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

dc.contributor.authorAngioni, R.
dc.contributor.authorRos, E.
dc.contributor.authorKadler, M.
dc.contributor.authorOjha, R.
dc.contributor.authorMüller, C.
dc.contributor.authorEdwards, P. G.
dc.contributor.authorBurd, P. R.
dc.contributor.authorCarpenter, B.
dc.contributor.authorDutka, M. S.
dc.contributor.authorGulyaev, S.
dc.contributor.authorHase, H.
dc.contributor.authorHoriuchi, S.
dc.contributor.authorKrauß, F.
dc.contributor.authorLovell, J. E. J.
dc.contributor.authorNatusch, T.
dc.contributor.authorPhillips, C.
dc.contributor.authorPlötz, C.
dc.contributor.authorQuick, J. F. H.
dc.contributor.authorRösch, F.
dc.contributor.authorSchulz, R.
dc.contributor.authorStevens, J.
dc.contributor.authorTzioumis, A. K.
dc.contributor.authorWeston, S.
dc.contributor.authorWilms, J.
dc.contributor.authorZensus, J. A.
dc.date.accessioned2020-04-13T13:41:57Z
dc.date.available2020-04-13T13:41:57Z
dc.date.issued2019-07-15
dc.description.abstractAims. In the framework of the multi-wavelength and very long baseline interferometry (VLBI) monitoring program TANAMI (Tracking Active Nuclei with Austral Milliarcsecond Interferometry), we study the evolution of the parsec-scale radio emission in radio galaxies in the southern hemisphere and their relationship to the γ-ray properties of the sources. Our study investigates systematically, for the first time, the relationship between the two energy regimes in radio galaxies. In this first paper, we focus on Fermi-LAT-detected sources. Methods. The TANAMI program monitors a large sample of radio-loud AGN at 8.4 GHz and 22.3 GHz with the Australian long baseline array (LBA) and associated telescopes in Antarctica, Chile, New Zealand and South Africa. We performed a kinematic analysis for five γ-ray detected radio galaxies using multi-epoch 8.4 GHz VLBI images, deriving limits on intrinsic jet parameters such as speed and viewing angle. We analyzed 103 months of Fermi-LAT data in order to study possible connections between the γ-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 (Monitoring Of Jets in Active galactic nuclei with VLBA Experiments) survey, with a total of fifteen sources. Results. We find that the first γ-ray detection of Pictor A might be associated with the passage of a new VLBI component through the radio core, which appears to be a defining feature of high-energy emitting Fanaroff-Riley type II radio galaxies. We detect subluminal parsec-scale jet motions in the peculiar AGN PKS 0521−36, and we confirm the presence of fast γ-ray variability in the source down to timescales of six hours, which is not accompanied by variations in the VLBI jet. We robustly confirm the presence of significant superluminal motion, up to βₐₚₚ ∼ 3, in the jet of the TeV radio galaxy PKS 0625−35. Our VLBI results constrain the jet viewing angle to be θ <  53°, allowing for the possibility of a closely aligned jet. Finally, by analyzing the first pc-scale multi-epoch images of the prototypical compact symmetric object (CSO) PKS 1718−649, we place an upper limit on the separation speed between the two mini-lobes. This in turn allows us to derive a lower limit on the age of the source. Conclusions. We can draw some preliminary conclusions on the relationship between pc-scale jets and γ-ray emission in radio galaxies, based on Fermi-LAT-detected sources with available multi-epoch VLBI measurements. We find that the VLBI core flux density correlates with the γ-ray flux, as seen in blazars. On the other hand, the γ-ray luminosity does not show any dependence on the core brightness temperature and core dominance, which are two common indicators of jet Doppler boosting. This seems to indicate that γ-ray emission in radio galaxies is not driven by orientation-dependent effects, as in blazars, in accordance with the unified model of jetted AGN.en_US
