NASA’s Webb to Explore Galaxies from Cosmic Dawn to Present Day

Abell 2744, nicknamed Pandora's Cluster, is a giant pile-up of four smaller galaxy clusters. The cluster is so massive that its powerful gravity bends the light from galaxies far behind it, making the background objects appear larger and brighter in a phenomenon called gravitational lensing. Shown in this Hubble image, the mammoth Abell 2744 cluster is located about 3.5 billion light-years away. Credits: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI). Hi-res images

How did the first galaxies in the universe form, and did they make the universe transparent to light? How did later galaxies produce and disperse into the universe the heavier elements that are the building blocks of stars, planets, and even humans? These are questions astronomers will address in some of the first observations made by NASA’s James Webb Space Telescope, slated to launch in March 2021. Astronomers hope the answers will lead to a better understanding of the origins and evolution of the universe. 

Through the combined power of NASA’s James Webb Space Telescope and gravity creating “natural telescopes” in space, astronomers hope to answer two science questions that are fundamental to understanding the origins and evolution of the universe:

- How did the first galaxies in the universe form, and did they make the universe transparent to light?

- How did later galaxies produce and disperse into the universe the heavier elements that are the building blocks of stars, planets, and even humans?

These questions will be addressed in some of the first observations made by the Webb telescope, slated to launch in March 2021. These observations will be part of the Director’s Discretionary-Early Release Science program, which provides time to selected projects early in the telescope’s mission. This program allows the astronomical community to quickly learn how best to use Webb’s capabilities, while also yielding robust science.

An international team led by Tommaso Treu of the University of California, Los Angeles, has been investigating how Webb can tackle these two key questions about the universe in the Early Release Science program.

Treu and his team will study the earliest, most distant galaxies to investigate their origins. After the big bang, the universe cooled down. As it cooled, protons and electrons combined to form neutral hydrogen atoms, until the universe became filled with hydrogen and opaque to light. Then at some point, the first galaxies formed, and scientists think these first galaxies emitted enough ultraviolet light to destroy the neutral hydrogen atoms and make the universe transparent to light. This is called the end of the “dark ages.”

“We’re not exactly sure when this happens, and we think it’s galaxies making the universe transparent, but we are not totally sure,” Treu said. “One of the things our proposal will try to do is establish whether indeed galaxies are the ones that are making the universe transparent — ending the cosmic dark ages — and what kind of galaxies they are, what are their properties, and when this happens.”

Using Gravity as a “Natural Telescope”

To see the faintest, farthest galaxies, the team will combine the power of Webb with the magnification of a “natural telescope” in space. The phenomenon, called gravitational lensing, occurs when a huge amount of matter, such as a cluster of galaxies, creates a gravitational field that distorts and magnifies the light from distant galaxies that are behind it, but in the same line of sight. The effect allows researchers to study the details of early galaxies too far away to be seen with current technology and telescopes.

One gravitational lens is Abell 2744, an enormous cluster of four smaller galaxy clusters. Also known as Pandora’s Cluster, this giant collection of galaxies has been well studied, including by NASA’s Hubble Space Telescope. Abell 2744 is one of many clusters that scientists can use in combination with Webb to peer back into the universe’s distant past.

“It’s a cluster that we know very well,” Treu said. “The fact that we know it so well means that we can calculate very precisely the properties of the lens. Using our models, we can compute very accurately how the background images have been distorted. Then we can invert that to figure out the intrinsic properties of the objects as they would look without the lens in front."

Simultaneously, the team will take deep images in the near and medium infrared of two fields offset from the cluster. “We will use those to count galaxies in the very early universe and figure out how many there are,” explained Treu. “Those are the sources that are suspected to eventually produce the ionizing photons that end the dark ages.”

Forming the Universe’s Heavier Elements

The big bang only formed hydrogen, helium, and traces of other light elements. Heavier elements like iron, oxygen, and carbon, which are made in stars, eventually ended up in the universe — but scientists don’t know exactly how this process happened.

“In astronomy, we think of hydrogen and helium as the light elements, and everything else we call a ‘metal,’” explained team member Alaina Henry of the Space Telescope Science Institute in Baltimore, Maryland. “We want to measure the metals that are produced by the first stars in the first supernovae. This tells us how the stars evolve, and how many end their lives as supernovae, where the heaviest elements — such as iron — are made.”

