scholarly journals Large Bent Jets in the Inner Region of CSS

1996 ◽  
Vol 175 ◽  
pp. 71-72
Author(s):  
F. Mantovani ◽  
W. Junor ◽  
M. Bondi ◽  
L. Padrielli ◽  
W. Cotton ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Radio Sources ◽  
Ambient Media ◽  
The Core ◽  
Gaseous Environment ◽  
Radio Jets ◽  
Large Size ◽  
Superluminal Motion ◽  
Inner Region ◽  
Quasars And Radio Galaxies

Recently we focussed our attention on a sample of Compact Steep-spectrum Sources (CSSs) selected because of the large bent radio jets seen in the inner region of emission. The largest distortions are often seen in sources dominated by jets, and there are suggestions that this might to some extent be due to projection effects. However, superluminal motion is rare in CSSs. The only case we know of so far is 3C147 (Alef at al. 1990) with a mildly superluminal speed of ≃ 1.3v/c. Moreover, the core fractional luminosity in CSSs is ≃ 3% and ≤ 0.4% for quasars and radio galaxies respectively. Similar values are found for large size radio sources i.e. both boosting and orientations in the sky are similar for the two classes of objects. An alternative possibility is that these bent-jet sources might also be brightened by interactions with the ambient media. There are clear indications that intrinsic distortions due to interactions with a dense inhomogeneous gaseous environment play an important role. Observational support comes from the large RMs found in CSSs (Taylor et al. 1992; Mantovani et al. 1994; Junor et al. these proc.) and often associated with strong depolarization (Garrington & Akujor, t.p.). The CSSs also have very luminous Narrow Line Regions emission, with exceptional velocity structure (Gelderman, t.p.).

scholarly journals Radio jet and lobe of 3C273

1986 ◽  
Vol 119 ◽  
pp. 211-214
Author(s):  
R.J. Davis
Keyword(s):  
Radio Emission ◽  
Opposite Direction ◽  
Dynamic Range ◽  
Bulk Flow ◽  
Radio Sources ◽  
Relativistic Motion ◽  
Ridge Line ◽  
The Core ◽  
Superluminal Motion ◽  
The One

The ‘superluminal’ motion observed in the cores of radio sources such as 3C273 is now accepted as evidence of relativistic motion within a few parsecs of the centre, but it is less clear whether such speeds persist out to kiloparsec scales. The one-sidedness of such sources is often cited as evidence of relativistic Doppler beaming, but could equally be intrinsic. New MERLIN maps of 3C273 at 151 MHz and 408 MHz have been made with dynamic range of 4.103:1 and 104:1 respectively. These show that (i) there is an extended region or lobe to the south of the main jet; (ii) the radio emission of the jet is continuous from the core to beyond the limit of the optical jet; (iii) no counter-component can be found in the opposite direction to the jet. The ridge-line of the jet shows a ‘wiggle’, the wavelength of which decreases by a factor of 6 along its length. This is interpreted as a deceleration of the bulk flow along the jet.

scholarly journals Active Galaxies and Candidate Remnants in the Core of the Shapley Concentration

2002 ◽  
Vol 199 ◽  
pp. 161-162
Author(s):  
T. Venturi ◽  
S. Bardelli ◽  
D. Dallacasa ◽  
R.W. Hunstead ◽  
R. Morganti ◽  
...  
Keyword(s):  
Spectral Properties ◽  
Radio Galaxies ◽  
Active Galaxies ◽  
Radio Sources ◽  
Nuclear Activity ◽  
The Core ◽  
Radio Jets ◽  
Extended Radio ◽  
Cluster Mergers ◽  
Compact Array

We present preliminary results of a multifrequency and multiresolution study carried out with the Australia Telescope Compact Array for nine of the ten extended radio galaxies located in the merging cluster complexes A3558 and A3528, at the centre of the Shapley Concentration. We found that 5 out of the 9 extended radio galaxies are active radio galaxies, i.e. they have a clear active radio nucleus coincident with the central region of the associated optical galaxy, radio jets and extended lobes; the remaining four lack an obvious radio nucleus, have a very diffuse and amorphous morphology and exhibit peculiar spectral properties. We call these radio sources as remnants and propose that they are (a) either radio galaxies where the nuclear activity has ceased; or (b) regions where pre-existing electrons have been reaccelerated as consequence of shocks due to cluster mergers.

scholarly journals Unified Models: Religion and Science

1994 ◽  
Vol 159 ◽  
pp. 301-309 ◽  
Author(s):  
Robert Antonucci
Keyword(s):  
Elliptical Galaxy ◽  
Opening Angle ◽  
Radio Sources ◽  
Religion And Science ◽  
Radio Structure ◽  
Radio Jets ◽  
Line Region ◽  
Superluminal Motion ◽  
Bulk Motion

The Unified Model states that the classification of individual AGN is a function of orientation, and that orientation effects are key to understanding the different classes. In its most extreme form, it states that every AGN has a featureless continuum (FC) source and a broad line region (BLR), both enclosed in an opaque torus. The torus is perpendicular to the associated radio structure axis. For the powerful radio sources (in Elliptical galaxy hosts), the jets undergo bulk relativistic motion, giving rise to phenomena such as superluminal motion associated with the blazar class. All strong radio sources have diffuse double radio lobes, although in the blazars one is sometimes seen projected onto the other. To take this to the extreme, we can suppose that all opaque tori are made of dust and have the same opening angle and that the radio jets are all narrow and have the same bulk-motion Γ factor.

