Hubble and ESO’s VLT provide unique 3D views of remote galaxies

Combining the twin strengths of the NASA/ESA Hubble Space Telescope’s acute eye, and the capacity of ESO’s Very Large Telescope (VLT) to probe the motions of gas in tiny objects. Astronomers have obtained exceptional 3D views of distant galaxies, seen when the Universe was half its current age. The VLT’s FLAMES/GIRAFFE spectrograph resolve the motions of the gas in these distant galaxies by measuring the velocity of the gas at various locations in these objects. This diagramme illustrates this by showing a sketch of a remote galaxy (in the box), how Hubble sees it (middle panel) and the gas motion measured with the VLT (left panel). In the latter, parts which are red are moving away from us, while those that are blue are moving towards us.



Measuring motions in 3 distant galaxies:

NASA/ESA Hubble Space Telescope images of the three galaxies studied by a team of astronomers who try to understand how galaxies formed when the Universe was half its current age (upper panels). The same galaxies were then studied with the FLAMES/GIRAFFE instrument on ESO’s Very Large Telescope (VLT) to probe the motions of gas in these objects (lower panels). Parts which are red are moving away from us, while those that are blue are moving towards us. By studying at these motions in detail, the astronomers try to read the history book of the Universe.

Tuesday, March 10, 2009

Astronomers have obtained exceptional 3D views of distant galaxies, seen when the Universe was half its current age, by combining the twin strengths of the NASA/ESA Hubble Space Telescope’s acute eye, and the capacity of ESO’s Very Large Telescope to probe the motions of gas in tiny objects. By looking at this unique “history book” of our Universe, at an epoch when the Sun and the Earth did not yet exist, scientists hope to solve the puzzle of how galaxies formed in the remote past.

For decades, distant galaxies that emitted their light six billion years ago were no more than small specks of light on the sky. With the launch of the Hubble Space Telescope in the early 1990s, astronomers were able to scrutinise the structure of distant galaxies in some detail for the first time. Under the superb skies of Paranal, the VLT’s FLAMES/GIRAFFE spectrograph — which obtains simultaneous spectra from small areas of extended objects — can now also resolve the motions of the gas in these distant galaxies.

“This unique combination of Hubble and the VLT allows us to model distant galaxies almost as nicely as we can close ones,” says François Hammer, who led the team. “In effect, FLAMES/GIRAFFE now allows us to measure the velocity of the gas at various locations in these objects. This means that we can see how the gas is moving, which provides us with a three-dimensional view of galaxies halfway across the Universe.”

The team has undertaken the Herculean task of reconstituting the history of about one hundred remote galaxies that have been observed with both Hubble and GIRAFFE on the VLT. The first results are coming in and have already provided useful insights for three galaxies.

In one galaxy, GIRAFFE revealed a region full of ionised gas, that is, hot gas composed of atoms that have been stripped of one or several electrons. This is normally due to the presence of very hot, young stars. However, even after staring at the region for more than 11 days, Hubble did not detect any stars! “Clearly this unusual galaxy has some hidden secrets,” says Mathieu Puech, lead author of one of the papers reporting this study. Comparisons with computer simulations suggest that the explanation lies in the collision of two very gas-rich spiral galaxies. The heat produced by the collision would ionise the gas, making it too hot for stars to form.

Another galaxy that the astronomers studied showed the opposite effect. There they discovered a bluish central region enshrouded in a reddish disc, almost completely hidden by dust. “The models indicate that gas and stars could be spiralling inwards rapidly,” says Hammer. This might be the first example of a disc rebuilt after a major merger.

Finally, in a third galaxy, the astronomers identified a very unusual, extremely blue, elongated structure — a bar — composed of young, massive stars, rarely observed in nearby galaxies. Comparisons with computer simulations showed the astronomers that the properties of this object are well reproduced by a collision between two galaxies of unequal mass.

“The unique combination of Hubble and FLAMES/GIRAFFE at the VLT makes it possible to model distant galaxies in great detail, and reach a consensus on the crucial role of galaxy collisions for the formation of stars in a remote past,” says Puech. “It is because we can now see how the gas is moving that we can trace back the mass and the orbits of the ancestral galaxies relatively accurately. Hubble and the VLT are real ‘time machines’ for probing the Universe’s history”, adds Sébastien Peirani, lead author of another paper reporting on this study.

The astronomers are now extending their analysis to the whole sample of galaxies observed. “The next step will then be to compare this with closer galaxies, and so, piece together a picture of the evolution of galaxies over the past six to eight billion years, that is, over half the age of the Universe,” concludes Hammer.

