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

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-mu m LF for the local universe and the Spitzer 15-mu m LF at higher-z as used by Le Floc'h et al. ( 2005, ApJ, in press) press). Both luminosity densities show a significant. evolutionary trend, but the IR evolves much faster than the FUV. Consequently, the ratio rho(dust)/rho(FUV) increases toward higher-z, from similar to 4 (local) to similar to 15 (z similar or equal to 1). It is also shown that more than 70% of the star formation activity in the universe is obscured by dust at 0.5 less than or similar to z less than or similar to 1.2.