Jets blow gas out of a galaxy

Optical image (blue) of the galaxy 4C12.50. The inset shows a zoom in of the plasma jet and the cold gas (orange). The gas is distributed in a compact cloud (dark orange) and filaments (light orange) as result of the strong impact with the plasma jet. Credit: optical: HST/STSci/Tadhunter et al.; radio: VLBI, Morganti et al. 2013. 

The jets which are shot away into space by the supermassive black hole in the centre of a galaxy, clear gas away from the galaxy. The first clear evidence of this was obtained by a team led by Raffaella Morganti (ASTRON, University of Groningen). The results will be published in Science on the 6th of September.

 

Astronomers have been puzzled by the fact that many galaxies in the Universe seem to be depleted of their gas and are therefore unable to form any new stars. Fast outflows of gas have been observed in the past, but the mechanism driving these outflows was not understood. The suspicion that the powerful plasma jets that are shot into space by the central supermassive black hole are responsible for the expulsion of the gas has now been confirmed.

 

The nucleus of the galaxy 4C12.50 was observed with ultra-high resolution using a global Very Long Baseline Interferometry (VLBI) network, an array of radio telescopes across different continents which form a telescope the size of the earth. The high-resolution images resulting from the VLBI observations allowed the team to pin down the location of the gas outflow and to determine the speed with which the gas leaves the galaxy.

 

Morganti: "We suspected the importance of these radio jets from previous studies using for example the Westerbork Synthesis Radio Telescope. With these observations at much higher resolution we were finally able to map the distribution of the gas. It could not have been in better agreement with our expectations!"

 

The astronomers found that the gas is flowing out of the galaxy at a velocity of 1000 kilometers per second. Despite the strong push received from the jet, the temperature of the gas is low. quot;This was quite unexpected", says coauthor Tom Oosterloo (ASTRON, University of Groningen). "But this is exactly what is needed to make theory of galaxy formation and observations to agree. It is in particular cold gas that is the fundamental building block of new stars, but this gas is being expelled by the jet".

 

Using a global array of radio telescopes we are able to peek into the nucleus of 4C12.50, located two billion light years from the earth. Zsolt Paragi, astronomer at JIVE and coauthor: "These observations, combining telescopes from both the European VLBI Network and the Very Long Baseline Array in the U.S., allowed us to trace gas at the immediate proximity - just 300 light years - of the black hole of 4C12.5."

 

The success of the observations means that VLBI is a suitable technique to study the effect of the super massive black hole on the gas in its vicinity. Morganti will use this technique to study more objects where gas outflows are suspected to exist in the project ‘Exploiting new radio telescopes to understand the role of AGN in galaxy evolution', for which Morganti received a ERC Advanced Grant last year.

 

***

More information:

 

About ASTRON

ASTRON is the Netherlands Institute for Radio Astronomy (www.astron.nl). Its mission is to make discoveries in radio astronomy happen, via the development of novel and innovative technologies, the operation of world-class radio astronomy facilities, and the pursuit of fundamental astronomical research.

 

About JIVE

The Joint Institute for VLBI in Europe (JIVE, www.jive.nl) is a scientific foundation with a mandate to support the operations of the European VLBI Network (EVN, www.evlbi.org). For this purpose it maintains, operates and develops the EVN data correlator, a powerful supercomputer that combines the signals from radio telescopes located across the planet.

 
Contact:
 
Prof. dr. Raffaella Morganti, ASTRON, RuG
E-mail: morganti@astron.nl
Tel:      +31(0)521-595100
Mob:   +31 (0)6-11952523
 
Prof. dr. Tom A. Oosterloo, ASTRON, RUG
E-mail: oosterloo@astron.nl
Tel:      +31(0)521-595779 
 
Dr. Zsolt Paragi
E-mail: paragi@jive.nl
Tel: +31(0)521-596536
 
Article:
 
Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action,  R. Morganti, J. Fogasy, Z. Paragi, T. Oosterloo, M. Orienti, Science, 6 September 201.
 

Black holes – no place left to hide!

 Click here for a high res image

Very sensitive, wide-field observations with a worldwide network of radio telescopes have uncovered black holes residing in the centre of dust obscured galaxies. In some cases, the amount of dust is so large that even x-rays from the accreting black holes are absorbed in these systems. This is the result of research done by astronomers Chi, Barthel and Garrett from Groningen and Dwingeloo, and is set to appear in an upcoming issue of Astronomy & Astrophysics.

Also in apparently normal galaxies, it seems black holes grow steadily by devouring matter. The bright, exotic radiation, usually the result of these so-called accretion processes, seems to be completely obscured in some galaxies. Only a network of highly sensitive radio telescopes can detect these processes is the conclusion of the Dutch astronomers. The suspicion that the faint radio waves, emitted by many galaxies in the distant early universe is the result of accretion by their black holes, has now been proven.

