Gamma-ray emission in radio galaxies under the VLBI scope -- I. Parsec-scale kinematics and high-energy properties of $\gamma$-ray detected TANAMI radio galaxies

Abstract

In the framework of the TANAMI multi-wavelength and VLBI monitoring, we study the evolution of the parsec-scale radio emission in radio galaxies in the southern hemisphere and their relationship to the $\gamma$-ray properties. In this first paper, we focus on Fermi-LAT-detected sources. We perform a kinematic analysis for five $\gamma$-ray detected radio galaxies using multi-epoch 8.4 GHz VLBI images, deriving limits on intrinsic jet parameters. We analyzed Fermi-LAT data in order to study possible connections between the $\gamma$-ray properties and the pc-scale jets of Fermi-LAT-detected radio galaxies, both in terms of variability and average properties. We discuss the individual source results and draw preliminary conclusions on sample properties including published VLBI results from the MOJAVE survey, with a total of fifteen sources. We find that the first $\gamma$-ray detection of Pictor A might be associated with the passage of a new VLBI component through the radio core. For the peculiar AGN PKS 0521-36, we detect subluminal parsec-scale jet motions, and we confirm the presence of fast $\gamma$-ray variability in the source down to timescales of 6 hours. We robustly confirm the presence of significant superluminal motion, up to ${\beta }_{app}\sim$3, in the jet of the TeV radio galaxy PKS 0625-35. Finally, we place a lower limit on the age of the Compact Symmetric Object (CSO) PKS 1718-649. We draw some preliminary conclusions on the relationship between pc-scale jets and $\gamma$-ray emission in radio galaxies. We find that the VLBI core flux density correlates with the $\gamma$-ray flux, as seen in blazars. On the other hand, the $\gamma$-ray luminosity does not show any dependence on the core brightness temperature and core dominance, two indicators of Doppler boosting, suggesting that $\gamma$-ray emission in radio galaxies is not driven by orientation-dependent effects.

Main text: 22 pages, 22 figures, 11 tables. Appendix: 19 pages, 10 figures, 9 tables. Accepted for publication in Astronomy and Astrophysics

References in corpus (11)

• MOJAVE: XV. VLBA 15 GHz Total Intensity and Polarization Maps of 437 Parsec-Scale AGN Jets From 1996-2017
• Fermi Gamma-ray Imaging of a Radio Galaxy
• The Dynamic Evolution of Young Extragalactic Radio Sources
• Relativistic Beaming and the Intrinsic Properties of Extragalactic Radio Jets
• Black hole lightning due to particle acceleration at subhorizon scales
• On the relation between AGN gamma-ray emission and parsec-scale radio jets
• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. XI. Spectral distributions
• TANAMI monitoring of Centaurus A: The complex dynamics in the inner parsec of an extragalactic jet
• A redshifted Fe K$\alpha$ line from the unusual gamma-ray source PMN J1603-4904
• Exploring the connection between radio and GeV-TeV gamma-ray emission in the 1FHL and 2FHL AGN samples
• The MHz-peaked radio spectrum of the unusual gamma-ray source PMN J1603-4904

Cited by in corpus (15)

• BASS XXII: The BASS DR2 AGN Catalog and Data
• TXS 0128+554: A Young Gamma-Ray Emitting AGN With Episodic Jet Activity
• A Quasi-periodic Oscillation in the gamma-ray Emission from the Non-blazar Active Galactic Nucleus PKS 0521-36
• Constraints on the abundance of supermassive primordial black holes from lensing of compact radio sources
• A search for Centaurus A-like features in the spectra of Fermi-LAT detected radio galaxies
• The Origin of High Energy Emission in the Young Radio Source PKS 1718-649
• Numerical Investigation of Dynamical and Morphological Trends in Relativistic Jets
• Highly Variable $\gamma$-Ray Emission of CTD 135 and Implications for its Compact Symmetric Structure
• A plausible link between dynamically unsettled molecular gas and the radio jet in NGC 6328
• First VLBI detection of Fornax A
• A search for $\gamma$-ray emission from a sample of local universe low-frequency selected radio galaxies
• TANAMI: Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry. III. First-epoch S band images
• Up around the bend: a multi-wavelength view of the quasar 3C 345
• The beaming effect for Fermi-LAT-detected FR-I radio galaxies
• Spatial variations of magnetic field along active galactic nuclei jets on sub-pc to Mpc scales