31.4- and 89.6-GHz flux density measurements of extragalactic radio sources

1981 ◽  
Vol 86 ◽  
pp. 1306 ◽  
Author(s):  
B. J. Geldzahler ◽  
A. Witzel
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Density Measurements ◽  
Extragalactic Radio Sources

scholarly journals Extreme Scattering Events

1988 ◽  
Vol 129 ◽  
pp. 301-302
Author(s):  
Ralph Fiedler ◽  
Brian Dennison ◽  
Kenneth Johnston
Keyword(s):  
Interstellar Medium ◽  
Flux Density ◽  
Light Curves ◽  
Small Scale ◽  
Radio Sources ◽  
Density Measurements ◽  
Extragalactic Radio Sources ◽  
Scattering Events

Dally flux density measurements of 36 extragalactic radio sources over a seven year period, obtained by the Green Bank interferometer, reveal several unusual minima in the light curves that do not follow typical source variations (Fiedler et al. 1987). The most significant departure from typical source variability occurred at both frequencies in the quasar 0954+658 between 1980.95 and 1981.3. Refractive focussing by small scale inhomogeneities in an ionized structure in the interstellar medium appears to be the most likely explanation.

scholarly journals VLBI Survey of a Complete Sample of Active Nuclei and Quasars

1984 ◽  
Vol 110 ◽  
pp. 15-24 ◽  
Author(s):  
T. J. Pearson ◽  
A.C.S. Readhead
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Complete Sample ◽  
Limited Sample ◽  
Extragalactic Radio Sources ◽  
5 Ghz ◽  
Number Of Classes ◽  
Compact Sources ◽  
Continuous Range

We have conducted a VLBI survey of a complete, flux-density limited sample of 65 extragalactic radio sources, selected at 5 GHz. We have made hybrid maps at 5 GHz of all of the sources accessible to the Mark-II system. The sources can be divided provisionally into a number of classes with different properties: central components of extended double sources, steep-spectrum compact sources, very compact (almost unresolved) sources, asymmetric sources (sometimes called “core-jet” sources), and “compact double” sources. It is not yet clear whether any of these classes is physically distinct from the others, or whether there is a continuous range of properties.

scholarly journals The Distant DRAGNs Survey

1996 ◽  
Vol 175 ◽  
pp. 513-514
Author(s):  
J. D. B. Law-Green
Keyword(s):  
Flux Density ◽  
Ambient Medium ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Cosmological Evolution ◽  
Radio Sources ◽  
Number Density ◽  
Extragalactic Radio Sources ◽  
Matched Samples

DRAGNs (Double Radio sources Associated with Galactic Nuclei, Leahy 1991) are the class of powerful extragalactic radio sources thought to be produced by the interaction of a jet with the ambient medium. They exhibit strong cosmological evolution in comoving number density; at z ≃ 2 the “classical double” FR II DRAGNs were ≃ 1000 times as common as they are now (Dunlop & Peacock 1990).To understand this, systematic studies of complete DRAGN samples at low and high z and differing levels of flux density are required, in order to resolve the P – z ambiguity. The Distant DRAGNs Survey is a long-term project to image with the VLA and MERLIN, matched samples of DRAGNs at high redshift.

7.8-GHz Flux Density Measurements of Variable Radio Sources

1972 ◽  
Vol 77 ◽  
pp. 819 ◽  
Author(s):  
William A. Dent ◽  
Gabriel Kojoian
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Density Measurements ◽  
Variable Radio

scholarly journals Spectral Index - Redshift Relation for Radio Galaxies and Quasars

1996 ◽  
Vol 175 ◽  
pp. 569-570
Author(s):  
R.D. Dagkesamanskii
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Cosmological Evolution ◽  
Radio Sources ◽  
Spectral Indices ◽  
Extragalactic Radio Sources

Cosmological evolution of synchrotron spectra of the powerful extragalactic radio sources was studied by many authors. Some indications of such an evolution had been found firstly by analysis of ‘spectral index - flux density’ (α – S) relation for the sample of relatively strong radio sources. Later Gopal-Krishna and Steppe extended the analysis to weaker sources and found that the slope of αmed(S) curve changes dramatically at intermediate flux densities. Gopal-Krishna and Steppe pointed out that the maxima of the αmed(S) curve and of differential source counts are at almost the same flux density ranges (see, Fig. 2). It has to be noticed that the all mentioned results were obtained using the low-frequency spectral indices and on the basis of low frequency samples.

scholarly journals The Angular Size Distribution of Radio Sources at Low Flux Densities

1982 ◽  
Vol 97 ◽  
pp. 393-400
Author(s):  
Ann Downes
Keyword(s):  
Size Distribution ◽  
Flux Density ◽  
Angular Size ◽  
Linear Size ◽  
Radio Sources ◽  
High Flux ◽  
Extragalactic Radio Sources ◽  
Size Evolution

Observations of complete samples of extragalactic radio sources at low and intermediate flux densities are described. Many types of source are found. The angular sizes form a smooth extrapolation from higher flux densities, and can be predicted from the known properties of samples at high flux density either with linear size evolution (for Ω = 1 or Ω = 0 Universes) or without linear size evolution (for Ω = 0). The question of whether such evolution is required therefore remains open.

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