarization, which would look like hurricanes in a hypothetical map of the polarization of the CMB.

"Now, we want to do an even more powerful experiment," Carlstrom said.

Switching experiments required more than just upgrading the technology for the telescope receiver. The shielding that prevents interference from the horizon must be augmented. That meant turning the telescope's round 10-meter reflector shield into an octagon by extending the shielding around the dish by about 1 meters.

"We're making a much quieter telescope. Guarding it from the ground, guarding it from the atmosphere, and making sure all the receiver can see is the sky," Carlstrom noted.

The SPT-Pol receiver, for polarization, is a three-year project. While the new experiment will focus on finding the inflation signal, or at least setting new constraints, the SPT will also continue to map galaxy clusters with even more sensitive sensors but on a small pie of the sky.

"We'll go much, much deeper, and do the same kind of science, but much more sensitive than what we have been doing. We're adding more capability; we're not walking away from what we've been doing, we're going much deeper with the dark energy experiment," Carlstrom said.

Other telescopes at the South Pole are also after the B-mode polarization predicted by the theory of inflation, including the Background Imaging of Cosmic Extragalactic Polarization telescope, or BICEP. Far smaller on the ground than the SPT, BICEP can scan the CMB on much larger angular scales.

In contrast, the SPT focuses on smaller angular scales with greater detail, even delving into particle physics, including revealing characteristics about subatomic particles called neutrinos. Another experiment at the South Pole, the IceCube Observatory, buried deep into the ice sheet, is attempting to detect high-energy neutrinos as the pass through the Earth to learn about cosmic events like supernovas.

"One of our goals is to search in complementary [fashion] with BICEP for B-modes," Carlstrom said. "We'll try to measure gravitational waves. At the same time, we'll do this very cool physics experiment figuring out what the total sum of the masses of the different neutrinos are."

Indeed, the SPT has proven itself to be the Swiss Army knife of CMB telescopes.

In addition to mapping galaxy clusters, it has also detected the bright thermal emissions from early star-forming galaxies -- something no one expected to see.

"It's a whole new window on the universe that was discovered with that," Carlstrom said.

Benson said the plan going forward in the years to come would be to also measure more of the dusty, star-generating galaxies of the early universe.

"We can potentially map out the entire star formation history of the universe, from the very first stars to the peak of star formation in the universe billions of years later," he said.

And that's just what the SPT has to say about this universe. Carlstrom explained that the theory of inflation, in one interpretation, assumes a pre-existing "piece" of space-time, something almost inconceivably small with such a high energy density capable of inflating the whole universe.

"It should happen all the time," he said nonchalantly. "Inflation gives you an answer to the question, 'Where did our universe come from?' It comes from some other space-time. People call it the multiverse."

Astronomy at the South Pole truly has reached the final frontier.

"We're thrilled. We're excited. We're just feeding on it," Carlstrom said.

NSF-funded research in this story: John Carlstrom, University of Chicago, Award Nos. 0638937 and 0959620.

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Related Links:
KICP Members: John E. Carlstrom
Scientific projects: South Pole Telescope (SPT)
 
South Pole Telescope homes in on dark energy, neutrinos
The University of Chicago News Office, April 2, 2012
New data from the South Pole Telescope is bolstering Albert Einstein's cosmological constant, an idea he considered to be his greatest blunder, to explain the modern mystery of dark energy. The SPT collaboration's latest analyses have been submitted to the Astrophysical Journal and was presented April 1 at the American Physical Society meeting in Atlanta.   Photo Credit: Daniel Luong-Van
New data from the South Pole Telescope is bolstering Albert Einstein's cosmological constant, an idea he considered to be his greatest blunder, to explain the modern mystery of dark energy. The SPT collaboration's latest analyses have been submitted to the Astrophysical Journal and was presented April 1 at the American Physical Society meeting in Atlanta.

Photo Credit: Daniel Luong-Van
by Steve Koppes, The University of Chicago News Office

Analysis of data from the 10-meter South Pole Telescope is providing new support for the most widely accepted explanation of dark energy - the source of the mysterious force that is responsible for the accelerating expansion of the universe.

The results also are beginning to hone in on the masses of neutrinos, the most abundant particles in the universe, which until recently were thought to be without mass.

The data strongly support Albert Einstein's cosmological constant - a slight amendment to his theory of general relativity and the leading model for dark energy - even though the analysis was based on only a fraction of the SPT data collected and only 100 of the more than 500 galaxy clusters detected so far.

"With the full SPT data set, we will be able to place extremely tight constraints on dark energy and possibly determine the mass of the neutrinos," said Bradford Benson, a postdoctoral scientist at the University of Chicago's Kavli Institute for Cosmological Physics. Benson presented the SPT collaboration's latest findings on April 1 at the American Physical Society meeting in Atlanta.

A series of papers detailing the SPT findings have been submitted to the Astrophysical Journal, written by lead authors Benson; Kavli postdoctoral scientist Ryan Keisler; and Christian Reichardt, postdoc at the University of California, Berkeley.

The results are based on a new method that combines measurements taken by the SPT and X-ray satellites, and extends these measurements to larger distances than previously achieved using galaxy clusters.

The most widely accepted property of dark energy is that it leads to a pervasive force acting everywhere and at all times in the universe. This force could be the manifestation of Einstein's cosmological constant, which effectively assigns energy to empty space, even when it is free of matter and radiation. Einstein introduced the cosmological constant into his theory of general relativity to accommodate a stationary universe, the dominant idea of his day. He later considered it to be his greatest blunder after the discovery of an expanding universe.

In the late 1990s, astronomers discovered that the expansion of the universe appeared to be accelerating, according to cosmic distance measurements based on the brightness of exploding stars. Gravity should have been slowing the expansion, but instead it was speeding up.

Einstein's cosmological constant is one explanation of the observed acceleration of the expanding universe, now supported by countless astronomical observations. Others hypothesize that gravity could operate differently on the largest scales of the universe. In either case, the astronomical measurements are pointing to new physics that have yet to be understood.

Clues to dark energy lurking in 'shadows'
The SPT was specifically designed to tackle the dark energy mystery. The 10-meter telescope operates at millimeter wavelengths to make high-resolution images of the cosmic microwave background radiation (CMB), the light left over from the big bang. Scientists use the CMB in their search for distant, massive galaxy clusters, which can be used to pinpoint the mass of the neutrino and the properties of dark energy.

"The CMB is literally an image of the universe when it was only 400,000 years old, from a time before the first planets, stars and galaxies formed in the universe," Benson said. "The CMB has travelled across the entire observable universe, for almost 14 billion years, and during its journey is imprinted with information regarding both the content and evolution of the universe."

As the CMB passes through galaxy clusters, the clusters effectively leave "shadows" that allow astronomers to identify the most massive clusters in the universe, nearly independent of their distance.

"Clusters of galaxies are the most massive, rare objects in the universe, and therefore they can be effective probes to study physics on the largest scales of the universe," said John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics, who heads the SPT collaboration.

"The unsurpassed sensitivity and resolution of the CMB maps produced with the South Pole Telescope provides the most detailed view of the young universe and allows us to find all the massive clusters in the distant universe," said Christian Reichardt, a postdoctoral researcher at the University of California, Berkeley, and lead author of the new SPT cluster catalog paper.

The number of clusters that formed over the history of the universe is sensitive to the mass of neutrinos and the influence of dark energy on the growth of cosmic structures.

"Neutrinos are amongst the most abundant particles in the universe," Benson said. "About one trillion neutrinos pass through us each second, though you would hardly notice them because they rarely interact with 'normal' matter."

The existence of neutrinos was proposed in 1930. They were first detected 25 years later, but their exact mass remains unknown. If they are too massive they would significantly affect the formation of galaxies and galaxy clusters, Benson said.

The SPT team has now placed tight limits on the neutrino masses, yielding a value that approaches predictions stemming from particle physics measurements.

"It is astounding how SPT measurements of the largest structures in the universe lead to new insights on the evasive neutrinos," said Lloyd Knox, professor of physics at the University of California at Davis and member of the SPT collaboration. Knox also will highlight the neutrino results in his presentation on Neutrinos in Cosmology at a special session of the APS on April 3.

The South Pole Telescope collaboration is led by the University of Chicago and includes research groups at Argonne National Laboratory, Cardiff University, Case Western Reserve University, Harvard University, Ludwig-Maximilians-Universitat, Smithsonian Astrophysical Observatory, McGill University, University of California at Berkeley, University of California at Davis, University of Colorado at Boulder, University of Michigan, as well as individual scientists at several other institutions.

Members of the Kavli Institute for Cosmological Physics participating in the South Pole Telescope collaboration include faculty members John Carlstrom, who leads the effort; Mike Gladders, Wayne Hu, Andrey Kravtsov and Steve Meyer; senior researchers Clarence Chang, Tom Crawford, Erik Leitch and Kathryn Schaffer; postdoctoral scientists Bradford Benson, F. William High, Steven Hoover, Ryan Keisler, Jared Mehl and Tom Plagge; and graduate students Lindsey Bleem, Abby Crites, Monica Mocanu, Tyler Natoli and Kyle Story.

The SPT is funded primarily by the National Science Foundation's Office of Polar Programs. Partial support also is provided by the NSF-funded Physics Frontier Center of the KICP, the Kavli Foundation, and the Gordon and Betty Moore Foundation.

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Related Links:
KICP Members: Bradford A. Benson; John E. Carlstrom; Clarence L. Chang; Thomas M. Crawford; Michael D. Gladders; Fredrick W. High; Stephen Hoover; Wayne Hu; Ryan Keisler; Andrey V. Kravtsov; Erik Leitch; Jared Mehl; Stephan S. Meyer; Tom Plagge; Kathryn K. Schaffer
KICP Students: Lindsey E. Bleem; Abigail T. Crites; Laura M Mocanu; Tyler Natoli; Kyle Story
Scientific projects: South Pole Telescope (SPT)
 
South Pole Telescope exhibit headed for Washington, New York
The University of Chicago News Office, April 27, 2012
Bo Rodda (far left), and members of his Manifest SPACE class at the School of the Art Institute Chicago gather in front of the South Pole Telescope exhibit, which they produced as a class project.
Bo Rodda (far left), and members of his Manifest SPACE class at the School of the Art Institute Chicago gather in front of the South Pole Telescope exhibit, which they produced as a class project.
by Steve Koppes, The University of Chicago News Office

Visitors to the USA Science and Engineering Festival in Washington, D.C. will get a taste of the South Pole Telescope when a traveling exhibit comes their way beginning April 28. The University of Chicago's Kavli Institute for Cosmological Physics will present the exhibit, "100 Years of Exploration @ South Pole: From Survival to Science," which was produced by a studio class at the School of the Art Institute of Chicago.

Part of the exhibit will appear at the World Science Festival, which takes place May 30 to June 3 in New York City, including the June 3 World Science Street Festival in Washington Square Park.

The exhibit was a class project led by Bo Rodda, an adjunct professor of the SAIC's department of architecture, interior architecture and designed objects. He also is a building intelligence and energy efficiency specialist at Argonne National Laboratory, which is a member of the SPT collaboration.

"The students, for the most part, all signed up for the class because they are naturally interested in space and science," said Rodda, whose class met with scientists at UChicago and Adler Planetarium before designing the exhibit.

"Artists and scientists have much more in common than most people would think. At the root of what drives us, I feel, is an insatiable curiosity about the world and a desire to discover. When artists and scientists begin to work together, amazing things happen," he said.

South Pole milestones
Exploration and research at the South Pole passed a milestone on Dec. 14, 2012, the centennial of Roald Amundsen's arrival at the South Pole. The SPT also has passed a milestone, having obtained some major results while completing its initial large survey of the sky. UChicago leads the SPT collaboration, which includes a dozen institutions worldwide.

"These all motivated the notion of looking for ways to share this with broader audiences: to allow them to explore the unique research environment that the Amundsen-Scott South Pole station offers, and to share in the excitement of discovery," said Randy Landsberg, the Kavli Institute's director of education and outreach.

The Kavli-SAIC collaboration sprouted from the 2007 Chicago Festival of Maps. The institute organized a five-day meeting in connection with the multi-institutional festival titled "Cosmic Cartography: Mapping the Universe from the Big Bang to the Present."

The involvement of both institutions in the festival led to a series of collaborative projects, including two UChicago Brinson Lectures at the Art Institute last year, one featuring Astronomer Royal Martin Rees, the other spotlighting Nobel laureate John Mather.

In another joint project, this spring the Art Institute also is offering a course titled "The Leading Edge of Astrophysics," taught by Kathryn Schaffer, a senior researcher at KICP and member of the SPT science team. A series of Kavli postdoctoral scientists have presented guest lectures about their current research as part of the course, then took questions from the students.

Surveys given before and after the presentations document how the presentations may have changed the perceptions that the art students had about scientists. The postdocs also took surveys to record how their interactions with the students may have changed what the scientists viewed as important about communicating their work to a lay audience.

Joint conversations on art and science also are in the offing in an initiative led by SAIC President Walter E. Massey, a former physics professor and vice president for research at UChicago, who also has served as director of Argonne and of the Nationabl Science Foundation.

Enhanced outreach
"We look for things that are of interest to both groups, and this year it came up that the South Pole Telescope collaboration wanted to do more outreach," said Landsberg, who took the exhibit idea to Doug Pancoast, chairman of SAIC's architecture department.

"We had originally just asked for a simple outdoor photography exhibit. We were thinking 10 nice photos mounted, and these guys came up with this engaging interactive exhibit, which is fantastic. The entire process was a wonderful collaborative experience that engaged both the artists and the scientists, and produced a tangible result," Landsberg said.

Exhibit visitors will have the opportunity to don a heavy jacket, gloves and boots and get photographed in front of a giant backdrop of the ceremonial South Pole. At a nearby multi-touch table, visitors also can use their fingers to manipulate electronic images taken at the South Pole and view SPT data.

Leul Bezane, a fourth-year in physics at UChicago, programmed the touch table and formatted its images. Bezane works as a research assistant in Adler's Space Visualization Laboratory and at the Kavli Institute, where he helps program galaxy simulations for Nick Gnedin, associate professor in astronomy & astrophysics.

The rest of the exhibit, though, was the work of the students.

"We had a real client, with real needs, with a real budget, and very, very real deadlines," said Rodda. The students brought interdisciplinary backgrounds to the project, spanning architecture, interior architecture, object design (industrial design), graphic design, education and even sculpture.

"Everyone had a vital role to play and working together they made an incredible exhibit. I am extremely proud of what they have accomplished and I know they are, too," Rodda said.

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Related Links:
KICP Members: John E. Carlstrom; Nickolay Y. Gnedin; Randall H. Landsberg; Tom Plagge; Kathryn K. Schaffer; Mark Subbarao
KICP Students: Leul Bezane; Lindsey E. Bleem; Abigail T. Crites; Tyler Natoli; Kyle Story
Scientific projects: South Pole Telescope (SPT)
 
UChicago scientists collect plethora of awards
The University of Chicago News Office, May 8, 2012
Daniel Holz, KICP senior member
Daniel Holz, KICP senior member
by Steve Koppes, The University of Chicago News Office

UChicago scientists receiving NSF CAREER Awards were Daniel Holz and David Schuster, assistant professors in physics. The NSF presents CAREER Awards to junior faculty members who exemplify the role of teacher-scholars through outstanding research, excellent education, and the integration of education and research.

