scholarly journals The Radio Brightness Distributions over Four Discrete Sources of Cosmic Noise

1953 ◽  
Vol 6 (4) ◽  
pp. 452 ◽  
Author(s):  
BY Mllls
Keyword(s):  
Azimuth Angle ◽  
Radio Sources ◽  
Radio Brightness ◽  
Cygnus A ◽  
Wide Range ◽  
Cosmic Noise ◽  
Centaurus A

Brightness distributions have been obtained across the four radio sources, Cygnus?A, Taurus?A, Virgo?A, and Centaurus-A, using a two-aerial interferometer of a special type in which the aerial spacing and the azimuth angle of the axis may be varied over a wide range. Radio isophotes have been constructed for three of the sources from these results, making some simple assumptions as to their form. The isophotes bear some relation to optical features of the nebulae with which the sources have been identified and their radio and optical sizes are similar. The remaining source, Cygnus?A, is unfavourably situated for observations from Sydney, and the results are less complete.

Observations of compact radio nuclei in Cygnus A, Centaurus A, and other extended radio sources

1975 ◽  
Vol 197 ◽  
pp. L113 ◽  
Author(s):  
K. I. Kellermann ◽  
B. G. Clark ◽  
A. E. Niell ◽  
D. B. Shaffer
Keyword(s):  
Radio Sources ◽  
Cygnus A ◽  
Extended Radio ◽  
Centaurus A

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 Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

2021 ◽  
Author(s):  
Michael Janssen ◽  
Heino Falcke ◽  
Matthias Kadler ◽  
Eduardo Ros ◽  
Maciek Wielgus ◽  
...  
Keyword(s):  
Black Holes ◽  
Event Horizon ◽  
Galactic Nuclei ◽  
Galactic Centre ◽  
Radio Jets ◽  
Long Baseline ◽  
Wide Range ◽  
Terahertz Frequencies ◽  
Source Structure ◽  
Centaurus A

AbstractVery-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5,6.

A Centaurus A : Spectra of the Optical Filament

1975 ◽  
Vol 2 (6) ◽  
pp. 366-367 ◽  
Author(s):  
B.A. Peterson ◽  
R.J. Dickens ◽  
R.D. Cannon
Keyword(s):  
Radio Source ◽  
Elliptical Galaxy ◽  
Brightness Distribution ◽  
Radio Brightness ◽  
Dust Lane ◽  
X Ray ◽  
The Galaxy ◽  
Centaurus A

The radio source, Cen A, is large and complex with many peaks in the brightness distribution over an area about 4 x 10 degrees. The peculiar elliptical galaxy NGC 5128 lies between the two strong inner radio brightness peaks and is centred on a weaker central radio source. This radio source is in the centre of the dust lane which divides the galaxy and may be related to the infrared, X-ray and γ-ray sources.

scholarly journals Extragalactic jets as probes of distant clusters of galaxies and the clusters occupied by bent radio AGN (COBRA) survey

2014 ◽  
Vol 10 (S313) ◽  
pp. 315-320
Author(s):  
Elizabeth L. Blanton ◽  
Rachel Paterno-Mahler ◽  
Joshua D. Wing ◽  
M. L. N. Ashby ◽  
Emmet Golden-Marx ◽  
...  
Keyword(s):  
Radio Galaxies ◽  
Radio Sources ◽  
Clusters Of Galaxies ◽  
Wide Range ◽  
Extragalactic Jets ◽  
Large Survey ◽  
Kinetic Mode ◽  
Group Environments ◽  
Initial Results ◽  
Quasars And Radio Galaxies

