scholarly journals CSS versus Large Size Sources

1996 ◽  
Vol 175 ◽  
pp. 63-66 ◽  
Author(s):  
R. Fanti ◽  
R. E. Spencer
Keyword(s):  
Flux Density ◽  
High Power ◽  
High Frequency ◽  
Large Fraction ◽  
Radio Sources ◽  
Frequency Spectra ◽  
Large Size ◽  
Spectrum Radio

A large fraction of the sources in flux density limited radio samples have angular sizes < 2 arcsec (and hence projected linear sizes ≤ 10–15 kpc for H0 = 100 Km/(sec Mpc), and steep (α > 0.5, S∝ v–α) high frequency spectra (Kapahi, 1981; Peacock and Wall 1982). The proportion of these Compact Steep–spectrum Sources (CSSs) is high (15–30% depending on the selection frequency) amongst distant (z > 0.2) radio sources of high power, both galaxies and quasars. We include in this class the GHz Peaked Spectrum Radio Sources (GPS), sub–kpc objects whose radio spectra are peaked at GHz frequencies (see, e.g., O'Dea et al, 1991).

scholarly journals Morphology of Steep Spectrum Radio Sources Showing Variability at Low Frequency

1988 ◽  
Vol 129 ◽  
pp. 125-126
Author(s):  
Franco Mantovani ◽  
Tom Muxlow ◽  
Lucia Padrielli
Keyword(s):  
Interstellar Medium ◽  
Flux Density ◽  
Large Fraction ◽  
Low Frequency ◽  
Line Of Sight ◽  
Radio Sources ◽  
Relativistic Motion ◽  
High Brightness ◽  
Spectrum Radio ◽  
Low Frequency Variability

The observed variability at low frequency of the radio sources can be explained within the framework of the generally accepted models either extrinsic (refractive scintillation in the interstellar medium) or intrinsic (bulk relativistic motion along direction near the line of sight) for variability. Both explanations require a large fraction of the source flux density to be contained in a small high brightness component, of tens of m.a.s. in size. Radio sources with steep straight spectral index are usually tens of Kpc sized, with weak central components and they do not generally show low frequency variability.

Intraday Variability of Flat-Spectrum Radio Sources

1998 ◽  
Vol 164 ◽  
pp. 257-264
Author(s):  
S. J. Wagner
Keyword(s):  
High Frequency ◽  
Large Fraction ◽  
Small Scale ◽  
Electromagnetic Spectrum ◽  
Radio Sources ◽  
Rapid Variability ◽  
Spectrum Radio ◽  
Interstellar Scattering ◽  
Polarization Characteristics ◽  
Intraday Variability

AbstractThe characteristics of rapid variability of flat-spectrum radio sources are reviewed. A large fraction of the blazar population is found to show variability on timescales shorter than one day throughout the entire electromagnetic spectrum. The spectral indices and polarization characteristics change equally fast.Structure functions of the well-monitored sources show pronounced breaks on scales of about 10 to 50 hours, with flatter slopes towards the fast end. This illustrates that Intraday Variability (IDV), i.e. the high frequency end of the power spectrum is qualitatively different and requires different mechanisms than slower variations.While intrinsic IDV provides direct clues on small-scale structure over fifteen decades in frequency, extrinsic contributions from interstellar scattering contributes at the lowest frequencies, and remains difficult to disentangle from the intrinsic effects.

scholarly journals Magnetic Field Strengths of GPS Radio Sources

1999 ◽  
Vol 194 ◽  
pp. 324-326
Author(s):  
V. G. Panajyan
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Radio Sources ◽  
Spectral Indices ◽  
The Past ◽  
Spectrum Radio ◽  
Field Strengths

GHz peaked spectrum radio sources (GPS) are believed to be a subclass of compact steep spectrum radio sources (CSS) with high frequency spectral indices α < −0.5 (5 ˜ vα), linear sizes of pc to kpc scale and turnover spectra near 1GHz. Due to the work of many radioastronomers during the past two decades many properties of CSS and GPS radio sources at present are known (O'Dea,C.P. et al.1998, and references therein).

Four Southern Intraday Variable Radio Sources

1998 ◽  
Vol 164 ◽  
pp. 271-272 ◽  
Author(s):  
L. L. Kedziora-Chudczer ◽  
D. L. Jauncey ◽  
M. H. Wieringa ◽  
J. E. Reynolds ◽  
A. K. Tzioumis
Keyword(s):  
Flux Density ◽  
Progress Report ◽  
Radio Sources ◽  
High Flux ◽  
Inverted Spectrum ◽  
Spectrum Radio ◽  
Variable Radio

AbstractThis is a progress report on the ATCA IDV survey of compact, flat or inverted spectrum radio sources. We found that four sources: PKS 0405–385, PKS 1034–293, PKS 1144–397, and PKS 1519–273 out of the sample of 125 show high flux density variability on the daily timescale. The characteristics of observed IDV are discussed and we reflect on its possible origin.

scholarly journals Unveiling the high-frequency radio source population with the AT20G survey

2013 ◽  
Vol 9 (S304) ◽  
pp. 205-208
Author(s):  
Elizabeth K. Mahony
Keyword(s):  
Radio Source ◽  
Flux Density ◽  
High Frequency ◽  
Gamma Ray ◽  
Low Frequency ◽  
Radio Sources ◽  
Source Population ◽  
Frequency Source ◽  
Galaxy Population ◽  
5 Ghz

