X-Ray Emission Properties of Large-Scale Jets, Hot Spots, and Lobes in Active Galactic Nuclei

By J. Kataoka, Ł. Stawarz. 2004

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We examine a systematic comparison of jet knots, hot spots, and radio lobes recently observed with Chandra and ASCA. This report discusses the origin of their X-ray emissions and investigates the dynamics of the jets. The data were compiled at well-sampled radio (5 GHz) and X-ray (1 keV) frequencies for more than 40 radio galaxies. We examine three models for the X-ray production: synchrotron (SYN), synchrotron self-Compton (SSC), and external Compton (EC) on cosmic microwave background (CMB) photons. For the SYN sources—mostly jet knots in nearby low-luminosity radio galaxies—X-ray photons are produced by ultrarelativistic electrons with energies 10-100 TeV that must be accelerated in situ. For the other objects, conservatively classified as SSC or EC sources, a simple formulation of calculating the "expected" X-ray fluxes under an equipartition hypothesis is presented. We confirm that the observed X-ray fluxes are close to the expected ones for nonrelativistic emitting plasma velocities in the case of radio lobes and the majority of hot spots, whereas a considerable fraction of jet knots are too bright in X-rays to be explained in this way. We examine two possibilities to account for the discrepancy in a framework of the inverse Compton model: (1) the magnetic field is much smaller than the equipartition value, and (2) the jets are highly relativistic on kiloparsec and megaparsec scales. We conclude that if the inverse Compton model is the case, the X-ray-bright jet knots are most likely far from the minimum-power condition. We also briefly discuss the other possibility, namely, that the observed X-ray emission from all the jet knots is synchrotron in origin.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/a8cb3ff0cd50f064bd80ae1b1c5e7ade26d2da9b

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Citations in the corpus

Radio galaxies and feedback from AGN jets (2020, background): “Observations of inverse-Compton emission from the lobes and hotspots of FRII RLAGN (Hardcastle et al., 2002, 2004; Kataoka and Stawarz, 2005; Croston et al., 2005; Ineson et al., 2017) measure the number of inverse-Compton-scattering electrons and so allow the characteristic magnetic field strength…”
An X-Ray Study of Magnetic Field Strengths and Particle Content in the Lobes of FR II Radio Sources (2005, background): “Our approach differs from that of Kataoka and Stawarz (2005) in that we do not only select sources with known hotspot, jet or lobe emission, but include sources whose extended components have not previously been detected in X-rays: this allows us to consider limits on the magnetic field strength,…”
Open Questions in Cosmic-Ray Research at Ultrahigh Energies (2019, unknown): “Inferred values of B and R for AGN lobes, hotspots, and knots, were presented in Kataoka and Stawarz (2005) and summarized in Ptitsyna and Troitsky (2010).”
General physical properties of bright Fermi blazars (2009, background): “…in TeV BL Lacs (Piner & Edward 2004; Piner, Pant & Edwards 2008), with the absence of strong extended radio structures, and with the result of theChandraobservations of extended X–ray jets at large scales, showing sub-luminal speed at large scal s (e.g. Worrall et al. 2001; Kataoka & Stawarz 2005).”
X-Ray Emission from Extragalactic Jets (2006, background): “In the case of Kataoka & Stawarz (2005), a small value of Γ was invoked based on radio asymmetry arguments (Wardle & Aaron 1997).”
Dynamics and high-energy emission of the flaring HST-1 knot in the M 87 jet (2006, background): “Hence, taking νmax νmin ∼ νR and α > 0.5, one obtains Beq ∝ ν1/7R f 2/7R R−6/7 δ−5/7 (B2) (see in this context Kataoka & Stawarz 2005).”