Thursday, April 30, 2009

Streams of Stars Provide "Missing Link" in the Evolution of Galaxy Disks

"Missing Link" Found
NASA/JPL-Caltech/University of the Witwatersrand

About this image: Here we see two different views of the spiral galaxy, Messier 81. On the left is an image taken in blue light, while on the right is a specially-processed version of an image taken with the Spitzer Space Telescope's infrared array camera (IRAC) at 4.5 microns. The processed image reveals myriads of tiny arclets, a representative sample of which are arrowed. Each of these arclets represents a young star stream in the disk of the galaxy.

Observing the galaxy in the infrared is the only way to directly see the youngest stars, since the shroud of dust and gas that surrounds them is opaque to visible light, but transparent in the IR. Even so, the unprocessed infrared image was still dominated by the light from the smooth, older disk of the galaxy rather than the faint tracks of young stars. Further processing using a mathematical technique called Fourier filtering allowed the team to pick out structures on the physical scale on which star formation occurs, revealing these streams of young stars flowing away from their stellar nurseries.

M81 is one of several galaxies that were observed in this way. Taken together, this sample is the first time that young star streams have been discovered in the disks of galaxies millions of light years distant, filling in the "missing link" in the evolution of galaxy disks.

Why Are Galaxies So Smooth?
NASA/JPL-Caltech

About this image: This latest image from NASA's Spitzer Space Telescope is of the spiral galaxy, NGC 2841. Located about 46 million light-years from Earth in the constellation Ursa Major, this spectacular galaxy is helping astronomers solve one of the oldest puzzles in astronomy: Why do galaxies look so smooth, with stars sprinkled evenly throughout? An international team of astronomers has discovered that rivers of young stars flow from their hot, dense stellar nurseries, dispersing out to form the large, smooth distribution that we see in spiral galaxies like this one.

This image is a composite of three different wavelengths from Spitzer's infrared array camera . The shortest wavelengths are displayed in blue, and mostly show the older stars in NGC 2841, as well as foreground stars in our own Milky Way galaxy. The cooler areas are highlighted in red, and show the dusty, gaseous regions of the galaxy. Blue shows infrared light of 3.6 microns, green represents 4.5-micron light and red, 8.0-micron light. The contribution from starlight measured at 3.6 microns has been subtracted from the 8.0-micron image to enhance the visibility of the dust features.

Using NASA's Spitzer Space Telescope, an international team of astronomers has discovered streams of young stars flowing from their natal cocoons in distant galaxies. These distant rivers of stars provide an answer to one of astronomy's most fundamental puzzles: how do young stars that form clustered together in dense clouds of dust and gas disperse to form the large, smooth distribution seen in the disks of spiral galaxies like the Milky Way?

"When you look at the disks of galaxies in the infrared they are remarkably smooth. All of the older stars are evenly distributed. But stars aren't born that way; they're born in clusters and associations like the Pleiades cluster, or the association of young stars in the Orion constellation of our own Milky Way galaxy. So the question is - why are the disks of galaxies so smooth?" said team leader David Block of the University of the Witwatersrand in South Africa.

Astronomers know that the clusters where stars form begin to disappear when their ages reach several hundred million years. A few mechanisms are thought to explain this: some clusters evaporate when random internal motions kick out stars one by one, and other clusters disperse as a result of collisions among the clouds where they were born. Zooming out to mechanisms operating on larger scales still, shearing motions caused by the galaxy's rotation around its center disperses the clusters of clusters of young stars.

"Our analysis now answers the grand puzzle. By finding a myriad of streams of young stars all over the disks of galaxies we studied, we see that the mechanism for pulling the clusters of young stars apart is shearing motions of the parent galaxy. These streams are the 'missing link' we needed to understand how the disks of galaxies evolve to look the way they do," said Block.

Crucial to this discovery was finding a way to image previously hidden young stellar streams in galaxies millions of light-years away. To do this the team used high-resolution infrared observations from the Spitzer.

Using infrared rather than visible light to look at the galaxies allowed the group to pick out stars at just the right age when the stars are just starting to spread out from their clusters.

"Spitzer observes in the infrared where 100-million-year-old populations of stars dominate the light," noted co-author Bruce Elmegreen, from IBM's Research Division in New York. "Younger regions shine more in the visible and ultraviolet parts of the spectrum, and older regions get too faint to see. So we can filter out all the stars we don't want by taking pictures with an infrared camera."

Infrared is also important because light in this part of the spectrum can penetrate the dense dust clouds surrounding the clusters where stars form.

"Dust blocks optical starlight very effectively," said Robert Gehrz of the University of Minnesota, "but infrared light with its longer wavelength goes right around the dust particles blocking our view. This allows the infrared light from young stars to be seen more clearly."

But even when the images are taken in the infrared, they are still dominated by the light from the smooth older disks of galaxies, not the faint tracks of young dispersing clusters. Special mathematical manipulations were needed to pick out the clusters, whose faint tracks can still be seen precisely because they are not smooth.

Team member Ivanio Puerari of the Instituto Nacional de Astrofisica in Puebla, Mexico used a technique invented by mathematician Jean Baptiste Fourier in the early 1800's. The technique is effectively a spatial filter that picks out structure on the physical scale where star formation occurs. "The structures cannot be seen on the original Spitzer images with the human eye," noted Puerari.

"The combination of the Fourier filtering and infrared images highlighted regions of just the right size and the right age. To then unveil so many star streams in the disks of galaxies was unimaginable a year ago. This discovery continues to highlight the enormous potential of the Spitzer Space Telescope to make contributions none of us could have dreamed possible," commented Giovanni Fazio from the Harvard-Smithsonian Center for Astrophysics, project leader for the Spitzer Infrared Array Camera team used to take the pictures, and co-author of the discovery.

"Galileo, as both astronomer and mathematician, would have been proud. It is a wonderful interplay between the use of astronomical observations and mathematics and computers, exactly 400 years since Galileo used his telescope to examine our Milky Way galaxy in 1609," Fazio concluded.

Debra Elmegreen, Maria Mitchell Professor at Vassar College and President elect of the American Astronomical Society was also a member of the team. The results appeared in the March 20, 2009 issue of the Astrophysical Journal.

Starbursts in Dwarf Galaxies are a Global Affair

Credit: NASA, ESA, K. McQuinn (University of Minnesota, Minneapolis),
and I. Karachentsev (Special Astrophysical Observatory of
the Russian Academy of Sciences, Russia)

These images, taken by NASA's Hubble Space Telescope, show myriad stars residing in the central regions of the three dwarf galaxies NGC 4163, NGC 4068, and IC 4662.

The bluish dots are younger stars; the reddish dots, older stars. The irregularly shaped red blobs in the images of NGC 4163 and IC 4662 are regions of current starburst activity. Starbursts are areas of intense star formation.

The three galaxies are part of a Hubble study of starbursts in nearby, small, or dwarf, galaxies. Based on this study, astronomers have found that starbursts continue 100 times longer than first thought, lasting 200 million to 400 million years. These galaxies show that starbursts are not isolated events, but sweep across a galaxy.

Each of the three starburst galaxies has a different shape. The collection of stars in NGC 4163 is more spherical, with a higher concentration of stars forming in the center.

