Astrometry of 25 Southern Hemisphere Radio Sources from a VLBI Short-Baseline Survey

Fey, A. L.; Ojha, R.; Reynolds, John E.; Ellingsen, S. P.; McCulloch, P. M.; Jauncey, D. L.; Johnston, K. J.

doi:10.1086/424941

Cited by 15 publications

(13 citation statements)

References 21 publications

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“…• , and hence the jet luminosity, roughly, L j πR 2 cΓ (2001), Fey et al (2004) and Burke-Spolaor et al (2009). The ASCA measurements of the lobes' and core spectra within the range 0.7−10 keV, as discussed in Tashiro et al (1998), are denoted by red and blue bow ties, respectively.…”

Section: Discussionmentioning

confidence: 99%

Fermi-LAT andSuzakuobservations of the radio galaxy Centaurus B

Katsuta

Tanaka

Stawarz

et al. 2013

A&A

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Centaurus B is a nearby radio galaxy positioned in the southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months of accumulated Fermi-LAT data of the γ-ray counterpart of the source initially reported in the 2nd Fermi-LAT catalog, and of newly acquired Suzaku X-ray data. We confirm its detection at GeV photon energies and analyze the extension and variability of the γ-ray source in the LAT dataset, in which it appears as a steady γ-ray emitter. The X-ray core of Centaurus B is detected as a bright source of a continuum radiation. We do not detect, however, any diffuse X-ray emission from the known radio lobes, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. Two scenarios that connect the X-ray and γ-ray properties are considered. In the first one, we assume that the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. In this case, modeling the inverse-Compton emission shows that the observed γ-ray flux of the source may in principle be produced within the lobes. This association would imply that efficient in-situ acceleration of the radiating electrons is occurring and that the lobes are dominated by the pressure from the relativistic particles. In the second scenario, with the diffuse X-ray emission well below the Suzaku upper limits, the lobes in the system are instead dominated by the magnetic pressure. In this case, the observed γ-ray flux is not likely to be produced within the lobes, but instead within the nuclear parts of the jet. By means of synchrotron self-Compton modeling, we show that this possibility could be consistent with the broad-band data collected for the unresolved core of Centaurus B, including the newly derived Suzaku spectrum.

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Section: Discussionmentioning

confidence: 99%

Fermi-LAT andSuzakuobservations of the radio galaxy Centaurus B

Katsuta

Tanaka

Stawarz

et al. 2013

A&A

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“…Twelve out of sixteen TANAMI radio galaxies are included in this sample 3 . We looked for existing VLBI measurements for each of these 83 sources individually on the NASA/IPAC Extragalactic Database (NED), and found existing data for six non-TANAMI radio galaxies, from the Very Long Baseline Array (VLBA) at 8.6 GHz (Petrov et al 2005) or the Long Baseline Array (LBA) at 8.4 GHz or 4.8 GHz (Fey et al 2004;Hancock et al 2009). Therefore, in total we found 22 southern radio galaxies with compact radio emission on VLBI scales.…”

Section: The Tanami Radio Galaxy Samplementioning

confidence: 99%

Gamma-ray emission in radio galaxies under the VLBI scope

Angioni

Ros

Kadler

et al. 2019

A&A

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Aims. 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.

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“…We have used the Australian Long Baseline Array (LBA), augmented by telescopes in South Africa, Hawaii, and Japan, to image 48 ICRF sources at a radio frequency of 8.4 GHz. These are the second set of results from a multiepoch observing program that seeks to image, at least twice, all existing southern hemisphere ICRF sources, as well as new additions being made as part of our astrometry program (Fey et al 2004a(Fey et al , 2004b. Images of 69 sources were reported in Ojha et al (2004b, hereafter Paper I ).…”

Section: Introductionmentioning

confidence: 99%

VLBI Observations of Southern Hemisphere ICRF Sources. I.

et al. 2004

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We present 8.4 GHz very long baseline interferometry (VLBI) observations of 48 southern hemisphere extragalactic sources from the International Celestial Reference Frame. These are the second in a series of observations intended to image all such sources in the southern hemisphere at milliarcsecond resolution and bring the total number of observed sources to 111. We use these data, together with previously published data, to quantify the magnitude of the expected effect of intrinsic source structure on astrometric bandwidth synthesis VLBI observations by calculating a ''structure index'' for the sources; the structure index yields an estimate of their astrometric quality. Approximately 35% of sources in our sample have a structure index indicative of compact or very compact structures. The remaining two-thirds of our sources are less compact and should probably be avoided in astrometric and geodetic VLBI experiments requiring the highest accuracy unless intrinsic source structure can be accounted for in the astrometric /geodetic analysis.

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Astrometry of 25 Southern Hemisphere Radio Sources from a VLBI Short-Baseline Survey

Cited by 15 publications

References 21 publications

Fermi-LAT andSuzakuobservations of the radio galaxy Centaurus B

Fermi-LAT andSuzakuobservations of the radio galaxy Centaurus B

Gamma-ray emission in radio galaxies under the VLBI scope

VLBI Observations of Southern Hemisphere ICRF Sources. I.

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