Effects of Synchrotron Loss on the Low-Frequency Spectra of Extragalactic Radio Sources with Inhomogeneities

2002 ◽  
Vol 199 ◽  
pp. 231-232
Author(s):  
N. Tsvyk
Keyword(s):  
Fine Structure ◽  
Low Frequency ◽  
New Method ◽  
Radio Sources ◽  
Frequency Spectra ◽  
Extragalactic Radio Sources ◽  
Spectrum Measurements

In this work we explain the integrated spectrum measurements (Braude et.al.,1978—1995) in terms of the synchrotron theory and the the recent measurements of radio fine structure in different classes of sources (Carilli et.al.,1991). This provides a new method of investigating extragalactic radio sources

scholarly journals Intensity Variations in Extragalactic Radio Sources at 13 cm

1972 ◽  
Vol 44 ◽  
pp. 224-224 ◽  
Author(s):  
G. D. Nicolson
Keyword(s):  
Low Frequency ◽  
Secular Change ◽  
Radio Sources ◽  
Complete Sample ◽  
Frequency Spectra ◽  
Extragalactic Radio Sources ◽  
The Relationship

Results of a three-year investigation into the variability of 55 Parkes sources at 13 cm are presented. Thirty-six of the sources comprise a complete sample of QSS with fluxes exceeding 2 flux units. The remaining sources include most other known or likely variables stronger than 2 flux units. The relationship between spectra and variability in QSS is investigated and it is confirmed that variables generally have flat low frequency spectra. A possible relationship between redshift and specific types of intensity variations is considered. Limits on the secular change in the intensity of non-variable QSS are set and are generally found to be ± 1.5% p.a. at 13 cm. Results for the remaining 19 sources are discussed and some preliminary findings of an extension patrol to include weaker sources in the range 1-2 flux units are given.

Low-frequency spectra of extragalactic radio sources

Astrophysics ◽  
1970 ◽  
Vol 4 (4) ◽  
pp. 252-255
Author(s):  
A. M. Aslanyan ◽  
V. G. Malumyan ◽  
V. A. Sanamyan
Keyword(s):  
Low Frequency ◽  
Radio Sources ◽  
Frequency Spectra ◽  
Extragalactic Radio Sources

The low-frequency spectra of a complete sample of extragalactic radio sources

1984 ◽  
Vol 89 ◽  
pp. 323 ◽  
Author(s):  
L. Gregorini ◽  
F. Mantovani ◽  
A. Eckart ◽  
P. Biermann ◽  
A. Witzel ◽  
...  
Keyword(s):  
Low Frequency ◽  
Radio Sources ◽  
Complete Sample ◽  
Frequency Spectra ◽  
Extragalactic Radio Sources

scholarly journals ENVIRONMENT DENSITY OF A GIANT RADIO STRUCTURE FOR GALAXIES AND QUASARS WITH STEEP RADIO SPECTRA

2021 ◽  
Vol 26 (2) ◽  
pp. 165-172
Author(s):  
A. P. Miroshnichenko ◽  
Keyword(s):  
Low Frequency ◽  
Radio Spectrum ◽  
Power Relation ◽  
Cosmological Evolution ◽  
Inverse Power ◽  
Radio Sources ◽  
Frequency Spectra ◽  
Radio Structure ◽  
Mean Values ◽  
Index Value

