ESO VLT: The dusty heart of Circinus, an active galaxy

Nuclear region of the Circinus galaxy. 

The right image shows the inner 1000 light years of the Circinus galaxy. 

Blinding light and gaseous material are ejected by the active nucleus (located at the black box). 

They escape only along a conical region towards the northwest (upper right part of the image), leading to the white V-shaped structure in this image. 

Along other directions, the nuclear region is hidden by dense gas and dust.

This obscuring dust has now been investigated with unprecedented detail with the ESO Very Large Telescope (VLT) Interferometer. 

The false-colour model image on the left shows the dust emission and corresponds to the region marked by the black box in the right image.

The emission comes from a relatively thin, disk-like structure (white) as well as dust elongated perpendicular to it. 

The disk is also seen by water emission (red-green-blue line). 

The dust emission is more absorbed towards the southeast (bottom left) than the northwest (top right), illustrated by the change from violet to green colours. 

Credit: Konrad Tristram; Right: NASA HST, STScI.

An international research team led by Konrad Tristram from the Max-Planck-Institute for Radio Astronomy in Bonn, Germany, obtained the most detailed view so far of the warm dust in the environment of a supermassive black hole in an active galaxy.

Konrad Tristram

The observations of the Circinus galaxy show, for the first time, that the dust directly illuminated by the central engine of the active galaxy is located in two distinct components: an inner warped disk and a surrounding larger distribution of dust.

Most likely, the larger component is responsible for most of the obscuration of the inner regions close to the supermassive black hole.

Such a configuration is significantly more complex than the simple dusty doughnut, which has been favoured for the last few decades.

The results are published in the current issue of Astronomy & Astrophysics.

In active galactic nuclei, enormous amounts of energy are released due to the feeding of the supermassive black hole in the centre of the galaxy.

Such black holes have masses of a million or billion times the mass of the sun.

The matter spiralling in onto the black hole becomes so hot and luminous that it outshines its entire galaxy with billions of stars. The huge amounts of energy released also affect the surrounding galaxy.

Active galactic nuclei are therefore thought to play an important role in the formation and evolution of galaxies and hence in the formation of the universe as presently seen.

Using the MIDI instrument at the ESO Very Large Telescope (VLT) Interferometer in the Atacama Desert of Chile, the research team obtained an unprecedented clear view of the warm dust in the nucleus of the Circinus galaxy.

At a distance of only 13 million light years, the Circinus galaxy contains one of the closest and brightest active galactic nuclei.

"We obtained at least twice the amount of interferometric data than for any other galaxy", proudly reports Konrad Tristram from the Max-Planck-Institute for Radio Astronomy (MPIfR), the lead author of the paper.

"Our observations make the Circinus galaxy by far the best observed extragalactic source in optical and infrared interferometry."

By combining the light of two telescopes, the interferometric observations increase the resolution to that of a telescope of 92 meters in diameter.

In the case of the Circinus galaxy, the scientists could, for the first time, show that the emission of the nuclear dust comes from two distinct components, an inner disk-like component and an extended component significantly elongated in polar direction.

The dust disk in the Circinus galaxy has a size of about 3 light years and agrees well with a warped molecular disk revealed by water emission.

More information: "The Dusty Torus in the Circinus Galaxy: A Dense Disk and the Torus Funnel," K. R. W. Tristram, L. Burtscher, W. Jaffe, K. Meisenheimer, S. F. Hönig, M. Kishimoto, M. Schartmann, and G. Weigelt, 2014, Astronomy & Astrophysics. dx.doi.org/10.1051/0004-6361/201322698; Preprint: arxiv.org/abs/1312.4534

ALMA: 'Death stars' in Orion blast planets before they even form - Video

This artist's concept shows two proplyds, or protostars, around a massive O-type star. 

The nearer proplyd is having its planet-forming dust and gas blasted away by the radiation from the star. 

The farther proplyd is able to retain its planet-making potential. 

Credit: NRAO /AUI /NSF, B. Saxton

The Orion Nebula is home to hundreds of young stars and even younger protostars known as proplyds.

Many of these nascent systems will go on to develop planets, while others will have their planet-forming dust and gas blasted away by the fierce ultraviolet radiation emitted by massive O-type stars that lurk nearby.

A team of astronomers from Canada and the United States has used the Atacama Large Millimeter/submillimeter Array (ALMA) to study the often deadly relationship between highly luminous O-type stars and nearby protostars in the Orion Nebula.

Their data reveal that protostars within 0.1 light-years (about 600 billion miles) of an O-type star are doomed to have their cocoons of dust and gas stripped away in just a few millions years, much faster than planets are able to form.

Rita Mann

"O-type stars, which are really monsters compared to our Sun, emit tremendous amounts of ultraviolet radiation and this can play havoc during the development of young planetary systems," remarked Rita Mann, an astronomer with the National Research Council of Canada in Victoria, and lead author on a paper in the Astrophysical Journal.

