Extragalactic Radio Jets

Bridle, A. H.; Perley, R. A.

doi:10.1146/annurev.aa.22.090184.001535

Cited by 549 publications

(407 citation statements)

References 98 publications

(155 reference statements)

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“…Agudo et al 2001) indicate stationary conical components in the observer frame in parsec-scale jets, which could be identified as recollimation shocks. We note that systems of repeated oblique (conical) shocks are observed in jet structures at vastly discrepant spatial resolutions, for instance in the radio galaxy NGC 6251 (Bridle & Perley 1984), interpreting this as a quasiself-similar pattern, with the local scales all proportional to radial distance along the jet. Marscher et al (2008Marscher et al ( , 2010 showed high-resolution radio images and optical polarization measurements of the BL Lac-type object PKS 1510-089, which revealed a bright feature in its jet that caused a double flare of radiation from optical frequencies to TeV gamma-ray energies as well as a delayed outburst at radio wavelengths.…”

Section: Jets and Multiple Oblique Shocksmentioning

confidence: 84%

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Meli¹,

Biermann

2013

A&A

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Context. Shocks in jets and hot spots of active galactic nuclei (AGN) are one prominent class of possible sources of very high-energy cosmic-ray particles (above 10 18 eV). Extrapolating their spectrum to their plausible injection energy from some shock implies an enormous hidden energy for a spectrum of index ∼−2. Some analyses suggest the particles' injection spectrum at source to be as steep as −2.4 to −2.7, which exacerbates the problem, by a factor of 10 6 . Nevertheless, it seems implausible that more than at the very best 1/3 of the jet energy goes into the required flux of energetic particles, thus one would need to allow for the possibility that there is an energy problem, which we would like to address in this work. Aims. Sequences of consecutive oblique shock features, or conical shocks, have been theoretically predicted and eventually observed in many AGN jets. Based on that, we use by analogy the Comptonization effect and propose a scenario of a single injection of particles consecutively accelerated by several oblique shocks along the axis of an AGN jet. Methods. We developed a test-particle approximation Monte Carlo simulations to calculate particle spectra by acceleration at such a shock pattern while monitoring the efficiency of acceleration by calculating differential spectra. Results. We find that the first shock of a sequence of oblique shocks establishes a low-energy power-law spectrum with ∼E −2.7 . The following consecutive shocks push the spectrum up in energy, rendering flatter distributions with steep cut-offs, and characteristic depletion at low energies, which could explain the puzzling apparent extra source power. Conclusions. Our numerical calculations show a variation of spectral indices, a general spectral flattening, and starved spectra, which connect to the relativistic nature of the shocks, the multiple shock acceleration conditions, and the steepness of the magnetic field to the shock normal. This helps in understanding the jet-magnetic field geometry and the irregular or flat spectra observed in many AGN jets (e.g., CenA, 3C 279, PKS 1510-089). Furthermore, the E −2.4 − E −2.7 ultra-high-energy cosmic-ray injected source spectra claimed by many authors might be explained by the superposition of several, perhaps many, emission sources, all of which end their particle shock-acceleration sequence with flatter, starved spectra produced by two or more consecutive oblique shocks along their jets. It might also imply a mixed component of the accelerated particles above 10 19 eV. Moreover, the present acceleration model can explain the variability of inverted gamma-ray spectra observed in high redshifted flaring extragalactic sources.

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Section: Jets and Multiple Oblique Shocksmentioning

confidence: 84%

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Meli¹,

Biermann

2013

A&A

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“…The luminosity boosting for these objects may help to make them just bright enough to be detectable above the FIRST survey flux limit. Finally, the magnetic field configurations derived from polarimetry studies (e.g., Bridle & Perley 1984) indicate that the magnetic field in FR-II radio-galaxies is predominantly aligned along the jet for most of its length, whereas FR-I objects are characterized by perpendicular and parallel components. This may suggest a correlation between the DMH mass and the efficiency in producing the magnetic field alignment required to produce brighter radio emission.…”

