A deep survey of the AKARI north ecliptic pole field

I. WSRT 20 cm radio survey description, observations and data reduction

¹ Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK e-mail: g.j.white@open.ac.uk
² Space Science and Technology Department, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
³ Institute for Space Imaging Science, University of Lethbridge, Lethbridge, Alberta, T1K 3M4, Canada

⁴ CSIRO Astronomy and Space Science, Australia Telescope National Facility, CSIRO, Marsfield NSW 2122, Australia
⁵ Institute of Space and Astronautical Science, JAXA, Yoshino-dai 3-1-1, Sagamihara, Kanagawa 229-8510, Japan
⁶ SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands
⁷ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
⁸ National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
⁹ Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
¹⁰ Physics Section, Faculty of Humanities and Social Sciences, Iwate University, Morioka 020-8550, Japan
¹¹ Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
¹² Department of Physics & Astronomy, School of Science and Technology, University of Sussex, Falmer, Brighton BN1 9QH, UK

Received: 28 September 2009
Accepted: 26 April 2010

Abstract

Aims. The Westerbork Radio Synthesis Telescope, WSRT, has been used to make a deep radio survey of an ~1.7 degree² field coinciding with the AKARI north ecliptic pole deep field. The observations, data reduction and source count analysis are presented, along with a description of the overall scientific objectives.

Methods. The survey consisted of 10 pointings, mosaiced with enough overlap to maintain a similar sensitivity across the central region that reached as low as 21 μJy beam^-1 at 1.4 GHz.

Results. A catalogue containing 462 sources detected with a resolution of 17.0 × 15.5 is presented. The differential source counts calculated from the WSRT data have been compared with those from the shallow VLA-NEP survey of Kollgaard et al. 1994, and show a pronounced excess for sources fainter than ~1 mJy, consistent with the presence of a population of star forming galaxies at sub-mJy flux levels.

Conclusions. The AKARI north ecliptic pole deep field is the focus of a major observing campaign conducted across the entire spectral region. The combination of these data sets, along with the deep nature of the radio observations will allow unique studies of a large range of topics including the redshift evolution of the luminosity function of radio sources, the clustering environment of radio galaxies, the nature of obscured radio-loud active galactic nuclei, and the radio/far-infrared correlation for distant galaxies. This catalogue provides the basic data set for a future series of paper dealing with source identifications, morphologies, and the associated properties of the identified radio sources.