Unveiling the population of high-redshift radio galaxies using centimeter GMRT survey

Veeresh Singh1*, Alexandre Beelen1, Yogesh Wadadekar2, Sandeep Sirothia2, C. H. Ishwara-Chandra2, Aritra Basu2, Alain Omont3 and Kim McAlpine4
1Institut d’Astrophysique Spatiale, Bˆat. 121, Université Paris-Sud, 91405 Orsay Cedex, France
2National Centre for Radio Astrophysics, TIFR, Post Bag 3, Ganeshkhind, Pune 411007, India
3UPMC Univ Paris 06 and CNRS, UMR 7095, Institut d’Astrophysique de Paris, F-75014, Paris, France
4Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7537, South Africa

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Ultra Steep Spectrum (USS) radio sources are one of the efficient tracers of High Redshift Radio Galaxies (HzRGs). To search for HzRGs candidates, we investigate properties of a large sample of faint USS sources derived from our deep 325 MHz GMRT observations combined with 1.4 GHz VLA data on the two subfields (i:e:; VLA-VIMOS VLT Deep Survey (VVDS) and Subaru X-ray Deep Field (SXDF)) in the XMM-LSS field. The available redshift estimates show that majority of our USS sample sources are at higher redshifts with the median redshifts  1.18 and ∼ 1.57 in the VLA-VVDS and SXDF fields. In the VLA-VVDS field, ∼ 20%of USS sources lack the redshift estimates as well as the detection in the deep optical, IR surveys, and thus these sources may be considered as potential high-z candidates. The radio luminosity distributions suggest that a substantial fraction (∼ 40%) of our USS sample sources are radio-loud sources, distributed over redshifts ∼ 0.5 to 4.

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Keywords : Radio: galaxies - Galaxies: nuclei - Galaxies: active