Posted on by Tammy Plotner

Astronomers Spy Early Galaxies Caught In A Cosmic Spiderweb

The Spiderweb, imaged by the Hubble Space Telescope – a central galaxy (MRC 1138-262) surrounded by hundreds of other star-forming 'clumps'. Credit: NASA, ESA, George Miley and Roderik Overzier (Leiden Observatory)

Once upon a time, when the Universe was just about three billion years old, galaxies started to form. Now astronomers using a CSIRO radio telescope have captured evidence of the raw materials these galaxies used to fashion their first stars… cold molecular hydrogen gas, H2. Even though we can’t see it directly, we know it is there by using another gas that reveals its presence – carbon monoxide (CO) – a radio wave emitter.

The telescope is CSIRO’s Australia Telescope Compact Array telescope near Narrabri, NSW. “It one of very few telescopes in the world that can do such difficult work, because it is both extremely sensitive and can receive radio waves of the right wavelengths,” says CSIRO astronomer Professor Ron Ekers.

One of the studies of these “raw” galaxies was performed by astronomer Dr. Bjorn Emonts of CSIRO Astronomy and Space Science. He and fellow researchers employed the Compact Array to observe and record a gigantic and distant amalgamation of “star forming clumps or proto-galaxies” which are congealing together to create a single massive galaxy. This framework is known as the “Spiderweb” and is theorized to be at least ten thousand million light years distant. The Compact Array radio telescope is capable of picking up the signature of star formation, giving astronomers vital clues about how early galaxies began star formation.

In blue, the carbon monoxide gas detected in and around the Spiderweb. Credit: B. Emonts et al (CSIRO/ATCA)
In blue, the carbon monoxide gas detected in and around the Spiderweb. Credit: B. Emonts et al (CSIRO/ATCA)
The “Spiderweb” was loaded. Here Dr. Emont and his colleagues found the molecular hydrogen gas fuel they were seeking. It covered an area of space almost a quarter of a million light-years across and contained at least sixty thousand million times the mass of the Sun! Surely this had to be the material responsible for the new stars seen sprinkled across the region. “Indeed, it is enough to keep stars forming for at least another 40 million years,” says Emonts.

In another research project headed by Dr. Manuel Aravena of the European Southern Observatory, the scientists measured the CO – the indicator of H2 – in two very distant galaxies. The signal of the faint radio waves was amped up by the gravitational fields of the additional galaxies – the “line of sight” members – which created gravitational lensing. Says Dr. Aravena, “This acts like a magnifying lens and allows us to see even more distant objects than the Spiderweb.”

Dr. Aravena’s team went to work measuring the amount of H2 in both of their study galaxies. One of these, SPT-S 053816-5030.8, produced enough radio emissions to allow them to infer how quickly it was forming stars – “an estimate independent of the other ways astronomers measure this rate.”

The Compact Array was tuned in. Thanks to an upgrade which increased its bandwidth – the amount of the radio spectrum which can be observed at any particular time – it is now sixteen times stronger and capable of reaching a range from 256 MHz to 4 GHz. That makes it a very sensitive ear!

“The Compact Array complements the new ALMA telescope in Chile, which looks for the higher-frequency transitions of CO,” says Ron Ekers.

Original Story Source: CSIRO News Release

Posted on by Elizabeth Howell

Where Is Dark Matter Most Dense? Subaru Telescope Gets Some Hints

The Subaru Telescope. Credit: National Astronomical Observatory of Japan

Put another checkmark beside the “cold dark matter” theory. New observations by Japan’s Subaru Telescope are helping astronomers get a grip on the density of dark matter, this mysterious substance that pervades the universe.

We can’t see dark matter, which makes up an estimated 85 percent of the universe, but scientists can certainly measure its gravitational effects on galaxies, stars and other celestial residents. Particle physicists also are on the hunt for a “dark matter” particle — with some interesting results released a few weeks ago.

The latest experiment with Subaru measured 50 clusters of galaxies and found that the density of dark matter is largest in the center of these clusters, and smallest on the outskirts. These measurements are a close match to what is predicted by cold dark matter theory, scientists said.

Cold dark matter assumes that this material can’t be observed in any part of the electromagnetic spectrum, the band of light waves that ranges from high-energy X-rays to low-energy infrared heat. Also, the theory dictates that dark matter is made up of slow-moving particles that, because they collide with each other infrequently, are cold. So, the only way dark matter interacts with other particles is by gravity, scientists have said.