AbstractUntil recently, the radio sky above 5 GHz was relatively unexplored. This has changed with the completion of the Australia Telescope 20 GHz survey (AT20G; Murphy et al., 2010); a blind survey of the southern sky down to a limiting flux density of 40 mJy. The AT20G survey provides by far the largest and most complete sample of high-frequency radio sources yet obtained, offering new insights into the nature of the high-frequency active galaxy population. Whilst the radio data provides a unique sample of objects, these data alone are insufficient to completely constrain models of radio source properties and the evolution of radio galaxies. Complementary multiwavelength data is vital in understanding the physical properties of the central black hole.In this talk I will provide a brief overview of the AT20G survey, followed by a discussion of the multiwavelength properties of the high-frequency source population. In particular, I will focus on the optical properties of AT20G sources, which are very different to those of a low-frequency selected sample, along with the gamma-ray properties where we find a correlation between high-frequency radio flux density and gamma-ray flux density. By studying the multiwavelength properties of a large sample of high-frequency radio sources we gain a unique perspective on the inner dynamics of some of the most active AGN.

scholarly journals Australian Journal of Physics Astrophysical Supplement

1976 ◽  
Vol 29 (5) ◽  
pp. 471
Author(s):  
JN Clarke ◽  
AG Little ◽  
BY Mills
Keyword(s):  
Flux Density ◽  
High Frequency ◽  
Magellanic Clouds ◽  
Australian Journal ◽  
The Other ◽  
Optical Data ◽  
Radio Sources ◽  
Angular Extent

The fourth catalogue of radio sources observed at 408 MHz with the Molonglo radiotelescope is presented. A total of 1349 sources is listed to a limiting flux density of 0�2 Jy, the catalogue being largely complete above 0� 25 Jy. The area of sky surveyed includes the Magellanic Clouds as well as a comparison region of similar angular extent. Detailed notes are provided on some of the Cloud sources, and maps are given for complex sources in the region of the Clouds. Those sources for which high-frequency or optical data are available are classified into two lists, one of Cloud members and the other of 'unidentified nonthermal sources', presumably not Cloud members.

scholarly journals Evolution of low-frequency contribution in emission of steep-spectrum radio sources

2014 ◽  
Vol 11 (S308) ◽  
pp. 631-635
Author(s):  
Alla P. Miroshnichenko
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Radio Spectrum ◽  
Unified Model ◽  
Linear Size ◽  
Radio Sources ◽  
Mean Values ◽  
Spectrum Radio ◽  
Size Characteristic ◽  
The Mean

AbstractWe consider evolution properties of galaxies and quasars with steep radio spectrum at the decametre band from the UTR-2 catalogue. The ratios of source's monochromatic luminosities at the decametre and high-frequency bands display the dependence on the redshift, linear size, characteristic age of examined objects. At that, the mean values of corresponding ratios for considered galaxies and quasars have enough close quantities,testifying on the unified model of sources. We analyse obtained relations for two types of steep-spectrum sources (with linear steep spectrum (S) and low-frequency steepness after a break (C+)) from the UTR-2 catalogue.

A Complete Flux-Density--limited VLBI Survey of 293 Flat-Spectrum Radio Sources

1996 ◽  
Vol 107 ◽  
pp. 37 ◽  
Author(s):  
G. B. Taylor ◽  
R. C. Vermeulen ◽  
A. C. S. Readhead ◽  
T. J. Pearson ◽  
D. R. Henstock ◽  
...  
Keyword(s):  
Flux Density ◽  
Radio Sources ◽  
Spectrum Radio

scholarly journals A Comparison of the Centimetre-to-Submillimetre Continuum Spectra of BL Lacertae Objects and Flat Spectrum Radio Quasars

1994 ◽  
Vol 159 ◽  
pp. 523-523
Author(s):  
J.A. Stevens ◽  
S.J. Litchfield ◽  
E.I. Robson ◽  
W. K. Gear ◽  
D.H. Hughes
Keyword(s):  
High Frequency ◽  
Spectral Shape ◽  
Continuum Emission ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Bl Lacertae Objects ◽  
Bl Lacertae ◽  
Spectrum Radio ◽  
Bl Lacs ◽  
The Continuum

A comparison of the centimetre to submillimetre continuum spectra of 22 BL Lacertae objects and 24 flat-spectrum radio quasars (FSRQ) has been conducted in order to search for systematic differences between the two classes. The same overall spectral shape is found for all sources and it is concluded that the same basic physical model applies to the continuum emission over this frequency range in both cases. There is clear evidence, however, for the BL Lacs to have flatter high frequency spectra and this difference is reconciled with an intrinsic difference in the underlying jets of the two classes.

The High Radio Frequency Spectra and Variability of Southern Flat-Spectrum Radio Sources

2000 ◽  
Vol 120 (5) ◽  
pp. 2278-2283 ◽  
Author(s):  
M. Tornikoski ◽  
M. Lainela ◽  
E. Valtaoja
Keyword(s):  
Radio Frequency ◽  
Radio Sources ◽  
Frequency Spectra ◽  
Spectrum Radio
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