By contrast, the grouping of stars in NGC 4068 is more elongated and has fewer new stars than the other two galaxies. Astronomers think the starburst in this galaxy is ending. In the image of IC 4662 the clumpy red blobs peppered throughout the galaxy indicate active regions of star birth. One such region extends off the image's top, right edge.

This galaxy exhibits the strongest star formation of the three galaxies in the study.

The distances of the galaxies range from 8 million to 14 million light-years away.
The images were taken in 2004 by the Advanced Camera for Surveys.


Bursts of star making in a galaxy have been compared to a Fourth of July fireworks display: They occur at a fast and furious pace, lighting up a region for a short time before winking out.

But these fleeting starbursts are only pieces of the story, astronomers say. An analysis of archival images of small, or dwarf, galaxies taken by NASA's Hubble Space Telescope suggests that starbursts, intense regions of star formation, sweep across the whole galaxy and last 100 times longer than astronomers thought. The longer duration may affect how dwarf galaxies change over time, and therefore may shed light on galaxy evolution.

"Our analysis shows that starburst activity in a dwarf galaxy happens on a global scale," explains Kristen McQuinn of the University of Minnesota in Minneapolis and leader of the study. "There are pockets of intense star formation that propagate throughout the galaxy, like a string of firecrackers going off." According to McQuinn, the duration of all the starburst events in a single dwarf galaxy would total 200 million to 400 million years.

These longer timescales are vastly more than the 5 million to 10 million years proposed by astronomers who have studied star formation in dwarf galaxies. "They were only looking at individual clusters and not the whole galaxy, so they assumed starbursts in galaxies lasted for a short time," McQuinn says.

Dwarf galaxies are considered by many astronomers to be the building blocks of the large galaxies seen today, so the length of starbursts is important for understanding how galaxies evolve.

"Astronomers are really interested to find out the steps of galaxy evolution," McQuinn says. "Exploring these smaller galaxies is important because, according to popular theory, large galaxies are created from the merger of smaller, dwarf galaxies. So understanding these smaller pieces is an important part of filling in that scenario."

McQuinn's team analyzed archival Advanced Camera for Surveys data of three dwarf galaxies, NGC 4163, NGC 4068, and IC 4662. Their distances range from 8 million to 14 million light-years away. The trio is part of a survey of starbursts in 18 nearby dwarf galaxies.

Hubble's superb resolution allowed McQuinn's team to pick out individual stars in the galaxies and measure their brightness and color, two important characteristics astronomers use to determine stellar ages. By determining the ages of the stars, the astronomers could reconstruct the starburst history in each galaxy.

Two of the galaxies, NGC 4068 and IC 4662, show active, brilliant starburst regions in the Hubble images. The most recent starburst in the third galaxy, NGC 4163, occurred 200 million years ago and has faded from view.

The team looked at regions of high and low densities of stars, piecing together a picture of the starbursts. The galaxies were making a few stars, when something, perhaps an encounter with another galaxy, pushed them into high star-making mode. Instead of forming eight stars every thousand years, the galaxies started making 40 stars every thousand years, which is a lot for a small galaxy, McQuinn says. The typical dwarf is 10,000 to 30,000 light-years wide. By comparison, a normal-sized galaxy such as our Milky Way is about 100,000 light-years wide.

About 300 million to 400 million years ago star formation occurred in the outer areas of the galaxies. Then it began migrating inward as explosions of massive stars triggered new star formation in adjoining regions. Starbursts are still occurring in the inner parts of NGC 4068 and IC 4662.

The total duration of starburst activity depends on many factors, including the amount of gas in a galaxy, the distribution and density of the gas, and the event that triggered the starburst. A merger or an interaction with a large galaxy, for example, could create a longer starburst event than an interaction with a smaller system.

McQuinn plans to expand her study to a larger sample of more than 20 galaxies. "Studying nearby dwarf galaxies, where we can see the stars in great detail, will help us interpret observations of galaxies in the distant universe, where starbursts were much more common because galaxies had more gas with which to make stars," McQuinn explains.

McQuinn's results appeared in the April 10 issue of The Astrophysical Journal.

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

Kristen McQuinn
University of Minnesota, Minneapolis, Minn.
612-626-1819
kmcquinn@astro.umn.edu

Rogue Black Holes May Roam the Milky Way

This artist's conception shows a rogue black hole floating near a globular star cluster on the outskirts of the Milky Way. New calculations by Ryan O'Leary and Avi Loeb suggest that hundreds of massive black holes, left over from the galaxy-building days of the early universe, may wander the Milky Way. Fortunately, the closest rogue black hole should reside thousands of light-years from Earth.Credit: David A. Aguilar (CfA)

It sounds like the plot of a sci-fi movie: rogue black holes roaming our galaxy, threatening to swallow anything that gets too close. In fact, new calculations by Ryan O'Leary and Avi Loeb (Harvard-Smithsonian Center for Astrophysics) suggest that hundreds of massive black holes, left over from the galaxy-building days of the early universe, may wander the Milky Way.

Good news, however: Earth is safe. The closest rogue black hole should reside thousands of light-years away. Astronomers are eager to locate them, though, for the clues they will provide to the formation of the Milky Way.

"These black holes are relics of the Milky Way's past," said Loeb. "You could say that we are archaeologists studying those relics to learn about our galaxy's history and the formation history of black holes in the early universe."

According to theory, rogue black holes originally lurked at the centers of tiny, low-mass galaxies. Over billions of years, those dwarf galaxies smashed together to form full-sized galaxies like the Milky Way.

Each time two proto-galaxies with central black holes collided, their black holes merged to form a single, "relic" black hole. During the merger, directional emission of gravitational radiation would cause the black hole to recoil. A typical kick would send the black hole speeding outward fast enough to escape its host dwarf galaxy, but not fast enough to leave the galactic neighborhood completely. As a result, such black holes would still be around today in the outer reaches of the Milky Way halo.

Hundreds of rogue black holes should be traveling the Milky Way's outskirts, each containing the mass of 1,000 to 100,000 suns. They would be difficult to spot on their own because a black hole is visible only when it is swallowing, or accreting, matter.

One telltale sign could mark a rogue black hole: a surrounding cluster of stars yanked from the dwarf galaxy when the black hole escaped. Only the stars closest to the black hole would be tugged along, so the cluster would be very compact.

Due to the cluster's small size on the sky, appearing to be a single star, astronomers would have to look for more subtle clues to its existence and origin. For example, its spectrum would show that multiple stars were present, together producing broad spectral lines. The stars in the cluster would be moving rapidly, their paths influenced by the gravity of the black hole.

"The surrounding star cluster acts much like a lighthouse that pinpoints a dangerous reef," explained O'Leary. "Without the shining stars to guide our way, the black holes would be all but impossible to find."

The number of rogue black holes in our galaxy depends on how many of the proto-galactic building blocks contained black holes at their cores, and how those proto-galaxies merged to form the Milky Way. Finding and studying them will provide new clues about the history of our galaxy.

Locating the star cluster signposts may turn out to be relatively straightforward.

"Until now, astronomers were not searching for such a population of highly compact star clusters in the Milky Way's halo," said Loeb. "Now that we know what to expect, we can examine existing sky surveys for this new class of objects."

