The Subparsec-Scale Structure and Evolution of Centaurus A: The Nearest Active Radio Galaxy

Tingay, S. J.; Jauncey, D. L.; Reynolds, John E.; Tzioumis, A. K.; King, E. A.; Preston, R. A.; Jones, Dayton L.; Murphy, D. W.; Meier, David L.; Ommen, T. D. van; McCulloch, P. M.; Ellingsen, S. P.; Costa, M. E.; Edwards, Philip; Lovell, J. E. J.; Nicolson, G. D.; Quick, J.; Kemball, A. J.; Migenes, V.; Harbison, P.; Jones, Peter N.; White, Graeme L.; Gough, R. G.; Ferris, R. H.; Sinclair, M. W.; Clay, R. W.

doi:10.1086/300257

Cited by 136 publications

(147 citation statements)

References 23 publications

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“…The overall jet structure is also similar to the earlier 5 GHz VSOP image (Horiuchi et al 2006). This similarity suggests that at least some characteristic structures are moving slowly compared to the jet speed measured in earlier works (0.1c-0.45c; Tingay et al 1998Hardcastle et al 2003). The spectral distribution along the jet constrains the physical properties of the radio emission.…”

Section: Fig 2 223 Ghz and 84 Ghz Images Of Cen A From 2008supporting

confidence: 71%

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Dual-frequency VLBI study of Centaurus A on sub-parsec scales

Müller

Kadler

Ojha

et al. 2011

A&A

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Context. Centaurus A is the closest active galactic nucleus. High resolution imaging using Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on sub-parsec scales, providing essential information for jet emission and formation models. Aims. Our aim is to study the structure and spectral shape of the emission from the central-parsec region of Cen A. Methods. As a target of the Southern Hemisphere VLBI monitoring program TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry), VLBI observations of Cen A are made regularly at 8.4 and 22.3 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, and South Africa. Results. The first dual-frequency images of this source are presented along with the resulting spectral index map. An angular resolution of 0.4 mas × 0.7 mas is achieved at 8.4 GHz, corresponding to a linear scale of less than 0.013 pc. Hence, we obtain the highest resolution VLBI image of Cen A, comparable to previous space-VLBI observations. By combining with the 22.3 GHz image, which has been taken without contributing transoceanic baselines at somewhat lower resolution, we present the corresponding dual-frequency spectral index distribution along the sub-parsec scale jet revealing the putative emission regions for recently detected γ-rays from the core region by Fermi/LAT. Conclusions. We resolve the innermost structure of the milliarcsecond scale jet and counterjet system of Cen A into discrete components. The simultaneous observations at two frequencies provide the highest resolved spectral index map of an AGN jet allowing us to identify multiple possible sites as the origin of the high energy emission.

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Section: Fig 2 223 Ghz and 84 Ghz Images Of Cen A From 2008supporting

confidence: 71%

“…angle of 50-80 degrees to the line of sight, with speeds ranging from v = 0.1c to 0.45c measured on different scales (Tingay et al 1998Hardcastle et al 2003). On subparsec scales, the radio jet-counterjet system was resolved with the VLBI Space Observatory Program (VSOP) by Horiuchi et al (2006).…”

Section: Introductionmentioning

confidence: 99%

Dual-frequency VLBI study of Centaurus A on sub-parsec scales

Müller

Kadler

Ojha

et al. 2011

A&A

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“…Note that increasing the viewing angle to 70 • (e.g. Jones et al 1996;Tingay et al 1998) in the Falcke & Biermann model boosts the jet power to ∼3.3 × 10 43 erg s −1 . Abdo et al (2010) computed Cen A's kinetic jet power of 7.7 × 10 42 erg s −1 based on the synchrotron age of the giant lobes of 30 Myr ) and on an estimated total energy in both giant lobes of ∼1.5 × 10 58 erg.…”

Section: Jet Powermentioning

confidence: 96%

Mass entrainment and turbulence-driven acceleration of ultra-high energy cosmic rays in Centaurus A

Wykes

Croston

Hardcastle

et al. 2013

A&A

127

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Observations of the FR I radio galaxy Centaurus A in radio, X-ray, and gamma-ray bands provide evidence for lepton acceleration up to several TeV and clues about hadron acceleration to tens of EeV. Synthesising the available observational constraints on the physical conditions and particle content in the jets, inner lobes and giant lobes of Centaurus A, we aim to evaluate its feasibility as an ultra-high-energy cosmic-ray source. We apply several methods of determining jet power and affirm the consistency of various power estimates of ∼1 × 10 43 erg s −1 . Employing scaling relations based on previous results for 3C 31, we estimate particle number densities in the jets, encompassing available radio through X-ray observations. Our model is compatible with the jets ingesting ∼3 × 10 21 g s −1 of matter via external entrainment from hot gas and ∼7 × 10 22 g s −1 via internal entrainment from jet-contained stars. This leads to an imbalance between the internal lobe pressure available from radiating particles and magnetic field, and our derived external pressure. Based on knowledge of the external environments of other FR I sources, we estimate the thermal pressure in the giant lobes as 1.5 × 10 −12 dyn cm −2 , from which we deduce a lower limit to the temperature of ∼1.6 × 10 8 K. Using dynamical and buoyancy arguments, we infer ∼440−645 Myr and ∼560 Myr as the sound-crossing and buoyancy ages of the giant lobes respectively, inconsistent with their spectral ages. We re-investigate the feasibility of particle acceleration via stochastic processes in the lobes, placing new constraints on the energetics and on turbulent input to the lobes. The same "very hot" temperatures that allow self-consistency between the entrainment calculations and the missing pressure also allow stochastic UHECR acceleration models to work.

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“…The dynamic age is then given by θ a /v a , where v a is the lobe advance speed (we adopt the commonly assumed v a ≈ 0.1 c; cf., Tingay et al 1998). Assuming that the fuelling of the low-surface-brightness lobes of the X-shaped sources had stopped after the high-surface ones were activated, the dynamic age of the passive lobes t p during their active stage can be estimated as…”

Section: Dynamic Age Of Radio Lobesmentioning

confidence: 99%

Black hole masses and starbursts in X-shaped radio sources

Mezcua

Lobanov

Chavushyan

2011

A&A

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It has been suggested that the X-shaped morphology observed in some radio sources can reflect either a recent merger of two supermassive black holes (SMBHs) or the presence of a second active black hole in the galactic nucleus. These scenarios are tested by studying the relationship between the black hole mass, radio and optical luminosity, starburst history, and dynamic age of radio lobes in a sample of 29 X-shaped radio galaxies drawn from a list of 100 X-shaped radio source candidates identified from the FIRST survey. The same relationships are also studied in a control sample consisting of 36 radio-loud active nuclei with similar redshifts and optical and radio luminosities. The X-shaped objects are found to have statistically higher black hole masses and older starburst activity compared with the objects from the control sample. Implications of these findings are discussed for the black hole merger scenario and for the potential presence of active secondary black holes in post-merger galaxies.

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The Subparsec-Scale Structure and Evolution of Centaurus A: The Nearest Active Radio Galaxy

Cited by 136 publications

References 23 publications

Dual-frequency VLBI study of Centaurus A on sub-parsec scales

Dual-frequency VLBI study of Centaurus A on sub-parsec scales

Mass entrainment and turbulence-driven acceleration of ultra-high energy cosmic rays in Centaurus A

Black hole masses and starbursts in X-shaped radio sources

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