Identifying the “Fingerprints” of Elements in the Light

Answering both questions requires the unique spectroscopic capabilities of the Webb telescope. Spectroscopy separates an object’s light into its component colors, allowing scientists to see the “fingerprints” of different elements. By analyzing these spectral fingerprints, astronomers can determine the physical properties of that object, including its temperature, mass, luminosity, and composition.

Treu and his team will use two different spectrographs on Webb, each with different strengths and functions. Comparing and contrasting these capabilities is an important technical goal of their program.

Webb’s Near Infrared Imager and Slitless Spectrograph (NIRISS) gives observers spatial information, so they can determine how a spectrum changes across the sky. However, it has relatively low spectral resolution, meaning it is harder to differentiate between very similar colors.

The telescope’s Near Infrared Spectrograph (NIRSpec) has a quarter of a million tiny microshutters, each as wide as a human hair. These shutters can be opened or closed individually to isolate the light from a particular object. “In exchange for that, you lose spatial information,” said Treu, “but you get much higher spectral information. You can see the motion of the gas, both within galaxies and flowing in and out of them.”

“Webb will effectively be a much more capable spectrograph than we have ever had in space,” Treu added. “It will have multiple instruments to disperse the light. We need to understand the strengths of each one and how they complement each other.”

Expectations

Looking deep into the cosmos, Treu and his team expect to get a very good idea of the opacity of the universe, and also learn how ionizing photons — particles of light — escaped from the very early galaxies. They will also observe nearer galaxies at later times, when the galaxies are forming stars very vigorously. “We will get the best view ever of this process of gas flowing in, forming stars, and then being blown out by super-winds,” Treu said.

“It would be really fun if we found spectral features that we hadn’t seen very often, or maybe not at all before,” added Henry.

The James Webb Space Telescope will be the world’s premier space science observatory when it launches in 2021. Webb will solve mysteries of our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

Source: NASA's James Webb Space Telescope/News

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The Frontier Fields: Where Primordial Galaxies Lurk

This image of galaxy cluster Abell 2744, also called Pandora's Cluster, was taken by the Spitzer Space Telescope. The cluster is also being studied by NASA's Hubble Space Telescope and Chandra X-Ray Observatory in a collaboration called the Frontier Fields project. Image credit:NASA/JPL-Caltech.  › Full image and caption

In the ongoing hunt for the universe's earliest galaxies, NASA's Spitzer Space Telescope has wrapped up its observations for the Frontier Fields project. This ambitious project has combined the power of all three of NASA's Great Observatories -- Spitzer, the Hubble Space Telescope and the Chandra X-ray Observatory -- to delve as far back in time and space as current technology can allow.

Even with today's best telescopes, it is difficult to gather enough light from the very first galaxies, located more than 13 billion light years away, to learn much about them beyond their approximate distance. But scientists have a tool of cosmic proportions to help in their studies. The gravity exerted by massive, foreground clusters of galaxies bends and magnifies the light of faraway, background objects, in effect creating cosmic zoom lenses. This phenomenon is called gravitational lensing.

The Frontier Fields observations have peered through the strongest zoom lenses available by targeting six of the most massive galaxy clusters known. These lenses can magnify tiny background galaxies by as much as a factor of one hundred. With Spitzer's new Frontier Fields data, along with data from Chandra and Hubble, astronomers will learn unprecedented details about the earliest galaxies.

"Spitzer has finished its Frontier Fields observations and we are very excited to get all of this data out to the astronomical community," said Peter Capak, a research scientist with the NASA/JPL Spitzer Science Center at Caltech in Pasadena, California, and the Spitzer lead for the Frontier Fields project.

A recent paper published in the journal Astronomy & Astrophysics presented the full catalog data for two of the six galaxy clusters studied by the Frontier Fields: Abell 2744 -- nicknamed Pandora's Cluster -- and MACS J0416, both located about four billion light years away. The other galaxy clusters selected for Frontier Fields are RXC J2248, MACS J1149, MACS J0717 and Abell 370.

