The Core Rocks!

Fig. 1. A simulated X-ray image and its residual image

One of the X-ray surface brightness profiles produced by their numerical simulation (left) and its X-ray residual image after removing its global profile calculated by their novel algorithm (right). Left: Brighter colors (e.g., red and white) and darker colors (e.g., blue) correspond to the bright and faint regions of the X-ray surface brightness, respectively. The cluster center is the center of this image. The white contours show the shape of the dark matter halo. Right: Brighter colors (e.g., red and white) and darker colors (e.g., blue) correspond to the larger positive and negative excess in the X-ray residual image. The white and black areas show the positive and negative excess regions detected by their novel algorithm. The shape of both regions look like spiral, which is a well-known feature of sloshing gas. Credit: Ueda Shutaro/ASIA

Fig. 2. One of the observed X-ray images in our cluster sample and its residual image.

One of the X-ray surface brightness profiles produced by their numerical simulation (left) and its X-ray residual image after removing its global profile calculated by their novel algorithm (right). Left: Brighter colors (e.g., red and white) and darker colors (e.g., blue) correspond to the bright and faint regions of the X-ray surface brightness, respectively. The cluster center is the center of this image. The white contours show the shape of the dark matter halo. Right: Brighter colors (e.g., red and white) and darker colors (e.g., blue) correspond to the larger positive and negative excess in the X-ray residual image. The white and black areas show the positive and negative excess regions detected by their novel algorithm. The shape of both regions look like spiral, which is a well-known feature of sloshing gas. Credit: Ueda Shutaro/ASIAA

Hunting the sloshing gas in the center of massive galaxy clusters

Galaxy clusters are the largest gravitationally bound objects in the universe. While it is well known that all galaxy clusters all galaxy clusters have experienced mergers and collisions through gravitational interactions, how mergers affect the evolution of galaxy clusters is still a mystery. Previous studies conducted by ASIAA astronomers including Dr. Shutaro Ueda have pointed out that “sloshing gas” holds the key to the answers. Now, the team led by Dr. Ueda has systematically evidenced that sloshing gas does exist in all of their clusters sample. The result strongly supports that mergers can always affect the evolution of galaxy clusters and their impacts brought to the entire galaxy clusters can last for a long time.

Dr. Ueda says: "We have analyzed 12 clusters and discovered sloshing gas in all of them. This progress may critically help our understanding towards the cool cores in cluster centers."

"The presence of cool cores is one of is one of the long-standing, well-known problems in astrophysics. They are found in the center of most of the galaxy clusters, the reason we call it "cool core" is because the temperature of the ICM in the center is cooler than that in the surroundings" Dr. Ueda continues: “Indeed, it is very difficult to keep the ICM “relatively-cool” for a long time. If gas temperature becomes low, gas pressure also decreases. Eventually, cool cores must be collapsed quickly. But galaxy clusters have no such collapsing cores, which means that they must have some hidden processes to prevent the collapses. Sloshing gas is one of the clues to trace down this problem.

Explaining how to spot sloshing gas, Dr. Ueda says, "Sloshing gas creates gas density perturbations in the center of galaxy clusters which also attributes a specific pattern of temperature profile. Therefore, spotting these differences is a well-known tool for identifying sloshing gas." The team selected 12 clusters out of CLASH, a world-famous pool for high-mass galaxy clusters images, taken by the Hubble Space Telescope. By analyzing their X-ray images taken by the Chandra X-ray Observatory, the team detected gas density perturbations in all of the selected clusters. They also measured the gas temperature difference. The results are in good agreement with what sloshing gas should look like.

In addition, to test how well their algorithm performs in detecting gas density perturbations and in identifying where those regions locate, the team used synthetic X-ray observations made by a hydrodynamic simulation.

Dr. Sandor M. Molnar from ASIAA performed a hydrodynamical simulation of a cluster merger to compare with observations. Dr. Molnar said “Numerical simulations are very powerful tools to understand astrophysics. They can be used to visualize and follow all of physical phenomena that human beings cannot see in their lifetime, namely, for example those, which are happening in colliding galaxy clusters during cosmological time-scale, billions of years. In addition, computer simulations enable us to identify the most important physical mechanisms which can reproduce the observational data and to check for biases in our analysis methods of real data. Thanks to the powerful computing resources at the National Center for High-Performance Computing in Taiwan, we succeeded in calculating physical parameters with very high angular resolution.” 