To check this out, Subaru peered at “gravitational lensing” in the sky — areas where the light of background objects are bent around dense, massive objects in front. Galaxy clusters are a prime example of these super-dense areas.

Several dark matter maps: one based on a sample of 50 individual galaxy clusters (left), another looking at an average galaxy cluster (center), and another based on dark matter theory (right). Red is the highest concentration of dark matter, followed by yellow, green and blue. At right, in the middle, is a map based on cold dark matter theory that comes close to the average galaxy cluster observed with the Suburu Telescope. Credit: NAOJ/ASIAA/School of Physics and Astronomy, University of Birmingham/Kavli IPMU/Astronomical Institute, Tohoku University)
Several dark matter maps: one based on a sample of 50 individual galaxy clusters (left), another looking at an average galaxy cluster (center), and another based on dark matter theory (right). Red is the highest concentration of dark matter, followed by yellow, green and blue. At right, in the middle, is a map based on cold dark matter theory that comes close to the average galaxy cluster observed with the Suburu Telescope. Credit: NAOJ/ASIAA/School of Physics and Astronomy, University of Birmingham/Kavli IPMU/Astronomical Institute, Tohoku University)

“The Subaru Telescope is a fantastic instrument for gravitational lensing measurements. It allows us to measure very precisely how the dark matter in galaxy clusters distorts light from distant galaxies and gauge tiny changes in the appearance of a huge number of faint galaxies,” stated Nobuhiro Okabe, an astronomer at Academia Sinica in Taiwan who led the study.

Next, the team members could compare where the matter was most dense with that predicted by cold dark matter theory. To do that, they measured 50 of the most massive, known clusters of galaxies. Then, they measured the “concentration parameter”, or the cluster’s average density.

 

“They found that the density of dark matter increases from the edges to the center of the cluster, and that the concentration parameter of galaxy clusters in the near universe aligns with CDM theory,” stated the National Astronomical Observatory of Japan.

The next step, researchers stated, is to measure dark matter density in the center of the galaxy clusters. This could reveal more about how this substance behaves. Check out more about this study in Astrophysical Journal Letters.

Sourcs: National Astronomical Observatory of Japan

Posted on by Nancy Atkinson

Watch Live Webcast: Space Warps

Hubble Space Telescope image shows Einstein ring of one of the SLACS gravitational lenses, with the lensed background galaxy enhanced in blue. A. Bolton (UH/IfA) for SLACS and NASA/ESA.

Want to join the hunt for new galaxies? During a special G+ Hangout today, June 5, a team of astronomers will share how you can help them find faint and distant galaxies by joining a search they’ve called “Space Warps.” This is a new project from the Zooniverse. The team of astronomers will discuss gravitational lensing, a strange phenomenon that actually makes it possible for us to see a galaxy far away and otherwise hidden by clusters of galaxies in front of them. They will also answer your questions about their ongoing search for distant galaxies, what this reveals about the cosmos, and how astronomers are beginning to fill out our picture of the universe.

You can watch in the window below, and the webcast starts at 21:00 UTC (2:00 p.m. PDT, 5:00 pm EDT). You can take part in thise live Google+ Hangout, and have your questions answered by submitting them before or during the webcast. Email questions to [email protected] or send a message on Twitter with the hashtag #KavliAstro.

If you miss it live, you can watch the replay below, as well.

The participants:
• ANUPREETA MORE is a co-Principal Investigator of Space Warps and a postdoctoral fellow at the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo.
• PHILIP MARSHALL is a researcher at the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and SLAC.
• ARFON SMITH is Director of Citizen Science at the Adler Planetarium in Chicago and Technical Lead of Zooniverse (www.zooniverse.org).

You can also get more info at the Kavli Foundation, and visit the Space Warps website here.

Posted on by Elizabeth Howell

Early Galaxies Churned Out Stars Like Crazy

The Southern Cross, the Milky Way, and the Large Magellanic Cloud shine above the Atacama Large Millimeter/submillimeter Array (ALMA) as it observes on a clear night sky during its Early Science phase. Image credit: C. Padilla, NRAO/AUI/NSF

Talk about an assembly line! Some early-stage galaxies created stars thousands of times faster than our Milky Way does today, according to new research. And it’s puzzling astronomers.

