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

TL;DR

This paper introduces a comprehensive mid-infrared source catalogue from the AKARI NEP-Deep survey, covering 7 to 24 microns, with detailed source detection, star-galaxy separation, and initial analysis of source counts and redshift effects.

Contribution

The paper provides the first extensive mid-IR source catalogue from AKARI NEP-Deep with multi-band coverage, source classification, and preliminary analysis of source density and redshifted PAH emission.

Findings

Detected 7284 sources in 0.67 deg^2 area.

Catalogue is ~80% complete at 200 micro Jy.

Observed increased source density at 15 micron likely due to redshifted PAH emission.

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 micron. 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 micron bands, and found 7284 sources in a 0.67 deg^2 area. From our simulations, we estimate that the catalogue is ~80 per cent complete to 200 micro Jy at 15 - 18 micron, 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 micron are presented for both stars and galaxies. A drastic increase in the source density is found in between 11 and 15 micron at the flux level of ~300 micro Jy. This is likely due to the redshifted PAH emission at 8 micron, 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.