ORCID Profile
0000-0001-5606-6154
Current Organisation
Julius-Maximilians-Universität Würzburg
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Publisher: IOP Publishing
Date: 24-02-2016
Publisher: EDP Sciences
Date: 09-2010
Publisher: EDP Sciences
Date: 02-2012
Publisher: Oxford University Press (OUP)
Date: 05-11-2012
Publisher: American Astronomical Society
Date: 04-12-2013
Publisher: EDP Sciences
Date: 09-2020
DOI: 10.1051/0004-6361/202038236
Abstract: Aims. This is the second paper in our series studying the evolution of parsec-scale radio emission in radio galaxies in the Southern Hemisphere. Following our study of the radio and high-energy properties of γ -ray-emitting sources, here we investigate the kinematic and spectral properties of the parsec-scale jets of radio galaxies that have not yet been detected by the Fermi Large Area Telescope ( Fermi -LAT) instrument on board NASA’s Fermi Gamma-ray Space Telescope. For many sources, these results represent the first milliarcsecond resolution information in the literature. These studies were conducted within the framework of the Tracking Active Nuclei with Austral Milliarcsecond Interferometry (TANAMI) monitoring program and in the context of high-energy γ -ray observations from Fermi -LAT. Methods. We took advantage of the regular 8.4 GHz and 22.3 GHz Very Long Baseline Interferometry (VLBI) observations provided by the TANAMI monitoring program, and explored the kinematic properties of six γ -ray-faint radio galaxies. We complemented this with ∼8.5 years of Fermi -LAT data, deriving updated upper limits on the γ -ray emission from this subs le of TANAMI radio galaxies. We included publicly available VLBI kinematics of γ -ray-quiet radio galaxies monitored by the MOJAVE program and performed a consistent Fermi -LAT analysis. We combined these results with those from our previous paper to construct the largest s le of radio galaxies with combined VLBI and γ -ray measurements to date. The connection between parsec-scale jet emission and high-energy properties in the misaligned jets of radio galaxies was explored. Results. For the first time, we report evidence of superluminal motion up to β app = 3.6 in the jet of the γ -ray-faint radio galaxy PKS 2153−69. We find a clear trend of higher apparent speed as a function of distance from the jet core, which indicates that the jet is still being accelerated on scales of tens of parsecs, or ∼10 5 R s , corresponding to the end of the collimation and acceleration zone in nearby radio galaxies. We find evidence of subluminal apparent motion in the jets of PKS 1258−321 and IC 4296, and no measurable apparent motion for PKS 1549−79, PKS 1733−565, and PKS 2027−308. For all these sources, TANAMI provides the first multi-epoch kinematic analysis on parsec scales. We then compare the VLBI properties of γ -ray-detected and undetected radio galaxies, and find that the two populations show a significantly different distribution of median core flux density, and, possibly, of median core brightness temperature. In terms of correlation between VLBI and γ -ray properties, we find a significant correlation between median core flux density and γ -ray flux, but no correlation with typical Doppler boosting indicators such as median core brightness temperature and core dominance. Conclusions. Our study suggests that high-energy emission from radio galaxies is related to parsec-scale radio emission from the inner jet, but is not driven by Doppler boosting effects, in contrast to the situation in their blazar counterparts. This implies that γ -ray loudness does not necessarily reflect a higher prevalence of boosting effects.
Publisher: EDP Sciences
Date: 09-2014
Publisher: EDP Sciences
Date: 30-03-2015
Publisher: EDP Sciences
Date: 04-05-2016
Publisher: EDP Sciences
Date: 02-03-2011
Publisher: Elsevier BV
Date: 09-2014
Publisher: Springer Science and Business Media LLC
Date: 02-2014
Publisher: American Astronomical Society
Date: 04-2021
Abstract: A search for astrophysical pointlike neutrino sources using the data collected by the ANTARES detector between 2007 January 29 and 2017 December 31 is presented. A likelihood method is used to assess the significance of an excess of muon neutrinos inducing track-like events in correlation with the location of a list of possible sources. Different sets of objects are tested in the analysis: (a) a subs le of the Fermi 3LAC catalog of blazars, (b) a jet-obscured population of active galactic nuclei, (c) a s le of hard X-ray selected radio galaxies, (d) a star-forming galaxy catalog, and (e) a public s le of 56 very-high-energy track events from the IceCube experiment. None of the tested sources shows a significant association with the s le of neutrinos detected by ANTARES. The smallest p -value is obtained for the catalog of radio galaxies with an equal-weights hypothesis, with a pre-trial p -value equivalent to a 2.8 σ excess, which is equivalent to 1.6 σ post-trial. In addition, the results of a dedicated analysis for the blazar MG3 J225517+2409 are also reported: this source is found to be the most significant within the Fermi 3LAC s le, with five ANTARES events located less than one degree from the source. This blazar showed evidence of flaring activity in Fermi data, in spacetime coincidence with a high-energy track detected by IceCube. An a posteriori significance of 2.6 σ for the combination of ANTARES and IceCube data is reported.
Publisher: EDP Sciences
Date: 09-2014
Publisher: EDP Sciences
Date: 28-06-2016
Publisher: IOP Publishing
Date: 06-05-2014
Publisher: Springer Science and Business Media LLC
Date: 29-01-2016
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-11-2014
Abstract: Supermassive black holes with masses of millions to billions of solar masses are commonly found in the centers of galaxies. Astronomers seek to image jet formation using radio interferometry but still suffer from insufficient angular resolution. An alternative method to resolve small structures is to measure the time variability of their emission. Here we report on gamma-ray observations of the radio galaxy IC 310 obtained with the MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes, revealing variability with doubling time scales faster than 4.8 min. Causality constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole. We suggest that the emission is associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the radio jet.
Publisher: Springer Science and Business Media LLC
Date: 10-2013
Publisher: IOP Publishing
Date: 23-06-2016
Publisher: American Astronomical Society
Date: 11-04-2014
Publisher: Oxford University Press (OUP)
Date: 08-2013
Publisher: EDP Sciences
Date: 09-2016
Publisher: EDP Sciences
Date: 06-2014
Publisher: Springer Science and Business Media LLC
Date: 26-08-2011
Publisher: American Astronomical Society
Date: 12-07-2019
Publisher: EDP Sciences
Date: 29-10-2013
Publisher: American Astronomical Society
Date: 25-11-2019
Publisher: American Astronomical Society
Date: 30-01-2017
Publisher: IOP Publishing
Date: 11-11-2014
Publisher: EDP Sciences
Date: 20-05-2011
Publisher: Springer Science and Business Media LLC
Date: 18-04-2016
DOI: 10.1038/NPHYS3715
Publisher: American Astronomical Society
Date: 22-03-2016
Publisher: EDP Sciences
Date: 04-2016
Publisher: EDP Sciences
Date: 30-01-2014
No related grants have been discovered for Matthias Kadler.