2010MNRAS.402.2666S

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 90µm. Our work is based on a far-IR selected sample both in the local Universe and at high redshift, the former consisting of IRAS 60µm-selected galaxies at z < 0.07 and the latter of Spitzer 70µm selected galaxies across 0.1 < 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. At z < 0.07, we observe the previously known results that moderate luminosity galaxies (L_IR < 10¹¹L_☉) dominate the total luminosity density and that the fraction of cold galaxies decreases with increasing luminosity, becoming negligible at the highest luminosities. Conversely, above z = 0.1, we find that luminous IR galaxies (L_IR > 10¹¹L_☉), the majority of which are cold, dominate the IRLD. We therefore infer that cold galaxies dominate the IRLD across the whole 0 < z < 1 range, hence appear to be the main driver behind the increase in SFR density up to z ∼ 1 whereas local luminous galaxies are not, on the whole, representative of the high-redshift population.