“We want to understand how and why these galaxies are forming stars at such incredibly fast rates, so soon after the Big Bang,” stated Scott Chapman of Dalhousie University, one of the researchers behind the discovery. “This could partially answer how our own galaxy, the Milky Way, was born billions of years ago.”

This is just a hint of the high-definition view we’ll receive from Chile’s Atacama Large Millimeter/submillimeter Array (ALMA), its astronomers promise, since the array of dozens of telescopes was officially inaugurated this spring. (ALMA has been working for years, but slowly adding telescopes and definition as it goes.)

There were actually three papers released today about ALMA. So what did the observatory find out this time? Here’s the nut graf:

Gravitational microlensing method requires that you have two stars that lie on a straight line in relation to us here on Earth. Then the light from the background star is amplified by the gravity of the foreground star, which thus acts as a magnifying glass.
Gravitational microlensing method requires that you have two stars that lie on a straight line in relation to us here on Earth. Then the light from the background star is amplified by the gravity of the foreground star, which thus acts as a magnifying glass.

– The observed galaxies are “gravitationally lensed”. Galaxies are so massive that they can bend light from other galaxies, if put in the right spot with respect to Earth. We’ve seen this effect over and over again with the Hubble Space Telescope, but observations are less well-known in the millimeter spectrum of light in which ALMA observes. “Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation,” stated a Nature paper on the discovery.

– These galaxies are further away than we thought. By measuring the time it takes light from carbon monoxide molecules to reach us, the astronomers concluded these galaxies are much further away than previously measured, with some reaching as far back as 12 billion light-years away. (That’s just 1.7 billion years after the Big Bang created the universe.)

– The galaxies put star creation on fast-forward. Looking back that far is like looking in a time machine — we can see things that were happening only 1 billion years after the Big Bang. At the time, those galaxies were as bright as 40 trillion suns and created new stars at an extreme rate of 4,000 suns per year. (That, by the way, is 4,000 times faster than what our own galaxy does.)

You can read more about these results in Nature and the Astrophysical Journal (here and here.)

Source: Canadian Astronomical Society (CASCA)

Posted on by Nancy Atkinson

NASA Finds a Space Invader

The image of a spiral galaxy has been stretched and mirrored by gravitational lensing into a shape similar to that of a simulated alien from the classic 1970s computer game Space Invaders Credit: NASA, ESA, and the Hubble Heritage/ESA-Hubble Collaboration

Pew pew! NASA has found a Space Invader, but they won’t be activating any laser cannons to shoot it down. If you remember the classic 1970s computer game “Space Invaders,” you’ll quickly see the resemblance of the game’s pixelated alien to this actual image from the Hubble Space Telescope. This strange-looking object is really a mirage created by the gravitational field of a foreground cluster of galaxies warping space and distorting the background images of more distant galaxies.

Here, Abell 68, a massive cluster of galaxies, acts as a natural lens in space to brighten and magnify the light coming from very distant background galaxies. Just like a fun house mirror, lensing creates a fantasy landscape of arc-like images and mirror images of background galaxies. The foreground cluster is 2 billion light-years away, and the lensed images come from galaxies far behind it.

This image was taken in infrared light by Hubble’s Wide Field Camera 3, and combined with near-infrared observations from Hubble’s Advanced Camera for Surveys.

Aliens from the Space Invaders game. Via HelloComputer.
Aliens from the Space Invaders game. Via HelloComputer.

The image was found as part of Hubble’s Hidden Treasures image processing competition, and was spotted by Nick Rose.

You can still play the Space Aliens game (just search for it online), or you might want to try this huge version:

Source: NASA

Posted on by Nancy Atkinson

Now Even Further: Ancient Galaxy is Latest Candidate for Most Distant

It seems that every few months or so comes a new discovery of a new “most distant galaxy ever found.” It’s not really a surprise that new benchmarks are reached with such an amazing frequency as our telescopes get better and astronomers refine their techniques for observing faraway and ancient objects. This latest “most distant” is pretty interesting in that it was found by combining observations from two space telescopes – Hubble and Spitzer – as well as using massive galaxy clusters as gravitational lenses to magnify the distant galaxy behind them. It’s also extremely small and may not even be a fully developed galaxy at the time we are seeing it.