The team is planning a larger number of numerical simulations that may reproduce many types of galaxy clusters. Dr. Ueda explains: “Expanding the number of our cluster samples can reveal how many galaxy clusters host sloshing gas. This information allows us to estimate a lifetime of sloshing gas, which is a key parameter not only to improve our simulations but also to study the property of the ICM.”

Article author: Dr. Shutaro Ueda

Edited by: Lauren Huang

Reviewed by: Dr. Keiichi Umetsu

Source: Academia Sinica Institute of Astronomy and Astrophysics (AASIA)

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Glossary:

Sloshing Gas: Almost all galaxy clusters experience mergers. When a merger takes place, a specific pattern of "spiral" often can be observed in X-ray images. Such a spiral feature is due to the motion of the gas, the so-called "sloshing gas" - induced by a merger. At the beginning of the sloshing gas study, spiral features had been the only recognizable evidence. Later on, in studies like this one, astronomers started using numerical simulations to investigate identifiable evidence of sloshing gas. By now there have been two evidence features that people can look for sloshing gas with.

ICM: the acronym for Intracluster medium, ICM is the superheated plasma that permeates a galaxy cluster. The gas consists mainly of ionized hydrogen and helium and accounts for most of the baryonic material in galaxy clusters. The ICM is heated to temperatures on the order of 10 to 100 mega kelvins, emitting strong X-ray radiation.

CLASH: Acronym for Cluster Lensing And Supernova survey with Hubble, CLASH is one of three first class Hubble multi-cycle treasury programs designed to tackle large questions unanswerable through normal observations. Observations for CLASH were conducted on the Hubble Space Telescope with images taken in 16 filters, selected to maximize the ability to detect distant galaxies behind each cluster.

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Notes:

Paper and Research Team

The paper was published as “Gas Density Perturbations in the Cool Cores of CLASH Galaxy Clusters” in Astrophysical Journal, Volume 892, Number 2

The team members are: Shutaro Ueda, Yuto Ichinohe, Sandor M. Molnar, Keiichi Umetsu, and Tetsu Kitayama

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Background Information

• Novel Technique turns Chandra/ ALMA images into a "Speedometer" for Sloshing Gas
• National Center for High-Performance Computing (Official website)

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Hubble Captures Massive Dead Disk Galaxy that Challenges Theories of Galaxy Evolution

Galaxy Cluster MACS J2129-0741 and Lensed Galaxy MACS2129-1

Credits: Science: NASA, ESA, and S. Toft (University of Copenhagen)

Acknowledgment: NASA, ESA, M. Postman (STScI), and the CLASH team

Released images

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Young, Dead, Compact, Disk Galaxy Surprises Astronomers, Offers New Clues to How Modern-Day Elliptical Galaxies Formed

By combining the power of a "natural lens" in space with the capability of NASA's Hubble Space Telescope, astronomers made a surprising discovery—the first example of a compact yet massive, fast-spinning, disk-shaped galaxy that stopped making stars only a few billion years after the big bang.

Finding such a galaxy early in the history of the universe challenges the current understanding of how massive galaxies form and evolve, say researchers.

When Hubble photographed the galaxy, astronomers expected to see a chaotic ball of stars formed through galaxies merging together. Instead, they saw evidence that the stars were born in a pancake-shaped disk.

This is the first direct observational evidence that at least some of the earliest so-called "dead" galaxies — where star formation stopped — somehow evolve from a Milky Way-shaped disk into the giant elliptical galaxies we see today.

This is a surprise because elliptical galaxies contain older stars, while spiral galaxies typically contain younger blue stars. At least some of these early "dead" disk galaxies must have gone through major makeovers. They not only changed their structure, but also the motions of their stars to make a shape of an elliptical galaxy.

"This new insight may force us to rethink the whole cosmological context of how galaxies burn out early on and evolve into local elliptical-shaped galaxies," said study leader Sune Toft of the Dark Cosmology Center at the Niels Bohr Institute, University of Copenhagen, Denmark. "Perhaps we have been blind to the fact that early "dead" galaxies could in fact be disks, simply because we haven't been able to resolve them."

Previous studies of distant dead galaxies have assumed that their structure is similar to the local elliptical galaxies they will evolve into. Confirming this assumption in principle requires more powerful space telescopes than are currently available. However, through the phenomenon known as "gravitational lensing," a massive, foreground cluster of galaxies acts as a natural "zoom lens" in space by magnifying and stretching images of far more distant background galaxies. By joining this natural lens with the resolving power of Hubble, scientists were able to see into the center of the dead galaxy.

