scholarly journals The core and halo structure of the quasar 4C18.68

1986 ◽  
Vol 119 ◽  
pp. 187-188
Author(s):  
Ann C. Gower ◽  
J.B. Hutchings
Keyword(s):  
Radio Source ◽  
Very Old ◽  
Halo Structure ◽  
The Core

We present new VLA observations of this complex low redshift quasar, which was previously modelled as a precessing twin-jet nucleus. A new 2cm map fails to show the predicted curvature near the nucleus. B and C configuration maps have been obtained, to study the halo of the source. These results suggest that the radio source is not very old, and appears to have undergone two major changes of orientation in its < 107 year history.

The Core and Halo Structure of the Quasar 4C18.68

Quasars ◽  
1986 ◽  
pp. 187-188
Author(s):  
Ann C. Gower ◽  
J. B. Hutchings
Keyword(s):  
Halo Structure ◽  
The Core

scholarly journals The peculiar radio structure of quasar 1320+299

1986 ◽  
Vol 119 ◽  
pp. 191-192
Author(s):  
T.J. Cornwell ◽  
D.J. Saikia ◽  
P. Shastri ◽  
L. Feretti ◽  
G. Giovannini ◽  
...  
Keyword(s):  
Radio Source ◽  
Linear Size ◽  
Core Component ◽  
Radio Structure ◽  
The Core ◽  
The One

The radio source B2 1320+299 is associated with a 20m QSO. Apart from the core component, it has two outer components on the same side of the QSO; it was therefore classified as of the one-sided (‘D2’) type. The radio structure is unusual in that the three slightly non-collinear components are apparently unconnected and the projected linear size for any plausible redshift is large for a ‘D2’ source (Feretti et al. 1982, Astron. Astrophys.115, 423). The radio structure has now been mapped with the VLA (λ20 & 6 cm, B array and λ20, 6 & 2 cm, A array; Figs.1a, b).

3C293: Beams in a Rotating Gaseous Disk

1983 ◽  
Vol 6 ◽  
pp. 739-740
Author(s):  
Wil van Breugel
Keyword(s):  
Optical Imaging ◽  
Radio Source ◽  
Gaseous Disk ◽  
Spectroscopic Observations ◽  
The Core ◽  
Extended Radio ◽  
Ram Pressure ◽  
Source Structure ◽  
Gaseous Halo

The radio source 3C293 has a bright, steep spectrum (α ≃ 0.7; Sν ∝ ν-α ) radio core with kiloparsec-sized structure (Bridle, Fomalont & Cornwell 1981, (BFC)). The core is misaligned by ~35° with respect to the extended radio lobes and both the core and lobes have a Z-shaped morphology. To explain this misalignment and morpholoqy. BFC propose a model in which beams ‘refract’ (buoyantly deflect) in a static hot gaseous halo. Alternatively, Wilson & Ulvestad (1982) have proposed that the source structure may be caused by ram pressure deflection of beams propagating through a rotating gaseous disk. Our optical imaging and spectroscopic observations reported here support the latter model.

scholarly journals The Two-Sided VLBI Source in the Seyfert Galaxy Mrk 231

1998 ◽  
Vol 164 ◽  
pp. 199-200 ◽  
Author(s):  
J. S. Ulvestad ◽  
J. M. Wrobel ◽  
C. L. Carilli
Keyword(s):  
Radio Source ◽  
Seyfert Galaxy ◽  
Central Component ◽  
Linear Scale ◽  
Radio Image ◽  
Total Size ◽  
The Core

AbstractThe Seyfert 1/starburst/IR galaxy Mrk 231 (UGC 08058), at z = 0.0422, has been imaged with the VLBA at frequencies ranging from 1.4 GHz to 22 GHz. The radio image shows a triple source of total size 50 mas (30h−1 pc), with a self-absorbed central component and two detached lobes. The northern lobe, located 12h−1 pc from the core, is free-free absorbed at the lowest frequencies; there also seems to be free-free absorption in the southern component. The linear scale over which this absorption takes place is several times larger than that seen in NGC1275/3C84.The axis of the 50-mas radio source is approximately 60° from the elongation of the central component on the 1-mas scale. The spectrum of this central component becomes optically thin between 5 and 8.4 GHz, and resolves into a small triple source of size ~ 1.0h−1 pc at 15 GHz. There is no hint of a jet or other structure directly connecting this central component to the outer VLBI lobes.

scholarly journals Gravitational Instability Caused by the Weight of Heat

Symmetry ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1435 ◽  
Author(s):  
Zacharias Roupas
Keyword(s):  
Thermal Energy ◽  
Gravitational Instability ◽  
Single Point ◽  
Rest Mass ◽  
Relativistic Effects ◽  
High Energy ◽  
Ideal Gas ◽  
Low Energy ◽  
Halo Structure ◽  
The Core