scholarly journals Superluminal Motion in Weak Quasar Cores

1984 ◽  
Vol 110 ◽  
pp. 157-161 ◽  
Author(s):  
R. W. Porcas
Keyword(s):  
Radio Sources ◽  
The Core ◽  
Superluminal Motion

The importance of studying the statistics of the occurrence of superluminal motion in an unbiased sample of radio sources is stressed, and methods for selecting such samples are reviewed. The weak radio cores of quasars exhibiting extended, double-lobed emission can be used for this purpose. Recent studies of the superluminal motion in the core of 3C 179, a quasar selected from such a sample, are described.

scholarly journals Bulk Relativistic Motion in a Complete Sample of Radio Selected AGN

1987 ◽  
Vol 121 ◽  
pp. 287-293
Author(s):  
C.J. Schalinski ◽  
P. Biermann ◽  
A. Eckart ◽  
K.J. Johnston ◽  
T.Ph. Krichbaum ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Radio Sources ◽  
Relativistic Motion ◽  
Complete Sample ◽  
Superluminal Motion ◽  
Spectrum Radio ◽  
Wide Range ◽  
Show Evidence

A complete sample of 13 flat spectrum radio sources is investigated over a wide range of frequencies and spatial resolutions. SSC-calculations lead to the prediction of bulk relativistic motion in all sources. So far 6 out of 7 sources observed with sufficient dynamic range by means of VLBI show evidence for apparent superluminal motion.

scholarly journals High Frequency Peakers

2003 ◽  
Vol 20 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Daniele Dallacasa
Keyword(s):  
Radio Source ◽  
High Frequency ◽  
Peak Frequency ◽  
Source Size ◽  
Host Galaxy ◽  
Radio Sources ◽  
Inner Region

AbstractThere is quite a clear anticorrelation between the intrinsic peak frequency and the overall radio source size in compact steep spectrum (CSS) and gigahertz peaked spectrum (GPS) radio sources. This feature is interpreted in terms of synchrotron self-absorption (although free–free absorption may play a role as well) of the radiation emitted by a small radio source which is growing within the inner region of the host galaxy. This leads to the hypothesis that these objects are young and that the radio source is still developing/expanding within the host galaxy itself.Very young radio sources must have the peak in their radio spectra occurring above a few tens of gigahertz, and for this reason they are termed high frequency peakers (HFPs). These newly born radio sources must be very rare given that they spend very little time in this stage. Ho = 100 km s−1 Mpc−1 and qo = 0.5 are used throughout this paper.

scholarly journals A simplified analysis of the Chernobyl accident

2021 ◽  
Vol 7 ◽  
pp. 1
Author(s):  
Bertrand Mercier ◽  
Di Yang ◽  
Ziyue Zhuang ◽  
Jiajie Liang
Keyword(s):  
Numerical Models ◽  
List Type ◽  
Flash Evaporation ◽  
The Core ◽  
Large Size ◽  
Reaction Coefficient ◽  
Pressure Tubes ◽  
Void Effect ◽  
Reactivity Coefficient ◽  
Reactivity Increase

We show with simplified numerical models, that for the kind of RBMK operated in Chernobyl: The core was unstable due to its large size and to its weak power counter-reaction coefficient, so that the power of the reactor was not easy to control even with an automatic system. Xenon oscillations could easily be activated. When there was xenon poisoning in the upper half of the core, the safety rods were designed in such a way that, at least initially, they were increasing (and not decreasing) the core reactivity. This reactivity increase has been sufficient to lead to a very high pressure increase in a significant amount of liquid water in the fuel channels thus inducing a strong propagating shock wave leading to a failure of half the pressure tubes at their junction with the drum separators. The depressurization phase (flash evaporation) following this failure has produced, after one second, a significant decrease of the water density in half the pressure tubes and then a strong reactivity accident due to the positive void effect reactivity coefficient. We evaluate the fission energy released by the accident

Radio jets at high red shift

1986 ◽  
Vol 64 (4) ◽  
pp. 445-448 ◽  
Author(s):  
Colin J. Lonsdale
Keyword(s):  
Red Shift ◽  
Radio Sources ◽  
Present Sample ◽  
Radio Jets ◽  
Flow Speeds ◽  
Relativistic Flow ◽  
Moving Jet ◽  
Luminosity Evolution ◽  
Radio Quasar ◽  
Observational Program

Using preliminary results from a large observational program targeting high red-shift radio quasars, we have increased the total number of radio jets known beyond a red shift of 1.5 from 5 to 26, thus generating one of the most uniform and complete samples of radio jets in existence. This sample enjoys relative freedom from cosmological and luminosity-evolution effects, which normally complicate statistical analyses of jets.An attempt has been made to test a type of radio-quasar model in which the appearance of a radio source is strongly influenced by its orientation relative to the line of sight, owing to Doppler boosting of the emission from relativistically moving jet material. Four "orientation indicators" are isolated, which should all be correlated with each other to some degree if the above-mentioned model is correct. It is found that only one pair of parameters shows a significant correlation, namely the jet prominence (relative to the lobes) and the jet curvature. This particular correlation finds a natural explanation in the physics of radio sources, and therefore may not be due to orientation effects.As a result of these findings, it is concluded that the present sample of high red-shift jets shows no evidence of relativistic flow speeds on kiloparsec scales.

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