Modelling TeV γ-ray emission from the kiloparsec-scale jets of Centaurus A and M87

Hardcastle, M. J.; Croston, J. H.

doi:10.1111/j.1365-2966.2011.18678.x

Cited by 62 publications

(58 citation statements)

References 51 publications

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“…This should be then considered as an important support for the MHD models of AGN jets, like the one presented in the particular context of the M 87 core and HST-1 knot by (Nakamura et al 2010), and discussed further from the observational perspective by Perlman et al (2011) and Chen et al (2011). Analogous constraints emerging from the VHE data can be investigated for the outer parts of the M 87 jet as well (Stawarz et al 2005;Hardcastle & Croston 2011).…”

Section: Discussionmentioning

confidence: 99%

The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

ApJ

171

146

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The giant radio galaxy M 87 with its proximity (16 Mpc), famous jet, and very massive black hole ((3−6)×10 9 M ) provides a unique opportunity to investigate the origin of very high energy (VHE; E > 100 GeV) γ -ray emission generated in relativistic outflows and the surroundings of supermassive black holes. M 87 has been established as a VHE γ -ray emitter since 2006. The VHE γ -ray emission displays strong variability on timescales as short as a day. In this paper, results from a joint VHE monitoring campaign on M 87 by the MAGIC and VERITAS instruments in 2010 are reported. During the campaign, a flare at VHE was detected triggering further observations at VHE (H.E.S.S.), X-rays (Chandra), and radio (43 GHz Very Long Baseline Array, VLBA). The excellent sampling of the VHE γ -ray light curve enables one to derive a precise temporal characterization of the flare: the single, isolated flare is well described by a two-sided exponential function with significantly different flux rise and decay times of τ rise (1-3) × 10 −11 photons cm −2 s −1 ), and VHE spectra. VLBA radio observations of 43 GHz of the inner jet regions indicate no enhanced flux in 2010 in contrast to observations in 2008, where an increase of the radio flux of the innermost core regions coincided with a VHE flare. On the other hand, Chandra X-ray observations taken ∼3 days after the peak of the VHE γ -ray emission reveal an enhanced flux from the core (flux increased by factor ∼2; variability timescale <2 days). The long-term (2001-2010) multi-wavelength (MWL) light curve of M 87, spanning from radio to VHE and including data from Hubble Space Telescope, Liverpool Telescope, Very Large Array, and European VLBI Network, is used to further investigate the origin of the VHE γ -ray emission. No unique, common MWL signature of the three VHE flares has been identified. In the outer kiloparsec jet region, in particular in HST-1, no enhanced MWL activity was detected in 2008 and 2010, disfavoring it as the origin of the VHE flares during these years. Shortly after two of the three flares (2008 and 2010), the X-ray core was observed to be at a higher flux level than its characteristic range (determined from more than 60 monitoring observations: [2002][2003][2004][2005][2006][2007][2008][2009]). In 2005, the strong flux dominance of HST-1 could have suppressed the detection of such a feature. Published models for VHE γ -ray emission from M 87 are reviewed in the light of the new data.

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Section: Discussionmentioning

confidence: 99%

The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

Abramowski¹,

Acero²,

Aharonian³

et al. 2012

ApJ

171

146

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“…2.1), the jet power that can be carried by the known particle population can be estimated. Considering the inner jet, that is the structure out to ∼3 kpc of projected length, where we know the electron distribution reasonably well (see Hardcastle et al 2006), we have a constraint on the bulk flow speed from the proper motion of the inner knots (0.5c, Hardcastle et al 2003), and we are also confident that the magnetic field cannot be much lower than the equipartition value (Hardcastle & Croston 2011). Do we require protons (thermal or relativistic) in order to transport 10 43 erg s −1 , if we make the additional assumption that the jet is not magnetically dominated?…”

Section: Constraints On Energy Density and Magnetic Fieldsmentioning

confidence: 99%

“…Do we require protons (thermal or relativistic) in order to transport 10 43 erg s −1 , if we make the additional assumption that the jet is not magnetically dominated? 1 Using the model of the jet from Hardcastle & Croston (2011) with a single electron spectrum, the mean energy density of the jet (assuming equipartition between magnetic field and electrons only) is U j = 8.77 × 10 −11 erg cm −3 . The total jet power follows from P j = Γ 2 4/3 U j πr 2 j υ j , where Γ = (1 − β 2 ) −1/2 is the bulk Lorentz factor and r j is the cross-sectional radius of the jet.…”

Section: Constraints On Energy Density and Magnetic Fieldsmentioning

confidence: 99%

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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“…[13], [19]) and M87 (e.g. [16], [24]), radio jets, hotspots, lobes (eg. [3]; [26]), as well as clusters of galaxies.…”

Section: Introductionmentioning

confidence: 99%

On the extragalactic jet asymmetry and composition, and the production of high energy cosmic rays

Gizani

2012

Nuclear Instruments and Methods in Physics Research Section A:

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We probe the role of the directional asymmetry between relativistic outflows to kilo-parsec scale jets in the propagation and acceleration of cosmic rays. Our sample contains powerful AGN hosting dense cluster environments. We attempt a thorough description of where and when ultra high energy cosmic ray production and acceleration takes place also using radio observations of the large scale stucture of the AGNs and X-ray data of the hot dense gas in which the AGNs are situated.As far as the cosmic ray primaries are concerned, the presence of relativistic protons or mildly relativistic electrons/positrons contributes substantially to the energy budget of the jets enabling them to heat efficiently the intracluster gas.

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Modelling TeV γ-ray emission from the kiloparsec-scale jets of Centaurus A and M87

Cited by 62 publications

References 51 publications

The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

The 2010 VERY HIGH ENERGY Γ-Ray FLARE AND 10 YEARS OF MULTI-WAVELENGTH OBSERVATIONS OF M 87

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

On the extragalactic jet asymmetry and composition, and the production of high energy cosmic rays

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