Holz will use his $600,000 CAREER Award to fund a project titled "Hearing and Seeing the Universe Through Multi-Messenger Astronomy." He will study how black holes and/or dead, compact stars spiral toward one another and eventually merge. These events produce copious gravitational waves, and are thought to be associated with gamma-ray bursts, which are some of the most powerful explosions in the universe.

In particular, Holz explores how the combination of electromagnetic (such as optical, gamma-ray, and X-ray) telescopes and future gravitational-wave observatories can elucidate these spectacular events. "Questions to be explored include how often these sources happen, how we might detect them both in gravitational waves and electromagnetically, and what we might learn from them," Holz said. He is particularly interested in the powerful cosmological measurements that multi-messenger observations will enable.

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KICP Members: Daniel E. Holz
 
Cosmos and Culture: Highlights of the UChicago/Argonne/Fermilab Joint Speaker Series Event
The University of Chicago, May 17, 2012
Cosmos and Culture: Highlights of the UChicago/Argonne/Fermilab Joint Speaker Series Event
The University of Chicago

Rocky Kolb, UChicago astrophysicist, Paul Knappenberger, President of Adler Planetarium, and other experts discuss "Cosmos and Culture," the fifth in a series of UChicago, Argonne and Fermilab Joint Speaker events.

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KICP Members: Edward W. Kolb
 
Good CARMA contributes to detection of rare gravitational phenomenon
The University of Chicago News Office, June 27, 2012
Good CARMA contributes to detection of rare gravitational phenomenon
by Donna Weaver and Steve Koppes, The University of Chicago News Office

Seeing is believing, except when you don't believe what you see.

Astronomers using NASA's Hubble Space Telescope have found a puzzling arc of light behind an extremely massive cluster of galaxies residing 10 billion light-years away. The galactic grouping, discovered by NASA's Spitzer Space Telescope, was observed when the universe was roughly a quarter of its current age of 13.7 billion years.

The CARMA (Combined Array for Research in Millimeter Wave Astronomy) also made key observations of the massive galaxy cluster. The University of Chicago is a partner in the CARMA consortium.

The giant arc is the stretched shape of a more distant galaxy whose light is distorted by the monster cluster's powerful gravity, an effect called gravitational lensing. The trouble is, the arc shouldn't exist.

"When I first saw it, I kept staring at it, thinking it would go away," said study leader Anthony Gonzalez of the University of Florida in Gainesville. "According to a statistical analysis, arcs should be extremely rare at that distance. At that early epoch, the expectation is that there are not enough galaxies behind the cluster bright enough to be seen, even if they were 'lensed' or distorted by the cluster.

"The other problem is that galaxy clusters become less massive the farther back in time you go. So it's more difficult to find a cluster with enough mass to be a good lens for gravitationally bending the light from a distant galaxy."

Galaxy clusters are collections of hundreds to thousands of galaxies bound together by gravity. They are the most massive structures in our universe. Astronomers frequently study galaxy clusters to look for faraway, magnified galaxies behind them that would otherwise be too dim to see with telescopes. Many such gravitationally lensed galaxies have been found behind galaxy clusters closer to Earth.

The surprise in these observations is spotting a galaxy lensed by an extremely distant cluster. Dubbed IDCS J1426.5+3508, the cluster is the most massive found at that epoch, weighing as much as 500 trillion suns. It is five to 10 times larger than other clusters found at such an early time in the universe's history.

Astronomers spotted the cluster in a search using NASA's Spitzer Space Telescope in combination with archival optical images taken as part of the National Optical Astronomy Observatory's Deep Wide Field Survey at the Kitt Peak National Observatory in Tucson, Ariz. The combined images allowed them to see the cluster as a grouping of very red galaxies, indicating they are far away.

This unique system constitutes the most distant cluster known to "host" a giant gravitationally lensed arc. Finding this ancient gravitational arc may yield insight into how, during the first moments after the big bang, conditions were set up for the growth of hefty clusters in the early universe.

The arc was spotted in optical images of the cluster taken in 2010 by Hubble's Advanced Camera for Surveys. The infrared capabilities of Hubble's Wide Field Camera 3 (WFC3) helped provide a precise distance, confirming it to be one of the farthest clusters yet discovered.

Once the astronomers determined the cluster's distance, they used Hubble, the CARMA radio telescope, and NASA's Chandra X-ray Observatory to independently show that the galactic grouping is extremely massive.

CARMA is an excellent observatory for studying such a distant cluster of galaxies because it images the shadow of the cluster against the cosmic microwave background radiation, the fossil light from the big bang, said KICP associate fellow Tom Plagge. This signal is independent of the distance to the cluster, allowing CARMA to quickly and robustly detect massive clusters across the observable universe, if one knows where in the sky to look.

"It was hard to believe they had found such a high-mass cluster at so great a distance, but we knew that CARMA observations would quickly provide a good estimate of its mass," Plagge said.

CARMA helped the astronomers determine the cluster's mass by measuring how primordial light from the big bang was affected as it passed through the extremely hot, tenuous gas that permeates the grouping. The astronomers then used the WFC3 observations to map the cluster's mass by calculating how much cluster mass was needed to produce the gravitational arc. Chandra data, which revealed the cluster's brightness in X-rays, also was used to measure the cluster's mass.

"The chance of finding such a gigantic cluster so early in the universe was less than 1 percent in the small area we surveyed," said team member Mark Brodwin of the University of Missouri-Kansas City. "It shares an evolutionary path with some of the most massive clusters we see today, including the Coma Cluster and the recently discovered El Gordo Cluster."

An analysis of the arc revealed that the lensed object is a star-forming galaxy that existed 10 billion to 13 billion years ago. Gonzalez has considered several possible explanations for the arc, though he remains unconvinced pending further study.

One explanation is that distant galaxy clusters, unlike nearby clusters, have denser concentrations of galaxies at their cores, making them better magnifying glasses. However, even if the distant cores were denser, the added bulk still should not provide enough gravitational muscle to produce the giant arc seen in Gonzalez's observations, according to a statistical analysis.

Another possibility is that the initial microscopic fluctuations in matter made right after the big bang were different from those predicted by standard cosmological simulations, and therefore produced more massive clusters than expected.

The team's results will be published in the July 10 issue of The Astrophysical Journal.

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KICP Members: Tom Plagge
 
Scientists discover that Milky Way was struck some 100 million years ago, still rings like a bell.
Fermilab, June 29, 2012
Scientists discover that Milky Way was struck some 100 million years ago, still rings like a bell.
Fermilab

Our galaxy, the Milky Way, is a large spiral galaxy surrounded by dozens of smaller satellite galaxies. Scientists have long theorized that occasionally these satellites will pass through the disk of the Milky Way, perturbing both the satellite and the disk. A team of astronomers from Canada and the United States have discovered what may well be the smoking gun of such an encounter, one that occurred close to our position in the galaxy and relatively recently, at least in the cosmological sense.

"We have found evidence that our Milky Way had an encounter with a small galaxy or massive dark matter structure about 100 million years ago," said Larry Widrow, professor at Queen's University in Canada. "We clearly observe unexpected differences in the Milky Way's stellar distribution above and below the Galaxy's midplane that have the appearance of a vertical wave -- something that nobody has seen before."

The discovery is based on observations of some 300,000 nearby Milky Way stars by the Sloan Digital Sky Survey. Stars in the disk of the Milky Way move up and down at a speed of about 20-30 kilometers per second while orbiting the center of the galaxy at a brisk 220 kilometers per second. Widrow and his four collaborators from the University of Kentucky, the University of Chicago, and Fermi National Accelerator Laboratory have found that the positions and motions of these nearby stars weren't quite as regular as previously thought.

"Our part of the Milky Way is ringing like a bell,' said Brian Yanny, of the Department of Energy's Fermilab. "But we have not been able to identify the celestial object that passed through the Milky Way. It could have been one of the small satellite galaxies that move around the center of our galaxy, or an invisible structure such as a dark matter halo." Adds Susan Gardner, professor of physics at the University of Kentucky:
"The perturbation need not have been a single isolated event in the past, and it may even be ongoing. Additional observations may well clarify its origin."

When the collaboration started analyzing the SDSS data on the Milky Way, they noticed a small but statistically significant difference in the distribution of stars north and south of the Milky Way's midplane. For more than a year, the team members explored various explanations of this north-south asymmetry, such as the effect of interstellar dust on distance determinations and the way the stars surveyed were selected. When those attempts failed, they began to explore the alternative explanation that the data was telling them something about recent events in the history of the Galaxy.

The scientists used computer simulations to explore what would happen if a satellite galaxy or dark matter structure passed through the disk of the Milky Way. The simulations indicate that over the next 100 million years or so, our galaxy will "stop ringing:" the north-south asymmetry will disappear and the vertical motions of stars in the solar neighborhood will revert back to their equilibrium orbits -- unless we get hit again.

The Milky Way is more than 9 billion years old with about 100 billion stars and total mass more than 300 billion times that of the sun. Most of the mass in and around the Milky Way is in the form of dark matter.

Scientists know of more than 20 visible satellite galaxies that circle the center of the Milky Way, with masses ranging from one million to one billion solar masses. There may also be invisible satellites made of dark matter. (There is six times as much dark matter in the universe as ordinary, visible matter.) Astronomers' computer simulations have found that this invisible matter formed hundreds of massive structures that move around our Milky Way.

Because of their abundance, these dark matter satellites are more likely than the visible satellite galaxies to cut through the Milky Way's midplane and cause vertical waves.

"Future astronomical programs, such as the space-based Gaia Mission, will be able to map out the vertical perturbations in our galaxy in unprecedented detail," Widrow said. "That will offer a strong test of our findings."

The results have been published in The Astrophysical Journal Letters:
Lawrence M. Widrow, Susan Gardner, Brian Yanny, Scott Dodelson, and Hsin-Yu Chen "GALACTOSEISMOLOGY: DISCOVERY OF VERTICAL WAVES IN THE GALACTIC DISK"



Media contacts:
Kurt Riesselmann, Fermilab Office of Communication, 630-840-3351, mediafnal.gov

Queen's University
University of Kentucky
The Sloan Digital Sky Survey

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KICP Members: Scott Dodelson
Scientific projects: Sloan Digital Sky Survey (SDSS)
 
Giant galaxy cluster sets record pace for creating stars
The University of Chicago News Office, August 15, 2012
The Phoenix Cluster, shown here as it appears in microwave (orange), optical (red, green, and blue) and ultraviolet (blue) wavelengths, is forming stars at the highest rate ever observed for the middle of a galaxy cluster. The Phoenix Cluster was discovered by a collaboration of astronomers from the University of Chicago's Kavli Institute for Cosmological Physics and elsewhere. (South Pole Telescope collaboration).  <i>(Credit: UV: NASA/JPL-Caltech/M.McDonald; Optical: AURA/NOAO/CTIO/MIT/M.McDonald; Microwave: NSF/SPT)</i>
The Phoenix Cluster, shown here as it appears in microwave (orange), optical (red, green, and blue) and ultraviolet (blue) wavelengths, is forming stars at the highest rate ever observed for the middle of a galaxy cluster. The Phoenix Cluster was discovered by a collaboration of astronomers from the University of Chicago's Kavli Institute for Cosmological Physics and elsewhere. (South Pole Telescope collaboration).

(Credit: UV: NASA/JPL-Caltech/M.McDonald; Optical: AURA/NOAO/CTIO/MIT/M.McDonald; Microwave: NSF/SPT)
by Steve Koppes, The University of Chicago News Office

Astronomers have found an extraordinary galaxy cluster - one of the largest objects in the universe - that is breaking several important cosmic records. The discovery of this cluster, known as the Phoenix Cluster, made with the National Science Foundation's South Pole Telescope, may force astronomers to rethink how these colossal structures, and the galaxies that inhabit them, evolve.

Follow-up observations made in ultraviolet, optical and infrared wavelengths show that stars are forming in this object at the highest rate ever seen in the middle of a galaxy cluster. The object also is the most powerful producer of X-rays of any known cluster, and among the most massive of clusters. The data also suggest that the rate of hot gas cooling in the central regions of the cluster is the largest ever observed.

Officially known as SPT-CLJ2344-4243, this galaxy cluster has been dubbed the "Phoenix Cluster" because it is located in the constellation of the Phoenix, and because of its remarkable properties. Scientists at the University of Chicago's Kavli Institute for Cosmological Physics and their collaborators initially found the cluster, located about 5.7 billion light years from Earth, using the Sunyaev-Zel'dovich effect, the shadow that the cluster makes in fossil light leftover from the big bang.

Predicted in 1972, the effect was first demonstrated to find previously unknown clusters of galaxies by the South Pole Telescope collaboration in 2009. Observations of the effect have since opened a new window for astronomers to discover the most massive, distant clusters in the universe.

"The mythology of the Phoenix - a bird rising from the dead - is a perfect way to describe this revived object," said Michael McDonald, a Hubble Fellow at the Massachusetts Institute of Technology's Kavli Institute for Astrophysics and Space Research. McDonald is the lead author of a paper appearing in the Aug. 16 issue of the journal Nature, which presents these findings. "While galaxies at the center of most clusters have been dead for billions of years, the central galaxy in this cluster seems to have come back to life," McDonald said.

Stars forming at incredible rates
Like other galaxy clusters, Phoenix holds a vast reservoir of hot gas that contains more normal matter than all of the galaxies in the cluster combined. The emission from this reservoir can only be detected with X-ray telescopes like NASA's Chandra X-ray Observatory. The prevailing wisdom had once been that this hot gas should cool over time and sink to the center of the cluster, forming huge numbers of stars.

However, most galaxy clusters have formed very few stars over the last few billion years. Astronomers think that the supermassive black hole in the central galaxy of clusters pumps energy into the system, preventing cooling of gas from causing a burst of star formation. The famous Perseus Cluster is an example of a black hole bellowing out energy and preventing the gas from cooling to form stars at a high rate.

With its black hole not producing powerful enough jets, the center of the Phoenix Cluster is buzzing with stars that are forming 20 times faster than in the Perseus Cluster. This rate is the highest seen in the center of a galaxy cluster and is comparable to the highest seen anywhere in the universe.

The frenetic pace of star birth and cooling of gas in Phoenix are causing both the galaxy and the black hole to add mass very quickly - an important phase that the researchers predict will be relatively short-lived.

"The galaxy and its black hole are undergoing unsustainable growth," said co-author Bradford Benson, a Kavli Institute Fellow at the University of Chicago. "This growth spurt can't last longer than about a hundred million years, otherwise the galaxy and black hole would become much bigger than their counterparts in the nearby universe."

Searching for additional galaxy clusters
Remarkably, the Phoenix Cluster and its central galaxy and supermassive black hole are already among the most massive known objects of their type. Because of their tremendous size, galaxy clusters are crucial objects for studying cosmology and galaxy evolution and so finding one with such extreme properties like the Phoenix Cluster is important.

"The beauty of the SZ effect for cosmology is that it is as easy to detect a cluster of galaxies in the distant reaches of the observable universe as it is for one nearby," said UChicago's John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics. "The magnitude of the effect depends on the mass of the object and not its distance from Earth."

