Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


The dusty heart of an active galaxy


Astronomers observe a dense disk and a bright funnel at the centre of the Circinus galaxy

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.

At the heart 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 Very Large Telescope 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.

© Left: Konrad Tristram; Right: NASA HST, News Release STScI-2000-37

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.

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 Very Large Telescope Interferometer of the European Southern Observatory (ESO) 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.

This inner disk is surrounded by a much bigger dust distribution with a size of at least 6 light years. We only see the inner edge of this dust distribution, which is directly illuminated by the radiation coming from the central region. This inner funnel appears elongated in polar direction. Its southeastern side is significantly more obscured by dust than the northwestern side. This leads to the observed strong asymmetry and colour change in the observed emission.

“From this, we deduce that it is the larger dust component, which is responsible for hiding the central engine and for collimating the visible ionisation cone”, explains Leonard Burtscher from the Max-Planck-Institute for Extraterrestrial Physics in Garching. “We can only see the inner, directly illuminated edges of that component. This is certainly in contrast to some earlier speculations.”

There appear to be two types of active galactic nuclei: one where we have a direct view to the inner part of the nucleus with the accretion disk where the energy is released (the “central engine”) and one where the inner part appears to be hidden. This dichotomy has been explained by a doughnut-shaped distribution of dense gas and dust surrounding the central part of the active nucleus, the so-called “torus”. If observed face-on, we can directly see the central engine through the hole in the torus, while if observed edge-on, the material of the torus obscures the view to the centre. The torus is also thought to play an important role in feeding the supermassive black hole, providing the material that will ultimately be swallowed. Trying to understand how the torus works is therefore important for understanding active galactic nuclei and their impact in general.

Although there is now a much clearer picture of a torus than before, there are some puzzles remaining: For example, both the dust disk and the polar dust have a temperature of about 300K (~30°C, i.e. about room temperature). Surprisingly, there is no evidence for hotter dust towards the centre as would be expected for a centrally heated dust distribution.

“The presence of both a bright disk-like component and a more extended polar dust component at a similar temperature were not predicted by the present models of active galactic nuclei”, concludes Gerd Weigelt, director at the MPIfR and head of the research group for infrared astronomy. “We need new models and new VLTI observations with the upcoming MATISSE instrument to improve our understanding of the three-dimensional dust distribution in the nuclei of active galaxies.”


Konrad R. W. Tristram

Max Planck Institute for Radio Astronomy, Bonn

Phone: +49 228 525-285
Fax: +49 228 525-229


Prof. Dr. Gerd Weigelt

Max Planck Institute for Radio Astronomy, Bonn

Phone: +49 228 525-243
Fax: +49 228 525-437


Dr. Norbert Junkes

Press and public relations

Max Planck Institute for Radio Astronomy, Bonn

Phone: +49 2 28525-399


Original publication

K. R. W. Tristram, L. Burtscher, W. Jaffe, K. Meisenheimer, S. F. Hönig, M. Kishimoto, M. Schartmann, G. Weigelt
The dusty torus in the Circinus galaxy: a dense disk and the torus funnel
Astronomy & Astrophysics, 13 March 2014; DOI: 10.1051/0004-6361/201322698 (

Konrad R. W. Tristram | Max-Planck-Institut

More articles from Physics and Astronomy:

nachricht Move over, lasers: Scientists can now create holograms from neutrons, too
21.10.2016 | National Institute of Standards and Technology (NIST)

nachricht Finding the lightest superdeformed triaxial atomic nucleus
20.10.2016 | The Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>