"Using ALMA, we looked at dozens of embryonic stars with planet-forming potential and, for the first time, found clear indications where protoplanetary disks simply vanished under the intense glow of a neighbouring massive star."

Many, if not all, Sun-like stars are born in crowded stellar nurseries similar to the Orion Nebula.

Over the course of just a few million years, grains of dust and reservoirs of gas combine into larger, denser bodies.

Left relatively undisturbed, these systems will eventually evolve into fully fledged star systems, with planets, large and small and ultimately drift away to become part of the galactic stellar population.

Astronomers believe that massive yet short-lived stars in and around large interstellar clouds are essential for this ongoing process of star formation.

At the end of their lives, massive stars explode as supernovas, seeding the surrounding area with dust and heavy elements that will get taken up in the next generation of stars.

These explosions also provide the kick necessary to initiate a new round of star and planet formation, but while they still shine bright, these larger stars can be downright deadly to planets if an embryonic solar systems strays too close.



"Massive stars are hot and hundreds of times more luminous than our Sun," said James Di Francesco, also with the National Research Council of Canada.

"Their energetic photons can quickly deplete a nearby protoplanetary disks by heating up its gas, breaking it up, and sweeping it away."

James Di Francesco

Earlier observations with the Hubble Space Telescope revealed striking images of proplyds in Orion.

Many had taken on tear-drop shapes, with their dust and gas trailing away from a nearby massive star.

These optical images, however, couldn't reveal anything about the amount of dust that was present or how the dust and gas concentrations changed in relation to massive stars.

The new ALMA observations detected these and other never-before-imaged proplyds, essentially doubling the number of protoplanetary disks discovered in that region.

"Taken together, our investigations with ALMA suggest that extreme UV regions are not just inhospitable, but they're downright hazardous for planet formation. With enough distance, however, it's possible to find a much more congenial environment," said Mann.

"This work is really the tip of the iceberg of what will come out of ALMA; we hope to eventually learn how common solar systems like our own are."

Journal Reference: Rita K. Mann, James Di Francesco, Doug Johnstone, Sean M. Andrews, Jonathan P. Williams, John Bally, Luca Ricci, A. Meredith Hughes, Brenda C. Matthews. ALMA OBSERVATIONS OF THE ORION PROPLYDS. The Astrophysical Journal, 2014; 784 (1): 82 DOI: 10.1088/0004-637X/784/1/82

Early universe was less dusty than believed

Credit: Swinburne University of Technology

Dust may be more rare than expected in galaxies of the early Universe, according to an international research team, led by Swinburne University of Technology astrophysicist Dr David Fisher.

In a galaxy named IZw 18, the team measured the lowest dust mass of a galaxy that has ever been measured.

"It's not just that the dust mass is low. We found that the dust mass is 100 times smaller than would be expected based on commonly assumed theories," Dr Fisher said.

The galaxy, I Zw 18, is nearby, which makes it easier to study, but has properties that are very similar to galaxies of the high redshift Univese.

"It's an extreme galaxy in the local Universe, but it tells us a lot about a stage that almost all galaxies have gone through, so it gives us a picture of what the first galaxies look like."

Dr Fisher said the results imply that galaxies of the early Universe may have less dust than has been expected.

"This means, firstly, that they will look different than we expect and make different populations of stars than we expect."

The Atacama Compact Array (ACA) is a sub-system of the ALMA telescope which allows enhanced imaging fidelity especially for extended astronomical sources. 

The ACA comprises of 16 (four 12-m and twelve 7-m) antennas, the last of which was delivered by Japan in May, 2012. 

Credit: ALMA(ESO/NAOJ/NRAO), R. Hills

"Secondly, that they will be much more difficult to observe, even with state-of-the-art facilities being built now such as the Atacama Large Millimeter/sub-millimeter Array (ALMA) of radio telescopes in northern Chile.

"IZw 18 is typical of very high redshift galaxies because it is very actively forming stars, and has a chemistry that is more like galaxies of the very early Universe with a very low abundance of metals and a lot of gas in the form of hydrogen," he said.

"Our result implies that current theories to describe the formation of stars when the Universe was very young are incomplete, and are built on invalid assumptions."

According to Dr Fisher, the amount of dust is very important for the formation of stars.

"What we think is going on, is that the harsh environment inside the galaxy we examined is adversely affecting the amount of dust in it.

"The radiation field measured inside I Zw 18 was roughly 200 times stronger than what we experience here in the Milky Way."

Dr Fisher said that based on the findings, theories should be amended to account for environment in making stars.

The research is published in Nature.

More information: Paper: dx.doi.org/10.1038/nature12765

ALMA Antenna: Final North American Antenna Delivered

After an odyssey of design and construction stretching across more than a decade, North America has delivered the last of the 25, 12-meter-diameter dish antennas that comprise its share of antennas for the international ALMA telescope.

This is an important milestone in the construction of an observatory that astronomers are already using to open up a "final frontier" of the spectrum of invisible light to high-resolution exploration.