The remote galaxy is three times as massive as the Milky Way but only half the size. Rotational velocity measurements made with the European Southern Observatory's Very Large Telescope (VLT) showed that the disk galaxy is spinning more than twice as fast as the Milky Way.

Using archival data from the Cluster Lensing And Supernova survey with Hubble (CLASH), Toft and his team were able to determine the stellar mass, star-formation rate, and the ages of the stars.

Why this galaxy stopped forming stars is still unknown. It may be the result of an active galactic nucleus, where energy is gushing from a supermassive black hole. This energy inhibits star formation by heating the gas or expelling it from the galaxy. Or it may be the result of the cold gas streaming onto the galaxy being rapidly compressed and heated up, preventing it from cooling down into star-forming clouds in the galaxy's center.

But how do these young, massive, compact disks evolve into the elliptical galaxies we see in the present-day universe? "Probably through mergers," Toft said. "If these galaxies grow through merging with minor companions, and these minor companions come in large numbers and from all sorts of different angles onto the galaxy, this would eventually randomize the orbits of stars in the galaxies. You could also imagine major mergers. This would definitely also destroy the ordered motion of the stars."

The findings are published in the June 22 issue of the journal Nature. Toft and his team hope to use NASA's upcoming James Webb Space Telescope to look for a larger sample of such galaxies.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.

The Very Large Telescope is a telescope facility operated by the European Southern Observatory on Cerro Paranal in the Atacama Desert of Northern Chile.

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Related Links

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• The science paper by S. Toft et al.
• NASA's Hubble Portal
• CLASH Project Website
• Journal Nature

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Contacts

Ann Jenkins / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4514
jenkins@stsci.edu / villard@stsci.edu

Sune Toft
Dark Cosmology Center, Niels Bohr Institute,
University of Copenhagen, Copenhagen, Denmark
sune@dark-cosmology.dk

Source: HubbleSit

NASA's Hubble Finds Evidence of Galaxy Star Birth Regulated by Black-Hole Fountain

CLASH Survey Brightest Cluster Galaxies and Simulations

In this comparison of actual observations with simulations, the top images show Hubble observations of the density of gas in the central portion of two galaxies. The bottom images are computer simulations that are remarkably similar to the Hubble observations. Knots of star formation in the two galaxies show how gas falling into a galaxy's center is controlled by jets from the central black hole. Credit: NASA, ESA, M. Donahue (Michigan State University), and Y. Li (University of Michigan)

Astronomers have uncovered a unique process for how the universe's largest elliptical galaxies continue making stars long after their peak years of star birth. NASA's Hubble Space Telescope's exquisite high resolution and ultraviolet-light sensitivity allowed the astronomers to see brilliant knots of hot, blue stars forming along the jets of active black holes found in the centers of giant elliptical galaxies.

Combining Hubble data with observations from a suite of ground-based and space telescopes, two independent teams found that the black hole, jets, and newborn stars are all parts of a self-regulating cycle. High-energy jets shooting from the black hole heat a halo of surrounding gas, controlling the rate at which the gas cools and falls into the galaxy.

"Think of the gas surrounding a galaxy as an atmosphere," explained the lead of the first study, Megan Donahue of Michigan State University. "That atmosphere can contain material in different states, just like our own atmosphere has gas, clouds, and rain. What we are seeing is a process like a thunderstorm. As the jets propel gas outward from the center of the galaxy, some of that gas cools and precipitates into cold clumps that fall back toward the galaxy's center like raindrops."

"The 'raindrops' eventually cool enough to become star-forming clouds of cold molecular gas, and the far-ultraviolet capabilities of Hubble allowed us to directly observe these 'showers' of star formation," explained the lead of the second study, Grant Tremblay of Yale University. "We know that these showers are linked to the jets because they're found in filaments and tendrils that wrap around the jets or hug the edges of giant bubbles that the jets have inflated," said Tremblay. "And they end up making a swirling 'puddle' of star-forming gas around the central black hole."

But what should be a monsoon of raining gas is reduced to a mere drizzle by the black hole. While some outwardly flowing gas will cool, the black hole heats the rest of the gas around a galaxy, which prevents the whole gaseous envelope from cooling more quickly. The entire cycle is a self-regulating feedback mechanism, like the thermostat on a house's heating and cooling system, because the "puddle" of gas around the black hole provides the fuel that powers the jets. If too much cooling happens, the jets become more powerful and add more heat. And if the jets add too much heat, they reduce their fuel supply and eventually weaken.

