The 6C** sample of steep-spectrum radio sources: I - Radio data, near-infrared imaging and optical spectroscopy
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 z > 4. The filtering criteria are a steep-spectral index and a sma...
| Main Authors: | , , , , , , , , , , |
|---|---|
| Format: | Journal article |
| Language: | English |
| Published: |
2006
|
| _version_ | 1797074748747808768 |
|---|---|
| author | Cruz, M Jarvis, M Blundell, K Rawlings, S Croft, S Klöckner, H McLure, R Simpson, C Targett, T Willott, C Kloeckner, H |
| author_facet | Cruz, M Jarvis, M Blundell, K Rawlings, S Croft, S Klöckner, H McLure, R Simpson, C Targett, T Willott, C Kloeckner, H |
| author_sort | Cruz, M |
| collection | OXFORD |
| description | 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 z > 4. 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 VLA 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 3-sigma 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 7 were previously known. Six sources are at z > 2.5. Four sources show broad emission lines in their spectra and are classified as quasars. Three of these show also an unresolved K-band identification. Eleven 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 1.2 < z < 1.8, or (ii) at a greater redshift, but feature weak emission line spectra. |
| first_indexed | 2024-03-06T23:40:40Z |
| format | Journal article |
| id | oxford-uuid:6f33bb5b-3f46-4d84-b7a0-c316a4bda131 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-06T23:40:40Z |
| publishDate | 2006 |
| record_format | dspace |
| spelling | oxford-uuid:6f33bb5b-3f46-4d84-b7a0-c316a4bda1312022-03-26T19:29:12ZThe 6C** sample of steep-spectrum radio sources: I - Radio data, near-infrared imaging and optical spectroscopyJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:6f33bb5b-3f46-4d84-b7a0-c316a4bda131EnglishSymplectic Elements at Oxford2006Cruz, MJarvis, MBlundell, KRawlings, SCroft, SKlöckner, HMcLure, RSimpson, CTargett, TWillott, CKloeckner, HWe 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 z > 4. 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 VLA 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 3-sigma 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 7 were previously known. Six sources are at z > 2.5. Four sources show broad emission lines in their spectra and are classified as quasars. Three of these show also an unresolved K-band identification. Eleven 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 1.2 < z < 1.8, or (ii) at a greater redshift, but feature weak emission line spectra. |
| spellingShingle | Cruz, M Jarvis, M Blundell, K Rawlings, S Croft, S Klöckner, H McLure, R Simpson, C Targett, T Willott, C Kloeckner, H The 6C** sample of steep-spectrum radio sources: I - Radio data, near-infrared imaging and optical spectroscopy |
| title | The 6C** sample of steep-spectrum radio sources: I - Radio data,
near-infrared imaging and optical spectroscopy |
| title_full | The 6C** sample of steep-spectrum radio sources: I - Radio data,
near-infrared imaging and optical spectroscopy |
| title_fullStr | The 6C** sample of steep-spectrum radio sources: I - Radio data,
near-infrared imaging and optical spectroscopy |
| title_full_unstemmed | The 6C** sample of steep-spectrum radio sources: I - Radio data,
near-infrared imaging and optical spectroscopy |
| title_short | The 6C** sample of steep-spectrum radio sources: I - Radio data,
near-infrared imaging and optical spectroscopy |
| title_sort | 6c sample of steep spectrum radio sources i radio data near infrared imaging and optical spectroscopy |
| work_keys_str_mv | AT cruzm the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT jarvism the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT blundellk the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT rawlingss the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT crofts the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT klocknerh the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT mclurer the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT simpsonc the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT targettt the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT willottc the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT kloecknerh the6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT cruzm 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT jarvism 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT blundellk 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT rawlingss 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT crofts 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT klocknerh 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT mclurer 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT simpsonc 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT targettt 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT willottc 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy AT kloecknerh 6csampleofsteepspectrumradiosourcesiradiodatanearinfraredimagingandopticalspectroscopy |