ALMA, the Atacama Large Millimeter/submillimeter Array, stretches across more than 75 square miles of a high-altitude desert plain in northern Chile.

The scientific communities of North America, Europe, and East Asia have banded together to build the observatory, and are sharing its $1.3 billion cost.

When completed, ALMA will have a total of 66 antennas, 25 from North America, 25 from Europe, and 16 from East Asia.


Completed Final North American ALMA Antenna.

CREDIT: General Dynamics SATCOM Technologies, Bill Johnson.

"We are delighted to deliver this final ALMA antenna from North America," said Mark McKinnon, the North American ALMA Project Director at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia.

"It is a real testimony to the production team that we were able to overcome many technical challenges to complete the antenna delivery."

Faint radio waves, emitted naturally by gas and dust in space, will be detected and measured by the antennas, with the measurements then processed by a supercomputer to generate images as detailed as would come from a single dish that was miles across.

These images will give astronomers insights into previously invisible or unresolved processes of planet, star, and galaxy evolution, both nearby and across cosmic time.

The technique of combining radio telescopes to form a virtual, high-resolution instrument has been in use for decades. For example, the National Science Foundation's (NSF's) recently revitalized Very Large Array (VLA) in New Mexico uses this technique to explore the Universe as seen in centimeter-wavelength light. ALMA is the first VLA-scale array to attempt this feat at millimeter and submillimeter wavelengths.

For these shorter wavelengths, an antenna dish surface must be more precise, able to maintain its parabolic curvature to within the thickness of a human hair amidst harsh conditions at the 16,500-foot high ALMA site.

Funding to build the 25, 110-ton North American antennas was provided by the NSF, in the largest single procurement in the history of the foundation's astronomy division.

Associated Universities, Inc. (AUI) managed the contract, while NRAO oversaw the integration and testing of the antennas, which were manufactured and assembled by General Dynamics SATCOM Technologies.

Each antenna's pedestal and dish structure components were shipped separately to the ALMA site, and assembled in a huge hanger building, also built by General Dynamics.

Once ALMA is completed next year, it is expected to serve as a state-of-the-art radio telescope for thirty years or more.

"This is a very exciting time in astronomy," commented Tony Beasley, NRAO Director. "With ALMA we are taking perhaps the greatest leap in observing power in the history of the science."

Ethan Schreier, president of AUI, said "ALMA is the largest, most expensive ground-based astronomy project ever attempted, and a model for international science collaborations.

The success of the partnership is manifest in the achievement of this milestone, but will be even more evident in the legacy of discovery and understanding that is going to emerge over the coming years, as tomorrow's eager astronomers get their hands on this fantastic telescope."

Spectacular New Image Exposes Carina Nebula's Cool Clouds

A new image of the Carina nebula reveal the cold dusty clouds from which stars form in the bustling stellar nursery.

CREDIT: ESO/APEX/T. Preibisch et al. (Submillimetre); N. Smith, University of Minnesota/NOAO/AURA/NSF (Optical)

A stunning new image of the Carina nebula reveals cold, dusty cosmic clouds where violent and dynamic star formation is taking place.

These clouds of dust and gas play host to some of the most massive and luminous stars in our galaxy, which make them scintillating test beds for studying the interactions between these young stars and their parent molecular clouds.

The new observations were made with the Atacama Pathfinder Experiment (APEX) telescope, which is located about 16,700 feet (5,100 meters) above sea level at the Llano de Chajnantor Observatory in the Atacama desert in northern Chile.

A team of astronomers led by Thomas Preibisch, from the University Observatory Munich in Germany, captured images of the star-forming region in the Carina nebula in submillimetre light.

At this wavelength, most of the light that can be seen is the weak heat glow from grains of cosmic dust, the researchers said.

Image Credit: NASA, ESA, N. Smith (U. California, Berkeley) et al., and The Hubble Heritage Team (STScI/AURA)

What dark forms lurk in the mists of the Carina Nebula? These ominous figures are actually molecular clouds, knots of molecular gas and dust so thick they have become opaque.

In comparison, however, these clouds are typically much less dense than Earth's atmosphere.

Pictured above is part of the most detailed image of the Carina Nebula ever taken where dark molecular clouds are particularly prominent.

The entire Carina Nebula spans more than 300 light years and lies about 7,500 light-years away in the constellation of Carina.

NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebula.

Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically.

Wide-field annotated and zoomable versions of the larger image composite are also available.

Moon over Cerro Paranal and the VLT

Our lunar neighbour looms large over Cerro Paranal, the home of the Very Large Telescope in Chile's Atacama desert.

The moon appears large because it is so close to the horizon.

The picture was taken from 14 kilometres away on the road to another mountain, the nearby Cerro Armazones, proposed site of the European Extremely Large Telescope – which as its name suggests is intended to be the biggest telescope on Earth.

(Image: ESO)

NASA Astronaut Soichi - ALMA, Atacama Large Millimeter Array, Chile

ALMA, Atacama Large Millimeter/submillimeter Array, Chile, as seen from the ISS. Operations Support Facilities.