Exceptionally deep view of strange galaxy

Unusual Spiral NGC 4921
This deep image taken with the NASA/ESA Hubble Space Telescope shows the spiral galaxy NGC 4921 along with a spectacular backdrop of more distant galaxies. It was created from a total of 80 separate pictures taken with yellow and near-infrared filters.
Credits: NASA, ESA and K. Cook (Lawrence Livermore National Laboratory, USA)

A spectacular new image of an unusual spiral galaxy in the Coma galaxy cluster has been created from data obtained by the Advanced Camera for Surveys on the Hubble Space Telescope. It reveals fine details of the galaxy, NGC 4921, and an extraordinary rich background of more remote galaxies stretching back to the early Universe.

The Coma galaxy cluster, in the northern constellation of Coma Berenices, the hair of Queen Berenice, is one of the closest, very rich collections of galaxies in the nearby Universe. The cluster, also known as Abell 1656, is about 320 million light-years from Earth and contains more than 1000 members. The brightest galaxies, including NGC 4921 shown here, were discovered back in the late 18th century by William Herschel.

The galaxies in rich clusters undergo many interactions and mergers that tend to gradually turn gas-rich spirals into elliptical systems without much active star formation. As a result, there are far more ellipticals and fewer spirals in the Coma Cluster than are found in quieter corners of the Universe.


Wide-field view of the Coma galaxy cluster:
A wide-field image of the region around the Coma galaxy cluster (Abell 1656) constructed from the images in the Digitized Sky Survey. NGC 4921 is the largest galaxy to the left, and slightly below, the pair of galaxies at the centre of the image. The field-of-view is approximately 2.7 x 2.85 degrees. Credits: NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble)

NGC 4921 is one of the rare spirals in Coma, and a rather unusual one — it is an example of an ‘anaemic spiral’ where the normal vigorous star formation that creates a spiral galaxy’s familiar bright arms is less intense. As a result there is just a delicate swirl of dust in a ring around the galaxy, accompanied by some bright young blue stars that are clearly separated out by Hubble’s sharp vision. Much of the pale spiral structure in the outer parts of the galaxy is unusually smooth and gives the whole galaxy the ghostly look of a vast translucent jellyfish.


Annotated deep Hubble Space Telescope image of NGC 4921 indictating the locations of some of the more interesting features of the galaxy and its surroundings.
Credits: NASA, ESA and K. Cook (Lawrence Livermore National Laboratory, USA)

The long exposure times and sharp vision of Hubble not only allowed it to image NGC 4921 in exquisite detail, it also permitted it to see far beyond into the distant Universe. All around, and even through the galaxy itself, thousands of remote galaxies of all shapes, sizes and colours are visible. Many have the spotty and ragged appearance of galaxies at a time before the familiar division into spirals and ellipticals became established.

The Hubble images used to make this picture were originally obtained by a team led by Kem Cook (Lawrence Livermore National Laboratory, California). The team used Hubble to search for Cepheid variable stars in NGC 4921 that could be used to measure the distance to the Coma cluster and hence the expansion rate of the Universe.

Unfortunately the failure of the Advanced Camera for Surveys in early 2007 meant that they had insufficient data to complete their original programme, although they hope to continue after the servicing mission. Very deep imaging data like this, which is available to anyone from the Hubble archives, may also be used for other interesting scientific exploration of this galaxy and its surroundings.


Ursa Major and Coma Berenices, wide-field view:
This picture taken with a small ground-based camera shows most of the famous constellation of Ursa Major, including the seven stars of the Big Dipper or Plough. The constellation of Coma Berenices appears at the lower left. Credits: A. Fujii

This image was created from 50 separate exposures with a yellow filter and another 30 exposures with a near-infrared filter using the Wide Field Channel of the Advanced Camera for Surveys on Hubble. The total exposure times were approximately 17 hours and 10 hours respectively.

5th Feb,2009

ESO captured the deepest ultraviolet image of the universe

The Chandra Deep Field South, observed in the U-, B-, and R-bands with ESO's VIMOS and WFI instruments. The U-band VIMOS observations were made over a period of 40 hours and constitute the deepest image ever taken from the ground in the U-band. The image covers a region of 14.1 x 21.6 arcmin on the sky and shows galaxies that are 1 billion times fainter than can be seen by the unaided eye. The VIMOS R-band image was assembled by the ESO/GOODS team from archival data, while the WFI B-band image was produced by the GABODS team. ESO Mario Nonino/Piero Rosati/ESO GOODS Team

November 7, 2008

Provided by the ESO

The European Southern Observatory's Very Large Telescope captured the deepest ground-based U-band image of the universe ever obtained. It contains more than 27 million pixels and is the result of 55 hours of observations with the VIsible Multi Object Spectrograph (VIMOS).

