Cosmic ray acceleration to ultrahigh energy in radio galaxies

Matthews, James H.; Bell, A. R.; Araudo, Anabella T.; Blundell, Katherine M.

doi:10.1051/epjconf/201921004002

Cited by 13 publications

(10 citation statements)

References 53 publications

(55 reference statements)

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“…However, a significant larger emission can be seen in case ii) in the region Z 10. The material in this region originates from the back-flow dynamics of the jet (Cielo et al 2014;Matthews, James H. et al 2019). If only shock energization is accounted for, the particle spectra become very steep in this region owing to radiative losses and the absence of strong shocks.…”

Section: Relativistic Magneto-hydrodynamic Jetmentioning

confidence: 99%

Numerical modeling and physical interplay of stochastic turbulent acceleration for non-thermal emission processes

Kundu,

Vaidya,

Mignone

2021

Preprint

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Particle acceleration is an ubiquitous phenomenon in astrophysical and space plasma. Diffusive shock acceleration (DSA) and stochastic turbulent acceleration are known to be the possible mechanisms for producing very high energetic particles, particularly in weakly magnetized regions. An interplay of different acceleration processes along with various radiation losses is typically observed in astrophysical sources. While DSA is a systematic acceleration process that energizes particles in the vicinity of shocks, stochastic turbulent acceleration (STA) is a random energizing process, where the interaction between cosmic ray particles and electromagnetic fluctuations results in particle acceleration. This process is usually interpreted as a biased random walk in energy space, modelled through a Fokker-Planck equation. In the present work, we describe a novel Eulerian algorithm, adopted to incorporate turbulent acceleration in the presence of DSA and radiative processes like synchrotron and Inverse-Compton emission. The developed framework extends the hybrid Eulerian-Lagrangian module in a full-fledged relativistic Magneto-hydrodynamic (RMHD) code PLUTO. From our validation tests and case studies, we showcase the competing and complementary nature of both acceleration processes. Axisymmetric simulations of an RMHD jet with this extended hybrid framework clearly demonstrate that emission due to shocks is localized while that due to turbulent acceleration originates in the backflow and is more diffuse, particularly in the high energy X-ray band.

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Section: Relativistic Magneto-hydrodynamic Jetmentioning

confidence: 99%

Numerical modeling and physical interplay of stochastic turbulent acceleration for non-thermal emission processes

Kundu,

Vaidya,

Mignone

2021

Preprint

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“…In comparison, a model of nearby γ-bright AGN (17 objects, including Cen A, M87, Mkn 421, Mkn 501, but not Fornax A), which attributes ∼ 7% of the total flux (> 60 EeV) to them, is (only) favoured against isotropy at ∼ 2.7σ . It has been suggested, however, that an incorporation of Fornax A (at a distance ∼ 20 Mpc) could change this picture in favour of radio galaxies once magnetic deflection is properly accounted for [17,18]. The analysis is certainly further complicated by the fact that the CR luminosity of individual AGN is not known.…”

Section: Correlations With Known Sourcesmentioning

confidence: 99%

UHE Cosmic Rays And Agn Jets

Rieger¹

2020

Proceedings of High Energy Phenomena in Relativistic Outflows VII — PoS(HEPRO VII)

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Active Galactic Nuclei (AGN) and their relativistic jets are believed to be potential sites of ultrahigh-energy (UHE) cosmic ray acceleration. This paper reviews basic observational findings as well as requirements on source energetics, and then discusses the relevance of different acceleration sites and mechanisms, such as black hole gap, shock in back-flows or jet shear acceleration. When put in context, the result suggests that Fermi-type particle acceleration at trans-relativistic shocks and/or in shearing, relativistic flows offers the most promising framework for UHECR production in AGN. Truly deciphering the astrophysical sources of UHECRs, however, still needs improved statistical information on arrival directions and source correlations.

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“…For this reason, they have long been discussed as potential UHECR sources (e.g. Hillas 1984;Norman et al 1995;Hardcastle et al 2009;Eichmann et al 2018;Matthews et al 2018Matthews et al , 2019a, along with other classes of AGN jets and alternative sources such as gamma-ray bursts (GRBs), starburst winds and cluster-scale shocks.…”

Section: Introductionmentioning

confidence: 99%

“…For reasonable departures from equipartition and accounting for a likely maximum energy some factor below 𝐸 𝐻 , UHECR acceleration probably requires kinetic jet powers in the region 𝑄 j 10 44 erg s −1 . There are relatively few nearby radio galaxies (within the various UHECR horizons) capable of reaching these powers, if the current jet power estimates are taken at face value (Massaglia 2007b,a;Matthews et al 2018Matthews et al , 2019a.…”

Section: Introductionmentioning

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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Cosmic ray acceleration to ultrahigh energy in radio galaxies

Cited by 13 publications

References 53 publications

Numerical modeling and physical interplay of stochastic turbulent acceleration for non-thermal emission processes

Numerical modeling and physical interplay of stochastic turbulent acceleration for non-thermal emission processes

UHE Cosmic Rays And Agn Jets

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

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