scholarly journals A search for high-redshift quasars among GB/FIRST flat-spectrum radio sources

1998 ◽  
Vol 297 (4) ◽  
pp. 1115-1122 ◽  
Author(s):  
I. M. Hook ◽  
R. H. Becker ◽  
R. G. McMahon ◽  
R. L. White
Keyword(s):  
High Redshift ◽  
Radio Sources ◽  
Spectrum Radio

scholarly journals Spatially resolved studies of extragalactic jets in high redshift radio galaxies

2014 ◽  
Vol 10 (S313) ◽  
pp. 231-235
Author(s):  
Leah K. Morabito ◽  
Adam Deller ◽  
J. B. R. Oonk ◽  
Huub Röttgering ◽  
George Miley
Keyword(s):  
High Redshift ◽  
Low Frequency ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Spatially Resolved ◽  
Long Baseline ◽  
Early Results ◽  
Spectrum Radio ◽  
Extragalactic Jets ◽  
Frequency Survey

AbstractThe correlation between radio spectral steepness and redshift has been successfully used to find high redshift (z ⩾ 2) radio galaxies, but the origin of this relation is unknown. The ultra-steep spectra of high-z radio sources make them ideally suited for studies with the Low Band Antenna of the new Low Frequency Array, which covers 10–80 MHz and has baselines up to about 1300 km. As part of an ongoing survey, we use the longest baselines to map the low-frequency (< 70 MHz) spatial distributions along the jets of 5 bright extended steep spectrum high-z radio sources. From this, we will determine whether the spectra change over these spatially resolved sources, thereby constraining particle acceleration processes. We present early results from our low-frequency survey of ultra-steep spectrum radio galaxies. The first low frequency long baseline images of these objects are presented.

scholarly journals A sample of 669 ultra steep spectrum radio sources to find high redshift radio galaxies

2000 ◽  
Vol 143 (2) ◽  
pp. 303-333 ◽  
Author(s):  
C. De Breuck ◽  
W. van Breugel ◽  
H. J.A. Röttgering ◽  
G. Miley
Keyword(s):  
High Redshift ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Spectrum Radio

scholarly journals Radio-optical Identification of Very-Steep Spectrum Radio Sources from the UTR-2 Catalogue

2002 ◽  
Vol 199 ◽  
pp. 217-218 ◽  
Author(s):  
H. Andernach ◽  
O.V. Verkhodanov ◽  
N.V. Verkhodanova
Keyword(s):  
Radio Source ◽  
High Redshift ◽  
Radio Galaxies ◽  
Image Databases ◽  
Radio Continuum ◽  
Radio Sources ◽  
Optical Identification ◽  
X Ray ◽  
Spectrum Radio

We used radio source catalogues accessible from the CATS database to establish radio continuum spectra for decametric radio sources in the UTR-2 catalogue. In an attempt to find further candidates for high-redshift radio galaxies, we searched the FIRST and NVSS surveys for counterparts of a sample of UTR sources with ultra-steep radio spectra (USS, α ≤ −1.2, S ∼ vα). We derived accurate positions and sizes for 23 of these USS sources. The search for optical counterparts from the APM (object) and DSS (image) databases, as well as infrared and X—ray identifications of these UTR sources are in progress.

Ultra--Steep-Spectrum Radio Sources. II. Radio, Infrared, Optical, and HST Imaging of High-Redshift 4C Objects

1996 ◽  
Vol 106 ◽  
pp. 247 ◽  
Author(s):  
K. C. Chambers ◽  
G. K. Miley ◽  
W. J. M. van Breugel ◽  
M. A. R. Bremer ◽  
J.-S. Huang ◽  
...  
Keyword(s):  
High Redshift ◽  
Radio Sources ◽  
Spectrum Radio

scholarly journals POLARIZATION ALIGNMENT IN JVAS/CLASS FLAT SPECTRUM RADIO SURVEYS

2013 ◽  
Vol 22 (12) ◽  
pp. 1350089 ◽  
Author(s):  
PRABHAKAR TIWARI ◽  
PANKAJ JAIN
Keyword(s):  
High Redshift ◽  
Large Error ◽  
Radio Sources ◽  
Physical Explanation ◽  
Full Data ◽  
Data Set ◽  
Significant Alignment ◽  
Spectrum Radio ◽  
Detailed Statistical Analysis ◽  
Fractional Error

We present a detailed statistical analysis of the alignment of polarizations of radio sources at high redshift. This study is motivated by the puzzling signal of alignment of polarizations from distant quasars at optical frequencies. We use a coordinate invariant measure of dispersion to test for alignment of polarizations of widely separated sources. The data from JVAS/CLASS 8.4 GHz surveys are used for our study. We find that the data set with polarization flux greater than 1 mJy shows a significant signal of alignment at distance scales of order 150 Mpc. The significance of alignment decreases as we go to larger distances. In contrast the data set with polarization flux less than 1 mJy does not show significant alignment at short distances. However this set, as well as the full data sample, shows a very significant signal at large distances of order 500–850 Mpc. Due to the presence of relatively large error in the low polarization sample, this signal needs to be tested further with more refined data. We also study the signal by imposing a cut on the error in polarization. We find that the significance of alignment increases with decrease in fractional error. We are unable to attribute our results to known sources of bias. We discuss a possible physical explanation of our results.

scholarly journals The Space Density of High-Redshift Quasars

1996 ◽  
Vol 175 ◽  
pp. 561-562
Author(s):  
P.A. Shaver ◽  
J.V. Wall ◽  
K.I. Kellermann ◽  
C. Jackson ◽  
M.R. Hawkins
Keyword(s):  
High Redshift ◽  
Radio Sources ◽  
Space Density ◽  
Large Sample ◽  
Upper Limit ◽  
Spectrum Radio ◽  
Complete Identification

An upper limit on the space density of quasars at z > 5 is obtained independent of any optical magnitude limit, from the complete identification of a large sample of flat-spectrum radio sources. This upper limit is below the observed space density at z ≃ 2 − 3, showing that the turnover in space density is real and not merely due to obscuration.

scholarly journals Multiwavelength characterization of faint ultra steep spectrum radio sources: A search for high-redshift radio galaxies

2014 ◽  
Vol 569 ◽  
pp. A52 ◽  
Author(s):  
V. Singh ◽  
A. Beelen ◽  
Y. Wadadekar ◽  
S. Sirothia ◽  
C. H. Ishwara-Chandra ◽  
...  
Keyword(s):  
High Redshift ◽  
Radio Galaxies ◽  
Radio Sources ◽  
Spectrum Radio

CTD 93 and the Nature of Gigahertz Peaked Spectrum Radio Sources

1999 ◽  
Vol 515 (2) ◽  
pp. 558-566 ◽  
Author(s):  
David B. Shaffer ◽  
K. I. Kellermann ◽  
T. J. Cornwell
Keyword(s):  
Radio Sources ◽  
Spectrum Radio
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