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J/ApJ/832/190   Radio sources in the NCP region with the 21CMA   (Zheng+, 2016)

Radio sources in the NCP region observed with the 21 Centimeter Array. Zheng Q., Wu X.-P., Johnston-Hollitt M., Gu J.-H., Xu H. <Astrophys. J., 832, 190-190 (2016)> =2016ApJ...832..190Z (SIMBAD/NED BibCode)
ADC_Keywords: Radio continuum ; Interferometry Keywords: instrumentation: interferometers; methods: observational; radio continuum: galaxies; radio continuum: general Abstract: We present a catalog of 624 radio sources detected around the North Celestial Pole (NCP) with the 21 Centimeter Array (21CMA), a radio interferometer dedicated to the statistical measurement of the epoch of reionization (EoR). The data are taken from a 12hr observation made on 2013 April 13, with a frequency coverage from 75 to 175MHz and an angular resolution of ∼4'. The catalog includes flux densities at eight sub-bands across the 21CMA bandwidth and provides the in-band spectral indices for the detected sources. To reduce the complexity of interferometric imaging from the so-called "w" term and ionospheric effects, the present analysis is restricted to the east-west baselines within 1500m only. The 624 radio sources are found within 5deg around the NCP down to ∼0.1Jy. Our source counts are compared, and also exhibit a good agreement, with deep low-frequency observations made recently with the GMRT and MWA. In particular, for fainter radio sources below ∼1 Jy, we find a flattening trend of source counts toward lower frequencies. While the thermal noise (∼0.4mJy) is well controlled to below the confusion limit, the dynamical range (∼104) and sensitivity of current 21CMA imaging are largely limited by calibration and deconvolution errors, especially the grating lobes of very bright sources, such as 3C061.1, in the NCP field, which result from the regular spacings of the 21CMA. We note that particular attention should be paid to the extended sources, and their modeling and removal may constitute a large technical challenge for current EoR experiments. Our analysis may serve as a useful guide to the design of next generation low-frequency interferometers like the Square Kilometre Array. Description: In the current work, we present the point radio sources observed with the 40 pods of the 21 Centimeter Array (21CMA) E-W baselines for an integration of 12hr made on 2013 April 13; centered on the North Celestial Pole (NCP). An extra deep sample with a higher sensitivity from a longer integration time of up to years will be published later. We have detected a total of 624 radio sources over the central field within 3° in a frequency range of 75-175MHz and the outer annulus of 3°-5° in the 75-125MHz bands. By performing a Monte-Carlo simulation, we have estimated a completeness of 50% at S∼0.2Jy. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table3.dat 131 624 Source catalog
See also: VIII/21 : 6C Survey of radio sources - II. (Hales+ 1988) VIII/35 : Radio Sources observed with Culgoora Circular Array (Slee 1995) VIII/79 : The VLA Low-frequency Sky Survey at 74MHz (Cohen+ 2007) VIII/84 : A final non-redundant catalogue for 7C 151-MHz survey (Hales+ 2007) VIII/98 : 180MHz Murchison Commissioning Survey (MWACS) (Hurley-Walker+, 2014) J/A+A/535/A38 : Observations of NOAO Bootes field at 153MHz (Intema+, 2011) J/ApJ/734/L34 : 145MHz source measurements by PAPER (Jacobs+, 2011) J/MNRAS/426/3295 : Complete 150MHz GMRT source catalogue (Ghosh+, 2012) J/A+A/549/A55 : GMRT 153MHz (2m) Radio Mini Survey I. (Williams+, 2013) J/ApJS/213/3 : Low-frequency flat spectrum sources (LORCAT) (Massaro+, 2014) Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
1- 2 I2 h RAh [0/23] Hour of Right Ascension (J2000) (1) 4- 5 I2 min RAm Minute of Right Ascension (J2000) 7- 10 F4.1 s RAs Second of Right Ascension (J2000) 12 A1 --- DE- [+] Sign of Declination (J2000) (1) 13- 14 I2 deg DEd [85/89] Degree of Declination (J2000) (1) 16- 17 I2 arcmin DEm Arcminute of Declination (J2000) 19- 24 F6.3 Jy Flux1 [0.01/10.3]?=0 Flux in 81.25MHz subband image 26- 30 F5.3 Jy e_Flux1 [0.002/1.5]?=0 Error of Flux1 32- 36 F5.3 Jy Flux2 [0.01/9.5]?=0 Flux in 93.75MHz subband image 38- 42 F5.3 Jy e_Flux2 [0.002/1]?=0 Error of Flux2 44- 48 F5.3 Jy Flux3 [0.01/8.3]?=0 Flux in 106.25MHz subband image 50- 54 F5.3 Jy e_Flux3 [0.001/0.9]?=0 Error of Flux3 56- 60 F5.3 Jy Flux4 [0.01/8.2]?=0 Flux in 118.75MHz subband image 62- 66 F5.3 Jy e_Flux4 [0.001/0.9]?=0 Error of Flux4 68- 73 F6.3 Jy Flux5 [0.007/32.9]?=0 Flux in 131.25MHz subband image 75- 79 F5.3 Jy e_Flux5 [0.001/5.2]?=0 Error of Flux5 81- 86 F6.3 Jy Flux6 [0.003/28.3]?=0 Flux in 143.75MHz subband image 88- 92 F5.3 Jy e_Flux6 [0.001/3.3]?=0 Error on Flux6 94- 99 F6.3 Jy Flux7 [0.003/27.8]?=0 Flux in 156.25MHz subband image 101-105 F5.3 Jy e_Flux7 [0.001/5.2]?=0 Error on Flux7 107-112 F6.3 Jy Flux8 [0.003/27.6]?=0 Flux in 168.75MHz subband image 114-118 F5.3 Jy e_Flux8 [0.001/5.7]?=0 Error on Flux8 120-125 F6.3 --- alpha [-6.6/0.5]?=0 Spectral index 127-131 F5.3 --- e_alpha [0.1/2.8]?=0 Error on alpha
Note (1): According to the author, the resolution is ∼arcmin, so the right ascension is too accurate and the precision should be several seconds, not 0.1s. This has been modified in the VizieR display.
History: From electronic version of the journal Acknowledgements: Qian Zheng [zq -at-]
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Mar-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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