Loeb and O'Leary's journal paper will be published in the Monthly Notices of the Royal Astronomical Society and is available online at http://arxiv.org/abs/0809.4262.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Galactic X-ray Ridge: Resolving a Galactic Mystery

Credit: X-ray (NASA/CXC/TUM/M.Revnivtsev et al.);
IR (NASA/JPL-Caltech/GLIMPSE Team)
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An extremely deep Chandra X-ray Observatory image of a region near the center of our Galaxy has resolved a long-standing mystery about an X-ray glow along the plane of the Galaxy. The glow in the region covered by the Chandra image was discovered to be caused by hundreds of point-like X- ray sources, implying that the glow along the plane of the Galaxy is due to millions of such sources.

This image shows an infrared view from the Spitzer Space Telescope of the central region of the Milky Way, with a pullout showing a Chandra image of a region located only 1.4 degrees away from the center of the Galaxy.

The so-called Galactic ridge X-ray emission was first detected more than two decades ago using early X-ray observatories such as v. The ridge was observed to extend about two degrees above and below the plane of the Galaxy and about 40 degrees along the plane of the galaxy on either side of the galactic center. It appeared to be diffuse.

One interpretation of the Galactic X-ray ridge is that it is emission from 100-million-degree gas. This interpretation is problematic because the disk of the Galaxy is not massive enough to confine such hot gas, which should flow away in a wind. Replenishing the gas would then be a problem, since plausible sources of energy such as supernovas are not nearly powerful enough.

A very deep Chandra observation, lasting for about 12 days, was used to study the nature of this ridge emission. The field was chosen to be close enough to the Galactic plane so that the ridge emission was strong, but in a region with relatively little absorption from dust and gas to maximize the number of sources that might be detected. A total of 473 sources were detected in an area on the sky only about 3% of the size of the full Moon, one of the highest densities of X-ray sources ever seen in our Galaxy.

It was found that more than 80% of the seemingly diffuse ridge of X-ray emission was resolved into individual sources. These are believed to be mostly white dwarfs pulling matter from companion stars and double stars with strong magnetic activity that are producing X-ray outbursts or flares that are similar to, but more powerful than the flares seen on the Sun. These stars are unrelated to the large-scale structures seen towards the center of the Spitzer image, which are probably caused by young massive stars.

The paper reporting these results appears in the April 30th issue of Nature. This work was led by Mikhail Revnivtsev from the Excellence Cluster Universe, Technical University Munich, in Garching, Germany and from the Space Research Institute, in Moscow, Russia. The co-authors were Sergey Sasanov of the Space Research Institute in Moscow, Russia; Eugene Churazov of the Max Planck Institute for Astrophysics (MPA) in Garching, Germany; William Forman and Alexey Vikhlinin from the Harvard- Smithsonian Center for Astrophysics and Rashid Sunyaev from MPA.

Fast Facts for Galactic X-ray Ridge:
Scale: Inset Image is 5.1 arcmin across
Category: Normal Galaxies & Starburst Galaxies, Milky Way Galaxy
Coordinates: (J2000) RA 17h 51m 29s | Dec -29° 34’ 26''
Constellation: Sagittarius
Observation Date: 2009: May 7; Jul 17, 20, 23, 27, 31; Aug 1
Observation Time: 250 hours
Obs. ID: 9500-9505, 9854-9855, 9892-9893
Color Code: X-ray (Blue); IR (Yellow, Orange & Violet)
Instrument: ACIS
Distance Estimate: About 26,000 light years

Wednesday, April 29, 2009

Watching solar activity muddle Earth’s magnetic field

Credits: ESA

Scientists have found that extreme solar activity drastically compresses the magnetosphere and modifies the composition of ions in near-Earth space. They are now looking to model how these changes affect orbiting satellites, including the GPS system.

The results were obtained from coordinated in-situ measurements performed by ESA’s four Cluster satellites along with the two Chinese/ESA Double Star satellites.

Under normal solar conditions, GPS satellites orbit within the magnetosphere—the protective magnetic bubble carved out by Earth’s magnetic field. But when solar activity increases, the picture changes significantly: compressed and particles become energized, exposing satellites to higher doses of radiation that can perturb signal reception.

Such increased solar activity affects all satellites, not only the GPS system. This is why monitoring and forecasting its impact on near-Earth space is becoming increasingly critical to safeguarding daily life on Earth. One way to do this is by studying the physics of near-Earth space and observing the impact of such activity in time.

During two extreme solar explosions, or solar flares, on 21 January 2005 and 13 December 2006, the Cluster constellation and the two Double Star satellites were favourably positioned to observe the events at a large scale. The satellites carried out coordinated measurements of the response of the magnetosphere to these events.

High-energy (X-3) solar flare on 13 December 2006. Credits: ESA/NASA/SOHO

During both events, the velocity of positively charged particles in the solar wind was found to be higher than 900 km/s, more than twice their normal speed. In addition, the density of charged particles around Earth was recorded as five times higher than normal. The measurements taken in January 2005 also showed a drastic change in ion composition.

These factors together caused the magnetosphere to be compressed. Data show that the ‘nose’ of the dayside magnetopause (the outer boundary of the magnetosphere), usually located about 60 000 km from Earth, was only 25 000 km away.

Artist's impression of the Cluster constellation.
ESA's mission Cluster consists of four identical spacecraft flying in formation between 19 000 and 119 000 km above the Earth. They study the interaction between the solar wind and Earth’s magnetosphere, or the Sun-Earth connection in 3D. Credits: ESA

The second explosion in December 2006 released extremely powerful high-energy X-rays followed by a huge amount of mass from the solar atmosphere (called a coronal mass ejection). During the event, GPS signal reception on ground was lost.

Typical nose-like ion structures in near-Earth space were washed out as energetic particles were injected into the magnetosphere. These nose-like structures, that had formed earlier in the ‘ring current’ in the equatorial region near Earth, were detected simultaneously on opposite sides of Earth. Measurements of the ring current showed that its strength had increased.

About five hours after the coronal mass ejection hit Earth’s magnetosphere, a Double Star satellite observed penetrating solar energetic particles on the night side. These particles are hazardous to astronauts as well as satellites.

An artist's impression of the Double Star mission in orbit.
Credits: ESA

“With these detailed observations, we’ll be able to plug in data and better estimate what happens to the inner magnetosphere and near-Earth space during such explosions on the Sun”, said Iannis Dandouras, lead author of the results published recently, and Principal Investigator of the Cluster Ion Spectrometer.

“Looking at such a large-scale physical phenomena with a single satellite is akin to predicting the impact of a tsunami with a single buoy,” added Matt Taylor, ESA’s Project Scientist for Cluster and Double Star. “With Cluster and Double Star we have monitored both sides of Earth simultaneously, and obtained valuable in-situ data.”

Notes for editors: These results appear in Dandouras, I.S., Rème, H., Cao, J. & Escoubet, P. (2009). Magnetosphere response to the 2005 and 2006 extreme solar events as observed by the Cluster and Double Star spacecraft. Advances in Space Research. Vol.43,618–623.

