| 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 ( $z=0\mbox{--}1$) based on GALEX has been reported by (Arnouts et al. (2005, ApJ, 619, L43), whilst for the IR LF, we used the IRAS PSC z 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 $\rho_{\rm dust}/\rho_{\rm FUV}$ increases toward higher- z, from ∼4 (local) to ∼15 ( $z\simeq 1$). It is also shown that more than $70\%$ of the star formation activity in the universe is obscured by dust at $0.5 \la z \la 1.2$.
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