This discovery explains the mystery of why many elliptical galaxies in the present-day universe are not ablaze with a higher rate of star birth. For many years, the question has persisted of why galaxies awash in gas don't turn all of that gas into stars. Theoretical models of galaxy evolution predict that present-day galaxies more massive than the Milky Way should be bursting with star formation, but that is not the case.

Now scientists understand this case of arrested development, where a cycle of heating and cooling keeps star birth in check. A light drizzle of cooling gas provides enough fuel for the central black hole's jets to keep the rest of the galaxy's gas hot. The researchers show that galaxies don't need fantastic and catastrophic events such as galaxy collisions to explain the showers of star birth they see.

The study led by Donahue looked at far-ultraviolet light from a variety of massive elliptical galaxies found in the Cluster Lensing And Supernova Survey with Hubble (CLASH), which contains elliptical galaxies in the distant universe. These included galaxies that are raining and forming stars, and others that are not. By comparison, the study by Tremblay and his colleagues looked at only elliptical galaxies in the nearby universe with fireworks at their centers. In both cases, the filaments and knots of star birth appear to be very similar phenomena. An earlier, independent study, led by Rupal Mittal of the Rochester Institute of Technology and the Max Planck Institute for Gravitational Physics, also analyzed the star-birth rates in the same galaxies as Tremblay's sample.

The researchers were aided by an exciting, new set of computer simulations of the hydrodynamics of the gas flows developed by Yuan Li of the University of Michigan. "This is the first time we now have models in hand that predict how these things ought to look," explained Donahue. "And when we compare the models to the data, there's a stunning similarity between the star-forming showers we observe and ones that occur in simulations. We're getting a physical insight that we can then apply to models."

Along with Hubble, which shows where the old and the new stars are, the researchers used the Galaxy Evolution Explorer (GALEX), the Herschel Space Observatory, the Spitzer Space Telescope, the Chandra X-ray Observatory, the X-ray Multi-Mirror Mission (XMM-Newton), the National Radio Astronomy Observatory (NRAO)'s Jansky Very Large Array (JVLA), the National Optical Astronomy Observatory (NOAO)'s Kitt Peak WIYN 3.5-meter telescope, and the Magellan Baade 6.5-meter telescope. Together these observatories paint the complete picture of where all of the gas is, from the hottest to the coldest. The suite of telescopes shows how galaxy ecosystems work, including the black hole and its influence on its host galaxy and the gas surrounding that galaxy.

Donahue's paper was published in the Astrophysical Journal on June 2, 2015. Tremblay's paper was published in the Monthly Notices of the Royal Astronomical Society on June 29, 2015.

Contact

Ann Jenkins / Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4514
jenkins@stsci.edu / villard@stsci.edu

Megan Donahue
Michigan State University, East Lansing, Michigan
donahue@pa.msu.edu

Grant Tremblay
Yale University, New Haven, Connecticut
grant.tremblay@yale.edu

Source: HubbleSite

Hubble Astronomers Check the Prescription of a Cosmic Lens

MACSJ1720, MACS J1720.2+3536

Release Images

 

What could be more exciting than watching the fireworks of cataclysmic stellar explosions outshining entire galaxies of stars? How about watching them through the funhouse lens of a massive cluster of galaxies whose powerful gravity warps space around it?

In fact, distant exploding stars observed by NASA's Hubble Space Telescope are providing astronomers with a powerful tool to check the prescription of these natural "cosmic lenses," which are used to provide a magnified view of the remote universe.

Two teams of astronomers working independently have found three such exploding stars, called supernovae, far behind massive clusters of galaxies. Their light was amplified and brightened by the immense gravity of the foreground clusters in a phenomenon called gravitational lensing. First predicted by Albert Einstein, this effect is similar to a glass lens bending light to form an image. Astronomers use the gravitational-lensing technique to search for distant objects that might otherwise be too faint to see, even with today's largest telescopes.

Astronomers from the Supernova Cosmology Project and the Cluster Lensing And Supernova survey with Hubble (CLASH), are using these supernovae in a new method to check the predicted magnification, or prescription, of the gravitational lenses. Luckily, two and possibly all three of the supernovae appear to be a special type of exploding star called Type Ia supernovae, prized by astronomers because they provide a consistent level of peak brightness that makes them reliable for making distance estimates.