Galaxy clusters contain enough hot gas to create detectable "shadows" in the light left over from the big bang, which also is known as the cosmic microwave background radiation. This light has literally traveled for 14 billion years across the entire observable universe to get to Earth. If it passes through a massive cluster on its way, then a tiny fraction of the light gets scattered to higher energies - the Sunyaev-Zel'dovich effect.

The South Pole Telescope collaboration has now completed an SZ survey of a large region of the sky finding hundreds of distant, massive galaxy clusters. Further follow-up observations of the clusters at X-ray and other wavelengths may reveal the existence of additional Phoenix-like galaxy clusters.

Also contributing observations of the Phoenix Cluster were the Gemini Observatory and the Blanco 4-meter and Magellan telescopes, all in Chile, while several space-based telescopes were used to measure the cluster's star-formation rate.

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Related Links:
KICP Members: Bradford A. Benson; John E. Carlstrom; Clarence L. Chang; Thomas M. Crawford; Michael D. Gladders; Fredrick W. High; Stephen Hoover; Ryan Keisler; Adam Mantz; Jared Mehl; Stephan S. Meyer; Stephen Padin; Tom Plagge; Kathryn K. Schaffer
KICP Students: Lindsey E. Bleem; Abigail T. Crites; Tyler Natoli; Kyle Story
Scientific projects: South Pole Telescope (SPT)
 
Phoenix Cluster Sets Record Pace at Forming Stars
NASA, August 15, 2012
An optical/UV/X-ray composite image of the Phoenix cluster, with a pull-out from the central region to an optical/UV image. The blue color of the central galaxy is one indication of the unusually large rate of star formation in the Phoenix cluster.  <i>(Credit: X-ray: NASA/CXC/MIT/M.McDonald; UV: NASA/JPL-Caltech/M.McDonald; Optical: AURA/NOAO/CTIO/MIT/M.McDonald)</i>
An optical/UV/X-ray composite image of the Phoenix cluster, with a pull-out from the central region to an optical/UV image. The blue color of the central galaxy is one indication of the unusually large rate of star formation in the Phoenix cluster.

(Credit: X-ray: NASA/CXC/MIT/M.McDonald; UV: NASA/JPL-Caltech/M.McDonald; Optical: AURA/NOAO/CTIO/MIT/M.McDonald)
NASA

WASHINGTON -- Astronomers have found an extraordinary galaxy cluster - one of the largest objects in the Universe - that is breaking several important cosmic records. Observations of this cluster, known as the Phoenix Cluster, with NASA's Chandra X-ray Observatory, the NSF's South Pole Telescope and eight other world-class observatories, may force astronomers to rethink how these colossal structures, and the galaxies that inhabit them, evolve.

Stars are forming in the Phoenix Cluster at the highest rate ever observed for the middle of a galaxy cluster. The object is also the most powerful producer of X-rays of any known cluster, and among the most massive of clusters. The data also suggest that the rate of hot gas cooling in the central regions of the cluster is the largest ever observed.
This galaxy cluster has been dubbed the "Phoenix Cluster" because it is located in the constellation of the Phoenix, and because of its remarkable properties. The cluster is located about 5.7 billion light years from Earth.

"The mythology of the Phoenix - a bird rising from the dead - is a great way to describe this revived object," said Michael McDonald, a Hubble Fellow at the Massachusetts Institute of Technology and the lead author of a paper appearing in the August 16th issue of the journal Nature. "While galaxies at the center of most clusters may have been dormant for billions of years, the central galaxy in this cluster seems to have come back to life with a new burst of star formation."
Like other galaxy clusters, Phoenix contains a vast reservoir of hot gas - containing more normal matter than all of the galaxies in the cluster combined - that can only be detected with X-ray telescopes like Chandra. The prevailing wisdom had once been that this hot gas should cool over time and sink to the galaxy at the center of the cluster, forming huge numbers of stars.

However, most galaxy clusters have formed very few stars over the last few billion years. Astronomers think that the supermassive black hole in the central galaxy of clusters pumps energy into the system, preventing cooling of gas from causing a burst of star formation.

The famous Perseus Cluster is an example of a black hole bellowing out energy and preventing the gas from cooling to form stars at a high rate. Repeated outbursts from the black hole in the center of Perseus, in the form of powerful jets, created giant cavities and produced sound waves with an incredibly deep B-flat note 57 octaves below middle C.

"We thought that these very deep sounds might be found in galaxy clusters everywhere," said co-author Ryan Foley, a Clay Fellow at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "The Phoenix Cluster is showing us this is not the case - or at least there are times the music stops. Jets from the giant black hole at the center of a cluster are apparently not powerful enough to prevent the cluster gas from cooling."
With its black hole not producing powerful enough jets, the center of the Phoenix Cluster is buzzing with stars that are forming about 20 times faster than in the Perseus cluster. The rate is not the highest seen anywhere in the Universe, but the overall record-holding galaxies, located outside clusters, have rates only about twice as high.

The frenetic pace of star birth and cooling of gas in Phoenix are causing both the galaxy and the black hole to add mass very quickly - an important phase that the researchers predict will be relatively short-lived.

"The galaxy and its black hole are undergoing unsustainable growth," said co-author Bradford Benson, of the University of Chicago. "This growth spurt can't last longer than about a hundred million years, otherwise the galaxy and black hole would become much bigger than their counterparts in the nearby Universe."

Remarkably, the Phoenix Cluster and its central galaxy and supermassive black hole are already among the most massive known objects of their type.

Because of their tremendous size, galaxy clusters are crucial objects for studying cosmology and galaxy evolution and so finding one with such extreme properties like the Phoenix Cluster is important.

"This spectacular star burst is a very significant discovery because it suggests we have to rethink how the massive galaxies in the centers of clusters grow," said Martin Rees of Cambridge University, who was not involved with the study. "The cooling of hot gas might be a much more important source of stars than previously thought."

The Phoenix Cluster was originally detected by the National Science Foundation's South Pole Telescope, and later was observed in optical light by the Gemini Observatory in Chile as well as the Blanco 4-meter and Magellan telescopes, also in Chile. The hot gas and its rate of cooling were estimated from Chandra data. To measure the star formation rate in the Phoenix Cluster, several space-based telescopes were used including NASA's WISE and GALEX, and ESA's Herschel.

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

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KICP Members: Bradford A. Benson; John E. Carlstrom; Clarence L. Chang; Thomas M. Crawford; Michael D. Gladders; Fredrick W. High; Stephen Hoover; Ryan Keisler; Adam Mantz; Jared Mehl; Stephan S. Meyer; Tom Plagge; Kathryn K. Schaffer
KICP Students: Lindsey E. Bleem; Abigail T. Crites; Tyler Natoli; Kyle Story
Scientific projects: South Pole Telescope (SPT)
 
Phoenix Rising: A Galaxy Cluster That's Breaking Cosmic Records
Kavli Foundation News, August 15, 2012
Bradford Benson, Kavli Institute for Cosmological Physics at the University of Chicago. (Courtesy: Bradford Benson)
Bradford Benson, Kavli Institute for Cosmological Physics at the University of Chicago. (Courtesy: Bradford Benson)
Kavli Foundation News

On the eve of their NASA press conference, Michael McDonald, Kavli Institute for Astrophysics and Space Research at MIT, and Bradford Benson, Kavli Institute for Cosmological Physics, University of Chicago, discuss the discovery of the Phoenix Cluster -- a galaxy cluster for the record books.

TODAY, NASA ANNOUNCED that astronomers have found a massive galaxy cluster with astounding and unexpected properties - producing stars at a prodigious rate astronomers have not seen in other galaxy clusters.

The discovery of the Phoenix Cluster, and its central galaxy producing 740 stars per year, is prompting astronomers to re-think how galaxy clusters, among the largest structures in the universe, form and evolve over cosmic time. No nearby galaxy clusters (and therefore closer in cosmic time) produce stars in their central galaxies at such a high rate. The vigorous starburst in Phoenix is not thought to be sustainable for more than a few hundred million years because anything exceeding that would make the central galaxy in the cluster larger than anything else seen in the universe.

On the eve of the NASA announcement, Hubble Fellow Michael McDonald, a researcher at the Kavli Institute for Astrophysics and Space Research at MIT and also the lead author of a paper appearing Aug. 16 in the journal Nature, and Bradford Benson, a researcher at the Kavli Institute for Cosmological Physics at the University of Chicago and a co-author of the paper in Nature, spoke with The Kavli Foundation about the discovery.


THE KAVLI FOUNDATION (TKF): Let's start with the basics. How large is the Phoenix Cluster, where is it and how old is it?

MICHAEL MCDONALD: It's one of the most massive clusters in the universe, maybe in the top two or three - and perhaps it is the largest that we know of in the universe. It's 5.7 billion light-years away, so we're seeing it as it looked 5.7 billion years ago.

TKF: So it's much older now than it was at the time we are observing it.

MCDONALD: That's right.

BENSON: It would also be more massive now, because the central galaxy in a cluster grows through mergers over time, and clusters themselves merge with other clusters and grow bigger. But even when we're observing it, at 5.7 billion years ago, it's already one of the most massive clusters in the universe that we know about - even today.

TKF: How did you become interested in this particular cluster, and did you know immediately that it was special and worth exploring?

BENSON: Originally this cluster was discovered by the South Pole Telescope (SPT), which is a ten-meter telescope that studies millimeter wavelength light from these objects. SPT finds clusters of galaxies in a really unique way. It detects them indirectly, by detecting the shadows these clusters make in the cosmic microwave background, which is the light that's left over from the Big Bang. Clusters of galaxies are one of the few things in the universe that are so massive, they're able to create shadows in the cosmic microwave background. Effectively, the light from the Big Bang travels 14 billion years across the entire observable universe, and these clusters of galaxies make shadows in that light. It turns out this is a very effective way to find the most massive distant clusters in the universe. The Phoenix Cluster was discovered as part of a survey by the South Pole Telescope that observed 2500 square degrees of the sky, or about 15-percent of the total sky.

TKF: At what point did the scientific community know this particular cluster was different from most others observed?

BENSON: After we detected the Phoenix Cluster, we followed it up to measure its redshift -- in other words to determine its distance -- and also made several other measurements in optical, X-ray, infrared, ultraviolet and other wavelengths to learn about the properties of gas and stars in the cluster.

Mike and I were particularly interested in X-ray observations. This same hot gas that scatters a small percentage of CMB photons as they pass through the cluster also emits X-rays very brightly. The gas is on the order of 100 million degrees Kelvin, which is hotter then the interior of the Sun. So these are very bright X-ray sources on the sky. The Chandra X-ray telescope was one of the first things we used to follow up this cluster. The Phoenix Cluster stood out as having very high X-ray emission from its center, so much that it made the entire cluster the most luminous X-ray cluster ever observed.

That immediately peaked our interest, because it suggested that cool gas was condensing in the center of the cluster. So we began to get as much data as we could to try to understand what else was happening in this cluster - in particular the star formation and the central black hole. And that's where Mike came in; he was instrumental in accumulating a lot of that extra data, to figure out how this hot gas is turning into stars.

TKF: What first hints did you have that the rate of star formation was so high in Phoenix?

MCDONALD: As Brad said, when we first got these X-ray measurements from Chandra, it was pretty obvious this was a unique cluster. Specifically, the center of the cluster was very dense and cooling very rapidly. This is a process I've studied in other galaxy clusters, so I thought immediately that there must be vigorous star formation if we see all this cooling. I started putting together some of the data that we already had, as well as data from observatory archives and new data from both space- and ground-based telescopes. With all this data in hand, we saw that the central galaxy was very blue, indicating it was forming a lot of young stars.

TKF: And that was a surprise for a cluster so far away, correct?

MCDONALD: Right. There are a significant number of nearby clusters that are what we call "cool core", or "cooling flow" clusters. There's been some evidence that this strong cooling is a recent phenomenon, and that it did not happen in the early universe. So this is one of the few - or one of the only - clusters that we know of at a high redshift in the early universe that is cooling very rapidly like this.

"The goal is to study more clusters to better understand their evolution. ...We need to compare other clusters to Phoenix - clusters of all ages - to see how they evolve over cosmic time and where the Phoenix Cluster fits into this evolutionary picture." - Bradford Benson

TKF: Why do we think that this didn't happen in the early universe with the same frequency that it does today?

MCDONALD: We don't know for sure that it did not happen in the early universe. It could be that previous surveys just had trouble finding these clusters. So for example a cluster like Phoenix may be hard to detect at X-ray wavelengths initially, because the energy is so concentrated at its center that it could look like a point source - like a quasar, for example. (Quasars are the energetic cores of distant galaxies that surround a central supermassive black hole and appear as point sources of light, as opposed to the energized gas falling into the core of a galaxy cluster)

So you can misidentify extreme clusters as something else, unless you have proof that it's a cluster by indirectly detecting its presence through these shadows on the CMB, or having optical follow-up. So it could be there are in fact very few of these at high redshifts, at earlier times, or it could be we just haven't been able to find them until now.

TKF: What specific roles did each of you play in this project?

BENSON: Originally, I started on this working with the South Pole Telescope, which was making observations of the cosmic microwave background. The primary goal is to use the cosmic microwave background to find clusters of galaxies in this manner that I talked about, with the shadows. So I started working with SPT by developing and building its microwave camera. My interest was primarily to study galaxy clusters in order to learn about dark energy.

Towards that goal, I've helped to identify clusters in the SPT survey, including the Phoenix Cluster, follow them up with observations at X-ray wavelengths to understand better what the gas is doing in the cluster at finer angular resolution, and also to work on determining the cluster's mass with Mike.

MCDONALD: I joined in when the X-ray follow-up really started to get off the ground, which Brad has been leading. My job was to look at these clusters at X-ray wavelengths and try to estimate their masses, which would then get fed into Brad's cosmology work on dark energy.

So I have been looking at all the clusters that the SPT observed in the X-ray, and from time-to-time we've seen very interesting ones that are useful for more than just cosmology - for dark energy studies. I'm interested more in the actual physics of these clusters, and understanding how they are evolving between the early universe and now. So, the Phoenix Cluster is particularly interesting to me because I'm really interested in these cool cores, these cooling flow clusters. When we saw this, I started to get excited and began gathering all this data, including data on the star formation rate. So I've worked on the follow-up analysis after the original detection.

TKF: At that point did you know the star formation rate was off the charts in this cluster, and what was the team's initial reaction? At first did you question the result?

MCDONALD: I am a very glass half-full guy. I immediately thought that it was extremely exciting, and I needed people to reign me in. So right away, as soon as we looked at the first spectrum, it was just booming in oxygen emission, which is an indicator of star formation. Then we looked at the cluster in ultraviolet wavelengths, and it was again exceptionally bright. So it was obvious from every angle right away this was really unique.

However, to go from there to something that can convince the science community required several months of checking results and getting additional data. We studied all the different scenarios that could have been biasing our results. We went through everything very carefully to make sure that we weren't missing anything fundamental, and that we were doing all the corrections we needed to do to finally get a convincing, robust estimate of the rate of star formation. That took some time.

TKF: Brad, what was your initial reaction?

BENSON: When the same measurements kept coming in, and they were very consistent with a very high star formation rate - however we measured it - it was extremely exciting to see. This cluster is extremely unique. It is sort of like "the missing link" in cluster evolution. If you look at galaxy clusters today, they are very inefficient at forming stars; they form far fewer stars than you would expect from simulations. At some point in the history of galaxy clusters, you expect the star formation rate to be much higher than what we see in nearby clusters - at essentially the present time. But we really need evidence of that.

