The 6C survey of radio sources - I. Declination zone Formula

Baldwin, John E.; Boysen, Roger C.; Hales, S. E. G.; Jennings, J. E.; Waggett, P. C.; Warner, P. J.; Wilson, Donald M.

doi:10.1093/mnras/217.4.717

Cited by 68 publications

(20 citation statements)

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“…Many of these sources have complex spatial structure and are modeled by multiple delta functions (or shaplets). The accuracy of our flux scale calibration is tested by cross-identifying the 100 brightest sources observed at a distance < 3°from the phase center with the 6C (Baldwin et al 1985) and 7C (Hales et al 2007) 151 MHz radio catalogs. We obtained the intrinsic flux of these sources by first applying a primary-beam correction, and then modeling their spectra over the 13 MHz bandwidth with a power-law to estimate their flux at 151 MHz.…”

Section: The Ncp Sky Modelmentioning

confidence: 99%

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

Mertens

Mevius

Koopmans

et al. 2020

Monthly Notices of the Royal Astronomical Society

292

263

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A new upper limit on the 21-cm signal power spectrum at a redshift of z ≈ 9.1 is presented, based on 141 hours of data obtained with the Low-Frequency Array (LOFAR). The analysis includes significant improvements in spectrally-smooth gain-calibration, Gaussian Process Regression (GPR) foreground mitigation and optimally-weighted power spectrum inference. Previously seen 'excess power' due to spectral structure in the gain solutions has markedly reduced but some excess power still remains with a spectral correlation distinct from thermal noise. This excess has a spectral coherence scale of 0.25 − 0.45 MHz and is partially correlated between nights, especially in the foreground wedge region. The correlation is stronger between nights covering similar local sidereal times. A best 2-σ upper limit of ∆ 2 21 < (73) 2 mK 2 at k = 0.075 h cMpc −1 is found, an improvement by a factor ≈ 8 in power compared to the previously reported upper limit. The remaining excess power could be due to residual foreground emission from sources or diffuse emission far away from the phase centre, polarization leakage, chromatic calibration errors, ionosphere, or low-level radio-frequency interference. We discuss future improvements to the signal processing chain that can further reduce or even eliminate these causes of excess power.

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Section: The Ncp Sky Modelmentioning

confidence: 99%

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

Mertens

Mevius

Koopmans

et al. 2020

Monthly Notices of the Royal Astronomical Society

292

263

View full text Add to dashboard Cite

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“…Table 1 lists their basic characteristics. The catalog "6Call" was compiled from all the Cambridge 6C surveys (6CI-6CVI: Baldwin et al 1985;Hales et al 1988Hales et al , 1990Hales et al , 1991Hales et al , 1993aHales et al , 1993b. The catalog at 232 MHz was presented by Zhang et al (1997) using the Miyun Synthesis Radio Telescope (MSRT).…”

Section: The Radio Source Samplesmentioning

confidence: 99%

On the Spectral Index-Flux Density Relation for Large Samples of Radio Sources

Zhang

Reich

et al. 2003

Chin. J. Astron. Astrophys.

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We present new statistical results on the spectral index-flux density relation for large samples of radio sources using archival data of the most sensitive surveys, such as 6C, Miyun, WENSS, B3, NVSS, GB87. Instrumental selection effects and the completeness of the catalogs are discussed. Based on the spectral indices calculated for about 200 000 sources from the WENSS (327 MHz) and NVSS (1.4 GHz) catalogs, we obtained (1) The median spectral index increases from α med ∼ −0.9 to α med ∼ −0.8 (S ν ∝ ν α), while S 327 flux densities decrease from 0.1 Jy down to 25 mJy. The median spectral indices nearly show no variation within the error bars when the flux density is larger than 0.1 Jy. (2) A dependence of the fraction of ultra-steep spectrum sources (USS, −1.5 ≤ α < −1.0), steep spectrum sources (SSS, −1.0 ≤ α < −0.5) and flat spectrum sources (FSS, −0.5 ≤ α ≤ 0.0) is partly responsible for the spectral flattening. Another contribution to the spectral flattening comes from the variation of α med of steep spectrum sources (α < −0.5) themselves which increases with decreasing flux densities. (3) The spectral flattening for faint sources (down to S 327 ∼ 20 mJy) with steep spectra (α < −0.5) suggests that α med is correlated with luminosity rather than redshift according to the Condon' model. (4) A strong spectral selection effect occurs when spectral indices are calculated from samples with a large frequency separation.

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“…The parameters of the 6C survey are given in Table 1. The 6C survey was published from 1985 -see Baldwin et al (1985) for the first portion of 22 [1985][1986][1987][1988][1989][1990][1991][1992][1993] the survey, which describes the telescope, its operation and the data analysis in detail, and Hales, Baldwin, & Warner (1988), Hales et al (1990Hales et al ( , 1991 and for the subsequent portions of the survey.…”

Section: The 6c Surveymentioning

confidence: 99%

Cambridge Low Frequency Surveys

Green

2002

Symp. - Int. Astron. Union

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Over many years low-frequency radio surveys have been made in Cambridge that cover much of the northern sky at both 38 and 151 MHz. The characteristics of the earlier surveys − 6C (at 151 MHz, δ above +30°) and 8C (at 38 MHz, δ above +60°), both with a resolution of about 4 arcmin — are reviewed, together with the results from more recent surveys made at 151 MHz, with a resolution of about 1·2 arcmin with the Cambridge Low-Frequency Synthesis Telescope (CLFST). These surveys include the 7C survey, which includes low declinations to complement 6C, selected regions at higher declinations, variability studies, and the 7C(G) survey of much of the northern Galactic plane.

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The 6C survey of radio sources - I. Declination zone Formula

Cited by 68 publications

References 0 publications

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

Improved upper limits on the 21 cm signal power spectrum of neutral hydrogen at z ≈ 9.1 from LOFAR

On the Spectral Index-Flux Density Relation for Large Samples of Radio Sources

Cambridge Low Frequency Surveys

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