"Here we have found Type Ia supernovae that can be used like an eye chart for each lensing cluster," explained Saurabh Jha of Rutgers University in Piscataway, N.J., a member of the CLASH team. "Because we can estimate the intrinsic brightness of the Type Ia supernovae, we can independently measure the magnification of the lens, unlike for other background sources."

Having a precise prescription for a gravitational lens will help astronomers probe objects in the early universe and better understand a galaxy cluster's structure and its distribution of dark matter, say researchers. Dark matter cannot be seen directly but is believed to make up most of the universe's matter.

How much a gravitationally lensed object is magnified depends on the amount of matter in a cluster, including dark matter, which is the source of most of a cluster's gravity. Astronomers develop maps that estimate the location and amount of dark matter in a cluster based on theoretical models and on the observed amplification and bending of light from sources behind the cluster. The maps are the lens prescriptions that predict how distant objects behind the cluster are magnified when their light passes through it.

"Building on our understanding of these lensing models also has implications for a wide range of key cosmological studies," explained Supernova Cosmology Project leader Saul Perlmutter of the E.O. Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley. "These lens prescriptions yield measurements of the cluster masses, allowing us to probe the cosmic competition between gravity and dark energy as matter in the universe gets pulled into galaxy clusters." Dark energy is a mysterious, invisible energy that is accelerating the universe's expansion.

The three supernovae in the Hubble study were each gravitationally lensed by a different cluster. The teams measured the brightnesses of the lensed supernovae and compared them to the explosions' intrinsic brightnesses to calculate how much they were magnified due to gravitational lensing. One supernova in particular stood out, appearing to be about twice as bright as would have been expected if not for the cluster's magnification power.

The supernovae were discovered in the CLASH survey, a Hubble census that probed the distribution of dark matter in 25 galaxy clusters. Two of the supernovae were found in 2012, the other in 2010. The three supernovae exploded between 7 billion and 9 billion years ago, when the universe was slightly more than half its current age of 13.8 billion years old.

To perform their analyses, both teams of astronomers used observations in visible light from Hubble's Advanced Camera for Surveys and in infrared light from the Wide Field Camera 3. The research teams also obtained spectra from both space and ground-based telescopes that provided independent estimates of the distances to these exploding stars. In some cases the spectra allowed direct confirmation of a Type Ia pedigree. In other cases the supernova spectrum was weak or overwhelmed by the light of its parent galaxy. In those cases the astronomers also used different colored filters on Hubble to help establish the supernova type.

Each team then compared its results with independent theoretical models of the clusters' dark-matter content, concluding that the predictions fit the models.

"It is encouraging that the two independent studies reach quite similar conclusions," explained Supernova Cosmology Project team member Jakob Nordin of Berkeley Lab and the University of California, Berkeley. "These pilot studies provide very good guidelines for making future observations of lensed supernovae even more accurate." Nordin also is the lead author on the team's science paper describing the findings.

Now that the researchers have proven the effectiveness of this method, they need to find more Type Ia supernovae behind behemoth lensing galaxy clusters. In fact, the astronomers estimate they need about 20 supernovae spread out behind a cluster so they can map the entire cluster field and ensure that the lens model is correct.

They are optimistic that Hubble and future telescopes, including NASA's James Webb Space Telescope, an infrared observatory, will nab more of these unique exploding stars.

"Hubble is already hunting for them in the Frontier Fields, a three-year Hubble survey of the distant universe using massive galaxy clusters as gravitational lenses," said CLASH team member Brandon Patel of Rutgers University, the lead author on the science paper announcing the CLASH team's results. Steven Rodney of Johns Hopkins University, and co-leader of the CLASH supernova team, will direct the search for Type Ia supernovae in the Frontier Fields data.

The CLASH team's results will appear in the May 1 issue of The Astrophysical Journal and the Supernova Cosmology Project's findings in the May 1 edition of the Monthly Notices of the Royal Astronomical Society.

The CLASH survey is led by Marc Postman of the Space Telescope Science Institute in Baltimore, Md. The CLASH supernova project is co-led by Rodney and Adam Riess of the Space Telescope Science Institute and Johns Hopkins University. Aiding with the analysis on the Hubble study are Curtis McCully of Rutgers University, Or Graur of the American Museum of Natural History in New York City, and Julian Merten and Adi Zitrin of the California Institute of Technology in Pasadena.