Section: Black Hole Properties Involved In Quasar Triggeringmentioning

confidence: 99%

Probing the radio loud/quiet AGN dichotomy with quasar clustering

Retana-Montenegro

Röttgering

2017

A&A

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We investigate the clustering properties of 45441 radio-quiet quasars (RQQs) and 3493 radio-loud quasars (RLQs) drawn from a joint use of the Sloan Digital Sky Survey (SDSS) and Faint Images of the Radio Sky at 20 cm (FIRST) surveys in the range 0.3 < z < 2.3. This large spectroscopic quasar sample allow us to investigate the clustering signal dependence on radio-loudness and black hole (BH) virial mass. We find that RLQs are clustered more strongly than RQQs in all the redshift bins considered. We find a real-space correlation length of r 0 = 6.59 +0.33 −0.24 h −1 Mpc and r 0 = 10.95 +1.22 −1.58 h −1 Mpc for RQQs and RLQs, respectively, for the full redshift range. This implies that RLQs are found in more massive host haloes than RQQs in our samples, with mean host halo masses of ∼ 4.9 × 10 13 h −1 M and ∼ 1.9 × 10 12 h −1 M , respectively. Comparison with clustering studies of different radio source samples indicates that this mass scale of 1 × 10 13 h −1 M is characteristic for the bright radio-population, which corresponds to the typical mass of galaxy groups and galaxy clusters. The similarity we find in correlation lengths and host halo masses for RLQs, radio galaxies and flat-spectrum radio quasars agrees with orientation-driven unification models. Additionally, the clustering signal shows a dependence on black hole (BH) mass, with the quasars powered by the most massive BHs clustering more strongly than quasars having less massive BHs. We suggest that the current virial BH mass estimates may be a valid BH proxies for studying quasar clustering. We compare our results to a previous theoretical model that assumes that quasar activity is driven by cold accretion via mergers of gas-rich galaxies. While the model can explain the bias and halo masses for RQQs, it cannot reproduce the higher bias and host halo masses for RLQs. We argue that other BH properties such as BH spin, environment, magnetic field configuration, and accretion physics must be considered to fully understand the origin of radio-emission in quasars and its relation to the higher clustering.

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“…Strong extended radio emission is indicative of powerful outflows interacting with the intracluster medium (e.g., Bridle & Perley 1984). In contrast, of the five well-fit clusters, only two (A1795 and A2199) are known to have strong extended radio sources in their centers (4C 26.42 and 3C 338, respectively).…”

Section: No 1 2003 Galaxy Clusters With Thermal Conductionmentioning

confidence: 99%

Models of Galaxy Clusters with Thermal Conduction

Zakamska

Narayan

2003

ApJ

214

306

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We present a simple model of hot gas in galaxy clusters, assuming hydrostatic equilibrium and energy balance between radiative cooling and thermal conduction. For five clusters, A1795, A1835, A2199, A2390, and RX J1347.5À1145, the model gives a good description of the observed radial profiles of electron density and temperature, provided that we take the thermal conductivity to be about 30% of the Spitzer conductivity. Since the required is consistent with the recent theoretical estimate of Narayan & Medvedev for a turbulent magnetized plasma, we consider a conduction-based equilibrium model to be viable for these clusters. We further show that the hot gas is thermally stable because of the presence of conduction. For five other clusters, A2052, A2597, Hydra A, Ser 159-03, and 3C 295, the model requires unphysically large values of to fit the data. These clusters must have some additional source of heat, possibly an active galactic nucleus, since all the clusters have strong radio galaxies at their centers. We suggest that thermal conduction, although not dominant in these clusters, may nevertheless play a significant role by preventing the gas from becoming thermally unstable.

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Extragalactic Radio Jets

Abstract: Baade & Minkowski (3) first used the term jet in an extragalactic context, describing the train of optical knots extending ,-~ 20" from the nucleus of M87 ; the knots resemble a fluid jet breaking into droplets. They suggested

Cited by 549 publications

References 98 publications

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Active galactic nuclei jets and multiple oblique shock acceleration: starved spectra

Probing the radio loud/quiet AGN dichotomy with quasar clustering

Models of Galaxy Clusters with Thermal Conduction

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