While this galaxy, named MACS0647-JD, appears as a diminutive blob in the new images, astronomers say it offers a peek back into a time when the universe was just 3 percent of its present age of 13.7 billion years. This newly discovered galaxy was observed 420 million years after the Big Bang, and its light has traveled 13.3 billion years to reach Earth.

“This object may be one of many building blocks of a galaxy,” said Dan Coe of the Space Telescope Science Institute, lead author of a new paper on the observations. “Over the next 13 billion years, it may have dozens, hundreds, or even thousands of merging events with other galaxies and galaxy fragments.”

The discovery comes from the Cluster Lensing And Supernova Survey with Hubble (CLASH), a program that combines the power of space telescopes with the natural zoom of gravitational lensing to reveal distant galaxies in the early Universe. Observations with Spitzer’s infrared eyes allowed for confirmation of this object.

The light from MACS0647-JD was magnified by a massive galaxy cluster named MACS J0647+7015, and without the cluster’s magnification powers, astronomers would not have seen the remote galaxy. Because of gravitational lensing, the CLASH research team was able to observe three magnified images of MACS0647-JD with the Hubble telescope. The cluster’s gravity boosted the light from the faraway galaxy, making the images appear about eight, seven, and two times brighter than they otherwise would that enabled astronomers to detect the galaxy more efficiently and with greater confidence.

“This cluster does what no manmade telescope can do,” said Marc Postman, also from STScI. “Without the magnification, it would require a Herculean effort to observe this galaxy.”

MACS0647-JD is just a fraction of the size of our Milky Way galaxy, and is so small it may not even be a fully formed galaxy. Data show the galaxy is less than 600 light-years wide. Based on observations of somewhat closer galaxies, astronomers estimate that a typical galaxy of a similar age should be about 2,000 light-years wide. For comparison, the Large Magellanic Cloud, a dwarf galaxy companion to the Milky Way, is 14,000 light-years wide. Our Milky Way is 150,000 light-years across.

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The galaxy was observed with 17 filters, spanning near-ultraviolet to near-infrared wavelengths, using Hubble’s Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS). Coe discovered the galaxy in February while poring over a catalogue of thousands of gravitationally lensed objects found in Hubble observations of 17 clusters in the CLASH survey. But the galaxy appeared only in the two reddest filters.

“So either MACS0647-JD is a very red object, only shining at red wavelengths, or it is extremely distant and its light has been ‘redshifted’ to these wavelengths, or some combination of the two,” Coe said. “We considered this full range of possibilities.”

The CLASH team identified multiple images of eight galaxies lensed by the galaxy cluster. Their positions allowed the team to produce a map of the cluster’s mass, which is primarily composed of dark matter. Dark matter is an invisible form of matter that makes up the bulk of the universe’s mass. “It’s like a big puzzle,” said Coe. “We have to arrange the mass in the cluster so that it deflects the light of each galaxy to the positions observed.” The team’s analysis revealed that the cluster’s mass distribution produced three lensed images of MACS0647-JD at the positions and relative brightness observed in the Hubble image.

Coe and his collaborators spent months systematically ruling out these other alternative explanations for the object’s identity, including red stars, brown dwarfs, and red (old or dusty) galaxies at intermediate distances from Earth. They concluded that a very distant galaxy was the correct explanation.

Redshift is a consequence of the expansion of space over cosmic time. Astronomers study the distant universe in near-infrared light because the expansion of space stretches ultraviolet and visible light from galaxies into infrared wavelengths. Coe estimates MACS0647-JD has a redshift of 11, the highest yet observed.

Images of the galaxy at longer wavelengths obtained with the Spitzer Space Telescope played a key role in the analysis. If the object were intrinsically red, it would appear bright in the Spitzer images. Instead, the galaxy barely was detected, if at all, indicating its great distance. The research team plans to use Spitzer to obtain deeper observations of the galaxy, which should yield confident detections as well as estimates of the object’s age and dust content.

MACS0647-JD galaxy, however, may be too far away for any current telescope to confirm the distance based on spectroscopy, which spreads out an object’s light into thousands of colors. Nevertheless, Coe is confident the fledgling galaxy is the new distance champion based on its unique colors and the research team’s extensive analysis. “All three of the lensed galaxy images match fairly well and are in positions you would expect for a galaxy at that remote distance when you look at the predictions from our best lens models for this cluster,” Coe said.