Eager astronomers will comb the Frontier Fields catalogs for the tiniest, dimmest-lensed objects, many of which should prove to be the most distant galaxies ever glimpsed. The current record-holder, a galaxy called GN-z11, was reported in March by Hubble researchers at the astonishing distance of 13.4 billion light-years, only a few hundred million years after the big bang. The discovery of this galaxy did not require gravitational lenses because it is an outlying, extremely bright object for its epoch. With the magnification boost provided by gravitational lenses, the Frontier Fields project will allow researchers to study typical objects at such incredible distances, painting a more accurate and complete picture of the universe's earliest galaxies.

Astronomers want to understand how these primeval galaxies arose, how their constituent mass developed into stars, and how these stars have enriched the galaxies with chemical elements fused in their thermonuclear furnaces. To learn about the origin and evolution of the earliest galaxies, which are quite faint, astronomers need to collect as much light as possible across a range of frequencies.

With sufficient light from these galaxies, astronomers can perform spectroscopy, pulling out details about stars' compositions, temperatures and their environments by examining the signatures of chemical elements imprinted in the light.

"With the Frontier Fields approach," said Capak, "the most remote and faintest galaxies are made bright enough for us to start to say some definite things about them, such as their star formation histories."

Because the universe has expanded over its 13.8-billion-year history, light from extremely distant objects has been stretched out, or redshifted, on its long journey to Earth. Optical light emitted by stars in the gravitational-lensed, background galaxies viewed in the Frontier Fields has therefore redshifted into infrared. Spitzer can use this infrared light to gauge the population sizes of stars in a galaxy, which in turn gives clues to the galaxy's mass. Combining the light seen by Spitzer and Hubble allows astronomers to identify galaxies at the edge of the observable universe.

Hubble, meanwhile, scans the Frontier Fields galaxy clusters in optical and near-infrared light, which has redshifted from ultraviolet light on its journey to Earth. Chandra, for its part, observes the foreground galaxy clusters in high-energy X-rays emitted by black holes and ambient hot gas. Along with Spitzer, the space telescopes size up the masses of the galaxy clusters, including their unseen but substantial dark matter content. Nailing down the clusters' total mass is a critical step in quantifying the magnification and distortion they produce on background galaxies of interest. Recent multi-wavelength results in this vein from the Frontier Fields project regarding the MACS J0416 and MACS J0717 clusters were published in October 2015 and February 2016. These results also brought in radio wave observations from the Karl G. Jansky Very Large Array to see star-forming regions otherwise hidden by gas and dust.

The Frontier Fields collaboration has inspired scientists involved in the effort as they look ahead to delving even deeper into the universe with the James Webb Space Telescope, which is planned for launch in 2018.

"The Frontier Fields has been an entirely community-led project, which is different from the way many projects of this magnitude are typically pursued," said Lisa Storrie-Lombardi of the Spitzer Science Center, also with the Frontier Fields project. "People have gotten together and really embraced Frontier Fields."

In addition to the six Frontier Fields galaxy clusters, Spitzer has done follow-up observations on other, slightly shallower fields Hubble has gazed into, expanding the overall number of cosmic regions where fairly deep observations have been taken. These additional fields will further serve as rich areas of investigation for Webb and future instruments.

NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive, housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA.

For more information about Spitzer, visit: http://www.nasa.gov/spitzer - http://spitzer.caltech.edu

Written by Adam Hadhaz

 

News Media Contact

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau@jpl.nasa.gov

Source: JPL-Caltech

Hubble Sees 'Ghost Light' From Dead GalaxiesGalaxy Cluster Abell 2744

Galaxy Cluster Abell 2744

Credit: NASA, ESA, M. Montes (IAC), and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI).  

Release images

NASA's Hubble Space Telescope has picked up the faint, ghostly glow of stars ejected from ancient galaxies that were gravitationally ripped apart several billion years ago. The mayhem happened 4 billion light-years away, inside an immense collection of nearly 500 galaxies nicknamed "Pandora's Cluster," also known as Abell 2744. The scattered stars are no longer bound to any one galaxy, and drift freely between galaxies in the cluster.

By observing the light from the orphaned stars, Hubble astronomers have assembled forensic evidence that suggests as many as six galaxies were torn to pieces inside the cluster over a stretch of 6 billion years. 

Computer modeling of the gravitational dynamics among galaxies in a cluster suggest that galaxies as big as our Milky Way are the likely candidates as the source of the stars. The doomed galaxies would have been pulled apart like taffy if they plunged through the center of the galaxy cluster where gravitational tidal forces are strongest. Astronomers have long hypothesized that the light from scattered stars should be detectable after such galaxies are disassembled. However, the predicted "intracluster" glow of stars is very faint and was therefore a challenge to identify.

