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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 131 624 Source catalog
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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
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Bytes Format Units Label Explanations
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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
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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.
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History:
From electronic version of the journal
Acknowledgements:
Qian Zheng [zq -at- bao.ac.cn]
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 01-Mar-2017