Traditional radio telescopes, such as the Westerbork Synthesis Radio Telescope (WSRT), cannot determine the exact nature of the radio emission. The technique of Very Long Baseline Interferometry (VLBI) is necessary, in which a network of radio telescopes in different countries or continents observe the same object. The many gigabytes of data of the individual telescopes are then combined. This method digitally simulates a radio telescope of thousands of kilometers in diameter, and as a consequence with a very high resolution and sensitivity.

Using such a VLBI-network of sixteen radio telescopes on two continents (Europe and the United States), a so far unimaginable record sensitivity and resolution could be reached, undoubtedly proving the accretion activity of the distant galaxies.

‘We know many galaxies have black holes. Of course these need to grow to what they are now and it seems that, thanks to these VLBI-observations of the galaxies in the Northern Hubble Deep Field, we can now really observe this growth', say prof. Peter Barthel of the Kapteyn Institute of the University of Gronignen and prof. Michael Garrett of ASTRON, the Netherlands Institute for Radio Astronomy in Dwingeloo.

Barthel adds: ‘We are proud of these results, but what is mostly in our minds is the fact that the one who had the largest part in this study is no longer with us.' Doctoral student Seungyoup Chi, from South-Korea, died from a serious illness in the year he would obtain his PhD doctorate in Groningen. ‘This publication appears posthumous, also in his memory', say Barthel and Garrett, at the time supervisors of Chi.

More information:

Contact:
 
Prof. dr. Peter Barthel, Kapteyn Institute, University of Groningen
Tel: 050-363 4064/ 06-11391826
E-mail: p.d.barthel@rug.nl  

Prof. Michael A. Garrett

General Director & Scientific Director ASTRON Netherlands Institute for Radio Astronomy

Tel: +31 521 595126/+31 521595119
E-mail: garrett@astron.nl

Article: The publication "Deep, wide-field, global VLBI observations of the Hubble Deep Field-North and the Hubble Flanking Fields" by S. Chi, P.D. Barthel and M.A. Garrett is published beginning 2013 in Astronomy & Astrophysics.

 Source: ASTRON

APEX takes part in sharpest observation ever

PR Image eso1229a

Artist’s impression of the quasar 3C 279

PR Image eso1229b
Positions of the telescopes used in the 1.3 mm
VLBI observations of the quasar 3C 279

PR Image eso1229c
The Atacama Pathfinder Experiment (APEX)

PR Image eso1229d
The Submillimeter Telescope (SMT)
at the Arizona Radio Observatory

PR Image eso1229e
The Submillimeter Array (SMA) on Mauna Kea, Hawaii

PR Image eso1229f
Position of the quasar 3C 279 in the constellation of Virgo

Videos

PR Video eso1229a
Artist’s impression of the quasar 3C 279

PR Video eso1229b
Positions of the telescopes used in the 1.3 mm
VLBI observations of the quasar 3C 279

PR Video eso1229c
Artist’s impression of the quasar 3C 279
(alternative version)

Telescopes in Chile, Hawaii, and Arizona reach sharpness two million times finer than human vision

An international team of astronomers has observed the heart of a distant quasar with unprecedented sharpness, two million times finer than human vision. The observations, made by connecting the Atacama Pathfinder Experiment (APEX) telescope [1] to two others on different continents for the first time, is a crucial step towards the dramatic scientific goal of the “Event Horizon Telescope” project [2]: imaging the supermassive black holes at the centre of our own galaxy and others.

Astronomers connected APEX, in Chile, to the Submillimeter Array (SMA) [3] in Hawaii, USA, and the Submillimeter Telescope (SMT) [4] in Arizona, USA. They were able to make the sharpest direct observation ever [5], of the centre of a distant galaxy, the bright quasar 3C 279, which contains a supermassive black hole with a mass about one billion times that of the Sun, and is so far from Earth that its light has taken more than 5 billion years to reach us. APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. APEX is operated by ESO.

The telescopes were linked using a technique known as Very Long Baseline Interferometry (VLBI). Larger telescopes can make sharper observations, and interferometry allows multiple telescopes to act like a single telescope as large as the separation — or “baseline” — between them. Using VLBI, the sharpest observations can be achieved by making the separation between telescopes as large as possible. For their quasar observations, the team used the three telescopes to create an interferometer with transcontinental baseline lengths of 9447 km from Chile to Hawaii, 7174 km from Chile to Arizona and 4627 km from Arizona to Hawaii. Connecting APEX in Chile to the network was crucial, as it contributed the longest baselines.

The observations were made in radio waves with a wavelength of 1.3 millimetres. This is the first time observations at a wavelength as short as this have been made using such long baselines. The observations achieved a sharpness, or angular resolution, of just 28 microarcseconds — about 8 billionths of a degree. This represents the ability to distinguish details an amazing two million times sharper than human vision. Observations this sharp can probe scales of less than a light-year across the quasar — a remarkable achievement for a target that is billions of light-years away.