The Phoenix Cluster is the first to show extremely high rates of star formation, consistent with what we've expected. So we are seeing this cluster possibly at a stage where it is transitioning from extremely high levels of star formation to a time when the supermassive black hole at the core of its central galaxy turns on, releases more energy into the gas, and only later suppresses star formation.

TKF: Mike, why was it so important to use several different instruments to study this one cluster?

MCDONALD: I think galaxy clusters are one of the few things in astronomy where you really need this full coverage, from all different wavelengths and energies, to get a sense of what's going on. Especially in this cluster, which is so exotic. So, you can only really understand the supermassive black hole at the core of the central galaxy in the Phoenix Cluster with a combination of radio, X-ray, and optical data. Those three things tell us what type of black hole it is, and how it's giving off its energy.

Meanwhile, the stars being formed are best observed in the ultraviolet and the infrared. You need the combination to get the bright young stars and the stars that are obscured by dust in the early stages of formation. So you need this UV and infrared combination. For the old stars that already exist there, you need more visible wavelength data. X-ray data also gives you total cluster properties. You see the cooling gas and the hot cluster halo.

So you really need this full range of data to piece everything together, and to get all the evidence of what is going on because there are so many different things at play. That is partially why I am very interested in galaxy clusters. I like to use this full range of detection methods and the different telescopes.

TKF: Is it correct to say that the supermassive black hole at the center of the central galaxy in the Phoenix Cluster - and the time we're observing it, 5.7 billion years ago - is not yet fully mature yet? In other words, that it's not yet creating the kind of feedback energy that would slow the cooling of gas and suppress the formation of stars?

MCDONALD: I think mature is a good term to use. But it's not that the black hole is giving off too little energy. It is actually one of the most powerful active black holes that we know about in cluster cores. Instead, it's giving off energy in the wrong way. It is giving off gamma rays and X-rays at a very large rate. Typically, these cluster-centric black holes are giving off a lot of radio emissions in the form of jets, which can sort of stir up the gas around galaxy. So it almost seems to be confused about where it is. It's sort of acting like it's in an ordinary spiral galaxy, whereas it is really in the center of a galaxy cluster and should be producing these radio jets. So maybe this is something that is in transition now between a quasar-like object and a radio-loud object.

TKF: And a radio jet emission would be more energetic and be able to slow this gas cooling?

MCDONALD: It would not be necessarily more energetic, but it would be the right kind of energy. It would be giving off energy that could couple to the intra-cluster gas. These radio jets can produce shocks and ripples in the intra-cluster medium that heat the gas up. It's kind of like trying to cook a turkey with a blowtorch. You're going to burn one little part of it but you won't cook the whole turkey very well. Whereas a slow gentle heat over a large area cooks the turkey much better.

TKF: And that "gentle" heating - driven by these radio jets from the central black hole - is what will slow the rate at which the gas cools and flows toward the central galaxy. And the result is a suppressed rate of star formation.

MCDONALD: Right. Exactly. Clusters in the local universe have the right amount of radio emission to offset cooling and so you get this really nice balance between radio jets coming from the central black hole heating up the gas, and the cooling of gas. The result is you don't have enough gas left over to form stars. Whereas in the Phoenix Cluster, there is very little radio emission from the central black hole, so you get this runaway cooling of gas that turns into stars. The gamma ray and x-ray emissions coming from central black hole aren't able to keep the gas hot enough to prevent star formation.

TKF: Let's talk a little about what this discovery means - the big picture. Before you studied the Phoenix Cluster, what was your 30-second description of how the central galaxy in clusters formed stars over cosmic time? And what's your new 30-second description?

MCDONALD: The picture as of a few months ago was that the central galaxies in clusters essentially formed via mergers. So you have thousands of galaxies in a cluster, and some of them are eventually going to merge with the central galaxy and you will slowly build up mass in the central galaxy. And it sort of just feeds off the other members. So that's the picture of how these supermassive galaxies form, just by accretion of smaller galaxies.

At the same time there was always another possibility that cooling should also play a role in the growth of a cluster's central galaxy. You have this reservoir of hot gas in the cluster, that should be able to fuel star formation - if it could cool enough. Computer simulations have suggested that this happens, but this was never really observed. Astronomers saw some star formation in the cores of some clusters, but never anywhere near the rate predicted by computer simulations. So this became known as "the cooling flow problem."

And so astronomers recently ruled out the idea that central galaxies in clusters grow by forming stars from the flow of cooling gas in the cluster toward the center.

The discovery of the Phoenix Cluster and its central galaxy throws a wrench into all this. Now we see a galaxy that appears to be forming a substantial number of its stars through this accretion of cooling material from the intra-cluster medium. Even if this goes on for just 100 million years, which is a cosmic blink of an eye, it's going to double the mass of the galaxy. So it's forming a large fraction of its stars not through mergers but through this accretion of cool gas. It's a channel predicted by simulations and by theory, but it's never really been observed until now. So maybe this is a new mechanism for how these galaxies can get so big.

BENSON: From my perspective, within the SPT collaboration, we are interested in this cluster in a slightly different way. It appears that in the Phoenix Cluster, the supermassive black hole at the core of its central galaxy has not turned on fully, at least not to the point where it has started suppressing star formation.

One of the reasons that we think supermassive black holes might be suppressing star formation in local clusters nearby is because we can see they are releasing energy into space between the cluster's galaxies through jets and explosions started by this central black hole.

So when we see something like this - a more distant galaxy cluster where the central black hole is not suppressing star formation - we need to see if we can find more clusters like it. The big question is, when do the black holes at the center of clusters turn on with the energy needed to suppress star formation - like we see in nearby clusters? The goal is to study more clusters to better understand their evolution, and when the black holes are turning on. We need to compare other clusters to Phoenix - clusters of all ages - to see how they evolve over cosmic time and where the Phoenix Cluster fits into this evolutionary picture.

TKF: Where are you both headed next with your research?

MCDONALD: First, I'll be getting more data on this one cluster, Phoenix. The Hubble Space Telescope will allow us to see where star formation is happening - whether there are filaments of star formation or whether it's more smoothly distributed. We'll also be able to separate the new stars from the older ones that lie closer to the core of the central galaxy.

We'll also hopefully obtain data from the new Atacama Large Millimeter/submillimeter Array in Chile, which will tell us how much cold gas there is. And that will give us an exact estimate of how long the starburst can last. If you know how much fuel you have and you know how quickly you're burning it, you can determine how long you can sustain the star formation.

Separately, we're going to try to find more clusters, either like this or unlike this. The reason is that it's really hard to draw any conclusion based on one galaxy cluster. So while this is exciting, it doesn't necessarily tell us about the overall evolution of galaxies and galaxy clusters.

BENSON: We'll be following up on many more clusters found in the SPT survey with the Chandra X-ray telescope. With that we are trying to assemble a larger statistical sample, to try to understand the percentages of how many clusters have similar properties in terms of these cooling cores, and how many of those exhibit similar signs of heightened star formation. Our goal is to better understand if the Phoenix Cluster is a unique, one-in-a-million thing, or if it's rare simply because it's in the midst of a short-lived period in its overall evolution that was more typical for clusters earlier in their formation.

"This discovery in the Phoenix Cluster suggests a whole new twist to that idea about how massive galaxies at the center of galaxy clusters grow. ...It makes the field more exciting from my perspective. It adds a lot of questions." - Michael McDonald

TKF: What excites you most about this discovery?

BENSON: Cosmology tries to answer some of the biggest questions about the universe, such as "How old is it?" and "How did it evolve?" I originally got involved in this from that perspective. For example, I'm trying to use clusters of galaxies to better understand dark energy, which is responsible for the mysterious force causing the universe to expand at an accelerating rate. At the same time, as you use all these astrophysical tools to try to understand cosmology better, you get more and more interested in the astrophysics, in the actual formation of these galaxies and galaxy clusters over time. We want to understand those things better so we can use them as cosmological tools. But they are also interesting by themselves. Unraveling that aspect of the mystery of how clusters form is also interesting.

MCDONALD: For me, this is exciting because in some ways it is reviving a long-held theory that never quite panned out. It has been thought over the last few years that this type of cooling-induced starburst doesn't happen, that galaxy evolution in clusters is very much based on mergers and the assembly of smaller galaxies to make a bigger galaxy.

This discovery in the Phoenix Cluster suggests a whole new twist to that idea about how massive galaxies at the center of galaxy clusters grow, and it allows for another mechanism for the growth of these galaxies. It opens up a whole new area of research, essentially. It allows us to understand the growth of galaxies via a variety of mechanisms, rather than just assembling from mergers. So it makes the field more exciting from my perspective. It adds a lot of questions, which gives us something new to do.

- August 2012

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KICP Members: Bradford A. Benson
Scientific projects: South Pole Telescope (SPT)
 
Stephan Meyer earns part of another Gruber Prize
The University of Chicago News Office, August 17, 2012
Stephan Meyer, professor in physics, astronomy & astrophysics, the Enrico Fermi Institute and the Kavli Institute for Cosmological Physics.  <i>(Photo by Jason Smith)</i>
Stephan Meyer, professor in physics, astronomy & astrophysics, the Enrico Fermi Institute and the Kavli Institute for Cosmological Physics.

(Photo by Jason Smith)
by Steve Koppes, The University of Chicago News Office

The University of Chicago's Stephan Meyer, professor in astronomy & astrophysics and the Kavli Institute for Cosmological Physics, has received a share of his second Gruber Cosmology Prize for his work as a member of the Wilkinson Microwave Anisotropy Probe.

This year's $500,000 Gruber Cosmology Prize went to John Hopkins University's Charles L. Bennett, who heads the 26-member WMAP collaboration, and his associates for building the WMAP satellite to make "observations of the so-called 'echo of the Big Bang,' the Cosmic Microwave Background radiation, to determine the universe's vital statistics - its age, content, geometry and origin." The prize citation further noted that, "This feat in turn has helped transform cosmology itself into a precision science."

NASA launched the WMAP satellite in 2001 to make precision measurements of the Microwave Background anisotropy, or structure. WMAP is named for the late David Wilkinson, who was Meyer's PhD advisor at Princeton University. In 1994 Wilkinson served as a distinguished visiting professor at UChicago's Enrico Fermi Institute, where he worked on the early ideas for the WMAP instrumentation.

Meyer previously had received a share of the 2006 Gruber Cosmology Prize with fellow members of the Cosmic Background Explorer collaboration.

NASA launched the COBE satellite in 1989 to precisely map the cosmic microwave background radiation. In 1992, the COBE team confirmed that the universe was born in a hot big bang. Two members of the COBE team, John Mather of NASA's Goddard Space Flight Center, and George Smoot of the University of California, Berkeley, also received the 2006 Nobel Prize in physics for this work.

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KICP Members: Stephan S. Meyer
Scientific projects: Wilkinson Microwave Anisotropy Probe (WMAP)
 
First stars, galaxies formed more rapidly than expected
The University of Chicago News Office, September 5, 2012
The South Pole Telescope recorded temperature fluctuations in the cosmic microwave background, the light left over from the big bang, to study the period of cosmological evolution when the first stars and galaxies formed early in the history of the universe.  <i>Courtesy of South Pole Telescope collaboration</i>
The South Pole Telescope recorded temperature fluctuations in the cosmic microwave background, the light left over from the big bang, to study the period of cosmological evolution when the first stars and galaxies formed early in the history of the universe.

Courtesy of South Pole Telescope collaboration
by Steve Koppes, The University of Chicago News Office

Analysis of data from the National Science Foundation's South Pole Telescope, for the first time, more precisely defines the period of cosmological evolution when the first stars and galaxies formed and gradually illuminated the universe. The data indicate that this period, called the epoch of reionization, was shorter than theorists speculated - and that it ended early.

"We find that the epoch of reionization lasted less than 500 million years and began when the universe was at least 250 million years old," said Oliver Zahn, a postdoctoral fellow at the Berkeley Center for Cosmological Physics at the University of California, Berkeley, who led the study. "Before this measurement, scientists believed that reionization lasted 750 million years or longer, and had no evidence as to when reionization began."

The findings by Zahn, his colleagues at UChicago's Kavli Institute for Cosmological Physics and elsewhere have been published in a pair of papers appearing in the Sept. 1, 2012 issue of the Astrophysical Journal. Their latest results are based on a new analysis that combines measurements taken by the South Pole Telescope at three frequencies, and extends these measurements to a larger area covering approximately 2 percent of the sky. The 10-meter South Pole Telescope operates at millimeter wavelengths to make high-resolution images of the cosmic microwave background, the light left over from the big bang.

"Studying the epoch of reionization is important because it represents one of the few ways by which we can study the first stars and galaxies," said study co-author John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics.

Before the first stars formed, most matter in the universe took the form of neutral hydrogen atoms. The radiation from the first stars transformed the neutral gas into an electron-proton plasma. Observations with the Wilkinson Microwave Anisotropy Probe satellite of polarized signals in the CMB indicate that this epoch occurred nearly 13 billion years ago, but these observations give no indication of when the epoch began or how long it lasted.

The first stars that formed were probably 30 to 300 times more massive than the sun and millions of times as bright, burning for only a few million years before exploding. The energetic ultraviolet light from these stars was capable of splitting hydrogen atoms back into electrons and protons, thus ionizing them.

Scientists believe that during reinoization, the first galaxies to form ionized "bubbles" in the neutral gas surrounding them. Electrons in these bubbles would scatter with light particles from the cosmic microwave background. This would create small hot and cold spots in the CMB depending on whether a bubble is moving toward or away from Earth. A longer epoch of reionization would create more bubbles, leading to a larger signal in the CMB.

The epoch's short duration indicates that reionization was more explosive than scientists had previously thought. It suggests that massive galaxies played a key role in reionization, because smaller galaxies would have formed much earlier. Rapid reionization also argues against many proposed astrophysical phenomena that would slow the process.

This is only the beginning of what astronomers expect to learn about reionization from the South Pole Telescope. The current results are based on only the first third of the telescope's full survey. Additional work is under way to combine South Pole Telescope maps with ones made by the Herschel satellite to further increase sensitivity to the reionization signal.

"We expect to measure the duration of reionization to within 50 million years with the current survey," said study co-author Christian Reichardt, a Berkeley astrophysicist. "With planned upgrades to the instrument, we hope to improve this even further in the next five years."

The 280-ton South Pole Telescope stands 75 feet tall and is the largest astronomical telescope ever built in Antarctica's clear, dry air. Sited at the National Science Foundation's Amundsen-Scott South Pole station at the geographic South Pole, it stands at an elevation of 9,300 feet on the polar plateau. Because of its location at the Earth's axis, it can conduct long-term observations of a single patch of sky.

UChicago leads the South Pole Telescope collaboration, which includes research groups from Argonne National Laboratory, Cardiff University, Case Western Reserve University, Harvard University, Ludwig-Maximilians-Universitat, Smithsonian Astrophysical Observatory, McGill University, University of California at Berkeley, University of California at Davis, University of Colorado at Boulder, University of Michigan and individual scientists at several other institutions.

