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Deep observations of the super-CLASS supercluster at 325 MHz with the GMRT: The low-frequency source catalogue

Lookup NU author(s): Dr Christopher Hales



This is the final published version of an article that has been published in its final definitive form by Oxford University Press, 2016.

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© 2016 The Authors.We present the results of 325 MHz Giant Metrewave Radio Telescope observations of a supercluster field, known to contain five Abell clusters at redshift z ~ 0.2. We achieve a nominal sensitivity of 34 μJy beam-1 towards the phase centre. We compile a catalogue of 3257 sources with fiux densities in the range 183 μJy-1.5 Jy within the entire ~6.5 deg2 field of view. Subsequently, we use available survey data at other frequencies to derive the spectral index distribution for a sub-sample of these sources, recovering two distinct populations - a dominant population which exhibit spectral index trends typical of steep-spectrumsynchrotron emission, and a smaller population of sources with typically flat or rising spectra. We identify a number of sources with ultrasteep spectra or rising spectra for further analysis, finding two candidate high-redshift radio galaxies and three gigahertz-peaked-spectrum radio sources. Finally, we derive the Euclidean-normalized differential source counts using the catalogue compiled in this work, for sources with flux densities in excess of 223 μJy. Our differential source counts are consistent with both previous observations at this frequency and models of the low-frequency source population. These represent the deepest source counts yet derived at 325MHz. Our source counts exhibit the well-known flattening atmJy flux densities, consistent with an emerging population of star-forming galaxies; we also find marginal evidence of a downturn at flux densities below 308 μJy, a feature so far only seen at 1.4 GHz.

Publication metadata

Author(s): Riseley CJ, Scaife AMM, Hales CA, Harrison I, Birkinshaw M, Battye RA, Beswick RJ, Brown ML, Casey CM, Chapman SC, Demetroullas C, Hung C-L, Jackson NJ, Muxlow T, Watson B

Publication type: Article

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 2016

Volume: 462

Issue: 1

Pages: 917-940

Online publication date: 19/07/2016

Acceptance date: 14/07/2016

Date deposited: 30/06/2017

ISSN (print): 0035-8711

ISSN (electronic): 1365-2966

Publisher: Oxford University Press


DOI: 10.1093/mnras/stw1734


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