The comoving infrared luminosity density: Domination of cold galaxies across 0 < z < 1

In this paper, we examine the contribution of galaxies with different infrared (IR) spectral energy distributions (SEDs) to the comoving IR luminosity density (IRLD), a proxy for the comoving star formation rate (SFR) density. We characterize galaxies as having either a cold or hot IR SED depending on whether the rest-frame wavelength of their peak IR energy output is above or below 90 μm. Our work is based on a far-IR selected sample both in the local Universe and at high redshift, the former consisting of IRAS60 μm-selected galaxies at z < 0.07 and the latter of Spitzer70 μm selected galaxies across0.1 < z≤ 1. We find that the total IR luminosity densities for each redshift/luminosity bin agree well with results derived from other deep mid-/far-IR surveys. Atz < 0.07, we observe the previously known results that moderate luminosity galaxies(L_IR < 10¹¹ L_⊙) dominate the total luminosity density and that the fraction of cold galaxies decreases with increasing luminosity, becoming negligible at the highest luminosities. Conversely, abovez= 0.1, we find that luminous IR galaxies(L_IR > 10¹¹ L_⊙), the majority of which are cold, dominate the IRLD. We therefore infer that cold galaxies dominate the IRLD across the whole0 < z < 1 range, hence appear to be the main driver behind the increase in SFR density up toz∼ 1 whereas local luminous galaxies are not, on the whole, representative of the high-redshift population.