Here we show recent research results from the Radio Astronomy/Very-Long-Baseline Interferometry department.
Data for 2.5 years from the Effelsberg Key Science Project F-GAMMA released
28 November 2016
The present issue of the journal Astronomy & Astrophysics reports the light curves and spectra of a sample of about 60 sources observed with the Radio Telescope Effelsberg (together with the IRAM 30 m telescope at Pico Veleta). This unprecedented data base reveals that all observed gamma-loud radio galaxies are variable accross all frequencies with variability increasing at the higher ones. Interestingly, radio flux at wavelengths of 3.5 mm and 2.0 mm correlate with gamma-ray fluxes. The F-GAMMA project is one of the most relevant radio astronomical projects at present, connecting the radio emission of blazars with their high-energy properties. More information is available at the original publication, led by the MPIfR astronomer L. Fuhrmann, here.
The puzzling Narrow-Line Seyfert Galaxy 1H 0323+342, observed at the highest resolution in the radio regime
1 November 2016
A team of astronomers led by L. Fuhrmann from the MPIfR has observed the radio galaxy 1H 0323+342 with an armada of telescopes including the Effelsberg 100-m and IRAM 30-m telescopes, in the course of the F-GAMMA program. The observations reveal superluminal motions with apparent speeds up to seven times the light speed. Those allowed the international team to estimate the viewing angle of the relativistic flow, to be smaller than 9º. These findings have been published in the present issue of the journal Research in Astronomy and Astrophysics. More information can be found at the original publication here.
The quasar 3C 273 and its γ-ray flares: results from a multi-band campaign
September 27, 2016
Total intensity and polarization observations of the quasar 3C 273 were carried out between 2013 December 28 and 2014 January 03 using the Fermi-Large Area Telescope, Swift-XRT, Swift-UVOT, and Korean VLBI Network telescopes. No relationship was found with the radio total intensity and polarised emission. However, the coincidence of the increase in radio polarization with the X-ray flux supports the picture that X-rays are produced via inverse-Compton scattering of radio photons. Correlation was found between a flare in the optical/near-UV passbands and a concurrent γ-ray flare These results are presented in the last issue of the journal Monthly Notices of the Royal Astronomical Society, see here.
Magnetism dominates environment of the central black hole
A battery of mathematical tools to attack the emission mechanisms in a remote blazar
May 11, 2016
A study based on the Master Thesis of Ms. Céline Chidiac and published in the present issue of Astronomy & Astrophysics shows the nature of the variability in the quasar 3C 279. This remote blazar shows violent variations in brightness through the electromagnetic spectrum. The relationship between the light curves at different bands (radio, X, and γ rays) has been studied by the power spectral density. Results show a delay between the variations at γ and radio waves, where the former lead, suggesting that the high-energy emission originates at a region 4 lt-yr inside the jet apex. A delay is also observed from the γ to the X rays. More details on the study are provided in the original publication here.
The location of the γ rays in the blazar PKS 1502+106
May 10, 2016
A team of MPIfR astronomers led by V. Karamanavis has addressed the location of the high-energy emission i the blazar PKS 1502+106 from multi-band studies of a radio flare. Single-dish observations were carried out at 12 frequencies in the range 2.5 to 227 GHz. The γ-ray active region is located 6.2 lt-yr away from the jet base of the source. The data used in this work have been collected within the framework of the Fermi-GST AGN Multi-frequency Monitoring Alliance (F-GAMMA) program. The results are published in the present issue of the journal Astronomy and Astrophysics. The original publication is available here.
The radio and γ-ray properties of the TANAMI sources
May 4, 2016
The TANAMI program observes parsec-scale radio jets of southern γ-ray bright active galactic nuclei simultaneously with Fermi/LAT monitoring of their γ-ray emission, via VLBI observations. A study published this week in Astronomy & Astrophysics and led by the MPIfR astronomer Moritz Böck shows that a 72% of these blazars can be associated with bright γ sources. The association differs from the optical class of sources, being 76% for quasars and 17% for galaxies. The birghtness temperatures of the radio cores increase with the γ-ray luinosity. The results show as well that there is a direct relationship between the γ-ray and the radio luminosities. More information about this study is available here.
