Contact

Prof. Dr. J. Anton Zensus

Director and Head of the Research Department
"Radio Astronomy/VLBI"

Phone: +49 228 525-298 (Secretary)

https://antonzensus.mpifr-bonn.mpg.de

Radio Astronomy / VLBI

Radio Astronomy / VLBI

 

Radiation from the heart of the powerful quasar RX J2314.9+2243

February 4, 2015

An international team lead by S. Komossa from the MPI for Radio Astronomy, has observed the quasar RX J2314.9+2243 in the optical, ultra-violet, X-rays, and radio bands.  A fifth of all active galaxies is radio loud.  A new class of these objects was discovered in the last years, the narrow-line Seyfert 1 galaxies.  Those objects have extreme emission properties.  One of them, with a high radio loudness, has been observed systematically by the Bonn team.  The results show an energy distribution originated by electrons under the influence of strong magnetic fields (synchrotron radioation).  This quasar shows as well a powerful outflow in the optical part of the spectrum.  The results of this work have been published in the latest issue of Astronomy & Astrophysics. [more]

How compact and bright can be a source in the sky?

January 30, 2015

The answer of this question can be better answered after the last development published in the last issue of Astronomy & Astrophysics by Andrei P. Lobanov from the MPI for Radio Astronomy.  The physical properties of compact sources can be characterised by the brightness temperature.  The new method presented by Lobanov, which allows us to compute the brightness temperature limits from interferometric measurements, has been successfully tested with data from the MOJAVE project and from mm-VLBI observations.  Its appliacation to space VLBI obsrvations promises new limits in the brightness temperature of compact, remote objects, for future observations. [more]

A new method to analyse astronomical images

January 27, 2015

A new, automatic method for astronomical image analysis has been developed by the graduate student Florent Mertens and his supervisor, Andrei Lobanov, both at the MPI for Radio Astronomy.  This mehtod is based on wavelet functions to determine distinct regions in astronomical images and to study their evolution, following the wavelet-based image segmentation and evaluation (WISE) approach.  This was successfully tested in the sources 3C 273 and 3C 120.  The two-dimensional evolution of the features of the jets in both sources was studied, and it is compatible with the effect of Kelvin-Helmholtz instabilities.  This work was published in the last issue of the journal Astronomy & Astrophysics [more]

Galaxy evolution studied with the 100-m telescope in Effelsberg

December 23, 2014

A study lead by MPIfR astronomer Mariangela Vitale has probed the importance of active galactic nuclei (AGN) in galaxy evolution.  Models need AGN feedback to explain the observed luminosity in galaxies.   The team studied a sample of radio emitters at distances between 580 Mio lt-yr and 7150 Mio lt-yr, to search for spectral evolution and al ink between optical and radio emission.  Some hints of spectral index flattening in high-metallicity star-forming galaxies, composite galaxies, and Seyferts have been found.  Therefore, galaxies along the sequence are transitioning from the active star-forming calaxies (blue cloud) to the passive elliptical galaxies (red sequence).  This supports the suggestion that AGN shut down star formation and allow transition from one galaxy class to the other.   These results have been published in the last issue of the journal Astronomy & Astrophysics, see the original publication here.

Galaxy in false colours: The chart shows IC 310 in the gamma ray range. The inset zooms into the centre of the galaxy and shows details of the jet, taken in the radiowave range by the European VLBI Network. The contour lines describe the jet’s structure, which starts near the black hole at the heart of IC310. Zoom Image
Galaxy in false colours: The chart shows IC 310 in the gamma ray range. The inset zooms into the centre of the galaxy and shows details of the jet, taken in the radiowave range by the European VLBI Network. The contour lines describe the jet’s structure, which starts near the black hole at the heart of IC310. [less]

Lightning flashes from a black hole - MAGIC telescopes observe an extremely short, powerful outburst of radiation in Galaxy IC 310