AbstractWe are conducting a large survey of distant clusters of galaxies using radio sources with bent jets and lobes as tracers. These radio sources are driven by AGN and achieve their bent morphologies through interaction with the surrounding gas found in clusters of galaxies. Based on low-redshift studies, these types of sources can be used to identify clusters very efficiently. We present initial results from our survey of 653 bent-double radio sources with optical hosts too faint to appear in the SDSS. The sample was observed in the infrared with Spitzer, and it has revealed ~200 distant clusters or proto-clusters in the redshift range z ~ 0.7 - 3.0. The sample of bent-doubles contains both quasars and radio galaxies enabling us to study both radiative and kinetic mode feedback in cluster and group environments at a wide range of redshifts.

scholarly journals Bulk Relativistic Motion in a Complete Sample of Flat Spectrum Radio Sources

1988 ◽  
Vol 129 ◽  
pp. 71-72
Author(s):  
C. J. Schalinski ◽  
A. Witzel ◽  
Th.P. Krichbaum ◽  
C. A. Hummel ◽  
P. L. Biermann ◽  
...  
Keyword(s):  
Flux Density ◽  
Status Report ◽  
Radio Sources ◽  
Supporting Evidence ◽  
X Rays ◽  
Relativistic Motion ◽  
Bl Lac Objects ◽  
Vlbi Observations ◽  
Wide Range ◽  
5 Ghz

As part of a multi-epoch and multi-wavelength study of the physics of core dominated radio sources we have investigated the occurrence of apparent superluminal motion and other indications for bulk relativistic motion (b.r.m) in a statistically complete, flux density limited (S5GHz ≥ 1Jy) sample of 13 objects with flat radio spectra These sources come from the S5-survey (Kühr et al., 1981) and are optically identified as 7 quasars and 6 BL-Lac objects. They have been observed over a wide range of frequencies, from radio through X-rays (s. Eckart et al., 1986 and references therein). Radiomaps have been obtained at frequencies from 327 MHz to 22.2 GHz with resolutions from arcseconds to 0.2 mas, using the VLA, MERLIN and telescopes of the US- and European-VLBI networks. A recent status report on the VLBI-observations is given by Witzel (1987). In this paper we summarize the results on the direct evidence for b.r.m. in this sample as derived from repeated VLBI-observations at 5 GHz, as well as supporting evidence from SSC-calculations and flux density variability of the 5GHz VLBI core components (Table 1).

scholarly journals The structure of the Cassiopeia A and Cygnus A radio sources measured at 127 Mc/s and 3000 Mc/s

1959 ◽  
Vol 9 ◽  
pp. 309-314
Author(s):  
R. C. Jennison
Keyword(s):  
Position Angle ◽  
Brightness Distribution ◽  
Radio Sources ◽  
Cassiopeia A ◽  
The Third ◽  
Cygnus A ◽  
Main Component ◽  
Main Region

The brightness distribution across the Cassiopeia A source in position angle 90 degrees consists of a primary region of emission 4.1 minutes of arc in width, with a much fainter extension offset from the main region of emission and having a brightness of only 10 per cent of that of the main component. Measurements were made up to the third maximum of the transform (2160 λ), and the position of the first zero was determined at 840 λ.

scholarly journals Radio Source Environments at Redshifts > 0.5

1996 ◽  
Vol 175 ◽  
pp. 321-322
Author(s):  
M. Lacy ◽  
S. Rawlings ◽  
M. Wold ◽  
A. Bunker ◽  
K.M. Blundell ◽  
...  
Keyword(s):  
Radio Source ◽  
High Redshift ◽  
Elliptical Galaxies ◽  
Radio Sources ◽  
Powerful Radio ◽  
Host Galaxies ◽  
Local Universe ◽  
Wide Range ◽  
Age Of The Universe ◽  
The Universe

The most powerful radio sources in the local Universe are found in giant elliptical galaxies. Looking back to a redshift of 0.5 (≈ half the age of the Universe for ω = 1), we see that these host galaxies are increasingly found in moderately rich clusters. This fact gives us hope that radio sources can be used as tracers of high density environments at high redshift. By exploiting radio source samples selected over a wide range in luminosity (Blundell et al., these proceedings), we will also be able to test whether the luminosities of radio sources are correlated with their environments.

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