"The Hubble data revealing the ghost light are important steps forward in understanding the evolution of galaxy clusters," said Ignacio Trujillo of the Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain, one of the researchers involved in this study of Abell 2744. "It is also amazingly beautiful in that we found the telltale glow by utilizing Hubble's unique capabilities."

"The results are in good agreement with what has been predicted to happen inside massive galaxy clusters," added Mireia Montes of the IAC, lead author of the paper published in the Oct. 1 issue of The Astrophysical Journal.

The team estimates that the combined light of about 200 billion outcast stars contributes approximately 10 percent of the cluster's brightness.

Because these extremely faint stars are brightest at near-infrared wavelengths of light, the team emphasized that this type of observation could only be accomplished with Hubble's infrared sensitivity to extraordinarily dim light.

Hubble measurements determined that the phantom stars are rich in heavier elements like oxygen, carbon, and nitrogen. This means the scattered stars must be second- or third-generation stars that were enriched with the elements forged in the hearts of the universe's first-generation stars. Spiral galaxies — like the ones believed to be torn apart — can sustain ongoing star formation that creates chemically enriched stars.

With the mass of 4 trillion suns, Abell 2744 is a target in the Frontier Fields program. This ambitious three-year effort teams Hubble and NASA's other Great Observatories to look at select massive galaxy clusters to help astronomers probe the remote universe. Galaxy clusters are so massive that their gravity deflects light passing through them, magnifying, brightening, and distorting light in a phenomenon called gravitational lensing. Astronomers exploit this property of space to use the clusters as a zoom lens to magnify the images of far-more-distant galaxies that otherwise would be too faint to be seen.

Montes' team used the Hubble data to probe the environment of the foreground cluster itself. There are five other Frontier Fields clusters in the program, and the team plans to look for the eerie "ghost light" in these clusters, too.

CONTACTS

Felicia Chou
NASA Headquarters, Washington, D.C.
202-358-0257
felicia.chou@nasa.gov

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

Mireia Montes
Instituto de Astrofísica de Canarias, La Laguna, Tenerife, Spain
mireia.montes.quiles@gmail.com

Source: HubbleSite

Hubble Finds Extremely Distant Galaxy through Cosmic Magnifying Glass

Hubble Uncovers One of the Smallest and Farthest Galaxies in the Universe

Credit: NASA, ESA, A. Zitrin (California Institute of Technology), and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

Release Images

Artist's Illustration of a Giant Cosmic Magnifying Glass

Illustration Credit: NASA, ESA, and Z. Levay (STScI). Science Credit: NASA, ESA, A. Zitrin (Caltech), and J. Lotz, M. Mountain, A. Koekemoer, and the HFF Team (STScI)

Peering through a giant cosmic magnifying glass, NASA's Hubble Space Telescope has spotted one of the farthest, faintest, and smallest galaxies ever seen. The diminutive object is estimated to be over 13 billion light-years away.

This new detection is considered one of the most reliable distance measurements of a galaxy that existed in the early universe, said the Hubble researchers. They used two independent methods to estimate its distance.

The galaxy appears as a tiny blob that is only a small fraction of the size of our Milky Way galaxy. But it offers a peek back into a time when the universe was only about 500 million years old, roughly 3 percent of its current age of 13.7 billion years. Astronomers have uncovered about 10 other galaxy candidates at this early era. But this newly found galaxy is significantly smaller and fainter than most of those other remote objects detected to date.

"This object is a unique example of what is suspected to be an abundant, underlying population of extremely small and faint galaxies at about 500 million years after the big bang," explained study leader Adi Zitrin of the California Institute of Technology in Pasadena. "The discovery is telling us that galaxies as faint as this one exist, and we should continue looking for them and even fainter objects so that we can understand how galaxies and the universe have evolved over time."

The galaxy was detected as part of the Frontier Fields program, an ambitious three-year effort, begun in 2013, that teams Hubble with NASA's other Great Observatories — the Spitzer Space Telescope and the Chandra X-ray Observatory — to probe the early universe by studying large galaxy clusters. These clusters are so massive that their gravity deflects light passing through them, magnifying, brightening, and distorting background objects in a phenomenon called gravitational lensing. These powerful lenses allow astronomers to find many dim, distant structures that otherwise might be too faint to see.