Other members of the Supernova Cosmology Project who worked on the supernova analysis are David Rubin of Florida State University in Tallahassee and Greg Aldering of Berkeley Lab. The project's galaxy cluster models were created by Johan Richard of the University of Lyon in France and Jean-Paul Kneib of École Polytechnique Fédérale de Lausanne in Switzerland.

Image Credits:

Credit: NASA, ESA, S. Perlmutter (UC Berkeley, LBNL), A. Koekemoer (STScI), M. Postman (STScI), A. Riess (STScI/JHU), J. Nordin (LBNL, UC Berkeley), D. Rubin (Florida State University), and C. McCully (Rutgers University)

Photo Credit: NASA, ESA, S. Perlmutter (UC Berkeley, LBNL), A. Koekemoer (STScI), M. Postman (STScI), A. Riess (STScI/JHU), J. Nordin (LBNL, UC Berkeley), D. Rubin (Florida State University), and C. McCully (Rutgers University)

Science Credit: NASA, ESA, the Supernova Cosmology Project [J. Nordin (E.O. Lawrence Berkeley National Lab/University of California, Berkeley), D. Rubin (Florida State University), J. Richard (University of Lyon), E. Rykoff (Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory), G. Aldering (E.O. Lawrence Berkeley National Lab), R. Amanullah (The Oskar Klein Centre, Stockholm University), H. Atek (École Polytechnique Fédérale de Lausanne), K. Barbary (Argonne National Laboratory), S. Deustua (STScI), H. Fakhouri (E.O. Lawrence Berkeley National Lab/University of California, Berkeley), A. Fruchter (STScI), A. Goobar (The Oskar Klein Centre, Stockholm University), I. Hook (University of Oxford/INAF-Osservatorio Astronomico di Roma), E. Hsiao (Carnegie Observatories, Chile), X. Huang (University of California, Berkeley/University of San Francisco) J.-P. Kneib (École Polytechnique Fédérale de Lausanne/Laboratoire d’Astrophysique de Marseille), C. Lidman (Australian Astronomical Observatory), J. Meyers (Stanford University), S. Perlmutter and C. Saunders (E.O. Lawrence Berkeley National Lab/University of California, Berkeley), A. Spadafora (E.O. Lawrence Berkeley National Lab), and N. Suzuki (Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo)], and the CLASH Team [B. Patel, C. McCully, and S. Jha (Rutgers University), S. Rodney and D. Jones (Johns Hopkins University), O. Graur (Johns Hopkins University/Tel Aviv University/American Museum of Natural History/New York University), J. Merten (Jet Propulsion Laboratory), A. Zitrin (California Institute of Technology), A. Riess (STScI/Johns Hopkins University), T. Matheson (National Optical Astronomy Observatory), M. Sako (University of Pennsylvania), T. W.-S. Holoien (Rutgers University), M. Postman and D. Coe (STScI), M. Bartelmann (University of Heidelberg), I. Balestra (INAF-Osservatorio Astronomico di Trieste/INAF- Osservatorio Astronomico di Capodimonte), N. Benitez (Instituto de Astrofisica de Andalucia), R. Bouwens (Leiden Observatory), L. Bradley (STScI), T. Broadhurst (University of the Basque Country), S.B. Cenko (Goddard Space Flight Center/University of California, Berkeley), M. Donahue (Michigan State University), A. Filippenko (University of California, Berkeley), H. Ford (Johns Hopkins University), P. Garnavich (University of Notre Dame), C. Grillo (Niels Bohr Institute), L. Infante (Pontificia Universidad Catolica de Chile), S. Jouvel (Institut de Ciències de l'Espai), D. Kelson (Observatories of the Carnegie Institution of Washington), A. Koekemoer (STScI), O. Lahav (University College, London), D. Lemze (Johns Hopkins University), D. Maoz (Tel Aviv University), E. Medezinski (Johns Hopkins University), P. Melchior (Ohio State University), M. Meneghetti (INAF-Osservatorio Astronomico di Bologna), A. Molino (Instituto de Astrofisica de Andalucia), J. Moustakas (Siena College), M. Nonino (INAF-Osservatorio Astronomico di Trieste), P. Rosati (Universita di Ferrara/ESO), S. Seitz (Universitats-Sternwarte), L. Strolger (STScI), K. Umetsu (Academia Sinica), and W. Zheng (Johns Hopkins University)]

CONTACT:

Donna Weaver / Ray Villard
Space Science Telescope Institute, Baltimore, Md.
410-338-4493 / 410-338-4514
dweaver@stsci.edu / villard@stsci.edu

Source: HubbleSite