For more information:

Iannis Dandouras
CESR, Université de Toulouse/CNRS, Toulouse, France
Email: iannis.dandouras@cesr.fr

Arnaud Masson, ESA Deputy Cluster Project Scientist
Email: Arnaud.Masson@esa.int

Matt Taylor, ESA Cluster Project Scientist
Email: Matthew.Taylor@esa.int

Philippe Escoubet, ESA Cluster Mission Manager
Email: Philippe.Escoubet@esa.int

IYA0910: The Portal to the Universe opens its doors


Keeping up-to-date with cutting-edge astronomy and space science breakthroughs has just become that much easier, thanks to the Portal To The Universe, the latest Cornerstone project of the International Year of Astronomy 2009 (IYA2009). As a high-tech website embracing Web 2.0 technologies, the Portal to the Universe aims to become a one-stop-shop for astronomy news.

Released during the European Week of Astronomy and Space Science (JENAM 2009), taking place this week at the University of Hertfordshire, UK, the Portal to the Universe website has been eagerly anticipated by journalists, science communicators, scientists, educators and members of the general public alike. The Portal to the Universe provides a global portal for online astronomy content, serving as an index and aggregator.

The site itself features news, blogs, video podcasts, audio podcasts, images, videos and more. Web 2.0 collaborative tools, such as the ranking of different services according to popularity, help the user to sift constructively through the wealth of information available and will promote interactions within the astronomy multimedia community. A range of "widgets" (small applications) have also been developed to tap into all sorts of existing "live data", such as near-live pictures of the Sun, live positions of spacecraft or live observations from telescopes.

Project Manager Lars Lindberg Christensen says: "It is clear that even in such a well-defined field as astronomy, there is much more ‘information confusion' than you might think. There is a real need in the community for this kind of site, where astronomy content is gathered in one place and is easily accessible. The International Year of Astronomy 2009 seeks to bring the Universe down to Earth, and this Portal is an excellent way of achieving this. This website will provide a single entry point to stars and galaxies".

The vision for the Portal is to enable real-time access to content by aggregating (pulling) from providers of dynamic content like blogs, images, news, etc. and distributing (pushing) to users, as well as indexing and archiving, collecting and maintaining a central repository of useful information.

Modern technology such as RSS feeds and standardised metadata make it possible to tie all the suppliers of astronomy information together with a single, semi-automatically updating portal. The result is a technologically advanced site that brings together strands of astronomy content from across the worldwide web.

Lead developer, Lars Holm Nielsen, says, "It has been a bit of a stretch to ensure that everything goes online just minutes after it has been released. We encourage everyone to participate and to submit RSS feeds for relevant news, images, videos, podcasts etc. to help make the Portal more complete."

Lars Lindberg Christensen says: "Today's release is just the beginning. The project will develop with, and around, the community's needs and lots of new features are planned, including adding resources such as educational materials, addresses for all astronomy stakeholders such as amateur clubs, planetariums and observatories."

The Portal to the Universe can be accessed at
http://www.portaltotheuniverse.org/

Links
Portal to the Universe website: http://www.portaltotheuniverse.org/
IYA2009 website: http://www.astronomy2009.org/

Notes

The vision of the IYA2009 is to help the citizens of the world rediscover their place in the Universe through the day and night-time skies, appreciate the impact of astronomy and basic sciences on our daily lives, and understand better how scientific knowledge can contribute to a more equitable and peaceful society. The aim of the IYA2009 is to stimulate worldwide interest, especially among young people, in astronomy and science under the central theme‚"The Universe, Yours to Discover". IYA2009 events and activities will promote a greater appreciation of the inspirational aspects of astronomy that embody an invaluable shared resource for all countries.
The IYA2009 activities are taking place at the global and regional levels, and especially at the national and local levels. National Nodes in each state have been formed to prepare activities for 2009. These Nodes establish collaborations between professional and amateur astronomers, science centres, educators and science communicators in preparing activities for 2009. The International Year of Astronomy was proclaimed by the United Nations on 20 December 2007. The IAU is the international astronomical organisation that brings together almost 10 000 distinguished astronomers from all nations of the world. Its mission is to promote and safeguard the science of astronomy in all its aspects through international cooperation. The IAU also serves as the internationally recognised authority for assigning designations to celestial bodies and the surface features on them. Founded in 1919, the IAU is the world's largest professional body for astronomers.

For more information

Lars Lindberg Christensen
Portal to the Universe Project Manager and IAU Press Officer
ESO ePOD, Garching, Germany
Tel: +49 89 3200 6761
Cellular: +49 173 3872 621
E-mail: lars@eso.org

Lars Holm Nielsen
Portal to the Universe Development Lead
ESO ePOD, Garching, Germany
Tel: +49 89 3200 6615
E-mail: lnielsen@eso.org

Further contacts

Pedro Russo
IAU IYA2009 Coordinator
ESO ePOD, Garching, Germany
Tel: +49 89 320 06 195
Cellular: +49 176 6110 0211
Fax: +49 89 320 23 62
E-mail: prusso@eso.org

Yolanda Berenguer
UNESCO Focal Point for the International Year of Astronomy 2009
UNESCO HQ, Paris
Tel: +33 1 45684171
E-mail: y.berenguer@unesco.org

Dr. Karel A. van der Hucht
General Secretary, International Astronomical Union
IAU Secretariat, Paris, France
Tel: +33 1 43 25 83 58
E-mail: K.A.van.der.Hucht@sron.nl

Tuesday, April 28, 2009

NASA's Galaxy-Exploring Mission Celebrates Sixth Anniversary

In these side-by-side images of M33, the ultraviolet image on the left was taken by the Galaxy Evolution Explorer, while the ultraviolet and infrared image on the right is a blend of the mission's M33 image and another taken by NASA's Spitzer Space Telescope. M33, one of our closest galactic neighbors, is about 2.9 million light-years away in the constellation Triangulum, part of what's known as our Local Group of galaxies. Credit: NASA/JPL-Caltech

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NASA's Galaxy Evolution Explorer Mission marks its sixth anniversary studying galaxies beyond our Milky Way through its sensitive ultraviolet telescope, the only such far-ultraviolet detector in space.

The mission studies the shape, brightness, size and distance of galaxies across 10 billion years of cosmic history, giving scientists a wealth of data to help us better understand the origins of the universe. One such object is pictured here, the galaxy NGC598, more commonly known as M33.

In these side-by-side images of M33, the ultraviolet image on the left was taken by the Galaxy Evolution Explorer, while the ultraviolet and infrared image on the right is a blend of the mission's M33 image and another taken by NASA's Spitzer Space Telescope. M33, one of our closest galactic neighbors, is about 2.9 million light-years away in the constellation Triangulum, part of what's known as our Local Group of galaxies.

The Galaxy Evolution Explorer has two detectors: one in far-ultraviolet, which reveals stars younger than about 10 million years old, and another in near-ultraviolet, which detects stars younger than about 100 million years old. The left ultraviolet image shows a map of the recent star formation history of M33. The bright blue and white areas are where star formation has been extremely active over the past few million years. The patches of yellow and gold are regions where star formation was more active around 100 million years ago. The ultraviolet image highlights the most massive young stars in M33. These stars burn their large supply of hydrogen fuel quickly, burning hot and bright while emitting most of their energy at ultraviolet wavelengths. Compared with low-mass stars like our sun, which live for billions of years, these massive stars never reach old age, having a lifespan as short as a few million years.