The new distance champion is the second remote galaxy uncovered in the CLASH survey, a multi-wavelength census of 25 hefty galaxy clusters with Hubble’s ACS and WFC3. Earlier this year, the CLASH team announced the discovery of a galaxy that existed when the universe was 490 million years old, 70 million years later than the new record-breaking galaxy. So far, the survey has completed observations for 20 of the 25 clusters.

The team hopes to use Hubble to search for more dwarf galaxies at these early epochs. If these infant galaxies are numerous, then they could have provided the energy to burn off the fog of hydrogen that blanketed the universe, a process called re-ionization. Re-ionization ultimately made the universe transparent to light.

Read the team’s paper (pdf).

Sources: HubbleSite, ESA Hubble

Posted on by Nancy Atkinson

Early Galaxy Found from the Cosmic ‘Dark Ages’

In the big image at left, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right. Image credit: NASA/ESA/STScI/JHU

Take a close look at the pixelated red spot on the lower right portion of the image above, as it might be the oldest thing humanity has ever seen. This is a galaxy from the very early days of the Universe, and the light from the primordial galaxy traveled approximately 13.2 billion light-years before reaching the Spitzer and Hubble space telescopes. The telescopes — and the astronomers using them — had a little help from a gravitational lens effect to be able to see such a faint and distant object, which was shining way back when our Universe was just 500 million years old.

“This galaxy is the most distant object we have ever observed with high confidence,” said Wei Zheng, a principal research scientist in the department of physics and astronomy at Johns Hopkins University in Baltimore who is lead author of a new paper appearing in Nature. “Future work involving this galaxy, as well as others like it that we hope to find, will allow us to study the universe’s earliest objects and how the dark ages ended.”

This ancient and distant galaxy comes from an important time in the Universe’s history — one which astronomers know little about – the early part of the epoch of reionization, when the Universe began to move from the so-called cosmic dark ages. During this period, the Universe went from a dark, starless expanse to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy opens a window onto the deepest, most remote epochs of cosmic history.

“In essence, during the epoch of reionization, the lights came on in the universe,” said paper co-author Leonidas Moustakas, from JPL.

Because both the Hubble and Spitzer telescopes were used in this observation, this newfound galaxy, named MACS 1149-JD, was imaged in five different wavebands. As part of the Cluster Lensing And Supernova Survey with Hubble Program, the Hubble Space Telescope registered the newly described, far-flung galaxy in four visible and infrared wavelength bands. Spitzer measured it in a fifth, longer-wavelength infrared band, placing the discovery on firmer ground.

Objects at these extreme distances are mostly beyond the detection sensitivity of today’s largest telescopes. To catch sight of these early, distant galaxies, astronomers rely on gravitational lensing, where the gravity of foreground objects warps and magnifies the light from background objects. A massive galaxy cluster situated between our galaxy and MACS 1149-JD magnified the newfound galaxy’s light, brightening the remote object some 15 times and bringing it into view.

Astronomers use redshift to describe cosmic distances, and the ancient but newly-found galaxy has a redshift, of 9.6. The term redshift refers to how much an object’s light has shifted into longer wavelengths as a result of the expansion of the universe.

Based on the Hubble and Spitzer observations, astronomers think the distant galaxy was less than 200 million years old when it was viewed. It also is small and compact, containing only about 1 percent of the Milky Way’s mass. According to leading cosmological theories, the first galaxies indeed should have started out tiny. They then progressively merged, eventually accumulating into the sizable galaxies of the more modern universe.

The epoch of reionization refers to the period in the history of the Universe during which the predominantly neutral intergalactic medium was ionized by the emergence of the first luminous sources, and these first galaxies likely played the dominant role in lighting up the Universe. By studying reionization, astronomers can learn about the process of structure formation in the Universe, and find the evolutionary links between the smooth matter distribution at early times revealed by cosmic microwave background studies, and the highly structured Universe of galaxies and clusters of galaxies at redshifts of 6 and below.

This epoch began about 400,000 years after the Big Bang when neutral hydrogen gas formed from cooling particles. The first luminous stars and their host galaxies emerged a few hundred million years later. The energy released by these earliest galaxies is thought to have caused the neutral hydrogen strewn throughout the Universe to ionize, or lose an electron, a state that the gas has remained in since that time.

The paper is available here (pdf document).

Source: JPL

Posted on by Nancy Atkinson

Mysterious Arc of Light Spotted with Spitzer Telescope

From a JPL press release:

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 as it existed when the universe was roughly a quarter of its current age of 13.7 billion years.

