scholarly journals Optical Observations of Radio Jets

1980 ◽  
Vol 5 ◽  
pp. 671-675
Author(s):  
Wil van Breugel ◽  
George Miley ◽  
Harvey R. Butcher
Keyword(s):  
Energy Transport ◽  
Optical Observations ◽  
Radio Sources ◽  
Optical Counterpart ◽  
Radio Structure ◽  
The Past ◽  
Radio Jets ◽  
Extended Radio ◽  
Considerable Body ◽  
Good Agreement

Over the past several years a considerable body of evidence has accumulated, suggesting that extended radio sources are powered quasi-continuously from the nuclei of their parent galaxies. This view is supported by the recent discovery that several radio galaxies have narrow radio jets which connect their active nuclei with the large radio lobes and which often extend for several tens of kiloparsecs. Because of their presumed association with the energy transport outward from the active nuclei, radio jets are at present being intensively studied with high-resolution radio techniques.The closest galaxy known to have a radio jet is the giant elliptical M87 (e.g., Wilkinson 1974), and in this case there is a well-known optical counterpart (e.g., Curtis 1918; de Vaucouleurs, Angione and Fraser 1968), This optical jet is highly polarized (Baade 1956), implying that at least part of the emission is non-thermal. This and the good agreement between the optical and radio structure suggests that these features are closely related.

scholarly journals Rotating Gas and the Shapes of Radio Sources

1982 ◽  
Vol 97 ◽  
pp. 25-26
Author(s):  
L. S. Sparke
Keyword(s):  
Seyfert Galaxies ◽  
External Pressure ◽  
Opening Angle ◽  
Radio Sources ◽  
Extragalactic Radio Source ◽  
Radio Structure ◽  
Radio Jets ◽  
Extended Radio ◽  
The Galaxy ◽  
Scale Properties

The power for a strong extragalactic radio source comes from deep within the nucleus, but the extended radio structure is clearly related to the larger-scale properties of the galaxy in which it lives. Very large sources are found in elliptical rather than spiral galaxies, and big galaxies have stronger radio sources than small ones. The narrow jets mapped in weaker radio galaxies do not expand with a constant opening angle, but become better focussed along their length, suggesting that they are confined by an external pressure. This paper discusses how the rotation of a radio galaxy affects the distribution of gas within it, and consequently the radio structure in elliptical and Seyfert galaxies. A model is proposed which leads to a specific prediction, relating the width of radio jets to the rotation speed of the galaxy in which they lie.

scholarly journals The Extended Radio Structure of Quasars

1986 ◽  
Vol 119 ◽  
pp. 173-179 ◽  
Author(s):  
Frazer N. Owen
Keyword(s):  
Energy Supply ◽  
Relativistic Effects ◽  
Activity Level ◽  
Intrinsic Activity ◽  
Radio Sources ◽  
Radio Structure ◽  
Extended Structure ◽  
Outstanding Problem ◽  
Extended Radio

Modern radio maps usually allow quasars to be recognized from their radio morphology alone. Most have strong central components, double lobed outer structure and one-sided jets connecting the inner and outer structures. The physics of the sources is poorly understood. The observed bending of the jets, the high minimum pressures observed, and the required energy supply to the lobes are major problems. However, the outstanding problem regarding the extended structure is whether or not this morphology is produced by special relativistic effects or the intrinsic activity level and physics of the radio sources.

scholarly journals Radio and optical observations of “optically quiet quasars”

1986 ◽  
Vol 119 ◽  
pp. 113-115
Author(s):  
W. D. Cotton ◽  
F. N. Owen ◽  
M. J. Mahoney
Keyword(s):  
Large Particle ◽  
Low Frequency ◽  
Optical Emission ◽  
Optical Observations ◽  
Radio Sources ◽  
Optical Counterpart ◽  
Vlbi Observations ◽  
Compact Radio Source ◽  
Weak Magnetic Fields ◽  
Sky Survey

