Spectral index of extragalactic radio sources as a function of the flux density

Astrophysics ◽  
1971 ◽  
Vol 5 (2) ◽  
pp. 140-143 ◽  
Author(s):  
R. D. Dagkesamanskii
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Radio Sources ◽  
Extragalactic Radio Sources

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 A Catalogue of Galactic Radio Sources

1968 ◽  
Vol 21 (3) ◽  
pp. 369 ◽  
Author(s):  
MJL Kesteven
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Galactic Plane ◽  
Radio Sources ◽  
Galactic Radio

The results of a survey of radio sources in the galactic plane in the longitude range 1800 to 400 with the 1 mile Molonglo Cross telescope at 408 MHz are presented. The methods of observation and reduction are described briefly. The catalogue lists the position, flux density, size, and spectral index for 80 sources

Some Features in the Spectra of Extragalactic Radio Sources

1981 ◽  
Vol 4 (2) ◽  
pp. 184-187 ◽  
Author(s):  
O. B. Slee
Keyword(s):  
Spectral Index ◽  
Recent Analysis ◽  
Radio Sources ◽  
Usual Definition ◽  
Extragalactic Radio Sources ◽  
Flux Data ◽  
Straight Line ◽  
Consistent Manner ◽  
Definition Of ◽  
Second Degree

A recent analysis of the spectra of about 2000 sources in the Culgoora-3 list (Slee 1977) of radio sources (Slee et al. 1981) has revealed some interesting features which may be the result of source evolution. The Culgoora-3 spectra were obtained by combining the 80 and 160 MHz flux densities from the Culgoora radioheliograph with other published flux data between 10 and 10,000 MHz; this is probably the most accurate set of spectra yet derived for a large number of sources selected for observation in a reasonably consistent manner. In addition to fitting the log S-log v data for each source with a straight line (its slope is the usual definition of spectral index) Slee et al. also fitted second-degree and third-degree polynomials to search for curvature in the spectra.

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.

On the Spectral Index-Flux Density Relation for Large Samples of Radio Sources

2003 ◽  
Vol 3 (4) ◽  
pp. 347-358 ◽  
Author(s):  
Xi-Zhen Zhang ◽  
W. Reich ◽  
P. Reich ◽  
R. Wielebinski
Keyword(s):  
Flux Density ◽  
Spectral Index ◽  
Radio Sources ◽  
Large Samples ◽  
Density Relation

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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