Helical magnetic fields in the bent jet of the quasar OJ 287
November 12, 2018
A team of astronomers led by I. Myserlis at the MPIfR has analysed the polarisation states of the radiation of the quasar OJ 2817 registered at the Effelsberg 100-m radio telescope and found that this emission is originated in the central region, helical magnetic fields in a strongly bent jet. These results, based on intensive monitoring of the source brightness, were possible thanks to a new, sophisticated model of analysis which brings forward the capabilities of the Effelsberg telescope to unmatched precisions in any other radio telescope. The helix arc length of the source is of 0.84 lt-yr and its radius smaller than 47 light days. These results were published in the latest issue of the Astronomy & Astrophysics journal, see here.
Deep in the heart of M 87
September 12, 2018
A new publication led by MPIfR astronomers (see here) presents Global mm-VLBI Array (GMVA) observations at 86 GHz (λ = 3.5 mm) of the nearby radio galaxy Messier 87 (M 87), the central galaxy of the Virgo cluster in a distance of about 50 million light years. The highlight image shows the central region of M 87 at an angular resolution of ~50 μas (7 Schwarzschild radii).
Charge in the hole
August 12, 2018
Black holes have mass, angular momentum and potentially a charge. While the first two were measured routinely for some time now, constraining a black hole’s charge is more difficult. A comment by Marios Karouzos in "Nature Astronomy" refers to an original paper by MPIfR authors led by Michal Zajaček in MNRAS, proposing an observational way to test limits on the charge of Sgr A*, the black hole at the centre of the Milky Way. The original publication is available here.
Extreme outflows in radio-loud narrow-line Seyfert 1 galaxies
April 17, 2018
A team of astronomers led by Stefanie Komossa from the MPI für Radioastronomie in Bonn has studied four narrow-line Seyfert 1 galaxies and discovered extremely shifted spectral lines in their spectra, which indicate gas flying away from the central regions at speeds as high as 2450 km/s. These galaxies are also emitteres in the radio part of the electromagnetic spectrum. These results suggest that those galaxies are relatively young (in astronomical terms) with lifetimes of the order of magnitude of a million year. The results are published in the present issue of the journal Monthly Notices of the Royal Astronomical Society, to be found here.
New images from the Southern radio sky
February 7, 2018
An international team of astronomers led by C. Müller (Radboud U. & MPI für Radioastronomie) has published new images from a sample of southern blazars in the framework of the TANAMI program. These results are presented in the actual issue of Astronomy & Astrophysics. A powerful array of Southern telescopes located in Australia, Antarctica, Chile, New Zealand, and South Africa was assembled to obtain these unprecedented images. The TANAMI team found that that γ-ray loud sources tend to be more compact on parsec-scales and have higher brightness density in their central regions than γ-ray quiet sources. More information can be found in the original publication here.
Synthetic images from remote galaxies: understanding obscured emission
January 12, 2018
Numerical simulations performed by a team of astronomers in Frankfurt, Bonn, and Valencia led by C.M. Fromm have managed to synthesize the emission from radio objects with an obscuring torus. The numerical code Ratpenat was used to model several jets embedded in various ambient medium and torus configurations and subsequently computed their images, including jet emission and torus absorption. These simulations help understanding the physics of jets and tori, and suggets observational methods such as the core-shift to discern between different physical scenarios in the jet (e.g., if they have equal pressure inside and outside the jet, or if the pressure outside is larger). These results are shown in the present issue of the journal Astronomy & Astrophysics, for more details see here.