The Evolution of the Visible and Hidden Star Formation in the Universe: Implication from the Luminosity Functions at FUV and FIR

Based on GALEX and IRAS/Spitzer datasets, we have found that both FUV and FIR luminosity functions (LFs) show a strong evolution from z = 0 to z = 1, but the FIR LF evolves much stronger than the FUV one. Consequently, the FIR/FUV luminosity density ratio increases from 4 (z = 0) to 15 (z = 1). It means that more than 80 % of the star-forming activity in the Universe is hidden by dust at z = 1. To explore this issue further, we have performed a combined analysis of the galaxy sample in FUV and FIR. For the Local Universe we used GALEX-IRAS sample, whereas at z = 1 we used the Lymanbreak galaxy sample selected by GALEX bands constructed by Burgarella et al. (2005), which is known to be representative of visible (i.e., non-obscured) star-forming galaxies at z = 1. From these datasets, we constructed the LFs of the FUV-selected galaxies by the survival analysis to, take into account the upper-limit data properly. We discovered that the FIR LF of the Lyman-break galaxies show a significant evolution comparing with the local FIR LF, but it is a factor of 2–3 lower than the global FIR LF (Le Floc’h et al. 2005). This indicates that the evolution of visible galaxies is not strong enough to explain the drastic evolution of the FIR LF. Namely, a FIR-luminous, rapidly diminishing population of galaxies is required.