The XXL Survey

XXIX. GMRT 610 MHz continuum observations^★

¹ Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia
² Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA, Leiden, The Netherlands
³ Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Puné 411 007, India
⁴ School of Physics and Astronomy, University of Birmingham, Birmingham B15 2TT, UK
⁵ Dept. of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
⁶ INAF, IASF Milano, via Bassini 15, 20133 Milano, Italy
⁷ H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
⁸ INAF - Istituto di Radioastronomia di Bologna, via P. Gobetti 101, 40129 Bologna, Italy
⁹ INAF - Osservatorio Astronomico di Bologna, P. Gobetti 93/3, 40129 Bologna, Italy
¹⁰ Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France
¹¹ Australian Astronomical Observatory, North Ryde, NSW 2113, Australia
¹² Western Sydney University, Locked Bag 1797, 1797 Penrith South, NSW, Australia
¹³ CSIRO Astronomy and Space Science, PO Box 76, 1710 Epping, NSW, Australia
¹⁴ AIM, CEA, CNRS, Université Paris-Saclay, Université Paris Diderot, Sorbonne Paris Cité, 91191 Gif-sur-Yvette, France
¹⁵ GEPI, Observatoire de Paris, CNRS, Université Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France
¹⁶ School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK

Received: 21 November 2017
Accepted: 6 February 2018

Abstract

We present the 25 square-degree GMRT-XXL-N 610 MHz radio continuum survey, conducted at 50 cm wavelength with the Giant Metrewave Radio Telescope (GMRT) towards the XXL Northern field (XXL-N). We combined previously published observations of the XMM-Large Scale Structure (XMM-LSS) field, located in the central part of XXL-N, with newly conducted observations towards the remaining XXL-N area, and imaged the combined data-set using the Source Peeling and Atmospheric Modeling (SPAM) pipeline. The final mosaic encompasses a total area of 30.4 square degrees, with rms <150 μJy beam⁻¹ over 60% of the area. The rms achieved in the inner 9.6 square degree area, enclosing the XMM-LSS field, is about 200 μJy beam⁻¹, while that over the outer 12.66 square degree area (which excludes the noisy edges) is about 45 μJy beam⁻¹. The resolution of the final mosaic is 6.5 arcsec. We present a catalogue of 5434 sources detected at ≥7 ×rms. We verify, and correct the reliability of, the catalog in terms of astrometry, flux, and false detection rate. Making use of the (to date) deepest radio continuum survey over a relatively large (2 square degree) field, complete at the flux levels probed by the GMRT-XXL-N survey, we also assess the survey’s incompleteness as a function of flux density. The radio continuum sensitivity reached over a large field with a wealth of multi-wavelength data available makes the GMRT-XXL-N 610 MHz survey an important asset for studying the physical properties, environments and cosmic evolution of radio sources, in particular radio-selected active galactic nuclei (AGN).