The AKARI Deep Field South: Spitzer 24 and 70 micron Observations, Catalogs and Counts

TL;DR

This paper presents deep Spitzer observations of the AKARI Deep Field South at 24 and 70 microns, producing catalogs, counts, and analysis of galaxy populations, including effects of a foreground galaxy cluster.

Contribution

It provides the first combined Spitzer and AKARI infrared catalogs and counts for the ADF-S, including completeness corrections and analysis of galaxy cluster influence.

Findings

Catalogs reach 0.2mJy at 24 micron and 20mJy at 70 micron.

Number counts are consistent with galaxy evolution models.

Foreground galaxy cluster may enhance 24 micron luminosity function.

Abstract

The AKARI Deep Field South (ADF-S) is a ~12 sq. deg. region near the South Ecliptic Pole that has been observed with deep scans in the far-infrared by the AKARI satellite. As such it is becoming one of the key extragalactic survey fields. We here present complementary observations of the ADF-S conducted by the Spitzer Space Telescope at wavelengths of 24 and 70 micron. We extract source catalogs at each of these wavelengths reaching depths of ~ 0.2mJy at 24 micron and ~ 20mJy at 70 micron. We also apply an K-to-24 micron colour criterion to select objects with galaxy-like colours in the 24 micron survey. Completeness corrections as a function of flux density are derived for both catalogs by injecting artificial sources of known flux density into the maps, and we find that our surbveys are 50% complete at 0.26mJy and 24mJy at 24 and 70 micron respectively. We can thus produce number counts as a function of flux density for the ADF-S at 24 and 70 micron. These are combined with existing literature counts and compared to four different number count models derived from galaxy evolution models. One complicating factor for the ADF-S counts is the presence of a foreground galaxy cluster at z=0.04 in the field. We examine the ranges of flux densities to which this cluster might make a contribution to the counts and find hints that the 24 micron luminosity function of the cluster galaxies might be enhanced above that of field galaxies. Full catalogs for these ADF-S Spitzer surveys at 24 and 70 micron are made available as part of this paper.