scholarly journals Dependence of Faraday Effects on Radio Luminosity and Redshift

1999 ◽  
Vol 52 (1) ◽  
pp. 147
Author(s):  
A. A. Ubachukwu ◽  
A. C. Ugwoke ◽  
A. E. Chukwude
Keyword(s):  
Radio Source ◽  
Ambient Medium ◽  
Cosmological Evolution ◽  
Significant Fraction ◽  
Selection Effects ◽  
Radio Luminosity ◽  
Quantitative Estimates ◽  
Source Sample ◽  
Faraday Effects ◽  
Bright Source

Quantitative estimates are provided for the influence of luminosity selection effects present in a bright source sample on the observed correlation of the depolarisation rate Λ ½ with redshift z . It is shown that the observed correlation is partly intrinsic and partly due to luminosity effects. More specifically, we find that ~46% of the observed Λ ½ correlation with z can be attributed to strong luminosity selection effects in the sample. This shows that a significant fraction (~54%) of the observed correlation is cosmological in origin. It is concluded that there is a cosmological evolution of Λ ½, over and above that resulting from luminosity selection effects, which may be related to the epoch dependent properties of the ambient medium through which the radio source components propagate.

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.

scholarly journals RC J0311+0507: A Candidate to Superpowerful Radio Galaxies with z = 4.514

2006 ◽  
Vol 2 (S235) ◽  
pp. 431-431
Author(s):  
A. I. Kopylov ◽  
Yu. N. Parijskij ◽  
N. S. Soboleva ◽  
A. V. Temirova ◽  
O. V. Verkhodanov ◽  
...  
Keyword(s):  
Radio Source ◽  
Radio Galaxies ◽  
Strong Line ◽  
Radio Luminosity ◽  
Spectrum Radio

AbstractThe investigations of the ultra steep spectrum radio source RC J0311+0507 (4C+04.11) in radio (RATAN-600, VLA) and optics (6-m telescope SAO RAS) are presented. The identification of a strong line at 6703 Å with Lyα gives a redshift z=4.514. The object belongs to the group of extremely distant radio galaxies of ultrahigh radio luminosity (P1400 = 1.3 × 1029WHz−1).

scholarly journals The Texas Radio Astrometric Survey

1974 ◽  
Vol 61 ◽  
pp. 141-141
Author(s):  
James N. Douglas
Keyword(s):  
Radio Source ◽  
Radio Sources ◽  
Selection Effects ◽  
Sky Survey ◽  
Coordinate Measurements ◽  
Discrete Radio Sources

The 5-element Texas Interferometer is engaged in a 365 MHz survey of the sky with a primary goal of establishing positions of about 50000 discrete radio sources with an accuracy of about 1″ in each coordinate. Measurements are made relative to optical positions of identified sources, and the 2000 positions thus far obtained support our expectations of the accuracy of the survey. In a companion program, optical positions of objects near radio source positions are being measured to ±1/2″ accuracy on glass copies of the Palomar Sky Survey, yielding both improved overall calibration of the radio positions and identification of associated optical objects on the basis of position coincidence alone, without the selection effects usually introduced by auxiliary identification criteria.

scholarly journals Radio Source Evolution Derived from Low Frequency Surveys

2002 ◽  
Vol 199 ◽  
pp. 50-53
Author(s):  
C.A. Jackson ◽  
J.V. Wall
Keyword(s):  
Radio Source ◽  
Luminosity Function ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Parametric Models ◽  
Radio Luminosity ◽  
Space Density ◽  
Radio Data ◽  
Radio Luminosity Function

We find simple parametric models to describe the space density evolution of radio-loud AGN, treating FRI and FRII radio galaxies separately as the two parent populations in our dual-population unified scheme. In this we use low frequency radio data (v < 500 MHz), where radio samples are unbiased by Doppler beaming. Incorporated into this latest analysis is a new determination of the local radio luminosity function at 1.4 GHz from galaxies common to both the 2dFGRS and NVSS surveys.

scholarly journals A Multi-Frequency VLBI Polarization Study of the CSS Quasar 3C 309.1

1998 ◽  
Vol 164 ◽  
pp. 105-106
Author(s):  
Scott E. Aaron ◽  
John F.C. Wardle ◽  
David H. Roberts
Keyword(s):  
Radio Source ◽  
Dynamic Range ◽  
Ambient Medium ◽  
High Dynamic Range ◽  
Field Of View ◽  
Large Field ◽  
General Properties ◽  
Polarization Study ◽  
Rotation Measure ◽  
High Dynamic

AbstractWe discuss the rotation measure properties of the CSS quasar 3C 309.1, determined from high dynamic range, large field of view VLBA images at several frequencies between 1.4 and 15 GHz. We consider the general properties of the ambient medium by considering the structure of the Faraday screen across various parts of the radio source.

scholarly journals The Australia Telescope 20-GHz (AT20G) Survey: the Bright Source Sample

2008 ◽  
Vol 384 (2) ◽  
pp. 775-802 ◽  
Author(s):  
Marcella Massardi ◽  
Ronald D. Ekers ◽  
Tara Murphy ◽  
Roberto Ricci ◽  
Elaine M. Sadler ◽  
...  
Keyword(s):  
Source Sample ◽  
Bright Source

scholarly journals Boundary Layers in Extragalactic Jets

1996 ◽  
Vol 175 ◽  
pp. 461-462
Author(s):  
DAVID S. DE YOUNG
Keyword(s):  
Energy Transfer ◽  
Ambient Medium ◽  
Surrounding Medium ◽  
Essential Elements ◽  
Energy Requirements ◽  
Radio Sources ◽  
Radio Luminosity ◽  
Central Engine ◽  
Extragalactic Jets ◽  
Loss Term

The radio morphology of extragalactic radio sources, in particular the FR I objects, has long been recognized to be suggestive of an outflow which is undergoing a strong interaction with the surrounding medium. Two essential elements must be noted in considering this interaction. First, it is inevitable. Second, the interaction will always provide mass and energy transfer from the jet to the ambient medium, and thus it is a loss term in the overall energy balance of the radio source. As will be seen, these losses can be comparable to the overall radio luminosity and hence are a nontrivial constraint on the energy requirements placed on the central engine.

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