Together, the Galaxy Evolution Explorer and Spitzer can see a larger range of the full spectrum of the sky. Spitzer, for example, can detect mid-infrared radiation from dust that has absorbed young stars' ultraviolet light. That's something the Galaxy Evolution Explorer cannot see. The combined image on the right shows in amazing detail the beautiful and complicated interlacing of hot dust and young stars. In some regions of M33, dust gathers where there is very little far-ultraviolet light, suggesting that the young stars are obscured or that stars farther away are heating the dust. In some of the outer regions of the galaxy, just the opposite is true: There are plenty of young stars and very little dust.

In the combined image, far-ultraviolet light from young stars glimmers blue, near-ultraviolet light from intermediate age stars glows green, near-infrared light from old stars burns yellow and orange, and dust rich in organic molecules burns red. The small blue flecks outside the spiral disk of M33 are most likely distant background galaxies. This image is a four-band composite that, in addition to the two ultraviolet bands, includes near infrared as yellow/orange and far infrared as red.

Since its launch from a Pegasus rocket on April 28, 2003, the Galaxy Evolution Explorer has imaged more than a half-billion objects across two-thirds of the sky. Highlights over the past six years include detecting star formation in unexpected regions of the universe and spotting Mira, a fast-moving older star called a red giant. Astronomers say that studying Mira's gargantuan cosmic tail is helping us learn how stars like our sun die and ultimately seed new solar systems.

Written by Rhea Borja

Mysterious Space Blob Discovered at Cosmic Dawn

This image of the Himiko object is a composite and in false color. The thick horizontal bar at the lower right corner presents a size of 10 thousand light year. This image is created by M. Ouchi et al., which is the reproduction of Figure 2 in the article of The Astrophysical Journal May 2009 - 10 v696 issue.

Using information from a suite of telescopes, astronomers have discovered a mysterious, giant object that existed at a time when the universe was only about 800 million years old. Objects such as this one are dubbed extended Lyman-Alpha blobs; they are huge bodies of gas that may be precursors to galaxies. This blob was named Himiko for a legendary, mysterious Japanese queen. It stretches for 55 thousand light years, a record for that early point in time. That length is comparable to the radius of the Milky Way’s disk.

The researchers are puzzled by the object. Even with superb data from the world’s best telescopes, they are not sure what it is. Because it is one of the most distant objects ever found, its faintness does not allow the researchers to understand its physical origins. It could be ionized gas powered by a super-massive black hole; a primordial galaxy with large gas accretion; a collision of two large young galaxies; super wind from intensive star formation; or a single giant galaxy with a large mass of about 40 billion Suns. Because this mysterious and remarkable object was discovered early in the history of the universe in a Japanese Subaru field, the researchers named the object after the legendary mysterious queen in ancient Japan.

“The farther out we look into space, the farther we go back in time, “ explained lead author Masami Ouchi, a fellow at the Observatories of the Carnegie Institution who led an international team of astronomers from the U.S., Japan, and the United Kingdom. “I am very surprised by this discovery. I have never imagined that such a large object could exist at this early stage of the universe’s history. According to the concordance model of Big Bang cosmology, small objects form first and then merge to produce larger systems. This blob had a size of typical present-day galaxies when the age of the universe was about 800 million years old, only 6% of the age of today’s universe!”

Extended blobs discovered thus far have mostly been seen at a distance when the universe was 2 to 3 billion years old. No extended blobs have previously been found when the universe was younger. Himiko is located at a transition point in the evolution of the universe called the reionization epoch—it’s as far back as we can see to date. And at 55 thousand light years, Himiko is a big blob for that time.

This reionizing chapter in the universe was at the cosmic dawn, the epoch between about 200 million and one billion years after the Big Bang. During this period, neutral hydrogen began to form quasars, stars, and the first galaxies. Astronomers probe this era by searching for characteristic hydrogen signatures from the scattering of photons created by ionized gas clouds.

The team initially identified Himiko among 207 distant galaxy candidates seen at optical wavelengths using the Subaru telescope from the Subaru/XMM-Newton Deep Survey Field located in the constellation of Cetus. They then made spectroscopic observations to measure the distance with the Keck/DEIMOS and Carnegie’s Magellan/IMACS instrumentation. Himiko was an extraordinarily bright and large candidate for a distant galaxy. “We hesitated to spend our precious telescope time by taking spectra of this weird candidate. We never believed that this bright and large source was a real distant object. We thought it was a foreground interloper contaminating our galaxy sample,” continued Ouchi. “But we tried anyway. Then, the spectra exhibited a characteristic hydrogen signature clearly indicating a remarkably large distance—12.9 billion light years!”

“Using infrared data from NASA’s Spitzer Space Telescope and the United Kingdom Infrared Telescope, radio data from the VLA, and X-ray imaging from the XMM-Newton satellite, we were able to estimate the star-formation rate and stellar mass of this galaxy and to investigate whether it contains an active nucleus powered by a super-massive black hole,” remarked James Dunlop a team member at Edinburgh. “We found that the stellar mass of Himiko is an order of magnitude larger than other objects known at a similar epoch, but we cannot as yet tell if the center houses an active and growing black hole.”

“One of the puzzling things about Himiko is that it is so exceptional,” said Carnegie’s Alan Dressler, a member of the team. “If this was the discovery of a class of objects that are ancestors of today’s galaxies, there should be many more smaller ones already found—a continuous distribution. Because this object is, to this point, one-of-a-kind, it makes it very hard to fit it into the prevailing model of how normal galaxies were assembled. On the other hand, that’s what makes it interesting!”

The research is published in the May 10, 2009, issue of The Astrophysical Journal. The work was funded by the NASA through an award issued by JPL/Caltech, the Department of Energy, and the Carnegie Institution. The research is based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA); the Spitzer Telescope, managed by JPL for NASA; the Magellan telescopes operated by a consortium consisting of the Carnegie Institution, Harvard University, MIT, the University of Michigan, and the University of Arizona; and the United Kingdom Infrared Telescope, which is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the UK.

An image of Himiko is at:
http://www.ciw.eduhttp_www_ciw_edu_prouchihimikoimage4_6_09_jpg

For podcast see: http://videos.ciw.edu/achilles_movies_download/space_blob.mov

To access spectra see: http://www.ciw.edu/prouchielargeobjectspectrapic4_8_09

The Most Distant Object Yet Discovered in the Universe

ESO PR Photo 17a/09
Artist's impression of a gamma-ray burst

Gamma-ray bursts (GRBs) are powerful flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous amount of energy in this short time making them the most powerful events in the Universe. They are thought to be mostly associated with the explosion of stars that collapse into black holes. In the explosion, two jets of very fast-moving material are ejected, as depicted in this artist’s illustration. If a jet happens to be aimed at Earth, we see a brief but powerful gamma-ray burst.

ESO's Very Large Telescope has shown that a faint gamma-ray burst detected last Thursday is the signature of the explosion of the earliest, most distant known object in the Universe (a redshift of 8.2). The explosion apparently took place more than 13 billion years ago, only about 600 million years after the Big Bang.

Gamma-ray bursts (GRBs) are powerful flashes of energetic gamma-rays lasting from less than a second to several minutes. They release a tremendous amount of energy in this short time making them the most powerful events in the Universe. They are thought to be mostly associated with the explosion of stars that collapse into black holes.