The South Pole Telescope is primarily funded by the NSF's Office of Polar Programs. Partial support also is provided by the NSF-funded Physics Frontier Center of UChicago's Kavli Institute for Cosmological Physics, the Kavli Foundation, and the Gordon and Betty Moore Foundation.

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KICP Members: John E. Carlstrom
Scientific projects: South Pole Telescope (SPT)
 
Supercomputer Recreates Universe From Big Bang to Today
SPACE.com, September 12, 2012
Supercomputer Recreates Universe From Big Bang to Today
by Clara Moskowitz, SPACE.com

Scientists would love to be able to rewind the universe and watch what happened from the start. Since that's not possible, researchers must create their own mini-universes inside computers and unleash the laws of physics on them, to study their evolution.

Now researchers are planning the most detailed, largest-scale simulation of this kind to date. One of the main mysteries they hope to solve with it is the origin of the dark energy that's causing the universe to accelerate in its expansion.

The new simulation is a project led by physicists Salman Habib and Katrin Heitmann of Illinois' Argonne National Laboratory, and will run on the lab's Mira supercomputer, the third-fastest computer in the world, starting in the next month or two. The program will use trillions of "particles" - elements in the simulation that stand in for small bits of matter. The computer will let time run, and watch as the particles move through space in response to the forces acting on them.

As the simulation progresses, these bits of matter will clump together under gravity to form larger and larger blobs representing galaxies, galaxy clusters and superclusters. To evolve the universe from the Big Bang 13.7 billion years forward to today, the simulation will take up to two weeks.

Testing the theory
The ultimate goal is to compare the best telescope observations of structure in the universe to the structure displayed in the computer model, to test the reigning theory of cosmology.

"We are trying to look for subtle ways in which it's wrong," Habib told SPACE.com. "That's why you need these very high-resolution, very large-scale simulations to see if the observations don't match the predictions."

Dark energy is the name given to whatever is causing the expansion of the universe to accelerate. When this acceleration was first discovered in the 1990s, it shocked the science community, because theories predicted the universe's expansion would be steady or slowing down, because of the inward pull of gravity.

The current reigning theory posits that dark energy is what's called the cosmological constant, a term Einstein first thought to put into his equations of general relativity to represent the vacuum energy of the universe. Although Einstein ultimately decided not to include the term, scientists later realized that it could explain the current observations of the expansion of the universe.

However, cosmologists aren't satisfied with this explanation, Habib said.

Another possibility
"It's just a single number entered as an extra term in the equations," he said. "The problem is that if you ask what its value should be, it's enormous - many orders of magnitude bigger than what is actually observed."

While simulations based on the cosmological constant so far appear to match what's seen in large-scale observations of the universe, scientists think that next-generation observations may reveal discrepant details.

If a cosmological constant is not to blame for the accelerated expansion of the universe, another possibility is that space contains some other type of mass or energy, such as a field, that is pulling everything apart.

"It's basically guesswork; it could be like this, or it could be like that," Habib said. "Either way it's very interesting."

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KICP Members: Salman Habib; Katrin Heitmann
 
World's most powerful digital camera opens eye, records first images in hunt for dark energy
Fermilab Press Room, September 18, 2012
Zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth.   <i>Credit: Dark Energy Survey Collaboration.</i>
Zoomed-in image from the Dark Energy Camera of the center of the globular star cluster 47 Tucanae, which lies about 17,000 light years from Earth.

Credit: Dark Energy Survey Collaboration.
Fermilab Press Room

Eight billion years ago, rays of light from distant galaxies began their long journey to Earth. That ancient starlight has now found its way to a mountaintop in Chile, where the newly-constructed Dark Energy Camera, the most powerful sky-mapping machine ever created, has captured and recorded it for the first time.

That light may hold within it the answer to one of the biggest mysteries in physics - why the expansion of the universe is speeding up.

Scientists in the international Dark Energy Survey collaboration announced this week that the Dark Energy Camera, the product of eight years of planning and construction by scientists, engineers, and technicians on three continents, has achieved first light. The first pictures of the southern sky were taken by the 570-megapixel camera on Sept. 12.

"The achievement of first light through the Dark Energy Camera begins a significant new era in our exploration of the cosmic frontier," said James Siegrist, associate director of science for high energy physics with the U.S. Department of Energy. "The results of this survey will bring us closer to understanding the mystery of dark energy, and what it means for the universe."

The Dark Energy Camera was constructed at the U.S. Department of Energy's (DOE) Fermi National Accelerator Laboratory in Batavia, Illinois, and mounted on the Victor M. Blanco telescope at the National Science Foundation's Cerro Tololo Inter-American Observatory (CTIO) in Chile, which is the southern branch of the U.S. National Optical Astronomy Observatory (NOAO). With this device, roughly the size of a phone booth, astronomers and physicists will probe the mystery of dark energy, the force they believe is causing the universe to expand faster and faster.

"The Dark Energy Survey will help us understand why the expansion of the universe is accelerating, rather than slowing due to gravity," said Brenna Flaugher, project manager and scientist at Fermilab. "It is extremely satisfying to see the efforts of all the people involved in this project finally come together."

The Dark Energy Camera is the most powerful survey instrument of its kind, able to see light from over 100,000 galaxies up to 8 billion light years away in each snapshot. The camera's array of 62 charged-coupled devices has an unprecedented sensitivity to very red light, and along with the Blanco telescope's large light-gathering mirror (which spans 13 feet across), will allow scientists from around the world to pursue investigations ranging from studies of asteroids in our own Solar System to the understanding of the origins and the fate of the universe.

"We're very excited to bring the Dark Energy Camera online and make it available for the astronomical community through NOAO's open access telescope allocation," said Chris Smith, director of the Cerro-Tololo Inter-American Observatory. "With it, we provide astronomers from all over the world a powerful new tool to explore the outstanding questions of our time, perhaps the most pressing of which is the nature of dark energy."

Scientists in the Dark Energy Survey collaboration will use the new camera to carry out the largest galaxy survey ever undertaken, and will use that data to carry out four probes of dark energy, studying galaxy clusters, supernovae, the large-scale clumping of galaxies and weak gravitational lensing. This will be the first time all four of these methods will be possible in a single experiment.

The Dark Energy Survey is expected to begin in December, after the camera is fully tested, and will take advantage of the excellent atmospheric conditions in the Chilean Andes to deliver pictures with the sharpest resolution seen in such a wide-field astronomy survey. In just its first few nights of testing, the camera has already delivered images with excellent and nearly uniform spatial resolution.

Over five years, the survey will create detailed color images of one-eighth of the sky, or 5,000 square degrees, to discover and measure 300 million galaxies, 100,000 galaxy clusters and 4,000 supernovae.

The Dark Energy Survey is supported by funding from the U.S. Department of Energy; the National Science Foundation; funding agencies in the United Kingdom, Spain, Brazil, Germany and Switzerland; and the participating DES institutions.

More information about the Dark Energy Survey, including the list of participating institutions, is available at the project website: www.darkenergysurvey.org.

For a summary of the major components contributed to the Dark Energy Camera by the participating institutions, read these symmetry articles: www.symmetrymagazine.org/cms/?pid=1000880, http://www.symmetrymagazine.org/article/september-2012/the-dark-energy-camera-opens-its-eyes

Released by Fermilab and the National Optical Astronomy Observatory (NOAO) on behalf of the Dark Energy Survey collaboration. NOAO is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under cooperative agreement with the National Science Foundation.

Fermilab is America's premier national laboratory for particle physics research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab's website at www.fnal.gov.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

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Related Links:
KICP Members: Joshua A. Frieman
Scientific projects: Dark Energy Survey (DES)
 
Dark Matter
Discovery Channel's "Daily Planet", September 21, 2012
Eric Dahl, a KICP fellow, at SNOLAB.
Eric Dahl, a KICP fellow, at SNOLAB.
Discovery Channel's "Daily Planet"

Discovery Channel's "Daily Planet" show visits the COUPP-4kg dark matter search at SNOLAB. COUPP-4kg is presently taking data in this underground laboratory, while the installation of the COUPP-60kg chamber proceeds. Eric Dahl, a former KICP Fellow and now faculty at Northwestern University, guides the tour. The collaboration is presently designing a larger and final chamber, COUPP-500kg.

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Related Links:
KICP Members: Juan I. Collar; Eric Dahl; Russell Neilson
KICP Students: Drew Fustin; Alan Robinson
Scientific projects: COUPP/PICO
 
World's most powerful digital camera begins hunt for dark energy
The University of Chicago News Office, September 21, 2012
The Dark Energy Camera, mounted on the Blanco telescope in Chile, is the most powerful sky-mapping machine ever created. It has captured and recorded ancient starlight for the first time. <i>Courtesy of Dark Energy Survey Collaboration</i>
The Dark Energy Camera, mounted on the Blanco telescope in Chile, is the most powerful sky-mapping machine ever created. It has captured and recorded ancient starlight for the first time.
Courtesy of Dark Energy Survey Collaboration
The University of Chicago News Office

Eight billion years ago, rays of light from distant galaxies began their long journey to Earth. That ancient starlight has now found its way to a mountaintop in Chile, where the newly constructed Dark Energy Camera, the most powerful sky-mapping machine ever created, has captured and recorded it for the first time.

That light may hold within it the answer to one of the biggest mysteries in physics: Why the expansion of the universe is speeding up.

Scientists in the international Dark Energy Survey collaboration, which includes the University of Chicago's Kavli Institute for Cosmological Physics, announced this week that the Dark Energy Camera, the product of eight years of planning and construction by scientists, engineers, and technicians on three continents, has achieved first light. The first pictures of the southern sky were taken by the 570-megapixel camera on Sept. 12.

"The achievement of first light through the Dark Energy Camera begins a significant new era in our exploration of the cosmic frontier," said James Siegrist, associate director of science for high-energy physics with the U.S. Department of Energy. "The results of this survey will bring us closer to understanding the mystery of dark energy, and what it means for the universe."

The Dark Energy Camera was constructed at the U.S. Department of Energy's Fermi National Accelerator Laboratory, and mounted on the Victor M. Blanco telescope at the National Science Foundation's Cerro Tololo Inter-American Observatory in Chile, which is the southern branch of the U.S. National Optical Astronomy Observatory. With this device, roughly the size of a phone booth, astronomers and physicists will probe the mystery of dark energy - the force they believe is causing the universe to expand faster and faster.

"The Dark Energy Survey will help us understand why the expansion of the universe is accelerating, rather than slowing due to gravity," said Brenna Flaugher, project manager and scientist at Fermilab. "It is extremely satisfying to see the efforts of all the people involved in this project finally come together."

The Dark Energy Camera is the most powerful survey instrument of its kind, able to see light from over 100,000 galaxies up to 8 billion light years away in each snapshot. The camera's array of 62 charged-coupled devices has an unprecedented sensitivity to very red light, and along with the Blanco telescope's large light-gathering mirror (which spans 13 feet across), will allow scientists from around the world to pursue investigations ranging from studies of asteroids in our own solar system to the understanding of the origins and the fate of the universe.

"We're very excited to bring the Dark Energy Camera online and make it available for the astronomical community through NOAO's open access telescope allocation," said Chris Smith, director of the Cerro-Tololo Inter-American Observatory. "With it, we provide astronomers from all over the world a powerful new tool to explore the outstanding questions of our time, perhaps the most pressing of which is the nature of dark energy."

Scientists in the Dark Energy Survey collaboration will use the new camera to carry out the largest galaxy survey ever undertaken, and will use that data to carry out four probes of dark energy, studying galaxy clusters, supernovae, the large-scale clumping of galaxies and weak gravitational lensing. This will be the first time all four of these methods will be possible in a single experiment.

The Dark Energy Survey is expected to begin in December, after the camera is fully tested, and will take advantage of the excellent atmospheric conditions in the Chilean Andes to deliver pictures with the sharpest resolution seen in such a wide-field astronomy survey. In just its first few nights of testing, the camera has already delivered images with excellent and nearly uniform spatial resolution.

Over five years, the survey will create detailed color images of one-eighth of the sky, or 5,000 square degrees, to discover and measure 300 million galaxies, 100,000 galaxy clusters and 4,000 supernovae.

The Dark Energy Survey is supported by funding from the U.S. Department of Energy; the National Science Foundation; funding agencies in the United Kingdom, Spain, Brazil, Germany and Switzerland; and the participating DES institutions.


Released by Fermilab and the National Optical Astronomy Observatory on behalf of the Dark Energy Survey collaboration. NOAO is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation.

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Related Links:
KICP Members: Joshua A. Frieman
Scientific projects: Dark Energy Survey (DES)
 
Leading the quest to crack cosmological mysteries
The University of Chicago News Office, September 27, 2012
Leading the quest to crack cosmological mysteries
by Steve Koppes, The University of Chicago News Office

Kavli Institute directs national collaboration on deepest questions of dark energy, dark matter, and cosmic inflation


Sometimes a scientist can only laugh in the face of a seemingly insurmountable challenge.

Such is the case with cracking the mystery of dark energy and its repulsive gravity, which is causing the expansion of the universe to accelerate.

"People don't even get the term 'repulsive gravity' because the defining feature of gravity is that it's attractive," says Michael Turner, director of the Kavli Institute for Cosmological Physics. "What do you mean, repulsive gravity? Do you mean the theory is repulsive?" he jokes.


The time is ripe to solve the dark matter problem. Our Physics Frontiers Center hopes to shed critical light on dark matter."
-Rocky Kolb
Professor


Turner calls dark energy "the most profound mystery in all of science." Cracking the problem requires collaborations of original thinkers working beyond the limits of current theories. That's why dark energy is one of three cosmological puzzles that the Kavli Institute is tackling with a five-year, $17 million Physics Frontiers Center grant from the National Science Foundation.

Also high on the institute's research agenda are the riddles of dark matter and cosmic inflation. Along with dark energy, these are the three pillars of modern cosmological theory, "and none of them can be explained with physics that we know," Turner says. "They're all pointing to new physics."

Transforming cosmology
During its first decade as a Physics Frontier Center, the Kavli Institute helped to establish the current cosmological paradigm. Originally called the Center for Cosmological Physics, the Institute was founded in 2001 with a $15 million NSF grant. The Institute is launching its second decade with 21 key collaborators around the country and 15 institutional partners, including Argonne National Laboratory and Fermi National Accelerator Laboratory.

The NSF created the Physics Frontiers Centers program to make significant advances at some of the most important intellectual frontiers in diverse physics subfields, says Joseph Dehmer, director of NSF's division of physics.

"By all measures, this has happened, and the 10 PFCs now operating reflect the extremely high standards of scholarship and synergy hoped for," Dehmer says. "An unexpected and most welcome benefit is that the PFCs act as talent magnets, drawing high levels of talent into physics. Another not unexpected benefit is that the triennial PFC competition constitutes a serious, high-level discussion across the subfields of physics - a rare 'unity of physics' event in an increasingly specialized field."

Argonne is a new partner in the UChicago PFC. Argonne and Kavli Institute scientists will develop large-scale cosmological simulations on the laboratory's supercomputers, as well as sensitive new detectors for the South Pole Telescope, which studies the cosmic microwave background radiation leftover from the birth of the universe. Kavli Institute scientists will investigate the dark energy question with the SPT and the Dark Energy Survey. The latter project, led by Fermilab, will collect data on approximately 300 million galaxies spanning two-thirds the history of the universe in order to measure dark energy with new precision.