Coincidence of a highly energetic outburst of an active galactic nucleus with a neutrino event at PeV energy
Magnetic field swings in the blazar 3C 279
April 28, 2016
A study of the polarised emission of thequasar 3C 279 led by the MPIfR astronomer Dr. Sebastian Kiehlmann reports in the present issue of the journal Astronomy and Astronomy about the changes in the field over the past few years. Data from optical polarimetry were combined and the location of the electric vector position angle of the linearly polarized emission were studied in detail. The most spectacular changes occurred in mid 2011 with a 360º rotation. The large team of astronomers conclude that during two different optical flxu states, two different processes govern the changes in polarisation, which has a stochastic nature during the low-brightness state and a deterministic nature during the flaring activity. More information is available here.
For the first time, VLBI images have been obtained of the archetypal radio galaxy Cygnus A at the frequency of 86 GHz. The high spatial resolution gives insight into the transverse width profile at the onset of the two-sided flow. The publication from an MPIfR research team led by Biagina Boccardi appears as highlight in the present issue of the research journal "Astronomy & Astrophysics"
Numerical simulations provide clue on the physics of flaring blazars
March 24, 2016
A team led by Christian M. Fromm from the VLBI group of the MPIfR has reported results of relativistic hydrodynamic simulations of jets. The goal was to investigate the evolution of the brightness of their source and the polychromatic properties in radio wavelenghts assuming the interaction of a traveling shock wave with a steady (recollimation) shock wave in the relativistic outflow of blazars. The results, published today in Astronomy and Astrophysics, reveal that the injection of porturbations in a jet have a signature in the emission of the source at centimetre wavelengths previously to the main flare. This is observed both in single-dish and in long-baseline interferometric observations. These results help interpreting early findings on the blazar CTA 102 during a major outburst in the mid 2000s.
More information can be found in the original publication here.
RadioAstron observations of the extremely hot heart of quasar 3C 273
LOFAR radio telescope catches signals from disintegrating cosmic particles, revealing their nature
A 'wise' method to study radio images and detect different speed patterns
February 12, 2016
Florent Mertens and Andrei Lobanov from the MPI für Radio Astronomy have proven multiple velocity components in partially overlapping emitting regions in radio images at parsec-scales. 3C 120, 3C 120, and M 87 images were addressed by the 'wavelet-based image segmenttion and evaluation' (WISE) technique of decomposition of two-dimensional structures. The method demonstrates the robust detection of a faster spine and a slower sheath speed in an extragalactic, relativistic outflow. This approach has potential application beyond the field of radio imaging.
More information is available at the original publication here.
A puzzling feature off-stream in the high-energy blazar Mrk 501
February 2, 2016
An international team led by Shoko Koyama from the MPI für Radio Astronomy has discovered an off-axis jet feature in the source Mrk 501. Her team used millimetre-wavelength very-long-baseline interferometry to probe the sub-parsec scales of the innermost regions of this region. All images show a new feature in the northeast direction, whereas the source shows a southward relativistic outflow in all earlier images. Her studies show spectral information between the 7mm and 3mm wavelengths as well.
Additional information on these findings can be found here.
Improving the images of the black hole at the centre of our Galaxy: mitigation of source variability
February 1st, 2016
A study led by the MPIfR astronomer RuSen Lu reports in the present issue of The Astrophysical Journal results on the mitigation of the brightness variability effect in the studies of the source. The ultimate goal of VLBI observations of this source and the nearby galaxy M 87 is to image the immediate neighbourhood of the central super-massive black hole at event horizon scales. The work presented by Lu shows methods to prevent degradation of the image of this source by source vriability, as predicted by general relativistic magnetohydrodynamic simulations. Additionally, interstellar scattering degrades the imaging process as well. These techniques will be applied to the source study for future Event Horizon Telescope (EHT) observations. More information can be found here.
A blazar at extreme angular resolution: PKS 1502+106
January 26, 2016
A study led by MPIfR astronomer V. Karamanavis, published this week in the journal Astronomy & Astrophysics, shows the compact morphology and superluminal motions of the blazar PKS 1502+106. This object was discovered by the Fermi/LAT satellite in gamma rays and shows a rapid variability. The source was studied in a multi-wavelength campaign, including also single-dish data from Effelsberg and other antennas in the F-GAMMA project. The values measured for the superluminal motions in the source range from 5 to 22 times the speed of light, suggesting a very small viewing angle to the source jet. More information can be found in the original publication here.
Radio astronomers look deep inside a galactic nucleus
Unveiling Gargantua: searching central cluster black holes
January 14, 2016
More information can be found in the original publication here.