This patchwork image, with its myriad of brightly colored galaxies, shows the Chandra Deep Field South (CDF-S) — arguably the most observed and best studied region in the entire sky. The CDF-S is one of the two regions selected as part of the Great Observatories Origins Deep Survey (GOODS), an effort of the worldwide astronomical community that unites the deepest observations from ground- and space-based facilities at all wavelengths from X-ray to radio. Its primary purpose is to provide astronomers with the most sensitive census of the distant universe to assist in their study of the formation and evolution of galaxies.

ESO's new image combines data obtained with the VIMOS instrument in the U- and R-bands, as well as data obtained in the B-band with the Wide-Field Imager (WFI) attached to the 2.2-meter MPG/ESO telescope at La Silla in Chile.

The U-band image — the result of 40 hours of staring at the same region of the sky and just made ready by the GOODS team — is the deepest image ever taken from the ground in this wavelength domain. At these depths, the sky is almost completely covered by galaxies, each one, like the Milky Way, home to hundreds of billions of stars.

The study detected galaxies that are a billion times fainter than the unaided eye can see and over a range of colors that the eye can't observe. This deep image has been essential to the discovery of a large number of new galaxies that are so far away that they are seen as they were when the universe was only 2 billion years old.

In this sea of galaxies, only a few stars belonging to the Milky Way are seen. One of them is so close, that it moves very fast on the sky. This "high proper motion star" is visible to the left of the second brightest star in the image. It appears as a funny elongated rainbow because the star moved during the data-gathering process.

Water in the early universe

100m radio telescope Max Planck Institute

December 17, 2008

Provided by Max Planck Institute, Bonn, Germany

A research group led by graduate student Violette Impellizzeri from the Max Planck Institute for Radio Astronomy used the 328 foot (100m) Effelsberg radio telescope to detect water at the greatest distance from Earth so far. The water vapor was discovered in the quasar MG J0414+0534 at redshift 2.64, which corresponds to light travel time of 11.1 billion years, a time when the universe was only a fifth of the age it is today. The water vapor is thought to exist in clouds of dust and gas that feed the super-massive black hole at the center of the distant quasar. The detection was later confirmed by high-resolution interferometric observations with the Expanded Very Large Array (EVLA).

This discovery of water in the early universe was possible due to the chance alignment of a foreground galaxy and the distant quasar MG J0414+0534. The foreground galaxy acts like a cosmic telescope, magnifying and distorting the light from the quasar, and forms four distinct images of the quasar. Without this gravitational-lensing effect, 580 days of continuous observations with the 328 foot (100m) telescope would have been needed instead of the 14 hours used to make this remarkable discovery.

The Effelsberg radio telescope also detected water from MG J0414+0534. The object is within the right redshift interval to stretch the line emission of the water molecule from its original frequency of 22 GHz to 6 GHz and so within the tuning range of the 6 GHz receiver installed at the telescope.

"It is interesting that we found water in the first gravitationally magnified object we observed from the distant universe", said co-author John McKean. "This suggests that water may be much more abundant in the early universe than first thought, and it can be used for further research into super-massive black holes and galaxy evolution at high redshift."

The water emission was seen in the form of a maser, which is beamed radiation similar to a laser, but at microwaves. The signal corresponds to a luminosity of 10,000 times the luminosity of the Sun. Such astrophysical masers are known to originate in regions of hot and dense dust and gas. With the detection of water from MG J0414+0534, it is the first time such a dense gas cloud has been observed in the early universe, and it shows that the conditions for the water molecule to form and survive already existed only 2.5 billion years after the Big Bang.

Water masers have been found in a number of galaxies at closer distances. Typically, they are thought to arise in the hot gas and dust closely orbiting a super-massive black hole at the galaxy's core. This amplified radio emission is more often observed when the orbiting disk is seen nearly edge-on. However, the astronomers say MG J0414+0534 is oriented with the disk almost face-on as seen from Earth. "This may mean that the water molecules in the masers we're seeing are not in the disk, but in the super-fast jets of material being ejected by the gravitational power of the black hole," said John McKean.

For the future, the detection of water in distant galaxies may still be challenging due to the sensitivity limitations of current-day telescopes. Of the nearby galaxies within half a billion light-years from Earth, only about one hundred galaxies show detectable water vapor emission, and almost all of them are relatively nearby. "In 2003, I was already participating in the detection of water mega-maser emission in the galaxy 3C 403," said Christian Henkel, co-author of the study. At that time, it was the most distant galaxy where water had been detected. Later on, this record went to a galaxy with water emission at redshift 0.66, (light travel time of 6 billion years). "Now MG J0414+0534 at redshift 2.64 is by far the most distant galaxy to show water vapor emission," he said.

"Because water masers arise close from the cores of galaxies, our result opens new interesting possibilities for studying super-massive black holes at a time when galaxies were forming," said Violette Impellizzeri. "It will also generate further searches for water in other distant galaxies with the telescopes we have at our disposal today and with the next generation of radio telescopes; we now know water is out there."