The gamma-ray burst GRB 090423 was detected by the NASA/STFC/ASI Swift satellite during the morning (CEST) of Thursday 23 April 2009. The 10 second burst was located in the constellation of Leo (the Lion). It was soon being followed by a whole range of telescopes on the ground, including the 2.2-metre ESO/MPG telescope at La Silla and ESO’s Very Large Telescope (VLT) at Paranal, both in Chile.

VLT infrared observations, made 17 hours after the burst detection, allowed astronomers to establish the distance to the explosion. “We find that the light coming from the explosion has been stretched, or redshifted, considerably by the expansion of the Universe”, says Nial Tanvir, the leader of the team who made the VLT observations. “With a redshift of 8.2 this is the most remote gamma-ray burst ever detected, and also the most distant object ever discovered — by some way.”

Because light moves at a finite speed, looking farther into the Universe means looking back in time. The explosion occurred when the Universe was about 600 million years old, less than 5 percent of its current age. It is believed that the very first stars only formed when the Universe was between 200 and 400 million years old.

“This discovery proves the importance of gamma-ray bursts in probing the most distant parts of the Universe”, says Tanvir. “We can now be confident that even more remote bursts will be found in the future, which will open a window to studying the very first stars and the ultimate end of the Dark Age of the Universe.”

The previous record holder for the most distant GRB — first detected by Swift last year and then also studied with the VLT — had a redshift of 6.7 [1]. The blast, designated GRB 080913, arose from a star exploding about 200 million years after GRB090423. The previous most distant object known in the Universe confirmed spectroscopically is a galaxy with a redshift of 6.96 [2].

More information:
The ISAAC observations at the VLT were done on behalf of an international collaboration by N. Tanvir (U. Leicester, UK), A. Levan (U. Warwick, UK), K. Wiersema (U. Leicester, UK), J. Fynbo and J. Hjorth (Dark Cosmology Centre, Copenhagen, Denmark), and P. Jakobsson (Reykjavik, Iceland).

The GROND observations with the 2.2-metre ESO/MPG telescope at La Silla were made by F. Olivares, T. Krühler, J. Greiner and R. Filgas (Max Planck Institute for Extraterrestrial Physics, Garching, Germany).

Gamma-ray bursts are discovered by telescopes in space. After releasing their intense burst of high-energy radiation, they become detectable for a short while in the optical and in the near-infrared. This ‘afterglow’ fades very rapidly, making detailed analysis possible for only a few hours after the gamma-ray detection. This analysis is important in particular in order to determine the GRB's distance and, hence, intrinsic brightness.

Gamma-ray bursts are the universe's most luminous explosions. Most occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, gas jets — driven by processes not fully understood — punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates short-lived afterglows in many wavelengths.

Notes:

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in the Atacama Desert region of Chile: La Silla, Paranal and Chajnantor.

Contacts:
Nial Tanvir
University of Leicester, UK
E-mail: nrt3@star.le.ac.uk
Phone: +44 116 2231217
Mobile: +44 7980 136499

Henri Boffin
ESO La Silla - Paranal - ELT Press Officer
E-mail: hboffin@eso.org
Phone: +49 89 3200 6222

Valeria Foncea
ESO Press Officer in Chile
E-mail: vfoncea@eso.org
Phone: +56 2 463 3123

National contacts for the media: http://www.eso.org/public/outreach/eson/

Thursday, April 23, 2009

Did 'Dark Gulping' Generate Black Holes in Early Universe?

The HST WFPC2 image of gravitational lensing in the galaxy cluster Abell 2218, indicating the presence of large amount of dark matter.  Credit Andrew Fruchter at STScI

A process called ‘dark gulping’ may solve the mystery of the how supermassive black holes were able to form when the Universe was less than a billion years old. Dr Curtis Saxton will be presenting the study at the European Week of Astronomy and Space Science at the University of Hertfordshire in Hatfield. Dr Saxton and Professor Kinwah Wu, both of UCL’s Mullard Space Science Laboratory, developed a model to study the gravitational interactions between the invisible halo of dark matter in a cluster of galaxies and the gas embedded in the dark matter halo. They found that the interactions cause the dark matter to form a compact central mass, which can be gravitationally unstable, depending on the thermal properties of the dark matter. If the cluster is disturbed, the dark matter central mass would undergo a very rapid collapse, without a trace of electro-magnetic radiation being emitted. This fast dynamical collapse of the unstable dark-matter is called dark gulping.

The affected dark mass in the compact core is compatible with the scale of supermassive black holes in galaxies today. There are several theories for how supermassive black holes form: one possibility is that a single large gas cloud collapses, another is that a black hole formed by the collapse of a giant star swallows up enormous amounts of matter; another possibility is that a cluster of small black holes merge together. However, all these options take many millions of years and are at odds with recent observations that suggest that black holes were present when the Universe was less than a billion years old. Dark gulping may provide a solution to how the slowness of gas accretion was circumvented, enabling the rapid emergence of giant black holes.

“Dark matter appears to gravitationally dominate the dynamics of galaxies and galaxy clusters. However, there is still a great deal of conjecture about origin, properties and distribution of dark particles. We can only be certain that dark matter is non-interactive with light, but it interacts with ordinary matter via gravity. Previous studies have ignored the interaction between gas and the dark matter but, by factoring it into our model, we’ve achieved a much more realistic picture that fits better with observations and may also have gained some insight into the presence of early supermassive black holes,” said Dr Saxton.

According to the model, the development of a compact mass at the core is inevitable. Cooling by the gas causes it to flow gently in towards the centre. The gas can be up to 10 million degrees at the outskirts of the halos, which are few million light years in diameter, with a cooler zone towards the core, which surrounds a warmer interior a few thousand light years across. The gas doesn't cool indefinitely, but reaches a minimum temperature, which fits well with X-ray observations of galaxy clusters. 

The model also investigates how many dimensions the dark particles move in, as these determine the rate at which the dark halo expands and absorbs and emits heat, and ultimately affect the distribution of dark mass the system. 

“In the context of our model, the observed core sizes of galaxy cluster halos and the observed range of giant black hole masses imply that dark matter particles have between seven and ten degrees of freedom,” said Dr Saxton. “With more than six, the inner region of the dark matter approaches the threshold of gravitational instability, opening up the possibility of dark gulping taking place.”

The findings have been published in the Monthly Notices of the Royal Astronomical Society.

Written by Anita Heward 

FURTHER INFORMATION

“Radial structure, inflow and central mass of stationary radiative galaxy clusters”, Curtis Saxton & Kinwah Wu, Monthly Notices of the Royal Astronomical Society, Volume 391 Issue 3, Pages 1403 – 1436.

CONTACTS

Dr Curtis Saxton
Mullard Space Science Laboratory
University College London
Holmbury St. Mary
Dorking
Surrey RH5 6NT
United Kingdom
E-mail:
cjs2@mssl.ucl.ac.uk

Solar wind tans young asteroids

ESO PR Photo 16a/09
Young Asteroids Look Old
Artist’s impression of how the solar wind makes young asteroids look old. After undergoing a catastrophic collision, the colour of an asteroid gets modified rapidly by the solar wind so that it resembles the mean colour of extremely old asteroids. After the first million years, the surface “tans” much more slowly. At that stage, the colour depends more on composition than on age.

