325-MHz observations of the ELAIS-N1 field using the Giant Metrewave Radio Telescope |
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| Authors: | S K Sirothia M Dennefeld D J Saikia H Dole F Ricquebourg J Roland |
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| Institution: | National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Post Bag 3, Ganeshkhind, Pune 411007, India;Institut d'Astrophysique de Paris, 98bis Boulevard Arago, F-75014 Paris, France;Institut d'Astrophysique Spatiale, Bât. 121, UniversitéParis-Sud 11 and CNRS (UMR 8617), F-91405 Orsay Cedex, France |
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| Abstract: | We present observations of the European Large-Area ISO Survey-North 1 (ELAIS-N1) at 325 MHz using the Giant Metrewave Radio Telescope (GMRT), with the ultimate objective of identifying active galactic nuclei and starburst galaxies and examining their evolution with cosmic epoch. After combining the data from two different days we have achieved a median rms noise of ≈40 μJy beam−1, which is the lowest that has been achieved at this frequency. We detect 1286 sources with a total flux density above ≈270 μJy . In this paper, we use our deep radio image to examine the spectral indices of these sources by comparing our flux density estimates with those of Garn et al. at 610 MHz with the GMRT, and surveys with the Very Large Array at 1400 MHz. We attempt to identify very steep spectrum sources which are likely to be either relic sources or high-redshift objects as well as inverted-spectra objects which could be Giga-Hertz Peaked Spectrum objects. We present the source counts, and report the possibility of a flattening in the normalized differential counts at low flux densities which has so far been reported at higher radio frequencies. |
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| Keywords: | catalogues surveys radio continuum: galaxies galaxies: active |
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