AKARI/IRC source catalogues and source counts for the IRAC Dark Field, ELAIS North and the AKARI Deep Field South

TL;DR

This paper presents detailed source counts from AKARI infrared observations across three extragalactic fields, compares them with existing surveys, and explores implications for galaxy evolution models and AGN selection.

Contribution

It provides the first detailed analysis of these fields using an optimized data analysis toolkit and compares source counts with models and other surveys, highlighting areas for refinement.

Findings

Source counts are consistent with previous AKARI and Spitzer surveys at mid-infrared wavelengths.

Discrepancies at wavelengths below 7 microns suggest issues with stellar subtraction or stellar models.

AKARI filters can be used for AGN selection up to redshift 2.

Abstract

We present the first detailed analysis of three extragalactic fields (IRAC Dark Field, ELAIS-N1, ADF-S) observed by the infrared satellite, AKARI, using an optimised data analysis toolkit specifically for the processing of extragalactic point sources. The InfraRed Camera (IRC) on AKARI complements the Spitzer space telescope via its comprehensive coverage between 8-24 microns filling the gap between the Spitzer IRAC and MIPS instruments. Source counts in the AKARI bands at 3.2, 4.1, 7, 11, 15 and 18 microns are presented. At near-infrared wavelengths, our source counts are consistent with counts made in other AKARI fields and in general with Spitzer/IRAC (except at 3.2 microns where our counts lie above). In the mid-infrared (11 - 18 microns) we find our counts are consistent with both previous surveys by AKARI and the Spitzer peak-up imaging survey with the InfraRed Spectrograph (IRS). Using our counts to constrain contemporary evolutionary models we find that although the models and counts are in agreement at mid-infrared wavelengths there are inconsistencies at wavelengths shortward of 7 microns, suggesting either a problem with stellar subtraction or indicating the need for refinement of the stellar population models. We have also investigated the AKARI/IRC filters, and find an AGN selection criteria out to $z<2$ on the basis of AKARI 4.1, 11, 15 and 18 microns colours.