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, whose team includes researchers from NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “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 further 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 this Hubble observation 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 5 to 10 times larger than other clusters found at such an early time in the history of the universe. The team 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, 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 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 Combined Array for Research in Millimeter-wave Astronomy (CARMA) radio telescope, and NASA’s Chandra X-ray Observatory to independently show that the galactic grouping is extremely massive.

“The chance of finding such a gigantic cluster so early in the universe was less than one 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. The team hopes to use Hubble again to obtain a more accurate distance to the lensed galaxy.

The team’s results are described in three papers, which will appear online today and will be published in the July 10, 2012 issue of The Astrophysical Journal. Gonzalez is the first author on one of the papers; Brodwin, on another; and Adam Stanford of the University of California at Davis, on the third. Daniel Stern and Peter Eisenhardt of JPL are co-authors on all three papers.

Lead image caption: These images, taken by NASA’s Hubble Space Telescope, show an arc of blue light behind an extremely massive cluster of galaxies residing 10 billion light-years away. Image credit: NASA/ESA/University of Florida, Gainsville/University of Missouri-Kansas City/UC Davis

Posted on by Tammy Plotner

Hubble Captures Giant Lensed Galaxy Arc

Thanks to the presence of a natural "zoom lens" in space, this is a close-up look at the brightest distant "magnified" galaxy in the universe known to date. 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)

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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.”

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)

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.

Original Story Source: Hubble News Release.

Posted on by Nancy Atkinson

Distant Invisible Galaxy Could be Made Up Entirely of Dark Matter

The gravitational lens B1938+666 as seen in the infrared when observed with the 10-meter Keck II telescope. Credit: D. Lagattuta / W. M. Keck Observatory

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Astronomers can’t see it but they know it’s out there from the distortions caused by its gravity. That statement describes dark matter, the elusive substance which scientists have estimated makes up about 25% of our universe and doesn’t emit or absorb light. But it also describes a distant, tiny galaxy located about 10 billion light years from Earth. This galaxy can’t be seen in telescopes, but astronomers were able to detect its presence through the small distortions made in light that passes by it. This dark galaxy is the most distant and lowest-mass object ever detected, and astronomers say it could help them find similar objects and confirm or reject current cosmological theories about the structure of the Universe.

“Now we have one dark satellite [galaxy],” said Simona Vegetti, a postdoctoral researcher at the Massachusetts Institute of Technology, who led the discovery. “But suppose that we don’t find enough of them — then we will have to change the properties of dark matter. Or, we might find as many satellites as we see in the simulations, and that will tell us that dark matter has the properties we think it has.”

This dwarf galaxy is a satellite of a distant elliptical galaxy, called JVAS B1938 + 666. The team was looking for faint or dark satellites of distant galaxies using gravitational lensing, and made their observations with the Keck II telescope on Mauna Kea in Hawaii, along with the telescope’s adaptive optics to limit the distortions from our own atmosphere.

They found two galaxies aligned with each other, as viewed from Earth, and the nearer object’s gravitational field deflected the light from the more distant object (JVAS B1938 + 666) as the light passed through the dark galaxy’s gravitational field, creating a distorted image called an “Einstein Ring.”

Using data from this effect, the mass of the dark galaxy was found to be 200 million times the mass of the Sun, which is similar to the masses of the satellite galaxies found around our own Milky Way. The size, shape and brightness of the Einstein ring depends on the distribution of mass throughout the foreground lensing galaxy.

Current models suggest that the Milky Way should have about 10,000 satellite galaxies, but only 30 have been observed. “It could be that many of the satellite galaxies are made of dark matter, making them elusive to detect, or there may be a problem with the way we think galaxies form,” Vegetti said.

The dwarf galaxy is a satellite, meaning that it clings to the edges of a larger galaxy. Because it is small and most of the mass of galaxies is not made up of stars but of dark matter, distant objects such as this galaxy may be very faint or even completely dark.

“For several reasons, it didn’t manage to form many or any stars, and therefore it stayed dark,” said Vegetti.

Vegetti and her team plan to use the same method to look for more satellite galaxies in other regions of the Universe, which they hope will help them discover more information on how dark matter behaves.

Their research was published in this week’s edition of Nature.

The team’s paper can be found here.

Sources: Keck Observatory, UC Davis, MIT