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The 6C** sample of steep-spectrum radio sources – I. Radio data, near-infrared imaging and optical spectroscopy.
- Source :
-
Monthly Notices of the Royal Astronomical Society . 12/21/2006, Vol. 373 Issue 4, p1531-1562. 32p. 10 Charts, 2 Graphs. - Publication Year :
- 2006
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Abstract
- We present basic observational data on the 6C** sample. This is a new sample of radio sources drawn from the 151-MHz 6C survey, which was filtered with radio criteria chosen to optimize the chances of finding radio galaxies at . The filtering criteria are a steep-spectral index and a small angular size. The final sample consists of 68 sources from a region of sky covering 0.421 sr. We present Very Large Array radio maps, and the results of K-band imaging and optical spectroscopy. Near-infrared counterparts are identified for 66 of the 68 sources, down to a 3σ limiting magnitude of K∼ 22 mag in a 3-arcsec aperture. Eight of these identifications are spatially compact, implying an unresolved nuclear source. The K-magnitude distribution peaks at a median K≈ 18.7 mag, and is found to be statistically indistinguishable from that of the similarly selected 6C* sample, implying that the redshift distribution could extend to z≳ 4. Redshifts determined from spectroscopy are available for 22 (32 per cent) of the sources, over the range of 0.2 ≲ z≲ 3.3. We measure 15 of these, whereas the other seven were previously known. Six sources are at . Four sources show broad emission lines in their spectra and are classified as quasars. Three of these show also an unresolved K-band identification. 11 sources fail to show any distinctive emission and/or absorption features in their spectra. We suggest that these could be (i) in the so-called ‘redshift desert’ region of or (ii) at a greater redshift, but feature weak emission-line spectra. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00358711
- Volume :
- 373
- Issue :
- 4
- Database :
- Academic Search Index
- Journal :
- Monthly Notices of the Royal Astronomical Society
- Publication Type :
- Academic Journal
- Accession number :
- 23408436
- Full Text :
- https://doi.org/10.1111/j.1365-2966.2006.11101.x