Purpose: Estimate of the environment density of giant (with the linear size of about megaparsec) radio structures for galaxies and quasars with steep low-frequency spectra taken from the UTR-2 catalogue. Study of the cosmological evolution of environment density of giant radio sources. Determination of dependence of contribution of radio lobes into the emission of giant sources with respect to their environment density. Design/methodology/approach: We use the sample of sources from the UTR-2 catalogue of extragalactic sources to estimate the environment density for giant sources with steep low-frequency spectra. The selection criteria for the examined objects are the following: 1) the spectral index value is equal or larger than 1; 2) the fl ux density of emission at the frequency of 25 MHz is larger than 10 Jy; 3) the sample sources are optically identifi ed. The value of environment density of examined sources is obtained with the assumption of equality of source jet luminosity (at the synchrotron mechanism of radio emission) and its corresponding kinetic luminosity. The analysis of the estimates of environment densities is made for different classes of the sample objects (for galaxies and quasars with linear steep spectra and with break steep spectra). Findings: The estimates of environment density have been derived for giant radio structures formed by the jets of sources with steep spectrum from the UTR-2 catalogue. On the average, the environment density for the quasar structure (~ 10-28 g/sm3) is lesser than the one for the galaxies (~ 10-27 g/sm3 to ~ 10-26 g/sm3). The larger jet environment density is typical for the galaxies and quasars with the break steep spectra than for those with the linear steep spectra. The inverse power relation of the jet environment density and the source redshift (the cosmological evolution of the jet environment density) has been derived. The contribution of jet-related radio lobes into the emission of sources displays the inverse power relation for the environment density of the corresponding radio structures. Conclusions: The mean values of obtained estimates of environment density of giant jets of radio sources with steep low-frequency spectra indicate the lesser environment density of quasar jets than that for the galaxy jets. Giant radio sources with steep low-frequency spectrum (especially, with break steep spectrum) reveal considerable evolution of environment density of jets. The larger contribution of radio lobes (jets) into the emission of sources corresponds to the lesser environment density of sources taken from the UTR-2 catalogue. It can be due to propagation of jets (surrounded by radio lobes) from powerful radio sources to distances of about megaparsec, until the balance of source’s environment density and extragalactic environment density is reached. Key words: steep low-frequency radio spectrum; giant radio structure; jets; radio lobes; galaxies; quasars; environment density

scholarly journals Results from a monitoring program of low frequency variable sources

1986 ◽  
Vol 119 ◽  
pp. 149-155
Author(s):  
L. Padrielli ◽  
R. Fanti ◽  
A. Ficarra ◽  
L. Gregorini ◽  
F. Mantovani
Keyword(s):  
Monitoring Program ◽  
Low Frequency ◽  
Radio Sources ◽  
Main Question ◽  
Extragalactic Radio Sources ◽  
Low Frequency Variability ◽  
Flux Variability

The flux variability of extragalactic radio sources at decimetric wavelengths (Low Frequency Variability LFV) is mostly associated with the nuclei of compact radio sources. But is a not yet well understood phenomenon. The main question still is: where does this phenomenon take place?

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 Centiarcsecond Structure and Variability of AGN

1994 ◽  
Vol 159 ◽  
pp. 389-389
Author(s):  
D.R. Altschuler ◽  
L.I. Gurvits ◽  
W. Alef ◽  
D. Graham ◽  
B. Dennison ◽  
...  
Keyword(s):  
Fine Structure ◽  
Radio Galaxy ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Vlbi Observations ◽  
Flux Variability ◽  
Source Sample ◽  
Flux Monitoring ◽  
Bl Lacs

One possible approach to distinguish between “intrinsic” and “external” mechanisms for variability implies a study of possible correlations between flux variability and the fine structure of sources. We present results of snapshot global VLBI observations at 327 MHz of a sample of 16 extragalactic radio sources (1 radio galaxy, 9 quasars, 4 BL Lacs, 2 unidentified) selected on the basis of the bi-monthly flux monitoring at five frequencies (1400, 880, 606, 430, and 318 MHz). The observed source sample is presented in the Table I.

A radio method of searching for fine structure in H 11 regions

1967 ◽  
Vol 31 ◽  
pp. 237
Author(s):  
O. B. Slee
Keyword(s):  
Fine Structure ◽  
Radio Emission ◽  
Electron Density ◽  
Path Length ◽  
Low Frequency ◽  
Radio Sources ◽  
Average Electron Density ◽  
Scale Size ◽  
Average Electron ◽  
Radio Method

Fine structure with a scale size of about 10-3pc in the galactic ionized hydrogen may scatter the low-frequency radio emission of extragalactic sources with intrinsically small angular diameters, thus making them apparently large. For example, application of the Chandrasekhar scattering formula to a path length of 100 pc through an H 11 region with an average electron density of 0·1 cm-3, and structure of scale size 10-3pc filling 1% of the volume, results in a scattering to half-brightness points of 8″ (arc) at 38 MHz. Radio sources with apparent angular sizes of this amount should be partially resolved by an interferometer with an effective baseline of about 10 000 wavelengths.

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