New form of matter?
The mystery of dark matter may be easier to solve. Kavli Institute scientists hope to accomplish this feat within the next decade. They suspect that dark matter is made of a new form of matter, something that does not consist of quarks, neutrons or protons.

Dark matter may reveal itself through any or all of three means: direct detection via ground-based detectors at the Chicagoland Observatory for Underground Particle Physics (COUPP), indirect detection in the galaxy halo via satellites, and production of the particles at the Large Hadron Collider at CERN, the European particle physics laboratory.

"Right now, there is confusion - claims of possible detections, counter-claims, and spirited debate - and the time is ripe to solve the dark matter problem. Our PFC hopes to shed critical light on dark matter," says Rocky Kolb, the University's Arthur Holly Compton Distinguished Service Professor in Astronomy & Astrophysics, who leads the PFC's dark matter effort.

Cosmic inflation is a different kind of problem. It has emerged as the most important cosmological concept since the Big Bang theory, but many of its claims have not yet been thoroughly tested. Inflation proposes that the universe expanded extremely rapidly in a tiny fraction of a second after the Big Bang. Such a swift expansion would explain some important questions that Big Bang theory alone has been unable to answer.

"We have some circumstantial evidence that inflation took place, but we'd like to make the case very strongly," says John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics. A more direct indication of inflation would be to look for a minute sign of polarization in the cosmic microwave background, the afterglow of the Big Bang.

For the last decade, center scientists, including Carlstrom and the late Bruce Winstein, have been developing a technology capable of measuring this polarization. Now they need to deploy that technology to see what they can find.

The successful Kavli Institute proposal for the Physics Frontiers Center was more than two years in the making and included significant support from the University administration and behind-the-scenes personnel.

Winstein, the Samuel K. Allison Distinguished Service Professor in Physics and founder of the original PFC, also played a big role in developing the proposal for renewed funding. Winstein, who lost a four-year battle with cancer in Feb. 2011, worked on the proposal until his last days, Turner says.

"During the last months of his life, he was parceling out his time only to the most important things, and we got a lot of his time. Our PFC is part of Bruce's legacy."

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Related Links:
KICP Members: John E. Carlstrom; Edward W. Kolb; Michael S. Turner; Bruce D. Winstein
 
Meet Mira, the Supercomputer That Makes Universes
The Atlantic, October 4, 2012
A view of the matter distribution in the universe from a trillion-particle simulation carried out during Mira's construction. The actual resolution of the simulation is much higher than is captured by this image, even the smallest box has substantial substructure. The side of the simulation box is a little over 9 billion parsecs -- a parsec is 3.26 light-years. (Argonne National Laboratory)
A view of the matter distribution in the universe from a trillion-particle simulation carried out during Mira's construction. The actual resolution of the simulation is much higher than is captured by this image, even the smallest box has substantial substructure. The side of the simulation box is a little over 9 billion parsecs -- a parsec is 3.26 light-years. (Argonne National Laboratory)
by Ross Andersen, The Atlantic

Next month, one of the world's fastest supercomputers will run the largest, most complex universe simulation ever attempted.

Cosmology is the most ambitious of sciences. Its goal, plainly stated, is to describe the origin, evolution, and structure of the entire universe, a universe that is as enormous as it is ancient. Surprisingly, figuring out what the universe used to look like is the easy part of cosmology. If you point a sensitive telescope at a dark corner of the sky, and run a long exposure, you can catch photons from the young universe, photons that first sprang out into intergalactic space more than ten billion years ago. Collect enough of these ancient glimmers and you get a snapshot of the primordial cosmos, a rough picture of the first galaxies that formed after the Big Bang. Thanks to sky-mapping projects like the Sloan Digital Sky Survey, we also know quite a bit about the structure of the current universe. We know that it has expanded into a vast web of galaxies, strung together in clumps and filaments, with gigantic voids in between.

How do you follow a galaxy through nearly all of time? You build a new universe.
The real challenge for cosmology is figuring out exactly what happened to those first nascent galaxies. Our telescopes don't let us watch them in time-lapse; we can't fast forward our images of the young universe. Instead, cosmologists must craft mathematical narratives that explain why some of those galaxies flew apart from one another, while others merged and fell into the enormous clusters and filaments that we see around us today. Even when cosmologists manage to cobble together a plausible such story, they find it difficult to check their work. If you can't see a galaxy at every stage of its evolution, how do you make sure your story about it matches up with reality? How do you follow a galaxy through nearly all of time? Thanks to the astonishing computational power of supercomputers, a solution to this problem is beginning to emerge: You build a new universe.

In October, the world's third fastest supercomputer, Mira, is scheduled to run the largest, most complex universe simulation ever attempted. The simulation will cram more than 12 billion years worth of cosmic evolution into just two weeks, tracking trillions of particles as they slowly coalesce into the web-like structure that defines our universe on a large scale. Cosmic simulations have been around for decades, but the technology needed to run a trillion-particle simulation only recently became available. Thanks to Moore's Law, that technology is getting better every year. If Moore's Law holds, the supercomputers of the late 2010s will be a thousand times more powerful than Mira and her peers. That means computational cosmologists will be able to run more simulations at faster speeds and higher resolutions. The virtual universes they create will become the testing ground for our most sophisticated ideas about the cosmos.

Salman Habib is a senior physicist at the Argonne National Laboratory and the leader of the research team working with Mira to create simulations of the universe. Last week, I talked to Habib about cosmology, supercomputing, and what Mira might tell us about the enormous cosmic web we find ourselves in.

Help me get a handle on how your project is going to work. As I understand it, you're going to create a computer simulation of the early universe just after the Big Bang, and in this simulation you will have trillions of virtual particles interacting with each other -- and with the laws of physics -- over a time period of more than 13 billion years. And once the simulation has run its course, you'll be looking to see if what comes out at the end resembles what we see with our telescopes. Is that right?

Habib: That's a good approximation of it. Our primary interest is large-scale structure formation throughout the universe and so we try to begin our simulations well after the Big Bang, and even well after the microwave background era. Let me explain why. We're not sure how to simulate the very beginning of the universe because the physics are very complicated and partially unknown, and even if we could, the early universe is structurally homogenous relative to the complexity that we see now, so you don't need a supercomputer to simulate it. Later on, at the time of the microwave background radiation, we have a much better idea about what's going on. WMAP and Planck have given us a really clear picture of what the universe looked like at that time, but even then the universe is still very homogenous -- its density perturbations are something like one part in a hundred thousand. With that kind of homogeneity, you can still do the calculations and modeling without a supercomputer. But if you fast forward to the point where the universe is about a million times denser than it is now, that's when things get so complicated that you want to hand over the calculations to a supercomputer.

Now the trillions of particles we're talking about aren't supposed to be actual physical particles like protons or neutrons or whatever. Because these trillions of particles are meant to represent the entire universe, they are extremely massive, something in the range of a billion suns. We know the gravitational mechanics of how these particles interact, and so we evolve them forward to see what kind of densities and structure they produce, both as a result of gravity and the expansion of the universe. So, that's essentially what the simulation does: it takes an initial condition and moves it forward to the present to see if our ideas about structure formation in the universe are correct.

At the largest scales, how would you describe the structure of the universe as we see it today through our telescopes? Some say it's web-like or that it's composed of sheets of filaments -- are those accurate descriptions?

Habib: That's a very accurate way to think about it. People often conceive of it as a cosmic web, a picture that dates back to the Soviet physicist Yakov Zel'dovich who had this very deep insight about how structure forms in the universe. The idea is that initially the universe is very smooth, very homogenous, with few perturbations. If you looked at it, you wouldn't see much. But then as the universe expands, gravity causes matter to attract and to form local structures. The first structures to form are sheets, and where the sheets intersect you get filaments, and where the filaments intersect you get clumps. As time progresses, you can start to see the basic structure where you have this enormous web of voids, filaments and clumps. The sheets are very thin, very ephemeral, so it is much harder to see them, but the rest of the structure is very sharp and clear, especially as seen by the Sloan Digital Sky Survey.

Have previous simulations been successful in producing the structure we see with telescopes?

Habib: Oh yes, the web-like structure is completely borne out by simulations. Simulations date back a long way; one of the earliest -- the one I consider to be the precursor to modern simulations -- was done in the late 1960s by the Canadian-American cosmologist Jim Peebles. He spent a summer at Los Alamos and while he was there he was able to perform a 300-particle simulation, which is of course quite small compared to today's simulations. People have been running larger and larger simulations since then, and when they do, they consistently see this same web-like structure.

Is there an aesthetic component to these simulations? Can you actually see galaxies forming?

Habib: There is definitely an aesthetic component. We're looking at an actual image of the structure, but you can't see galaxies forming. It's not quite that granular, and besides these are gravity-only simulations. For large-scale structure simulations, gravity is all you need to understand how you get sheets and filaments and clumps. If you want to see how galaxies form, you need the rest of physics -- you need individual atoms, angular momentum, gas physics, etc. These are enormously complicated processes and we don't yet have the computing power to run them on the scale of the entire universe. There are people who do simulate galaxy formation with supercomputers, but they have to do it over much smaller volumes of the universe.

Some of the inflationary models for the early Universe suggest a process that would continue to produce additional universes, perhaps with their own laws of physics. Certainly that's not something we could model with a computer now, but might it be someday?

Habib: It could be, but we'd have to understand the theory better. The theory you're talking about, eternal inflation, has two issues. First, the sheer difficulty of the calculations, but second the theory itself is not well defined yet. I would argue that, at the moment, theories like eternal inflation are in the realm of speculative physics. There are models for eternal inflation -- I've written papers about them, and so have a lot of other people -- but if you go and look at the equations, they are not very well defined. That's because when you talk about producing new universes, you're talking about the intersection between quantum mechanics and gravity, and we don't yet have a satisfactory theory of quantum gravity. We have candidates for what might someday morph into an satisfactory theory, but we can't say for sure. The multiverse idea is interesting and provocative, but it's a work in progress.

What happens when you let the models run past the present? Time-wise, what's the farthest that someone has taken one of these simulations?

Habib: That's an interesting question. We usually just stop the simulations at the present, because we're still trying to understand how we got here, but there's no particular reason to stop them. You can continue to run them forward and some people have done that in the past. What they've found is that if you run the universe far enough into the future it expands into a pretty bleak place.

"If you run the universe far enough into the future it expands into a pretty bleak place."
All the matter runs away from each other, because space is being created at an ever-accelerating rate. In fact, people often joke that this is the right time to do cosmology because trillions of years from now we won't be able to see anything: Everything will have receded out of sight. So yes, we can run these simulations into the future, but it's not that interesting. The universe is much more interesting now than it's going to be in the future, provided that this accelerating expansion phase of the universe continues as we expect it to.

Your project was made possible by the development of the Mira supercomputer, the third-fastest computer in the world. Can you describe what makes Mira so special?

Habib: Let me say one or two things about supercomputers. Every few years supercomputers become about 10 times more powerful, so with each new generation you get quite a leap in capabilities. Not only do supercomputers get faster, but they get much larger, which allows you to run much bigger problems. What distinguishes a supercomputer like Mira from a normal computer is that it has a very large number of computational units. A simplified way to think about it is to imagine having a million laptops that you've networked in such a way that they're able to communicate with each other very quickly. Now you split your problem up into a million chunks and you give each chunk to a laptop, and the laptop works on its chunk and passes the data around as needed, and eventually your problem gets solved.

What makes all of these simulations possible is the sheer size of the supercomputers. For example, the Mira has close to a petabyte of memory. If you tried to do a simulation like this on a normal computer, you wouldn't be able to fit it, and even if you could fit it, if you tried to run it, it would never finish. With Mira, we're able to complete these universe simulations in the span of a week or two.

I know that supercomputers like Mira are used for all kinds of scientific experiments outside of cosmology. What else will it be used for in the next few years?

Habib: There are a large number of applications. People use supercomputers to determine the properties of materials, to understand combustion, to figure out how a flame works. They're also used to determine fluid dynamics; for instance you might want to know how air flows around the wing of an aircraft, and you can calculate that quite precisely with a supercomputer. In astrophysics there are all sorts of applications; people use supercomputers to study intergalactic gas, the formation of stars, supernovae and so on.

Moore's Law tells us that processing power increases exponentially. Assuming the next few years bring a huge leap in processing power, would you rather use it to perform these experiments quicker, or at a higher complexity?

Habib: There's a difficulty that we're running up against with Moore's Law. If you want to get more performance out of these computers, you can do it two ways: You can make the computational units switch faster or you can add more computational units. It turns out that if you want to make the units switch faster, you need more power. We've reached a limit where we can, in principle, build a faster machine, but it would cost us many gigawatts of power to actually run it and we simply can't afford to do that. So conventional Moore's Law is already reaching a breaking point because of this power barrier.

Now if you want to solve this problem by reducing the amount of power used by the switches in the computer, then you have to reduce the voltage, but if you reduce the voltage you get more errors. So the next generation of computers -- in five years or so -- promises to be very different. We may have to program them in different ways, and we may have to think about how to power them differently, or how to correct for errors. It's going to be interesting and in some senses it's going to be more painful than it is now.

Now around 2018 or 2020, somewhere around that time scale, these machines are supposed to become a thousand times faster than they are right now. There are a lot of studies being done to figure out what you could do with a machine like that, but whether we'll actually get there, I don't know. It's not yet clear that there will be investment in the technologies we need to get us there. There is some hope that there will be investment, because supercomputer simulations are increasingly being used outside the basic sciences. Supercomputers are playing a big role in the development of new technologies. For instance, you can design a diesel engine without ever building a prototype simply by simulating it with a supercomputer.

It seems like a large, sped up version of one of these universe simulations would be perfect as a piece of public art. Has anyone tried anything like that?

Habib: That's an interesting thought. The question is how you would actually show it, because it is a dynamic object. You could have it as a projection like you see at planetariums and that would be very beautiful, but really you have to see it in three dimensions. Until you see it in three dimensions you cannot appreciate how beautiful the structure is. What would be neat is a large-scale hologram -- something where you could actually see the structure pop up around you. That would really be something to see.

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Related Links:
KICP Members: Salman Habib
 
Live Q&A, webcast on Dark Energy Camera set for Oct. 12
The University of Chicago News Office, October 10, 2012
The Dark Energy Camera, mounted on the Blanco telescope in Chile. <i>Courtesy of Dark Energy Survey Collaboration</i>
The Dark Energy Camera, mounted on the Blanco telescope in Chile.
Courtesy of Dark Energy Survey Collaboration
by Steve Koppes, The University of Chicago News Office

Scientists at the University of Chicago's Kavli Institute for Cosmological Physics have great expectations for the newly operational Dark Energy Camera, which may significantly advance understanding of the mysterious force expanding the universe at an ever-accelerating rate. Two scientists at Fermi National Accelerator Laboratory will answer questions from viewers about the camera and what it's expected to reveal during a live Q&A and webcast from noon to 12:30 p.m. Friday, Oct. 12.

Participating in the event will be Brenna Flaugher, project manager for the Dark Energy Camera; and Joshua Frieman, director of the Dark Energy Survey and professor in astronomy & astrophysics at UChicago. The Dark Energy Survey is an international collaboration of more than 130 scientists from 27 institutions, including UChicago.