In this new discovery, the lensing power of the mammoth galaxy cluster Abell 2744, nicknamed Pandora's Cluster, produced three magnified images of the same galaxy. Each magnified image makes the galaxy appear as much as 10 times larger and brighter than it would look without the intervening lens.

An analysis of the distant galaxy shows that it measures merely 850 light-years across, 500 times smaller than the Milky Way, and is estimated to have a mass of only 40 million suns. The galaxy's star formation rate is about one star every three years (one-third the star formation rate in the Milky Way). Although this may seem low, Zitrin said that given its small size and low mass, the tiny galaxy is in fact rapidly evolving and efficiently forming stars.

"Galaxies such as this one are probably small clumps of matter that are starting to form stars and shine light, but they don't have a defined structure yet," Zitrin said. "Therefore, it's possible that we only see one bright clump magnified due to the lensing, and this is one possibility as to why it is smaller than typical field galaxies of that time."

Zitrin's team spotted the galaxy's gravitationally multiplied images using near-infrared and visible-light photos of the galaxy cluster taken by Hubble's Wide Field Camera 3 and Advanced Camera for Surveys. But at first they didn't know how far away it was from Earth.

Normally, astronomers use spectroscopy to determine an object's distance. The farther away a galaxy, the more its light has been stretched by the universe's expansion. Astronomers can precisely measure this effect through spectroscopy, which characterizes an object's light.

But the gravitationally lensed galaxy and other objects found at this early epoch are too far away and too dim for astronomers to use spectroscopy. Astronomers instead analyze an object's color to estimate its distance. The universe's expansion reddens an object's color in predictable ways, which scientists can measure.

Members of Zitrin's team not only performed the color-analysis technique, but they also took advantage of the multiple images produced by the gravitational lens to independently confirm their distance estimate. The astronomers measured the angular separation between the three magnified images of the galaxy in the Hubble photos. The greater the angular separation due to lensing, the farther away the object is from Earth. To test this concept, the astronomers compared the three magnified images with the locations of several other multiply imaged objects lensed by Abell 2744 that are not as far behind the cluster. The angular distance between the magnified images of the closer galaxies was smaller.

"These measurements imply that, given the large angular separation between the three images of our background galaxy, the object must lie very far away," Zitrin explained. "It also matches the distance estimate we calculated, based on the color-analysis technique. So we are about 95 percent confident that this object is at a remote distance, at redshift 10 (a measure of the stretching of space since the big bang). The lensing takes away any doubt that this might be a heavily reddened, nearby object masquerading as a far more distant object."

Astronomers have long debated whether such early galaxies could have provided enough radiation to warm the hydrogen that cooled soon after the big bang. This process, called "reionization," is thought to have occurred 200 million to 1 billion years after the birth of the universe. Reionization made the universe transparent to light, allowing astronomers to look far back into time without running into a "fog" of cold hydrogen.

"We tend to assume that galaxies ionized the universe with their ultraviolet light," Zitrin said. "But we do not see enough galaxies or light that could do that. So we need to look at fainter and fainter galaxies, and the Frontier Fields and galaxy cluster lensing can help us achieve this goal."

The team's results appeared in the Sept. 5 online edition of The Astrophysical Journal Letters.

CONTACT

Felicia Chou
NASA Headquarters, Washington, D.C.
202-358-0257
felicia.chou@nasa.gov

Donna Weaver
Space Telescope Science Institute, Baltimore, Md.
410-338-4493
dweaver@stsci.edu

Source: HubbleSite  

Hubble's First Frontier Field Finds Thousands of Unseen, Faraway Galaxies

Hubble Frontier Field Abell 2744

Credit: NASA, ESA, and J. Lotz, M. Mountain, A. Koekemoer, 

and the HFF Team (STScI) 
Highest-quality image

The first of a set of unprecedented, super-deep views of the universe from an ambitious collaborative program called The Frontier Fields is being released today (Jan 7, 2014) at the 223rd meeting of the American Astronomical Society in Washington, D.C.

The long-exposure image taken with NASA's Hubble Space Telescope is the deepest-ever picture taken of a cluster of galaxies, and also contains images of some of the intrinsically faintest and youngest galaxies ever detected.