dc.description.sponsorshipWe thank Laura Vega García for the development of the Python GUI-based code that was used for the kinematic analysis and the spectral index maps. We thank the anonymous journal referee, the Fermi-LAT internal referee, Bindu Rani, the MPIfR internal referee, Rocco Lico, as well as Marcello Giroletti, David Thompson and Nicola Omodei for useful comments which improved the manuscript. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration; data from the MOJAVE database that is maintained by the MOJAVE team (Lister et al. 2018); APLpy, an open-source plotting package for Python (Robitaille & Bressert 2012); Astropy, (http://www.astropy.org) a community-developed core Python package for Astronomy (Astropy Collaboration 2013, 2018) C.M. acknowledges support from the ERC Synergy Grant “BlackHoleCam: Imaging the Event Horizon of Black Holes” (Grant 610058). R.S. gratefully acknowledge support from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007–2013)/ERC Advanced Grant RADIOLIFE-320745. The Fermi-LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT, as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States; the Commissariat á l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France; the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy; the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK), and Japan Aerospace Exploration Agency (JAXA) in Japan; and the K. A. Wallenberg Foundation, the Swedish Research Council, and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Etudes Spatiales in France. The Long Baseline Array is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. This study made use of data collected through the AuScope initiative. AuScope Ltd is funded under the National Collaborative Research Infrastructure Strategy (NCRIS), an Australian Commonwealth Government Programme. This work made use of the Swinburne University of Technology software correlator, developed as part of the Australian Major National Research Facilities Programme. This work was supported by resources provided by the Pawsey Supercomputing Centre with funding from the Australian Government and the Government of Western Australia. Hartebeesthoek Radio Astronomy Observatory (HartRAO) is a facility of the National Research Foundation (NRF) of South Africa. This research was funded in part by NASA through Fermi Guest Investigator grants NNH10ZDA001N, NNH12ZDA001N, and NNH13ZDA001N-FERMI (proposal numbers 41213, 61089, and 71326, respectively). This research was supported by an appointment to the NASA Postdoctoral Program at the Goddard Space Flight Center, administered by Universities Space Research Association through a contract with NASA. This work was performed in part under DOE Contract DE-AC02-76SF00515. We would like to thank the Institute of Radio Astronomy and Space Research, AUT University, New Zealand for the use and operational support of their radio telescopes in the collection of data for this work.en_US
dc.description.urihttps://www.aanda.org/articles/aa/abs/2019/07/aa35697-19/aa35697-19.htmlen_US
dc.format.extent35 pagesen_US
dc.genrejournal articlesen_US
dc.identifierdoi:10.13016/m2je0q-v79y
dc.identifier.citationGamma-ray emission in radio galaxies under the VLBI scope - I. Parsec-scale jet kinematics and high-energy properties of γ-ray-detected TANAMI radio galaxies, R. Angioni, E. Ros, M. Kadler, R. Ojha, C. Müller, P. G. Edwards, P. R. Burd, B. Carpenter, M. S. Dutka, S. Gulyaev, H. Hase, S. Horiuchi, F. Krauß, J. E. J. Lovell, T. Natusch, C. Phillips, C. Plötz, J. F. H. Quick, F. Rösch, R. Schulz, J. Stevens, A. K. Tzioumis, S. Weston, J. Wilms and J. A. Zensus A&A, 627 (2019) A148, https://doi.org/10.1051/0004-6361/201935697en_US
dc.identifier.urihttps://doi.org/10.1051/0004-6361/201935697
dc.identifier.urihttp://hdl.handle.net/11603/18021
dc.identifier.urihttp://simbad.u-strasbg.fr/simbad/sim-ref?querymethod=bib&simbo=on&submit=submit+bibcode&bibcode=2019A%26A...627A.148A
dc.identifier.urihttps://ned.ipac.caltech.edu/cgi-bin/objsearch?search_type=Search&refcode=2019A%26A...627A.148A
dc.identifier.urihttp://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/A+A/627/A148
dc.language.isoen_USen_US
dc.publisherEDP sciencesen_US
dc.relation.isAvailableAtThe University of Maryland, Baltimore County (UMBC)
dc.relation.ispartofUMBC Physics Department Collection
dc.relation.ispartofUMBC Faculty Collection
dc.relation.ispartofUMBC Center for Space Sciences and Technology (CSST) / Center for Research and Exploration in Space Sciences & Technology II (CRSST II)
dc.rightsThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
dc.rightsAttribution 3.0 United States*
dc.rights.urihttp://creativecommons.org/licenses/by/3.0/us/*
dc.titleGamma-ray emission in radio galaxies under the VLBI scope I. Parsec-scale jet kinematics and high-energy properties of γ-ray-detected TANAMI radio galaxiesen_US
dc.typeTexten_US

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