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Related Links:
KICP Members: Joshua A. Frieman
Scientific projects: Dark Energy Survey (DES)
 
The Big Bang - View from the South Pole
Medill Reports, October 18, 2012
Krisztina Eleki takes a photo of Benjamin Brookes dressed in the clothing used in the Antartic at the South Pole telescope talk at the School of the Art Institute of Chicago. Both work for Chicago Council on Science and Technology, one of the organizations that sponsored the event. The clothing and photographs are part of an interactive SAIC exhibit.
Krisztina Eleki takes a photo of Benjamin Brookes dressed in the clothing used in the Antartic at the South Pole telescope talk at the School of the Art Institute of Chicago. Both work for Chicago Council on Science and Technology, one of the organizations that sponsored the event. The clothing and photographs are part of an interactive SAIC exhibit.
by Stephanie Sunata, Medill Reports

It sits about two miles above sea level on an icy shelf at the most southern part of the globe. It probes microwaves from the farthest points in space. It surveys the southern sky and scientists hope it will help answer some of the universe's biggest questions.

The South Pole telescope is one of the pivotal tools scientists use to study the universe. It explores the enigmas of dark energy and was the topic of cosmologist John Carlstrom's recent public presentation at the School of the Art Institute of Chicago.

Carlstrom, professor of astronomy and astrophysics at the University of Chicago, uses the South Pole telescope to study the early universe and wants to make his research accessible to everyone.

"If you do your science and never share it, what's the point?" Carlstrom said.

At the talk Thursday, Carlstrom shared the construction process of the telescope and gave an overview of the mysteries it's trying to solve to an audience of about 100 people.

The telescope aimed at the heavens from Antarctica focuses on the edge of space where traces remain from when the Big Bang was plasma that radiated visible light, Carlstrom told the audience.

As the universe expanded, these light waves lengthened to microwaves during the 14-billion-light-year trip to reach Earth.

The South Pole telescope detects these microwaves that paint a picture of the early universe. The image contains temperature variations, and when analyzed, create a diminishing harmonic plot.

This is similar to the harmonics of musical instruments. Just as scientists can determine certain characteristics about a violin from plotting its acoustics, they can use the cosmic radiation graph to learn about early space.

"Our universe is ringing like a bell," Carlstrom said.

The telescope project also analyzes galaxy clusters, which act as a measurement tool in the battle between dark energy and the combination of dark matter and gravity, Carlstrom said.

Dark matter and gravity hold things together, but scientists believe the elusive dark energy pulls things apart. Galaxy clusters are sensitive to these opposing forces.

The clusters act as a rope in the tug-of-war in space. The South Pole telescope looks at this "rope" to see who's winning and, right now, it's dark energy, Carlstrom said.

This means the universe is not only expanding, but the expansion rate is accelerating due to dark energy.

"It's for everyone to appreciate," Carlstrom said in an interview. "It's your universe too."

Representatives from the Chicago Council on Science and Technology, one of the organizations that sponsored the talk, emphasized that part of scientific research means getting the public involved.

One effective way to do this is to hold public talks with scientists, said Andrea Poet, council public relations coordinator. "I think for people to hear about dark energy from a leading expert is exciting," Poet said.

Attendee Francesca Costa said she enjoyed Carlstrom's presentation, even though she studied humanities, not science.

Costa said Carlstrom's ideas were "clear" and "accessible" to a non-scientist and the concepts of cosmic microwaves and dark energy were interesting.

Even if she doesn't fully understand the science behind all the material, she believes the South Pole telescope project is important, Costa said.

Her husband, Bill Dague, a physics major at University of Chicago, said this research could answer an ages-old question: "How did it all get started?"

"Having an understanding of who we are and where we are is good overall for humanity," Dague said.

The presentation combined complex scientific data with simple analogies. Carlstrom tailored the speech to appeal to all types of people.

Though the topic of discussion was scientific, the venue was artistic.

Though he didn't decide on the location, Carlstrom said liked the idea of hosting the talk at an art school because both science and art require creativity.

An exhibit inpsired by the telescope project - created and designed by students at the school - helped exemplify the collaboration between art and science.

Instructor Bo Rodda led the Art Institute class that made the exhibit, which opened at the USA Science and Engineering Festival in Washington, D.C. earlier this year.

"Both artists and scientists are curious about the world," he said. Each discipline requires a person to make abstract ideas conceivable to the public, he added.

There were multiple pictures of the Antarctic, a touch-screen unit with information about the project and a station where people could put on a coat and boots worn in the freezing landscape.

The art students made the interactive exhibit with children in mind, Rodda said.

About a dozen teenagers attended Thursday's event, and Carlstrom spoke to some of them individually.

"It's always really neat when you meet high school kids who are turned on by science," he said.

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Related Links:
KICP Members: John E. Carlstrom
Scientific projects: South Pole Telescope (SPT)
 
UChicago Awards $375,000 to Fermilab-University collaborators
The University of Chicago News Office, October 22, 2012
by Lisa La Vallee, The University of Chicago News Office

Five teams of University of Chicago and Fermi National Accelerator Laboratory researchers, including one team with an Argonne National Laboratory member, recently received $375,000, collectively, in Strategic Collaborative Initiative seed grants from UChicago. Three of the five teams received second-year funding.

The FY 2012 recipients include:
* "Simulating the Universe with Realistic Physics" (Year 2) UChicago investigator Andrey Kravtsov, Associate Professor in Astronomy and Astrophysics, and Fermilab investigator Nickolay Gnedin, Scientist I in the Theoretical Astrophysics Group
* "Understanding Ultrahigh Quality Factor Accelerator Cavities in the Quantum Regime" (Year 2) UChicago investigator David Schuster, Assistant Professor in Physics, and Fermilab investigator Lance Cooley, Scientist in the Superconducting Materials Department
* "A New Photodetection System for PET Imaging Using Silicon Photomultipliers" (Year 2) UChicago investigator Chin-Tu Chen, Associate Professor in Radiology, and Fermilab investigator Erik Ramberg, Scientist II in the Particle Physics Division
* "Optical Modulation with Wavelength Division Multiplexing from HEP Data Readout" UChicago investigator Mark Oreglia, Professor in Physics; Argonne investigator Robert Stanek, Physicist in the High Energy Physics Division; and Fermilab investigator Simon Kwan, Scientist II in the Computing Division
* "Development of Low Noise Electronics for the First Direct Dark Matter Search Using CCDs" UChicago investigator Paolo Privitera, Professor in Physics, and Fermilab investigators Juan Estrada, Scientist II in the Particle Physics Division and Gustavo Cancelo, Engineer IV in the Computing Division

The Strategic Collaborative Initiatives Program began in 2005, when the University renewed its contract with the DOE to manage Argonne. It includes collaborative research projects, strategic joint appointments and joint institutes. The University extended the program to Fermilab when it became co-manager of the lab in 2006.

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Related Links:
KICP Members: Nickolay Y. Gnedin; Andrey V. Kravtsov; Paolo Privitera
 
The Cosmic Microwave Background: A New View from the South Pole
AMNH Science Bulletin, October 24, 2012
The Cosmic Microwave Background: A New View from the South Pole
AMNH Science Bulletin

The icy South Pole desert is a harsh and desolate landscape in which few life-forms can flourish. But the extreme cold and isolation are perfect for astronomical observations. Taking advantage of the severe conditions, scientists are using the new South Pole Telescope - the largest ever deployed in Antarctica - to observe the oldest light in the Universe, the cosmic microwave background (CMB).

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Related Links:
KICP Members: Bradford A. Benson; John E. Carlstrom; Randall H. Landsberg
Scientific projects: South Pole Telescope (SPT)
 
Four on faculty elected fellows of American Association for the Advancement of Science
The University of Chicago News Office, December 13, 2012
Angela Olinto, KICP senior member, Chair of the Department of Astronomy and Astrophysics
Angela Olinto, KICP senior member, Chair of the Department of Astronomy and Astrophysics
by Steve Koppes, William Harms, The University of Chicago News Office

Four University of Chicago faculty members were elected as fellows of the American Association for the Advancement of Science, the organization announced on Nov. 29.

The UChicago fellows are: Anthony Kossiakoff, the Otho S.A. Sprague Professor of Biochemistry and Molecular Biology and the Institute for Biophysical Dynamics; Angela Olinto, Professor in Astronomy & Astrophysics; Steven Shevell, the Eliakim Hastings Moore Distinguished Service Professor in Psychology and Ophthalmology & Visual Science; and Melvyn Shochet, Professor in Physics.

In all this year, 702 scholars were named AAAS fellows for their scientifically or socially distinguished efforts to advance science or its applications. The new fellows will be presented with an official certificate and pin at the AAAS Fellows Forum during the 2013 AAAS annual meeting in Boston. The AAAS is an international organization that promotes scientific understanding through many programs, including publication of the prestigious journal Science.

Angela Olinto
Olinto is being recognized for her distinguished contributions to the field of astrophysics, particularly exotic states of matter and extremely high-energy cosmic ray studies at the Auger Observatory.

Olinto's research interests span theoretical astrophysics, particle and nuclear astrophysics, and cosmology. She has focused much of her work on understanding the origins of the highest energy cosmic rays and the ultra-compressed core of matter in neutron stars. Ultra-high-energy cosmic rays enter the atmosphere with so much energy that they produce a giant cascade of many tens of billions of secondary particles, which can be observed by large detectors such as the Auger Observatory.

Olinto now leads the Japanese Experiment Module-Extreme Universe Space Observatory mission to observe these ultra-energy particles from the International Space Station.

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Related Links:
KICP Members: Angela V. Olinto
Scientific projects: Pierre Auger Observatory (AUGER)
 
Roundtable Discussion: Are We Closing In On Dark Matter?
Kavli Foundation News, December 17, 2012
Image, dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies.  <i>Credit:Chandra/NASA</i>
Image, dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies.
Credit:Chandra/NASA
Kavli Foundation News

As the search for dark matter intensifies, the Kavli Institute for Cosmological Physics at the University of Chicago and the National Academy of Sciences organized a colloquium that brings together cosmologists, particle physicists and observational astrophysicists - three fields now united in the hunt to determine what is dark matter.

DARK MATTER IS ONE OF THE BIGGEST MYSTERIES IN MODERN PHYSICS. We believe it makes up about 23 percent of the mass-energy content of the universe, even though we don't know what it is or have yet to directly see it (which is why it's called "dark"). So how can we detect it and when we do, what will it reveal about the universe?

In mid-October, more than 100 cosmologists, particle physicists and astrophysicists gathered for a meeting called Dark Matter Universe: On the Threshold of Discovery at the National Academy of Sciences' Beckman Center in Irvine, CA. Their goal: to take stock of the latest theories and findings about dark matter, assess just how close we are to detecting it and spark cross-disciplinary discussions and collaborations aimed at resolving the dark matter puzzle. Following the meeting, The Kavli Foundation met with three leading participants and organizers of the meeting:
* Michael S. Turner - Rauner Distinguished Service Professor and Director of the Kavli Institute for Cosmological Physics at the University of Chicago.
* Edward "Rocky" Kolb - Professor in the Department of Astronomy and Astrophysics at the University of Chicago, where he is also a member of the Enrico Fermi Institute and the Kavli Institute for Cosmological Physics.
* Maria Spiropulu - Professor of Physics at California Institute of Technology who also works on experiments at the Large Hadron Collider, and a former fellow at the Enrico Fermi Institute.

The following is an edited transcription of the discussion.

THE KAVLI FOUNDATION: This meeting brought together theoretical cosmologists, observational astrophysicists and experimental particle physicists. Why this mix of researchers and why now?

MICHAEL TURNER: Figuring out what is dark matter has become a problem that astrophysicists, cosmologists and particle physicists all want to solve, because dark matter is central to our understanding of the universe. We now have a compelling hypothesis, namely that dark matter is comprised of WIMPs (Weakly Interacting Massive Particle), particles that don't radiate light and interact rarely with ordinary matter. After decades of trying to figure out how to test the idea that dark matter is made up of WIMPs, we have three ways to test this hypothesis. Best of all, all three methods are closing in on being able to either confirm or falsify the WIMP. So the stars have truly aligned.

ROCKY KOLB: The title to this meeting is a great answer to your question. It's "On the Threshold of Discovery," and it could happen within the next one or two years. It's so important to get the different communities here - experimentalists working at colliders, people analyzing gamma ray data from space, and those involved in direct detection.

TKF: So dark matter is a mystery that everyone wants to solve.


Michael Turner - Director of the Kavli Institute for Cosmological Physics (KICP) at the University of Chicago, and a theoretical cosmologist trained in both particle physics and astrophysics. Dr. Turner coined the term "dark energy" and helped establish the interdisciplinary field that combines cosmology and elementary particle physics. His research focuses on the earliest moments of creation, and he has made important contributions to inflationary cosmology, particle dark matter and structure formation, the theory of big bang nucleosynthesis, and the nature of dark energy.

TURNER: Ten years ago, I don't think you would've found astronomers, cosmologists, and particle physicists all agreeing that dark matter was really important. And now, they do. And all of them believe we can solve the problem soon. It's wonderful listening to particle physicists explain the evidence for dark matter, and vice versa -astronomers explaining WIMPs as dark matter. At this meeting nobody said, "Oh, I don't really believe in the evidence. Nor did anyone say, "Yikes - a new form of matter. That's crazy."

MARIA SPIROPULU: One important thing we've seen at this meeting is a crossing of professional boundaries that have separated researchers in many different fields in the past. These boundaries have been strict. Cosmologists, astrophysicists and particle physicists, however, have now really started talking to one another about dark matter. We're only beginning and our language - the way speak to each other - is not yet settled so that we completely understand each other; but we are on the threshold of discovering something very important for all of us. This is critical because cosmologists and particle physicists have talked for a long time about how the very big and very small might be linked. And while the particle physicists study the very small with colliders, cosmologists study the galaxies and billions and billions of stars that make up the large-scale structure we see in the universe.

KOLB: Ten years ago, it was "Call me maybe" and now it's ...

TURNER: "Let's do lunch."

SPIROPULU: Yes, it's, "Let's do lunch and talk physics."

TURNER: I do want to make one point: the convergence of inner space and outer space really started in the 1980s. Back then it began with the origin of the baryon asymmetry, the monopole problem and dark matter to a lesser extent. Particle physicists agreed that dark matter was a real problem but said, "The solution could be astrophysics - faint stars, 'Jupiters', black holes and the like." It's been a long road to get to where we are now, namely where we all agree that the most compelling solution is particle dark matter. And even today, the different fields are still, in a sense, getting to know one another.

TKF: Let's cover a few basics. Why is the question of dark matter important?


"Rocky" Kolb - A professor of Astronomy & Astrophysics at the University Of Chicago, "Rocky" Kolb is a member of the Enrico Fermi Institute and the Kavli Institute for Cosmological Physics, studies the application of elementary-particle physics to the very early Universe. He is the co-author with Michael Turner of The Early Universe, the standard textbook on particle physics and cosmology.