A new study published in Nature this week reveals that asteroid surfaces age and redden much faster than previously thought — in less than a million years, the blink of an eye for an asteroid. This study has finally confirmed that the solar wind is the most likely cause of very rapid space weathering in asteroids. This fundamental result will help astronomers relate the appearance of an asteroid to its actual history and identify any after effects of a catastrophic impact with another asteroid.

“Asteroids seem to get a ‘sun tan’ very quickly,” says lead author Pierre Vernazza. “But not, as for people, from an overdose of the Sun’s ultraviolet radiation, but from the effects of its powerful wind.”

It has long been known that asteroid surfaces alter in appearance with time — the observed asteroids are much redder than the interior of meteorites found on Earth [1] — but the actual processes of this “space weathering” and the timescales involved were controversial.

Thanks to observations of different families of asteroids [2] using ESO’s New Technology Telescope at La Silla and the Very Large Telescope at Paranal, as well as telescopes in Spain and Hawaii, Vernazza’s team have now solved the puzzle.

When two asteroids collide, they create a family of fragments with “fresh” surfaces. The astronomers found that these newly exposed surfaces are quickly altered and change colour in less than a million years — a very short time compared to the age of the Solar System.

“The charged, fast moving particles in the solar wind damage the asteroid’s surface at an amazing rate [3]”, says Vernazza. Unlike human skin, which is damaged and aged by repeated overexposure to sunlight, it is, perhaps rather surprisingly, the first moments of exposure (on the timescale considered) — the first million years — that causes most of the aging in asteroids.

By studying different families of asteroids, the team has also shown that an asteroid’s surface composition is an important factor in how red its surface can become. After the first million years, the surface “tans” much more slowly. At that stage, the colour depends more on composition than on age. Moreover, the observations reveal that collisions cannot be the main mechanism behind the high proportion of “fresh” surfaces seen among near-Earth asteroids. Instead, these “fresh-looking” surfaces may be the results of planetary encounters, where the tug of a planet has “shaken” the asteroid, exposing unaltered material.

Thanks to these results, astronomers will now be able to understand better how the surface of an asteroid — which often is the only thing we can observe — reflects its history.

More information
This result was presented in a paper published this week in the journal Nature, “Solar wind as the origin of rapid reddening of asteroid surfaces”, by P. Vernazza et al. The team is composed of Pierre Vernazza (ESA), Richard Binzel (MIT, Cambridge, USA), Alessandro Rossi (ISTI-CNR, Pisa, Italy), Marcello Fulchignoni (Paris Observatory, France), and Mirel Birlan (IMCCE, CNRS-8028, Paris Observatory, France). A PDF file can be downloaded here.

Notes
[1] Meteorites are small fragments of asteroids that fall on Earth. While a meteorite enters the Earth's atmosphere its surface can melt and be partially charred by the intense heat. Nevertheless, the meteorite interior remains unaffected, and can be studied in a laboratory, providing a wealth of information on the nature and composition of asteroids.

[2] An asteroid family is a group of asteroids that are on similar orbits around the Sun. The members of a given family are believed to be the fragments of a larger asteroid that was destroyed during a collision.

[3] The surface of an asteroid is affected by the highly energetic particles forming the solar wind. These particles partially destroy the molecules and crystals on the surface, re-arranging them in other combinations. Over time, these changes give formation of a thin crust or irradiated material with distinct colours and properties.

Contacts
Pierre Vernazza
European Space Agency, Noordwijk, Netherlands
Tel: +31 71 565 3154
E-mail: pierre.vernazza@esa.int

ESO La Silla - Paranal - ELT Press Officer: Dr. Henri Boffin - +49 89 3200 6222 - hboffin@eso.org
ESO Press Officer in Chile: Valentina Rodriguez - +56 2 463 3123 - vrodrigu@eso.org

'Pillars of Creation' Formed in the Shadows


Research by astronomers at the Dublin Institute of Advanced Studies suggests that shadows hold the key to how giant star-forming structures like the famous “Pillars of Creation” take shape. The pillars are dense columns within giant clouds of dust and gas where massive stars form. Several theories have been proposed to explain why the pillars develop around the edge of ionised gas bubbles surrounding young, very hot stars. Using computer models, the Dublin group has found that partially-shadowed clumps of gas tend to creep towards darker areas, causing pile-ups behind dense knots of gas and dust that screen the intense ultraviolet light emitted by the stars.
Jonathan Mackey, who is presenting the results at the European Week of Astronomy and Space Science in Hatfield said, “We created a simulation with a random distribution of lots of dense clouds with different sizes and shapes. We found that in certain cases a number of clouds can merge together in the shadows to form structures that look very like observed pillars. They are sufficiently dense to match the observations, can form in about 150 000 years and can survive for about 100 000 years. Although this is a preliminary study, we believe our results are quite robust and will be confirmed by more detailed modelling.”

The team, led by Dr Andrew Lim, found that the configuration of clumps of gas had to be favourable for the pillars to form. Some age estimates put the Eagle Nebula pillars at no more than 100 000 years old, and models show that the shadow from a single clump would not attain the density to form a pillar in that relatively short timescale.

“Many of our models do not produce pillars that are as long and narrow as those in the Eagle Nebula, at least not at the observed gas density. It needs the right configuration of dense clumps of gas to form a long pillar. Unless the shadowed region is already very dense to begin with, it just takes too long to collect and organise the gas into a pillar,” said Lim.

The group plans to add increasing levels of realism to the model over the next couple of years, bringing in more accurate representations of the complex chemistry of interstellar gas, the effects of radiation from diffuse sources. Adding in the effects of gravity will also be important as the pillars contain dense gas condensations which are in the process of collapsing under their own weight to form the next generation of stars.
Mackey said, "Gravity is relatively unimportant when the pillars are forming, but there comes a point when they get very dense and it cannot be ignored any longer. We plan to include gravitation in future work so that we can study the next generation of stars which are forming in the pillars."

Written by Anita Heward


CONTACTS:


Jonathan Mackey
Dublin Institute for Advanced Studies,
31 Fitzwilliam Place
Dublin 2, Ireland.
Tel: +353-86-0509310
E-mail: jmackey@cp.dias.ie

Andrew Lim
Dublin Institute for Advanced Studies,
31 Fitzwilliam Place
Dublin 2, Ireland.
E-mail: andy@cp.dias.ie

Wednesday, April 22, 2009

Hubble Survey Reveals the Formation of the First Massive Galaxies

NICMOS Image of the GOODS North Field
Credit: C Conselice, A Bluck, GOODS NICMOS Team

NICMOS Image of the GOODS North Field
Credit: C Conselice, A Bluck, GOODS NICMOS Team

NICMOS Image of the GOODS North Field
Credit: C Conselice, A Bluck, GOODS NICMOS Team

NICMOS Image of the GOODS North Field
Credit: C Conselice, A Bluck, GOODS NICMOS Team

First results from the GOODS NICMOS survey, the largest Hubble Space Telescope programme ever led from outside of the United States, reveal how the most massive galaxies in the early Universe assembled to form the most massive objects in the Universe today. Dr Chris Conselice from the University of Nottingham will present the results at the European Week of Astronomy and Space Science at the University of Hertfordshire on Wednesday 22nd April.