06 November 2014

The radio galaxy IC 310 in the Perseus constellation is approximately 260 million light years away from Earth. Astronomers assume there is a supermassive black hole at its centre. This black hole was the setting for an extremely powerful outburst of gamma rays which was observed by the MAGIC telescopes on La Palma in the Canary Islands. The source exhibited one of the fastest radiation variations which researchers have ever been able to detect in an extragalactic object at these energies.  Ancillary observations from the European VLBI Network reveal a powerful radio jet.  Uwe Bach and Eduardo Ros from the MPI für Radioastronomie are co-authors of this work, published in today's issue of the journal Science.  [more]

Media Impact: IFLScience, Universe Today, Science Daily, SpaceRef, MSN (Spanish)

 

Discovery of a correlation between gamma-ray emission and jet position angle in a blazar

06 November 2014

A team of researchers led by Bindu Rani from the VLBI department of the MPI für Radioastronomie reports for the first time the correlation between gamma-ray emission and the position angle of a jet in a blazar, namely, in the object S5 0716+714.  This implies that the inner jet morphology of AGN jets has a direct connection to the emission of gamma-ray flares.  The observations of this BL Lac objects were carried between August 2008 and September 2013.  The mm-VLBI core radio brightness variations are delayed with respect to the γ-ray flux by 82±32 days.  These results are published in the last issue of the journal Astronomy & Astrophysics, and are part of the successful PhD work of Bindu Rani, presently a postdoctoral fellow at the MPIfR. [more]

The central engine of broad-absorption-line quasars has the same properties for sources with or without a jet

29 September 2014

A study led by Gabriele Bruni from the MPI für Radioastronomie has focused in the study of two samples of broad-absorption-line quasars, aiming for explaining the reasons for the rarity of the radio-loud ones.  The study, carried out with the Telescopio Nazionale Galileo, could show that both classes of objects have the same black-hole mass, the broad-line region radius, and Eddington ratio.  These results are presented in the last issue of Astronomy & Astrophysics. [more]

Type Ia supernovae stem from the explosion of white dwarfs coupled with twin stars

August 20, 2014

Study discards possibility that type Ia supernovae might stem from explosions of white dwarfs nourished by normal stars. Were these conclusions to become generalized, type Ia supernovae might no longer serve as “standard candles” to measure astronomical distances.  This work, using the European VLBI Network and the 100-m radio telescope in Effelsberg, was done in collaboration with the MPIfR VLBI Department. [more]
Black holes are thought to dominate their surroundings by their extremely powerful gravitational pull. However, other forces which are usually considered to be weaker are also at work near these objects. These include forces exerted by the pressure of the in-falling hot gas and magnetic forces. In a surprising twist, a team of astronomers at the Max Planck Institute for Radio Astronomy (MPIfR) and Lawrence Berkeley National Laboratory (LBNL) has found that in fact magnetic forces can be as strong as gravity near supermassive black holes. These findings are published in this week's issue of Nature.

Powerful magnetic fields challenge black holes' pull

June 04, 2014

Black holes are thought to dominate their surroundings by their extremely powerful gravitational pull. However, other forces which are usually considered to be weaker are also at work near these objects. These include forces exerted by the pressure of the in-falling hot gas and magnetic forces. In a surprising twist, a team of astronomers at the Max Planck Institute for Radio Astronomy (MPIfR) and Lawrence Berkeley National Laboratory (LBNL) has found that in fact magnetic forces can be as strong as gravity near supermassive black holes. These findings are published in this week's issue of Nature. [more]
Where in powerful jets of distant active galaxies – the mightiest and most energetic objects known – are the violent outbursts of high energy gamma-ray emission produced? Very close to the central supermassive black hole and accretion disk powering these systems, or at larger distances from the "central engine", i.e. further downstream in the jet? New insights into this long-standing question became possible recently, thanks to intensive, multi-frequency radio observations of powerful active galaxies. An international team of astronomers led by Lars Fuhrmann from the Max Planck Institute for Radio Astronomy in Bonn, Germany, used some of the best single-dish radio telescopes for several years, in combination with NASA’s <em>Fermi</em> Gamma-ray Space Telescope, to study the place where the high energy outbursts occur. For the first time a connection between dramatic outbursts of high energy gamma-ray emission and their counterparts at many radio frequencies has been established for a large sample of galaxies. Measuring delays in time between these events finally produced better constraints on the exact location in the vicinity of supermassive black holes where the gamma-ray outbursts take place.   <br />The results were published in the current issue of "Monthly Notices of the Royal Astronomical Society" (Oxford University Press).