Astronomers Find Most Distant Water in the Universe

Credit: Milde Science Communication,
STScI, CFHT, J.-C. Cuillandre, Coelum.

About this image: The spectrum -- a radio "fingerprint" that revealed radio emission from water masers in the distant quasar MG J0414+0534. The background image is an infrared image of the quasar, made with the Hubble Space Telescope. The quasar appears broken up into four components by a foreground galaxy (diffuse object in the center), acting as a gravitational lens and strengthening the signal by a factor of 35. The inset with the galaxy M87 shows how the quasar might be seen from nearby.

Wednesday, December 17, 2008

Astronomers have found the most distant water yet seen in the Universe, in a galaxy more than 11 billion light-years from Earth. Previously, the most distant water had been seen in a galaxy less than 7 billion light-years from Earth.

Using the giant, 100-meter-diameter radio telescope in Effelsberg, Germany, and the National Science Foundation's Very Large Array (VLA) in New Mexico, the scientists detected a telltale radio "fingerprint" of water molecules in the distant galaxy.

The soggy galaxy, dubbed MG J0414+0534, harbors a quasar -- a supermassive black hole powering bright emission -- at its core. In the region near the core, the water molecules are acting as masers, the radio equivalent of lasers, to amplify radio waves at a specific frequency.

The astronomers say their discovery indicates that such giant water masers were more common in the early Universe than they are today. MG J0414+0534 is seen as it was when the Universe was roughly one-sixth of its current age.

At the galaxy's great distance, even the strengthening of the radio waves done by the masers would not by itself have made them strong enough to detect with the radio telescopes. However, the scientists got help from nature in the form of another galaxy, nearly 8 billion light-years away, located directly in the line of sight from MG J0414+0534 to Earth. That foreground galaxy's gravity served as a lens to further brighten the more-distant galaxy and make the emission from the water molecules visible to the radio telescopes.

"We were only able to discover this distant water with the help of the gravitational lens," said Violette Impellizzeri, an astronomer with the Max-Planck Institute for Radioastronomy (MPIfR) in Bonn, Germany. "This cosmic telescope reduced the amount of time needed to detect the water by a factor of about 1,000," she added.

The astronomers first detected the water signal with the Effelsberg telescope. They then turned to the VLA's sharper imaging capability to confirm that it was indeed coming from the distant galaxy. The gravitational lens produces not one, but four images of MG J0414+0534 as seen from Earth. Using the VLA, the scientists found the specific frequency attributable to the water masers in the two brightest of the four lensed images. The other two lensed images, they said, are too faint for detecting the water signal.

The radio frequency emitted by the water molecules was Doppler shifted by the expansion of the Universe from 22.2 GHz to 6.1 GHz.

Water masers have been found in numerous galaxies at closer distances. Typically, they are thought to arise in disks of molecules closely orbiting a supermassive black hole at the galaxy's core. The amplified radio emission is more often observed when the orbiting disk is seen nearly edge-on. However, the astronomers said MG J0414+0534 is oriented with the disk almost face-on as seen from Earth.

"This may mean that the water molecules in the masers we're seeing are not in the disk, but in the superfast jets of material being ejected by the gravitational power of the black hole," explained John McKean, also of MPIfR.

Impellizzeri and McKean worked with Alan Roy, Christian Henkel, and Andreas Brunthaler, also of the Max-Planck Institute; Paola Castangia of the Max-Planck Institute and the INAF Astronomical Observatory of Cagliari in Italy; and Olaf Wucknitz of the Argelander Institute for Astronomy in Bonn, Germany. The scientists reported their results in the December 18 issue of the scientific journal Nature.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Distant Galaxies In the Hubble Ultra Deep Field

photo: Credit: NASA, ESA,R. Bouwens and G. Illingworth (University of California, Santa Cruz)

This Hubble Space Telescope image shows 28 of the more than 500 young galaxies that existed when the universe was less than 1 billion years old. The galaxies were uncovered in a study of two of the most distant surveys of the cosmos, the Hubble Ultra Deep Field (HUDF), completed in 2004, and the Great Observatories Origins Deep Survey (GOODS), made in 2003.

Just a few years ago, astronomers had not spotted any galaxies that existed significantly less than 1 billion years after the Big Bang. The galaxies spied in the HUDF and GOODS surveys are blue galaxies brimming with star birth.

The large image at left shows the Hubble Ultra Deep Field, taken by the Hubble telescope. The numbers next to the small boxes correspond to close-up views of 28 of the newly found galaxies at right. The galaxies in the postage-stamp size images appear red because of their tremendous distance from Earth. The blue light from their young stars took nearly 13 billion years to arrive at Earth. During the journey, the blue light was shifted to red light due to the expansion of space.