KOLB: As cosmologists, one of our jobs is to understand what the universe is made of. To a good approximation, the galaxies and other structures we see in the universe are made predominantly of dark matter. We have concluded this from a tremendous body of evidence, and now we need to discover what exactly is dark matter. The excitement now is that we are closing in on an answer, and only once in the history of humans will someone discover it. There will be some student or postdoc or experimentalist someplace who is going to look in the next 10 years at their data, and of the seven or so billion people in the world that person will discover what galaxies are mostly made of. It's only going to happen once.

TURNER: The dark matter story started with fragmentary evidence discovered by Fritz Zwicky, a Swiss American. He found that there were not enough stars in the galaxy clusters he observed to hold them together. Slowly, more was understood and finally dark matter became a centerpiece of cosmology. And now, we have established that dark matter is about 23 percent of the universe; ordinary matter is only 4.5 percent; and dark energy is that other 73 percent - which is an even bigger puzzle.

Nothing in cosmology makes sense without dark matter. We needed it to form galaxies, stars and other structures in the Universe. And so it's absolutely central to cosmology. We also know that none of the particles known to exist can be the dark matter particle. So it has to be a new particle of nature. Remarkably, our most conservative hypothesis right now is that the dark matter is a new form of matter - out there to be discovered and to teach us about particle physics.


Maria Spiropulu - A Professor of Physics at the California Institute of Technology (Caltech) in Pasadena, CA. An experimental particle physicist, Spiropulu is interested in the search for dark matter at the Large Hadron Collider at CERN (The European Organization for Nuclear Research), and questions about dark matter that cut across particle physics, astrophysics and cosmology. Spiropulu was previously a senior physics researcher in the Physics Department at CERN from 2004-2012. She was also an Enrico Fermi Fellow from 2001-2004.

SPIROPULU: I just want to say one thing. The phenomenon of dark matter was discovered from astronomical observations. We know that galaxies hang together and they don't fly apart, and it's the same with clusters of galaxies. So we know that we have structure in the universe. Whatever it is that keeps it there, in whatever form it is, we call that dark matter. This is the way I teach it to undergraduates. It's a fantastical story. It's still a mystery and so it's "dark," but the universe and its structures - galaxies and everything else we observe in the macroscopic world - are being held together because of it.

TKF: Dark matter is often described in the media as something that is inferred because of its gravitational effects on ordinary matter. But the case for dark matter is much more expansive than that, as astrophysicist Jeremiah [Jerry] Ostriker from Princeton University said at this meeting.

TURNER: Absolutely. Dark matter is absolutely central to cosmology and the evidence for it comes from many different measurements: the amount of deuterium produced in the big bang, the cosmic microwave background, the formation of structure in the Universe, galaxy rotation curves, gravitational lensing, and on and on. Jerry said that as far as he is concerned, the dark matter problem has been solved. And that's because this idea that dark matter is just a swarm of particles that are very shy, that rarely interact with ordinary matter and then only weakly, works perfectly. And at the end of his talk, he said, as a kind of footnote: "By the way, I would be interested in knowing what the dark matter is." This is a testimony to how central dark matter is to cosmology and culturally to how particle physicists and astrophysicists look at dark matter differently. Dr. Gross, the particle physicist, wanted to know what dark matter is made of.


The Search for Dark Matter
What is dark matter? We don't know, but cosmologists, astrophysicists and experimental particle physicists say they are closing in on an answer. Read a short explanation of what scientists consider the leading candidate, as well as the methods being used to detect dark matter.

TKF: So for Dr. Ostriker, knowing exactly what dark matter is is less important than the work done already - measuring its gravitational influence on ordinary matter, estimating how much of the universe is made from it, and affirming that what we do know about it fits with the standard model of cosmology.

TURNER: That was Jerry's point, yes. There is five times more dark matter than ordinary matter, and its existence allows us to understand the history of the universe beginning from a formless particle soup until where we are today. If you said, "You no longer have dark matter," our current cosmological model would collapse. We would be back to square one.

TKF: Dr. Ostriker also argued that we should be open to dark matter being a variety of fundamental particles and not only WIMPs. Other possibilities could be neutrinos and axions.

TURNER: Because he doesn't care what it is. They all work equally well. The flip side is that cosmology tells us little about dark matter except it is cold.

TKF: Do they all work equally well for each of you?

KOLB: Well, for cold dark matter - which is made from particles that move slowly compared with the speed of light, and is the kind needed for forming galaxies and galaxy clusters - they all work equally well. The thing about the WIMP, as opposed to some of these other candidate particles, is that it's a very compelling possibility we can test right now. So we don't have to wait for the next 30 years or the next century, as we might if we were trying to detect another type of hypothesized particle. We don't have to build an accelerator larger than LHC.

It's a magical moment when astronomers, astrophysicists, string theorists, particle experimentalists and cosmologists get together because they all have a common purpose. There is a common problem that excites them.

TKF: What makes you most optimistic that we're on the threshold of discovery?

KOLB: First of all, the hypothesis that dark matter is made up of WIMPs - and that it was produced by normal particles, say quarks, in the early universe - is an amazing achievement all by itself. Independent of a lot of the details of what goes on there and exactly how that happens, we expect that you should be able to reverse things and produce WIMPs in particle accelerators. We also expect they should be annihilating today in the galaxy, which we should be able to detect indirectly. Now, it's another issue who will be the first to find WIMPs. It's possible that it will be another 30 years before we do that, but we should be able to make a detection - whether it's direct or indirect.

SPIROPULU: With the Large Hadron Collider, and before that the Tevatron collider, we have been chasing and targeting the dark matter candidate. For us, the optimism is because the LHC is working and we're collecting a lot of data. In the standard model of particle physics, when we enlarge it to help explain how the universe began and evolved, we have a story that is a mathematical story. It's very good at describing how we can have dark matter. And if the mathematics accurately describes reality, then the LHC is now achieving the energies that are needed to produce dark matter particles.

Getting to these high energies is critical, and we are even going to higher energies. When we were building the standard model of particle physics, we kept saying that the next particle discovery that we predicted was "right around the corner." In other words, we were not, and we are not, flying in the dark. We are guided by a huge amount of data and knowledge, and while you might think there are infinite possibilities of what can happen, the data actually points you to something that is more probable. For example, we have found the Higgs-like particle, but that was predicted. So the next big step for this edifice of knowledge is to find something that will look like supersymmetry - a hypothesis that, if true, offers a perfect candidate for dark matter. We call it a miracle, because the mathematics works. But the way nature works, in the end, is what you see in the data. So if we find it, there is no miracle.


"Cosmologists, astrophysicists and particle physicists have now really started talking to one another about dark matter. We're only beginning and our language - the way speak to each other - is not yet settled... but we are on the threshold of discovering something very important for all of us. - Maria Spiropulu

TURNER: These dark matter particles, or WIMPs, don't interact with ordinary matter often. It's taken 25 years to improve the sensitivity of our detectors by a factor of a million, and now they have a good shot at detecting the dark matter particles. Because of the technological developments, we think we are on the cusp of a direct detection.

Likewise for indirect detection. We now have instruments like the Fermi satellite (the Fermi Gamma-ray Space Telescope) and the IceCube detector (the IceCube Neutrino Observatory at the South Pole) that can detect the ordinary particles (positrons, gamma rays or neutrinos) that are produced when dark matter particles annihilate, indirectly allowing dark matter to be detected. IceCube is big enough to detect neutrinos that are produced by dark matter annihilations in the sun.

TKF: A few people over the past two days have said the dark matter particle might not be detectable.

TURNER: For many of us, for 20 to 30 years, this idea that dark matter is part of a unified theory has been our Holy Grail and has led to the WIMP hypothesis and the belief that the dark matter particle is detectable. But there's a new generation of physicists that is saying, "Well, there's an alternative view. Dark matter is actually just the tip of an iceberg of another world that is unrelated to our world. And I cannot even tell you about that world. There are no rules for that other world, at least that we know of yet." Sadly, this point of view could be correct and might mean the solution to the dark matter problem is still very far away. That is what led Jerry to say that discovering what dark matter actually is could be 100 years away.

TKF: Michael Witherell, Professor of Physics at the University of California, Santa Barbara, also said that nature doesn't guarantee an observation.

TURNER: Also true. But we have the WIMP hypothesis and it is falsifiable. And there's a good chance it's true. A "good chance" in this business means 10 percent or 20 percent. But when you're trying to solve a problem of this magnitude, if you have a 10-20 percent chance, I say let's double down on that.

TKF: When do you predict we'll detect WIMPs?

KOLB: It's easy to say, "A decade." LHC is turning on now. It'll be another year or so before they are at full energy, and they may run a couple of years to accumulate data. Meanwhile, the Fermi satellite is in space making observations. And then we have experiments underground: a detection may come with Xenon100, one dark matter experiment now underway in central Italy, or some successor to Xenon100.

TKF: And programs like LUX, the Large Underground Xenon dark matter experiment in South Dakota, are just coming online.

KOLB: In ten years, if there is no indication of supersymmetry or a WIMP - either from direct detection or indirect detection searches - then there is going to be a sea change. Now, there is not going to be one experiment announcement that says, "OK, let's look at something else." But if ten years from now there is no evidence, then we are going to other possibilities. You could not have said that ten years ago, or even five years ago. Today, I think you can say that.

TKF: Because we have so much work behind us and have already eliminated numerous possibilities.

KOLB: As in Ghostbusters, we have the tools. We have the talent.

SPIROPULU: I think it's fair to say the discovery is "around the corner." If we continue with exclusions, then we have to come up with better ideas. We are doing all this because we want to characterize dark matter. We are not just saying, "It is dark matter." We don't want to just say, "The universe is." We want to know exactly what it is made of. We want to know the dynamics and what it involves. A lot of work is ahead of us. Somebody said that it's not going to be as easy as finding the Higgs. Well, finding the Higgs was extremely nontrivial. Of course, once we find it, it goes in the pool of knowledge and then you say, "Well, it was easy."


"[W]e need to discover what exactly is dark matter. The excitement now is that we are closing in on an answer, and only once in the history of humans will someone discover it." - Rocky Kolb

TKF: Painting a picture for the general public about how incredible it would be to discover a WIMP is challenging. How do you convey just how sensitive this measurement would be?

TURNER: I keep saying these particles are very shy. Here's one way to think about this: if you had 100 kilograms of material, one of these shy particles - one of these WIMPS - would interact with that 100 kg once in a year or even less often. So you really have to build very sensitive detectors. Because of the cosmic rays and other particles that light up your detector and obscure the WIMP signal you're looking for, you have to put WIMP detectors underground. And even underground you still get natural radioactivity clouding your signal, so you have to discriminate against that as well.

Now, we also expect there's a seasonal modulation in the dark matter signal as the Earth orbits the sun through the sea of dark matter particles that permeate space. The modulation signal is expected to be only a few percent of the rare, dark-matter signal I talked about a minute ago. We do have the equipment in place to make these detections, but we just need Nature to cooperate.

KOLB: It's a fantastical story. One hundred years ago, if I told you that we are surrounded by these invisible particles and they're passing through us - you don't feel them yet they form the entire structure of the universe - you would have locked me up.

TKF: Do any of you expect that learning about dark matter will help us also learn about the other big mystery in cosmology - dark energy?

KOLB: Possibly nothing. It depends on what the answer will be. It is possible it won't shed any light on the nature of dark energy.

TURNER: There are two views. One is a conservative view, which is that dark matter is just made up of particles that don't give off light. It's just particles that happened to be more important than the stuff that we are made out of, which we only discovered in the past 70 years. And dark energy is a new problem that is unrelated.

TKF: And the only thing they share at this point is being unknown?

TURNER: That's right. The conservative point of view is that dark energy is unrelated to dark matter. Recall, dark energy is the stuff that is causing the universe to speed up. This is the simple view where we are solving problems one at a time.

A more radical view which we heard about at this meeting from Erik Verlinde (from the University of Amsterdam) is, "You know, guess what? Don't you guys get it? The two of them are related. It has nothing to do with particles. It's something much, much bigger. The two are related and are pointing to a much richer explanation. You are trying to explain things in a simple-minded way: dark matter particles and dark energy. Just like Ptolemy's epicycles (the epicycles of Claudius Ptolemy, a Greek astronomer who lived in Alexandria, Egypt under Roman rule, is a false construction of an Earth-centered universe, specifically describing the observed retrograde motion of planets), a desperate attempt to make a wrong hypothesis work.

And so those are the two extremes. One is that we are just about to solve dark matter and then we will go on to dark energy and they're probably not related; the other is that together, they make this big flashing sign: You guys really need to sit down and reconsider the whole framework.

SPIROPULU: I think it's worth noting that the dark sector (i.e. dark matter and dark energy) has to do with gravity. They are linked via gravity. Gravity is a force that in particle physics we have not been able to put together with the rest of the forces. Somehow, if you could stand outside the universe - that's an absurd statement, of course - but stand outside it and see how everything relates, you could say something about the dark sector and gravity.

TURNER: You're right that gravity could be the connector, because in cosmology and astrophysics gravity is the most important force. In particle physics, it's the least important force. Consequently particle physicists are just getting around to worrying about it, and in cosmology we mostly worry about gravity. And so now, we have come together because of a common interest in gravity - gravity revealed to us through dark matter and dark energy.

SPIROPULU: Here we are, with dark matter between us. It's a beautiful story of how we are trying to solve the problems, the challenges of characterizing our physical world.

KOLB: Dark matter holds together the galaxies. It holds together cosmologists and particle physicists.

TURNER: We know that Einstein didn't get the last word on gravity, because his theory doesn't have quantum mechanics in it. And so any problem that involves gravity, you are thinking, nervously and excitedly, that this could be the clue to the grander theory of gravity.

KOLB: I don't think the general public appreciates that we would love to find something wrong with what we think about the universe, about the laws of nature. And that's because it points the way toward new discoveries. I don't think most people work that way, thinking that, "Boy, I would love to be shown that I'm wrong about something that I really thought was true for 30 years or 100 years."


"[T]he universe is vast....but we are at a point in time where we really think we understand it and that we can identify what dark matter is. ...This is the time to be a dark cosmologist." - Michael Turner

TURNER: We want new puzzles.

SPIROPULU: Always. And I have to say that in particle physics, there is a list of experiments and projects that have been built in the past 30 years that did not find what they were built for. None. They found other things, other important things. It's incredible. One example of this is the Hubble Space Telescope, which has revealed more about the universe than we ever could have imagined when it was conceived. The series of deep field images of the very distant universe, which has given us glimpses of the earliest galaxies, is just one example of this. So, when you write a proposal for something and you say what you are building it for, and you get the money and you go and build it and you find something completely unexpected - Wow. Our physical world is surprising. And it's very surprising that we can get it, even at the level we do. Or that we can do the experiments that we do.

TURNER: I think the universe is vast. It's often beyond the reach of our instruments and our minds, but we are at a point in time here where we really think we understand it and that we can identify what dark matter is. We have an accounting of the universe and a compelling hypothesis for dark matter. It is not unexpected that the younger generation of scientists wants a more radical solution to dark matter. The older generation developed the WIMP hypothesis, and this is our solution and we want to see it come true. The younger generation wants the excitement of solving a problem.

TKF: Would any of you trade this point in time with another in the history of physics?

KOLB: No, no. For dark matter, I think this is the time. I can't see everything converging at another time like it is now.

TURNER: This is the time to be a dark cosmologist.


- Fall 2012

Read more >>

Related Links:
KICP Members: Edward W. Kolb; Michael S. Turner