Violent gamma-ray outbursts near supermassive black holes

May 22, 2014

Where in powerful jets of distant active galaxies – the mightiest and most energetic objects known – are the violent outbursts of high energy gamma-ray emission produced? Very close to the central supermassive black hole and accretion disk powering these systems, or at larger distances from the "central engine", i.e. further downstream in the jet? New insights into this long-standing question became possible recently, thanks to intensive, multi-frequency radio observations of powerful active galaxies. An international team of astronomers led by Lars Fuhrmann from the Max Planck Institute for Radio Astronomy in Bonn, Germany, used some of the best single-dish radio telescopes for several years, in combination with NASA’s Fermi Gamma-ray Space Telescope, to study the place where the high energy outbursts occur. For the first time a connection between dramatic outbursts of high energy gamma-ray emission and their counterparts at many radio frequencies has been established for a large sample of galaxies. Measuring delays in time between these events finally produced better constraints on the exact location in the vicinity of supermassive black holes where the gamma-ray outbursts take place.  
The results were published in the current issue of "Monthly Notices of the Royal Astronomical Society" (Oxford University Press). [more]

An armada of telescopes decipher the emission of the powerful galaxy GB 1310+487

April 28, 2014

An international team of astronomers led by K. Sokolovsky and F. Schinzel at the MPIfR has deciphered the broadband emission of the narrow-line gamma-ray-loud AGN GB 1310+487.  Observations include data from the Fermi, AGILE and Swift space telescopes at high frequencies and from the Kanata, NOT, Keck, OAGH, WISE, IRAM 30-m, OVRO 40-m, Effelsberg 100-m, RATAN-600 and the VLBA in the optical-infrared-radio area.  Fermi/LAT observations reveal a strong correlation between the gamma-ray flux and spectral index, being harder at the brighter flux.  The gamma flares occurred before and during a slow rising trend of the radio eission, but no direct association between gamma and radio flares could be stablishesd.  The results are published in Astronomy & Astrophysics.  [more]

A pair of supermassive black holes in orbit around one another have been discovered by an international research team including Stefanie Komossa from the Max Planck Institute for Radio Astronomy in Bonn, Germany. This is the first time such a pair could be found in an ordinary galaxy. They were discovered because they ripped apart a star when ESA’s space observatory XMM-Newton happened to be looking in their direction.<br /><br />The findings are published in the May 10 issue of the “Astrophysical Journal”, and appeared online today at the astrophysics preprint server.<br /><br />

A Dance of Black Holes

April 22, 2014

A pair of supermassive black holes in orbit around one another have been discovered by an international research team including Stefanie Komossa from the Max Planck Institute for Radio Astronomy in Bonn, Germany. This is the first time such a pair could be found in an ordinary galaxy. They were discovered because they ripped apart a star when ESA’s space observatory XMM-Newton happened to be looking in their direction.

The findings are published in the May 10 issue of the “Astrophysical Journal”, and appeared online today at the astrophysics preprint server.

[more]

Merging galaxies and the size of their cores

February 26, 2014

A study of a sample of 52 double nucleus disk galaxies, led by M. Mezcua and A.P. Lobanov from the MPIfR, derived the luminosity of each of the nuclei and their relative separation from a multi-component photometric fit of the galaxies in the Sloan Digital Sky Survey optical images.  The nuclei in moft of the sources have projected separations smaller than 10000 light-years.  A sample of 19 double nucleus disk galaxies have separations smaller than 3000 light-years and are candidates to be binary active galactic nuclei. [more]

 
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