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 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 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 5 Years of VLBI and X-Ray Observations of NRAO 140

1988 ◽  
Vol 129 ◽  
pp. 35-36
Author(s):  
Alan P. Marscher
Keyword(s):  
Flux Density ◽  
Low Frequency ◽  
Total Flux ◽  
X Ray ◽  
The Core ◽  
Vlbi Observations ◽  
Superluminal Motion ◽  
Low Frequency Variability ◽  
Jet Structure

The author and his collaborators have observed NRAO 140 twice at X-ray energies and numerous times with multifrequency VLBI. The VLBI observations reveal a knotty jet structure with superluminal motion of the innermost two knots relative to the core. The VLBI core decreased by about a factor of 2 in flux density between 1980 and late 1984. The X-ray flux also declined by about the same factor during this period. Monitoring at 18 cm during periods of low-frequency variability has revealed pronounced changes in the relative brightnesses of the components of the source while the total flux density has varied by ≲ 10%.

Detection of superluminal motion in the core-dominated quasar 0106 + 013

1990 ◽  
Vol 351 ◽  
pp. L1 ◽  
Author(s):  
Ann E. Wehrle ◽  
Marshall H. Cohen ◽  
Stephen C. Unwin
Keyword(s):  
The Core ◽  
Superluminal Motion

scholarly journals LOFAR view of NGC 3998, a sputtering AGN

2020 ◽  
Vol 634 ◽  
pp. A108 ◽  
Author(s):  
Sarrvesh S. Sridhar ◽  
Raffaella Morganti ◽  
Kristina Nyland ◽  
Bradley S. Frank ◽  
Jeremy Harwood ◽  
...  
Keyword(s):  
Low Power ◽  
Galaxy Evolution ◽  
Spectral Index ◽  
Surface Brightness ◽  
Large Scale ◽  
Radio Sources ◽  
The Core ◽  
Low Surface Brightness ◽  
High Turbulence ◽  
The Rich

Low-power radio sources dominate the radio sky. They tend to be small in size and dominated by their cores, but the origin of their properties and the evolution of their radio plasma are not well constrained. Interestingly, there is mounting evidence that low-power radio sources can significantly affect their surrounding gaseous medium and may therefore be more relevant for galaxy evolution than previously thought. In this paper, we present low radio frequency observations obtained with LOFAR at 147 MHz of the radio source hosted by NGC 3998. This is a rare example of a low-power source that is extremely dominated by its core, but that has two large-scale lobes of low surface brightness. We combine the new 147 MHz image with available 1400 MHz data to derive the spectral index over the source. Despite the low surface brightness, reminiscent of remnant structures, the lobes show an optically thin synchrotron spectral index (∼0.6). We interpret this as being due to rapid decollimation of the jets close to the core, to high turbulence of the plasma flow, and to entrainment of thermal gas. This could be the result of intermittent activity of the central active galactic nucleus, or, more likely, temporary disruption of the jet due to the interaction of the jet with the rich circumnuclear interstellar matter. Both would result in sputtering energy injection from the core, which would keep the lobes fed, albeit at a low rate. We discuss these results in connection with the properties of low-power radio sources in general. Our findings show that amorphous low surface brightness lobes should not be interpreted by default as remnant structures. Large deep surveys (in particular the LOFAR 150 MHz LoTSS and the recently started 1400 MHz Apertif survey) will identify a growing number of objects similar to NGC 3998 where these ideas can be further tested.

scholarly journals Superluminal Motion in the Parsec-Scale Jet of 3C 380

1998 ◽  
Vol 164 ◽  
pp. 77-78
Author(s):  
A.G. Polatidis ◽  
P.N. Wilkinson
Keyword(s):  
The Core ◽  
Vlbi Observations ◽  
Superluminal Motion

AbstractMulti-epoch VLBI observations of the quasar 3C 380 reveal a bent parsec-scale radio jet with complex substructure and superluminal motion out to ~100 pc from the core.

scholarly journals Dual Relativistic Effects in Compact Radio Sources

1988 ◽  
Vol 129 ◽  
pp. 89-90
Author(s):  
S. J. Qian
Keyword(s):  
Relativistic Effects ◽  
Radio Sources ◽  
Flux Variation ◽  
Superluminal Motion ◽  
Apparent Diameter ◽  
Superluminal Expansion

Dual relativistic effects in compact radio sources are discussed, and as an illustrative example we try to show that the observed features of the knot C4 in 3C345 (superluminal motion, superluminal expansion, apparent diameter and flux variation etc.) can be interpreted simultaneously.

Sign in / Sign up

Export Citation Format

Share Document