Thermal energy points towards a disordered, completely uniform state act to counter gravity’s tendency to generate order and structure through gravitational collapse. It is, therefore, expected to contribute to the stabilization of a self-gravitating, classical ideal gas over collapse. However, I identified an instability that always occurs at sufficiently high energies: the high-energy or relativistic gravothermal instability. I argue here that this instability presents an analogous core–halo structure as its Newtonian counterpart, the Antonov instability. The main difference is that in the former case the core is dominated by the gravitation of thermal energy and not rest mass energy. A relativistic generalization of Antonov’s instability—the low-energy gravothermal instability—also occurs. The two turning points, which make themselves evident as a double spiral of the caloric curve, approach each other as relativistic effects become more intense and eventually merge in a single point. Thus, the high and low-energy cases may be realized as two aspects of a single phenomenon—the gravothermal instability—which involves a core–halo separation and an intrinsic heat flow. Finally, I argue that the core formed during a core-collapse supernova is subject to the relativistic gravothermal instability if it becomes sufficiently hot and compactified at the time of the bounce. In this case, it will continue to collapse towards the formation of a black hole.

scholarly journals Core-halo quasi-stationary states in the Hamiltonian mean-field model

2016 ◽  
Vol 30 (12) ◽  
pp. 1630007
Author(s):  
Eiji Konishi
Keyword(s):  
Initial Phase ◽  
Field Model ◽  
Mean Field ◽  
Stationary States ◽  
Mean Field Model ◽  
Halo Structure ◽  
The Core ◽  
Low Energies ◽  
Quasi Stationary State ◽  
Interacting Systems

A characteristic feature of long-range interacting systems is that they become trapped in a non-equilibrium and long-lived quasi-stationary state (QSS) during the early stages of their development. We present a comprehensive review of recent studies of the core-halo structure of QSSs, in the Hamiltonian mean-field model (HMF), which is a mean-field model of mutually coupled ferromagnetic XY spins located at a point, obtained by starting from various unsteady rectangular water-bag type initial phase-space distributions. The main result exposed in this review is that the core-halo structure can be described by the superposition of two independent Lynden–Bell distributions. We discuss the completeness of collisionless relaxation of this double Lynden–Bell distribution by using both of Lynden–Bell entropy and double Lynden–Bell entropy for the systems at low energies per particle.

scholarly journals The Extraordinary Radio Galaxy MRC B1221–423

2003 ◽  
Vol 20 (1) ◽  
pp. 1-5 ◽  
Author(s):  
V. Safouris ◽  
R. W. Hunstead ◽  
O. R. Prouton
Keyword(s):  
Radio Source ◽  
Radio Galaxy ◽  
Early Stage ◽  
Elliptical Galaxy ◽  
Empirical Relationship ◽  
Host Galaxy ◽  
Narrow Line ◽  
Powerful Radio ◽  
Double Structure ◽  
The Core

AbstractMRC B1221–423 is a compact steep spectrum (CSS) radio source in the core of a remarkable elliptical galaxy. We examine its environment with long-slit spectra and multicolour images. A high-resolution synthesis image shows the radio source to have a 1″.5 (5.7 kpc) double structure. We use the empirical relationship between jet kinetic power and narrow line luminosity to infer a source age of ˜105 yr. The z = 0.1706 host galaxy is clearly disturbed, with tidal features and shells providing plausible evidence for a merger with one or more close companions. This evidence leads us to conclude that B1221–423 may be the progenitor of a much larger source, caught at an early stage in its radio evolution. We speculate that it is the interaction and accompanying events which have triggered this young powerful radio source.

scholarly journals 200 Milliarcsecond Structure in 3C 120

1984 ◽  
Vol 110 ◽  
pp. 125-126 ◽  
Author(s):  
J. M. Benson ◽  
R. C. Walker ◽  
G. A. Seielstad ◽  
S. C. Unwin
Keyword(s):  
Radio Source ◽  
Spatial Resolution ◽  
Vlbi Observation ◽  
Data Set ◽  
The Core ◽  
3C 120 ◽  
Extended Emission

We present VLBI and VLA maps of the superluminal radio source 3C 120 (z = 0.03). The 18 cm VLBI maps shown in Figures 1 and 2c were constructed from a 14 station VLBI observation on 10, 11 October 1982. The map in Figure 1 is at full spatial resolution. The Figure 2c map was made from a uv-tapered data set and shows the extended emission. The VLBI maps show a jet ~175 pc long with distinct knots and bends (H0 = 55 kms−1 Mpc−1). The 18 cm jet smoothly connects to the 6 cm superluminal jet (Figure 2d). The VLBI jet remains well collimated through several bends and only begins to spread out 100 pc beyond the core. At 175 pc from the core, the jet is wide and weak, and disappears into the under-sampled region of the uv-plane (< 2(10)6 λ's).

scholarly journals Superluminal Acceleration of the New Component in 3C 345

1984 ◽  
Vol 110 ◽  
pp. 109-110 ◽  
Author(s):  
R. L. Moore ◽  
J. A. Biretta ◽  
A. C. S. Readhead ◽  
L. Bååth
Keyword(s):  
Radio Source ◽  
Individual Component ◽  
Position Angle ◽  
Radial Motion ◽  
Extragalactic Radio Source ◽  
Apparent Velocity ◽  
The Core ◽  
Vlbi Observations

VLBI observations of 3C 345 at 10.8 GHz and 22.2 GHz show that the position angle of the new component is increasing as it separates from the core. Also, the apparent velocity of the component is increasing. This is the first clear evidence for non-radial motion and acceleration of an individual component in an extragalactic radio source.

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