The target is the massive cluster Abell 2744, which contains several hundred galaxies as they looked 3.5 billion years ago. The immense gravity in this foreground cluster is being used as a "gravitational lens," which warps space to brighten and magnify images of far-more-distant background galaxies as they looked over 12 billion years ago, not long after the big bang.

"The Frontier Fields is an experiment; can we use Hubble's exquisite image quality and Einstein's theory of General Relativity to search for the first galaxies?" said Space Telescope Science Institute Director Matt Mountain. "With the other Great Observatories, we are undertaking an ambitious joint program to use galaxy clusters to explore the first billion years of the universe's history."

Simultaneous observations of this field are being done with NASA's two other Great Observatories, the Spitzer Space Telescope and the Chandra X-ray Observatory. The assembly of all this multispectral information is expected to provide new insights into the origin and evolution of galaxies and their accompanying black holes.

The Hubble exposure reveals nearly 3,000 of these background galaxies interleaved with images of hundreds of foreground galaxies in the cluster. The many background galaxies would otherwise be invisible without the boost from gravitational lensing. Their images not only appear brighter, but also smeared, stretched, and duplicated across the field.

Thanks to the gravitational lensing phenomenon, the background galaxies are magnified to appear up to 10 to 20 times larger than they would normally appear. What's more, the faintest of these highly magnified objects have intrinsic brightnesses roughly 10 to 20 times fainter than any galaxies ever previously observed.

The Hubble data are immediately being made available to the worldwide astronomy community where teams of researchers will do a detailed study of the visual crazy quilt of intermingled background and cluster galaxies to better understand the stages of galaxy development.

Though the foreground cluster Abell 2744 has been intensively studied as one of the most massive clusters in the universe, the Frontier Fields exposure reveals new details of the cluster population. Hubble sees dwarf galaxies in the cluster as small as 1/1,000th the mass of the Milky Way. At the other end of the size spectrum, Hubble detects the extended light from several monster central cluster galaxies that are as much as 100 times more massive than our Milky Way. Also visible is faint intra-cluster light from stars inside the cluster that have been stripped out of galaxies by gravitational interactions. These new deep images will also help astronomers map out the dark matter in the cluster with unprecedented detail, by charting its distorting effects on background light. An unseen form of matter, dark matter makes up the bulk of the mass of the cluster.

As the Abell cluster was being photographed with Hubble's Wide Field Camera 3, the telescope's Advanced Camera for Surveys was trained on a nearby parallel field that is 6 arc minutes away from the cluster. In this field, Hubble resolves roughly 10,000 galaxies seen in visible light, most of which are randomly scattered galaxies. The blue galaxies are distant star-forming galaxies seen from up to 8 billion years ago; the handful of larger, red galaxies are in the outskirts of the Abell 2744 cluster.

Hubble will again view these two Frontier Fields in May 2014, but Hubble's visible-light and infrared camera will switch targets. This will allow for both fields to be observed over a full range of colors, from ultraviolet light to near-infrared.

With each new camera installed on Hubble, the space telescope has been used to make successively deeper, groundbreaking views of the universe. To get a better assessment of whether doing more deep field observations was scientifically compelling or urgent, the Space Telescope Science Institute or STScI in Baltimore, Md., chartered a "Hubble Deep Field Initiative" working group. The Hubble Frontier Fields initiative grew out of the working group's high-level discussions at STScI concerning what important, forward-looking science Hubble should be doing in upcoming years. Despite several deep field surveys, astronomers realized that a lot was still to be learned about the far universe. Such knowledge would help in planning the observing strategy for the upcoming James Webb Space Telescope.

The astronomers also considered synergies with other observatories, such as Spitzer, Chandra, and the new Atacama Large Millimeter/submillimeter Array or ALMA. Over the coming years five more pairs of fields will be imaged. The next scheduled target is the massive cluster MACS J0416.1-2403, for which observations are starting this week.

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

NASA's Great Observatories Begin Deepest Ever Probe of the Universe

Abell 2744, Pandora's Cluster, MACS J0416.1-2403, MACS J0717.5+3745, MACS J1149.5+2223. Credit: NASA, ESA, and J. Lotz and M. Mountain (STScI).  Release Images

NASA's Great Observatories are teaming up to look deeper into the universe than ever before. With a boost from natural "zoom lenses" found in space, they should be able to uncover galaxies that are as much as 100 times fainter than what the Hubble, Spitzer, and Chandra space telescopes can typically see.

