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

Takagi, T.; Matsuhara, H.; Goto, T.; Hanami, H.; Im, M.; Imai, K.; Ishigaki, T.; Lee, H. M.; Lee, M. G.; Malkan, M.; Ohyama, Y.; Oyabu, S.; Pearson, C. P.; Serjeant, S.; Wada, T. and White, G. J. (2012). The AKARI NEP-Deep survey: a mid-infrared source catalogue. Astronomy & Astrophysics, 537, article no. A24.

DOI: https://doi.org/10.1051/0004-6361/201117759

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.

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