J/ApJ/832/190ivo://CDS.VizieR/J/ApJ/832/190doi:10.26093/cds/vizier.18320190CDSZheng Q.Wu X.-P.Johnston-Hollitt M.Gu J.-H.Xu H.2017-07-03T13:15:31Z2017-04-06T07:47:25ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frradio-continuum-emissioninterferometryWe 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 (~10^4^) 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.2016ApJ...832..190Zhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/832/190CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toVIII/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)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/832/190https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/832/190http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/832/190https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/832/190https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/832/190http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/832/190GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/ApJ/832/190/table3 (Source catalog)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/ApJ/832/190/table3?https://vizier.iucaa.in/viz-bin/conesearch/J/ApJ/832/190/table3?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/ApJ/832/190/table3?GETtext/xml+votable180.050000true142.319689.68330.0055555555555555564/255 767 1023 5/1015 1019 2043 2045 2046 2047 3063 3067 4087 4091 6/4059 4071 8151 8157 8158 8159 8167 8177 8178 8179 12247 12251 12263 12267 16343 16347 16359 163635.383681328402997e-26 1.118149259736703e-25https://cdsarc.cds.unistra.fr/viz-bin/moc/J/ApJ/832/190?format=asciiRadiodefaultJ/ApJ/832/190/table3Source catalogrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintRAJ2000[0/23] Hour of Right Ascension (J2000) (1)pos.eq.ra;meta.mainDEJ2000[85/89] Degree of Declination (J2000) (1)pos.eq.dec;meta.mainFlux1[0.01/10.3]? Flux in 81.25MHz subband imageJyphot.flux.density;em.radio.20-100MHzfloatnullablee_Flux1[0.002/1.5]? Error of Flux1Jystat.errorfloatnullableFlux2[0.01/9.5]? Flux in 93.75MHz subband imageJyphot.flux.density;em.radio.20-100MHzfloatnullablee_Flux2[0.002/1]? Error of Flux2Jystat.errorfloatnullableFlux3[0.01/8.3]? Flux in 106.25MHz subband imageJyphot.flux.density;em.radio.100-200MHzfloatnullablee_Flux3[0.001/0.9]? Error of Flux3Jystat.errorfloatnullableFlux4[0.01/8.2]? Flux in 118.75MHz subband imageJyphot.flux.density;em.radio.100-200MHzfloatnullablee_Flux4[0.001/0.9]? Error of Flux4Jystat.errorfloatnullableFlux5[0.007/32.9]? Flux in 131.25MHz subband imageJyphot.flux.density;em.radio.100-200MHzfloatnullablee_Flux5[0.001/5.2]? Error of Flux5Jystat.errorfloatnullableFlux6[0.003/28.3]? Flux in 143.75MHz subband imageJyphot.flux.density;em.radio.100-200MHzfloatnullablee_Flux6[0.001/3.3]? Error on Flux6Jystat.errorfloatnullableFlux7[0.003/27.8]? Flux in 156.25MHz subband imageJyphot.flux.density;em.radio.100-200MHzfloatnullablee_Flux7[0.001/5.2]? Error on Flux7Jystat.errorfloatnullableFlux8[0.003/27.6]? Flux in 168.75MHz subband imageJyphot.flux.density;em.radio.100-200MHzfloatnullablee_Flux8[0.001/5.7]? Error on Flux8Jystat.errorfloatnullablealpha[-6.6/0.5]? Spectral indexspect.indexfloatnullablee_alpha[0.1/2.8]? Error on alphastat.error;pos.eq.rafloatnullable