The evolution of the ultraviolet and infrared luminosity densities in the universe at 0 < z <1

Abstract

The ratio between far-ultraviolet (FUV) and infrared (IR) luminosity densities from z = 0 to z = 1 is discussed by using the luminosity functions (LFs) of both wavelengths. The FUV LF (z = 0-1) based on GALEX has been reported by Arnouts et al. (2005, ApJ, 619, L43), whilst for the IR LF, we used the IRAS PSCz 60-μm LF for the local universe and the Spitzer 15-μm LF at higher-z as used by Le Floc'h et al. (2005, ApJ, in press). Both luminosity densities show a significant evolutionary trend, but the IR evolves much faster than the FUV. Consequently, the ratio ρdust/ρFUV increases toward higher-z, from ∼4 (local) to ∼15 (z ≃ 1). It is also shown that more than 70% of the star formation activity in the universe is obscured by dust at 0.5 ≲ z ≲ 1.2. © ESO 2005.