In recent years a number of very steep spectrum, compact radio sources have been discovered (e.g. Cotton 1983, Cotton and Owen 1985, Ulvestad 1985) which have no optical counterpart to the limit of the Palomar Sky Survey. VLBI observations of a number of these have confirmed the very compact (<10 mas) nature of several of these sources. Analysis of the available data in terms of the standard synchrotron modal suggest that they contain very weak magnetic fields, large particle densities and may emit detectable infrared and optical emission by inverse Campton scattering in the compact radio source (Cotton 1983). This paper will report on an analysis including new VLBI observations, infrared and optical imaging at KPNO and low frequency radio observations at CLRO of a number of these objects.

scholarly journals Optical and Radio Occultation Analysis

1971 ◽  
Vol 2 ◽  
pp. 607-621
Author(s):  
C. Hazard
Keyword(s):  
Binary Star ◽  
Angular Size ◽  
Optical Observations ◽  
Radio Sources ◽  
Resolution Limit ◽  
Simple Derivation ◽  
The Past ◽  
Methods Of Analysis ◽  
Stellar Diameters ◽  
Receiver Bandwidth

The study of occultations of radio sources by the Moon has proved a powerful method of studying the structure of radio sources with a resolution limit, in some cases, as small as 0″.1 and at the same time of obtaining positions of the radio components with an accuracy of the order of 0″.1 to 1″. Recent optical observations of occultations suggest that the method is likely to play an important role in the measurement of stellar diameters down to about 0″.001 and in the detection and measurement of binary star systems. Over the past several years considerable experience has been gained in the analysis of the occultation curves of radio sources and, since the problems encountered are common to both the optical and radio analysis, our conclusions on how best to analyse occultation curves may be of some interest to the optical workers and also to radio observers who have recently entered the field. Before discussing the methods of analysis and also before discussing some essential differences between the optical and radio work it is useful to consider in some detail the nature of the occultation curve of a simple source of small angular size. It is not proposed here to give a detailed account of the methods of analysis but to indicate the general principles along which the analysis should proceed so as to enable the choice of the most appropriate method in a particular case. A simple treatment of Scheuer’s convolution procedure is given and a simple derivation of the resolution limit imposed by the receiver bandwidth.

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 Distortion Effects in BL Lac Radio Jets

1996 ◽  
Vol 175 ◽  
pp. 477-478 ◽  
Author(s):  
H. Sol ◽  
S. Appl ◽  
L. Vicente
Keyword(s):  
Large Scale ◽  
Lorentz Factor ◽  
Radio Sources ◽  
Misalignment Angle ◽  
Bl Lac Objects ◽  
Radio Structure ◽  
Radio Jets ◽  
Bl Lac ◽  
Different Types ◽  
Bl Lacs

BL Lac objects often show a quite distorted radio morphology. Almost 75% of the BL Lacs for which the information is available show an apparent misalignment angle ΔPA between the VLBI jet and the large scale radio structure larger than 45 degrees. This can be explained by strong enhancement of slight bending due to projection effects, especially if BL Lacs are the most highly beamed sources. However we recently performed a statistical analysis of misalignment angle histograms for 155 extragalactic radio sources of different types and found that the intrinsic distortion is significantly more important in BL Lacs than in quasars and even CSS sources. Indeed the best fits of the δPA histograms by a simple bend model correspond to γɸ = 123° for BL Lacs, 37° for quasars and 36° for CSS sources, where ɸ and γ are the jet typical intrinsic bend and Lorentz factor within a given class of sources (Appl et al, 1995). If, as currently thought, jets in BL Lacs have smaller Lorentz factors than in quasars, high intrinsic bending and misalignment appear to be the rule in BL Lac sources.

The Gaseous Environments of Powerful Extended Radio Sources

1997 ◽  
Vol 480 (1) ◽  
pp. 96-114 ◽  
Author(s):  
Greg F. Wellman ◽  
Ruth A. Daly ◽  
Lin Wan
Keyword(s):  
Radio Sources ◽  
Extended Radio

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.).

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