The AKARI NEP-Deep survey: a mid-infrared source catalogue^⋆

¹ Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Sagamihara, 229-8510, Kanagawa Japan
e-mail: takagi@ir.isas.jaxa.jp
² Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI, 96822, USA
³ Subaru Telescope 650 North A’ohoku Place Hilo, HI 96720, USA
⁴ Physics Section, Faculty of Humanities and Social Sciences, Iwate University, 020-8550 Morioka, Japan
⁵ Department of Physics and Astronomy, FPRD, Seoul National University, Shilim-Dong, Kwanak-Gu, 151-742 Seoul, Korea
⁶ TOME R&D Inc. Kawasaki, 213-0012 Kanagawa, Japan
⁷ Department of Physics and Astronomy, UCLA, Los Angeles, CA, USA
⁸ Academia Sinica, Institute of Astronomy and Astrophysics, Taiwan
⁹ Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Aichi, Japan
¹⁰ Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX, UK
¹¹ Astrophysics Group, Department of Physics, The Open University, Milton Keynes, MK7 6AA, UK

Received: 22 July 2011
Accepted: 8 November 2011

Abstract

We present a new catalogue of mid-IR sources using the AKARI NEP-Deep survey. The InfraRed Camera (IRC) onboard AKARI has a comprehensive mid-IR wavelength coverage with 9 photometric bands at 2–24 μm. We utilized all of these bands to cover a nearly circular area adjacent to the north ecliptic pole (NEP). We designed the catalogue to include most of sources detected in 7, 9, 11, 15 and 18 μm bands, and found 7284 sources in a 0.67 deg² area. From our simulations, we estimate that the catalogue is  ~80 per cent complete to 200 μJy at 15–18 μm, and  ~10 per cent of sources are missed, owing to source blending. Star-galaxy separation is conducted using only AKARI photometry, as a result of which 10 per cent of catalogued sources are found to be stars. The number counts at 11, 15, 18, and 24 μm are presented for both stars and galaxies. A drastic increase in the source density is found in between 11 and 15 μm at the flux level of  ~ 300 μJy. This is likely due to the redshifted PAH emission at 8 μm, given our rough estimate of redshifts from an AKARI colour–colour plot. Along with the mid-IR source catalogue, we present optical-NIR photometry for sources falling inside a Subaru/Sprime-cam image covering part of the AKARI NEP-Deep field, which is deep enough to detect most of AKARI mid-IR sources, and useful to study optical characteristics of a complete mid-IR source sample.