A 1D fluid model of the Centaurus A jet

Wykes, S.; Snios, Bradford; Nulsen, P. E. J.; Kraft, Ralph; Birkinshaw, Mark; Hardcastle, M. J.; Worrall, D. M.; McDonald, Iain; Rejkuba, M.; Jones, T. W.; Stark, D. J.; Forman, W.; Meyer, Eileen T.; Jones, C.

doi:10.1093/mnras/stz348

Cited by 9 publications

(4 citation statements)

References 103 publications

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“…The kinetic power of a one-sided relativistic jet can be derived from the equations of relativistic hydrodynamics (e.g. Taub 1948;Landau & Lifshitz 1975;Wykes et al 2019) and is given by…”

Section: Synthetic Jet Power Historiesmentioning

confidence: 99%

Particle acceleration in radio galaxies with flickering jets: GeV electrons to ultrahigh energy cosmic rays

Matthews,

Taylor

2021

Preprint

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Variability is a general property of accretion discs and their associated jets. We introduce a semi-analytic model for particle acceleration and radio jet/lobe evolution and explore the effect of Myr timescale jet variability on the particles accelerated by an AGN jet. Our work is motivated by the need for local powerful ultrahigh energy cosmic ray (UHECR) sources and evidence for variability in AGN and radio galaxies. Our main results are: i) UHECR and nonthermal radiative luminosities track the jet power but with a response set by the escape and cooling times, respectively; ii) jet variability produces structure in the electron, synchrotron and UHECR spectra that deviates from that produced for a constant jet power -in particular, spectral hardening features may be signatures of variability; iii) the cutoff in the integrated CR spectrum is stretched out due to the variation in jet power (and, consequently, maximum CR energy). The resulting spectrum is the convolution of the jet power distribution and the source term. We derive an approximate form for a log-normal distribution of powers; iv) we introduce the idea of ∼ 10 GeV 'proxy electrons' that are cooling at the same rate that UHECRs of rigidity 10 EV are escaping from the source, and determine the corresponding photon frequencies that probe escaping UHECRs. Our results demonstrate the link between the history of an astrophysical particle accelerator and its particle contents, nonthermal emission and UHECR spectrum, with consequences for observations of radio galaxies and UHECR source models.

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“…The kinetic power of a one-sided relativistic jet can be derived from the equations of relativistic hydrodynamics (e.g. Taub 1948;Landau & Lifshitz 1975;Wykes et al 2019) and is given by…”

Section: Synthetic Jet Power Historiesmentioning

confidence: 99%

Particle acceleration in radio galaxies with flickering jets: GeV electrons to ultrahigh energy cosmic rays

Matthews,

Taylor

2021

Preprint

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“…We use an opening angle of θ = 0.2θ 0.2 rad, which results in R = 200θ 0.2 pc. This might appear an overestimate for the jet radius at 1 kpc (e.g., Wykes et al 2019). However, since we adopt a cylindrical approximation, we consider it to be appropriate as the mean radius of the kpc jet.…”

Section: Jet Energy Balancementioning

confidence: 99%

Physical Conditions and Particle Acceleration in the Kiloparsec Jet of Centaurus A

Sudoh,

Khangulyan,

Inoue

2020

Preprint

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The non-thermal emission from the kiloparsec-scale jet of Centaurus A exhibits two notable features, bright diffuse emission and many compact knots, which have been intensively studied in X-ray and radio observations. H.E.S.S. recently reported that the very-high-energy gamma-ray emission from this object is extended along the jet direction beyond a kiloparsec from the core. Here, we combine these observations to constrain the physical conditions of the kpc-jet and study the origin of the non-thermal emission. We show that the diffuse jet is weakly magnetized (η b ∼ 10 −2 ) and energetically dominated by thermal particles. We also show that knots are the sites of both amplified magnetic field and particle (re-)acceleration. To keep sufficient energy in thermal particles, the magnetic and non-thermal particle energy in the knot regions are tightly constrained. The most plausible condition is an energy equipartition between them, η b ∼ η e ∼ 0.1. Such weak magnetic energy implies that particles in the knots are in the slow cooling regime. We suggest that the entire kpc-scale diffuse emission could be powered by particles that are accelerated at and escaped from knots.

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“…The inner jet of Virgo A is one sided, hinting at the existence of bulk relativistic motions; superluminal motions found in optical and X-ray observations indicate the mean Lorentz factor of the jet-spine flow, 〈Γ〉 spine  6 (e.g., Biretta et al 1999;Snios et al 2019a). The jet of Centaurus A is also one sided, but the flow looks mildly relativistic with 〈Γ〉 spine ∼ 1.2-2 (e.g., Snios et al 2019b;Wykes et al 2019). Meanwhile, Fornax A exhibits two inner jets embedded in the core of the host galaxy, implying recent low-power jet activity, alongside large diffuse lobes in the outer region (e.g., Geldzahler & Fomalont 1984;Maccagni et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Model Spectrum of Ultrahigh-energy Cosmic Rays Accelerated in FR-I Radio Galaxy Jets

Seo,

Ryu,

Kang

2024

ApJ

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Nearby radio galaxies (RGs) of Fanaroff–Riley Class I (FR-I) are considered possible sites for the production of observed ultrahigh-energy cosmic rays (UHECRs). Among those, some exhibit blazar-like inner jets, while others display plume-like structures. We reproduce the flow dynamics of FR-I jets using relativistic hydrodynamic simulations. Subsequently, we track the transport and energization of cosmic ray (CR) particles within the simulated jet flows using Monte Carlo simulations. The key determinant of flow dynamics is the mean Lorentz factor of the jet-spine flow, 〈Γ〉spine. When 〈Γ〉spine ≳ 6, the jet spine remains almost unimpeded, but for 〈Γ〉spine ≲ 3, substantial jet deceleration occurs. CRs gain energy mainly through diffusive shock acceleration for E ≲ 1 EeV and shear acceleration for E ≳ 1 EeV. The time-asymptotic energy spectrum of CRs escaping from the jet can be modeled by a double power law, transitioning from ∼E −0.6 to ∼E −2.6 around a break energy, E break, with an exponential cutoff at E break 〈 Γ 〉 spine 2 . E break is limited either by the Hillas confinement condition or by particle escape from the cocoon via fast spatial diffusion. The spectral slopes primarily arise from multiple episodes of shock and relativistic shear acceleration, and the confinement–escape processes within the cocoon. The exponential cutoff is determined by nongradual shear acceleration that boosts the energy of high-energy CRs by a factor of ∼ 〈 Γ 〉 spine 2 . We suggest that the model spectrum derived in this work could be employed to investigate the contribution of RGs to the observed population of UHECRs.

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A 1D fluid model of the Centaurus A jet

Cited by 9 publications

References 103 publications

Particle acceleration in radio galaxies with flickering jets: GeV electrons to ultrahigh energy cosmic rays

Particle acceleration in radio galaxies with flickering jets: GeV electrons to ultrahigh energy cosmic rays

Physical Conditions and Particle Acceleration in the Kiloparsec Jet of Centaurus A

Model Spectrum of Ultrahigh-energy Cosmic Rays Accelerated in FR-I Radio Galaxy Jets

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