This ambitious collaborative program is called The Frontier Fields. Astronomers will spend the next three years peering at six massive clusters of galaxies. Researchers are interested not only as to what's inside the clusters, but also what's behind them. The gravitational fields of the clusters brighten and magnify distant background galaxies that are so faint they would otherwise be unobservable.

The clusters themselves are among the most massive assemblages of matter known.

Astronomers anticipate that these observations will reveal populations of never-before-seen galaxies that existed when the universe was only a few hundred million years old. The Hubble and Spitzer data will be combined to measure the galaxies' distances and masses more accurately than either observatory could measure alone, demonstrating the synergy of these Great Observatories for such studies. The Chandra X-ray Observatory will also peer deep into the fields, imaging them at X-ray wavelengths to help determine the masses and lensing power of the clusters, as well as identify background galaxies with massive black holes.

"The idea is to use nature's natural telescopes in combination with the Great Observatories to look much deeper than before and find the most distant and faint galaxies we can possibly see," said principal investigator Jennifer Lotz of the Space Telescope Science Institute (STScI) in Baltimore, Md.

"We want to understand when and how the first stars and galaxies formed in the universe, and each Great Observatory gives us a different piece of the puzzle. Hubble tells you which galaxies to look at and how many stars are being born in those systems. Spitzer tells you how old the galaxy is and how many stars have formed," said Peter Capak, the Spitzer principal investigator of the Frontier Fields program.

The high-resolution Hubble data from the Frontier Fields program will also be used to trace the distribution of dark matter within the foreground clusters. Accounting for the bulk of the universe's mass, dark matter is the underlying, invisible scaffolding attached to galaxies. "The apparent positions of those lensed galaxies then tell you what's happening with the cluster itself, where the dark matter is in that cluster," Lotz said. "We'll use that information to make a better model of the cluster to better understand its lensing power."

The Hubble and Spitzer observations will be much more challenging for researchers than previous deep fields that have been studied by this powerful pair of observatories with great success. "With a deep image, you've got a direct image — what you see is what you get. But when we use a gravitational lens, background galaxies appear distorted and brighter," Lotz said. "In order to understand the true properties of a background galaxy, you have to understand how it is distorted and how it is magnified. This depends on the distribution of dark matter in the gravitational lens — the foreground cluster."

What's more, the galaxies seen in previous ultra-deep fields are just the most massive at those epochs. "They are the tip of the iceberg. If you want to see the galaxies that will turn into ones like our Milky Way, you have to go much fainter," Lotz said. Without using the big natural telescopes in space, astronomers would have to wait for the James Webb Space Telescope. In fact, the Frontier Fields offer a sneak peek of what the Webb telescope will routinely see anywhere it points in space, when it is launched in 2018.

The Hubble Frontier Fields initiative grew out of high-level discussions at STScI concerning what important, forward-looking science Hubble should be doing in upcoming years. Despite several deep field surveys, astronomers realized that a lot was still to be learned about the distant universe. And, such knowledge would help in planning the observing strategy for the Webb telescope.

To get a better assessment of whether doing more deep field observations was scientifically interesting or urgent, STScI chartered a "Hubble Deep Field Initiative" working group, which included U.S. and European astronomers who were expert users of the Great Observatories. The astronomers also considered synergies with other observatories, such as Spitzer, Chandra, and the new Atacama Large Millimeter Array. STScI Director Matt Mountain allocated his director's discretionary time to the program.

The first object to be looked at this month is called Pandora's Cluster (Abell 2744), which has been previously observed by all three Great Observatories but not to the depth of the new observations. The giant galaxy cluster appears to be the result of a simultaneous pile-up of at least four separate, smaller galaxy clusters that took place over a span of 350 million years.

Join several members of the Frontier Fields collaboration during the live Hubble Hangout event at 4:00pm (EDT) on Thursday, October 24 to discuss more on what's to come from these observations, how the clusters were chosen, and what we hope to learn from them. Visit: https://plus.google.com/u/0/events/cpl8pr6rjvls7en3c9ltrgelc80 . 

CONTACT

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

Jennifer Lotz
Space Telescope Science Institute, Baltimore, Md.
410-338-4467
lotz@stsci.edu