Radio sources in the NCP region with the 21CMA Virtual Observatory Resource

Authors
  1. Zheng Q.
  2. Wu X.-P.
  3. Johnston-Hollitt M.
  4. Gu J.-H.
  5. Xu H.
  6. Published by
    CDS
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 (~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.

Keywords
  1. radio-continuum-emission
  2. interferometry
Bibliographic source Bibcode
2016ApJ...832..190Z
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/832/190
IVOA Identifier IVOID
ivo://CDS.VizieR/J/ApJ/832/190
Document Object Identifer DOI
doi:10.26093/cds/vizier.18320190

Access

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https://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/832/190
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http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/832/190
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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?

History

2017-04-06T07:47:25Z
Resource record created
2017-04-06T07:47:25Z
Created
2017-07-03T13:15:31Z
Updated

Contact

Name
CDS support team
Postal Address
CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France
E-Mail
cds-question@unistra.fr