The observations represent a new milestone towards imaging supermassive black holes and the regions around them. In future it is planned to connect even more telescopes in this way to create the so-called Event Horizon Telescope. The Event Horizon Telescope will be able to image the shadow of the supermassive black hole in the centre of our Milky Way galaxy, as well as others in nearby galaxies. The shadow — a dark region seen against a brighter background — is caused by the bending of light by the black hole, and would be the first direct observational evidence for the existence of a black hole’s event horizon, the boundary from within which not even light can escape.

The experiment marks the first time that APEX has taken part in VLBI observations, and is the culmination of three years hard work at APEX’s high altitude site on the 5000-metre plateau of Chajnantor in the Chilean Andes, where the atmospheric pressure is only about half that at sea level. To make APEX ready for VLBI, scientists from Germany and Sweden installed new digital data acquisition systems, a very precise atomic clock, and pressurised data recorders capable of recording 4 gigabits per second for many hours under challenging environmental conditions [6]. The data — 4 terabytes from each telescope — were shipped to Germany on hard drives and processed at the Max Planck Institute for Radio Astronomy in Bonn.

The successful addition of APEX is also important for another reason. It shares its location and many aspects of its technology with the new Atacama Large Millimeter/submillimeter Array (ALMA) telescope [7]. ALMA is currently under construction and will finally consist of 54 dishes with the same 12-metre diameter as APEX, plus 12 smaller dishes with a diameter of 7 metres. The possibility of connecting ALMA to the network is currently being studied. With the vastly increased collecting area of ALMA’s dishes, the observations could achieve 10 times better sensitivity than these initial tests. This would put the shadow of the Milky Way's supermassive black hole within reach for future observations.

Notes

[1] APEX is a collaboration between the Max Planck Institute for Radio Astronomy (MPIfR), the Onsala Space Observatory (OSO) and ESO. Operation of APEX at Chajnantor is entrusted to ESO. APEX is a pathfinder for the next-generation submillimetre telescope, the Atacama Large Millimeter/submillimeter Array (ALMA), which is being built and operated on the same plateau.

[2] The Event Horizon Telescope project is an international collaboration, coordinated by the MIT Haystack Observatory (USA).

[3] The Submillimeter Array (SMA) on Mauna Kea, Hawaii, consisting of 8 dishes of 6 m diameter each, is operated by the Smithsonian Astrophysical Observatory (USA) and the Academia Sinica Institute of Astronomy and Astrophysics (Taiwan).

[4] The Submillimeter Telescope (SMT) of 10 m diameter on top of Mount Graham, Arizona, is operated by the Arizona Radio Observatory (ARO) in Tucson, Arizona (USA).

[5] Some indirect techniques have been used to probe finer scales, for example using microlensing (see heic1116) or interstellar scintillation, but this is a record for direct observations.

[6] These systems were developed in parallel in the USA (MIT-Haystack observatory) and in Europe (MPIfR, INAF — Istituto di Radioastronomia Noto VLBI Station, and HAT-Lab). A hydrogen maser time standard (T4Science) was installed as the very precise atomic clock. The SMT and SMA had already been equipped similarly for VLBI.

[7] The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ESO is the European partner in ALMA.
More information

The year 2012 marks the 50th anniversary of the founding of the European Southern Observatory (ESO). ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, 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 Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links

• Press release from MPIfR: in English and in German

• Information about APEX

• APEX telescope

• Max-Planck-Institute für Radioastronomie (MPIfR), Bonn, Germany

• Submillimeter Array, Hawaii

• Submillimeter Telescope, Arizona Radio Observatory

• Event Horizon Telescope

• MIT Haystack Observatory, USA
  

• INAF/Noto Digital BaseBand Converter Project

• ESO ALMA pages

• Joint ALMA Observatory

Contacts

Alan Roy
APEX VLBI Project Lead, Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 191
Email: aroy@mpifr-bonn.mpg.de

Thomas Krichbaum
APEX VLBI Project Scientist, Max-Planck-Institut für Radioastronomie
Bonn, Germany
Tel: +49 228 525 295
Email: tkrichbaum@mpifr-bonn.mpg.de

Shep Doeleman
MIT Haystack Observatory
Westford, USA
Tel: +1 781 981 5400 x5904
Email: dole@haystack.mit.edu

Michael Lindqvist
Onsala Space Observatory
Onsala, Sweden
Tel: +46 31 772 5508
Email: michael.lindqvist@chalmers.se

Lucy Ziurys
Director, Arizona Radio Observatory
Tucson, USA
Tel: +1 520 621-6525
Email: lziurys@as.arizona.edu

Jonathan Weintroub
Harvard-Smithsonian Center for Astrophysics
Cambridge, USA
Tel: +1 617 495 7319
Email: jweintroub@cfa.harvard.edu

Douglas Pierce-Price
APEX Public Information Officer, ESO
Garching bei München, Germany
Tel: +49 89 3200 6759
Email: dpiercep@eso.org