The observations are part of the Great Observatories Origins Deep Survey GOODS), a campaign that is using NASA's Spitzer, Hubble and Chandra space telescopes together with ESA's XMM Newton X-ray observatory to study the
most distant Universe. A team of scientists from six countries used the NICMOS near infrared camera on the Hubble Space Telescope to carry out the
deepest ever survey of its type at near infrared wavelengths. Early results show that the most massive galaxies, which have masses roughly 10 times larger than the Milky Way, were involved in significant levels of galaxy mergers and interactions when the Universe was just 2-3 billion years old.

"As almost all of these massive galaxies are invisible in the optical wavelengths, this is the first time that most of them have been observed," said Dr Conselice, who is the Principal Investigator for the survey. "To assess the level of interaction and mergers between the massive galaxies, we searched for galaxies in pairs, close enough to each other to merge within a given time-scale. While the galaxies are very massive and at first sight may appear fully formed, the results show that they have experienced an average of two significant merging events during their life-times."

The GOODS NICMOS results show that these galaxies did not form in a simple collapse in the early universe, but that their formation is more gradual over the course of the Universe's evolution, taking about 5 billion years. 

Dr Conselice said, "The findings support a basic prediction of the dominant model of the Universe, known as Cold Dark Matter, so they reveal not only how the most massive galaxies are forming, but also that the model that's been developed to describe the Universe, based on the distribution of galaxies that we've observed overall, applies in its basic form to galaxy formation."

The preliminary results are based on a paper led by PhD student Asa Bluck at the University of Nottingham.

NOTES FOR EDITORS

THE EUROPEAN WEEK OF ASTRONOMY AND SPACE SCIENCE
More than 1000 astronomers and space scientists will gather at the University of Hertfordshire for the European Week of Astronomy and Space Science (EWASS), incorporating the 2009 Royal Astronomical Society National Astronomy Meeting (RAS NAM 2009) and the European Astronomical Society Joint Meeting (JENAM 2009). The meeting runs from 20th to 23rd April 2009.

EWASS is held in conjunction with the UK Solar Physics (UKSP) and Magnetosphere Ionosphere and Solar-Terrestrial Physics (MIST) meetings. The
conference includes scientific sessions organised by the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) and the European Space Agency (ESA).

EWASS is principally sponsored by the Royal Astronomical Society (RAS), the Science and Technology Facilities Council (STFC) and the University of Hertfordshire, Hatfield.

THE ROYAL ASTRONOMICAL SOCIETY
The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 3000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

CONTACTS

Dr. Christopher J. Conselice
Associate Professor and Reader of Astrophysics
School of Physics and Astronomy
Senior Tutor, Cripps Hall
University of Nottingham
University Park
Nottingham, NG7 2RD
United Kingdom
Tel: 44 0115 951 5137

Most distant detection of water in the Universe

Astronomers have found the most distant signs of water in the Universe to date. Dr John McKean of the Netherlands Institute for Radio Astronomy (ASTRON) will be presenting the discovery at the European Week of Astronomy and Space Science in Hatfield on Wednesday 22nd April.

The water vapour is thought to be contained in a jet ejected from a supermassive black hole at the centre of a galaxy, named MG J0414+0534. The water emission is seen as a maser, where molecules in the gas amplify and emit beams of microwave radiation in much the same way as a laser emits beams of light. The faint signal is only detectable by using a technique called gravitational lensing, where the gravity of a massive galaxy in the foreground acts as a cosmic telescope, bending and magnifying light from the distant galaxy to make a clover-leaf pattern of four images of MG J0414+0534. The water maser was only detectable in the brightest two of these images.

Written by Anita Heward

Images

An image of the gravitationally lensed images of MG J0414+0534 can be found at:





(The two versions are the same image but with the contrast adjusted slightly)

Caption: The image is made from HST data and shows the four lensed images of the dusty red quasar, connected by a gravitational arc of the quasar host galaxy. The lensing galaxy is seen in the centre, between the four lensed images. Credit: John McKean/HST Archive data

Contacts

Dr. John McKean

Netherlands Institute for Radio Astronomy (ASTRON)

Tel: +31 521 595 780 (Office)

Tel: +31 6 243 28991 (mobile)



Dr. Violette Impellizzeri

National Radio Astronomy Observatory (NRAO)

Tel: +1 434 244 6811


Dr McKean said, "We have been observing the water maser every month since the detection and seen a steady signal with no apparent change in the velocity of the water vapour in the data we've obtained so far. This backs up our prediction that the water is found in the jet from the supermassive black hole, rather than the rotating disc of gas that surrounds it."

The radiation from the water maser was emitted when the Universe was only about 2.5 billion years old, a fifth of its current age.

"The radiation that we detected has taken 11.1 billion years to reach the Earth. However, because the Universe has expanded like an inflating balloon in that time, stretching out the distances between points, the galaxy in which the water was detected is about 19.8 billion light years away," explained Dr McKean.

Although since the initial discovery the team has looked at five more systems that have not had water masers, they believe that it is likely that there are many more similar systems in the early Universe. Surveys of nearby galaxies have found that only about 5% have powerful water masers associated with active galactic nuclei. In addition, studies show that very powerful water masers are extremely rare compared to their less luminous counterparts. The water maser in MG J0414+0534 is about 10 000 times the luminosity of the Sun, which means that if water masers were equally rare in the early Universe, the chances of making this discovery would be improbably slight.

"We found a signal from a really powerful water maser in the first system that we looked at using the gravitational lensing technique. From what we know about the abundance of water masers locally, we could calculate the probability of finding a water maser as powerful as the one in MG J0414+0534 to be one in a million from a single observation. This means that the abundance of powerful water masers must be much higher in the distant Universe than found locally because I’m sure we are just not that lucky!" said Dr McKean.

The discovery of the water maser was made by a team led by Dr Violette Impellizzeri using the 100-metre Effelsberg radio telescope in Germany during July to September 2007. The discovery was confirmed by observations with the Expanded Very Large Array in the USA in September and October 2007. The team included Alan Roy, Christian Henkel and Andreas Brunthaler, from the Max Planck Institute for Radio Astronomy, Paola Castangia from Cagliari Observatory and Olaf Wucknitz from the Argelander Institute for Astronomy at Bonn University. The findings were published in Nature in December 2008.

The team is now analysing high-resolution data to find out how close the water maser lies to the supermassive black hole, which will give them new insights into the structure at the centre of active galaxies in the early Universe.

"This detection of water in the early Universe may mean that there is a higher abundance of dust and gas around the super-massive black hole at these epochs, or it may be because the black holes are more active, leading to the emission of more powerful jets that can stimulate the emission of water masers. We certainly know that the water vapour must be very hot and dense for us to observe a maser, so right now we are trying to establish what mechanism caused the gas to be so dense," said Dr McKean.

Notes for Editors

The Effelsberg radio telescope is operated by the Max Planck Institute for Radio Astronomy (MPIfR) and has played an important role in finding water masers and using them to study the properties of black holes in nearby galaxies. The first extragalactic water maser was found using Effelsberg in 1977 (in the nearby galaxy M33).


The Very Large Array is operated by the National Radio Astronomy Observatory and consists of twenty-seven 25 m radio telescopes that are linked to form an interferometer. It is currently undergoing an upgrade to become the Expanded Very Large Array (EVLA) which opens up new frequency ranges for radio astronomers to use. The new 4 GHz to 8 GHz receiver on nine EVLA radio telescopes were used for this work.