Spitzer Deep and Wide Legacy Mid- and Far-Infrared Number Counts and Lower Limits of Cosmic Infrared Background

TL;DR

This study uses Spitzer data to measure galaxy number counts at mid- and far-infrared wavelengths, establishing new lower limits for the Cosmic Infrared Background and providing publicly available data products.

Contribution

It provides homogeneous galaxy counts across multiple wavelengths, employing stacking and clustering methods to refine CIB estimates and extend detection limits.

Findings

New lower limits for CIB at 24, 70, and 160 um.

Deeper flux density limits achieved through stacking analysis.

Public release of catalogs, counts, and software.

Abstract

Aims: We want to place stronger lower limits on the Cosmic Infrared Background (CIB) brightness at 24, 70 and 160 um and measure the extragalactic number counts at these wavelengths in an homogeneous way from various surveys. Methods: Using Spitzer legacy data over 53.6 deg^2 of various depths, we build catalogs with the same extraction method at each wavelength. [...] Number count uncertainties are estimated with a counts-in-cells moment method, in order to take into account galaxy clustering. Furthermore, we use a stacking analysis to estimate number counts of sources not detected at 70 and 160 um. [...] Results: Number counts reach 35 muJy (resp. 3.5 mJy and 40 mJy) at 24 um (resp. 70 and 160um). We reach deeper flux densities of 0.38 mJy at 70 and 3.1 at 160 um using a stacking analysis. [...] Conclusions: These counts are integrated to estimate new CIB firm lower limits of 2.21-0.09+0.09 nW.m^-2.sr^-1 (resp. 5.2-0.4+0.4 and 9.0-1.1+1.1 nW.m^-2.sr^-1) at 24 um (resp. 70 and 160 um), and extrapolated to give new estimates of the CIB due to galaxies of 2.78-0.16+0.18 nW.m^-2.sr^-1 (resp. 6.4-0.6+0.7 and 14.6-2.9+7.1 nW.m^-2.sr^-1). Products (PSF, counts, CIB contributions, software) are publicly available for download at http://www.ias.u-psud.fr/irgalaxies/